JPH06213620A - Optical object shape measuring device - Google Patents

Abstract

PURPOSE:To measure the data concerning an object without touching it by means of a device with a simple constitution. CONSTITUTION:An optical object shape measurement device, which has plural photoelectric transfer elements outputting luminance signals according to a received light level, is provided with an image sensor 5 arranged so as to face the edge of a silicon wafer, a binarization converting part 62 carrying out binarization according to the luminance signal level from the photoelectric transfer elements, a counter 63 counting the data of one side level between these binary data, a resister 64 outputting the counted value to a central control part 67, and the like. The central control part, 67 measures a diameter of the silicon wafer and the like on the basis of the counted value.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a measuring device for contactlessly measuring the length, position, etc. of an object using an optical sensor having photoelectric conversion elements arranged in an array.

[0002]

2. Description of the Related Art Conventionally, a measuring device for measuring the length, position, etc. of an object without contact has been known. This measuring device has an area image sensor including a photoelectric conversion element, a TV camera, or the like. The area image sensor or the like is used to two-dimensionally image an object, and the imaged image is processed. The length, position, etc. of the object are measured based on the obtained image signal.

[0003]

However, since the image captured by the area image sensor or the like is two-dimensional, it is necessary to perform image processing based on the two-dimensional data. Therefore, there are problems that the circuit becomes extremely complicated and that image processing requires a relatively long time. Moreover, since the area image sensor, the TV camera, and the like are relatively expensive, it is desirable to use a low-cost sensor.

The present invention solves the above problems, and an object of the present invention is to provide an optical object shape measuring apparatus for contactlessly measuring data on an object with a relatively simple structure.

[0005]

In order to achieve the above object, the present invention provides an optical sensor in which a plurality of photoelectric conversion elements for outputting a luminance signal according to a light receiving level are arranged in an array, and an optical sensor. A light source arranged to face the sensor at a predetermined distance, a binarizing means for binarizing in accordance with the level of the luminance signal from the photoelectric conversion element, and one level of these binary data. Is provided with a counting means for counting the data and a converting means for converting the count value into a measured value, and an object to be measured is interposed between the optical sensor and the light source.

According to the second aspect of the invention, there is provided a rotation driving means for rotating the object while the object is interposed between the optical sensor and the light source.

[0007]

According to the optical object shape measuring apparatus of the first aspect, the brightness signal is output from each photoelectric conversion element of the optical sensor in accordance with the object to be measured which is interposed between the optical sensor and the light source. The luminance signal is binarized, data of one level of the binarized data is counted, and the count value is converted into an actual measurement value to measure the size of the object or the like. .

According to the optical object shape measuring apparatus of the second aspect, the optical sensor which receives the light in a one-dimensional manner by rotating the object while the object is interposed between the optical sensor and the light source. It is possible to measure two-dimensional data such as the position of an object.

[0009]

1 is a perspective view showing an embodiment of an optical object shape measuring apparatus according to the present invention. This measuring apparatus can be applied to the dimension inspection of a disk-shaped silicon wafer (object to be measured) S in a semiconductor manufacturing line. In the figure, reference numeral 1 is a chuck on which the silicon wafer S is placed, 2 is a drive motor connected to the chuck 1 and 5
Is a linear image sensor disposed slightly above the upper surface of the chuck 1 and apart from the center of rotation of the chuck 1 by a predetermined dimension, and 3 and 4 are below the linear image sensor 5 and a linear image sensor 5 Reference numeral 6 denotes a light source and a convex lens, which are arranged so as to face each other, and 6 is a main body of the apparatus.

The chuck 1 is formed such that the diameter of its upper portion is larger than the diameter of its lower portion, and a suction port 10 connected to the lower surface of the lower portion is formed on the upper surface of the upper portion thereof, while the toothed pulley 12 is formed on the lower portion thereof. Is provided. The suction port 10 is connected to an air suction means (not shown) via a hose 100 connected to the lower part. Then, the silicon wafer S is attracted to the suction port 10 by sucking air from the suction port 10 to the air suction means. The chuck 1 is rotatably supported by a support body (not shown) at an appropriate position on the upper part or the lower part. The above toothed pulley 1
A synchronous belt 11 for transmitting the rotational force of the drive motor 2 to the chuck 1 is stretched between the rotary shaft 2 and the rotary shaft of the drive motor 2. The rotation force of the drive motor 2 is transmitted to the chuck 1 by directly connecting the rotation shaft of the drive motor 2 to the chuck 1 or by connecting the rotation shaft of the drive motor 2 to the chuck 1 via a transmission mechanism such as a gear. You may do it.

The drive motor 2 rotates according to a control signal from the apparatus body 6. An encoder 20 is connected to the lower part of the drive motor 2. The encoder 20 detects the rotation angle of the chuck 1 and outputs it to the apparatus body 6. When the drive motor 2 whose rotation angle is accurately controlled by a control signal from the apparatus body 6 is used, the encoder 20
Can be omitted.

The light source 3 is composed of a point light source such as an LED, and is arranged at the focal position of the convex lens 4. The convex lens 4 converts the diffused light from the light source 3 into parallel rays and guides them to the linear image sensor 5.

The linear image sensor 5 has photoelectric conversion elements arranged in one direction (in the form of an array), and a voltage signal (luminance signal) corresponding to the light receiving level of these photoelectric conversion elements is sent to the apparatus main body 6. It is designed to output. The linear image sensor 5 is arranged so that the arrangement direction of the photoelectric conversion elements is the radial direction of the chuck 1. Then, when the silicon wafer S is rotated while being attracted onto the chuck 1, the edges of the silicon wafer S are aligned with the photoelectric conversion element of the linear image sensor 5 and the convex lens 4.
I am trying to be in between. The position of the linear image sensor 5 may be adjustable.

The linear image sensor 5 has a transfer section and an output section (not shown), and transfers the accumulated charges received by each photoelectric conversion element by receiving a shift pulse signal SH from a CCD control section 60 described later. It is designed to be transferred to the department all at once. In addition, the transfer unit transfers the transferred accumulated charge to C
1 in synchronization with the clock signal CLK from the CD controller 60
The pixels (one photoelectric conversion element) are sequentially transferred to the output section. The output section converts the accumulated charge corresponding to each pixel from the transfer section into a voltage signal and sequentially outputs the voltage signal to a binarization conversion section 62 described later.

The apparatus body 6 controls the drive motor 2 and the like, and based on signals from the encoder 20 and the linear image sensor 5, the diameter of the silicon wafer S, the center of the silicon wafer S, and the center of rotation of the chuck 1. The data regarding the silicon wafer S such as the deviation of the angle and the orientation flat (hereinafter, abbreviated as the orientation flat) are measured. The orientation flat is used for the silicon wafer S in the photolinography process (not shown).
It serves as a reference when aligning the mask with the mask and is formed as a linear notch in a part of the circumference of the silicon wafer S.

Next, the internal structure of the apparatus body 6 will be described with reference to the block diagram of FIG. Device body 6
Is a binarization conversion unit 62 for binarizing the output signal from the linear image sensor 5, a counter 63, a register 64, a 3-state buffer 65 as an output means to the central control unit 67, and the 3-state buffer 65. A central control unit (CPU) 67 that performs measurement calculation of data on the silicon wafer S based on the data of 1), a display unit 68 that outputs the calculation result and the like, a printer 69, and the like.

The CCD control unit 60 sends a shift pulse signal S of a predetermined cycle to the linear image sensor 5 based on a master clock signal from a clock generator (not shown).
H (see FIG. 3) and the clock signal CLK (see FIG. 3) are output, and the clock signal CL is sent to the measurement control unit 61.
It outputs K. The linear image sensor 5 outputs a dummy signal until a predetermined period (a predetermined number of pixels) elapses from the rising of the shift pulse signal SH, and then outputs a voltage signal corresponding to each pixel (photoelectric conversion element). It is like this. The linear image sensor 5 outputs an invalid signal during the period from the output of all the voltage signals corresponding to each pixel to the input of the next shift pulse signal SH.

The measurement control unit 61 outputs a window signal W having a predetermined width to the counter 63 based on the clock signal CLK from the CCD control unit 60 and a set signal ST having a predetermined width to the register 64. . In addition,
As shown in FIG. 3, the window signal W determines the output period of the voltage signal and is output as a high level during this period, and the set signal ST determines the output period of the invalid signal during the high period. Output as a level.

The binarization conversion unit 62 compares the voltage signal V from the linear image sensor 5 corresponding to each pixel with a preset reference voltage E, and compares the voltage signal V corresponding to each pixel. Is binarized and converted. Then, as shown in FIG. 4, the binarization conversion unit 62 sets the voltage signal V (reference voltage E or higher) corresponding to the pixel receiving the light from the light source 3 to a high level, and the light from the light source 3 is converted into silicon. The voltage signal V corresponding to the pixels shielded by the wafer S
(Less than the reference voltage E) is converted to a low level and sequentially output to the counter 63. Counter 63
Is, for example, a high-level output from the binarization conversion unit 62 is counted for each pixel only during the output period of the window signal W,
This count value is output to the register 64.
The register 64 stores the count value from the counter 63, and stores it and outputs it to the 3-state buffer 65 at least until the output period of the set signal ST elapses. The 3-state buffer 65 has a register 6
The count value from 4 is sent from the central control unit 67 to the set signal S
The signal is output to the central control unit 67 via the data bus 66 according to the read signal CS output immediately after the output period of T has elapsed.

The central control section 67 controls the operation of each section of the measuring apparatus such as the drive motor 2. Further, the central control unit 67 has a calculation means 670 and a memory 671, outputs a read signal CS to the 3-state buffer 65 as necessary, and the register 64 obtained by this is output.
The stored value (count value) is stored in the memory 671 in association with the rotation angle from the encoder 20. Further, the central control unit 67 stores the dimension from the rotation center of the chuck 1 to the linear image sensor 5 and the pitch of the photoelectric conversion elements of the linear image sensor 5, and the register 64 of the register 64 is stored based on these dimensions and pitch. Count value from the center of rotation of chuck 1 to silicon wafer S
It is designed to be converted to the measured dimensions up to the edge of.
The calculation means 670 is for measuring and calculating data relating to the silicon wafer S such as the diameter of the silicon wafer S, the amount of deviation and the dimension of the orientation flat based on the stored contents of the memory 671. Then, the central control unit 67 displays the calculation result on the display unit 68 or the printer 6 as necessary.
9 to output.

The display unit 68 displays according to a control signal from the central control unit 67. The printer 69 prints out in response to a control signal from the central control unit 67. The operation unit 70 has various operation switches such as a measurement start switch.

Next, the operation of the above measuring apparatus will be described with reference to FIG.
~ It demonstrates using FIG. Here, a case will be described in which the deviations X and Y between the center A of the silicon wafer S placed on the chuck 1 and the rotation center B of the chuck 1, the diameter D of the silicon wafer S and the dimension 1 of the orientation flat S1 are measured. . Here, as shown in FIG. 5, a secondary flat (hereinafter referred to as a second flat) S2, which is a linear notch for identifying the crystal orientation of the silicon wafer S, is formed on the peripheral surface of the silicon wafer S. I will explain what you have. The second flat S2 has a smaller size than the orientation flat S1, and in the type of FIG. 5, it is formed at a position deviated from the orientation flat S1 in the clockwise direction by 90 ° in the figure.

After the silicon wafer S is placed on the upper surface of the chuck 1 about the center of rotation of the chuck 1 by a robot or the like (not shown), the silicon wafer S is attracted to the chuck 1 by the air suction force of the suction port 10. When a measurement instruction is given using the operation unit 70 or the like, the above-described measurement for the silicon wafer S is started.

That is, the drive motor 2 is driven, the chuck 1 is rotated, and the silicon wafer S is rotated. Simultaneously with the start of the rotation, the rotation angle is detected in real time by the encoder 20 and output to the central control unit 67, the light source 3 is further turned on, and the linear image sensor 5 receives light at each rotation angle. Then, the voltage signal V corresponding to each pixel is obtained and further binarized. This 2
Of the digitized data, for example, a high level output is counted, and this count value is output to the central control unit 67 as measurement data for each time.

The central control unit 67 converts the count value at each rotation angle into actual measurement data L from the rotation center of the chuck 1 at each rotation angle to the edge of the silicon wafer S, and the actual measurement data L is converted into each rotation angle. It is associated and stored in the memory 671.

Next, the central controller 67 determines the positions of the orientation flat S1 and the second flat S2 of the silicon wafer S from the measured data L at each rotation angle as shown in FIG. That is, if the silicon wafer S does not have the orientation flat S1 and the second flat S2, the measured data L changes sinusoidally with respect to the rotation angle according to the deviation between the center of the silicon wafer S and the rotation center of the chuck 1. However, due to the presence of the orientation flat S1 and the second flat S2, the orientation flat S1 and the second flat S
At the position of 2, the measured data L changes so as to drop relatively rapidly. Therefore, the central control unit 67 determines the change of the actually measured data L with respect to the rotation angle, and the range of the rotation angle at which the actually measured data L changes relatively rapidly as compared with the rotation angle is the orientation flat S1 (S1 in FIG. 6). Is shown) and the second flat S2 (shown as S2 in FIG. 6). The central controller 67 distinguishes the orientation flat S1 and the second flat S2 from the degree of change of the actual measurement data L.

Subsequently, the central control unit 67 determines the orientation flat S1.
In order to calculate the diameter and the like of the silicon wafer S based on the actual measurement data L excluding the actual measurement data L of the rotation angle corresponding to the position of the second flat S2, as shown in FIG. A rotation angle separated by a predetermined angle is set to 0 °, and actual measurement data L corresponding to the rotation angles separated by 45 °, 135 °, and 225 ° are extracted with reference to the rotation angle 0 °.

Then, the central control unit 67 controls the above 45 °,
The deviation between the center of rotation of the chuck 1 and the center of the silicon wafer S and the diameter D of the silicon wafer S are calculated from the measured data L for the rotation angles of 135 ° and 225 °.

That is, as shown in FIG. 5, the measured data from the rotation center B of the chuck 1 at the rotation angle 45 ° to the edge C of the silicon wafer S is set to L1, and the rotation center of the chuck 1 at the rotation angle 135 °. The measured data from B to the edge E of the silicon wafer S is L2, the measured data from the rotation center B of the chuck 1 at the rotation angle of 225 ° to the edge F of the silicon wafer S is L3, and C-B- Assuming that the line connecting F is the x-axis and the line connecting E-B orthogonal to this x-axis is the y-axis, the rotation center B of the chuck 1 and the center A of the silicon wafer S in the x-direction and the y-direction are The deviations X and Y are calculated by the following equation. However, X is positive in the B-C direction and Y is positive in the B-E direction.

X = (L1−L3) / 2 (1) Y = (L2 ² −L1 · L3) / (2 · L2) (2) The above equation (2) is derived from the following equation. Get burned.

(L1-X) ² + Y ² = (L2-Y) ² + X ² = (D / 2) ^{2 Further} , the diameter D of the silicon wafer S is obtained by the above equations (1) and (2). It is calculated by the following formula using X and Y.

D = 2√ ((X−L1) ² + Y ² ) ... (3) Further, the dimension 1 of the orientation flat S1 is obtained by the following equation.

L = 2√ ((D / 2) ² −L4 ² ) (4) Here, a method of obtaining L4 used in the above equation (4) will be described with reference to FIG. This L4 is a silicon wafer S
From the center A to the midpoint H of the edge of the orientation flat S1. The A-H line is geometrically oriented by the orientation flat S.
It becomes perpendicular to the edge of 1. The dimension of the line A-H is the shortest distance from the center A of the silicon wafer S to an arbitrary edge position of the orientation flat S1.

First, the rotation angles θ1 and θ2 corresponding to both end positions of the orientation flat S1 are extracted from the above-mentioned FIG. Next, the rotation angles θ1 and θ2
The rotation angle θ3, which is the intermediate point of
Measured data L5 corresponding to 3 is the rotation center B of the chuck 1.
To the midpoint H of the edge of the orientation flat S1. This is because the rotation angle θ3 is the orientation flat S
It is because whether or not the rotation angle corresponding to the midpoint H of the edge 1 accurately matches the extraction accuracy of the rotation angles θ1 and θ2.

Next, the angle θ4 of the line B-A from the deviations X and Y is calculated using the following equation, and the rotation angle θ3 and the angle θ are calculated.
The angle difference θ5 with respect to No. 4 is calculated using the following equation, and the dimension L6 from the rotation center B of the chuck 1 to the center A of the silicon wafer S is calculated using the following equation.

Θ4 = 225 ° + tan to ¹ (Y / X) (5) θ5 = θ4-θ3 (6) L6 = √ (X ² + Y ² ) (7) Then, the above L5 and L6 , L5 using L, θ5
Calculate ´.

L4 ′ = √ (L5 ² + L6 ² −2 · L5 · L6 · cos θ5) (8) Equation (8) is derived from the following equation.

L4 ′ ² = (L6 · sin θ5) ² + (L5-L6 · cos θ5) ² This L4 ′ is obtained by measuring the measured data L5 from the rotation center B of the chuck 1 to the midpoint H of the edge of the orientation flat S1. This is assumed to be actual measurement data, and may be slightly deviated from the true actual measurement data from the rotation center B of the chuck 1 to the midpoint H of the edge of the orientation flat S1. Therefore, in view of the fact that the line A-H is the shortest distance from the center A of the silicon wafer S to any edge position of the orientation flat S1 as described above, a range of a predetermined angle with the rotation angle θ3 as the center. In the above, actual measurement data L5 corresponding to each rotation angle is extracted, and the actual measurement data L5 and the above equations (5) to (8) are extracted.
L4 'corresponding to each of the above rotation angles is obtained by using the formula, and of these L4', the one having the smallest value of L4 'is determined as the true dimension L4.

Then, the central control unit 67 shifts X, Y between the rotation center B of the chuck 1 and the center A of the silicon wafer S obtained by the above equations, and the diameter D of the silicon wafer S.
It is determined whether or not the dimension 1 of the orientation flat S1 is within the standard of the silicon wafer S, and the calculated value and the determination result are output from the display unit 68 and the printer 69. The silicon wafer S for which the above measurement and discrimination have been completed is removed from the chuck 1 by a robot (not shown) or the like, and is transferred to, for example, a photolinography process.

As described above, based on the count value as the one-dimensional data obtained by using the linear image sensor 5 which images the object to be measured one-dimensionally, the rotation center B of the chuck 1 which is the two-dimensional data. Since the deviations X and Y between the center and the center A of the silicon wafer S, the diameter D of the silicon wafer S, and the dimension 1 of the orientation flat S1 can be obtained, it is possible to obtain an image by using an area image sensor, a TV camera, or the like 2
The configuration can be simplified as compared with the case where the deviations X and Y, the diameter D, and the dimension 1 of the orientation flat S1 are obtained based on the dimension data.

In the above description, the dimension 1 of the orientation flat S1 was obtained based on the data shown in FIG.
Using a robot or the like, the upper silicon wafer S is moved by the displacements X and Y determined by the above equations (1) and (2) to rotate the center of rotation B of the chuck 1 and the center A of the silicon wafer S.
Alternatively, the silicon wafer S may be again attracted to the chuck 1 in this state, and the actual measurement data L for each rotation angle may be obtained again. In this case, the diameter D of the silicon wafer S and the dimension L4 from the center A of the silicon wafer S to the midpoint H of the edge of the orientation flat S1 can be directly obtained from the actual measurement data L. Therefore, the calculation process of the diameter D of the silicon wafer S can be omitted, and the calculation process of the dimension 1 of the orientation flat S1 can be simplified.

Since the second flat S2 is formed for identifying the crystal orientation of the silicon wafer S,
The orientation flat S depends on the crystal orientation of the silicon wafer S.
The positional relationship between 1 and the second flat S2 is fixed. Therefore, the type of crystal orientation of the silicon wafer S can be identified from the measured data L for each rotation angle.

Further, the apparatus main body 6 may output data such as the above-mentioned deviations X and Y and the rotation angle corresponding to the positions of the orientation flat S1 and the second flat S2 to the photolinography process, for example. In this case, in the photolithography process, the centering of the silicon wafer S can be performed based on the data of the displacement X, Y and the like.

The object to be measured is a silicon wafer S.
However, it may be a processed product such as a linear product or a square plate. When inspecting the dimensions of the linear object, the count value from the 3-state buffer 65 is compared with a preset reference value while the linear object is placed between the linear image sensor 5 and the convex lens 4. You can inspect just by doing.

Further, in the above description, since the deviations X and Y, the diameter D of the silicon wafer S and the dimension 1 of the orientation flat S1 are simultaneously measured, the actual measurement data L is obtained for each rotation angle. , Y and the diameter D of the silicon wafer S can be obtained by substituting only the three actual measurement data L1 to L3 into the equations (1) to (3) described above. Therefore, when measuring only the deviations X and Y and the diameter D of the silicon wafer S, the encoder 20 detects the rotation angles of 45 °, 135 °, and 225 ° apart from the predetermined rotation angle of the chuck 1 as a reference. It is only necessary to actually measure the actual measurement data L corresponding to these rotation angles by the linear image sensor 5 or the like. In this case, the amount of data to be measured is reduced, so that the deviations X and Y and the diameter D of the silicon wafer S can be measured at higher speed.

[0046]

According to the present invention, the luminance signal from each photoelectric conversion element is binarized, and one level data of the binarized data is counted, and the size of the object is calculated based on the counted value. Since the measured values such as are converted, the dimensions and the like of the object can be appropriately measured with a simple configuration.

Further, since the count value is obtained by rotating the object while interposing the light source and the optical sensor, it is possible to measure two-dimensional data such as the position of the object.

[Brief description of drawings]

FIG. 1 is a perspective view showing an embodiment of an optical object shape measuring apparatus according to the present invention.

FIG. 2 is a block configuration diagram showing an internal configuration of a device body of the optical object shape measuring device according to the present invention.

FIG. 3 is a timing chart showing a relationship between a shift pulse signal, a clock signal and the like and an output from the linear image sensor.

FIG. 4 is an operation diagram showing the relationship between the output of the linear image sensor and the output of the binarization conversion unit.

FIG. 5 is a plan view showing the relationship between the center of rotation of a chuck and data on a silicon wafer.

FIG. 6 is an image diagram showing an example of a relationship between a rotation angle of a silicon wafer and actually measured data.

FIG. 7 is a plan view for explaining how to determine the orientation flat dimension of a silicon wafer.

[Explanation of symbols]

 1 chuck 2 drive motor 3 light source 4 convex lens 5 linear image sensor 6 device body 60 CCD control unit 61 measurement control unit 62 binarization conversion unit 63 counter 64 register 65 3 state buffer 66 data bus 67 central control unit (CPU) 68 display Part 69 Printer 70 Operation part S Silicon wafer S1 Orientation flat S2 Secondary flat

Claims (2)

[Claims] 1. An optical sensor in which a plurality of photoelectric conversion elements that output a luminance signal according to a light receiving level are arranged in an array, a light source that is arranged facing the optical sensor at a predetermined distance from each other, and Binarizing means for binarizing according to the level of the luminance signal from the photoelectric conversion element, counting means for counting data of one level of these binarized data, and this count value as an actual measurement value. An optical object shape measuring apparatus, comprising: a converting means for converting, wherein an object to be measured is interposed between the optical sensor and the light source. 2. The optical object shape measuring apparatus according to claim 1, further comprising a rotation driving means for rotating the object in a state where the object is interposed between the optical sensor and the light source. Type object shape measuring device.