Modeling of moderate pressure H2/CH4 and Ar/H_2/CH_4 microwave plasmas used for diamond deposition

摘要

This presentation deals with some aspects of the modeling of H_2, H_2/CH_4 and Ar/H_2/CH_4 microwave plasmas used for diamond film deposition.rnThe first part of the paper deals with the kinetic modeling and the development of a collisional radiative model for moderate pressure pure H_2 plasma. The investigation of the effect of excited states on the overall dissociation and ionization kinetics performed with these models will be also presented. Then, the reduction of this model to obtain simple and accurate chemical models that may be used in transport codes and in the full self consistent modeling of H_2 discharges obtained in microwave cavity coupling devices and of the modeling of the more complex H_2/CH_4 and Ar/H_2/CH_4 plasmas will be discussed.rnThe second part deals with the two-dimensional self consistent modeling of H_2 plasmas obtained in microwave cavity coupling system. In this part the procedure used for coupling the plasma transport equations to the electromagnetic field equations will be presented. The main difficulties encountered when performing such a coupling procedure will be discussed. Some process simulation and optimization that may be performed using the self consistent model will be presented.rnThe last part of the presented work addresses the one-dimensional transport modeling of H_2/CH_4 and Ar/H_2/CH_4 plasmas used for diamond deposition. The main phenomena and processes that govern the spatial distribution of plasma temperatures and active species in thesernplasmas will be presented. The consequences resulting from the difference between the two feed gas compositions on the plasma behavior and the structures of the diamond films obtained (poly-crystalline versus nano-crystalline films) will be also discussed.rnThroughout all the presentation, the results will be analyzed to determine the main collisional processes that govern the investigated discharge. The main collisional data necessary for accurate prediction of the discharge characteristics and process simulation will be discussed. The sensitivity of the results to the value of some collision cross sections will be also presented and a general conclusion will be given on the different collisional data for which accurate measurements or theoretical prediction are still needed for the modeling of moderate pressure H_2/CH_4 and Ar/H_2/CH4discharges.