AVS 53rd International Symposium
    Plasma Science and Technology Thursday Sessions
       Session PS1-ThA

Paper PS1-ThA2
Plasma Etching of HfO2 in High-Density Chlorine-Containing Plasmas without RF Biasing

Thursday, November 16, 2006, 2:20 pm, Room 2009

Session: Plasma Processing for High-K/III-V’s and Smart Materials
Presenter: K. Nakamura, Kyoto University, Japan
Authors: K. Nakamura, Kyoto University, Japan
K. Osari, Kyoto University, Japan
D. Hamada, Kyoto University, Japan
K. Eriguchi, Kyoto University, Japan
K. Ono, Kyoto University, Japan
Correspondent: Click to Email
As ultra large scale integrated circuit dimensions continue to be scaled down, high dielectric constant (high-k) materials such as HfO@sub 2@, ZrO@sub 2@, and Al@sub 2@O@sub 3@ are being required as gate dielectric to maintain the gate capacitance in smaller size. For the fabrication of high-k gate stacks, a better understanding of the etching characteristics and mechanisms is indispensable for high-k dielectrics. We have investigated the etching of high-k materials of HfO@sub 2@ using high-density chlorine-containing plasmas excited by electron cyclotron resonance. Experiments were performed in BCl@sub 3@/Cl@sub 2@ gas mixtures at a pressure of 5 mTorr without rf biasing. In pure BCl@sub3@ plasma, some deposition was found to occur on HfO@sub 2@ surface to inhibit etching. By adding Cl@sub 2@ to BCl@sub 3@, the deposition was suppressed to result in etching of HfO@sub 2@. The HfO@sub 2@ etch rates increased with increasing Cl@sub 2@ concentration ratio, and the maximum HfO@sub 2@ etch rate was ~100 nm/min at 60% Cl@sub 2@ addition. At the Cl@sub 2@ concentration ratio in the range 25-50%, the HfO@sub 2@ etch rate was more than 20 nm/min, while the Si etch rate remained almost zero, thus giving extremely high selectivity over Si. In addition, by adding a small amount of O@sub 2@ to BCl@sub3@/Cl@sub 2@, the HfO@sub 2@ etch rate was further enhanced. The maximum HfO@sub 2@ etch rate was ~150 nm/min at 5% O@sub 2@ addition to BCl@sub 3@/60%-Cl@sub 2@ plasma, while the Si etch rate also increased to deteriorate the selectivity over Si down to 4. These results were compared with plasma and surface diagnostics, to understand plasma-surface reaction mechanisms responsible for selective etching of HfO@sub 2@.