AVS 49th International Symposium
    Plasma Science Monday Sessions
       Session PS-MoM

Paper PS-MoM9
ICP Etching of Poly-crystalline Si-Ge as a Gate Material

Monday, November 4, 2002, 11:00 am, Room C-105

Session: Conductor Etch I
Presenter: W.J. Yoo, National University of Singapore
Authors: K.M. Tan, National University of Singapore
W.J. Yoo, National University of Singapore
W.K. Choi, National University of Singapore
Y.H. Wu, National University of Singapore
J.H. Chen, National University of Singapore
D. Chan, National University of Singapore
Correspondent: Click to Email
In recently years, silicon germanium (Si@sub 1-x@Ge@sub x@) is receiving significant attention as a candidate gate material to replace polycrystalline silicon, since Si-Ge can have advantages over poly-Si in achieving small threshold voltage and high trans-conductance required in sub 100 nm CMOS devices. In this work, we wish to demonstrate etching properties of the Si@sub 1-x@Ge@sub x@ films using an inductively coupled plasma. The polycrystalline Si@sub 1-x@Ge@sub x@ films were deposited by sputtering at 250°C and annealed at 900°C subsequently. The amount of Ge in the Si@sub 1-x@Ge@sub x@ films varied from 10% to 60% by changing the sputtering target. According to preliminary results obtained using ICP of CF@sub 4@+H@sub 2@, the etching rates were strongly dependent on the amount of Ge in the Si@sub 1-x@Ge@sub x@ films. The maximum etching rate was obtained at the chamber pressure of 20mTorr: 2.2 µ/min at 60% Ge and of 0.9 µ/min at 10% Ge when an inductive RF power of 1000W was applied. The etching rates were increased almost linearly as a function of %Ge. We were able to obtain anisotropic etching profiles over the entire experimental range of %Ge, despite that photoresist profiles prior to the ICP etching were not anisotropic. To control critical dimension of gate structures precisely and to obtain high selectivity with respect to thin oxide under-layer, we propose etching mechanisms of Si@sub 1-x@Ge@sub x@ gates in ICP using Cl@sub 2@, HBr, and O@sub 2@, and also reveal their sidewall passivation properties.