| AVS 59th Annual International Symposium and Exhibition | |
| Plasma Science and Technology | Monday Sessions |
| Session PS-MoM |
| Session: | Advanced FEOL/Gate Etching 1 |
| Presenter: | W. Zhu, University of Houston |
| Authors: | W. Zhu, University of Houston H. Shin, University of Houston S. Sridhar, University of Houston L. Liu, University of Houston V.M. Donnelly, University of Houston D.J. Economou, University of Houston C. Lenox, Texas Instruments T. Lii, Texas Instruments |
| Correspondent: | Click to Email |
The etching properties of metal nitrides (TiN, TaN) for high-k metal-gate integration were investigated in a Faraday-shielded inductively coupled plasma. The effect of operating conditions such as pressure, bias, and gas composition in HCl/He plasmas were explored for isotropic, highly selective etching of TiN over TaN. High selectivity is required for advanced device architectures incorporating metal gates integrated with high-k gate dielectrics and etch-stop layers. Etch rates were obtained separately for TiN and TaN blanket films on Si using end-point detection (by monitoring the Si 288nm emission signal) and reflectance measurements using a He-Ne laser, verified by post-etching TEM cross-sectional profiles. The etching rates were measured to be 130±20 and 60±10 nm/min for TiN and TaN, respectively, using 30% HCl/He chemistry at 70mTorr and 400W in continuous wave plasma with no bias on the substrate. The higher etching rate of TiN compared to that of TaN can be attributed to the lower binding energy of TiN and higher volatility of TiCl4 etch byproducts. The etching selectivity was 2:1 (TiN:TaN) under the condition investigated. Higher selectivity between TiN and TaN was achieved by adding trace amounts of O2 (O2 partial pressure <1x10-4Torr): for very small oxygen additions, the etching rate of TiN remained unchanged, whereas that of TaN decreased significantly. At high enough additions of O2, etching of both TiN and TaN was completely suppressed. A narrow window of selectivity was found by varying O2 partial pressure. The film surface was characterized after etching using X-ray photoelectron spectroscopy (XPS). Cl2/He plasmas were also studied and their similarities and differences with HCl/He plasmas will be discussed.
Work supported by Texas Instruments.