Method to grow thin epitaxial films at low temperature

A method of processing a substrate in a processing chamber, comprising:

• forming an epitaxial film over a semiconductor fin formed on the substrate, wherein the epitaxial film comprises a top surface having a first facet and a second facet, the first facet having exposed {111} plane and the second facet having exposed {111} plane;
• exposing the epitaxial film to a first precursor gas comprising silane (SiH4) or disilane (Si2H6) at a temperature of about 425° C. or less;
• pulsing the first precursor gas for a first period of time;
• introducing a purge gas into the processing chamber;
• exposing the epitaxial film to a second precursor gas comprising chlorinated silanes at a temperature less than about 425° C. or less;
• pulsing the second precursor gas for a second period of time;
• and
• introducing the purge gas into the processing chamber.