A grinding method for indium phosphide substrate
Through the two-step method of chemical corrosion and mechanical grinding, the problems of long grinding time, low efficiency and product quality in the indium phosphide substrate grinding process are solved, and efficient and low-cost grinding processing is achieved, ensuring high quality and low warpage of the wafer.
Patent Information
- Application Number
- CN202411993059.5
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-12-31
- Publication Date
- 2025-04-08
AI Technical Summary
The existing indium phosphide substrate grinding process has problems such as long grinding time, low production efficiency, increased warpage, high fragmentation rate and pharmaceutical printing, making it difficult to ensure the grinding efficiency and product quality at the same time.
A two-step method was adopted: first chemical corrosion was performed using a mixture of hydrobromic acid, phosphoric acid, hydrochloric acid and acetic acid, thinning the surface of the wafer to make it a bone cancellous structure; then mechanically grinding was performed using a mixture of high-purity alumina powder, polyethylene glycol, triethanolamine and pure water until the target thickness.
It significantly reduces grinding time, improves grinding efficiency, reduces the occurrence of scratches and drug marks, ensures high quality and low warpage of the wafer, and improves production cost-effectiveness.
Abstract
Description
Technical Field
[0001] The invention relates to an indium phosphide substrate grinding method, belonging to the technical field of semiconductor processing. Background Art
[0002] Indium phosphide substrates are widely used in microwave, millimeter wave microelectronic devices and other fields. Their processing flow includes slicing, grinding, polishing, cleaning and other processes. Among them, the grinding process is to thin the wafer by mechanical grinding to achieve the thickness required for polishing. Moreover, grinding can remove the knife marks or damaged layers produced by the slicing process, and at the same time repair the TTV of the wafer to make the wafer thickness converge. At present, there are two ways to grind indium phosphide. One is pure mechanical grinding, which uses aluminum oxide powder of a certain particle size as an abrasive to gradually reduce the thickness of the wafer through physical grinding; the other is mechanical chemical grinding, in which the abrasive not only contains aluminum oxide abrasive, but also mixes acid or alkali solution and oxidant that are corrosive to indium phosphide. Mechanical grinding and chemical corrosion are carried out simultaneously, with mechanical grinding as the main method and chemical corrosion as the auxiliary method. The advantage of pure mechanical grinding is that the grinding surface is uniform, which is conducive to the corrosion processing of the subsequent process, and the corrosion surface is uniform and no drug marks are produced. However, the disadvantage of pure mechanical grinding is that it requires multiple steps, the grinding time is long, and the production efficiency is low, which is not conducive to reducing production costs. In addition, due to the long grinding time, a large stress accumulates on the surface of the wafer, which increases the wafer warpage. The advantage of mechanical chemical grinding is that it saves grinding time, but the disadvantage is that the processing qualification rate is low. The grinding surface layer is soft due to chemical corrosion, which is easy to scratch, and the residual chemical grinding sheet is easy to produce drug marks in the subsequent corrosion processing, thereby increasing the production cost. Therefore, a grinding method is proposed, which can not only ensure grinding efficiency, but also avoid grinding scratches, subsequent corrosion drug marks and severe warpage. Summary of the invention
[0003] The invention provides a new grinding method for indium phosphide substrate, which combines the advantages of chemical thinning and mechanical grinding, improves grinding efficiency, reduces grinding scratch ratio, and reduces production cost.
[0004] In order to solve the above technical problems, the technical solutions adopted by the present invention are as follows:
[0005] A grinding method for an indium phosphide substrate comprises the following steps: firstly, chemically etching an indium phosphide wafer using a chemical etching liquid to make the surface of the wafer a cancellous structure; then, mechanically grinding the indium phosphide wafer using a grinding liquid to a target thickness; wherein the chemical etching liquid is a mixture of hydrobromic acid, phosphoric acid, hydrochloric acid and acetic acid, and the mass ratio of the hydrobromic acid, phosphoric acid, hydrochloric acid and acetic acid is (20-50):(40-60):(10-30):(20-50).
[0006] The first step is chemical etching to reduce the thickness by 5um-20um; the second step is mechanical grinding of the indium phosphide wafer to remove a certain thickness to meet the polishing requirements. In this application, after chemical etching, a mechanical grinding step is performed.
[0007] Due to the significant differences in the physical properties of different wafers, the corrosion effects of the same etching solution on different wafers are completely different. This application is specially developed for indium phosphide wafers.
[0008] In order to further improve the etching efficiency and ensure the grinding effect, the mass ratio of hydrobromic acid, phosphoric acid, hydrochloric acid and acetic acid in the chemical etching solution is (30-40):(45-55):(15-25):(30-40).
[0009] The temperature of chemical etching in the present application is 20° C. to 60° C., and the time is 10s to 900s. More preferably, the temperature of chemical etching is 40° C. to 50° C., and the time is 50s to 300s.
[0010] The mass concentration of the hydrobromic acid is 35-40%; the mass concentration of the phosphoric acid is 80-85%; the mass concentration of the hydrochloric acid is 35-37%; and the mass concentration of the acetic acid is 98-99%.
[0011] Unless otherwise specified, % in this application are all mass percentages.
[0012] In order to improve the grinding efficiency, the grinding liquid is a mixture of high-purity alumina powder, polyethylene glycol, triethanolamine and pure water, wherein the mass of high-purity alumina powder, polyethylene glycol, triethanolamine and pure water is (30-60): (5-15): (1-5): (30-60).
[0013] The inventors found that polyethylene glycol not only stabilizes the suspension, but also has a certain lubricating effect, further reducing the occurrence of scratches; triethanolamine is a dispersant, which prevents the alumina particles from agglomerating and makes the particles more evenly distributed.
[0014] The polyethylene glycol is preferably PEG400.
[0015] More preferably, the mass of high-purity alumina powder, polyethylene glycol, triethanolamine and pure water is (40-50):(8-10):(3-4):(45-55).
[0016] In order to improve the quality of the wafer, the particle size of the high-purity alumina powder is 800-2000 mesh, preferably 1200-1500 mesh. The inventors found that mixing high-purity alumina powder of a specific fineness with polyethylene glycol and triethanolamine in a specific ratio is suitable for grinding indium phosphide wafers with a high removal rate.
[0017] In order to take into account both the quality and effect of grinding, the mechanical grinding time is 300s to 900s, the grinding pressure is 10N to 30N, and the grinding disc speed is 2rpm to 10rpm. More preferably, the mechanical grinding time is 400s to 600s, the grinding pressure is 15N to 25N, and the grinding disc speed is 4rpm to 6rpm.
[0018] The technologies not mentioned in the present invention are all referred to the prior art.
[0019] The existing indium phosphide wafer grinding has the following problems: 1. The mechanical grinding process of indium phosphide wafers is generally multi-step grinding, and it must go through rough grinding and fine grinding processes before its surface can meet the requirements of post-process corrosion, which makes the grinding time longer and the production efficiency lower. In addition, due to the long grinding time, a large stress accumulates on the wafer surface, which increases the wafer warpage and the fragmentation rate. 2. Indium phosphide wafer mechanical chemical grinding uses a corrosive grinding liquid during the wafer grinding process, which causes the grinding surface to be in a corroded state all the time, making the grinding surface layer softer and easily scratched by the abrasive particles. In addition, the residual agent on the grinding sheet is prone to drug marks in the post-process corrosion processing, and the final delivery qualification rate is low.
[0020] The present invention adopts a two-step method. The first step is chemical preferential corrosion, and the indium phosphide wafer is quickly thinned by 5um-20um, the grinding thickness is reduced, and the processing time is greatly reduced; at the same time, the surface of the indium phosphide wafer has a spongy structure due to directional corrosion, and the Mohs hardness of this spongy structure is lower than that of indium phosphide, which is easy to grind. At the same time, the spongy structure can also prevent the extension of the scratch line, thereby reducing the proportion of scratches. The grinding liquid selected for the second step of mechanical grinding has high removal efficiency, and polyethylene glycol not only has the effect of stabilizing the suspension, but also has a certain lubricating effect, further reducing the generation of scratches; triethanolamine is a dispersant, which prevents aluminum oxide particles from agglomerating and makes the particle distribution more uniform. The present invention improves the efficiency and the surface quality of the obtained wafer through chemical corrosion and mechanical grinding, and ensures the qualified rate. DETAILED DESCRIPTION
[0021] In order to better understand the present invention, the content of the present invention is further explained below in conjunction with the embodiments, but the content of the present invention is not limited to the following embodiments.
[0022] Example 1
[0023] 1. Prepare chemical corrosion solution:
[0024] Medicines: 350g of hydrobromic acid with a concentration of 40%; 500g of phosphoric acid with a concentration of 85%; 200g of hydrochloric acid with a concentration of 37%; 350g of acetic acid with a concentration of 99%.
[0025] Preparation: First pour 500g of 85% phosphoric acid into the corrosion tank, then add 350g of 40% hydrobromic acid, stir evenly, then add 200g of 37% hydrochloric acid, stir evenly, and finally add 350g of 99% acetic acid, stir evenly.
[0026] 2. Prepare the grinding fluid:
[0027] Drugs: 1000 mesh high-purity alumina powder (purity 99.99%) 450g; polyethylene glycol (PEG400) 90g; triethanolamine 35g; pure water 500g.
[0028] Preparation: First weigh 500g of pure water. Then add 90g of polyethylene glycol to the pure water and stir evenly, then add 35g of triethanolamine and stir evenly, and finally pour 450g of high-purity alumina powder into the mixture and stir well.
[0029] 3. Grinding:
[0030] The indium phosphide single crystal was cut by multi-wire cutting to obtain 150 2-inch wafers with a thickness of 650±5um. The 150 2-inch indium phosphide wafers were ground by the following method:
[0031] 1) 150 indium phosphide wafers were chemically etched using a chemical etching solution at a temperature of 40° C. for 200 seconds, with a thickness reduction of 16 μm. The wafer surface showed a cancellous bone structure;
[0032] 2) Then the indium phosphide wafer was mechanically double-sided ground using the grinding liquid. The mechanical grinding time was 600s, the grinding pressure was 18N, the grinding disc speed was 5rpm, and the thinning was 35±5um. After grinding, 150 wafers were qualified, with a qualified rate of 100%, warpage <1um, TTV <1um, roughness Ra 1.0nm, fragmentation rate 0%, and scratch rate 0%. There was no residual agent, which did not affect the subsequent processing.
[0033] Example 2
[0034] 1. Prepare chemical corrosion solution:
[0035] Medicines: 400g of hydrobromic acid with a concentration of 40%; 450g of phosphoric acid with a concentration of 85%; 250g of hydrochloric acid with a concentration of 37%; 300g of acetic acid with a concentration of 99%.
[0036] Preparation: First pour 450g of 85% phosphoric acid into the corrosion tank, then add 400g of 40% hydrobromic acid, stir evenly, then add 250g of 37% hydrochloric acid, stir evenly, and finally add 300g of 99% acetic acid, stir evenly.
[0037] 2. Prepare the grinding fluid:
[0038] Drugs: 1000 mesh high-purity alumina powder (purity 99.99%) 400g; polyethylene glycol (PEG400) 100g; triethanolamine 30g; pure water 520g.
[0039] Preparation: First weigh 520g of pure water. Then add 100g of polyethylene glycol to the pure water and stir evenly, then add 30g of triethanolamine and stir evenly, and finally pour 400g of high-purity alumina powder into the mixture and stir well.
[0040] 3. Grinding:
[0041] The indium phosphide single crystal was cut by multi-wire cutting to obtain 100 3-inch wafers with a thickness of 750±5um. The 100 3-inch indium phosphide wafers were ground by the following method:
[0042] 1) The indium phosphide wafer is chemically corroded by using a chemical etching solution, the chemical etching temperature is 45° C., the time is 300 s, the wafer is thinned by 20 μm, and the surface of the wafer presents a cancellous structure;
[0043] 2) Then the indium phosphide wafer is mechanically double-sided ground using the grinding liquid. The mechanical grinding time is 500s, the grinding pressure is 15N, the grinding disc speed is 5rpm, and the thinning is 30±5um. The qualified rate is 100%, the warpage is less than 1um, the TTV is less than 1um, the roughness Ra is 1.1nm, the fragmentation rate is 0%, and the scratch rate is 0%. There is no residual agent, which does not affect the subsequent processing.
[0044] Comparative Example 1
[0045] The difference from Example 1 is that hydrobromic acid is replaced by hydrochloric acid of equal mass, and the rest is referred to Example 1.
[0046] Results: After processing 120 2-inch indium phosphide wafers, 115 were qualified, 5 were scratched, the scratch rate was 4.2%, the warpage was 8-10um, and the TTV was 2-8um.
[0047] Comparative Example 2
[0048] The difference from Example 1 is that phosphoric acid is replaced by hydrochloric acid of equal mass, and the rest is referred to Example 1.
[0049] Results: After processing 98 3-inch indium phosphide wafers, 85 were qualified, 13 were scratched, the scratch rate was 13.3%, the warpage was 15-20um, and the TTV was 5-10um.
[0050] Comparative Example 3
[0051] The difference from Example 1 is that acetic acid is replaced by hydrochloric acid of equal mass, and the rest is referred to Example 1.
[0052] Results: After processing 118 2-inch indium phosphide wafers, 101 were qualified, 17 were scratched, the scratch rate was 14.4%, the warpage was 15-20um, and the TTV was 6-12um.
[0053] Comparative Example 4
[0054] The difference from Example 1 is that polyethylene glycol is replaced by propylene glycol of equal mass, and the rest is the same as Example 1.
[0055] Results: After processing 101 3-inch indium phosphide wafers, 58 were qualified, 40 were scratched, the scratch rate was 39.6%, 3 were broken, the fragmentation rate was 3%, the warpage was 25-36um, and the TTV was 16-26um.
[0056] Comparative Example 5
[0057] The difference from Example 1 is that triethanolamine is replaced by an equal mass of sodium stearate, and the rest is referred to Example 1.
[0058] Results: After processing 111 2-inch indium phosphide wafers, 101 were qualified, 10 were scratched, the scratch rate was 9%, the warpage was 12-15um, and the TTV was 8-15um.
Claims
1. A method for grinding an indium phosphide substrate, characterized in that: Firstly, a chemical etching liquid is used to chemically etch an indium phosphide wafer so that the surface morphology of the wafer is a cancellous bone structure; then, a grinding liquid is used to mechanically grind the indium phosphide wafer to a target thickness; wherein the chemical etching liquid is a mixture of hydrobromic acid, phosphoric acid, hydrochloric acid and acetic acid, and the mass ratio of hydrobromic acid, phosphoric acid, hydrochloric acid and acetic acid is (20-50):(40-60):(10-30):(20-50).
2. The indium phosphide substrate grinding method according to claim 1, characterized in that: In the chemical etching solution, the mass ratio of hydrobromic acid, phosphoric acid, hydrochloric acid and acetic acid is (30-40):(45-55):(15-25):(30-40).
3. The indium phosphide substrate grinding method according to claim 1 or 2, characterized in that: The temperature of chemical etching is 20℃~60℃, and the time is 10s~900s.
4. The indium phosphide substrate grinding method according to claim 3, characterized in that: The temperature of chemical etching is 40℃~50℃, and the time is 50s~300s.
5. The indium phosphide substrate grinding method according to claim 1 or 2, characterized in that: The mass concentration of hydrobromic acid is 35-40%; the mass concentration of phosphoric acid is 80-85%; the mass concentration of hydrochloric acid is 35-37%; and the mass concentration of acetic acid is 98-99%.
6. The indium phosphide substrate grinding method according to claim 1 or 2, characterized in that: The grinding liquid is a mixture of high-purity aluminum oxide powder, polyethylene glycol, triethanolamine and pure water, wherein the mass of the high-purity aluminum oxide powder, polyethylene glycol, triethanolamine and pure water is (30-60): (5-15): (1-5): (30-60).
7. The indium phosphide substrate grinding method according to claim 6, characterized in that: The masses of high-purity alumina powder, polyethylene glycol, triethanolamine and pure water are (40-50):(8-10):(3-4):(45-55).
8. The indium phosphide substrate grinding method according to claim 1 or 2, characterized in that: The particle size of high purity alumina powder is 800 mesh to 2000 mesh.
9. The indium phosphide substrate grinding method according to claim 1 or 2, characterized in that: The mechanical grinding time is 300s to 900s, the grinding pressure is 10N to 30N, and the grinding disc speed is 2rpm to 10rpm.
10. The indium phosphide substrate grinding method according to claim 1 or 2, characterized in that: The mechanical grinding time is 400s to 600s, the grinding pressure is 15N to 25N, and the grinding disc speed is 4rpm to 6rpm.