JP2001044263A - Substrate carrying method and substrate carrying apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make it possible to precisely carry a substrate, such as a wafer, specially a substrate having orientation flat or the like, to a previously set reference position, at a high throughput. SOLUTION: Carrying of a substrate is executed by a method, where the substrate is carried to a substrate support part along a prescribed carrying path by a substrate carrying part. In this case, the method consists of processors S1 to S3 of continuously detecting the external shape of the substrate, which is carried, by an optical sensor having the longitudinal direction in the direction orthogonally intersecting the carrying direction of the substrate, processes S4 to S12 of finding the amount of the shift of the reference position of the substrate, where it is set on the carrying path beforehand on the basis of the detected result, from the position of the substrate which is carried, and a process S13 of correcting the amount of the shift of the substrate.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for transporting a substrate, and more particularly to a method and a transport device for detecting a position where a semiconductor substrate, a liquid crystal substrate, or the like is disposed, and transporting the substrate to a predetermined reference position.

[0002]

2. Description of the Related Art In the field of manufacturing semiconductor devices, when a semiconductor wafer (hereinafter, referred to as "wafer") is moved between a wafer cassette and a processing apparatus, the semiconductor wafer is taken out of the wafer cassette by a transfer mechanism such as a robot arm and processed. The wafer is introduced into a predetermined position in the apparatus, and the processed wafer is transferred to and stored in a wafer cassette.

In a processing apparatus, various processes are performed on a wafer. Therefore, it is desired that the wafer be accurately transferred to a predetermined position. In a conventional transfer mechanism, as disclosed in, for example, Japanese Patent Publication No. 7-27953, a plurality of light sources (light emitters) are provided near an upper portion of a wafer in the middle of a transfer path, and a plurality of light sources corresponding to the light sources are provided near a lower portion. An optical sensor is provided for each. When the wafer conveyed by the robot arm crosses the pair of light sources and the sensor, the light from the light source is blocked, and when the wafer passes, the light from the light source is incident on the sensor again. Further, since the plurality of sensors are provided along the transfer path, the light is sequentially blocked by the transferred wafer. The output signal is captured by using the trigger at the moment when the light from the light source is blocked by the wafer and at the moment when the sensor receives the light again due to the passage.

[0004] Then, by performing arithmetic processing based on these output signals, a deviation (difference) between the center position of the wafer being actually conveyed and a preset reference position is calculated, and the result is sent to the conveyance system. The wafer is transported to the reference position by feeding back and canceling the shift amount.

[0005]

However, according to the above-mentioned conventional procedure, the calculation for calculating the center position of the wafer takes a long time, so that the throughput is reduced. In addition, a wafer is formed by forming a part of a circular arc portion of a circular wafer in a so-called orientation flat (hereinafter, referred to as “orientation flat”) in order to recognize the orientation of the wafer, or a notch. In some cases, a notch is provided on the circumference. In order to detect the orientation flat and the notch and remove the influence by the method of the related art, for example, at least 3
Since it is necessary to perform arithmetic processing based on output signals from a pair of sensors, it takes a long time to perform the arithmetic operation, which further reduces the throughput.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-described problems, and a substrate transport method and a substrate capable of accurately transporting a substrate such as a wafer, in particular, a substrate having an orientation flat or the like, to a predetermined reference position with high throughput. An object is to provide a transport device.

[0007]

According to the present invention, there is provided a method for transferring a substrate to a substrate support along a predetermined transfer path by a substrate transfer unit. A step of continuously detecting the shape by an optical sensor having a longitudinal direction in a direction perpendicular to the transport direction, and based on the detected result, a reference position of the substrate preset in the transport path and A method of transporting a substrate, comprising: a step of calculating a deviation amount from a position of the substrate to be transported; and a step of correcting the deviation amount of the substrate.

Further, according to the present invention, the substrate has a circular shape having a notched portion in at least a part of a circumference thereof. The notched portion is detected in the step of obtaining the shift amount, and output data of the optical sensor is obtained. It is desirable to further include a step of correcting.

In the present invention, the step of calculating the amount of deviation further includes a step of calculating secondary differential information of output data from the optical sensor, and the secondary differential information includes at least two peak values. Interpolating the output data between the two peak values, and determining a minimum value of the output data or the interpolated output data,
A step of calculating the position of the substrate from the minimum value and the amount of movement of the substrate in the transport direction; and a step of calculating a difference between the reference position and the calculated position. Preferably, the step includes a step of relatively moving the substrate transport unit and the substrate support unit based on the deviation amount.

When the optical sensor detects a change in the amount of light blocked by the substrate, it is preferable to obtain the minimum value of the output data. However, when the optical sensor detects a change in the amount of light reflected by the substrate, the output value is determined. It is preferable to find the maximum value of the data. When detecting the latter change in the amount of reflected light, it is preferable to further calculate the position of the substrate from the maximum value of the output data and the amount of movement of the substrate in the transport direction.

Further, the present invention provides a substrate transport section for transporting a substrate along a predetermined path to a substrate support section, wherein the substrate transport section has a longitudinal direction in a direction orthogonal to the transport direction, and is provided outside the substrate to be transported. An optical sensor for continuously detecting a shape, and an arithmetic processing for obtaining a shift amount between a preset reference position of the substrate and a position of the substrate to be conveyed on the conveyance path based on the detected result. And a drive unit configured to relatively move the substrate transfer unit and the substrate support unit based on a displacement amount of the substrate.

[0012]

Embodiments of the present invention will be described below with reference to the accompanying drawings. FIGS. 1A and 1B are diagrams illustrating a configuration of a transport device according to an embodiment of the present invention. FIG. 1A is a diagram illustrating a state in which a circular wafer 2 is transported in the direction of arrow D and crosses a line-shaped light source 3A as viewed from above the substrate (Z direction). FIG. 1B is a perspective view, in which a wafer cassette (carrier) 1 contains a plurality of circular wafers coated with a photoresist on the upper surface in layers. Here, only one wafer 2 is shown for simplicity. The vertical position of the wafer 2 changes as the wafer cassette 1 moves up and down in the Z direction in the figure.

The robot arm 4 can be moved up and down (Z direction) by a drive unit MT, and can move linearly and rotate in a horizontal plane. The robot arm 4 moves inside the wafer cassette 1 and places the wafer 2 thereon, and then takes out the wafer 2 from the wafer cassette 1. Then, the wafer 2 is transferred to a predetermined substrate supporting unit 5 along a transfer path (direction) D. A line-type light source 3A is provided near the upper part of the wafer 2 in the middle of the transfer path, and a line-type light receiving sensor 3B corresponding to the light source 3A is provided near the lower part. The line sensor 3B has a longitudinal direction in a direction (Y direction) orthogonal to the transfer direction D, and continuously detects the outer shape of the wafer 2 transferred along the transfer path. In the figure, a circle indicated by a dashed line with reference symbol E indicates a state in which the wafer 2 being conveyed is passing through the sensor 3B, and a circle indicated by a dotted line with reference symbol F indicates that the amount of displacement has been corrected and the substrate support portion 5 has been corrected.
The state where it is mounted on each is shown.

[0014] Figure 2 is a diagram showing the relationship between the moving amount in the X direction of the wafer 2 intensity of the output signal of the (horizontal axis) and sensor 3B (the vertical axis), the minimum output at the position of the moving amount C ₁ and it has a value P _1. When the line-type optical sensor is a photodiode, the change in the amount of incident light blocked by the wafer is a downwardly convex curve. Conversely, when the change in the amount of light reflected by the wafer is plotted, the curve becomes an upwardly convex curve. When the line-type sensor is a CCD or the like, the position of the wafer edge directly detected is as shown in an output signal curve shown in FIG.

Next, the output signal from the sensor 3B is stored in the memory M. Then, the arithmetic processing unit CP stores the memory M
The position of the wafer 2 being conveyed is calculated by reading the above data and performing a series of arithmetic processing described later. Then, the arithmetic processing unit CP calculates a deviation amount between a predetermined position (hereinafter, referred to as a “reference position”) and the actual position of the wafer 2, and corrects (cancels) the deviation amount by the driving unit M.
The arm 4 and the substrate support 5 are relatively moved by T.
As a result, the wafer 2 can be set at the reference position.

Next, the above procedure and calculation processing will be described with reference to the flowchart of FIG. In step S1, the wafer 2 is extracted from the wafer carrier 1 by the arm 4. Then, the arm 4 is moved by the driving unit MT, and the wafer 2 is transferred in the direction D. Step S2
And output signal data from the line-type optical sensor 3B,
The movement amount of the wafer 2 and the movement amount of the wafer 2 are continuously taken into the memory M. Then, when the wafer 2 passes through the position indicated by the symbol E, light from the light source 3A is blocked by the wafer 2 and the amount of light received by the optical sensor 3B decreases. In step S3, the writing of the output signal data to the memory M is completed at the point in time when the wafer 2 has passed through the optical sensor 3B or at a point in time after a lapse of a predetermined time.

Steps S4 to S4 described next
9 shows an arithmetic processing procedure for accurately calculating the position of the wafer 2 (the position of the wafer 2 on the arm 4) even when the wafer 2 has an orientation flat or a notch. . The arithmetic processing unit CP reads the data stored in the memory M (step S4), and calculates secondary differential (difference) information of the data. The arithmetic processing unit CP compares a preset threshold level (threshold) with the second derivative information, and obtains second derivative information having a value larger than the threshold level (step 6). If the second derivative information having a value larger than the threshold level exists continuously, the continuous values are regarded as one group, and the number G of the group is detected (step 7).

When the number G of groups is zero (G = 0)
Has an orientation flat (abbreviated as “OF” in FIG. 3) outside the range continuously detected by the optical sensor 3B. When the number G of groups is 1 (G = 1), an orientation flat or the like exists at the end of the range continuously detected by the optical sensor 3B. Further, when the number G of groups is 2 (G = 0), the orientation flat or the like exists in the range continuously detected by the optical sensor 3B.

The relationship between the number G of these groups and the detection position of the orientation flat will be described with reference to FIGS. FIG.
5 and FIG. 5, the horizontal axis represents the movement amount of the transferred wafer,
The thick solid line SO indicates the output signal of the sensor (left vertical axis: arbitrary unit), and the thin solid line DF indicates the second derivative (right vertical axis: arbitrary unit). Since there are two secondary differential values exceeding a predetermined threshold level (not shown), PK1 and PK2, the number of groups G = 2
It is. The positions of the peak values PK1 and PK2 in FIG. 4 correspond to the position where the orientation flat portion of the wafer 2 being conveyed starts passing through the sensor 3B and the position where the orientation flat portion has passed, and the peak values PK1 and PK2 in FIG. The positions correspond to the position where the notch portion of the wafer 2 being conveyed starts to pass through the sensor 3B and the position where it passes.

If the orientation flat is outside or at the end of the sensor detection range, the sensor output SO is used as it is to determine the sensor output minimum value P ₁ and the wafer movement amount C ₁ at that time. (Step 8).
On the other hand, when the orientation flat portion or the like exists in the sensor detection range (FIGS. 4 and 5), the orientation flat portion is classified into, for example, the sixth order by using the sensor output value corresponding to the portion excluding the orientation flat portion. Interpolation is performed by approximation with a polynomial (step 9). 4 and 5 indicate the interpolated data. Then, the minimum value P1 of the curve approximated by the polynomial
Calculating a and the wafer moving amount C ₁ at that time (Step 1
0).

Next, in step 11, the following equation (1)
Converting the output value P ₁ of the sensor 3B to the length of the light shielding portion of the sensor 3B by. Incidentally, the wafer position X ₁ of the conveying direction (X-direction) corresponds directly to the amount of movement C ₁ of the conveying arm. (1) Y ₁ = L × (P _max −P ₁ ) / P _max Here, P _max is the output value of the sensor when no light is shielded, P ₁ is the minimum value of the sensor output, and L is the validity of the sensor. The length is indicated respectively.

When the predetermined wafer reference position coordinates are (X _std , Y _std ), the wafer deviation amounts (ΔX, ΔY) from the reference position coordinates are calculated by the following equation (2). (Step 12). (2) ΔX = X ₁ −X _std ΔY = Y ₁ −Y _std Here, Y _std indicates the length of the sensor that is shielded from light when the wafer is at the reference position.

When transferring the wafer 2 from the arm 4 to the substrate support 5, the drive unit MT makes the arm 4 and the substrate support 5 move so that the above-mentioned displacement amounts (ΔX, ΔY) are canceled out to be zero. Move relatively. As a result, the wafer 2 can be transferred to a predetermined reference position.

The case where the wafer 2 is transferred linearly in the transfer direction D has been described. However, after the wafer 2 is extracted from the wafer carrier 1, the wafer 2 is transferred to the substrate support 5 along an arcuate path. The present invention can be applied to such cases. Further, in the above embodiment, the present invention is applied to the transfer of a wafer used for manufacturing a semiconductor device. However, the present invention is not limited to this, and the present invention is also applied to transport of a glass plate used for manufacturing a display including a reticle or a liquid crystal display element, a ceramic wafer used for manufacturing a thin-film magnetic head, and the like. be able to. The embodiments described above are described to facilitate understanding of the present invention,
It is not intended to limit the invention. Therefore, each element disclosed in the above embodiment is intended to include all design changes and equivalents belonging to the technical scope of the present invention.

[0025]

As described above, according to the present invention,
While the substrate is being conveyed, the outer shape of the substrate is continuously detected by an optical sensor, and the position of the substrate is obtained by calculating the minimum value of the output of the optical sensor. Therefore, the substrate can be accurately and efficiently transported to the preset reference position with high throughput by simple arithmetic processing. Further, since the orientation flat and the notch can be detected only by one set of light source (light emitting portion) and optical sensor (light receiving portion) without using a plurality of sensors, the orientation flat and the notch within the range detected by the optical sensor can be detected. Regardless of the presence or absence, the position of the substrate can be easily detected. Therefore, even if there is a chipped portion on the circumference of the circular substrate, the substrate can be accurately conveyed to a predetermined reference position.

[Brief description of the drawings]

FIG. 1A shows the relationship between a light source and a substrate in an upward direction (Z direction).
FIG. 2B is a perspective view of the substrate transfer apparatus according to the embodiment of the present invention.

FIG. 2 is a diagram showing an output waveform of an optical sensor 3B.

FIG. 3 is a flowchart of a substrate transfer method according to the present invention.

FIG. 4 is a diagram illustrating an example of a sensor output waveform when a wafer having an orientation flat portion is transferred.

FIG. 5 is a diagram illustrating an example of a sensor output waveform when a wafer having a notch portion is transferred.

[Explanation of symbols]

 Reference Signs List 1 wafer carrier 2 wafer 3A light source 3B line-type optical sensor 4 arm 5 substrate support unit M memory CP arithmetic processing unit MT drive unit

Claims (4)

[Claims] 1. A method for transporting a substrate to a substrate supporter along a predetermined transport path by a substrate transporter, wherein the optical device has a longitudinal direction in a direction perpendicular to a transport direction of an outer shape of the substrate to be transported. Continuously detecting by a sensor; and, based on the detected result, obtaining a shift amount between a preset reference position of the substrate on the transport path and a position of the transported substrate. Correcting the amount of displacement of the substrate. 2. The method according to claim 1, wherein the substrate has a circular shape having a notched portion in at least a part of a circumference thereof, and a step of detecting the notched portion and correcting output data of the optical sensor in the step of obtaining the shift amount. 2. The method according to claim 1, further comprising: 3. The method of claim 2, further comprising: calculating secondary differential information of output data from the optical sensor; and determining the secondary differential information when the secondary differential information includes at least two peak values. Interpolating the output data between two peak values; obtaining the minimum value of the output data or the interpolated output data; and calculating the minimum value and the amount of movement of the substrate in the transport direction of the substrate. A step of calculating a position, and a step of calculating a difference between the reference position and the calculated position, wherein the step of correcting the shift amount is performed based on the shift amount. 3. The method according to claim 1, further comprising the step of relatively moving the unit. 4. A substrate transport section for transporting a substrate to a substrate support section along a predetermined path, and a longitudinal direction in a direction orthogonal to the transport direction. An arithmetic processing unit that calculates a deviation amount between a preset reference position of the substrate and a position of the conveyed substrate in the conveyance path based on the detected result; A substrate transport apparatus, comprising: a drive unit that relatively moves the substrate transport unit and the substrate support unit based on a displacement amount of the substrate.