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Double-Wafer-Chuck System to Facilitate Rapid and Accurate Alignment

IP.com Disclosure Number: IPCOM000062174D
Original Publication Date: 1986-Oct-01
Included in the Prior Art Database: 2005-Mar-09
Document File: 3 page(s) / 52K

Publishing Venue

IBM

Related People

Lin, BJ: AUTHOR

Abstract

This article relates generally to integrated circuit fabrication techniques which utilize the optical patterning of photoresists to fabricate integrated circuits and more particularly to a technique and apparatus which aligns semiconductor wafer prior to photoresist exposure. Still more particularly it relates to a double-wafer-chuck system which facilitates rapid and accurate alignment. To pattern a wafer using a mask aligner, many time-consuming operations are required. The wafer has to be loaded, aligned, exposed, and unloaded. Alignment occupies a significant portion of the total handling time of the wafer, and, therefore, any reduction in alignment time would be a strong factor in enhancing throughput.

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Double-Wafer-Chuck System to Facilitate Rapid and Accurate Alignment

This article relates generally to integrated circuit fabrication techniques which utilize the optical patterning of photoresists to fabricate integrated circuits and more particularly to a technique and apparatus which aligns semiconductor wafer prior to photoresist exposure. Still more particularly it relates to a double-wafer- chuck system which facilitates rapid and accurate alignment. To pattern a wafer using a mask aligner, many time-consuming operations are required. The wafer has to be loaded, aligned, exposed, and unloaded. Alignment occupies a significant portion of the total handling time of the wafer, and, therefore, any reduction in alignment time would be a strong factor in enhancing throughput. Generally, when alignment accuracy is not critical, one alignment is done for the entire wafer, regardless of whether or not the wafer is exposed by one full wafer exposure, by scanning with a full-length illuminated slit or by stepping and repeating the exposures field-by-field (FBF). The reduction from a FBF alignment scheme to this so-called "global alignment" scheme improves wafer throughput at the expense of alignment accuracy. When the highest alignment accuracy is required, FBF alignment becomes necessary to accommodate secondary random displacements from field-to-field. This can easily reduce wafer throughput by a factor of 1/3 to 1/2. In this article, a double-wafer-chuck is used to facilitate FBF position measurement as a wafer undergoes step-and- repeat exposures, combining the advantages of global and FBF alignment schemes. A double-wafer-chuck system 1 shown in side and top views incorporates double-wafer-chuck 2, an imaging lens arrangement 3, a pair of alignment sensors 4,5 and rigid interconnections 6 which position sensors 4,5 in fixed positions relative to lens arrangement 3. Using double- chuck 2 not only facilitates the simultaneous execution of exposure and position detection, but it also permits the measured wafer to stay on the same chuck between measurement and exposure to eliminate chucking- induced positioning errors. Double-chuck 2 is moved in the x and y directions on a precision table controlled by laser int...