Method for preparing Micro-LED light-emitting module through semitransparent metal bonding layer

Abstract

The invention discloses a method for preparing a Micro-LED light-emitting module through a semitransparent metal bonding layer. The method comprises the following steps: growing an epitaxial layer with light transmission on a substrate; depositing a semitransparent metal bonding layer on the whole surface of the epitaxial layer; preparing a metal bonding unit and a photoetching register mark on the driving substrate, wherein the metal bonding unit is arranged on the surface of a driving electrode of the driving substrate; bonding the semitransparent metal bonding layer and the metal bonding unit; removing the substrate; and carrying out photoetching and patterning treatment on the epitaxial layer and the semitransparent metal bonding layer according to the photoetching register mark, reserving the epitaxial layer and the semitransparent metal bonding layer at the positions corresponding to the metal bonding units, preparing a single Micro-LED pixel unit, and completing the preparation of the Micro-LED light-emitting module. According to the method for preparing the Micro-LED light-emitting module through the semitransparent metal bonding layer, not only can non-aligned bonding be achieved, but also the semitransparent metal bonding layer does not affect subsequent photoetching register, and the preparation efficiency and the yield of Micro-LED light-emitting module preparation are improved.

Description

Technical Field

[0001] The invention relates to the field of semiconductor display devices, and is a method for preparing a Micro-LED light-emitting module through a semi-transparent metal bonding layer. Background Art

[0002] Micro-LED light-emitting modules are composed of micron-sized LED chip arrays and driver circuits. They have the advantages of self-luminescence, high efficiency, low power consumption, high integration, high stability, and all-weather operation. They are considered to be one of the most promising next-generation new display and light-emitting devices. At present, there are two main process routes for preparing Micro-LED light-emitting modules.

[0003] The first process route: technology integrated through point-to-point bonding. The point-to-point bonding technology route is to first prepare metal units on the driver substrate and the chip respectively, and then use a precise bonding process to bond the metal units on the driver substrate and the chip. The point-to-point bonding integration technology has very high requirements for bonding accuracy. It not only requires high-precision and expensive alignment and bonding equipment, but also has a low bonding yield and low production efficiency.

[0004] The second process route: using point-to-surface bonding integration technology. In this process, point metal units are usually prepared on the driving substrate first, and a whole surface of metal for bonding is prepared on the epitaxial wafer. Subsequently, the driving substrate is directly bonded to the epitaxial wafer using a non-alignment process, and finally the epitaxial wafer is processed for pixel array. Compared with the first type of point-to-point bonding technology, the point-to-surface bonding technology does not require precise alignment and can directly achieve bonding, which significantly improves the bonding efficiency. However, this technology also has certain limitations. When the epitaxial wafer is processed for pixel array after bonding is completed, the lithography alignment points on the driving substrate cannot be seen, and the lithography alignment is difficult. This is a technical problem that needs to be solved urgently. Summary of the invention

[0005] Based on this, the present invention provides a method for preparing a Micro-LED light-emitting module through a semi-transparent metal bonding layer, which solves the problem of difficulty in lithography alignment in point-to-surface bonding integration technology.

[0006] A method for preparing a Micro-LED light-emitting module through a semi-transparent metal bonding layer comprises the following steps: S1, growing an epitaxial layer on a substrate, the epitaxial layer having light transmittance; S2, depositing a semi-transparent metal bonding layer on the entire surface of the epitaxial layer; S3, preparing a metal bonding unit and a photolithography alignment mark on the driving substrate, wherein the metal bonding unit is arranged on the surface of the driving electrode of the driving substrate; S4, bonding the semi-transparent metal bonding layer and the metal bonding unit; S5, removing the substrate; S6. Perform photolithography according to the photolithography plate markings, pattern the epitaxial layer and the semi-transparent metal bonding layer, retain the epitaxial layer and the semi-transparent metal bonding layer at the corresponding position of the metal bonding unit, prepare a single Micro-LED pixel unit, and complete the preparation of the Micro-LED light-emitting module.

[0007] Optionally, the material of the semi-transparent metal bonding layer is one or more combinations of Ni, Pt, and Au, and the thickness of the semi-transparent metal bonding layer ranges from 1 nm to 250 nm, including endpoint values.

[0008] Optionally, the thickness of the semi-transparent metal bonding layer ranges from 1 nm to 100 nm, including end points.

[0009] Optionally, the semi-transparent metal bonding layer and the epitaxial layer have a transmittance in the visible light range of 20%-90%, including end points.

[0010] Optionally, the metal bonding unit and the photolithography alignment mark are prepared simultaneously in the same process step.

[0011] Optionally, the material and thickness of the metal bonding unit and the photolithography alignment mark are the same, and the material of the metal bonding unit and the photolithography alignment mark is one or more combinations of Cr, Pt, Au, and Ni.

[0012] Optionally, the pixel size of the Micro-LED pixel unit is less than 5 microns, and the spacing between pixel units is less than 1 micron.

[0013] Optionally, the method for bonding the semi-transparent metal bonding layer and the metal bonding unit in step S4 is hot pressing bonding, and the hot pressing bonding conditions are: temperature of 250°C-400°C, pressure of 5MPa-100MPa, and time of 1000s-5000s, including endpoint values.

[0014] Optionally, the substrate is a silicon substrate, and removing the silicon substrate in step S5 includes the following two steps: S51, thinning the substrate to a thickness of less than 100 microns by mechanical grinding; S52, removing the silicon substrate by wet etching or dry etching process.

[0015] Optionally, the patterning of the epitaxial layer in step S6 includes the following three steps: S61, preparing a mask layer on the entire surface of the epitaxial layer; S62, performing plate registration photolithography according to the photolithography plate marking; S63, ICP etching the mask layer and the epitaxial layer between the metal bonding units, and finally removing the mask layer at the corresponding position of the metal bonding unit.

[0016] The present invention adopts a translucent metal bonding layer and a translucent epitaxial layer to prepare a Micro-LED light-emitting module. After the bonding is completed and the substrate is removed, the photolithography alignment marks on the driving substrate can be directly seen through the epitaxial layer and the translucent metal bonding layer. The epitaxial layer and the translucent metal bonding layer are directly patterned according to the photolithography alignment marks without opening a window. The process is simple and the production yield is improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 It is a schematic diagram of the corresponding cross-sectional structure after step S1 is completed in the embodiment of the present application.

[0018] Figure 2 It is a schematic diagram of the corresponding cross-sectional structure after step S2 in the embodiment of the present application is completed.

[0019] Figure 3 It is a schematic diagram of the corresponding cross-sectional structure after step S3 is completed in the embodiment of the present application.

[0020] Figure 4 It is a schematic diagram of the top view structure corresponding to the completion of step S3 in the embodiment of the present application.

[0021] Figure 5 It is a schematic diagram of the corresponding cross-sectional structure after step S4 is completed in the embodiment of the present application.

[0022] Figure 6 It is a schematic diagram of the corresponding cross-sectional structure after step S5 is completed in the embodiment of the present application.

[0023] Figure 7 Schematic diagram of the cross-sectional structure corresponding to the patterning of the epitaxial layer in step S6 in the embodiment of the present application.

[0024] Figure 8 Schematic diagram of the cross-sectional structure corresponding to the patterning process of the semi-transparent metal bonding layer in step S6 in the embodiment of the present application.

[0025] Reference numerals: substrate 100 , n-type GaN layer 200 , light-emitting quantum well layer 300 , p-type GaN layer 400 , semi-transparent metal bonding layer 500 , driving substrate 600 , driving electrode 700 , photolithography alignment mark 800 , metal bonding unit 900 . DETAILED DESCRIPTION

[0026] In order to make the technical problems, technical solutions and advantages to be solved by the present application clearer, a detailed description will be given below in conjunction with specific embodiments.

[0027] like Figure 1-8 The present application provides a method for preparing a Micro-LED light-emitting module through a semi-transparent metal bonding layer, comprising the following steps: S1, growing an epitaxial layer on a substrate, the epitaxial layer having light transmittance; S2, depositing a semi-transparent metal bonding layer on the entire surface of the epitaxial layer; S3, preparing a metal bonding unit and a photolithography alignment mark on the driving substrate, wherein the metal bonding unit is arranged on the surface of the driving electrode of the driving substrate; S4, bonding the semi-transparent metal bonding layer and the metal bonding unit; S5, removing the substrate; S6. Perform photolithography according to the photolithography plate markings, pattern the epitaxial layer and the semi-transparent metal bonding layer, retain the epitaxial layer and the semi-transparent metal bonding layer at the corresponding position of the metal bonding unit, prepare a single Micro-LED pixel unit, and complete the preparation of the Micro-LED light-emitting module.

[0028] It should be noted that the present application uses a translucent metal bonding layer and a translucent epitaxial layer to prepare a Micro-LED light-emitting module. After the bonding is completed and the substrate is removed, there is no need to open a lithography window. The lithography alignment marks on the driving substrate can be seen directly through the epitaxial layer and the translucent metal bonding layer. The epitaxial layer and the translucent metal bonding layer are directly patterned according to the lithography alignment marks. The process is simple and the production yield is improved.

[0029] In some embodiments of the present application, the material of the semi-transparent metal bonding layer is one or more combinations of Ni, Pt, and Au, and the thickness of the semi-transparent metal bonding layer ranges from 1nm to 250nm, and is exemplified by 1nm, 2nm, 10nm, 50nm, 100nm, 110nm, 150nm, 180nm, 200nm, 220nm, and 250nm, but is not limited thereto. With the selection of this material and thickness, the semi-transparent metal bonding layer has good light transmittance, and the photolithography alignment mark can be seen without opening a window in the subsequent process; and it has a certain bonding strength and good conductivity, which ensures the stability of subsequent bonding and improves the production yield.

[0030] In some embodiments of the present application, the thickness of the semi-transparent metal bonding layer ranges from 1nm to 100nm, exemplified by 1nm, 5nm, 10nm, 20nm, 30nm, 40nm, 50nm, 60nm, 70nm, 80nm, 90nm, and 100nm, but not limited thereto. Under the premise of ensuring bonding stability, further reducing the thickness of the semi-transparent metal bonding layer not only increases the light transmittance of the semi-transparent metal bonding layer and improves the accuracy of the plate lithography, but also enables the semi-transparent metal bonding layer to be quickly removed during subsequent patterning processing to avoid affecting other layers.

[0031] In some embodiments of the present application, the transmittance of the semi-transparent metal bonding layer and the epitaxial layer in the visible light range is 20%-90%, and exemplary examples are 20%, 30%, 40%, 45%, 50%, 60%, 70%, 80%, 90%, but not limited thereto. Within this range, the lithography machine can accurately identify the lithography alignment mark through the semi-transparent metal bonding layer and the epitaxial layer, thereby improving the lithography accuracy in step S6.

[0032] In some embodiments of the present application, the metal bonding unit and the photolithography alignment mark are prepared simultaneously in the same process step, which not only saves process steps but also improves the relative position accuracy of the metal bonding unit and the photolithography alignment mark, which is beneficial to the control of the patterning processing accuracy in step S6.

[0033] In some embodiments of the present application, a photolithography lift-off method is used to simultaneously prepare a metal bonding unit and a photolithography alignment mark.

[0034] In some embodiments of the present application, the metal bonding unit and the photolithography alignment mark have the same material and thickness, and the material of the metal bonding unit and the photolithography alignment mark is one or more combinations of Cr, Pt, Au, and Ni. The same material selection facilitates the preparation of the metal bonding unit and the photolithography alignment mark in the same process step.

[0035] In some embodiments of the present application, the pixel size of the Micro-LED pixel unit is less than 5 microns, and the interval between the pixel units is less than 1 micron.

[0036] In some embodiments of the present application, the method for bonding the semi-transparent metal bonding layer and the metal bonding unit in step S4 is hot pressing bonding, and the hot pressing bonding conditions are: temperature at 250°C-400°C, pressure at 5MPa-100MPa, and time at 1000s-5000s, including endpoint values. Since the thickness of the semi-transparent metal bonding layer is relatively thin, the process parameters need to be strictly controlled during bonding to improve the production yield.

[0037] In some embodiments of the present application, the substrate is a silicon substrate, and the removal of the silicon substrate in step S5 includes the following two steps: S51, mechanically grinding and thinning the thickness to less than 100 microns; S52, removing the silicon substrate by wet etching or dry etching. Since the substrate is removed after bonding with the drive substrate, in order to avoid damage to the drive substrate by removing the substrate, a silicon substrate that is easy to remove is selected, and a two-step process is used to remove the silicon substrate to protect the drive substrate to the maximum extent.

[0038] In some embodiments of the present application, patterning the epitaxial layer in step S6 includes the following three steps: S61, preparing a mask layer on the entire surface of the epitaxial layer; S62, performing plate registration photolithography according to the photolithography plate markings; S63, ICP etching the mask layer and the epitaxial layer between the metal bonding units, and finally removing the mask layer at the corresponding position of the metal bonding unit. Example 1

[0039] A method for preparing a Micro-LED light-emitting module by a semi-transparent metal bonding layer, comprising the following steps: Step S1, such as Figure 1 As shown, on a silicon substrate 100, a luminescent GaN epitaxial layer is grown by MOCVD epitaxial growth, and the GaN epitaxial layer is, from bottom to top, an n-type GaN layer 200, a luminescent quantum well layer 300, and a p-type GaN layer 400.

[0040] Step S2, such as Figure 2 As shown, a semi-transparent metal bonding layer 500 is deposited on the entire surface of the epitaxial layer. The material of the semi-transparent metal bonding layer 500 is Ni / Au, and the thicknesses of Ni and Au are 0.1 nm and 200 nm respectively.

[0041] Step S3, such as Figure 3 As shown, a metal bonding unit 900 and a photolithography alignment mark 800 are prepared on a driving substrate 600 by a photolithography stripping method. The metal bonding unit 900 is prepared on the surface of the driving electrode 700 of the driving substrate 600. The driving substrate 600 is a CMOS driving substrate. Figure 4 As shown, the surface of the metal bonding unit 900 is a square, the side length of the square is L=3 microns, and the interval d=1 micron of the metal bonding unit 900. The materials of the metal bonding unit 900 and the photolithography alignment mark 800 are Cr / Pt / Au, and the thicknesses of Cr, Pt, and Au are 30nm, 50nm, and 600nm respectively.

[0042] Step S4, using a bonding machine, the semi-transparent metal bonding layer 500 prepared in step S2 and the metal bonding unit 900 prepared in step S3 are bonded by hot pressing bonding. The hot pressing bonding conditions are: temperature at 250°C-400°C, pressure at 5MPa-100MPa, and time at 1000s-5000s. The cross-sectional structure after bonding is as follows: Figure 4 shown.

[0043] Step S5, after step S4 is completed, the silicon substrate 100 of the epitaxial wafer is firstly removed to within 100 microns by using a thinning machine, and then the remaining silicon substrate 100 is removed by using a mixed acid solution of HF, CH3COOH and HNO3. The cross-sectional structure after removing the silicon substrate is as follows: Figure 5 shown.

[0044] Step S6, after step S5 is completed, the epitaxial layer is patterned first: first, a 1100nm SiO2 mask layer is grown on the epitaxial wafer, and then 5312 positive photoresist is spin-coated on the surface of the SiO2 mask layer for development and lithography. During lithography, the plate is aligned according to the lithography alignment mark 800, and the development pattern is set to a square, which corresponds one-to-one with the metal bonding unit 900, and has the same shape, size and spacing. The development and lithography only retains the 5312 positive photoresist above the metal bonding unit 900. Finally, ICP is used to etch the SiO2 mask layer in the area not covered by the 5312 positive photoresist, and then continue to etch through the p-type GaN layer 400, the light-emitting quantum well layer 300, and the n-type GaN layer 200. After ICP etching, the 5312 positive photoresist is removed by soaking in a stripping solution, and then soaked in a BOE solution for 60 seconds to remove the SiO2 mask layer below the area covered by the 5312 positive photoresist. The cross-sectional structure of the epitaxial layer after patterning is as follows. Figure 6 As shown, only the epitaxial layer above the metal bonding unit 900 is retained.

[0045] After the epitaxial layer is patterned, the semi-transparent metal bonding layer 500 is patterned by wet etching. The cross-sectional structure of the semi-transparent metal bonding layer 500 after patterning is as follows: Figure 7 As shown. Only the epitaxial layer and the semi-transparent metal bonding layer 500 at the corresponding position of the metal bonding unit 900 are retained to prepare a single Micro-LED pixel unit, and the preparation of the Micro-LED light-emitting module is completed. The shape of each Micro-LED pixel unit is the same as the shape of the metal bonding unit 900, the pixel size of each Micro-LED pixel unit is L=3 microns, and the interval between the pixel units is d=1 micron. Example 2

[0046] A method for preparing a Micro-LED light-emitting module by a semi-transparent metal bonding layer, comprising the following steps: Step S1, such as Figure 1 As shown, on a silicon substrate 100, a luminescent GaN epitaxial layer is grown by MOCVD epitaxial growth, and the GaN epitaxial layer is, from bottom to top, an n-type GaN layer 200, a luminescent quantum well layer 300, and a p-type GaN layer 400.

[0047] Step S2, such as Figure 2 As shown, a semi-transparent metal bonding layer 500 is deposited on the entire surface of the epitaxial layer. The material of the semi-transparent metal bonding layer 500 is Pt, and the thickness of Pt is 50 nm.

[0048] Step S3, such as Figure 3As shown, a metal bonding unit 900 and a photolithography alignment mark 800 are prepared on a driving substrate 600 by a photolithography stripping method. The metal bonding unit 900 is prepared on the surface of the driving electrode 700 of the driving substrate 600. The driving substrate 600 is an A driving substrate. Figure 4 As shown, the surface of the metal bonding unit 900 is a square, the side length of the square is L=3 microns, and the interval d=1 micron of the metal bonding unit 900. The material of the metal bonding unit 900 and the photolithography alignment mark 800 is Cr / Pt / Ni, and the thickness of Cr, Pt, and Ni are 30nm, 50nm, and 100nm respectively.

[0049] Step S4, using a bonding machine, the semi-transparent metal bonding layer 500 prepared in step S2 and the metal bonding unit 900 prepared in step S3 are bonded by hot pressing bonding. The hot pressing bonding conditions are: temperature at 250°C-400°C, pressure at 5MPa-100MPa, and time at 1000s-5000s. The cross-sectional structure after bonding is as follows: Figure 4 shown.

[0050] Step S5, after step S4 is completed, the silicon substrate 100 of the epitaxial wafer is firstly removed to within 100 microns by using a thinning machine, and then the remaining silicon substrate 100 is removed by using a mixed acid solution of HF, CH3COOH and HNO3. The cross-sectional structure after removing the silicon substrate is as follows: Figure 5 shown.

[0051] Step S6, after step S5 is completed, first grow a 1100nm SiO2 mask layer on the epitaxial wafer, and then spin-coat a 5312 positive photoresist on the surface of the SiO2 mask layer for development photolithography. During photolithography, the photolithography alignment mark 800 is used for alignment, and the development pattern is set to a square, which corresponds to the metal bonding unit 900 one by one, and the shape, size and spacing are the same. The development photolithography only retains the 5312 positive photoresist above the metal bonding unit 900. Finally, use ICP to etch the SiO2 mask layer in the area not covered by the 5312 positive photoresist, and then continue to etch through the p-type GaN layer 400, the light-emitting quantum well layer 300, the n-type GaN layer 200 and the semi-transparent metal bonding layer 500. After ICP etching, the 5312 positive photoresist is removed by soaking the glue solution, and then soaking the BOE solution for 60 seconds to remove the SiO2 mask layer below the 5312 positive photoresist coverage area. The cross-sectional structure after patterning the epitaxial layer and the semi-transparent metal bonding layer 500 is as follows: Figure 7As shown, only the epitaxial layer and the semi-transparent metal bonding layer 500 at the corresponding position of the metal bonding unit 900 are retained to prepare a single Micro-LED pixel unit, thereby completing the preparation of the Micro-LED light-emitting module. The shape of each Micro-LED pixel unit is the same as the shape of the metal bonding unit 900, the pixel size of each Micro-LED pixel unit is L=3 microns, and the interval between the pixel units is d=1 micron.

[0052] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for preparing a Micro-LED light-emitting module by a semi-transparent metal bonding layer, characterized in that: The method comprises the following steps: S1. growing an epitaxial layer on a substrate, wherein the epitaxial layer has light transmittance; S2, depositing a semi-transparent metal bonding layer on the entire surface of the epitaxial layer; S3, preparing a metal bonding unit and a photolithography alignment mark on the driving substrate, wherein the metal bonding unit is arranged on the surface of the driving electrode of the driving substrate; S4, bonding the semi-transparent metal bonding layer and the metal bonding unit; S5, removing the substrate; S6. Perform photolithography according to the photolithography plate markings, pattern the epitaxial layer and the semi-transparent metal bonding layer, retain the epitaxial layer and the semi-transparent metal bonding layer at the corresponding position of the metal bonding unit, prepare a single Micro-LED pixel unit, and complete the preparation of the Micro-LED light-emitting module.

2. The method according to claim 1, characterized in that: The material of the semi-transparent metal bonding layer is one or more combinations of Ni, Pt, and Au, and the thickness of the semi-transparent metal bonding layer ranges from 1 nm to 250 nm, including endpoint values.

3. The method according to claim 1, characterized in that: The thickness of the semi-transparent metal bonding layer ranges from 1 nm to 100 nm, including end points.

4. The method according to claim 1, characterized in that: The semi-transparent metal bonding layer and the epitaxial layer have a light transmittance in the visible light range of 20%-90%, including end points.

5. The method according to claim 1, characterized in that: The metal bonding unit and the photolithography alignment mark are prepared simultaneously in the same process step.

6. The method according to claim 1, characterized in that: The metal bonding unit and the photolithography alignment mark have the same material and thickness, and the material of the metal bonding unit and the photolithography alignment mark is one or more combinations of Cr, Pt, Au, and Ni.

7. The method according to claim 1, characterized in that: The pixel size of the Micro-LED pixel unit is less than 5 microns, and the interval between pixel units is less than 1 micron.

8. The method according to claim 2 or 3, characterized in that: In step S4, the method for bonding the semi-transparent metal bonding layer and the metal bonding unit is hot pressing bonding, and the hot pressing bonding conditions are: temperature at 250°C-400°C, pressure at 5MPa-100MPa, and time at 1000s-5000s, including endpoint values.

9. The method according to claim 1, characterized in that: The substrate is a silicon substrate. Removing the silicon substrate in step S5 includes the following two steps: S51, thinning the silicon substrate to a thickness of less than 100 microns by mechanical grinding; S52, removing the silicon substrate by wet etching or dry etching process.

10. The method according to claim 1, characterized in that: The patterning process of the epitaxial layer in step S6 includes the following three steps: S61, preparing a mask layer on the entire surface of the epitaxial layer; S62, performing plate alignment photolithography according to the photolithography plate alignment mark; S63, ICP etching the mask layer and the epitaxial layer between the metal bonding units, and finally removing the mask layer at the corresponding position of the metal bonding unit.

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