A thinning device and method

Abstract

The present application relates to a thinning device and method. The thinning device includes: a polishing platen for carrying a wafer, the polishing platen being rotatable about an axis; a grinding wheel disposed above the polishing platen, the grinding wheel being used for vertically feeding to act on the wafer to grind the wafer; and a magnetorheological fluid layer located below the polishing platen and connected to the polishing platen; establishing a damage function model of wafer damage; based on the collected vibration acceleration signals and the damage function model, determining the grinding wheel rotation speed, the grinding fluid flow rate, the grinding fluid supply flow rate, the grinding fluid injection angle, the grinding wheel feeding pressure, the polishing platen rotation speed, the magnetorheological fluid regulation pressure, and the magnetorheological fluid support stiffness, and applying them to the next wafer processing. By adjusting the parameters, the wafer damage layer is reduced and the wafer quality is improved.

Description

Technical Field

[0001] This application relates to the field of semiconductor wafer W processing, and in particular, to a thinning device and method. Background Art

[0002] In the semiconductor manufacturing process, wafer W thinning is a crucial step, which directly affects the smooth progress of subsequent processes such as packaging and interconnection, as well as the performance of the final product.

[0003] In the prior art, during the thinning process, wafer W is thinned by grinding with a grinding wheel 200. However, the grinding wheel 200 acting on wafer W will cause inevitable vibrations, and the vibrations will cause deviations in the positions between wafer W and the grinding wheel 200. It is very difficult to offset the influence of vibrations on wafer W by simply controlling and adjusting the grinding wheel 200 or the polishing pad 100 alone, resulting in a relatively thick damaged layer on wafer W and poor thinning quality of wafer W.

[0004] Therefore, the technical problem of the prior art is that the quality of wafer W is poor. Summary of the Invention

[0005] This application provides a thinning device and method to reduce the damaged layer of the wafer and improve the wafer quality by adjusting parameters.

[0006] On the one hand, a thinning method provided by this application adopts the following technical solution:

[0007] A thinning method applicable to a thinning device, the thinning device comprising:

[0008] A polishing pad for carrying the wafer, the polishing pad being rotatable about an axis;

[0009] A grinding wheel disposed above the polishing pad, the grinding wheel being used for vertically feeding and acting on the wafer to grind the wafer; and

[0010] A magneto - fluid layer located below the polishing pad and connected to the polishing pad;

[0011] The thinning method includes:

[0012] Establishing a damage function model of wafer damage regarding vibration acceleration signal , eddy current influence factor , grinding wheel feed pressure and magneto - fluid influence factor ;

[0013] The eddy current influence factor includes grinding wheel speed , grinding fluid flow rate , grinding fluid supply flow rate and the grinding fluid injection angle ;

[0014] The magnetic fluid influence factor includes the polishing pad rotation speed , the magnetic fluid regulating pressure , and the magnetic fluid support stiffness ;

[0015] Based on the collected vibration acceleration signals and the damage function model, determine the grinding wheel rotation speed , the grinding fluid flow rate , the grinding fluid supply flow rate and the grinding fluid injection angle , the grinding wheel feed pressure , the polishing pad rotation speed , the magnetic fluid regulating pressure , and the magnetic fluid support stiffness , and apply them to the next wafer processing.

[0016] Preferably, the "grinding wheel rotation speed , the grinding fluid flow rate , the grinding fluid supply flow rate and the grinding fluid injection angle , the grinding wheel feed pressure , the polishing pad rotation speed , the magnetic fluid regulating pressure , and the magnetic fluid support stiffness " includes:

[0017] Collect vibration acceleration signals ;

[0018] Adjust the grinding wheel rotation speed , the grinding fluid flow rate , the grinding fluid supply flow rate and the grinding fluid injection angle , the grinding wheel feed pressure , the polishing pad rotation speed , the magnetic fluid regulating pressure , and the magnetic fluid support stiffness ;

[0019] Minimize the damage function model and iteratively converge to the threshold;

[0020] Determine the grinding wheel rotation speed , the grinding fluid flow rate , the grinding fluid supply flow rate and the grinding fluid injection angle , the grinding wheel feed pressure , the polishing pad rotation speed 、Magnetic fluid regulates pressure 、and magnetic fluid support stiffness 。

[0021] Preferably, the damage function model is as follows:

[0022]

[0023] Wherein, is the control coefficient of the eddy current influence factor ;

[0024] is the control coefficient of the grinding wheel feed pressure ;

[0025] is the control coefficient of the magnetic fluid influence factor 。

[0026] Preferably, it further includes:

[0027] Establish an eddy current function model of the grinding wheel speed , the flow rate of the grinding fluid , the supply flow rate of the grinding fluid and the injection angle of the grinding fluid with respect to the eddy current influence factor ;

[0028] Based on the collected grinding wheel speed , the flow rate of the grinding fluid , the supply flow rate of the grinding fluid , the injection angle of the grinding fluid and the eddy current function model, determine the eddy current influence factor 。

[0029] Preferably, the eddy current function model is as follows:

[0030]

[0031] Wherein, is the density of the grinding fluid;

[0032] is the viscosity of the grinding fluid; is the reference viscosity;

[0033] is the radius of the grinding wheel;

[0034] is the included angle between the injection direction of the grinding fluid and the normal of the wafer.

[0035] Preferably, it further includes:

[0036] Establish the rotational speed of the polishing pad 、Magnetorheological fluid regulation pressure 、Magnetorheological fluid support stiffness Regarding the magnetorheological fluid influence factor Magnetorheological fluid function model;

[0037] Based on the rotational speed of the polishing pad 、Magnetorheological fluid regulation pressure 、Magnetorheological fluid support stiffness And the magnetorheological fluid function model to determine the magnetorheological fluid influence factor 。

[0038] Preferably, the magnetorheological fluid function model is:

[0039]

[0040] Wherein, Is the magnetorheological fluid layer support stiffness;

[0041] Is the radius of the polishing pad;

[0042] Is the magnetorheological fluid density.

[0043] On the other hand, a thinning device provided by the present application adopts the following technical solution:

[0044] A thinning device includes:

[0045] A polishing pad for carrying a wafer, and the polishing pad can rotate around an axis;

[0046] A grinding wheel disposed above the polishing pad for vertically feeding and acting on the wafer to grind the wafer; and

[0047] A magnetorheological fluid layer located below the polishing pad and connected to the polishing pad;

[0048] Further includes:

[0049] A function establishment module for establishing a damage function model regarding vibration acceleration signal 、Eddy current influence factor 、Grinding wheel feed pressure And magnetorheological fluid influence factor Regarding wafer damage;

[0050] The eddy current influence factor Includes the grinding wheel rotational speed 、Grinding fluid flow rate 、Grinding fluid supply flow rate And grinding fluid injection angle ;

[0051] The magnetic fluid influence factor includes the grinding disk rotation speed , the magnetic fluid regulating pressure , and the magnetic fluid support stiffness ;

[0052] A parameter confirmation module, which is used to determine the grinding wheel rotation speed , the grinding fluid flow rate , the grinding fluid supply flow rate , and the grinding fluid injection angle , as well as the grinding wheel feed pressure , the grinding disk rotation speed , the magnetic fluid regulating pressure , and the magnetic fluid support stiffness based on the collected vibration acceleration signal .

[0053] Preferably, the function establishment module further includes:

[0054] A first function establishment module, which is used to establish an eddy current function model of the grinding wheel rotation speed , the grinding fluid flow rate , the grinding fluid supply flow rate , and the grinding fluid injection angle with respect to the eddy current influence factor ;

[0055] A second function establishment module, which is used to establish a magnetic fluid function model of the grinding disk rotation speed , the magnetic fluid regulating pressure , and the magnetic fluid support stiffness with respect to the magnetic fluid influence factor .

[0056] Preferably, the parameter confirmation module further includes:

[0057] A first parameter confirmation module, which is used to determine the eddy current influence factor , the grinding fluid flow rate , the grinding fluid supply flow rate , the grinding fluid injection angle based on the collected grinding wheel rotation speed , and the eddy current function model to confirm the grinding wheel rotation speed , the grinding fluid flow rate , the grinding fluid supply flow rate , the grinding fluid injection angle ;

[0058] A second parameter confirmation module, which is used to confirm the grinding wheel feed pressure ; and

[0059] The third parameter confirmation module is used to determine the magnetorheological fluid influence factor based on the polishing pad rotation speed , the magnetorheological fluid regulation pressure , the magnetorheological fluid support stiffness and the magnetorheological fluid function model, so as to confirm the magnetorheological fluid influence factor , in order to confirm the polishing pad rotation speed , the magnetorheological fluid regulation pressure , the magnetorheological fluid support stiffness .

[0060] In summary, the present application includes at least one of the following beneficial technical effects:

[0061] By introducing the eddy current influence factor , the grinding wheel feed pressure and the magnetorheological fluid influence factor into the damage function , combined with the calibration coefficient of the orthogonal experiment and the gradient descent optimization, the process parameters can be dynamically adjusted, significantly reducing the subsurface damage of the wafer and improving the quality of the thinned wafer. Description of the Drawings

[0062] Figure 1 is the first schematic diagram of the thinning device described in the present application;

[0063] Figure 2 is the schematic flow chart of the thinning method described in the present application;

[0064] Figure 3 is the method for determining the eddy current influence factor in the thinning method described in the present application;

[0065] Figure 4 is the method for determining the magnetorheological fluid influence factor in the thinning method described in the present application;

[0066] Figure 5 is the second schematic diagram of the thinning device described in the present application.

[0067] Description of the Reference Numerals:

[0068] 100, polishing pad; 200, grinding wheel; 300, magnetorheological fluid layer; 400, function establishment module; 410, first function establishment module; 420, second function establishment module; 500, parameter confirmation module; 510, first parameter confirmation module; 520, second parameter confirmation module; 530, third parameter confirmation module; W, wafer. Detailed Embodiment

[0069] The serial numbers assigned to the components in this document itself, such as "first", "second", etc., are only used to distinguish the described objects and do not have any sequential or technical meaning. And the "connection" and "coupling" mentioned in this application, unless otherwise specified, both include direct and indirect connection (coupling). In the description of this application, it should be understood that the orientation or positional relationship indicated by the terms "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", etc. is based on the orientation or positional relationship shown in the drawings, and is only for the convenience of describing this application and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be construed as a limitation to this application.

[0070] In this application, unless otherwise clearly specified and limited, the first feature being "on" or "under" the second feature may be that the first and second features are in direct contact, or the first and second features are in indirect contact through an intermediate medium. Moreover, the first feature being "above", "over" and "on top of" the second feature may be that the first feature is directly above or obliquely above the second feature, or merely indicates that the first feature has a higher horizontal height than the second feature. The first feature being "under", "beneath" and "underneath" the second feature may be that the first feature is directly below or obliquely below the second feature, or merely indicates that the first feature has a lower horizontal height than the second feature.

[0071] The embodiments of this application provide a thinning device and method, which reduce the damaged layer of the wafer W by adjusting parameters and improve the quality of the wafer W.

[0072] To better understand the above technical solutions, the above technical solutions will be described in detail below in conjunction with the accompanying drawings of the specification and specific implementation manners. It should be understood that the specific embodiments described herein are only used to explain this application and are not used to limit this application.

[0073] In the wafer W thinning process, the grinding of the grinding wheel 200 is a key step to achieve the ultra-thinning of the wafer W. However, due to factors such as bearing clearance, dynamic balance error or motor electromagnetic pulsation of the main shaft of the grinding wheel 200, vibration inevitably occurs during operation, resulting in a dynamic error between the grinding wheel 200 and the wafer W. It is often necessary to adjust the relative position between the grinding wheel 200 and the wafer W to make up for it.

[0074] To compensate for vibration errors, the device needs to adjust the relative position of the grinding wheel 200 and the wafer W in real time. However, during the dynamic adjustment process, the fluctuation of the distance between the grinding wheel 200 and the wafer W will significantly affect the flow state of the grinding fluid. In the scenario where the wafer W rotates, the grinding fluid is prone to form eddy currents, and its intensity and distribution are directly regulated by the distance between the grinding wheel 200 and the wafer W. When the distance decreases, the hydrodynamic pressure in the grinding area increases to form a stagnation zone, resulting in a decrease in the local flow velocity and an increase in temperature, weakening the cooling and chip removal efficiency; while when the distance increases, although the flow velocity increases, the increase in the eddy current intensity will cause uneven stress on the surface of the wafer W, forming a coupled disturbance of vibration and flow field. Further, when adjusting the position of the grinding wheel 200, the rotational speed of the grinding wheel must be adjusted. However, the disturbance effect of the rotational speed on the grinding fluid is closely related and will also have a greater impact on the eddy current situation of the grinding fluid.

[0075] The closed-loop effect of "vibration-flow field-quality" is amplified step by step like the butterfly effect: the initial vibration changes the flow pattern of the grinding fluid, causing distortion of the local temperature field and stress field, and ultimately resulting in large surface defects or thickness deviations of the wafer W.

[0076] This application proposes a thinning method, as Figure 1 shown, applicable to a thinning device. The thinning device includes a polishing pad 100, a grinding wheel 200, and a magnetorheological fluid layer 300. The polishing pad 100 is used to carry the wafer W, and the polishing pad 100 can rotate around an axis; the grinding wheel 200 is arranged above the polishing pad 100, and the grinding wheel 200 is used for vertical feeding to act on the wafer W to grind the wafer W; the magnetorheological fluid layer 300 is located below the polishing pad 100 and connected to the polishing pad 100. It can be understood that the wafer W is arranged on the polishing pad 100, and the grinding wheel 200 above acts on the wafer W. The grinding wheel 200 grinds the wafer W to perform the thinning operation. During the thinning process, the grinding wheel 200 can axially feed the wafer W; the magnetorheological fluid layer 300 is arranged below the polishing pad 100, and the magnetorheological fluid layer 300 has a magnetorheological fluid structure, and the state of the magnetorheological fluid layer 300 can be adjusted by controlling the magnetic field, so that the force exerted by the magnetorheological fluid layer 300 on the polishing pad 100 can be changed, that is, fine and precise position adjustment can be achieved between the polishing pad 100 and the grinding wheel 200.

[0077] Further, the thinning device further includes a nozzle for supplying grinding fluid to the polishing pad 100 or the wafer W, and the angle between the jet direction of the grinding fluid and the normal direction of the wafer W is , which is defined as the grinding fluid jet angle; an angle encoder can be set on the nozzle to detect ; the flow velocity of the grinding fluid can be measured on the nozzle , the supply flow rate of the grinding fluid .

[0078] A grinding force measurement sensor is arranged on the main shaft of the grinding wheel 200 for detecting the feed pressure of the grinding wheel ; A magnetoelectric sensor, a Hall effect sensor, or the like for detecting the rotational speed of the grinding wheel is provided on the main shaft of the grinding wheel 200 ; A piezoelectric sensor is provided on the main shaft of the grinding wheel 200 for collecting vibration acceleration signals .

[0079] A pressure sensor is provided between the magnetorheological fluid layer 300 and the polishing pad 100 for detecting the magnetorheological fluid regulating pressure of the magnetorheological fluid layer 300 on the polishing pad 100 ; A rotary encoder, a magnetoelectric sensor, a Hall effect sensor, or the like for detecting the rotational speed of the polishing pad 100 is provided on the rotating shaft of the polishing pad 100 .

[0080] As Figure 2 shown, the thinning method includes:

[0081] S1.1: A damage function model of the wafer W with respect to vibration acceleration signals , eddy current influence factors , grinding wheel feed pressure and magnetorheological fluid influence factors ;

[0082] Among them, the eddy current influence factors include the rotational speed of the grinding wheel , the flow rate of the grinding fluid , the supply flow rate of the grinding fluid and the injection angle of the grinding fluid ; The magnetorheological fluid influence factors include the rotational speed of the polishing pad , the magnetorheological fluid regulating pressure , and the magnetorheological fluid support stiffness ;

[0083] S1.2: Based on the collected vibration acceleration signals and the damage function model, determine the rotational speed of the grinding wheel , the flow rate of the grinding fluid , the supply flow rate of the grinding fluid and the injection angle of the grinding fluid , the grinding wheel feed pressure , the rotational speed of the polishing pad , the magnetorheological fluid regulating pressure , and the magnetorheological fluid support stiffness ;

[0084] S1.3: And apply it to the processing of the next wafer W.

[0085] Specifically, first establish a damage function model of the wafer W, and the damage function model includes the rotational speed of the grinding wheel , the flow rate of the grinding fluid , grinding fluid supply flow rate and grinding fluid injection angle , grinding wheel feed pressure , lapping plate rotation speed , magnetorheological fluid regulation pressure , and magnetorheological fluid support stiffness ;

[0086] The vibration acceleration signal of the spindle of the grinding wheel 200 during the machining process is collected in real time through a sensor ;

[0087] The gradient descent algorithm is used to minimize and iterate the damage function, and dynamically adjust the grinding wheel rotation speed , grinding fluid flow velocity , grinding fluid supply flow rate and grinding fluid injection angle , grinding wheel feed pressure , lapping plate rotation speed , magnetorheological fluid regulation pressure , and magnetorheological fluid support stiffness ;

[0088] When the damage function converges to the threshold value, the currently set grinding wheel rotation speed , grinding fluid flow velocity , grinding fluid supply flow rate and grinding fluid injection angle , grinding wheel feed pressure , lapping plate rotation speed , magnetorheological fluid regulation pressure , and magnetorheological fluid support stiffness ; And apply the currently set parameters to the processing of the next wafer W.

[0089] The damage during the thinning process of the wafer W mainly comes from the non-linear coupling effect of mechanical vibration energy and process parameters. The design of the damage function is to quantify the instantaneous damage accumulation and reflect the total damage amount during the entire processing cycle in the form of integration. The establishment basis includes the coupling of vibration energy and process parameters. The vibration energy is the square of the vibration acceleration signal reflecting the instantaneous mechanical impact energy, which is positively correlated with the crack propagation rate; The coupling of process parameters refers to the eddy current influence factor , grinding wheel feed pressure , magnetorheological fluid influence factor , respectively characterizing the contributions of fluid disturbance, mechanical load and magnetorheological effect.

[0090] Specifically, the damage function model adopts the form of time-domain integration as:

[0091]

[0092] Among them, is the eddy current influence factor control coefficient;

[0093] is the control coefficient of the grinding wheel feed pressure ;

[0094] is the control coefficient of the magneto - fluid influence factor ;

[0095] This application captures the cumulative damage effect during the entire processing time , rather than the instantaneous value; the vibration acceleration signal is multiplied by the parameter coupling term to characterize the non - linear relationship between the vibration energy modulated by the process parameters; through the weighting coefficient quantify the eddy current influence factor , the grinding wheel feed pressure , and the contribution of the magneto - fluid influence factor .

[0096] Among them, is the vibration acceleration signal, which can be measured by installing a piezoelectric accelerometer (model PCB 356A15) on the spindle flange of the grinding wheel 200;

[0097] is the eddy current influence factor, and a mathematical model for quantifying the damage of the grinding fluid flow to the wafer W is established. The formula is: ;

[0098] is the grinding wheel feed pressure, which can be measured by integrating a pressure sensor (Honeywell 26PC) into the hydraulic circuit of the feed mechanism of the grinding wheel 200;

[0099] is the magneto - fluid influence factor, combined with the lapping plate rotation speed , the magneto - fluid regulation pressure , and the magneto - fluid support stiffness , the formula is: .

[0100] Furthermore, the control coefficient of the eddy current influence factor , the control coefficient of the grinding wheel feed pressure , and the control coefficient of the magneto - fluid influence factor can be obtained through calibration.

[0101] Specifically, a five-factor and four-level orthogonal experiment was designed to cover the parameter range:

[0102] ,

[0103] ,

[0104] ,

[0105] ,

[0106] ;

[0107]

[0108] The number of experimental groups: Using the orthogonal array, a total of 32 groups of experiments were conducted to cover the combined effects of all parameters.

[0109] 12-inch single-crystal silicon wafers were used, and each group of experiments was repeated 3 times to eliminate random errors.

[0110] A laser confocal microscope (Keyence VK-X1000) was used to measure the depth of subsurface damage , and the average value of 5 points in the radial direction of the wafer W (center, R / 4, R / 2, 3R / 4, edge) was taken;

[0111] Experimental data:

[0112]

[0113] Establish and , as well as quantitative relationships, and extract the control coefficients of the eddy current influence factor , the control coefficient of the grinding wheel feed pressure , and the control coefficient of the magneto-fluid influence factor .

[0114] Establish a linear regression model:

[0115]

[0116] Among them, is the random error term;

[0117] Matrix form:

[0118]

[0119] Among them,​​ is a 32×1 damage thickness vector;

[0120] is a 32×3 design matrix (columns corresponding to 、 and );

[0121] is a 3×1 coefficient vector ;

[0122] Least squares solution:

[0123]

[0124] Input the experimental data matrix and the observation vector ; Calculate and ; Invert the matrix ; Solve to get:

[0125] , , ,( ).

[0126] Characterize the eddy current influence factor For every 1 unit increase, the damage thickness increases by 0.15μm; Reflect the influence of the grinding fluid eddy current on the damage of the wafer W;

[0127] Characterize the grinding wheel feed pressure For every 0.1MPa increase, the damage thickness increases by 0.08μm; Reflect the influence of mechanical stress (from the grinding wheel 200) on the damage of the wafer W;

[0128] Characterize the magnetorheological fluid influence factor For every 1 unit increase, the damage thickness increases by 0.12μm; Reflect the influence of the magnetorheological fluid on the damage of the wafer W.

[0129] Furthermore, as Figure 3 shown, the thinning method proposed in this application further includes:

[0130] S2.1: Establish an eddy current function model of the grinding wheel speed , the grinding fluid flow rate , the grinding fluid supply flow rate and the grinding fluid injection angle with respect to the eddy current influence factor ;

[0131] S2.2: Based on the collected grinding wheel speed 、Flow rate of grinding fluid 、Supply flow rate of grinding fluid 、Jet angle of grinding fluid and a vortex function model to determine the vortex influence factor 。

[0132] The vortex function model is as follows:

[0133]

[0134] Among them, is the density of the grinding fluid;

[0135] is the viscosity of the grinding fluid; is the reference viscosity;

[0136] is the radius of the grinding wheel 200;

[0137] The included angle between the jet direction of the grinding fluid and the normal direction of the wafer W.

[0138] In this embodiment, a mathematical model for quantifying the damage of the grinding fluid flow to the wafer W is established, correlating controllable process parameters (rotation speed, flow rate, jet angle, etc.) with the surface damage mechanism of the wafer W. During the thinning process, the rotation of the grinding wheel 200 drives the centrifugal diffusion of the grinding fluid to form a dynamic flow field; the shear action and impact momentum transfer between the grinding fluid and the grinding wheel 200 / wafer W; the viscosity of the grinding fluid affects the flow resistance and energy dissipation; correlating the above relevant process parameters, the damage of the wafer W is obtained.

[0139] The vortex function model is as follows:

[0140]

[0141] Density-corrected centrifugal-jet term Quantify the combined effect of the centrifugal flow field and the jet impact in:

[0142] Centrifugal flow velocity: Rotation speed of the grinding wheel The centrifugal acceleration generated , driving the grinding fluid to diffuse outward, with a flow velocity ;

[0143] Jet momentum: Flow rate of the grinding fluid and the supply flow rate of the grinding fluid The product of characterizes the fluid momentum; is the effective vertical component of the jet direction and the normal of the wafer W;

[0144] Density correction: The density of the grinding fluid determines the inertial force, centrifugal impact force ;

[0145] Normalization: Divide by the square of the radius of the grinding wheel 200 , eliminating the size effect.

[0146] Shear momentum term which reflects the combined damage mechanism of shear force and fluid momentum:

[0147] Shear rate: The shear rate at the interface between the grinding wheel 200 and the grinding fluid , where is the liquid film thickness;

[0148] Momentum coupling: Through experiments, the shear action and momentum transfer show a non-linear relationship, comprehensively characterizing the synergistic effect of the grinding wheel speed and fluid velocity.

[0149] Viscosity resistance term which quantifies the influence of viscosity on flow resistance and energy loss:

[0150] Viscous dissipation: The viscosity of the grinding fluid increasing leads to an increase in flow resistance and dissipated power ;

[0151] Experimental fitting: In actual processes, the viscosity resistance is related to (simplification of the boundary layer effect);

[0152] Non-dimensionalization: eliminating the dimension, is the reference viscosity (such as the viscosity of water).

[0153]

[0154] Use a high-speed camera (Phantom V2512) to photograph the flow of the grinding fluid, and combine with PIV (Particle Image Velocimetry) technology to extract the vorticity field; it should be noted that in this application, to accurately measure the eddy current influence factor, the grinding wheel 200 is made of sapphire as the grinding wheel 200, allowing light to penetrate and observe the flow, so that the high-speed camera can accurately photograph the flow of the grinding fluid; or adjust the position and shooting angle of the high-speed camera so that the high-speed camera shoots laterally or obliquely.

[0155] Adopt the orthogonal experiment method to control the grinding wheel speed , the flow rate of the grinding fluid , the supply flow rate of the grinding fluid , the injection angle of the grinding fluid and the viscosity of the grinding fluid , and measure value (through PIV flow field analysis or pressure sensor), and the experimental matrix covers the parameter range:

[0156] ,

[0157] ,

[0158] After multivariate non - linear regression, substitute the experimental data into the model:

[0159]

[0160] Solve using the least - squares method , , , and obtain:

[0161] , , , .

[0162] Furthermore, as shown in Figure 4 , the thinning method proposed in this application further includes:

[0163] S3.1: Establish a magnetorheological fluid function model for the rotational speed of the polishing pad , the regulating pressure of the magnetorheological fluid , and the supporting stiffness of the magnetorheological fluid with respect to the magnetorheological fluid influence factor ;

[0164] S3.2: Determine the magnetorheological fluid influence factor based on the rotational speed of the polishing pad , the regulating pressure of the magnetorheological fluid , the supporting stiffness of the magnetorheological fluid and the magnetorheological fluid function model.

[0165] The magnetorheological fluid function model is:

[0166]

[0167] where is the supporting stiffness of the magnetorheological fluid layer 300;

[0168] is the radius of the polishing pad 100;

[0169] is the density of the magnetorheological fluid.

[0170] The magnetorheological fluid function needs to quantify the influence of the magnetorheological effect on the dynamic characteristics of the polishing pad 100. The key parameters include the supporting stiffness of the magnetorheological fluid , the regulating pressure of the magnetorheological fluid and the rotational speed of the polishing pad , the magnetorheological fluid function model includes a magnetorheological fluid pressure term and a centrifugal inertia term:

[0171] The magnetorheological fluid pressure term refers to the relationship between the support pressure of the magnetorheological fluid on the polishing pad 100 and the density. The magnetorheological fluid adjusts the pressure and the magnetorheological fluid density is inversely proportional, reflecting the effective support under unit density;

[0172] The centrifugal inertia term refers to the centrifugal force generated by the rotation of the polishing pad 100, which is proportional to the square of the rotational speed and the square of the radius, and affects the dynamic distribution and stability of the magnetorheological fluid.

[0173] The support pressure of the magnetorheological fluid under the action of a magnetic field can be expressed as:

[0174]

[0175] where is the magnetorheological fluid regulating pressure, is the magnetorheological fluid density.

[0176] When the polishing pad 100 rotates, the inertial pressure generated by the centrifugal force is:

[0177]

[0178] After simplification, the geometric and kinematic parameters are retained: .

[0179] The magnetorheological fluid influence factor is the sum of the magnetorheological fluid pressure term and the centrifugal inertia term, multiplied by the magnetorheological fluid support stiffness :

[0180]

[0181] is to amplify the comprehensive mechanical effect of the magnetorheological fluid layer 300;

[0182] reflects the static support ability of magnetic field regulation;

[0183] quantifies the contribution of the dynamic centrifugal inertia force.

[0184] The magnetorheological fluid regulating pressure of the magnetorheological fluid layer 300 can be dynamically adjusted by the externally applied magnetic field strength. Specifically, the calibration of the magnetorheological fluid density and the magnetorheological fluid support stiffness is used to determine the magnetorheological fluid density and the magnetorheological fluid support stiffness :

[0185] Specifically, fix the rotational speed of the polishing pad , adjust the pressure of the magnetic fluid , measure the displacement of the magnetic fluid layer 300 (laser displacement sensor); fix the pressure of the magnetic fluid , adjust the rotation speed of the grinding wheel , measure the displacement increment caused by the centrifugal force.

[0186] Experimental parameter range:

[0187] , ,

[0188] According to the static experimental data ( ), fit the density of the magnetic fluid and the support stiffness of the magnetic fluid :

[0189]

[0190] Obtained by linear regression:

[0191] , ( )

[0192] Verify the centrifugal term in the dynamic experiment:

[0193]

[0194] Incorporate the eddy current influence factor , the grinding wheel feed pressure and the magnetic fluid influence factor into the damage function. The damage function is the time-domain integral of the coupling of the vibration energy and the process parameters, defined as:

[0195]

[0196] Among them, is the vibration acceleration signal;

[0197] is the eddy current influence factor;

[0198] is the grinding wheel feed pressure;

[0199] is the magnetic fluid influence factor;

[0200] is the control coefficient of the eddy current influence factor ;

[0201] is the grinding wheel feed pressure Control coefficient;

[0202] is the magneto - fluid influence factor Control coefficient.

[0203] Eddy - current influence factor : The eddy current formed by the rotation of the grinding wheel 200 and the injection of the grinding fluid will cause local flow - field disorder, trigger temperature gradient and stress concentration, and exacerbate the subsurface damage of the wafer W;

[0204] Grinding - wheel feed pressure : Increasing the grinding - wheel feed pressure directly increases the mechanical stress on the surface of the wafer W, which may lead to the expansion of micro - cracks;

[0205] Magneto - fluid influence factor : The magneto - fluid layer 300 indirectly affects the processing stability by adjusting the support stiffness and pressure to suppress or amplify the vibration of the grinding disk 100.

[0206] Furthermore, the eddy - current related parameters are the grinding - wheel rotation speed 、the flow rate of the grinding fluid 、the supply flow rate of the grinding fluid and the injection angle of the grinding fluid ;

[0207] The magneto - fluid related parameters are the rotation speed of the grinding disk 、the magneto - fluid regulation pressure 、and the magneto - fluid support stiffness ;

[0208] Sensor data: Vibration acceleration signal 、grinding - wheel feed pressure .

[0209] Eddy - current influence factor is:

[0210]

[0211] Magneto - fluid influence factor is:

[0212]

[0213] Use discretized integration (such as the gradient rule) to calculate the damage function:

[0214]

[0215] N is the number of time - sampling points; △t is the sampling interval, for example, 1ms.

[0216] Use orthogonal array to cover , , , , parameter combinations; using 12-inch single-crystalline silicon wafers, with each group of experiments repeated 3 times; measurement index: subsurface damage depth (laser confocal microscope).

[0217] Establish a linear regression model:

[0218]

[0219] where is the random error term;

[0220] Obtain the coefficients through the least squares method:

[0221] , , , ([[]] ).

[0222] Furthermore, minimize the damage function:

[0223]

[0224] Initialize the process parameters;

[0225] Calculate under the current parameters;

[0226] Calculate the gradient ;

[0227] Update the parameters along the negative gradient direction:

[0228] ( is the learning rate, for example )

[0229] Iterate until converges to the threshold (for example ).

[0230] By introducing the eddy current influence factor , the grinding wheel feed pressure and the magnetohydrodynamic influence factor into the damage function , combining orthogonal experiment calibration coefficients and gradient descent optimization, the process parameters can be dynamically regulated, significantly reducing the subsurface damage of wafer W and improving the quality of the thinned wafer W; realizing the coupled analysis of "vibration-fluid field-magnetohydrodynamics" multi-physical fields, providing a theoretical basis and real-time control strategy for the ultra-precision thinning process.

[0231] The present application also provides a thinning device, as Figure 1 shown, including a grinding disk 100, a grinding wheel 200, and a magneto-fluid layer 300; the grinding disk 100 is used to carry a wafer W, and the grinding disk 100 can rotate around an axis; the grinding wheel 200 is arranged above the grinding disk 100, and the grinding wheel 200 is used for vertical feeding to act on the wafer W to grind the wafer W; the magneto-fluid layer 300 is located below the grinding disk 100 and is connected to the grinding disk 100;

[0232] As Figure 5 shown, it further includes: a function establishment module 400, which is used to establish a damage function model of vibration acceleration signal , eddy current influence factor , grinding wheel feeding pressure and magneto-fluid influence factor with respect to the damage of the wafer W; the eddy current influence factor includes grinding wheel rotation speed , grinding fluid flow rate , grinding fluid supply flow rate and grinding fluid injection angle ; the magneto-fluid influence factor includes grinding disk rotation speed , magneto-fluid regulation pressure and magneto-fluid support stiffness ;

[0233] A parameter confirmation module 500, which is used to determine the grinding wheel rotation speed , grinding fluid flow rate , grinding fluid supply flow rate , grinding fluid injection angle , grinding wheel feeding pressure , grinding disk rotation speed , magneto-fluid regulation pressure , magneto-fluid support stiffness and magneto-fluid support stiffness based on the collected vibration acceleration signal

[0234] The function establishment module 400 further includes:

[0235] A first function establishment module 410, which is used to establish an eddy current function model of grinding wheel rotation speed , grinding fluid flow rate , grinding fluid supply flow rate and grinding fluid injection angle with respect to the eddy current influence factor ;

[0236] A second function establishment module 420, which is used to establish a grinding disk rotation speed , magneto-fluid regulation pressure , Magnetic fluid support stiffness Regarding the magnetic fluid influence factor of the magnetic fluid function model.

[0237] The parameter confirmation module 500 further includes:

[0238] The first parameter confirmation module 510, which is used to determine the eddy current influence factor based on the collected grinding wheel rotation speed , grinding fluid flow rate , grinding fluid supply flow rate , grinding fluid injection angle and the eddy current function model to confirm the eddy current influence factor , so as to confirm the grinding wheel rotation speed , grinding fluid flow rate , grinding fluid supply flow rate , grinding fluid injection angle ;

[0239] The second parameter confirmation module 520, which is used to confirm the grinding wheel feed pressure ; and

[0240] The third parameter confirmation module 530, which is used to determine the magnetic fluid influence factor based on the polishing disc rotation speed , magnetic fluid regulation pressure , magnetic fluid support stiffness and the magnetic fluid function model to confirm the magnetic fluid influence factor , so as to confirm the polishing disc rotation speed , magnetic fluid regulation pressure , magnetic fluid support stiffness .

[0241] Although the preferred embodiments of the present application have been described, those skilled in the art can make additional changes and modifications to these embodiments once they learn the basic creative concepts. Therefore, the appended claims are intended to be construed as including the preferred embodiments and all changes and modifications falling within the scope of the present application.

[0242] Obviously, those skilled in the art can make various changes and modifications to the present application without departing from the spirit and scope of the present application. Thus, if these modifications and variations of the present application fall within the scope of the claims of the present application and their equivalent technologies, the present application is also intended to include these modifications and variations.

Claims

1. A thinning method, characterized in that, Applicable to a thinning device, the thinning device comprising: A polishing platen (100) for carrying a wafer (W), the polishing platen (100) being rotatable about an axis; A grinding wheel (200) disposed above the polishing platen (100), the grinding wheel (200) being used for vertical feeding to act on the wafer (W) to grind the wafer (W); and A magnetorheological fluid layer (300) located below the polishing platen (100) and connected to the polishing platen (100); The thinning method comprises: Establish a vibration acceleration signal , eddy current influence factor , grinding wheel feed pressure and magneto - fluid influence factor A damage function model for wafer (W) damage; among them, the vibration acceleration signal is the vibration acceleration signal of the grinding wheel spindle; The eddy current influence factor includes the grinding wheel speed , the flow rate of the grinding fluid , the supply flow rate of the grinding fluid and the injection angle of the grinding fluid ; is the included angle between the injection direction of the grinding fluid and the normal of the wafer (W); The magnetic fluid influence factor includes the rotational speed of the polishing pad , the regulating pressure of the magnetic fluid , and the supporting stiffness of the magnetic fluid ; Based on the collected vibration acceleration signals and the damage function model, determine the grinding wheel speed , the flow rate of the grinding fluid , the supply flow rate of the grinding fluid and the injection angle of the grinding fluid , the feed pressure of the grinding wheel , the rotational speed of the lapping plate , the magnetic fluid regulation pressure , and the magnetic fluid support stiffness , and apply them to the processing of the next wafer (W); The damage function model is: ； Among them, is the eddy current influence factor control coefficient; is the control coefficient of the grinding wheel feed pressure ; is the influencing factor of the magnetofluid is the control coefficient 2. The thinning method according to claim 1, wherein The "determining the grinding wheel speed and the damage function model, and determining the grinding fluid flow rate , the grinding fluid supply flow rate , and the grinding fluid injection angle , the grinding wheel feed pressure , the lapping plate speed , the magnetorheological fluid regulation pressure , and the magnetorheological fluid support stiffness " includes:​ Adjust the grinding wheel speed , the flow rate of the grinding fluid , the supply flow rate of the grinding fluid and the injection angle of the grinding fluid , the feed pressure of the grinding wheel , the rotation speed of the grinding disc , the regulating pressure of the magnetic fluid , and the supporting stiffness of the magnetic fluid ; Minimizing the damage function model and iteratively converging to a threshold value; Determine the grinding wheel speed , the flow rate of the grinding fluid , the supply flow rate of the grinding fluid and the injection angle of the grinding fluid , the feed pressure of the grinding wheel , the rotation speed of the polishing disc , the regulation pressure of the magnetic fluid , and the support stiffness of the magnetic fluid .

3. A thinning method according to claim 1 or 2, characterized in that, Further comprising: Establish the grinding wheel rotation speed , the flow rate of the grinding fluid , the supply flow rate of the grinding fluid and the injection angle of the grinding fluid Regarding the eddy current influence factor of the eddy current function model; Based on the collected grinding wheel speed , grinding fluid flow rate , grinding fluid supply flow rate , grinding fluid injection angle and the eddy current function model to determine the eddy current influence factor .

4. A thinning method according to claim 3, characterized in that, The eddy current function model is: ； Among them, is the density of the grinding fluid; is the viscosity of the grinding fluid; is the reference viscosity; is the radius of the grinding wheel (200).

5. A thinning method according to claim 1 or 2, characterized in that Further comprising: Establish the rotational speed of the polishing pad 、Adjust the pressure of the magnetic fluid 、Support stiffness of the magnetic fluid Regarding the influencing factor of the magnetic fluid Magnetic fluid function model; Based on the rotational speed of the polishing pad , the pressure regulated by the magnetic fluid , the supporting stiffness of the magnetic fluid and the magnetic fluid function model to determine the magnetic fluid influence factor .

6. A thinning method according to claim 5, characterized in that, The magnetorheological fluid function model is: ； Among them, is the support stiffness of the magnetohydrodynamic layer (300); is the radius of the polishing pad (100); is the density of the magnetic fluid.

7. A thinning device, characterized in that, Comprising: A polishing platen (100) for carrying a wafer (W), the polishing platen (100) being rotatable about an axis; A grinding wheel (200) disposed above the polishing platen (100), the grinding wheel (200) being used for vertical feeding to act on the wafer (W) to grind the wafer (W); and A magnetorheological fluid layer (300) located below the polishing platen (100) and connected to the polishing platen (100); Further comprising: A function establishment module (400) for establishing a vibration acceleration signal , an eddy current influence factor , a grinding wheel feed pressure and a magnetohydrodynamic influence factor for a damage function model regarding damage to a wafer (W); wherein, the vibration acceleration signal is a vibration acceleration signal of a grinding wheel spindle The eddy current influence factor includes the grinding wheel rotational speed , the grinding fluid flow velocity , the grinding fluid supply flow rate and the grinding fluid injection angle ; The magnetic fluid influence factor includes the rotation speed of the polishing pad , the regulated pressure of the magnetic fluid , and the support stiffness of the magnetic fluid ; A parameter confirmation module (500) for determining the grinding wheel speed based on the collected vibration acceleration signal and the damage function model , the flow rate of the grinding fluid , the supply flow rate of the grinding fluid , and the injection angle of the grinding fluid , the feed pressure of the grinding wheel , the rotational speed of the grinding disc , the regulating pressure of the magnetic fluid , and the supporting stiffness of the magnetic fluid ; The damage function model is: ； Among them, is the eddy current influence factor control coefficient; is the control coefficient of the grinding wheel feed pressure ; is the influence factor of the magnetic fluid and the control coefficient.

8. A thinning device according to claim 7, wherein The function establishment module (400) further comprises: The first function establishing module (410) is used to establish an eddy current function model regarding the eddy current influence factor for the grinding wheel rotation speed , the grinding fluid flow rate , the grinding fluid supply flow rate and the grinding fluid injection angle ; ​ A second function establishment module (420) for establishing the rotational speed of the polishing pad , the regulating pressure of the magnetic fluid , the supporting stiffness of the magnetic fluid with respect to the magnetic fluid influence factor magnetic fluid function model.

9. A thinning device according to claim 8, characterized in that, The parameter confirmation module (500) further comprises: The first parameter confirmation module (510) is used to confirm the grinding wheel speed based on the collected , Grinding fluid flow rate , Grinding fluid supply flow , Grinding fluid spray angle And the eddy current function model determines the eddy current influence factor , to confirm the grinding wheel speed , Grinding fluid flow rate , Grinding fluid supply flow , Grinding fluid spray angle ; A second parameter confirmation module (520) for confirming the grinding wheel feed pressure ; and A third parameter confirmation module (530) for determining a magnetic fluid influence factor based on the polishing pad rotation speed , the magnetic fluid regulation pressure , the magnetic fluid support stiffness and a magnetic fluid function model, so as to confirm the polishing pad rotation speed , the magnetic fluid regulation pressure , the magnetic fluid support stiffness . ​

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