AVS 53rd International Symposium
    Plasma Science and Technology Wednesday Sessions
       Session PS1-WeM

Paper PS1-WeM3
Control of Atomic Layer Degradation on Si Substrate

Wednesday, November 15, 2006, 8:40 am, Room 2009

Session: Plasma-Surface Interactions II
Presenter: Y. Nakamura, Sony Semiconductor Kyushu Corporation, Japan
Authors: T. Tatsumi, Sony Corporation, Japan
Y. Nakamura, Sony Semiconductor Kyushu Corporation, Japan
T. Harano, Sony Semiconductor Kyushu Corporation, Japan
K. Kugimiya, Sony Corporation, Japan
T. Kawase, Osaka University, Japan
S. Hamaguchi, Osaka University, Japan
S. Iseda, Sony Semiconductor Kyushu Corporation, Japan
Correspondent: Click to Email
To suppress the fluctuation of transistor properties, the degradation on Si substrate must be minimized. We quantitatively evaluated the relationship between ion energy at high energy peak of IEDF, the thickness of a C-F polymer (T@sub C-F@), and the thickness of damage (T@sub d@) formed during the etching of SiO@sub 2@ on an Si substrate. CH@sub 2@F@sub 2@/CF@sub 4@/Ar/O@sub 2@ plasma was used for experiments. The T@sub d@ were evaluated using XPS, TEM, and RBS. The changes of surface layers in the early stage of damage formation were estimated using molecular dynamics (MD) simulations. By increasing the O/CF@sub 2@ ratio in the plasma, T@sub C-F@ decreased, and T@sub d@ was a minimum under conditions where the penetration depth of ions (T@sub ion@) was equal to T@sub C-F@ (the balance point: P@sub b@). When O/CF@sub 2@ > P@sub b@, T@sub d@ increased when T@sub C-F@ decreased because the ion energy consumption by the polymer was smaller. On the other hand, when O/CF@sub 2@ was less than P@sub b@, T@sub C-F@ increased with time, and T@sub d@ increased when the rate at which the polymer was deposited was increased. We used MD simulations to evaluate the surface around the transition from SiO@sub 2@ etching to Si etching. Damage started forming just before the SiO@sub 2@ was completely removed, and when the SiO@sub 2@ was etched off, the highest T@sub d@ was observed. Then, T@sub C-F@ began to increase, and T@sub d@ slightly decreased by desorbing unstable SiC@sub x@F@sub y@ species. When T@sub C-F@ became larger than T@sub ion@, the damaged layer was buried, and changes in T@sub d@ stopped. T@sub d@ can only decrease until T@sub C-F@ reaches the ion penetration depth. We carefully adjusted T@sub ion@ to be equal to T@sub C-F@ under low ion energy conditions; T@sub d@ was reduced to below 1 nm. Thus, the precise control of ion energy and the prediction of several atomic layers on an actual etched surface will be indispensable in the fabrication of 32nm-node devices.