Browse Prior Art Database

Package Mask for Photolithography

IP.com Disclosure Number: IPCOM000085295D
Original Publication Date: 1976-Mar-01
Included in the Prior Art Database: 2005-Mar-02
Document File: 2 page(s) / 31K

Publishing Venue

IBM

Related People

Via, GG: AUTHOR

Abstract

The lifetime of a chromium mask is extended when packaged in a frame and covered with a transparent polymer. Mask contamination problems from dust and particulate are eliminated when the back side of the chromium mask faces a reducing lens, and serves as the optical plane in a step and repeat or projection printing apparatus. The back side of the chromium mask is optically flat. Light rays passing through the mask leave the back surface of the mask in parallel relation. Mask distortion is eliminated by focusing the optical system through the glass thickness.

This text was extracted from a PDF file.
At least one non-text object (such as an image or picture) has been suppressed.
This is the abbreviated version, containing approximately 81% of the total text.

Page 1 of 2

Package Mask for Photolithography

The lifetime of a chromium mask is extended when packaged in a frame and covered with a transparent polymer. Mask contamination problems from dust and particulate are eliminated when the back side of the chromium mask faces a reducing lens, and serves as the optical plane in a step and repeat or projection printing apparatus. The back side of the chromium mask is optically flat. Light rays passing through the mask leave the back surface of the mask in parallel relation. Mask distortion is eliminated by focusing the optical system through the glass thickness.

In the figure, a conventional chrome mask includes a glass carrier 2O with a front surface 22 and a back surface 24 that are parallel and optically flat. A layer of chrome 26 is deposited on the front surface 22 and suitably etched, to define a pattern for reproduction by photolithography. The mask is disposed in a frame
28. A transparent polymer 30 covers the pattern and bonds the mask to the frame 28. The mask is used in a projection printing or step and repeat apparatus, the latter employing a reducing lens 32.

The mask is disposed between a light supply 34 and the reducing lens 32. The back side or surface 24 of the mask faces the lens 32.

The light rays coming through the mask are parallel by reason of the optically flat back surface 24.

Since the polymer layer 30 is not in the optical plane there is no requirement for flatness. However, air bubbles in the polymer exceed...