INTERFEROMETRIC METHOD FOR IMPROVING THE RESOLUTION OF A LITHOGRAPHIC SYSTEM

• US 20080174847A1
• Filed: 06/15/2007
• Published: 07/24/2008
• Est. Priority Date: 01/24/2007
• Status: Active Grant

• Current Assignee: Adelphi University
• Original Assignee: Adelphi University
• Inventors: Bentley, Sean J.
• Granted Patent: US 7,859,646 B2
• Time in Patent Office: Days
• US Class Current: 359/237
• CPC Class Codes: G02B 27/58 Optics for apodization or superresolution; Optical synthetic aperture systems
• CPC Class Codes: G03F 7/70291 Addressable masks, e.g. spatial light modulators [SLMs], digital micro-mirror devices [DMDs] or liquid crystal display [LCD] patterning devices
• CPC Class Codes: G03F 7/70408 Interferometric lithography; Holographic lithography; Self-imaging lithography, e.g. utilizing the Talbot effect

Abstract

According to one exemplary embodiment of the present invention, a method for writing an arbitrary, two-dimensional pattern using interferometric lithography and classical techniques includes the steps of: (1) creating a pixel array defined by a number of pixels having specific coordinates; (2) mapping pixel information based on the desired pattern, the pixel information including a list of which pixels are activated to define the desired two-dimensional pattern; (3) controlling a relative strength of each pixel for indicating a feature height of a portion of the desired two-dimensional pattern; and (4) controlling a degree that one pixel is shifted in an x-direction and a y-direction relative to original coordinates of the pixel in order to define the desired two-dimensional pattern pixel by pixel.

Claims

1. A method for writing an arbitrary, two-dimensional pattern on a recording material using interferometric lithography and classical techniques comprising the steps of:

generating first and second light beams that carry horizontal (x) information;

generating third and fourth light beams that carry vertical (y) information;

interfering the first and second beams in a horizontal manner on the recording material and interfering the third and fourth beams in a vertical manner on the recording material such that each of the four beams reaches the recording material at the same point and same time; and

repeating the process to write the two-dimensional pattern pixel by pixel on the recording material.

2. A method for writing an arbitrary, two-dimensional pattern using interferometric lithography comprising the steps of:

creating a pixel array defined by a number of pixels having specific coordinates;

mapping pixel information based on the desired pattern, the pixel information including a list of which pixels are activated to define the desired two-dimensional pattern;

controlling a relative strength of each pixel for indicating a feature height of a portion of the desired two-dimensional pattern;

controlling a degree that one pixel is shifted in an x-direction and a y-direction relative to original coordinates of the pixel in order to define the desired two-dimensional pattern pixel by pixel; and

writing the two-dimensional pattern pixel by pixel on a recording material.

3. The method of claim 2, wherein each pixel includes an M×

M subarray of pixels, where M≦

N, where M is a level of resolution enhancement and N is the order of absorption of the N photon absorber which comprises the recording material.

4. The method of claim 2, wherein each pixel can be one of a completely activated state, a partially activated state and a completely inactivated state where the pattern is not present.

5. The method of claim 2, wherein the two-dimensional pattern includes at least one non-linear feature formed as a part of the pattern.

6. The method of claim 2, wherein the two-dimensional pattern includes at least two linear sections with a curved section located therebetween.

7. The method of claim 2, wherein the step of controlling the relative strength of each pixel includes the step of:

only partially activating one or more pixels to differentiate this area from an area where the pixels are completely activated or completely inactivated.

8. The method of claim 2, wherein each pixel has an associated A coefficient value, α

coefficient value and the β

coefficient value, the A coefficient value representing the relative intensity of the pixel, the α

coefficient value representing the degree that the pixel is shifted horizontally (x-direction) relative to base coordinates of the pixel, the β

coefficient value representing the degree that the pixel is shifted vertically (y-direction) relative to the base coordinates of the pixel, wherein the shifting of one or more pixels forms non-linear features of the pattern.

9. The method of claim 8, wherein a resulting electric field for a given pixel is determined by the equation:

E_i,j=A_i,j{e<sup>iδ

i,j</sup>[e^ikx+e<sup>−

ikx</sup>e<sup>iφ

i,j</sup>]+[e^iky+e<sup>−

iky</sup>e<sup>iθ

i,j</sup>]}

where δ

_i,j=[θ

_i,j−

φ

_i,j]/2 with φ

_i,j=2π

(i+α

_i,j)/M and θ

_i,j=2π

(j+β

_i,j)/M; and

wherein the value of the A coefficient is from 0 to 1.

10. The method of claim 9, wherein the total deposition on the recording material is given by a two-dimensional sum over the pixel array and is defined as:

11. The method of claim 2, further including the steps of:

outputting a first beam of light;

splitting the first beam of light into a second beam that carries horizontal (x) information of the pixel and a third beam that carries vertical (y) information of the pixel;

splitting the second beam into two x-beams and splitting the third beam into two y-beams;

causing the two y-beams to interfere in a vertical manner and causing the two x-beams to interfere in a horizontal manner, each of the four beams reaching the recording material at the same point and same time.

12. The method of claim 11, further including the steps of:

disposing a first spatial light modulator (SLM) in the path of the first beam prior to the first beam being split into the second and third beams by a first beam splitter, the first SLM functioning to impose amplitude structures of the pixels on each spatial region of the array;

disposing a second beam splitter in the path of the second beam to split it into an x-beam 1 and an x-beam 2;

disposing a third beam splitter in the path of the third beam to split it into a y-beam 1 and a y-beam 2;

disposing a second SLM in the path of the x-beam 1 and disposing a third SLM in the path of the x-beam 2 and disposing a fourth SLM in the path of the y-beam 1; and

arranging a plurality of optical components and positioning them relative to the x-beam 1, x-beam 2, y-beam 1 and y-beam 2 so that the y-beam 1 and y-beam 2 interfere in a vertical manner and the x-beam 1 and x-beam 2 interfere in a horizontal manner and each of the four beams reaches the recording material at the same point and same time.

13. The method of claim 12, wherein each of the second, third and fourth SLMs controls the phase factors of the respective beam.

14. The method of claim 12, wherein the third beam splitter comprises a vertically-aligned beam splitter.

15. The method of claim 12, wherein each optical component comprises at least one mirror and at least one lens.

16. The method of claim 12, wherein each optical component comprises a focusing mirror.

17. The method of claim 2, wherein the writing on the recording material is repeated M² times such that all pixels are written for each array until the complete two-dimensional pattern is formed, where M is a level of resolution enhancement.

18. The method of claim 2, wherein the recording material comprises an N-photon absorbing lithographic substrate.

19. The method of claim 2, further including the steps of:

determining the non-linear aspects of the desired two-dimensional pattern and selecting target pixels and subarray pixels; and

shifting subarray pixels in at least one of the x-direction and the y-direction in order to define the non-linear aspects of the two-dimensional pattern.

20. The method of claim 11, further including the steps of:

splitting the first beam into the second and third beams by a first beam splitter,

disposing a second beam splitter in the path of the second beam to split it into an x-beam 1 and an x-beam 2;

disposing a third beam splitter in the path of the third beam to split it into a y-beam 1 and a y-beam 2;

disposing a first spatial light modulator (SLM) in the path of the x-beam 1;

disposing a second SLM in the path of the x-beam 2;

disposing a third SLM in the path of the y-beam 2 and disposing a fourth SLM in the path of the y-beam 1; and

arranging a plurality of optical components and positioning them relative to the x-beam 1, x-beam 2, y-beam 1 and y-beam 2 so that the y-beam 1 and y-beam 2 interfere in a vertical manner and the x-beam 1 and x-beam 2 interfere in a horizontal manner and each of the four beams reaches the recording material at the same point and same time;

wherein each pixel has an associated A coefficient value, α

coefficient value and the β

coefficient, the A coefficient value representing the relative intensity of the pixel, the α

coefficient value representing the degree that the pixel is shifted horizontally (x-direction) relative to base coordinates of the pixel, the β

coefficient value representing the degree that the pixel is shifted vertically (y-direction) relative to the base coordinates of the pixel, wherein the shifting of one or more pixels forms non-linear features of the pattern; and

wherein the SLMs have associated phase factors for controlling the amplitude and phase shifts of the respective beams to cause the four beams to reach the recording material at the same point and same time.

21. A system for writing an arbitrary, two-dimensional pattern using interferometric lithography on a recording material comprising:

a source of a light beam having a prescribed wavelength;

a program that creates a pixel array defined by a number of pixels having specific coordinates and permits the two-dimensional pattern to be mapped on the pixel array;

a first means for splitting the light beam into a first beam that carries horizontal (x) information of the pixel and a second beam that carries vertical (y) information of the pixel;

a second means for splitting the second beam into two x-beams and splitting the third beam into two y-beams; and

a third means for causing the two y-beams to interfere in a vertical manner and causing the two x-beams to interfere in a horizontal manner, each of the four beams reaching the recording material at the same point and same time to create pixel by pixel the arbitrary two-dimensional pattern having enhanced resolution.

22. The system of claim 21, wherein the first means comprises a first beam splitter;

the second means comprises a second beam splitter that is horizontally aligned for generating the x-beam 1 and x-beam 2 and a third beam splitter that is vertically aligned for generating the y-beam 1 and y-beam 2, and the third means comprises a plurality of spatial light modulators for imposing phase factors on at least three of the x-beam 1, x-beam 2, y-beam 1, and y-beam 2 and a plurality optical components arranged to cause the four beams to reach the recording material at the same point and the same time.

23. A system for writing an arbitrary, two-dimensional pattern using interferometric lithography on a recording material comprising:

a source of a light beam having a prescribed wavelength;

a program that creates a pixel array defined by a number of pixels having specific base coordinates and permits the two-dimensional pattern to be mapped on the pixel array, wherein each pixel has a corresponding A coefficient, α

coefficient value and the β

coefficient, the A coefficient value representing the relative intensity of the pixel, the α

coefficient value representing the degree that the pixel is shifted horizontally (x-direction) relative to base coordinates of the pixel, the β

coefficient value representing the degree that the pixel is shifted vertically (y-direction) relative to the base coordinates of the pixel, wherein the shifting of one or more pixels forms one or more non-linear features of the pattern, wherein based on inputted information regarding the desired two-dimensional pattern, the program determines the corresponding A coefficient value, α

coefficient value and the β

coefficient value needed for each pixel to form the two-dimensional pattern pixel by pixel; and

a device that communicates with the program and writes the two-dimensional pattern on a recording material using classical interferometric lithography techniques that act on the light beam.

24. A method for writing an arbitrary, two-dimensional pattern on a recording material using interferometric lithography and classical techniques comprising the steps of:

creating a pixel array defined by a number of main pixels having specific coordinates;

dividing each main pixel into a subarray of pixels to permit a specific region within one main pixel to be identified by subarray coordinates to permit finer patterns to be established with precise detail on the recording material;

generating and treating a light beam classically as a composite electromagnetic wave, the light beam being divided into first and second light beams that carry horizontal (x) information and third and fourth light beams that carry vertical (y) information; and

interfering the first and second beams in a horizontal manner on the recording material and interfering the third and fourth beams in a vertical manner on the recording material such that each of the four beams reaches the recording material at the same point same time to write the two-dimensional pattern pixel by pixel.