Rapid thermal low-pressure metalorganic chemical vapour deposition of local diffused W(Zn) contacts
Selective deposition of W(Zn) metallization, for formation of diffused ohmic contacts onto InP-based material, was realized by means of rapid thermal, low-pressure metalorganic chemical vapour deposition (RT-LPMOCVD). The W(Zn) layers were deposited using a reactive gas mixture that contained diethylzinc (DEZn), WF6, H2 and Ar, at temperatures of 450 to 550 degrees C and pressures in the of 2-3 Torr. Uniform and continuous layers of W(Zn), 30 to 120 nm thick, were obtained. These layers contained Zn at concentrations higher than 1*1018 cm-3, which was subsequently in-diffused into the underlying semiconductor layers to form highly doped semiconductor layers as thick as 0.2 mu m. As a result, the specific contact resistance of the W(Zn)/In0.53Ga0.47As contact was reduced to a minimum value of 5*10-6 Omega cm2. The W(Zn) films were found to be mechanically stable with a small compressive stress of 5*108 dyn cm-2, and were dry etched at rates of up to 90 nm min-1.