EFFECT OF METALLIZATION ON CRYSTALLINE PERFECTION AND LEVEL OF STRESS IN SEMI-INSULATING AND N-TYPE GALLIUM-ARSENIDE SINGLE-CRYSTAL WAFERS

Results obtained by x-ray diffractometry, topography, and curvature measurements made with a quadruple-crystal x-ray diffractometer used in (+,-,+) setting and as a Lang system are reported. About 0.1-mm-thick semi-insulating (SI) (Cr-compensated) and n-type wafers with dimensions ∼10×10 mm 2 or less were used. The metallizations were (i) Ge-Ni-WSi 2-Au and (ii) Ge-Au-Ni-WSi2-Au, with layer thicknesses as follows: Ge: 20 nm; Au: 5 nm; Ni: 10 nm; WSi2: 100 nm; and Au: 100 nm. Both types of metallizations were deposited on n-type crystals, whereas only the second type was used with SI wafers. Diffraction curve half-widths of the wafers without deposits were in the range 15-22 arcsec (SI) and 18-30 arcsec (n type). Radii of curvature (R) were around 6 and 3 m for SI and n-type crystals, respectively. Topographs showed low defect density. Metallization decreased the level of perfection and enhanced curvature. Diffraction curve half-widths increased up to 155 arcsec (SI) and 180 arcsec (n type). High-strain field and bandlike features were observed in topographs, indicating nonhomogeneous distribution of strain. R values decreased to 0.8 m (SI) and 0.3 m (n type). These correspond to stress values of 1.7×1010 and 4.5×1010 dyn cm-2, respectively. Anisotropy in R values was studied by changing diffracting planes. Lattice planes parallel to the metallization were also curved, but in small regions the degree of perfection was high. The five-layered metallization produced more stress in n-type crystals in comparison to the other deposit.