# US 6,845,145 B2 · Method of improving x-ray lithography in the sub 100nm range to create high quality semiconductor devices

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- Number: US 6,845,145 B2
- Document ID: US6845145B2
- Status: Granted
- Kind: B2
- Application number: 09/876,443
- Filed: 2001-06-07
- Published: 2001-10-04
- Granted: 2005-01-18
- Earliest claimed: 1999-06-12
- Assignees: SAL, Inc.
- Inventors: Robert Allen Selzer; Franz Ludwig Rauch; Heinz Siegert; Klaus Simon; William Rudolf Friml; Joe Baker Gagnon; Robert Harrison Macklin
- Web page: https://patentgrep.com/patent/US6845145B2

## CPC

- G03F 7/70216: {Mask projection systems}
- G03F 7/708: {Construction of apparatus, e.g. environment aspects, hygiene aspects or materials}
- G21K 5/00: Irradiation devices (discharge tubes for irradiating H01J37/00)
- Y10S 430/168: X-ray exposure process
- 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)
- G21K: HANDLING OF PARTICLES OR IONISING RADIATION NOT OTHERWISE PROVIDED FOR; IRRADIATION DEVICES; GAMMA RAY OR X-RAY MICROSCOPES
- Y10S: TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS

## Abstract

The present invention is directed to the production of high quality semi-conductor devices created at speeds and in sizes that far exceed current x-ray lithography capabilities. The steps involved in the method include the use and development of horizontal beams from a synchrotron or point source of x-ray beams; preparation of submicrometer, transverse horizontal and vertical stepper stages and frames; providing a stepper base frame for the proper housing and mating of the x-ray beam; minimizing the effects of temperature and airflow control by means of a environmental chamber; transporting, handling and prealigning wafers and other similar items for tight process control; improving the control and sensing of positional accuracy through the use of differential variable reluctance transducers; controlling the continuous gap and all six degrees of freedom of the wafer being treated with a multiple variable stage control; incorporating alignment systems using unambiguous targets to provide data to align one level to the next level; beam transport, shaping or shaping devices, to include x-ray point sources; using an inline collimator or concentrator for collimating or concentrating the x-ray beams; and, imaging the mask pattern at the precise moment for optimum effectiveness.

## Claims

### Claim 1

A method of exposing a resist on a substrate comprising the steps of:
a) providing the substrate with a film of resist;
b) placing the substrate on stage; and
c) sensing the position of the substrate with a displacement sensor, wherein said displacement sensor comprises a differential variable reluctance transducer (DVRT); and
d) providing a source of radiation, and exposing said resist with said radiation.

### Claim 2 (depends on 1)

The method as recited in claim 1, wherein the substrate comprises a wafer.

### Claim 3 (depends on 2)

The method as recited in claim 2, wherein said wafer comprises a semiconductor.

### Claim 4 (depends on 1)

The method as recited in claim 1, wherein said radiation has a wavelength to provide a structure having a dimension less than 100 nm.

### Claim 5 (depends on 4)

The method as recited in claim 4, wherein said radiation comprises x-ray radiation.

### Claim 6 (depends on 5)

The method as recited in claim 5, further comprising the step of collimating said x-ray radiation.

### Claim 7 (depends on 5)

The method as recited in claim 5, further comprising the step of concentrating said x-ray radiation.

### Claim 8 (depends on 1)

The method as recited in claim 1, further comprising the step of providing a mask for defining exposure of said resist.

### Claim 9 (depends on 8)

The method as recited in claim 8, wherein said mask is spaced from said substrate by a gap, said method further comprising the step of moving said to stage to adjust said gap.

### Claim 10 (depends on 8)

The method as recited in claim 8, further comprising the step of using output of said displacement sensor to control said exposing step.

### Claim 11 (depends on 10)

The method as recited in claim 10, wherein said mask is positioned with respect to said substrate, said method further comprising the step of exposing said resist at a time when said displacement sensor output indicates that position of said mask with respect to said substrate is optimum.

### Claim 12 (depends on 11)

The method as recited in claim 11, wherein said mask is spaced from said substrate by a gap, said method further comprising the step of exposing said resist at a time when said displacement sensor output indicates that said gap is optimum.

### Claim 13 (depends on 8)

The method as recited in claim 8, further comprising the step of using said displacement sensor output to control mask to wafer misalignment.

### Claim 14 (depends on 1)

The method as recited in claim 1, further comprising the step of using said displacement sensor output to control substrate x, y, z, rotation, and magnification.

### Claim 15

A system for exposing a substrate comprising a stepper and an X ray source, vibration insulation there between.

### Claim 16

A method of exposing a resist on a substrate comprising the steps of:
a) providing the substrate with a film of resist;
b) placing the substrate on a stage;
c) providing x-ray radiation from a point source;
d) using an inline collimator to collimate said x-ray radiation;
e) providing a mask for defining exposure of said resist;
f) illuminating said mask with said x-ray radiation after said collimating step (d); and
g) exposing said resist with x-ray radiation passing through said mask;
h) sensing position of the substrate with a displacement sensor wherein displacement sensor comprises a differential variable reluctance transducer (DVRT).

### Claim 17 (depends on 16)

The method as recited in claim 16, wherein said x-ray radiation has a wavelength to provide a structure having a dimension less than 100 nm.

### Claim 18 (depends on 16)

The method as recited in claim 16, wherein the substrate comprises a wafer.

### Claim 19 (depends on 18)

The method as recited in claim 18, wherein said wafer comprises a semiconductor.

### Claim 20 (depends on 16)

The method as recited in claim 16, wherein said mask is spaced from said substrate by a gap, said method further comprising the step of moving said stage to adjust said gap.

### Claim 21 (depends on 16)

The method as recited in claim 16, further comprising the step of using output of said displacement sensor to control said exposing step.

### Claim 22 (depends on 21)

The method as recited in claim 21, wherein said mask is positioned with respect to said substrate, said method further comprising the step of exposing said resist at a time when said displacement sensor output indicates that position of said mask with respect to said substrate is optimum.

### Claim 23 (depends on 21)

The method as recited in claim 21, wherein said mask is spaced from said substrate by a gap, said method further comprising the step of exposing said resist at a time when said displacement sensor output indicates that said gap is optimum.

### Claim 24 (depends on 16)

The method as recited in claim 16, further comprising the step of using displacement sensor output to control mask to wafer misalignment.

### Claim 25 (depends on 16)

The method as recited in claim 16, further comprising the step of using displacement sensor output to control substrate x, y, z, rotation, and magnification.

### Claim 26 (depends on 16)

The method as recited in claim 16, wherein said x-ray radiation passes through a beam transport chamber having helium or other low attenuation gas or helium and another low attenuation gas at atmospheric pressure or at lower pressure.

### Claim 27

A method of exposing a resist on a substrate comprising the steps of:
a) providing the substrate with a film of resist;
b) placing the substrate on a stage;
c) providing x-ray radiation from a point source;
d) collimating said x-ray radiation;
e) providing a mask for defining exposure of said resist;
f) illuminating said mask with said x-ray radiation after said collimating step (d);
g) exposing said resist with x-ray radiation passing through said mask; and
h) sensing position of the substrate with a displacement sensor wherein said displacement sensor comprises a differential variable reluctance transducer (DVRT).

### Claim 28 (depends on 27)

The method as recited in claim 27, further comprising the step of using output of said DVRT to control said exposing step.

### Claim 29 (depends on 28)

The method as recited in claim 28, wherein said mask is positioned with respect to said substrate, said method further comprising the step of exposing said resist at a time when said output of said DVRT indicates that position of said mask with respect to said substrate is optimum.

### Claim 30 (depends on 28)

The method as recited in claim 28, wherein said mask is spaced from said substrate by a gap, said method further comprising the step of exposing said resist at a time when said output of said DVRT indicates that said gap is optimum.

### Claim 31 (depends on 27)

The method as recited in claim 27, further comprising the step of using output of said DVRT to control mask to wafer misalignment.

### Claim 32 (depends on 27)

The method as recited in claim 27, further comprising the step of using output of said DVRT to control substrate x, y, z, rotation, and magnification.

### Claim 33 (depends on 27)

The method as recited in claim 27, further comprising the step of using output of said DVRT to provide positional feedback for six degrees of freedom alignment of the substrate.

### Claim 34 (depends on 33)

The method as recited in claim 33, further comprising the step of controlling all six degrees of freedom of the substrate.

### Claim 35

A method of exposing a resist on a substrate comprising the steps of:
a) providing the substrate with a film of resist;
b) placing the substrate on a stage;
c) providing x-ray radiation from a point source;
d) using an inline concentrator to concentrate said x-ray radiation;
e) providing a mask for defining exposure of said resist;
f) illuminating said mask with said x-ray radiation after said concentrating step (d); and
g) exposing said resist with x-ray radiation passing through said mask;
h) sensing position of the substrate with a displacement sensor wherein displacement sensor comprises a differential variable reluctance transducer (DVRT).

### Claim 36

A method of exposing a resist on a substrate comprising the steps of:
a) providing the substrate with a film of resist;
b) placing the substrate on a stage;
c) providing x-ray radiation from a point source;
d) concentrating said x-ray radiation;
e) providing a mask for defining exposure of said resist;
f) illuminating said mask with said x-ray radiation after said concentrating step (d);
g) exposing said resist with x-ray radiation passing through said mask; and
h) sensing position of the substrate with a displacement sensor wherein said displacement sensor comprises a differential variable reluctance transducer (DVRT).