# US 11,112,698 B2 · Photoresist with gradient composition for improved uniformity

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- Number: US 11,112,698 B2
- Document ID: US11112698B2
- Status: Granted
- Kind: B2
- Application number: 15/723,582
- Filed: 2017-10-03
- Published: 2018-05-31
- Granted: 2021-09-07
- Earliest claimed: 2016-11-29
- Assignees: Taiwan Semiconductor Manufacturing Company, Ltd.
- Applicants: Taiwan Semiconductor Manufacturing Co., Ltd.
- Inventors: Chang Lilin; Ching-Yu Chang; Chin-Hsiang Lin
- Web page: https://patentgrep.com/patent/US11112698B2

## CPC

- G03F 7/30: Imagewise removal using liquid means
- G03F 7/0045: {with organic non-macromolecular light-sensitive compounds not otherwise provided for, e.g. dissolution inhibitors}
- G03F 7/0046: {with perfluoro compounds, e.g. for dry lithography (G03F7/0048 takes precedence)}
- G03F 7/0397: {the macromolecular compound having an alicyclic moiety in a side chain}
- G03F 7/091: {characterised by antireflection means or light filtering or absorbing means, e.g. anti-halation, contrast enhancement}
- G03F 7/095: having more than one photosensitive layer (G03F7/075 takes precedence)
- G03F 7/40: Treatment after imagewise removal, e.g. baking
- G03F 7/423: {containing mineral acids or salts thereof, containing mineral oxidizing substances, e.g. peroxy compounds}
- G03F 7/70: {Microphotolithographic exposure; Apparatus therefor (photo-masks G03F1/00)}
- H10P 76/2043: {using an anti-reflective coating}
- G03F 7/38: Treatment before imagewise removal, e.g. prebaking {(G03F7/265 takes precedence)}
- 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)
- H10P: GENERIC PROCESSES OR APPARATUS FOR THE MANUFACTURE OR TREATMENT OF DEVICES COVERED BY CLASS H10

## Abstract

The present disclosure provides an embodiment of a method for lithography patterning. The method includes coating a photoresist layer over a substrate, wherein the photoresist layer includes a first polymer, and a first photo-acid generator (PAG), and a chemical additive mixed in a solvent; performing an exposing process to the photoresist layer; and performing a developing process to the photoresist layer to form a patterned photoresist layer. The chemical additive has a non-uniform distribution in the photoresist layer.

## Claims

### Claim 1

A method for lithography patterning, comprising:
providing a photoresist solution,
wherein the photoresist solution includes a first polymer, a second polymer different from the first polymer in composition, a first photo-acid generator (PAG), and a second PAG different from the first PAG in composition,
wherein the first polymer includes a chemical structure formulated as
wherein the second polymer includes a chemical structure formulated as
with each of parameters X, Y, and Z being a positive integer and selected such that the second polymer has a higher molecular weight than the first polymer,
wherein the first PAG includes a chemical structure having two chemical units bonded together, the first PAG being formulated as
and
wherein the second PAG includes a chemical structure having two chemical units bonded together, the second PAG being formulated as
coating the photoresist solution over a substrate to form a photoresist layer, the photoresist layer having a top surface facing away from the substrate and a bottom surface facing the substrate, wherein the coating of the photoresist solution results in the first polymer and the first PAG being distributed uniformly from the top surface to the bottom surface of the photoresist layer, the second polymer having a continuous concentration gradient decreasing from the top surface to the bottom surface of the photoresist layer, and the second PAG having a continuous concentration gradient increasing from the top surface to the bottom surface of the photoresist layer;
performing an exposing process to the photoresist layer; and
dissolving portions of the exposed photoresist layer using a solvent to form a patterned photoresist layer, wherein the continuous concentration gradients of the second polymer and the second PAG cause solubility of the exposed photoresist layer to increase from the top surface to the bottom surface.

### Claim 2 (depends on 1)

The method of claim 1, further comprising performing an etching process using the patterned photoresist layer as a mask, wherein the second polymer has an etch resistance greater than the first polymer.

### Claim 3 (depends on 1)

The method of claim 1, wherein the coating of the photoresist solution over the substrate results in the second polymer and the first polymer to phase-separate in the photoresist layer.

### Claim 4 (depends on 1)

The method of claim 1, wherein the second polymer has a solubility less than that of the first polymer during the dissolving process.

### Claim 5 (depends on 1)

The method of claim 1, wherein the first PAG has a uniform distribution from the top surface to the bottom surface of the photoresist layer.

### Claim 6 (depends on 1)

The method of claim 1, further comprising, prior to the coating of the photoresist solution over the substrate,
forming a carbon-rich bottom layer over the substrate; and
forming a silicon-rich middle layer over the carbon-rich bottom layer.

### Claim 7 (depends on 1)

The method of claim 1, wherein the forming of the photoresist layer causes the first PAG and the second PAG to phase-separate in the photoresist layer.

### Claim 8

A method for lithography patterning, comprising:
forming a photoresist layer over a substrate, wherein the photoresist layer has a bottom surface facing the substrate and a top surface facing away from the substrate,
wherein the photoresist layer includes a polymer, a first photo-acid generator (PAG), a second PAG different from the first PAG in composition, a first quencher, and a second quencher different from the first quencher in composition,
wherein the first PAG includes a chemical structure having two chemical units bonded together, the first PAG being formulated as
wherein the second PAG includes a chemical structure having two chemical units bonded together, the second PAG being formulated as
the second PAG having a continuous gradient concentration increasing from a top surface to a bottom surface of the photoresist layer,
wherein the first quencher includes a chemical structure having two chemical units bonded together, the first quencher being formulated as
wherein the second quencher includes a chemical structure having two chemical units bonded together, the second quencher being formulated as,
the second quencher having a continuous gradient concentration decreasing from the top surface to the bottom surface of the photoresist layer;
performing an exposing process to the photoresist layer; and
developing the photoresist layer, wherein developing the photoresist layer removes a greater portion of the photoresist layer near the bottom surface than the top surface.

### Claim 9 (depends on 8)

The method of claim 8, wherein the first PAG has a uniform distribution from the top surface to the bottom surface of the photoresist layer.

### Claim 10 (depends on 8)

The method of claim 8, further comprising, prior to the forming of the photoresist layer over a substrate,
forming a carbon-rich bottom layer over the substrate; and
forming a silicon-rich middle layer over the carbon-rich bottom layer.

### Claim 11 (depends on 10)

The method of claim 10, wherein the second PAG has stronger interaction with the silicon-rich middle layer than with the polymer, thereby causing the second PAG to have the continuous gradient concentration increasing from the top surface to the bottom surface of the photoresist layer.

### Claim 12 (depends on 8)

The method of claim 8, wherein the forming of the photoresist layer causes the second PAG and the first PAG to phase-separate in the photoresist layer.

### Claim 13 (depends on 8)

The method of claim 8, wherein the first quencher has a uniform distribution from the top surface to the bottom surface of the photoresist layer.

### Claim 14 (depends on 8)

The method of claim 8, wherein the forming of the photoresist layer causes the second quencher and the first quencher to phase-separate in the photoresist layer.

### Claim 15

A method for lithography patterning, comprising:
providing a semiconductor substrate;
forming a photoresist layer over the semiconductor substrate, wherein the photoresist layer includes a polymer, a photo-acid generator (PAG), and a dissolution additive,
wherein the polymer is formulated as
wherein the dissolution additive includes a first functional unit containing fluorine and a second functional unit bonded to the first functional unit, the dissolution additive being formulated as
with X and Y each being a positive integer and selected such that a molecular weight of the dissolution additive is greater than that of the polymer, and
wherein a concentration gradient of the dissolution additive continuously decreases from a top surface to a bottom surface of the photoresist layer;
exposing the photoresist layer to a radiation source;
applying a developer to the exposed photoresist layer, thereby forming a patterned photoresist layer, wherein the developer removes a greater amount of the photoresist layer near the bottom surface than the top surface; and
etching the semiconductor substrate using the patterned photoresist layer as a mask.

### Claim 16 (depends on 15)

The method of claim 15, wherein the dissolution additive is formulated with a polar unit ratio greater than that of the polymer.

### Claim 17 (depends on 15)

The method of claim 15, wherein the first functional unit of the dissolution additive is configured to lower surface tension of the dissolution additive.

### Claim 18 (depends on 17)

The method of claim 17, wherein the surface tension of the dissolution additive is less than 20 mN/m.

### Claim 19 (depends on 15)

The method of claim 15, wherein the second functional unit of the dissolution additive is configured to reduce dissolution rate of the photoresist layer in the developer.

### Claim 20 (depends on 15)

The method of claim 15, wherein the dissolution additive has an etching resistance greater than that of the polymer during the etching process.