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General-Purpose Pattern Generator for E-Beam Lithography

IP.com Disclosure Number: IPCOM000044318D
Original Publication Date: 1984-Dec-01
Included in the Prior Art Database: 2005-Feb-05
Document File: 3 page(s) / 34K

Publishing Venue

IBM

Related People

Coane, PJ: AUTHOR [+3]

Abstract

In a computer-controlled pattern writing system of the type wherein a pattern to be written has been subdivided into elementary shapes and the elementary shapes are written in succession by a beam which is controlled by a pattern generator (i.e., a vector scan system), an improvement is described wherein the set of possible elementary shapes includes both rectangular coordinate system-defined elementary shapes and polar coordinate system-defined elementary shapes. The rectangular elementary shapes are written by the beam while the beam is under the control of a rectangular coordinate system pattern generator, and the polar elementary shapes are written by the same beam while it is under the control instead of a polar coordinate system pattern generator.

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General-Purpose Pattern Generator for E-Beam Lithography

In a computer-controlled pattern writing system of the type wherein a pattern to be written has been subdivided into elementary shapes and the elementary shapes are written in succession by a beam which is controlled by a pattern generator (i.e., a vector scan system), an improvement is described wherein the set of possible elementary shapes includes both rectangular coordinate system- defined elementary shapes and polar coordinate system-defined elementary shapes. The rectangular elementary shapes are written by the beam while the beam is under the control of a rectangular coordinate system pattern generator, and the polar elementary shapes are written by the same beam while it is under the control instead of a polar coordinate system pattern generator. Conventional electron beam lithography systems are designed to generate patterns in cartesian coordinates, which dictates how hardware, software and pattern data is structured and organized. There are two major exposure strategies for pattern generation, namely raster scan and vector scan. In the raster scan technique, the beam is scanned across the whole target and it is turned on and off depending on whether it is inside or outside of the area to be exposed. There is no limitation as to the types of shapes that can be exposed. The disadvantages, however, are high data volume, long exposure time and the lack of means for correcting for proximity effects. In the vector scan technique, the beam is positioned to the corner of a shape using a high resolution low speed D/A (digital- to-analog) unit. The shape then is filled by a rectilinear scan using a separate lower resolution high speed D/A unit. In order to generate curved structures in the conventional vector scan system, small rectangular shapes are used to approximate the curvature. This approach requires a large data volume and overlapping shapes. The use of overlapping shapes can lead to asymmetrical dose variations in a resist, which can result in poor edge definition on the periphery of the curved structure. The data volume necessary to pattern many circular elements also can become unwieldy and cumbersome. Since many millions of shapes must be accurately placed by using this patterning method, exposure times can become so excessive that any addition to the data volume (such as form proximity corrections) is prohibitive in cost. Furthermore, any device pattern whi...