US EPA

6590276 

Journal Article 

Nonisothermality effects in a plasmochemical reactor 

Grigor'Ev, YN; Gorobchuk, AG 

1998 

27 

4 

250-258 

CCC:000075025100006 

The effect of the nonisothermality of a working medium on the etch rate and quality in a planar plasmochemical reactor was studied by means of numeric simulation. Free convection, thermal diffusion of reactive particles, and the temperature dependence of the heterogeneous etch reaction rate were considered as possible consequences of temperature nonuniformity. Convection, molecular heat conduction, and radiation were included in the heat exchange process. The temperature of the lower electrode was assumed to be preset and varied in a range typical of reactors of the given type. The etching of silicon in a carbon tetrafluoride plasma was simulated for usual working conditions in industrial reactors. The reactive particle fluxes to the sample were shown to be controlled by concentration and thermal diffusions. The latter accounts for up to 20% of the total flux and may substantially influence the etch uniformity in the presence of radial gradients. Heat transfer over the sample was equally accomplished by heat conduction and radiation. The latter considerably affects the temperature distribution in the gas. Convective heat and mass transfer over the sample surface is ignorable. If the temperatures of the sample and surrounding electrode are equal and constant, the thermal nonuniformity of the working medium does not affect the etch uniformity.