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Novel Mask to Substrate Alignment Procedure for Sub-Micron Photolithography

IP.com Disclosure Number: IPCOM000041190D
Original Publication Date: 1987-Nov-01
Included in the Prior Art Database: 2005-Feb-02
Document File: 1 page(s) / 11K

Publishing Venue

IBM

Related People

Fredericks, EC: AUTHOR [+3]

Abstract

Excessive random noise in optical alignment of mask to substrate in optical projection exposure tools can be filtered out using a spatial filter representative of the fourier transform of the existing mask targets. These targets, usually a set of diagonal chrome on glass or quartz lines, found in each mask quadrant, or on previous substrate layers, are represented by the ramp function F(x). Each line has a frequency component representative of the line. The fourier transform filter, created in glass, quartz or electronically, enhances true intensity.

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Novel Mask to Substrate Alignment Procedure for Sub-Micron Photolithography

Excessive random noise in optical alignment of mask to substrate in optical projection exposure tools can be filtered out using a spatial filter representative of the fourier transform of the existing mask targets. These targets, usually a set of diagonal chrome on glass or quartz lines, found in each mask quadrant, or on previous substrate layers, are represented by the ramp function F(x). Each line has a frequency component representative of the line. The fourier transform filter, created in glass, quartz or electronically, enhances true intensity.

Mask substrate alignment signal strength rate of change is monitored digitally or by oscilloscope display with optional discreet audio signal to the tool operator.

Disclosed anonymously.

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