AVS 52nd International Symposium
    Plasma Science and Technology Wednesday Sessions
       Session PS-WeM

Paper PS-WeM8
ICP Etching of p-type Conducting Materials with High Work Function for CMOS Application

Wednesday, November 2, 2005, 10:40 am, Room 304

Session: Advanced Gate Stack Fabrication
Presenter: W.J. Yoo, National University of Singapore
Authors: W.S. Hwang, National University of Singapore
Y.Q. Wang, National University of Singapore
W.J. Yoo, National University of Singapore
V.N. Bliznetsov, Institute of Microelectronics, Singapore
Correspondent: Click to Email
As metal electrode / high-k dielectric gate stacks are expected to be integrated for future complementary metal oxide semiconductor (CMOS) device process, extensive research on new conducting electrodes as a replacement for poly-Si is currently underway. Many candidate materials have already been identified as potential n-type conducting materials in the work function range of 4.0-4.5 eV. However, only a few conducting materials have high work functions above 5.0 eV to replace p-type poly-Si, and thus IrO@sub 2@, Ir, Ni, and Pt which meet this requirement are receiving significant attention as candidates of p-type conducting materials. Plasma etching of these materials is one of the most challenging issues in the integration of advanced CMOS gate stacks because of their chemically inert property. In this work, the etching properties of the p-type conductors / high-k gate stacks are investigated in SF@sub 6@ / Cl@sub 2@ / O@sub 2@ using inductively coupled plasma (ICP). Gas composition and plasma parameters of pressure, source power and bias power were changed to understand the etching mechanisms. The linear dependence of etch rates on the square root of bias voltages obtained from most of the above p-type conducting films indicated the dominance of ion induced etch mechanism in both SF@sub 6@ and Cl@sub 2@ etching. The effect of byproducts generated during etching on surface properties showed two different trends, depending on which type of by-product formation is predominant: volatile or nonvolatile. This phenomenon was well explained by evaporation temperature and Gibbs free energy of formation of byproducts in SF@sub 6@ and Cl@sub 2@. X-ray photoelectron spectroscopy (XPS) also revealed that more residues remain after the Cl@sub 2@ etching than the SF@sub 6@ etching. Using the optical emission of fluorines and other halogenated compounds, we were able to control the etch endpoints from the gate stack using p-type conducting materials.