WHISKER GROWTH ON SPUTTERED ALSN (20-WT-PERCENT SN) FILMS

AlSn films (20 wt.% Sn) with a thickness of 20 mu m were prepared by m agnetron sputter deposition in an argon gas plasma. It has been found that the oxygen content in the argon gas during deposition strongly in fluences film properties and surface morphology. From 0.005% up to 0.0 2% oxygen the films show a uniform and fairly smooth surface character ized by a roughness (RZ) of 3-5 mu m. From 0.05 up to 0.15% oxygen num erous whiskers of different shape and dimensions appear on the film su rface. The whisker growth leads to an increase of surface roughness wi th peak values around 25 mu m. Above 0.5% oxygen no whiskers can be fo und on the film surface, but the film morphology changes from a dense structure to a loosely bonded one built up by spherolitic crystals. Th e microhardness of the films increases from 95 to 155 HV (Vickers hard ness) with increasing oxygen content. Increasing either substrate temp erature (110-160 degrees C) or film thickness (2-50 mu m) increases th e surface roughness from 2 to 25 mu m or from 2 to 65 mu m, respective ly, whereas moderately low roughness (8 mu m) can be obtained at argon gas pressures above 1 Pa.