# US 9,040,910 B2 · Multi-column electron beam inspection that uses custom printing methods

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- Number: US 9,040,910 B2
- Document ID: US9040910B2
- Status: Granted
- Kind: B2
- Application number: 14/281,772
- Filed: 2014-05-19
- Published: 2014-11-27
- Granted: 2015-05-26
- Earliest claimed: 2013-05-23
- Assignees: Tao Luo
- Applicants: Tao Luo
- Inventors: Tao Luo
- Web page: https://patentgrep.com/patent/US9040910B2

## CPC

- H01J 37/02: Details
- H01J 37/265: {Controlling the tube; circuit arrangements adapted to a particular application not otherwise provided, e.g. bright-field-dark-field illumination}
- H01J 37/28: with scanning beams {(H01J37/268, H01J37/292, H01J37/2955 take precedence)}
- H01J 2237/2826: Calibration
- H01J: ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS (spark-gaps H01T; electric arc lamps H05B31/00; particle accelerators H05H)

## Abstract

A method of testing for photomask print errors includes dividing a photomask print into sub-regions and inspecting each sub-region with a different (e.g., electron) beam column, each sub-region aligned with a beam column axis during a calibration process. The different sub-regions may be inspected on different photomask prints on a wafer plane.

## Claims

### Claim 1

A semiconductor wafer inspection process, comprising:
creating an inspection test wafer from a custom arrangement of photomask exposure layout different from a production print layout of a production wafer;
inspecting the inspection test wafer for defects using a multi-column electron beam system;
processing the inspection test wafer under the same conditions as the production wafer, except that the photolithography exposure step is modified to create an arrangement of photomask prints on the inspection test wafer plane to allocate and align sub-regions of each photomask print to a different beam column; and
inspecting each one of the sub-regions in the repeated photomask prints on the wafer plane using a different column of the multi-column electron beam system.

### Claim 2 (depends on 1)

The process of claim 1, where the sub-regions within each photomask print are offset from one another both in the x and y dimensions on the wafer plane by determined amounts.

### Claim 3 (depends on 1)

The process of claim 1, wherein physical multi-column beam axis positions are first calibrated using a calibration wafer to obtain each beam axis' wafer coordinates, which includes designed hardware arrangements, mechanical errors, and assembly tolerances.

### Claim 4 (depends on 1)

The process of claim 1, wherein if a beam column fails over time, the photomask print is re-generated and re-divided into a different number of sub-regions so that complete photomask print defect information continues to be inspected collectively and entirely by the remaining working beam columns.

### Claim 5 (depends on 1)

The process of claim 1, wherein if a beam column fails over time, follow-up inspection is carried out by a single column electron beam system that scans for defects in the uninspected region corresponding to the beam column that failed.

### Claim 6 (depends on 1)

The process of claim 1, wherein each sub-region is defined each with the same dimensions and orientations.

### Claim 7 (depends on 1)

The process of claim 1, wherein critical regions of a repeated photomask print are divided into sub-regions, and a column beam condition for each sub-region is custom set for optimum detection of defects in the corresponding sub-region.

### Claim 8 (depends on 1)

The process of claim 1, wherein critical areas of a repeated photomask print are divided into inspection sub-regions, each custom aligned to the physical positions of a corresponding beam column in order to optimize throughput and defect sensitivity during inspection.

### Claim 9 (depends on 8)

The process of claim 8, wherein sub-regions are further allocated into different groups, and different groups on different inspection test wafers are inspected by different multi-column beam systems simultaneously.

### Claim 10 (depends on 1)

The process of claim 1, wherein each beam column inspects a sub-region in a different photomask print on the inspection test wafer plane.

### Claim 11 (depends on 1)

The process of claim 1, wherein more than one inspection test layout, each on a separate wafer, and more than one multi-column beam inspection system, are used for inspection of different sub-regions of an overall photomask print.

### Claim 12 (depends on 1)

The process of claim 1, wherein a review process is applied to the inspection test wafer in order to further analyze and classify defects, and a photomask reparation process is carried out based on mapping from a collective defect distribution on the wafer plane to physical photomask coordinates corresponding to the detected defects.

### Claim 13 (depends on 1)

The process of claim 1, wherein repeated photomask prints are arranged on the inspection test wafer plane so that each beam column scans a different corresponding sub-region of each photomask print.