EFFECTS OF TARGET POLYCRYSTALLINE STRUCTURE AND SURFACE GAS COVERAGE ON MAGNETRON IV CHARACTERISTICS

The effects of Al target surface grain structure and surface gas cover age on sputtering magnetron I-V characteristics have been investigated to reveal the net effect of variations in the ion-induced electron em ission yield (IIEEY) on I-V characteristics. One (110) single-crystal and three polycrystalline Al-1 wt % Cu targets with the similar (110) crystallographic orientations and grain sizes of 0.25, 0.95, and 5.5 m m were studied. The partial pressures were monitored before, during, a nd after sputtering. The direct IIEEY was measured under 600-900 eV Ar + and He+ beam bombardment as a function of grain size and gas coverag e at specimen temperatures of 19 and 74-degrees-C. The IIEEY measureme nts demonstrated that both the surface grain structure and the gas cov erage affect the electron emission. The direct IIEEY was highest in th e small grain size and lowest in the large grain size specimens. An in crease in specimen temperature raised the emission yield due to increa sed chemisorption of residual gas species. In contrast magnetron I-V c haracteristics suggested the highest IIEEY for medium grain size targe t. This difference is explained by the combined effect of residual gas adsorption and plasma sheath distortion around surface relief which r esults in IIEEY increase.