Influence of Laser Fluence on Resistance Characteristics of Cobalt Ohmic Contacts Fabricated on Silicon Surface by Laser-Induced Diffusion

Abstract

In this work, the influence of laser fluence on the resistance characteristics of cobalt Ohmic contacts produced on n-type silicon using laser-induced diffusion technique was introduced. A Q-switched Nd:YAG laser provided a quick, low-heat way to create a conductive CoSi₂ layer. The results show a direct link between the number of laser pulses and the contact's electrical performance with an optimum value of laser fluence that produces the lowest resistance. Initially, as the number of pulses increased, the sheet resistance dropped and conductivity improved. This is because the laser helped dopant atoms diffuse and become active, creating more free charge carriers. However, using too many pulses beyond a certain point caused the electrical properties to worsen, with the sheet resistance rising again. This degradation is due to the formation of crystal defects, which act as obstacles that slow down charge carriers.