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Switching Pattern Control in an Electron Beam Writing System Between Bidirectional and Unidirectional Writing Without Altering Pattern Drive Code

IP.com Disclosure Number: IPCOM000089071D
Original Publication Date: 1977-Sep-01
Included in the Prior Art Database: 2005-Mar-04
Document File: 3 page(s) / 32K

Publishing Venue

IBM

Related People

Muir, AW: AUTHOR [+2]

Abstract

The basic electron-beam writing system exposes patterns on a target or wafer on alternating forward and backward scans of the writing field, as shown in Fig. 1A. This allows relatively slow, narrow-bandwidth magnetic deflection signals, but requires precise adjustment of the writing field so that spots exposed on successive lines will be aligned. Failure to achieve this adjustment greatly degrades the exposed image.

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Switching Pattern Control in an Electron Beam Writing System Between Bidirectional and Unidirectional Writing Without Altering Pattern Drive Code

The basic electron-beam writing system exposes patterns on a target or wafer on alternating forward and backward scans of the writing field, as shown in Fig. 1A. This allows relatively slow, narrow-bandwidth magnetic deflection signals, but requires precise adjustment of the writing field so that spots exposed on successive lines will be aligned. Failure to achieve this adjustment greatly degrades the exposed image.

In many applications, some degree of repeatable nonlinearity may be tolerated without serious image degradation; images of high quality may be exposed and overlaid (on a single system) with an unadjusted writing field provided the exposure is done on successive lines moving in the same direction (Fig. 1B). A hardware switching scheme, described here, allows both unidirectional and bidirectional exposure of patterns developed for bidirectional exposure, without requiring any changes in the pattern code, library structure, access methods, or pattern-handling programs.

In normal bidirectional operation the contents of the pattern cache controlling spot exposure and offset are presented sequentially to the analog circuitry, in ascending address order during even lines and in descending address order during odd lines. As each spot is used, the information read from the cache at that address is updated to reflect the exposure and offset desired at that address in the next line of exposure.

Thus, both delivery of exposure and offset to the analog unit circuits, and the updating of that data in preparation for the next line are performed together in every line. In the unidirectional mode, the low order two bits of the line number (Y counter) are used to gate separately, the functions...