Wafer thinning apparatus and thinning method

Abstract

The application provides wafer thinning equipment and a thinning method, the method comprising: obtaining a grinding force parameter and a speed parameter of a current period of a grinding wheel in a wafer thinning process; wherein the grinding force parameter of the current period has a corresponding delay parameter; performing compensation factor calculation based on the speed parameter to obtain a compensation factor; obtaining a change rate of the grinding force parameter of the current period based on a predicted grinding force parameter of the previous two periods of the current period and a sampling period; the change rate of the grinding force parameter of the current period is used to correct distortion of the grinding force parameter caused by sampling delay of the grinding force parameter of the current period; and inputting the grinding force parameter of the current period, the change rate of the grinding force parameter of the current period, the delay parameter and the compensation factor into a grinding force parameter prediction model to obtain a predicted grinding force parameter of the current period to reduce distortion of the grinding force parameter. The wafer thinning equipment and the wafer thinning method provided by the embodiment of the application improve the accuracy of grinding force detection.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of semiconductor equipment, in particular to a wafer thinning device and a thinning method. BACKGROUND

[0002] Three-dimensional integrated circuit (3D IC) is an important technical path for the semiconductor industry to continue Moore's Law and improve chip performance and integration. The core idea is to stack multiple chips or functional layers in the vertical direction, and realize electrical connection between layers through Through-Silicon Via (TSV) interconnection technology, so as to realize higher functional density in limited space.

[0003] Wafer thinning is a key supporting process in 3D IC manufacturing, and its main purpose is to thin the wafer from the original thickness to a super-thin state suitable for vertical integration. The super-thin wafer is the physical basis for realizing three-dimensional stacking, and is crucial for optimizing electrical performance and thermal management. With the increase of the number of 3D IC stacking layers, the requirement for the thinning thickness of a single wafer is increasingly stringent. At the same time, 3D IC puts forward very high requirements on the surface quality of the thinned wafer, including excellent Total Thickness Variation (TTV) and extremely low Roughness Average (Ra), to ensure the accuracy, consistency and stability of the subsequent bonding process.

[0004] To achieve the above thinning target, the wafer thinning device usually uses the physical grinding action of the grinding wheel to process the super-thin wafer. Such a device must precisely design and control its grinding structure and grinding process, so as to meet the processing requirements of the super-thin wafer (such as thickness ≤10μm, TTV ≤1.5μm and Ra ≤5nm) while taking into account the manufacturing cost and production efficiency.

[0005] In the wafer thinning process, the grinding force is detected, and the detection of the grinding force may be delayed. If the detected grinding force signal is directly used, the delay will cause a lag in the related regulation and control, resulting in a misalignment of the adjustment timing of the related regulation and control. Therefore, how to improve the accuracy of the grinding force detection has become an important issue to be solved in the field. SUMMARY

[0006] To solve the problems in the prior art, the embodiments of the present application provide a wafer thinning device and a thinning method, which can at least partially solve the problems in the prior art.

[0007] In a first aspect, the present application provides a wafer thinning method, comprising:

[0008] obtain a grinding force parameter and a speed parameter of a current period of a grinding wheel in a wafer thinning process; wherein the grinding force parameter of the current period has a corresponding delay parameter;

[0009] perform compensation factor calculation based on the speed parameter to obtain a compensation factor; wherein the compensation factor is used to correct non-linear variation of the grinding force parameter caused by the speed parameter;

[0010] obtain a variation rate of the grinding force parameter of the current period based on the predicted grinding force parameter of the previous two periods of the current period and a sampling period; the variation rate of the grinding force parameter of the current period is used to correct distortion of the grinding force parameter caused by sampling delay of the grinding force parameter of the current period;

[0011] input the grinding force parameter of the current period, the variation rate of the grinding force parameter of the current period, the delay parameter and the compensation factor into a grinding force parameter prediction model to obtain a predicted grinding force parameter of the current period to reduce distortion of the grinding force parameter.

[0012] Further, the wafer thinning method further comprises:

[0013] obtain a control parameter of the current period based on the predicted grinding force parameter of the current period and a reference grinding force parameter;

[0014] control grinding action of a grinding spindle of a wafer thinning device based on the control parameter of the current period to reduce deviation between a real-time grinding force parameter of the current period and the reference grinding force parameter.

[0015] Further, the obtaining of the control parameter of the current period based on the predicted grinding force parameter of the current period and the reference grinding force parameter comprises:

[0016] determining the control parameter of the current period through the predicted grinding force parameter of the current period and the reference grinding force parameter and a feedback control algorithm.

[0017] Further, the grinding force parameter comprises a normal direction grinding force of the grinding wheel, and the speed parameter comprises a feed speed of the grinding spindle; and / or, the grinding force parameter comprises a first direction grinding force and a second direction grinding force of the grinding wheel, and the speed parameter comprises a rotating speed of the grinding spindle; wherein the normal direction grinding force of the grinding wheel is perpendicular to a plane on which the first direction grinding force and the second direction grinding force of the grinding wheel are located, and the first direction grinding force and the second direction grinding force of the grinding wheel are perpendicular.

[0018] Further, the speed parameter is a feed speed of the grinding spindle; correspondingly, the compensation factor calculation based on the speed parameter to obtain a compensation factor comprises:

[0019] The feed speed compensation factor speed_factor(k) is calculated according to the formula speed_factor(k)=K0+K1(v-v0) / v0, wherein K0 represents an ideal gain at the feed speed of the grinding spindle, K1 represents a feed speed sensitivity coefficient, v represents the feed speed of the grinding spindle, and v0 represents a reference feed speed.

[0020] Further, the speed parameter is the rotational speed of the grinding spindle; accordingly, the compensation factor calculation based on the speed parameter comprises:

[0021] The rotational speed compensation factor rpm_factor(k) is calculated according to the formula rpm_factor(k)=1+γ(n ref -n) / n ref , wherein γ represents a rotational speed sensitivity coefficient, n represents the rotational speed of the grinding spindle, and n ref represents a rated reference rotational speed.

[0022] Further, the change rate of the grinding force parameter in the current period is obtained based on the predicted grinding force parameters in the previous two periods of the current period and the sampling period, and the change rate of the grinding force parameter in the current period comprises:

[0023] The change rate dF(k) / dt(k) of the grinding force parameter in the current period is calculated according to the formula dF(k) / dt(k)=[F_pred(k-1) - F_pred(k-2)] / T, wherein F_pred(k-1) represents the predicted grinding force parameter in the previous period of the current period, F_pred(k-2) represents the predicted grinding force parameter in the previous period of the previous period of the current period, and T represents the sampling period.

[0024] Further, the grinding force parameter prediction model is F_pred(k)=[F(k)+dF(k) / dt(k)L]factor(k), wherein F_pred(k) represents the predicted grinding force parameter in the current period, F(k) represents the grinding force parameter in the current period, dF(k) / dt(k) represents the change rate of the grinding force parameter in the current period, L represents the delay parameter, and factor(k) represents the compensation factor.

[0025] Further, the wafer thinning method further comprises:

[0026] If the predicted grinding force parameter in the current period exceeds a preset range, an alarm signal is sent.

[0027] In a second aspect, the present application provides a wafer thinning device for executing the wafer thinning method according to any one of the above embodiments, comprising:

[0028] A worktable is provided with a plurality of chuck turntables, and is configured to rotate about a vertical central axis to drive the plurality of chuck turntables to rotate as a whole so as to switch the chuck turntables between different stations, and the chuck turntables are used to hold wafers and drive the wafers to rotate;

[0029] A grinding device is used to grind the wafers to thin the wafers.

[0030] A control device is used to determine a predicted grinding force parameter and a control parameter of a current period based on a grinding force parameter and a speed parameter of the current period, and control the worktable and / or the grinding device to thin the wafers.

[0031] The wafer thinning device and the wafer thinning method provided by the embodiments of the present application obtain a grinding force parameter and a speed parameter of a current period of a grinding wheel in a wafer thinning process, wherein the grinding force parameter of the current period has a corresponding delay parameter; a compensation factor is calculated based on the speed parameter to obtain a compensation factor, wherein the compensation factor is used to correct a nonlinear change of the grinding force parameter caused by the speed parameter; a change rate of the grinding force parameter of the current period is obtained based on a predicted grinding force parameter of a previous two periods of the current period and a sampling period, wherein the change rate of the grinding force parameter of the current period is used to correct distortion of the grinding force parameter caused by sampling delay of the grinding force parameter of the current period; the grinding force parameter of the current period, the change rate of the grinding force parameter of the current period, the delay parameter and the compensation factor are input into a grinding force parameter prediction model to obtain a predicted grinding force parameter of the current period, so as to reduce distortion of the grinding force parameter; and the grinding force parameter is corrected based on the compensation factor, the change rate of the grinding force parameter of the current period and the grinding force parameter prediction model, thereby improving the accuracy of grinding force detection. BRIEF DESCRIPTION OF DRAWINGS

[0032] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the drawings needed to be used in the embodiments or the prior art description will be briefly introduced. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can be obtained by those skilled in the art without any creative effort. In the drawings:

[0033] Figure 1 is a structural schematic diagram of a wafer thinning device provided by an embodiment of the present application.

[0034] Figure 2 is a flow schematic diagram of a wafer thinning method provided by an embodiment of the present application.

[0035] Figure 3 is a flow schematic diagram of a wafer thinning method provided by another embodiment of the present application.

[0036] Figure 4 This is a schematic flowchart of a wafer thinning method provided in another embodiment of the present invention.

[0037] Figure 5 This is a schematic flowchart of a wafer thinning method provided in another embodiment of the present invention.

[0038] Figure 6 This is a schematic diagram of providing grinding water during the wafer thinning process according to an embodiment of the present invention.

[0039] Figure 7 This is a schematic flowchart of a wafer thinning method provided in another embodiment of the present invention.

[0040] Figure 8 This is a schematic diagram of the processed surface of the TSV region after wafer thinning according to a conventional scheme provided in an embodiment of the present invention.

[0041] Figure 9 This is a schematic diagram of the processed surface of the TSV region after wafer thinning according to an embodiment of the present invention.

[0042] Figure 10 This is a schematic diagram comparing the Ra of a traditional solution provided in an embodiment of the present invention with that of the solution in this application after wafer thinning.

[0043] Figure 11 This is a schematic diagram comparing the copper ion concentration after wafer thinning in a conventional scheme provided by an embodiment of the present invention with that of the scheme in this application. Detailed Implementation

[0044] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the embodiments of the present invention will be further described in detail below with reference to the accompanying drawings. Here, the illustrative embodiments and their descriptions are used to explain the present invention, but are not intended to limit the present invention. It should be noted that, unless otherwise specified, the embodiments and features in the embodiments of this application can be combined with each other. The acquisition, storage, use, and processing of data in the technical solutions of this application all comply with relevant laws and regulations. The user information in the embodiments of this application is obtained through legal and compliant means, and the acquisition, storage, use, and processing of user information have been authorized and agreed upon by the customer.

[0045] To facilitate understanding of the technical solution provided in this application, the relevant content of the technical solution in this application will be explained below.

[0046] During wafer thinning, the measured grinding force is delayed, and direct use leads to lag in related adjustments. For example, this invention proposes a wafer thinning method for 3D IC bonding wafer thinning, which regulates the amount of grinding water used for thinning. It can dynamically identify the passivation state of the grinding wheel and / or the shear force in the through-silicon via (TSV) region based on the rate of change of grinding force, thereby controlling the amount of grinding water used for thinning. By independently controlling two water paths for cooling the wafer and cooling the grinding wheel, and automatically switching the water flow mode, it can accurately protect against thermal damage to heterogeneous TSV regions in 3D ICs, improve wafer surface quality, and enhance process adaptability for multiple materials or structures. To achieve the above-mentioned regulation of the amount of grinding water used for thinning, it is necessary to first detect the grinding force of the grinding wheel to obtain the total grinding force of the grinding wheel characterizing the passivation degree, and the horizontal grinding force of the grinding wheel characterizing the shear force in the TSV region. The delay in detecting the grinding force of the grinding wheel affects the timing of adjusting the amount of grinding water used for thinning.

[0047] To address the inaccuracy in grinding force detection caused by the delay in grinding force measurement in existing technologies, embodiments of the present invention provide a wafer thinning device and a thinning method. By correcting the nonlinear changes in grinding force parameters caused by speed parameters and the distortion of grinding force parameters caused by the sampling delay of grinding force parameters, the accuracy of grinding force parameter detection is improved.

[0048] Figure 1 This is a schematic diagram of the structure of a wafer thinning device provided in an embodiment of the present invention, as shown below. Figure 1 As shown, the wafer thinning apparatus provided in this embodiment of the invention includes:

[0049] The worktable 1 is provided with multiple suction cup turntables 11. The worktable 1 can rotate around its vertical central axis to drive the multiple suction cup turntables 11 to rotate and move as a whole, thereby allowing the suction cup turntables 11 to switch between different workstations. The suction cup turntables 11 are used to hold the wafer and drive the wafer to rotate.

[0050] The grinding device 2 is used to grind the wafer to reduce its thickness;

[0051] A control device (not shown in the figure) is used to determine the predicted grinding force parameters for the current cycle based on the grinding force parameters and speed parameters of the current cycle, so as to control the grinding device to grind the wafer.

[0052] The grinding device 2 includes a grinding wheel 3 located at its lower part, which can grind the wafer to reduce its thickness. The grinding process involves pressing the grinding wheel onto the wafer surface and rotating it to grind away a certain thickness. The grinding wheel 3 generates grinding heat during the wafer thinning process, which needs to be dissipated and cooled by grinding water.

[0053] The control device is capable of executing the wafer thinning method provided in this embodiment of the invention. Based on the grinding force parameters and speed parameters of the current cycle, it determines the predicted grinding force parameters and control parameters for the current cycle to reduce distortion of the grinding force parameters. The control device is capable of controlling the worktable 1 and / or the grinding device 2 to thin the wafer. The control device can also be used to control the grinding device 2 to grind the wafer according to the predicted grinding force parameters of the current cycle.

[0054] The wafer thinning equipment provided in this embodiment of the invention can reduce the distortion of grinding force parameters by correcting the grinding force parameters of the current cycle based on the grinding force parameters and speed parameters of the current cycle.

[0055] Figure 2 This is a schematic flowchart of a wafer thinning method provided in an embodiment of the present invention, as shown below. Figure 2 As shown, the wafer thinning method provided in this embodiment of the invention includes:

[0056] S201. Obtain the grinding force parameters and speed parameters of the grinding wheel in the current cycle during the wafer thinning process; wherein, the grinding force parameters in the current cycle have corresponding delay parameters;

[0057] Specifically, during the wafer thinning process, the grinding force of the grinding wheel can be detected by a grinding force sensor in each cycle, serving as the grinding force parameter for the current cycle. This grinding force parameter can include the grinding force in the normal direction of the grinding wheel, the grinding force in a first direction, and the grinding force in a second direction. The grinding force in the normal direction is perpendicular to the horizontal plane, while the grinding forces in the first and second directions are perpendicular to each other and located within the horizontal plane. Due to the inherent delay in grinding force acquisition, the grinding force parameter obtained in each cycle has a corresponding delay parameter, indicating the duration of the grinding force acquisition delay. The delay parameter is set according to actual conditions, for example, 0.5 ms; this embodiment of the invention does not impose a limitation.

[0058] Non-limiting, during the wafer thinning process, the feed rate of the grinding spindle can be obtained in real time using a linear encoder, and the rotational speed of the grinding spindle can also be obtained in real time using a rotary encoder. The speed parameters may include both the feed rate and the rotational speed of the grinding spindle.

[0059] S202. Calculate the compensation factor based on the speed parameters to obtain the compensation factor; wherein, the compensation factor is used to correct the nonlinear changes in the grinding force parameters caused by the speed parameters;

[0060] Specifically, the speed parameter causes nonlinear changes in the grinding force parameter, so a compensation factor is introduced to compensate for the grinding force parameter. The compensation factor can be obtained by calculating the speed parameter. When the speed parameter includes the feed rate of the grinding spindle, the compensation factor can be calculated using the feed rate to obtain the feed rate compensation factor. When the speed parameter includes the rotational speed of the grinding spindle, the compensation factor can be calculated using the rotational speed to obtain the rotational speed compensation factor.

[0061] S203. Based on the predicted grinding force parameters of the previous two cycles and the sampling period, obtain the rate of change of the grinding force parameters in the current cycle; the rate of change of the grinding force parameters in the current cycle is used to correct the distortion of the grinding force parameters caused by the sampling delay of the grinding force parameters in the current cycle.

[0062] Specifically, the dynamic delay of the sensor itself can be compensated by the predicted grinding force parameters of the previous two cycles, correcting the distortion of the grinding force parameters caused by the sampling delay of the current cycle. The rate of change of the grinding force parameters in the current cycle can be obtained based on the predicted grinding force parameters of the previous two cycles and the sampling period. The sampling period is set according to actual conditions, and this embodiment of the invention does not impose any limitations.

[0063] In some embodiments, the rate of change of the grinding force parameter in the current cycle is obtained by calculating the difference between the predicted grinding force parameter of the previous cycle and the predicted grinding force parameter of the cycle before the current cycle, and then dividing by the sampling period.

[0064] S204. Input the grinding force parameter of the current cycle, the rate of change of the grinding force parameter of the current cycle, the delay parameter, and the compensation factor into the grinding force parameter prediction model to obtain the predicted grinding force parameter of the current cycle in order to reduce the distortion of the grinding force parameter.

[0065] Specifically, due to the acquisition delay of the grinding force parameters in the current cycle, the acquisition delay of the grinding force parameters in the current cycle is compensated by using the predicted grinding force parameters from the previous two cycles. Furthermore, since the change in grinding force parameters is not linear and is affected by the speed parameter, a compensation factor is introduced to correct the nonlinear change in grinding force parameters caused by the speed parameter. By inputting the grinding force parameters of the current cycle, the rate of change of the grinding force parameters of the current cycle, the delay parameter, and the compensation factor into the grinding force parameter prediction model, the predicted grinding force parameters for the current cycle are obtained, which can reduce the distortion of the grinding force parameters. The grinding force parameter prediction model is pre-established.

[0066] In some embodiments, the grinding force parameter prediction model includes the sum of the product of the rate of change of the grinding force parameter in the current cycle and the delay parameter, and then multiplied by a compensation factor.

[0067] This invention provides a wafer thinning method that obtains the grinding force and speed parameters of the grinding wheel in the current cycle during wafer thinning. The grinding force parameter in the current cycle has a corresponding delay parameter. A compensation factor is calculated based on the speed parameter to obtain a compensation factor. This compensation factor is used to correct the nonlinear change in the grinding force parameter caused by the speed parameter. The rate of change of the grinding force parameter in the current cycle is obtained based on the predicted grinding force parameters of the previous two cycles and the sampling cycle. This rate of change is used to correct the distortion of the grinding force parameter caused by the sampling delay in the current cycle. The grinding force parameter in the current cycle, the rate of change of the grinding force parameter in the current cycle, the delay parameter, and the compensation factor are input into a grinding force parameter prediction model to obtain the predicted grinding force parameter in the current cycle, thereby reducing the distortion of the grinding force parameter. Based on the compensation factor, the rate of change of the grinding force parameter in the current cycle, and the grinding force parameter prediction model, the grinding force parameter is corrected, improving the accuracy of grinding force detection.

[0068] Figure 3 This is a schematic flowchart of a wafer thinning method provided in another embodiment of the present invention, as shown below. Figure 3 As shown, based on the above embodiments, the wafer thinning method provided by the embodiments of the present invention further includes:

[0069] S301. Based on the predicted grinding force parameters and reference grinding force parameters of the current cycle, obtain the control parameters for the current cycle;

[0070] Specifically, the magnitude of the grinding force parameter affects the wafer processing quality and the grinding wheel life. A reference grinding force parameter is preset during the wafer thinning process. During wafer thinning, the actual grinding force parameter needs to be adjusted in real time to stabilize it within the preset reference grinding force parameter. The control parameters for the current cycle can be obtained based on the predicted grinding force parameter and the reference grinding force parameter for the current cycle. The reference grinding force parameter is preset and set according to actual conditions; this embodiment of the invention does not impose limitations on its setting.

[0071] In some embodiments, the predicted grinding force parameters and reference grinding force parameters for the current cycle can be input into the PID controller, which outputs the control parameters for the current cycle. The deviation between the actual grinding force parameters and the reference grinding force parameters is reduced through real-time adjustment by the PID controller.

[0072] S302. Based on the control parameters of the current cycle, control the grinding action of the grinding spindle of the wafer thinning equipment to reduce the deviation between the real-time grinding force parameters and the reference grinding force parameters of the current cycle.

[0073] Specifically, after obtaining the control parameters for the current cycle, the grinding action of the grinding spindle of the wafer thinning equipment can be controlled using these parameters to reduce the deviation between the real-time grinding force parameter and the reference grinding force parameter for the current cycle. This allows the actual grinding force to approach the desired grinding force, thereby achieving the desired wafer grinding surface profile and surface smoothness. Specifically, if the predicted grinding force parameter for the current cycle is the grinding force in the normal direction of the grinding wheel, the control parameter can be used to control the feed rate of the grinding spindle, thus adjusting the grinding force in the normal direction of the grinding wheel. If the predicted grinding force parameter for the current cycle is the predicted grinding force in the horizontal direction of the grinding wheel, the control parameter can be used to control the rotational speed of the grinding spindle, thus adjusting the grinding force in the horizontal direction of the grinding wheel.

[0074] Based on the above embodiments, further, obtaining the control parameters for the current cycle based on the predicted grinding force parameters and the reference grinding force parameters of the current cycle includes:

[0075] The control parameters for the current cycle are determined using the predicted grinding force parameters, the reference grinding force parameters, and the feedback control algorithm.

[0076] Specifically, the control parameters for the current cycle can be calculated based on the predicted grinding force parameters and reference grinding force parameters of the current cycle, as well as the feedback control algorithm.

[0077] In some embodiments, the feedback control algorithm may employ a PID control algorithm, for a given reference normal force F of the grinding spindle. z_ref And the predicted grinding force F in the normal direction of the grinding wheel for the current cycle. z _pred(k) calculates the control parameter u z (k) can be calculated using the following formula: u z (k).

[0078] e z (k)= F z_ref - F z _pred(k)

[0079]

[0080] Among them, K zp K represents the first proportional gain coefficient. zi K represents the first integral gain coefficient. zdLet represent the first differential gain coefficient, where j is an integer greater than or equal to 0 and less than or equal to k. After calculating u... z (k) after which u z (k) Perform digital signal to analog signal conversion, drive the servo system of the grinding spindle through the converted analog signal, control the feed speed of the grinding spindle, and realize the adjustment of the normal force of the grinding spindle.

[0081] In some embodiments, the feedback control algorithm may employ a PID control algorithm, for a given first reference grinding force F of the grinding wheel. x_ref And the predicted grinding force F in the first direction of the current cycle of the grinding wheel. x _pred(k), and the second reference grinding force F of the given grinding wheel. y_ref And the predicted grinding force F in the second direction of the grinding wheel during the current cycle. y _pred(k) calculates the control parameter u x (k) and u y (k) can be calculated using the following formula: u x (k) and u y (k).

[0082] e x (k)= F x_ref - F x _pred(k)

[0083] e y (k)= F y_ref - F y _pred(k)

[0084]

[0085]

[0086] Among them, K xp K represents the second proportional gain coefficient. xi K represents the second integral gain coefficient. xd K represents the second differential gain coefficient. yp K represents the third proportional gain coefficient. yi K represents the third integral gain coefficient. yd Let represent the third differential gain coefficient, where j is an integer greater than or equal to 0 and less than or equal to k. After calculating u... x (k) and u y (k) after which u x (k) and u y(k) Convert digital signals to analog signals, drive the servo system of the grinding spindle through the converted analog signals, control the rotation speed of the grinding spindle, and adjust the grinding force of the grinding wheel in the horizontal direction.

[0087] Based on the above embodiments, further, the grinding force parameter is the grinding force in the normal direction of the grinding wheel, and the speed parameter is the feed speed of the grinding spindle; and / or, the grinding force parameter is the grinding force in the first direction and the grinding force in the second direction of the grinding wheel, and the speed parameter is the rotational speed of the grinding spindle; wherein, the grinding force in the normal direction of the grinding wheel is perpendicular to the plane containing the grinding force in the first direction and the grinding force in the second direction of the grinding wheel, and the grinding force in the first direction and the grinding force in the second direction of the grinding wheel are perpendicular.

[0088] Specifically, the grinding force parameter is the grinding force in the normal direction of the grinding wheel, and the speed parameter is the feed rate of the grinding spindle. A compensation factor is calculated based on the feed rate of the grinding spindle to obtain a feed rate compensation factor. This feed rate compensation factor is used to correct the nonlinear change in the grinding force parameter caused by the feed rate of the grinding spindle. Based on the predicted grinding force in the normal direction of the grinding wheel for the previous two cycles and the sampling period, the rate of change of the grinding force in the normal direction of the grinding wheel for the current cycle is obtained. This rate of change is used to correct the distortion of the grinding force in the normal direction of the grinding wheel caused by the sampling delay. The grinding force in the normal direction of the grinding wheel for the current cycle, the rate of change of the grinding force in the normal direction of the grinding wheel for the current cycle, the delay parameter, and the compensation factor are input into the grinding force parameter prediction model to obtain the predicted grinding force parameter in the normal direction of the grinding wheel for the current cycle, thereby reducing the distortion of the grinding force in the normal direction of the grinding wheel.

[0089] The grinding force parameter refers to the grinding force in the first direction and the grinding force in the second direction of the grinding wheel, and the speed parameter refers to the rotational speed of the grinding spindle. A speed compensation factor is obtained by calculating a compensation factor based on the rotational speed of the grinding spindle. This speed compensation factor is used to correct the nonlinear change in the grinding force parameter caused by the rotational speed of the grinding spindle. Based on the predicted grinding force in the first direction of the grinding wheel in the previous two cycles and the sampling period, the rate of change of the grinding force in the first direction of the grinding wheel in the current cycle is obtained. Similarly, based on the predicted grinding force in the second direction of the grinding wheel in the previous two cycles and the sampling period, the rate of change of the grinding force in the second direction of the grinding wheel in the current cycle is obtained. The rate of change of the grinding force in the first direction of the grinding wheel in the current cycle is used to correct the distortion of the grinding force in the first direction of the grinding wheel caused by the sampling delay in the first direction of the grinding wheel in the current cycle, and the rate of change of the grinding force in the second direction of the grinding wheel in the current cycle is used to correct the distortion of the grinding force in the second direction of the grinding wheel caused by the sampling delay in the second direction of the grinding wheel in the current cycle. The grinding force in the first direction of the grinding wheel in the current cycle, the rate of change of the grinding force in the first direction of the current cycle, the delay parameter, and the speed compensation factor are input into the grinding force parameter prediction model to obtain the predicted grinding force in the first direction of the grinding wheel in the current cycle, thereby reducing the distortion of the grinding force in the first direction of the grinding wheel; the grinding force in the second direction of the grinding wheel in the current cycle, the rate of change of the grinding force in the second direction of the current cycle, the delay parameter, and the speed compensation factor are input into the grinding force parameter prediction model to obtain the predicted grinding force in the second direction of the current cycle, thereby reducing the distortion of the grinding force in the second direction of the grinding wheel.

[0090] Based on the above embodiments, the speed parameter is further defined as the feed speed of the grinding spindle; correspondingly, the calculation of the compensation factor based on the speed parameter to obtain the compensation factor includes:

[0091] The feed rate compensation factor speed_factor(k) is calculated according to the formula speed_factor(k)=K0+K1(v-v0) / v0, where K0 represents the ideal gain at the feed rate of the grinding spindle, K1 represents the feed rate sensitivity coefficient, v represents the feed rate of the grinding spindle, and v0 represents the reference feed rate.

[0092] Specifically, during the grinding process where the grinding wheel and wafer transition from relative rest to relative motion, there exists a transitional zone from static friction to dynamic friction. Within this transitional zone, the feed rate is extremely low, leading to grinding instability. The reference feed rate can be set as the critical speed at which the grinding wheel transitions from static friction to dynamic friction, i.e., the upper limit of the transitional zone. At the reference feed rate, the system is at the ideal frictional state transition point. When the feed rate v of the grinding spindle is less than the reference feed rate v0, the contact surface between the grinding wheel and the wafer is dominated by static friction. Additional force needs to be applied to overcome the static friction threshold. This additional force does not contribute to the actual wafer removal, resulting in the measured grinding force in the normal direction of the grinding wheel being artificially high due to the force required to overcome the static friction threshold. Therefore, it is necessary to reduce the feed rate compensation factor. Based on the time delay compensation of the grinding force in the normal direction of the grinding wheel through the rate of change of the grinding force in the normal direction of the grinding wheel and the delay parameter, it is multiplied by a feed rate compensation factor less than K0 to correct the amplitude distortion of the grinding force in the normal direction of the grinding wheel caused by the feed rate of the grinding spindle.

[0093] When the feed rate v of the grinding spindle is greater than the reference feed rate v0, the contact surface between the grinding wheel and the wafer enters a state of dynamic friction. The frictional resistance decreases as the feed rate of the grinding spindle increases, resulting in a lower measured grinding force in the normal direction of the grinding wheel. It is necessary to increase the feed rate compensation factor. Based on the time delay compensation of the grinding force in the normal direction of the grinding wheel by the rate of change of the grinding force in the normal direction of the grinding wheel and the delay parameter, it is multiplied by a feed rate compensation factor greater than K0 to correct the amplitude distortion of the grinding force in the normal direction of the grinding wheel caused by the feed rate of the grinding spindle.

[0094] This application uses a feed rate compensation factor, speed_factor(k), to correct the nonlinear variation of the grinding force in the normal direction of the grinding wheel caused by the feed rate of the grinding spindle. This can correct the distortion of the grinding force in the normal direction of the grinding wheel caused by nonlinear friction. The feed rate compensation factor, speed_factor(k), can be calculated by substituting the feed rate v of the grinding spindle into the formula speed_factor(k) = K0 + K1(v - v0) / v0. K0 and K1 are constants, and v0 is preset.

[0095] Based on the above embodiments, the speed parameter is further defined as the rotational speed of the grinding spindle; correspondingly, the calculation of the compensation factor based on the speed parameter to obtain the compensation factor includes:

[0096] According to the formula rpm_factor(k)=1+γ(n) ref -n) / n ref The speed compensation factor rpm_factor(k) is calculated, where γ represents the speed sensitivity coefficient, n represents the speed of the grinding spindle, and nref This indicates the rated reference speed.

[0097] Specifically, changes in the rotational speed of the grinding spindle affect the measurement signal of the tangential force of the grinding spindle through two physical effects: centrifugal force and cutting effect, leading to measurement distortion. On the one hand, due to manufacturing processes and other factors, the mass distribution of the grinding wheel cannot be perfectly uniform. When the grinding wheel rotates, the centrifugal forces generated by the abrasive grains cannot completely cancel each other out, thus forming an unbalanced centrifugal force. Increasing the rotational speed leads to dynamic imbalance of the grinding wheel, causing an increase in centrifugal force and resulting in a "falsely high" measurement value. On the other hand, decreasing the rotational speed results in an extremely short contact time (on the microsecond scale) between a single abrasive grain of the grinding wheel and the wafer, leading to a "falsely low" measurement value.

[0098] Rated reference speed n ref The speed is set to the rated optimal speed of the grinding wheel after dynamic balancing, corresponding to the operating point where system vibration is minimized and operation is most stable. When the grinding spindle speed n is greater than the rated reference speed n... ref When the grinding spindle speed increases, the centrifugal force increases, causing the signal amplitude measured by the vibration sensor to be artificially high. This means the measured horizontal cutting force of the grinding wheel is artificially high, necessitating a reduction in the speed compensation factor. This involves compensating for the time delay of the horizontal cutting force by adjusting the rate of change of the horizontal cutting force and the delay parameter, then multiplying by a speed compensation factor less than 1 to correct the distortion in the measured amplitude of the horizontal cutting force caused by the change in the grinding spindle speed. When the grinding spindle speed *n* is less than the rated reference speed *n*... ref When the rotational speed of the grinding spindle decreases, the centrifugal force decreases, and the signal amplitude measured by the vibration sensor is too low. It is necessary to increase the rotational speed compensation factor. Based on the time delay compensation of the horizontal cutting force of the grinding wheel by the rate of change of the horizontal cutting force of the grinding wheel and the delay parameter, the rotational speed compensation factor greater than 1 is multiplied to correct the measurement amplitude distortion of the horizontal cutting force of the grinding wheel caused by the change of the rotational speed of the grinding spindle.

[0099] This application corrects the nonlinear variation of the horizontal cutting force of the grinding wheel caused by the rotational speed of the grinding spindle using a speed compensation factor rpm_factor(k), which can correct the amplitude drift of the tangential force measurement. Substituting the rotational speed n of the grinding spindle into the formula rpm_factor(k) = 1 + γ(n) ref -n) / n ref In this context, the speed compensation factor rpm_factor(k) can be calculated, where γ is a constant and n ref It is preset.

[0100] Based on the above embodiments, further, obtaining the rate of change of the grinding force parameter in the current cycle based on the predicted grinding force parameters of the previous two cycles and the sampling cycle includes:

[0101] The rate of change of the grinding force parameter in the current cycle, dF(k) / dt(k), is calculated using the formula dF(k) / dt(k)=[F_pred(k-1) - F_pred(k-2)] / T, where F_pred(k-1) represents the predicted grinding force parameter of the previous cycle, F_pred(k-2) represents the predicted grinding force parameter of the cycle before the current cycle, and T represents the sampling period.

[0102] Specifically, when the grinding force parameter is the grinding force in the normal direction of the grinding wheel, the formula dF(k) / dt(k)=[F_pred(k-1) - F_pred(k-2)] / T substitutes the grinding force F in the normal direction of the grinding wheel from the previous cycle in the current cycle. z _pred(k-1) and the grinding force F in the normal direction of the grinding wheel in the previous cycle of the current cycle. z _pred(k-2) calculates the rate of change of the grinding force dF in the normal direction of the grinding wheel during the current cycle. z (k) / dt(k), i.e., dF z (k) / dt(k)=[F z _pred(k-1) - F z _pred(k-2)] / T, where the sampling period T is predetermined, F z _pred(k-1) and F z _pred(k-2) is pre-calculated and stored.

[0103] When the grinding force parameter is the grinding force in the first direction of the grinding wheel, the formula dF(k) / dt(k)=[F_pred(k-1) -F_pred(k-2)] / T substitutes the grinding force F in the first direction of the grinding wheel from the previous cycle in the current cycle. x _d(k-1) and the grinding force F of the grinding wheel in the first direction of the previous cycle. x _pred(k-2) calculates the rate of change of the grinding force dF in the first direction of the grinding wheel during the current cycle. x (k) / dt(k), i.e., dF x (k) / dt(k) =[F x _pred(k-1) -F x _pred(k-2)] / T, where the sampling period T is predetermined, F x _pred(k-1) and Fx _pred(k-2) is pre-calculated and stored.

[0104] When the grinding force parameter is the grinding force in the second direction of the grinding wheel, the formula dF(k) / dt(k)=[F_pred(k-1) -F_pred(k-2)] / T substitutes the grinding force F in the second direction of the grinding wheel from the previous cycle in the current cycle. y _pred(k-1) and the grinding force F in the second direction of the grinding wheel in the previous cycle of the current cycle. y _pred(k-2) calculates the rate of change of the grinding force dF in the second direction of the grinding wheel during the current cycle. y (k) / dt(k), i.e., dF y (k) / dt(k) =[F y _pred(k-1) - F y _pred(k-2)] / T, where the sampling period T is predetermined, F y _pred(k-1) and F y _pred(k-2) is pre-calculated and stored.

[0105] Based on the above embodiments, the grinding force parameter prediction model is further defined as: F_pred(k)=[F(k)+dF(k) / dt(k)L]factor(k), where F_pred(k) represents the predicted grinding force parameter for the current cycle, F(k) represents the grinding force parameter for the current cycle, dF(k) / dt(k) represents the rate of change of the grinding force parameter for the current cycle, L represents the delay parameter, and factor(k) represents the compensation factor.

[0106] Specifically, the grinding force parameter prediction model uses the rate of change of the grinding force parameter in the current cycle and a compensation factor to predict the grinding force parameter in the current cycle, in order to compensate for the dynamic delay of the sensor itself.

[0107] When the grinding force parameter is the grinding force in the normal direction of the grinding wheel, the rate of change dF of the grinding force in the normal direction of the grinding wheel in the current cycle is used. z The product of / dt(k) and the delay parameter L is then used in conjunction with the grinding force F in the normal direction of the grinding wheel for the current cycle. z Add the values ​​of (k) together, then multiply the sum by the feed rate compensation factor speed_factor(k) to obtain the predicted grinding force in the normal direction of the grinding wheel for the current cycle. Then, calculate the rate of change dF of the grinding force in the normal direction of the grinding wheel for the current cycle. z / dt(k), delay parameter L, grinding force F in the normal direction of the grinding wheel in the current cycle zSubstituting (k) and the feed rate compensation factor speed_factor(k) into the formula F_pred(k)=[F(k)+dF(k) / dt(k)L]factor(k), the predicted grinding force F in the normal direction of the grinding wheel in the current cycle can be calculated. z _pred(k).

[0108] When the grinding force parameter is the grinding force in the first direction of the grinding wheel, the rate of change dF of the grinding force in the first direction of the grinding wheel in the current cycle is used. x The product of (k) / dt(k) and the delay parameter L, and then the result of this product is combined with the grinding force F of the grinding wheel in the first direction of the current cycle. x Add the values ​​of (k) together, then multiply the sum by the speed compensation factor rpm_factor(k) to obtain the predicted grinding force of the grinding wheel in the first direction for the current cycle. Then, calculate the rate of change of the grinding force dF in the first direction of the grinding wheel for the current cycle. x (k) / dt(k), delay parameter L, grinding force F of the grinding wheel in the first direction of the current cycle. x Substituting (k) and the speed compensation factor rpm_factor(k) into the formula F_pred(k)=[F(k)+dF(k) / dt(k)L]factor(k), the predicted grinding force F of the grinding wheel in the first direction of the current cycle can be calculated. x _pred(k).

[0109] When the grinding force parameter is the grinding force in the second direction of the grinding wheel, the rate of change dF of the grinding force in the second direction of the grinding wheel in the current cycle is used. y The product of (k) / dt(k) and the delay parameter L, and then the result of this product is combined with the grinding force F of the grinding wheel in the second direction of the current cycle. y Add the values ​​of (k) together, then multiply the sum by the speed compensation factor rpm_factor(k) to obtain the predicted grinding force of the grinding wheel in the second direction for the current cycle. Then, calculate the rate of change of the grinding force dF in the second direction of the grinding wheel for the current cycle. y (k) / dt(k), delay parameter L, grinding force F of the grinding wheel in the second direction of the current cycle. y Substituting (k) and the speed compensation factor rpm_factor(k) into the formula F_pred(k)=[F(k)+dF(k) / dt(k)L]factor(k), the predicted grinding force F in the second direction of the grinding wheel in the current cycle can be calculated. y _pred(k).

[0110] Based on the above embodiments, the wafer thinning method provided by the embodiments of the present invention further includes:

[0111] If the predicted grinding force parameter for the current cycle exceeds the preset range, an alarm signal will be issued.

[0112] Specifically, the predicted grinding force parameter for the current cycle should be limited to a reasonable range. It is determined whether the predicted grinding force parameter for the current cycle exceeds a preset range. If it does, an alarm signal is issued, and grinding is paused to avoid damage to the wafer. The preset range is set according to actual conditions, and this embodiment of the invention does not impose any limitations.

[0113] In some embodiments, the predicted grinding force parameter for the current cycle includes the predicted grinding force in the normal direction of the grinding wheel for the current cycle, and the grinding force in the normal direction of the grinding wheel has a reasonable value range F. z_min ~F z_max The predicted grinding force in the normal direction of the grinding wheel during the current cycle should be within the range F. z_min ~F z_max Inside.

[0114] In some embodiments, the predicted grinding force parameter for the current cycle includes the predicted grinding force of the grinding wheel in a first direction for the current cycle, wherein the grinding force in the first direction of the grinding wheel has a reasonable value range F. x_min ~F x_max The predicted grinding force in the first direction of the grinding wheel during the current cycle should be within the range F. x_min ~F x_max Inside.

[0115] In some embodiments, the predicted grinding force parameter for the current cycle includes the predicted grinding force of the grinding wheel in the second direction for the current cycle, wherein the grinding force of the grinding wheel in the second direction has a reasonable value range F. y_min ~F y_max The predicted grinding force in the second direction of the grinding wheel during the current cycle should be within the range F. y_min ~F y_max Inside.

[0116] Figure 4 This is a schematic flowchart of a wafer thinning method provided in another embodiment of the present invention, as shown below. Figure 4 As shown, the wafer thinning method provided in this embodiment of the invention includes:

[0117] S401. Obtain the grinding force in the normal direction of the grinding wheel and the feed rate of the grinding spindle;

[0118] Specifically, the grinding force F in the normal direction of the grinding wheel can be acquired using a grinding force sensor. z The feed speed v of the grinding spindle is collected by a linear encoder.

[0119] S402. Calculate the compensation factor based on the feed rate of the grinding spindle to obtain the feed rate compensation factor;

[0120] Specifically, by substituting the feed rate v of the grinding spindle into the formula speed_factor(k) = K0 + K1(v - v0) / v0, the feed rate compensation factor speed_factor(k) can be calculated. The feed rate compensation factor is used to correct the nonlinear change in the grinding force in the normal direction of the grinding wheel caused by the feed rate of the grinding spindle.

[0121] S403. Based on the predicted grinding force in the normal direction of the grinding wheel in the previous two cycles and the sampling period, obtain the rate of change of the grinding force in the normal direction of the grinding wheel in the current cycle.

[0122] Specifically, the grinding force F in the normal direction of the grinding wheel in the previous cycle of the current cycle. z _pred(k-1) and the grinding force F in the normal direction of the grinding wheel in the previous cycle of the current cycle. z Substituting _pred(k-2) and the sampling period T into the formula dF(k) / dt(k)=[F_pred(k-1) - F_pred(k-2)] / T, the rate of change of the grinding force dF in the normal direction of the grinding wheel in the current period can be calculated. z (k) / dt(k). The rate of change of the grinding force in the normal direction of the grinding wheel in the current cycle is used to correct the distortion of the grinding force in the normal direction of the grinding wheel caused by the sampling delay of the grinding force in the normal direction of the grinding wheel in the current cycle.

[0123] S404. Input the grinding force in the normal direction of the grinding wheel in the current cycle, the rate of change of the grinding force in the normal direction of the grinding wheel in the current cycle, the delay parameter, and the feed rate compensation factor into the grinding force parameter prediction model to obtain the predicted grinding force in the normal direction of the grinding wheel in the current cycle, so as to reduce the distortion of the grinding force in the normal direction of the grinding wheel.

[0124] Specifically, the grinding force F in the normal direction of the grinding wheel in the current cycle z (k) The rate of change of grinding force dF in the normal direction of the grinding wheel during the current cycle. z The parameters (k) / dt(k), delay parameter L, and feed rate compensation factor speed_factor(k) are input into the grinding force parameter prediction model F_pred(k)=[F(k)+dF(k) / dt(k)L]factor(k) to calculate the predicted grinding force F in the normal direction of the grinding wheel for the current cycle. z _pred(k), i.e., F z _pred(k)=[F z (k)+ dF z(k) / dt(k)L]speed_factor(k).

[0125] Figure 5 This is a schematic flowchart of a wafer thinning method provided in another embodiment of the present invention, as shown below. Figure 5 As shown, the wafer thinning method provided in this embodiment of the invention includes:

[0126] S501, Obtain the grinding force of the grinding wheel in the first direction and the grinding force in the second direction, as well as the feed speed of the grinding spindle;

[0127] Specifically, the grinding force of the grinding wheel in the first direction and the grinding force in the second direction can be collected by a grinding force sensor, and the rotational speed n of the grinding spindle can be collected by a rotary encoder.

[0128] S502. Calculate the compensation factor based on the rotational speed of the grinding spindle to obtain the rotational speed compensation factor.

[0129] Specifically, the rotational speed n of the grinding spindle is substituted into the formula rpm_factor(k)=1+γ(n) ref -n) / n ref In this calculation, the speed compensation factor rpm_factor(k) can be obtained. The speed compensation factor rpm_factor(k) is used to correct the nonlinear change in the horizontal cutting force of the grinding wheel caused by the rotational speed of the grinding spindle. The horizontal grinding force of the grinding wheel includes the grinding force in the first direction and the grinding force in the second direction.

[0130] S503. Based on the predicted grinding force of the grinding wheel in the first direction of the previous two cycles and the sampling period, obtain the rate of change of the grinding force in the first direction of the grinding wheel in the current cycle, and based on the predicted grinding force of the grinding wheel in the second direction of the previous two cycles and the sampling period, obtain the rate of change of the grinding force in the second direction of the grinding wheel in the current cycle.

[0131] Specifically, the grinding force F of the grinding wheel in the first direction of the previous cycle is... x _pred(k-1) and the grinding force F of the grinding wheel in the first direction of the previous cycle. x Substituting _pred(k-2) and the sampling period T into the formula dF(k) / dt(k)=[F_pred(k-1) - F_pred(k-2)] / T, the rate of change of the grinding force dF in the first direction of the grinding wheel in the current period can be calculated. x (k) / dt(k). The rate of change of the grinding force in the first direction of the grinding wheel in the current cycle is used to correct the distortion of the grinding force in the first direction of the grinding wheel caused by the sampling delay of the grinding force in the first direction of the grinding wheel in the current cycle.

[0132] The grinding force F in the second direction of the grinding wheel in the previous cycle is increased in the current cycle. y _pred(k-1) and the grinding force F in the second direction of the grinding wheel in the previous cycle of the current cycle. y Substituting _pred(k-2) and the sampling period T into the formula dF(k) / dt(k)=[F_pred(k-1) - F_pred(k-2)] / T, the rate of change of the grinding force dF in the second direction of the grinding wheel in the current period can be calculated. y (k) / dt(k). The rate of change of the grinding force in the second direction of the grinding wheel in the current cycle is used to correct the distortion of the grinding force in the second direction of the grinding wheel caused by the sampling delay of the grinding force in the second direction of the grinding wheel in the current cycle.

[0133] S504. Input the grinding force of the grinding wheel in the first direction of the current cycle, the rate of change of the grinding force of the grinding wheel in the first direction of the current cycle, the delay parameter, and the speed compensation factor into the grinding force parameter prediction model to obtain the predicted grinding force of the grinding wheel in the first direction of the current cycle, so as to reduce the distortion of the grinding force of the grinding wheel in the first direction; input the grinding force of the grinding wheel in the second direction of the current cycle, the rate of change of the grinding force of the grinding wheel in the second direction of the current cycle, the delay parameter, and the speed compensation factor into the grinding force parameter prediction model to obtain the predicted grinding force of the grinding wheel in the second direction of the current cycle, so as to reduce the distortion of the grinding force of the grinding wheel in the second direction.

[0134] Specifically, the grinding force F of the grinding wheel in the first direction of the current cycle x (k) The rate of change of grinding force dF in the first direction of the grinding wheel during the current cycle. x The grinding force parameter prediction model F_pred(k) = [F(k) + dF(k) / dt(k)L]factor(k) is input into the grinding force parameter prediction model F_pred(k) = [F(k) + dF(k) / dt(k)L]factor(k). The predicted grinding force F in the first direction of the grinding wheel in the current cycle can be calculated. x _pred(k), i.e., F x _pred(k) = [F x (k)+ dF x (k) / dt(k)L]rpm_factor(k).

[0135] The grinding force F in the second direction of the grinding wheel in the current cycle y (k) The rate of change of grinding force dF in the second direction of the grinding wheel during the current cycle. yThe grinding force parameter prediction model F_pred(k) = [F(k) + dF(k) / dt(k)L]factor(k) is input into the grinding force parameter prediction model F_pred(k) = [F(k) + dF(k) / dt(k)L]factor(k) to calculate the predicted grinding force F in the second direction of the grinding wheel in the current cycle. y _pred(k), i.e., F y _pred(k) = [F y (k)+ dF y (k) / dt(k)L] rpm_factor(k).

[0136] The wafer thinning equipment and method provided in this invention correct the nonlinear changes in grinding force parameters by feedforward compensation of grinding feed speed and spindle speed, and correct the distortion of grinding force parameters caused by sampling delay by the rate of change of grinding force parameters, thereby achieving composite compensation of grinding force parameters and effectively improving the accuracy of grinding force feedback signal of control layer.

[0137] Other embodiments according to the application are provided below from the perspective of grinding force and grinding heat.

[0138] As a cutting-edge technology in the packaging field, hybrid bonding has been widely used in high-end 3D integrated circuits (i.e., 3D ICs, such as high-bandwidth memory HBM stacked structures) and wafer-to-wafer (W2W) bonding scenarios. This technology places stringent requirements on process precision; the surface roughness of the bonding interface should be less than or equal to 0.5 nm. This indicator dictates that the control precision in the thinning process must reach an extremely high level to achieve high-precision thinning processing.

[0139] Meanwhile, in the TSV region, the significant differences in grinding force between the constituent materials lead to differences in the grinding thermal field: copper (Cu) has high thermal conductivity, while silicon dioxide (SiO2) is a typical high-hardness thermal insulation material. This causes nonlinear changes in grinding force and heat accumulation effects to easily occur in the TSV region during thinning. Under the same grinding force process parameters, the temperature of the Cu material region in the TSV region is significantly higher than that of the silicon substrate region. This local temperature imbalance makes it difficult to meet the system-level heat dissipation requirements of advanced packaging, further highlighting the necessity of heat dissipation through hybrid bonding technology.

[0140] During wafer thinning, grinding debris is difficult to remove during TSV (Thin Slip Form) grinding, easily leading to blockage and adhesion, causing rapid passivation of the grinding wheel. As grinding progresses during wafer thinning, the grinding wheel surface gradually becomes passivated. This passivation manifests as wear, chipping, or dulling of the abrasive cutting edges, reducing its effective cutting capability on the wafer. Due to the decreased effective cutting action, the abrasive grains cannot efficiently remove material from the wafer surface, and grinding debris cannot be smoothly discharged through the pore channels on the grinding wheel surface, accumulating inside and on the surface of the pores, exacerbating the pore blockage problem. The blockage of the grinding wheel pores further worsens the chip removal conditions and heat dissipation environment in the grinding zone. On the one hand, it increases the frictional resistance between the abrasive grains, the wafer, and the grinding debris, leading to a significant increase in grinding force; on the other hand, the heat generated by friction cannot be dissipated in time through the pores, causing continuous heat accumulation in the grinding zone, ultimately leading to increased grinding heat. Increased grinding heat leads to heat accumulation in the TSV region, resulting in thermal damage in the TSV region. Grinding wheel passivation can also deepen the damage layer on the wafer surface, resulting in a significant increase in wafer surface roughness (Ra).

[0141] In existing technologies, thinning processes use a fixed water volume for cooling, making it impossible to precisely control the grinding water flow according to requirements. In 3D IC scenarios, thermal stress protection at the TSV (Transient Vibration Vessel) heterogeneous interface cannot be achieved. During rough grinding, a fixed water volume can easily induce micro-vibration fatigue of the copper pillars in the TSV region due to water flow impact. During fine grinding, a fixed water volume cannot cope with the localized high temperatures in the TSV region. Furthermore, it is impossible to control the depth of the damage layer on ultra-thin wafers. With a fixed water volume, the damage layer thickness caused by wafer thinning can exceed 2.5μm, which is unacceptable for ultra-thin wafers. In addition, a fixed water volume is insufficient to effectively suppress grinding wheel clogging, further exacerbating the depth of the damage layer on the wafer surface. Therefore, the control of thermal stress during heterogeneous material thinning and the precise control of the thinning water volume have become key bottlenecks restricting the further development of 3D IC technology.

[0142] To address the aforementioned issues, the wafer thinning method proposed in this application further includes a process for regulating the amount of grinding water used for thinning. For 3D IC bonding wafer thinning, regulating the amount of grinding water used for thinning can dynamically identify the passivation state of the grinding wheel and / or the shear force of the through-silicon via (TSV) region based on the rate of change of grinding force. By independently controlling two water paths for cooling the wafer and cooling the grinding wheel, the water volume mode can be automatically switched, which can accurately protect against thermal damage in heterogeneous TSV regions in 3D ICs and improve the wafer surface quality, while also enhancing the process adaptability of multiple materials or structures.

[0143] Based on the above embodiments, the wafer thinning apparatus provided in this embodiment of the invention further includes:

[0144] The control equipment is also used to determine the rate of change of the total predicted grinding force of the grinding wheel based on the predicted grinding force in the horizontal direction and the predicted grinding force in the normal direction of the grinding wheel during the wafer thinning process, and to determine the rate of change of the predicted grinding force in the horizontal direction of the grinding wheel based on the predicted grinding force in the horizontal direction of the grinding wheel during the wafer thinning process, as well as to determine the amount of grinding water used for thinning; wherein, the predicted grinding force parameters include the predicted grinding force in the horizontal direction and the predicted grinding force in the normal direction of the grinding wheel.

[0145] Specifically, the control equipment can determine the rate of change of the total predicted grinding force of the grinding wheel based on the predicted grinding force in the horizontal direction and the predicted grinding force in the normal direction during the wafer thinning process. The control equipment can also determine the rate of change of the predicted grinding force in the horizontal direction of the grinding wheel based on the predicted grinding force in the horizontal direction during the wafer thinning process. The control equipment can execute the wafer thinning method provided in this embodiment of the invention and determine the amount of grinding water used for thinning. The grinding water includes two independent streams for cooling the wafer and for cooling the grinding wheel. After determining the amount of grinding water used for thinning, the amounts of grinding water used for cooling the wafer and for cooling the grinding wheel can be adjusted respectively using the flow control valves of the two independent grinding water streams.

[0146] like Figure 6 As shown, grinding heat is generated during the thinning process of wafer 5 by grinding wheel 3, which needs to be dissipated and cooled by grinding water. During the grinding process of wafer 5 by grinding wheel 3, grinding water is continuously injected into the grinding area through water channel 4 for cooling wafer and water channel 6 for cooling grinding wheel, which carries away the heat generated by grinding and washes away the grinding debris.

[0147] The wafer thinning equipment provided in this invention can identify the changing state of the grinding wheel and the thermal damage state of the wafer in real time and dynamically by the rate of change of grinding force. It can adjust the amount of two independent grinding water streams used to cool the wafer and the grinding wheel, thereby reducing thermal damage in the through-silicon via region, reducing surface damage of the thinned wafer, improving the surface quality of the thinned wafer, increasing wafer yield, and reducing the overall amount of grinding water used for thinning, thus reducing equipment operating costs.

[0148] Based on the above embodiments, the wafer thinning method provided by the embodiments of the present invention further includes:

[0149] Figure 7 This is a schematic flowchart of a wafer thinning method provided in another embodiment of the present invention, as shown below. Figure 7 As shown, the wafer thinning method provided in this embodiment of the invention further includes:

[0150] S701. Determine the amount of grinding water used for thinning based on the passivation degree of the grinding wheel and / or the shear force in the through-silicon via (TSV) region to reduce thermal damage in the TSV region and reduce the overall amount of grinding water used for thinning; wherein, the passivation degree is characterized by the rate of change of the total predicted grinding force of the grinding wheel, and the shear force in the TSV region is characterized by the rate of change of the predicted grinding force in the horizontal direction of the grinding wheel; the grinding water includes two independent grinding water streams for cooling the wafer and for cooling the grinding wheel.

[0151] In a specific implementation, before step S701, the method may further include: obtaining the predicted grinding force in the horizontal direction and the predicted grinding force in the normal direction of the grinding wheel, and calculating the total predicted grinding force parameter of the grinding wheel; the predicted grinding force parameter includes the predicted grinding force in the normal direction and the predicted grinding force in the horizontal direction of the grinding wheel. After step S701, the method may further include: S702, providing grinding water to the wafer and the grinding wheel respectively.

[0152] Specifically, this application proposes to characterize the passivation degree of the grinding wheel by the rate of change of the total predicted grinding force. The larger the rate of change of the total predicted grinding force, the more severe the passivation of the grinding wheel, and the more likely it is to cause thermal damage in the TSV region. The shear force in the through-silicon via (TSV) region is characterized by the rate of change of the predicted grinding force in the horizontal direction of the grinding wheel. The larger the rate of change of the predicted grinding force in the horizontal direction, the more likely the TSV region is to experience thermal damage.

[0153] Because the delay in grinding force measurement in existing technologies affects the timing of adjusting the amount of grinding water used for thinning, this application employs modified grinding force parameters, namely predicted grinding force parameters, to calculate the rate of change of the total predicted grinding force of the grinding wheel and the rate of change of the predicted grinding force in the horizontal direction of the grinding wheel. The predicted grinding force parameters include the predicted grinding force in the normal direction of the grinding wheel, the predicted grinding force in the first direction of the grinding wheel, and the predicted grinding force in the second direction of the grinding wheel. The predicted grinding force in the normal direction of the grinding wheel is a correction to the grinding force in the normal direction of the grinding wheel. The predicted grinding force in the first direction of the grinding wheel is a correction to the grinding force in the first direction of the grinding wheel. The predicted grinding force in the second direction of the grinding wheel is a correction to the grinding force in the second direction of the grinding wheel. The modified grinding force parameters are used to obtain the rate of change of the total predicted grinding force and the rate of change of the predicted grinding force in the horizontal direction. This allows for adjustment of the amount of grinding water used for thinning, resulting in more precise timing of the adjustment, improved temperature rise suppression in the TSV region, and ultimately, better wafer surface quality and yield after thinning. The rate of change of the total predicted grinding force can be obtained by differentiating the total predicted grinding force with respect to time. The total grinding force can be calculated by combining the grinding force in the normal direction, the grinding force in the first direction, and the grinding force in the second direction. For example, the total grinding force can be obtained by summing the squares of the grinding forces in the normal direction, the first direction, and the second direction, and then taking the square root. After modifying the grinding force parameters, the total predicted grinding force of the grinding wheel can be obtained. The total predicted grinding force of the grinding wheel can be obtained by summing the squares of the predicted grinding forces in the normal direction, the first direction, and the second direction, and then taking the square root. The rate of change of the total predicted grinding force of the grinding wheel can be obtained by differentiating the total predicted grinding force of the grinding wheel with respect to time, and is expressed as dF in this application. p / dt.

[0154] The rate of change of the predicted grinding force in the horizontal direction of the grinding wheel includes the rate of change of the predicted grinding force in the first direction and the rate of change of the predicted grinding force in the second direction. The rate of change of the predicted grinding force in the first direction can be obtained by differentiating the predicted grinding force in the first direction with respect to time, and is expressed as dF in this application. x _ p / dt; The rate of change of the predicted grinding force in the second direction of the grinding wheel can be obtained by differentiating the predicted grinding force in the second direction of the grinding wheel with respect to time, and is expressed as dF in this application. y _ p / dt. The rate of change of the predicted grinding force in the normal direction of the grinding wheel can be obtained by differentiating the predicted grinding force in the normal direction of the grinding wheel with respect to time, and is expressed as dF in this application. z_p / dt.

[0155] The grinding force in the normal direction of the grinding wheel is the perpendicular indentation force between the grinding wheel and the wafer. The rate of change of the predicted grinding force in the normal direction of the grinding wheel affects the stability of the material removal rate and is directly related to the degree of wheel passivation. The instantaneous fluctuation of the material removal rate (MRR) is directly reflected in the predicted grinding force F in the normal direction of the grinding wheel. z _ p The mutation. Under ideal grinding conditions, stable grinding removes material from the wafer, F z_p Small fluctuations; the rate of change of the predicted grinding force dF in the normal direction of the grinding wheel. z_p / dt is relatively small. When grinding wheel passivation occurs, the wear of the abrasive cutting edges of the grinding wheel exceeds the threshold, the number of effective abrasive cutting edges decreases, the effective cutting action weakens, and the proportion of "cutting-squeezing-slipping" during grinding becomes unbalanced, with the proportion of squeezing or slipping increasing. The enhanced squeezing and slipping effects lead to a continuous accumulation of contact load between the grinding wheel and the wafer, resulting in F z_p Continue to rise and dF z _ p / dt fluctuations intensified.

[0156] The grinding forces in the first and second directions of the grinding wheel are the shear work done between the grinding wheel and the wafer. The rate of change of the predicted grinding force in the horizontal direction of the grinding wheel is, in other words, the rate of change of the predicted grinding force in the first direction, dF. x _ p / dt and the predicted rate of change of grinding force dF in the second direction of the grinding wheel y_p / dt reflects the abrupt change in shear force within the micro-region of the TSV region metal pillar (e.g., copper pillar). In the TSV region of a wafer, the metal (e.g., copper) has high ductility and significantly lower shear strength than the surrounding brittle material, creating a sudden change in mechanical properties between the metal pillar and the silicon substrate. At the instant the grinding wheel cuts into the metal pillar, the sudden drop in the material's yield strength causes a sharp decrease in both the grinding force in the first and second directions of the wheel, leading to a significant drop in dF. x _ p / dt and / or dF y _ p / dt forms a significant negative spike, and the corresponding spike signal reflects F x _ p or F y _ p The maximum rate of change over time; at the instant the grinding wheel cuts through the metal pillar: the material strength increases sharply, and the grinding force in the first direction and the grinding force in the second direction of the grinding wheel rise dramatically, leading to dF x _ p / dt and / or dF y _ p / dt forms a significant positive spike.

[0157] The rate of change of the total predicted grinding force of the grinding wheel, dF p / dt can be used to characterize the overall passivation degree of the grinding wheel. Compared with the grinding force component, this parameter is more robust to disturbances such as sudden changes in the TSV region or vibration.

[0158] In this embodiment of the application, during wafer thinning, the amount of grinding water used for thinning is determined based on the passivation degree of the grinding wheel. Specifically, the amounts of two independent grinding water streams—one for cooling the wafer and the other for cooling the grinding wheel—are adjusted. When the grinding wheel is passivated, the amount of grinding water used for thinning is increased to enhance cooling and reduce thermal damage to the through-silicon via (TSV) region. When the grinding wheel is not passivated, the amount of grinding water used for thinning is decreased to suppress uneven grinding conditions caused by hydraulic vibration. This embodiment of the application also determines the amount of grinding water used for thinning based on the shear force in the TSV region. Specifically, when it is determined that the shear force in the TSV region is causing thermal damage, the amount of grinding water used for thinning is increased to enhance cooling and reduce thermal damage to the TSV region. Because this embodiment of the application can adjust the amount of grinding water used for thinning based on the passivation degree of the grinding wheel and / or the shear force in the TSV region, it can reduce thermal damage to the TSV region while also reducing the overall amount of grinding water used for thinning, thus lowering grinding costs.

[0159] The grinding water used to cool the wafers, also known as the table cooling water, is used to cool the wafers, especially the through-silicon via (TSV) areas. The grinding water used to cool the grinding wheels, also known as the spindle cooling water, cools both the grinding wheels and the spindle, preventing thermal deformation of these components. The table cooling water and the spindle cooling water are managed independently.

[0160] The wafer thinning method provided in this invention adjusts the amount of grinding water used for thinning based on the passivation degree of the grinding wheel and / or the shear force in the through-silicon via (TSV) region. By using two independent grinding water streams to cool the wafer and grinding wheel respectively, it can reduce thermal damage in the TSV region, reduce surface damage to the thinned wafer, improve the surface quality of the thinned wafer, increase the wafer yield, and reduce the overall amount of grinding water used for thinning, thereby reducing equipment operating costs.

[0161] Based on the above embodiments, further, before step S701, the following is also included:

[0162] S700: Obtain the predicted grinding force in the horizontal direction and the predicted grinding force in the normal direction of the grinding wheel, and calculate the total predicted grinding force of the grinding wheel; the total predicted grinding force includes the predicted grinding force in the normal direction and the predicted grinding force in the horizontal direction of the grinding wheel.

[0163] Specifically, the total predicted grinding force includes the predicted grinding force in the normal direction and the predicted grinding force in the horizontal direction of the grinding wheel. The predicted grinding force in the horizontal direction of the grinding wheel includes the predicted grinding force in the first direction and the predicted grinding force in the second direction. The total predicted grinding force of the grinding wheel can be obtained by combining the predicted grinding force in the normal direction, the predicted grinding force in the first direction, and the predicted grinding force in the second direction.

[0164] Based on the above embodiments, further, after step S701, the method includes:

[0165] S702 provides grinding water to the wafer and grinding wheel respectively.

[0166] Specifically, after determining the amount of grinding water used for thinning based on the passivation degree of the grinding wheel and / or the shear force in the through-silicon via region, the amounts of grinding water used to cool the wafer and the grinding wheel can be determined. Then, according to the amount of grinding water used to cool the wafer, grinding water is supplied to the wafer through the water channel for cooling the wafer, and according to the amount of grinding water used to cool the grinding wheel, grinding water is supplied to the grinding wheel through the water channel for cooling the grinding wheel.

[0167] Based on the above embodiments, further determining the amount of grinding water used for thinning according to the passivation degree of the grinding wheel includes:

[0168] If the rate of change of the total predicted grinding force of the grinding wheel is greater than a first threshold, it is determined that the grinding wheel has become passivated, and the usage of two independent grinding water streams for cooling the wafer and cooling the grinding wheel is increased through a first water flow mode to enhance cooling.

[0169] Specifically, the rate of change of the total predicted grinding force of the grinding wheel is compared with a first threshold. If the rate of change of the total predicted grinding force of the grinding wheel is greater than the first threshold, it can be determined that the grinding wheel has become passivated. Then, the amount of grinding water used for thinning is adjusted through a first water flow mode, that is, the usage of two independent grinding water streams for cooling the wafer and cooling the grinding wheel is increased to enhance the cooling of the wafer and the grinding wheel. The first threshold is set based on practical experience, for example, 5 N / s, and this embodiment of the invention does not limit this setting. Based on the above embodiments, further determining the amount of grinding water used for thinning according to the shear force in the silicon through-hole region of the grinding wheel includes:

[0170] If the rate of change of the predicted grinding force in the horizontal direction of the grinding wheel is greater than the second threshold, it is determined that the shear force in the through-silicon via region causes thermal damage to the through-silicon via region, and the usage of two independent grinding water streams for cooling the wafer and cooling the grinding wheel is increased through the first water flow mode to enhance cooling.

[0171] Specifically, the rate of change of the predicted grinding force in the horizontal direction of the grinding wheel is compared with a second threshold. If the rate of change of the predicted grinding force in the horizontal direction of the grinding wheel is greater than the second threshold, it can be determined that the shear force in the through-silicon via (TSV) region causes thermal damage to the TSV region. In this case, the amount of grinding water used for thinning is adjusted through a first water flow mode, that is, the usage of two independent grinding water streams for cooling the wafer and cooling the grinding wheel is increased to enhance the cooling of the grinding wheel and the wafer. The second threshold is set based on practical experience, for example, 3 N / s, but this embodiment of the invention is not limited to this.

[0172] The rate of change of the predicted grinding force in the horizontal direction of the grinding wheel includes the rate of change of the predicted grinding force in the first direction of the grinding wheel and the rate of change of the predicted grinding force in the second direction of the grinding wheel. The rate of change of the predicted grinding force in the horizontal direction of the grinding wheel being greater than the second threshold means that the rate of change of the predicted grinding force in the first direction of the grinding wheel is greater than the second threshold, or the rate of change of the predicted grinding force in the second direction of the grinding wheel is greater than the second threshold.

[0173] During wafer thinning, adjusting the amount of grinding water used for thinning via the first water volume mode increases the amount of grinding water used to cool the wafer, effectively removing grinding debris generated in the grinding zone and preventing its accumulation on the grinding wheel surface and within pores. Effective debris removal creates favorable exposure conditions for the abrasive grains on the grinding wheel: on the one hand, it reduces abnormal wear on the cutting edges caused by debris compression; on the other hand, it makes the dulled abrasive grains on the grinding wheel surface more prone to chipping or detachment under cutting forces, thereby promoting efficient self-sharpening of the grinding wheel and maintaining its continuous and stable cutting performance. The improved self-sharpening of the grinding wheel effectively suppresses the decay of cutting ability, curbing the increase in cutting resistance between the abrasive grains and the wafer during grinding, thus slowing the increase in grinding force. This results in a lower rate of change in the total predicted grinding force of the grinding wheel. Increasing the amount of grinding water used to cool the wafer enhances cooling of the TSV region of the wafer, suppresses the temperature of the TSV region, and reduces the Ra of the wafer surface due to efficient cleaning of the grinding debris.

[0174] During the wafer thinning process, adjusting the amount of grinding water used for thinning through the first water volume mode increases the amount of grinding water used to cool the grinding wheel, which can enhance the cooling of the grinding spindle and the grinding wheel. The cooling of the grinding wheel can assist the cooling of the wafer.

[0175] Furthermore, by triggering the first water flow mode for enhanced cooling when the rate of change of the total predicted grinding force of the grinding wheel is greater than the first threshold or the rate of change of the predicted grinding force in the horizontal direction of the grinding wheel is greater than the second threshold, the cooling response time can be compressed, and the wafer and grinding wheel can be cooled in a timely manner.

[0176] Based on the above embodiments, the first water volume mode further includes:

[0177] The amount of grinding water used for cooling wafers is increased to a first range; and the amount of grinding water used for cooling grinding wheels is increased to a second range; wherein the first range and the second range are determined based on conventional water volume.

[0178] Specifically, the first water volume mode includes increasing the amount of grinding water used to cool the wafer to a first range to enhance the cooling effect on the wafer, and increasing the amount of grinding water used to cool the grinding wheel to a second range to enhance the cooling effect on the grinding wheel. The first and second ranges are determined based on conventional water volumes. Conventional water volumes can be fixed grinding water volumes used in existing thinning processes, or fixed values ​​of grinding water set based on practical experience.

[0179] Understandably, when the amount of grinding water used for thinning is in the first mode, the amount of grinding water used for cooling the wafer is in the first range, and the amount of grinding water used for cooling the grinding wheel is in the second range.

[0180] In some embodiments, the first range is 150–200% of the normal water volume, and the second range is 100–120% of the normal water volume.

[0181] Based on the above embodiments, further, in the first water volume mode, the increase in the amount of grinding water used to cool the grinding wheel is less than the increase in the amount of grinding water used to cool the wafer, so as to prevent the water flow fluctuation of the grinding water from inducing the vibration of the grinding wheel.

[0182] Specifically, when the usage of two independent grinding water streams for cooling the wafer and cooling the grinding wheel is increased through the first water volume mode, the increase in the usage of grinding water for cooling the grinding wheel is less than the increase in the usage of grinding water for cooling the wafer, so as to prevent the water flow fluctuations of the grinding water from inducing grinding wheel vibration.

[0183] Based on the above embodiments, the wafer thinning method provided by the embodiments of the present invention further includes:

[0184] If the rate of change of the total predicted grinding force of the grinding wheel is less than the third threshold and continues for a first preset duration, then exit the first water volume mode and reduce the usage of the two independent grinding water streams used for cooling the wafer and cooling the grinding wheel through the second water volume mode, so as to maintain the basic cooling of the wafer and the grinding wheel and reduce hydraulic vibration and temperature fluctuation.

[0185] Specifically, in the first water flow mode, the amount of grinding water used for thinning is adjusted by comparing the rate of change of the total predicted grinding force of the grinding wheel with a third threshold. If the rate of change of the total predicted grinding force of the grinding wheel is less than the third threshold and remains so for a first preset duration, it indicates that the amount of grinding water used for thinning does not need to be maintained in the first water flow mode. The first water flow mode can be exited, and the usage of the two independent grinding water streams used for cooling the wafer and cooling the grinding wheel can be reduced through the second water flow mode. The amount of grinding water used for thinning in the second water flow mode is a temporary state. The second water flow mode is used to achieve the transition between the first and third water flow modes, which can maintain the basic cooling of the wafer and the grinding wheel and reduce hydraulic vibration and temperature fluctuations, avoiding overcooling or microcracks in the non-TSV region of the wafer.

[0186] The third threshold and the first preset duration are set based on practical experience, and are not limited in this embodiment of the invention. For example, the third threshold is 3N / s, and the first preset duration is 10 seconds.

[0187] Based on the above embodiments, the wafer thinning method provided by the embodiments of the present invention further includes:

[0188] If the rate of change of the predicted grinding force in the horizontal direction is less than the fourth threshold and continues for a second preset duration, the usage of the two independent grinding water streams used for cooling the wafer and cooling the grinding wheel will be adjusted through the third water volume mode to reduce hydraulic vibration and temperature fluctuations.

[0189] Specifically, in the second water flow mode, the amount of grinding water used for thinning is adjusted by comparing the rate of change of the total predicted grinding force of the grinding wheel with a fourth threshold. If the rate of change of the total predicted grinding force of the grinding wheel is less than the fourth threshold and continues for a second preset duration, it indicates that the amount of grinding water used for thinning no longer needs to be maintained in the second water flow mode. The second water flow mode can then be exited, and the usage of the two independent grinding water streams used for cooling the wafer and cooling the grinding wheel can be reduced through the third water flow mode. In this embodiment of the invention, the amount of grinding water used for thinning does not directly change from the first water flow mode to the third water flow mode, but rather transitions through the second water flow mode before entering the third water flow mode. This reduces hydraulic vibration and temperature fluctuations, preventing overcooling or microcracks in the non-TSV region of the wafer.

[0190] The fourth threshold and the second preset duration are set based on practical experience, and this embodiment of the invention does not impose any limitations. For example, the fourth threshold is 2N / s, and the second preset duration is 5 seconds.

[0191] Based on the above embodiments, the second water volume mode further includes:

[0192] Reduce the amount of grinding water used to cool the wafer to a first water volume; and adjust the amount of grinding water used to cool the grinding wheel to a second water volume; wherein the first water volume and the second water volume are determined based on the conventional water volume.

[0193] Specifically, the second water volume mode includes reducing the amount of grinding water used to cool the wafer to a first water volume to maintain basic cooling of the wafer, and adjusting the amount of grinding water used to cool the grinding wheel to a second water volume to maintain basic cooling of the grinding wheel. The first and second water volumes are determined based on conventional water volumes.

[0194] In some embodiments, the first water consumption is 120% of the normal water consumption, and the second water consumption is 110% of the normal water consumption.

[0195] Based on the above embodiments, further determining the amount of grinding water used for thinning according to the passivation degree of the grinding wheel includes:

[0196] If the rate of change of the total predicted grinding force of the grinding wheel is less than the fifth threshold, the usage of the two independent grinding water streams used for cooling the wafer and cooling the grinding wheel is reduced through the fourth water volume mode to suppress hydraulic vibration and maintain the thermal stability of the grinding spindle.

[0197] Specifically, the rate of change of the total predicted grinding force of the grinding wheel is compared with a fifth threshold. If the rate of change of the total predicted grinding force of the grinding wheel is less than the fifth threshold, it indicates that the contact between the grinding wheel and the wafer is unstable and the grinding wheel has not become passivated. In this case, the amount of grinding water used for thinning will be reduced through the fourth water flow mode, that is, the usage of the two independent grinding water flows used for cooling the wafer and cooling the grinding wheel will be reduced. The fifth threshold is set based on practical experience, for example, 2 N / s, but this embodiment of the invention does not limit it.

[0198] During the wafer thinning process, the amount of grinding water used for thinning is adjusted by the fourth water volume mode, which reduces the amount of grinding water used to cool the wafer. This can suppress hydraulic vibration and prevent excessive impact load when the grinding wheel re-contacts the wafer, thus preventing the induction of microcracks in the TSV region.

[0199] During wafer thinning, adjusting the amount of grinding water used for thinning through the fourth water volume mode reduces the amount of grinding water used to cool the grinding wheel, thus maintaining the thermal stability of the grinding spindle.

[0200] Based on the above embodiments, the circular thinning method provided by the embodiments of the present invention further includes:

[0201] If the rate of change of the total predicted grinding force of the grinding wheel is greater than or equal to the fifth threshold, then exit the fourth water volume mode and adjust the usage of the two independent grinding water streams for cooling the wafer and cooling the grinding wheel through the third water volume mode to avoid heat accumulation.

[0202] Specifically, in the fourth water volume mode, the amount of grinding water used for thinning is adjusted by comparing the rate of change of the total predicted grinding force of the grinding wheel with a fifth threshold. If the rate of change of the total predicted grinding force of the grinding wheel is greater than or equal to the fifth threshold, it indicates that the amount of grinding water used for thinning no longer needs to be maintained in the fourth water volume mode. The fourth water volume mode can then be exited, and the usage of the two independent grinding water streams used for cooling the wafer and cooling the grinding wheel can be adjusted through the third water volume mode. After exiting the fourth water volume mode, the amount of grinding water used for thinning directly enters the third water volume mode without transition, thus avoiding heat accumulation.

[0203] Based on the above embodiments, the fourth water volume mode further includes:

[0204] Reduce the amount of grinding water used to cool the wafer to a third range; and reduce the amount of grinding water used to cool the grinding wheel to a fourth range; wherein the third range and the fourth range are determined based on the conventional water volume.

[0205] Specifically, the fourth water volume mode includes reducing the amount of grinding water used to cool the wafer to the third range to suppress hydraulic vibration, and reducing the amount of grinding water used to cool the grinding wheel to the fourth range to maintain spindle thermal stability. The third and fourth ranges are determined based on conventional water volumes.

[0206] Understandably, when the amount of grinding water used for thinning is in the fourth mode, the amount of grinding water used for cooling the wafer is in the third range, and the amount of grinding water used for cooling the grinding wheel is in the fourth range.

[0207] In some embodiments, the third range is 60–70% of the normal water volume, and the fourth range is 80–100% of the normal water volume.

[0208] Based on the above embodiments, further determining the amount of grinding water used for thinning according to the passivation degree of the grinding wheel includes:

[0209] If the rate of change of the total predicted grinding force of the grinding wheel is greater than or equal to the fifth threshold and less than or equal to the sixth threshold, the usage of two independent grinding water streams for cooling the wafer and cooling the grinding wheel is adjusted through the third water volume mode to balance the cooling of the wafer and the thermal stability of the grinding spindle.

[0210] Specifically, the rate of change of the total predicted grinding force of the grinding wheel is compared with the fifth threshold and the sixth threshold respectively. If the rate of change of the total predicted grinding force of the grinding wheel is greater than or equal to the fifth threshold and less than or equal to the sixth threshold, it indicates that the self-sharpening property of the grinding wheel is good and the grinding wheel has not become dull. Then, the usage of the two independent grinding water streams used for cooling the wafer and cooling the grinding wheel can be adjusted through the third water volume mode to achieve a balance between the cooling of the wafer and the stability of the grinding performance.

[0211] When a grinding wheel exhibits good self-sharpening properties, it indicates that during wafer thinning, the abrasive grains on the wheel surface, which gradually become dulled by the cutting action, can promptly fracture, detach, or microscopically break under appropriate cutting forces or thermal effects. This allows new abrasive grains with sharp cutting edges to be continuously exposed on the wheel surface. This dynamic self-renewal capability of the grinding wheel effectively prevents the decline in cutting ability caused by excessive abrasive grain dulling, ensuring the stability of cutting performance during grinding, while reducing adverse phenomena such as sudden increases in grinding force and excessive accumulation of grinding heat.

[0212] Based on the above embodiments, the third water volume mode further includes:

[0213] The amount of grinding water used to cool the wafer is adjusted within a fifth range based on the rate of change of the total predicted grinding force of the grinding wheel; and the amount of grinding water used to cool the grinding wheel is adjusted within a sixth range based on the rate of change of the total predicted grinding force of the grinding wheel; wherein the fifth range and the sixth range are determined based on the conventional water volume.

[0214] Specifically, the third water volume mode includes adjusting the amount of grinding water used to cool the wafer within a fifth range based on the rate of change of the total predicted grinding force of the grinding wheel, and adjusting the amount of grinding water used to cool the grinding wheel within a sixth range based on the rate of change of the total predicted grinding force of the grinding wheel, so that the grinding wheel has good self-sharpening properties. The fifth and sixth ranges are determined based on conventional water volume.

[0215] The method of adjusting the amount of grinding water used to cool the wafer within a fifth range based on the rate of change of the total predicted grinding force of the grinding wheel includes: determining the amount of grinding water used to cool the wafer based on the rate of change of the total predicted grinding force and a first linear adaptive adjustment relationship, wherein the amount of grinding water used to cool the wafer is within a fifth range; the first linear adaptive adjustment relationship is a linear relationship between the rate of change of the total predicted grinding force and the amount of grinding water used to cool the wafer within a fifth range, and is established in advance.

[0216] The method of adjusting the amount of grinding water used to cool the grinding wheel within a sixth range based on the rate of change of the total predicted grinding force of the grinding wheel includes: determining the amount of grinding water used to cool the grinding wheel based on the rate of change of the total predicted grinding force and a second linear adaptive adjustment relationship, wherein the amount of grinding water used to cool the grinding wheel is within a sixth range; the second linear adaptive adjustment relationship is a linear relationship between the rate of change of the total predicted grinding force and the amount of grinding water used to cool the grinding wheel within a sixth range, and is established in advance.

[0217] Understandably, when the amount of grinding water used for thinning is in the third mode, the amount of grinding water used for cooling the wafer is in the fifth range, and the amount of grinding water used for cooling the grinding wheel is in the sixth range.

[0218] In some embodiments, the fifth range is 80–120% of the normal water volume, and the sixth range is 90–110% of the normal water volume.

[0219] In some embodiments, the wafer thinning method provided by the present invention includes:

[0220] The first step is to obtain the grinding force parameters of the grinding wheel. This involves obtaining the grinding force and speed parameters of the grinding wheel for the current cycle during wafer thinning. The grinding force parameters for the current cycle have corresponding delay parameters. The grinding force parameters include the grinding force in the normal direction and the grinding force in the horizontal direction of the grinding wheel. The grinding force in the horizontal direction includes the grinding force in the first direction and the grinding force in the second direction. The speed parameters include the feed rate and rotational speed of the grinding spindle.

[0221] The second step is to correct the grinding force parameters of the grinding wheel. This involves correcting the grinding force in the normal direction of the grinding wheel to obtain the predicted grinding force F in the normal direction. z _ p The grinding force in the first direction and the grinding force in the second direction of the grinding wheel are corrected to obtain the predicted grinding force F in the first direction of the grinding wheel. x _ p Predicted grinding force F in the second direction y _ p The specific process for correcting the grinding force parameters of the grinding wheel is detailed above and will not be repeated here.

[0222] The third step involves combining the predicted grinding forces in the normal direction, the first direction, and the second direction of the grinding wheel to obtain the total predicted grinding force. The derivative of the total predicted grinding force with respect to time is then calculated to obtain the rate of change dF of the total predicted grinding force. p / dt. Calculate the derivative of the predicted grinding force in the first direction of the grinding wheel with respect to time to obtain the rate of change dF of the predicted grinding force in the first direction of the grinding wheel. x _p / dt, calculate the derivative of the predicted grinding force in the second direction of the grinding wheel with respect to time, and obtain the rate of change dF of the predicted grinding force in the second direction of the grinding wheel. y _ p / dt.

[0223] Step 4: Determine the rate of change of the total predicted grinding force. (The last part, "dF", appears to be an error and doesn't translate directly.) p / dt is compared with the first threshold of 5 N / s and the fifth threshold of 2 N / s respectively. If dF p If / dt is greater than 5 N / s, it is determined that the grinding wheel has become passivated, then proceed to step six; if dF p If / dt is less than 2 N / s, then proceed to step eleven; if dF p If / dt is greater than or equal to 2 N / s and less than or equal to 5 N / s, then proceed to step nine.

[0224] Step 5: Determine the rate of change of the predicted grinding force in the horizontal direction of the grinding wheel. (The last part, "dF", appears to be an error and doesn't need a direct translation.) x _ p / dt is compared with the second threshold 3N / s, and dF is... y _ p / dt is compared with the second threshold 3 N / s, if dF x _ p / dt greater than 3 N / s or dF y _ p If / dt is greater than 3 N / s, it is determined that the shear force in the through-silicon via region causes thermal damage to the through-silicon via region, then proceed to step six.

[0225] Step 6: Enter the first water volume mode. In the first water volume mode, increase the usage of the two independent grinding water streams used for cooling the wafer and cooling the grinding wheel. Specifically, increase the usage of grinding water used for cooling the wafer to 150–200% of the normal water volume, and increase the usage of grinding water used for cooling the grinding wheel to 100–120% of the normal water volume.

[0226] Step 7: Determine the rate of change of the total predicted grinding force. Determine dF p If / dt is less than the third threshold of 3 N / s and lasts for the first preset duration of 10 seconds, then proceed to step eight; otherwise, the amount of grinding water used for thinning will remain in the first water volume mode, and return to step six.

[0227] Step 8: Enter the second water volume mode. In the second water volume mode, reduce the usage of the two independent grinding water streams used for cooling the wafer and cooling the grinding wheel. Specifically, reduce the usage of grinding water used for cooling the wafer to 120% of the normal water volume, and adjust the usage of grinding water used for cooling the grinding wheel to 110% of the normal water volume.

[0228] Step 9: Determine the rate of change of the predicted grinding force in the horizontal direction of the grinding wheel. Determine dF x _ p Whether / dt is less than the fourth threshold of 2 N / s and lasts for the second preset duration of 5 seconds, and whether dF is determined. y _ p If / dt is less than the fourth threshold of 2 N / s and lasts for the second preset duration of 5 seconds, then proceed to step ten; otherwise, the amount of grinding water used for thinning will remain in the second water volume mode, and return to step eight.

[0229] Step 10: Enter the third water volume mode. The third water volume mode reduces the usage of the two independent grinding water streams used for cooling the wafer and cooling the grinding wheel. Specifically, the usage of grinding water for cooling the wafer is adjusted within 80–120% of the normal water volume based on the rate of change of the total predicted grinding force of the grinding wheel; and the usage of grinding water for cooling the grinding wheel is adjusted within 90–110% of the normal water volume based on the rate of change of the total predicted grinding force of the grinding wheel.

[0230] Step 11: Enter the fourth water volume mode. The fourth water volume mode reduces the usage of the two independent grinding water streams used for cooling the wafer and cooling the grinding wheel. Specifically, the usage of grinding water for cooling the wafer is reduced to 60–70% of the normal water volume, and the usage of grinding water for cooling the grinding wheel is reduced to 80–100% of the normal water volume.

[0231] Step 12: Determine the rate of change of the total predicted grinding force. Determine dF p If / dt is greater than or equal to the fifth threshold 2N / s, then exit the current fourth water volume mode and proceed to step ten; if not, then the amount of grinding water used for thinning will remain in the fourth water volume mode, and return to step eleven.

[0232] In existing technologies, wafer thinning processes using a fixed water volume are prone to wheel passivation. After passivation, the frictional heat between the wheel and the wafer increases dramatically. The TSV (Through Silicon Via) region of the wafer accumulates heat due to the high thermal conductivity of the metal (e.g., Cu), causing the TSV region temperature to spike. The wafer thinning method of this application determines wheel passivation by measuring the rate of change of the total predicted grinding force. Once passivation is confirmed, the method increases the usage of two independent grinding water streams—one for cooling the wafer and the other for cooling the wheel—using a first water volume mode to enhance cooling, stabilize the TSV region temperature, and reduce thermal damage. Furthermore, the method uses the rate of change of the predicted grinding force in the horizontal direction of the wheel to determine the shear force in the through-silicon via (TSV) region. If the shear force in the TSV region causes thermal damage, the method further increases the usage of the two independent grinding water streams to enhance cooling and reduce thermal damage in the TSV region.

[0233] The wafer thinning method with dynamic water volume control provided in this invention (i.e., the solution of this application) has the following advantages over the wafer thinning process with fixed water volume in the prior art (i.e., the conventional solution):

[0234] (1) Thermal protection of the TSV region: The solution in this application dynamically controls the amount of grinding water used for thinning, solving the problem in the prior art where the metal pillars in the wafer TSV region are deformed and damaged due to localized instantaneous high temperature caused by CTE (Coefficient of Thermal Expansion) mismatch between the metal pillars and Si. A wafer has multiple TSV regions, each with copper pillars. In the prior art, a wafer thinning process with a fixed water volume (i.e., the traditional solution) is used. The surface of the copper pillars in the TSV region after wafer thinning is imaged using an electron microscope, as shown in the image. Figure 8 As shown, Figure 8 The lighter-colored area represents the machined surface of the copper pillars. Due to excessively high temperatures during grinding, the copper pillar surface underwent significant deformation and damage. Using the wafer thinning method described in this application, the machined surface of the copper pillars in the TSV region after wafer thinning was imaged using an electron microscope, as shown below. Figure 9 As shown, Figure 9 The light-colored area represents the machined surface of the copper pillar. Since no thermal damage occurred in the TSV zone, the machined surface of the copper pillar is circular and has not been deformed or damaged.

[0235] (2) Optimization of wafer surface roughness: Using the scheme of this application, in the passivated state of the grinding wheel, the amount of grinding water used for thinning is increased to strongly cool and reduce the temperature, suppress thermal damage to the wafer surface, and enhance lubrication to reduce friction, thereby reducing the surface roughness Ra of the wafer. Figure 10 As shown, wafers 1, 2, and 3 were thinned using the conventional method and the wafer thinning method of this application, respectively. Ra measurements were performed on each wafer at its center, the middle (0.5 times the wafer radius from the center), and the edge (10 mm from the outer edge). The results are shown below. Figure 10 As shown, Figure 10 The unit of surface roughness is nm. For the thinned wafers 1, 2, and 3, the Ra at the same location is superior to the conventional solution at all locations except the middle location of wafer 3.

[0236] (3) Reducing Cu ion contamination: In this application, when wheel passivation occurs, the temperature in the grinding zone is lowered by increasing the amount of grinding water used for thinning, thus reducing the copper oxidation reaction rate in the TSV zone and effectively inhibiting the generation of Cu metal ions, thereby reducing Cu metal ion contamination. For example... Figure 11As shown, 10 wafers were thinned using both the conventional method and the method described in this application. The Cu metal ion concentration was measured after thinning, with the unit being atoms / cm². 2 Except for wafers 3 and 10, the Cu metal ion concentration of the wafers thinned using the method described in this application is significantly lower than that of the wafers thinned using the conventional method.

[0237] Based on this, this application corrects the grinding force parameters used in the dynamic control of grinding water volume by establishing a grinding force parameter prediction model, thereby improving the accuracy of the grinding force parameters and making the timing of grinding water volume adjustment more precise. This further improves the adaptability of dynamic control of grinding water volume to the wafer thinning process, enhances the effectiveness of thermal protection in the TSV area, is more conducive to wafer surface roughness optimization and reduces Cu ion contamination, thereby improving the yield of wafer thinning processing.

[0238] Those skilled in the art will understand that embodiments of the present invention can be provided as methods, systems, or computer program products. Therefore, the present invention can take the form of a completely hardware embodiment, a completely software embodiment, or an embodiment combining software and hardware aspects. Furthermore, the present invention can take the form of a computer program product embodied on one or more computer-usable storage media (including, but not limited to, disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code.

[0239] This invention is described with reference to flowchart illustrations and / or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of the invention. It will be understood that each block of the flowchart illustrations and / or block diagrams, and combinations of blocks in the flowchart illustrations and / or block diagrams, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, special-purpose computer, embedded processor, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, generate instructions for implementing the flowchart illustrations and / or block diagrams. Figure 1 One or more processes and / or boxes Figure 1 A device that provides the functions specified in one or more boxes.

[0240] These computer program instructions may also be stored in a computer-readable storage medium that can direct a computer or other programmable data processing device to function in a particular manner, such that the instructions stored in the computer-readable storage medium produce an article of manufacture including instruction means, which are implemented in a process Figure 1 One or more processes and / or boxes Figure 1 The function specified in one or more boxes.

[0241] These computer program instructions may also be loaded onto a computer or other programmable data processing equipment to cause a series of operational steps to be performed on the computer or other programmable equipment to produce a computer-implemented process, thereby providing instructions that execute on the computer or other programmable equipment for implementing the process. Figure 1 One or more processes and / or boxes Figure 1 The steps of the function specified in one or more boxes.

[0242] In the description of this specification, the references to terms such as "an embodiment," "a specific embodiment," "some embodiments," "for example," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0243] The specific embodiments described above further illustrate the purpose, technical solution, and beneficial effects of the present invention. It should be understood that the above descriptions are merely specific embodiments of the present invention and are not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A wafer thinning method, characterized in that, include: The grinding force and speed parameters of the grinding wheel in the current cycle are obtained during the wafer thinning process; wherein the grinding force parameter in the current cycle has a corresponding delay parameter; The compensation factor is calculated based on the speed parameters to obtain the compensation factor; wherein, the compensation factor is used to correct the nonlinear changes in the grinding force parameters caused by the speed parameters; Based on the predicted grinding force parameters of the previous two cycles and the sampling period, the rate of change of the grinding force parameters in the current cycle is obtained; the rate of change of the grinding force parameters in the current cycle is used to correct the distortion of the grinding force parameters caused by the sampling delay of the grinding force parameters in the current cycle. The grinding force parameters of the current cycle, the rate of change of the grinding force parameters of the current cycle, the delay parameter, and the compensation factor are input into the grinding force parameter prediction model to obtain the predicted grinding force parameters of the current cycle in order to reduce the distortion of the grinding force parameters. The grinding force parameter prediction model is: F_pred(k)=[F(k)+dF(k) / dt(k)L]factor(k), where F_pred(k) represents the predicted grinding force parameter for the current cycle, F(k) represents the grinding force parameter for the current cycle, dF(k) / dt(k) represents the rate of change of the grinding force parameter for the current cycle, L represents the delay parameter, and factor(k) represents the compensation factor.

2. The wafer thinning method according to claim 1, characterized in that, Also includes: Based on the predicted grinding force parameters and reference grinding force parameters for the current cycle, the control parameters for the current cycle are obtained; Based on the control parameters of the current cycle, the grinding action of the grinding spindle of the wafer thinning equipment is controlled to reduce the deviation between the real-time grinding force parameters and the reference grinding force parameters of the current cycle.

3. The wafer thinning method according to claim 2, characterized in that, The process of obtaining control parameters for the current cycle based on the predicted grinding force parameters and reference grinding force parameters for the current cycle includes: The control parameters for the current cycle are determined using the predicted grinding force parameters, the reference grinding force parameters, and the feedback control algorithm.

4. The wafer thinning method according to claim 1, characterized in that, The grinding force parameter includes the grinding force in the normal direction of the grinding wheel, and the speed parameter includes the feed speed of the grinding spindle; and / or, the grinding force parameter includes the grinding force in a first direction and the grinding force in a second direction of the grinding wheel, and the speed parameter includes the rotational speed of the grinding spindle; wherein the grinding force in the normal direction of the grinding wheel is perpendicular to the plane containing the grinding force in the first direction and the grinding force in the second direction of the grinding wheel, and the grinding force in the first direction and the grinding force in the second direction of the grinding wheel are perpendicular.

5. The wafer thinning method according to claim 1, characterized in that, The speed parameter is the feed speed of the grinding spindle; correspondingly, the calculation of the compensation factor based on the speed parameter to obtain the compensation factor includes: The feed rate compensation factor speed_factor(k) is calculated according to the formula speed_factor(k)=K0+K1(v-v0) / v0, where K0 represents the ideal gain at the feed rate of the grinding spindle, K1 represents the feed rate sensitivity coefficient, v represents the feed rate of the grinding spindle, and v0 represents the reference feed rate.

6. The wafer thinning method according to claim 1, characterized in that, The speed parameter is the rotational speed of the grinding spindle; correspondingly, the calculation of the compensation factor based on the speed parameter to obtain the compensation factor includes: According to the formula rpm_factor(k) = 1 + γ(n) ref -n) / n ref The speed compensation factor rpm_factor(k) is calculated, where γ represents the speed sensitivity coefficient, n represents the speed of the grinding spindle, and n ref This indicates the rated reference speed.

7. The wafer thinning method according to claim 1, characterized in that, The method of obtaining the rate of change of the grinding force parameter in the current cycle based on the predicted grinding force parameters of the previous two cycles and the sampling cycle includes: The rate of change of the grinding force parameter in the current cycle, dF(k) / dt(k), is calculated according to the formula dF(k) / dt(k)=[F_pred(k-1) - F_pred(k-2)] / T, where F_pred(k-1) represents the predicted grinding force parameter of the previous cycle, F_pred(k-2) represents the predicted grinding force parameter of the cycle before the current cycle, and T represents the sampling period.

8. The wafer thinning method according to any one of claims 1 to 7, characterized in that, Also includes: If the predicted grinding force parameter for the current cycle exceeds the preset range, an alarm signal will be issued.

9. A wafer thinning apparatus for performing the wafer thinning method according to any one of claims 1-8, characterized in that, include: A worktable is provided with multiple suction cup turntables. The worktable is configured to rotate around its vertical central axis to drive the multiple suction cup turntables to rotate and move as a whole, thereby allowing the suction cup turntables to switch between different workstations. The suction cup turntables are used to hold the wafer and drive the wafer to rotate. A grinding apparatus for grinding the wafer to reduce its thickness; A control device is used to determine the predicted grinding force parameters and control parameters for the current cycle based on the grinding force parameters and speed parameters of the current cycle, and to control the worktable and / or grinding device to thin the wafer.

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