US20170365505A1 - Filling processes - Google Patents
Filling processes Download PDFInfo
- Publication number
- US20170365505A1 US20170365505A1 US15/343,151 US201615343151A US2017365505A1 US 20170365505 A1 US20170365505 A1 US 20170365505A1 US 201615343151 A US201615343151 A US 201615343151A US 2017365505 A1 US2017365505 A1 US 2017365505A1
- Authority
- US
- United States
- Prior art keywords
- layer
- thermal process
- semiconductor structure
- subjecting
- cavity
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Granted
Links
- 238000005429 filling process Methods 0.000 title description 4
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 claims abstract description 165
- 238000000034 method Methods 0.000 claims abstract description 144
- 230000008569 process Effects 0.000 claims abstract description 94
- 239000000377 silicon dioxide Substances 0.000 claims abstract description 81
- 235000012239 silicon dioxide Nutrition 0.000 claims abstract description 70
- 239000004065 semiconductor Substances 0.000 claims abstract description 57
- 239000000463 material Substances 0.000 claims abstract description 52
- 229920001709 polysilazane Polymers 0.000 claims abstract description 27
- 238000011049 filling Methods 0.000 claims abstract description 23
- 230000008021 deposition Effects 0.000 claims abstract description 19
- 239000000126 substance Substances 0.000 claims abstract description 7
- 239000010410 layer Substances 0.000 claims description 146
- 239000002356 single layer Substances 0.000 claims description 18
- 238000005530 etching Methods 0.000 claims description 9
- 238000002955 isolation Methods 0.000 claims description 7
- 238000009279 wet oxidation reaction Methods 0.000 claims description 7
- 238000004519 manufacturing process Methods 0.000 abstract description 11
- 230000008859 change Effects 0.000 abstract description 6
- 238000000576 coating method Methods 0.000 description 17
- LIVNPJMFVYWSIS-UHFFFAOYSA-N silicon monoxide Chemical compound [Si-]#[O+] LIVNPJMFVYWSIS-UHFFFAOYSA-N 0.000 description 17
- 238000000151 deposition Methods 0.000 description 16
- 239000011248 coating agent Substances 0.000 description 14
- 229910018557 Si O Inorganic materials 0.000 description 11
- 238000005033 Fourier transform infrared spectroscopy Methods 0.000 description 6
- XUIMIQQOPSSXEZ-UHFFFAOYSA-N Silicon Chemical compound [Si] XUIMIQQOPSSXEZ-UHFFFAOYSA-N 0.000 description 5
- 238000000280 densification Methods 0.000 description 5
- 230000003647 oxidation Effects 0.000 description 5
- 238000007254 oxidation reaction Methods 0.000 description 5
- 229910052710 silicon Inorganic materials 0.000 description 5
- 239000010703 silicon Substances 0.000 description 5
- QGZKDVFQNNGYKY-UHFFFAOYSA-N Ammonia Chemical compound N QGZKDVFQNNGYKY-UHFFFAOYSA-N 0.000 description 4
- 238000000137 annealing Methods 0.000 description 4
- 239000006227 byproduct Substances 0.000 description 4
- 239000011800 void material Substances 0.000 description 4
- 230000015572 biosynthetic process Effects 0.000 description 3
- 229910052814 silicon oxide Inorganic materials 0.000 description 3
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 description 2
- UFHFLCQGNIYNRP-UHFFFAOYSA-N Hydrogen Chemical compound [H][H] UFHFLCQGNIYNRP-UHFFFAOYSA-N 0.000 description 2
- 230000008901 benefit Effects 0.000 description 2
- 230000006870 function Effects 0.000 description 2
- 239000001257 hydrogen Substances 0.000 description 2
- 229910052739 hydrogen Inorganic materials 0.000 description 2
- 150000004706 metal oxides Chemical class 0.000 description 2
- 238000010943 off-gassing Methods 0.000 description 2
- 230000009467 reduction Effects 0.000 description 2
- -1 silicon dioxide Chemical compound 0.000 description 2
- 229910021529 ammonia Inorganic materials 0.000 description 1
- 230000000295 complement effect Effects 0.000 description 1
- 238000001723 curing Methods 0.000 description 1
- 230000007547 defect Effects 0.000 description 1
- 230000005669 field effect Effects 0.000 description 1
- 230000014509 gene expression Effects 0.000 description 1
- 238000013035 low temperature curing Methods 0.000 description 1
- 238000013507 mapping Methods 0.000 description 1
- 229910044991 metal oxide Inorganic materials 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 229910052757 nitrogen Inorganic materials 0.000 description 1
- 229910000069 nitrogen hydride Inorganic materials 0.000 description 1
- 229920000642 polymer Polymers 0.000 description 1
- 239000000758 substrate Substances 0.000 description 1
- 238000004627 transmission electron microscopy Methods 0.000 description 1
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 1
Images
Classifications
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L21/00—Processes or apparatus adapted for the manufacture or treatment of semiconductor or solid state devices or of parts thereof
- H01L21/70—Manufacture or treatment of devices consisting of a plurality of solid state components formed in or on a common substrate or of parts thereof; Manufacture of integrated circuit devices or of parts thereof
- H01L21/71—Manufacture of specific parts of devices defined in group H01L21/70
- H01L21/76—Making of isolation regions between components
- H01L21/762—Dielectric regions, e.g. EPIC dielectric isolation, LOCOS; Trench refilling techniques, SOI technology, use of channel stoppers
- H01L21/76202—Dielectric regions, e.g. EPIC dielectric isolation, LOCOS; Trench refilling techniques, SOI technology, use of channel stoppers using a local oxidation of silicon, e.g. LOCOS, SWAMI, SILO
- H01L21/76205—Dielectric regions, e.g. EPIC dielectric isolation, LOCOS; Trench refilling techniques, SOI technology, use of channel stoppers using a local oxidation of silicon, e.g. LOCOS, SWAMI, SILO in a region being recessed from the surface, e.g. in a recess, groove, tub or trench region
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L21/00—Processes or apparatus adapted for the manufacture or treatment of semiconductor or solid state devices or of parts thereof
- H01L21/70—Manufacture or treatment of devices consisting of a plurality of solid state components formed in or on a common substrate or of parts thereof; Manufacture of integrated circuit devices or of parts thereof
- H01L21/71—Manufacture of specific parts of devices defined in group H01L21/70
- H01L21/76—Making of isolation regions between components
- H01L21/762—Dielectric regions, e.g. EPIC dielectric isolation, LOCOS; Trench refilling techniques, SOI technology, use of channel stoppers
- H01L21/76224—Dielectric regions, e.g. EPIC dielectric isolation, LOCOS; Trench refilling techniques, SOI technology, use of channel stoppers using trench refilling with dielectric materials
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L21/00—Processes or apparatus adapted for the manufacture or treatment of semiconductor or solid state devices or of parts thereof
- H01L21/70—Manufacture or treatment of devices consisting of a plurality of solid state components formed in or on a common substrate or of parts thereof; Manufacture of integrated circuit devices or of parts thereof
- H01L21/71—Manufacture of specific parts of devices defined in group H01L21/70
- H01L21/76—Making of isolation regions between components
- H01L21/762—Dielectric regions, e.g. EPIC dielectric isolation, LOCOS; Trench refilling techniques, SOI technology, use of channel stoppers
- H01L21/76224—Dielectric regions, e.g. EPIC dielectric isolation, LOCOS; Trench refilling techniques, SOI technology, use of channel stoppers using trench refilling with dielectric materials
- H01L21/76229—Concurrent filling of a plurality of trenches having a different trench shape or dimension, e.g. rectangular and V-shaped trenches, wide and narrow trenches, shallow and deep trenches
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L21/00—Processes or apparatus adapted for the manufacture or treatment of semiconductor or solid state devices or of parts thereof
- H01L21/02—Manufacture or treatment of semiconductor devices or of parts thereof
- H01L21/02104—Forming layers
- H01L21/02107—Forming insulating materials on a substrate
- H01L21/02225—Forming insulating materials on a substrate characterised by the process for the formation of the insulating layer
- H01L21/0226—Forming insulating materials on a substrate characterised by the process for the formation of the insulating layer formation by a deposition process
- H01L21/02282—Forming insulating materials on a substrate characterised by the process for the formation of the insulating layer formation by a deposition process liquid deposition, e.g. spin-coating, sol-gel techniques, spray coating
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L21/00—Processes or apparatus adapted for the manufacture or treatment of semiconductor or solid state devices or of parts thereof
- H01L21/02—Manufacture or treatment of semiconductor devices or of parts thereof
- H01L21/04—Manufacture or treatment of semiconductor devices or of parts thereof the devices having potential barriers, e.g. a PN junction, depletion layer or carrier concentration layer
- H01L21/18—Manufacture or treatment of semiconductor devices or of parts thereof the devices having potential barriers, e.g. a PN junction, depletion layer or carrier concentration layer the devices having semiconductor bodies comprising elements of Group IV of the Periodic Table or AIIIBV compounds with or without impurities, e.g. doping materials
- H01L21/22—Diffusion of impurity materials, e.g. doping materials, electrode materials, into or out of a semiconductor body, or between semiconductor regions; Interactions between two or more impurities; Redistribution of impurities
- H01L21/225—Diffusion of impurity materials, e.g. doping materials, electrode materials, into or out of a semiconductor body, or between semiconductor regions; Interactions between two or more impurities; Redistribution of impurities using diffusion into or out of a solid from or into a solid phase, e.g. a doped oxide layer
- H01L21/2251—Diffusion into or out of group IV semiconductors
- H01L21/2254—Diffusion into or out of group IV semiconductors from or through or into an applied layer, e.g. photoresist, nitrides
- H01L21/2257—Diffusion into or out of group IV semiconductors from or through or into an applied layer, e.g. photoresist, nitrides the applied layer being silicon or silicide or SIPOS, e.g. polysilicon, porous silicon
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L21/00—Processes or apparatus adapted for the manufacture or treatment of semiconductor or solid state devices or of parts thereof
- H01L21/02—Manufacture or treatment of semiconductor devices or of parts thereof
- H01L21/04—Manufacture or treatment of semiconductor devices or of parts thereof the devices having potential barriers, e.g. a PN junction, depletion layer or carrier concentration layer
- H01L21/18—Manufacture or treatment of semiconductor devices or of parts thereof the devices having potential barriers, e.g. a PN junction, depletion layer or carrier concentration layer the devices having semiconductor bodies comprising elements of Group IV of the Periodic Table or AIIIBV compounds with or without impurities, e.g. doping materials
- H01L21/30—Treatment of semiconductor bodies using processes or apparatus not provided for in groups H01L21/20 - H01L21/26
- H01L21/302—Treatment of semiconductor bodies using processes or apparatus not provided for in groups H01L21/20 - H01L21/26 to change their surface-physical characteristics or shape, e.g. etching, polishing, cutting
- H01L21/306—Chemical or electrical treatment, e.g. electrolytic etching
- H01L21/30604—Chemical etching
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L21/00—Processes or apparatus adapted for the manufacture or treatment of semiconductor or solid state devices or of parts thereof
- H01L21/02—Manufacture or treatment of semiconductor devices or of parts thereof
- H01L21/04—Manufacture or treatment of semiconductor devices or of parts thereof the devices having potential barriers, e.g. a PN junction, depletion layer or carrier concentration layer
- H01L21/18—Manufacture or treatment of semiconductor devices or of parts thereof the devices having potential barriers, e.g. a PN junction, depletion layer or carrier concentration layer the devices having semiconductor bodies comprising elements of Group IV of the Periodic Table or AIIIBV compounds with or without impurities, e.g. doping materials
- H01L21/30—Treatment of semiconductor bodies using processes or apparatus not provided for in groups H01L21/20 - H01L21/26
- H01L21/324—Thermal treatment for modifying the properties of semiconductor bodies, e.g. annealing, sintering
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L21/00—Processes or apparatus adapted for the manufacture or treatment of semiconductor or solid state devices or of parts thereof
- H01L21/70—Manufacture or treatment of devices consisting of a plurality of solid state components formed in or on a common substrate or of parts thereof; Manufacture of integrated circuit devices or of parts thereof
- H01L21/71—Manufacture of specific parts of devices defined in group H01L21/70
- H01L21/768—Applying interconnections to be used for carrying current between separate components within a device comprising conductors and dielectrics
- H01L21/76801—Applying interconnections to be used for carrying current between separate components within a device comprising conductors and dielectrics characterised by the formation and the after-treatment of the dielectrics, e.g. smoothing
- H01L21/76822—Modification of the material of dielectric layers, e.g. grading, after-treatment to improve the stability of the layers, to increase their density etc.
Definitions
- One or more aspects of embodiments according to the present invention relate to fabrication processes for semiconductor structures, and more particularly to a method, within such processes, for filling gaps or voids.
- CMOS complementary metal oxide
- aspects of embodiments of the present disclosure are directed toward a method of filling cavities in a semiconductor structure during fabrication.
- a layer of a first material e.g., a polysilazane
- a first thermal process to change its chemical composition, e.g., to change it to silicon oxide (e.g., silicon dioxide, or silicon monoxide, or silicon trioxide).
- silicon oxide e.g., silicon dioxide, or silicon monoxide, or silicon trioxide.
- the etch-back may also be repeated in one or more of the cycles after the first cycle, and a second thermal process, that may increase the density of one or more of the deposited layers, may be performed in one or more of the cycles.
- a method for filling a cavity in a semiconductor structure including: forming a first layer of a first material in the cavity; subjecting the semiconductor structure to a first thermal process including subjecting the semiconductor structure to a temperature of at least 100° C. for interval of time; etching back the first layer to form a reduced first layer, having a reduced thickness; forming a second layer of a second material, in the cavity; and subjecting the semiconductor structure to a second thermal process including subjecting the semiconductor structure to a temperature of at least 100° C. for interval of time, to form, from at least the reduced first layer and the second layer, a single layer of uniform composition and density.
- the second material is the same as the first material.
- the first material is a polysilazane.
- the forming of the second layer of the second material is performed by substantially the same process as the forming of the first layer of the first material, and wherein the second thermal process is substantially the same as the first thermal process.
- the forming of the second layer of the second material, in the cavity includes forming the second layer directly on the reduced first layer.
- the method includes: performing a third thermal process after performing the second thermal process, the third thermal process increasing the density of the single layer by at least about 20%.
- the forming of the first layer includes forming the first layer by a spin-on deposition, and/or the forming of the second layer includes forming the second layer by a spin-on deposition.
- the single layer substantially fills the cavity.
- the first material and/or the second material includes, as a major component, an inorganic polysilazane.
- the first material includes, as a major component, an inorganic polysilazane, and, after the subjecting of the semiconductor structure to the first thermal process, the first layer includes, as a major component, silicon dioxide, and/or the second material includes, as a major component, an inorganic polysilazane, and, after the subjecting of the semiconductor structure to the second thermal process, the second layer includes, as a major component, silicon dioxide.
- the subjecting of the semiconductor structure to the first thermal process includes subjecting the semiconductor structure to the first thermal process in a wet oxidation environment
- the subjecting of the semiconductor structure to the second thermal process includes subjecting the semiconductor structure to the second thermal process in a wet oxidation environment.
- the first thermal process includes subjecting the semiconductor structure to a temperature between 100° C. and 250° C. for an interval of time
- the second thermal process includes subjecting the semiconductor structure to a temperature between 500° C. and 850° C. for an interval of time.
- the cavity is a trench for a shallow trench isolation (STI) structure.
- STI shallow trench isolation
- the single layer includes, as a major component, an oxide.
- a width of the cavity is less than 40 nm.
- a width of the cavity is less than 20 nm.
- the method includes: etching back the single layer to form a reduced single layer, having a reduced thickness, wherein a thickness of the reduced first layer is greater than 5 nm and less than 50 nm, and a thickness of the reduced single layer is greater than 10 nm and less than 100 nm.
- a method for filling a cavity in a semiconductor structure including: forming a first layer of a first material in the cavity; subjecting the semiconductor structure to a first thermal process including subjecting the semiconductor structure to a temperature of at least 100° C. for interval of time, to form, from the first layer, a second layer of a second material having a chemical composition different from that of the first material; etching back the second layer to form a reduced second layer, having a reduced thickness; forming a third layer of a third material, in the cavity; and subjecting the semiconductor structure to a second thermal process including subjecting the semiconductor structure to a temperature of at least 100° C. for interval of time, to form from at least the reduced second layer and the third layer, a single layer of uniform composition and density.
- the second thermal process increases the density of the second material by at least about 20%.
- a method for filling a cavity in a semiconductor structure including: forming a first layer of a first material in the cavity; subjecting the semiconductor structure to a first thermal process including subjecting the semiconductor structure to a temperature of at least 100° C. for interval of time, to form, from the first layer, a second layer of a second material having a chemical composition different from that of the first material; etching back the second layer to form a reduced second layer, having a reduced thickness; forming a third layer of the first material, in the cavity; and subjecting the semiconductor structure to a second thermal process including an subjecting the semiconductor structure to a temperature of at least 100° C. for interval of time, to form from at least the reduced second layer and the third layer, a single layer, of uniform composition and density, of the second material.
- FIGS. 1A-1I are schematic cross sectional views of an intermediate structure during the fabrication of an integrated circuit according to an embodiment of the present invention.
- FIGS. 2A-2J are schematic cross sectional views of an intermediate structure during the fabrication of an integrated circuit according to an embodiment of the present invention.
- FIGS. 3A-3L are schematic cross sectional views of an intermediate structure during the fabrication of an integrated circuit according to an embodiment of the present invention.
- Embodiments of the present invention may be employed to fill narrow trenches, holes or gap structures (having, e.g., lateral dimensions of about 50 nm or less) that may have high aspect ratios, with a significant reduction of void and pinhole issues (e.g., a significant reduction, compared to related art methods, in the number of voids and pinholes in the filled region).
- the filling method may include repeated iterations of a cycle that may include a deposition, a first anneal step, an etch-back step, and a second anneal step.
- the second anneal step may be omitted in some or all of the cycles.
- the last cycle may include only some of the steps (i.e., it may be a “partial” cycle rather than a complete cycle).
- the different cycles may also include some variation of the parameters of each step from cycle to cycle (e.g., the deposition thickness, the anneal conditions, or the thickness etched back).
- the deposition is achieved by a spin-on coating.
- the method is applied to the filling of shallow trench isolation trenches.
- the method is applied to the filling of shallow trench isolation trenches and the deposition is achieved by a spin-on coating. In one embodiment, the method is applied to the filling of shallow trench isolation trenches and the deposition is achieved by a spin-on coating of a polysilazane material. In some embodiments SiO2 (or “SiO 2 ”) fillings of narrow trenches (e.g., having dimensions of less than 40 nm) is accomplished using polysilazane-based spin-on coatings. As used herein, “narrow lateral dimensions” refers to lateral dimensions of about 50 nm or less.
- Embodiments of the present invention may be applied in a fabrication flow for nano-scale devices such as in memory or logic CMOS flows.
- the method may be applied to the filling of narrow trench, hole or gap structures, for which accomplishing the filling without voids or pinholes may be challenging. Some embodiments may result in fewer voids compared to related art methods, for the same structures. Some embodiments may be employed to fill trenches or holes having widths in the range of 5 nm to 50 nm.
- the filling process in some embodiments includes (e.g., consists of) (i) the iteration of at least one cycle consisting of the sequence of a deposition step, a first annealing step, an etch-back step, and an optional second annealing step, and (ii) a final cycle that includes at least a deposition step and an annealing step, to accomplish the filling.
- Each of the annealing steps may include a thermal process that may have a temperature profile involving several different ramps and soak temperatures, and that may involve several different ambients, and that may include the use of more than one chamber or tool to complete.
- a “temperature profile” is a mapping from time to temperature, i.e., a prescription of the temperature, as a function of time, in a thermal process.
- the conditions and parameters of the different steps in each cycle can be preserved to be substantially the same through the iteration of cycles, or may be varied from cycle to cycle, so that they are different for different cycles in the sequence.
- the depositions are achieved by spin-on coatings.
- the method is used, e.g., as part of the fabrication flow of fin field effect transistor (finFET) devices, to fill narrow trenches or holes, such as the trenches for forming shallow-trench isolation (STI) structures, using at the deposition steps the spin-on coating of an inorganic-polysilazane.
- Polysilazanes are polymers containing silicon (Si), nitrogen (N) and hydrogen (H); they may be represented by the notation [R1R2Si—NR3] n . Curing and oxidation of polysilazanes may result in good quality silicon dioxide (SiO2) films.
- the inorganic polysilazane may be applied as a spin-on coating, and followed by thermal cycles in wet and/or dry oxidation environments, in order to transform the structure to become substantially SiO2. This is accompanied by the release of byproducts which are outgassed from the film, and by densification of the film. Both processes (outgassing and densification) may lead to void or pinhole formation. In related art processes, it may be difficult to achieve void-free fillings for trenches with widths of about 20 nm or less. The outgassing of byproducts and densification of the film during thermal processes may lead to voids.
- Embodiments of the present invention include methods for filling that are less prone to the formation of voids.
- a “thermal process” is a process including an interval of time in which the structure being fabricated is maintained at an elevated temperature (i.e., a temperature of at least 100° C.).
- the thermal process may involve several different temperature ramps and soak temperatures and several different ambients, and may include the use of more than one chamber or tool to complete.
- ambients may include wet oxidation or dry oxidation environments.
- a thermal process does not include deposition or etching steps.
- “anneal” is equivalent to “thermal process”.
- a “semiconductor structure” is an intermediate or final structure in the fabrication flow for a semiconductor device (e.g., an integrated circuit, or a discrete device such as a transistor).
- a semiconductor structure is a silicon wafer used to fabricate a CMOS integrated circuit, the silicon wafer having on it one or more a partially or fully formed transistors.
- a “cavity” in a semiconductor structure is a hole, a trench, or a gap.
- a cavity has a depth, measured in a direction perpendicular to the plane of the wafer or substrate.
- the cavity also has a “length” (the largest transverse dimension of the cavity) and a “width” (the longest dimension in a direction perpendicular to the length).
- the length is the major axis of the ellipse and the width is the minor axis of the ellipse.
- Cavities filled using embodiments of the present invention may include cavities in which STI structures are formed, and may have widths of 40 nm or less, 30 nm or less, or 20 nm or less.
- the trenches filled may be more than about 100 nm deep; and in some embodiments, they may be about 200 nm or more than about 200 nm deep.
- a structure to be filled may include one or more high aspect ratio trenches 105 .
- a first polysilazane coating 110 is formed on the structure (e.g., it is spun on to the structure) ( FIG. 1B ) and subjected to a thermal process to form a first layer 115 of SiO2, illustrated in FIG. 1C .
- the thermal process may be one that results in high density SiO2.
- the first layer 115 of SiO2 may then be etched back to form a first reduced layer 120 of SiO2, illustrated in FIG. 1D .
- the second thermal process is omitted in the first cycle, and in this embodiment, the etch-back step completes the first cycle.
- the thickness t 1 of the first reduced layer 120 may be between 5 and 50 nm, or, in some embodiments, between 5 and 25 nm. Each further cycle after the first cycle may increase the thickness of the layer formed (during that cycle and the preceding cycles) by between 5 and 50 nm, or, in some embodiments, by between 5 and 25 nm.
- a second polysilazane coating 125 is formed on the structure (e.g., it is spun on to the structure) ( FIG. 1E ) and subjected to a thermal process to form a second layer 130 of SiO2, illustrated in FIG. 1F , which may also be composed of high density SiO2.
- the newly formed portion of the second layer 130 of SiO2 may be substantially identical (e.g., in composition and density) to the first reduced layer 120 of SiO2, so that the second layer 130 of SiO2 may be a continuous, uniform structure.
- the second layer 130 of SiO2 may then be etched back to form a second reduced layer 135 of SiO2, illustrated in FIG. 1G .
- the second reduced layer 135 of SiO2 may also be a continuous, uniform structure.
- the second thermal process is omitted in the second cycle, and the etch-back step completes the second cycle.
- the thickness t 2 of the second reduced layer 135 may exceed the thickness t 1 of the first reduced layer by between 5 and 50 nm, or, in some embodiments, between 5 and 25 nm.
- a third polysilazane coating 140 is formed on the structure (e.g., it is spun on to the structure) ( FIG. 1H ) and subjected to a thermal process to form a third layer 145 of SiO2, illustrated in FIG. 1I , which may also be composed of high density SiO2.
- the newly formed portion of the third layer 145 of SiO2 may be substantially identical (e.g., in composition and density) to the second reduced layer 135 of SiO2, so that the third layer 145 of SiO2 may be a continuous, uniform structure.
- the second thermal process is omitted in the third cycle, and in this embodiment, the first thermal process of the third cycle completes the third cycle and completes the filling process.
- a structure to be filled may include one or more high aspect ratio trenches 105 .
- a first polysilazane coating 210 is formed on the structure (e.g., it is spun on to the structure) ( FIG. 2B ) and subjected to a thermal process to form a first layer 215 of SiO2, illustrated in FIG. 2C .
- the thermal process may be one that results in low density SiO2.
- the first layer 215 of SiO2 may then be etched back to form a first reduced layer 220 of SiO2, illustrated in FIG. 2D .
- the second thermal process is omitted in the first cycle, and in this embodiment, the etch-back step completes the first cycle.
- a second polysilazane coating 225 is formed on the structure (e.g., it is spun on to the structure) ( FIG. 2E ) and subjected to a thermal process to form a second layer 230 of SiO2, illustrated in FIG. 2F , which may also be composed of low density SiO2.
- the newly formed portion of the second layer 230 of SiO2 may be substantially identical (e.g., in composition and density) to the first reduced layer 220 of SiO2, so that the second layer 230 of SiO2 may be a continuous, uniform structure.
- the second layer 230 of SiO2 may then be etched back to form a second reduced layer 235 of SiO2, illustrated in FIG. 2G .
- the second reduced layer 235 of SiO2 may also be a continuous, uniform structure.
- the second thermal process is omitted in the second cycle, and the etch-back step completes the second cycle.
- a third polysilazane coating 240 is formed on the structure (e.g., it is spun on to the structure) ( FIG. 2H ) and subjected to a thermal process to form a third layer 245 of SiO2, illustrated in FIG. 2I , which may also be composed of low density SiO2.
- the newly formed portion of the third layer 245 of SiO2 may be substantially identical (e.g., in composition and density) to the second reduced layer 235 of SiO2, so that the third layer 245 of SiO2 may be a continuous, uniform structure.
- the third layer 245 of SiO2 is then subjected to a second thermal process (or, equivalently, the first thermal process of the third cycle is continued) to increase the density of the SiO2 in this layer, forming a continuous, uniform layer 250 of high density SiO2 ( FIG. 2J ).
- a structure to be filled may include one or more high aspect ratio trenches 105 .
- a first polysilazane coating 310 is formed on the structure (e.g., it is spun on to the structure) ( FIG. 3B ) and subjected to a thermal process to form a first layer 315 of SiO2, illustrated in FIG. 3C .
- the thermal process may be one that results in low density SiO2.
- the first layer 315 of SiO2 may then be etched back to form a first reduced layer 320 of SiO2, illustrated in FIG. 3D .
- a second thermal process is performed in the first cycle, to increase the density of the first reduced layer 320 , forming a first high-density SiO 2 layer 325 ; this second thermal process completes the first cycle.
- a second polysilazane coating 330 is formed on the structure (e.g., it is spun on to the structure) ( FIG. 3F ) and subjected to a thermal process to form a second layer 335 of SiO2, illustrated in FIG. 3G , which may also be composed of low density SiO2.
- the second layer 335 of SiO2 may then be etched back to form a second reduced layer 340 of low density SiO2, illustrated in FIG. 3H .
- a second thermal process is performed in the second cycle, to increase the density of the second reduced layer 340 , so that its composition and density become substantially the same as those of the first high-density SiO 2 layer 325 , and the two components together (the first high-density SiO 2 layer 325 , and the second reduced layer 340 , with density increased by the second thermal process of the second cycle) form a single high-density SiO 2 layer 345 ( FIG. 3I ), which is a continuous, uniform structure.
- a third polysilazane coating 350 is formed on the structure e.g., it is spun on to the structure) ( FIG. 3J ) and subjected to a thermal process to form a third layer 355 of SiO2, illustrated in FIG. 3K , which may also be composed of low density SiO2.
- the third layer 355 of SiO2 is then subjected to a second thermal process (or, equivalently, the first thermal process of the third cycle is continued) to increase the density of the SiO2 in this layer, so that its composition and density become substantially the same as those of the high-density SiO 2 layer 345 formed during the second cycle, and the two components together (the high-density SiO 2 layer 345 formed during the second cycle, and the third layer 355 of SiO2, with density increased by the second thermal process of the third cycle) form a single continuous, uniform, high-density SiO 2 layer 360 ( FIG. 3L ).
- a second thermal process or, equivalently, the first thermal process of the third cycle is continued
- the thickness of filling material added in each cycle is of about 5 to 50 nm, or, in some embodiments, between 5 and 30 nm.
- ambients may include wet oxidation or dry oxidation environments for example.
- the first of these thermal processes may include an initial slow ramp and may include soak steps at temperatures ranging from 100° C. to 250° C. and subsequent steps at higher temperatures ranging from 500° C. to 850° C.
- This first thermal processing step may result in the release of byproducts from the film.
- the film is substantially comprised of SiO2 after such a first thermal processing step.
- the second thermal processing step may include further densification of the film at temperatures ranging from 500° C. to 850° C., so that the film is composed of good quality, high density SiO2 after these steps.
- the increase in density produced by a higher temperature thermal process may be an increase of about 20% or more. Densification may occur gradually at higher temperatures; accordingly the density of the film after the first thermal processing step may depend on the amount of time spent at higher temperatures in that thermal processing step.
- Si—O bond density is the area of the Si—O peak (having a wave number of about 1050-1100 cm ⁇ 1 ) obtained in Fourier-Transform Infra-Red (FTIR) spectroscopy. As a film's Si—O bond density increases, the intensity of this peak increases. Comparisons of Si—O FTIR intensities for films of similar thicknesses give a measure of relative Si—O bond densities. State of the art oxidation processes may be considered to achieve optimized high density SiO2 films from polysilazane coatings, and used as references to the Si—O bond density. Otherwise, a high quality SiO 2 layer, e.g. with a density of about 2.2. g/cm 3 , may be used as a reference of a high density SiO 2 film (for example, an SiO 2 film thermally grown on Si).
- FTIR Fourier-Transform Infra-Red
- the final film i.e., the fill material formed in the cavity at the end of the final cycle
- the final film is an SiO2 layer with a uniform Si—O density throughout the thickness of the film, with this density being characterized by a relative Si—O bond density compared to state of the art films or high density films of at least 80%.
- the non-uniformity (NU), throughout the film thickness, of the Si—O bond density may be less than 20% (1 sigma).
- the non-uniformity of the Si—O bond density may be measured in a similar way by FTIR, e.g., by comparing films of different thicknesses (FTIR peak intensities normalized to film thickness), or by comparing densities before and after an etch-back (FTIR peak intensities normalized to film thickness, with thicknesses calibrated, e.g., by transmission-electron microscopy).
- FTIR peak intensities normalized to film thickness e.g., by comparing films of different thicknesses
- FTIR peak intensities normalized to film thickness e.g., by comparing densities before and after an etch-back
- Other ways of measuring Si—O bond density are possible.
- the final fill material is described in some embodiments as being silicon dioxide, in some embodiments it may include other forms of silicon oxide (e.g., silicon monoxide) or other oxides, or other materials that are not oxides.
- some embodiments provide a method of filling cavities in a semiconductor structure during fabrication.
- a layer of a first material e.g., a polysilazane
- a first thermal process to change its chemical composition, e.g., to change it to silicon oxide (e.g., silicon dioxide, or silicon monoxide, or silicon trioxide). It is then etched back, and the cycle of deposition, and thermal processing is repeated.
- silicon oxide e.g., silicon dioxide, or silicon monoxide, or silicon trioxide
- first”, “second”, “third”, etc. may be used herein to describe various elements, components, regions, layers and/or sections, these elements, components, regions, layers and/or sections should not be limited by these terms. These terms are only used to distinguish one element, component, region, layer or section from another element, component, region, layer or section. Thus, a first element, component, region, layer or section discussed below could be termed a second element, component, region, layer or section, without departing from the spirit and scope of the inventive concept.
- spatially relative terms such as “beneath”, “below”, “lower”, “under”, “above”, “upper” and the like, may be used herein for ease of description to describe one element or feature's relationship to another element(s) or feature(s) as illustrated in the figures. It will be understood that such spatially relative terms are intended to encompass different orientations of the device in use or in operation, in addition to the orientation depicted in the figures. For example, if the device in the figures is turned over, elements described as “below” or “beneath” or “under” other elements or features would then be oriented “above” the other elements or features. Thus, the example terms “below” and “under” can encompass both an orientation of above and below.
- the device may be otherwise oriented (e.g., rotated 90 degrees or at other orientations) and the spatially relative descriptors used herein should be interpreted accordingly.
- a layer is referred to as being “between” two layers, it can be the only layer between the two layers, or one or more intervening layers may also be present.
- the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the inventive concept.
- the terms “substantially,” “about,” and similar terms are used as terms of approximation and not as terms of degree, and are intended to account for the inherent deviations in measured or calculated values that would be recognized by those of ordinary skill in the art.
- the term “major component” means a component constituting at least half, by weight, of a composition, and the term “major portion”, when applied to a plurality of items, means at least half of the items.
- any numerical range recited herein is intended to include all sub-ranges of the same numerical precision subsumed within the recited range.
- a range of “1.0 to 10.0” is intended to include all subranges between (and including) the recited minimum value of 1.0 and the recited maximum value of 10.0, that is, having a minimum value equal to or greater than 1.0 and a maximum value equal to or less than 10.0, such as, for example, 2.4 to 7.6.
- Any maximum numerical limitation recited herein is intended to include all lower numerical limitations subsumed therein and any minimum numerical limitation recited in this specification is intended to include all higher numerical limitations subsumed therein.
Landscapes
- Engineering & Computer Science (AREA)
- Microelectronics & Electronic Packaging (AREA)
- Condensed Matter Physics & Semiconductors (AREA)
- General Physics & Mathematics (AREA)
- Manufacturing & Machinery (AREA)
- Computer Hardware Design (AREA)
- Physics & Mathematics (AREA)
- Power Engineering (AREA)
- Chemical & Material Sciences (AREA)
- Chemical Kinetics & Catalysis (AREA)
- General Chemical & Material Sciences (AREA)
- Element Separation (AREA)
- Formation Of Insulating Films (AREA)
- Semiconductor Memories (AREA)
Abstract
Description
- The present application claims priority to and the benefit of U.S. Provisional Application No. 62/351,249, filed Jun. 16, 2016, entitled “FILLING PROCESSES”, the entire content of which is incorporated herein by reference.
- One or more aspects of embodiments according to the present invention relate to fabrication processes for semiconductor structures, and more particularly to a method, within such processes, for filling gaps or voids.
- With scaling both in memory and complementary metal oxide (CMOS) logic fabrication, a method for achieving void free and pinhole free fillings of narrow cavities, trenches, gaps, etc. which may have high aspect ratios, may be desired. For example, void free and pinhole free fillings of shallow trench isolation structures, that have lateral dimensions below 40 nm, with an adequate dielectric, may be used in some integrated circuits.
- Thus, there is a need for a method for forming fillings in integrated circuits.
- Aspects of embodiments of the present disclosure are directed toward a method of filling cavities in a semiconductor structure during fabrication. A layer of a first material, e.g., a polysilazane, is deposited on the semiconductor, and subjected to a first thermal process to change its chemical composition, e.g., to change it to silicon oxide (e.g., silicon dioxide, or silicon monoxide, or silicon trioxide). It is then etched back, and the cycle of deposition, and thermal processing is repeated. The etch-back may also be repeated in one or more of the cycles after the first cycle, and a second thermal process, that may increase the density of one or more of the deposited layers, may be performed in one or more of the cycles.
- According to an embodiment of the present invention there is provided a method for filling a cavity in a semiconductor structure, the method including: forming a first layer of a first material in the cavity; subjecting the semiconductor structure to a first thermal process including subjecting the semiconductor structure to a temperature of at least 100° C. for interval of time; etching back the first layer to form a reduced first layer, having a reduced thickness; forming a second layer of a second material, in the cavity; and subjecting the semiconductor structure to a second thermal process including subjecting the semiconductor structure to a temperature of at least 100° C. for interval of time, to form, from at least the reduced first layer and the second layer, a single layer of uniform composition and density.
- In one embodiment, the second material is the same as the first material.
- In one embodiment, the first material is a polysilazane.
- In one embodiment, the forming of the second layer of the second material is performed by substantially the same process as the forming of the first layer of the first material, and wherein the second thermal process is substantially the same as the first thermal process.
- In one embodiment, the forming of the second layer of the second material, in the cavity, includes forming the second layer directly on the reduced first layer.
- In one embodiment, the method includes: performing a third thermal process after performing the second thermal process, the third thermal process increasing the density of the single layer by at least about 20%.
- In one embodiment, the forming of the first layer includes forming the first layer by a spin-on deposition, and/or the forming of the second layer includes forming the second layer by a spin-on deposition.
- In one embodiment, the single layer substantially fills the cavity.
- In one embodiment, the first material and/or the second material includes, as a major component, an inorganic polysilazane.
- In one embodiment, the first material includes, as a major component, an inorganic polysilazane, and, after the subjecting of the semiconductor structure to the first thermal process, the first layer includes, as a major component, silicon dioxide, and/or the second material includes, as a major component, an inorganic polysilazane, and, after the subjecting of the semiconductor structure to the second thermal process, the second layer includes, as a major component, silicon dioxide.
- In one embodiment, the subjecting of the semiconductor structure to the first thermal process includes subjecting the semiconductor structure to the first thermal process in a wet oxidation environment, and/or the subjecting of the semiconductor structure to the second thermal process includes subjecting the semiconductor structure to the second thermal process in a wet oxidation environment.
- In one embodiment, the first thermal process includes subjecting the semiconductor structure to a temperature between 100° C. and 250° C. for an interval of time, and the second thermal process includes subjecting the semiconductor structure to a temperature between 500° C. and 850° C. for an interval of time.
- In one embodiment, the cavity is a trench for a shallow trench isolation (STI) structure.
- In one embodiment, the single layer includes, as a major component, an oxide.
- In one embodiment, a width of the cavity is less than 40 nm.
- In one embodiment, a width of the cavity is less than 20 nm.
- In one embodiment, the method includes: etching back the single layer to form a reduced single layer, having a reduced thickness, wherein a thickness of the reduced first layer is greater than 5 nm and less than 50 nm, and a thickness of the reduced single layer is greater than 10 nm and less than 100 nm.
- According to an embodiment of the present invention there is provided a method for filling a cavity in a semiconductor structure, the method including: forming a first layer of a first material in the cavity; subjecting the semiconductor structure to a first thermal process including subjecting the semiconductor structure to a temperature of at least 100° C. for interval of time, to form, from the first layer, a second layer of a second material having a chemical composition different from that of the first material; etching back the second layer to form a reduced second layer, having a reduced thickness; forming a third layer of a third material, in the cavity; and subjecting the semiconductor structure to a second thermal process including subjecting the semiconductor structure to a temperature of at least 100° C. for interval of time, to form from at least the reduced second layer and the third layer, a single layer of uniform composition and density.
- In one embodiment, the second thermal process increases the density of the second material by at least about 20%.
- According to an embodiment of the present invention there is provided a method for filling a cavity in a semiconductor structure, the method including: forming a first layer of a first material in the cavity; subjecting the semiconductor structure to a first thermal process including subjecting the semiconductor structure to a temperature of at least 100° C. for interval of time, to form, from the first layer, a second layer of a second material having a chemical composition different from that of the first material; etching back the second layer to form a reduced second layer, having a reduced thickness; forming a third layer of the first material, in the cavity; and subjecting the semiconductor structure to a second thermal process including an subjecting the semiconductor structure to a temperature of at least 100° C. for interval of time, to form from at least the reduced second layer and the third layer, a single layer, of uniform composition and density, of the second material.
- These and other features and advantages of the present invention will be appreciated and understood with reference to the specification, claims, and appended drawings wherein:
-
FIGS. 1A-1I are schematic cross sectional views of an intermediate structure during the fabrication of an integrated circuit according to an embodiment of the present invention; -
FIGS. 2A-2J are schematic cross sectional views of an intermediate structure during the fabrication of an integrated circuit according to an embodiment of the present invention; and -
FIGS. 3A-3L are schematic cross sectional views of an intermediate structure during the fabrication of an integrated circuit according to an embodiment of the present invention. - The detailed description set forth below in connection with the appended drawings is intended as a description of exemplary embodiments of an improved method for filling provided in accordance with the present invention and is not intended to represent the only forms in which the present invention may be constructed or utilized. The description sets forth the features of the present invention in connection with the illustrated embodiments. It is to be understood, however, that the same or equivalent functions and structures may be accomplished by different embodiments that are also intended to be encompassed within the spirit and scope of the invention. As denoted elsewhere herein, like element numbers are intended to indicate like elements or features.
- Embodiments of the present invention may be employed to fill narrow trenches, holes or gap structures (having, e.g., lateral dimensions of about 50 nm or less) that may have high aspect ratios, with a significant reduction of void and pinhole issues (e.g., a significant reduction, compared to related art methods, in the number of voids and pinholes in the filled region). The filling method may include repeated iterations of a cycle that may include a deposition, a first anneal step, an etch-back step, and a second anneal step. In some embodiments, the second anneal step may be omitted in some or all of the cycles. The last cycle may include only some of the steps (i.e., it may be a “partial” cycle rather than a complete cycle).
- The different cycles may also include some variation of the parameters of each step from cycle to cycle (e.g., the deposition thickness, the anneal conditions, or the thickness etched back). In some embodiments, there are a minimum of two full cycles and one final cycle (which may be partial or full), the final cycle including at least deposition and anneal steps. In some embodiments, there are a minimum of one full cycle and one final cycle (which may be partial or full), the final cycle including at least deposition and anneal steps. In one embodiment, the deposition is achieved by a spin-on coating. In some embodiments, the method is applied to the filling of shallow trench isolation trenches. In some embodiments, the method is applied to the filling of shallow trench isolation trenches and the deposition is achieved by a spin-on coating. In one embodiment, the method is applied to the filling of shallow trench isolation trenches and the deposition is achieved by a spin-on coating of a polysilazane material. In some embodiments SiO2 (or “SiO2”) fillings of narrow trenches (e.g., having dimensions of less than 40 nm) is accomplished using polysilazane-based spin-on coatings. As used herein, “narrow lateral dimensions” refers to lateral dimensions of about 50 nm or less.
- Embodiments of the present invention may be applied in a fabrication flow for nano-scale devices such as in memory or logic CMOS flows. The method may be applied to the filling of narrow trench, hole or gap structures, for which accomplishing the filling without voids or pinholes may be challenging. Some embodiments may result in fewer voids compared to related art methods, for the same structures. Some embodiments may be employed to fill trenches or holes having widths in the range of 5 nm to 50 nm.
- Once narrow trenches, holes or gaps have been fabricated and are ready for the filling process (as in related art flows), the filling process in some embodiments includes (e.g., consists of) (i) the iteration of at least one cycle consisting of the sequence of a deposition step, a first annealing step, an etch-back step, and an optional second annealing step, and (ii) a final cycle that includes at least a deposition step and an annealing step, to accomplish the filling.
- Each of the annealing steps may include a thermal process that may have a temperature profile involving several different ramps and soak temperatures, and that may involve several different ambients, and that may include the use of more than one chamber or tool to complete. As used herein, a “temperature profile” is a mapping from time to temperature, i.e., a prescription of the temperature, as a function of time, in a thermal process.
- The conditions and parameters of the different steps in each cycle can be preserved to be substantially the same through the iteration of cycles, or may be varied from cycle to cycle, so that they are different for different cycles in the sequence. In some embodiments, the depositions are achieved by spin-on coatings.
- In one embodiment the method is used, e.g., as part of the fabrication flow of fin field effect transistor (finFET) devices, to fill narrow trenches or holes, such as the trenches for forming shallow-trench isolation (STI) structures, using at the deposition steps the spin-on coating of an inorganic-polysilazane. Polysilazanes are polymers containing silicon (Si), nitrogen (N) and hydrogen (H); they may be represented by the notation [R1R2Si—NR3]n. Curing and oxidation of polysilazanes may result in good quality silicon dioxide (SiO2) films. During low temperature curing and wet oxidation to form SiO2, byproducts (such as ammonia (NH3), hydrogen (H2), and water (H2O)) are released and/or outgassed from the film and the film density increases; during this process, the film may shrink.
- In the related art, for example, the inorganic polysilazane may be applied as a spin-on coating, and followed by thermal cycles in wet and/or dry oxidation environments, in order to transform the structure to become substantially SiO2. This is accompanied by the release of byproducts which are outgassed from the film, and by densification of the film. Both processes (outgassing and densification) may lead to void or pinhole formation. In related art processes, it may be difficult to achieve void-free fillings for trenches with widths of about 20 nm or less. The outgassing of byproducts and densification of the film during thermal processes may lead to voids. This problem is exacerbated at small trench widths particularly for large aspect ratio trenches, and can also be exacerbated by defects on the surfaces of the trenches or non-uniformities of the trench geometries, which may promote the local formation of voids. Embodiments of the present invention include methods for filling that are less prone to the formation of voids.
- As used herein, a “thermal process” is a process including an interval of time in which the structure being fabricated is maintained at an elevated temperature (i.e., a temperature of at least 100° C.). The thermal process may involve several different temperature ramps and soak temperatures and several different ambients, and may include the use of more than one chamber or tool to complete. As examples, ambients may include wet oxidation or dry oxidation environments. A thermal process does not include deposition or etching steps. As used herein, “anneal” is equivalent to “thermal process”.
- As used herein, a “semiconductor structure” is an intermediate or final structure in the fabrication flow for a semiconductor device (e.g., an integrated circuit, or a discrete device such as a transistor). An example of a semiconductor structure is a silicon wafer used to fabricate a CMOS integrated circuit, the silicon wafer having on it one or more a partially or fully formed transistors. As used herein, a “cavity” in a semiconductor structure is a hole, a trench, or a gap. As used herein, a cavity has a depth, measured in a direction perpendicular to the plane of the wafer or substrate. If, in a plan view, the edge of the cavity is a convex shape, then the cavity also has a “length” (the largest transverse dimension of the cavity) and a “width” (the longest dimension in a direction perpendicular to the length). For an elliptical cavity, for example, the length is the major axis of the ellipse and the width is the minor axis of the ellipse. Cavities filled using embodiments of the present invention may include cavities in which STI structures are formed, and may have widths of 40 nm or less, 30 nm or less, or 20 nm or less. In some embodiments, the trenches filled may be more than about 100 nm deep; and in some embodiments, they may be about 200 nm or more than about 200 nm deep.
- In a first exemplary embodiment, a structure to be filled (
FIG. 1A ) may include one or more highaspect ratio trenches 105. Afirst polysilazane coating 110 is formed on the structure (e.g., it is spun on to the structure) (FIG. 1B ) and subjected to a thermal process to form a first layer 115 of SiO2, illustrated inFIG. 1C . The thermal process may be one that results in high density SiO2. The first layer 115 of SiO2 may then be etched back to form a first reducedlayer 120 of SiO2, illustrated inFIG. 1D . The second thermal process is omitted in the first cycle, and in this embodiment, the etch-back step completes the first cycle. The thickness t1 of the first reducedlayer 120 may be between 5 and 50 nm, or, in some embodiments, between 5 and 25 nm. Each further cycle after the first cycle may increase the thickness of the layer formed (during that cycle and the preceding cycles) by between 5 and 50 nm, or, in some embodiments, by between 5 and 25 nm. - In a second cycle, a
second polysilazane coating 125 is formed on the structure (e.g., it is spun on to the structure) (FIG. 1E ) and subjected to a thermal process to form asecond layer 130 of SiO2, illustrated inFIG. 1F , which may also be composed of high density SiO2. The newly formed portion of thesecond layer 130 of SiO2 may be substantially identical (e.g., in composition and density) to the first reducedlayer 120 of SiO2, so that thesecond layer 130 of SiO2 may be a continuous, uniform structure. Thesecond layer 130 of SiO2 may then be etched back to form a second reducedlayer 135 of SiO2, illustrated inFIG. 1G . The second reducedlayer 135 of SiO2 may also be a continuous, uniform structure. The second thermal process is omitted in the second cycle, and the etch-back step completes the second cycle. The thickness t2 of the second reducedlayer 135 may exceed the thickness t1 of the first reduced layer by between 5 and 50 nm, or, in some embodiments, between 5 and 25 nm. - In a third cycle, a
third polysilazane coating 140 is formed on the structure (e.g., it is spun on to the structure) (FIG. 1H ) and subjected to a thermal process to form athird layer 145 of SiO2, illustrated inFIG. 1I , which may also be composed of high density SiO2. The newly formed portion of thethird layer 145 of SiO2 may be substantially identical (e.g., in composition and density) to the second reducedlayer 135 of SiO2, so that thethird layer 145 of SiO2 may be a continuous, uniform structure. In this embodiment, the second thermal process is omitted in the third cycle, and in this embodiment, the first thermal process of the third cycle completes the third cycle and completes the filling process. - In a second exemplary embodiment, a structure to be filled (
FIG. 2A ) may include one or more highaspect ratio trenches 105. Afirst polysilazane coating 210 is formed on the structure (e.g., it is spun on to the structure) (FIG. 2B ) and subjected to a thermal process to form afirst layer 215 of SiO2, illustrated inFIG. 2C . The thermal process may be one that results in low density SiO2. Thefirst layer 215 of SiO2 may then be etched back to form a first reducedlayer 220 of SiO2, illustrated inFIG. 2D . In this embodiment, the second thermal process is omitted in the first cycle, and in this embodiment, the etch-back step completes the first cycle. - In a second cycle, a
second polysilazane coating 225 is formed on the structure (e.g., it is spun on to the structure) (FIG. 2E ) and subjected to a thermal process to form asecond layer 230 of SiO2, illustrated inFIG. 2F , which may also be composed of low density SiO2. The newly formed portion of thesecond layer 230 of SiO2 may be substantially identical (e.g., in composition and density) to the first reducedlayer 220 of SiO2, so that thesecond layer 230 of SiO2 may be a continuous, uniform structure. Thesecond layer 230 of SiO2 may then be etched back to form a second reducedlayer 235 of SiO2, illustrated inFIG. 2G . The second reducedlayer 235 of SiO2 may also be a continuous, uniform structure. The second thermal process is omitted in the second cycle, and the etch-back step completes the second cycle. - In a third cycle, a
third polysilazane coating 240 is formed on the structure (e.g., it is spun on to the structure) (FIG. 2H ) and subjected to a thermal process to form athird layer 245 of SiO2, illustrated inFIG. 2I , which may also be composed of low density SiO2. The newly formed portion of thethird layer 245 of SiO2 may be substantially identical (e.g., in composition and density) to the second reducedlayer 235 of SiO2, so that thethird layer 245 of SiO2 may be a continuous, uniform structure. Thethird layer 245 of SiO2 is then subjected to a second thermal process (or, equivalently, the first thermal process of the third cycle is continued) to increase the density of the SiO2 in this layer, forming a continuous,uniform layer 250 of high density SiO2 (FIG. 2J ). - In a third exemplary embodiment, a structure to be filled (
FIG. 3A ) may include one or more highaspect ratio trenches 105. A first polysilazane coating 310 is formed on the structure (e.g., it is spun on to the structure) (FIG. 3B ) and subjected to a thermal process to form a first layer 315 of SiO2, illustrated inFIG. 3C . The thermal process may be one that results in low density SiO2. The first layer 315 of SiO2 may then be etched back to form a first reducedlayer 320 of SiO2, illustrated inFIG. 3D . A second thermal process is performed in the first cycle, to increase the density of the first reducedlayer 320, forming a first high-density SiO2 layer 325; this second thermal process completes the first cycle. - In a second cycle, a second polysilazane coating 330 is formed on the structure (e.g., it is spun on to the structure) (
FIG. 3F ) and subjected to a thermal process to form asecond layer 335 of SiO2, illustrated inFIG. 3G , which may also be composed of low density SiO2. Thesecond layer 335 of SiO2 may then be etched back to form a second reducedlayer 340 of low density SiO2, illustrated inFIG. 3H . A second thermal process is performed in the second cycle, to increase the density of the second reducedlayer 340, so that its composition and density become substantially the same as those of the first high-density SiO2 layer 325, and the two components together (the first high-density SiO2 layer 325, and the second reducedlayer 340, with density increased by the second thermal process of the second cycle) form a single high-density SiO2 layer 345 (FIG. 3I ), which is a continuous, uniform structure. - In a third cycle, a
third polysilazane coating 350 is formed on the structure e.g., it is spun on to the structure) (FIG. 3J ) and subjected to a thermal process to form athird layer 355 of SiO2, illustrated inFIG. 3K , which may also be composed of low density SiO2. Thethird layer 355 of SiO2 is then subjected to a second thermal process (or, equivalently, the first thermal process of the third cycle is continued) to increase the density of the SiO2 in this layer, so that its composition and density become substantially the same as those of the high-density SiO2 layer 345 formed during the second cycle, and the two components together (the high-density SiO2 layer 345 formed during the second cycle, and thethird layer 355 of SiO2, with density increased by the second thermal process of the third cycle) form a single continuous, uniform, high-density SiO2 layer 360 (FIG. 3L ). - In some embodiments the thickness of filling material added in each cycle (as measured vertically in the schematics drawings shown) is of about 5 to 50 nm, or, in some embodiments, between 5 and 30 nm. As mentioned above, ambients may include wet oxidation or dry oxidation environments for example.
- When two thermal processes are employed to first create low density SiO2 and, second, to subsequently increase the density of the low density SiO2 to form high density SiO2, the first of these thermal processes may include an initial slow ramp and may include soak steps at temperatures ranging from 100° C. to 250° C. and subsequent steps at higher temperatures ranging from 500° C. to 850° C. This first thermal processing step may result in the release of byproducts from the film. In some embodiments, the film is substantially comprised of SiO2 after such a first thermal processing step. The second thermal processing step may include further densification of the film at temperatures ranging from 500° C. to 850° C., so that the film is composed of good quality, high density SiO2 after these steps. The increase in density produced by a higher temperature thermal process may be an increase of about 20% or more. Densification may occur gradually at higher temperatures; accordingly the density of the film after the first thermal processing step may depend on the amount of time spent at higher temperatures in that thermal processing step.
- An indication of Si—O bond density is the area of the Si—O peak (having a wave number of about 1050-1100 cm−1) obtained in Fourier-Transform Infra-Red (FTIR) spectroscopy. As a film's Si—O bond density increases, the intensity of this peak increases. Comparisons of Si—O FTIR intensities for films of similar thicknesses give a measure of relative Si—O bond densities. State of the art oxidation processes may be considered to achieve optimized high density SiO2 films from polysilazane coatings, and used as references to the Si—O bond density. Otherwise, a high quality SiO2 layer, e.g. with a density of about 2.2. g/cm3, may be used as a reference of a high density SiO2 film (for example, an SiO2 film thermally grown on Si).
- In some embodiments, the final film (i.e., the fill material formed in the cavity at the end of the final cycle) is an SiO2 layer with a uniform Si—O density throughout the thickness of the film, with this density being characterized by a relative Si—O bond density compared to state of the art films or high density films of at least 80%. The non-uniformity (NU), throughout the film thickness, of the Si—O bond density may be less than 20% (1 sigma).
- The non-uniformity of the Si—O bond density may be measured in a similar way by FTIR, e.g., by comparing films of different thicknesses (FTIR peak intensities normalized to film thickness), or by comparing densities before and after an etch-back (FTIR peak intensities normalized to film thickness, with thicknesses calibrated, e.g., by transmission-electron microscopy). Other ways of measuring Si—O bond density are possible.
- Although the final fill material is described in some embodiments as being silicon dioxide, in some embodiments it may include other forms of silicon oxide (e.g., silicon monoxide) or other oxides, or other materials that are not oxides.
- In view of the foregoing, some embodiments provide a method of filling cavities in a semiconductor structure during fabrication. A layer of a first material, e.g., a polysilazane, is deposited on the semiconductor, and subjected to a first thermal process to change its chemical composition, e.g., to change it to silicon oxide (e.g., silicon dioxide, or silicon monoxide, or silicon trioxide). It is then etched back, and the cycle of deposition, and thermal processing is repeated.
- It will be understood that, although the terms “first”, “second”, “third”, etc., may be used herein to describe various elements, components, regions, layers and/or sections, these elements, components, regions, layers and/or sections should not be limited by these terms. These terms are only used to distinguish one element, component, region, layer or section from another element, component, region, layer or section. Thus, a first element, component, region, layer or section discussed below could be termed a second element, component, region, layer or section, without departing from the spirit and scope of the inventive concept.
- Spatially relative terms, such as “beneath”, “below”, “lower”, “under”, “above”, “upper” and the like, may be used herein for ease of description to describe one element or feature's relationship to another element(s) or feature(s) as illustrated in the figures. It will be understood that such spatially relative terms are intended to encompass different orientations of the device in use or in operation, in addition to the orientation depicted in the figures. For example, if the device in the figures is turned over, elements described as “below” or “beneath” or “under” other elements or features would then be oriented “above” the other elements or features. Thus, the example terms “below” and “under” can encompass both an orientation of above and below. The device may be otherwise oriented (e.g., rotated 90 degrees or at other orientations) and the spatially relative descriptors used herein should be interpreted accordingly. In addition, it will also be understood that when a layer is referred to as being “between” two layers, it can be the only layer between the two layers, or one or more intervening layers may also be present.
- The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the inventive concept. As used herein, the terms “substantially,” “about,” and similar terms are used as terms of approximation and not as terms of degree, and are intended to account for the inherent deviations in measured or calculated values that would be recognized by those of ordinary skill in the art. As used herein, the term “major component” means a component constituting at least half, by weight, of a composition, and the term “major portion”, when applied to a plurality of items, means at least half of the items.
- As used herein, the singular forms “a” and “an” are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms “comprises” and/or “comprising”, when used in this specification, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof. As used herein, the term “and/or” includes any and all combinations of one or more of the associated listed items. Expressions such as “at least one of,” when preceding a list of elements, modify the entire list of elements and do not modify the individual elements of the list. Further, the use of “may” when describing embodiments of the inventive concept refers to “one or more embodiments of the present invention”. Also, the term “exemplary” is intended to refer to an example or illustration. As used herein, the terms “use,” “using,” “used,” and “step” may be considered synonymous with the terms “utilize,” “utilizing,” “utilized,” and “act” respectively.
- It will be understood that when an element or layer is referred to as being “on”, “connected to”, “coupled to”, or “adjacent to” another element or layer, it may be directly on, connected to, coupled to, or adjacent to the other element or layer, or one or more intervening elements or layers may be present. In contrast, when an element or layer is referred to as being “directly on”, “directly connected to”, “directly coupled to”, or “immediately adjacent to” another element or layer, there are no intervening elements or layers present.
- Any numerical range recited herein is intended to include all sub-ranges of the same numerical precision subsumed within the recited range. For example, a range of “1.0 to 10.0” is intended to include all subranges between (and including) the recited minimum value of 1.0 and the recited maximum value of 10.0, that is, having a minimum value equal to or greater than 1.0 and a maximum value equal to or less than 10.0, such as, for example, 2.4 to 7.6. Any maximum numerical limitation recited herein is intended to include all lower numerical limitations subsumed therein and any minimum numerical limitation recited in this specification is intended to include all higher numerical limitations subsumed therein.
- Although exemplary embodiments of an improved method for filling have been specifically described and illustrated herein, many modifications and variations will be apparent to those skilled in the art. Accordingly, it is to be understood that an improved method for filling constructed according to principles of this invention may be embodied other than as specifically described herein. The invention is also defined in the following claims, and equivalents thereof.
Claims (20)
Priority Applications (4)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
US15/343,151 US9847245B1 (en) | 2016-06-16 | 2016-11-03 | Filling processes |
KR1020170022012A KR20170142098A (en) | 2016-06-16 | 2017-02-20 | Method for fabricating a semiconductor device |
CN201710441952.0A CN107527859A (en) | 2016-06-16 | 2017-06-13 | Method for manufacturing semiconductor device |
TW106119725A TWI724181B (en) | 2016-06-16 | 2017-06-14 | Method of filling cavities in semiconductor structure |
Applications Claiming Priority (2)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
US201662351249P | 2016-06-16 | 2016-06-16 | |
US15/343,151 US9847245B1 (en) | 2016-06-16 | 2016-11-03 | Filling processes |
Publications (2)
Publication Number | Publication Date |
---|---|
US9847245B1 US9847245B1 (en) | 2017-12-19 |
US20170365505A1 true US20170365505A1 (en) | 2017-12-21 |
Family
ID=60629268
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
US15/343,151 Active US9847245B1 (en) | 2016-06-16 | 2016-11-03 | Filling processes |
Country Status (4)
Country | Link |
---|---|
US (1) | US9847245B1 (en) |
KR (1) | KR20170142098A (en) |
CN (1) | CN107527859A (en) |
TW (1) | TWI724181B (en) |
Families Citing this family (3)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
JP6950737B2 (en) * | 2017-04-17 | 2021-10-13 | 東京エレクトロン株式会社 | Insulating film film forming method, insulating film film forming equipment and substrate processing system |
JP7203515B2 (en) | 2017-06-06 | 2023-01-13 | アプライド マテリアルズ インコーポレイテッド | Bottom-up growth of silicon oxide and silicon nitride using a sequential deposition-etch-processing method |
US10431492B1 (en) * | 2018-05-28 | 2019-10-01 | Nanya Technology Corporation | Method of manufacturing a semiconductor structure |
Citations (8)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US20020072198A1 (en) * | 2000-12-08 | 2002-06-13 | Ahn Dong-Ho | Method of forming a trench type isolation layer |
US20020127817A1 (en) * | 2001-03-12 | 2002-09-12 | Samsung Electronics Co., Ltd. | Semiconductor device having trench isolation layer and a method of forming the same |
US20040173812A1 (en) * | 2003-03-07 | 2004-09-09 | Amberwave Systems Corporation | Shallow trench isolation process |
US20060110941A1 (en) * | 2004-11-22 | 2006-05-25 | Taiwan Semiconductor Manufacturing Co., Ltd. | Method of improving via filling uniformity in isolated and dense via-pattern regions |
US20060281336A1 (en) * | 2005-06-07 | 2006-12-14 | Osamu Arisumi | Semiconductor device and method of manufacturing the same |
US20090137094A1 (en) * | 2007-11-27 | 2009-05-28 | Samsung Electronics Co., Ltd. | Method of filling a trench in a substrate |
US20120208346A1 (en) * | 2011-02-10 | 2012-08-16 | Renesas Electronics Corporation | Method of manufacturing semiconductor device |
US20130214383A1 (en) * | 2010-11-05 | 2013-08-22 | Az Electronic Materials Usa Corp. | Method for forming isolation structure |
Family Cites Families (21)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
JP2001203263A (en) * | 2000-01-20 | 2001-07-27 | Hitachi Ltd | Method of manufacturing semiconductor integrated circuit device and semiconductor integrated circuit device |
KR100568100B1 (en) | 2001-03-05 | 2006-04-05 | 삼성전자주식회사 | Trench type isolation film formation method |
US7118987B2 (en) * | 2004-01-29 | 2006-10-10 | Taiwan Semiconductor Manufacturing Co., Ltd. | Method of achieving improved STI gap fill with reduced stress |
US9257302B1 (en) | 2004-03-25 | 2016-02-09 | Novellus Systems, Inc. | CVD flowable gap fill |
US7521378B2 (en) | 2004-07-01 | 2009-04-21 | Micron Technology, Inc. | Low temperature process for polysilazane oxidation/densification |
JP2007221058A (en) | 2006-02-20 | 2007-08-30 | Toshiba Corp | Manufacturing method of semiconductor device |
US20070232019A1 (en) * | 2006-03-30 | 2007-10-04 | Hynix Semiconductor Inc. | Method for forming isolation structure in nonvolatile memory device |
CN101330035B (en) * | 2007-06-18 | 2010-05-19 | 中芯国际集成电路制造(上海)有限公司 | Isolation structure of shallow plough groove and manufacturing method thereof |
US7541297B2 (en) * | 2007-10-22 | 2009-06-02 | Applied Materials, Inc. | Method and system for improving dielectric film quality for void free gap fill |
KR101002493B1 (en) | 2007-12-28 | 2010-12-17 | 주식회사 하이닉스반도체 | Device Separation Method of Semiconductor Memory Device |
KR20110024629A (en) | 2009-09-02 | 2011-03-09 | 주식회사 하이닉스반도체 | Method of manufacturing device isolation film of semiconductor device |
US8466067B2 (en) | 2009-10-05 | 2013-06-18 | Applied Materials, Inc. | Post-planarization densification |
JP2011171500A (en) | 2010-02-18 | 2011-09-01 | Elpida Memory Inc | Semiconductor device and method of fabricating the same |
JP2012142528A (en) | 2011-01-06 | 2012-07-26 | Elpida Memory Inc | Manufacturing method of semiconductor device |
JP2012231007A (en) | 2011-04-26 | 2012-11-22 | Elpida Memory Inc | Method of manufacturing semiconductor device |
US20120276714A1 (en) * | 2011-04-28 | 2012-11-01 | Nanya Technology Corporation | Method of oxidizing polysilazane |
US8461016B2 (en) | 2011-10-07 | 2013-06-11 | Micron Technology, Inc. | Integrated circuit devices and methods of forming memory array and peripheral circuitry isolation |
US8975155B2 (en) | 2013-07-10 | 2015-03-10 | Taiwan Semiconductor Manufacturing Company, Ltd. | Method of forming a shallow trench isolation structure |
CN103531522B (en) * | 2013-10-30 | 2016-08-17 | 上海华力微电子有限公司 | Fleet plough groove isolation structure preparation method |
CN105244269B (en) * | 2014-07-09 | 2018-10-23 | 中芯国际集成电路制造(上海)有限公司 | A kind of semiconductor devices and its manufacturing method |
US9349631B2 (en) * | 2014-10-02 | 2016-05-24 | Globalfoundries Inc. | Method for defining an isolation region(s) of a semiconductor structure |
-
2016
- 2016-11-03 US US15/343,151 patent/US9847245B1/en active Active
-
2017
- 2017-02-20 KR KR1020170022012A patent/KR20170142098A/en not_active Withdrawn
- 2017-06-13 CN CN201710441952.0A patent/CN107527859A/en active Pending
- 2017-06-14 TW TW106119725A patent/TWI724181B/en not_active IP Right Cessation
Patent Citations (9)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US20020072198A1 (en) * | 2000-12-08 | 2002-06-13 | Ahn Dong-Ho | Method of forming a trench type isolation layer |
US20020127817A1 (en) * | 2001-03-12 | 2002-09-12 | Samsung Electronics Co., Ltd. | Semiconductor device having trench isolation layer and a method of forming the same |
US20040173812A1 (en) * | 2003-03-07 | 2004-09-09 | Amberwave Systems Corporation | Shallow trench isolation process |
US20060110941A1 (en) * | 2004-11-22 | 2006-05-25 | Taiwan Semiconductor Manufacturing Co., Ltd. | Method of improving via filling uniformity in isolated and dense via-pattern regions |
US7226873B2 (en) * | 2004-11-22 | 2007-06-05 | Taiwan Semiconductor Manufacturing Co., Ltd. | Method of improving via filling uniformity in isolated and dense via-pattern regions |
US20060281336A1 (en) * | 2005-06-07 | 2006-12-14 | Osamu Arisumi | Semiconductor device and method of manufacturing the same |
US20090137094A1 (en) * | 2007-11-27 | 2009-05-28 | Samsung Electronics Co., Ltd. | Method of filling a trench in a substrate |
US20130214383A1 (en) * | 2010-11-05 | 2013-08-22 | Az Electronic Materials Usa Corp. | Method for forming isolation structure |
US20120208346A1 (en) * | 2011-02-10 | 2012-08-16 | Renesas Electronics Corporation | Method of manufacturing semiconductor device |
Also Published As
Publication number | Publication date |
---|---|
US9847245B1 (en) | 2017-12-19 |
TWI724181B (en) | 2021-04-11 |
TW201810531A (en) | 2018-03-16 |
CN107527859A (en) | 2017-12-29 |
KR20170142098A (en) | 2017-12-27 |
Similar Documents
Publication | Publication Date | Title |
---|---|---|
US7786016B2 (en) | Methods of uniformly removing silicon oxide and a method of removing a sacrificial oxide | |
US20050179112A1 (en) | Filling high aspect ratio isolation structures with polysilazane based material | |
US9847245B1 (en) | Filling processes | |
US7776689B2 (en) | Semiconductor device and method of fabricating the same | |
CN102637720A (en) | Isolation structure profile for gap filling | |
US8592321B2 (en) | Method for fabricating an aperture | |
JP2004363595A5 (en) | ||
US8501632B2 (en) | Methods of fabricating isolation regions of semiconductor devices and structures thereof | |
US6100160A (en) | Oxide etch barrier formed by nitridation | |
US20150200127A1 (en) | Mechanisms for forming semiconductor device having isolation structure | |
US9691664B1 (en) | Dual thick EG oxide integration under aggressive SG fin pitch | |
TW201639010A (en) | Semiconductor structure and method of manufacturing same | |
JP2006344659A (en) | Semiconductor device and its manufacturing method | |
TW202004913A (en) | Method for forming semiconductor device | |
DE102004054818B4 (en) | Method for the reversible oxidation protection of microcomponents | |
US6960509B1 (en) | Method of fabricating three dimensional gate structure using oxygen diffusion | |
JP2024503439A (en) | CD dependent gap filling and conformal membranes | |
TWI400769B (en) | Method for shallow trench isolation | |
US8633113B2 (en) | Method for fabricating a bottom oxide layer in a trench | |
JP5026718B2 (en) | Manufacturing method of semiconductor device | |
KR101342038B1 (en) | Semiconductor device and method for fabricating the same | |
US20160020139A1 (en) | Gap-filling dielectric layer method for manufacturing the same and applications thereof | |
JP4461441B2 (en) | Manufacturing method of semiconductor device | |
CN111211091B (en) | Semiconductor device and method for manufacturing the same | |
KR101914038B1 (en) | Manufacture method of three dimensional memory device |
Legal Events
Date | Code | Title | Description |
---|---|---|---|
AS | Assignment |
Owner name: SAMSUNG ELECTRONICS CO., LTD, KOREA, REPUBLIC OF Free format text: ASSIGNMENT OF ASSIGNORS INTEREST;ASSIGNORS:KITTL, JORGE A.;OH, KYUNGSEOK;KIM, SUNG MIN;SIGNING DATES FROM 20161101 TO 20161103;REEL/FRAME:040840/0774 |
|
STCF | Information on status: patent grant |
Free format text: PATENTED CASE |
|
FEPP | Fee payment procedure |
Free format text: SURCHARGE FOR LATE PAYMENT, LARGE ENTITY (ORIGINAL EVENT CODE: M1554); ENTITY STATUS OF PATENT OWNER: LARGE ENTITY |
|
MAFP | Maintenance fee payment |
Free format text: PAYMENT OF MAINTENANCE FEE, 4TH YEAR, LARGE ENTITY (ORIGINAL EVENT CODE: M1551); ENTITY STATUS OF PATENT OWNER: LARGE ENTITY Year of fee payment: 4 |