Double-sided grinding method for workpiece, manufacturing method for workpiece, and double-sided grinding apparatus for workpiece

Abstract

In the present invention, the sum and ratio of the torques of the sun gear torque and the internal gear torque are controlled within a predetermined range.

Description

Technical Field

[0001] The present invention relates to a method for double-sided grinding of a workpiece, a method for manufacturing a workpiece, and a double-sided grinding apparatus for a workpiece. Background Art

[0002] In the manufacture of workpieces such as semiconductor wafers, there is sometimes a process of grinding the surface of the workpiece. For example, the wafer is clamped between upper and lower platens each having a polishing pad, and both surfaces are polished simultaneously. In recent years, with the miniaturization of semiconductors, the requirements for the polishing accuracy of wafers have been gradually increasing. Moreover, in order to increase the integration degree of large-scale integrated circuits, in addition to improving the polishing accuracy, it is also necessary to improve the flatness of the wafers. Generally, the flatness of a wafer is represented, for example, by a GBIR value (Global Backside Indicated Reading) and an ESFQR value (Edge flatness metric, Sector based, Front surface referenced, Site Front least squares range). The GBIR value is mainly used to represent the overall flatness of the wafer, and the ESFQR value is mainly used to represent the peripheral flatness of the wafer.

[0003] When polishing a wafer, it is necessary to strictly control the polishing conditions, use a specified polishing liquid at a specified platen temperature, and keep the rotation of the wafer in the carrier plate in the double-sided polishing apparatus in a desired rotation state. Therefore, in order to achieve the purpose of improving the polishing accuracy and the flatness of the wafer, how to set the rotation conditions of the polishing apparatus is one of the important issues.

[0004] For example, Patent Document 1 discloses a polishing method in which, during double-sided polishing, a polishing resistance measurement unit calculates the polishing resistance of the wafer and transmits the polishing resistance to a control unit, and the control unit controls the self-rotation ratio of the carrier plate (i.e., the self-rotation speed during one revolution of the carrier plate).

[0005] Prior Art Documents

[0006] Patent Documents

[0007] Patent Document 1: Japanese Unexamined Patent Application Publication No. 2011-056630. Summary of the Invention

[0008] Technical Problem to be Solved by the Invention

[0009] However, in Patent Document 1, although the decrease in the grinding accuracy of the wafer can be avoided by controlling the rotation ratio of the carrier plate, there are limitations in improving the grinding accuracy of the wafer. Moreover, such problems not only occur in wafers, but may generally occur in workpieces used for double-sided grinding.

[0010] An object of the present invention is to provide a method for double-sided grinding of a workpiece, a method for manufacturing a workpiece, and a double-sided grinding apparatus for a workpiece, which can accurately control the thickness of the workpiece after double-sided grinding of the workpiece, and further can obtain a workpiece with high flatness.

[0011] Solution for Solving Technical Problems

[0012] The key structure of the present invention is as follows.

[0013] The present invention provides a method for double-sided grinding of a workpiece, which is a method for grinding a workpiece inside a carrier plate that rotates through a sun gear and an internal gear. The method for double-sided grinding of the workpiece is characterized by including:

[0014] A step of setting grinding conditions according to the target processing shape of the workpiece;

[0015] A step of starting grinding based on the grinding conditions;

[0016] A step of detecting the torque (Ti) of the sun gear and the torque (To) of the internal gear during grinding through a torque detector;

[0017] A step of calculating the value of the sum of torques (Ti + To) and the value of the torque ratio (Ti / To) of the detected torque (Ti) of the sun gear and the torque (To) of the internal gear through a calculation processing unit;

[0018] A step of setting the control ranges of the sum of torques (Ti + To) and the torque ratio (Ti / To) through a condition setting unit; and

[0019] A step of determining whether it is necessary to change the grinding conditions through the condition setting unit based on whether the value of the sum of torques (Ti + To) and the value of the torque ratio (Ti / To) are within the control ranges.

[0020] In one technical solution, it further includes: a step of obtaining in advance the relationship between the sum of torques (Ti + To) and the torque ratio (Ti / To) with respect to the target processing shape of the workpiece before the start of double-sided grinding,

[0021] The step of setting the control ranges of the sum of torques (Ti + To) and the torque ratio (Ti / To) is performed based on the obtained relationship.

[0022] In one technical solution, the target machining shape of the workpiece is determined by the GBIR value and / or the ESFQR value. Additionally, in this specification, "GBIR" and "ESFQR" are defined by the SEMI standard.

[0023] In one technical solution, through the calculation processing unit, the value of the torque (Ti) of the sun gear and the value of the torque (To) of the internal gear are respectively transformed into the ratio of the action output of the motor driving the sun gear and the action output of the motor driving the internal gear to their respective rated outputs. When determining the target machining shape of the workpiece according to the GBIR value, the condition setting unit sets the control range of the sum of the torques (Ti + To) to 30 to 35, and sets the control range of the torque ratio (Ti / To) to 1.5 to 2.1.

[0024] The ratio of the action output of the motor to the rated output can be calculated by the following formula:

[0025] (Value of the output of the motor in operation / Value of the rated output of the motor) × 100.

[0026] In one technical solution, through the calculation processing unit, the value of the torque (Ti) of the sun gear and the value of the torque (To) of the internal gear are respectively transformed into the ratio of the action output of the motor driving the sun gear and the action output of the motor driving the internal gear to their respective rated outputs. When determining the target machining shape of the workpiece according to the ESFQR value, the condition setting unit sets the control range of the sum of the torques (Ti + To) to 25 to 30, and sets the control range of the torque ratio (Ti / To) to 1.4 to 1.9.

[0027] The ratio of the action output of the motor to the rated output can be calculated by the following formula:

[0028] (Value of the output of the motor in operation / Value of the rated output of the motor) × 100.

[0029] In one technical solution, the carrier plate is disposed between the upper platform and the lower platform of the rotating platform.

[0030] The grinding condition is the rotational speed of the lower platform or the machining load applied by the rotating platform to the workpiece.

[0031] In one technical solution, it further includes:

[0032] A process of measuring the shape of the workpiece before the start of grinding by a measuring unit; and

[0033] The process of the computing and processing unit dividing the double-sided grinding process of the workpiece into a plurality of sub-processes based on the measured shape of the workpiece

[0034] The process of setting the control range of the sum of the torques (Ti + To) and the ratio of the torques (Ti / To), which is performed separately in each of the sub-processes

[0035] The process of determining whether it is necessary to change the grinding conditions based on whether the value of the sum of the torques (Ti + To) and the value of the ratio of the torques (Ti / To) are within the control range, which is performed separately in each of the sub-processes.

[0036] In one aspect, the plurality of sub-processes include:

[0037] A sub-process of reducing the deviation degree of the workpiece in the circumferential direction; and

[0038] A sub-process of reducing the deviation degree of the workpiece in the radial direction.

[0039] The manufacturing method of the workpiece of the present invention manufactures the workpiece by any of the above double-sided grinding methods of the workpiece.

[0040] The double-sided grinding device of the workpiece of the present invention includes:

[0041] A rotating platform having an upper platform and a lower platform capable of rotating;

[0042] A sun gear disposed at the center of the rotating platform;

[0043] An internal gear disposed at the outer periphery of the rotating platform;

[0044] A carrier plate configured to be disposed on the lower platform, capable of placing the workpiece, and rotating between the upper platform and the lower platform through the sun gear and the internal gear;

[0045] A first torque detector that detects the torque (Ti) of the sun gear during double-sided grinding;

[0046] A second torque detector that detects the torque (To) of the internal gear during double-sided grinding;

[0047] A calculation processing unit that receives the detected torque information and calculates the sum (Ti + To) and ratio (Ti / To) of the torques of the sun gear (Ti) and the internal gear (To) based on the torque information; and a condition setting unit that is configured to set the target machining shape and polishing conditions of the workpiece and receives the values of the sum (Ti + To) of the torques and the ratio (Ti / To) of the torques. The double-sided polishing apparatus for the workpiece is characterized in that

[0048] The condition setting unit determines whether it is necessary to change the polishing conditions based on whether the values of the sum (Ti + To) of the torques and the ratio (Ti / To) of the torques are within the control range.

[0049] In one aspect, the double-sided polishing apparatus further includes a storage unit and / or the condition setting unit includes a communication unit capable of receiving the relationship. The storage unit prestores the relationship between the sum (Ti + To) of the torques and the ratio (Ti / To) of the torques with respect to the target machining shape of the workpiece.

[0050] Before the start of double-sided polishing, the condition setting unit obtains the relationship from the storage unit or receives and obtains the relationship from the outside through the receiving unit, and sets the control ranges of the sum (Ti + To) of the torques and the ratio (Ti / To) of the torques based on the obtained relationship.

[0051] In one aspect, the condition setting unit determines the target machining shape of the workpiece from the GBIR value and / or the ESFQR value.

[0052] In one aspect, through the calculation processing unit, the values of the torque (Ti) of the sun gear and the torque (To) of the internal gear are respectively transformed into the ratios of the action outputs of the motors driving the sun gear and the internal gear to their respective rated outputs. When determining the target machining shape of the workpiece according to the GBIR value, the condition setting unit sets the control range of the sum (Ti + To) of the torques to 30 to 35 and sets the control range of the ratio (Ti / To) of the torques to 1.5 to 2.1.

[0053] The ratio of the action output of the motor to the rated output can be calculated by the following formula:

[0054] (The value of the output of the motor in operation / The value of the rated output of the motor) × 100.

[0055] In one technical solution, the calculation and processing unit converts the value of the torque (Ti) of the sun gear and the value of the torque (To) of the internal gear into the ratios of the action outputs of the motors driving the sun gear and the internal gear to their respective rated outputs. When determining the target machining shape of the workpiece based on the ESFQR value, the condition setting unit sets the control range of the sum of the torques (Ti + To) to 25 to 30, and sets the control range of the torque ratio (Ti / To) to 1.4 to 1.9.

[0056] The ratio of the action output of the motor to the rated output can be calculated by the following formula:

[0057] (Value of the output of the motor in operation / Value of the rated output of the motor) × 100.

[0058] In one technical solution, the condition setting unit further includes:

[0059] A machine learning device that, through machine learning, enables the condition setting unit to automatically set the grinding conditions based on the sum of the torques (Ti + To) and the torque ratio (Ti / To) to meet the desired GBIR value and / or ESFQR value.

[0060] In one technical solution, it further includes: a first motor connected to the sun gear; and a second motor connected to the internal gear. The first torque detector detects the torque of the sun gear rotated by the first motor as the torque (Ti) of the sun gear, and the second torque detector detects the torque of the internal gear rotated by the second motor as the torque (To) of the internal gear.

[0061] In one technical solution, it further includes: a lower platform motor connected to the lower platform.

[0062] The condition setting unit is configured to control the rotational speed of the lower platform via the lower platform motor.

[0063] The rotating platform applies a machining load to the workpiece in the vertical direction, and the condition setting unit is configured to control the machining load.

[0064] The condition setting unit changes the grinding conditions by changing the rotational speed of the lower platform or the machining load.

[0065] Advantages of the Invention

[0066] According to the present invention, it is possible to provide a method for double-sided grinding of a workpiece, a method for manufacturing a workpiece, and a double-sided grinding apparatus for a workpiece, which can accurately control the thickness of the workpiece after double-sided grinding, and further obtain a workpiece with high flatness. BRIEF DESCRIPTION OF THE DRAWINGS

[0067] Figure 1A FIG. is a perspective view of a double-sided grinding apparatus for a workpiece according to an embodiment of the present invention.

[0068] Figure 1B FIG. is a partial cross-sectional view of a double-sided grinding apparatus for a workpiece according to an embodiment of the present invention.

[0069] Figure 2 FIG. is a block diagram of a double-sided grinding apparatus for a workpiece according to an embodiment of the present invention.

[0070] Figure 3 FIG. is a diagram for explaining the state of forces acting on a wafer when it is ground in a double-sided grinding apparatus.

[0071] Figure 4A FIG. is a diagram showing the relationship between the sum of torques (Ti + To) of a sun gear and an internal gear and the change rate of GBIR.

[0072] Figure 4B FIG. is a diagram showing the relationship between the torque ratio (Ti / To) of a sun gear and an internal gear and the change rate of GBIR.

[0073] Figure 4C FIG. is a diagram showing the relationship between the sum of torques (Ti + To) of a sun gear and an internal gear and the change rate of ESFQR.

[0074] Figure 4D FIG. is a diagram showing the relationship between the torque ratio (Ti / To) of a sun gear and an internal gear and the change rate of ESFQR.

[0075] Figure 5 FIG. is a flowchart of a method for double-sided grinding of a workpiece according to an embodiment of the present invention.

[0076] Figure 6 is a continuation Figure 5 of the flowchart.

[0077] Figure 7A FIG. is a diagram showing the thickness of a ground wafer in Example 1 in Table 1.

[0078] Figure 7B FIG. is a diagram showing the thickness of a ground wafer in Example 2 in Table 1.

[0079] Figure 7C FIG. is a diagram showing the thickness of a ground wafer in Example 3 in Table 1.

[0080] Figure 7D It is a diagram showing the thickness of the polished wafer of Example 4 in Table 1.

[0081] Figure 8A It is a diagram showing the thickness of the polished wafer of Example 5 in Table 2.

[0082] Figure 8B It is a diagram showing the thickness of the polished wafer of Example 6 in Table 2.

[0083] Figure 8C It is a diagram showing the thickness of the polished wafer of Example 7 in Table 2. Detailed implementation manners

[0084] Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

[0085] As Figure 1A and Figure 1B shown, a double-sided polishing apparatus 1 according to an embodiment of the present invention includes: a rotary table 2, an upper table motor 11, a lower table motor 13, (five in the illustrated example) carrier plates 14, an upper polishing pad 15, a lower polishing pad 16, a sun gear 20, and an internal gear 30. The rotary table 2 includes a rotatable upper table 10 and a lower table 12. The upper table motor 11 rotates the upper table 10, and the lower table motor 13 rotates the lower table 12. Moreover, the upper polishing pad 15 and the lower polishing pad 16 for polishing are respectively adhered to the lower surface of the upper table 10 and the upper surface of the lower table 12. The sun gear 20 is provided at the central portion of the rotary table 2, and the internal gear 30 is provided at the outer peripheral portion of the rotary table 2. In the present embodiment, the carrier plates 14 are arranged to surround the sun gear 20 and carry the wafers W. The carrier plates 14 rotate between the upper table 10 and the lower table 12 through the sun gear 20 and the internal gear 30. In addition, the number of the carrier plates 14 is not limited and can be appropriately adjusted. For example, only one carrier plate 14 may be provided.

[0086] As Figure 1A shown, in the present embodiment, when polishing the wafer W, the rotation direction A1 of the upper table 10 is counterclockwise in the illustrated example, the rotation direction A2 of the lower table 12 is clockwise in the illustrated example, the rotation direction A3 of the sun gear 20 is clockwise in the illustrated example, and the rotation direction A4 of the internal gear 30 is clockwise in the illustrated example. However, it is not limited thereto and can be appropriately adjusted. For example, the rotation direction A1 may be clockwise and the rotation direction A2 may be counterclockwise.

[0087] Moreover, as Figure 1BAs shown, when grinding the wafer W, the polishing liquid 17 is supplied into the double-sided polishing apparatus 1. The carrier plate 14 is disposed between the lower polishing pad 16 of the lower table 12 and the upper polishing pad 15 of the upper table 10. The wafer W placed on the carrier plate 14 is chemically mechanically polished on both sides simultaneously by the lower polishing pad 16 of the lower table 12, the upper polishing pad 15 of the upper table 10, and the polishing liquid 17 supplied to the wafer W.

[0088] Reference Figure 2 , the double-sided polishing apparatus 1 further includes: a sun gear motor (first motor) 21, a first torque detector 22, an internal gear motor (second motor) 31, and a second torque detector 32. The sun gear 20 is driven (rotated) by the sun gear motor 21. The first torque detector 22 is connected to the sun gear 20 and the sun gear motor 21 (electrically in this example). During polishing, the first torque detector 22 directly detects the torque Ti of the sun gear 20, or uses the torque of the rotating sun gear 20 of the sun gear motor 21 as the torque Ti of the sun gear 20. And, the internal gear 30 is driven (rotated) by the internal gear motor 31. The second torque detector 32 is connected to the internal gear 30 and the internal gear motor 31 (electrically in this example). During polishing, the second torque detector 32 directly detects the torque To of the internal gear 30, or uses the torque of the rotating internal gear 30 of the internal gear motor 31 as the torque To of the internal gear 30. Any known torque sensor or the like can be used as the torque detector.

[0089] Continue to refer to Figure 2 , the double-sided polishing apparatus 1 further includes: a calculation processing unit 40, a condition setting unit 50, a storage unit 60, and a pressurizing device 70. The calculation processing unit 40 is connected to the first torque detector 22 and the second torque detector 32 (electrically in this example) and receives torque information. Based on the torque information, the calculation processing unit 40 calculates the sum value Ti + To of the torque Ti of the sun gear 20 and the torque To of the internal gear 30 and the ratio value Ti / To of the torques, and sends them to the condition setting unit 50 after processing. Additionally, it can also be configured such that the calculation processing unit 40 includes a communication unit and receives the torque information wirelessly through this communication unit. Any known computer or the like can be used as the calculation processing unit 40.

[0090] The condition setting unit 50 sets the processing shape and polishing conditions of the wafer W, and is connected to the calculation processing unit 40 (electric in this example) to receive the values of the sum of torques Ti + To and the torque ratio Ti / To of the sun gear 20 and the internal gear 30, thereby determining how to control the rotational speeds of the upper platform 10 and the lower platform 12 and / or control the pressing device 70. Additionally, the condition setting unit 50 can be configured to include a communication unit that receives the values of the sum of torques and the torque ratio value (wirelessly) through this communication unit. The condition setting unit 50 can be any known processor. The pressing device 70 can apply a processing load F to the wafer W in the vertical direction along the rotating platform 2. The storage unit 60 is connected to the condition setting unit 50 (electric in this example) and pre-stores the relationships of the sum of torques (Ti + To) and the torque ratio (Ti / To) with respect to the processing shape of the wafer W. The storage unit 60 can be any known memory.

[0091] Next, the reasons for the condition setting unit 50 to control the rotational speed of the platform or the processing load are explained. In a double-sided polishing device, control elements related to the force on the wafer are, for example, the torque of the upper platform, the torque of the lower platform, the torque of the internal gear, the torque of the sun gear, etc. When the present inventor analyzed the correlation between the force condition of the wafer in the carrier plate in the double-sided polishing device and the wafer shape, it was found that the torques of the sun gear and the internal gear are the main factors affecting the GBIR value and the ESFQR value of the wafer. Moreover, the present inventor found that by controlling the sum of torques and the torque ratio of the torques of the sun gear and the internal gear within a specified range, the polishing accuracy of the wafer can be well controlled.

[0092] Simultaneously referring to Figure 1A and Figure 3 , the force condition of the wafer W during polishing is explained. As described above, the rotation direction A2 of the lower platform 12 is clockwise, the rotation direction A3 of the sun gear 20 is clockwise, the rotation direction A4 of the internal gear 30 is clockwise, and the revolution direction A5 of the carrier plate 14 is clockwise, and the rotation direction A6 of the carrier plate 14 is counterclockwise. In this case, the wafer W during polishing is subjected to a total of 4 forces, which are respectively: the force Fi applied to the carrier plate 14 by the rotation of the sun gear 20, the force Fo applied to the carrier plate 14 by the rotation of the internal gear 30, the force Fd applied to the carrier plate 14 by the lower polishing pad 16 (generated by the rotation of the lower platform 12), and the frictional force Fs generated by the carrier plate 14 (vertical resistance, that is, the force generated by the processing load F). The present inventor envisioned the case where the carrier plate 14 can revolve clockwise and rotate counterclockwise, and conducted mechanical analysis using the torque principle respectively.

[0093] First, in the case where the carrier plate 14 can revolve clockwise, the following formula (1) can be obtained. In the formula, ri is the outer diameter of the sun gear 20, ro is the inner diameter of the internal gear 30, and rc is the radius of the carrier plate 14.

[0094] Fo×ro + Fi×ri + Fd×(rc + ri) > Fs×(rc + ri) …… Equation (1)

[0095] Rearranging Equation (1) can obtain the following Equation (2). In the equation, To is the torque of the sun gear 20, Ti is the torque of the internal gear 30, F is the machining load, m is the mass of the lower platform 12, and α is the angular acceleration of the lower platform 12.

[0096] To + Ti + m×(rc + ri)×α×(rc + ri) > μ×F×(rc + ri) …… Equation (2)

[0097] Rearranging Equation (2) can obtain the following Equation (3). In the equation, X and Y are constants.

[0098] To + Ti > F×X - α×Y …… Equation (3)

[0099] Next, when the carrier plate 14 can rotate counterclockwise, the following Equation (4) can be obtained.

[0100] Fi×rc > Fo×rc …… Equation (4)

[0101] If both sides of Equation (4) are multiplied by ro and ri at the same time, the following Equation (5) can be obtained.

[0102] Fi×rc×ro×ri > Fo×rc×ro×ri …… Equation (5)

[0103] Rearranging Equation (5) can obtain the following Equation (6). In the equation, the number of ri divided by ro is a constant.

[0104] Ti / To > ri / ro …… Equation (6)

[0105] Furthermore, if both sides of Equation (3) are divided by To and then rearranged, the following Equation (7) can be obtained.

[0106] Ti / To > (F×X - α×Y) / To - 1 …… Equation (7)

[0107] If Equation (6) and Equation (7) are combined and rearranged, the following Equation (8) can be obtained.

[0108] Ti / To > (F×X - α×Y) / To - 1 > ri / ro …… Equation (8)

[0109] Finally, according to Equation (3) and Equation (8), it can be known that the sum of the torques Ti + To and the torque ratio Ti / To of the sun gear 20 and the internal gear 30 are related to the machining load F and the angular acceleration of the lower platform 12.

[0110] That is, by controlling the machining load F and the rotational speed of the lower platform 12 (i.e., controlling the output of the lower platform motor 13), the sum of the torques Ti+To and the torque ratio Ti / To of the sun gear 20 and the internal gear 30 can be controlled.

[0111] Moreover, as described above, the inventors of the present invention found that the sum of the torques Ti+To and the torque ratio Ti / To of the torque of the sun gear 20 and the torque of the internal gear 30 are the main factors affecting the GBIR value and the ESFQR value of the wafer. Therefore, based on the results of the above mechanical analysis, experiments were conducted to obtain the Figures 4A to 4D relationship diagrams of the GBIR and ESFQR change rates with the sum of the torques Ti+To and the torque ratio Ti / To. The GBIR change rate and the ESFQR change rate on the vertical axis are ratios, and the unit of Ti / To on the horizontal axis is a ratio. Additionally, it should be particularly mentioned that Figure 4A 、 Figure 4C and the unit of the sum of the torques Ti+To in this specification is not a general torque unit, but a value obtained by respectively converting the values of the torque Ti of the sun gear 20 and the torque To of the internal gear 30 into the ratio of the operating output of the sun gear motor 21 and the internal gear motor 31 of the corresponding motors to the rated output and then adding the ratios of the operating outputs of the two motors. And the ratio of the operating output of each motor to the rated output of each motor can be calculated by the following formula,

[0112] (Value of the output of the operating motor / Value of the rated output of the motor) × 100.

[0113] That is to say, when the ratio of the operating output of the motor to the rated output is, for example, 15, it means that the operating output of the operating motor is 15% of its rated output. And in the case of a motor with constant voltage current control, the output value can be replaced with the current value.

[0114] Refer to Figure 4A and Figure 4B , when the control range of the sum of the torques Ti+To is between 30 and 35 and when the control range of the torque ratio Ti / To is between 1.5 and 2.1, the change rate of GBIR is relatively small, that is, the overall flatness of the wafer W is relatively high. Therefore, in the present embodiment, when determining the processing shape of the wafer W based on the GBIR value, it is preferable to set the control range of the sum of the torques Ti+To to 30 to 35 and the control range of the torque ratio Ti / To to 1.5 to 2.1. Additionally, in Figure 4A and Figure 4BIn the relationship diagram of the GBIR change rate, it should be particularly mentioned that as the value on the horizontal axis increases, the overall shape of the wafer W gradually changes from a concave shape to a convex shape. And, as described above, the GBIR change rate is a ratio, which is defined as the GBIR value of each wafer / the GBIR value of the smallest wafer. That is, in Figure 4A and Figure 4B , for the wafer with the best (minimum) GBIR value, its GBIR change rate is 1.

[0115] Next, referring to Figure 4C and Figure 4D , when the control range of the sum of torques Ti+To is 25 to 30 and the control range of the torque ratio Ti / To is 1.4 to 1.9, the change rate of ESFQR is relatively small, that is, the flatness of the outer periphery of the wafer W is relatively high. Therefore, in the present embodiment, when determining the processing shape of the wafer W based on the ESFQR value, it is preferable to set the control range of the sum of torques Ti+To to 25 to 30 and the control range of the torque ratio Ti / To to 1.4 to 1.9. In addition, in Figure 4C and Figure 4D In the relationship diagram of the ESFQR change rate, it should be particularly mentioned that as the value on the horizontal axis increases, the outer peripheral shape of the wafer W gradually changes from an inclined shape with a lower inner part and a higher outer part to an inclined shape with a higher inner part and a lower outer part. And, as described above, the change rate of ESFQR is a ratio, which is defined as the ESFQR value of each wafer / the ESFQR value of the smallest wafer. That is, in Figure 4C and Figure 4D , for the wafer with the best (minimum) ESFQR value, its ESFQR change rate is 1.

[0116] Regarding the reason for the change in the shape of the above-mentioned wafer W, the present inventor made the following explanation. That is, if the sum of torques Ti+To is too low, the revolution effect of the carrier plate 14 is suppressed because the moving speed of the wafer W during grinding decreases, the contact rate of the abrasive grains in the grinding liquid 17 with the center of the wafer W increases, and the grinding amount at the center of the wafer W is more than that at the outer periphery of the wafer W. Therefore, the shape of the wafer W is likely to become a concave shape. On the other hand, if the sum of torques Ti+To is too large, the revolution speed of the carrier plate 14 increases because the moving speed of the wafer W during grinding increases, the contact rate of the abrasive grains in the grinding liquid 17 with the outer periphery of the wafer W increases, and the grinding amount at the outer periphery of the wafer W is more than that at the center of the wafer W. Therefore, the shape of the wafer W is likely to become a convex shape.

[0117] Moreover, if the torque ratio Ti / To is too small, the shape after grinding tends to become unstable. Since the rotation of the carrier plate 14 becomes unsmooth and the grinding amount for each outer periphery of the wafer W becomes uneven, the outer periphery shape of the wafer W tends to become unstable. On the other hand, if the torque ratio Ti / To is too large, the rotation speed of the carrier plate 14 increases, and the grinding amount for each outer periphery of the wafer W becomes larger. Therefore, the wafer W tends to become convex-shaped.

[0118] Next, please refer to Figure 5 and Figure 6 together. These are flowcharts for explaining a double-sided grinding method for a workpiece according to an embodiment of the present invention.

[0119] In step S01, before the start of double-sided grinding, the condition setting unit 50 obtains the correlation between the sum of torques Ti + To for controlling GBIR and ESFQR, the torque ratio Ti / To, and the shape of the wafer W from the storage unit 60. Alternatively, this correlation can be received from the outside through the communication unit.

[0120] Next, in step S02, the measurement unit measures the current (before the start of double-sided grinding) shape of the wafer W. The measurement unit can use any known measuring instrument such as a sensor capable of measuring the wafer thickness.

[0121] Next, in step S03, grinding using the double-sided grinding device 1 is started.

[0122] After starting the grinding, in step S04, first, grinding for controlling GBIR (i.e., grinding to flatten the entire wafer) is performed. At this time, the condition setting unit 50 sets the grinding conditions based on the correlation between the sum of torques Ti + To and the torque ratio Ti / To related to GBIR obtained previously and the shape of the wafer W, according to the desired processed shape of the wafer W. Specifically, the condition setting unit 50 sets the rotation speed of the lower table 12 or the processing load F applied by the pressurizing device.

[0123] Then, in step S05, the wafer W is continuously ground under the grinding conditions set in step S04.

[0124] While the wafer W is being continuously ground, in step S06, the first torque detector 22 detects the torque Ti of the sun gear motor 21, and the second torque detector 32 detects the torque To of the internal gear motor 31.

[0125] Next, in step S07, the calculation processing unit 40 obtains the torques Ti and To from the first torque detector 22 and the second torque detector 32, and after transforming the values of the torque Ti and the torque To into the ratios of the operation outputs of the corresponding motors to the rated outputs respectively, obtains the sum of torques Ti + To and the torque ratio Ti / To.

[0126] Next, in step S08, the condition setting unit 50 sets the control ranges of the sum of torques Ti + To and the ratio of torques Ti / To based on the correlation between the sum of torques Ti + To and the ratio of torques Ti / To related to the previously obtained GBIR and the shape of the wafer W, according to the desired shape of the wafer W.

[0127] Next, in step S09, the condition setting unit 50 receives the values of the sum of torques Ti + To and the ratio of torques Ti / To from the calculation processing unit 40, and determines whether the value of the sum of torques Ti + To and the value of the ratio of torques Ti / To are within the control ranges. If either the value of the sum of torques Ti + To or the value of the ratio of torques Ti / To is not within the control range, the process proceeds to step S04 to reset the rotational speed of the lower stage 12 or the processing load F applied by the pressing device. If the values of both the sum of torques Ti + To and the ratio of torques Ti / To satisfy the control range, the process proceeds to step S10.

[0128] In step S10, it is determined whether the polishing of the GBIR is completed. If it is not completed, the process proceeds to step S05. If it is completed, the process proceeds to step S11 to perform the polishing of ESFQR (i.e., the polishing to flatten the outer periphery of the wafer).

[0129] In step S11, the condition setting unit 50 sets the polishing conditions based on the correlation between the sum of torques Ti + To and the ratio of torques Ti / To related to the previously obtained ESFQR and the shape of the wafer W, according to the desired processed shape of the wafer W. Specifically, the condition setting unit 50 sets the rotational speed of the lower stage 12 or the processing load F applied by the pressing device.

[0130] Next, in step S12, the polishing is continuously performed based on the polishing conditions set in step S11.

[0131] While continuously polishing the wafer W, in step S13, the first torque detector 22 detects the torque Ti of the sun gear motor 21, and the second torque detector 32 detects the torque To of the internal gear motor 31.

[0132] Next, in step S14, the calculation processing unit 40 obtains the torques Ti and To from the first torque detector 22 and the second torque detector 32, and after converting the values of the torques Ti and To into the ratios of the operating outputs of the corresponding motors to the rated outputs, obtains the sum of torques Ti + To and the ratio of torques Ti / To.

[0133] Next, in step S15, based on the correlation between the sum of torques Ti + To and the torque ratio Ti / To of ESFQR obtained previously and the shape of the wafer W, the condition setting unit 50 sets the control ranges of the sum of torques Ti + To and the torque ratio Ti / To according to the desired shape of the wafer W.

[0134] Next, in step S16, the condition setting unit 50 receives the values of the sum of torques Ti + To and the torque ratio Ti / To from the calculation processing unit 40, and determines whether the values of the sum of torques Ti + To and the torque ratio Ti / To are within the control ranges. If any of the values of the sum of torques Ti + To and the torque ratio Ti / To is not within the control range, the process proceeds to step S11 to reset the rotational speed of the lower platen 12 or the processing load F applied by the pressurizing device. If the values of both the sum of torques Ti + To and the torque ratio Ti / To satisfy the control range, the process proceeds to step S17.

[0135] In step S17, it is determined whether the grinding of ESFQR is completed. If it has not been completed, the process proceeds to step S12. If it has been completed, the process proceeds to step S18 and the grinding is finished.

[0136] Next, in step S19, the wafer W is sent to the next manufacturing process. Specifically, the wafer W is removed from the double-sided grinding device 1 and sent to the next device.

[0137] Examples

[0138] The grinding results of the experimental examples according to the present invention are described in Tables 1 and 2 below. Table 1 shows the setting of the processing load, the measured torque, and the grinding results for each experimental example. In each experimental example, a silicon wafer on which no device was formed was used as the wafer to be ground.

[0139] [Table 1]

[0140]

[0141] Furthermore, the setting of the common grinding conditions for each example in Table 1 is as follows:

[0142] Grinding pad: A grinding pad having basic characteristics such as a material of foamed polyurethane, a thickness of about 1 mm, a hardness (Shore A) of 80 to 88 (degrees), and a compression ratio of 1.4 to 3.4 (%) Grinding liquid: A grinding liquid having basic characteristics such as an average particle diameter of abrasive grains of 45 to 65 (nm), a specific gravity of 1.15 to 1.16, and a pH value of 10.8 to 11.8

[0143] Carrier plate type: DLC plating material is plated on a stainless steel substrate

[0144] Upper platform rotation speed: -9.4 rpm (the negative sign indicates counterclockwise rotation)

[0145] Lower platform rotation speed: 25 rpm

[0146] Sun gear rotation speed: 25 rpm

[0147] Internal gear rotation speed: 4 rpm

[0148] The shape of the polished wafer can be measured using existing measuring instruments. For the measurement of GBIR, the measurement range is 298 mm, excluding 1 mm of the outer periphery. For the measurement of ESFQR, the measurement range is 298 mm, excluding 1 mm of the outer periphery (length is 35 mm, arc is 5 degrees).

[0149] Figures 7A to 7D Successively represent the wafer shapes of Experimental Examples 1 to 4. In Experimental Example 1, a processing load of 1000 daN was used, and the shape of the polished wafer was a concave shape as shown Figure 7A In contrast, in Experimental Example 2, since the processing load was reduced, the values of the sum of torques Ti + To and the torque ratio Ti / To became smaller. Therefore, the shape of the polished wafer was as shown Figure 7B and was likely to become a more concave shape. Also, in Experimental Examples 3 and 4, since the processing load was increased, the values of the sum of torques Ti + To and the torque ratio Ti / To became larger. Therefore, the shapes of the polished wafers were as shown Figure 7C and Figure 7D and were likely to become flat or convex shapes.

[0150] Table 2 shows the settings of the lower platform rotation speed, the measured torques, and the polishing results for each experimental example.

[0151] [Table 2]

[0152]

[0153]

[0154] Also, the settings of the common polishing conditions for each example in Table 2 are as follows:

[0155] Polishing pad: A polishing pad with basic properties such as a material of foamed polyurethane, a thickness of about 1 mm, a hardness (Shore A) of 80 to 88 (degrees), and a compression ratio of 1.4 to 3.4 (%) Polishing liquid: A polishing liquid with basic properties such as an average particle size of abrasive grains of 45 to 65 (nm), a specific gravity of 1.15 to 1.16, and a pH value of 10.8 to 11.8

[0156] Carrier plate type: DLC coating material plated on a stainless steel substrate

[0157] Processing load: 1000 daN

[0158] Upper platform speed: -18.4rpm (minus sign indicates counterclockwise rotation)

[0159] Sun gear speed: 25rpm

[0160] Internal gear speed: 4rpm

[0161] The shape of the polished wafer can be measured using existing measuring instruments. For GBIR measurement, the measurement range is 298 mm, excluding the outer circumference of 1 mm. For ESFQR measurement, the measurement range is 298 mm, excluding the outer circumference of 1 mm (length 35 mm, arc 5 degrees).

[0162] Figures 8A to 8C The wafer shapes of Experimental Examples 5 to 7 are shown in sequence. In Experimental Example 5, the rotation speed of the lower platform is set to 25 rpm, and the shape of the wafer after grinding is as follows Figure 8A In contrast, in Experimental Examples 6 and 7, since the rotation speed of the lower platform was reduced, the sum of the torques Ti+To and the torque ratio Ti / To became larger, and thus the shape of the wafer after grinding was as follows: Figure 8B and Figure 8C As shown, it is easy to become a flat shape or a convex shape.

[0163] As mentioned above, although embodiment was given and this invention was specifically described, this invention is not limited to this, Various changes are possible.

[0164] For example, in a modified example, the condition setting unit 50 may also include a machine learning device. The machine learning device may perform machine learning by any existing algorithm, for example, learning the relationship between the sum of the torques (Ti+To) and the torque ratio (Ti / To) of the sun gear 20 and the internal gear 30 and the shape of the wafer by an algorithm such as a neural network. Thus, the condition setting unit 50 can automatically set the grinding conditions based on the sum of the torques (Ti+To) and the torque ratio (Ti / To) of the sun gear 20 and the internal gear 30 to meet the desired GBIR value and / or ESFQR value.

[0165] Furthermore, in the polishing flow chart of the present invention, GBIR polishing and ESFQR polishing are performed sequentially, but the present invention is not limited thereto, and the order of polishing may be changed, or only one of the polishings may be performed.

[0166] Furthermore, the condition setting unit 50 may also divide the double-side polishing process of the wafer W into a plurality of sub-processes based on the measured shape of the wafer W. For example, the sub-processes may include: a sub-process for reducing the degree of deviation of the wafer W in the circumferential direction; and a sub-process for reducing the degree of deviation of the wafer W in the radial direction.

[0167] Furthermore, the condition setting unit 50 can set the control ranges of the sum of torques Ti + To and the ratio of torques Ti / To in each of the plurality of sub-processes, and determine whether the values of the sum of torques Ti + To and the ratio of torques Ti / To are within the control ranges, thereby determining whether it is necessary to change the polishing conditions.

[0168] Description of Reference Numerals

[0169] 1 - Double-sided polishing apparatus, 2 - Rotary table, 11 - Upper table motor, 13 - Lower table motor, 14 - Carrier plate, 15 - Upper polishing pad, 16 - Lower polishing pad, 17 - Polishing liquid, 20 - Sun gear, 30 - Internal gear, 21 - Sun gear motor (first motor), 22 - First torque detector, 31 - Internal gear motor (second motor), 32 - Second torque detector, 40 - Calculation processing unit, 50 - Condition setting unit, 60 - Storage unit, 70 - Pressurizing device, F - Processing load, A1, A2, A3, A4 - Rotation directions, A5 - Revolution direction, A6 - Rotation direction, Fd, Fi, Fo, Fs - Forces, S01 to S19 - Steps, W - Wafer.

Claims

1. A method for double-sided grinding of a workpiece, which is a method for grinding a workpiece inside a carrier plate rotated by a sun gear and an internal gear, characterized in that the method for double-sided grinding of the workpiece includes: A step of setting grinding conditions according to the target machining shape of the workpiece; A step of starting grinding based on the grinding conditions; A step of detecting the torque (Ti) of the sun gear and the torque (To) of the internal gear during grinding by a torque detector; A step of calculating, by a calculation processing unit, the value of the sum of torques (Ti + To) and the value of the torque ratio (Ti / To) of the detected torque (Ti) of the sun gear and the torque (To) of the internal gear; A step of setting, by a condition setting unit, the control ranges of the sum of torques (Ti + To) and the torque ratio (Ti / To); and A step of determining, by the condition setting unit, whether it is necessary to change the grinding conditions based on whether the value of the sum of torques (Ti + To) and the value of the torque ratio (Ti / To) are within the control ranges.

2. The method for double-sided grinding of a workpiece according to claim 1, further including: A step of obtaining in advance the relationships of the sum of torques (Ti + To) and the torque ratio (Ti / To) with respect to the target machining shape of the workpiece before the start of double-sided grinding, The step of setting the control ranges of the sum of torques (Ti + To) and the torque ratio (Ti / To) is carried out based on the obtained relationships.

3. The method for double-sided grinding of a workpiece according to claim 2, wherein The target machining shape of the workpiece is determined by the GBIR value and / or the ESFQR value.

4. The method for double-sided grinding of a workpiece according to claim 3, wherein By the calculation processing unit, the values of the torque (Ti) of the sun gear and the torque (To) of the internal gear are respectively transformed into the ratios of the operation outputs of the motor driving the sun gear and the motor driving the internal gear to their respective rated outputs. When the target machining shape of the workpiece is determined according to the GBIR value, the condition setting unit sets the control range of the sum of torques (Ti + To) to 30 to 35, and sets the control range of the torque ratio (Ti / To) to 1.5 to 2.1, The ratio of the operation output of the motor to the rated output can be calculated by the following formula: (Value of the output of the motor in operation / Value of the rated output of the motor) × 100.

5. The method for double-sided grinding of a workpiece according to claim 3, wherein Through the calculation and processing unit, the values of the torque (Ti) of the sun gear and the torque (To) of the internal gear are respectively converted into the ratios of the operation outputs of the motors driving the sun gear and the internal gear to their respective rated outputs. When determining the target machining shape of the workpiece according to the ESFQR value, the condition setting unit sets the control range of the sum of the torques (Ti + To) to 25 to 30, and sets the control range of the torque ratio (Ti / To) to 1.4 to 1.

9. The ratio of the operation output of the motor to the rated output can be calculated by the following formula. (Value of the output of the motor in operation / Value of the rated output of the motor) × 100.

6. The double-sided grinding method for a workpiece according to any one of claims 1 to 5, wherein The carrier plate is arranged between the upper platform and the lower platform of the rotating platform. The grinding condition is the rotational speed of the lower platform or the machining load applied by the rotating platform to the workpiece.

7. The double-sided grinding method for a workpiece according to any one of claims 1 to 5 further includes: A process of measuring the shape of the workpiece before the start of grinding by a measuring unit; And A process in which the calculation and processing unit divides the double-sided grinding process of the workpiece into multiple sub-processes based on the measured shape of the workpiece. The process of setting the control ranges of the sum of the torques (Ti + To) and the torque ratio (Ti / To) is performed separately in each of the sub-processes. The process of determining whether it is necessary to change the grinding condition based on whether the values of the sum of the torques (Ti + To) and the torque ratio (Ti / To) are within the control ranges is performed separately in each of the sub-processes.

8. The double-sided grinding method for a workpiece according to claim 7, wherein The multiple sub-processes include: A sub-process of reducing the deviation degree of the workpiece in the circumferential direction; and A sub-process of reducing the deviation degree of the workpiece in the radial direction.

9. A method for manufacturing a workpiece, which manufactures a workpiece by the double-sided grinding method for a workpiece according to any one of claims 1 to 8.

10. A double-sided grinding device for a workpiece, comprising: A rotating platform having a rotatable upper platform and a lower platform; A sun gear arranged at the center of the rotating platform; An internal gear arranged at the outer periphery of the rotating platform; A carrier plate configured to be arranged on the lower platform, capable of carrying a workpiece, and rotating between the upper platform and the lower platform through the sun gear and the internal gear; A first torque detector that detects the torque (Ti) of the sun gear during double-sided grinding; A second torque detector that detects the torque (To) of the internal gear during double-sided grinding; A calculation and processing unit that receives the detected torque information and calculates the value of the sum of the torques (Ti + To) and the torque ratio (Ti / To) of the torque (Ti) of the sun gear and the torque (To) of the internal gear based on the torque information; and A condition setting unit configured to set a target machining shape and polishing conditions of the workpiece, and receive values of the sum of the torques (Ti + To) and the ratio of the torques (Ti / To). The double-sided polishing apparatus for a workpiece is characterized in that the condition setting unit determines whether it is necessary to change the polishing conditions based on whether the values of the sum of the torques (Ti + To) and the ratio of the torques (Ti / To) are within a control range.

11. The double-sided polishing apparatus for a workpiece according to claim 10, wherein the double-sided polishing apparatus further includes a storage unit that pre-stores the relationship between the sum of the torques (Ti + To) and the ratio of the torques (Ti / To) with respect to the target machining shape of the workpiece, and / or the condition setting unit includes a communication unit capable of receiving the relationship. Before the start of double-sided polishing, the condition setting unit obtains the relationship from the storage unit or receives and obtains the relationship from the outside through the communication unit, and sets the control ranges of the sum of the torques (Ti + To) and the ratio of the torques (Ti / To) based on the obtained relationship.

12. The double-sided polishing apparatus for a workpiece according to claim 11, wherein the condition setting unit determines the target machining shape of the workpiece based on the GBIR value and / or the ESFQR value.

13. The double-sided polishing apparatus for a workpiece according to claim 12, wherein through the calculation processing unit, the values of the torque (Ti) of the sun gear and the torque (To) of the internal gear are respectively converted into the ratios of the operation outputs of the motor driving the sun gear and the motor driving the internal gear with respect to their respective rated outputs. When determining the target machining shape of the workpiece based on the GBIR value, the condition setting unit sets the control range of the sum of the torques (Ti + To) to 30 to 35, and sets the control range of the ratio of the torques (Ti / To) to 1.5 to 2.

1. The ratio of the operation output of the motor with respect to the rated output can be calculated by the following formula (Value of the output of the motor in operation / Value of the rated output of the motor) × 100.

14. The double-sided polishing apparatus for a workpiece according to claim 12, wherein through the calculation processing unit, the values of the torque (Ti) of the sun gear and the torque (To) of the internal gear are respectively converted into the ratios of the operation outputs of the motor driving the sun gear and the motor driving the internal gear with respect to their respective rated outputs. When determining the target machining shape of the workpiece based on the ESFQR value, the condition setting unit sets the control range of the sum of the torques (Ti + To) to 25 to 30, and sets the control range of the ratio of the torques (Ti / To) to 1.4 to 1.

9. The ratio of the operation output of the motor with respect to the rated output can be calculated by the following formula (Value of the output of the motor in operation / Value of the rated output of the motor) × 100.

15. The double-sided grinding device for workpieces according to claim 12, wherein the condition setting unit further includes: a machine learning device that automatically sets the grinding conditions based on the sum of the torques (Ti + To) and the ratio of the torques (Ti / To) by means of machine learning so as to satisfy a desired GBIR value and / or ESFQR value.

16. The double-sided grinding device for workpieces according to any one of claims 10 to 15, further comprising: a first motor connected to the sun gear; and a second motor connected to the internal gear, wherein the first torque detector detects the torque of the sun gear when the first motor rotates the sun gear as the torque (Ti) of the sun gear, and the second torque detector detects the torque of the internal gear when the second motor rotates the internal gear as the torque (To) of the internal gear.

17. The double-sided grinding device for workpieces according to any one of claims 10 to 15, further comprising: a lower table motor connected to the lower table, wherein the condition setting unit is configured to control the rotational speed of the lower table via the lower table motor, the rotating table applies a processing load to the workpiece in the vertical direction, and the condition setting unit is configured to control the processing load, and the condition setting unit changes the grinding conditions by changing the rotational speed of the lower table or the processing load.

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