JP3528785B2 - Wafer pre-alignment apparatus and wafer edge position detection method - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pre-alignment apparatus used in a semiconductor manufacturing apparatus for detecting the position of a substantially circular semiconductor wafer, the position of an orientation flat, a notch or the like, and for positioning.

[0002]

2. Description of the Related Art A conventional pre-alignment sensor device will be described with reference to FIG. In FIG. 12, the table 4 is fixed to the tip of the shaft on the upper side of the motor 2 so that it can rotate. When the wafer 1 is placed on the table 4, the light source 7 provided below the outer periphery of the wafer 1 It is possible to block the space between the CCD linear sensor 5 which is the light receiving portion provided above. 26 is a pre-alignment sensor, which includes a light source 7, a lens 8, a CCD linear sensor 5, and C
It is composed of a CD linear sensor mounting substrate 6 and a frame 35 in which the side surfaces are U-shaped and fixed to each other. The light from the light source 7 is collimated by the lens 8 and received by the CCD linear sensor 5. Reference numeral 10 denotes a sensor controller, which is composed of a CCD linear sensor drive unit 11, a wafer edge detection unit 12, a light emission drive unit 13, a memory 14, a CPU 15, and a data transfer unit 16. The system controller 17 includes a memory 18, a CPU 19, a data transfer unit 20, an encoder signal processing unit 21, a motor command unit 22,
It comprises a wafer presence / absence sensor signal section 23 and a wafer transfer control section 24. The light emission drive section 13 gives a current to the light source 7 to cause it to emit light. The CCD linear sensor driving unit 11 is a CC that is composed of a large number of pixels arranged in a straight line and having a fixed order.
A readout gate pulse (ROG) signal and a transfer pulse signal, which are timing signals for converting the accumulated charge of the pixel into an electric signal, are sent to the D linear sensor 5, and the first signal at the scan start end is sent according to the transfer pulse signal. The accumulated charges are sequentially read from the pixels of No. 1 and the accumulated charges of all the pixels are sequentially output as detection signals, and the detection signals and the like are received by the wafer edge detection unit 12 to detect the position. The detection information is output to the outside via the data transfer unit 16. The motor commander 22 of the system controller 17 outputs a rotation command signal to the motor 2 to rotate the motor 2. The wafer presence / absence sensor 25 is an optical type, a contact type, or a capacitance type sensor, and is provided separately from the pre-alignment sensor 26. It is possible to detect whether or not there is a wafer. Encoder signal processing unit 21
Receives the rotation signal of the encoder 3 connected to the motor 2 and detects the rotation speed of the motor 2.

Here, the CCD linear sensor 5 will be supplementarily described. In order to project a bright and dark image on the CCD linear sensor 5 to generate a wafer edge signal, it is necessary to accumulate electric charges in the CCD linear sensor 5 for an optimum fixed time. As a method of accumulating the charges for the optimum fixed time, (1) ON / OFF of the light emission is controlled by the light emission drive unit 13 in synchronization with the measurement command so that a fixed amount of the charges is stored in the CCD linear sensor 5 for each measurement. A method of controlling the irradiation light 9 and the ROG signal so as to be accumulated, (2) the CCD linear sensor mounting substrate 6 is equipped with an electronic shutter function of the CCD linear sensor, and the light emission drive unit 13 constantly emits the irradiation light 9 to emit the irradiation light 9. A method of irradiating with a constant amount of light and controlling the accumulation time of charges accumulated in the CCD linear sensor 5 independently of the ROG signal, (3) The CCD linear sensor driving unit 11 outputs the ROG signal and the transfer pulse signal at a constant cycle. A method of outputting and accumulating electric charges accumulated in the CCD linear sensor 5 is known. The method (1) has a problem that the repeated measurement cycle becomes slow and the processing of the sensor controller 10 becomes complicated, and the method (2) requires the electronic shutter function of the CCD linear sensor to be mounted. There are problems that wiring is increased, cost is increased, and processing of the sensor controller 10 is complicated. Therefore,
Conventionally, the method (3) is often adopted in consideration of speeding up of the pre-alignment time, simplification of processing, and cost reduction of the apparatus.

With the above configuration, the system controller 17 and the sensor controller 10 operate as follows. When there is no wafer on the table 4, the system controller 17 rotates the table 4 after the wafer transfer system (not shown) transfers the wafer to the table 4, and the encoder signal processing unit 21 measures the signal from the encoder 3. Then, when the predetermined rotation position is reached, a measurement command is output to the sensor controller 10 via the data transfer unit 20 to start the measurement. Sensor controller 10
Receives the measurement command output, the CCD linear sensor 5
The wafer edge signal output by the wafer edge detector 12
And outputs the wafer edge detection value to the system controller 17 via the data transfer unit 16. The system controller 17 stores the received wafer edge detection value and measurement rotation position in the memory 18, and the wafer 1
The same operation is repeated until the rotation is completed or more, and the outer circumference data for one round of the wafer is recorded in the memory 18. The central position of the wafer 1 and the orientation flat or notch position are obtained by the CPU 19 based on the outer circumference data for one round of the wafer recorded in the memory 18.

As a second conventional technique, Japanese Patent Laid-Open No. 8-64660 discloses a method for accurately positioning a point light source instead of a parallel light. This will be described with reference to the block diagram of the detection device. The table 4 can be rotated by a motor 2, and a light source 7 is provided on the lower side of the wafer 1 on the table 4 and a CCD linear sensor 5 as a light receiving section is provided on the upper side. The light projected from the light source 7 onto the outer peripheral portion of the wafer 1 is blocked by the wafer 1 and a bright and dark image is projected on the CCD linear sensor 5. This image is binarized by the signal processing unit 34b of the sensor controller 10c, and the value of the data at the moment of changing from dark to bright in the binarized data is held by the latch, and is stored in the memory 3 of the system controller 17c.
It is recorded in 2b. The above operation is repeated until the wafer 1 makes one revolution, and the outer peripheral data for one round of the wafer is stored in the memory 3
It is recorded in 2b. At the same time, the signal from the encoder 3 directly connected to the motor 2 that rotates the table 4 is input to the system controller 17c, and the motor rotation position and wafer edge position data are simultaneously recorded in the memory 32b. Based on the outer circumference data for one round of the wafer recorded in the memory 32b, the arithmetic unit 33b calculates the center position of the wafer 1, the orientation flat,
The notch position is obtained.

[0006]

However, conventionally, when a wafer presence / absence sensor is attached in addition to the pre-alignment sensor, there are problems that the device size becomes large, the cost is high, and the wiring is increased. If the CCD linear sensor drive cycle is set to a fixed cycle, the table 4
When the rotation position obtained by processing the signal of the encoder 3 by the encoder signal processing unit 21 becomes the same as the measurement position by outputting the measurement command to the sensor controller 10 to detect the wafer edge. Since the measurement command and the CCD linear sensor drive cycle are asynchronous, the measured wafer edge detection value is different from the original measurement position and becomes a measurement value that includes an uncertain error, which hinders high-speed pre-alignment and high accuracy. There is a problem that the diameter of the wafer is increased and the throughput is improved.

Therefore, an object of the present invention is to provide a wafer presence / absence detection method and a wafer presence / absence detection apparatus which can easily detect the presence / absence of a wafer by adding a device and a process to a pre-alignment sensor. It is an object of the present invention to provide a method capable of performing highly accurate position measurement by correcting an error between the measurement position of (1) and the measurement position at which the accumulation of the CCD linear sensor is output.

Further, in the prior art, when a wafer made of an opaque material such as silicon is handled, the CCD linear sensor is hardly affected by dust that may be attached to the CCD linear sensor. It is known that it is better to scan the CCD linear sensor from the direction opposite to the wafer insertion direction, since when the wafer made of a transparent material such as glass is handled, only the edge portion is shielded from light. However, in the conventional wafer edge position detection sensor, the scan direction of the CCD linear sensor is fixed, and the same wafer edge position detection sensor cannot handle both opaque and transparent wafers. There was a point. Therefore, the present invention is highly versatile in handling wafers made of both opaque and transparent materials, and is not affected by any surface treatment on the surface of a wafer made of a transparent material. An object of the present invention is to provide a method capable of detecting a position and a wafer edge position detection sensor device.

[0009]

In order to solve the above problems, the present invention provides a wafer rotating means capable of holding a substantially circular wafer on a table having a vertical rotation axis and rotating the wafer. Rotation detection means for detecting the rotation angle of the wafer rotation means and converting it into an electric signal; and light projection means for projecting light onto the peripheral portion of the wafer held by the wafer rotation means,
It consists of a large number of pixels arranged in a straight line in a fixed order,
A CCD linear sensor that sequentially reads the accumulated charge from the first pixel according to the transfer pulse signal and sequentially outputs the accumulated charge of all pixels as an electric signal, and one pixel of the CCD linear sensor within the light projecting range of the light projecting unit. Turn on / off the photodiode provided near the eye and the light projecting means.
When the light emission drive unit that performs F, the wafer edge detection unit that receives the signal of the CCD linear sensor to detect the edge of the wafer, and the signal of the CCD linear sensor and the signal of the rotation detection unit, the outer periphery of the wafer is detected. Repeatedly detecting the edge position of the wafer at a plurality of arbitrary points across,
In a wafer pre-alignment apparatus that stores in a built-in memory, and a signal processing unit that determines at least one of an orientation flat position, a notch position, and a central position of the wafer based on the detected value, a signal of the photodiode is detected. A light amount signal processing unit that receives and detects the light amount, and a comparison determination unit that determines the presence or absence of the wafer by comparing the light amount of the photodiode and the signal of the wafer edge detection unit, and the edge of the wafer is detected. When the comparison / determination means determines that the wafer is present, the signal processing means determines that the unwanted matter is attached to the CCD linear sensor if the light amount is the same as the value at the time of light entry. It is characterized by that.

Further, according to the present invention, a wafer rotating means capable of holding and rotating a substantially circular wafer on a table having an axis of rotation in the vertical direction, and a rotation angle of the wafer rotating means are detected and converted into an electric signal. It comprises a rotation detecting means for converting, a light projecting means for projecting light on the peripheral portion of the wafer held by the wafer rotating means, and a large number of pixels arranged linearly and having a predetermined order. A CCD linear sensor that sequentially reads the accumulated charges from the pixels and sequentially outputs the accumulated charges of all pixels as an electric signal, a light emission drive unit that controls ON / OFF of the light emission of the light projecting unit, and the CCD that is triggered by a measurement command. Wafer edge detector for detecting a wafer edge signal that changes from one pixel to the last pixel of the linear sensor, the CCD linear sensor signal and the rotation detection When the step signal is received, the edge position of the wafer is repeatedly detected at a plurality of detection positions planned in advance over the outer circumference of the wafer and stored in the built-in memory. Based on the detected value, the orientation flat of the wafer is detected. In a wafer pre-alignment apparatus including a signal processing means for determining at least one of a position, a notch position, and a center position, the signal processing means converts the charge accumulated in the pixel into an electric signal in the CCD linear sensor at a constant cycle. A CCD that outputs a ROG signal and a transfer pulse signal, which are timing signals for conversion, accumulates charges for an optimum fixed time in the CCD linear sensor, and sequentially outputs the accumulated charges of all pixels of the CCD linear sensor as an electric signal. From the linear sensor driving unit and the measurement command corresponding to a plurality of pre-planned measurement positions over the outer circumference of the wafer, the R A first timer for measuring the time τ until the G signal, and a second timer for measuring the time T between measurement commands corresponding to a plurality of pre-planned measurement positions over the outer circumference of the wafer. The ROG signal is used as a trigger to correct an angular error between the circumferential position of the wafer that has output the accumulated charge of the CCD linear sensor and the measurement position, using the time τ and the time T. It is characterized by that.

The function of correcting the angle error is that when the light projecting means projects a constant light, the angle between a plurality of pre-planned measurement positions over the outer circumference of the wafer is θ [de].
g], the time measured by the first timer is τ [se
c], the time measured by the second timer is T [se
c], a plurality of pre-planned measurement positions along the outer periphery of the wafer and the C by the ROG signal.
The angle error φ [deg] between the position where the accumulated charge of the CD linear sensor is output is φ = θ × (τ / T), and φ is set at a plurality of pre-planned measurement positions over the outer circumference of the wafer.
Is characterized by adding and correcting.

By the above means, the presence / absence of a wafer can be detected without providing a wafer presence / absence sensor separately from the pre-alignment sensor, and the measurement position can be detected without synchronizing the measurement command with the driving cycle of the CCD linear sensor. It is possible to correct the error and enable highly accurate measurement.

Wafer rotating means capable of holding and rotating a substantially circular wafer on a table having a vertical rotation axis, and rotation detecting means for detecting the rotation angle of the wafer rotating means and converting it into an electric signal. And a light projecting means for projecting light on the peripheral portion of the wafer held by the wafer rotating means, and a large number of pixels arranged in a straight line and having a predetermined order. The first pixel at the scan start end according to the transfer pulse signal. A CCD linear sensor that sequentially reads accumulated charges from pixels and sequentially outputs accumulated charges of all pixels as an electric signal, and binarizes when a signal from the CCD linear sensor is received, and scans from the scan start end to binarize Data first goes from L level (or H level) to H level (or L
Signal processing means for setting the number of transfer pulses up to a change point that changes to a level) as the edge position of the wafer, and detecting the edge position of the opaque wafer in the wafer pre-alignment device for detecting the edge position of the wafer. At the time, the scan start end is detected in the direction of the central axis of the wafer rotating means, and when detecting the edge position of the transparent wafer, the scan start end is opposite to the central axis of the wafer rotating means. When the signal of the CCD linear sensor is received by the signal processing means, the signal processing means performs binarization and then inversion, and scans from the scan start end, and the inverted data is first L level (or H level). ) To an H level (or L level) change point is detected as the edge position of the wafer. There.

Wafer rotating means capable of holding and rotating a substantially circular wafer on a table having a vertical rotation axis, and rotation detecting means for detecting the rotation angle of the wafer rotating means and converting it into an electric signal. And a light projecting means for projecting light onto the peripheral portion of the wafer held by the wafer rotating means, and a large number of pixels arranged linearly and having a predetermined order. The first pixel located at the scan start end according to the transfer pulse signal. A CCD linear sensor that sequentially reads out the accumulated charges from all the pixels and sequentially outputs the accumulated charges of all pixels as an electric signal; and a signal processing unit that receives the signal from the CCD linear sensor and detects the edge position of the wafer. In the wafer pre-alignment apparatus, when the signal processing means inputs a linear sensor installation direction inversion signal,
When the signal from the CCD linear sensor is received, it is binarized, then inverted, and scanned from the scan start end, and the inverted data is first changed from L level (or H level) to H level.
It is characterized by having a function of setting the number of transfer pulses up to a change point changing to a level (or L level) as an edge position of the wafer. Therefore, the same wafer pre-alignment device can be used to handle both opaque and transparent wafers with a simple operation, and even if a surface treatment is performed on a wafer surface made of a transparent material, The wafer edge position can be correctly detected without being affected.

[0015]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings. 1 is a block diagram showing the configuration of a wafer pre-alignment apparatus which is a first embodiment of the present invention. FIG. 2 is a flow chart showing the processing procedure of the system controller used in the wafer pre-alignment apparatus of the present invention,
FIG. 3 is a flowchart showing the processing procedure of the sensor controller used in the wafer pre-alignment apparatus of the present invention. In FIG. 1, reference numeral 29 denotes a wafer positioning mechanism, which is composed of a table 4 which holds a wafer 1 to be measured and is rotated by a motor 2, and an encoder 3 which is connected to the motor 2 and detects a rotational position of the motor 2. Has been done. 26
Is a pre-alignment sensor, which has a U-shaped frame 35 when viewed from the side, a light source 7 provided at the bottom of the frame, a lens 8 for collimating the light of the light source 7, and a collimated light. It is composed of a CCD linear sensor 5 and a photodiode 27 provided near the first pixel of the CCD linear sensor 5. The CCD linear sensor 5 is composed of a large number of pixels arranged linearly and having a fixed order.
The accumulated electric charge that is substantially proportional to the incident light from the light source 7 is read by sequentially scanning from the second pixel, and the accumulated electric charges of all the pixels are sequentially output as an electric signal. Reference numeral 10 denotes a sensor controller, which includes a CCD linear sensor driving unit 11 that drives the CCD linear sensor 5, and a wafer edge detection unit that detects a wafer edge signal at a point where the signal changes by scanning from one pixel to the last pixel of the CCD linear sensor 5. 12, a light emission drive unit that controls ON / OFF of the light emission of the light source 7, a photodiode signal processing unit 28 that acquires the light amount value of the photodiode 27, and when the light from the light source 7 is received by the photodiode 27 and on the wafer 1. CP for determining the presence / absence of a wafer by using the signals of the memory 14, the wafer edge detection unit 12, and the memory 14 that store the light amount value when the light is blocked
It is composed of a U15 and a data transfer unit 16 that transfers signals with the outside. 17 is a system controller,
A motor command unit 22 for rotating the motor 4 and an encoder signal processing unit 2 for processing the rotational position signal of the encoder 3.
1. A memory 16, C for storing the measured rotational position in advance and storing the wafer edge detection value in association with the measured rotational position
The PU 19 includes a sensor controller 10 and a data transfer unit 20 that transfers signals. When the CPU 19 calculates at least one of the orientation flat, the notch position, and the center position of the wafer from the measured rotation position and the wafer edge detection value stored in the memory 16, it sends a command to a wafer transfer system (not shown) to place the wafer 1 on the table 4. To the destination. These wafer positioning mechanism 29, pre-alignment sensor 26, sensor controller 10,
The system controller 17 forms a wafer pre-alignment device.

Next, the processing procedure of the system controller 17 will be described with reference to the flowchart of FIG. 201: First, the sensor controller 10 receives information as to whether or not the preparation for measurement is completed, and confirms that the sensor controller 10 is in a measurable state. 202: Next, a measurement command is output to the sensor controller 10 to check whether or not the wafer 1 exists in the wafer positioning mechanism 29. 203: Waiting for the wafer presence / absence information input from the sensor controller 10, 204: Input If the wafer presence / absence information thus obtained is an alarm signal, the measurement is terminated. 205: Based on the wafer presence / absence information input here, it is determined whether or not the wafer 1 is present in the table 4, or even if it is present, it is placed in a normal position, and the wafer 1 is present in the table 4. If not, or if it is placed in an abnormal position, proceed to 206. If not, proceed to 207. 206: A wafer transfer system (not shown) transfers the wafer 1 to a normal position on the table 4. 207: When the wafer positioning mechanism is rotated by the motor commander 22, 208: The rotation position of the encoder signal processing unit 21 is compared with the measurement rotation position stored in the memory 16 in advance, and if the same position is reached, the process proceeds to 209, Otherwise, return to 208. 209: Output a measurement command to the sensor controller 10. 210: Wait for the wafer edge detection value input from the sensor controller 10, and when input, store the wafer edge detection value in the memory 16 in association with the measurement rotation position. 211: If the measurement of the measurement rotational position stored in the memory 16 in advance is completed, the process proceeds to 212. If not, the process returns to 207 and the steps 207 to 211 are repeated. 212: The CPU 19 calculates at least one of the orientation flat, notch position, and center position of the wafer using the measured rotational position of the memory 16 and the detected value of the wafer edge. Transport to the destination. 213: If all the necessary pre-alignment work is completed, the series of steps is terminated, and if not, return to 202 and perform 20.
The procedure from 2 to 213 is repeated.

Next, the processing procedure of the sensor controller 10 will be described with reference to the flowchart of FIG. 301: First, the light source 7 is made to emit light, and the CCD linear sensor 5
To prepare the measurement and drive the system controller 17
The ready signal is output to. 302: Next, the system controller 17 waits for a measurement command input. If the signal is input, the process proceeds to 303, and if not input, the process returns to 302. 303: Wafer edge detection unit 12 starts measurement, CC
A wafer edge signal that changes from one pixel to the last pixel of the D linear sensor 5 is detected. If it cannot be detected, an undetected signal is output to the CPU 15. At the same time, the light amount value of the photodiode 27 is acquired and output to the CPU 15. 304: The CPU 15 determines whether or not the wafer edge is detected. If not detected, the process proceeds to 305, and if detected, the process proceeds to 306. 305: The obtained light amount value of the photodiode 27, the light amount value stored in the memory 14 in advance when the light source 7 emits light, and the irradiation light 9 is incident on the photodiode, and the irradiation light 9 is emitted by the wafer 1. The light amount value when the light is shielded is compared, and if it is the same as when the light is incident, the process proceeds to 307, and if not, the process proceeds to 309. 306: The obtained light amount value of the photodiode 27, the light amount value previously stored in the memory 14 when the light source 7 emits light and the light 9 is incident on the photodiode, and the light 1 is emitted by the wafer 1. The light amount value when the light is shielded is compared, and if it is the same as when the light is incident, the process proceeds to 311. If not, the process proceeds to 313. 307: Judge that the wafer 1 does not exist in the table 4, 308: Output a wafer no signal and an edge undetected signal to the system controller 17, and proceed to 315. 309: The wafer 1 exists on the table 4, but it is judged that the wafer edge exceeds the measurement range of the CCD linear sensor and the table 4 is placed in an abnormal position. 310: The system controller 17 notifies the wafer presence signal. The edge undetected signal is output and the process proceeds to 315. 311: The wafer 1 is not present on the table 4, but the wafer edge is detected, and it is determined that an unnecessary substance is attached to the CCD line sensor 5. 312: An alarm signal is output to the system controller 17 and the process proceeds to 315. 313: The wafer 1 is on the table 4, and the wafer edge is within the measurement range of the CCD linear sensor.
314: The wafer presence signal and the wafer edge detection value are output to the system controller 17, and the process proceeds to 315. 315: The system controller 17 determines that all of the necessary pre-alignment work has been completed, and if a command to end the measurement is received, the series of procedures is ended, otherwise, the process returns to 302 and the steps 302 to 315 are executed. Is repeated.

With such a structure, the wafer pre-alignment apparatus of the present invention operates as follows. First, the system controller 17 outputs a measurement command to the sensor controller 10 in order to determine whether the wafer 1 exists on the table 4. Upon receiving the command, the sensor controller 10 controls the pre-alignment sensor 26 to cause the light source 7 to emit light and drive the CCD linear sensor 5 to prepare for measurement. When the measurement command is input, the measurement is started and the wafer edge detection unit 12 detects the wafer edge signal, and if it cannot be detected, the undetected signal is output. At the same time, the photodiode signal processing unit 28 acquires the light amount value of the photodiode 27. CPU15
Is a wafer edge detection value or a non-detection signal output from the wafer edge detector 12 and the acquired photodiode 27.
Light amount value, the light amount value stored in advance in the memory 14 when the light source 7 emits light and the irradiation light 9 enters the photodiode, and the light amount when the irradiation light 9 is blocked by the wafer 1. The presence or absence of a wafer is determined by comparing the value with the value, and the result is output to the system controller 17. Upon receiving the information, the system controller 17 starts the prealignment work.

Next, a second embodiment of the present invention will be described with reference to the drawings. FIG. 4 is a block diagram showing the configuration of the wafer pre-alignment apparatus of the present invention, FIG. 5 is a time chart for explaining the correction times T and τ, and FIG. 6 is a view for explaining the relationship between the measurement position and the angle to be corrected. is there. In FIG. 4, reference numeral 29 denotes a wafer positioning mechanism, which detects the rotational position of the motor 2 integrally with the motor 2 and the table 4 which holds the wafer 1 as the object to be measured and is rotated by the motor 2. It is composed of an encoder 3. Two
Reference numeral 6 denotes a pre-alignment sensor, which includes a light source 7, a lens 8 for converting the diffused light into parallel light, a CCD linear sensor 5,
The U-shaped frame 35 has a shape in which these are viewed from the mounting side surface. The parallel light between the lens 8 and the CCD linear sensor 5 is the wafer 1 held on the table 4.
It is designed to be blocked by the outer periphery of the.

Reference numeral 10 is a sensor controller, which is a CCD
The linear sensor 5 outputs a readout gate signal (ROG signal) and a transfer pulse signal, which are timing signals for converting the electric charge accumulated in the pixel into an electric signal at a constant period, and outputs the transfer pulse signal to the CCD linear sensor 5 for a predetermined constant time. CCD linear sensor drive unit 11 for accumulating charges and sequentially outputting the accumulated charges of all pixels of the CCD linear sensor as electric signals
And a time correction time T timer 31 for measuring a time T between measurement commands corresponding to a plurality of pre-planned measurement positions on the outer circumference of the wafer, and a time τ between the measurement command corresponding to the measurement position and the ROG signal. A timer 30 for the correction time τ, a wafer edge detection unit 12 that detects a wafer edge signal that changes from one pixel to the last pixel of the CCD linear sensor 5 by using a measurement command as a trigger, and ON / OFF control of light projection of the light source 7 can be performed. The light emission drive unit 13, the time T and the time τ, the memory 14 that stores the wafer edge detection value, the CPU 15 that reads out the data and simultaneously outputs the value necessary for calculating the detection position correction of the wafer edge, the system controller 1
7 and a data transfer unit 16 that transfers signals.

Reference numeral 17 denotes a system controller, which is a motor commander 22 for rotating the motor 4, an encoder signal processing unit 21 for processing the rotational position signal of the encoder 3, an angle θ [deg] between the rotational positions to be measured in advance, and measurement. A memory 16 that stores the rotational position and stores the correction time T, the correction time τ, and the wafer edge detection value obtained at the measured rotational position in association with the measured rotational position, the CPU 19, the sensor controller 10, and the exchange of signals. Data transfer unit 2
It consists of 0. The CPU 19 determines at least one of the orientation flat, notch position, and center position of the wafer from the measured angle θ [deg] between the rotational positions, the measured rotational position, the correction time T, the correction time τ, and the wafer edge detection value stored in the memory 16. Then, a command is sent to a wafer transfer system (not shown) to transfer the wafer 1 from the table 4 to the transfer destination. The wafer positioning mechanism 29, the pre-alignment sensor 26, the sensor controller 10 and the system controller 17 constitute a wafer pre-alignment apparatus.

Now, the processing method of the wafer pre-alignment apparatus of the present invention will be described with reference to the time chart shown in FIG. 5 and the relationship diagram shown in FIG. Light emission drive unit 13
Illuminates the light source 7 constantly and irradiates the CCD linear sensor 5 with a constant irradiation light 9. The CCD linear sensor drive unit 11 outputs the ROG signal 201 and the transfer pulse signal 202 to the CCD linear sensor 5 at a constant cycle, and regardless of whether or not the measurement is performed, the CCD linear sensor 5 has constant and optimal charge accumulation and wafer edge signal reading. Repeat. When the wafer 1 is present on the table 4, the system controller 17 compares the rotational position of the motor 2 to be rotated with the measurement position (n + 1) 309 stored in the memory 14, and if it is determined that the wafer 1 is rotated to the same position, The measurement command 204 is output to the sensor controller 10.

The sensor controller 10 measures the measurement position (n
When a measurement command corresponding to +1) 309 is input, the measurement is started, and the wafer edge detection unit 12 outputs the wafer edge signal 20
6 is detected and the wafer edge detection value is measured. At this time, at the same time, the timer 31 for the time correction time T causes the measurement position (n
+1) 309 measurement command and measurement position (n) 3
Correction time T of the time interval with the measurement command corresponding to 05
(N) 208 is measured, and the measurement command corresponding to the measurement position (n + 1) 309 is measured by the timer 30 for the correction time τ and the CCD.
The correction time τ (n + 1) 207 of the deviation time from the latest ROG signal output by the linear sensor driving unit 11 is measured.
Here, since the CCD linear sensor 5 is driven by the ROG signal and the transfer pulse signal which are asynchronous with the measurement command input and have a constant cycle, the CCD linear sensor 5 is actually acquired by the measurement command input at the measurement position (n + 1) 309. The wafer edge detection value is the angle φ (n +) rotated by the correction time τ (n + 1).
1) The wafer edge detection value L (n + 1) 'at the measurement position (n + 1)' 310 delayed by [deg] is obtained.

Next, the wafer edge detection value L (n + 1) 'measured by the CPU 15, the correction time T (n), and the correction time τ
(N + 1) is stored in the memory 14. Then, if there is a measurement command corresponding to the measurement position (n) 305 until the measurement command corresponding to the next measurement position (n + 1) 309 is input, it is measured by the same process and stored in the memory 14. Wafer edge detection value L (n) ′, correction time T
(N), the correction time τ (n) is read from the memory 14.
After that, the value is output to the system controller 17 as a value used for correcting the wafer edge detection position of the measurement position (n) 305. The system controller 17 determines the wafer edge detection value L (n) ′ measured by the measurement command corresponding to the measurement position (n) 305, the correction time T (n), and the correction time τ.
When (n) is input, θ (n) [deg] is set between the measurement position (n) 305 and the measurement position (n + 1) 309 on the outer circumference of the wafer which is planned in advance by the system.
Φ (n) in the equation (1) from 301, T (n), and τ (n)
Calculate [deg]. φ (n) = θ (n) × (τ (n) / T (n)) (1) where θ (n) [deg] 301 is an angle stored in the memory 18 in advance, and T (n) ), Τ (n) are the input data correction time and correction time, and φ (n) [de
g] is CC depending on the measurement position (n) 305 and the ROG signal.
This is the angular error at the position where the charge of the D linear sensor is read. Thereafter, φ (n) is added to the measurement position (n) 305 to correct the measurement position angle error, and the corrected measurement position (n) ′ and wafer edge detection value L (n) ′ are recorded.
To store. The same operation is repeated until the wafer 1 makes one rotation or more, and the outer circumference data for one round of the wafer is recorded in the memory 18. Based on the outer circumference data for one round of the wafer recorded in the memory 18, the CPU 19 determines the central position of the wafer 1,
At least one of orientation flat and notch position is calculated.

Next, a third embodiment of the present invention will be described with reference to the drawings. FIG. 7 is a block diagram showing the configuration of the wafer pre-alignment apparatus of the present invention. In the figure, a wafer 1 as an object to be measured is placed on a table 4 rotatable by a motor 2. The CCD linear sensor 5 provided with the wafer 1 sandwiched between it and the lens 8 for collimating the diffused light of the light source 7 into parallel light are attached to the upper and lower inner sides of a frame 35 having a U-shape when viewed from the side. The light projected by the light source 7 is blocked by the wafer 1, a bright and dark image is projected on the CCD linear sensor 5, and a signal corresponding to this image is CC.
It is output from the D linear sensor 5. The output signal of the CCD linear sensor 5 is binarized by the signal processing unit 34 in the sensor controller 10b, and from the binarized data,
The value of the change point at the moment of changing from L (or H) to H (or L) is held by the latch circuit and is set as wafer edge position data, which is recorded in the memory 32 of the system controller 17b. The above operation is repeated until the wafer 1 makes one revolution, and the outer peripheral position data for one round of the wafer is recorded in the memory 32. The calculation unit 33 calculates at least one of the center position, orientation flat, and notch position of the wafer 1 based on the data. Here, the system controller 17b is CC
The normal mode in which the CCD linear sensor 5 is installed so that the scanning direction of the D linear sensor 5 is the same as the wafer insertion direction, and the CCD linear sensor 5 is such that the scanning direction of the CCD linear sensor 5 is opposite to the wafer insertion direction. Information indicating either of the inversion modes in which the sensor 5 is installed, that is, the sensor direction setting signal, is sent to the sensor controller 10b.
Output to.

When the wafer 1 is opaque, the CCD linear sensor 5 scans in the same direction as the wafer insertion direction, which is less affected by dust adhering to the CCD linear sensor 5.
And outputs a sensor direction setting signal from the system controller 17b to the sensor controller 10b informing that the installation direction of the CCD linear sensor 5 is in the normal mode. The signal processing unit 34 in the sensor controller 10b that receives the sensor direction setting signal indicating the normal mode
Converts the CCD output signal of the CCD linear sensor 5 into a binary value. The edge position of the wafer 1 is a change point at which the L (or H) level of the binary data changes from the L (or H) level to the H (or L) level. Is being detected.

Next, the above operation will be described in detail with reference to FIG. In FIG. 8, C of the CCD linear sensor 5
In order to obtain the CD output signal, the signal processing unit 34 outputs RO
By outputting the G signal to the CCD linear sensor 5 and further inputting the transfer pulse signal to the CCD linear sensor 5, the CCD output signal of the CCD linear sensor 5 can be obtained. By the way, each pixel of the CCD linear sensor is generally arranged as shown in FIG. And N at one end
o. 1 to the other end No. It scans up to M in a fixed direction and converts the amount of received light into an electric signal. That is, the pixel output signal synchronized with the transfer pulse signal shown in FIG. 8 is the CCD output signal, and this CCD output signal has a dark level at the portion where the light projected from the light source 7 is shielded by the wafer, The light level becomes bright in the part that is not shaded. Therefore, the No. corresponding to the edge portion of the wafer is set. In the X pixel, the dark level changes to the bright level. This CCD output signal is binarized by a threshold level set in advance by the signal processing unit 34, and the transfer clock pulse up to the point where the CCD output binarized signal changes from L to H is counted. The edge position of the opaque wafer on the sensor 5 can be detected.

Next, a method for detecting the wafer edge position when the wafer 1 is made of a transparent or semitransparent material such as a glass wafer will be described with reference to FIG. When the light projected by the light source 7 is shielded by the glass wafer, only the edge portion is shielded in the case of the glass wafer, and the edge of the glass wafer cannot be correctly detected in the normal mode. Therefore, as shown in FIG. 10, the CCD linear sensor 5 is arranged so that the scanning is performed in the direction opposite to the wafer insertion direction, and the system controller 17b to C
The sensor controller 10 sends a sensor direction setting signal indicating that the installation direction of the CD linear sensor 5 is in the reverse mode.
Send to b. Sensor controller 1 that received the signal
The signal processing unit 34 in 0b is the C of the CCD linear sensor 5.
The CD output signal is inverted and binarized at a preset threshold level, and the binarized data is further inverted. Then, the transfer clock from the point where this signal changes from L to H is counted and the value is counted.
It is output as the edge position of.

Next, the above operation will be described in detail with reference to FIG. Since the light projected by the light source 7 is shielded in a slight range of the edge portion of the glass wafer, the CCD output signal indicates the No. corresponding to the glass wafer edge position as shown in FIG. Only a small range of pixels after the Y pixel have a dark level. This CCD output signal is sent to the signal processing unit 34.
When is binarized at the preset threshold level as in the normal mode, the CCD output binarized signal of FIG. 11 is obtained. The signal processing unit 34 further inverts the CCD output binarized signal by receiving the sensor direction setting signal in the inversion mode, and generates the CCD output binarized inversion signal shown in FIG. Then, as in the normal mode, by counting the transfer clock pulse from the L level of the CCD output binarized inverted signal to the change point of changing to the H level,
The edge position on the CCD linear sensor 5 can be detected. According to such a measuring method of the present invention, even if the surface of the glass wafer 1b is subjected to some surface treatment to change the transmittance of the glass wafer 1b and affect the CCD output waveform, the CCD output is binarized. Since the point where the signal first changes from the L level to the H level is the wafer edge position,
The correct edge position can be obtained without any problems.

Next, a method for outputting a signal indicating the same position in the reverse mode at the same position as in the normal mode when the CCD linear sensor 5 is set from the normal mode to the reverse mode will be described. The pixel of CCD linear sensor 5 is N
o. 1 to No. When there are up to M pixels, the M / 2nd pixel No. 1 as shown in FIG. The CCD linear sensor 5 is arranged so that M / 2 pixels are on the optical axis. By doing so, even in the case of the reversal mode in which the CCD linear sensor 5 is turned by 180 degrees, a signal indicating the same position as that in the normal mode can be obtained with the same edge position of the glass wafer 11. Specifically, as shown in FIG. 11, the system controller 17b uses the No. 1 which is the edge position of the glass wafer 1b in the reverse mode. When the Y pixel position is detected, X
= M−Y to calculate X, this X corresponds to the edge position in the normal mode, that is, a pixel position signal corresponding to the edge position in the normal mode can be obtained. In the normal mode, the output signal of the CCD linear sensor is not inverted when binarized, and the CCD output binarized signal is changed from H to L.
The change point that changes to may be used as the wafer edge signal.
In connection with this, similarly in the case of the inversion mode as well, the CC linear sensor is not inverted when it is binarized when the output signal of the CCD linear sensor is binarized.
It is also possible to generate a D output binarized signal and further use a change point of the CCD output binarized inversion signal obtained by inverting the CCD output binarized signal from H to L as a wafer edge signal. Further, in the CCD linear sensor mounting substrate 6, the CCD output binary signal may be generated from the output signal of the CCD linear sensor 5. A function similar to that of the above configuration can be obtained.

[0031]

As described above, according to the present invention, the wafer pre-alignment apparatus has the wafer presence / absence detection function including the light emission drive section, the wafer edge detection section, the photodiode, the light amount signal processing section, the comparison determination means, and the output means. If the wafer edge detection unit cannot detect the wafer edge and the light intensity value of the photodiode is the same as the value when light is received, it is determined that there is no wafer, and the wafer edge detection unit cannot detect the wafer edge and the light intensity value of the photodiode is blocked. If it is the same as the value of, it is determined that the wafer exists, the wafer edge detection unit detects the wafer edge, and if the light intensity value of the photodiode is the same as the value when the light is blocked, it is determined that the wafer exists, and the wafer edge detection unit detects the wafer edge If the light intensity value of the photodiode is the same as the value when the light is incident, it is determined that there is an unwanted substance attached to the CCD linear sensor. Since the determination result is output to the system controller, the presence / absence of a wafer can be detected without providing a wafer presence / absence sensor separately from the pre-alignment device, and the size and cost of the device can be reduced. There is. Further, according to the second embodiment of the present invention, the wafer is provided with a time measuring unit including a timer for measuring the time between the measurement command and the ROG signal and a timer for measuring the time between the measurement commands corresponding to the measurement positions. Measurement command and C corresponding to a plurality of pre-planned measurement positions on the outer circumference
Using the time obtained from the timer that measures the time with the ROG signal of the CD linear sensor and the time obtained from the timer that measures the time between measurement commands corresponding to a plurality of pre-planned measurement positions on the wafer periphery , The original measurement position,
Since the angle error from the position where the charge of the CCD linear sensor is read is corrected, the signal processing can be simplified and the pre-alignment time can be shortened. An advantage is that an alignment device can be provided. Further, according to the third embodiment of the present invention, when the CCD linear sensor is arranged at a position where the direction can be changed by 180 degrees and the CCD line sensor is changed by 180 degrees, the binary output signal of the CCD linear sensor is output. By reversing and outputting the same signal at the same position as before the direction change, wafers made of either opaque material or transparent material can be handled, and wafer edge position detection with high versatility can be performed. The effect is that you can.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of a wafer pre-alignment apparatus of the present invention.

FIG. 2 is a flowchart showing a processing procedure of a system controller.

FIG. 3 is a flowchart showing a processing procedure of a sensor controller.

FIG. 4 is a block diagram showing the configuration of a second embodiment of the present invention.

FIG. 5 is a time chart explaining correction times T and τ of the second embodiment.

FIG. 6 is a diagram illustrating a relationship between a measurement position and an angle to be corrected according to the second embodiment.

FIG. 7 is a block diagram showing the configuration of a wafer pre-alignment apparatus for carrying out the wafer edge position detecting method of the present invention.

FIG. 8 is a timing chart when detecting an edge position of an opaque wafer.

FIG. 9 is a diagram illustrating a CCD linear sensor.

FIG. 10 is a diagram for explaining edge position detection of a transparent or translucent glass wafer.

FIG. 11 is a timing chart when detecting an edge position of a transparent or translucent glass wafer.

FIG. 12 is a block diagram showing a configuration of a conventional wafer pre-alignment apparatus.

FIG. 13 is a block diagram showing the configuration of a wafer pre-alignment apparatus that implements a conventional wafer edge position detection method.

[Explanation of symbols]

1 wafer 1b glass wafer 2 motor 3 encoder 4 tables 5 CCD linear sensor 6 CCD linear sensor mounting board 7 light source 8 lenses 9 Irradiation light 10, 10b, 10c Sensor controller 11 CCD linear sensor driver 12 Wafer edge detector 13 Light emission drive 14, 18, 32 memory 15, 19 CPU 16, 20 Data transfer unit 17, 17b, 17c System controller 21 Encoder signal processor 22 Motor commander 23 Wafer Presence Sensor Signal Processing Unit 24 Wafer transfer control unit 25 Wafer presence / absence sensor 26 Pre-alignment sensor 27 photodiode 28 Photodiode signal processor 29 Wafer positioning mechanism 30 Timer for correction time τ 31 Timer for correction time T 33 Operation part 34 Signal processing unit 35 frames 51 CCD pixels

─────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-63-70436 (JP, A) JP-A-6-255707 (JP, A) JP-A-3-136264 (JP, A) (58) Field (Int.Cl. ⁷ , DB name) H01L 21/68 G01B 11/00

Claims (5)

(57) [Claims] 1. A wafer rotation means capable of holding and rotating a substantially circular wafer on a table having a vertical rotation axis, and rotation for detecting a rotation angle of the wafer rotation means and converting it into an electric signal. A detection means, a light projection means for projecting light on the peripheral portion of the wafer held by the wafer rotation means, and a large number of pixels arranged in a straight line in a predetermined order,
A CCD linear sensor that sequentially reads the accumulated charge from the first pixel in accordance with the transfer pulse signal and sequentially outputs the accumulated charge of all pixels as an electric signal; and a CCD linear sensor within the light projecting range of the light projecting unit.
A photodiode provided near the first pixel of the wafer, a light emission drive section for turning on / off the light projecting means, and a signal from the CCD linear sensor to receive an image of the wafer.
A wafer edge detection unit for detecting a Tsu di, the the signal of the CCD linear sensor and receiving the signal of said rotation detecting means detects the edge position of the wafer repeatedly in multiple arbitrary point over the outer periphery of the wafer, In the wafer pre-alignment apparatus, the signal of the photodiode is stored in a built-in memory, and signal processing means for determining at least one of the orientation flat position, the notch position, and the center position of the wafer based on the detection value thereof. receiving with a light quantity signal processing unit for detecting a light amount, the comparison and determination means determines the presence or absence of the wafer by comparing the signal of the light amount and the wafer edge detecting portion of the photo diode, the edge of the wafer is detected Can be done before the comparison and determination means
When it is determined that the wafer is present, the signal processing means
If the amount of light is the same as the value when light is received, then a CCD linear sensor
A wafer pre-alignment device, which determines that unnecessary substances are attached to the wafer. 2. A wafer rotation means capable of holding and rotating a substantially circular wafer on a table having a vertical rotation axis, and rotation for detecting a rotation angle of the wafer rotation means and converting it into an electric signal. A detection means, a light projection means for projecting light on the peripheral portion of the wafer held by the wafer rotation means, and a large number of pixels arranged in a straight line in a predetermined order,
A CCD linear sensor that sequentially reads the accumulated charges from the first pixel according to the transfer pulse signal and sequentially outputs the accumulated charges of all pixels as an electric signal, and a light emission drive unit that controls ON / OFF of the light projection of the light projecting unit.
And one screen of the CCD linear sensor triggered by the measurement command
Detects wafer edge signal that changes from raw to final pixel
A wafer edge detection unit for out vessel, the the signal of the CCD linear sensor and receiving the signal of said rotation detecting means detects the edge position of the wafer repeatedly at a pre-planned plurality of detection positions over the outer periphery of the wafer A signal processing means for storing at least one of the orientation flat position, the notch position, and the center position of the wafer based on the detection value stored in a built-in memory, and the signal processing means, , The CCD linear sensor charges the pixel with a constant period.
RO that is a timing signal when converting a load into an electric signal
CCD linear sensor that outputs G signal and transfer pulse signal
Is stored in the CCD linear
The accumulated charge of all the pixels of the sensor is sequentially output as an electric signal.
CCD linear sensor drive unit and a measurement command corresponding to a plurality of pre-planned measurement positions over the outer circumference of the wafer .
A first timer for measuring the time τ to the ROG signal, and a second timer for measuring the time T between measurement commands corresponding to a plurality of pre-planned measurement positions over the outer periphery of the wafer, And the time τ and the time T are triggered by the ROG signal.
Is used to output the accumulated charge of the CCD linear sensor.
The angular error between the circumferential position of the wafer and the measurement position is compensated for.
A wafer pre-alignment apparatus having a corrective function . 3. The function for correcting the angle error is the light projection.
When the means projects a constant light, the angle between a plurality of pre-planned measurement positions over the outer circumference of the wafer is θ [deg], the time measured by the first timer is τ [sec], When the time measured by the second timer is T [sec], a plurality of pre-planned measurement positions over the outer circumference of the wafer and a position at which the accumulated charge of the CCD linear sensor is output by the ROG signal are set. Angle error φ [deg]
3. The wafer pre-alignment apparatus according to claim 2 , wherein φ is set to φ = θ × (τ / T), and φ is added to a plurality of pre-planned measurement positions over the outer circumference of the wafer to correct . 4. A wafer rotation means capable of holding and rotating a substantially circular wafer on a table having a vertical rotation axis, and rotation for detecting a rotation angle of the wafer rotation means and converting it into an electric signal. A detection means, a light projection means for projecting light on the peripheral portion of the wafer held by the wafer rotation means, and a large number of pixels arranged in a straight line in a predetermined order,
A CCD linear sensor that sequentially reads the accumulated charge from the first pixel at the scan start end according to the transfer pulse signal, and sequentially outputs the accumulated charge of all pixels as an electric signal, and binarizes when the signal of the CCD linear sensor is received, A signal having the number of transfer pulses from the scan start end to the change point where the binarized data first changes from L level (or H level) to H level (or L level) as an edge position of the wafer. In a wafer pre-alignment apparatus that includes a processing means and detects the edge position of a wafer, when detecting the edge position of an opaque wafer, the scan start end is detected in the direction of the central axis of the wafer rotating means. However, when detecting the edge position of the transparent wafer, the scan start end is set opposite to the central axis of the wafer rotating means. When the signal processing means receives the signal from the CCD linear sensor, the data is binarized and then inverted, and the inverted data is first scanned at the L level (or H level). A wafer edge position detecting method, characterized in that the number of transfer pulses from a change point from a level) to an H level (or an L level) is detected as an edge position of the wafer. 5. A wafer rotation means capable of holding and rotating a substantially circular wafer on a table having a vertical rotation axis, and rotation for detecting a rotation angle of the wafer rotation means and converting it into an electric signal. A detection means, a light projection means for projecting light onto the peripheral portion of the wafer held by the wafer rotation means, and a large number of pixels arranged linearly and having a predetermined order,
A CCD linear sensor that sequentially reads the accumulated charge from the first pixel at the scan start end according to the transfer pulse signal and sequentially outputs the accumulated charge of all pixels as an electric signal, and the edge of the wafer by receiving the signal from the CCD linear sensor. In a wafer pre-alignment apparatus including a signal processing unit for detecting a position, the signal processing unit binarizes when a signal from the CCD linear sensor is received when a linear sensor installation direction inversion signal is input, Invert, scan from the scan start edge, and the inverted data is L level (or H level) first
A wafer pre-alignment apparatus having a function of setting the number of transfer pulses from the change point to the H level (or L level) as the edge position of the wafer.