# US 6,720,116 B1 · Process flow and pellicle type for 157 nm mask making

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- Number: US 6,720,116 B1
- Document ID: US6720116B1
- Status: Granted
- Kind: B1
- Application number: 10/339,186
- Filed: 2003-01-09
- Granted: 2004-04-13
- Earliest claimed: 2003-01-09
- Assignees: Taiwan Semiconductor Manufacturing Company, Ltd.
- Inventors: San-De Tzu; Anthony Yen; Chung Hsing Chang; Chen-Hao Hsieh
- Web page: https://patentgrep.com/patent/US6720116B1

## CPC

- G03F 1/62: Pellicles, e.g. pellicle assemblies, e.g. having membrane on support frame; Preparation thereof
- G03F 1/48: Protective coatings
- G03F 1/54: Absorbers, e.g. of opaque materials
- G03F 1/60: Substrates
- 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 for forming a photomask and pellicle suitable for use in photolithography with incident electromagnetic radiation in a wavelength range from above 250 nm to below 150 nm. The opaque regions of the photomask are formed directly within a transparent F-doped quartz layer by either gallium ion staining using a focused ion beam (FIB) or by deposition of carbon atoms within trenches formed in the transparent layer, said carbon atom deposition being a result of the interaction of a FIB with styrene molecules. An alignment boundary formed on the resulting mask allows a hard pellicle to be fit directly over it so as to avoid warping.

## Claims

### Claim 1

A method for forming a photolithographic mask and pellicle comprising:
providing a substrate comprising a transparent layer over which is formed an opaque layer, said layers being respectively transparent and opaque to a preselected range of wavelengths;
transferring a mask pattern to the opaque layer of said substrate by removing pattern shaped portions from said opaque layer, thereby exposing corresponding surface portions of said transparent layer beneath said opaque layer;
inspecting said patterned opaque layer and repairing any discovered defects using a focused ion-beam repair method;
transferring said mask pattern to said transparent layer by applying said focused ion-beam, through said patterned opaque layer, to said exposed surface portions of said transparent layer, thereby staining a bulk portion of said transparent layer beneath said exposed surfaces and rendering said bulk portion opaque to said preselected range of radiation wavelengths;
removing at least the portion of said opaque material layer remaining over said patterned transparent layer, leaving behind a peripherally disposed portion to serve as an alignment boundary for a pellicle, the exposed portion of said transparent layer forming thereby a photolithographic mask.

### Claim 2 (depends on 1)

The method of claim 1 wherein the removal of portions of said opaque layer is by etching said opaque layer through a mask formed of photoresistive material which is patterned by e-beam or laser writing.

### Claim 3 (depends on 2)

The method of claim 2 wherein the layer of transparent material is a layer of material chosen from among the group of materials transparent to electromagnetic radiation of wavelength range extending from above 250 nm to below 150 nm.

### Claim 4 (depends on 2)

The method of claim 2 wherein the layer of transparent material is a layer of fluorine-doped quartz, formed to a thickness between approximately 0.6 and 0.7 cm.

### Claim 5 (depends on 1)

The method of claim 1 wherein the layer of opaque material is a layer of material chosen from among the group of materials opaque to electromagnetic radiation of wavelength range extending from above 250 nm to below 150 nm.

### Claim 6 (depends on 4)

The method of claim 4 wherein the layer of opaque material is a layer of chromium formed to a thickness of between approximately 600 and 800 angstroms.

### Claim 7 (depends on 6)

The method of claim 6 wherein the photoresistive layer is patterned by exposure to an e-beam or a laser beam.

### Claim 8 (depends on 1)

The method of claim 1 wherein the method used to etch the layer of opaque material is an isotropic etch or an anisotropic etch.

### Claim 9 (depends on 8)

The method of claim 8 wherein the isotropic etch is a chemical wet etch and wherein the anisotropic etch is a plasma assisted etch.

### Claim 10 (depends on 1)

The method of claim 1 wherein the focused ion-beam (FIB) method uses a focused beam of singly positive gallium ions which are deposited at a deposition rate greater than 1.5 J/cm2.

### Claim 11 (depends on 1)

The method of claim 1 further comprising the formation of a pellicle of the same transparent material as the transparent layer of the mask substrate and the placing of said pellicle within the alignment boundary of said photomask.

### Claim 12

A method for fabricating a photomask and pellicle comprising:
providing a substrate comprising a transparent layer over which is formed an opaque layer, said layers being respectively transparent and opaque to a preselected range of wavelengths;
transferring a mask pattern to the opaque layer of said substrate by removing pattern shaped portions from said opaque layer, thereby exposing corresponding surface portions of said transparent layer beneath said opaque layer;
inspecting said patterned opaque layer and repairing any discovered defects using a focused ion-beam repair method;
etching trenches in the transparent material layer through said pattern shaped portions in the opaque layer;
using a focused ion-beam method as a means for filling each of said trenches with a deposition of carbon atoms sufficient to render said trenches opaque;
removing at least the portion of said opaque material layer remaining over said patterned transparent layer, leaving behind a peripherally disposed portion to serve as an alignment boundary for a pellicle, the exposed portion of said transparent layer forming thereby a photolithographic mask.

### Claim 13 (depends on 1)

The method of claim 1 wherein the removal of portions of said opaque layer is by etching said opaque layer through a mask formed of photoresistive material which is patterned by e-beam or laser writing.

### Claim 14 (depends on 13)

The method of claim 13 wherein the layer of transparent material is a layer of material chosen from among the group of materials transparent to electromagnetic radiation of wavelength range extending from above 250 nm to below 150 nm.

### Claim 15 (depends on 14)

The method of claim 14 wherein the layer of transparent material is a layer of fluorine-doped quartz, formed to a thickness of between approximately 0.600 and 0.700 cm.

### Claim 16 (depends on 15)

The method of claim 15 wherein the layer of opaque material is a layer of material chosen from among the group of materials opaque to electromagnetic radiation of wavelength range extending from above 250 nm to below 150 nm.

### Claim 17 (depends on 16)

The method of claim 16 wherein the layer of opaque material is a layer of chromium formed to a thickness of between approximately 600 and 800 angstroms.

### Claim 18 (depends on 17)

The method of claim 17 wherein the method used to etch the layer of opaque material is an isotropic etch or an anisotropic etch.

### Claim 19 (depends on 18)

The method of claim 18 wherein the isotropic etch is a chemical wet etch and the anisotropic etch is a plasma assisted etch.

### Claim 20 (depends on 19)

The method of claim 19 wherein said layer of transparent material is etched with an isotropic chemical wet etch.

### Claim 21 (depends on 20)

The method of claim 20 wherein the focused ion-beam method comprises application of a focused beam of singly positive gallium ions which are deposited at a deposition rate greater than 1.5 J/cm2 in the presence of styrene molecules, producing thereby a deposition of carbon atoms.

### Claim 22 (depends on 21)

The method of claim 21 further comprising the formation of a pellicle of the same transparent material as the transparent layer of the mask substrate and the placing of said pellicle within the alignment boundary of said photomask.

### Claim 23

A photomask to be used in photolithography for transferring a mask pattern by means of incident electromagnetic radiation within a preselected range of wavelengths comprising:
a layer of material transparent to said preselected range of wavelengths, in which is formed, in the mask pattern to be transferred or its complement, regions opaque to the transmission of incident electromagnetic radiation of said preselected wavelength range, said opaque regions being regions of the transparent material stained by the deposition of singly positive gallium ions;
a raised alignment boundary on said layer peripherally disposed about said mask pattern.

### Claim 24 (depends on 23)

The fabrication of claim 23 wherein the layer of transparent material is a layer of material chosen from among the group of materials transparent to electromagnetic radiation of wavelength range extending from above 250 nm to below 150 nm.

### Claim 25 (depends on 24)

The fabrication of claim 24 wherein the layer of transparent material is a layer of fluorine-doped quartz, formed to a thickness of between approximately 0.600 and 0.700 cm.

### Claim 26 (depends on 23)

The fabrication of claim 23 further comprising a pellicle formed of the same material as that of the transparent material layer, said pellicle being placed over said photomask within said alignment boundary.

### Claim 27

A photomask and pellicle to be used in photolithography for transferring a mask pattern by means of incident electromagnetic radiation within a preselected range of wavelengths comprising:
a layer of material transparent to said preselected range of wavelengths, in which are formed, in the mask pattern to be transferred or its complement, regions opaque to the transmission of incident electromagnetic radiation of said preselected wavelength range, said opaque regions being trenches formed within the transparent material and filled by carbon atoms;
a raised alignment boundary peripherally disposed about said mask pattern.

### Claim 28 (depends on 27)

The fabrication of claim 27 wherein the layer of transparent material is a layer of material chosen from among the group of materials transparent to electromagnetic radiation of wavelength range extending from above 250 nm to below 150 nm.

### Claim 29 (depends on 28)

The fabrication of claim 28 wherein the layer of transparent material is a layer of fluorine-doped quartz, formed to a thickness of between approximately 0.600 and 0.700 cm.

### Claim 30 (depends on 27)

The fabrication of claim 27 wherein the carbon atoms are deposited by the action of a focused ion beam interacting with styrene molecules.

### Claim 31 (depends on 30)

The fabrication of claim 30 further comprising a pellicle formed of the same material as that of the transparent material layer, said pellicle being placed over said photomask within said alignment boundary.