AVS 49th International Symposium
    Electronic Materials and Devices Monday Sessions
       Session EL+SC+MI-MoA

Invited Paper EL+SC+MI-MoA5
Contact Metallurgy for the Antimonide Based Compound Semiconductors

Monday, November 4, 2002, 3:20 pm, Room C-107

Session: Metal-Semiconductor Interfaces
Presenter: S.E. Mohney, Penn State University
Authors: S.E. Mohney, Penn State University
W.E. Liu, Penn State University
H.S. Wang, Penn State University
J.A. Robinson, Penn State University
Correspondent: Click to Email
Antimonide based compound semiconductors are promising candidates for both high frequency, low power electronic devices and optoelectronic devices, and the performance of electrical contacts to these semiconductors is critical for some of the devices currently under development, particularly the electronic devices. Control of the interfacial reactions between the contact metals and the semiconductors is necessary during device processing and packaging since interfacial reactions between the metals and semiconductors occur at very low temperatures. Therefore, we have examined the condensed phase equilibria in the metal-III-Sb systems to guide our selection of shallow, thermally stable contact metallizations. We have performed thermodynamic calculations to estimate ternary phase diagrams in the transition metal-Ga-Sb, transition metal-In-Sb and selected metal-Al-Sb systems. We find that W, Re, and Os are the only transition metals predicted to be in thermodynamic equilibrium with both GaSb and InSb under the conditions considered in our calculations, while W is the only transition metal predicted to be in equilibrium with AlSb. Finally, we give an example of our use of the information we have gathered for the design of a very shallow, thermally stable low resistance ohmic contact to p-type GaInSb. Since we have observed using transmission electron microscopy that Pd reacts uniformly with GaSb at low temperatures, we chose a very thin layer of Pd as the first metal in our contact. We then deposited W because of our prediction that it would be in thermodynamic equilibrium with both GaSb and InSb and that it could serve as a diffusion barrier between layers. Finally, we capped the films with Au, which was important for lowering the metal sheet resistance. A contact resistance of 3 x 10@super-7@ ohm-cm@super 2@ was measured with good stability at 250 °C for 100 h, as verified using contact resistance measurements and Auger depth profiles.