Browse Prior Art Database

Focusing and Alignment for Projection Photolithography System by Wave Front Conjugation

IP.com Disclosure Number: IPCOM000048242D
Original Publication Date: 1982-Jan-01
Included in the Prior Art Database: 2005-Feb-08
Document File: 2 page(s) / 38K

Publishing Venue

IBM

Related People

Levenson, MD: AUTHOR [+2]

Abstract

A projection photolithography system is described in which a fine adjustment in focus and alignment of a pattern on a substrate can be achieved by wavefront conjugation.

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 53% of the total text.

Page 1 of 2

Focusing and Alignment for Projection Photolithography System by Wave Front Conjugation

A projection photolithography system is described in which a fine adjustment in focus and alignment of a pattern on a substrate can be achieved by wavefront conjugation.

A previous article (*) describes a high resolution projection photolithography system employing conjugate wavefront generation. This system employs a conjugate wave generator 10 and a beam splitter cube 12 to image the desired pattern on a substrate.

The present article describes a means of shifting the position of the image in the previously described system by a small (micron scale) amount by altering the characteristics of the backward-propagating pump wave. It is assumed that the wavefront conjugator material produces its images as a result of interference between the object wave and the forward-propagating pump, and that the backward-propagating pump is incoherent with the object wave, therefore producing no images due to interference.

The maximum efficiency and perfect conjugation occurs when the phase fronts of the forward and backward pumps are phase conjugate of one another. However, substantial efficiency and nearly perfect conjugation can still be obtained when that condition is not met. The image produced, however, is deviated from its ideal position. By controlling the characteristics of the backward pump, this deviation in position can be employed for focusing and alignment. Assume that the forward pump wavefronts are plane. Then if the backwards pump wavefronts are plane, but tilted...