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Method of Exposing Semiconductor Wafers by Electron Beam Proximity Printing

IP.com Disclosure Number: IPCOM000049725D
Original Publication Date: 1982-Jul-01
Included in the Prior Art Database: 2005-Feb-09
Document File: 3 page(s) / 33K

Publishing Venue

IBM

Related People

Bohlen, H: AUTHOR [+4]

Abstract

This article describes a method of exposing semiconductor wafers by electron beam proximity printing and in particular the problem of minimizing image distortions in proximity printing with electron or ion beams.

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Method of Exposing Semiconductor Wafers by Electron Beam Proximity Printing

This article describes a method of exposing semiconductor wafers by electron beam proximity printing and in particular the problem of minimizing image distortions in proximity printing with electron or ion beams.

An electron beam shadow-projects a mask image on to a wafer. To ensure that the wafer is homogeneously illuminated, the beam is raster scanned across the mask. In transparent areas, the pattern is printed on the wafer. The inclination of the beam can be varied to influence and improve the positioning of the image. As unwanted beam inclination leads to distortions, these must be prevented. Beam scanning is effected by two deflection yokes. The first yoke deflects the beam from the optical axis and the second deflects it back in the original direction, so that the beam is finally raster-scanned but remains parallel to itself.

This beam parallelism must meet, for example, the following two requirements:
Homogeneous mask illumination. During scanning, the scanning lines must be equidistant within a range of 7.5 (mu)m to ensure homogeneous illumination varying by not more than 3 percent. As the distance between the scanning lines is 750 (mu)m, the relative accuracy must be 1 percent.

Beam inclination with respect to mask. The mask pattern is shadow-projected on to the wafer, with the distance between mask and wafer being 5O0 (mu) m. In submicron lithography, the pattern must be positioned with an accuracy of + 0.05 (mu) m, so that the accuracy of beam inclination is (see original)

For the beam scanning motion, these two requirements must be simultaneously met.

The basic concept is that both yokes are driven by one amplifier, so that the same current I flows in both of them. Thus, assuming that both yokes are identical and without any field inhomogeneities, their field strength is also identical. Inaccuracies o...