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Photolithographic Printer With High Resolution

IP.com Disclosure Number: IPCOM000046649D
Original Publication Date: 1983-Aug-01
Included in the Prior Art Database: 2005-Feb-07
Document File: 2 page(s) / 54K

Publishing Venue

IBM

Related People

Jaerisch, W: AUTHOR [+3]

Abstract

Diffraction effects produced by photolithographic mask patterns in the micron range are suppressed at the location of the limiting aperture in the imaging system with the help of a stop, whose geometry is especially adapted to the optical path of the imaging rays. In the photolithographic printer of Fig. 1, a mask 1 is imaged on to wafer 6 by a catadioptric system along a path comprising a plane mirror in mirror block 2, a concave main mirror 3, an auxiliary mirror 4, and a roof mirror 5 in mirror block 2. To transfer the entire mask, a banana-shaped light band (marked by dashed lines) is moved across mask 1. In the imaging system, auxiliary mirror 4 acts as the limiting aperture.

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Photolithographic Printer With High Resolution

Diffraction effects produced by photolithographic mask patterns in the micron range are suppressed at the location of the limiting aperture in the imaging system with the help of a stop, whose geometry is especially adapted to the optical path of the imaging rays. In the photolithographic printer of Fig. 1, a mask 1 is imaged on to wafer 6 by a catadioptric system along a path comprising a plane mirror in mirror block 2, a concave main mirror 3, an auxiliary mirror 4, and a roof mirror 5 in mirror block 2. To transfer the entire mask, a banana-shaped light band (marked by dashed lines) is moved across mask 1. In the imaging system, auxiliary mirror 4 acts as the limiting aperture. If the mask contains a grating-like, horizontally oriented pattern with grating constants of less than 5 microns, the diffraction orders generated by this grating are outside the normal optical path (hatched areas 7a, 7b on main mirror 3) and pass beyond auxiliary mirror 4 to roof mirror 5, generating disturbing lines 8a, 8b on wafer 6. For suppressing these disturbing lines, a stop 9 is placed on auxiliary mirror 4. The shape of stop 9 must be such that no regular light, passing from mirror 3 to roof mirror 5, is blocked. In the optical system described, this is achieved by the stop, illustrated in Fig. 2, which has two lobes that affect only the unwanted diffracted light. The stop is preferably made of plastic and snapped on to auxiliary...