Plasma etching of Al is a recently development process of patterqing A1 layers in microand submicrodimensions (SCHAIBLE, SCHWARTZ; SCHAIBLE et al.; TILLER). The A1 etching process is successful only in a planar reactor (VOSSBN) requiring a direct plasma substrate interaction, that means an interaction of the surface with ions of sufficient energy, respectively. The influence of ions can be attributed to reaction steps concerned with the formation of volatile AlCl, as one reaction product or with the necessity to desorb nonvolatile reaction products adsorbed on the A1 surface. Such products are glow polymers and further possible Al compounds. The deposition of glow polymers in CCl, , discharges is visible on nonetched layers and on nonetchable substrate materials. The C/Cl ratio, analyzed by chemical methods and Rutherford back scattering, attains values between 3 and 6 dependeing on discharge conditions.
The starting conditions of A1 etching will be complicated by the etching of the Al,O, layer concerned with another etching mechanism. Therefore other plasma starting conditions are required.
The etching process was investigated on the r. f. electrode of a planar reactor (diameter of the electrode 8 cm, electrode distance 4 cm, pressure 1-50 Pa, power density A redeposition of sputtered target material must be expected besides deposition of reactions products on the A1 layer. Plasma etching of Al is achieved in a pressure range between 1 and 50 Pa. The redeposition of layer material on the substrate proceeds with increasing pressure.