Synchronized integrated metrology for overlay-shift reduction

Patent metadata

Field	Value
Publication number	US-9841687-B2
Application number	US-201514798563-A
Country	US
Kind code	B2
Filing date	Jul 14, 2015
Priority date	Jul 14, 2015
Publication date	Dec 12, 2017
Grant date	Dec 12, 2017

Abstract

The present disclosure relates to a method of semiconductor processing. The method includes, receiving a first wafer having a photoresist coating on a face of the first wafer. An exposure unit is used to perform a first number of radiation exposures on the photoresist coating, thereby forming an exposed photoresist coating. The exposed photoresist coating is developed, thereby forming a developed photoresist coating. An OVL measurement zone pattern is selected from a number of different, pre-determined OVL measurement zone patterns based on at least one of: the first number of radiation exposures performed on the first wafer or a previous number of radiation exposures performed on a previously processed wafer, which was processed before the first wafer. A number of OVL measurements are performed on the developed photoresist coating within the selected OVL measurement zone pattern.

First claim

The invention claimed is:

1. A method of semiconductor processing, including:
receiving a first wafer having a photoresist coating on a face of the first wafer;
using an exposure unit to perform a first number of radiation exposures on the photoresist coating, thereby forming an exposed photoresist coating;
developing the exposed photoresist coating, thereby forming a developed photoresist coating;
after the exposed photoresist coating has been developed selecting a first OVL measurement zone pattern from a number of different, pre-determined OVL measurement zone patterns based on at least one of: the first number of radiation exposures performed on the first wafer or a previous number of radiation exposures performed on a previously processed wafer, which was processed before the first wafer; and
performing a number of OVL measurements on the developed photoresist coating within the selected first OVL measurement zone pattern.

2. The method of claim 1 , further comprising:
determining whether the developed photoresist coating is aligned to an underlying feature on the first wafer based on the number of OVL measurements.

3. The method of claim 1 , wherein the first OVL measurement zone pattern is a ring-shaped region along an outer edge of the face of the first wafer.

4. The method of claim 3 , wherein an area of the ring-shaped region is proportional to the first number of radiation exposures performed on the photoresist coating.

5. The method of claim 1 , further comprising:
after performing the first number of radiation exposures on the photoresist coating of the first wafer, using the exposure unit to perform a second number of radiation exposures on a photoresist coating of a second wafer, the second number of radiation exposures differing from the first number of radiation exposures;
developing the exposed photoresist coating on the second wafer, thereby forming a second developed photoresist coating;
selecting a second OVL measurement zone pattern for the second wafer from the number of different, pre-determined OVL measurement zone patterns, the second OVL measurement zone pattern differing from the first OVL measurement zone pattern; and
performing a second number of OVL measurements on the second developed photoresist coating within the second OVL measurement zone pattern.

6. The method of claim 5 , wherein the second number of radiation exposures is less than the first number of radiation exposures, and wherein the second OVL measurement zone pattern has a smaller area than that of the first OVL measurement zone pattern.

7. The method of claim 5 , wherein the second number of radiation exposures is greater than the first number of radiation exposures, and wherein the second OVL measurement zone pattern has a larger area than that of the first OVL measurement zone pattern.

8. The method of claim 7 , wherein the first and second OVL measurement zone patterns are ring-shaped patterns with outer diameters corresponding to an outer edge of the first wafer, and inner diameters that are different from one another.

9. The method of claim 7 , a difference in area between the first and second OVL measurement zone patterns, is proportional to a difference in number between the first and second number of radiation exposures.

10. The method of claim 1 , wherein performing a number of OVL measurements comprises, moving an IM scanner along the first wafer in a circular motion corresponding to the first OVL measurement zone pattern starting from an outer edge of the first OVL measurement zone pattern.

11. The method of claim 1 , wherein the number of different, pre-determined OVL measurement zone patterns includes three or more different, pre-determined OVL measurement zone patterns.

12. A method of processing first and second wafers, which are consecutively processed in a fabrication facility which includes an exposure unit and an OVL metrology unit, the method including:
receiving the first and second wafers, wherein a first photoresist coating is disposed over a first face of the first wafer and a second photoresist coating is disposed over a second face of the second wafer;
using the exposure unit to irradiate a plurality of exposure fields on the first photoresist coating according to a first number of radiation exposures, thereby forming a first exposed photoresist coating; and
after forming the first exposed photoresist coating, using the OVL metrology unit to perform a second number of OVL measurements on the first exposed photoresist coating to determine an alignment of the first exposed photoresist coating with a first underlying layer on the first wafer, wherein the second number of OVL measurements for the first wafer is based on a third number of radiation exposures to be performed on the second photoresist coating of the second wafer.

13. The method of claim 12 , further comprising:
after the second number of OVL measurements are performed on the first exposed photoresist coating, using the OVL metrology unit to perform a fourth number of OVL measurements on the second exposed photoresist coating to determine an alignment of the second exposed photoresist coating with a second underlying layer on the second wafer, wherein the fourth number of OVL measurements for the second wafer is based on the third number of radiation exposures to be performed on the second wafer.

14. The method of claim 13 , further comprising:
irradiating the second photoresist coating with the third number of radiation exposures concurrently with performance of the second number of OVL measurements on the first wafer.

15. The method of claim 13 , wherein:
the second number of OVL measurements are performed on a first OVL measurement zone pattern, which is selected from a number of different, pre-determined OVL measurement zone patterns based on at least one of: the first number of radiation exposures performed on the first wafer or a previous number of radiation exposures performed on a previously processed wafer, which was processed before the first wafer; and
the fourth number of OVL measurements are performed on a second OVL measurement zone pattern, which is based on the third number of radiation exposures.

16. The method of claim 15 , wherein the first OVL measurement zone pattern is a ring-shaped region along an outer edge of the face of the first wafer.

17. The method of claim 15 , a difference in area between the first and second OVL measurement zone patterns, is proportional to a difference in number between the first and third number of radiation exposures.

18. A method of semiconductor processing, including:
receiving a first wafer having a photoresist coating on a face of the first wafer;
using an exposure unit to perform a first number of radiation exposures on the photoresist coating, thereby forming an exposed photoresist coating;
developing the exposed photoresist coating, thereby forming a developed photoresist coating;
selecting a first OVL measurement zone pattern from a number of different, pre-determined OVL measurement zone patterns based on the first number of radiation exposures;
performing a number of OVL measurements on the developed photoresist coating within the selected first OVL measurement zone pattern;
after performing the first number of radiation exposures on the photoresist coating of the first wafer, using the exposure unit to perform a second number of radiation exposures on a photoresist coating of a second wafer, the second number of radiation exposures differing from the first number of radiation exposures;
devel

Assignees

• Taiwan Semiconductor Mfg Co Ltd

Inventors

• Lee Yung-Yao
• Liu Heng-Hsin
• Peng Jui-Chun
• Chen Yung-Cheng

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