REACTIVE ION ETCHING OF POLYSILICON/OXIDE USING CCl2F2 + H2 GAS MIXTURES
Original Publication Date: 1987-Dec-01
Included in the Prior Art Database: 2005-Feb-02
A highly selective, residue free and anisotropic etching process for polysilicon/silicon dioxide used in the fabrication of VLSI gate electrodes is described. When polysilicon is used for VLSI gate electrodes, etching is important in the definition of these very small structures. Technology advances now dictate the need for vertical gate profiles and selectivity between the polysilicon gate material and the thin gate oxide used. Dry etching with CCl2F2 + NH3 gas mixtures frequently leaves a polymer formation on wafer surfaces and inside the reactive ion etch (RIE) chamber. The degree of anisotropic etching of polysilicon and the selectivity over oxides is a function of the NH3 flow rate ratio variations, resulting in a narrow process window which is difficult to use in a manufacturing environment.