GAS-PHASE TRANSPORT OF WF6 THROUGH ANNULAR NANOPIPES IN TIN DURING CHEMICAL-VAPOR-DEPOSITION OF W ON TIN TI/SIO2 STRUCTURES FOR INTEGRATED-CIRCUIT FABRICATION/

Delamination of TiN/Ti bilayers on SiO2 is a serious problem during W chemical vapor deposition (CVD) using WF6 to form vertical interconnec ts in integrated circuits. In order to obtain insight into the delamin ation mechanism, we have determined depth-distributions of W and F in sputter-deposited TiN/Ti bilayers on SiO2 as a function of WF6 exposur e time t(WF6) at 445 degrees C. Even for t(WF6)<6 s, significant conce ntrations of both W (approximate to 3.5 at. %) and F (approximate to 2 at. %) penetrate through the 106-nm-thick TiN film. W piles up at the TiN/Ti interface, while F rapidly saturates the TiN layer and accumul ates in the Ti underlayer at concentrations up to approximate to 10 at . % for t(WF6)=60 s. Cross-sectional and scanning transmission electro n microscopy analyses demonstrate that WF6 penetrates into the TiN lay er through nanometer-scale intercolumnar voids spanning the entire fil m thickness and reacts with the Ti underlayer. We propose that the hig h F concentrations in the Ti layer weakens the Ti/SiO2 interface leadi ng to adhesion failure of the TiN/Ti bilayer. (C) 1996 American Instit ute of Physics.