# US 11,442,364 B2 · Materials and methods for forming resist bottom layer

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- Number: US 11,442,364 B2
- Document ID: US11442364B2
- Status: Granted
- Kind: B2
- Application number: 16/414,648
- Filed: 2019-05-16
- Published: 2020-01-02
- Granted: 2022-09-13
- Earliest claimed: 2018-06-28
- Assignees: Taiwan Semiconductor Manufacturing Company, Ltd.
- Applicants: Taiwan Semiconductor Manufacturing Co., Ltd.
- Inventors: Jing Hong Huang; Chien-Wei Wang; Shang-Wern Chang; Ching-Yu Chang
- Web page: https://patentgrep.com/patent/US11442364B2

## CPC

- G03F 7/38: Treatment before imagewise removal, e.g. prebaking {(G03F7/265 takes precedence)}
- G03F 7/0388: {with ethylenic or acetylenic bands in the side chains of the photopolymer}
- G03F 7/094: {Multilayer resist systems, e.g. planarising layers}
- G03F 7/16: Coating processes; Apparatus therefor (applying coatings to base materials in general B05; applying photosensitive compositions to base for photographic purposes G03C1/74)
- G03F 7/168: {Finishing the coated layer, e.g. drying, baking, soaking}
- 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 method includes forming a bottom layer over a semiconductor substrate, where the bottom layer includes a polymer bonded to a first cross-linker and a second cross-linker, the first cross-linker being configured to be activated by ultraviolet (UV) radiation and the second cross-linker being configured to be activated by heat at a first temperature. The method then proceeds to exposing the bottom layer to a UV source to activate the first cross-linker, resulting in an exposed bottom layer, where the exposing activates the first cross-linker. The method further includes baking the exposed bottom layer, where the baking activates the second cross-linker.

## Claims

### Claim 1

A method comprising:
forming a bottom layer over a semiconductor substrate, wherein the bottom layer includes a polymer bonded to a first cross-linker, a second cross-linker, and a hybrid cross-linker, wherein the first cross-linker is activatable by ultraviolet (UV) radiation, wherein the second cross-linker is activatable by heat at a first temperature, and wherein the hybrid cross-linker is activatable by both UV radiation and heat;
exposing the bottom layer to a UV source, resulting in an exposed bottom layer, wherein the exposing activates the first cross-linker and a first portion of the hybrid cross-linker; and
baking the exposed bottom layer, wherein the baking activates the second cross-linker and a second portion of the hybrid cross-linker.

### Claim 2 (depends on 1)

The method of claim 1, wherein the first cross-linker and the hybrid cross-linker include H2C═CHR, and wherein R includes (C═O), (C═O)O, —CH═CH, phenyl, phenol, or combinations thereof.

### Claim 3 (depends on 1)

The method of claim 1, wherein the second cross-linker and the hybrid cross-linker include phenyl, alkyl-substituted phenyl, epoxy, hydroxyl, ether, ester, novolac, or combinations thereof.

### Claim 4 (depends on 1)

The method of claim 1, wherein the baking is a first baking process, further comprising performing a second baking process to the bottom layer before the exposing of the bottom layer, the second baking process being configured to smooth a top surface of the bottom layer.

### Claim 5 (depends on 4)

The method of claim 4, wherein a temperature of the second baking process is lower than the first temperature.

### Claim 6 (depends on 4)

The method of claim 4, wherein a temperature of the first baking process is greater than the first temperature.

### Claim 7 (depends on 1)

The method of claim 1, wherein the third hybrid cross-linker includes H2C═CH(C═O)OX, and wherein X includes an alkyl chain, an aromatic ring, a heteroaromatic ring, or combinations thereof.

### Claim 8 (depends on 1)

The method of claim 1, wherein an amount of the first cross-linker and the hybrid cross-linker is greater than an amount of the second cross-linker in the bottom layer.

### Claim 9

A method, comprising:
spin-coating a semiconductor substrate with a material layer, wherein the material layer includes a polymer attached to ultraviolet (UV) cross-linkers and thermal cross-linkers, wherein an amount of the UV cross-linkers in the material layer is greater than an amount of thermal cross-linkers in the material layer, and wherein at least one of the UV cross-linkers includes a thermally activatable functional group;
exposing the material layer to a first UV source having a first wavelength, resulting in an exposed material layer, wherein the exposing induces cross-linking of the UV cross-linkers;
thermally curing the exposed material layer, resulting in a cured material layer, wherein the curing induces cross-linking of the thermal cross-linkers and the thermally activatable functional group of the at least one of the UV cross-linkers; and
forming a photoresist layer over the cured material layer.

### Claim 10 (depends on 9)

The method of claim 9, further comprising:
exposing the photoresist layer to a second UV source having a second wavelength, resulting in an exposed photoresist layer, wherein the second wavelength is different from the first wavelength; and
developing the exposed photoresist layer to form a pattern.

### Claim 11 (depends on 10)

The method of claim 10, wherein the second wavelength is less than the first wavelength.

### Claim 12 (depends on 9)

The method of claim 9, wherein a ratio of the amount of the thermal cross-linkers to the amount of the UV cross-linkers is at least about 25% but no more than about 67%.

### Claim 13 (depends on 9)

The method of claim 9, further comprising forming a middle layer over the cured material layer before the forming of the photoresist layer.

### Claim 14 (depends on 9)

The method of claim 9, wherein each UV cross-linker includes a UV-activatable functional group including (C═O)—, (C═O)O, CH═CH, phenyl, phenol, or combinations thereof.

### Claim 15 (depends on 14)

The method of claim 14, wherein the UV-activatable functional group attaches to the polymer via an alkyl chain, an aromatic ring, a heteroaromatic ring, or combinations thereof.

### Claim 16 (depends on 9)

The method of claim 9, further comprising performing a baking process to the material layer before the exposing of the material layer.

### Claim 17

A method, comprising:
forming a bottom layer over a semiconductor substrate, the bottom layer including a polymer, a first cross-linker activatable by ultraviolet (UV) exposure, and a second cross-linker activatable by heat exposure at a first temperature, and a hybrid cross-linker activatable by both UV exposure and heat exposure at the first temperature, wherein the first cross-linker, the second cross-linker, and the hybrid cross-linker are bonded to the polymer;
performing a first heat exposure to the bottom layer at a second temperature lower than the first temperature;
after the performing of the first heat exposure, performing a UV exposure to the bottom layer to induce cross-linking of the first cross-linker, resulting in an exposed bottom layer;
performing a second heat exposure to the exposed bottom layer at a third temperature, thereby activating the second cross-linker to form a cured bottom layer, wherein the third temperature is higher than the first temperature;
forming a middle layer over the cured bottom layer; and
forming a photoresist layer over the middle layer.

### Claim 18 (depends on 17)

The method of claim 17, wherein an amount of the second cross-linker is less than an amount of the first cross-linker.

### Claim 19 (depends on 17)

The method of claim 17, wherein the polymer includes an acrylate-based polymer, a poly(norbornene)-co-maleic anhydride (COMA) polymer, a poly(hydroxystyrene)-based polymer, or combinations thereof.

### Claim 20 (depends on 17)

The method of claim 17, the UV exposure being a first UV exposure implemented at a first wavelength, the method further comprising:
performing a second UV exposure to the photoresist layer, wherein the second UV exposure is implemented at a second wavelength that is less than the first wavelength; and
developing the exposed photoresist layer to form a pattern.