AVS 58th Annual International Symposium and Exhibition
    Plasma Science and Technology Division Friday Sessions
       Session PS-FrM

Paper PS-FrM7
Simulations of SF6 Plasma Etching in the GEC Reference Cell

Friday, November 4, 2011, 10:20 am, Room 201

Session: Plasma Modeling
Presenter: Sergio Lopez-Lopez, Quantemol - University College London, UK
Authors: S. Lopez-Lopez, Quantemol - University College London, UK
J.J. Munro, Quantemol Ltd., UK
D. Brown, Quantemol Ltd., UK
J. Tennyson, University College London, UK
Correspondent: Click to Email
Electrically driven plasmas containing halogens are very used in different material modification and surface cleaning processes. Sulfur Hexafluoride (SF6) is used industry-wide in a range of processes for the dry etching of silicon or silicon dioxide for microelectronic feature definition, such as the Bosch process. However, the performance and efficiency of different processes and machines can vary widely, and the use of simulations can give us significant insight into the optimization problem and provide a low cost means for further development. That is especially relevant in the case of SF6, given its environmental impact, with a Greenhouse Warming Potential that is 22,000 times that of CO2. It is therefore vital to use SF6 sparingly and efficiently in every process, and simulation can help to find ways of remediating harmful waste gases and optimize the process for typical processing goals (e.g. etch rate, uniformity) as well as improving SF6 consumption efficiency and other environmental measures.

A key aspect of the plasma processes here considered is that some type of work is done at the plasma / surface boundary layer, and realistic simulations must therefore incorporate the surface material and the etch product chemistry. This increases drastically the complexity of the problem but is the only way to represent all of the appropriate physics. Radical species from the surface entering the gas phase will take part in the phase and surface reactions that are associated with the parent gas, including negative ion formation and electron dissociation among others.

Here we present 2D simulations of an inductively driven SF6 silicon etch process in the GEC Reference Cell [1], building upon previous calculations of SF6 plasma chemistries using Quantemol-P [2]. Etch rate, pressure and power trends along with chamber wide contour plots of gas-phase species concentrations and fundamental plasma properties are considered. We have found a good agreement with experimental results [3], which validates the underlying model and points to the important role of simulation-assisted plasma process development and optimization.

REFERENCES

[1] P. J. Hargis et al, Rev. Sci. Instrum. 65, 140 (1994).

[2] J. J. Munro and J. Tennyson, J. Vac. Sci. Technol. A 26, 865 (2008).

[3] G. A. Hebner, I. G. Abraham, J. R. Woodworth, “Characterization of SF6/Argon Plasmas for Microelectronics Applications”, Sandia Report, Sand2002-0340 Unlimited Release, March 2002.