Process to Prove Reliability of Refractory Metal Gate MOS Devices
Original Publication Date: 1987-Dec-01
Included in the Prior Art Database: 2005-Feb-02
Because of their low resistivities, refractory metals such as tungsten (W) have been employed as materials for gate electrodes and interconnections in VLSIs with sub-micron dimensions. However, these metals have poor oxidation resistance, making device processing in high- temperature oxidizing atmospheres difficult, and limiting their applicability to MOSFET fabrication. Experiments have shown that during high-temperature annealing even in N2 or N2+10%H2, oxygen contaminant in the annealing atmosphere, and oxygen as an impurity in the W layer itself tends to diffuse through the W layer, and then accumulate at the W interface with SiO2 (the gate oxide), where it reacts with Si from the substrate to form SiO2 .