Adjustable grinding device based on single crystal silicon wafer and grinding method for single crystal silicon wafer

Abstract

The application relates to an adjustable grinding device based on a single crystal silicon wafer and a grinding processing method of the single crystal silicon wafer, which is suitable for small-batch reprocessing of a silicon wafer face type that does not meet the standards after precision grinding processing or conventional grinding processing. In the grinding processing, according to the visual curve of the displacement sensor and the online measurement result of the silicon wafer face type parameter, a signal is transmitted to an embedded driving device of the displacement sensor in the device and a hydraulic directional control loop of each adjustable supporting shaft, so that the grinding disc that is inclined in processing is leveled and each supporting shaft independently and accurately adjusts the convexity and concavity delta and fullness epsilon of the grinding face type, so that the processed silicon wafer has high competitive quality and precision.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of semiconductor wafer processing, and particularly relates to an adjustable grinding device based on a monocrystalline silicon wafer and a grinding processing method for the monocrystalline silicon wafer. BACKGROUND

[0002] Monocrystalline silicon is a kind of crystal with a complete lattice structure, and at high temperature, it has relatively active chemical properties, forms a heterojunction with a functional material, participates in the realization of device functions, and becomes the most widely used substrate material in semiconductor devices at the present stage. In order to increase chip yield and reduce manufacturing cost, silicon wafers show the characteristics of large diameter, and the diameter of the mainstream silicon wafer products reaches 12 inches, and some enterprises and research institutes are developing 18-inch silicon wafers. The processing precision and surface quality of large-size monocrystalline silicon wafers have higher requirements, and need to have an ultra-flat and damage-free surface.

[0003] Silicon wafer grinding technology has the advantages of high processing efficiency, high quality and easy realization of processing automation. In the preparation stage of the silicon wafer substrate, it is used for the flattening processing of the silicon wafer to remove the surface saw marks and damage layer generated by the cutting processing of the silicon wafer, and to prepare a high-precision and low-damage surface for the CMP stage; in the later process, it is used for the single-side thinning processing of the silicon wafer to remove the excess silicon substrate material on the back surface of the silicon wafer, reduce the thickness of the silicon wafer, and meet the wafer processing requirements.

[0004] Combined with the technical experience and actual production conditions, silicon wafer manufacturers have differences in the monocrystalline silicon wafer manufacturing process. For example, before the CMP process, the manufacturer will adopt a process route of double-side grinding, single-side thinning and double-side polishing, or a process route of double-side grinding, single-side thinning and double-side polishing, or a process route of double-side grinding and etching which has more stringent technical requirements.

[0005] Taking the grinding process as an example, a commercial grinding machine adopts planetary grinding, which is divided into an upper grinding disc, a retainer, a silicon wafer and a lower grinding disc. For a 12-inch silicon wafer, the equipment is installed with 5 retainers, and 3 or 4 silicon wafers are placed in each retainer. The silicon wafers placed in the retainers become planetary gears, and make planetary motion around the sun gear. 15 or 20 silicon wafers are completed in the same batch; or a double-spindle multi-station structure is adopted, and each spindle respectively completes the rough grinding and fine grinding processes. The stations are sequentially corresponding to the standby station, the rough grinding station, the fine grinding station and the cleaning station.

[0006] The continuous development of the information industry puts forward new requirements for silicon wafer grinding technology, and the silicon wafer needs to ensure high quality and high precision. For example, the prior art CN102229087A proposes a double-spindle three-station wafer grinding machine inclination adjustment device and method, and CN101402178A proposes a pad adjustable wafer grinding device. Both of them are provided with an inclination adjustment structure, and the angle of the grinding unit is adjusted according to the surface type parameters or grinding conditions, so as to ensure the high-precision silicon wafer of the desired thickness. The inclination adjustment device of the above-mentioned prior art grinding machine needs to be adjusted, tested, adjusted again, until the surface type meets the requirements; when multi-station processing is adopted, not only the planetary wheel processing movement, the inclination of the station and the relative position relationship of the main shafts need to be considered, but also the adjustable main shafts corresponding to different stations and the number of fixed feet are different, the adjustment method is complicated and a lot of time is consumed; in addition, the application occasion is relatively single, and the adjustment of the device parameters according to the processing conditions will increase the production cost.

[0007] Therefore, there is still a need for a grinding adjustable device and method capable of online real-time monitoring and real-time adjustment, which can obtain silicon wafers with high competitiveness in quality and precision. SUMMARY

[0008] In order to solve the problems existing in the prior art, the purpose of the present application is to provide a single-station adjustable grinding device based on single crystal silicon wafer, which can adjust in real time and independently and accurately adjust the convexity and concavity δ and fullness ε of the grinding surface type of each support shaft according to the working conditions and the surface shape parameters of the silicon wafer, so as to process high-quality silicon wafers.

[0009] Another purpose of the present application is to provide a grinding processing method for single crystal silicon wafer using the device.

[0010] In order to achieve the above purposes, the present application adopts the following technical solutions:

[0011] An adjustable grinding device based on single crystal silicon wafer, the device comprises a silicon wafer spindle adjustment member, a grinding wheel spindle adjustment member and a surface type measurement member;

[0012] The silicon wafer spindle adjustment member comprises a bearing turntable, a silicon wafer spindle, a grinding disc support shaft and a grinding disc; the bearing turntable is located at the bottom, and the silicon wafer spindle and three grinding disc support shafts uniformly distributed at intervals of 120° on the same circumference are coaxially installed on the bearing turntable, and the grinding disc is supported by the grinding disc support shafts A1, A2, A3 and the silicon wafer spindle; wherein the grinding disc support shafts A1 and A2 are fixed supports, and the grinding disc support shaft A3 is an adjustable support; displacement sensors are respectively installed at the same radial position on the outer edge and the inner edge of the grinding disc;

[0013] The grinding wheel spindle adjustment component includes a diamond grinding wheel, a grinding wheel spindle, a grinding wheel spindle seat, and a spindle seat support shaft. The diamond grinding wheel is installed at the lower end of the grinding wheel spindle. The grinding wheel spindle section is sleeved inside the grinding wheel spindle seat, and the grinding wheel spindle section is coaxial with the grinding wheel spindle seat. Three spindle seat support shafts are installed between the grinding wheel spindle seat and the upper shoulder of the grinding wheel spindle, and are evenly distributed at 120° intervals on the same circumference. Among them, spindle seat support shafts B1 and B2 are fixed supports, and spindle seat support shaft B3 is an adjustable support.

[0014] The surface measurement component is located at the lower end of the shoulder on the grinding wheel spindle.

[0015] In one specific implementation, with the center of the silicon wafer placed on the grinding disc as the origin O, and the diamond grinding wheel mounted at the lower end of the grinding wheel spindle performing grinding, at any position, the line connecting the center of the silicon wafer, the edge of the diamond grinding wheel, and the intersection point C of the silicon wafer edge is the y-axis; the line connecting the center of the silicon wafer and the y-axis perpendicularly is the x-axis; and the line connecting the center of the silicon wafer and the xoy plane perpendicularly is the z-axis. The silicon wafer rotation radius R0 and the diamond grinding wheel radius R1 are set, and... Establish a coordinate system based on the line connecting the center of the silicon wafer and the intersection point. In this coordinate system, the intersection point of the x-axis and the edge of the silicon wafer away from the diamond grinding wheel is A3. A1 and A2 are evenly distributed with a 120° interval from A3 on the circumference with the origin O as the center and R0 as the radius. The intersection point of the perpendicular line to the x-axis and passing through the center O1 of the diamond grinding wheel and the edge of the grinding wheel away from the x-axis is B3. B1 and B2 are evenly distributed with a 120° interval from B3 on the circumference with the origin O1 as the center and R1 as the radius.

[0016] In one specific implementation, the displacement sensor is embedded at a distance of 20 mm from the outer edge and 20 mm from the inner edge of the grinding disc, and is located in the same radial direction. During the grinding process, it continuously monitors the height of its position and transmits signals to the displacement sensor drive device, which drives the outer edge and / or inner edge of the grinding disc to rise or fall, thereby reducing the height difference between the outer edge and inner edge of the grinding disc and controlling the form and position error of the grinding disc.

[0017] In one specific implementation, the drive device is equipped with a hydraulic directional control circuit with a one-way valve locking. When the position height monitored by the displacement sensor changes, a signal is transmitted to a three-position four-way solenoid valve to change the flow direction of the hydraulic circuit, thereby causing the piston hydraulic cylinder to push the inner and outer edges of the grinding disc to make corresponding adjustments.

[0018] In one specific implementation, the surface shape measurement component consists of a sensor, a converging lens, a receiving lens, and a detector. The sensor emits light, which is focused by the converging lens and incident perpendicularly onto the surface of the silicon wafer being ground. The receiving lens receives the scattered light from the incident light point to form an imaging point. The incident light spot moves with the change in the surface morphology of the silicon wafer, and the imaging point moves accordingly on the light receiving detector. The change in the surface shape of the silicon wafer is measured online based on the image movement of the imaging point and the structural parameters of the surface shape measurement component.

[0019] In one specific implementation, the surface shape measuring component transmits the monitored surface shape change signal to the driving device. The driving device is a reversing valve with a neutral position unloading circuit controlled by a throttle valve under the same hydraulic motor as the displacement sensor driving device. It transmits the surface shape change signal to the solenoid valve and changes the flow direction of the hydraulic circuit, thereby driving the adjustable grinding disc support shaft A3 and the adjustable spindle seat support shaft B3 to adjust their height.

[0020] In another aspect of the present invention, the aforementioned adjustable grinding device is used for grinding a single-crystal silicon wafer. The silicon wafer is placed on a grinding disc. During grinding, the silicon wafer spindle controls the grinding disc to rotate the silicon wafer counterclockwise or clockwise. The grinding wheel spindle drives the diamond grinding wheel to rotate counterclockwise or clockwise, while simultaneously feeding along the axial direction of the grinding wheel spindle. The silicon wafer and the diamond grinding wheel rotate in opposite directions. The outer diameter of the diamond grinding wheel is at least equal to the outer diameter of the silicon wafer. The outer edge of the diamond grinding wheel always passes through the center of the silicon wafer. The silicon wafer is ground using a diamond grinding wheel mounted at the lower end of the grinding wheel spindle.

[0021] In a specific implementation, the angle between the diamond wheel axis and the silicon wafer axis in the yoz plane, i.e., the swing angle around the x-axis, is set as α, and the angle between the diamond wheel axis and the silicon wafer axis in the xoz plane, i.e., the swing angle around the y-axis, is set as β. The relative angular coordinate relationship between the silicon wafer surface, edge feature points, and each main axis is established. Based on the spatial geometric relationship between the diamond wheel main axis and the silicon wafer main axis, the correspondence between the silicon wafer grinding surface profile and the coordinate system based on the silicon wafer center-intersection line is obtained: the convexity δ of the single crystal silicon wafer is determined by the adjustment amount of the swing angle α around the x-axis, and the fullness ε is determined by the adjustment amount of the swing angle β around the y-axis.

[0022] In one specific implementation, based on the adjustment method of the relative angles of each axis and the grinding surface profile of the silicon wafer according to the coordinate system of the silicon wafer center-intersection line, grinding disc support shafts A1, A2, and A3 are evenly distributed at 120° intervals on the same circumference on the bearing turntable. Spindle seat support shafts B1, B2, and B3 are evenly distributed at 120° intervals on the same circumference between the grinding wheel spindle seat and the upper shoulder of the grinding wheel spindle. Grinding disc support shafts A1 and A2 are fixed, while adjustable grinding disc support shaft A3 controls the relative swing angle β of the spindle, thereby controlling the silicon wafer fullness ε. Spindle seat support shafts B1 and B2 are fixed, while adjustable spindle seat support shaft B3 controls the relative swing angle α of the spindle, thereby controlling the silicon wafer bump δ.

[0023] In one specific implementation, the signals measured by the displacement sensor on the grinding disc and the surface shape measuring component are fed back to the drive device. According to the control circuit, the signal is transmitted to the three-position four-way solenoid valve to change the hydraulic circuit flow direction and drive the adjustable grinding disc support shaft A3 and / or the adjustable spindle seat support shaft B3 to perform height adjustment work, thereby realizing the leveling of the grinding disc and the surface shape trimming of the silicon wafer.

[0024] Compared with the prior art, the present invention has the following beneficial effects:

[0025] 1) The adjustable grinding device and method of the present invention can adjust the grinding parameters of the device according to the process requirements; at the same time, the adjustable spindle support shaft and the grinding disc support shaft are optimized to be one each. According to the silicon wafer precision grinding theory, the entire device system is easier to achieve precision control during the processing, thereby producing high-quality silicon wafers.

[0026] 2) The adjustable grinding apparatus and method of the present invention, during the grinding process, includes a displacement sensor to monitor the position of the grinding disc and a surface profile measuring component to measure the surface profile of the silicon wafer online. Based on the signals from the displacement sensor and the surface profile measuring component, the drive device is fed back to the control circuit, which drives the inner edge and / or outer edge of the grinding disc to rise or fall in height, and drives the adjustable grinding disc support shaft A3 and / or the adjustable spindle support shaft B3 to perform height adjustment, thereby achieving the horizontal leveling of the grinding disc and the surface profile trimming of the silicon wafer.

[0027] 3) The adjustable grinding device and method of the present invention are equipped with an adjustable grinding disc, a single adjustable grinding disc support shaft and a spindle seat support shaft, which simplifies the silicon wafer spindle and grinding wheel spindle position adjustment process and helps to improve the horizontal adjustment accuracy of the grinding disc and the adjustment quality of the silicon wafer surface shape; the device is equipped with a hydraulic circuit with different flow and unloading control methods, so that each adjustment work is independent and accurate; through the setting of single-station grinding processing, it is easier to change the grinding processing parameters of the device according to the process route, so that it can be used for fine grinding processing or small batch reprocessing of silicon wafers that do not meet the surface shape standards after conventional grinding processing, ensuring that the silicon wafers have a highly competitive precision level. Attached Figure Description

[0028] Figure 1 This is a schematic diagram of the adjustable grinding device based on a single-crystal silicon wafer according to the present invention.

[0029] Figure 2 This is a top view of the adjustable grinding device based on a single-crystal silicon wafer according to the present invention.

[0030] Figure 3 This is a schematic diagram of the fine adjustment of the grinding disc position of the adjustable grinding device of the present invention, wherein (a) is the case where one side of the grinding disc is too high, (b) is the case where both sides of the grinding disc are too low, and (c) is the case where one side of the grinding disc is too high and the other side is too low.

[0031] Figure 4 This is a schematic diagram of the coordinate system based on the silicon wafer center-intersection point connection of the present invention.

[0032] Figure 5 This is a schematic diagram illustrating the adjustment of the relative angles of each principal axis based on the coordinate system connecting the center and intersection of the silicon wafer in this invention.

[0033] Figure 6 This is a measurement of the silicon wafer surface profile according to an embodiment of the present invention.

[0034] Figure 7 This is a schematic diagram of the displacement sensor embedded drive device and the hydraulic direction control circuit of each adjustable support shaft of the present invention.

[0035] Figure 8 This is a schematic diagram of the measurement principle of the surface shape measuring component of the present invention.

[0036] Label Explanation:

[0037] 1- Silicon wafer spindle adjustment component; 2- Grinding wheel spindle adjustment component; 3- Surface shape measuring component; 4- Bearing turntable; 5- Silicon wafer spindle; 6- Grinding disc; 7, 8, and 9- Grinding disc support shafts; 10- Diamond grinding wheel; 11- Grinding wheel spindle; 12- Grinding wheel spindle seat; 13, 14, and 15- Spindle seat support shafts; 16 and 17- Displacement sensors; 18- Laser; 19- Converging lens; 20- Receiving lens; 21- Detector; 22- Silicon wafer; 23- Lower shoulder; 24- Upper shoulder; 25- Overflow valve; 26- Hydraulic motor. 27 Outer three-position four-way solenoid valve, 28 Outer piston hydraulic cylinder, 29 Inner piston hydraulic cylinder, 30 Check valve, 31 Inner three-position four-way solenoid valve, 32 Signal transmission device, 33 Throttle valve, 34 Adjustable grinding disc support shaft A3 control three-position four-way solenoid valve, 35 Adjustable grinding disc support shaft A3 adjustment piston hydraulic cylinder, 36 Adjustable spindle support shaft B3 adjustment piston hydraulic cylinder, 37 Adjustable spindle support shaft B3 control three-position four-way solenoid valve, 38 Surface-type signal transmission device. Detailed Implementation

[0038] To better understand the technical solution of the present invention, the apparatus and method provided by the present invention will be further described below with reference to the accompanying drawings. However, the present invention is not limited to the listed embodiments, but should also include any other known modifications within the scope of the claims of the present invention.

[0039] Figure 1 and Figure 2 The diagram shows a schematic and top view of an adjustable grinding device based on a single-crystal silicon wafer according to the present invention. Hidden lines are visible in the top view to show the internal structure of the device. The device comprises three main components:

[0040] The silicon wafer spindle adjustment component 1 consists of a bearing turntable 4, a silicon wafer spindle 5, a grinding disc 6, and grinding disc support shafts 7, 8, and 9. Specifically, the bearing turntable 4 is located at the bottom end, and grinding disc support shafts 7, 8, and 9, and the silicon wafer spindle 5 are evenly distributed at 120° intervals in the same counterclockwise direction on the bearing turntable 4. The silicon wafer spindle 5 is coaxially installed with the bearing turntable 4. Three grinding disc support shafts are evenly distributed at 120° intervals on the same circumference of the silicon wafer spindle 5. Grinding disc support shafts A1(7) and A2(8) are fixed. The grinding disc 6 is supported by the grinding disc support shaft A3(9), which is an adjustable support. The grinding disc 6 is supported by the grinding disc support shafts A1(7), A2(8), A3(9) and the silicon wafer spindle 5. The silicon wafer spindle 5 passes through the grinding disc 6 and is distributed concentrically with the grinding disc 6. The grinding disc 6 is a ring. Displacement sensors 16 and 17 are installed at 20 mm from the outer edge and 20 mm from the inner edge of the grinding disc 6 in the same radial direction, respectively. The inner edge and the outer edge are the inner circumference and the outer circumference of the grinding disc ring, respectively.

[0041] The grinding wheel spindle adjustment component 2 consists of a diamond grinding wheel 10, a grinding wheel spindle 11, a grinding wheel spindle seat 12, and spindle seat support shafts 13, 14, and 15. Specifically, the grinding wheel spindle 11 has an integral lower shoulder 23 at its lower end. The grinding wheel spindle 11 is fitted inside the grinding wheel spindle seat 12, and the shaft section of the grinding wheel spindle 11 is coaxial with the grinding wheel spindle seat 12. The diamond grinding wheel 10 is assembled at the lower end of the grinding wheel spindle 11. The spindle seat support shafts 13, 14, and 15, which are evenly distributed at 120° intervals in the counterclockwise direction on the same circumference, are installed between the grinding wheel spindle seat 12 and the upper shoulder 24 of the grinding wheel spindle 11. Among them, the spindle seat support shafts B1 (13) and B2 (14) are fixed supports, and the spindle seat support shaft B3 (15) is an adjustable support.

[0042] The positioning of the grinding disc support shafts A1(7), A2(8), A3(9) and the spindle seat support shafts B1(13), B2(14), B3(15) can be, for example, based on the following reference system, such as... Figure 4 , Figure 5 As shown: Taking the center of the silicon wafer placed on the grinding disc as the origin O, during grinding with the diamond grinding wheel mounted at the lower end of the grinding wheel spindle, at any position, the line connecting the center of the silicon wafer, the edge of the diamond grinding wheel, and the edge of the silicon wafer at point C is the y-axis; the line connecting the center of the silicon wafer and the y-axis perpendicularly is the x-axis; and the line connecting the center of the silicon wafer and the xoy plane perpendicularly is the z-axis. The silicon wafer rotation radius R0 and the diamond grinding wheel radius R1 are set to establish a system based on the silicon wafer... In the coordinate system connecting the center and the intersection point, the intersection of the x-axis and the edge of the silicon wafer furthest from the diamond wheel is A3. A1 and A2 are evenly distributed 120° apart from A3 on a circle with the origin O as the center and R0 as the radius. The intersection of the perpendicular line to the x-axis passing through the center O1 of the diamond wheel and the edge of the wheel furthest from the x-axis is B3. B1 and B2 are evenly distributed 120° apart from B3 on a circle with the origin O1 as the center and R1 as the radius. It is worth noting that... Figure 4 and Figure 5 This is only to illustrate the relative positional relationship of the grinding disc support shafts A1(7), A2(8), A3(9) and the spindle seat support shafts B1(13), B2(14), B3(15). Specifically, the spacing between the grinding disc support shafts A1(7), A2(8), A3(9) and the spindle seat support shafts B1(13), B2(14), B3(15) and the silicon wafer spindle 5 and the grinding wheel spindle 11 can be reasonably arranged according to the size of the device and the size and position of the silicon wafer spindle 5 and the grinding wheel spindle 11. It is only necessary that A1(7), A2(8), A3(9) and the spindle seat support shafts B1(13), B2(14), B3(15) satisfy the aforementioned positioning relationship.

[0043] The surface measurement component 3 is installed on the lower end of the shoulder of the grinding wheel spindle 11; in one specific embodiment, such asFigure 8 As shown, for example, a laser triangulation displacement sensor is used. Based on the principle of direct triangulation measurement, online measurement is completed through laser 18, converging lens 19, receiving lens 20 and detector 21.

[0044] like Figure 1 , Figure 2 As shown, when using this device for grinding, the silicon wafer 22 is placed concentrically on the grinding disc 6 with the center of the grinding disc 6 as the base point. The recommended outer diameter of the silicon wafer is 8 inches or 12 inches. The diamond grinding wheel 10 installed at the lower end of the grinding wheel spindle 11 processes it. The outer diameter of the diamond grinding wheel 10 is at least equal to the outer diameter of the silicon wafer 22. During the grinding process, the silicon wafer spindle 5 is driven by a power device (not shown) to rotate counterclockwise or clockwise at a certain speed, such as screw and nut drive, ball linear guide drive and hydraulic drive, thereby controlling the grinding disc 6 to make the silicon wafer 22 rotate counterclockwise or clockwise. The grinding wheel spindle 11 is driven to rotate by a drive mechanism (not shown), thereby causing the diamond grinding wheel 10 to rotate counterclockwise or clockwise. Simultaneously, the grinding wheel spindle seat 12 is connected to a feed mechanism (not shown), which, along with the up-and-down movement of the feed mechanism, causes the grinding wheel spindle adjustment component 2 to move up and down as a whole, enabling the grinding wheel 10 to be fed axially along the grinding wheel spindle 11 to grind the silicon wafer 22. The silicon wafer 22 and the diamond grinding wheel 10 rotate in opposite directions, and the outer edge of the diamond grinding wheel 10 always passes through the center of the silicon wafer 22. Furthermore, depending on the requirements of the preceding or following processes, appropriate processing parameters can be adjusted, such as the grinding time of the adjustable grinding device, the rotation direction and speed of the silicon wafer spindle 5, the axial feed speed of the grinding wheel spindle 11, and the material and grit size of the diamond grinding wheel 10.

[0045] like Figure 2 , Figure 3 As shown, displacement sensors 16 and 17 are installed inside the surface of the grinding disc 6, 20 mm from the outer edge of the grinding disc 6 and 20 mm from the inner edge of the grinding disc 6. They can also be located at any radial position through the center of the grinding disc 6 to monitor the position height at any time during the grinding process, output a visual curve, and transmit signals to the embedded drive device of the displacement sensor 16 to drive the position height of the outer edge of the grinding disc 6 to rise or fall, or transmit signals to the embedded drive device of the displacement sensor 17 to make the position height of the inner edge of the grinding disc 6 rise or fall, or transmit signals to the embedded drive devices of the outer displacement sensor 16 and the inner displacement sensor 17 to reduce the position height difference between the outer edge and the inner edge of the grinding disc 6 and control the form and position error caused by vibration on the surface of the grinding disc 6.

[0046] The displacement sensors 16 and 17 are embedded structures, namely an embedded high-precision micro-displacement measurement system. This system collects minute changes in displacement, converts them into electrical signals, then into digital signals via a PSD signal circuit. These signals are then sent to an embedded processing system, which transmits them to the embedded drive device of the displacement sensors 16 and 17 to complete the adjustment of the surface position and height of the grinding disc 6. Figure 3 As shown, it can precisely adjust the shape and position errors caused by vibration on the surface of the grinding disc 6 in cases where the grinding disc is too high on one side, too low on both sides, or too high on one side and too low on the other.

[0047] Figure 4 The diagram shows a coordinate system based on the silicon wafer center-intersection point. With the center of the silicon wafer 22 placed on the grinding disc 6 as the origin O, and the diamond grinding wheel 10 mounted on the lower end of the grinding wheel spindle 11 performing grinding, at any position, the line connecting the center of the silicon wafer 22, the edge of the diamond grinding wheel 10, and the intersection point C of the edge of the silicon wafer 22 is the y-axis; the line connecting the center of the silicon wafer 22 perpendicular to the y-axis is the x-axis; and the line connecting the center of the silicon wafer 22 perpendicular to the xoy plane is the z-axis. The rotation radius R0 of the silicon wafer 22 and the diamond grinding wheel are set as follows: With a radius of R1, establish a coordinate system based on the line connecting the center and intersection of the silicon wafer. In this coordinate system, set the angle between the axis of the diamond wheel 10 and the axis of the silicon wafer 22 in the yoz plane, i.e., the swing angle around the x-axis, as α. Set the angle between the axis of the diamond wheel 10 and the axis of the silicon wafer 22 in the xoz plane, i.e., the swing angle around the y-axis, as β. Establish the relative angular coordinate relationship between the surface and edge feature points of the silicon wafer 22 and each principal axis. Based on the spatial geometric relationship between the principal axis of the diamond wheel 10 and the principal axis of the silicon wafer 22, the calculation method is as shown in equations (1) and (2):

[0048]

[0049]

[0050] According to equations (1) and (2), the calculation methods for the convexity / concavity δ and fullness / ε of silicon wafer 22 in the coordinate system connecting the center and intersection of the silicon wafer are shown in equations (3) and (4):

[0051] δ=R0·tanα (3)

[0052]

[0053] According to equations (3) and (4), the correspondence between the grinding surface profile of silicon wafer 22 and the coordinate system based on the center-intersection line of the silicon wafer is obtained: In one grinding process, the rotation radius R0 of silicon wafer 22 and the radius R1 of diamond wheel 10 are constant values. Then, the convexity δ is determined by the adjustment amount of the swing angle α around the x-axis, and the fullness ε is determined by the adjustment amount of the swing angle β around the y-axis. Therefore, the surface profile parameters of silicon wafer 22, convexity δ and fullness ε, are controlled by only a single angle adjustment parameter and are independent of each other. Therefore, by setting adjustable support shafts on diamond wheel 10 and silicon wafer 22 as adjustment points, the surface profile parameters of silicon wafer 22 can be controlled independently and accurately.

[0054] Figure 5 The diagram shows the adjustment method for the relative angles of each axis and the grinding surface profile of silicon wafer 22 based on the coordinate system connecting the center and intersection of the silicon wafer. Grinding disc support shafts A1(7), A2(8), and A3(9) are evenly distributed on the same circumference at 120° intervals on the bearing turntable. Spindle seat support shafts B1(13), B2(14), and B3(15) are evenly distributed on the same circumference at 120° intervals between the grinding wheel spindle seat and the upper shoulder of the grinding wheel spindle. Grinding disc support shafts A1(7) and A2(8) are fixed, while the adjustable grinding disc support shaft A3(9) controls the relative swing angle β of the spindle, thereby controlling the fullness ε of the silicon wafer. Spindle seat support shafts B1(13) and B2(14) are fixed, while the adjustable spindle seat support shaft B3(15) controls the relative swing angle α of the spindle, thereby controlling the convexity δ of the silicon wafer 22.

[0055] In one specific embodiment, for example, the device is located in a clean room at 25°C, the silicon wafer 22 has a diameter of 300mm, and the diamond grinding wheel has a diameter of 500mm; the surface profile measured by the surface profile measuring component 3 is as follows: Figure 6 As shown, analysis shows that the convexity δ of silicon wafer 22 is 3μm and the fullness ε is 2μm. According to equations (1) and (2), the swing angle α around the x-axis is 0.00057° and the swing angle β around the y-axis is 0.00498°. Accordingly, the height of the adjustable spindle support shaft B3 (15) and the adjustable grinding disc support shaft A3 (9) is adjusted to meet the aforementioned α and β angle relationship. Based on the surface parameters measured online in real time, the α and β angles are continuously corrected by adjusting the adjustable spindle support shaft B3 (15) and the adjustable grinding disc support shaft A3 (9) to make them infinitely close to this theoretical value, thereby realizing the control of the surface parameters of silicon wafer 22.

[0056] like Figure 7As shown, the embedded drive device specifically includes a hydraulic directional control circuit locked by a one-way valve 30. When the height of the position monitored by the displacement sensor 16 changes, a signal is transmitted to the outer three-position four-way solenoid valve 27 to change the flow direction of the hydraulic circuit, thereby causing the outer piston-type hydraulic cylinder 28 to push the outer edge of the grinding disc 6 for corresponding adjustment; when the height of the position monitored by the displacement sensor 17 changes, a signal is transmitted to the inner three-position four-way solenoid valve 31 to change the flow direction of the hydraulic circuit, thereby causing the inner piston-type hydraulic cylinder 29 to push the outer edge of the grinding disc 6 for corresponding adjustment; when the height of the position monitored by the displacement sensor 16 changes, a signal is transmitted to the inner three-position four-way solenoid valve 31 to change the flow direction of the hydraulic circuit, thereby causing the inner piston-type hydraulic cylinder 29 to push the outer edge of the grinding disc 6 for corresponding adjustment; when the displacement sensor 16 and the embedded drive device and the position change change, the hydraulic control circuit is locked by a one-way valve 30 for corresponding adjustment. When both the embedded drive device of the motion sensor 17 and the motion sensor 29 need adjustment, the hydraulic motor 26 simultaneously supplies oil to both. Through the signal transmission element 32, the outer three-position four-way solenoid valve 27, and the inner three-position four-way solenoid valve 31, the outer piston hydraulic cylinder 28 and the inner piston hydraulic cylinder 29 can be independently extended and retracted, thereby ensuring that the outer and inner edges of the grinding disc 6 reach the desired adjustment values. The hydraulic circuit is also equipped with a relief valve 25 and a locking circuit of a hydraulically controlled check valve 30, so that the actuator can stay in any position and will not move under external force after staying in position, further improving the adjustment accuracy of the adjustable grinding device. The drive is not limited to a hydraulic linear drive structure, but can also be a magnetostrictive structure or a micro-motion mechanism such as electrostriction.

[0057] like Figure 7 As shown, an adjustable grinding device based on a single-crystal silicon wafer is further provided with a mid-position functional unloading circuit under the same hydraulic motor 26. Since the surface shape change is usually at the micron level, the adjustment range of each adjustable support shaft is smaller than that of the grinding disc 6. Therefore, a throttle valve 33 is installed on the hydraulic circuit to control its pressure and flow. When the surface shape of the silicon wafer 22 changes, the surface shape measuring component 3 transmits the monitoring data to the surface shape signal transmitting component 38, the three-position four-way solenoid valve 34 for controlling the adjustable grinding disc support shaft A3, and the three-position four-way solenoid valve 37 for controlling the adjustable spindle support shaft B3. This changes the hydraulic circuit flow direction of the piston-type hydraulic cylinder 35 for adjusting the adjustable grinding disc support shaft A3 and the piston-type hydraulic cylinder 36 for adjusting the adjustable spindle support shaft B3, driving the adjustable grinding disc support shaft A3 (9) and the adjustable spindle support shaft B3 (15) to perform height adjustment work, thus completing the surface shape trimming work of the silicon wafer 22.

[0058] Figure 8The surface profile measuring component 3 can measure the surface profile of a silicon wafer 22 online. The component 3 contains a laser 18 that emits light, which is focused by a converging lens 19 and incident perpendicularly onto the surface of the silicon wafer 22 undergoing grinding. A receiving lens 20 receives the scattered light from the incident light point, forming an imaging point. The incident light spot moves with the surface morphology of the silicon wafer 22, and the imaging point moves accordingly on the light receiving detector 21. Based on the image movement of the imaging point and the structural parameters of the surface profile measuring component 3, the change in the surface profile of the silicon wafer under test can be determined. The surface profile measuring component 3 is not limited to using a laser triangulation displacement measurement method; it can also use an optical interferometry measurement method or a laser autocollimation measurement method, etc.

[0059] The following section uses precision grinding as an example to introduce the usage method and steps of an adjustable grinding device based on a single-crystal silicon wafer.

[0060] 1) When the grinding process begins, the silicon wafer 22 is placed using a pick-up robot. Figure 1 On the grinding disc 6 shown, a vacuum chuck clamps a silicon wafer 22, with the center of the silicon wafer 22 coinciding with the center of the grinding disc 6. The outer diameter of the silicon wafer 22 is recommended to be 8 inches or 12 inches. A diamond grinding wheel 10, mounted on the lower end of the shoulder 23 of the grinding wheel spindle 11, processes the wafer. The outer diameter of the diamond grinding wheel 10 is at least equal to the outer diameter of the silicon wafer 22.

[0061] 2) During grinding, Figure 1 The silicon wafer spindle 5 controls the grinding disc 6 to rotate the silicon wafer 22 counterclockwise or clockwise. The grinding wheel spindle 11 drives the diamond grinding wheel 10 to rotate counterclockwise or clockwise, while simultaneously feeding along the axial direction of the grinding wheel spindle 11. The silicon wafer 22 and the diamond grinding wheel 10 rotate in opposite directions, and the outer edge of the diamond grinding wheel 10 always passes through the center of the silicon wafer 22. The diamond grinding wheel 10 only performs continuous axial infeed grinding, and its contact length, contact area, and infeed angle with the silicon wafer 22 are fixed. The simple structure and movement help ensure the accuracy and rigidity of the device. At the same time, the surface shape measuring component 3 and displacement sensors 16 and 17 monitor the surface shape of the silicon wafer 22 and the horizontal position of the grinding disc 6 in real time.

[0062] 3) The entire grinding process adopts fixed-stroke speed control grinding, which is divided into five stages: fast approach, fast advance, slow advance, finishing grinding, and fast retraction. The feed speed of the grinding wheel changes constantly in each stage. The feed speed of the diamond grinding wheel 10 varies with the axial grinding force. When the grinding force is small, the feed speed is fast, and when the grinding force is large, the feed speed is slow. In the fast approach and fast retraction stages, the speed is increased to shorten the idle stroke and improve efficiency. In the fast advance stage, the silicon wafer is processed at the maximum grinding speed while avoiding grinding force overload. In the slow advance stage, constant grinding force grinding is achieved. In the finishing grinding stage, the grinding force is controlled to form a better plastic deformation layer, reduce the possibility of cracking, and thus improve the strength and surface properties of the silicon wafer.

[0063] 4) The vibrations and heat changes generated during the grinding process will cause the grinding disc 6 to tilt.Figure 2 Displacement sensors 16 and 17, as shown, monitor the positional changes of the outer and inner edges of the grinding disc 6 in real time and output visualized curves. Implementation example... Figure 3 (a) When the sensor transmits a signal to the outer three-position four-way solenoid valve 27, it changes the direction of the hydraulic circuit, thereby causing the outer piston-type hydraulic cylinder 28 to push the outer edge of the grinding disc 6 down to the position indicated by the dotted line, until the entire grinding disc 6 is kept horizontal with the end face of the silicon wafer spindle 5; for example, Figure 3 (b) When the embedded drive devices of displacement sensor 16 and displacement sensor 17 transmit signals to the outer three-position four-way solenoid valve 27 and the inner three-position four-way solenoid valve 31 respectively, the hydraulic motor 26 supplies oil to both of them. Through the signal transmission device 32, the outer three-position four-way solenoid valve 27 and the inner three-position four-way solenoid valve 31, the outer piston hydraulic cylinder 28 and the inner piston hydraulic cylinder 29 are independently extended and retracted, and the two sides of the grinding disc 6 are adjusted to the position of the dotted line until the entire grinding disc 6 is kept horizontal with the end face of the silicon wafer spindle 5; similarly, it can be seen that, for example, Figure 3 (c) When the inner and outer sensors transmit signals to the embedded drive devices of displacement sensor 16 and displacement sensor 17 respectively, the hydraulic circuit is driven so that one edge of the grinding disk 6 is raised and the other edge is lowered to the position of the dotted line, until the entire grinding disk 6 is kept horizontal with the end face of the silicon wafer spindle 5.

[0064] 5) such as Figure 4 , Figure 5 , Figure 7 , Figure 8As shown, an adjustable grinding device based on a single-crystal silicon wafer can monitor surface shape changes online. The surface shape of the silicon wafer 22 is adjusted by adjusting the relative angles of each axis based on the coordinate system connecting the center and intersection points of the silicon wafer. A surface shape measuring component 3 measures the surface shape of the silicon wafer 22 online. A sensor within the surface shape measuring component 3 emits light, which is focused by a converging lens 19 and incident perpendicularly onto the surface of the silicon wafer 22 being ground. A receiving lens 20 receives the scattered light from the incident light point, forming an imaging point. The incident light spot moves with the surface morphology of the silicon wafer 22, and the imaging point moves accordingly on the light receiving sensor. Based on the image movement of the imaging point and the structural parameters of the surface shape measuring component 3, the surface shape change of the measured silicon wafer can be determined. According to the monitoring situation, the signal is transmitted to the surface signal transmitter 38 and the three-position four-way solenoid valve 37 for controlling the adjustable spindle support shaft B3, which drives the piston hydraulic cylinder 36 for adjusting the adjustable spindle support shaft B3 to perform height adjustment work. The spindle support shaft B3 (15) controls the relative swing angle α of the spindle, thereby controlling the convexity δ of the silicon wafer 22. The signal is transmitted to the surface signal transmitter 38 and the three-position four-way solenoid valve 34 for controlling the adjustable grinding disc support shaft A3, which drives the piston hydraulic cylinder 35 for adjusting the adjustable grinding disc support shaft A3 to perform height adjustment work. The grinding disc support shaft A3 (9) is adjusted to control the relative swing angle β of the spindle, thereby controlling the fullness ε of the silicon wafer.

[0065] Furthermore, the adjustable grinding device based on monocrystalline silicon wafers of the present invention can adjust the grinding time, the rotation direction and speed of the silicon wafer spindle 5, the axial feed speed of the grinding wheel spindle 11, and the material and grit size of the diamond grinding wheel 10 according to the requirements of the preceding or following processes. The device processes one silicon wafer 22 at a time, with the diamond grinding wheel 10 performing continuous axial infeed grinding. The machining allowance is unrestricted, and the grinding feed is not affected by uneven machining allowances between silicon wafers. Therefore, it is also suitable for the reprocessing of small batches of silicon wafers whose surface shape does not meet the standards after conventional grinding.

[0066] Although the present invention has been described in detail through the above specific embodiments, it should be understood that the above description should not be considered as a limitation of the present invention. Those skilled in the art will understand that modifications or adjustments can be made to the present invention based on the teachings of this specification. These modifications or adjustments should also be within the scope defined by the claims of the present invention.

Claims

1. An adjustable grinding device based on a single-crystal silicon wafer, characterized in that, The device includes a silicon wafer spindle adjustment component, a grinding wheel spindle adjustment component, and a surface shape measurement component; The silicon wafer spindle adjustment component includes a support turntable, a silicon wafer spindle, a grinding disc support shaft, and a grinding disc. The support turntable is located at the bottom, and the silicon wafer spindle and three grinding disc support shafts evenly distributed at 120° intervals on the same circumference are coaxially mounted on the support turntable. The grinding disc is supported by the grinding disc support shafts A1, A2, and A3 and the silicon wafer spindle. Among them, the grinding disc support shafts A1 and A2 are fixed supports, and the grinding disc support shaft A3 is an adjustable support. Displacement sensors are installed on the outer edge and inner edge of the grinding disc at the same radial position. The displacement sensors monitor their position height at any time during the grinding process and transmit signals to the displacement sensor drive device to drive the position height of the outer edge and / or inner edge of the grinding disc to rise or fall, thereby reducing the position height difference between the outer edge and inner edge of the grinding disc and controlling the shape and position error of the grinding disc. The grinding wheel spindle adjustment component includes a diamond grinding wheel, a grinding wheel spindle, a grinding wheel spindle seat, and a spindle seat support shaft. The diamond grinding wheel is installed at the lower end of the grinding wheel spindle. The grinding wheel spindle section is sleeved inside the grinding wheel spindle seat, and the grinding wheel spindle section is coaxial with the grinding wheel spindle seat. Three spindle seat support shafts are installed between the grinding wheel spindle seat and the upper shoulder of the grinding wheel spindle, and are evenly distributed at 120° intervals on the same circumference. Among them, spindle seat support shafts B1 and B2 are fixed supports, and spindle seat support shaft B3 is an adjustable support. The surface measurement component is located at the lower end of the shoulder on the grinding wheel spindle; With the center of the silicon wafer placed on the grinding disc as the origin O, and the diamond grinding wheel mounted at the lower end of the grinding wheel spindle performing grinding, at any position, the line connecting the center of the silicon wafer, the edge of the diamond grinding wheel, and the edge of the silicon wafer at point C is the y-axis; the line connecting the center of the silicon wafer and the y-axis perpendicularly is the x-axis; and the line connecting the center of the silicon wafer and the xoy plane perpendicularly is the z-axis. The silicon wafer rotation radius R0 and the diamond grinding wheel radius R1 are set, establishing a system based on the center of the silicon wafer... In the coordinate system connecting the center and the intersection point, the intersection of the x-axis and the edge of the silicon wafer furthest from the diamond wheel is A3. A1 and A2 are evenly distributed 120° apart from A3 on the circumference with the origin O as the center and R0 as the radius. The intersection of the perpendicular line to the x-axis and passing through the center O1 of the diamond wheel with the edge of the wheel furthest from the x-axis is B3. B1 and B2 are evenly distributed 120° apart from B3 on the circumference with the origin O1 as the center and R1 as the radius. In this coordinate system, let α be the angle between the diamond wheel axis and the silicon wafer axis in the yoz plane, i.e., the swing angle around the x-axis, and let β be the angle between the diamond wheel axis and the silicon wafer axis in the xoz plane, i.e., the swing angle around the y-axis. Then, in the coordinate system, the silicon wafer convexity / concavity δ and fullness ε satisfy the following: δ=R0·tanα The displacement sensor drive device is equipped with a hydraulic directional control circuit with a one-way valve lock. When the height of the position monitored by the displacement sensor changes, it transmits a signal to a three-position four-way solenoid valve to change the flow direction of the hydraulic circuit, thereby causing the piston hydraulic cylinder to push the inner and outer edges of the grinding disc to make corresponding adjustments. The surface shape measuring component transmits the monitored surface shape change signal to the driving device. The driving device is a reversing valve with a throttle valve controlled by a throttle valve and a neutral unloading circuit under the same hydraulic motor as the displacement sensor driving device. It transmits the surface shape change signal to the solenoid valve and changes the flow direction of the hydraulic circuit, thereby driving the adjustable grinding disc support shaft A3 and the adjustable spindle seat support shaft B3 to adjust their height.

2. The adjustable grinding device based on a single-crystal silicon wafer according to claim 1, characterized in that, The displacement sensor is embedded and installed at a distance of 20 mm from the outer edge and 20 mm from the inner edge of the grinding disc, and at the same radial position.

3. The adjustable grinding device based on a single-crystal silicon wafer according to claim 1, characterized in that, The surface shape measurement component consists of a sensor, a converging lens, a receiving lens, and a detector. The sensor emits light, which is focused by the converging lens and incident perpendicularly onto the surface of the silicon wafer being ground. The receiving lens receives the scattered light from the incident light point to form an imaging point. The incident light spot moves with the change in the surface morphology of the silicon wafer, and the imaging point moves accordingly on the light receiving detector. The change in the surface shape of the silicon wafer is measured online based on the image movement of the imaging point and the structural parameters of the surface shape measurement component.

4. The adjustable grinding apparatus based on a single-crystal silicon wafer according to any one of claims 1-3, used for grinding a single-crystal silicon wafer, characterized in that... The silicon wafer is placed on the grinding disc. During the grinding process, the silicon wafer spindle controls the grinding disc to make the silicon wafer rotate counterclockwise or clockwise. The grinding wheel spindle drives the diamond grinding wheel to rotate counterclockwise or clockwise, and feeds along the axis of the grinding wheel spindle. The silicon wafer and the diamond grinding wheel rotate in opposite directions. The outer diameter of the diamond grinding wheel is at least equal to the outer diameter of the silicon wafer. The outer edge of the diamond grinding wheel always passes through the center of the silicon wafer. The silicon wafer is ground using the diamond grinding wheel installed at the lower end of the grinding wheel spindle.

5. The grinding method according to claim 4, characterized in that, Define the angle between the diamond wheel axis and the silicon wafer axis in the yoz plane, i.e., the swing angle around the x-axis, as α. Define the angle between the diamond wheel axis and the silicon wafer axis in the xoz plane, i.e., the swing angle around the y-axis, as β. Establish the relative angular coordinate relationship between the silicon wafer surface, edge feature points, and each principal axis. Based on the spatial geometric relationship between the diamond wheel principal axis and the silicon wafer principal axis, obtain the correspondence between the silicon wafer grinding surface profile and the coordinate system based on the silicon wafer center-intersection line: the convexity / concavity δ of the single crystal silicon wafer is determined by the adjustment amount of the swing angle α around the x-axis, and the fullness ε is determined by the adjustment amount of the swing angle β around the y-axis.

6. The grinding method according to claim 5, characterized in that, Based on the adjustment method of the relative angles of each axis and the grinding surface profile of the silicon wafer according to the coordinate system of the silicon wafer center-intersection line, grinding disc support shafts A1, A2, and A3 are evenly distributed at 120° intervals on the same circumference on the bearing turntable. Spindle seat support shafts B1, B2, and B3 are evenly distributed at 120° intervals on the same circumference between the grinding wheel spindle seat and the upper shoulder of the grinding wheel spindle. Grinding disc support shafts A1 and A2 are fixed, while adjustable grinding disc support shaft A3 controls the relative swing angle β of the spindle, thereby controlling the silicon wafer fullness ε. Spindle seat support shafts B1 and B2 are fixed, while adjustable spindle seat support shaft B3 controls the relative swing angle α of the spindle, thereby controlling the silicon wafer convexity δ.

7. The grinding method according to claim 6, characterized in that, The signals measured by the displacement sensor on the grinding disc and the surface shape measuring component are fed back to the drive device. According to the control circuit, the signal is transmitted to the three-position four-way solenoid valve to change the flow direction of the hydraulic circuit and drive the adjustable grinding disc support shaft A3 and / or the adjustable spindle support shaft B3 to perform height adjustment, thereby realizing the leveling of the grinding disc and the surface shape trimming of the silicon wafer.

Images