WO2008139370A1

WO2008139370A1 - Method for the manufacturing of an optoelectronic device

Info

Publication number: WO2008139370A1
Application number: PCT/IB2008/051754
Authority: WO
Inventors: Herbert Lifka; Eric A. Meulenkamp; Cristina Tanase; Peter Van De Weijer
Original assignee: Koninklijke Philips Electronics N.V.
Priority date: 2007-05-10
Filing date: 2008-05-06
Publication date: 2008-11-20
Also published as: TW200913335A

Abstract

The present invention relates to a method for the manufacturing of an optoelectronic device (10). The method comprising the steps of: providing a substantially rigid carrier substrate (16) having a structured surface (18); depositing a substrate (20) over the structured surface (18) of the carrier substrate (16) so that the inverse of the structured surface (18) is formed on the deposited substrate (20); forming at least one optoelectronic unit (26) on the deposited substrate (20) opposite the carrier substrate (16); and releasing the deposited substrate (20) and the at least one optoelectronic unit (26) from the carrier substrate (16) using radiation after forming the at least one optoelectronic unit (26). The present invention also relates to an optoelectronic device (10) manufactured by such a method

Description

Method for the manufacturing of an optoelectronic device

FIELD OF THE INVENTION

The present invention relates to a method for the manufacturing of an optoelectronic device. The present invention also relates to an optoelectronic device manufactured by such a method.

BACKGROUND OF THE INVENTION

Optoelectronics relates generally to electronic devices interacting with light. Conventional methods for the manufacturing of optoelectronic devices, for instance an OLED unit with an out-coupling structure or a photovoltaic unit with an in-coupling structure, include first forming an optoelectronic unit (e.g. OLED or photovoltaic unit) on a substrate, and then processing an optical structure (e.g. out- or in-coupling structure) on top of the optoelectronic unit or placing an optical structure formed on a separate carrier on top of the optoelectronic unit. However, such conventional methods are usually expensive (requires for instance one substrate per device). Also, the distance between the optical structure and the actual OLED may be relatively large due to the substrate thickness, which can impair the in- or out-coupling functionality. The larger distance can also cause cross-talk. Also, problems of aligning the optical structure to the optoelectronic unit may cause low yield.

Further, a method for the manufacturing of a display, for instance an OLED or LCD display, is disclosed in the US patent application publication no. US20060054594 to Lifka et al. The method comprises providing a substrate having through holes, depositing a removable layer on the substrate, depositing an etch and temperature resistant layer on the removable layer, processing a display on the etch and temperature resistant layer, and removing the removable layer by etching, namely leading an etchant through the substrate holes. This method allows the substrate to be reused, reducing the manufacturing costs. Additionally, if a special front plate of the display is required, for instance small lenses or out-coupling structures, the substrate could have the opposite shape.

However, US20060054594 fails to explicitly disclose how the display should be processed taking into account the structure of the substrate. In fact, only simple out- coupling structures can be fabricated without much extra processing this way. Also, the step of depositing an etch and temperature resistant layer is essential just to allow the subsequent processing and removal, it contributes nothing to the resulting display.

SUMMARY OF THE INVENTION

It is an object of the present invention to at least partly overcome these problems, and to provide an improved method for the manufacturing of an optoelectronic device, which method in particular is inexpensive and efficient and produces an optoelectronic device having improved performance. These and other objects that will be apparent from the following summary and description are achieved by a method for the manufacturing of an optoelectronic device, and an optoelectronic device manufactured by such a method, according to the appended claims.

In an aspect of the present invention, there is provided a method for the manufacturing of an optoelectronic device, the method comprising the steps of: providing a substantially rigid carrier substrate having a structured surface; depositing a substrate over the carrier substrate so that the inverse of the structured surface of the carrier substrate is formed on the deposited substrate; forming at least one optoelectronic unit on the deposited substrate opposite the carrier substrate; and releasing the deposited substrate and the at least one optoelectronic unit from the carrier substrate using radiation after forming the at least one optoelectronic unit.

Thus, the deposited substrate becomes the main substrate of the final optoelectronic device. Also, the deposited substrate gets a structured surface (e.g. for out- or in-coupling of light) already in the step of depositing it over the carrier substrate, making subsequent structuring or addition of a separate optical structure not required. Further, releasing the carrier substrate by radiation means that no impairing through holes in the carrier substrate are required. Especially, small scale structures can now be provided without extra processing. Further, the radiation release may be performed without having to provide any protection layer or the like, the provision of which could lengthen the manufacturing process, and which layer otherwise could hamper the performance of the final device or require additional measures for subsequent removal. Further, the carrier substrate can be reused, making the present method less costly compared to conventional methods. Further, the structured deposited substrate (functioning e.g. as in- or out-coupling structure) may be optically thin (e.g. no intermediate substrates or layers required), which in turn may enhance the in- or out-coupling efficiency. Further, this method allows easy manufacturing of flexible devices, since the device can be processed as if it was a rigid device due to the (subsequently released) rigid carrier substrate.

It should be noted that release by radiation is known per se, for instance from the international patent application publication no. WO2005050754, wherein the manufacturing of a display device using a planar carrier substrate and subsequent UV laser release is disclosed. This method is known as the EPLaR process (Electronics on Plastic by Laser Release).

Preferably, a surface of the deposited substrate opposite the carrier substrate is essentially planar, for easy processing of the optoelectronic unit. Thus, once the carrier and deposited substrate combination has been prepared, the planar surface facilitates processing of the optoelectronic unit using existing equipment, which in turn makes implementation of the present method inexpensive and feasible.

In one embodiment, the deposited substrate is radiation release compatible, meaning that the deposited substrate and the release radiation (i.e. the radiation wavelength(s) used for release) are match so that the deposited substrate will separate from the carrier substrate upon exposure of the release radiation (e.g. UV light). Thus, the deposited substrate acts as a release layer, and no separate release layer has to be provided, making the present method time and cost efficient. Hereto, a preferred material to be used for the release compatible deposited substrate is polyimide. Except for being UV release compatible, it may be transparent, colorless, planarising, spin-coatable, and temperature resistant, which makes it suitable for use in the present method. Also, polyimide has a refractive index similar to other components of the device, allowing an refractive index matched device, which in turn means that light typically not gets confined in some part of the device (which otherwise could hamper the device performance), but is evenly distributed in the entire device. Alternatively, a separate release layer having substantially uniform thickness may be formed between the carrier substrate and the deposited substrate, conformal to the structured surface of the carrier substrate. Like above, the separate release layer and the release radiation wavelength(s) should be matched to allow the release between the carrier substrate and the deposited substrate. The conformal, equally thick release layer will not interfere with the process of passing the structure of the carrier substrate onto the overlying deposited substrate. Using a separate release layer means that the deposited substrate material does not have to be compatible with the release process, allowing a broader range of materials to be used for the deposited substrate, for instance sol-gel, BCB, etc. As indicated above, the radiation may be UV radiation, i.e. electromagnetic radiation in the ultraviolet spectrum. The UV radiation is preferably produced by a laser, which may provide a short pulse of high energy UV radiation usable for the release. Instead of a laser, another radiation source could be used, for instance an UV lamp. In one embodiment, the structured surface of the carrier substrate comprises the inverse of an out-coupling structure. Thus, the resulting structure on the deposited substrate becomes an out-coupling structure in the deposited substrate/air interface. The out- coupling structure may be used for enhancing extraction of light from the optoelectronic device, which hereto for instance may comprise an organic light emitting diode (OLED), in order to enhance the overall efficiency of the optoelectronic device. The OLED device with an out-coupling structure (as manufactured by the present method) may for instance be about 2x more efficient than an OLED without out-coupling structures. The out-coupling structure may for instance comprise or be comprised of small lenses, pyramids, a surface roughness, etc., which may be of nano- or micro scale dimensions. In another embodiment, the structured surface of the carrier substrate comprises the inverse of an in-coupling structure. Thus, the resulting structure on the deposited substrate becomes an in-coupling structure in the deposited substrate/air interface. The in-coupling structure may be used for enhancing introduction of light to the optoelectronic device, which hereto for instance may comprise an organic or inorganic photovoltaic cell (i.e. a solar cell), in order to enhance the overall efficiency of the optoelectronic device. Preferably, after the carrier substrate has been released, an anti-reflex coating is provided on the in-coupling structure of the deposited substrate, to further enhance the in-coupling of light.

In yet another embodiment, the structured surface of the carrier substrate comprises the inverse of a light-redirecting structure. Thus, the resulting structure on the deposited substrate becomes a light-redirecting structure in the deposited substrate/air interface. The light-redirecting structure may for instance be adapted to change the beam shape of the light or to direct the light in a predetermined direction for e.g. 3D video or 3D television. Hereto, the optoelectronic device may for instance comprise a liquid crystal display (LCD) element or an OLED. Also, directional lamps can be fabricated with this method.

Preferably, the structured surface of the carrier substrate comprises alignment structures. The alignment structure may for instance be a small alignment mark, such as a cross. The alignment structures will be passed on to the deposited substrate, allowing easy and accurate alignment of the optoelectronic unit on the deposited substrate, since the processing equipment may sense the alignment structure and be positioned accordingly. Easier alignment means that the manufacturing yield may be enhanced, providing a more efficient manufacturing method. The alignment structures are particularly useful in case the structure of the deposited substrate is position dependent.

Further, the deposited substrate may comprise scattering particles. The scattering particles may be added to the material of the deposited layer before it is provided over the carrier substrate, so that the scattering particles become embedded in the deposited substrate. The scattering particles may for instance enhance out-coupling of light from the deposited substrate, since the previously confined light changes angles when it strikes the scattering particles. Hereto, in an advantageous embodiment of the invention, the substantially rigid carrier substrate having a structured surface is replaced by a substantially rigid carrier substrate having an essentially planar surface instead of the structured surface. This means that no structuring is passed on to the deposited substrate, which becomes essentially planar in the deposited substrate/air interface. Instead, only the scattering particles of the deposited substrate provide for the enhanced out-coupling. Thus, in this embodiment, there is no need to structure the carrier surface, which facilitates the manufacturing method. In another aspect of the present invention, there is provided an optoelectronic device manufactured by a method according to the firstly discussed aspect of the present invention. Such an optoelectronic device may feature refractive index matched constituting components, a thin structured deposited substrate, scattering particles in the deposited substrate, small scale structuring of the deposited substrate, etc., resulting in an optoelectronic device with improved performance, as discussed in relation to the firstly described aspect of the present invention.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other aspects of the present invention will now be described in more detail, with reference to the appended drawings showing currently preferred embodiments of the invention. Figs. Ia-If are schematic cross-sectional side views illustrating a method for the manufacturing of an optoelectronic device according to an embodiment of the present invention. Fig. 2 is a schematic side view illustrating a stage of a method for the manufacturing of an optoelectronic device according to another embodiment of the present invention.

Fig. 3 is a schematic side view of the resulting optoelectronic device of a method for the manufacturing of an optoelectronic device according to yet another embodiment of the present invention.

Fig. 4 is a schematic side view illustrating a step of a method for the manufacturing of an optoelectronic device according to still another embodiment of the present invention.

DETAILED DESCRIPTION

Figs. Ia-If are schematic cross-sectional side views illustrating a method for the manufacturing of an optoelectronic device 10 according to an embodiment of the present invention. Namely, the optoelectronic device 10 in figs. Ia-If is an OLED (organic light emitting diode) device. OLEDs can for instance be used in various displays (TVs, mobile devices, etc.), as a light source, etc.

In a first step illustrated in fig. Ia, a planar substrate 12 is provided. The substrate 12 should be transparent for ultraviolet (UV) radiation, and it is preferably made of glass. On top of the planar glass substrate 12, there is provided a structure 14, as illustrated in fig. Ib. The structure 14 may be formed by photo/mechanical embossing or wet/dry etching combined with lithography. The structure 14 should also be UV transparent, and it can for instance be made of SiO.

The glass substrate 12 and the structure 14 together form a substantially rigid carrier substrate 16 having a structured top surface 18.

Onto the structured surface 18, there is deposited a polymer layer 20, preferably a polyimide layer, as illustrated in fig. Ic. The polyimide layer 20 may for instance be formed by spin coating the polyimide onto the structured surface 18. The polyimide layer 20 is so thick that it fills the voids in the underlying structured surface 18. In this way, the inverse of the structured surface 18 is formed on the bottom surface 22 of the polyimide layer 20. Further, the top surface 24 of the polyimide layer 20 opposite the carrier substrate 16 is made planar. The polyimide will generally become this planar when it is spin coated onto the structured surface 18. If necessary, the top surface 24 of the polyimide layer 20 may be further planarised after it has been applied to the carrier substrate 16. In the next step of the method, the deposited polyimide layer 20 functions as a substrate onto which an OLED unit 26 is processed (fig. Id). First, a barrier layer 28 is processed over the planar surface 24 of the polyimide 20. The barrier layer 28 may for instance be made of SiON which is refractive index matched with the rest of the device. Alternatively, an optically corrected NONON (SiliconNitride-SiliconOxide-SiliconNitride- SiliconOxide-SiliconNitride) stack may be used, as well as other barrier stacks. An OLED 30 is then processed onto the barrier layer 28, and after the fabrication of the OLED 30, the OLED 30 is encapsulated with a thin film packaging layer 32, for instance a NONON-stack as mentioned above. Finally, a topcoat 34 is applied over the packaging layer 32. Thereafter, electromagnetic radiation is applied. In this embodiment, the radiation is UV radiation, for instance from a laser. The UV radiation radiates through the UV transparent carrier substrate 16 as illustrated in fig. Ie, but not through the polyimide layer 20. Instead, the UV radiation is absorbed by the polyimide layer 20, whereby the interface between the carrier substrate 16 and the polyimide layer 20 burns and the carrier substrate 16 is released from the rest of the stack, leaving the OLED device 10 comprising the OLED unit 26 (and topcoat 34) and structured polyimide layer 20. Since polyimide is compatible with the UV release process, no dedicated release layer is necessary in this embodiment of the invention. Polyimide is also advantageous in that it has a refractive index (n∞l.6-1.8), which is similar, usually, to those of the other components in the device 10. This allows for an refractive index matched device, which in turn means that light typically not gets confined in some part of the device.

To increase the out-coupling efficiency of the OLED device (i.e. make sure that too much light is not confined in the device itself), the optical structure of the bottom surface 22 of the polyimide layer 20 is preferably an out-coupling structure, in which case the structure 14 prepared in the step illustrated in fig. Ib is the inverse of the desired out- coupling structure. By having a structured surface at the polyimide-air interface, more non- collimated light originating from the OLED will generally be extracted from the device compared to a case where the outer polyimide surface is planar. Hereto, various out-coupling structures are possible, for instance pyramids, small lenses, holes, etc. Further, in the present method the out-coupling structures can be nano- or micro sized. Further, the polyimide layer may be optically thin, allowing increased out-coupling.

The final device 10 may be flexible, in case a thin and/or flexible polymer layer and optoelectronic unit is used. The manufacturing can still be carried out as for a rigid device, since the rigid carrier substrate 16 gives stability and is only removed after the optoelectronic unit etc. has been processed.

For less flexible devices or rigid devices, an additional element 36 may optionally be applied on top of the coating 34, as illustrated in fig. If. In this case, the top coating 34 is preferably a glue. The additional element 36 may for instance be a glass or metal substrate, or a device e.g. a battery which can be used to power the OLED. The additional element 36 may be applied before or after the release step.

Also, especially in case the out-coupling structure is position dependent, i.e. it has to be aligned with the OLED for optical performance, the structured surface 18 of the carrier substrate 16 may comprise alignment structures (not shown). The alignment structure may for instance be a small alignment mark, such as a cross (top view). The alignment structures will be passed on to the layer 20, allowing easy alignment when processing the optoelectronic unit 26, since the processing equipment may sense the alignment structure and be positioned accordingly. Except for the above OLED device, various other optoelectronic devices can also advantageously be manufactured by the present method. In one example, the optoelectronic unit 26 may be a solar cell unit comprising an organic or inorganic photovoltaic cell. To increase the in-coupling efficiency of the solar cell device (i.e. make sure that as much light as possible enters the device), the optical structure of the bottom surface 22 of the layer 20 is preferably an in-coupling structure, in which case the structure 14 prepared in the step illustrated in fig. Ib is the inverse of the desired in-coupling structure. Various in-coupling structures are possible, for instance inverse pyramids, holes, hollow lenses, etc. Further, in the present method the in-coupling structures can be nano- or micro sized. Also, after the carrier substrate 16 has been released, the bottom surface 22 interfacing with the air may be coated with an anti-reflex layer (not shown), to further enhance the in- coupling of light to the device. Also, the above optional battery 36 may be charged by the photovoltaic cell.

In another example, the optoelectronic unit 26 may be an LCD unit comprising an LCD element. For e.g. 3D video, the optical structure of the bottom surface 22 of the layer 20 may be a light re-directing structure, in which case the optical structure 14 prepared in the step illustrated in fig. Ib should be the inverse of the desired light re-directing structure. The light-redirecting structure may for instance be adapted to change the beam shape of the light or to direct the light in a predetermined direction. Now turning to fig. 2, which is a schematic side view illustrating a stage of a method for the manufacturing of an optoelectronic device according to another embodiment of the present invention. The method of this embodiment is similar to the firstly described embodiment of fig. 1, but here a separate release layer 38 is used. The release layer 38 is applied over the structured surface 18 of the carrier substrate 16 before the layer 20 is deposited. Thus, in the stack the release layer 38 is interposed between the carrier substrate 16 and the layer 20, as in fig. 2, which illustrates the stack before the release process. The release layer 38 should be equally thick, conformal with the structured surface 18, whereby the transfer of the structure 14 of the carrier substrate 16 to the layer 20 is not significantly affected. The release layer 38 can be made of any material compatible with the UV release process. Hereto, one suitable material is amorphous silicon. During the release step, the release layer 38 reacts on the UV radiation, resulting in the separation of the carrier substrate 16 from the device 10. Thus, in this embodiment, the deposited layer 20 is not necessarily UV release compatible. It can for instance be made of sol-gel, BCB, etc. In a method for the manufacturing of an optoelectronic device according to yet another embodiment of the present invention, which otherwise is similar to the firstly described embodiment of fig. 1, scattering particles 40 are added to the polyimide layer 20. The scattering particles 40 may for instance be TiO or ZrO. Basically, the scattering particles 10 should not be absorbing and have a big difference in refractive index compared to the deposited polyimide layer 20, either higher or lower. The size of the scattering particles 40 can range from nano to micro scale. The scattering particles 40 (and any needed stabilizers) may for instance be added to the polymer solution before spin-coating, after which the total solution is spin-coated to form the on one side structured polyimide layer 20 with embedded scattering particles 40. The resulting device 10 is illustrated in fig. 3. In case of an OLED device, the scattering particles 40 scatters the light originating from the OLED, which in turn enhances the out-coupling due to the changing angles of the previously confined light.

When scattering particles 40 are embedded in the layer 20, the surface of the layer 20 interfacing with the air can be planar instead of structured, with maintained sufficient out-coupling efficiency. To this end, the above step of providing an optical structure on the planar glass plate can be omitted, which speeds up the manufacturing.

Instead, the layer 20 can be deposited directly onto the planar glass plate (no optical structure on the glass plate means no structuring on the overlying deposited substrate layer). Thus, the method according to this embodiment comprises the steps of: providing a substantially rigid carrier substrate having an essentially planar surface (e.g. the glass substrate 12); depositing a substrate (e.g. the polyimide or other polymer layer 20) over the planar surface of the carrier substrate, the deposited substrate comprising scattering particles 40; forming at least one optoelectronic unit (e.g. the OLED unit 26) on the deposited substrate opposite the carrier substrate; and releasing the deposited substrate and the at least one optoelectronic unit from the carrier substrate using radiation (for instance UV radiation from a laser) after forming the at least one optoelectronic unit. The release step of the present embodiment is illustrated in fig. 4.

The person skilled in the art realizes that the present invention by no means is limited to the preferred embodiments described above. On the contrary, many modifications and variations are possible within the scope of the appended claims. For instance, the sealing and packaging of the OLED in fig. 1 is provided as an example. Other or no sealing or packaging in the various optoelectronic units is envisaged. Also, various combinations of the above embodiments are possible. For instance, the scattering particles (figs. 3 and 4) can be combined with the separate release layer (fig. 2). Also, several optoelectronic devices can be manufactured on a single carrier substrate.

Claims

CLAIMS:

1. A method for the manufacturing of an optoelectronic device (10), the method comprising the steps of: providing a substantially rigid carrier substrate (16) having a structured surface (18); depositing a substrate (20) over the structured surface (18) of the carrier substrate (16) so that the inverse of the structured surface (18) is formed on the deposited substrate (20); forming at least one optoelectronic unit (26) on the deposited substrate (20) opposite the carrier substrate (16); and releasing the deposited substrate (20) and the at least one optoelectronic unit

(26) from the carrier substrate (16) using radiation after forming the at least one optoelectronic unit (26).

2. A method according to claim 1, wherein a surface (24) of the deposited substrate opposite the carrier substrate is essentially planar.

3. A method according to claim 1 or 2, wherein the deposited substrate is radiation release compatible.

4. A method according to claim 3, wherein the deposited substrate comprises polyimide.

5. A method according to claim 1 or 2, wherein a release layer having substantially uniform thickness is formed between the carrier substrate and the deposited substrate.

6. A method according to any one of the preceding claims, wherein the radiation is UV radiation, which UV radiation preferably is provided by a laser.

7. A method according to any one of the preceding claims, wherein the structured surface of the carrier substrate comprises the inverse of an out-coupling structure.

8. A method according to any one of the claims 1-6, wherein the structured surface of the carrier substrate comprises the inverse of an in-coupling structure.

9. A method according to claim 8, further comprising the step of providing, after the release step, an anti-reflex coating on the resulting in-coupling structure of the deposited substrate.

10. A method according to any one of the claims 1-6, wherein the structured surface of the carrier substrate comprises the inverse of a light-redirecting structure.

11. A method according to any one of the preceding claims, wherein each of the at least one optoelectronic unit comprises one of an OLED, a photovoltaic cell, an LCD element, and a organic sensor.

12. A method according to any one of the preceding claims, wherein the structured surface of the carrier substrate comprises alignment structures.

13. A method according to any one of the preceding claims, wherein the deposited substrate comprises scattering articles.

14. A method according to claim 13, wherein the substantially rigid carrier substrate having a structured surface is replaced by a substantially rigid carrier substrate having an essentially planar surface instead of the structured surface.

15. An optoelectronic device manufactured by a method according to any one of the claim 1-14.