Experimental study of the process dependence of Mo, Cr, Ti, and W silicon Schottky diodes and contact resistance

Abstract

This paper reports on the process dependence and electrical characterization of Schottky diodes and ohmic contacts fabricated on p- and n-type silicon wafers. Four metals are systematically studied using identical test structures and characterization methods: Mo, Ti, W, and Cr. The choice of these metals is motivated by their midgap barriers and compatibility with an integrated circuit technology. For these, a thorough investigation of the variation in Schottky-barrier height and contact resistance is carried out for the following process parameters: 1) predeposition wafer preparation, 2) deposition method (sputtering and e-beam evaporation), 3) deposition temperature for the sputtered samples, and 4) annealing. It is found that RF etching previous to metal deposition increases the contact resistance and the barrier height for diodes on p-type silicon. This is of great importance, since RF etching is a very common in situ cleaning process in microelectronic and microelectromechanical systems technologies. Annealing can be used to restore the values of barrier height and contact resistance on wafers exposed to the RF etching.