A low-mechanical-damage polishing method for indium phosphide wafers

Abstract

This application belongs to the field of semiconductor substrate technology, and particularly relates to a low-mechanical-damage polishing method for indium phosphide wafers. The provided low-mechanical-damage polishing method for indium phosphide wafers involves preparing first, second, and third diamond abrasives with gradually decreasing particle sizes into first, second, and third diamond polishing slurries with gradually decreasing concentrations. These three diamond polishing slurries of different specifications are then used to perform the first, second, and third polishing processes sequentially. The polishing process effectively suppresses the generation of new damage while ensuring the removal of most of the machining allowance. Through gentle, light-touch polishing and stress release, mechanical damage to the brittle indium phosphide wafer is minimized during the polishing process, resulting in an indium phosphide wafer with excellent overall flatness and a low surface damage layer. This method solves the technical problem of damage layers and flatness defects that easily occur during the polishing of indium phosphide wafers in existing technologies.

Description

Technical Field

[0001] This application belongs to the field of semiconductor substrate technology, and in particular relates to a low-mechanical-damage polishing method for indium phosphide wafers. Background Technology

[0002] Semiconductor substrate materials typically require processing steps such as single crystal growth, slicing, grinding, and polishing to obtain an ultra-flat semiconductor substrate, followed by the growth of epitaxial functional layers to obtain semiconductor devices.

[0003] Indium phosphide (IP) substrates are key substrate materials for manufacturing high-end semiconductor devices such as optical communication devices and high-frequency microwave devices. The performance of IPP devices, especially photoelectric conversion efficiency and frequency characteristics, is closely related to the surface quality and flatness of the IPP substrate. Poor surface quality and flatness of the IPP substrate can lead to uneven epitaxial growth, distorted photolithography patterns, and ultimately affect the yield and reliability of IPP devices.

[0004] Before obtaining an ultra-flat indium phosphide substrate through the polishing process, a grinding process is required for rapid and efficient leveling to obtain an indium phosphide polished wafer, laying the foundation for subsequent polishing processes. However, unlike the first-generation semiconductor material silicon (Si), indium phosphide (InP) material itself has properties such as high brittleness, which makes it easy to have defects such as surface / subsurface damage and low flatness during the grinding process. These damage layers and flatness defects are difficult to completely remove in subsequent polishing, reducing the performance and yield of indium phosphide devices. The main reasons for the damage layers and flatness defects in indium phosphide polished wafers are, on the one hand, improper selection of abrasives in the polishing slurry. During the polishing process, the pressing and scratching of the abrasives can easily generate deep cracks, dislocations and other damage layers on the surface and subsurface of indium phosphide. On the other hand, improper setting of process parameters such as polishing pressure can easily lead to defects such as collapsed edges, rolled edges or central bulges on the surface of indium phosphide, making it difficult to control the total flatness (TTV) of the wafer at a low level.

[0005] The goal of the polishing process is to minimize damage layers and flatness defects in indium phosphide polished wafers while ensuring a high material removal rate, and to reduce mechanical damage introduced by the polishing process. Therefore, it is necessary to develop a low-mechanical-damage polishing process suitable for indium phosphide. Summary of the Invention

[0006] In view of this, this application provides a low-mechanical-damage polishing method for indium phosphide wafers to solve the technical problem that damage layers and flatness defects are easily generated during the polishing of indium phosphide wafers in the prior art.

[0007] The first aspect of this application provides a low-mechanical-damage polishing method for indium phosphide wafers, comprising the following steps:

[0008] The preparation steps of the first diamond polishing fluid are as follows: Mix the first diamond abrasive, dispersant, deionized water and alkaline pH buffer to obtain the first diamond polishing fluid.

[0009] The preparation steps of the second diamond polishing fluid are as follows: Mix the second diamond abrasive, dispersant, deionized water and alkaline pH buffer to obtain the second diamond polishing fluid.

[0010] The preparation steps of the third diamond polishing fluid are as follows: Mix the third diamond abrasive, dispersant, deionized water and alkaline pH buffer to obtain the third diamond polishing fluid.

[0011] The steps of rough grinding are as follows: the sliced ​​indium phosphide wafer to be processed is fixed on the wafer support table of the grinding machine, the grinding machine is started and the first diamond grinding fluid is supplied in sequence for the first grinding, the second diamond grinding fluid is supplied for the second grinding, and the third diamond grinding fluid is supplied for the third grinding, so as to obtain the indium phosphide polished wafer;

[0012] The mass concentration of the first diamond abrasive in the first diamond polishing slurry is greater than the mass concentration of the second diamond abrasive in the second diamond polishing slurry, and the mass concentration of the second diamond abrasive in the second diamond polishing slurry is greater than the mass concentration of the third diamond abrasive in the third diamond polishing slurry.

[0013] The particle size of the first diamond abrasive is larger than that of the second diamond abrasive, and the particle size of the second diamond abrasive is larger than that of the third diamond abrasive.

[0014] In the first grinding process, the grinding disc rotation speed is lower than that in the second grinding process, while the grinding pressure is higher than that in the second grinding process.

[0015] In the second grinding process, the grinding disc rotation speed is lower than that in the third grinding process, while the grinding pressure is higher than that in the third grinding process.

[0016] Preferably, the first diamond polishing fluid comprises, by weight, 5-7 parts by weight of first diamond abrasive, 0.8-1.5 parts by weight of dispersant, 91.5-94.2 parts by weight of deionized water, and has a pH of 9-10.

[0017] Preferably, the second diamond polishing fluid comprises, by weight, 3-5 parts by weight of second diamond abrasive, 1-2 parts by weight of dispersant, 93-96 parts by weight of deionized water, and has a pH of 9-10.

[0018] Preferably, the third diamond abrasive fluid comprises, by weight, 1-1.5 parts third diamond abrasive, 1.5-2.5 parts dispersant, and 96-97.5 parts deionized water, with a pH of 9-10.

[0019] Preferably, the dispersant is selected from at least one of sodium polyacrylate dispersant, ammonium polyacrylate dispersant, sodium polymethacrylate dispersant, or ammonium polymethacrylate dispersant.

[0020] Preferably, the alkaline pH buffer is selected from at least one of sodium bicarbonate, sodium carbonate, sodium citrate, and disodium hydrogen phosphate.

[0021] Preferably, the first grinding process includes: controlling the rotation speed of the grinding disc to 30-50 rpm and continuously applying 10-20 N / cm. 2 The grinding pressure is 6-10 minutes.

[0022] Preferably, the second grinding process includes: controlling the rotation speed of the grinding disc to 40~60 rpm and continuously applying 5~10 N / cm. 2 The grinding pressure is [value], and the grinding time is 8-12 minutes.

[0023] Preferably, the third grinding process includes: controlling the rotation speed of the grinding disc to 60~80 rpm and intermittently applying 1~3 N / cm. 2 The grinding pressure is [value], and the grinding time is 10-14 minutes.

[0024] Preferably, the intermittent application is 1~3 N / cm 2 The grinding pressure cycle is 30~60s, during which 1~3N / cm is applied. 2 The grinding pressure is applied for 25-50 seconds, with a pause of 1-3 N / cm. 2 The grinding pressure is applied for 5 to 10 seconds.

[0025] Preferably, the support platform is selected from at least one of ceramic support platforms, resin support platforms, metal support platforms, and composite material support platforms.

[0026] The second aspect of this application provides an indium phosphide polishing wafer, which is prepared by the low mechanical damage polishing method for indium phosphide wafers described in the first aspect.

[0027] The third aspect of this application provides an indium phosphide polished wafer, which is obtained by polishing the indium phosphide polished wafer described in the second aspect.

[0028] The fourth aspect of this application provides an indium phosphide device, including an indium phosphide substrate and an epitaxial functional layer, wherein the indium phosphide substrate is selected from the indium phosphide polished wafer described in the third aspect.

[0029] Compared with the prior art, the low-mechanical-damage polishing method for indium phosphide wafers provided in this application has at least the following advantages:

[0030] This application provides a low-mechanical-damage polishing method for indium phosphide wafers. Through sequential first, second, and third polishing processes, different specifications of diamond polishing slurry and polishing techniques are used. While ensuring that most of the machining allowance is removed during polishing, the method effectively suppresses the generation of new damage. Furthermore, by gently polishing with light touches and releasing polishing stress, the mechanical damage to the brittle indium phosphide wafers during the polishing process can be minimized, thus meeting the quality requirements of high-end indium phosphide device manufacturing. Attached Figure Description

[0031] To more clearly illustrate the technical solutions in the specific embodiments of this application or the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this application. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0032] Figure 1 This is a schematic flowchart of a low-mechanical-damage polishing method for indium phosphide wafers provided in Embodiment 1 of this application. Detailed Implementation

[0033] This application provides a low-mechanical-damage polishing method for indium phosphide wafers, which solves the technical problem that damage layers and flatness defects are easily generated during the polishing of indium phosphide wafers in the prior art.

[0034] The technical solutions of this application will now be clearly and completely described with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this application. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0035] Example 1

[0036] This embodiment provides a low-mechanical-damage polishing method for indium phosphide wafers, the process flow diagram of which is shown below. Figure 1 As shown, this includes the steps for preparing the diamond polishing slurry and the polishing process.

[0037] The preparation steps for diamond polishing slurry include:

[0038] Weigh W7 diamond abrasive (particle size approximately 7 μm), sodium polyacrylate dispersant, and deionized water according to a mass ratio of 6:1:93. Mix the weighed diamond abrasive, sodium polyacrylate dispersant, and deionized water evenly, and add alkaline pH buffer sodium bicarbonate to adjust to 9 to obtain the first diamond grinding fluid for later use.

[0039] Weigh W2 (approximately 2 μm in particle size), sodium polyacrylate dispersant, and deionized water according to a mass ratio of 4:1.5:94.5. Mix the weighed diamond abrasive, sodium polyacrylate dispersant, and deionized water evenly, and add sodium bicarbonate as an alkaline pH buffer to adjust to 9 to obtain the second diamond grinding fluid for later use.

[0040] Weigh out W0.5 (particle size approximately 0.5 μm) of diamond abrasive, sodium polyacrylate dispersant, and deionized water according to a mass ratio of 1:2:7. Mix the weighed diamond abrasive, sodium polyacrylate dispersant, and deionized water evenly, and add alkaline pH buffer sodium bicarbonate to adjust to 9 to obtain the third diamond grinding fluid for later use.

[0041] The grinding process includes:

[0042] The indium phosphide slices with a diameter of 4 inches and a thickness of 650 μm were used as indium phosphide wafers to be processed.

[0043] The indium phosphide wafer to be processed is fixed onto the ceramic substrate of the polishing machine. The polishing machine is started and the first diamond polishing slurry is supplied. A polishing slurry of 15 N / cm is continuously applied at an upper polishing disc speed of 40 rpm and 35 rpm. 2 The first grinding was performed under the grinding pressure for 8 minutes. The thickness of the indium phosphide wafer removed was about 12 μm, as measured by a dial indicator, resulting in a coarsely ground indium phosphide wafer.

[0044] After replacing the polishing disc or cleaning the polishing machine, fix the coarsely ground indium phosphide wafer onto the ceramic substrate of the polishing machine, start the polishing machine and supply the second diamond polishing slurry, continuously applying 8 N / cm at a polishing disc speed of 50 rpm. 2 The second grinding was performed under the grinding pressure for 10 minutes. The thickness of the indium phosphide wafer removed was measured by a dial indicator to be about 6 μm, resulting in a finely ground indium phosphide wafer.

[0045] After replacing the polishing disc or cleaning the polishing machine, fix the finely polished indium phosphide wafer onto the ceramic substrate of the polishing machine, start the polishing machine and supply the third diamond polishing slurry, and intermittently apply 2.9 N / cm at a polishing disc speed of 60 rpm. 2 The third grinding process was carried out under the appropriate grinding pressure, with the grinding pressure applied intermittently for 45 seconds, i.e., 2.9 N / cm. 2After applying grinding pressure for 40 seconds, the application of 2.9 N / cm was paused. 2 After 5 seconds of grinding pressure, the wafer was ground for 12 minutes. A dial indicator was used to measure the thickness of the removed indium phosphide wafer surface, which was approximately 2 μm. After the third grinding, the wafer was ultrasonically cleaned with organic solvents such as toluene, acetone, or alcohol and then dried with nitrogen to obtain the indium phosphide polished wafer.

[0046] Comparative Example 1

[0047] This comparative example provides a method for polishing indium phosphide wafers, including the preparation of diamond polishing slurry and the polishing process.

[0048] The preparation steps for diamond polishing slurry include:

[0049] Weigh W7 diamond abrasive (particle size approximately 7 μm), sodium polyacrylate dispersant, and deionized water according to a mass ratio of 6:1:93. Mix the weighed diamond abrasive, sodium polyacrylate dispersant, and deionized water evenly, and add alkaline pH buffer sodium bicarbonate to adjust to 9 to obtain the first diamond grinding fluid for later use.

[0050] Weigh W2 (approximately 2 μm particle size) of diamond abrasive, sodium polyacrylate dispersant, and deionized water according to a mass ratio of 4:1.5:94.5. Mix the weighed diamond abrasive, sodium polyacrylate dispersant, and deionized water evenly, and add alkaline pH buffer sodium bicarbonate to adjust to 9 to obtain the second diamond grinding fluid for later use.

[0051] The grinding process includes:

[0052] Indium phosphide with a diameter of 4 inches and a thickness of 650 μm obtained from the same batch of slices as in Example 1 was used as the indium phosphide wafer to be processed.

[0053] The indium phosphide wafer to be processed is fixed onto the ceramic substrate of the polishing machine. The polishing machine is started and the first diamond polishing slurry is supplied. A polishing slurry of 15 N / cm is continuously applied at an upper polishing disc speed of 40 rpm and 35 rpm. 2 The first grinding was performed under the grinding pressure for 8 minutes. The thickness of the indium phosphide wafer removed was about 12 μm, as measured by a dial indicator, resulting in a coarsely ground indium phosphide wafer.

[0054] After replacing the polishing disc or cleaning the polishing machine, fix the coarsely ground indium phosphide wafer onto the ceramic substrate of the polishing machine, start the polishing machine and supply the second diamond polishing slurry, continuously applying 8 N / cm at a polishing disc speed of 50 rpm. 2 The second grinding was performed under the grinding pressure for 13.5 minutes. The thickness of the indium phosphide wafer removed was measured to be about 8 μm using a dial indicator. After the second grinding, the wafer was ultrasonically cleaned with organic solvents such as toluene, acetone or alcohol and dried with nitrogen to obtain the indium phosphide polished wafer.

[0055] Comparative Example 2

[0056] This comparative example provides a method for polishing indium phosphide wafers, including the preparation of diamond polishing slurry and the polishing process.

[0057] The preparation steps for diamond polishing slurry include:

[0058] Weigh W2 (approximately 2 μm particle size) of diamond abrasive, sodium polyacrylate dispersant, and deionized water according to a mass ratio of 4:1.5:94.5. Mix the weighed diamond abrasive, sodium polyacrylate dispersant, and deionized water evenly, and add alkaline pH buffer sodium bicarbonate to adjust to 9 to obtain the second diamond grinding fluid for later use.

[0059] The grinding process includes:

[0060] Indium phosphide with a diameter of 4 inches and a thickness of 650 μm obtained from the same batch of slices as in Example 1 was used as the indium phosphide wafer to be processed.

[0061] The indium phosphide wafer to be processed is fixed onto the ceramic substrate of the polishing machine. The polishing machine is started and a second diamond polishing slurry is supplied. A polishing slurry of 10 N / cm is continuously applied at a polishing disc speed of 45 rpm. 2 The second grinding was performed under the grinding pressure for 30 minutes. The thickness of the indium phosphide wafer removed was measured by a dial indicator to be approximately 19.5 μm. After the second grinding, the wafer was ultrasonically cleaned with organic solvents such as toluene, acetone or alcohol and dried with nitrogen to obtain the indium phosphide polished wafer.

[0062] Experimental Example 1

[0063] This experiment tests the total surface flatness (TTV) and subsurface damage layer thickness (μm) of indium phosphide polished wafers prepared by the polishing methods provided in Example 1 and Comparative Examples 1-2.

[0064] The testing procedures for total surface flatness (TTV) and subsurface damage layer thickness (μm) include:

[0065] The indium phosphide polishing wafer prepared in Example 1 was used as polishing wafer sample 1, the indium phosphide polishing wafer prepared in Comparative Example 1 was used as polishing wafer sample 2, and the indium phosphide polishing wafer prepared in Comparative Example 2 was used as polishing wafer sample 3.

[0066] The total flatness (TTV) of polished wafer sample 1, polished wafer sample 2, and polished wafer sample 3 was tested using a Tropel FM100 leveling instrument. The subsurface damage layer thickness (μm) of the cross-section of polished wafer sample 1, polished wafer sample 2, and polished wafer sample 3 was observed using a scanning electron microscope. The results are shown in Table 1.

[0067] Table 1: Test results of global flatness and subsurface damage layer of polished wafer samples

[0068]

[0069] As shown in Table 1, the overall flatness of polished wafer samples 2-3 is between 2.5 and 4.0 μm, and the subsurface damage layer thickness is between 3.0 and 4.0 μm. In contrast, polished wafer sample 1 has an overall flatness of approximately 0.8 μm and a subsurface damage layer thickness of approximately 0.5 μm, showing almost no mechanical damage and exhibiting a better polishing effect. This indicates that the polished wafer samples provided in Comparative Examples 1-2 experienced significant mechanical loss during the polishing process of indium phosphide wafers. This is because the polished wafer samples provided in Example 1 underwent three polishing processes sequentially—first, second, and third polishing—using different specifications of diamond polishing slurry and polishing processes. The first polishing was coarse polishing, using a high concentration of coarse diamond abrasive combined with polishing pressure to remove most of the machining allowance. The first grinding process is fine grinding, which uses moderate diamond abrasive with low pressure to effectively remove the damage layer caused by coarse grinding and inhibit the formation of new damage. The second grinding process is ultra-fine grinding, which uses low-concentration diamond abrasive with extremely low grinding pressure to achieve a gentle, light-touch grinding. Furthermore, because the grinding pressure is applied intermittently, the pause in applying the grinding pressure helps to release the stress accumulated in the previous grinding process for the brittle indium phosphide (InP) wafer and minimizes elastic deformation of the wafer during the grinding process. This truly corrects the overall flatness rather than flattening it, making it less prone to mechanical damage when grinding indium phosphide wafers. Surface / subsurface damage and flatness are maintained at an extremely high level, meeting the quality requirements of high-end indium phosphide device manufacturing.

[0070] The above embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them. Although this application 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 or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of this application.

Claims

1. A low-mechanical-damage polishing method for indium phosphide wafers, characterized in that, Includes the following steps: The first diamond abrasive, the second diamond abrasive, and the third diamond abrasive are respectively mixed with a dispersant, deionized water, and an alkaline pH buffer to obtain the first diamond polishing slurry, the second diamond polishing slurry, and the third diamond polishing slurry. The sliced ​​indium phosphide wafer to be processed is fixed on the wafer support table of the polishing machine. The polishing machine is started and the first diamond polishing fluid is supplied for the first polishing, the second diamond polishing fluid is supplied for the second polishing, and the third diamond polishing fluid is supplied for the third polishing to obtain the polished indium phosphide wafer. The mass concentration of the first diamond abrasive in the first diamond polishing slurry is greater than the mass concentration of the second diamond abrasive in the second diamond polishing slurry, and the particle size is greater than the particle size of the second diamond abrasive. The mass concentration of the second diamond abrasive in the second diamond polishing slurry is greater than the mass concentration of the third diamond abrasive in the third diamond polishing slurry, and the particle size is greater than the particle size of the third diamond abrasive. In the first grinding process, the grinding disc rotation speed is lower than that in the second grinding process, while the grinding pressure is higher than that in the second grinding process. In the second grinding process, the grinding disc rotation speed is lower than that in the third grinding process, while the grinding pressure is higher than that in the third grinding process.

2. The low-mechanical-damage polishing method for indium phosphide wafers according to claim 1, characterized in that, The first diamond polishing fluid comprises, by mass, 5-7 parts of first diamond abrasive, 0.8-1.5 parts of dispersant, and 91.5-94.2 parts of deionized water, with a pH of 9-10.

3. The low-mechanical-damage polishing method for indium phosphide wafers according to claim 1, characterized in that, The second diamond polishing fluid comprises, by mass, 3-5 parts of second diamond abrasive, 1-2 parts of dispersant, 93-96 parts of deionized water, and has a pH of 9-10.

4. The low-mechanical-damage polishing method for indium phosphide wafers according to claim 1, characterized in that, The third diamond abrasive fluid comprises, by mass, 1-1.5 parts third diamond abrasive, 1.5-2.5 parts dispersant, and 96-97.5 parts deionized water, with a pH of 9-10.

5. The low-mechanical-damage polishing method for indium phosphide wafers according to claim 1, characterized in that, The first grinding process includes: controlling the rotation speed of the grinding disc to 30~50 rpm and continuously applying 10~20 N / cm. 2 The grinding pressure.

6. The low-mechanical-damage polishing method for indium phosphide wafers according to claim 1, characterized in that, The second grinding process includes: controlling the grinding disc rotation speed to 40~60 rpm and continuously applying 5~10 N / cm. 2 The grinding pressure.

7. The low-mechanical-damage polishing method for indium phosphide wafers according to claim 1, characterized in that, The third grinding process includes: controlling the rotation speed of the grinding disc to 60~80 rpm and intermittently applying 1~3 N / cm. 2 The grinding pressure; the intermittent application of 1~3 N / cm 2 The grinding pressure is applied for 1 to 10 seconds.

8. An indium phosphide polished wafer, characterized in that, It is prepared by the low mechanical damage polishing method of indium phosphide wafer as described in any one of claims 1-7.

9. An indium phosphide polished wafer, characterized in that, The indium phosphide wafer described in claim 8 is obtained by polishing.

10. An indium phosphide device, characterized in that, The indium phosphide substrate used is selected from the indium phosphide polished wafer described in claim 9.

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