Electronically switchable off-axis illumination blade for stepper illumination system

• US 6,215,578 B1
• Filed: 09/17/1998
• Issued: 04/10/2001
• Est. Priority Date: 09/17/1998
• Status: Expired due to Term

• Current Assignee: Vanguard International Semiconductor Corporation
• Original Assignee: Vanguard International Semiconductor Corporation
• Inventors: Lin, Chin-Hsiang
• Primary Examiner(s): Epps, Georgia
• Assistant Examiner(s): Spector, David N.
• Application Number:
  US09/156,056
• Time in Patent Office: 936 Days
• Field of Search: 355/53, 355/67, 355/71, 359/558, 359/559, 359/561-563, 359/285-287, 359/292, 359/310, 359/305, 359/306, 362/231, 378/145-153, 382/42, 382/210, 382/211
• US Class Current: 359/292
• CPC Class Codes: G03F 7/70091 Illumination settings, i.e. intensity distribution in the pupil plane or angular distribution in the field plane; On-axis or off-axis settings, e.g. annular, dipole or quadrupole settings; Partial coherence control, i.e. sigma or numerical aperture [NA]
• CPC Class Codes: G03F 7/70116 Off-axis setting using a programmable means, e.g. liquid crystal display [LCD], digital micromirror device [DMD] or pupil facets
• CPC Class Codes: G03F 7/70125 Use of illumination settings tailored to particular mask patterns details of setting means G03F7/70091
• 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

Abstract

An off axis illumination stepper exposure system includes an illumination system with an aperture element and lenses. The aperture element comprises an array of electronically switchable pixels in a matrix. The aperture element can be a transmissive spatial light modulator. An annular pattern of transmissivity through an aperture element is provided by a spatial light modulator operated under computer control. The computer can select and provide variable dimensions of the pattern to optimize operation of the device. In addition to a first transmissive spatial light modulator providing an aperture in the illumination system with a pattern of transmissivity operated under computer control, a mask is provided in the form of a second transmissive spatial light modulator operated under computer control operating cooperatively to provide images projected through a projection system onto a workpiece supported upon a stepper tool.

Claims

1. An off axis illumination system in a stepper tool includes an aperture element, a lens, and a mask wherein said aperture element comprises a transmissive spatial light modulator in the form of an array of electronically switchable pixels in a matrix providing off-axis light-transmitting regions patterned for enhanced critical dimension control.

3. A system in accordance with claim 1 wherein said aperture element comprises a transmissive spatial light modulator with an annular pattern of transmissivity.

4. A system in accordance with claim 1 wherein said aperture element comprises a transmissive spatial light modulator operated under computer control.

5. A system in accordance with claim 1 wherein said aperture element comprises a transmissive spatial light modulator with a pattern of transmissivity operated under computer control.

6. A system in accordance with claim 1 wherein said aperture element comprises a spatial light modulator with a pattern of transmissivity operated under computer control to provide variable dimensions of said pattern with dimensions selected by said computer to optimize operation of said spatial light modulator in a stepper tool.

7. A system in accordance with claim 1 wherein said aperture element comprises a first transmissive spatial light modulator with a pattern of transmissivity operated under computer control, and a mask comprising a second transmissive spatial light modulator operated under computer control operating cooperatively to provide an image upon a workpiece being exposed in a stepper tool by said mask.

2. An off axis illumination system in a stepper tool including:

a lens,

a mask, and

an aperture element comprising an array of electronically switchable pixels in a matrix and said aperture element comprising a spatial light modulator with an annular pattern of transmissivity.

8. A method of operating an off axis illumination system in a stepper tool including the steps as follows:

provide illumination light,

provide a lens,

provide a mask,

provide an aperture element comprising a transmissive spatial light modulator including electronically switchable pixels in a pixel matrix providing off-axis light-transmitting regions patterned for enhanced critical dimension control which permit selective transmission of light therethrough with patterns selected electronically,

apply an element image to said pixel matrix, and

project said illumination light for selective transmission through said lens, through said mask and through said transmissive spatial light modulator as a function of said selective transmission of said illumination light as a function of operation of said electronically switchable pixels.

9. A method in accordance with claim 8 wherein said aperture element comprises a transmissive spatial light modulator with an annular pattern of transmissivity.

10. A method in accordance with claim 8 wherein said aperture element comprises a transmissive spatial light modulator operated under computer control.

11. A method in accordance with claim 8 wherein said aperture element comprises a spatial light modulator with a pattern of transmissivity operated under computer control.

12. A method in accordance with claim 8 wherein said aperture element comprises a spatial light modulator with a pattern of transmissivity operated under computer control to provide variable dimensions of said pattern with dimensions selected by said computer to optimize operation of said spatial light modulator in a stepper tool.

13. An method in accordance with claim 8 wherein said aperture element comprises a first transmissive spatial light modulator with a pattern of transmissivity operated under computer control, and a mask comprising a second transmissive spatial light modulator operated under computer control operating cooperatively to provide an image upon a workpiece being exposed in a stepper tool by said mask.