| AVS 55th International Symposium & Exhibition | |
| Plasma Science and Technology | Friday Sessions |
| Session PS2-FrM |
| Session: | Plasma Processing for 3-D Integration, Photonics, Optoelectronics, and Memory Devices |
| Presenter: | F. Boulard, IMN CNRS France |
| Authors: | F. Boulard, IMN CNRS France C. Cardinaud, IMN CNRS France J. Baylet, LETI-CEA, MINATEC France |
| Correspondent: | Click to Email |
CH4/H2 based dry etch chemistry is still under study for patterning of high aspect ratio trenches or holes in II-VI compound semiconductor cadmium mercury telluride (CdxHg1-xTe) used for high performance infrared detectors.1 Since energetic ions bombardment induces electrical damages,2 development of a gentle, low bias and chemistry assisted process is investigated. Plasma diagnostics and materials characterizations are developed to obtain a better description of etching fundamental mechanism. Inductively Coupled Plasma (ICP) reactor, allowing decoupling of plasma generation and substrate polarization, is used. Process parameters under study include gas mixture (using CH4, H2, N2 and Ar), bias voltage, source power and substrate holder temperature. Experiments are carried out on alloys which composition varies from x=0.23 to 1. Langmuir probe and mass spectrometry measurements are used to correlate plasma modification induced by N2 addition to the gas mixture with etched surface characteristics and etch rate. Etch product identification confirms the formation of TeH2, while direct evidence of Cd(CH3)2, as proposed in the literature3,4 is discussed. Post etch quasi in-situ X-ray photoelectron spectroscopy and spectroscopic ellipsometry suggest that etching occurs through a carbonaceous, Cd-rich and Hg-depleted layer. When the bias is significantly decreased to a value as low as 10V and the substrate holder temperature is raised, an average etch rate increase and a strong reduction of the extreme surface Cd/Hg ratio are observed, confirming an enhancement of chemically assisted elimination of Cd. The process developed offers smooth, mirror like, surface morphology and etch rate higher than 300nm.mn-1 on Cd0.23Hg0.77Te.
1A. Rogalski, Infrared Physics and Technology, 50 (2007) 240-52
2E. Elkind, J. Vac. Sci. Technol., A 10 (4), (1992), 1106-12
3R.C. Keller, M. Seelman-Eggebert, H.J. Richter; J. of Elec. Mat, 24 (9), (1995), 1155-1160
4C.R. Eddy, D. Leonhardt, V.A. Shamamian, J.R. Meyer, C.A. Hoffman, and J.E Butler, J. Elec. Mat., 28 (4), (1999), 347-54.