Thinning control method and system for TTV detection and thinning machine

Abstract

The invention discloses a thinning control method and system based on TTV detection and a thinning machine. According to the thinning control method, when a wafer on a wafer bearing table is thinned at a coarse grinding position and a fine grinding position respectively, the wafer on the wafer bearing table is thinned; determining a first height variation at the first detection point and a second height variation at the second detection point according to data measured by the first height measurement mechanism and the second height measurement mechanism in the thinning process; determining the TTV of the wafer on the wafer bearing table according to the first height variation and the second height variation; determining whether the TTV of the wafer exceeds a threshold; if yes, thinning is stopped; and if not, thinning is continued. According to the method, the TTV of the wafer is determined on line in real time based on the structure of the existing thinning machine, the structure of a wafer bearing table does not need to be changed, an additional detection structure does not need to be added, implementation is easy, meanwhile, whether the TTV exceeds the threshold value or not is determined after the TTV is calculated, when the TTV exceeds the threshold value, the thinning machine can be controlled to stop thinning immediately, the wafer bearing table can be adjusted conveniently, and the efficiency is improved. And the thinning quality can be ensured.

Description

Technical Field

[0001] The present invention relates to the field of semiconductor device processing, in particular to a thinning control method, system and thinning machine for TTV detection. Background Art

[0002] TTV is the difference between the maximum thickness and the minimum thickness of a silicon wafer. This parameter is an important indicator for measuring the thickness uniformity of a silicon wafer.

[0003] During wafer thinning, especially for wafers with extremely high hardness, the thinning mechanism needs to apply a large downward pressure to the wafer chuck. Therefore, during the thinning process, the elastic deformation of the wafer chuck is relatively large, and the surface profile attitude of the wafer chuck relative to the spindle changes, which will cause the TTV of the wafer to exceed the tolerance. An existing processing method is to greatly increase the stiffness of the wafer chuck to reduce the influence of elastic deformation. This method increases the volume of the wafer chuck and the cost is relatively high.

[0004] The invention patent application with the application publication number CN113251936A discloses a wafer TTV interference testing device. This solution requires adding a large number of additional components on the basis of the existing thinning machine, with great implementation difficulty and high cost. Summary of the Invention

[0005] The purpose of the present invention is to solve the above problems existing in the prior art, and provide a thinning control method, system and thinning machine based on TTV detection.

[0006] The purpose of the present invention is achieved by the following technical solutions:

[0007] A thinning control method based on TTV detection includes the following steps:

[0008] S1. During the process of thinning the wafer on the wafer chuck at the rough grinding position, determine the first height change amount at the first detection point according to the data measured by the first height measuring mechanism during the thinning process and the data measured before thinning. The first probe of the first height measuring mechanism is mounted at the first detection point on the wafer chuck at the rough grinding position;

[0009] S2. During the process of thinning the wafer on the wafer chuck at the fine grinding position, determine the second height change amount at the second detection point according to the data measured by the second height measuring mechanism during the thinning process and the data measured before thinning. The second probe of the second height measuring mechanism is mounted at the second detection point on the wafer chuck at the fine grinding position;

[0010] S3. Determine the TTV of the wafer on the wafer chuck according to the first height change amount and the second height change amount;

[0011] S4. Determine whether the TTV of the wafer exceeds the threshold;

[0012] In S5, when it is determined that the TTV of the wafer exceeds the threshold, the thinning is stopped; when it is determined that the TTV of the wafer does not exceed the threshold, the thinning is continued.

[0013] Preferably, the susceptor is connected to a three-point leveling mechanism. The three-point leveling mechanism includes the axis of the first adjusting rod, the second adjusting support point, and a fixed support point that are distributed in an equilateral triangle. The equilateral triangle is concentric with the susceptor.

[0014] Preferably, the axis of the first adjusting rod and the second adjusting support point are the connection points of the servo hydraulic cylinder and the susceptor.

[0015] Preferably, in S3, the TTV of the wafer is calculated according to the following formula:

[0016]

[0017] where R1 is the effective diameter of the susceptor; R is the diameter of the circle where the axes of the first adjusting rod, the second adjusting rod, and the leg of the three-point leveling mechanism are located; P1 is the first height change; P2 is the second height change; k1 is the distance between the axis of the first probe and the first virtual line, and the first virtual line is the straight line of the axis of the first adjusting rod and the axis of the leg; k2 is the distance between the axis of the second probe and the first virtual line; k3 is the distance between the axis of the first probe and the second virtual line, and the second virtual line is the straight line connecting and perpendicular to the axis of the second adjusting rod and the leg of the fixed support point; k4 is the distance between the axis of the second probe and the second virtual line; They are successively the distances from the knife entry point, the rotation center, and the knife exit point on the susceptor to the grinding wheel on the lifted main shaft after the deformation of the susceptor.

[0018] Preferably, k3 is determined according to the following formula:

[0019]

[0020] where R 01 is the diameter of the trajectory circle traced by the axis of the first measuring rod of the first height measuring component on the susceptor.

[0021] Preferably, k4 is determined according to the following formula:

[0022]

[0023] where R 02 is the diameter of the trajectory circle traced by the axis of the second measuring rod of the second height measuring component on the susceptor.

[0024] Preferably, when it is determined that the TTV of the wafer exceeds the threshold, the first adjusting rod and / or the second adjusting rod are adjusted to adjust the wafer stage to the target state.

[0025] Preferably, first, the axis of the first adjusting rod and the second adjusting support point are adjusted to level or substantially level the wafer stage;

[0026] Then, the axis of the first adjusting rod or the second adjusting support point is adjusted to match the state of the wafer stage with the target TTV.

[0027] A thinning control system based on TTV detection includes:

[0028] A first change amount determination unit, configured to, during the process of thinning the wafer on the wafer stage at the rough grinding position, determine the first height change amount at the first detection point according to the data measured by the first height measuring mechanism during the thinning process and the data measured before thinning, and the first probe of the first height measuring mechanism is mounted at the first detection point on the wafer stage at the rough grinding position;

[0029] A second change amount determination unit, configured to, during the process of thinning the wafer on the wafer stage at the fine grinding position, determine the second height change amount at the second detection point according to the data measured by the second height measuring mechanism during the thinning process and the data measured before thinning, and the second probe of the second height measuring mechanism is mounted at the second detection point on the wafer stage at the fine grinding position;

[0030] A TTV calculation unit, configured to determine the TTV of the wafer on the wafer stage according to the first height change amount and the second height change amount;

[0031] A judgment unit, configured to determine whether the TTV of the wafer exceeds the threshold;

[0032] A control unit, configured to stop thinning when it is determined that the TTV of the wafer exceeds the threshold; and continue thinning when it is determined that the TTV of the wafer does not exceed the threshold.

[0033] A thinning machine includes a processor and a memory, and the memory stores a program executable by the processor, and when the program is executed, it implements the thinning control method based on TTV detection as described in any one of the above.

[0034] The advantages of the technical solution of the present invention are mainly reflected in:

[0035] The method of the present invention is based on the structure of the existing thinning machine, and determines the TTV of the wafer online and in real time according to the height measurement data of the height measurement component. It does not require changing the structure of the wafer chuck and adding additional detection structures, which is easy to implement. At the same time, after calculating the TTV, it determines whether it exceeds the threshold. When it exceeds the threshold, the thinning machine can be controlled to stop thinning immediately, which is convenient for adjusting the wafer chuck and is beneficial to ensuring the thinning quality.

[0036] The calculation process of the method of the present invention is simple and can be realized with only a small amount of data.

[0037] When the present invention determines that the TTV of the wafer exceeds the threshold, it can automatically adjust the three-point leveling structure of the wafer chuck, so that the TTV of the wafer meets the requirements during subsequent processing, which can save manual intervention and is beneficial to improving the thinning quality and product consistency. Description of the Drawings

[0038] Figure 1 is a perspective view of the wafer chuck of the present invention connected to a three-point leveling mechanism;

[0039] Figure 2 is a schematic diagram of the tool entry point, rotation center and tool exit point on the wafer chuck of the present invention;

[0040] Figure 3 is a schematic diagram of the principle of the parameters used to calculate the TTV of the wafer in the present invention;

[0041] Figure 4 is a flowchart of the method of the present invention;

[0042] Figure 5 is a flowchart of the method of the present invention with an adjustment process. Detailed Embodiments

[0043] The objectives, advantages and features of the present invention will be illustrated and explained by the following non-limiting description of preferred embodiments. These embodiments are only typical examples of applying the technical solutions of the present invention, and any technical solutions formed by equivalent replacement or equivalent transformation fall within the scope of the present invention.

[0044] In the description of the solution, it should be noted that the orientation or positional relationship indicated by the terms "center", "upper", "lower", "left", "right", "front", "rear", "vertical", "horizontal", "inner", "outer", etc. is based on the orientation or positional relationship shown in the drawings, and is only for the convenience of description and simplification of the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the present invention. In addition, the terms "first", "second", "third" are only used for descriptive purposes and cannot be construed as indicating or implying relative importance.

[0045] The thinning control method based on TTV detection disclosed by the present invention will be described below in conjunction with the accompanying drawings. The thinning control method is based on the thinning machine disclosed in the patent application with the publication number CN115338717A, which will not be elaborated here.

[0046] As shown in the Figure 1 - accompanying Figure 3 drawings, the thinning machine includes three wafer carriers 100, a rough grinding mechanism and a fine grinding mechanism. When the wafer carrier 100 rotates below the rough grinding mechanism, it is in the rough grinding position; when the wafer carrier 100 rotates below the fine grinding mechanism, it is in the fine grinding position. Similar to the prior art, at the rough grinding position, the thickness of the workpiece on the wafer carrier 100 is measured by a first height measuring mechanism and a third height measuring mechanism. Specifically, during detection, the first probe 200 of the first height measuring mechanism is placed at the first detection point on the surface (table surface) of the wafer carrier 100 at the rough grinding position, and the third probe of the third height measuring mechanism is placed on the wafer. Then, the thickness of the workpiece is calculated based on the data measured by the two.

[0047] Similarly, when a wafer carrier 100 is in the fine grinding position, the thickness of the workpiece on it is measured by a second height measuring mechanism and a fourth height measuring mechanism. The second probe 300 of the second height measuring mechanism is placed at the second detection point on the surface (table surface) of the wafer carrier 100 at the fine grinding position. The specific thickness measuring principle is the same as that when measuring the thickness of the workpiece when the wafer carrier 100 is in the first position, which will not be elaborated here.

[0048] As shown in the Figure 1 drawings, the wafer carrier 100 includes a chuck assembly 101 and a rotation driving assembly 102 for driving the chuck assembly 101 to rotate. The specific structures of the chuck assembly and the rotation driving assembly are known technologies, which will not be elaborated here. The surface of the wafer carrier is a conical surface with a large taper, and the wafer on the chuck assembly 101 also shows a shape that is slightly higher in the middle than the outer periphery. The rotation driving assembly is connected to a three-point leveling mechanism. The three-point leveling mechanism includes a first adjuster 400, a second adjuster 500 and a support leg 600 that are connected to the rotation driving assembly 102 and fixed on the indexing table. The first adjuster 400 and the second adjuster 500 are known servo hydraulic cylinders. The support leg 600 can be a support column, and of course, it can also be other feasible structures, which are not limited here. The first adjusting rod 401 of the first adjuster 400 and the second adjusting rod 502 of the second adjuster 500 extend in the vertical direction. The axes of the first adjusting rod, the second adjusting rod and the axis of the support leg are distributed in an equilateral triangle, and the equilateral triangle is concentric with the wafer carrier 100. Moreover, the tops of the first adjusting rod, the second adjusting rod and the top of the fixed fulcrum support leg can adopt spherical heads, and grooves matching the spherical heads are provided on the rotation driving assembly to facilitate adjustment.

[0049] Correspondingly, as shown in the appended Figure 4 figures, the thinning control method based on TTV detection includes the following steps:

[0050] S1. During the process of thinning the wafer on the susceptor 100 at the rough grinding position, determine the first height change amount at the first detection point according to the data measured by the first height measuring mechanism during the thinning process and the data measured before thinning. The first height change amount is the maximum value among the absolute values of the differences between the data measured during the thinning process and the data measured before thinning. The first probe 200 of the first height measuring mechanism is mounted at the first detection point on the susceptor 100 at the rough grinding position;

[0051] S2. During the process of thinning the wafer on the susceptor 100 at the fine grinding position, determine the second height change amount at the second detection point according to the data measured by the second height measuring mechanism during the thinning process and the data measured before thinning. The second height change amount is the maximum value among the absolute values of the differences between the data measured during the thinning process and the data measured before thinning. The second probe 300 of the second height measuring mechanism is mounted at the second detection point on the susceptor 100 at the fine grinding position;

[0052] S3. Determine the TTV of the wafer on the susceptor 100 according to the first height change amount and the second height change amount;

[0053] S4. Determine whether the TTV of the wafer exceeds the threshold;

[0054] S5. When it is determined that the TTV of the wafer exceeds the threshold, stop thinning; when it is determined that the TTV of the wafer does not exceed the threshold, continue thinning.

[0055] As shown in the appended Figure 2 , appended Figure 3 figures, during thinning, assuming that the grinding wheel rotates counterclockwise, among the two intersection points of the outer circle of the susceptor 100 and the outer circle of the grinding wheel, the point where the grinding teeth of the grinding wheel face its movement is the tool entry point 103, and the other point is the tool entry point 105. When the thinning is completed and the spindle is lifted by a height h, therefore, the distances from the tool entry point 103, the rotation center 104, and the tool exit point 105 of the susceptor 100 to the grinding wheel on the lifted spindle are successively When the susceptor 100 is normal, it satisfies When the pressure-bearing posture of the susceptor 100 changes, correspondingly, the will change, and, excluding the maximum value among the three, the difference between the other two is the TTV of the wafer.

[0056] Let the diameter of the wafer stage 100 be R1. When the posture of the wafer stage 100 changes under pressure, the change amount e1 of the distance from the corresponding tool entry point 103 to the grinding wheel on the lifted main shaft, the change amount e2 of the distance from the tool exit point 105 to the grinding wheel on the lifted main shaft, and the change amount e0 of the distance from the rotation center 104 to the grinding wheel on the lifted main shaft can be determined according to the following formula:

[0057]

[0058] When the rotation directions of the main shafts of the rough grinding mechanism and the fine grinding mechanism are counterclockwise, usually the height of the tool exit point 105 to the grinding wheel on the lifted main shaft is the largest. At this time, the TTV of the wafer is the difference between the change amount e1 and the change amount e0. However, there is also a situation where the downward deformation of the wafer stage 100 is relatively large, resulting in the largest. At this time, the TTV of the wafer is the difference between the change amount e2 and the change amount e0. When the lifting distance h of the main shaft and the initial surface profile parameters of the wafer stage are known, the changed For example, if the initial surface profile parameters of the wafer stage are (0, 0, -20), then when the wafer stage is not deformed and the main shaft is lifted by h, After the wafer stage is deformed, the changed can be determined in sequence according to the following formula:

[0059]

[0060]

[0061]

[0062] Therefore, the TTV of the wafer can be calculated according to the following formula;

[0063]

[0064] wherein, R1 is the effective diameter of the wafer stage; R is the diameter of the circle where the axes of the first adjusting rod, the second adjusting rod, and the leg of the three-point leveling mechanism are located; P1 is the first height change amount; P2 is the second height change amount; k1 is the distance between the axis of the first probe 200 and the first virtual line, and the first virtual line is the straight line of the axis of the first adjusting rod and the axis of the leg; k2 is the distance between the axis of the second probe 300 and the first virtual line; k3 is the distance between the axis of the first probe 200 and the second virtual line, and the second virtual line is the straight line connecting and perpendicular to the axis of the second adjusting rod and the connecting line of the fixed fulcrum and the axis of the leg; k4 is the distance between the axis of the second probe 300 and the second virtual line. They are, respectively, the distances from the entry point, the rotation center, and the exit point on the wafer table to the grinding wheel on the raised spindle after the wafer table is deformed.

[0065] The k3 is determined according to the following formula:

[0066]

[0067] Among them, R 01 It is the diameter of the trajectory circle drawn by the axis of the first measuring rod of the first height measuring assembly on the wafer stage.

[0068] The k4 is determined according to the following formula:

[0069]

[0070] Among them, R 02 It is the diameter of the trajectory circle drawn by the axis of the second measuring rod of the second height measuring assembly on the wafer stage.

[0071] In actual calculation, the R1, R, k1, k2, R 01 , R 02 All of them are known parameters and stored in the memory. When calculating, it is only necessary to read the above data and calculate the first height change and the second height change and substitute them into the formula for calculation.

[0072] Further, as attached Figure 5 As shown, when it is determined that the TTV of the wafer exceeds the threshold, the wafer stage is adjusted to a target state by adjusting the first adjustment rod and / or the second adjustment rod.

[0073] Specifically, the axis of the first adjustment rod and the second adjustment support point can be adjusted first to make the wafer table 100 return. At this time, the adjustment amount of the axis of the first adjustment rod and the second adjustment support point of the wafer table 100 can be determined according to the following formula:

[0074]

[0075] Wherein, a is the adjustment amount of the axis of the first adjustment rod, and b is the adjustment amount of the second adjustment support point. After adjustment according to a and b, the wafer stage 100 is in a leveled or approximately leveled state.

[0076] In order to reduce the risk of edge collapse of the workpiece when the knife is inserted, a single point adjustment can be performed to make the subsequent thinned wafer meet the target TTV. Since the pressure area of ​​the wafer stage 100 at the fine grinding position is the area from the knife entry point 103 to the rotation center 104, which is located at the second adjustment rod, and the wafer is only allowed to be thick in the middle and thin around the edges, the adjustment amount b1 of the second adjustment rod is not 0, and the adjustment amount of the axis of the No. 1 adjustment rod is a=0.

[0077] Then, the variation e1 of the distance from the tool entry point 103 to the grinding wheel on the lifted main shaft, the variation e2 of the distance from the tool exit point 105 to the grinding wheel on the lifted main shaft, and the variation e0 of the distance from the rotation center 104 to the grinding wheel on the lifted main shaft are as follows:

[0078]

[0079] Therefore, the b1 can be determined according to the following formula:

[0080]

[0081] Wherein, TTV1 is the target TTV, and its specific value is set according to needs. For example, it can be the maximum acceptable TTV of the wafer, which is not limited here.

[0082] After the second adjusting rod adjusts the adjustment amount b1, the susceptor reaches the target state, and the thinning can be resumed.

[0083] Embodiment 2

[0084] This embodiment discloses a thinning control system based on TTV detection, including:

[0085] A first variation determination unit, configured to determine a first height variation at a first detection point according to data measured by a first height measuring mechanism during the thinning process and data measured before thinning when thinning the wafer on the susceptor 100 at the rough grinding position, and the first probe 200 of the first height measuring mechanism is mounted at the first detection point on the susceptor 100 at the rough grinding position;

[0086] A second variation determination unit, configured to determine a second height variation at a second detection point according to data measured by a second height measuring mechanism during the thinning process and data measured before thinning when thinning the wafer on the susceptor 100 at the fine grinding position, and the second probe 300 of the second height measuring mechanism is mounted at the second detection point on the susceptor 100 at the fine grinding position;

[0087] A TTV calculation unit, configured to determine the TTV of the wafer on the susceptor 100 according to the first height variation and the second height variation;

[0088] A judgment unit, configured to determine whether the TTV of the wafer exceeds a threshold;

[0089] A control unit, configured to stop thinning when it is determined that the TTV of the wafer exceeds the threshold; and continue thinning when it is determined that the TTV of the wafer does not exceed the threshold.

[0090] Embodiment 2

[0091] This embodiment discloses a thinning machine, including a processor and a memory. The memory stores a program executable by the processor, and when the program is executed, it implements the thinning control method based on TTV detection as described above.

[0092] There are still many implementation manners of the present invention. All technical solutions formed by adopting equivalent transformations or equivalent substitutions fall within the protection scope of the present invention.

Claims

1. A thinning control method based on TTV detection, characterized in that, It includes the following steps: S1. During the process of thinning the wafer on the susceptor at the rough grinding position, determine the first height change amount at the first detection point according to the data measured by the first height measuring mechanism during the thinning process and the data measured before thinning. The first probe of the first height measuring mechanism is mounted at the first detection point on the susceptor in the rough grinding position; S2. During the process of thinning the wafer on the susceptor at the fine grinding position, determine the second height change amount at the second detection point according to the data measured by the second height measuring mechanism during the thinning process and the data measured before thinning. The second probe of the second height measuring mechanism is mounted at the second detection point on the susceptor in the fine grinding position; S3. Determine the TTV of the wafer on the susceptor according to the first height change amount and the second height change amount; S4. Determine whether the TTV of the wafer exceeds the threshold; S5. When it is determined that the TTV of the wafer exceeds the threshold, stop thinning; when it is determined that the TTV of the wafer does not exceed the threshold, continue thinning.

2. The thinning control method based on TTV detection according to claim 1, wherein: The susceptor is connected to a three-point leveling mechanism. The three-point leveling mechanism includes a first regulator, a second regulator and legs. The axes of the first adjusting rod of the first regulator, the second adjusting rod of the second regulator and the legs are distributed in an equilateral triangle, and the equilateral triangle is concentric with the susceptor.

3. The thinning control method based on TTV detection according to claim 2, wherein: The first regulator and the second regulator are servo hydraulic cylinders.

4. The thinning control method based on TTV detection according to claim 2, wherein: In S3, calculate the TTV of the wafer according to the following formula; Wherein, R1 is the effective diameter of the wafer stage; R is the diameter of the circle where the axes of the first adjusting rod, the second adjusting rod and the leg of the three-point leveling mechanism are located; P1 is the first height change; P2 is the second height change; k1 is the distance between the axis of the first probe and the first virtual line, and the first virtual line is a straight line connecting and perpendicular to the axes of the first adjusting rod and the leg; k2 is the distance between the axis of the second probe and the first virtual line; k3 is the distance between the axis of the first probe and the second virtual line, and the second virtual line is a straight line connecting and perpendicular to the axis of the second adjusting rod and the leg of the connecting line of the fixed fulcrum; k4 is the distance between the axis of the second probe and the second virtual line; They are successively the distances from the knife entry point, the rotation center and the knife exit point on the wafer stage to the grinding wheel on the lifted main shaft after the deformation of the wafer stage.

5. The thinning control method based on TTV detection according to claim 4, characterized in that: The k3 is determined according to the following formula: Wherein, R 01 is the diameter of the circular trajectory traced by the axis of the first height measuring rod of the first height measuring assembly on the wafer stage.

6. The thinning control method based on TTV detection according to claim 4, wherein: The k4 is determined according to the following formula: wherein, R 02 is the diameter of the circular trajectory traced by the axis of the second measuring rod of the second height measuring component on the wafer stage.

7. The thinning control method based on TTV detection according to claim 2, wherein: When it is determined that the TTV of the wafer exceeds the threshold, adjust the first adjusting rod and / or the second adjusting rod to adjust the susceptor to the target state.

8. The thinning control method based on TTV detection according to claim 7, characterized in that: First, adjust the axis of the first adjusting rod and the second adjusting support point to level or roughly level the susceptor; Then, adjust the axis of the first adjusting rod or the second adjusting support point to match the state of the susceptor with the target TTV.

9. A thinning control system based on TTV detection, characterized in that, It includes: A first change amount determination unit, which is used to determine the first height change amount at the first detection point according to the data measured by the first height measuring mechanism during the thinning process and the data measured before thinning during the process of thinning the wafer on the susceptor at the rough grinding position. The first probe of the first height measuring mechanism is mounted at the first detection point on the susceptor in the rough grinding position; A second change amount determination unit, which is used to determine the second height change amount at the second detection point according to the data measured by the second height measuring mechanism during the thinning process and the data measured before thinning during the process of thinning the wafer on the susceptor at the fine grinding position. The second probe of the second height measuring mechanism is mounted at the second detection point on the susceptor in the fine grinding position; A TTV calculation unit, which is used to determine the TTV of the wafer on the susceptor according to the first height change amount and the second height change amount; A judgment unit, which is used to determine whether the TTV of the wafer exceeds the threshold; The control unit is configured to stop thinning when it is determined that the TTV of the wafer exceeds the threshold, and continue thinning when it is determined that the TTV of the wafer does not exceed the threshold.

10. Thinning machine, comprising a processor and a memory, the memory storing a program executable by the processor, characterized in that: When the program is executed, it implements the thinning control method based on TTV detection according to any one of claims 1-8.

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