SHADOW PROJECTING MASK FOR ION IMPLANTATION AND LITHOGRAPHY BY ION BEAM RADIATION

摘要

The mask is made using a silicon wafer(b), which is coated with a thin, p+ doped Si Layer(a). Wafer(b) contains troughs so it forms a grid of ribs below layer(a), which contains through holes(c) extending into the troughs. The bores of holes(c) and the surface of layer(a) are covered with an electrically-and thermally- conducting material(I), which resists attack by the ions, and has a thickness which prevents the ions from entering the silicon(a,b). Material (I) does not cause any deformation of the mask due to temp. changes or internal stress. Material (I) absorbs ions, and is esp. tungsten or tantalum; but a combination of materials which absorb or resist ions may be used. A diffusion barrier of Si3N4 may be located between material (I) and layer(a). Extremely small semiconductor devices can be made using masks which are dimensionally stable and which do not contaminate semiconductors being treated by ions.