Imaging Proximity printing

Figure 3.36. SEMs of dry-developed images generated by the process shown in Figure 3.35 a) J.0- xm images printed with a Perkin-Elmer M500, UV-2 mode (b) 0.75-p.m images printed with a Perkin-Elmer M500, UV-2 mode and (c) 0.5- xm images proximity printed with a synchrotron X-ray source. (Reproduced with permission from reference 127. Copyright 1985 Society of...

The quality of pattern transfer differs greatly among the three modes of printing. As an example, a mask with parallel bundles of slits and spaces between slits with dimensions comparable with the slits can be considered. In this case, optical interference results in distorted images. The theoretical minimum dimension (for both space and slit) that allows resolvable interference peaks for contact or proximity printing is approximated by ... 

In proximity printing spacing the mask away from the substrate minimizes defects that result from contact, but increases the diffraction of the transmitted light which reduces the resolution. The degree of reduction in resolution and image distortion depends on the mask to substrate distance which may vary across the wafer. For proximity printing, equation (3.1) can be rewritten as... 

The shadow mask proximity printing technique projects the shadow image of the transmission mask onto a resist-coated wafer by scanning a 1-mm-diameter... 

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