Etching Characteristics of n+ Poly-Si and Al Employing a Magnetron Plasma

Phosphorous doped Poly-Si and Al etching characteristics in and outside a magnetron plasma have been investigated. Although the ion accelerating voltage is very low in a magnetron plasma, both materials with resist mask are etched anisotropically owing to the side wall Protection film which arises from resist sputtered by intense ion bombardments. Outside the plasma, though, some undercutting occurs due to poor protection film caused by an insufficient amount of ions, despite the higher ion energy. Thus, anisotropic etching of the whole wafer is achieved by scanning the magnetron plasma. Magnetic field dependencies for Al and n+ Poly-Si etch rates reveal that Al etch rate due to plasma scanning is not enhanced by the magnetic field, in contrast to the case for n+ Poly-Si.