JPH0615971B2 - Plane shape accuracy measurement method - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a planar shape accuracy measuring method, and more specifically,
For example, the present invention relates to a method for measuring the planar shape accuracy of the surface of a large work such as a surface plate of a lapping machine for polishing a silicon wafer.

Conventional technology and its problems Small-sized workpieces with a diameter of 200 mm or less, for example, the accuracy of the planar shape of the surface of a silicon wafer, has already been measured by optical interferometry or a method of arranging multiple sensors so as to cover the entire surface of the workpiece. It has been put to practical use. However, some lapping machines for polishing silicon wafers have a diameter of 2000 mm, and the above method cannot be applied to such a large workpiece. For this reason, conventionally, a standard bar with a high degree of straightness on the lower surface was placed on the surface of a large work, and the clearance between the work surface and the standard bar was successively measured with a clearance gauge, which relied on the skill and subjectivity of the operator. Although the measurement is performed by the method, there is a problem that such a method requires skill, accuracy is low, and measurement takes time.

An object of the present invention is to solve the above problems and provide a method capable of efficiently and accurately measuring the planar shape accuracy of a large work.

Means for Solving the Problems A method for measuring the planar shape accuracy according to the present invention is such that a plurality of distance sensors are linearly arranged in one plane substantially parallel to the surface of a workpiece with respect to the surface of a rotating workpiece. The distances to the corresponding points on the work surface are measured with a plurality of distance sensors at a plurality of rotation positions, and the distances to the respective reference points for the three reference points on the work surface are measured at two different rotation positions of the work. A plurality of distance sensors at a plurality of rotational positions of the work so that the distances to the same reference point measured by the two different distance sensors at the two different rotational positions of the work are equal to each other. The output signal from the work, the rotation angle at each rotation position of the work, and the positional relationship of the multiple distance sensors are associated with each other. By doing so, the planar shape accuracy of the work surface is measured.

Embodiment FIG. 1 shows a lower surface plate (workpiece) (11) of a lapping machine (10) and a plane attached to the lapping machine (10) for measuring the planar shape accuracy of the surface (upper surface) of the work (11). 1 shows a shape accuracy measuring device.

The plane shape accuracy measuring device includes one measuring bar (12). Height adjusting screws (13) are provided at both ends of the measuring bar (12), and the adjusting screw (13) is lapped on the lapping machine (10) so that the measuring bar (12) straddles the work (11). Has been installed in. A plurality of (for example, about 10) distance sensors (14) are linearly arranged on the measuring lever (12). Further, an optical switch for height adjustment (15) is provided at a portion near both ends of the measurement bar (12). These switches (15)
By adjusting the adjusting screw (13) with the height of the measuring bar (12) so that the sensors (14) are all located in one plane, preferably horizontal, substantially parallel to the surface of the workpiece (11). Has been adjusted. Work (11)
A marker (16) is attached to the periphery of the surface of
The wrapping machine (10) is equipped with a marker detection sensor (17) for detecting the rotation angle of the work (11) by detecting the marker (16). The distance sensor (14) of the measuring bar (12), the height adjusting optical switch (15), and the marker detection sensor- (17) are connected to the processing device (19) via the sensor controller (18). Processor (19)
Is, for example, a personal computer, to which a graphic display (20) or the like is connected.

The processing device (19) outputs the plurality of distance sensors (14) of the measurement bar (12) and the distance sensors (1).
The planar shape accuracy of the work (11) is measured by performing the processing in which the positional relationship of 4) and the rotation angle of the work (11) are associated with each other.

Next, with reference to FIG. 2, the principle of planar shape accuracy measurement by the above apparatus will be described.

FIG. 2 shows a lapping machine (10) for a measuring bar (12).
The measurement line at each rotation position of 40 ° when the work (11) is installed and rotated is shown. About 10 distance sensors (14) are attached to the measuring bar (12), but in this figure, six distance sensors (1
4) position j = ,,,,.
The position of the i = 1, 2 of the measurement by the rotation of the workpiece (11) bar (12), ..., are represented by 9.

The output d _{i, j} of the distance sensor (14) of the measurement bar (12) is expressed as d _{i, j} = a _i · x _j + b _i + f _{i, j} (1). However, i is the rotational position of the work of 1 , ..., 9 and j is the sensor position of. Further, a and b are parameters of a straight line on the upper surface of the cut surface when the surface moving with the rotation of the work is cut by the measuring bar, and f is a deviation amount from the straight line, that is, a plane strain amount.

The basic idea of the method of the present invention is 3 in FIG.
Based on the measured values at the two reference points A, B and C, it is assumed that these points are in the horizontal plane and f _{i, j} is obtained from the measured values d _{i, j} other than the points A, B and C. is there. Then, by doing so, there is a possibility that the rotation axis of the work is displaced, or that the rotation axis and the work surface are not exactly perpendicular to each other and the work surface is fluctuated (end surface run-out). Even in these cases, these effects are removed, and the planar shape accuracy of the work surface is accurately measured. The specific procedure will be described below.

First, f _{i, j} on positions 1 , 4 , and 7 passing points A, B, and C is obtained.

The measurement data at point A is1of,FourGiven as
From the formula (1), d _{1 ,}= A ₁ ・ X + B ₁ + F _{1 ,} … (2) d _{4 ,}= A _Four ・ X + B _Four + F _{4 ,} … (3)1 NotoFourAre in the same position (point A), so f _{1 ,}= F _{4 ,} Is.

Since this position is used as a reference, f _{1 ,}= 0
Good. On the other hand, x = 0 at the center of the measuring bar (12)
Then, from the symmetry of the position of the sensor (14),
x = -X Becomes

Since the same applies to the positions of the points B and C, d _{7 ,}= A ₇ ・ X + B ₇ + F _{7 ,} (4) d _{1 ,}= A ₁ ・ X + B ₁ + F _{1 ,} … (5) d _{4 ,}= A _Four ・ X + B _Four + F _{4 ,} (6) d _{7 ,}= A ₇ ・ X + B ₇ + F _{7 ,} … (7) and f _{7 ,}= F _{1 ,}= 0 f _{4 ,}= F _{7 ,}= 0.

From equations (2) and (5), a ₁ = (D _{1 ,}-D _{1 ,}) / (2x )… (8) b ₁ = (D _{1 ,}+ D _{1 ,}) / 2 ... (9) From equations (3) and (6), a _Four = (D _{4 ,}-D _{4 ,}) / (2x )… (10) b _Four = (D _{4 ,}+ D _{4 ,}) / 2 ... (11) From formulas (4) and (7), a ₇ = (D _{7 ,}-D _{7 ,}) / (2x )… (12) b ₇ = (D _{7 ,}+ D _{7 ,}) / 2 ... (13) Therefore,1The plane strain f above is the value of the equations (8) and (9).
Using f _{1 , j}= D _{1 , j}-A ₁ ・ X_j-B ₁  It is obtained by (14).

Similarly, the plane strain f on 4 is calculated from equations (10) and (11) as follows:
The plane strain f on 7 is obtained from equations (12) and (13).

Next, f _{i, j} at positions other than 1 , 4 , and 7 is obtained. 1, 4, 7 at a position other than the values of a, b are determined from the relationship between 1, 4, 7.

For example, in FIG. 2 , a and b at position 2 are obtained as follows. Since 2 and 4 and 1 and 2 are the same point, f _{2 ,} = f _{4 ,} ... (15) f _{2 ,} = f _{1 ,} ... (16) where f ₄ and f _{1 ,} Have already been obtained at positions 4 and 1 as described above.

Therefore, d _{2 ,}= A _Two ・ X + B _Two + F _{2 ,} … (17) d _{2 ,}= A _Two ・ X + B _Two + F _{2 ,} (18), so a _Two = [D _{2 ,}-D _{2 ,} -(F _{2 ,}-F _{2 ,})] / (X -X )… (19) b _Two = D _{2 ,}-F _{2 ,}-A _Two ・ X  … (20) Therefore,TwoAll the above f are required
Will be.

For the other positions 3 , 5 , 6 , 8 , 8 and 9 , similarly, f
Can be obtained.

Although d _{i, j} is a measured value, it is desirable to use a smoothed value for each position i when processing by the above-mentioned procedure.

Also, it is desirable to input the data at each position i at the same time, but in reality, the sensor is scanned, and the work (1
Since 1) rotates, it will measure a position that deviates from the original position. Now, if a workpiece with a diameter of 1 m is rotating at 10 rpm, the outermost peripheral side is about 500 mm / sec. Therefore, if the input can be made within 10 msec, the maximum amount of measurement position deviation is 5 mm, and it is considered that there is no practical problem.

In the above embodiment, the work (11) is measured in the plane shape in the state of being attached to the lapping machine (10).
Work (11) removed from lapping machine (10)
May be rotated by an appropriate means to measure. Further, the method of the present invention can of course be applied to works other than the surface plate of the lapping machine.

EFFECTS OF THE INVENTION According to the method of the present invention, as described above, even with a large-sized work, the rotation of the work may cause shaft runout of the work or wobbling of the end surface of the work surface. Even in such a case, these effects can be removed and the planar shape accuracy can be measured efficiently and accurately.

[Brief description of drawings]

FIG. 1 is a perspective view of a planar shape accuracy measuring apparatus showing an embodiment of the present invention, and FIG. 2 is a drawing for explaining the principle of measurement. (11) ... surface plate (work), (14) ... distance sensor, A, B, C ... reference point.

Claims (1)

[Claims] 1. A plurality of distance sensors are linearly arranged in one plane substantially parallel to the surface of a rotating work, and the plurality of distance sensors at a plurality of rotation positions of the work surface the work. The distances to the corresponding points above are measured, and the distances to each of the three reference points on the surface of the work are measured by two different distance sensors at two different rotational positions of the work, respectively. Output signals from multiple distance sensors at multiple rotation positions of the work and rotation at each rotation position of the work so that the distance to the same reference point measured by two different distance sensors at two different rotation positions becomes equal. A planar shape that measures the planar shape accuracy of the work surface by performing processing that associates the angle with the positional relationship of multiple distance sensors. Precision measurement method.