# US 2020/0401053 A1 · Scan Signal Characterization Diagnostics

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- Number: US 2020/0401053 A1
- Document ID: US20200401053A1
- Status: Published application
- Kind: A1
- Application number: 16/961,081
- Filed: 2018-12-19
- Published: 2020-12-24
- Earliest claimed: 2018-01-17
- Assignees: ASML Netherlands B.V.; ASML Holding N.V.
- Applicants: ASML Netherlands B.V.; Asml Holding N.V.
- Inventors: Cornelis Melchior BROUWER; Krishanu SHOME
- Web page: https://patentgrep.com/patent/US20200401053A1

## CPC

- G03F 7/70633: {Overlay, i.e. relative alignment between patterns printed by separate exposures in different layers, or in the same layer in multiple exposures or stitching}
- G03F 7/70616: {Monitoring the printed patterns}
- G03F 9/7065: {Production of alignment light, e.g. light source, control of coherence, polarization, pulse length, wavelength}
- G03F 9/7076: {Mark details, e.g. phase grating mark, temporary mark}
- G03F 9/7088: {Alignment mark detection, e.g. TTR, TTL, off-axis detection, array detector, video detection}
- G03F 9/7092: {Signal processing}
- 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)

## Abstract

A system for and method of processing a wafer in which a scan signal is analyzed locally to extract information about alignment, overlay, mark quality, wafer quality, and the like.

## Claims

### Claim at position 1

-21. (canceled)

### Claim 22

An apparatus for controlling processing of a wafer in a lithographic apparatus, the apparatus comprising:
a light source configured to illuminate at least a portion of the wafer;
a sensor configured to sense light after interacting with the portion of the wafer and generate a scan signal indicative of the sensed light; and
a processor configured to receive the scan signal and to generate a plurality of local fit coefficients respectively for each of a plurality of samples of the scan signal and to generate a control signal based at least in part on the plurality of local fit coefficients; and
a controller configured to receive the control signal and control at least one aspect of processing the wafer based at least in part on the control signal.

### Claim 23 (depends on 22)

The apparatus of claim 22, wherein the at least one aspect is overlay alignment and the portion comprises at least one alignment mark.

### Claim 24 (depends on 22)

The apparatus of claim 22, wherein the at least one aspect is chemical mechanical polishing and the portion comprises at least one mark sensitive to variation in chemical mechanical polishing.

### Claim 25 (depends on 22)

The system of claim 22, wherein the sensor has an objective and the processor is configured to use at least a subset of the plurality of local fit coefficients to determine a distance between the objective and a reflecting layer on the wafer, and wherein the controller generates the control signal based at least in part on the distance to control exposure focus at least in part on the control signal.

### Claim 26 (depends on 22)

The apparatus of claim 22, wherein the plurality of local fit coefficients comprises a plurality of local DC offset coefficients.

### Claim 27 (depends on 22)

The apparatus of claim 22, wherein the plurality of local fit coefficients comprises a plurality of local amplitude coefficients.

### Claim 28 (depends on 27)

The apparatus of claim 27, wherein the plurality of local amplitude coefficients are calculated using a fast Fourier transform.

### Claim 29 (depends on 22)

The system of claim 22, wherein the plurality of local fit coefficients comprises a plurality of local phase coefficients.

### Claim 30 (depends on 29)

The apparatus of claim 29, wherein the plurality of local phase coefficients are calculated using a Hilbert transform.

### Claim 31 (depends on 22)

The apparatus of claim 22, wherein the plurality of local fit coefficients are smoothed.

### Claim 32

A system for aligning a wafer in a lithographic apparatus, the wafer including at least one alignment mark, the system comprising:
a light source configured to illuminate the mark;
a sensor configured to sense light after interacting with the mark and to generate an alignment scan signal indicative of the light from the mark; and
a processor configured to receive the signal and to generate a respective at least one local fit coefficient for each of a plurality of samples of the signal,
wherein the lithographic apparatus is configured to use the at least one local fit coefficient to adjust alignment of the wafer.

### Claim 33 (depends on 32)

The system of claim 32, wherein the mark is transmissive.

### Claim 34 (depends on 32)

The system of claim 32, wherein the mark is reflective.

### Claim 35 (depends on 32)

The system of claim 32, wherein the at least one fit coefficient is a local fast Fourier transform fit coefficient.

### Claim 36 (depends on 32)

The system of claim 32, wherein the at least one fit coefficient is smoothed.

### Claim 37 (depends on 32)

The system of claim 32, wherein the at least one fit coefficient is a local DC offset fit coefficient.

### Claim 38 (depends on 32)

The system of claim 32, wherein the at least one fit coefficient is a local Hilbert transform fit coefficient.

### Claim 39 (depends on 32)

The system of claim 32, wherein the processor is further configured to generate a respective at least one local fit coefficient for each of a plurality of samples of the signal to generate a plurality of local fit coefficients, and to subtract the plurality of fit coefficients from the alignment signal to generate a residual signal, and wherein the lithographic apparatus is adapted to use the residual signal to adjust alignment of the wafer.

### Claim 40 (depends on 32)

The system of claim 32, wherein the processor is further configured to use the at least one local fit coefficient to determine a deformation of the mark.

### Claim 41 (depends on 32)

The system of claim 32, wherein the processor is further configured to use the at least one local fit coefficient to determine high spatial frequency grid content by evaluating a local phase per subsegment of the signal from a single scan of the mark.

### Claim 42

A system for aligning a wafer in a lithographic apparatus, the wafer including at least one alignment mark, the system comprising:
a light source configured to illuminate the mark;
a sensor configured to sense light after interacting with the mark and to generate an alignment scan signal indicative of the light from the mark; and
a processor configured to receive the signal and to generate a respective local FFT fit coefficient for each of a plurality of samples of the signal to generate a corresponding plurality of local FFT fit coefficients for the plurality of samples, and to generate a respective local DC fit coefficient for each of a plurality of samples of the signal to generate a corresponding plurality of local DC fit coefficients for the plurality of samples, and for each sample subtract a respective one of the plurality of local FFT fit coefficients and a respective one of the plurality of DC fit coefficients from the alignment signal for the sample to obtain a residual signal for the plurality of samples,
wherein the lithographic apparatus is configured to use the residual signal to adjust alignment of the wafer.