Radio frequency magnetron sputtering of radio frequency biased quartz on a scanning pallet

Abstract

The microstructure and step coverage of silicon dioxide was studied with respect to its use as a planarization layer. The bonded 37.75×12 cm SiO2 target and the 31×31 cm pallet were independently driven by two rf amplifiers using a common exciter. A sliding rf contact was made to the pallet. Target power was fixed at 2.5 kW while rf induced dc offset voltage at the pallet was varied between 0 and 120 V negative on different runs. During each scan the dc offset voltage at the pallet was kept constant, and hence, the rf power to the pallet was increased when it came in front of the denser magnetron target plasma. The average film growth rate was 800 Å/min. The argon pressure in the system was varied between 5.3×10−1 to 2 Pa. It was observed that ion bombardment during film growth, when bias is used, eliminates the columnar morphology and nodular growth and results in SiO2 films that approach the quality of those grown thermally. Such films provide good step coverage for planarization.