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ISSN Online: 2377-424X

ISBN Print: 1-56032-797-9

International Heat Transfer Conference 11
August, 23-28, 1998, Kyongju, Korea

TRANSPORT AND DEPOSITION IN MOCVD FOR THIN FILM FABRICATION OF HIGH TEMPERATURE SUPERCONDUCTORS

Get access (open in a dialog) DOI: 10.1615/IHTC11.170
pages 99-104

摘要

Metalorganic chemical vapor deposition (MOCVD) reactors for semiconductor growth are typically operated in the transport limited regime where the deposition shows a depletion (decreasing downstream) profile. In superconducting thin film growth by MOCVD the presence of very heavy reactant precursors can result in large thermal diffusion transport which can significantly change the deposition profile. The complex interactions of thermal diffusion, ordinary (multicomponent) concentration gradient diffusion, convection, and surface chemistry are examined in a horizontal channel reactor model. Three trace species and a reacting carrier gas enter the channel as a uniform mixture; reactions occur on a portion of the lower surface (the hot susceptor). Thermal diffusion causes the heavy reactants to move from regions of high to low temperature resulting in separation of the species whereas ordinary (multicomponent) concentration gradient diffusion tends to eliminate concentration gradients and hence opposes the effects of thermal diffusion. Results include 2D fields of temperature, species mole fraction, and convective and diffusive mass fluxes. Transverse profiles of mass fluxes due to convection, thermal diffusion, and concentration gradient diffusion, and the deposition rate on the lower heated surface are presented.

Over a typical wafer dimension (7.5 cm) it is shown that uniform deposition in horizontal channel reactors is possible and in some cases even increases downstream; this promising result is in contrast to the usual depletion profile. For small surface reaction rates (reaction limited case) uniform deposition is obtained but the deposition rate is small and therefore impractical. Decreasing the flow rate is shown to yield significant depletion; increasing thermal diffusion in this case should lead to more uniform deposition. Uniform superconducting thin films can be fabricated with MOCVD using combinations of flow rate, surface chemistry, and thermal and concentration gradient diffusion.