Implementation of tungsten metallization in multilevel interconnection technologies

The techniques of experimental design and response-surface methodology have been used to produce empirical models of the deposition and etchback of tungsten in commercially available reactors for a tungsten plug technology. Deposition was carried out in a Genus 8402 LPCVD (low-pressure chemical vapor deposition) batch reactor by the H/sub 2/ reduction of WF/sub 6/. Response-surfaces for deposition rate, sheet resistance uniformity, resistivity, and film stress were developed as a function of reactor pressure, reactor temperature, and flow rate of WF/sub 6/ at a fixed H/sub 2/ flow rate using linear-interactive models. A thin layer of TiN was used to ensure adhesion of tungsten to SiO/sub 2/. Etchback of the composite layer of W/TiN to form via plugs was performed in a Tegal 804 single-wafer system with a two-step process using mixtures of SF/sub 6/ with C/sub 2/F/sub 6/ and He with Cl/sub 2/ in step 1 and step 2, respectively. Process parameters for both steps were obtained from quadratic models of etch rate and etch uniformity.< >