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Methods and systems to optimize wafer placement repeatability in semiconductor manufacturing equipment using a controlled series of wafer movements are provided. In one embodiment, a preliminary station calibration is performed to teach a robot position for each station interfaced to facets of a vac

Methods and systems to optimize wafer placement repeatability in semiconductor manufacturing equipment using a controlled series of wafer movements are provided. In one embodiment, a preliminary station calibration is performed to teach a robot position for each station interfaced to facets of a vacuum transfer module used in semiconductor manufacturing. The method also calibrates the system to obtain compensation parameters that take into account the station where the wafer is to be placed, position of sensors in each facet, and offsets derived from performing extend and retract operations of a robot arm. In another embodiment where the robot includes two arms, the method calibrates the system to compensate for differences derived from using one arm or the other. During manufacturing, the wafers are placed in the different stations using the compensation parameters.

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1. A method to optimize wafer placement repeatability in a system with semiconductor manufacturing equipment using a controlled series of wafer movements, the method comprising: (a) performing a preliminary station calibration to teach a robot position for each station interfaced to facets of a vacu

1. A method to optimize wafer placement repeatability in a system with semiconductor manufacturing equipment using a controlled series of wafer movements, the method comprising: (a) performing a preliminary station calibration to teach a robot position for each station interfaced to facets of a vacuum transfer module (VTM) used in semiconductor manufacturing;(b) calibrating the system to obtain compensation parameters that take into account the station where the wafer is to be placed, position of sensors in each facet, and offsets derived from performing extend and retract operations of a robot arm, the calibrating further including accessing a table having nominal sensor locations for each facet, and creating an offset table to compensate for error induced by the nominal sensor locations;(c) fine tuning the compensation parameters and robot position for each station by obtaining data from placing and picking of the wafer; and(d) placing wafers in stations during manufacturing using the compensation parameters. 2. A method to optimize wafer placement repeatability in a system with semiconductor manufacturing equipment using a controlled series of wafer movements, the method comprising: (a) performing a preliminary station calibration to teach a robot position for each station interfaced to facets of a vacuum transfer module (VTM) used in semiconductor manufacturing;(b) calibrating the system to obtain compensation parameters that take into account the station where the wafer is to be placed, position of sensors in each facet, and offsets derived from performing extend and retract operations of a robot arm;(c) placing wafers in stations during manufacturing using the compensation parameters, wherein operations (a) and (b) are performed with a first arm identified as a reference arm of the robot;(d) performing operations (a) and (b) with a second arm of the robot;(e) dropping off a picked wafer once to swap arms after performing operation (a) with the first arm and before performing operation (a) with the second arm, the dropping being performing at a reduced speed to reduce effects of wafer shifting; and(f) dropping off the picked wafer once to swap arms after performing operation (b) with the first arm and before performing operation (b) with the second arm. 3. A method to optimize wafer placement repeatability in a system with semiconductor manufacturing equipment using a controlled series of wafer movements, the method comprising: (a) performing a preliminary station calibration to teach a robot position for each station interfaced to facets of a vacuum transfer module (VTM) used in semiconductor manufacturing;(b) calibrating the system to obtain compensation parameters that take into account the station where the wafer is to be placed, position of sensors in each facet, and offsets derived from performing extend and retract operations of a robot arm, wherein operation (b) further includes: (i) accessing a table having nominal sensor locations for each facet;(ii) identifying a reference station, a reference transfer direction, and a reference robot arm;(iii) picking at the reference station a wafer that is known to be properly positioned;(iv) passing the picked wafer through the facets and measuring extend and retract offsets when the robot passes the wafer into and out of the stations with each arm;(v) creating an offset table to compensate for repeatable measurement error induced by differences between extend and retract direction, as well as error induced by using nominal sensor locations; and(vi) adjusting robot values for each station;(c) placing wafers in stations during manufacturing using the compensation parameters, wherein operations (a) and (b) are performed with a first arm identified as a reference arm of the robot; and(d) performing operations (a) and (b) with a second arm of the robot. 4. The method as recited in claim 3, wherein rows in the offset table include, an identifier for a combination of station and arm used,a pair of values associated with an extend operation, the pair of values including a radius and an angle, anda pair of values associated with a retract operation. 5. The method as recited in claim 4, wherein operation (b) further comprises: (vii) refining station locations using metrology based alignment; and(viii) fine tuning offset table values and robot position for each station by obtaining data from repeatedly placing and picking of the wafer. 6. The method as recited in claim 5, wherein (viii) fine tuning the offset table values further includes, performing multiple measurements of each combination for placing the wafer with one arm and then picking up the wafer with the same or a different arm,getting a cluster of values from the multiple measurements for each combination, andcalculating a representative value for each cluster associated with each combination to adjust a second arm placement position and the retract values in the offset table. 7. The method as recited in claim 4, wherein operation (c) further includes, using dynamic alignment to measure wafer center after passing the wafer thorough station sensors;calculating a compensation offset as a distance between the measured wafer center and the offset table values; andcentering the wafer during wafer placement adjusting for the compensation offset. 8. The method as recited in claim 4, further comprising (e) measuring wafer position when picking the wafer from a station, the measuring wafer position including, (i) picking the wafer from a station and using dynamic alignment to measure the wafer center, and(ii) using offset table values to calculate where the wafer center is relative to a station center. 9. The method as recited in claim 4, wherein rows in the table having nominal sensor locations include, a station identification,a sensor identification,a radius value, andan angle value. 10. The method as recited in claim 1, wherein (a) further includes, using dynamic alignment to teach the robot position in each station. 11. A method to optimize wafer placement repeatability in a system with semiconductor manufacturing equipment using a controlled series of wafer movements, the method comprising: (a) performing a preliminary station calibration to teach a robot position for each station interfaced to facets of a VTM used in semiconductor manufacturing;(b) calibrating the system, the calibrating including, (i) accessing a table having nominal sensor locations for each facet;(ii) identifying a reference station, a reference transfer direction, and a reference robot arm;(iii) picking at the reference station a wafer that is known to be properly positioned;(iv) passing the picked wafer through the facets and measuring extend and retract offsets when the robot passes the wafer into and out of the stations with each arm;(v) creating an offset table to compensate for repeatable measurement error induced by differences between extend and retract direction, as well as error induced by using nominal sensor locations; and(vi) adjusting robot values for each station; and(c) placing wafers in stations during manufacturing using calibration results. 12. The method as recited in claim 11 wherein operations (a) and (b) are performed with a first arm identified as a reference arm of the robot, the method further comprising performing operations (a) and (b) with a second arm of the robot. 13. The method as recited in claim 11, wherein operation (b) further includes, (vii) refining station locations using metrology based alignment. 14. The method as recited in claim 11, wherein operation (b) further includes, (viii) fine tuning offset table values and robot position for each station by obtaining data from repeatedly placing and picking of the wafer. 15. The method as recited in claim 11, wherein during operation (b) the wafer is replaced by a calibration fixture. 16. A method to optimize wafer placement repeatability in a system with semiconductor manufacturing equipment using a controlled series of wafer movements, the method comprising: (a) performing a preliminary station calibration to teach a robot position for each station interfaced to facets of a VTM used in semiconductor manufacturing;(b) calibrating the system, the calibrating including, (i) accessing a table having nominal sensor locations for each facet;(ii) identifying one of the stations as a reference station;(iii) picking at the reference station a wafer that is known to be properly positioned;(iv) passing the picked wafer through the facets and measuring extend and retract offsets when the robot passes the wafer into and out of the stations;(v) creating an offset table to compensate for repeatable measurement error induced by differences between extend and retract direction, as well as error induced by using the nominal sensor locations;(vi) adjusting robot values for each station;(vii) refining station locations using metrology based alignment; and(viii) fine tuning offset table values and robot position for each station by obtaining data from repeatedly placing and picking of the wafer; and(c) placing wafers in stations during manufacturing using calibration results. 17. The method as recited in claim 16, wherein the passing the picked wafer of (iv) is repeated multiple times through each facet, andwherein the creating the offset table of (v) is performed by averaging the results from the passing the picked wafer multiple times in (iv). 18. The method as recited in claim 16, wherein the wafer is properly positioned in (iii) by centering the wafer in the reference station using an aligner. 19. The method as recited in claim 16, wherein a vertical velocity of the robot is reduced at the beginning of each operation in (b). 20. The method as recited in claim 16 wherein operations (a) and (b) are performed with a first arm identified as a reference arm of the robot, the method further comprising performing operations (a) and (b) with a second arm of the robot. 21. The method as recited in claim 20, wherein operation (viii) further includes, performing multiple measurements of different combinations for placing the wafer with one arm and then picking up the wafer with the same or a different arm,getting a cluster of values from the multiple measurements for each combination, andcalculating a representative value for each cluster associated with each combination to adjust a second arm placement position and retract values in the offset table. 22. A system to optimize wafer placement repeatability in semiconductor manufacturing equipment using a controlled series of wafer movements, comprising: a vacuum transfer module (VTM) used in semiconductor manufacturing;a robot in the VTM;a plurality of stations interfaced to facets in the VTM;a plurality of sensors in each facet;a computer device having a processor;a display to show results of the wafer movements; anda memory, the memory including,a wafer placement program, a table having nominal sensor locations for each facet,an offset table, andfine tuning values for station locations;wherein program instructions from the wafer placement program when executed by the processor cause the processor to, (a) perform a preliminary station calibration to teach a robot position for each station;(b) calibrate the system, which causes the processor to, (i) access the table having nominal sensor locations;(ii) identify one of the stations as a reference station;(iii) pick at the reference station a wafer that is known to be properly positioned;(iv) pass the picked wafer through the plurality of facets and measuring the extend and retract offsets when the robot passes the wafer into and out of the stations;(v) create the offset table to compensate for repeatable measurement error induced by differences between extend and retract direction, as well as error induced by using nominal sensor locations;(vi) adjust robot values for each station;(vii) refine the station locations using metrology based alignment; and(viii) fine tune offset table values and robot position for each station by obtaining data from repeatedly placing and picking of the wafer; and(c) place wafers in stations during manufacturing using calibration results.