STUDY OF THIN-FILM DEPOSITION PROCESSES EMPLOYING VARIABLE KINETIC-ENERGY, HIGHLY COLLIMATED NEUTRAL MOLECULAR-BEAMS

Supersonic molecular beams have been investigated as alternative sourc es for thin film deposition employing a custom designed ultrahigh vacu um reactor. Molecular beam flux produced in this reactor has been meas ured as a function of gas flow rate, gas composition, and nozzle tempe rature. An efficient method to measure kinetics of thin film depositio n has been developed that allows a large amount of kinetic data (i.e., deposition rate and incubation time) to be gathered per deposition ex periment on a single substrate. Film thickness uniformity has been mea sured under two limiting conditions, which permitted the estimation of both flux and temperature spatial variations across the substrate. Th e kinetics of epitaxial silicon thin film deposition using Si2H6 has b een examined as a function of incident beam kinetic energy (0.5-2.2 eV ) and substrate temperature (550-750 degrees C). Calculated Si incorpo ration probabilities agree favorably with reaction probabilities previ ously measured in our laboratory employing a different apparatus and a n alternative technique. The kinetics of Si1-xGex thin film growth usi ng mixtures of Si2H6 and GeH4 were also investigated as a function of substrate temperature. In this case the Ge thin film composition was m easured as a function of Ge composition of the beam. The incubation pe riod associated with polycrystalline Si deposition on SiO2 has been in vestigated as a function of substrate temperature and incident beam ki netic energy. The incubation period decreases with both increasing sub strate temperature and incident beam kinetic energy. SiC thin film dep osition on Si(100) using SiH3CH3 (E-i= 2.0 eV) has been investigated a nd the growth rate depends rather weakly on substrate temperature. Thi n film morphology has been characterized using atomic force microscopy , while film crystallinity for polycrystalline and epitaxial films has been examined using x-ray diffraction and low energy electron diffrac tion, respectively. Epitaxial Si films exhibit a strong (2X1)+(1X2) pa ttern and a root-mean-square (rms) roughness of <1 nm, while polycryst alline films show [111]; [220], and [311] reflections and a rms roughn ess of 8-25 nm, which increases with film thickness and deposition tem perature. (C) 1998 American Vacuum Society. [S0734-2101(98)06006-0].