Wafer transfer apparatus, wafer transfer method and storage medium

• US 20090053023A1
• Filed: 08/24/2007
• Published: 02/26/2009
• Est. Priority Date: 08/25/2006
• Status: Active Grant

• Current Assignee: Tokyo Electron Limited
• Original Assignee: Tokyo Electron Limited
• Inventors: Wakabayashi, Shinji
• Granted Patent: US 8,025,475 B2
• Time in Patent Office: Days
• US Class Current: 414/222.130
• CPC Class Codes: H01L 21/67748 horizontal transfer of a single workpiece
• CPC Class Codes: H01L 21/681 using optical controlling means
• CPC Class Codes: Y10S 414/136 including wafer orienting means

Abstract

One sensor constituted of a light emission element and a light-receiving element is provided in a path through which a wafer is transferred. The sensor is positioned so that the wafer passes through an area between the light emission element and the light-receiving element. Coordinates of the center of the wafer are calculated based on encoder values obtained when the wafer starts passing through the sensor and when the wafer completes passing through the sensor, position data of wafer transfer means corresponding to the encoder value, and the diameter of the wafer; and thereby the amount of positional deviation of the center of the wafer from a reference position is calculated.

Claims

1. A wafer transfer apparatus that transfers a wafer while the wafer is mounted on a movable transfer arm, comprising:

one wafer detection sensor provided at a position at which it is possible for the detection sensor to judge whether or not a wafer mounted on the transfer arm is passing through a detection area of the detection sensor when the transfer arm moves;

position data acquiring means that acquires position data of the transfer arm based on an amount of driving of the transfer arm;

a storage unit that stores reference position data corresponding to a reference position of the wafer mounted on the transfer arm; and

calculation means that determines, based on the position data acquired by the position data acquiring means and a result of judgment of the wafer detection sensor, position data of the transfer arm at a point of time at which the wafer starts passing through the detection area of the wafer detection sensor, and position data of the transfer arm at a point of time at which the wafer completes passing through the detection area, and then calculates an amount of positional deviation of a center of the wafer based on those position data of the transfer arm thus determined, the reference position data and a diameter of the wafer.

2. The wafer transfer apparatus according to claim 1, wherein the transfer arm is configured to be driven such that the wafer passes linearly through the detection area of the wafer detection sensor.

3. The wafer transfer apparatus according to claim 1, wherein the calculation means is configured to calculate the amount of positional deviation of the center of the wafer by using, as said diameter of wafer, a correct diameter of the wafer that is determined based on position data of a periphery of the wafer obtained when the wafer is rotated by a rotary stage to adjust an orientation of the wafer.

4. The wafer transfer apparatus according to claim 1,

wherein the position at which the wafer detection sensor is provided is such a position that at which it is also possible for the detection sensor to judge whether or not the transfer arm passing through the detection area of the wafer detection sensor,

said apparatus further comprising:

judgment means that determines, based on a position data acquired by the position data acquiring means and the result of judgment by the wafer detection sensor, position data of the transfer arm at a point of time at which the transfer arm starts passing through the detection area of the wafer detection sensor or position data of the transfer arm at a point of time at which the transfer arm completes passing through the detection area, and then judges, by comparing the position data thus determined with position data to be obtained when the transfer arm is in normal operation, whether or not the transfer arm is in normal operation.

6. The wafer transfer apparatus according to claim 1, further comprising:

judgment means that judges whether or not the amount of the positional deviation of the center of the wafer exceeds a threshold value; and

alarm means that alarms that the amount of deviation exceeds the threshold value.

5. A wafer transfer apparatus that transfers a wafer while the wafer is mounted on a movable transfer arm, comprising:

at least one wafer detection sensor provided at a position at which it is possible for the detection sensor to judge whether or not a wafer mounted on the transfer arm is passing through a detection area of the detection sensor when the transfer arm moves;

position data acquiring means that acquires position data of the transfer arm based on an amount of driving of the transfer arm;

a storage unit that stores reference position data corresponding to a reference position of the wafer mounted on the transfer arm; and

calculation means that calculates an amount of positional deviation of a center of the wafer based on the position data acquired by the position data acquiring means, a result of judgment of the wafer detection sensor and a diameter of the wafer, the diameter of wafer being obtained based on position data of a periphery of the wafer obtained when the wafer is rotated by a rotary stage to adjust an orientation of the wafer.

7. The wafer transfer apparatus according to claim 5, further comprising judgment means that judges whether or not the amount of the positional deviation of the center of the wafer exceeds a threshold value, wherein the transfer arm is configured to mount the wafer to a transfer destination so that the positional deviation of the center of the wafer is corrected, if it is judged that the amount of the positional deviation does not exceed the threshold value.

8. A wafer transfer method for transferring a wafer while the wafer is mounted on movable transfer arm, said method comprising the steps of:

moving the transfer arm to allow the wafer to pass through a detection area of one wafer detection sensor, the wafer detection sensor being configured to be capable of judging whether or not the wafer mounted on the transfer arm is passing through the detection area of the detection sensor;

detecting passage of the wafer through the detection area of the wafer detection sensor by means of the wafer detection sensor;

acquiring first position data of the transfer arm at a point of time when the wafer starts passing through the detection area, based on an amount of driving of the transfer arm;

acquiring second position data of the transfer arm at a point of time when the wafer completes passing through the detection area, based on an amount of driving of the transfer arm; and

calculating an amount of positional deviation of a center of the wafer based on the first and second position data of the transfer arm, reference position data corresponding to a reference position of the wafer mounted on the transfer arm, and a diameter of the wafer.

9. The wafer transfer method according to claim 8, wherein, in the step of moving the transfer arm, the transfer arm is driven such that the wafer passes linearly through the detection area of the wafer detection sensor.

10. The wafer transfer method according to claim 8, wherein the step of calculating the amount of positional deviation is performed by using, as said diameter of wafer, a correct diameter of the wafer that is determined based on position data of a periphery of the wafer obtained when the Wafer is rotated by a rotary stage to adjust an orientation of the wafer.

11. The wafer transfer method according to claim 8, further comprising the steps of:

detecting passage of the transfer arm through the detection area of the wafer detection sensor by means of the wafer detection sensor, when moving the transfer arm;

acquiring third position data of the transfer arm at a point of time when the transfer arm starts passing or completes passing through the detection area, based on an amount of driving of the transfer arm; and

judging whether or not the transfer arm is in normal operation, by comparing the third position data of the transfer arm with position data to be obtained when the transfer arm is in normal operation.

13. The wafer transfer method according to claim 8, further comprising a step of judging whether or not the amount of the positional deviation of the center of the wafer exceeds a threshold value, and notifying that an abnormality occurs if it is judged that the amount of the positional deviation of the center of the wafer exceeds the threshold value.

14. The wafer transfer method according to claim 8, further comprising a step of judging whether or not the amount of the positional deviation of the center of the wafer exceeds a threshold value, and mounting the wafer to a transfer destination so that the positional deviation of the center of the wafer is corrected if it is judged that the amount of the positional deviation does not exceed the threshold value.

15. A storage medium storing a computer program operable on a computer for controlling a wafer transfer apparatus,

wherein the computer program includes programmed steps of executing the wafer transfer method according to claim 8.

12. A wafer transfer method for transferring a wafer while the wafer is mounted on a movable transfer arm, said method comprising the steps of:

moving the transfer arm to allow the wafer to pass through a detection area of at least one wafer detection sensor, the wafer detection sensor being configured to be capable of judging whether or not the wafer mounted on the transfer arm is passing through the detection area of the detection sensor;

detecting passage of the wafer through the detection area of the wafer detection sensor by means of the wafer detection sensor;

acquiring first position data of the transfer arm at a point of time when the wafer starts passing through the detection area, based on an amount of driving of the transfer arm;

acquiring second position data of the transfer arm at a point of time when the wafer completes passing through the detection area, based on an amount of driving of the transfer arm; and

calculating an amount of positional deviation of a center of the wafer based on the first and second position data of the transfer arm, reference position data corresponding to a reference position of the wafer mounted on the transfer arm, and a diameter of the wafer that is determined based on position data of a periphery of the wafer obtained when the wafer is rotated by a rotary stage to adjust an orientation of the wafer.