A method for preparing a micro-LED light-emitting module through a semi-transparent metal bonding layer

Abstract

The application discloses a method for preparing a Micro-LED light-emitting module through a translucent metal bonding layer, and comprises the following steps: growing an epitaxial layer with light transmission on a substrate; depositing a translucent metal bonding layer on the epitaxial layer; preparing a metal bonding unit and a photoetching counterpart mark on a driving substrate, wherein the metal bonding unit is arranged on the surface of a driving electrode of the driving substrate; bonding the translucent metal bonding layer and the metal bonding unit; removing the substrate; photoetching according to the photoetching counterpart mark, patterning the epitaxial layer and the translucent metal bonding layer, retaining the epitaxial layer and the translucent metal bonding layer at the corresponding position of the metal bonding unit, preparing a single Micro-LED pixel unit, and completing the preparation of the Micro-LED light-emitting module. The method for preparing the Micro-LED light-emitting module through the translucent metal bonding layer can realize non-alignment bonding, the translucent metal bonding layer does not affect subsequent photoetching counterpart, and the preparation efficiency and yield of the Micro-LED light-emitting module preparation are improved.

Description

Technical Field

[0001] This invention relates to the field of semiconductor display devices, and to a method for fabricating a Micro-LED light-emitting module using a semi-transparent metal bonding layer. Background Technology

[0002] Micro-LED light-emitting modules are composed of micrometer-sized LED chip arrays integrated with driving circuits. They possess advantages such as self-illumination, high efficiency, low power consumption, high integration, high stability, and all-weather operation, and are considered one of the most promising next-generation display and light-emitting devices. Currently, there are two main types of fabrication processes for Micro-LED light-emitting modules.

[0003] The first type of process route involves point-to-point bonding integration. This route first fabricates metal units on both the driver substrate and the chip, then uses a precise bonding process to bond the metal units on both surfaces. Point-to-point bonding integration requires very high bonding precision, necessitating not only high-precision and expensive alignment and bonding equipment, but also resulting in low bonding yield and low production efficiency.

[0004] The second process route employs point-to-surface bonding integration technology. In this process, point metal units are typically fabricated on the driving substrate, while a full-surface metal layer for bonding is fabricated on the epitaxial wafer. Subsequently, a non-aligned process is used to directly bond the driving substrate and the epitaxial wafer, and finally, pixel array processing is performed on the epitaxial wafer. Compared to the first type of point-to-point bonding technology, point-to-surface bonding technology does not require precise alignment and can directly achieve bonding, significantly improving bonding efficiency. However, this technology also has certain limitations. When performing pixel array processing on the epitaxial wafer after bonding, the photolithographic alignment points on the driving substrate cannot be seen, making photolithographic alignment difficult, which is a technical problem that urgently needs to be solved. Summary of the Invention

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

[0006] A method for fabricating a Micro-LED light-emitting module using a semi-transparent metal bonding layer includes the following steps: S1. An epitaxial layer is grown on the substrate, and the epitaxial layer is transparent; S2. Deposit a semi-transparent metallic bonding layer across the entire surface of the epitaxial layer; S3. Prepare metal bonding units and photolithographic alignment marks on the driving substrate. The metal bonding units are disposed on the surface of the driving electrode of the driving substrate. S4, bonding a semi-transparent metal bonding layer and metal bonding units; S5, Remove substrate; S6. Perform photolithography according to the photolithography 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 positions of the metal bonding units, and prepare a single Micro-LED pixel unit to 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 the endpoint values.

[0008] Optionally, the thickness of the translucent metallic bonding layer ranges from 1 nm to 100 nm, including the endpoint values.

[0009] Optionally, the translucent metallic bonding layer and epitaxial layer have a transmittance range of 20%-90% in the visible light range, including endpoint values.

[0010] Optionally, the metal bonding unit and the photolithographic alignment mark can be fabricated simultaneously in the same process step.

[0011] Optionally, the metal bonding unit and the photolithographic alignment mark are made of the same material and have the same thickness, and the material of the metal bonding unit and the photolithographic 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 micrometers, and the spacing between pixel units is less than 1 micrometer.

[0013] Optionally, the method for bonding the translucent metal bonding layer and the metal bonding unit in step S4 is hot-press bonding. The hot-press bonding conditions are: temperature between 250℃ and 400℃, pressure between 5MPa and 100MPa, and time between 1000s and 5000s, including the endpoint values.

[0014] Optionally, the substrate is a silicon substrate. Step S5, which removes the silicon substrate, includes the following two steps: S51, mechanically grinding to thin it to a thickness of less than 100 micrometers; S52, removing the silicon substrate using a wet etching or dry etching process.

[0015] Optionally, 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 photolithography according to the photolithography alignment marks; S63, etching the mask layer and epitaxial layer between the metal bonding units using ICP etching, and finally removing the mask layer at the corresponding position of the metal bonding unit.

[0016] This invention uses a semi-transparent metal bonding layer and a light-transmitting epitaxial layer to fabricate a Micro-LED light-emitting module. After bonding is completed and the substrate is removed, the photolithographic alignment marks on the driving substrate can be directly seen through the epitaxial layer and the semi-transparent metal bonding layer. The epitaxial layer and the semi-transparent metal bonding layer can be directly patterned according to the photolithographic alignment marks without the need to open windows, which simplifies the process and improves the production yield. Attached Figure Description

[0017] Figure 1 This is a schematic cross-sectional view of the structure after step S1 is completed in the embodiments of this application.

[0018] Figure 2 This is a schematic cross-sectional view of the structure after step S2 is completed in the embodiment of this application.

[0019] Figure 3 This is a schematic cross-sectional view of the structure after step S3 is completed in the embodiment of this application.

[0020] Figure 4 This is a top view of the structure after step S3 is completed in the embodiment of this application.

[0021] Figure 5 This is a schematic cross-sectional view of the structure after step S4 is completed in the embodiment of this application.

[0022] Figure 6 This is a schematic cross-sectional view of the structure after step S5 is completed in the embodiment of this application.

[0023] Figure 7 This is a schematic diagram of the cross-sectional structure corresponding to the patterned epitaxial layer in step S6 of this embodiment.

[0024] Figure 8 This is a schematic diagram of the cross-sectional structure corresponding to the patterned semi-transparent metal bonding layer in step S6 of this application embodiment.

[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 Implementation

[0026] To make the technical problems, technical solutions and advantages of this application clearer, a detailed description will be given below in conjunction with specific embodiments.

[0027] like Figure 1-8 This application provides a method for fabricating a Micro-LED light-emitting module through a semi-transparent metal bonding layer, comprising the following steps: S1. An epitaxial layer is grown on the substrate, and the epitaxial layer is transparent; S2. Deposit a semi-transparent metallic bonding layer across the entire surface of the epitaxial layer; S3. Prepare metal bonding units and photolithographic alignment marks on the driving substrate. The metal bonding units are disposed on the surface of the driving electrode of the driving substrate. S4, bonding a semi-transparent metal bonding layer and metal bonding units; S5, Remove substrate; S6. Perform photolithography according to the photolithography 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 positions of the metal bonding units, and prepare a single Micro-LED pixel unit to complete the preparation of the Micro-LED light-emitting module.

[0028] It should be noted that this application uses a semi-transparent metal bonding layer and a light-transmitting epitaxial layer to fabricate a Micro-LED light-emitting module. After bonding is completed and the substrate is removed, there is no need to open a photolithography window. The photolithography registration marks on the driving substrate can be seen directly through the epitaxial layer and the semi-transparent metal bonding layer. The epitaxial layer and the semi-transparent metal bonding layer can be directly patterned according to the photolithography registration marks, which simplifies the process and improves the production yield.

[0029] In some embodiments of this 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, with exemplary thicknesses of 1nm, 2nm, 10nm, 50nm, 100nm, 110nm, 150nm, 180nm, 200nm, 220nm, and 250nm, but not limited to these. With this choice of material and thickness, the semi-transparent metal bonding layer possesses good light transmittance, allowing the photolithography alignment marks to be seen without opening windows in subsequent processes; it also possesses sufficient bonding strength and good conductivity, ensuring the stability of subsequent bonding and improving production yield.

[0030] In some embodiments of this application, the thickness of the semi-transparent metal bonding layer ranges from 1 nm to 100 nm, with exemplary thicknesses of 1 nm, 5 nm, 10 nm, 20 nm, 30 nm, 40 nm, 50 nm, 60 nm, 70 nm, 80 nm, 90 nm, and 100 nm, but not limited to these. While ensuring bonding stability, further reducing the thickness of the semi-transparent metal bonding layer not only increases its light transmittance and improves the accuracy of photolithography, but also allows for rapid removal of the semi-transparent metal bonding layer during subsequent patterning processes, avoiding impact on other layers.

[0031] In some embodiments of this application, the transmittance of the semi-transparent metal bonding layer and the epitaxial layer in the visible light range is 20%-90%, with exemplary values ​​of 20%, 30%, 40%, 45%, 50%, 60%, 70%, 80%, and 90%, but not limited to these. Within this range, the lithography machine can accurately identify the lithography registration marks through the semi-transparent metal bonding layer and the epitaxial layer, improving the lithography accuracy in step S6.

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

[0033] In some embodiments of this application, a photolithographic stripping method is used to simultaneously prepare metal bonding units and photolithographic alignment marks.

[0034] In some embodiments of this application, the metal bonding unit and the photolithographic alignment mark are made of the same material and have the same thickness. The material of the metal bonding unit and the photolithographic alignment mark is one or more combinations of Cr, Pt, Au, and Ni. Choosing the same material facilitates the fabrication of the metal bonding unit and the photolithographic alignment mark in the same process step.

[0035] In some embodiments of this application, the pixel size of the Micro-LED pixel unit is less than 5 micrometers, and the spacing between pixel units is less than 1 micrometer.

[0036] In some embodiments of this application, the method for bonding the translucent metal bonding layer and the metal bonding unit in step S4 is hot-press bonding. The hot-press bonding conditions are: temperature between 250℃ and 400℃, pressure between 5MPa and 100MPa, and time between 1000s and 5000s, including the endpoint values. Because the translucent metal bonding layer is relatively thin, strict control of process parameters is required during bonding to improve production yield.

[0037] In some embodiments of this application, the substrate is a silicon substrate. Step S5, removing the silicon substrate, includes the following two steps: S51, mechanically grinding to thin its thickness to within 100 micrometers; S52, removing the silicon substrate using a wet etching or dry etching process. Since substrate removal occurs after bonding with the driving substrate, to avoid damage to the driving substrate during substrate removal, an easily removable silicon substrate is selected, and a two-step process is used to remove the silicon substrate, maximizing the protection of the driving substrate.

[0038] In some embodiments of this application, 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 photolithography according to the photolithography alignment marks; S63, etching the mask layer and the epitaxial layer between the metal bonding units using ICP etching, and finally removing the mask layer at the corresponding position of the metal bonding unit. Example 1

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

[0040] Step S2, as follows 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, as follows Figure 3 As shown, metal bonding units 900 and photolithographic alignment marks 800 are fabricated on a driving substrate 600 using a photolithographic lift-off method. The metal bonding units 900 are fabricated on the surface of the driving electrode 700 of the driving substrate 600, which is a CMOS driving substrate. Figure 4 As shown, the surface of the metal bonding unit 900 is square, with a side length L = 3 micrometers, and the spacing d = 1 micrometer between the metal bonding units 900. The materials of the metal bonding unit 900 and the photolithographic alignment mark 800 are Cr / Pt / Au, with thicknesses of 30 nm, 50 nm, and 600 nm for Cr, Pt, and Au, 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 together by hot-press bonding. The hot-press bonding conditions are: temperature 250℃-400℃, pressure 5MPa-100MPa, and time 1000s-5000s. The cross-sectional structure after bonding is shown below. Figure 4 As shown.

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

[0044] Step S6: After step S5, the epitaxial layer is patterned: First, an 1100nm SiO2 mask layer is grown on the epitaxial wafer. Then, 5312 positive resist is spin-coated onto the surface of the SiO2 mask layer for development lithography. During lithography, alignment is performed according to the lithography alignment mark 800. The development pattern is set as a square, corresponding one-to-one with the metal bonding units 900, with identical shape, size, and spacing. Development lithography only retains the 5312 positive resist above the metal bonding units 900. Finally, ICP etching is used to etch the SiO2 mask layer in the areas not covered by the 5312 positive resist, and then the etching continues down 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 resist is removed by soaking in the resist solution, and then soaked in BOE solution for 60 seconds to remove the SiO2 mask layer below the area covered by the 5312 positive resist. 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 was patterned, the semi-transparent metal bonding layer 500 was patterned using wet etching. The cross-sectional structure of the semi-transparent metal bonding layer 500 after patterning is shown below. Figure 7 As shown, only the epitaxial layer and the semi-transparent metal bonding layer 500 at the corresponding positions of the metal bonding unit 900 are retained to fabricate a single Micro-LED pixel unit, thus completing the fabrication of the Micro-LED light-emitting module. The shape of each Micro-LED pixel unit is the same as that of the metal bonding unit 900, the pixel size of each Micro-LED pixel unit is L=3 micrometers, and the spacing between pixel units is d=1 micrometer. Example 2

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

[0047] Step S2, as follows 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, as follows Figure 3As shown, metal bonding units 900 and photolithographic alignment marks 800 are fabricated on a driving substrate 600 using a photolithographic lift-off method. The metal bonding units 900 are fabricated on the surface of the driving electrode 700 of the driving substrate 600, and the driving substrate 600 is an A-type driving substrate. Figure 4 As shown, the surface of the metal bonding unit 900 is square, with a side length L = 3 micrometers, and the spacing d = 1 micrometer between the metal bonding units 900. The materials of the metal bonding unit 900 and the photolithographic alignment mark 800 are Cr / Pt / Ni, with thicknesses of 30 nm, 50 nm, and 100 nm for Cr, Pt, and Ni, 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 together by hot-press bonding. The hot-press bonding conditions are: temperature 250℃-400℃, pressure 5MPa-100MPa, and time 1000s-5000s. The cross-sectional structure after bonding is shown below. Figure 4 As shown.

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

[0051] Step S6: After step S5, firstly, an 1100nm SiO2 mask layer is grown on the epitaxial wafer. Then, 5312 positive resist is spin-coated onto the surface of the SiO2 mask layer for development lithography. During lithography, alignment is performed according to the lithography alignment mark 800. The development pattern is set as a square, corresponding one-to-one with the metal bonding units 900, with identical shape, size, and spacing. Development lithography only retains the 5312 positive resist above the metal bonding units 900. Finally, ICP etching is used to etch the SiO2 mask layer in the areas not covered by the 5312 positive resist, and then the etching continues down 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 resist is removed by soaking in the resist solution, and then soaked in BOE solution for 60 seconds to remove the SiO2 mask layer below the area covered by the 5312 positive resist. The cross-sectional structure of the patterned epitaxial layer and the semi-transparent metallic bonding layer after 500 mm processing is as follows: Figure 7As shown, only the epitaxial layer and the semi-transparent metal bonding layer 500 at the corresponding positions of the metal bonding unit 900 are retained to fabricate a single Micro-LED pixel unit, thus completing the fabrication of the Micro-LED light-emitting module. The shape of each Micro-LED pixel unit is the same as that of the metal bonding unit 900, the pixel size of each Micro-LED pixel unit is L=3 micrometers, and the spacing between pixel units is d=1 micrometer.

[0052] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for fabricating a Micro-LED light-emitting module using a semi-transparent metal bonding layer, characterized in that, The method includes the following steps: S1. An epitaxial layer is grown on a substrate, the epitaxial layer being transparent; S2. Deposit a semi-transparent metallic bonding layer across the entire surface of the epitaxial layer; S3. Prepare metal bonding units and photolithographic alignment marks on the driving substrate, wherein the metal bonding units are disposed on the surface of the driving electrode of the driving substrate; S4, bonding a semi-transparent metal bonding layer and metal bonding units; S5, Remove substrate; S6. Perform photolithography according to the photolithography 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 positions of the metal bonding units, and prepare a single Micro-LED pixel unit to complete the preparation of the Micro-LED light-emitting module.

2. The method as described in 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 the endpoint values.

3. The method as described in claim 1, characterized in that: The thickness of the semi-transparent metal bonding layer ranges from 1 nm to 100 nm, including the endpoint values.

4. The method as described in claim 1, characterized in that: The translucent metallic bonding layer and epitaxial layer have a transmittance range of 20%-90% in the visible light range, including endpoint values.

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

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

7. The method as described in claim 1, characterized in that: The pixel size of the Micro-LED pixel unit is less than 5 micrometers, and the spacing between pixel units is less than 1 micrometer.

8. The method as described in 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-press bonding. The hot-press bonding conditions are: temperature between 250℃ and 400℃, pressure between 5MPa and 100MPa, and time between 1000s and 5000s, including the endpoint values.

9. The method as described in claim 1, characterized in that: The substrate is a silicon substrate. Step S5 involves removing the silicon substrate, which includes the following two steps: S51, mechanically grinding to thin it to a thickness of less than 100 micrometers; S52, removing the silicon substrate using a wet etching or dry etching process.

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

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