| AVS 55th International Symposium & Exhibition | |
| Plasma Science and Technology | Thursday Sessions |
| Session PS2-ThM |
| Session: | Plasma Modeling |
| Presenter: | G. Kokkoris, NCSR Demokritos, Institute of Microelectronics, Greece |
| Authors: | G. Kokkoris, NCSR Demokritos, Institute of Microelectronics, Greece E. Gogolides, NCSR Demokritos, Institute of Microelectronics, Greece A. Goodyear, Oxford Instruments Plasma Technology, UK M. Cooke, Oxford Instruments Plasma Technology, UK |
| Correspondent: | Click to Email |
C4F8 plasma has been used for dielectric etching in microelectronics and, in combination with SF6 plasma, for deep Si etching during the Bosch process in the area of micro-electro-mechanical systems fabrication. C4F8 is also met in plasma enhanced chemical vapor deposition of fluorocarbon (fc) films. Several models for C4F8 plasmas have been reported,1 while there is a lack of models for SF6 plasmas2 in low pressure conditions. None of the models has focused on the interaction of the bulk phase with the reactor surfaces. The importance of the interaction increases as the constraints for manufacturing become stricter; it can affect the reproducibility of the process.3 In this work, a 0D or global type model for C4F8 and SF6 plasmas is formulated and is combined with a surface reaction model. The combined model, not only takes into account the effect of the surface reactions on the species densities in the bulk, but also allows the calculation of derived outputs which extend the potential experimental measurements for the validation of global models. In particular, it allows the calculation of a) the pressure change after the ignition of the discharge which links to the degree of dissociation of the parent gas, b) the effective sticking coefficients of the species which signify the net consumption of the species on the reactor surfaces and are the values measured in the experiments, and c) the deposition rate and the ratio of F/C of the fc film (C4F8 case), which can affect e.g. the SiO2 etching selectivity over Si and the dielectric constant of the film. The results of the combined model compare well with measurements of pressure change and densities of F atoms, CFx radicals, and ion flux versus power and pressure in an inductively coupled plasma reactor. For C4F8, the parent gas is vastly dissociated, CF4 dominates after 1000 W, and production of CF3 at the reactor walls is predicted. For SF6, the loading phenomenon during Si etching is predicted.
1 G. I. Font, W. L. Morgan, and G. Mennenga, J. Appl. Phys. 91, 3530-3538 (2002).
2 C. Riccardi, R. Barni, F. De Colle, and M. Fontanesi, IEEE Trans. Plasma Sci. 28, 278-287 (2000).
3 G. Cunge, B. Pelissier, O. Joubert, R. Ramos, and C. Maurice, Plasma Sources Sci. Technol. 14, 599-609 (2005).