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WO2008037960A1 - Ensemble valve pour cellule d'effusion - Google Patents

Ensemble valve pour cellule d'effusion Download PDF

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Publication number
WO2008037960A1
WO2008037960A1 PCT/GB2007/003544 GB2007003544W WO2008037960A1 WO 2008037960 A1 WO2008037960 A1 WO 2008037960A1 GB 2007003544 W GB2007003544 W GB 2007003544W WO 2008037960 A1 WO2008037960 A1 WO 2008037960A1
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WO
WIPO (PCT)
Prior art keywords
valve
assembly according
valve assembly
actuator
axis
Prior art date
Application number
PCT/GB2007/003544
Other languages
English (en)
Inventor
Peter Butcher
Original Assignee
Oxford Instruments Plasma Technology Limited
Priority date (The priority date 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 date listed.)
Filing date
Publication date
Application filed by Oxford Instruments Plasma Technology Limited filed Critical Oxford Instruments Plasma Technology Limited
Publication of WO2008037960A1 publication Critical patent/WO2008037960A1/fr

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Classifications

    • C—CHEMISTRY; METALLURGY
    • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
    • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
    • C23C14/00—Coating by vacuum evaporation, by sputtering or by ion implantation of the coating forming material
    • C23C14/22—Coating by vacuum evaporation, by sputtering or by ion implantation of the coating forming material characterised by the process of coating
    • C23C14/24—Vacuum evaporation
    • C23C14/243—Crucibles for source material
    • C—CHEMISTRY; METALLURGY
    • C30—CRYSTAL GROWTH
    • C30B—SINGLE-CRYSTAL GROWTH; UNIDIRECTIONAL SOLIDIFICATION OF EUTECTIC MATERIAL OR UNIDIRECTIONAL DEMIXING OF EUTECTOID MATERIAL; REFINING BY ZONE-MELTING OF MATERIAL; PRODUCTION OF A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; SINGLE CRYSTALS OR HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; AFTER-TREATMENT OF SINGLE CRYSTALS OR A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; APPARATUS THEREFOR
    • C30B23/00—Single-crystal growth by condensing evaporated or sublimed materials
    • C30B23/02—Epitaxial-layer growth
    • C30B23/06—Heating of the deposition chamber, the substrate or the materials to be evaporated
    • C30B23/066—Heating of the material to be evaporated

Definitions

  • This invention relates to an effusion and cracking cell for use in materials depositing systems such as molecular beam epitaxy (MBE) devices.
  • MBE molecular beam epitaxy
  • the invention is concerned with a valve assembly for use in such a effusion and cracker cell.
  • MBE systems One of the main uses of deposition devices such as MBE systems is the growth of semiconductor devices.
  • An MBE system allows the epitaxial growth of semiconductor materials under clean and well controlled conditions using one or more effusion cells to evaporate material into a chamber, where it is deposited onto a substrate.
  • a 500 cubic cm cell capacity could be sufficient, but for larger, industrial systems, capacities of up to 10 litres may be required.
  • Arsenic is a key material in such processes for growing GaAs-related semiconductor devices. Arsenic normally evaporates as As 4 molecules which, due to a poor sticking coefficient, results in inefficient growth material. As such, it is preferable to pass the evaporated arsenic through a cracker where it can be changed to a predominantly As 2 species. As 2 has a much higher sticking coefficient compared to As 4 .
  • the first effusion cells used for evaporating arsenic produced only As 4 and consisted of a simple cell for heating a crucible containing the solid arsenic. To control the flux of evaporant, either a shutter had to be placed in front of the cell or the temperature of the crucible varied. These techniques suffered from a number of problems. Arsenic evaporates at a comparatively low temperature, around 350 0 C, and at this temperature any temperature changes can take an unacceptable time to stabilise. A shutter in front of the cell's orifice, while stopping the direct line of sight to a substrate, does not control the arsenic pressure in the MBE deposition chamber, resulting in poor control over growth conditions and the possibility of saturating the vacuum pumps.
  • More recent arsenic cells have a crucible/valve/cracker configuration.
  • the crucible temperature remains constant and the valve controls the flux to the substrate.
  • the valve is in the fully closed position, the flux is stopped completely.
  • valve presents difficulties in that moving parts must be actuated from outside the cell without reducing the integrity of the cell seals, which could lead to leakage.
  • the valve components must be very accurately aligned with one another to operate correctly and this is difficult to achieve within the constraints of the sealed cell.
  • a valve assembly for an effusion and cracker cell, the cell comprising a transfer path for transferring a substance from a crucible region to a cracker region via a valve chamber, the valve assembly comprising a valve channel in the transfer path, through which the substance passes between the crucible region and the valve chamber, a valve plug which is movable relative to the valve channel between a sealed position in which the valve plug obstructs passage of the substance through the valve channel and an open position in which the substance can pass through the valve channel between the crucible region and the valve chamber, an actuator for moving the valve plug between the sealed and open positions, and a sealing rod connected between the valve plug and the actuator, and passing through a wall of the valve chamber, for transferring movement from the actuator to the valve plug, wherein the sealing rod is connected to the actuator by a first flexible joint and the sealing rod is connected to the valve plug by a second flexible joint.
  • valve plug is automatically positioned by the flexible arrangement to be in full alignment with the valve chamber, thereby ensuring the creation of a full seal when the valve is in its closed position and conversely ensuring that the valve plug is not so positioned as to cause hindrance to the flow of evaporant when the vaive is in its open state.
  • the first flexible joint permits angular and/or translational movement between the actuator and the sealing rod
  • the second flexible joint permits angular and/or translational movement between the sealing rod and the valve plug.
  • the flexible joints may provide full freedom of movement between the adjoining components, for example through the use of a universal joint.
  • a lesser degree of freedom is convenient, and therefore it is preferred that, where the actuator is aligned with a first axis, the first flexible joint is adapted to permit angular movement of the sealing rod relative to the actuator about a second axis which is perpendicular to the first axis.
  • the first flexible joint is adapted to permit translational movement of the sealing rod relative to the actuator along a second axis which is perpendicular to the first axis and/or along a third axis which is perpendicular to the first and second axes.
  • the second flexible joint is adapted to permit angular movement of the sealing rod relative to the valve plug about a fifth axis which is perpendicular to the fourth axis.
  • the second flexible joint is adapted to permit translational movement of the sealing rod relative to the valve plug along a fifth axis which is perpendicular to the fourth axis and/or along a sixth axis which is perpendicular to the fourth and fifth axes.
  • the first and fourth axes are substantially parallel. That is, the actuator and the valve plug are disposed approximately parallel to one another, and in many cases they may be coaxial.
  • the second and fifth axes are substantially parallel and the third and sixth axes are substantially parallel. In this way, the first and second flexible joints can be arranged to have the same degrees of freedom as one another.
  • the first and second flexible joints are adapted to restrict longitudinal movement between the actuator and the sealing rod, and between the sealing rod and the valve plug, respectively. This ensures that there is positive movement of the components in each direction within the flexible joint.
  • the first flexible joint is fixed to an end of the actuator and comprises a bore for receiving a first end of the sliding rod therein, the bore having a larger diameter than that of the sliding rod to enable relative movement between them, the first flexible joint being provided with means for retaining the first end of the sliding rod within the bore.
  • the first end of the sliding rod is provided with at least one recess which co-operates with a corresponding at least one keying protrusion provided in the bore to retain the first end of the sliding rod within the bore.
  • the keying protrusions are provided by bolts passing through the flexible joint.
  • two recesses and two keying protrusions are provided in the first flexible joint, and about which the sealing rod is pivotable relative to the actuator.
  • the second flexible joint is constructed in the same manner as the first flexible joint.
  • each flexible joint further comprises packing material disposed inside the respective bore in order to restrict longitudinal movement of the sealing rod relative to the joint.
  • the sealing rod passes through a bushing provided in the wall of the valve chamber to thereby seal the valve chamber from the exterior.
  • a bushing provided in the wall of the valve chamber to thereby seal the valve chamber from the exterior.
  • the sealing rod is slidable relative to the bushing.
  • the sliding rod comprises tungsten, which has been determined to be a suitable material for withstanding the operating conditions which the sliding rod will experience in use.
  • the bushing comprises a ceramic material, preferably alumina or pyrolytic boron nitride. A combination of the ceramic bushing and the tungsten sliding rod has been found to be particularly advantageous since a close sealing fit can be achieved and the components withstand the operating conditions well.
  • an O-ring is disposed between the sliding rod and the bushing.
  • the O-ring comprises graphite, preferably flexible graphite.
  • graphite is an excellent sealing material since it is soft enough to create a seal without damaging the cell components on either side, and does not react with the adjacent materials.
  • valve plug and valve channel co-operate such that, in its sealed position, an end of the valve plug inserted into the valve channel substantially prevents transfer of the substance past the end of the valve plug.
  • the evaporant is constrained some distance away from the end of the valve channel, such that there is no contact between the evaporant and any moving part of the valve assembly. This minimises the possibility of long term corrosion or leakage in this region.
  • the valve plug and valve channel constitute a needle valve.
  • at least a portion of the transfer path is defined by a transfer tube and the valve channel comprises an end portion of the transfer tube.
  • the transfer tube comprises a bellows for aligning the crucible region with the valve region. The provision of a bellows gives the transfer tube a degree of flexibility which assists in aligning each of its ends with the neighbouring components.
  • a heater is provided at the valve chamber for controlling the temperature of the substance therein.
  • This has the advantage that the evaporant can be maintained at a suitable temperature to prevent condensation in the valve region, which could lead to blockages and seizing of the valve movement.
  • This concept is discussed further in our co-pending British Patent Application No. XXXXXX filed on even date entitled "Effusion and Cracking Cell".
  • the substance to be deposited by the cell is arsenic, but the cell could also be adapted for use with other substances such as phosphorous.
  • the effusion and cracking cell is for use in a molecular beam epitaxy (MBE) system.
  • MBE molecular beam epitaxy
  • the cell could be employed in any suitable deposition system making use of an effusion cell.
  • Figure 1 is a perspective view showing an effusion and cracking cell
  • Figure 2 is a cross-section of the effusion and cracking cell shown in Figure 1
  • Figure 3 shows an enlarged portion of the cross-section shown in Figure 2, depicting the crucible region of the cell;
  • Figure 4 is a schematic cross-section of a portion of the effusion and cracking cell depicting the valve region
  • Figure 5 shows in more detail a portion of the valve assembly visible in Figure 4;
  • Figure 6 is an enlarged portion of the cross-section of Figure 4, showing the valve assembly in more detail;
  • Figures 7A to D show a sliding rod, forming part of the valve assembly shown in Figure 6, in side view, top view, end view and perspective view respectively;
  • Figures 8A to D show an actuator, forming part of the valve assembly shown in Figure 6, in side view, cross-section, end view and perspective view respectively;
  • Figures 9A to D show a valve plug, forming part of the valve assembly shown in Figure 6, in side view, cross-section, end view and perspective view respectively;
  • Figure 10 shows a cross-section of the sliding rod, actuator and valve plug of Figures 7, 8 and 9, as assembled in use;
  • Figure 11 shows a cross-section through the cracker region of the cell shown in Figure 2.
  • Figure 1 shows an overview of an effusion and cracking cell 10.
  • the material to be deposited such as arsenic or phosphorous
  • the cell shown in Figure 1 is used predominantly for arsenic, but it can also be used to deposit other materials, such as phosphorous.
  • the description below will focus mainly on the use of the cell to deposit arsenic, however it will be appreciated that other materials can be deposited by the cell, and its applications are not restricted to arsenic deposition.
  • the crucible is heated to a temperature at which the substance evaporates or sublimes producing a gaseous species. In the case of arsenic, this evaporant is typically As 4 .
  • the evaporated substance passes through a transfer region 30 into a valve region 40 through which it reaches a cracker region 50.
  • the flux of evaporated material passes through a heated region where the gaseous species can be cracked, for example from As 4 to As 2 , if required.
  • the substance exits the cracker region 50 into a deposition chamber (not shown).
  • the crucible capacity is approximately one litre or greater.
  • the version shown has a three litre capacity crucible.
  • Figure 2 shows a cross-section of the whole cell 10.
  • Arsenic is placed in a crucible 22 and is heated to a temperature where it evaporates or sublimes.
  • the evaporating arsenic flux from the crucible 22 passes through a transfer tube 31 to a valve chamber 41 in which a valve assembly determines the arsenic vapourflow. From the valve, the evaporant passes through an injector tube 51 to the cracker region 50.
  • the cracker can either be kept at a temperature that allows vapour flow but does not crack the molecule, or the temperature can be raised by heaters 52 so that the arsenic is converted from As 4 to As 2 . From the cracker region 50, the vapour exits the cell 10, the end of which is positioned at a predetermined effusion distance from a substrate onto which the arsenic is to be deposited.
  • the substrate is enclosed in a deposition chamber (not shown), which is kept at a very low pressure or vacuum in order not to impede the passage of molecules from the effusion cell(s) to the substrate.
  • the effusion cell 10 is coupled to the deposition chamber through a port in the chamber wall and sealed by a chamber mounting flange
  • more than one effusion cell 10 may be coupled to a single deposition chamber in order to allow for deposition of more than one material either sequentially or simultaneously. There may also be more than one substrate in the deposition chamber such that multiple substrates can be deposited on at any one time.
  • the crucible region 20, transfer region 30, valve region 40, and cracker region 50 are housed within a vacuum enclosure E suitable for MBE and ultra high vacuum operation. Apertures are provided in the enclosure surrounding the cracker region so which enable fluid communication between the vacuum enclosure E and the deposition chamber such that the cell enclosure E is evacuated by the deposition chamber pumps. At various stages of operation, it is also necessary to internally evacuate the cell. For example, when the crucible is cold and during initial pump-down the valve is fully opened to allow the crucible to be pumped internally. It is also usual to have the valve open whilst raising the crucible temperature in order to release any contaminant gases. In addition, the valve must be open during venting in order to return the crucible to atmospheric pressure and prevent possible damage.
  • FIG 3 shows the crucible region 20 in greater detail.
  • the crucible 22 is housed in a water-cooled vacuum enclosure 21.
  • the entry and exit ports 21 a and 21 b for the flow of water (or other cooling fluid) are shown in Figures 2 and 3.
  • Water cooling prevents parts of the cell which should remain cold from becoming hot and contaminating the substrate with out-gassing components during semiconductor growth.
  • radiation shields are positioned adjacent to the heaters to reduce heat loss.
  • the crucible 22 consists of a first cylindrical portion 22a and a second cylindrical portion 22b, of smaller diameter.
  • the second cylindrical portion 22b is arranged above the cylindrical portion 22a.
  • Crucible heaters 24a and 24b are arranged around the circumference of the second cylindrical portion 22b and adjacent to its flat surface towards the top of the cell.
  • the heaters typically comprise wire heaters which radiate heat, although any other suitable heating arrangement could alternatively be employed.
  • Positioning the crucible heaters 24a and 24b adjacent the top half of the crucible 22 gives preferential heating to this part of the crucible 22. This is preferred in order that, after a short period of heating, the unevaporated substance migrates to the colder base of the crucible 22 (i.e. the first cylindrical region 22a) where it adheres as a solid mass. This occurs as a result of the dynamic flux between solid and gaseous states of the substance. When arsenic is heated, it creates a vapour pressure.
  • the gas vapour When the valve is closed, the gas vapour continually solidifies and reevaporates to maintain a stable vapour pressure. Even when the valve is open most of the vapour carries on in this cycle. The vapour is most likely to solidify at the coldest part of the crucible (i.e. furthest from the heating elements) and so, during initial operation, there is a mass migration from the original location of the arsenic to the crucible base which is intentionally kept cooler. To maintain the evaporation rate, the crucible temperature has to be increased slightly to compensate. This has two advantages: firstly, the mass is stable and this provides a stable evaporation rate.
  • a filter 25 such as a pepper pot filter, is provided on the entrance to the transfer tube 31 in order to prevent any solid material entering the transfer tube 31 , which could otherwise happen, for example, if material were to fall into the second cylindrical region 22b when the crucible is first loaded.
  • the crucible 22 has two loading ports, the first loading port 23 located at the base of the crucible region 20 adjacent to the first cylindrical region 22a of the crucible 22, and the second loading port 26 located near the top of the crucible region 20 adjacent to the second cylindrical portion 22b of the crucible 22.
  • the first loading port 23 located at the base of the crucible region 20 adjacent to the first cylindrical region 22a of the crucible 22
  • the second loading port 26 located near the top of the crucible region 20 adjacent to the second cylindrical portion 22b of the crucible 22.
  • the second loading port 26 is used since the first loading port 22 tends to be obstructed with unevaporated material.
  • the crucible 22 is heated to between 350 0 C and 450 0 C to provide an acceptable rate of evaporation or sublimation.
  • the temperature is measured using a thermocouple 27 positioned inside the crucible 22 to ensure an accurate reading.
  • the temperature measurement is output to a control system which monitors the temperature and, in some examples, operates under feedback control to adjust the power supplied to the crucible heaters 24a and 24b so as to maintain the crucible 22 at a predetermined temperature.
  • the crucible region 20 connects to the rest of the cell via transfer region 30 which contains transfer tube 31.
  • the vacuum enclosure E surrounding the transfer tube 31 joins the crucible region 20 to the valve region 40, sealed coupling being achieved by flanges 32 and 33.
  • the flanges 32 and 33 are sealed using a copper gasket, as is conventional in ultra high vacuum systems.
  • the crucible region 20 can be quickly removed and capped in the field, which is important since materials such as arsenic tend to oxidise very quickly and may become unusable if exposed to the atmosphere for more than approximately one hour.
  • the MBE system is let out to an atmosphere of dry nitrogen and then the valve in valve region 40 closed.
  • the crucible enclosure 21 is removed by unbolting the flange holding it to the transfer region 30 and sliding it away from the valve region to reveal the crucible 22.
  • the transfer tube is then disconnected from the crucible and the coupling between the top heater plate and crucible released such that the crucible 22 can be removed.
  • the crucible 22 can then be capped at the transfer tube port and back filled with nitrogen to replace the residual air.
  • the transfer tube 31 is shown in full in Figure 2 and partially in Figures 3 and 4.
  • the transfer tube 31 is provided with a heater (not shown) which maintains the transfer tube 31 at a temperature above that of the crucible 22, thus avoiding any condensation or blockage in this region.
  • the transfer tube heater is wired in series with the crucible heaters 24a and 24b, allowing them to be powered from a single supply.
  • the transfer tube 31 is preferably made of titanium and, in the embodiment shown, is provided with a bellows 34 along a portion of its length to assist alignment between the crucible region 20 and the valve region 40.
  • the bellows 34 are welded into the transfer tube 31 to form an integral component.
  • the bellows 34 permit both longitudinal movement parallel to the axis of the transfer tube 31 and lateral movement in a direction perpendicular to its axis.
  • valve region 40 Details of the valve region 40 are shown in Figures 4 to 10.
  • the valve region 40 is shown in Figures 4 to 10.
  • valve 40 is surrounded by a water-cooled enclosure 62 to prevent outgassing.
  • Water or other coolant enters the enclosure 62 through input 62a and exits through output channel 62b.
  • the evaporant from the transfer tube 31 enters the valve region 40 through channel D in valve block 65.
  • a portion of the channel D is defined by a valve jet 44 through which evaporant passes from transfer tube 31 into valve chamber 41.
  • the valve chamber 41 consists of regions A, B and C shown in Figure 4 which provides passage through the valve block 65 to the cracker region 50.
  • the valve mechanism essentially comprises a needle valve.
  • valve plug 43 which is approximately conical in shape and is moveable between a first position, in which the plug is inserted into the jet 44, thus preventing passage of evaporant therethrough, and a second, open position in which the plug 43 is at least partially removed from jet 44 and evaporant is able to flow from the transfer tube 31 into the valve chamber 41.
  • valve block 65 When the valve plug 43 is fully inserted into the jet 44 there is a complete seal by two mating flanges, and the valve block 65 is arranged such that, when the valve is closed, the evaporant is kept a distance away from any moving parts within the valve assembly, thus minimising the chance of long term corrosion or leakage in this region.
  • the valve assembly has to be actuated from outside the cell and it is important that this can be achieved without evaporant leaking from the valve region 41.
  • this is achieved by using a actuator assembly 42, 48 and 49 connected to the valve plug 43 via a sliding rod 46.
  • the sliding rod 46 passes through a bushing 64 mounted in the wall of valve chamber 41.
  • the bushing extends along more than half of the length of the sliding rod 46 in order to improve the seal.
  • the sliding rod 46 is made of tungsten and the bushing 64 of a ceramic such as alumina or pyrolytic boron nitride.
  • Alumina is the preferred material because it is a relatively clean material yet is machinable. Pyrolytic boron nitride would provide even higher levels of cleanliness but it is more difficult to machine, and therefore more expensive. This configuration has been tested and there is no evidence of arsenic leaking or the mechanism sticking.
  • an O-ring shaped graphite seal 65 is fitted between the components and held in place by a metal collar 65A.
  • Graphite seals are also provided at the join between the bushing 64 and the wall of the valve region 41.
  • the graphite gaskets are made from 0.2mm thick flexible graphite, as defined by the supplier Goodfellow.
  • Flexible graphite is a layered material as opposed to other forms which are generally sintered. The material is "soft" in so much that it does not deform the joint components it sits between.
  • seal 65 between the sliding rod 46 and the bushing 64 which as described above is an O-ring shape. It has a square cross-section and is approximately 4mm in diameter having a cross-section of about 1 mm 2 .
  • An initial alignment can be made by adjusting the position of the bushing 64 relative to the valve chamber wall, but there can be alignment difficulties if the valve jet 44 is not absolutely square to the valve plug 43.
  • the relative positions of the mechanism can change when the valve region is heated.
  • first flexible joint 47 connects the actuator assembly via extension 42B to the first end of the sliding rod 46, which is outside the valve region 41.
  • the second flexible joint 45 connects the second end of the sliding rod 46 to the valve plug 43, both of which are inside the valve region 41. This configuration is shown in Figures 5, 6 and 10.
  • Each flexible joint 45 and 47 permits angular and/or translation movement between the components it connects.
  • Any type of flexible joint could be used, such as a hinge or a universal joint.
  • the flexible joints are formed as shown in Figures 7 to 10.
  • the sliding rod 46 is shown in Figures 7A to D.
  • the sliding rod 46 is provided with two slots 46a, 46b at each end of the rod, positioned a short distance away from the extremities. With tungsten, normal machining is difficult and as such these slots are preferably formed by grinding.
  • the sliding rod 46 which is of generally circular cross-section, is inserted into flexible joint 47 at its first end and into flexible joint 45 at its second end.
  • Flexible joint 47 and the actuator 42B with which it is integrally formed, are shown in Figure 8.
  • Flexible joint 47 takes the form of a body having a bore 47A extending at least partially therethrough, parallel to the axis of the joint 47 and actuator
  • the position of the bolts through bores 47B co-operates with slots 46A in rod 46 such that the rod is secured within bore 47A whilst a degree of movement remains.
  • rod 46 and actuator 42B are rotatably moveable with respect to one another about axes provided by the bolts through holes 47B.
  • the sliding rod is rotatably moveable relative to the actuator in a horizontal plane, however, the components could readily be reorientated to permit vertical adjustment.
  • annular movement in more than one plane perpendicular to the axis of the actuator may be permitted. It will be seen that some translational movement is also permitted between the rod and the bore in the flexible joint.
  • packing material such as a thin washer (not shown) is placed between the end of the rod 46 and the closed end of the bore 47A. This also has an important function in that it takes up backlash and thereby ensures there is positive linear movement of the sliding rod 46 in both directions. By choosing the correct clearances between the sliding rod 46 and the bore 47A, X-Y and angular flexibility is achieved, whereas linear movement in the Z direction is minimised.
  • the second flexible joint 45 has a similar construction to that of the first flexible joint 47. Again, angular movement between the valve plug 43 and sliding rod 46 is permitted as well as a degree of translational movement. Packing material (not shown) is disposed between the sliding rod 46 and the base of the bore 45A to take up backlash.
  • the flexible joint 45 is formed integrally with valve plug 43 which is typically of conical shape to allow for mating with the valve jet 44.
  • the actuator is driven by a linear drive assembly 48 and 49 which moves the actuator 42b towards and away from the seal 64, thereby operating the valve.
  • a linear drive assembly 48 and 49 which moves the actuator 42b towards and away from the seal 64, thereby operating the valve.
  • Any suitable linear drive could be employed, but in the present example a screw-driven linear drive is depicted, the drive screw being accommodated inside drive shaft 48, connected to stepper motor 49.
  • the motor 49 has "on board" intelligence which allows the motor to operate without a complex controller.
  • the linear drive may be manually operated, in which case the motor 49 is replaced by a manual drive arrangement.
  • suitable linear drive assemblies are available from VG Scienta, of Hastings, United Kingdom.
  • the valve region 40 is provided with a heater 63 for controlling the temperature of the evaporant in the valve chamber 41.
  • the heater 63 may be provided in the form of a plate heater underneath the valve chamber 41 , as depicted in Figure 6, or could be provided in the form of elements surrounding the valve block 65.
  • the valve heater is used to maintain the temperature of the evaporant to prevent it condensing in the 44
  • valve heater 63 is preferably supplied from a constant current source which maintains the valve chamber 41 at approximately 470-475 c C, although this temperature will vary depending on the crucible and cracker temperatures. In the case of arsenic, maintaining such temperatures essentially prevents condensation. In some embodiments, it may be preferable to utilise feedback control to maintain the valve region at a particular temperature and in this case a thermometer will be included in the valve region 41.
  • the cell has at least three heaters: the crucible heater 24, the valve heater 63 and the cracker heater 51 (described below).
  • these three heaters are each controlled independently so that each region can be maintained at its optimum operating temperature.
  • a controller (not shown) supplies power to the three heaters and this can be adjusted to maintain the associated region at the desired temperature.
  • it is preferred to use feedback control in which case a means for measuring temperature is provided in the relevant region.
  • the crucible and cracker heaters are controlled in this way but in other embodiments it may be advantageous to control the valve heater in the same manner.
  • constant current control is used for the valve heater but could alternatively or in addition be used to control the crucible and/or cracker heaters.
  • the transfer tube 31 may be provided with a heater which is preferably in series with the crucible heater.
  • the transfer tube heater could be controlled independently.
  • Evaporant flux from the valve region 40 passes into the injector tube 51 ( Figure 11).
  • the injector tube 51 carries the flux from the valve region to the end of the cell where it enters the deposition chamber.
  • Adjacent to the end of the injector tube 51 is the cracker, which is provided with heating elements 52 and a number of baffles 53 within the injector tube 51.
  • the baffles 53 force the evaporant to have many self collisions before exiting the cell.
  • the cracker is heated to around 900 0 C, evaporated arsenic is cracked from As 4 to As 2 . If the temperature of the cracker is reduced to around 600 0 C, there is very little cracking.
  • the heater 52 is positioned around the injector tube 51 in the cracker region to heat it uniformly.
  • thermocouple 54 is provided to monitor the temperature of the cracker region, which may be controlled using feedback.
  • the cracker is surrounded by a water-cooled enclosure 72 to prevent contamination by out-gassing components of the cell.

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  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Materials Engineering (AREA)
  • Metallurgy (AREA)
  • Organic Chemistry (AREA)
  • Crystallography & Structural Chemistry (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Mechanical Engineering (AREA)
  • Physical Deposition Of Substances That Are Components Of Semiconductor Devices (AREA)

Abstract

L'invention concerne un ensemble valve destiné à une cellule d'effusion et de craquage, cette cellule comprenant un conduit de transfert destiné à transférer une substance d'une zone creuset (20) à une zone de craquage (50) par l'intermédiaire d'une chambre de valve (41). L'ensemble valve comprend un passage de valve dans le conduit de transfert, à travers lequel passe la substance entre la zone creuset (20) et la chambre de valve (41). Un obturateur de valve (43) peut se déplacer par rapport au passage de valve entre une position de fermeture étanche, dans laquelle l'obturateur de valve empêche la substance de traverser le passage de valve, et une position ouverte, dans laquelle la substance peut traverser le passage de valve entre la zone creuset et la chambre de valve. L'invention concerne également un actionneur (49) destiné à déplacer l'obturateur de valve entre la position de fermeture étanche et la position ouverte, ainsi qu'une tige d'étanchéité (46) disposée entre l'obturateur de valve (43) et l'actionneur (49) et traversant une paroi de la chambre de valve, cette tige permettant le transfert du mouvement de l'actionneur (49) à l'obturateur de valve (43).
PCT/GB2007/003544 2006-09-28 2007-09-19 Ensemble valve pour cellule d'effusion WO2008037960A1 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
GB0619160.5 2006-09-28
GB0619160A GB0619160D0 (en) 2006-09-28 2006-09-28 Valve assembly

Publications (1)

Publication Number Publication Date
WO2008037960A1 true WO2008037960A1 (fr) 2008-04-03

Family

ID=37434853

Family Applications (1)

Application Number Title Priority Date Filing Date
PCT/GB2007/003544 WO2008037960A1 (fr) 2006-09-28 2007-09-19 Ensemble valve pour cellule d'effusion

Country Status (2)

Country Link
GB (1) GB0619160D0 (fr)
WO (1) WO2008037960A1 (fr)

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP3455385A4 (fr) * 2016-04-25 2020-02-26 Innovative Advanced Materials, Inc. Cellules d'effusion, systèmes de dépôt comprenant des cellules d'effusion, et procédés associés

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR3102189B1 (fr) * 2019-10-17 2022-08-05 Riber Cellule d’évaporation pour chambre d’évaporation sous vide et procédé d’évaporation associé

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB2291602A (en) * 1994-07-16 1996-01-31 Oxford Appl Res Ltd Cracker apparatus and components having inert contact-surfaces
US6030458A (en) * 1997-02-14 2000-02-29 Chorus Corporation Phosphorus effusion source
US20050247267A1 (en) * 2004-03-02 2005-11-10 Osamu Kobayashi Molecular beam source for use in accumulation of organic thin-films

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB2291602A (en) * 1994-07-16 1996-01-31 Oxford Appl Res Ltd Cracker apparatus and components having inert contact-surfaces
US6030458A (en) * 1997-02-14 2000-02-29 Chorus Corporation Phosphorus effusion source
US20050247267A1 (en) * 2004-03-02 2005-11-10 Osamu Kobayashi Molecular beam source for use in accumulation of organic thin-films

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP3455385A4 (fr) * 2016-04-25 2020-02-26 Innovative Advanced Materials, Inc. Cellules d'effusion, systèmes de dépôt comprenant des cellules d'effusion, et procédés associés

Also Published As

Publication number Publication date
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