AVS 53rd International Symposium
    Plasma Science and Technology Monday Sessions
       Session PS2-MoM

Paper PS2-MoM6
Impact of Plasma Damage on Cobalt Silicidation

Monday, November 13, 2006, 9:40 am, Room 2011

Session: Advanced Gate Fabrication
Presenter: T. Kimura, Sony Corporation, Japan
Authors: T. Kimura, Sony Corporation, Japan
K. Kugimiya, Sony Corporation, Japan
K. Fuke, Sony Corporation, Japan
T. Ohchi, Sony Corporation, Japan
T. Kataoka, Sony Corporation, Japan
T. Tatsumi, Sony Corporation, Japan
Y. Kamide, Sony Corporation, Japan
Correspondent: Click to Email
Silicides must be introduced to ULSI circuits to improve sheet and contact resistance. Generally, silicidation on the source and drain depends strongly on the surface, so controlling damage to the silicon substrate from sidewall etching is very important. We studied sidewall etching using a capacitive coupled plasma type etcher. RF power supplies with different frequencies (2 and 13.56 MHz) were used for the lower electrode. The thickness of the damage layer in the silicon surface resulting from sidewall etching was conveniently evaluated by ellipsometry. As Vpp is increasing, the thickness of the damage layer is increasing in the case of sidewall etching with CH@sub 2@F@sub 2@ gas chemistry and the thickness is decreasing in the case of etching with a RF power supply of higher frequency under conditions where the same Vpp was obtained. We calculated the ion energy distribution function. The thickness of the damage layer has a clear relationship to ion energy at the high energy peaks for both frequencies. The damage thickness also depends on gas chemistry. When we used the CF@sub 4@ plasma, the thickness of the damage layer was thinner than that induced by the CH@sub 2@F@sub 2@ plasma and did not seem to depend on RF bias power. This is presumably due to the absence of H ions, which can penetrate Si more deeply. We could successfully form conformal CoSi@sub x@ on the source and drain after sidewall etching with CF@sub 4@ gas chemistry, but we could not after etching with CH@sub 2@F@sub 2@ gas chemistry. For mass production to occur, high quality CoSi@sub x@ must be formed to create 32-nm devices and the control of ion energy distribution in the dry etching system must be improved.