ANHYDROUS HF ETCH REDUCES PROCESSING STEPS FOR DRAM CAPACITORS

A new anhydrous hydrogen fluoride (AHF) vapor-phase etch process, at t he heart of a commercial single-wafer system, dramatically reduces the number of process steps for fabrication of complex three-dimensional device structures, including cylindrical capacitors for 256-Mbit and 1 -Gbit DRAMs. Controlling process temperature, HF concentration, and va por flow, the process enhances natural etch-selectivity differences of doped and undoped oxides. These natural differences stem from adsorbe d water content in oxides. The process is capable of routine doped-to- undoped oxide etch selectivities > 1000:1.