Deposition properties of silicon films formed from silane in a vertical-flow reactor

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The growth of silicon films by low pressure chemical vapor deposition in an unique vertical-flow reactor and in a conventional tube reactor is studied, with emphasis on the vertical-flow reactor. For a hydrogen-carried silane process in the vertical-flow reactor, the growth rate depends on both the partial pressure and the flow rate of silane. A growth rate expression incorporating both of these parameters is derived which accounts for a nearly linear dependence on either parameter for small values and saturation at large values. No dependence on hydrogen partial pressure is observed. An Arrhenius-type dependence of growth rate on temperature is observed for both type of reactors, with an activation energy of 1.5 eV. Thickness uniformity of the films deposited in the vertical-flow reactor is compared to that found in the conventional reactor. For high temperatures (above 650 °C) depletion effects degrade the thickness uniformity of the deposited films. Such effects are more pronounced in the conventional reactor than in the vertical-flow reactor. These effects can be attributed to the shorter gas flow path in the vertical-flow reactor. The vertical-flow reactor can be operated without a temperature gradient along the deposition chamber so that uniform film properties can be obtained over the entire load.