Etch Characteristics of Cobalt Thin Films in High Density Plasma of Cl₂/O₂/Ar Gas Mixture

Inductively coupled plasma reaction ion etching (ICP-RIE) of cobalt thin films patterned with SiO 2 hard masks was performed using Cl 2 /O 2 /Ar gas mixture. The etch characteristics of cobalt films in Cl 2 /Ar gas were examined to determine the roles of Cl 2 and O 2 , respectively. The etch rates and etch profiles of cobalt films were investigated by varying the O 2 concentration in Cl 2 /O 2 /Ar gas mixture. In the optimized Cl 2 /Ar gas mixture, systematic etching of cobalt films was performed by changing the etch parameters including ICP RF power, DC-bias voltage, and process pressure. As the DC-bias voltage and process pressure was increased, the etch rate increased and the etch profile improved. Through the etching parameters variation experiment, the etching properties were investigated by adding O 2 to Cl 2 /Ar under optimized conditions. X-ray photoelectron spectroscopy and optical emission spectroscopy were used to investigate the etch mechanism in the Cl 2 /O 2 /Ar gas mixture. In addition, scanning probe microscope was used to observe roughness on the etched cobalt surface. Finally, the etching of cobalt films patterned with nanometer-scale in the optimized Cl 2 /O 2 /Ar gas mixture was successfully achieved with good etch profile. Acknowledgment This research was supported by the Ministry of Trade, Industry & Energy (MOTIE) (20019504) and Korea Semiconductor Research Consortium (KSRC) support program for the development of future semiconductor devices. This work was supported by Korea Institute for Advancement of Technology (KIAT) grant funded by the Korea Government (MOTIE) (P0008458, HRD Program for Industrial Innovation).