REACTIVE ION-BEAM ETCHING OF SI/SIO2 SYSTEMS USING SF6/O2 CHEMISTRY

A reactive ion beam etching (RIBE) of Si/SiO2 structures using SF6 + O2 feed gas has been investigated. A novel 13.56 MHz, capacitively coupled ion source, equipped with a three-grid extraction optics has been used for generating a broad ion beam. The etching behavior of the Si/SiO2 system is being studied extensively by appropriately changing the physically alterable parameters like O2 to O2 + SF6 ratio (0-100%), total pressure (4 × 10-4-1.2 × 10-3 mbar), RF power (40-500 W), axial magnetic field (5-22 mT), and total extraction voltage (200-400 V). An etch rate of silicon as high as 110 nm/min (over 1.1 (μm/min)/(mA/cm2)), and etching selectivity of Si/SiO2 on the order of 16 has been achieved. Our experience shows that the ion source can be used for more than 100 h without facing the problem of wear and tear. A correlation between etching results and ion current density has been established. © 1990.