Graphoepitaxy

摘要

Graphoepitaxy of silicon films, 0.5 micron thick, has been achieved on amorphous fused silica substrates by laser crystallization of amorphous silicon deposited over surface-relief gratings etched into the substrates by reactive-ion etching. The gratings had a square-wave cross section with a 3.8 micron spatial period, a 100-mm depth, and corner radii of about 5 nm. The <100> directions in the silicon were parallel to the grating to within + or - 15 deg, and perpendicular to the substrate plane to within + or - 1.5 deg. A simple model for the graphoepitaxy process is presented. Sheet resistivity of phosphorus-doped graphoepitaxial silicon was 2.5 times larger than that of bulk silicon of the same doping. A technique is described for exposing patterns of spatial period p/n using near-field diffraction from masks of spatial period p. The technique, called 'spatial-period-division,' can be used with visible, UV or X-ray radiation. With soft X-rays, it is possible to produce gratings of much finer spatial period than can be achieved by current laser holographic methods. The feasibility of the technique was demonstrated at the 4.5-nm carbon K X-ray wavelength by 'doubling' a 196.8-nm-period grating-pattern X-ray mask to produce a 98.4-nm-period pattern in polymethyl methacrylate (PMMA). Exposure of higher spatial-frequency-multiples appears feasible. A new technique for fabricating high-contrast X-ray masks with precisely controlled linewidths is described. The technique is based on the deposition at an oblique angle ('shadowing') of X-ray absorber material onto relief structures of triangular or square cross section in a polyimide plastic membrane. (Author)