Photolithographic technique and illuminator using real-time addressable phase shift light shift

• US 5,539,567 A
• Filed: 06/16/1994
• Issued: 07/23/1996
• Est. Priority Date: 06/16/1994
• Status: Expired due to Term

• Current Assignee: Texas Instruments, Inc.
• Original Assignee: Texas Instruments, Inc.
• Inventors: Palmer, Shane R., Brown, Jay M., Lin, Tsen-Hwang, Gustafson, Steven C.
• Primary Examiner(s): Ben, Loha
• Application Number:
  US08/260,389
• Time in Patent Office: 768 Days
• Field of Search: 369/281, 385/1, 385/4, 385/5, 385/15, 385/28, 372/26, 372/27, 359/279, 359/291, 359/294, 359/295, 359/212, 359/223, 359/315, 359/316, 359/254, 359/263, 359/245
• US Class Current: 359/281
• CPC Class Codes: G02B 26/06 for controlling the phase of light G02B26/08 takes precedence , measuring optical phase difference G01J9/00
• CPC Class Codes: G03F 1/26 Phase shift masks [PSM]; PSM blanks; Preparation thereof
• CPC Class Codes: G03F 7/2002 with visible light or UV light, through an original having an opaque pattern on a transparent support, e.g. film printing, projection printing; by reflection of visible or UV light from an original such as a printed image
• CPC Class Codes: G03F 7/70191 Optical correction elements, filters or phase plates for controlling intensity, wavelength, polarisation, phase or the like
• CPC Class Codes: G03F 7/70283 Mask effects on the imaging process
• 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 7/70566 Polarisation control

Abstract

A phase shift illuminator (700) is comprised of a light source (704) and a phase modulator (716), typically a flexure beam micromirror array, which transversely modulates the incident light beam. When a flexure beam micromirror array is used as the phase modulator (716) a polarizing beam splitter (712) and a quarter-wave plate (714) are used to separate the incident and reflected light beams. The phase modulated light beam (720) from the optical illuminator may be used in optical lithography by passing the light beam through a lithography mask (724), typically after the light beam is phase modulated, and focusing the light beam onto a target wafer (726).

Claims

1. An optical lithography system for projecting an image onto a target, said lithography system comprising:

a light source for projecting a beam of light along a light path;

a phase modulator disposed along said light path for imparting a phase modulation pattern transverse said beam of light, Wherein said phase modulation pattern is determined by at least one electrical control signal;

a lithography mask disposed along said light path for spatially modulating said beam of light to produce said image, said lithography mask comprised of at least two regions, a first region for preventing incident light from continuing along said light path, and a second region for allowing incident light to continue along said light path, wherein portions of said beam of light are diffracted by a boundary between said first region and said second region; and

wherein said phase modulation pattern maximizes a destructive interference among said diffracted portions of said beam of light.

2. The optical lithography system of claim 1 wherein said phase modulator is a flexure beam micromirror device.

3. The optical lithography system of claim 1 further comprising a beam splitter disposed along said light path between said light source and said phase modulator.

4. The optical lithography system of claim 3 wherein said beam splitter is a polarized beam splitter.

5. The optical lithography system of claim 1 further comprising a beam splitter disposed along said light path between said phase modulator and said lithography mask.

6. The optical lithography system of claim 5 wherein said beam splitter is a polarized beam splitter.

7. The optical lithography system of claim 1 wherein said beam of light has a coherence of at least 30 percent.

8. A method of exposing a light sensitive material, said method comprising:

transversely phase modulating a beam of light in response to at least one electrical control signal;

spatially modulating said beam of light; and

focusing said phase and spatially modulated beam of light onto said light sensitive material, wherein said step of transversely phase modulating maximizes a destructive interference among portions of said phase and spatially modulated beam of light.

9. The method of claim 8 wherein said step of transversely phase modulating said beam of light comprises reflecting said beam of light with a flexure beam micromirror device.

10. The method of claim 8 wherein said step of spatially modulating said beam of light comprises passing said beam of light through a lithography mask.

11. The method of claim 8 wherein said focusing step comprises focusing said phase and spatially modulated beam of light onto a photoresist.

12. The method of claim 8 further comprising the step of sweeping said focused beam of light across the surface of said light sensitive material, wherein said step of spatially modulating said beam of light further comprises varying the spatial modulation of said beam of light in concert with said sweeping step.

13. The method of claim 12 wherein said step of transversely phase modulating said beam of light further comprises varying the phase modulation of said beam of light in concert with said sweeping step.

14. A lithographic illuminator which comprises:

means for providing a beam of light;

a spatial light modulator for receiving and then reflecting said beam of light, wherein said spatial light modulator transversely phase modulates said beam of light in response to at least one electrical control signal; and

means for spatially filtering said beam of light.

15. The illuminator of claim 14 further comprising a beam splitter, wherein said beam of light passes through said beam splitter before impinging on said means for transversely modulating.

16. The illuminator of claim 15 wherein said beam splitter is a polarized beam splitter.

17. The illuminator of claim 15 wherein said beam of light has a coherence of at least 30 percent.

18. The illuminator of claim 14 wherein said means for spatially filtering said beam of light is a lithography mask for receiving and spatially filtering said beam of light, said lithography mask comprising at least one aperture for allowing light to pass through said lithography mask, wherein said beam of light is diffracted by said at least one aperture and said phase modulation increases destructive interference among diffracted portions of said spatially filtered beam of light.

19. The illuminator of claim 14 wherein said spatial light modulator comprises a flexure beam micromirror device.