JP3166146B2 - Surface grinding method and apparatus - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

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

[0002]

2. Description of the Related Art For example, the surface of a wafer sliced 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 a grindstone, then rotates the grindstone and presses the grindstone against the surface of the wafer to grind the surface of the wafer. I do.

[0003]

Recently, as circuit patterns have become more highly integrated, the flatness and parallelism of the wafer surface have been demanded with high precision. However, in the conventional surface grinding apparatus, the parallelism between the wafer surface and the grindstone is deteriorated due to a change in the ambient temperature or the temperature of the processing liquid during the 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]

According to the present invention, in order to attain the above object, a rotating grindstone is pressed against a surface of a workpiece supported by a workpiece support table so that the surface of the workpiece is reduced. In the surface grinding method for grinding, at least the thickness of three points having different radii of the workpiece during grinding is measured, and from the difference in the measured thicknesses of the three points, The whetstone is tilted
The lowest point of rotation of the workpiece when it is
The phase angle from the line connecting the rotation center of the stone and the lowest point
By calculating the virtual thickness of the workpiece in
Relative to the workpiece support table
A power control amount is calculated, and a posture of the workpiece support table and / or the grindstone is controlled to grind a surface of the workpiece.

Further, in order to achieve the above object, the present invention provides a surface grinding method in which a rotating grindstone is pressed against a surface of a workpiece supported by a workpiece support table to grind the surface of the workpiece. in a combination, at least of the workpiece during grinding, the measurement means that measuring the thickness of the radii of three different points provided, or difference in thickness of the three points measured in measurement means
The lowermost point of the workpiece when the grinding wheel is tilted.
Phase from the line connecting the rotation center and the rotation center of the whetstone
The corner and the virtual thickness of the workpiece at the lowest point.
By calculating, the workpiece support table
A calculating means for calculating a relative attitude control amount of the wheel shaft, wherein said providing a workpiece support table and / or control means for posture control the grinding wheel.

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 during the grinding process is measured at three points having different radii by a three-point measuring means, and
From the difference in thickness at the three points measured by the three measuring means,
The center of rotation of the workpiece at the lowest point when the
At the phase angle from the line connecting the rotation center and the lowest point
By calculating the virtual thickness of the workpiece,
Calculates the relative attitude control amount of the grinding wheel axis with respect to the support table
Then , the posture of the workpiece support table and / or the grindstone is controlled by the control means.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of a surface grinding method and apparatus according to the present invention will be described below in detail with reference to the accompanying drawings. FIG. 1 is a main part structural view 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 FIG. 1 includes a table 12 for holding a semiconductor wafer 10 and a grindstone 14 for grinding the surface of the semiconductor wafer 10. The table 12
Has a vacuum suction portion formed on the upper surface thereof, and the semiconductor wafer 10 is supported by the vacuum suction portion with the ground 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 a rotational force from the motor via a spindle 16.

The grinding wheel 14 is formed in a cup shape and is fixed to a lower portion of a grinding wheel shaft 20. The grinding wheel 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 when the grinding wheel 14 is rotated by the motor and lowered by the elevating and moving mechanism to be pressed against the surface of the semiconductor wafer 10 and the table 12 is rotated.

By the way, three non-contact sensors 22, 24 and 26 are arranged above the semiconductor wafer 10. These non-contact sensors 22, 24, and 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 detected by the non-contact sensors 22, 24 and 26 is C
Output to PU28. The CPU 28 controls the piezoelectric element control device 30 based on the thickness information to control the attitude of the grinding wheel shaft 20. A method of controlling the attitude of the grinding wheel shaft 20 by the CPU 28 will be described later.

On the other hand, four piezoelectric elements 32, 34, 36,
38 is a disk-shaped flange 41 fixed to the grinding wheel shaft 20
(A piezoelectric element 38).
Is at a position diametrically opposed to the piezoelectric element 36). The piezoelectric elements 32 to 38 are arranged at equal intervals every 90 °, and can be driven vertically in the drawing when a voltage is applied from the piezoelectric element control device 30. Therefore, the piezoelectric elements 32 to 38
Is driven, the grindstone shaft 20 swings with respect to the gantry 40 to control the posture. Thus, by controlling each of the voltages applied to the piezoelectric elements 32 to 38, the perpendicularity of the grinding wheel shaft 20 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 , and L _C from the non-contact sensors 22, 24, 26 shown in FIG. The respective distances l _A , l _B , l _C to the ground surface of the wafer 10 are subtracted, and the subtracted dimensions are used as the thickness H _A ,
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 three locations are equal. Next, the control method will be described with reference to the schematic view of the semiconductor wafer 10 and the grindstone 14 shown in FIG.

FIG. 2 is a diagram showing a positional relationship between the semiconductor wafer 10 and the grindstone 14. A large circle in the drawing indicates the semiconductor wafer 10, and a small circle in the drawing indicates the grindstone 14. Also,
The O ₁ point shown in FIG semiconductor wafer 10 (Table 1
2) is the rotation center, and the O ₂ point is the axis of the grinding wheel shaft 20. Three non-contact sensor 22, 24 and 26 have been arranged to C _1, B _1, A ₁ point of FIG. 2, H _C as the thickness above the semiconductor wafer 10 at this point, H _B, H _A.

The points A, B and C in FIG.₁, B₁,
C₁Point and table 12 (center O₁At the point on the concentric circle above
Yes, the thickness of the semiconductor wafer 10 at points A, B and C is also
H_A, H _B, H_CIt is. Also, on the x and y axes of the grindstone 14
The virtual thickness at the X and Y points of_X, H_YAnd the whetstone 14 tilts
The lowest point is K point, and the virtual thickness of 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 of the line O ₂ K by drawing a perpendicular from each of the points A, B and C to the line O ₂ K. Therefore, if the value of Rm in the proportional expression of Hm = (H _K / R) Rm is selected, the thickness at each intersection can be obtained.

When the point K coincides with the point Y in FIG.
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
(Ie, (α + β) / 2 and (β + γ) /
2), the semiconductor wafer 10
Is as shown in FIG. 5, where 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 becomes as shown in FIG.
A _C> H _B> H _A. Furthermore, (when it comes to the point with the highest Y point) K point when matching the opposite side of the point Y, the sectional shape of the semiconductor wafer 10 becomes 7, the _{H C> H B> H A} . That is, if the magnitudes of H _A , H _B , and H _C are constantly determined during grinding, the shape of the semiconductor wafer 10 that is currently being ground can be determined. By calculating the value by the CPU 28, the grinding wheel shaft 20 and the table 12 Can be calculated for the phase and magnitude of the squareness change.

In FIG. 2, H_K= √ (H_X ^Two+ H_Y ^Two) 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_Kcosθ tanθ = H_X/ H_Y Tanθ =-[(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, and therefore, from the difference in thickness between points A, B, and C during grinding,
Phase angle θ and thickness H at the lowest point_K, And H_X, H_YAsk for
be able to. Move the grinding wheel shaft 20 in the X direction by -H_XIn the Y direction
-H_YThe squareness that was tilted by swinging only
The grinding wheel shaft 20 moves in the X direction by -H_XIn the Y direction
-H_YThe piezoelectric element 3 by the CPU 28 so that
The voltage applied to 2 to 38 is controlled. This allows the whetstone
The axis 20 is on 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 flattened and its flatness is improved.

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

In this embodiment, the apparatus for grinding a surface of a semiconductor wafer has been described, but the present invention can also be applied to a surface grinding apparatus for other plate-like materials. Further, in this embodiment, the description has been given of the grinding wheel axis control for flat grinding the surface of the workpiece, but by setting the thickness of the workpiece to a predetermined value, for example, as shown in FIG. 10
A can be ground into a spherical shape. In this case, the inclination angle θ ± Δθ ° of the grinding wheel shaft 20 is set so as to correspond to the curvature of the wafer surface 10A.

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 32-38 constitute the controlling means of the present invention.

[0022]

According to the surface grinding method and apparatus according to the present invention, as described above, according to the present invention, by measuring the thickness of different radii three thicknesses of the workpiece during grinding, 3 points Thickness
Of the workpiece at the lowest point when the grinding wheel is tilted.
The phase angle from the line connecting the center of rotation and the center of rotation of the grinding wheel and
To calculate the virtual thickness of the workpiece at the lowest point
The relative attitude of the grindstone axis to the workpiece support table
Since the control amount is calculated and the attitude of the workpiece support table and / or the grindstone is controlled, the flatness and parallelism of the workpiece surface can be improved.

[Brief description of the drawings]

FIG. 1 is a main part structural diagram 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 as seen from the line LL in FIG. 2;

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

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

FIG. 6 is an explanatory diagram of a thickness of a semiconductor wafer obtained from a sensor.

FIG. 7 is an explanatory diagram of a thickness of a semiconductor wafer obtained from a sensor.

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

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

[Explanation of symbols]

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

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) B24B 49/02 B24B 49/04 B24B 7/04

Claims (2)

(57) [Claims] 1. A surface grinding method in which a rotating grindstone is pressed against a surface of a workpiece supported by a workpiece support table to grind the surface of the workpiece. At least different radius of objects
Measure the thickness at three points and determine the difference between the measured thicknesses at the three points.
The lowermost point of the workpiece when the grinding wheel is tilted.
Phase from the line connecting the rotation center and the rotation center of the whetstone
The corner and the virtual thickness of the workpiece at the lowest point.
By calculating, the workpiece support table
A surface grinding method comprising calculating a relative attitude control amount of a grinding wheel shaft, and controlling the attitude of the workpiece support table and / or the grinding wheel to grind a surface of a workpiece. 2. A surface grinding apparatus for grinding a surface of a workpiece by pressing a rotating grindstone onto a surface of the workpiece supported by a workpiece support table, wherein the workpiece during the grinding is processed. At least different radius of objects
Constant means measuring you measure the thickness of the three points provided, the difference in thickness of the three points measured in surveying constant means, when the grinding wheel is inclined
During the rotation of the grinding center and the rotation center of the workpiece at the lowest point of
The phase angle from the line connecting the heart and the phase angle at the lowest point
By calculating the virtual thickness of the workpiece,
The relative attitude control amount of the grindstone axis to the workpiece support table
Calculating means for calculation for the surface grinding device, characterized in that the workpiece support table and / or the grinding wheel is provided and control means for posture control.