Red light Micro-LED with inclined side wall and etching method thereof

Abstract

The invention discloses a semiconductor etching process, and particularly relates to a red light Micro-LED with an inclined side wall and an etching method thereof.The red light Micro-LED with the inclined side wall comprises an unetched area and a table top, and the included angle beta between the top of the unetched area and the side wall of the table top ranges from 0 degree to 90 degrees. Different side wall shapes including but not limited to vertical shapes, inclined shapes and concave shapes are obtained, different side walls are different in light reflection and light extraction efficiency, and the light extraction efficiency of the red light Micro-LED is improved, so that the external quantum efficiency of the red light Micro-LED is improved.

Description

Technical Field

[0001] The present invention relates to a semiconductor etching process, and in particular to a red light Micro-LED with inclined side walls and an etching method thereof. Background Art

[0002] With the rapid development of chip manufacturing technology, display technology has also ushered in a huge change. Especially in the field of 4K and 8K high-definition display, higher requirements are placed on the size and performance of display devices. In this context, Micro-LED (less than 200 microns in size) as an emerging display technology has become a key technology in the field of high-definition display due to its excellent brightness, high contrast, fast response time and low energy consumption.

[0003] At present, gallium nitride materials have been proven to have high luminous efficiency in the blue and green bands. However, when it comes to the preparation of red light Micro-LEDs, gallium nitride materials face some challenges. Due to the high indium component doping, the luminous efficiency of gallium nitride in the red band is limited.

[0004] Given the limitations of gallium nitride materials in the red light band, researchers began looking for alternatives. AlGaInP (aluminum gallium indium phosphide) material has become a promising choice due to its high luminous efficiency in the red light band. AlGaInP is a quaternary compound semiconductor and also a direct bandgap semiconductor, and its bandgap width can be adjusted by adjusting the ratio of Al, Ga, In and P. This enables AlGaInP to cover a wide spectral range from red to yellow light, making it very suitable for the preparation of red light Micro-LEDs. AlGaInP-based red light is currently a commonly used material for the preparation of Micro-LED red light devices.

[0005] Although AlGaInP has shown great potential in the preparation of red light Micro-LEDs, its preparation difficulty increases accordingly as the device size decreases. In particular, in the preparation of small-sized (less than 200 microns) AlGaInP devices, etching becomes a major difficulty. During the etching process, due to the thick thickness of the AlGaInP red light epitaxial wafer itself, the etching depth is usually required to be 4-8 microns (gallium nitride materials usually only need to be etched 2 microns), which results in a considerable height difference between the n and p electrodes. According to the preparation experience of GaN-based Micro-LEDs, the etching morphology requires vertical or trapezoidal etching sidewalls to have good performance in subsequent preparation. However, there is relatively little research on AlGaInP-based Micro-LED etching, especially almost no research on etching morphology, which has become a technical bottleneck for the preparation of high-performance AlGaInP red light Micro-LEDs.

[0006] Therefore, those skilled in the art are committed to developing a red light Micro-LED with inclined sidewalls and an etching method thereof. Summary of the invention

[0007] In view of the above-mentioned defects of the prior art, the technical problem to be solved by the present invention is to provide a red light Micro-LED with inclined sidewalls and an etching method thereof.

[0008] To achieve the above objectives, the present invention provides a red light Micro-LED with inclined side walls, including an unetched area and a table, wherein the angle β between the top of the unetched area and the side wall of the table is greater than or equal to 0° and less than or equal to 90°.

[0009] Furthermore, the angle of β is 30°, 50° or 70°.

[0010] Further, the unetched area includes a substrate and an unetched P-type confinement layer stacked sequentially from bottom to top;

[0011] The mesa comprises an etched P-Space layer, a multi-quantum well layer, an N-Space layer, an N-type confinement layer and an N-surface ohmic contact layer which are sequentially stacked from bottom to top.

[0012] The present invention also provides an etching method for a red light Micro-LED with an inclined sidewall, comprising the red light Micro-LED with an inclined sidewall as described above, and further comprising the following steps:

[0013] S1, etching SiO2, dripping heat dissipation oil on the back of the sample, sealing it with high-temperature tape, fixing it on a clean tray, placing it in the ICP and closing the cavity, using high-power etching to obtain a patterned SiO2 hard mask, and taking out the epitaxial wafer;

[0014] S2, degumming and cleaning the sample, soak the sample in acetone and isopropyl alcohol on a wet bench, then rinse with ionized water, blow dry, bake on a 100°C hot plate, and then cool to room temperature;

[0015] S3, etching the sample, placing the sample on a clean tray, putting it into the ICP and closing the chamber, selecting the debugged process menu to perform etching, and taking out the epitaxial wafer after completion;

[0016] S4. To corrode excess SiO2, immerse the sample with SiO2 in BOE solution, then take out the sample, rinse it with deionized water, blow it dry, and bake it at 100°C.

[0017] Further, in step S3, when the etching angle is 0° to 89°, the etching gas is a mixed gas of BCl3, Cl2 and Ar.

[0018] Further, in step S3, the etching gas pressure is 3-5 mTorr, the SRF is 750w-800w, the BRF is 200W, the etching temperature is 20°C, the back helium is 10 Torr, and the etching gas includes BCl3 with a flow rate of 10 sccm, Cl2 with a flow rate of 5-15 sccm, and Ar with a flow rate of 8-12 sccm.

[0019] Further, in step S3, when the etching angle is 90°, the etching gas is a mixture of Cl 2 and Ar.

[0020] Furthermore, in step S3, the etching gas pressure is 2 mTorr, the SRF is 500 W, the BRF is 120 W, the etching temperature is 175° C., and the etching gas includes Cl 2 with a flow rate of 4 sccm and Ar with a flow rate of 24 sccm.

[0021] Furthermore, in step S3, when etching the concave structure, the etching gas is a mixture of BCl3 and Cl2.

[0022] Further, in step S3, the etching gas pressure is 3 mTorr, the SRF is 750 W, the BRF is 200 W, the etching temperature is 20° C., and the etching gas includes BCl 3 with a flow rate of 30 sccm and Cl 2 with a flow rate of 40 sccm.

[0023] The beneficial effects of the present invention are as follows: the present invention aims to obtain different sidewall morphologies, including but not limited to vertical morphologies, inclined morphologies and concave morphologies, by regulating the etching gas and temperature. Different sidewalls have different light reflections and different light extraction efficiencies, aiming to increase the light extraction efficiency of red light Micro-LEDs and thus increase their external quantum efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 It is a structural schematic diagram of a specific implementation mode of the present invention.

[0025] Figure 2 It is a schematic diagram of a specific embodiment of the present invention when the etching angle β is 30°.

[0026] Figure 3 It is a schematic diagram of a specific embodiment of the present invention when the etching angle β is 50°.

[0027] Figure 4 It is a schematic diagram of a specific embodiment of the present invention when the etching angle β is 70°.

[0028] Figure 5 It is a schematic diagram of a specific embodiment of the present invention when the etching angle β is 90°.

[0029] Figure 6It is a schematic diagram of a specific embodiment of the present invention when the etching angle β is a concave structure. DETAILED DESCRIPTION

[0030] The present invention is further described below in conjunction with the accompanying drawings and embodiments. It should be noted that in the description of the present invention, the terms "upper", "lower", "left", "right", "inner", "outer", etc. indicate directions or positional relationships based on the directions or positional relationships shown in the accompanying drawings, which are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific direction, be constructed and operated in a specific manner, and therefore cannot be understood as limiting the present invention. The terms "first", "second", "third", etc. are only used for descriptive purposes and cannot be understood as indicating or implying relative importance.

[0031] like Figure 1-6 As shown in the figure, a red light Micro-LED with inclined sidewalls is formed by etching an unetched area and a table on the epitaxial wafer during the production process of Micro-LED. The unetched area and the table are formed in one piece, and the angle β between the top of the unetched area and the sidewall of the table is 0° to 90°. When in use, if the gradient angle β is too small, the spacing between the two devices needs to be larger, otherwise the devices will be connected together, which will affect the number of pixels per inch of the array design, and ultimately cannot meet the high PPI display expected by Micro-LED. Secondly, the trapezoidal inclined etching morphology and the vertical etching morphology each have advantages and disadvantages, and are suitable for different In the application scenario, the trapezoidal etching THK morphology can enhance the optical properties of optoelectronic devices and reduce stress concentration, but it may reduce the integration density of the device. In contrast, the vertical etching morphology can improve the integration density and electrical performance, but it may be detrimental to the extraction and transmission of light, and may cause stress concentration in some cases. The solution provided by the present invention can perform trapezoidal or vertical etching according to the needs of the device to determine the most suitable etching method. The purpose of etching angle is achieved by regulating the etching gas and temperature. Different gas ratios will result in different etching rates for the epitaxial wafer, and the change of the etching angle is achieved by regulating the ratio.

[0032] In this embodiment: the angle of β is 30°, 50° or 70°, and the above three angles can adapt to most usage situations.

[0033] In this embodiment: the unetched area includes a substrate and an unetched P-type confinement layer stacked in sequence from bottom to top, and the table includes an etched P-Space layer, a multi-quantum well layer, an N-Space layer, an N-type confinement layer and an N-side ohmic contact layer stacked in sequence from bottom to top, wherein the unetched P-type confinement layer and the etched P-Space layer are integrally formed and formed by etching definition, and are now divided into two parts for the convenience of writing this application, and the multi-quantum well layer is arranged in an overlapping manner of P layer-N layer-P layer-N layer-P layer-N layer. In this embodiment, only three layers are shown to represent its structure, and other numbers of layers may be stacked in other embodiments.

[0034] The present invention also provides an etching method for a red light Micro-LED with an inclined sidewall, comprising the red light Micro-LED with an inclined sidewall as described above, and further comprising the following steps:

[0035] S1. Etch SiO2. Use Oxford PlasmaPro100Cobra ICP etching equipment. Drip heat dissipation oil on the back of the sample, seal it with high-temperature tape, fix it on a clean tray, put it in the ICP and close the cavity. Use high-power etching to obtain a patterned SiO2 hard mask, and then take out the epitaxial wafer.

[0036] S2, degumming and cleaning the sample, soak the sample in acetone (ACE) and isopropyl alcohol (IPA) for 5 minutes each on a wet bench (ultrasound can be used as an alternative), then rinse with deionized water for 5 minutes, blow dry, place on a 100°C hot plate and bake for 2 minutes, then remove and cool to room temperature;

[0037] S3, etch the sample, use Oxford Plasma Pro 100 Cobra ICP etching equipment, this equipment is specially used for etching GaN and A1GanP, avoid cross contamination, place the sample on a clean tray, put it into the ICP and close the cavity, select the debugged process menu for etching, and take out the epitaxial wafer after completion. The etching depth of red light samples with different epitaxial structures is different, ranging from 4.3 to 7 microns;

[0038] S4. Corrode excess SiO2. Soak the sample with SiO2 in BOE solution for 5 minutes to remove the SiO2 on the surface. Then take out the sample, rinse it with deionized water for 10 minutes, blow dry it, and bake it at 100°C for 1 minute.

[0039] In this embodiment: in step S3, when the etching angle is 0°~89°, the etching gas is a mixed gas of BCl3, Cl2 and Ar, the etching gas pressure is 3~5mTorr, SRF is 750w~800w, BRF is 200W, the etching temperature is 20°C, the back helium is 10Torr, and the etching gas includes BCl3 with a flow rate of 10sccm, Cl2 with a flow rate of 5-15sccm and Ar with a flow rate of 8-12sccm. The purpose of etching angle is achieved by regulating the etching gas and temperature. Different gas ratios result in different etching rates for the epitaxial wafer, and the change of etching angle is achieved by regulating the ratio.

[0040] Specifically, the following is an example of the specific angle of β:

[0041] Specific method 1: Figure 2 As shown, when the etching angle β is required to be 30°, the etching gas is a mixture of 10 sccm BCl3, 5 sccm Cl2 and 12 sccm Ar, the etching gas pressure is 3 mTorr, the SRF is 750W, the BRF is 200W, the temperature is 20°C, and the back helium is 10 Torr.

[0042] Specific method 2: Figure 3 As shown, when the etching angle β is required to be 50°, the etching gas is a mixture of 10 sccm BCl3, 10 sccm Cl2 and 10 sccm Ar, the etching gas pressure is 3 mTorr, SRF is 750W, BRF 200W, temperature is 20°C, and back helium is 10 Torr.

[0043] Specific method three: Figure 4 As shown, when the etching angle β is required to be 70°, the etching gas is a mixture of 10 sccm BCl3, 15 sccm Cl2 and 8 sccm Ar, the etching gas pressure is 5 mTorr, the SRF is 800 W, the BRF is 200 W, the temperature is 20°C, and the back helium is 10 Torr.

[0044] In this embodiment: Figure 5 As shown, in step S3, when the etching angle is 90°, the etching gas includes Cl2 with a flow rate of 4 sccm and Ar with a flow rate of 24 sccm, the etching gas pressure is 2 mTorr, the SRF is 500 W, the BRF is 120 W, and the etching temperature is 175°C.

[0045] In this embodiment: Figure 6 As shown, in step S3, when etching the concave structure, the etching gas includes BCl3 with a flow rate of 30 sccm and Cl2 with a flow rate of 40 sccm, the etching gas pressure is 3 mTorr, the SRF is 750 W, the BRF is 200 W, and the etching temperature is 20°C.

[0046] The preferred specific embodiments of the present invention are described in detail above. It should be understood that a person skilled in the art can make many modifications and changes based on the concept of the present invention without creative work. Therefore, any technical solution that can be obtained by a person skilled in the art through logical analysis, reasoning or limited experiments based on the concept of the present invention on the basis of the prior art should be within the scope of protection determined by the claims.

Claims

1. A red light micro-LED with inclined sidewalls, comprising an unetched area (1) and a mesa (2), characterized in that: The included angle between the top of the unetched area (1) and the side wall of the table (2) is β, and the angle β is greater than or equal to 0° and less than or equal to 90°.

2. The red light Micro-LED with inclined sidewalls as claimed in claim 1, characterized in that: The angle β is 30°, 50° or 70°.

3. The red light Micro-LED with inclined sidewalls as claimed in claim 1, characterized in that: The unetched area (1) comprises a substrate (101) and an unetched P-type confinement layer (102) stacked in sequence from bottom to top; The mesa (2) comprises an etched P-Space layer (201), a multi-quantum well layer (202), an N-Space layer (203), an N-type confinement layer (204) and an N-face ohmic contact layer (205) which are stacked in sequence from bottom to top.

4. The etching method of a red light Micro-LED with inclined sidewalls according to any one of claims 1 to 3, characterized in that: The following steps are involved: S1, etching SiO2, dripping heat dissipation oil on the back of the sample, sealing it with high-temperature tape, fixing it on a clean tray, placing it in the ICP and closing the cavity, using high-power etching to obtain a patterned SiO2 hard mask, and taking out the sample; S2, degumming and cleaning the sample, soak the sample in acetone and isopropyl alcohol on a wet bench, then rinse with ionized water, blow dry, bake on a 100°C hot plate, and then cool to room temperature; S3, etching the sample, placing the sample on a clean tray, putting it into the ICP and closing the chamber, selecting the debugged process menu to perform etching, and taking out the epitaxial wafer after completion; S4. To corrode excess SiO2, immerse the sample with SiO2 in BOE solution, then take out the sample, rinse it with deionized water, blow it dry, and bake it at 100°C.

5. The etching method of a red light Micro-LED with inclined sidewalls as claimed in claim 4, characterized in that: In step S3, when the etching angle β is between 0° and 89°, the etching gas is a mixture of BCl3, Cl2 and Ar.

6. The etching method of a red light Micro-LED with inclined sidewalls as claimed in claim 5, characterized in that: In step S3, the etching gas pressure is 3-5 mTorr, the SRF is 750w-800w, the BRF is 200W, the etching temperature is 20°C, the back helium is 10 Torr, and the etching gas includes BCl3 with a flow rate of 10 sccm, Cl2 with a flow rate of 5-15 sccm, and Ar with a flow rate of 8-12 sccm.

7. The etching method of a red light Micro-LED with inclined sidewalls as claimed in claim 4, characterized in that: In step S3, when the etching angle β is 90°, the etching gas is a mixture of Cl2 and Ar.

8. The etching method of a red light Micro-LED with inclined sidewalls as claimed in claim 7, characterized in that: In step S3, the etching gas pressure is 2 mTorr, the SRF is 500 W, the BRF is 120 W, the etching temperature is 175° C., and the etching gas includes Cl 2 with a flow rate of 4 sccm and Ar with a flow rate of 24 sccm.

9. The etching method of a red light Micro-LED with inclined sidewalls as claimed in claim 4, characterized in that: In step S3, when the etching angle β is a concave structure, the etching gas is a mixture of BCl3 and Cl2.

10. The etching method of a red light Micro-LED with inclined sidewalls according to claim 9, characterized in that: In step S3, the etching gas pressure is 3 mTorr, the SRF is 750 W, the BRF is 200 W, the etching temperature is 20° C., and the etching gas includes BCl 3 with a flow rate of 30 sccm and Cl 2 with a flow rate of 40 sccm.

Images