AVS 59th Annual International Symposium and Exhibition
    Plasma Science and Technology Thursday Sessions
       Session PS-ThP

Paper PS-ThP43
Atomic Layer Etching of Ultra-thin High-k Dielectric Film for Gate Oxide in MOSFET Devices

Thursday, November 1, 2012, 6:00 pm, Room Central Hall

Session: Plasma Science and Technology Poster Session
Presenter: C.K. Kim, Sungkyunkwan University, Republic of Korea
Authors: C.K. Kim, Sungkyunkwan University, Republic of Korea
J.K. Kim, Samsung Electronics Co. Ltd., Republic of Korea
G.Y. Yeom, Sungkyunkwan University, Republic of Korea
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As the dimensions of integrated circuit devices, such as metal-oxide-semiconductor field effect transistors (MOSFETs), etc., continue to be scaled down, the thickness of gate dielectrics, such as SiO2, etc., also continues to be scaled down to nanosize. Tunneling currents through the gate dielectric, however, limit the scaling of SiO2 to approximately a few nanometers. Therefore, for further scaling down of devices, alternate gate dielectric materials with higher dielectric constants need to be used to reduce the gate leakage current while maintaining the gate dielectric capacitance with a thicker material. Considerable research attention has focused on the potential of HfO2 as a next generation gate dielectric material due to many advantages in comparison with SiO2, such as a high dielectric constant (15–25), good thermal stability, wide band gap (5.6 eV) and large band offsets (1.5 eV). However, conventional RIE of ultra-thin HfO2 film tends to cause electrical and physical damage to the surface of the devices due to use of energetic reactive ions and the difficulty in the precise etch rate (depth) control at an atomic scale. Precise etch depth control of ultra-thin HfO2 (3.5 nm) films applied as a gate oxide material was investigated by using atomic layer etching (ALET) with an energetic Ar neutral beam and BCl3 gas to minimize etch damage. A monolayer etching condition of 1.2 Å/cycle with a low surface roughness and an unchanged surface composition was observed for ultra-thin, ALET-etched HfO2 by supplying BCl3 gas and an Ar neutral beam at higher levels than the critical pressure and dose, respectively. When HfO2-nMOSFET devices were fabricated by ALET, a 70% increase in the drain current and a lower leakage current were observed compared with the device fabricated by conventional reactive ion etching, which was attributed to the decreased structural and electrical damage.