AVS 52nd International Symposium
    Plasma Science and Technology Monday Sessions
       Session PS2-MoA

Paper PS2-MoA6
Atomic Scale Etching of Poly-Si in Inductively Coupled Ar and He Plasmas

Monday, October 31, 2005, 3:40 pm, Room 304

Session: Silicon Etching
Presenter: C.-K. Kim, Ajou University, Korea
Authors: J.-H. Min, Seoul National University, Korea
S.H. Moon, Seoul National University, Korea
Y.W. Kim, FOI Korea Corporation, Korea
C.B. Shin, Ajou University, Korea
C.-K. Kim, Ajou University, Korea
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For fabrication of novel Si-based devices, device structures with a high aspect ratio are increasingly required. The reactive ion etching is widely used for defining fine features, but energetic ions generated in a plasma are known to cause serious radiation damages. In a low-energy ion system, isotropic chemical reactions caused by neutrals become predominant and the deterioration of the pattern definition will occur. Therefore, a new concept of directional etching with minimum reaction energy is needed. In this work, atomic scale etching of poly-Si was performed by using a cyclic process of etchant adsorption and ion beam irradiation. This process is the same as the so-called atomic layer etching of single crystalline Si. Cl@sub 2@ was used as an etchant gas, and Ar or He ions generated in an inductively coupled plasma was used as an ion beam. The self-limiting characteristic of the etch rate with respect to the duration of ion irradiation for poly-Si etching was significantly different from that for single crystalline Si etching. That is, as the duration of the ion irradiation increased, the poly-Si etch rate was initially increased and converged to about 0.6Å/cycle and then rapidly increased, eventually showing a characteristic S curve. When He ions were used as an ion beam, the bias voltage region where the etch rates were smaller than the sputtering rates was observed, which was in contrast to the case where Ar ions were used as an ion beam. It is believed that this is because the size and mass of He ions are much smaller than those of chlorine atoms adsorbed on the poly-Si surface and therefore the chlorine atoms effectively prevent the poly-Si layer from being sputtered by the He ions.