System and method for wafer-by-wafer overlay feedforward and lot-to-lot feedback control

Patent metadata

Field	Value
Publication number	US-11221561-B2
Application number	US-202016742209-A
Country	US
Kind code	B2
Filing date	Jan 14, 2020
Priority date	Jan 14, 2020
Publication date	Jan 11, 2022
Grant date	Jan 11, 2022

Abstract

An overlay control system is disclosed. In embodiments, the system may include a controller configured to: acquire a set of feedback overlay measurements based on a plan of record (POR) sampling map on a second layer of samples of at least one previous lot of samples; generate a reference wafer overlay map based on the set of feedback overlay measurements; acquire a set of feedforward overlay measurements based on a feedforward sampling map on a first layer of a set of samples of a current lot of samples; generate a set of artificial overlay vector maps for the set of samples of the current lot of samples based on the set of feedforward overlay measurements; and cause a lithography tool to fabricate a second layer of samples of the current lot of samples based on the reference wafer overlay map and the set of artificial overlay vector maps.

First claim

What is claimed:

1. An overlay control system, comprising:
a controller including one or more processors, the one or more processors configured to execute a set of program instructions stored in memory, the set of program instructions configured to cause the one or more processors to:
acquire a set of feedback overlay measurements based on a plan of record (POR) sampling map on a second layer of one or more samples of at least one previous lot of samples, wherein the POR sampling map includes a plurality of points;
generate a reference wafer overlay map based on the set of feedback overlay measurements;
acquire a set of feedforward overlay measurements based on a feedforward sampling map on a first layer of a set of samples of a current lot of samples;
apply an overlay correction vector associated to each point of the feedforward sampling map within the reference wafer overlay map to generate a set of artificial overlay vector maps for the set of samples of the current lot of samples based on the set of feedforward overlay measurements; and
generate one or more control signals configured to cause a lithography tool to fabricate a second layer of one or more samples of the current lot of samples based on the reference wafer overlay map and the set of artificial overlay vector maps.

2. The overlay control system of claim 1 , wherein the set of artificial overlay vector maps comprise feedforward overlay corrections.

3. The overlay control system of claim 1 , wherein the reference wafer overlay map is used to carry out feedback overlay corrections.

4. The overlay control system of claim 1 , wherein the controller is configured to generate an artificial overlay vector map for each sample of the set of samples of the current lot of samples.

5. The overlay control system of claim 1 , wherein the controller is configured to cause the lithography tool to fabricate a second layer of a first sample of the current lot of samples based on the reference wafer overlay map and the set of artificial overlay vector maps by:
selectively modifying the reference wafer overlay map with a first artificial overlay vector map to generate a first modified reference wafer overlay map; and
generating one or more control signals configured to cause the lithography tool to fabricate a second layer of the first sample of the current lot of samples based on the modified reference wafer overlay map.

6. The overlay control system of claim 5 , wherein the controller is configured to cause the lithography tool to fabricate a second layer of an additional sample of the current lot of samples based on the reference wafer overlay map and the artificial overlay vector maps by:
selectively modifying the reference wafer overlay map with an additional artificial overlay vector map to generate an additional modified reference wafer overlay map; and
generating one or more control signals configured to cause the lithography tool to fabricate a second layer of the additional sample of the current lot of samples based on the additional modified reference wafer overlay map.

7. The overlay control system of claim 1 , wherein the artificial overlay vector map includes an overlay correction vector for each point of the plurality of points.

8. The overlay control system of claim 1 , wherein the plurality of points of the feedforward sampling map comprises a plurality of points proximate to an edge of the first set of samples.

9. The overlay control system of claim 1 , wherein the plurality of points of the feedforward sampling map comprise a sub-set of points selected from the POR sampling map.

10. The overlay control system of claim 9 , wherein the controller is configured to select the plurality of points of the feedforward sampling map by:
identifying a sub-set of points of the POR sampling map which exhibit the highest sample-to-sample overlay variation; and
selecting the sub-set of points as the plurality of points of the feedforward sampling map.

11. The overlay control system of claim 10 , wherein the controller is configured to identify the sub-set of points of the POR sampling map which exhibit the highest sample-to-sample overlay variation via one or more principal component analysis processes.

12. The overlay control system of claim 1 , wherein the POR sampling map includes a set of points which are dispersed across the entirety of each sample of the lot of samples.

13. The overlay control system of claim 1 , wherein the first set of samples comprises each sample of the lot of samples.

14. The overlay control system of claim 1 , wherein the second layer of the lot of samples is fabricated on top of the first layer of the lot of samples.

15. The overlay control system of claim 1 , wherein the set of feedforward overlay measurements of the first layer and the set of feedback overlay measurements of the second layer are measured with respect to a single reference layer.

16. The overlay control system of claim 1 , wherein the controller is further configured to:
acquire a set of feedback overlay measurements based on the POR sampling map on the first layer of a set of samples of the Nth lot of samples;
generate an additional reference wafer overlay map based on the set of feedback overlay measurements; and
generate one or more control signals configured to cause the lithography tool to fabricate a first layer of one or more samples of an N+1 th lot of samples based at least in part on the additional reference wafer overlay map.

17. The overlay control system of claim 1 , wherein the at least one previous lot of samples comprises a first previous lot of samples and a second previous lot of samples,
wherein the set of feedback overlay measurements include feedback overlay measurements on the first previous lot of samples and the second previous lot of samples,
wherein the reference wafer overlay map is generated as a weighted average of the feedback overlay measurements on the first previous lot of samples and the feedback overlay measurements on the second previous lot of samples.

18. An overlay control system, comprising:
a lithography tool; and
a controller communicatively coupled to the lithography tool, the controller including one or more processors, the one or more processors configured to execute a set of program instructions stored in memory, the set of program instructions configured to cause the one or more processors to:
acquire a set of feedback overlay measurements based on a plan of record (POR) sampling map on a second layer of one or more samples of an at least one previous lot of samples;
generate a reference wafer overlay map based on the set of feedback overlay measurements;
acquire a set of feedforward overlay measurements based on a feedforward sampling map on a first layer of a set of samples of a current lot of samples, wherein the feedforward sampling map includes a plurality of points;
apply an overlay correction vector to each point of the feedforward sampling map within the reference wafer overlay map to generate a set of artificial overlay vector maps for each sample of the current lot of samples based on the set of feedforward overlay measurements; and
generate one or more control signals configured to cause the lithography tool to fabricate a second layer of each sample of the current lot of samples based on the reference wafer overlay map and the set of artificial overlay vector maps.

19. A method for feedforward and feedback overlay control comprising:
acquiring a set of feedback overlay measurements based on a plan of rec

Assignees

• Kla Corp

Inventors

• Demirer Onur Nihat
• Anis Fatima
• Smith Mark D

Classifications

• G03F7/70633 Primary

  Overlay, i.e. relative alignment between patterns printed by separate exposures in different layers, or in the same layer in multiple exposures or stitching · CPC title

• G03F7/70525

  Controlling normal operating mode, e.g. matching different apparatus, remote control or prediction of failure · CPC title

• G03F9/7019

  Calibration · CPC title

• G03F7/706837

  Data analysis, e.g. filtering, weighting, flyer removal, fingerprints or root cause analysis · CPC title

• G03F7/706833

  Sampling plan selection or optimisation, e.g. select or optimise the number, order or locations of measurements taken per die, workpiece, lot or batch · CPC title