# US 9,195,139 B2 · Apparatus and method of direct writing with photons beyond the diffraction limit using two-color resist

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- Number: US 9,195,139 B2
- Document ID: US9195139B2
- Status: Granted
- Kind: B2
- Application number: 14/244,942
- Filed: 2014-04-04
- Published: 2015-07-02
- Granted: 2015-11-24
- Earliest claimed: 2013-12-30
- Assignees: Periodic Structures, Inc.
- Applicants: David A. Markle; John S. Petersen
- Inventors: David A. Markle; John S. Petersen
- Web page: https://patentgrep.com/patent/US9195139B2

## CPC

- G03F 7/26: Processing photosensitive materials; Apparatus therefor (G03F7/12 - G03F7/24 take precedence)
- G03F 7/2022: {Multi-step exposure, e.g. hybrid; backside exposure; blanket exposure, e.g. for image reversal; edge exposure, e.g. for edge bead removal; corrective exposure}
- G03F 7/203: {comprising an imagewise exposure to electromagnetic radiation or corpuscular radiation}
- G03F 7/2051: {Exposure without an original mask, e.g. using a programmed deflection of a point source, by scanning, by drawing with a light beam, using an addressed light or corpuscular source (G03F7/70 takes precedence)}
- G03F 7/7015: {Details of optical elements}
- G03F 7/70383: {Direct write, i.e. pattern is written directly without the use of a mask by one or multiple beams (maskless lithography using a programmable mask G03F7/70291)}
- G03F 7/70466: {Multiple exposures, e.g. combination of fine and coarse exposures, double patterning or multiple exposures for printing a single feature (stitching G03F7/70475)}
- 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

Methods of and apparatus for performing direct-write lithography in a two-color photoresist layer are disclosed. The method includes exposing the two-color photoresist layer with transducer and inhibition images that respectively define bright spots and dark spots. The transducer image generates excited-state photo-molecules while the inhibition image converts the exited-state photo-molecules to an unexcited state that is not susceptible to conversion to an irreversible exposed state. The dark spots and bright spots are aligned, with the dark spots being smaller than the bright spots so that a portion of the excited-state photo-molecules adjacent the periphery of the bright spots absorb the inhibition radiation and transition to the unexcited state while a portion of the excited photo-molecules at the center of bright spots are not exposed to the inhibition light and transition to an irreversible exposed state. This forms in the two-color photoresist layer a pattern of sub-resolution photoresist pixels.

## Claims

### Claim 1

A method of performing direct-write lithography in a two-color photoresist layer that contains photo-molecules that are initially in an unexcited state, comprising:
exposing the two-color photoresist layer with a transducer image formed from exposure radiation having an exposure wavelength and comprising a first array of bright spots each having a periphery, with the exposure radiation associated with the bright spots exciting corresponding photo-molecules in the two-color photoresist layer to an excited state, thereby generating excited-state photo-molecules that are susceptible to absorption by inhibition radiation having an inhibition wavelength; and
exposing the two-color photoresist layer with an inhibition image comprising the inhibition radiation having the inhibition wavelength, the inhibition image defining an array of dark spots that are aligned with the bright spots of the transducer image and that are smaller than the bright spots so that a portion of the excited-state photo-molecules adjacent the periphery of the bright spots absorb the inhibition radiation and transition to an unexcited state that is not susceptible to conversion to an irreversible exposed state while a portion of the excited photo-molecules at the center of bright spots are not exposed to the inhibition light and transition to an irreversible exposed state, thereby forming in the two-color photoresist a set of sub-resolution photoresist pixels each having a size smaller than would be formed in the absence of the dark spots.

### Claim 2 (depends on 1)

The method according to claim 1, wherein the acts of exposing the two-color photoresist layer with the transducer image and the inhibition image are repeated to form additional sets of sub-resolution photoresist pixels at different locations in the two-color photoresist layer.

### Claim 3 (depends on 2)

The method of claim 2, further comprising changing the transducer image between forming sets of sub-resolution, permanently exposed photoresist pixels.

### Claim 4 (depends on 1)

The method of claim 1, wherein said exposing the two-color photoresist layer with a transducer image precedes exposing the two-color photoresist layer with the inhibition image.

### Claim 5 (depends on 1)

The method of claim 1, wherein said exposing the two-color photoresist layer with the inhibition mage precedes exposing the two-color photoresist layer with the transducer image.

### Claim 6 (depends on 1)

The method of claim 1, wherein said exposing the two-color photoresist layer with the inhibition image is performed concurrently with and for at least a same amount of time as said exposing the two-color photoresist layer with the transducer image.

### Claim 7 (depends on 1)

The method of claim 1, wherein said exposing the two-color photoresist layer with the inhibition image is performed for a longer period of time than said exposing the two-color photoresist layer with the transducer image.

### Claim 8 (depends on 2)

The method of claim 2, wherein said exposing the two-color photoresist layer with the inhibition image is substantially continuous between forming sets of sub-resolution photoresist pixels, and wherein the interference image is repositioned relative to the two-color photoresist layer between forming sets of sub-resolution photoresist pixels.

### Claim 9 (depends on 2)

The method of claim 2, wherein the transducer image is formed by illuminating and imaging a programmable image transducer, and wherein said exposing the two-color photoresist layer with a inhibition image is substantially continuous between forming sets of sub-resolution photoresist pixels, and wherein the interference image is repositioned relative to the two-color photoresist layer while the programming the programmable image transducer.

### Claim 10 (depends on 1)

The method of claim 1, wherein the inhibition image is formed by imaging a phase mask containing a pattern that generates an array of black holes when imaged onto the two-color photoresist layer.

### Claim 11 (depends on 1)

The method of claim 1, wherein the inhibition image is formed by causing collimated beams to interfere at the two-color photoresist layer.

### Claim 12 (depends on 1)

The method of claim 1, wherein the acts of exposing the two-color photoresist layer with the transducer image and the inhibition image occur within an exposure frame, and wherein the two-layer photoresist has a resist time constant τ that is substantially the same duration as the exposure frame.

### Claim 13 (depends on 2)

The method of claim 2, wherein the acts of exposing the two-color photoresist layer with the transducer image and the inhibition image are repeated in respective exposure frames to form additional sets of sub-resolution photoresist pixels at different locations in the two-color photo resist layer, and wherein the two-color photoresist layer has a time constant τ that is substantially the same as a time between the exposure frames.

### Claim 14 (depends on 2)

The method of claim 2, including maintaining the transducer image and the inhibition image in relative alignment and moving the transducer image and inhibition image together relative to the substrate between forming the additional sets of sub-resolution photoresist pixels.

### Claim 15 (depends on 2)

The method of claim 2, wherein the additional sets of sub-resolution photoresist pixels at different locations define a photoresist pattern having an edge, and edge position and an edge resolution, and wherein the edge resolution is defined by a partial exposure when forming the photoresist pixels at the edge of the photoresist pattern.