Browse Prior Art Database

Homogeneous Illumination of Electron Beam Transmission Masks

IP.com Disclosure Number: IPCOM000042453D
Original Publication Date: 1984-May-01
Included in the Prior Art Database: 2005-Feb-03
Document File: 2 page(s) / 51K

Publishing Venue

IBM

Related People

Bohlen, H: AUTHOR [+3]

Abstract

A transmission mask for electron beam lithography is repeatedly scanned by an electron beam, the diameter of which is small in relation to the mask size and which is offset for each scan by a distance W from the previous scanning path to compensate for inhomogeneous intensity distributions across the beam diameter. Fig. 1 shows a transmission mask with two complementary patterns 1, 2 (as described in U.S. Patent 4,169,230). Pattern 1 to be projected onto a photoresist-covered substrate is scanned along a meander path 4 by an electron beam in the form of a hexagon 3. The tips of hexagon 3 overlap in the X-direction during scanning to allow small beam displacements without changing the electron dose deposited at the boundaries of the scanning path.

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Homogeneous Illumination of Electron Beam Transmission Masks

A transmission mask for electron beam lithography is repeatedly scanned by an electron beam, the diameter of which is small in relation to the mask size and which is offset for each scan by a distance W from the previous scanning path to compensate for inhomogeneous intensity distributions across the beam diameter. Fig. 1 shows a transmission mask with two complementary patterns 1, 2 (as described in U.S. Patent 4,169,230). Pattern 1 to be projected onto a photoresist- covered substrate is scanned along a meander path 4 by an electron beam in the form of a hexagon 3. The tips of hexagon 3 overlap in the X-direction during scanning to allow small beam displacements without changing the electron dose deposited at the boundaries of the scanning path. To avoid excessive local heating of the transmission mask, the total dose required for exposing the photoresist cannot be supplied by a slowly moving beam; instead, pattern 1 is repeatedly and rapidly scanned along path 4. If the intensity distribution across hexagon 3 is not uniform, the electron dose received by the substrate varies in the X-direction in a ripplelike pattern, as indicated by curve 5, where a maximum intensity is assumed for the center of the hexagon. To achieve a more uniform dose distribution, it is proposed to offset the scanning path in the X-direction during each scan by a distance W relative to the previous scanning path, as shown by th...