Method of manufacturing an electroluminescent device
The method addresses pixel degradation and etching stoppages in electroluminescent device manufacturing by using directional and selective chemical etching techniques, ensuring effective protection of the pixels and consistent etching processes even with thick dielectric layers.
Patent Information
- Application Number
- FR2023007326
- Authority / Receiving Office
- FR · FR
- Patent Type
- Patents
- Current Assignee / Owner
- Filing Date
- 2023-07-09
- Publication Date
- 2025-05-23
- Estimated Expiration
- 2043-07-09
AI Technical Summary
Existing methods for manufacturing electroluminescent devices, particularly nanofiber-based electroluminescent diodes made of gallium nitride, face issues such as pixel degradation due to ionized gas bombardment and etching stoppages caused by variations in plasma composition during dielectric layer etching.
A method involving directional etching along the normal to the substrate surface of a portion of the dielectric layer between pixels, followed by selective chemical etching using a chemical agent that preferentially etches the dielectric layer relative to the encapsulation layer, thereby protecting the pixels and avoiding etching stoppages.
This method effectively protects the columnar pixels from degradation and overcomes etching stoppage issues, especially when the dielectric layer is thick, by selectively etching the dielectric layer without significantly affecting the upper parts of the pixels.
Smart Images
Figure 00000012_0000 
Figure 00000012_0001 
Figure 00000013_0000
Abstract
Description
Title of the invention: Method for manufacturing an electroluminescent device Technical field
[0001] The invention relates to the technical field of manufacturing electroluminescent devices.
[0002] The invention finds particular application in the manufacture of nanofiber-based electroluminescent diodes, in particular made of gallium nitride GaN. State of the art
[0003] A method for manufacturing an electroluminescent device, known from the state of the art, comprises the steps: A) using a stack successively comprising: - a substrate, having a surface; - pixel matrices, formed on the surface of the substrate, the pixels having a columnar shape extending along the normal to the surface of the substrate; - an encapsulation layer, arranged to cover the pixel matrices; - a dielectric layer, formed on the encapsulation layer; B) perform plasma etching of the dielectric layer; C) forming a colored resin on the encapsulation layer at the end of step B), the colored resin being suitable for filtering an emission spectrum of an underlying pixel.
[0004] The encapsulation layer can be made of silicon nitride Si3N4. The dielectric layer is generally made of silicon dioxide SiO2.
[0005] Such a method of the state of the art is not entirely satisfactory insofar as the strong bombardment of ionized gas in step B) is likely to cause significant degradation of the pixels. This degradation is all the more marked as the form factor (ratio between the height and the width of the pixels) of the pixels is high. It has been observed experimentally that the upper part of the pixels can become beveled at the end of step B).
[0006] Furthermore, when the dielectric layer is made of silicon dioxide SiO2, step B) is conventionally carried out with a fluorine plasma, such as a carbon tetrafluoride CF4 plasma. However, the etching depth depends strongly on the carbon / fluorine ratio of the plasma. A variation in the relative surface area of the carbon mask can cause an etch stop, this unwanted phenomenon being all the more marked as the thickness of the dielectric layer to be etched is significant. Statement of the invention
[0007] The invention aims to remedy all or part of the aforementioned drawbacks. To this end, the invention relates to a method for manufacturing an electroluminescent device, comprising the steps: a) use a stack comprising successively: - a substrate, having a surface; - pixel matrices, formed on the surface of the substrate, the pixels having a columnar shape extending along the normal to the surface of the substrate; - an encapsulation layer, arranged to cover the pixel matrices; - a dielectric layer, formed on the encapsulation layer; b) performing a directional etching, along the normal to the surface of the substrate, of a portion of the dielectric layer extending between the pixels of the pixel matrices; the dielectric layer having a remaining portion at the end of step b); c) performing selective chemical etching of the remaining part of the dielectric layer; step c) being carried out with a chemical etching agent allowing selective etching of the remaining part of the dielectric layer relative to the encapsulation layer.
[0008] Thus, such a method according to the invention makes it possible to better protect the columnar pixels compared to the state of the art, thanks to steps b) and c). Indeed, the directional etching (e.g. plasma) carried out during step b) only concerns inter-pixel zones. The upper part of the pixels is preserved from possible strong ionized bombardment, because the part of the dielectric layer overhanging the upper part of the pixels is not etched during step b). The selective chemical etching carried out during step c) makes it possible to etch the remaining part of the dielectric layer without significantly affecting the upper part of the pixels, unlike ionized gas bombardment.
[0009] Furthermore, the selective chemical etching carried out during step c) makes it possible to overcome the etching stoppage problems of the prior art, linked to plasma etching, when the dielectric layer has a high thickness (eg 8 μm to 10 μm).
[0010] The method according to the invention may comprise one or more of the following characteristics.
[0011] According to a characteristic of the invention, the method comprises a step d) of forming at least one colored resin on the encapsulation layer at the end of step c), said at least one colored resin being suitable for filtering an emission spectrum of an underlying pixel.
[0012] According to a characteristic of the invention: - step b) is performed with a photolithography mask having patterns arranged to face the pixels of the pixel matrices; - step c) is preceded by a step c0) of removing the photolithography mask.
[0013] Thus, an advantage provided is to protect the upper part of the pixels during step b). The part of the dielectric layer overhanging the upper part of the pixels is not etched during step b), thanks to the photolithography mask having patterns arranged to face the pixels of the pixel matrices.
[0014] According to a characteristic of the invention, step b) is preceded by the steps: bOi) forming a trench between adjacent pixel matrices, having a bottom wall and side walls; b02) depositing a barrier layer on the bottom wall and on the side walls, the barrier layer being made of a material chosen according to the chemical etching agent with which step c) is carried out, so as to obtain an etching stop layer when step c) is carried out.
[0015] Thus, an advantage provided by a trench formed between two adjacent pixel matrices is to limit the effects of crosstalk. In addition, the barrier layer allows better control of the extent of the selective (isotropic) chemical etching carried out during step c).
[0016] According to a characteristic of the invention, the chemical etching agent with which step c) is carried out is hydrofluoric acid HF in the vapor phase.
[0017] Thus, an advantage provided by hydrofluoric acid HF in the vapor phase is to be compatible, in terms of etching selectivity, with several materials, notably aluminum Al, alumina A12O3, aluminum nitride AIN, which allows a greater choice than wet etching for the materials of the barrier layer and the encapsulation layer.
[0018] According to a characteristic of the invention, the barrier layer deposited during step b02) is made of at least one material chosen from aluminum Al, alumina Al2O3, aluminum nitride AlN.
[0019] According to a characteristic of the invention, step b) is preceded by a step b03) of filling the tungsten trench W at the end of step b02).
[0020] Thus, an advantage provided is to reinforce the mechanical strength of the trenches.
[0021] According to a characteristic of the invention, step b) is preceded by an initial directional etching, along the normal to the surface of the substrate, of a superficial part of the dielectric layer so as to reach a position of the stack located above the pixels of the pixel matrices, at a distance from the encapsulation layer.
[0022] Thus, an advantage provided is to limit the operating time of the selective chemical etching carried out during step c), the superficial part of the dielectric layer being already etched beforehand. Of course, the position reached at the end of the initial directional etching (e.g. plasma etching) must be sufficiently far from the encapsulation layer so as not to damage the upper part of the pixels. by the strong bombardment of ionized gas.
[0023] According to a characteristic of the invention, the encapsulation layer of the stack used during step a) is made of at least one material chosen from aluminum Al, alumina Al2O3, aluminum nitride AlN.
[0024] According to a characteristic of the invention, the dielectric layer of the stack used during step a) is made of silicon dioxide SiO2.
[0025] Definitions
[0026] - By “substrate” is meant a self-supporting physical support, made of a material base material from which a light-emitting device can be formed. A substrate can be a "wafer," also called a "platelet," which is generally in the form of a disc cut from an ingot of a crystalline material.
[0027] - By “pixels” we mean light-emitting (emissive) cells.
[0028] - By "columnar shape" we mean that the pixels each have a factor of aspect ratio strictly greater than 1, preferably strictly greater than 2, more preferably strictly greater than 3. The aspect ratio is the ratio between the height (i.e. thickness) of the pixel and its width. The height (thickness) of the pixel is its dimension along the normal to the surface of the substrate. An example of structures with such a columnar shape can be a nanowire.
[0029] - By "successively", we mean that the elements of the stack are arranged on top of each other in a defined order from bottom to top under normal conditions of use, i.e. following the normal to the surface of the substrate in general.
[0030] - By "layer" is meant a single layer or a plurality of sub-layers of same nature.
[0031] - By "directional etching" is meant an anisotropic etching carried out on a preferred direction, in this case following the normal to the surface of the substrate.
[0032] - By "selective etching" is meant that the remaining part of the dielectric layer can be etched without attacking the encapsulation layer. In practice, the etchant is generally chosen so that the etching rate of the remaining part of the dielectric layer is at least 3 times higher (preferably at least 5 times higher, more preferably at least 10 times higher) than the etching rate of the encapsulation layer. Brief description of the drawings
[0033] Other characteristics and advantages will appear in the detailed description of different embodiments of the invention, the description being accompanied by examples and references to the attached drawings.
[0034] [Fig.l] is a schematic sectional view, illustrating step a) of a method according to the invention.
[0035] [Fig.2] is a schematic sectional view, illustrating step bOi) of a method according to the invention.
[0036] [Fig.3] is a schematic sectional view, illustrating step b02) of a method according to the invention.
[0037] [Fig.4] is a schematic sectional view, illustrating the application of a mask of photolithography for etching the barrier layer.
[0038] [Fig.5] is a schematic sectional view, illustrating the etching of the barrier layer.
[0039] [Fig.6] is a schematic sectional view illustrating the removal of the photolithographic mask. thography illustrated in [Fig.4].
[0040] [Fig.7] is a schematic sectional view, illustrating the application of a mask of photolithography for the directional etching of step b) of a method according to the invention.
[0041] [Fig.8] is a schematic sectional view, illustrating the directional engraving of step b) of a method according to the invention.
[0042] [Fig.9] is a schematic sectional view, illustrating step c0) of removing the mask photolithography shown in [Fig.7].
[0043] [Fig. 10] is a schematic sectional view, illustrating the selective chemical etching of step c) of a method according to the invention.
[0044] [Fig. 11] is a schematic sectional view illustrating an initial directional etching of a surface portion of the dielectric layer that can be performed before step b).
[0045] [Fig. 12] is a schematic sectional view, illustrating step d) of a method according to the invention.
[0046] [Fig. 13] is a schematic sectional view, illustrating step b03) of a method according to the invention.
[0047] It should be noted that the drawings described above are schematic, and are not necessarily to scale for the sake of readability and to simplify their understanding. The sections are made along the normal to the surface of the substrate. Detailed description of the implementation methods
[0048] Elements that are identical or provide the same function will bear the same references for the different embodiments, for the sake of simplification.
[0049] An object of the invention is a method of manufacturing an electroluminescent device, comprising the steps: a) use a stack comprising successively: - a substrate 1, having a surface 10; - pixel matrices 2, formed on the surface 10 of the substrate 1, the pixels 2 having a columnar shape extending along the normal to the surface 10 of the substrate 1; - an encapsulation layer 3, arranged to cover the pixel matrices 2; - a dielectric layer 4, formed on the encapsulation layer 3; b) performing a directional etching, along the normal to the surface 10 of the substrate 1, of a part of the dielectric layer 4 extending between the pixels 2 of the pixel matrices 2; the dielectric layer 4 having a remaining part 40 at the end of step b); c) performing selective chemical etching of the remaining part 40 of the dielectric layer 4; step c) being carried out with a chemical etching agent allowing selective etching of the remaining part 40 of the dielectric layer 4 relative to the encapsulation layer 3.
[0050] Step a)
[0051] The stack used during step a) successively comprises: - a substrate 1, having a surface 10; - pixel matrices 2, formed on the surface 10 of the substrate 1, the pixels 2 having a columnar shape extending along the normal to the surface 10 of the substrate 1; - an encapsulation layer 3, arranged to cover the pixel matrices 2; - a dielectric layer 4, formed on the encapsulation layer 3.
[0052] The substrate 1 is advantageously made of a semiconductor material. By way of non-limiting example, the substrate 1 may be made of silicon Si.
[0053] By way of non-limiting example, the pixels 2 may be nanowires, in particular made of gallium nitride GaN. The pixels 2 advantageously form periodic patterns.
[0054] The encapsulation layer 3 of the stack used during step a) is advantageously made of at least one material chosen from aluminum Al, alumina Al2O3, aluminum nitride AlN. By "at least one material", it is meant that the encapsulation layer 3 can be made of a multilayer material comprising at least one material chosen from aluminum Al, alumina Al2O3, aluminum nitride AlN. The encapsulation layer 3 of the stack used during step a) can have a thickness of the order of 1 μm.
[0055] The dielectric layer 4 of the stack used during step a) is advantageously made of silicon dioxide SiO2. The dielectric layer 4 of the stack used during step a) may have a thickness of between 8 μm and 10 μm.
[0056] Step b)
[0057] The directional etching carried out during step b) is a directional etching, along the normal to the surface 10 of the substrate 1, of a part of the dielectric layer 4 extending between the pixels 2 of the pixel matrices 2.
[0058] By way of non-limiting example, the directional etching carried out during step b) is a dry plasma etching. When the dielectric layer 4 is made of silicon dioxide, step b) can be carried out with a fluorinated plasma, such as a carbon tetrafluoride CF4 plasma.
[0059] Step b) is advantageously carried out with a photolithography mask M1 having patterns arranged to face the pixels 2 of the pixel matrices 2. In other words, the patterns of the photolithography mask M1 overhang the pixels 2 of the pixel matrices 2.
[0060] The dielectric layer 4 has a remaining portion 40 at the end of step b). The remaining portion 40 of the dielectric layer 4 extends under the patterns of the photolithography mask M1.
[0061] Step b) is advantageously preceded by the steps: bOi) forming a trench 5 between the adjacent pixel matrices 2, having a bottom wall 50 and side walls 51; bta) depositing a barrier layer 6 on the bottom wall 50 and on the side walls 51, the barrier layer 6 being made of a material chosen according to the chemical etching agent with which step c) is carried out, so as to obtain an etching stop layer when step c) is carried out.
[0062] The side walls 51 of the trench 5 are formed by the dielectric layer 4. The bottom wall 50 of the trench 5 is formed by the surface 10 of the substrate 1. As a non-limiting example, step bOi) can be carried out by dry plasma etching. When the dielectric layer 4 is made of silicon dioxide SiO2, step bOi) can comprise etching by a C4F8 plasma. Step bOi) can comprise etching of the encapsulation layer 3, for example by a chlorine plasma (eg Cl2 or BC13) when the encapsulation layer 3 is made of aluminum Al or alumina A12O3. Step bOi) is advantageously carried out by directional etching along the normal to the surface 10 of the substrate 1.
[0063] Step b02) is performed by a deposition technique allowing the barrier layer 6 to follow the surface topology of the stack. It is not strictly necessary for the deposition technique to produce a conformal deposition (conformity rate equal to 100%). In other words, the deposition technique is chosen to have a conformity rate (ratio between the width of the sides of the deposited barrier layer 6 and the surface thickness of the deposited barrier layer 6) allowing the surface topology of the stack to be followed. As non-limiting examples, the barrier layer 6 may be formed during step b02) by chemical vapor deposition or by atomic layer deposition (ALD for “Atomic Layer Deposition” in English language), these filing techniques having a good compliance rate.
[0064] The barrier layer 6 deposited during step b02) is advantageously made of at least one material chosen from aluminum Al, alumina Al2O3, aluminum nitride AlN. By "at least one material", it is meant that the barrier layer 6 can be made of a multilayer material comprising at least one material chosen from aluminum Al, alumina Al2O3, aluminum nitride AlN.
[0065] In order to prepare the directional etching of step b), a portion of the barrier layer 6 (extending between the trenches 5) is etched using a photolithography MO mask whose patterns cover the trenches 5. The photolithography MO mask may be a photosensitive resin which is then removed from the stack by a removal technique (“stripping” in English).
[0066] Step b) is advantageously preceded by a step b03) of filling the trench 5 with a material 52 of tungsten W type at the end of step b02). Step b03) is advantageously followed by a step of chemical-mechanical polishing so that the material 52 of tungsten W type is flush with the stack.
[0067] Step b) is advantageously preceded by an initial directional etching, along the normal to the surface 10 of the substrate 1, of a superficial part of the dielectric layer 4 so as to reach a position P of the stack located above the pixels 2 of the pixel matrices 2, at a distance D from the encapsulation layer 3. The position P reached at the end of the initial directional etching (e.g. dry plasma etching) must be at a sufficiently large distance D from the encapsulation layer 3 so as not to damage the upper part of the pixels 2 by the strong bombardment of ionized gas. As a non-limiting example, the distance D may be of the order of a hundred nanometers. More precisely, it is possible to consider a distance D greater than or equal to 100 nm with an etching uniformity of the order of 3%.
[0068] Step c)
[0069] The selective chemical etching carried out during step c) is a selective chemical etching of the remaining portion 40 of the dielectric layer 4. As illustrated in [Fig. 10], the selective chemical etching carried out during step c) is an isotropic etching, but may not be total in the sense that certain portions 400 of the remaining portion 40 of the dielectric layer 4 (in particular at the ends of the pixel matrices 2) may remain at the end of step c). However, in practice, the selective chemical etching carried out during step c) may be total or almost total in the sense that all or almost all of the remaining portion 40 of the dielectric layer 4 is removed at the end of step c).
[0070] Step c) is carried out with a chemical etching agent allowing selective etching of the remaining part 40 of the dielectric layer 4 relative to the layer encapsulation 3. The chemical etching agent with which step c) is carried out is advantageously hydrofluoric acid HF in vapor phase.
[0071] Step c) is advantageously preceded by a step c0) of removing the photolithography mask M1 with which step b) can be carried out. The photolithography mask M1 can be a photosensitive resin which is removed from the stack during step c0) by a removal technique (“stripping” in English).
[0072] Step d)
[0073] The method advantageously comprises a step d) of forming at least one colored resin 7 on the encapsulation layer 3 at the end of step c). Said at least one colored resin 7 is adapted to filter an emission spectrum of an underlying pixel 2.
[0074] Said at least one colored resin 7 may be a resin of the polymer matrix type with quantum wells (“quantum dot” in English). Said at least one colored resin 7 may be a resin with pigments capable of acting as a colored filter.
[0075] The invention is not limited to the embodiments disclosed. Those skilled in the art are able to consider their technically effective combinations and to substitute equivalents for them.
Claims
Claims
1. A method of manufacturing a light-emitting device, comprising the steps of: a) using a stack successively comprising: - a substrate (1), having a surface (10); - pixel matrices (2), formed on the surface (10) of the substrate (1), the pixels (2) having a columnar shape extending along the normal to the surface (10) of the substrate (1); - an encapsulation layer (3), arranged to cover the pixel matrices (2); - a dielectric layer (4), formed on the encapsulation layer (3); b) performing a directional etching, along the normal to the surface (10) of the substrate (1), of a portion of the dielectric layer (4) extending between the pixels (2) of the pixel matrices (2); the dielectric layer (4) having a remaining portion (40) at the end of step b); c) performing selective chemical etching of the remaining part (40) of the dielectric layer (4);step c) being carried out with a chemical etching agent allowing selective etching of the remaining part (40) of the dielectric layer (4) relative to the encapsulation layer (3).;
2. Method according to claim 1, comprising a step d) of forming at least one colored resin (7) on the encapsulation layer (3) at the end of step c), said at least one colored resin (7) being adapted to filter an emission spectrum of an underlying pixel (2).
3. Method according to claim 1 or 2, wherein: - step b) is carried out with a photolithography mask (Ml) having patterns arranged to face the pixels (2) of the pixel matrices (2); - step c) is preceded by a step c0) of removing the photolithography mask (Ml).
4. Method according to one of claims 1 to 3, in which step b) is preceded by the steps: b0i) forming a trench (5) between the adjacent pixel matrices (2), having a bottom wall (50) and side walls (51); b02) depositing a barrier layer (6) on the bottom wall (50) and on the side walls (51), the barrier layer (6) being made of a material chosen according to the chemical etching agent with which step c) is performed so as to obtain an etching stop layer when step c) is performed.
5. Method according to one of claims 1 to 4, in which the chemical etching agent with which step c) is carried out is hydrofluoric acid HF in the vapor phase.
6. Method according to claim 5 in combination with claim 4, in which the barrier layer (6) deposited during step b02) is made of at least one material chosen from aluminum Al, alumina Al2O3, aluminum nitride AlN.
7. Method according to claim 5 in combination with claim 4, or according to claim 6, in which step b) is preceded by a step b03) of filling the trench (5) with tungsten W at the end of step b02).
8. Method according to one of claims 1 to 7, step b) is preceded by an initial directional etching, along the normal to the surface (10) of the substrate (1), of a superficial part of the dielectric layer (4) so as to reach a position (P) of the stack located above the pixels (2) of the pixel matrices (2), at a distance (D) from the encapsulation layer (3).
9. Method according to one of claims 1 to 8, in which the encapsulation layer (3) of the stack used during step a) is made of at least one material chosen from aluminum Al, alumina A12O 3, aluminum nitride AIN.
10. Method according to one of claims 1 to 9, in which the dielectric layer (4) of the stack used during step a) is made of silicon dioxide SiO2.