Rotary Bonded Multi-Segment Cast Silicon Targets as a Replacement for Sprayed Silicon
August 6, 2013 12:00 am
Plasma sprayed non-Al alloyed Si(:B) rotary sputtering targets suffer from strong nodule formation both in SiO2 (display industry) and SiNx:H (PV industry) reactive deposition processes using MF-AC technology. Such problems can be resolved with multi-segment, bonded cast-Si rotary targets having a much higher density (> 99.5 % of theoretical density, TD; max. 96 % of TD for sprayed targets) combined with a much better chemical purity (appr. 5N; 3N7 for sprayed equivalents). This paper presents coating results for both SiO2 and SiNx deposition using bonded, cast Si rotary targets in MF-AC sputtering processes on a vertical dynamic pilot glass coating line. The sputter stability in a real industrial coating system has also been evaluated. Finally, a detailed coating cost comparison using both cast Si and sprayed Si targets for a typical application in the display industry has been performed. The higher machine up time with cast Si targets (no need for regular nodule removal by mechanical abrasion, fewer target changes), combined with a higher power load potential and increased product yield due to less arcing and with a considerably higher amount of available Si per target (factor of 2.5-3) give rise to a 20 % lower coating cost for cast Si despite higher target costs on a mass basis.