Laserhyphen;assisted chemical vapor deposition of Si: Lowhyphen;temperature (600thinsp;deg;C) growth of epitaxial and polycrystalline layers

摘要

Pulsed KrF laser irradiation (248hyphen;nm or 5hyphen;eV photons)duringthe chemical vapor deposition of Si from SiH4has been used to periodically melt and rapidly resolidify thin layers of continuously deposited material. From onehyphen;dimensional heathyphen;flow calculations, the increase in the average film growth temperature for the conditions used in these experiments was less than 1deg;thinsp;C, the melt depth ranged from sim;5 to 40 nm, and the resolidification velocity was 2 to 3 msminus;1. By proper choice of laser energy densityE, pulse repetition ratef, and film deposition rateR, the melt depth was adjusted to correspond to a value slightly larger than the film thickness deposited between pulses. Using this procedure, we have grown polycrystalline Si films on SiO2and Si single crystals on (100)Si substrates at average growth temperaturesTsbetween 535 and 650thinsp;deg;C. The polycrystalline films had average grain sizes of 1 to 2 mgr;m with a (111) preferred orientation. Films grown without laser irradiation, but otherwise under the same conditions, were amorphous atTs580thinsp;deg;C and finehyphen;grained polycrystalline at higher temperatures. The roomhyphen;temperature conductivity of irradiated Inhyphen;doped polycrystalline films grown atTs=565thinsp;deg;C was sim;5 orders of magnitude higher than the conductivity of unirradiated films. Irradiated singlehyphen;crystal films doped withBexhibited roomhyphen;temperature hole mobilities which were near the maximum theoretical bulk values for the corresponding carrier concentrations (sim;1018cmminus;3).