# US 2014/0191375 A1 · Methods for fabricating three-dimensional nano-scale structures and devices

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- Number: US 2014/0191375 A1
- Document ID: US20140191375A1
- Status: Published application
- Kind: A1
- Application number: 14/238,547
- Filed: 2012-08-21
- Published: 2014-07-10
- Earliest claimed: 2011-08-23
- Assignees: The Research Foundation of State University of New York
- Inventors: John G. Hartley; Ravi K. Bonam
- Web page: https://patentgrep.com/patent/US20140191375A1

## CPC

- G03F 7/70416: {2.5D lithography}
- B81C 1/00031: {Regular or irregular arrays of nanoscale structures, e.g. etch mask layer (photomechanical, e.g. photolithographic, production of textured or patterned surfaces G03F7/00; lithographic processes for making patterned surfaces using printing and stamping G03F7/0002)}
- G03F 7/0048: {characterised by the solvents or agents facilitating spreading, e.g. tensio-active agents}
- G03F 7/038: Macromolecular compounds which are rendered insoluble or differentially wettable (G03F7/075 takes precedence; macromolecular azides G03F7/012; macromolecular diazonium compounds G03F7/021)
- G03F 7/039: Macromolecular compounds which are photodegradable, e.g. positive electron resists (G03F7/075 takes precedence; macromolecular quinonediazides G03F7/023)
- G03F 7/0755: {Non-macromolecular compounds containing Si-O, Si-C or Si-N bonds (G03F7/0752 takes precedence)}
- G03F 7/095: having more than one photosensitive layer (G03F7/075 takes precedence)
- G03F 7/2059: {using a scanning corpuscular radiation beam, e.g. an electron beam}
- G03F 7/325: {Non-aqueous compositions}
- G03F 7/38: Treatment before imagewise removal, e.g. prebaking {(G03F7/265 takes precedence)}
- H10D 62/00: Semiconductor bodies, or regions thereof, of devices having potential barriers
- H10D 62/01: {Manufacture or treatment}
- H10P 50/691: {for Group IV materials or Group III-V materials}
- B81C 2201/0157: Gray-scale mask technology
- H10P 76/2045: {Electron beam lithography processes}
- 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)
- B81C: PROCESSES OR APPARATUS SPECIALLY ADAPTED FOR THE MANUFACTURE OR TREATMENT OF MICROSTRUCTURAL DEVICES OR SYSTEMS (making microcapsules or microballoons B01J13/02; processes or apparatus specially adapted for the manufacture or treatment of piezoelectric, electrostrictive or magnetostrictive elements per se H10N30/01)
- H10D: INORGANIC ELECTRIC SEMICONDUCTOR DEVICES
- H10P: GENERIC PROCESSES OR APPARATUS FOR THE MANUFACTURE OR TREATMENT OF DEVICES COVERED BY CLASS H10

## Abstract

A method of fabricating a 3 dimensional structure, includes: forming a stack of at least 2 layers of photo resist material having different photo resist sensitivities upon a substrate; exposing the stack to beams of electromagnetic radiation or charged particles of different dosages to achieve selective solubility along a height of the stack; and dissolving soluble portions of the stack with a solvent to produce a 3 dimensional structure of desired geometry.

## Claims

### Claim 1

A method for producing structures, the method comprising:
depositing a plurality of layers of photo resist onto a substrate, the plurality of layers having an upper surface and at least one layer having a higher photo resist sensitivity than a photoresist sensitivity of at least one other layer of the plurality of layers;
exposing a first area of the upper surface to a first beam of one of electromagnetic radiation and charged particles wherein a portion of each of the plurality of layers beneath the first area of the upper surface becomes substantially insoluble when contacted with a predetermined solvent;
exposing a second area of the upper surface, contiguous with the first area, to a second beam of one of electromagnetic radiation and charged particles wherein a portion of the at least one layer having a higher photo resist sensitivity beneath the second area becomes substantially insoluble when contacted with the predetermined solvent; and
contacting the plurality of layers with the predetermined solvent to dissolve soluble portions to provide the structure.

### Claim 2 (depends on 1)

The method recited in claim 1, wherein the plurality of layers of photo resist comprises at least three layers of photo resist.

### Claim 3 (depends on 2)

The method recited in claim 2, wherein the at least one layer having the higher photo resist sensitivity comprises at least two layers having the higher photo resist sensitivity.

### Claim 4 (depends on 1)

The method recited in claim 1, wherein the method further comprises exposing at least a third area of the upper surface, contiguous with the second area, to a third beam of one of electromagnetic radiation and charged particles capable of making a portion of the at least one layer having a higher photo resist sensitivity beneath the third area substantially insoluble when contacted with the predetermined solvent.

### Claim 5 (depends on 1)

The method recited in claim 1, wherein the first area of the upper surface exposed to the first beam and the second area of the upper surface exposed to the second beam each comprise one of a polygonal area and a circular area.

### Claim 6 (depends on 5)

The method recited in claim 5, wherein the first area of the upper surface exposed to the first beam and the second area of the upper surface exposed to the second beam each comprise rectangular areas.

### Claim 7 (depends on 1)

The method as recited in claim 1, wherein the structure comprises a cavity.

### Claim 8 (depends on 7)

The method as recited in claim 7, wherein the cavity comprises a mold cavity.

### Claim 9 (depends on 1)

The method recited in claim 1, wherein a power delivered by the first beam is different from a power delivered by the second beam.

### Claim 10 (depends on 1)

The method recited in claim 1, wherein the plurality of layers comprise a plurality of photo resist sensitivities.

### Claim 11 (depends on 10)

The method as recited in claim 10, wherein each of the plurality of layers comprises a photo resist sensitivity as a function of a beam energy to which each of the plurality of layers is exposed.

### Claim 12 (depends on 10)

The method as recited in claim 10, wherein the plurality of photo resist sensitivities vary through a depth of the plurality of layers.

### Claim 13 (depends on 10)

The method as recited in claim 10, wherein each of the plurality of photo resist sensitivities varies as a function of a depth of each of the plurality of layers.

### Claim 14 (depends on 1)

The method as recited in claim 1, wherein exposing the first area of the upper surface and exposing the second area of the upper surface are practiced substantially simultaneously.

### Claim 15 (depends on 1)

The method as recited in claim 1, wherein exposing the first area of the upper surface and exposing the second area of the upper surface are practiced sequentially.

### Claim 16

A method for producing structures, the method comprising:
depositing a plurality of layers of photo resist onto a substrate, the plurality of layers having an upper surface and at least one layer having a higher photo resist sensitivity than a photo resist sensitivity of at least one other layer of the plurality of layers;
preventing exposure of a first area of the upper surface to any beam of electromagnetic or charged particles to ensure that a portion of each of the plurality of layers beneath the first area of the upper surface is substantially insoluble when contacted with a predetermined solvent;
exposing a second area of the upper surface, contiguous with the first area, to a first beam of one of electromagnetic radiation and charged particles wherein a portion of the at least one layer having a higher photo resist sensitivity beneath the second area becomes substantially soluble when contacted with the predetermined solvent;
exposing at least one third area of the upper surface, contiguous with at least one of the first area and the second area, to a second beam of one of electromagnetic radiation and charged particles wherein a portion of each of the plurality of layers beneath the at least one third area becomes substantially soluble when contacted with the predetermined solvent; and
contacting the plurality of layers with the predetermined solvent to dissolve the soluble portions to provide the structure.

### Claim 17 (depends on 16)

The method recited in claim 16, wherein the plurality of layers of photo resist comprises at least three layers of photo resist.

### Claim 18 (depends on 17)

The method recited in claim 17, wherein the at least one layer having the higher photo resist sensitivity comprises at least two layers having the higher photo resist sensitivity.

### Claim 19 (depends on 16)

The method recited in claim 16, wherein the first area of the upper surface prevented from being exposed to any beam and the second area of the upper surface exposed to the first beam each comprise one of a polygonal area and a circular area.

### Claim 20 (depends on 19)

The method recited in claim 19, wherein the first area of the upper surface prevented from being exposed to any beam and the second area of the upper surface exposed to the first beam each comprise rectangular areas.

### Claim 21 (depends on 16)

The method as recited in claim 16, wherein the structure comprises a cavity.

### Claim 22 (depends on 21)

The method as recited in claim 21, wherein the cavity comprises a mold cavity.

### Claim 23 (depends on 16)

The method recited in claim 16, wherein a power delivered by the first beam is different from a power delivered by the second beam.

### Claim 24 (depends on 16)

The method recited in claim 16, wherein the plurality of layers comprises a plurality of photo resist sensitivities.

### Claim 25 (depends on 24)

The method as recited in claim 24, wherein each of the plurality of layers comprises a photo resist sensitivity as a function of a beam energy to which each layer is exposed.

### Claim 26 (depends on 24)

The method as recited in claim 24, wherein the plurality of photo resist sensitivities vary through a depth of the plurality of layers.

### Claim 27 (depends on 24)

The method as recited in claim 24, wherein each of the plurality of photo resist sensitivities varies as a function of a depth of each of the plurality of layers.

### Claim 28 (depends on 16)

The method as recited in claim 16, wherein preventing exposure of the first area of the upper surface and exposing the second area of the upper surface are practiced substantially simultaneously.

### Claim 29 (depends on 16)

The method as recited in claim 16, wherein exposing of the at least one third area of the upper surface and exposing the second area of the upper surface are practiced substantially simultaneously.

### Claim 30 (depends on 16)

The method as recited in claim 16, wherein exposing of the at least one third area of the upper surface and exposing the second area of the upper surface are practiced sequentially.

### Claim 31 (depends on 16)

The method as recited in claim 16, wherein preventing exposure of the first area of the upper surface, exposing the second area of the upper surface, and exposing the at least one third area of the upper surface are practiced substantially simultaneously.

### Claim 32

A method of fabricating a 3 dimensional structure, comprising: forming a stack of at least 2 layers of photo resist material having different photo resist sensitivities upon a substrate; exposing the stack to beams of electromagnetic radiation or charged particles of different dosages to achieve selective solubility along a height of the stack; and dissolving soluble portions of the stack with a solvent to produce a 3 dimensional structure of desired geometry.

### Claim 33 (depends on 32)

The method as recited in claim 32, further comprising at least one of: adding a reinforcing member to the structure, and adding a reinforcing additive to at least one photo resist material.

### Claim 34 (depends on 32)

The method as recited in claim 32, further comprising adding porosity or cavities to the structure.

### Claim 35 (depends on 32)

The method as recited in claim 32, further comprising selecting a photo resist material for at least one of said layers having a property, in addition to solubility, affected by exposure to at least one of the first beam and the second beam.

### Claim 36 (depends on 35)

The method as recited in claim 35, wherein the property comprises at least one of index of refraction, glass transition temperature, electronic properties and polarity.

### Claim 37 (depends on 32)

The method as recited in claim 32, wherein at least one of tone and sensitivity of the photo resist material varies as a function of depth within the stack.

### Claim 38 (depends on 32)

The method as recited in claim 32, further comprising at least one of: introducing an adhesive layer, a uniform coating or a buffering layer between two adjoining photo resist layers; employing mutually exclusive solvents for different layers of photo resist material; and employing mutually compatible solvents for different layers of photo resist material.

### Claim 39 (depends on 36)

A structure fabricated from the method recited in claim 36.

### Claim 40 (depends on 39)

The structure as recite in claim 39, wherein the structure comprises one of a micro-scale structure, a nano-scale structure, and a sub-nano-scale structure.

### Claim 41 (depends on 40)

The structure as recite in claim 40, wherein the photo resist comprises at least one of a positive-tone photo resist and a negative-tone photo resist.

### Claim 42 (depends on 39)

The structure as recited in claim 39, wherein type of structure fabricated depends on penetration depth of the electromagnetic radiation or charged particles, tone and contrast of the photo resist material.

### Claim 43

A structure fabricated from photo resist, the structure comprising:
at least one support member; and
a plurality of projections mounted to the at least one support and directed substantially perpendicular to an axis of the support member.

### Claim 44 (depends on 43)

The structure as recited in claim 43, wherein the plurality of projections comprises at least two sets of opposing projections.

### Claim 45 (depends on 43)

The structure as recite in claim 43, wherein the structure comprises one of a micro-scale structure, a nano-scale structure, and a sub-nano-scale structure.

### Claim 46 (depends on 39)

The structure as recited in claim 39, wherein the structure comprises one of a NEMS structure, a MEMS structure, an electronic component; a medical device; a sensor; and a photonic device.

### Claim 47 (depends on 43)

The structure as recited in claim 43, wherein the structure comprises one of a NEMS structure, a MEMS structure, an electronic component; a medical device; a sensor; and a photonic device.