JPH10125755A - Wafer flatness measuring mechanism - Google Patents

Abstract

PROBLEM TO BE SOLVED: To measure the distance between the front and back surfaces of a wafer clamped, without straining it by smoothly rotating it an a high speed. SOLUTION: The flatness measuring mechanism 10 comprises a wafer rotator 4 and distance meter part 5. The rotator 4 comprises a cylindrical motor 41 and support to support its rotor 412 through an air bearing 424 and the distance meter part 5 has two optical distance meters 52a, 52b corresponding to both surfaces of the wafer 1 to measure the distances from both surfaces by moving the motor 41 to spirally scan the surfaces of the wafer 1. Clamp claws 414 clamp the wafer 1, without straining it, through balls K inserted in a fixed piece 4141 and pressing piece 4142 such that the wafer is pointpressed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a mechanism for measuring flatness of a wafer.

[0002]

2. Description of the Related Art A wafer made of semiconductor material such as silicon has irregularities on its surface, which adversely affects the quality of the formed semiconductor. Therefore, the quality of the semiconductor is inspected by measuring the amount of irregularities using a flatness inspection device. Have been. FIG.
Shows the configuration of the flatness inspection device used initially. The wafer 1 to be inspected has a surface 1a on which a semiconductor is formed.
Is turned to the upper side, and the center of the back surface 1b is rotated by suctioning air to the suction head 21 of the rotation mechanism 2. On the other hand, the optical distance measuring device 31 of the distance measuring unit 3 is moved in the direction of the radius R of the wafer 1 by the carriage mechanism 32 to scan the surface 1a in a spiral shape, and the distance of each scanning point is sequentially reduced. The measured data are input to the unevenness amount calculating circuit 33 to calculate the unevenness amount. When the unevenness amount on the entire surface is equal to or less than the reference value, the wafer 1
Is determined as having good flatness, and when there is an unevenness amount exceeding the reference value, it is determined to be defective, and OK or N is determined, respectively.
The G signal is output.

[0003] The inspection apparatus described above has several disadvantages. First, when the size of the wafer 1 becomes larger than the suction head 21 to some extent or more, the wafer 1 bends due to its own weight. Not exactly shown. For accurate measurement, a distance measuring device must be used for the front surface 1a and the back surface 1b.
The distance between the two distance measuring devices 31 and the difference between the distances on both sides are obtained by measuring the respective distances on both sides with the provision of 31 to obtain the amount of unevenness. However, since the suction head 21 is provided on the back surface 1b side, the distance measuring device 31 cannot be provided. In other words, there is a method of evacuating the suction head 21 when measuring the portion thereof. However, if the evacuating makes the rotation of the wafer 1 impossible, this idea cannot be executed. In addition, a certain size or more, for example, 12
For an inch wafer, the back surface 1b is also required to be in non-contact, so that the back surface suction method itself is inappropriate.

FIG. 5 shows an inspection apparatus having a rotating mechanism 2 'and a distance measuring unit 3' as one solution for solving the above-mentioned drawbacks. The rotation mechanism 2 ′ clamps the entire circumference of the outer peripheral edge of the wafer 1 with a clamp ring 22 so as not to contact the back surface 1 b, and rotates a gear 23 connected to the outer circumference of the clamp ring 22 by a motor (M) 24. The distance measuring unit 3 ′ has two fixed distances corresponding to the front surface 1 a and the back surface 1 b of the wafer 1.
It is assumed that the distance measuring devices 31a and 31b are used to measure the distance between both surfaces, and the difference between the two measurement data is calculated by the unevenness amount calculating circuit 33 to obtain the unevenness amount.

[0005]

The above-mentioned rotating mechanism 2 'can be established in principle, but has problems in practical use. That is,
In order to reduce the flatness inspection time, the wafer 1 is rotated at a high speed, for example, 3000 rpm. In the above-described method of the gear 23 and the motor 24, the clamp ring 22 is rotated stably and smoothly at such a high speed. It is difficult to do. It is also necessary that no distortion occurs in the clamped wafer 1. The present invention has been made in view of the above, and it is an object of the present invention to provide a flatness measuring mechanism that clamps a wafer 1 without causing distortion, smoothly rotates at a high speed, and measures a distance between both surfaces.

[0006]

SUMMARY OF THE INVENTION The present invention relates to a flatness measuring mechanism for a wafer, which has a cylindrical shape.
And a motor (hereinafter referred to as a motor) that moves in a direction perpendicular to the rotation axis along a guide groove of a fixed plate fixed to a base, the cylindrical rotor being fitted into the stator and supported by an air bearing. A cylindrical motor), a wafer rotating mechanism having a plurality of clamp claws provided on an end face of a rotor and clamping a wafer to be inspected, and fixed to a base at a fixed interval corresponding to both surfaces of the clamped wafer Then, the front and back surfaces of the wafer are spirally scanned by the movement of the cylindrical motor to measure the respective distances.
And an optical distance measuring device. Each of the above-mentioned clamp claws has a fixed piece fixed to the end face of the rotor, and a pressing piece joined to the fixed piece and urged by a spring. It clamps by point pressing.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In the above flatness measuring mechanism, the cylindrical motor of the wafer rotating mechanism comprises a cylindrical stator and a cylindrical rotor fitted therein, and the rotor is an air bearing. , Which enables smooth high-speed rotation. The wafer is clamped by a plurality of clamp claws provided on the end face of the rotor. Two optical distance measuring devices fixed at fixed intervals corresponding to both surfaces of the wafer respectively scan the front and back surfaces of the wafer in a spiral shape by moving a cylindrical motor. Since the cylindrical motor is hollow, there is no hindrance to the distance measuring device corresponding to the back surface of the wafer, and the distance to the entire surface of both sides of the clamped wafer is measured by both distance measuring devices. The difference between the distance between the two distance measuring devices is calculated to obtain the amount of unevenness. According to each of the clamp claws described above, the wafer is point-pressed by the balls fitted into the fixed piece and the pressing piece, respectively.
Clamped without distortion.

[0008]

FIG. 1 is an exploded view of a flatness measuring mechanism 10 according to an embodiment of the present invention, FIG. 2 is a sectional view of the flatness measuring mechanism 10, and FIG. 1, a flatness measuring mechanism 10 includes a wafer rotating mechanism 4 and a distance measuring unit 5 (FIG. 2). The wafer rotation mechanism 4 includes a cylindrical motor 41 including a cylindrical stator 411 and a rotor 412, and a support portion 42 for the rotor 412. The stator 411 has two support members 41.
The mobile platform 4111 is fixed to the mobile platform 4111 by 13, 4113.
It is moved in the direction of the arrow by a drive mechanism (not shown) along the guide groove M of the fixed base 4112 fixed to the base B.
The rotor 412 has a length longer than that of the stator 411, and is provided with two step rings 413a and 413b at two locations on the outer peripheral surface as shown in FIG. Also, three clamp claws 414a, 414b, 414c are symmetrically attached to the end face of the rotor 412. The support portion 42 includes a cylinder 421 having an inner diameter slightly larger than the outer diameter of the two step rings 413a, 413b, mounting members 422a, 422b, 422c provided at the three positions, and an air press-in hole formed at an appropriate position. Consists of 423.

In assembling the wafer rotating mechanism 4, the right side portion of the step ring 413a of the rotor 412 is fitted into the stator 411, and then the cylinder 421 is fitted into both step rings 413a and 413b. Inserted cylinder 421 and double step ring 413
After the metal or graphite porous material is filled into the gap G between the cylinders 421a and 413b, the cylinder 421 is bolted to the outer peripheral surface of the stator 411 by the fixtures 422a to 422c. Here, when air A is injected into the porous material through the air injection hole 433, an air bearing 424 (FIG. 2) is formed, and the rotor 412 is supported by the air bearing 424 and can smoothly rotate at high speed.

In FIG. 2, a distance measuring unit 5 is attached to two support columns 51a and 51b erected on a base B and upper ends thereof, and is fixed at a fixed interval corresponding to the front surface 1a and the back surface 1b of the wafer 1. And two optical distance measuring devices 52a and 52b. In FIG. 3, each of the clamp claws 414 is composed of a fixed piece 4141 and a pressing piece 4142 which are connected to each other by a PIN.
Symmetrically mounted on the end face of the rotor 412, the pressing piece 4142 is urged in the direction of the arrow by a spring S _P, the wafer 1 that is inserted between the two is the point pressed by the two balls K biased Thus, it is clamped without distortion.

Referring again to FIG. 2, the clamped wafer 1 rotates with the rotor 412 while rotating the cylindrical motor 41.
Move in the direction of the radius R. The wafer 1 that rotates and moves is moved by two distance measuring devices 52a and 52a fixed to the base B.
The front surface 1a and the back surface 1b are respectively scanned spirally by b, and the distances between the respective scanning points are measured. The difference between the two measured data is calculated by the unevenness amount calculating circuit 33 (see FIG. 5) in the same manner as in the related art, and the unevenness amount is obtained, and the quality of the flatness is determined.

In the above embodiment, the wafer rotating mechanism 4 is horizontal and the wafer 1 is clamped in the vertical direction. However, a method in which the wafer rotating mechanism 4 is vertical and the wafer 1 is clamped in the horizontal direction is also possible. Yes, in that case, the two distance measuring devices 52a and 52b are arranged so as to conform to this.

[0013]

As described above, the flatness measuring mechanism of the present invention focuses on the use of a cylindrical motor and an air bearing. The wafer is point-pressed by each clamp claw to cause distortion. Without being clamped
The rotor is supported by air bearings and rotates the wafer smoothly at high speed. The two optical distance measuring devices scan the entire surface of both sides of the wafer in a spiral and measure each distance. The amount of unevenness on the entire surface of the wafer is accurately calculated from the data, and there is a great effect that contributes to the flatness measurement technique.

[Brief description of the drawings]

FIG. 1 is an exploded view of a flatness measuring mechanism according to an embodiment of the present invention.

FIG. 2 is a sectional view of a flatness measuring mechanism.

FIG. 3 is a configuration diagram of a clamp claw.

FIG. 4 is a configuration diagram of an initial flatness inspection apparatus.

FIG. 5 is a configuration diagram of one proposal of a flatness inspection device.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Wafer, 1a ... Front surface, 1b ... Back surface, 2 ... Rotation mechanism,
Reference numeral 3 denotes a distance measuring unit, 31, 31a, 31b: an optical distance measuring device, 32: a carriage mechanism 33: an unevenness calculating circuit, 4: a wafer rotating mechanism, 41: a cylindrical motor, 411: a cylindrical stator, 4111 ... Moving table, 4112: Fixed table, 4113: Support plate, 412: Cylindrical rotor, 413a, 413b
… Step ring, 414a to 414c… clamp claw, 4141… fixing piece, 4142… pressing piece, 42… support, 421… cylinder, 422a
422c: mounting bracket, 423: air injection hole, 424: air bearing, 5: distance measuring unit, 51a, 51b: support column, 52a, 52b: optical distance measuring device, 10: flatness measuring mechanism of the present invention, B
... Base, M ... Guide groove, G ... Gap, K ... Ball,
_SP : spring, R: radius of wafer.

Claims (2)

[Claims] The present invention comprises a cylindrical stator and a cylindrical rotor fitted in the stator and supported by an air bearing, and is arranged along a guide groove of a fixed plate fixed to a base with respect to a rotating shaft. A wafer rotating mechanism having a motor that moves in a right angle direction, a plurality of clamp claws provided on an end face of the rotator, and that clamps a wafer to be inspected, and a fixed interval corresponding to both surfaces of the clamped wafer And two optical distance measuring devices that scan the front and back surfaces of the wafer in a spiral manner by moving the motor and measure the respective distances. A wafer flatness measurement mechanism. 2. Each of the clamp claws includes a fixed piece fixed to an end face of the rotor, wherein a ball is fitted on a surface of the clamp claw, and a pressing piece joined to the fixed piece and urged by a spring. 2. The flatness measuring mechanism for a wafer according to claim 1, wherein the wafer is point-pressed and clamped by the two balls.