Effect of external magnetic field on compact inductively-coupled reactive ion etching reactor

A compact inductively-coupled plasma etching reactor with inner diameter of 38 mm without diffusion chamber (i.e., chamber diameter of plasma etching area is the same as that of plasma discharge area) has been developed. An external magnetic field, created by a solenoid current of ≥10 A that means magnetic field strength of ≥0.02 T at the center of solenoid coil, can effectively reduce losses of plasma at the chamber wall. At low RF power of around 50 W, a discharge-mode transited from capacitively- to inductively-coupled plasmas, high electron density plasma was generated and the optical emissions of fluorine increased in intensity. In summary, the external magnetic field maintains the high plasma density and the compact reactor for a processing area as small as 10 mm diameter has been demonstrated. The basic etching characteristics were evaluated in the case of a Si wafer masked with a SiO₂ film. Typical etching rate of ≥0.3 μm/min was obtained at conditions with a solenoid current of 30 A, a RF power of 500 W, a pulsed plasma discharge with duty ratio of 10z, and a chamber pressure at 0.2 Pa.