AVS 50th International Symposium
    Plasma Science and Technology Wednesday Sessions
       Session PS2-WeM

Paper PS2-WeM4
Investigation of Etching Properties of Hafnium Oxide Based High-K Materials Using Inductively Coupled Plasma

Wednesday, November 5, 2003, 9:20 am, Room 315

Session: Etching Difficult Materials
Presenter: J. Chen, National University of Singapore
Authors: J. Chen, National University of Singapore
W.J. Yoo, National University of Singapore
S.H.D. Chan, National University of Singapore
Correspondent: Click to Email
The HfO-based high dielectric constant (K) materials are being investigated as the most promising candidates to replace the conventional SiO-based dielectrics for CMOS device applications. Development of etching processes for these materials is challenging since their etch products are mostly non-volatile and therefore adversely affect device properties due to difficulties to control effective gate length and to reduce contact resistance and Si over-consumption. In this work, we investigated etching properties of HfO@sub 2@, HfO@sub x@N@sub y@, HfSi@sub x@O@sub y@, HfAl@sub x@O@sub y@ deposited by CVD and PVD, using ICP of Cl@sub 2@/HBr/CF@sub 4@/O@sub 2@. The results showed that the etch rates of the HfO-based high-K materials were only ~ 100Å/min in CF@sub 4@ plasmas but increased up to 1000Å/min in Cl@sub 2@/HBr plasmas. The etch rates increased rapidly with increasing inductive power, rf bias power, and/or the amount of Cl@sub 2@. It was interesting to find out that in Cl@sub 2@ plasmas, etch rates varied differently depending on the chemical components added to HfO. That is, etch rates increased with the addition of Si or N, but decreased with the addition of Al. The XPS analysis showed that, a significant amount of fluorides (F: 10%~16%) existed on surfaces of all the HfO-based materials after CF@sub 4@ plasma etching, whereas amounts of chloride and bromide were little (Cl: 1.0%~2.2% and Br: 0.6%~1.7%) after Cl@sub 2@/HBr plasma etching. We suggest that non-volatile etch products from the CF4 plasmas are responsible for the low etch rates, whereas more volatile etch products from Cl@sub 2@/HBr plasmas result in higher etch rates. Analyzing the etch rates and XPS results for various concentrations of O in the HfO-based materials, we also found that low-reactivity of the Hf-O bonds and low-volatility of etch by-products from HfO-based materials could be responsible for the low etch rates.