Substituting low-energy (<30 eV) ion bombardment for elevated temperature in silicon epitaxy

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Abstract
Normally required high substrate temperature for achieving epitaxial film growth can be replaced by low‐energy (2) ion bombardment during film deposition. For this a Si substrate wafer was immersed like a large negative Langmuir probe in a low‐pressure (5×10−4 Torr) mercury vapor plasma while receiving Si atoms sputtered from a Si wafer target. The Hg plasma was created by extracting a 4‐A discharge current at 25‐V discharge voltage from a Hg cathode spot on a liquid‐Hg pool. Electron channeling patterns proved that uniform Si spitaxial films can be obtained over the whole substrate wafer area at temperatures not exceeding 300 °C. The best epitaxial films were obtained when the substrate is bombarded (by biasing) during deposition with 23‐eV Hg ions. The electrical properties of the coatings indicated that the films were close, but not yet of device quality because of the impurities inherent in our non‐ultrahigh‐vacuum nonbakable Pyrex chamber pumped only with a 12‐l/s Hg diffusion pump.