CN115945981A - A kind of substrate grinding method - Google Patents

Abstract

The invention discloses a substrate grinding method, which includes: detecting the grinding force received by the grinding substrate in real time; calculating the change of the inclination angle of the grinding table caused by the grinding force; Determine the adjustment scheme of the inclination angle of the grinding table to compensate for the inclination angle change caused by the grinding force.

Description

A substrate grinding method

Technical Field

The invention belongs to the technical field of substrate grinding, and in particular relates to a substrate grinding method.

Background Art

In the back-end process stage of integrated circuit/semiconductor (IC) manufacturing, in order to reduce the package mounting height, reduce the chip package volume, improve the chip's thermal diffusion efficiency, electrical performance, mechanical properties, and reduce the chip processing volume, the substrate needs to be ground before subsequent packaging. The chip thickness after grinding can even reach less than 5% of the initial thickness.

Substrate grinding technology is mainly used for back grinding of substrates. The so-called back refers to the side of the substrate without devices, generally silicon, silicon oxide, silicon nitride, silicon carbide, sapphire and other substrates. When grinding the substrate, the grinding wheel and the grinding table need to be completely parallel to grind the substrate flat. This requires adjusting the inclination of the grinding table to meet the process requirements of substrate flatness and surface shape.

In the prior art, the inclination of the grinding table is usually adjusted by a three-point support method, that is, one fixed support point and two adjustable support points. The two adjustable support points are raised and lowered by screw threads to achieve the inclination adjustment of the grinding table.

The existing grinding table tilt angle adjustment scheme has the problems of small adjustment range and low adjustment accuracy. It cannot provide real-time feedback on the impact of grinding force on the grinding table tilt angle adjustment, and cannot compensate for the grinding force as an influencing factor, which affects the processing quality of substrate grinding to a certain extent.

Summary of the invention

An embodiment of the present invention provides a substrate grinding method, aiming to solve at least one of the technical problems existing in the prior art.

A first aspect of an embodiment of the present invention provides a substrate grinding method, comprising:

S1, real-time detection of the grinding force on the grinding substrate;

S2, calculate the change in the tilt angle of the grinding table caused by the grinding force;

S3, determining a tilt angle adjustment scheme of the grinding table according to the processed surface shape and the target surface shape of the substrate to compensate for the tilt angle change caused by the grinding force.

Further, in step S1, the grinding force F is:

Wherein, _Fx is the component of the grinding force along the x-direction; _Fy is the component of the grinding force along the y-direction; _Fxi is the grinding force along the x-axis detected by the i-th sensor; _Fyi is the grinding force along the y-axis detected by the i-th sensor; i=1, 2; the x-axis is a straight line perpendicular to the grinding mark and passing through one end point thereof, and the y-axis is a straight line passing through the end point of the grinding mark.

Furthermore, in step S2, the inclination angle of the grinding table caused by the grinding force changes:

Among them, △α _F is the angular change of the axis of the grinding table around the x-axis caused by the grinding force, △β _F is the angular change of the axis of the grinding table around the y-axis caused by the grinding force; _vs is the rotation speed of the grinding wheel; _vw is the rotation speed of the substrate; A and B are adjustment coefficients.

Furthermore, in step S3, the inclination angle of the grinding table changes:

Among them, △α is the angular change of the axis of the grinding table around the x-axis; △β is the angular change of the axis of the grinding table around the y-axis; _Tr is the thickness value corresponding to the processed substrate; _Tt is the thickness value corresponding to the substrate with the target surface shape.

In some embodiments, the adjustment point of the grinding workbench is configured with a detection module, and the detection module includes a piezoelectric sensor to measure the grinding force applied to the substrate during the grinding process.

In some embodiments, the adjustment point of the grinding workbench is also configured with a micro-adjustment module, which includes a screw, a servo motor and a nut. The output shaft of the servo motor is connected to the screw, and the nut is threadedly connected to the screw. The rotating screw drives the nut thereon to move to adjust the inclination of the grinding workbench.

In some embodiments, the adjustment point of the grinding table is further configured with a precision adjustment module, and the precision adjustment module includes a piezoelectric actuator, which determines the adjustment voltage corresponding to the precision adjustment module according to the inclination angle adjustment scheme of the grinding table.

Furthermore, in step S3, the grinding table is first adjusted using the micro-adjustment module, and then the grinding table is adjusted using the precision adjustment module.

A second aspect of an embodiment of the present invention provides a control device, which includes a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor implements the steps of the substrate grinding method described above when executing the computer program.

A third aspect of an embodiment of the present invention provides a computer-readable storage medium, wherein the computer-readable storage medium stores a computer program, and when the computer program is executed by a processor, the steps of the substrate grinding method described above are implemented.

The beneficial effects of the present invention include:

a. Through the detection module in the posture adjustment mechanism, the grinding force on the substrate during the grinding process is measured in real time, and the influence of the grinding force on the inclination of the grinding table is calculated;

b. The micro-adjustment module and the precision adjustment module are configured in the posture adjustment mechanism to achieve um-level and nm-level adjustments respectively, so as to compensate for the inclination error caused by the grinding force and improve the flatness of the substrate grinding; c. The detection module in the posture adjustment mechanism can measure the grinding force on the substrate in real time, and based on the measured value of the grinding force, adaptively adjust the grinding parameters such as the grinding wheel feed speed and feed amount, which is beneficial to improve the processing quality of substrate grinding.

The advantages of the present invention will become clearer and easier to understand through the detailed description made in conjunction with the following drawings, which are only schematic and do not limit the scope of protection of the present invention, wherein:

FIG1 is a schematic diagram of a substrate grinding device provided by an embodiment of the present invention;

FIG2 is a schematic diagram of a grinding workbench provided in one embodiment of the present invention;

FIG3 is a flow chart of a substrate grinding method provided by one embodiment of the present invention;

FIG4 is a schematic diagram of a posture adjustment mechanism provided by an embodiment of the present invention;

FIG5 is a schematic diagram of a coordinate system corresponding to the grinding marks formed by the grinding wheel on the grinding workbench;

FIG6 is a schematic diagram of the definition of substrate convexity and fullness provided by an embodiment of the present invention;

7 is a flow chart of a substrate grinding method provided by another embodiment of the present invention;

FIG. 8 is a schematic diagram of a control device provided by an embodiment of the present invention.

DETAILED DESCRIPTION

The technical scheme of the present invention is described in detail below in conjunction with specific embodiments and their accompanying drawings. The embodiments recorded herein are specific embodiments of the present invention, which are used to illustrate the concept of the present invention; these descriptions are explanatory and exemplary and should not be construed as limitations on the embodiments of the present invention and the scope of protection of the present invention. In addition to the embodiments recorded herein, those skilled in the art can also adopt other obvious technical solutions based on the contents disclosed in the claims of this application and its specification, including technical solutions that adopt any obvious replacements and modifications to the embodiments recorded herein.

The drawings of this specification are schematic diagrams, which assist in explaining the concept of the present invention and schematically show the shapes of various parts and their mutual relationships. It should be understood that in order to clearly show the structures of various components of the embodiments of the present invention, the drawings are not drawn according to the same scale, and the same reference numerals are used to represent the same parts in the drawings.

In the present invention, grinding is also called thinning (Grinding), and substrate (Substrate) is also called substrate (Wafer, W), and their meanings and actual functions are equivalent.

At present, the semiconductor industry uses electronic circuits such as IC (Integrated Circuit) or LSI (Large Scale Integration) formed on the surface of semiconductor wafers to manufacture semiconductor chips. Before the wafer is divided into semiconductor chips, the back side opposite to the device surface with the electronic circuit is ground by a substrate grinding device, thereby grinding the substrate to a predetermined thickness.

The present invention relates to a substrate grinding device for removing material from a substrate surface according to process requirements. FIG1 is a schematic diagram of a substrate grinding device 100 provided by an embodiment of the present invention. The substrate grinding device 100 comprises:

Base 1;

The turntable 2 is arranged above the base 1 and can rotate around the central axis of the turntable 2 under the drive of the driving device; a grinding table 3 is arranged on the upper part of the turntable 2 for holding the substrate and driving the substrate to rotate;

The grinding module 4 is disposed on the base 1 and located above the grinding workbench 3 ; a grinding wheel disposed at the bottom of the grinding module 4 abuts against the surface of the substrate to grind the surface of the substrate to achieve material removal.

The grinding module 4 includes a rough grinding part 41 and a fine grinding part 42. The rough grinding part 41 is provided with a rough grinding wheel for rough grinding of the substrate, and the fine grinding part 42 is provided with a fine grinding wheel for fine grinding of the substrate. The grinding process is to press the grinding wheel on the surface of the substrate and rotate it to grind away a certain thickness of the material layer.

The rough grinding part 41 includes a rough grinding wheel in the shape of a cup-shaped structure, a rough grinding spindle, a rough grinding spindle seat and a rough grinding feed mechanism. The rough grinding wheel is connected to the bottom of the rough grinding spindle so that the rough grinding spindle drives the rough grinding wheel to rotate so as to realize the rotational grinding of the rough grinding wheel on the surface of the substrate. The rough grinding spindle is connected to the rough grinding feed mechanism through the rough grinding spindle seat to realize up and down movement. The rough grinding feed mechanism controls the rough grinding wheel to approach or move away from the substrate to perform axial cut-in feed grinding. The rough grinding wheel can be a diamond grinding wheel, and its surface is relatively rough to realize rapid substrate grinding and reduce substrate grinding time. During rough grinding, the feed speed of the rough grinding wheel relative to the substrate is 2 to 10 μm/s, thereby realizing high-speed feeding, and the rotation speed of the rough grinding wheel is 2000 to 4000 rpm.

The fine grinding part 42 includes a fine grinding wheel in the shape of a cup-shaped structure, a fine grinding spindle, a fine grinding spindle seat and a fine grinding feed mechanism. The fine grinding wheel is connected to the bottom of the fine grinding spindle so that the fine grinding spindle drives the fine grinding wheel to rotate, thereby realizing the fine grinding wheel rotating grinding on the substrate surface. The fine grinding spindle is connected to the fine grinding feed mechanism through the fine grinding spindle seat to realize up and down movement. The fine grinding feed mechanism controls the fine grinding wheel to approach or move away from the substrate to perform axial cut-in feed grinding. The fine grinding wheel can be a diamond grinding wheel, and its surface roughness is lower than that of the rough grinding wheel. Since the rough grinding quickly removes the surface material of the substrate, serious surface defects and losses will be generated. The fine surface of the fine grinding wheel is used for low-speed grinding to reduce the thickness of the substrate surface damage layer and improve the surface quality of the substrate. During fine grinding, the feed speed of the fine grinding wheel relative to the substrate is 0.1-1 μm/s, so as to realize low-speed feeding to improve the grinding accuracy, and the rotation speed of the fine grinding wheel is 2000-4000rpm.

In the embodiment shown in FIG1 , three grinding workbenches 3 are evenly arranged on the upper part of the turntable 2. Specifically, the center of the three grinding workbenches 3 and the center line of the turntable 2 form an angle of 120°. The three suction cup workbenches 1 rotate in the rough grinding station, the fine grinding station and the loading and unloading station, wherein the two stations opposite to the grinding module 4 perform rough grinding and fine grinding respectively, and the remaining station is used for loading and unloading and cleaning of the substrate.

Fig. 2 is a schematic diagram of a grinding table 3 provided in an embodiment of the present invention, wherein the grinding table 3 is provided with three supporting points 3A, 3B and 3C to adjust the position and posture of the grinding table 3. Among them, the supporting point 3A is a fixed supporting point, and the supporting points 3B and 3C are adjustable supporting points, hereinafter referred to as adjustable points.

At the same time, the present invention also provides a substrate grinding method, and its flow chart is shown in FIG3. A substrate grinding method comprises:

S1, real-time detection of the grinding force on the grinding substrate;

S2, calculating the change in the tilt angle of the grinding table 3 caused by the grinding force;

S3, determining a tilt angle adjustment scheme for the grinding table 3 according to the processed surface shape and the target surface shape of the substrate to compensate for the tilt angle change caused by the grinding force.

In the present invention, the support points 3B and 3C are provided with a posture adjustment mechanism 30 as shown in Fig. 4. The posture adjustment mechanism 30 includes a detection module 31, which can measure the grinding force applied to the substrate in real time during the grinding process.

Furthermore, the detection module 31 includes a piezoelectric sensor to measure the grinding force applied to the substrate during the grinding process.

Furthermore, the posture adjustment mechanism 30 also includes a micro-adjustment module 32, which includes a screw 32a, a servo motor 32b and a nut 32c, wherein the output shaft of the servo motor 32b is connected to the screw 32a, and the nut 32c is threadedly connected to the screw 32a. The rotating screw 32a drives the nut 32c thereon to move up and down in the vertical direction to adjust the inclination of the grinding worktable 3 to meet the requirements of the grinding process.

In FIG. 4 , the posture adjustment mechanism 30 further includes a precision adjustment module 33 , which includes a piezoelectric actuator, which determines the adjustment voltage corresponding to the precision adjustment module according to the inclination angle adjustment scheme of the grinding table 3 to adaptively adjust the inclination of the grinding table 3 .

In step S1, the grinding force F is:

Wherein, _Fx is the component of the grinding force along the x-direction; _Fy is the component of the grinding force along the y-direction; _Fxi is the grinding force along the x-axis detected by the i-th sensor; _Fyi is the grinding force along the y-axis detected by the i-th sensor; i=1, 2; the x-axis is a straight line perpendicular to the grinding mark and passing through one end point thereof, and the y-axis is a straight line passing through the end point of the grinding mark.

Fig. 5 is a schematic diagram of a coordinate system corresponding to the grinding marks formed by the grinding wheel on the grinding workbench 3, wherein the grinding wheel is represented by a dotted line. Fig. 6 is a schematic diagram of the definition of convexity and fullness of a substrate provided in an embodiment of the present invention.

In FIG6 , the r-axis represents the distance between each measuring point and the starting measuring point, and the t-axis represents the measured thickness of the substrate. According to the present invention, the convexity δ ₁ can be defined as the difference between the thickness at the final measuring point and the thickness at the starting measuring point. In the example of FIG6 , the starting measuring point is the center point C of the upper surface of the substrate, and the final measuring point is an edge point A of the substrate. At this time, the convexity δ ₁ is the difference between the thickness of the center point C of the substrate and the thickness of the edge point A. In other words, the convexity δ ₁ at this time is the distance from the center point C of the upper surface of the substrate to the reference thickness line. The position of the reference thickness line is determined by the thickness value of the edge point A of the substrate, and the reference thickness line is parallel to the r-axis. When the center point C of the upper surface of the substrate is above the reference thickness line, the convexity δ ₁ is positive (i.e., δ ₁ >0), otherwise it is negative (i.e., δ ₁ <0).

Further, the fullness δ ₂ can be defined as the maximum value of the vertical distance between the intermediate measurement point and the convexity line, and the convexity line is the straight line formed by connecting the starting measurement point and the final measurement point. In the example of 6, the starting measurement point is the center point C of the upper surface of the substrate, and the final measurement point is an edge point A of the substrate, with multiple intermediate measurement points in between. Of course, in an extreme example, only one intermediate measurement point can be selected, such as selecting at half the radius of the substrate. At this time, the maximum value of the vertical distance between the intermediate measurement point and the convexity line is the vertical distance between the intermediate measurement point and the convexity line itself. In this example, the convexity line is a straight line connecting the center point C and the edge point of the substrate, and the fullness δ ₂ is the maximum distance from the contour point on the upper surface of the substrate to the convexity line. When the point corresponding to the maximum distance is above the convexity line, the fullness δ ₂ is positive (i.e., δ ₂ >0), otherwise δ ₂ is negative (i.e., δ ₂ <0).

In the present invention, when grinding the substrate, the grinding table 3 that adsorbs the substrate is first processed into a conical surface with a certain height; then, the substrate is adsorbed on the grinding table 3, and the convexity and concavity of the substrate surface are adjusted by rotating it around the x-axis at an angle α, and the fullness of the substrate surface is adjusted by rotating it around the y-axis at an angle β, thereby achieving the grinding of the target surface shape of the substrate.

In the embodiment shown in Fig. 2, the support points 3B and 3C are provided with a posture adjustment mechanism 30 shown in Fig. 4. The detection module 31 provided with the posture adjustment mechanism 30 can measure the grinding force applied to the substrate during the grinding process.

Furthermore, in step S2, the grinding force F causes the inclination angle of the grinding table 3 to change:

Wherein, Δα _F is the angle change of the axis of the grinding table 3 around the x-axis caused by the grinding force, Δβ _F is the angle change of the axis of the grinding table 3 around the y-axis caused by the grinding force; _vs is the rotation speed of the grinding wheel; _vw is the rotation speed of the substrate; A and B are adjustment coefficients. The adjustment coefficients A and B are 0 to 1, preferably, the adjustment coefficient A is 0.1 to 0.6, and the adjustment coefficient B is 0.4 to 0.8.

In step S3, the inclination angle of the grinding table 3 changes:

Among them, △α is the angular change of the axis of the grinding table around the x-axis; △β is the angular change of the axis of the grinding table around the y-axis; _Tr is the thickness value corresponding to the processed substrate; _Tt is the thickness value corresponding to the substrate with the target surface shape.

FIG. 7 is a flow chart of a substrate grinding method provided by another embodiment of the present invention, which comprises:

S10, calculating and adjusting the position and posture of the grinding table 3 according to the target thickness and surface shape of the substrate to be ground;

S20, grinding the substrate and measuring the grinding force exerted on the substrate in real time through the detection module 31;

S30, calculating the change in the tilt angle of the grinding table 3 caused by the grinding force;

S40, determining a tilt angle adjustment scheme for the grinding table 3 according to the processed surface shape and the target surface shape of the substrate;

S50 , using the fine motion adjustment module 32 and the fine motion adjustment module 33 to adjust the grinding table 3 .

Specifically, the grinding table 3 is first adjusted using the micro-adjustment module 32, and then the grinding table 3 is adjusted using the precision adjustment module 33. The micro-adjustment module 32 is adjusted by the screw 32a and the nut 32c through thread lifting, which can achieve um-level adjustment accuracy; the precision adjustment module 33 realizes displacement adjustment through the piezoelectric sensor, which can achieve nm-level adjustment accuracy.

That is, during the substrate grinding process, the configured detection module 31 realizes real-time monitoring of the grinding force and compensates for the inclination error caused by the grinding force on the substrate, which is beneficial to improving the flatness of the substrate.

In addition, the detection module 31 in the posture adjustment mechanism 30 can measure the grinding force on the substrate in real time; the control module of the substrate grinding system can adaptively adjust the grinding parameters such as the grinding wheel feed speed and feed amount based on the measured value of the grinding force, which is conducive to improving the processing quality of substrate grinding and improving the flatness of substrate grinding. That is, the substrate grinding system can adaptively adjust the feeding parameters of the grinding wheel according to the change of the grinding force to ensure the processing quality of substrate grinding.

FIG8 is a schematic diagram of a control device provided by an embodiment of the present invention. In this embodiment, the control device includes: a processor, a memory, and a computer program stored in the memory and executable on the processor. When the processor executes the computer program, the steps in each embodiment of the above method embodiment are implemented. Alternatively, when the processor executes the computer program, the functions of each module/unit in each embodiment of the above system embodiment are implemented.

Control devices refer to terminals with data processing capabilities, including but not limited to computers, workstations, servers, and even some high-performance smart phones, PDAs, tablet computers, personal digital assistants (PDAs), smart TVs, etc.

The control device may include, but is not limited to, a processor and a memory. Those skilled in the art will appreciate that FIG8 is only an example of a control device and does not constitute a limitation on the control device, and may include more or fewer components than shown in the figure, or a combination of certain components, or different components, for example, the control device may also include an input/output device, a network access device, a bus, etc.

The processor may be a central processing unit (CPU), other general-purpose processors, digital signal processors (DSP), application-specific integrated circuits (ASIC), field-programmable gate arrays (FPGA) or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components, etc.

The memory may be an internal storage unit of the control device, such as a hard disk or memory of the control device. The memory may also be an external storage device of the control device, such as a plug-in hard disk equipped on the control device, a smart memory card (SmartMedia Card, SMC), a secure digital (Secure Digital, SD) card, a flash card (Flash Card), etc. Further, the memory may also include both an internal storage unit of the control device and an external storage device. The memory is used to store computer programs and other programs and data required by the control device. The memory may also be used to temporarily store data that has been output or is to be output.

In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "illustrative embodiments", "examples", "specific examples", or "some examples" means that the specific features, structures, materials, or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representation of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials, or characteristics described may be combined in any one or more embodiments or examples in a suitable manner.

Although the embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the claims and their equivalents.

Claims (10)

1. A method of grinding a substrate, comprising:

s1, detecting grinding force borne by a grinding substrate in real time;

s2, calculating the change of the inclination angle of the grinding workbench caused by the grinding force;

and S3, determining an inclination angle adjusting scheme of the grinding workbench according to the processed surface shape and the target surface shape of the substrate so as to compensate inclination angle change caused by grinding force.

2. The substrate grinding method according to claim 1, wherein in step S1, the grinding force F is:

wherein, F _x The component force of the grinding force along the x direction; f _y The component force of the grinding force along the y direction; f _xi Detecting the obtained grinding force along the x axis for the ith sensor; f _yi Detecting the obtained grinding force along the y axis for the ith sensor; i =1, 2; the x-axis is a line perpendicular to the grinding mark and passing through one end point thereof, and the y-axis is a line passing through the end point of the grinding mark.

3. The substrate grinding method according to claim 2, wherein in step S2, the inclination angle of the grinding table is changed by the grinding force:

wherein, delta alpha _F For the angular change of the axis of the grinding table about the x-axis caused by the grinding force, Δ β _F An angular change of an axis of the grinding table about the y-axis caused by the grinding force; v. of _s Is the rotational speed of the grinding wheel; v. of _w Is the rotation speed of the substrate; A. and B is an adjusting coefficient.

4. The substrate grinding method according to claim 3, wherein in step S3, the inclination angle of the grinding table is changed by:

wherein Δ α is the angular change of the axis of the grinding table about the x-axis; delta beta is the angular change of the axis of the grinding table around the y-axis; t is _r The thickness value corresponding to the processed substrate; t is _t The thickness value corresponding to the substrate with the target surface shape is obtained.

5. The substrate grinding method of claim 1, wherein the adjustment point of the grinding table is provided with a detection module including a piezoelectric sensor to measure a grinding force to which the substrate is subjected during grinding.

6. The substrate grinding method according to claim 1, wherein the adjustment point of the grinding table is further provided with a fine adjustment module including a screw, a servo motor, and a nut, an output shaft of the servo motor is connected to the screw, the nut is threadedly connected to the screw, and the rotating screw moves the nut thereon to adjust the inclination of the grinding table.

7. The substrate grinding method of claim 6 wherein the adjustment points of the grinding table are further configured with a fine adjustment module comprising a piezoelectric actuator that determines an adjustment voltage corresponding to the fine adjustment module based on the tilt angle adjustment profile of the grinding table.

8. The substrate grinding method according to claim 7, wherein in step S3, the grinding table is adjusted using the fine adjustment module and then the grinding table is adjusted using the fine adjustment module.

9. A control apparatus comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, the processor implementing the steps of the substrate grinding method according to any one of claims 1 to 8 when executing the computer program.

10. A computer-readable storage medium, characterized in that the computer-readable storage medium stores a computer program which, when executed by a processor, implements the steps of the substrate grinding method according to any one of claims 1 to 8.

Images