IJM025 Characteristics of Cobalt Ohmic Contacts Fabricated on Silicon Surface by Laser-Induced Diffusion

Abstract

This study investigates the fabrication and characterization of cobalt Ohmic contacts on n-type silicon substrates using laser-induced diffusion. A Q-switched Nd:YAG laser was used to provide a low thermal budget method for forming a conductive CoSi₂ layer. Results demonstrate a critical relationship between the number of laser pulses and the electrical properties of the contact. A significant decrease was observed in sheet resistance and a corresponding increase in electrical conductivity up to an optimal number of pulses. This is attributed to the enhanced diffusion and activation of dopant atoms, leading to a high concentration of free charge carriers. However, excessive laser pulses beyond this optimal range result in a degradation of electrical properties, as evidenced by a rise in sheet resistance. This is due to the formation of crystallographic defects that act as scattering centers, thereby reducing carrier mobility. The findings underscore the importance of precise process control to achieve high-performance Ohmic contacts while avoiding thermal damage.