ELECTRON CYCLOTRON-RESONANCE PLASMA REACTOR FOR SIO2 ETCHING - PROCESS DIAGNOSTICS, END-POINT DETECTION, AND SURFACE CHARACTERIZATION

An electron cyclotron resonance plasma reactor for low-pressure etchin g of SiO2 layers on Si is described. Under typical operating condition s of 1.1 mTorr neutral pressure, 5 seem CF4/46 seem He, and 400 W net microwave power, an average etch rate of 35-40 nm/min is obtained. Ion densities were measured by using a quadrupole mass analyzer (QMA) imm ersed in the downstream plasma; an optical multichannel analyzer was u sed for actinometric measurements of atomic F and O concentrations. Th e results are correlated with process variables and SiO2 etch rates. R eal-time end-point detection was effected by actinometry and by monito ring the concentrations of etch products using a differentially pumped QMA. H-2 addition inhibits SiO2 etching but improves SiO2/Si etch sel ectivity. For selective etching, in situ, off-line surface analysis by Auger electron spectroscopy demonstrated an increase in the surface C concentration during SiO2 etching and deposition of a fluorocarbon la yer at the end point which strongly inhibits Si etching. (C) 1995 Amer ican Vacuum Society.