# US 2021/0278760 A1 · Method of fabricating a photomask and method of inspecting a photomask

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- Number: US 2021/0278760 A1
- Document ID: US20210278760A1
- Status: Published application
- Kind: A1
- Application number: 17/330,482
- Filed: 2021-05-26
- Published: 2021-09-09
- Earliest claimed: 2017-11-07
- Assignees: Taiwan Semiconductor Manufacturing Company, Ltd.
- Applicants: Taiwan Semiconductor Manufacturing Company, Ltd.
- Inventors: Tsun-Cheng Tang; Cheng-Ming Lin; Sheng-Chang Hsu; Hao-Ming Chang; Way-Len Chang
- Web page: https://patentgrep.com/patent/US20210278760A1

## CPC

- G03F 1/84: Inspecting
- G01B 11/02: for measuring length, width or thickness (G01B11/08 takes precedence)
- G01N 21/8806: {Specially adapted optical and illumination features}
- G01N 21/9501: {Semiconductor wafers (manufacturing processes per se of semiconductor devices implementing a measuring step H10P74/20)}
- G01N 21/956: Inspecting patterns on the surface of objects {(contactless testing of electronic circuits G01R31/308; testing currency G07D; manufacturing processes per se of semiconductor devices implementing a measuring step H10P74/20)}
- G03F 1/42: Alignment or registration features, e.g. alignment marks on the mask substrates
- G03F 7/2002: {with visible light or UV light, through an original having an opaque pattern on a transparent support, e.g. film printing, projection printing; by reflection of visible or UV light from an original such as a printed image}
- G01N 2021/8835: {Adjustable illumination, e.g. software adjustable screen}
- G01N 2021/95676: {Masks, reticles, shadow masks}
- G01N 2201/127: Calibration; base line adjustment; drift compensation
- G03F: PHOTOMECHANICAL PRODUCTION OF TEXTURED OR PATTERNED SURFACES, e.g. FOR PRINTING, FOR PROCESSING OF SEMICONDUCTOR DEVICES; MATERIALS THEREFOR; ORIGINALS THEREFOR; APPARATUS SPECIALLY ADAPTED THEREFOR; (phototypographic composing devices B41B; photosensitive materials or processes for photographic purposes G03C; electrophotography, sensitive layers or processes therefor G03G)
- G01B: MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
- G01N: INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES (measuring or testing apparatus or processes other than immunoassay, involving enzymes or microorganisms C12M, C12Q)

## Abstract

In accordance with some embodiments of the present disclosure, an inspection method of a photomask includes performing a first inspection process, unloading the photomask from the inspection system, and performing a second inspection process. In the first inspection process, a common Z calibration map of an objective lens of an optical module with respect to the photomask is generated and stored, and a first image of the photomask is captured by using an image sensor while focusing the objective lens of the optical module based on the common Z calibration map. The photomask is unloaded from the inspection system. In the second inspection process, the photomask is loaded on the inspection system and a second image of the photomask is captured by using an image sensor while focusing an objective lens of an optical module based on the common Z calibration map generated in the first inspection process.

## Claims

### Claim 1

A method of fabricating a photomask, comprising:
forming a pattern portion on a substrate of the photomask;
performing a first inspection on the photo mask using an inspection system;
forming a pellicle on the substrate to cover the pattern portion; and
performing a second inspection using the inspection system, wherein the second inspection comprises capturing an image of the photomask having the pellicle by focusing an objective lens of an optical module of an inspection system based on a common Z calibration map generated in the first inspection.

### Claim 2 (depends on 1)

The method of claim 1, wherein the first inspection comprises generating the common Z calibration map by scanning the photomask with the pattern portion formed thereon along a plurality of scanning paths using the optical module of the inspection system while the objective lens of the optical module is maintained in a common level and determining focus of the objective lens at respective points on the scanning paths.

### Claim 3 (depends on 1)

The method of claim 1, wherein the first inspection comprises capturing a first image of the photomask with the pattern portion formed thereon by using an image sensor of the inspection system while focusing the objective lens of the optical module of the inspection system based on the common Z calibration map.

### Claim 4 (depends on 3)

The method of claim 3, wherein the second inspection comprises capturing a second image of the photomask having the pellicle by using the image sensor of the inspection system while focusing the objective lens of the optical module of the inspection system based on the common Z calibration map.

### Claim 5 (depends on 4)

The method of claim 4, further comparing the second image with a reference image.

### Claim 6 (depends on 5)

The method of claim 5, wherein the first image is the reference image.

### Claim 7 (depends on 1)

The method of claim 1, wherein the pellicle is a transparent film.

### Claim 8

A method of inspecting a photomask, comprising:
performing a first inspection on the photomask using a first inspection apparatus and obtaining a first Z calibration map in the first inspection;
sharing the first Z calibration map from the first inspection apparatus to a second inspection apparatus;
uploading the photomask to the second inspection apparatus; and
performing a second inspection on the photomask using the second inspection apparatus by focusing an objective lens of an optical module of the second inspection apparatus based on at least the first Z calibration map generated in the first inspection.

### Claim 9 (depends on 8)

The method of claim 8, further performing a third inspection on the photomask using the second inspection apparatus and obtaining a second Z calibration map in the third inspection.

### Claim 10 (depends on 9)

The method of claim 9, further generating a compensation data based on a variation between the first Z calibration map generated in the first inspection and the second Z calibration map generated in the second inspection.

### Claim 11 (depends on 10)

The method of claim 10, wherein the second inspection comprises capturing an image of the photomask by using an image sensor of the second inspection apparatus while focusing the objective lens of the optical module of the second inspection apparatus based on the first Z calibration map and the compensation data.

### Claim 12 (depends on 8)

The method of claim 8, wherein the first inspection comprises capturing an image of the photomask by focusing an objective lens of an optical module of the first inspection apparatus based on the first Z calibration map.

### Claim 13 (depends on 8)

The method of claim 8, wherein the second inspection comprises capturing an image of the photomask by focusing the objective lens of the optical module of the second inspection apparatus based on the first Z calibration map.

### Claim 14

A method of fabricating a photomask, comprising:
performing a first process on the photomask using a first tool;
performing a first inspection on the photomask and generating a first Z calibration map with respect to the photomask from the first inspection;
performing a second process on the photomask that is processed by the first process, using a second tool;
performing a second inspection on the photo mask and generating a second Z calibration map with respect to the photomask from the second inspection; and
comparing the first Z calibration map generated in the first inspection with the second Z calibration map generated in the second inspection to check a status of the first process or the second process.

### Claim 15 (depends on 14)

The method of claim 14, wherein the second tool comprises an etching tool or a stripping tool.

### Claim 16 (depends on 14)

The method of claim 14, wherein a pattern portion is formed on a substrate of the photomask through the first process and the second process.

### Claim 17 (depends on 14)

The method of claim 14, wherein the first inspection and the second inspection are performed using a same inspection apparatus.

### Claim 18 (depends on 17)

The method of claim 17, wherein the first inspection comprises capturing an image of the photomask by focusing an objective lens of an optical module of the inspection apparatus based on the first Z calibration map.

### Claim 19 (depends on 17)

The method of claim 17, wherein the second inspection comprises capturing an image of the photomask by focusing an objective lens of an optical module of the inspection apparatus based on the second Z calibration map.

### Claim 20 (depends on 14)

The method of claim 14, wherein an abnormal status is determined based on one or more extraordinary peak determined from comparing the first Z calibration map generated in the first inspection and the second Z calibration map generated in the second inspection.