JPH0985619A - Surface grinding method and device therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the flatness and prallelism of the surface of a workpiece by performing a grinding process therefor under the control of the attitude of a workpiece support table and/or a grinding wheel so as to keep the prescribed values for respective measured thickness at several positions. SOLUTION: CPU 28 subtracts each of 1A, 1B and 1C obtained with non- contact sensors 22, 24 and 26 as distances up to the grinding surface of semiconductor wafer 10, on the basis of the values LA, LB and LC of height from the non-contact sensors 22, 24 and 26 to the adsorption part of a table 12, and judges values after the subtraction as the values of the thickness HA, HB and HC of the semiconductor wafer 10. Then, the CPU 28 controls a piezoelectric element control device 30 on the basis of the thickness values HA, HB and HC. According to this construction, the values of the thickness HA, HB and HC at three positions become equal, when the thickness of the semiconductor wafer 10 is uniform and the surface thereof is completely flat.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a surface grinding method and an apparatus thereof, and more particularly to a surface grinding method and an apparatus thereof for semiconductor wafers, hard disks and the like.

[0002]

2. Description of the Related Art For example, the surface of a wafer cut into thin pieces by a slicing machine is ground by a surface grinding device as a post-process. The surface grinding device supports the wafer on a chuck table, adjusts the parallelism between the surface of the wafer and the grindstone, and then rotates the grindstone and presses the grindstone onto the surface of the wafer to grind the surface of the wafer. To do.

[0003]

Recently, as the circuit pattern is highly integrated, the flatness and parallelism of the wafer surface are required with high accuracy. However, in the conventional surface grinding apparatus, the parallelism between the wafer surface and the grindstone deteriorates due to the change in the atmospheric temperature and the temperature of the working liquid during grinding, or the bending of the grindstone. There is a drawback that flatness and parallelism deteriorate.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a surface grinding method and apparatus capable of improving the flatness and parallelism of the surface of a workpiece.

[0005]

SUMMARY OF THE INVENTION In order to achieve the above-mentioned object, the present invention presses a rotating grindstone against the surface of a work piece supported by a work piece support table to move the surface of the work piece. In the surface grinding method of grinding, the thickness of the workpiece during grinding is measured at three or more points, and the measured thicknesses of the plurality of points are respectively predetermined values.
It is characterized in that the surface of the workpiece is ground by controlling the attitude of the workpiece support table and / or the grindstone.

Further, in order to achieve the above object, the present invention is a surface grinding for pressing a rotating grindstone against the surface of a work piece supported by a work piece support table to grind the surface of the work piece. The apparatus is provided with three or more measuring means for measuring the thickness of the workpiece during grinding, and the thicknesses of the plurality of points measured by the plurality of measuring means have predetermined values, respectively. Therefore, a control means for controlling the attitude of the workpiece support table and / or the grindstone is provided.

According to the present invention, first, the workpiece is held on the workpiece support table, and a rotating grindstone is pressed against the surface of the workpiece to start grinding the surface of the workpiece. Then, the thickness of the workpiece being ground is measured at a plurality of points by a plurality of measuring means, and the thickness of the plurality of points measured by the plurality of measuring means is adjusted to a predetermined value. The attitude of the object support table and / or the grindstone is controlled by the control means.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION Preferred embodiments of a surface grinding method and apparatus therefor according to the present invention will be described in detail below with reference to the accompanying drawings. FIG. 1 is a structural diagram of a main part showing an embodiment in which a surface grinding apparatus according to the present invention is applied to a wafer surface grinding apparatus. The surface grinding apparatus shown in the figure includes a table 12 for holding the semiconductor wafer 10 and a grindstone 14 for grinding the surface of the semiconductor wafer 10. Table 12
Has a vacuum suction portion formed on the upper surface thereof, and the semiconductor wafer 10 is supported by this vacuum suction portion with the grinding surface facing upward. A spindle 16 is provided below the table 12, and a motor (not shown) is connected to the spindle 16. The table 12 can be rotated by transmitting the rotational force from the motor via the spindle 16.

The grindstone 14 is formed in a cup shape and fixed to the lower part of the grindstone shaft 20. The grindstone shaft 20 is connected to a motor (not shown) and a lifting device (not shown). Therefore, the surface of the semiconductor wafer 10 is ground by rotating the grindstone 14 with the motor and lowering it with the lifting mechanism to press it against the surface of the semiconductor wafer 10, and then rotating the table 12.

By the way, three non-contact sensors 22, 24 and 26 are arranged above the semiconductor wafer 10. These non-contact sensors 22, 24, 26 detect the thickness H of the semiconductor wafer 10 during grinding, and are arranged at predetermined intervals in the radial direction as shown in FIG. The thickness information of each of the non-contact sensors 22, 24 and 26 is C
It is output to the PU 28. The CPU 28 controls the piezoelectric element control device 30 based on the thickness information to control the attitude of the grindstone shaft 20. A method of controlling the attitude of the grindstone shaft 20 by the CPU 28 will be described later.

On the other hand, four piezoelectric elements 32, 34, 36,
38 is a disc-shaped flange 41 fixed to the grindstone shaft 20.
And the pedestal 40 are sandwiched and arranged (the piezoelectric element 38
Is in a diametrically opposed position to the piezoelectric element 36). The piezoelectric elements 32 to 38 are arranged at regular intervals of 90 °, and can be driven in the vertical direction in the figure when a voltage is applied from the piezoelectric element control device 30. Therefore, the piezoelectric elements 32 to 38
When is driven, the grindstone shaft 20 swings with respect to the gantry 40 and its posture is controlled. Accordingly, by controlling the voltage applied to each of the piezoelectric elements 32 to 38, the perpendicularity of the grindstone shaft 20 with respect to the ground surface of the semiconductor wafer 10 can be obtained.

Next, a method of controlling the attitude of the table 12 by the CPU 28 will be described. The CPU 28 obtains the semiconductors obtained by the non-contact sensors 22, 24, 26 based on the heights L _A , L _B , L _C from the non-contact sensors 22, 24, 26 shown in FIG. The respective distances l _A , l _B , and l _C to the grinding surface of the wafer 10 are subtracted, and the subtracted dimensions are the thickness H _{A of} the semiconductor wafer 10,
Judge as H _B and H _C. Then, the CPU 28 controls the piezoelectric element control device 30 based on the thicknesses H _A , H _B and H _C.
Control. If the thickness of the semiconductor wafer 10 is uniform and the surface is completely flat, the thicknesses H _A , H _B and H _C at the three locations are equal. Next, the control method will be described with reference to the schematic diagrams of the semiconductor wafer 10 and the grindstone 14 shown in FIG.

FIG. 2 is a diagram showing the positional relationship between the semiconductor wafer 10 and the grindstone 14. In the figure, the large-diameter circle represents the semiconductor wafer 10 and the small-diameter circle in the drawing represents the grindstone 14. Also,
The point O ₁ shown in FIG.
It is the rotation center of 2) and the O ₂ point is the axis of the grindstone shaft 20. The three non-contact sensors 22, 24 and 26 are arranged at points C ₁ , B ₁ and A _{1 in} FIG. 2, and the thickness of the semiconductor wafer 10 at these points is H _C , H _B , and H _A.

Further, points A, B and C in FIG.₁, B₁,
C₁Point and table 12 (center O₁) At the point on the concentric circle above
Yes, the thickness of the semiconductor wafer 10 at points A, B and C
H_A, H _B, H_CIt is. Also, on the x and y axes of the grindstone 14.
The virtual thickness of the X and Y points of H_X, H_YAnd the whetstone 14 is tilted
The lowest point is set as K point, and the virtual thickness at K point is
H_KAnd

Here, as shown in FIG. 3, the wafer thickness Hm at an arbitrary point Rm on the line segment O ₂ K is Hm = (H _K /
R) Rm, and thus each point A on the circle shown in FIG.
The thicknesses H _A , H _B , and H _C of _B and _C are equal to the thickness at the intersection point position of the line segment O ₂ K by drawing a perpendicular line from the points A, B, and C to the line segment O ₂ K. Therefore, by selecting the value of Rm in the proportional expression of Hm = (H _K / R) Rm, the thickness at each intersection position can be obtained.

When the K point coincides with the Y point in FIG. 2 (that is, Y
When the point becomes the lowest point), the semiconductor wafer 1 being ground
The cross-sectional shape of 0 is shown in FIG. 4, and H _A > H _B > H _C.
Further, the angle θ of the K point is (α + β) / 2 and (β + γ) / 2
And (ie (α + β) / 2 and (β + γ) /
Semiconductor wafer 10)
5 has a cross-sectional shape of H _A > H _C > H _B.

When the angle θ at the point K is larger than (α + β) / 2, the shape of the semiconductor wafer 10 is as shown in FIG.
_C > H _B > _HA . Further, when the point K coincides with the opposite side of the point Y (when the point Y is the highest point), the sectional shape of the semiconductor wafer 10 becomes as shown in FIG. 7, and H _C > H _B > H _A. That is, if the magnitudes of H _A , H _B , and H _C are constantly discriminated during grinding, the shape of the semiconductor wafer 10 being ground at present can be known. By calculating the value by the CPU 28, the grindstone shaft 20 and the table 12 are The phase and magnitude of the squareness change of can be calculated.

In FIG. 2, H_K= √ (H_X ²+ H_Y ²) H_A= H_Kcos (θ−α) H_B= H_Kcos (θ−β) H_C= H_Kcos (θ−γ) H_X= H_Ksin θ H_Y= H_Kcos θ tan θ = H_X/ H_Y , Tan θ = − [(H_B-H_C) Cosα + (H_C−
H_A) Cosβ + (H_A-H_B) Cosγ] / [(H_B
-H_C) Sinα + (H_C-H_A) Sinβ + (H _A−
H_B) Sinγ] H_K= (H_A-H_B) / [Cos (θ−α) -cos
(Θ-β)] H_X= H_Ksin θ H_Y= H_Kcos θ, so from the difference in thickness at points A, B and C during grinding
Phase angle θ at bottom point and thickness H_K, Further H_X, H_YAsk for
be able to. -H in the X direction_X, In the Y direction
-H_YThe tilted squareness is corrected by swinging only
Since it can be corrected, the grindstone shaft 20 moves in the X direction by -H._X, In the Y direction
-H_YThe CPU 28 causes the piezoelectric element 3 to tilt only
The voltage applied to 2 to 38 is controlled. This makes the whetstone
The shaft 20 with respect to the ground surface of the semiconductor wafer 10 being ground
Since the attitude is controlled at a right angle, the surface of the semiconductor wafer 10
Is ground flat and its flatness is improved.

In this embodiment, the piezoelectric element 3 is provided on the grindstone shaft 20 side.
2 to 38 are provided to control the attitude of the grindstone 14, the piezoelectric element 32 is provided on the table 12 side as shown in FIG.
′, 34 ′, 36 ′, 38 ′ may be provided to control the attitude of the table 12 side, or both the table 12 and the grindstone 14 may be provided with piezoelectric elements to control the attitude of both. In this embodiment, non-contact sensors 22, 24, and
Although 26 is used, a contact type sensor may be used, and the number of sensors may be 3 or more.

Further, although the surface grinding apparatus for the semiconductor wafer has been described in this embodiment, the present invention can be applied to the surface grinding apparatus for other plate-shaped materials. Further, in this embodiment, the grindstone axis control for flatly grinding the surface of the work piece has been described. However, by setting the thickness of the work piece to a predetermined value, for example, as shown in FIG. 10
It is also possible to grind A into a spherical shape. In this case, the inclination angle θ ± Δθ ° of the grindstone shaft 20 is set so as to correspond to the curvature of the wafer surface 10A.

The non-contact sensors 22, 24, 26 of this embodiment.
Constitutes the measuring means of the present invention, and the CPU 28, the piezoelectric element control device 30, and the piezoelectric elements 32 to 38 constitute the controlling means of the present invention.

[0022]

As described above, according to the surface grinding method and the apparatus therefor according to the present invention, the thickness of the workpiece being ground is measured at a plurality of points, and the thickness of each of the plurality of points is predetermined. Since the postures of the workpiece support table and / or the grindstone are controlled so as to obtain the values, the flatness and parallelism of the workpiece surface can be improved.

[Brief description of drawings]

FIG. 1 is a structural diagram of a main part in which a surface grinding apparatus according to the present invention is applied to a wafer surface grinding apparatus.

FIG. 2 is a schematic diagram showing a positional relationship between a semiconductor wafer and a grindstone.

FIG. 3 is a view seen from the line LL in FIG.

FIG. 4 is an explanatory diagram of the thickness of a semiconductor wafer obtained from a sensor.

FIG. 5 is an explanatory diagram of the thickness of the semiconductor wafer obtained from the sensor.

FIG. 6 is an explanatory view of the thickness of the semiconductor wafer obtained from the sensor.

FIG. 7 is an explanatory view of the thickness of the semiconductor wafer obtained from the sensor.

FIG. 8 is an explanatory view of grinding a semiconductor wafer into a spherical shape.

FIG. 9 is an explanatory diagram for detecting the thickness of a semiconductor wafer.

[Explanation of symbols]

10 ... Semiconductor wafer 12 ... Table 14 ... Grinding stone 20 ... Grinding stone axis 22, 24, 26 ... Non-contact sensor 28 ... CPU 30 ... Piezoelectric element control device 32, 34, 3
6, 38 ... Piezoelectric element

Claims (2)

[Claims] 1. A surface grinding method for grinding a surface of a workpiece by pressing a rotating grindstone against the surface of the workpiece supported by the workpiece support table, wherein the workpiece during the grinding process. The thickness of the object is measured at three or more points, and the workpiece support table and / or the grindstone is attitude-controlled so that the thickness of each of the measured points becomes a predetermined value. A surface grinding method characterized by grinding the surface of a workpiece. 2. A surface grinding apparatus which grinds the surface of a workpiece by pressing a rotating grindstone against the surface of the workpiece supported by the workpiece support table. A plurality of three or more measuring means for measuring the thickness of the object are provided, and the workpiece support table and / or the workpiece support table are provided so that the thicknesses of the plurality of points measured by the plurality of measuring means each have a predetermined value. Alternatively, the surface grinding apparatus is provided with control means for controlling the attitude of the grindstone.