Browse Prior Art Database

Resist Thickness Filter Matching in E Beam Registration System

IP.com Disclosure Number: IPCOM000088430D
Original Publication Date: 1977-Jun-01
Included in the Prior Art Database: 2005-Mar-04
Document File: 2 page(s) / 28K

Publishing Venue

IBM

Related People

Davis, DE: AUTHOR [+3]

Abstract

In an electron(E)-beam lithography pattern generator, automatic alignment must be made on many types of wafers and at different stages of fabrication. Optimization of such a system includes anticipation of the type of wafer with its particular alignment mark structure and Ebeam resist coating.

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Resist Thickness Filter Matching in E Beam Registration System

In an electron(E)-beam lithography pattern generator, automatic alignment must be made on many types of wafers and at different stages of fabrication. Optimization of such a system includes anticipation of the type of wafer with its particular alignment mark structure and Ebeam resist coating.

In this system wafers are grouped into two categories: those with thick resist coatings and those with thin resist coatings. The backscattered signal from thin resist wafers contain higher frequency components requiring a wide bandwidth to retain the signal shape without distortion. The signals from the thick resist wafers do not require as large a bandwidth, but do require filtering in order to attenuate the beam shot noise and provide an improved signal-to-noise ratio. This is accomplished by reading a "filter select" parameter from a disk into the CPU at wafer start time, along with other parameters that are normally used to control the collection of alignment data. The "filter select" parameter is communicated to the detection circuits via a digital control unit, and the appropriate filter is then switched into the detection channel during registration time.

The resultant programmable filter is used to optimize the alignment mask signals for a variety of resist thicknesses by a simple specification previous to wafer writing, thereby enhancing the E-beam alignment mark detection capability without affecting s...