Tungsten silicide/ tungsten polycide anisotropic dry etch process

A method of forming a self-aligned butted contact, comprising:

• arranging a layer of silicide over a layer of polysilicon;
• arranging a layer of insulator over the layer of silicide;
• etching the insulator layer in a reactive ion etch process using a gas mixture formed from CHF.sub.3 and C.sub.2 F.sub.6 ;
• etching the silicide layer in a reactive ion etch process using a gas mixture formed from Cl.sub.2 and C.sub.2 F.sub.6, the proportions of Cl.sub.2 and C.sub.2 F.sub.6 being chosen to produce a tapered sidewall profile;
• etching the polysilicon layer in a reactive ion etch process using a gas mixture formed from Cl.sub.2 and C.sub.2 F.sub.6 ;
• and
• arranging a layer of metal over the tapered sidewall.

A method of forming an opening having a physical dimension smaller than a limit of a photolithographic process in a structure which includes a layer of insulator arranged over a layer of silicide, comprising:

• defining a feature in the structure having a physical dimension equal to the limit of the photographic process;
• etching the insulator layer on a sidewall of the defined feature in a reactive ion etch process using a gas mixture formed from CHF.sub.3 and C.sub.2 F.sub.6 ;
• and
• etching the silicide layer on the sidewall in a reactive ion etch process using a gas mixture formed from Cl.sub.2, C.sub.2 F.sub.6, and O.sub.2.