A method for increasing the etching angle of LED chips

Abstract

The present invention provides a method for increasing the etching angle of an LED chip, comprising the steps of: applying photoresist on an epitaxial wafer, the epitaxial wafer being composed of a sapphire substrate with an epitaxial layer grown thereon; pre-baking the epitaxial wafer for 120 to 130 seconds; exposing and developing the epitaxial wafer to obtain an epitaxial wafer with a preset pattern template; post-baking the developed epitaxial wafer for 170 to 180 seconds at a temperature of 115 to 125°C to obtain an epitaxial wafer with a photolithography pattern with a preset angle, and etching to obtain an epitaxial wafer with a desired pattern. The present invention increases the pre-baking time to evaporate the water in the photoresist on the basis of the existing photolithography process, while keeping the exposure energy and its time unchanged with the development time, reducing the post-baking temperature and extending the post-baking time, so that the photoresist is more solid and resistant to etching, ensuring that the preset angle of the photolithography pattern etched by the final epitaxial wafer is about 41°, ensuring that the final chip can both meet the angle requirements of the process and increase the luminous area.

Description

Technical Field

[0001] The invention relates to the technical field of LED lighting, and in particular to a method for increasing the etching angle of an LED chip. Background Art

[0002] LED (Light Emitting Diode) is a solid-state semiconductor device that converts electrical energy into light energy. As a new type of light-emitting device, LED has the advantages of high light efficiency, energy saving, long service life, short response time, and environmental protection. Therefore, it is called the most potential new generation of light source and is very common in the field of lighting.

[0003] In the LED manufacturing process, it is essential to use plasma etching of epitaxial materials to produce specific patterns. For example, all chips need to etch N-type gallium nitride to form positive and negative electrodes, and flip-chips need to etch deep grooves to form isolation layers.

[0004] In the plasma etching process, photoresist or silicon dioxide can be used as a mask layer for the area that needs to be protected. Since the selectivity of silicon dioxide is higher than that of photoresist, the angle formed by using silicon dioxide as a mask layer is generally above 70°. However, for example, for high-voltage LED chips, metal bridges are required between multiple chips, so the angle after etching should not be too steep. Normally, photoresist is used as a mask, and its pre-baking time is usually 90-100s, the pre-baking temperature is 100-110℃, and the exposure energy is maintained at 18mj / cm 2 , exposure time is 5s, development time is 60-80s, post-baking time is 140-150s, and post-baking temperature is 130-140°C. However, the selectivity of photoresist is less than that of silicon dioxide, so the angle formed is between 20° and 30°, but too gentle an angle will lead to the sacrifice of too many epitaxial active layers, thereby reducing the light-emitting area. Summary of the invention

[0005] The technical problem to be solved by the present invention is to provide a method for increasing the etching angle of an LED chip, which can not only meet the angle requirements of the process but also increase the light-emitting area.

[0006] In order to solve the above technical problems, the technical solution adopted by the present invention is:

[0007] A method for increasing the etching angle of an LED chip, comprising the steps of:

[0008] S1. Applying photoresist on an epitaxial wafer, wherein the epitaxial wafer is composed of a sapphire substrate on which an epitaxial layer is grown;

[0009] S2, pre-baking the epitaxial wafer for 120 to 130 seconds;

[0010] S3, exposing and developing the epitaxial wafer to obtain the epitaxial wafer having a preset pattern template;

[0011] S4, post-baking the developed epitaxial wafer for 170-180 seconds at a temperature of 115-125° C. to obtain the epitaxial wafer with a photolithography pattern of a preset angle, and then etching to obtain the epitaxial wafer with a desired pattern.

[0012] The beneficial effect of the present invention is that the present invention provides a method for increasing the etching angle of an LED chip. On the basis of the existing photolithography process, the pre-baking time is increased to evaporate the water in the photoresist, while the exposure energy and its time are kept unchanged with the development time, the post-baking temperature is reduced and the post-baking time is extended, so that the photoresist is more durable and resistant to etching. If the baking temperature after development is too high, the photoresist is prone to collapse, which will make the angle flatter. In order to make the photoresist angle steeper, the baking temperature after the photoresist is developed must be reduced. However, in order to make the photoresist more durable, the photoresist baking time needs to be extended to ensure that the preset angle of the photolithography pattern etched on the final epitaxial wafer is about 41°, so as to ensure that the final chip can meet the process requirements for the angle and increase the light-emitting area. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 A flow chart of a photolithography process in a method for increasing an etching angle of an LED chip according to an embodiment of the present invention;

[0014] Figure 2 It is a schematic diagram of the angle of the photoresist before being etched by plasma;

[0015] Figure 3 is a schematic diagram of the angle of the photoresist after plasma etching;

[0016] Figures 4 to 8 Schematic diagram of the etching angle of the photolithography pattern obtained under different conditions in the photolithography process. DETAILED DESCRIPTION

[0017] In order to explain the technical content, achieved objectives and effects of the present invention in detail, the following is an explanation in conjunction with the implementation modes and the accompanying drawings.

[0018] Please refer to Figure 1 and Figure 8 , a method for increasing the etching angle of an LED chip, comprising the steps of:

[0019] S1. Applying photoresist on an epitaxial wafer, wherein the epitaxial wafer is composed of a sapphire substrate on which an epitaxial layer is grown;

[0020] S2, pre-baking the epitaxial wafer for 120 to 130 seconds;

[0021] S3, exposing and developing the epitaxial wafer to obtain the epitaxial wafer having a preset pattern template;

[0022] S4, post-baking the developed epitaxial wafer for 170-180 seconds at a temperature of 115-125° C. to obtain the epitaxial wafer with a photolithography pattern of a preset angle, and then etching to obtain the epitaxial wafer with a desired pattern.

[0023] From the above description, it can be seen that the beneficial effect of the present invention is that: on the basis of the existing photolithography process, by increasing the pre-baking time to evaporate the moisture in the photoresist, while keeping the exposure energy and its time and the development time unchanged, reducing the post-baking temperature and extending the post-baking time, the photoresist is made stronger and more resistant to etching. Because if the baking temperature after development is too high, the photoresist is prone to collapse and will make the angle flatter. In order to make the photoresist angle steeper, the baking temperature after the photoresist is developed must be lowered. However, in order to make the photoresist stronger, the photoresist baking time needs to be extended to ensure that the preset angle of the photolithography pattern to be etched on the final epitaxial wafer is about 41°, ensuring that the final chip can both meet the process requirements for angles and increase the light-emitting area.

[0024] Furthermore, in step S1, photoresist is applied on the epitaxial wafer, specifically:

[0025] A positive photoresist with a thickness of 9000 to 10000 nm is evenly applied on the epitaxial wafer.

[0026] From the above description, it can be seen that the photoresist is applied with a thickness of 9000 to 10000 nm, which improves the thickness and clarity of the subsequent photolithography patterns after pre-baking, exposure, development and post-baking, meets the process requirements, and improves the overall quality of the final chip product.

[0027] Furthermore, the pre-baking temperature is 100-110°C.

[0028] It can be seen from the above description that the pre-bake temperature is not changed to reduce the influence of various variables in the photolithography process on the final etching angle.

[0029] Furthermore, in step S3, the epitaxial wafer is exposed, specifically:

[0030] The epitaxial wafer is placed in an exposure machine and the energy is 18 mj / cm 2 , exposure time is 5s.

[0031] Furthermore, the exposure machine is a DNK exposure machine.

[0032] Furthermore, in step S3, the epitaxial wafer is developed, specifically:

[0033] The exposed epitaxial wafer is developed for 60 to 80 seconds.

[0034] From the above description, it can be seen that the exposure energy, exposure time and development time are not changed to reduce the influence of various variables in the photolithography process on the final etching angle; at the same time, the exposure machine adopts the DNK exposure machine to ensure the quality of the epitaxial wafer after exposure.

[0035] Furthermore, in step S4, the epitaxial wafer having the expected pattern is obtained after etching, specifically:

[0036] The epitaxial wafer with the photolithographic pattern is placed in a plasma etcher, and is subjected to pure dry etching with boron chloride and chlorine gas, followed by de-resistance to obtain the epitaxial wafer with the expected pattern.

[0037] From the above description, it can be seen that a plasma etcher is used to remove the photolithography pattern, thereby obtaining an epitaxial wafer with better quality and effect, thereby ensuring the overall quality of the final chip product.

[0038] Furthermore, the plasma etcher is an ICP etcher.

[0039] From the above description, it can be seen that the plasma etcher uses an ICP etcher to ensure the degumming effect.

[0040] A method for increasing the etching angle of an LED chip provided by the present invention is applicable to a photolithography process in a LED chip manufacturing process, and is specifically described below in conjunction with an embodiment.

[0041] Please refer to Figure 1 , Embodiment 1 of the present invention is:

[0042] A method for increasing the etching angle of LED chips, such as Figure 1 As shown, the steps include:

[0043] In the photolithography process:

[0044] S1. applying photoresist on an epitaxial wafer, wherein the epitaxial wafer is composed of a sapphire substrate on which an epitaxial layer is grown;

[0045] Among them, in this embodiment, positive photoresist is used as the photoresist, and a layer with a thickness of 9000 to 10000 nm is evenly coated on the sapphire substrate after the epitaxial layer is grown, so as to improve the thickness and clarity of the subsequent photolithography pattern after pre-baking, exposure, development and post-baking, meet the process requirements, and further improve the overall quality of the final chip product.

[0046] S2. Pre-bake the epitaxial wafer for 120 to 130 seconds at a temperature of 100 to 110°C.

[0047] S3, exposing and developing the epitaxial wafer to obtain an epitaxial wafer having a preset pattern template;

[0048] In this embodiment, the exposure and development of the epitaxial wafer in the above step S2 is specifically as follows:

[0049] The epitaxial wafer is placed in the exposure machine for exposure with an energy of 18mj / cm 2 After exposure for 5 seconds, it is taken out and then developed for 60 to 80 seconds. It can be seen that the exposure energy, exposure time and development time are not changed compared with the existing photolithography technology, so as to fully reduce the influence of various variables in the photolithography process on the final etching angle.

[0050] Meanwhile, in the present embodiment, the exposure machine used for exposure is a DNK exposure machine to ensure the quality of the epitaxial wafer after exposure.

[0051] S4, post-baking the developed epitaxial wafer for 170-180 seconds at a temperature of 115-125° C. to obtain an epitaxial wafer with a photolithography pattern of a preset angle, and then etching to obtain an epitaxial wafer with a desired pattern.

[0052] In this embodiment, the preset angle of the photolithography pattern finally obtained is about 41°, that is, in this embodiment, by increasing the pre-baking time to evaporate the moisture in the photoresist on the basis of the existing photolithography process, while keeping the exposure energy and its time and the development time unchanged, reducing the post-baking temperature and extending the post-baking time, the photoresist is made stronger and more resistant to etching. If the baking temperature after development is too high, the photoresist will easily collapse and make the angle flatter. In order to make the photoresist angle steeper, the baking temperature after the photoresist is developed must be lowered. However, in order to make the photoresist stronger, the photoresist baking time needs to be extended to ensure that the preset angle of the photolithography pattern etched on the final epitaxial wafer is about 41°, ensuring that the final chip can meet the process requirements for angles and increase the light-emitting area.

[0053] Meanwhile, after obtaining the epitaxial wafer with the photolithographic pattern having an angle of about 41° in step S4, etching is required to obtain the epitaxial wafer with the expected pattern, specifically:

[0054] The epitaxial wafer with the photolithography pattern is placed in a plasma etcher, and is subjected to pure dry etching with boron chloride and chlorine gas, followed by de-resistance to obtain an epitaxial wafer with the expected pattern.

[0055] That is, a plasma etcher is used to remove the photolithography pattern, thereby obtaining an epitaxial wafer with better quality and effect, ensuring the overall quality of the final chip product.

[0056] Among them, in this embodiment, the plasma etcher is an ICP etcher to effectively ensure the degumming effect and further improve the overall quality of the final chip product.

[0057] Please refer to Figures 2 to 8 , Embodiment 2 of the present invention is:

[0058] A method for increasing the etching angle of an LED chip. Based on the above-mentioned embodiment 1, in this embodiment, the etching angle of an LED epitaxial layer, i.e., a photolithography pattern, under several different pre-baking, exposure, development and post-baking conditions in a plasma etching process and a photolithography process is described in detail.

[0059] First, the principle of plasma etching of the photolithography pattern obtained after the photolithography process is explained as follows:

[0060] like Figure 2 The figure shows the etching angle of the photolithography pattern before plasma etching. During plasma etching, if the photoresist is bombarded by plasma, the photoresist is prone to collapse and the angle becomes gentle, such as Figure 3 Therefore, the present invention proposes a method of increasing the etching angle of the photolithography pattern finally obtained by adjusting the pre-baking, exposure, development and post-baking temperature and time after the photoresist is spread in the photolithography process, so that the photoresist is more solid, more resistant to plasma etching, and less prone to deformation.

[0061] Among them, Figure 4 In order to maintain the existing process of pre-baking time of 90-100s, pre-baking temperature of 100-110℃, exposure energy of 18mj / cm2 on the basis of the existing photolithography process, 2 , exposure time of 5s, development time of 60-80s, post-baking time of 140-150s and post-baking temperature of 130-140°C, the etching angle of the final photolithography pattern, i.e., the LED epitaxial layer, is only about 27° on average;

[0062] like Figure 5 Based on the existing photolithography process, the pre-bake time is extended to 120-130s, but the pre-bake temperature remains unchanged at 100-110℃ and the exposure energy remains unchanged at 18mj / cm 2 , the exposure time is kept unchanged at 5s, the development time is kept unchanged at 60-80s, the post-bake time is reduced to 120-130s, and the post-bake temperature is reduced to 115-125°C. Finally, the average etching angle of the photolithography pattern obtained is about 30°;

[0063] like Figure 6 Based on the existing photolithography process, the pre-bake time is extended to 120-130s, but the pre-bake temperature remains unchanged at 100-110℃ and the exposure energy remains unchanged at 18mj / cm 2, the exposure time is kept unchanged at 5s, the development time is kept unchanged at 60-80s, the post-bake time is reduced to 130-140s, and the post-bake temperature is reduced to 115-125°C. Finally, the average etching angle of the photolithography pattern obtained is about 35°;

[0064] like Figure 7 In order to adopt a method of increasing the etching angle of the LED chip in the first embodiment, based on the existing photolithography process, the pre-baking time is extended to 120-130s, but the pre-baking temperature remains unchanged at 100-110°C, and the exposure energy remains unchanged at 18mj / cm 2 , the exposure time is kept unchanged at 5s, the development time is kept unchanged at 60-80s, the post-baking time is extended to 170-180s, and the post-baking temperature is reduced to 115-125°C. Finally, the average etching angle of the photolithographic pattern obtained is about 41°;

[0065] like Figure 8 Based on the existing photolithography process, the pre-bake time is extended to 120-130s, but the pre-bake temperature remains unchanged at 100-110℃ and the exposure energy remains unchanged at 18mj / cm 2 , the exposure time is kept unchanged at 5s, the development time is kept unchanged at 60-80s, the post-bake time is extended to 230-240s, and the post-bake temperature is reduced to 115-125°C. Finally, the etching angle of the photoresist pattern obtained is about 40° on average, which is lower than the above-mentioned etching angle of 41°. It is not difficult to know that too long post-bake time will still cause the photoresist etching angle to tend to be flat, causing the photoresist pattern to collapse easily in the subsequent plasma etching process. Therefore, the above-mentioned "extending the pre-bake time to 120-130s but keeping the pre-bake temperature unchanged at 100-110°C, and the exposure energy unchanged at 18mj / cm 2 , the exposure time remains unchanged at 5s, the developing time remains unchanged at 60-80s, the post-bake time is extended to 170-180s, and the post-bake temperature is reduced to 115-125°C". That is, a method for increasing the etching angle of the LED chip in the above-mentioned embodiment 1 can ensure that the etching angle of the final photolithography pattern is optimal and maintained at about 41°, thereby avoiding the collapse of the photolithography pattern after subsequent plasma etching, thereby further ensuring that the final LED chip can meet the process requirements for the angle and increase the light-emitting area.

[0066] In summary, the method for increasing the etching angle of an LED chip provided by the present invention has the following beneficial effects:

[0067] 1. Ensure that the final chip can meet the angle requirements of the process.

[0068] 2. It can effectively increase the light-emitting area of ​​the final chip.

[0069] The above are only embodiments of the present invention, and are not intended to limit the patent scope of the present invention. Any equivalent transformations made using the contents of the specification and drawings of the present invention, or directly or indirectly applied in related technical fields, are also included in the patent protection scope of the present invention.

Claims

1. A method for increasing the etching angle of an LED chip, characterized in that: Includes steps: S1. Applying photoresist on an epitaxial wafer, wherein the epitaxial wafer is composed of a sapphire substrate on which an epitaxial layer is grown; S2, pre-baking the epitaxial wafer for 120-130 seconds, increasing the pre-baking time to evaporate the water in the photoresist; S3, exposing and developing the epitaxial wafer to obtain the epitaxial wafer having a preset pattern template; S4, post-baking the developed epitaxial wafer for 170-180 seconds at a temperature of 115-125° C. to obtain the epitaxial wafer with a photolithography pattern of a preset angle, and etching to obtain the epitaxial wafer with a desired pattern, reducing the post-baking temperature and extending the post-baking time to make the photoresist more durable and resistant to etching; The step S3 of exposing the epitaxial wafer is specifically as follows: The epitaxial wafer is placed in an exposure machine for exposure at an energy of 18 mj / cm2 and a time of 5 s; In step S3, the epitaxial wafer is developed, specifically: The exposed epitaxial wafer is developed for 60 to 80 seconds.

2. A method for increasing the etching angle of an LED chip according to claim 1, characterized in that: In the step S1, photoresist is applied on the epitaxial wafer, specifically: Evenly apply positive photoresist with a thickness of 9000~10000nm on the epitaxial wafer.

3. A method for increasing the etching angle of an LED chip according to claim 1, characterized in that: The pre-baking temperature is 100-110°C.

4. The method for increasing the etching angle of an LED chip according to claim 1, characterized in that: The exposure machine is a DNK exposure machine.

5. The method for increasing the etching angle of an LED chip according to claim 1, characterized in that: The step S4 is to obtain the epitaxial wafer having the expected pattern after etching, specifically: The epitaxial wafer with the photolithographic pattern is placed in a plasma etcher, and is subjected to pure dry etching with boron chloride and chlorine gas, followed by de-resistance to obtain the epitaxial wafer with the expected pattern.

6. A method for increasing the etching angle of an LED chip according to claim 5, characterized in that: The plasma etcher is an ICP etcher.

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