New ultra-high-frequency plasma source for large-scale etching processes

A low temperature, uniform, high-density plasma is produced by an ultra-high-frequency (UHF) discharge using a new spokewise antenna. The plasma is uniform within ±5% over a diameter of 30 cm. The plasma density, 1 x 10¹¹cm^-3, for low electron temperatures of 1.5-2.0 eV, is almost proportional to the UHF power even at a lowUHF power. No magnetic field is needed to maintain a high-density plasma. Consequently, the plasma source isfairly simple and lightweight. The plasma source can accomplish a notch-free poly-Si etching profile with a highetching rate at a narrow space pattern of less than 0.3 μm.