Robot arm device and method for transferring wafer

1. A method comprising:

repeating a cyclic operation having a sequence of a first step, a second step and a third step, wherein the first step comprises lowering an end effector, the second step comprises detecting an object distance from an object in a front opening united pod (FOUP) to the end effector, and the third step comprises assigning a height of the end effector as a height of the object in the FOUP when the detected object distance is equal to or less than a predetermined distance;

stopping repeating the cyclic operation when the height of the end effector is lower than a predetermined height; and

moving the end effector into the FOUP from a first position between the assigned height of one of the objects and the assigned height of another of the objects.

2. The method according to claim 1 , wherein the cyclic operation further comprises determining the height of the end effector after lowering the end effector.

3. The method according to claim 1 , further comprising:

identifying the object as a wafer when the detected object distance in front of the end effector is equal to or less than the predetermined distance.

4. The method according to claim 3 , wherein moving the end effector into the FOUP comprises:

horizontally moving the end effector from the first position to a second position under the wafer in the FOUP, when the detected object distance in front of the end effector is greater than the predetermined distance;

detecting a wafer backside property of the wafer;

analyzing the wafer backside property, to obtain an analysis result for the wafer backside property; and

reporting an alarm signal if the analysis result is anomalous.

5. A method comprising:

repeating a cyclic operation having a sequence of a first step, a second step and a third step, wherein the first step comprises vertically moving an end effector, the second step comprises detecting an object distance from an object in a front opening united pod (FOUP) to the end effector while vertically moving the end effector, and the third step comprises identifying the object as a wafer when the detected object distance in front of the end effector is equal to or less than a predetermined distance;

stopping repeating the cyclic operation when the end effector is moved longer than a predetermined vertical distance;

moving the end effector to a position under the wafer after stopping repeating the cyclic operation; and

lifting the wafer using the end effector.

6. The method according to claim 5 , further comprising:

detecting a wafer backside property of the wafer by using a sensor on the end effector before lifting the wafer; and

analyzing the wafer backside property to obtain an analysis result.

7. The method according to claim 6 , further comprising:

reporting an alarm signal when the analysis result is anomalous.

8. The method according to claim 6 , further comprising:

transferring the wafer to a process chamber when the analysis result is not anomalous.

9. The method according to claim 6 , wherein the wafer backside property is a two dimensional image of the wafer, and the sensor includes two image cameras.

10. The method according to claim 6 , wherein the wafer backside property is distances between a plurality of positions on the wafer and the sensor, and the sensor is a distance detector.

11. The method according to claim 6 , wherein the wafer backside property is an acoustic property, and the sensor is an acoustic detector.

12. The method according to claim 11 , further comprising generating sound waves by using a sound wave generator.

13. The method according to claim 6 , wherein analyzing the wafer backside property uses a predetermined algorithm.

14. The method according to claim 5 , further comprising:

positioning the end effector at a height lower than a height of the wafer, prior to moving the end effector to the position under the wafer.

15. A method comprising:

lowering an end effector;

detecting a first object distance from a first wafer in a front opening united pod (FOUP);

identifying a first position of the first wafer when the detected first object distance is equal to or less than a predetermined distance;

lowering the end effector and detecting a second object distance from a second wafer in the FOUP;

identifying a second position of the second object when the detected second object distance is equal to or less than the predetermined distance; and

moving the end effector into the FOUP from a third position at a height between heights of the first and second positions.

16. The method according to claim 15 , further comprising:

ending moving the end effector when a height of the end effector is lower than a predetermined height.

17. The method according to claim 16 , wherein lowering the end effector is performed when a height of the end effector is higher than the predetermined height.

18. The method according to claim 15 , further comprising:

lifting the first wafer after moving the end effector into the FOUP.

19. The method according to claim 15 , further comprising:

detecting a wafer backside property of the first wafer by using a camera after moving the end effector into the FOUP; and

analyzing the wafer backside property, to obtain an analysis result for the wafer backside property.

20. The method according to claim 19 , wherein the wafer backside property is a two dimensional image of the first wafer, distances between a plurality of positions on the first wafer and a sensor on the end effector, or an acoustic property.