Browse Prior Art Database

Method for Generating Structures Smaller Than Normal Resolution Limit

IP.com Disclosure Number: IPCOM000035847D
Original Publication Date: 1989-Aug-01
Included in the Prior Art Database: 2005-Jan-28
Document File: 2 page(s) / 49K

Publishing Venue

IBM

Related People

Bajuk, SP: AUTHOR [+3]

Abstract

By means of double exposure of photoresist (PR), a first exposure being to an image of photo-limited size and a second to the same image after displacement, a photoresist image is formed which is smaller than normal, single exposure photo resolution permits. Image displacement may be accomplished by standard laser interferometer stage motion control. An image may also be displaced with high precision by rotating a planar refracting element placed in the optical path of a projection exposure system. The technique permits elements to be constructed having smaller than standard resolution-limited dimensions for benefits other than device density, e.g., semiconductor device performance.

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Method for Generating Structures Smaller Than Normal Resolution Limit

By means of double exposure of photoresist (PR), a first exposure being to an image of photo-limited size and a second to the same image after displacement, a photoresist image is formed which is smaller than normal, single exposure photo resolution permits. Image displacement may be accomplished by standard laser interferometer stage motion control. An image may also be displaced with high precision by rotating a planar refracting element placed in the optical path of a projection exposure system. The technique permits elements to be constructed having smaller than standard resolution-limited dimensions for benefits other than device density, e.g., semiconductor device performance.

A positive PR, one which is made soluble in its developer by exposure to appropriate radiant energy, is used to describe the method but negative or reversal PRs, with appropriate masks, may also be used.

Referring to Fig. 1, an opaque rectangular area in a photomask first has its image projected onto a positive PR at position 2, thus exposing a line hatched region of PR. The image position is shifted relative to the PR to create, on a second exposure, an image at position 4, thus exposing a dot hatched region of PR. The only unexposed PR after the two exposures is region 6 which will remain after development. Thus, an image 6 is formed in PR which is smaller than the image projected from the mask.

While exposure sta...