JP3295915B2 - Semiconductor wafer positioning method and apparatus - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and an apparatus for positioning a semiconductor wafer and, more particularly, to a method and an apparatus for positioning a semiconductor wafer at a desired position after confirming that the center position of the semiconductor wafer is accurate. It is.

[0002]

2. Description of the Related Art Semiconductor wafers (hereinafter abbreviated as wafers) are manufactured by slicing an ingot in a horizontal direction perpendicular to a longitudinal direction. Since the outer periphery of the ingot is polished while being rotated, the roundness is extremely high, and thus the wafer is also substantially round. However, there is a manufacturing tolerance for the diameter, and an orientation flat or a V notch is formed at a predetermined position on the circumference. In the situation where the wafer is stored in the wafer cassette, it is not known in which direction the position of the orientation flat or the V notch is located.

Therefore, in various processing steps such as formation of an impurity diffusion mask, positioning is performed such that the center and the direction of each wafer are aligned with respect to a processing apparatus.

In a conventional wafer positioning device, a wafer is placed on a rotary table, and the rotary table is rotated to detect a peripheral edge position of the wafer with a one-dimensional sensor, and an orientation flat or a wafer provided on the wafer is detected. A device for calculating the deviation (deviation) between the position of the V notch and the center of rotation of the rotary table and the center of the wafer (JP-A-1-184844, JP-A-1-303737)
Or a wafer is placed on a table, the table is moved in one axis direction, the peripheral position of the wafer is detected by a one-dimensional sensor, and the position of an orientation flat or V notch provided on the wafer is determined. There is one that calculates a shift between the center of the table and the center of the wafer (Japanese Patent Laid-Open No. Hei 7-263518). Then, the deviation between the center of each table and the center position of the wafer is performed by temporarily moving the wafer onto an XY table attached to each table to perform the center position adjustment. After that, the wafer is transferred and positioned at a desired location such as a processing apparatus by a handling arm or the like.

[0005]

A conventional wafer positioning apparatus is provided with a sampling device for digitally processing sensor detection data due to sensor detection data error or noise caused by mechanical wear due to long-term use or noise. There was a positioning failure based on a sensor erroneous detection or the like due to a shift of the detection position in a cycle. In addition, since there is no means for confirming whether or not the center position of the semiconductor wafer is accurate after the positioning, the positioning failure cannot be prevented. Therefore, the production yield of the semiconductor device is adversely affected.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a method and an apparatus for positioning a semiconductor wafer capable of confirming whether or not the center position of the semiconductor wafer is accurate with a simple configuration and reliably positioning the semiconductor wafer at a desired position. To provide.

[0007]

According to the present invention, there is provided a robot hand having an articulated arm capable of rotating around a first rotation center and extending and contracting in a radial direction about the first rotation center. And a rotary table that is disposed within a movement range of the robot hand and that rotates around a second rotation center; and a rotation table that is disposed on both sides of the rotation table and that moves from the first rotation center to the second rotation center. A method of positioning a semiconductor wafer using a pair of sensors capable of detecting a position in a second direction orthogonal to one direction, the method comprising: rotating the robot hand to move a semiconductor wafer placed thereon in the first direction. A first detection step of detecting the end of the semiconductor wafer in the second direction with the pair of sensors and calculating the center of the semiconductor wafer; Mounting A second detecting step of rotating the semiconductor wafer around the second center of rotation, detecting a periphery of the semiconductor wafer using at least one of the pair of sensors, and calculating a center of the semiconductor wafer; Confirming the center position of the semiconductor wafer obtained in one of the first and second detection steps with the center position of the semiconductor wafer obtained in the other detection step.

A feature of the apparatus of the present invention that achieves the above object is that a robot hand provided with a hand on which a semiconductor wafer can be placed at the tip of an articulated arm that moves vertically, horizontally, and rotationally is provided. A rotary table within the moving range of the robot hand for transferring the semiconductor wafer to the robot hand; and a rotary table provided on both sides of the rotary table, the semiconductor wafer on the rotary table or on the hand. A pair of sensors for detecting a peripheral edge position and the semiconductor wafer mounted on the robot hand are horizontally moved so as to pass between the sensors in a direction orthogonal to a direction connecting the pair of sensors. Control means having a first drive mode and a second drive mode for rotating the turntable on which the semiconductor wafer is placed; First calculating means for determining the center position of the semiconductor wafer from the peripheral position data of the semiconductor wafer on the hand detected by both sensors in the horizontal movement of the hand in the drive mode, and driving the rotary table to the second drive Second arithmetic means for determining the center position of the semiconductor wafer from the peripheral edge position data of the semiconductor wafer on the turntable detected by at least one of the two sensors by rotating in the mode. The means further calculates the center position of the semiconductor wafer and the center of rotation of the rotary table by the robot hand from the deviation between the center position data of the semiconductor wafer and the center of rotation data of the rotary table obtained by one of the arithmetic means. A third drive mode for making the rotary table coincide with the rotary table. For the semiconductor wafer having to match the center on the rolling center position is to have a confirmation means the center position data of the semiconductor wafer obtained by other computing means to check if it matches the rotation center position of the rotary table.

[0009]

FIG. 1 is a perspective view showing an embodiment of the apparatus of the present invention.

In FIG. 1, 1 is a wafer, 2 is a robot hand, 3 is a wafer cassette (hereinafter abbreviated as a cassette), 4 is a rotary table, 5 and 6 are optical dimension measuring devices (a pair of sensors). , 7 is a motor of the rotary table 4, 8 is an encoder for detecting the amount of rotation of the motor 7, 9,
Reference numeral 10 denotes a storage unit for storing data detected by the dimension measuring devices 5 and 6, reference numeral 11 denotes a storage unit for storing the output of the encoder 8, and reference numerals 12 and 13 denote movement amounts of the robot hand 2 in the radial direction and the rotation direction, respectively. A storage unit for storing, 14 is a control unit for the robot hand 2 and the motor 7, and 15 is an arithmetic processing unit.

The directions of the X axis, Y axis, and Z axis, which are rectangular coordinate systems, are determined as shown in the figure. That is, the Z-axis direction is the height direction, and the XY plane is orthogonal to the Z-axis. The X-axis direction is a direction from the center of rotation of the robot hand 2 to the center of rotation of the turntable 4. The Y axis direction is a direction orthogonal to the X axis in the XY plane. Further, the azimuth direction (the rotation direction of the robot hand 2 and the rotation direction of the turntable 4) in the XY plane is defined as the θ-axis direction.

The wafers 1 are accommodated in a cassette 3 in multiple stages with their orientation flats or V notches oriented in any direction. The individual wafers 1 are taken out of the cassette 3 by the robot hand 2 and stored. The robot hand 2 has an arm that performs vertical movement in the Z-axis direction, horizontal bending movement (radial movement) in the XY plane, and rotational movement (rotational movement) in the θ-axis direction. It is an articulated type provided with a hand that can be placed.

First, the wafer 1 is taken out of the cassette 3 using the robot hand 2. That is, the height of the robot hand 2 is set to a position lower than the height of the wafer 1 storage shelf of the cassette 3 by a predetermined height.
Is inserted into the cassette 3. Next, the height of the robot hand 2 is raised, and the wafer 1 is placed on the hand. Subsequently, the robot hand 2 is contracted in the radial direction, and the hand is positioned at a radial position at a predetermined distance from the rotation center of the robot hand 2. Next, the robot hand is rotated by θ axis (rotational movement), the wafer 1 is directed in a direction (X-axis direction) from the rotation center of the robot hand 2 toward the center of the rotary table 4, and the Z-axis operation (vertical movement) of the robot hand 2 is performed. (Moving) to position the wafer at a predetermined height. The rotation amount of the θ-axis of the robot hand 2 is stored in the storage unit 13.
Take in.

Next, the robot hand 2 is extended, and the wafer 1 is moved in the X-axis direction. Here, robot hand 2
The distance between the X axis origin (center of rotation) and the center of rotation of the rotary table 4 is an arbitrarily determined value within the moving range of the robot hand 2. The center of the wafer 1 once passes through the center of the turntable 4. For example, the robot hand 2 is controlled so that the entire wafer 1 passes over the turntable 4.

The direction orthogonal to the X axis at the center of rotation of the rotary table 4 is defined as the Y axis, and the optical dimension measuring devices 5 and 6 are arranged at an equal distance from the center of rotation of the rotary table 4 on the Y axis. The position of the end in the Y-axis direction of the wafer 1 moving in the direction is measured (detected), and the data is synchronously stored in the storage units 9 and 10. These optical dimension measuring devices 5 and 6 are
A large number of light rays traveling in the Z-axis direction are arranged along the Y-axis direction, and the peripheral position of the wafer 1 in the Y-axis direction is measured (detected) depending on which of these many light rays is blocked by the wafer 1. . In addition, the dimension measuring devices 5 and 6 may reflect the energy beam emitted in the Y-axis direction on the peripheral side surface of the wafer 1 and measure (detect) the peripheral position of the wafer 1 from the time until it returns. .

The wafer 1 is moved to X using the robot hand 2.
When it is moved along the axis and passes between the optical dimension measuring devices 5 and 6 on the rotary table 4, the optical dimension measuring device 5
Numeral 6 generates peripheral position data corresponding to a change in the outer peripheral shape of the wafer 1. This is taken into the storage units 9 and 10 in synchronization. Further, the movement amount of the robot hand 2 in the X-axis direction in this operation is fetched in synchronization with the storage unit 12.

FIG. 2 shows that the wafer 1 is conveyed in the X-axis direction by the robot hand 2 and passed between the optical dimension measuring devices 5 and 6, so that the peripheral edge position data d1 and d2 of the diameter portion of the wafer 1 are obtained. The appearance obtained is shown. If the diameter portion does not overlap the orientation flat or the V notch, the diameter and center of the wafer can be immediately obtained. That is, since the optical dimension measuring devices 5 and 6 are installed at the same distance (s) from the rotation center P of the rotary table 4 in the Y axis direction orthogonal to the X axis direction, the wafer 1
And the deviation y between the center position O of the wafer 1 on the robot hand 2 and the rotation center P of the turntable 4 can be calculated by the calculation processing unit 15.

When the diameter portion overlaps the orientation flat or the V notch, another method can be adopted. For example, instead of the peripheral position data of the diameter portion of the wafer 1, the peripheral (part of) is detected from the on / off of the light when the wafer 1 passes through the optical dimension measuring devices 5 and 6, and the peripheral edge shown in FIG. Position data h1 to h4 are obtained. The arithmetic processing unit 15 obtains the center (circumcenter) position G of a circumscribed circle of a triangle having the vertices at any three points h1 to h3 (choose an orientation flat or a V notch according to a known technique).
The position G may be set as the center position O of the wafer 1. The first detection step described above detects the center of the wafer by moving the wafer in the X-axis direction.

Here, the deviation y is calculated by the arithmetic processing unit 15 and the deviation y is eliminated by the robot hand 2.
That is, the wafer 1 is placed on the turntable 4 such that the center position O of the wafer 1 and the rotation center P of the turntable 4 match.

When the edge position data d1, d2 and h1 to h4 are detected by analog processing, the deviation y is only in the Y-axis direction, but in digital processing, the sampling cycle involves a deviation in the X-axis direction. There is.

Further, the center position O of the wafer 1 and the rotation center P
Check to see if they match.

This confirmation process is executed based on the peripheral position data corresponding to the change of the outer peripheral shape of the wafer 1 detected by the dimension measuring devices 5 and 6 by rotating the rotary table 4.

That is, the wafer 1 is placed on the turntable 4 by the robot hand 2 and the turntable 4 is rotated by the motor 7. The rotation amount is detected by the encoder 8, and its output is stored in the storage unit 11. Peripheral position data corresponding to a change in the outer peripheral shape of the wafer 1 detected by the dimension measuring devices 5 and 6 by rotation of the wafer 1 is stored in the storage units 9 and 10.

It should be noted that all drive commands for the robot hand 2 and the motor 7 are issued from the control unit 14 which stores a processing program, and each unit receives the drive command and performs its operation. The processing of the data stored in synchronization with each of the storage units 9 to 13 is executed by the arithmetic processing unit 15.

FIG. 3 is a graph plotting the peripheral position data of the wafer 1 detected by the dimension measuring devices 5 and 6 when the rotary table 4 is rotated, in comparison with the rotation angle of the wafer 1 detected by the encoder 8. This is a simulation of the outer shape PE of No. 1. Any three points H1 to H3 excluding the range of θa to θb corresponding to the position of the orientation flat
An outer-center position G of the triangle TRY drawn by extracting H3, that is, a center position O of the wafer 1 is obtained. The second explained above
In the detection step, the center of the wafer is detected by rotating the wafer 1 in the θ-axis direction.

The center position O of the wafer 1 and the rotary table 4
If the rotation center P of the robot hand 2 coincides, it can be confirmed that the robot hand 2 has placed the wafer 1 on the turntable 44, that is, that the positioning has been performed correctly (normally).

In the case where the positioning is not performed accurately (abnormal) or in the case of erroneous detection, as shown in FIG. 3, the deviation amount between the center position O of the wafer 1 and the rotation center P of the rotary table 4 and the rotation The shift amounts x and y in the X and Y axis directions can be detected based on the rotation angle of the table 4.

The shifts x and y are moved by the robot hand 2 to a desired position such as a semiconductor wafer mounting table scheduled next to the wafer 1, for example, a mask alignment table in a photolithography process where precise alignment is required. The correction can be made by correcting the transfer distance when loading.

Although it is a simple one using the same components,
Since the center position of the wafer 1 can be obtained by a different method, the second one is a confirmation processing of the first processing, and even if there is a deviation due to the sampling cycle, the detection accuracy can be improved by the two processings. Therefore, positioning by the robot hand 2 is sufficient, and a precise XY table or the like for positioning is unnecessary, and the apparatus can be simplified. Further, since the robot hand 2 directly transfers and positions the desired position, the processing time is shortened.

Even if a sensor detection data error occurs due to mechanical wear or noise due to long-term use, the detection accuracy can be improved by twice processing, as in the case of a sampling cycle shift, and the wafer 1 can be placed at a desired location. Accurate positioning can be achieved. Therefore, the production yield of the semiconductor device is improved.

In the above embodiment, the center position of the wafer 1 is obtained by first detecting the center of the wafer by moving in the X-axis direction and later by detecting the center of the wafer by rotating in consideration of the influence of the sampling period. , And its center position is checked, but if high accuracy is not required, the center of the wafer is first detected by rotational movement, and
The center of the wafer may be detected by horizontal movement in the axial direction.

The number of optical dimension measuring devices is not limited to two, and three or more optical dimension measuring devices may be provided for movement in the X-axis direction in order to eliminate the influence of the position of the orientation flat or the V notch. In addition, as long as the detection time does not matter in the rotational movement, one detection can be sufficiently performed.

The control program executed by the control unit 14 may be stored in a recording medium, managed separately from hardware, and upgraded.

[0034]

As described above, according to the present invention,
With a simple configuration, the positioning accuracy can be verified and the wafer can be reliably positioned at a desired position.

[Brief description of the drawings]

FIG. 1 is a perspective view showing an embodiment of the device of the present invention.

FIG. 2 is a diagram showing an example of peripheral position data of a semiconductor wafer detected by a sensor while horizontally moving the semiconductor wafer in the apparatus of the present invention shown in FIG. 1;

FIG. 3 is a diagram showing an example of peripheral position data of a semiconductor wafer detected by a sensor while rotating and moving the semiconductor wafer in the apparatus of the present invention shown in FIG. 1;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Semiconductor wafer 2 ... Robot hand 3 ... Wafer cassette 4 ... Rotary table 5, 6 ... Optical dimension measuring device (one pair of sensors) 7 ... Motor 8 ... Encoder 9-13 ... Storage part 14 ... Control part 15 ... Arithmetic processing unit

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-6-85038 (JP, A) JP-A-64-71144 (JP, A) JP-A-6-177230 (JP, A) (58) Field (Int.Cl. ⁷ , DB name) H01L 21/68

Claims (4)

(57) [Claims] A robot hand of an articulated arm capable of rotating around a first center of rotation and extending and contracting in a radial direction about the first center of rotation. A rotary table that rotates around the center of rotation,
A second direction orthogonal to a first direction from the first rotation center to the second rotation center, the second direction being arranged on both sides of the rotation table;
A method of positioning a semiconductor wafer using a pair of sensors capable of detecting a position in a direction, wherein the robot hand is rotated, and a semiconductor wafer placed thereon is aligned with the first direction, and then the first direction A first detection step of detecting the end of the semiconductor wafer in the second direction with the pair of sensors and calculating the center of the semiconductor wafer; and moving the semiconductor wafer placed on the turntable to the Rotating about a second center of rotation, wherein at least one of the pair of sensors
And a second detecting step of calculating the center of the semiconductor wafer by detecting the peripheral edge of the semiconductor wafer, and the center position of the semiconductor wafer obtained in one of the first and second detecting steps. Confirming at the center position of the semiconductor wafer obtained in the other detection step. 2. After the first detection step, the calculated center of the semiconductor wafer is aligned with the second rotation center of the turntable,
2. The method according to claim 1, further comprising a step of transferring the semiconductor wafer from the robot hand to the rotary table, and thereafter performing the second detection step. 3. A robot hand provided with a hand on which a semiconductor wafer can be placed at the tip of an articulated arm which moves vertically, horizontally and rotationally, and is provided within a moving range of the robot hand. A rotary table on which the robot hand and the semiconductor wafer are transferred; a pair of sensors provided on both sides of the rotary table for detecting the peripheral position of the semiconductor wafer on the rotary table or on the hand; A first drive mode for horizontally moving the hand so that the semiconductor wafer placed on the hand passes between the sensors in a direction orthogonal to the direction connecting the pair of sensors, and the semiconductor wafer is placed on the first drive mode; Control means having a second drive mode for rotating the turntable; and both sensors for horizontal movement of the hand in the first drive mode First calculating means for determining the center position of the semiconductor wafer from the peripheral edge position data of the semiconductor wafer on the hand, and at least one of the two sensors by rotating the turntable in the second drive mode. Second arithmetic means for obtaining the center position of the semiconductor wafer from the peripheral position data of the semiconductor wafer on the rotary table detected by one of the sensors, wherein the control means is further obtained by any one of the arithmetic means. A third drive mode in which the robot hand matches the center position of the semiconductor wafer with the center of rotation of the rotary table from the deviation between the center position data of the semiconductor wafer and the center of rotation of the rotary table; The semiconductor wafer whose center is coincident with the center of rotation of the rotary table in the alignment mode. Te positioning device for a semiconductor wafer having a confirmation means for confirming whether the center position data of the semiconductor wafer obtained by the other computing means coincides with the rotation center position of the rotary table. 4. The apparatus according to claim 3, wherein said control means further comprises a data on a deviation between the center position data of the semiconductor wafer obtained by the confirmation processing by said confirmation means and the rotation center position data of said turntable. A semiconductor wafer positioning device having a fourth drive mode for transferring the semiconductor wafer to a desired position on an arbitrary semiconductor wafer mounting table by the robot hand based on the above.