The influence of Si content on the work function of W_1-xSi _x (x ≤ 14 atom %) gate electrodes

W1-x Six (W0.90 Si0.10 and W0.86 Si0.14) films are deposited on SiO2 /Si substrates by cosputtering from W and Si targets to form metal-oxide- semiconductor capacitors. After deposition, the samples are subjected to a thermal anneal at 700°C in flowing N2 ambient. Only body-centered-cubic W and/or Β-W are present in the W1-x Six films and no tungsten silicide can be found. However, the lattice constant of W is changed by adding Si and annealing treatment. Work functions of as-deposited W0.90 Si0.10 and W0.86 Si0.14 are 4.57 and 4.47 eV, respectively. After annealing at 700°C, the work functions of W0.90 Si0.10 and W0.86 Si0.14 become 4.52 and 4.38 eV, respectively. The connection between the work function and material characteristics of W1-x Six is discussed.