A method for etching an epitaxial layer of a GaP quaternary chip

Abstract

The application relates to a kind of LED quaternary chip GaP epitaxial layer etching method, the method comprises the following steps: coating positive photoresist on the surface of LED quaternary chip GaP epitaxial layer, then exposure, development, baking, the electrode pattern of positive photoresist is reserved on the surface of GaP epitaxial layer; using plasma cleaning machine to clean glue; under the protection of the reserved positive photoresist electrode pattern, GaP etching liquid is used to etch, and the current spreading channel of P electrode is prepared; the etching method of the application is a special etching method for GaAs-based LED epitaxial wafer current expansion layer GaP, GaP etching control stability is strong, according to etching time, etching depth can be controlled, operability is strong, and GaAs substrate has no etching effect, reduces the influence of N face chemical pollution, and the electrode hole of GaP current expansion layer is clean and free of residue after etching, which greatly reduces the downgrade caused by unqualified appearance.

Description

TECHNICAL FIELD

[0001] The application relates to a method for etching an LED quaternary chip GaP epitaxial layer and belongs to the technical field of LED quaternary chip preparation. BACKGROUND

[0002] LED is the first commercial compound semiconductor to enter the market. The earliest LED is a red GaAsP LED made by LPE (liquid phase epitaxial growth) technology, but the performance of these LEDs is relatively low compared with the current one. In the 1990s, due to the introduction of new materials and new epitaxial technologies into the research of red light LEDs, GaAs-based AlGaInP LEDs made by MOCVD (metal organic chemical vapor deposition) greatly improved the performance of LEDs in the red and yellow spectral regions.

[0003] In the 1950s, with the efforts of many well-known research institutions represented by IBM Thomas J. Watson Research Center, III-V semiconductors represented by GaAs rapidly rose in the field of semiconductor light emission. After that, with the emergence of MOCVD (metal organic chemical vapor deposition) technology, the growth of high-quality III-V semiconductors broke through the technical barriers, and semiconductor light-emitting diode devices of various wavelengths have flooded the market. Due to the high efficiency, long service life and strong mechanical impact resistance of semiconductor light-emitting diodes compared with current light-emitting devices, they are regarded as a new generation of lighting devices worldwide. However, due to the high refractive index of III-V semiconductors (GaP: 3.2) in general, this leads to the fact that the light emitted by the light-emitting region of the LED is subject to the phenomenon of interface total reflection when it is emitted from the chip surface to the air. Only a small part of the light can be emitted outside the device (GaP is about 2.4%). The phenomenon of interface total reflection leads to low external quantum efficiency of the LED, which is the main reason for restricting the replacement of existing lighting devices by LEDs.

[0004] To solve the problem of low external quantum efficiency of LEDs, current spreading means are usually used to achieve it. At present, to achieve current spreading for P-electrode fabrication of GaP window layer, chemical etching or ICP etching is generally used. The existing chemical etching or ICP etching has different defects: ICP etching has strict requirements on process and equipment, and the use of special gas requires high cost of environmental protection; chemical etching is a common method for LED manufacturers to achieve GaP window layer etching at present, and the stability of chemical etching is poor, which is prone to uneven etching and etching inactivity, resulting in appearance defects.

[0005] Chinese patent document CN104393115A discloses a kind of multi-junction gallium arsenide solar cell primary etching process method, 1) coating photoresist mask is coated on epitaxial sheet positive photoresist;2) after coating, put into oven and bake;3) after exposure and baking, the epitaxial sheet covered with photoresist is placed on photoetch machine and exposed using mask;4) after exposure, immerse in alkaline developer and develop;5) after hard film development, epitaxial sheet is placed into oven and post-bake, and the hard film temperature after post-baking is 120-150 DEG C;6) primary etching, gel removal, washing and drying are carried out on the epitaxial sheet covered with photoresist mask layer, which is immersed in primary etching solution containing nitric acid / hydrobromic acid / buffer, and after etching for a certain time, it is taken out and placed in gel removal solution, and finally washed and dried;On the basis of primary etching, diode electrode pattern is prepared by photolithography, and integrated bypass diode can be prepared by applying electron beam evaporation AuGeNi / Au / Ag / Au electrode.The etching process method etches GaAs, GaInP, InGaAs, Ge and other materials, the etching solution has strong corrosion, and the etching depth of epitaxial layer is not controllable, and the photoresist thickness of 10-20 μm is not easy to realize, and the photoresist thickness is too thin to play a protective role when etching the epitaxial layer.

[0006] Therefore, it is necessary to develop a kind of etching method for GaP epitaxial layer of LED quaternary chip, which has stable etching performance and low cost. SUMMARY

[0007] In view of the deficiencies of the prior art GaP etching technology, especially the current etching method is not suitable for etching GaP epitaxial layer of LED quaternary chip, the present application provides a kind of etching method for GaP epitaxial layer of LED quaternary chip, which has stable performance, low cost and short cycle.

[0008] To achieve the above effects, the present application is realized by the following technical scheme:

[0009] An etching method for GaP epitaxial layer of LED quaternary chip, comprising the following steps:

[0010] (1) coating positive photoresist on the surface of GaP epitaxial layer of LED quaternary chip, then exposing, developing and baking, and retaining the electrode pattern of positive photoresist on the surface of GaP epitaxial layer;

[0011] (2) using plasma cleaning machine to clean the glue on the surface of GaP epitaxial layer of LED quaternary chip treated in step (1);

[0012] (3) under the protection of positive photoresist electrode pattern retained in step (1), using GaP etching solution to etch GaP epitaxial layer of LED quaternary chip after cleaning in step (2), and preparing current expansion channel of P electrode;

[0013] The GaP etching solution is a mixture of hydrobromic acid, bromine water and pure water.

[0014] According to the application, preferably, in step (1), the thickness of the positive photoresist is 1.6-3.5 μm.

[0015] According to the application, preferably, in step (1), the baking temperature is 90-110 ℃, and the baking time is 5-15 minutes.

[0016] According to the application, preferably, in step (2), the power of the plasma cleaning machine is 15-30 W, and the cleaning time is 4-10 minutes.

[0017] According to the application, preferably, in step (3), the volume ratio of hydrobromic acid, bromine water and pure water in the GaP etching solution is (30-45):(0.8-5):(700-900).

[0018] According to the application, preferably, in step (3), when the GaP etching solution is prepared, a glass rod is used for stirring or an ultrasonic machine is used for accelerating the mutual solubility of the solution.

[0019] According to the application, preferably, in step (3), the etching is carried out at a temperature of 19-26 ℃ and a humidity of 30 wt%-65 wt% for 10 seconds-30 seconds.

[0020] According to the application, preferably, in step (3), the validity of the GaP etching solution is 12 hours.

[0021] As an equivalent alternative of the application, the etching method of the application can also be carried out in the following order: step (3) first, and then step (2).

[0022] An etching method of a GaP epitaxial layer of an LED quaternary chip, comprising the following steps:

[0023] (1) applying a positive photoresist on the surface of the GaP epitaxial layer of the LED quaternary chip, and then carrying out exposure, development and baking to reserve an electrode pattern of the positive photoresist on the surface of the GaP epitaxial layer;

[0024] (2) etching the GaP epitaxial layer of the LED quaternary chip of step (1) by using a GaP etching solution under the protection of the electrode pattern of the positive photoresist reserved in step (1) to prepare a current spreading channel of a P electrode;

[0025] The GaP etching solution is a mixture of hydrobromic acid, bromine water and pure water.

[0026] (3) cleaning the glue on the surface of the GaP epitaxial layer of the LED quaternary chip after step (2) by using a plasma cleaning machine.

[0027] The beneficial effects and advantages of the present application are as follows:

[0028] 1、The corrosion method of the present application is a special corrosion method for GaP current expansion layer of GaAs-based LED epitaxial wafer, and the GaP corrosion has strong control stability, the corrosion depth can be controlled according to the corrosion time, the operation is strong, and the GaAs substrate has no corrosion effect, and the influence of N surface chemical pollution is reduced.

[0029] 2、The corrosion method of the present application can clean the electrode hole of GaP current expansion layer without residue, greatly reducing the downgrade caused by unqualified appearance.

[0030] 3、The photoresist thickness of the corrosion method of the present application is conventional, easy to operate, and has good protection effect.

[0031] 4、The corrosion method of the present application is simple to operate, stable in corrosion performance, low in cost, short in production cycle, stable in chip quality, and improves the good product rate of LED quaternary chip. BRIEF DESCRIPTION OF DRAWINGS

[0032] Figure 1 It is the LED chip surface photo after the glue removal of example 1.

[0033] Figure 2 It is the LED chip surface photo after the glue removal of example 2.

[0034] Figure 3 It is the chip surface photo before GaP corrosion without glue.

[0035] Figure 4 It is the photo of direct corrosion without using glass rod stirring during the preparation of GaP etching solution.

[0036] Figure 5 It is the chip surface photo after corrosion when the etching solution is more than 12 hours. DETAILED DESCRIPTION

[0037] In order to make the technical problems, technical solutions and advantages of the present application more clear, the following will be described in detail in combination with the drawings and specific examples, but not limited to this, the not fully described in the present application is according to the conventional technology in the art.

[0038] The present application will be further described in combination with examples and drawings, but the scope of protection of the present application is not limited to this.

[0039] Example 1

[0040] A corrosion method of LED quaternary chip GaP epitaxial layer, comprising the following steps:

[0041] (1) In the GaP epitaxial layer surface of the LED quaternary chip, a positive photoresist is coated, the thickness of the positive photoresist is 3.0 μm, then exposure, development, baking are carried out, and the electrode pattern of the positive photoresist is reserved on the GaP epitaxial layer surface;

[0042] The baking temperature is 90-110 ℃, and the time is 5-15 minutes;

[0043] (2) The GaP epitaxial layer surface of the LED quaternary chip after step (1) is cleaned by using a plasma cleaning machine; the surface photo of the LED chip after degumming is shown in Figure 1 ;

[0044] The plasma cleaning machine cleaning power is 15-30 W, and the cleaning time is 4-10 minutes;

[0045] (3) GaP etching solution is configured;

[0046] Hydrobromic acid and pure water are mixed according to the volume ratio of 300-450 ml to 7000-9000 ml to configure a mixed solution, and 8-50 ml of bromine water is added to the mixed solution to configure a GaP etching solution;

[0047] The GaP etching solution is stirred with a glass rod for 5-10 minutes until completely miscible or the miscibility of the solution is accelerated by ultrasonic machine, the ultrasonic power is 10-20 KHz, and the time is 5-10 minutes;

[0048] Under the protection of the positive photoresist electrode pattern reserved in step (1), the GaP epitaxial layer of the LED quaternary chip after step (2) is etched by using the GaP etching solution at a temperature of 19-26 ℃ and a humidity of 30%-65% for 10 seconds-30 seconds to prepare a current expansion channel of the P electrode, and the GaP etching solution is used within 12 hours after being configured.

[0049] Example 2

[0050] A GaP epitaxial layer etching method of an LED quaternary chip, comprising the following steps:

[0051] (1) In the GaP epitaxial layer surface of the LED quaternary chip, a positive photoresist is coated, the thickness of the positive photoresist is 3.0 μm, then exposure, development, baking are carried out, and the electrode pattern of the positive photoresist is reserved on the GaP epitaxial layer surface;

[0052] The baking temperature is 90-110 ℃, and the time is 5-15 minutes;

[0053] (2) GaP etching solution is configured;

[0054] Mixing hydrogen bromide and pure water according to the proportion of 300-450ml to 7000-9000ml to prepare a mixed solution, and then adding 8-50ml of bromine water to the mixed solution to prepare a GaP etching solution;

[0055] Stirring the GaP etching solution with a glass rod for 5-10 minutes until complete mutual solubility or using an ultrasonic machine to accelerate the mutual solubility of the solution, with an ultrasonic power of 10-20KHz and a time of 5-10 minutes;

[0056] Under the protection of the positive photoresist electrode pattern reserved in step (1), the GaP epitaxial layer of the LED quaternary chip in step (1) is etched using the GaP etching solution at a temperature of 19-26℃ and a humidity of 30%-65% for 10-30 seconds to prepare a current spreading channel of the P electrode, and the GaP etching solution is used within 12 hours after preparation.

[0057] (3) Using a plasma cleaning machine to clean the glue on the surface of the GaP epitaxial layer of the LED quaternary chip after step (2); the surface photo of the LED chip after glue removal is shown in Figure 2 ; the glue removal power of the plasma cleaning machine is 15-30W, and the cleaning time is 4-10 minutes.

[0058] Comparative Example 1

[0059] A method for etching the GaP epitaxial layer of an LED quaternary chip, which is performed according to the method of Example 1, except that,

[0060] The method does not perform steps (1) and (2), and the GaP epitaxial layer of the LED quaternary chip is directly etched using the GaP etching solution, and the LED quaternary chip after etching is shown in Figure 3 , and it can be seen from Figure 3 that the chip surface has obvious uneven etching.

[0061] Comparative Example 2

[0062] A method for etching the GaP epitaxial layer of an LED quaternary chip, which is performed according to the method of Example 1, except that,

[0063] The GaP etching solution is not stirred with a glass rod during preparation, and the LED quaternary chip after etching is shown in Figure 4 , and it can be seen from Figure 4 that the chip surface has obvious uneven etching.

[0064] Comparative Example 3

[0065] A method for etching the GaP epitaxial layer of an LED quaternary chip, which is performed according to the method of Example 1, except that,

[0066] GaP etching solution was used 12 hours after preparation. The etched LED quaternary chip is shown in Figure 5 Figure 5 It can be seen that there is obvious etching inactivity on the surface of the chip.​

Claims

1. A method for etching GaP epitaxial layer of LED quaternary chip, comprising the following steps: (1) applying positive photoresist on the surface of GaP epitaxial layer of LED quaternary chip, the thickness of the positive photoresist being 3.0 μm, then performing exposure, development and baking to reserve the electrode pattern of the positive photoresist on the surface of GaP epitaxial layer; the baking temperature being 90-110 ℃ and the baking time being 5-15 minutes; (2) cleaning the GaP epitaxial layer of LED quaternary chip treated in step (1) by using a plasma cleaning machine; (3) preparing GaP etching solution; mixing hydrobromic acid and pure water in a volume ratio of 300-450 ml to 7000-9000 ml to prepare a mixed solution, then adding 8-50 ml of bromine water to the mixed solution to prepare GaP etching solution; stirring the GaP etching solution with a glass rod for 5-10 minutes until complete mutual solubility or accelerating the mutual solubility of the solution by ultrasonic machine, the ultrasonic power being 10-20 KHz and the time being 5-10 minutes; under the protection of the positive photoresist electrode pattern reserved in step (1), etching the GaP epitaxial layer of LED quaternary chip treated in step (2) by using GaP etching solution at a temperature of 19-26 ℃ and a humidity of 30%-65% for 10 seconds-30 seconds to prepare the current expansion channel of P electrode, the GaP etching solution being used within 12 hours after preparation; 2. A method for etching GaP epitaxial layer of LED quaternary chip, comprising the following steps: (1) applying positive photoresist on the surface of GaP epitaxial layer of LED quaternary chip, the thickness of the positive photoresist being 3.0 μm, then performing exposure, development and baking to reserve the electrode pattern of the positive photoresist on the surface of GaP epitaxial layer; the baking temperature being 90-110 ℃ and the baking time being 5-15 minutes; (2) preparing GaP etching solution; mixing hydrobromic acid and pure water in a volume ratio of 300-450 ml to 7000-9000 ml to prepare a mixed solution, then adding 8-50 ml of bromine water to the mixed solution to prepare GaP etching solution; stirring the GaP etching solution with a glass rod for 5-10 minutes until complete mutual solubility or accelerating the mutual solubility of the solution by ultrasonic machine, the ultrasonic power being 10-20 KHz and the time being 5-10 minutes; under the protection of the positive photoresist electrode pattern reserved in step (1), etching the GaP epitaxial layer of LED quaternary chip treated in step (1) by using GaP etching solution at a temperature of 19-26 ℃ and a humidity of 30%-65% for 10 seconds-30 seconds to prepare the current expansion channel of P electrode, the GaP etching solution being used within 12 hours after preparation; (3) cleaning the GaP epitaxial layer of LED quaternary chip treated in step (2) by using a plasma cleaning machine; the cleaning power of the plasma cleaning machine being 15-30 W and the cleaning time being 4-10 minutes. ​ ​ ​

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