Method of producing a .lambda./4-shifted diffraction grating

• US 5,236,811 A
• Filed: 07/06/1992
• Issued: 08/17/1993
• Est. Priority Date: 04/19/1990
• Status: Expired due to Fees

• Current Assignee: Mitsubishi Denki Kabushiki Kaisha (Mitsubishi Electric Corporation)
• Original Assignee: Mitsubishi Denki Kabushiki Kaisha (Mitsubishi Electric Corporation)
• Inventors: Fujiwara, Masatoshi
• Primary Examiner(s): Bowers, Jr., Charles L.
• Assistant Examiner(s): ANGEBRANNDT, MARTIN J
• Application Number:
  US07/908,781
• Time in Patent Office: 407 Days
• Field of Search: 430/1, 430/2, 430/320, 430/321, 430/394, 430/330, 359/573, 359/566, 359/567
• US Class Current: 430/321
• CPC Class Codes: G03F 7/001 Phase modulating patterns, e.g. refractive index patterns

Abstract

A method of producing a λ/4 shifted diffraction grating, includes applying an image reversible resist on a substrate on which a diffraction grating is to be formed, exposing a predetermined with light of a first predetermined region of the resist with light of a first predetermined energy, exposing all of the resist with light interference fringes of a second predetermined energy, baking, and thereafter developing the image reversible resist.

Claims

1. A method of producing a diffraction grating including a λ

/4 shifted region comprising sequentially;

applying an image-reversible resist to a substrate on which a diffraction grating is to be formed, said image-reversible resist changing from a negative-type resist to a positivetype resist upon cumulative exposure to light energy approximately equal to A and to a negative-type resist upon cumulative exposure to light energy approximately equal to twice A;

exposing a predetermined portion of said image-reversible resist with light energy of approximately A;

exposing all of said image-reversible resist to a pattern of light interference fringes wherein the maximum light energy of the fringes is approximately A;

baking said image-reversible resist;

developing said image-reversible resist; and

etching said substrate using said developed image-reversible resist as a mask to produce a λ

/4 shifted diffraction grating.

2. The method of claim 1 including:

before exposing a predetermined portion of said image-reversible resist to light, covering a portion of said image-reversible resist with a mask, leaving the predetermined portion of said image-reversible resist unmasked; and

after exposing the predetermined portion of said image-reversible resist with light energy of approximately A, and before exposing all of said image-reversible resist to the pattern of interference fringes having a maximum light energy of approximately A, removing the mask.