A method for processing a silicon substrate polishing sheet for high-quality SOI
By combining liquid wax and organic solvents, the problem of surface morphology and flatness of silicon substrate polished wafers was solved, enabling the processing of high-quality silicon substrate polished wafers for SOI, which are suitable for high-quality SOI devices.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- SHANDONG GRINM SEMICON MATERIALS CO LTD
- Filing Date
- 2025-07-15
- Publication Date
- 2026-05-29
AI Technical Summary
Existing technologies make it difficult to manufacture silicon substrate polished wafers with special 'concave' morphology and high surface flatness, which cannot meet the requirements of high-quality SOI chips.
A combination of liquid wax and organic solvents is used to form a uniform wax film by controlling the rotation speed and spray position. After baking with a heat source, the film is polished with wax to achieve a concave shape with upturned edges and control the surface flatness.
It enables the processing of high-quality SOI silicon substrate polished wafers, meeting the special requirements of different customers for morphology and flatness, and is suitable for high-quality SOI devices.
Smart Images
Figure CN120824193B_ABST
Abstract
Description
Technical Field
[0001] This invention relates to a processing method for high-quality SOI silicon substrate polished wafers, belonging to the field of integrated circuit technology. Background Technology
[0002] Currently, silicon-on-insulator (SOI) has become one of the mainstream products in most electronic materials fields. With the rapid development of new energy vehicles, the integration density of automotive-grade SOI materials for automotive chips is gradually increasing, thus the market demand for high-quality SOI is growing. Consequently, the market demand for silicon substrate polished wafers suitable for SOI chips is also increasing. Some high-quality SOI devices require the substrate polished wafer to have a special morphology, namely a concave morphology with thick edges and a thin center. Simultaneously, while possessing this concave morphology, the surface flatness of the substrate polished wafer is also required; the values of GBIR (Global Flatness Back Ideal Range) and SFQR (Site Flatness Front Least-squares Range), which represent the flatness level, cannot be too high. Summary of the Invention
[0003] The purpose of this invention is to provide a processing method for high-quality SOI silicon substrate polished wafers. This method can produce silicon substrate polished wafers with a special "concave" morphology, and the degree of "concavity" of the substrate polished wafer can be controlled by process flow and process parameters to meet the special needs of different customers.
[0004] To achieve the above objectives, the present invention adopts the following technical solution:
[0005] A method for processing a high-quality SOI silicon substrate polished wafer, the method comprising the following steps:
[0006] (1) Fix the single crystal silicon substrate on a circular chuck, with the center of the substrate coinciding with the center of the chuck. The chuck rotates the silicon substrate at a speed of 100-500 rpm. At this time, inject 0.3-8 mL of liquid wax into the center of the substrate. The chuck and substrate continue to rotate for 1-10 seconds. Under the action of centrifugal force, the liquid wax is coated on the back surface of the substrate. Then, increase the speed of the chuck to 1000-2500 rpm and continue to rotate for 1-10 seconds.
[0007] (2) Reduce the chuck speed to 800-1500 rpm. At this time, spray organic solvent into the area 1-3 mm away from the edge of the substrate at a spray speed of 1-8 m / s for a duration of 0.1-10 s.
[0008] (3) After being baked by a heat source, it is pasted onto a special tooling fixture for wax polishing and then wax polished.
[0009] Furthermore, the following steps are added between step (2) and step (3):
[0010] (a) Increase the speed of the suction cup to 2800-3700 rpm. At this time, inject 0.5-5 mL of liquid wax into the center of the substrate. The suction cup and the substrate continue to rotate for 0.8-7 seconds. Under the action of centrifugal force, the liquid wax is coated on the back surface of the substrate.
[0011] Furthermore, the liquid wax used in step (1) is composed of the following components by mass percentage: rosin content 15%-40%, isopropanol content 40%-65%, and butanol content 20%-45%.
[0012] Further, the liquid wax used in step (a) comprises, by mass percentage: 5%-15% rosin, 50%-60% isopropanol, and 35%-45% butanol.
[0013] Further, in step (2), the composition of the organic solvent by mass percentage is: 10%-20% diethanolamine, 1%-5% tetramethylamine hydroxide, and the remainder is pure water. Further, the concentration of the organic solvent is 1%-10%.
[0014] Furthermore, in step (2), the distance from the organic solvent spray nozzle to the contact point between the organic solvent and the substrate is 5-100 mm, and the angle between the spray stream and the substrate is 30°-60°.
[0015] Furthermore, the substrate is fixed to the suction cup by vacuum.
[0016] The advantages of this invention are:
[0017] This invention relates to the processing of single-sided polished substrates for SOI applications. By coating a wax film and then removing the edge wax film, a concave morphology with upturned edges is obtained after single-sided polishing. This is suitable for providing single-sided polished substrates for high-quality SOI devices. Furthermore, to meet the different requirements of various customers regarding the degree of upturn, optional adaptive solutions are provided. Attached Figure Description
[0018] Figure 1 This is a schematic diagram of step (2) to remove the edge wax film.
[0019] Figure 2 This is a cross-sectional view of the substrate and wax film after step (2) is completed.
[0020] Figure 3This is a cross-sectional view of the substrate and wax film after step (a) is completed.
[0021] Figure 4 This is a cross-sectional view of the geometric morphology of the polished surface of the substrate after processing in Example 1.
[0022] Figure 5 This is a cross-sectional view of the geometric morphology of the polished surface of the substrate after processing in Example 2. Detailed Implementation
[0023] The present invention will be further described below with reference to the accompanying drawings and specific embodiments. It should be noted that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention.
[0024] The present invention provides a processing method for obtaining high-quality SOI silicon substrate polished wafers, comprising: applying wax at a low rotation speed, continuously spinning the wax at a medium-high rotation speed, removing the wax film adhering to the edge of the substrate wafer with an organic solvent at a medium-low rotation speed, baking with a heat source, and then attaching it to a special polishing fixture. After completing the chemical mechanical polishing operation of the substrate wafer, the surface morphology and geometric parameters such as GBIR and SFQR of the silicon substrate polished wafer are measured.
[0025] Specifically, the processing method of the present invention includes the following steps:
[0026] (1) such as Figure 1 As shown, a single-crystal silicon substrate 102 is fixed on a circular chuck 101, with the center of the substrate coinciding with the center of the chuck. The chuck rotates the silicon substrate at a speed of 100-500 rpm. At this time, 0.3-8 mL of liquid wax is injected into the center of the substrate. The chuck and substrate continue to rotate for 1-10 seconds, and the liquid wax is coated on the back surface of the substrate under the action of centrifugal force. Then, the speed of the chuck is increased to 1000-2500 rpm and rotated for 1-10 seconds. The liquid wax used has the following composition by mass percentage: rosin content 15%-40%, isopropanol content 40%-65%, and butanol content 20%-45%.
[0027] (2) Reduce the suction cup speed to 800-1500 rpm. At this time, if Figure 1 As shown, organic solvent is sprayed through organic solvent spray pipe 103 into an area 1-3 mm from the edge of the substrate at a spray speed of 1-8 m / s for a duration of 0.1-10 s. The organic solvent is Kilala dewaxing cleaning agent produced by Nippon Ka Seiko, whose main components are 10%-20% diethanolamine, 1%-5% tetramethylamine hydroxide, and the remainder being pure water. Kilala is diluted to a concentration of 1%-10%. The distance from the spray pipe nozzle to the contact point between the organic solvent and the substrate is 5-100 mm, and the angle between the spray stream and the substrate is 30°-60°.
[0028] (3) After being baked by a heat source, it is pasted onto a special tooling fixture for wax polishing and then wax polished.
[0029] In step (1), the chuck initially rotates the substrate at 100-500 rpm, then drips liquid wax onto the center of the silicon wafer. After maintaining this speed for a period of time, the rotation speed of the chuck and substrate is increased to 1000-2500 rpm and maintained for a period of time. The purpose of this step is that after the liquid wax drips onto the rotating substrate surface, it will disperse under the action of centrifugal force, forming a wax film with a thickness of micrometers on the substrate surface. When the rotation speed of the substrate is low, the thickness of the wax film formed is visibly uneven. Therefore, it is necessary to increase the rotation speed further. Under the action of high centrifugal force, the liquid wax adhering to the substrate surface will flow again on the substrate surface, forming a wax film with better uniformity. Its uniform distribution is much more uniform than the wax film formed by dripping wax once at a high rotation speed.
[0030] In step (2), the suction cup rotates at a speed of 800-1500 rpm, and organic solvent is sprayed into a range of 1-3 mm from the edge of the substrate. The purpose is to remove the wax film adhering to the edge of the substrate. After single-sided polishing, a substrate with an upturned edge can be obtained. Figure 2 The image shows a cross-sectional view of the substrate 102 and the wax film 202 after the first spraying and edge removal, after step (2) is completed. By carefully controlling the ratio of the organic solvent, spraying speed, spraying angle, and spraying time, it is ensured that the sprayed organic solvent can completely dissolve and remove the wax film in the target area, while also preventing excess organic solvent from splashing onto other areas of the substrate. If organic solvent splashes onto other areas of the substrate, it will dissolve the wax film in that area, disrupting the uniformity of the wax film thickness and deteriorating the geometry of the substrate after single-sided polishing.
[0031] Further, an optional step (a) is added between step (2) and step (3): the suction cup rotation speed is increased to 2800-3700 rpm. At this time, 0.5-5 mL of liquid wax is injected into the center of the substrate. The suction cup and the substrate continue to rotate for 0.8-7 seconds. Under the action of centrifugal force, the liquid wax is coated on the back surface of the substrate. The purpose of this step is that the second drop of liquid wax, under the action of centrifugal force, spreads out on the back of the substrate that is already covered with a layer of wax film, forming a new layer of wax film, and at the same time, it can fill the area where the wax film was removed by organic solvent in step (2). At this time, the thickness difference of the wax film in this area is smaller than that of the wax film in other areas of the substrate, and a slight upward curl of the polished edge can be obtained. Figure 3 The diagram shows cross-sectional views of the substrate 102, the wax film 202 after the first coating and edge removal, and the wax film 303 after the second coating, after step (a) is completed.
[0032] In step (a), the liquid wax used is composed of the following components by mass percentage: 5%-15% rosin, 50%-60% isopropanol, and 35%-45% butanol.
[0033] Example 1
[0034] An 8-inch silicon substrate was selected and rotated at 400 rpm by a vacuum chuck. 1.5 mL of liquid wax was sprayed onto the center of the substrate. The substrate was rotated at 400 rpm for 3 seconds, then the chuck speed was increased to 1500 rpm and maintained for 5 seconds. During rotation, the center of the substrate coincided with the center of the vacuum chuck. The liquid wax composition was: 25% rosin, 50% isopropanol, and 25% butanol.
[0035] The rotation speed of the substrate and the vacuum chuck is reduced to 1000 rpm. At this time, Kilala dewaxing cleaner produced by Nippon Chemical Seiko is sprayed into a 2.5 mm area on the edge of the substrate. The dewaxing cleaner is diluted to a concentration of 5%, the spraying speed is 3 m / s, the duration is 5 s, the distance between the spray nozzle and the spray contact point is 10 mm, and the angle between the spray flow and the silicon wafer is 45°.
[0036] After the substrate rotation speed is reduced to 0, it is baked by a heat source and then attached to a special tooling fixture for wax polishing, where it is polished on one side with wax.
[0037] The silicon substrate wafer processed using the method described in this embodiment was subjected to surface flatness testing using an ADE flatness tester (ADE9600), and the geometric parameters of the silicon wafer after polishing were measured using two evaluation standards: GBIR (Global Flatness Back Ideal Range) and SFQR (Site Flatness Front Least-squares Range). GBIR and SFQR are two evaluation standards in the semiconductor industry for evaluating the geometric parameter levels of substrate materials; the lower the value, the better the local flatness.
[0038] Figure 4 The table shows a cross-sectional view of the polished surface geometry of the substrate after processing in Example 1. The ADE flatness test results are shown in Table 1. The surface flatness of the silicon substrate is 1.13 micrometers, with a slight upward tilt of approximately 0.5 micrometers at the edges. This meets the needs of customers who require a high degree of tilt reduction but do not have high requirements for flatness.
[0039] Example 2
[0040] Select an 8-inch silicon substrate. Rotate the substrate at 300 rpm using a vacuum chuck. Spray 2 mL of liquid wax onto the center of the substrate. Maintain the 300 rpm rotation for 4 seconds, then increase the chuck speed to 2000 rpm and continue rotating for 4 seconds. During rotation, the center of the substrate coincides with the center of the vacuum chuck. The liquid wax composition is: 25% rosin, 50% isopropanol, and 25% butanol.
[0041] The rotation speed of the substrate and the vacuum chuck is reduced to 1000 rpm. At this time, Kilala dewaxing cleaner produced by Nippon Chemical Seiko is sprayed into a 2.5 mm area on the edge of the substrate. The dewaxing cleaner is diluted to a concentration of 5%, the spraying speed is 3 m / s, the duration is 5 s, the distance between the spray nozzle and the spray contact point is 15 mm, and the angle between the spray flow and the silicon wafer is 60°.
[0042] The substrate and vacuum chuck are rotated at 3000 rpm. At this point, 2.5 mL of liquid wax is injected into the center of the substrate, and the chuck and substrate continue to rotate for 4 seconds. During rotation, the center of the substrate coincides with the center of the vacuum chuck. The liquid wax has the following composition: 10% rosin, 60% isopropanol, and 40% butanol.
[0043] After the substrate rotation speed is reduced to 0, it is baked by a heat source and then attached to a special tooling fixture for wax polishing, where it is polished on one side with wax.
[0044] The silicon substrate wafer processed in this embodiment was subjected to surface flatness testing using an ADE flatness tester (ADE9600).
[0045] Figure 5 The table shows a cross-sectional view of the polished surface geometry of the substrate after processing in Example 2. The ADE flatness test results are shown in Table 1. The surface flatness of the silicon substrate is 0.56 micrometers, with a slight upward tilt of approximately 0.2 micrometers at the edges. This meets the needs of customers requiring high flatness but only a slight upward tilt at the edges.
[0046] Table 1. Results of ADE flatness test
[0047]
[0048] The above description describes the preferred embodiments of the present invention and the technical principles applied thereto. For those skilled in the art, any obvious changes such as equivalent transformations or simple substitutions based on the technical solutions of the present invention, without departing from the spirit and scope of the present invention, shall fall within the protection scope of the present invention.
Claims
1. A method for processing high-quality SOI silicon substrate polished wafers, characterized in that, The method for manufacturing a polished silicon substrate wafer with a concave shape and upturned edges after polishing includes the following steps: (1) Fix the single crystal silicon substrate on a circular chuck, with the center of the substrate coinciding with the center of the chuck. The chuck rotates the silicon substrate at a speed of 100-500 rpm. At this time, inject 0.3-8 mL of liquid wax into the center of the substrate. The chuck and substrate continue to rotate for 1-10 seconds. Under the action of centrifugal force, the liquid wax is coated on the back surface of the substrate. Then, increase the speed of the chuck to 1000-2500 rpm and continue to rotate for 1-10 seconds. The liquid wax used in step (1) has the following composition by mass percentage: rosin content 15%-40%, isopropanol content 40%-65%, and butanol content 20%-45%; (2) Reduce the chuck speed to 800-1500 rpm. At this time, spray organic solvent into the area 1-3 mm away from the edge of the substrate at a spray speed of 1-8 m / s for a duration of 0.1-10 s. The composition of the organic solvent by mass percentage is: 10%-20% diethanolamine, 1%-5% tetramethylamine hydroxide, and the remainder is pure water; The distance from the nozzle of the organic solvent spray pipe to the contact point between the organic solvent and the substrate is 5-100 mm, and the angle between the spray flow and the substrate is 30°-60°. (a) Increase the suction cup speed to 2800-3700 rpm. At this time, inject 0.5-5 mL of liquid wax into the center of the substrate. The suction cup and the substrate continue to rotate for 0.8-7 seconds. Under the action of centrifugal force, the liquid wax is coated on the back surface of the substrate. The liquid wax used in step (a) has the following composition by mass percentage: 5%-15% rosin, 50%-60% isopropanol, and 35%-45% butanol; (3) After being baked by a heat source, it is pasted onto a special tooling fixture for wax polishing and then wax polished.
2. The processing method for high-quality SOI silicon substrate polished wafers according to claim 1, characterized in that, The organic solvent is diluted to a concentration of 1%-10%.
3. The processing method for a high-quality SOI silicon substrate polished wafer according to claim 1 or 2, characterized in that, The substrate is fixed to the suction cup by vacuum.