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Method and Apparatus to Provide Rapid Interpretation of Digital Source Information During Electron Beam Pattern Writing of Rectangular Shapes

IP.com Disclosure Number: IPCOM000049011D
Original Publication Date: 1982-Apr-01
Included in the Prior Art Database: 2005-Feb-09
Document File: 5 page(s) / 69K

Publishing Venue

IBM

Related People

Muir, AW: AUTHOR

Abstract

Earlier work (*) described a hardware implementation for digital control of an E-beam pattern writer (rectangle generator) which, upon receipt of rectangle definitions, automatically develops all digital spot shape and position values required to expose those rectangles. However, the raster scanning hardware described there has limitations. Though primitive in function, it is complex in implementation. With technological advances in electron-beam lithography, changes in exposure algorithms are a certainty. The number of repeated additions, subtractions, and lengthy multibit comparisons required will become prohibitive with conventional approaches. The delays of such logic, with its many separate circuit elements, will prevent practical implementations.

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Method and Apparatus to Provide Rapid Interpretation of Digital Source Information During Electron Beam Pattern Writing of Rectangular Shapes

Earlier work (*) described a hardware implementation for digital control of an E-beam pattern writer (rectangle generator) which, upon receipt of rectangle definitions, automatically develops all digital spot shape and position values required to expose those rectangles. However, the raster scanning hardware described there has limitations. Though primitive in function, it is complex in implementation. With technological advances in electron-beam lithography, changes in exposure algorithms are a certainty. The number of repeated additions, subtractions, and lengthy multibit comparisons required will become prohibitive with conventional approaches. The delays of such logic, with its many separate circuit elements, will prevent practical implementations.

While arithmetic functions of the prior design cannot be eliminated, they can be reduced and logical decisions can, predictably, be contained within the cycle time of ambitious future pattern writers. This article describes a new control circuit for the above-mentioned rectangle generator. As shown in Fig. 1, memory device 1, count down counter 3 and compare circuits 5 provide width (X) and height (Y) line characteristics directly. It should be noted that the same reference characters have been used to identify like devices in both the X and Y control function channels. Successive data words stored in memory 1 are precalculated values depicting the integer number of full spot and partial spot value(s) required to expose written lines. The line dimension values serve as memory addresses for related data, providing a complete set over the range of anticipated line lengths at an acceptable resolution. When addressed as a rectangular dimension, the resultant memory output provides an initialization of counter 3 and the partial spot dimension(s). Both the counter and partial value(s) are monitored by simple logic AND gate compares at 5. The results, full spot counter (FS Cnt.) equals 0, 1, partial value (PAR VAL) equals 0, plus alternate axis data, descriptive of that dimension, serve as input to a programmable logic array sequencer. Additional inputs may be required for more complex algorithms. The sequencer, a programmable logic array (PLA) 7 and state latch 9, is capable of advancing through complex microcoded state tables depicting spot stepping algorithms. An extension of memory 1 provides rectangle characteristics portraying relationships between a rectangular dimension and preprogrammed spot characteristics. This plus alternate axis data serve as input to a starting point PLA 11 which, when enabled by the shared AND gate 13 output, defines the micro-code entree point for the rectangle generating algorithm.

The state latch 9 output is representative of individual spot characteristics and is the control function output for following rectangle...