Etching plasma generator diffusor and cap

摘要

A plasma generator includes a cap (20) having a sintered porous aluminium cuttings diffusor disc (28) spaced from the underside of a horizontal apertured top of the cap to prevent arcing therebetween and formation of a plasma plume affecting the wafer being etched. A plasma zone of reactive gases is formed between the cap and the wafer by rf energy. Process gases are conducted through cap top apertures (26) to the zone and the resultant plasma etches the semiconductor wafer spaced in parallelism from the cap top. Arcing between the metal diffusor and the metal cap is prevented by a ledge (27) on the cap interior periphery forming a gap between the bottom surface of the cap top and top surface of the diffusor. Etching or sputtering of the cap is also prevented by increasing the surface area of the apertures in the cap top to prevent ions from gaining a level of kinetic energy greater than the sputter threshold energy. This is done by increasing the number, changing the pattern and increasing the diameter of the apertures in the cap top as well as the thickness of the cap top, the latter increasing the height of the apertures. In the perferred embodiment, a central portion of the apertured cap is indented so as to provide for uniform etching across the width of the juxtaposed wafer by lessening the power density at a central location of the wafer.