O C 5 References Cited U.S. PATENT DOCUMENTS 4,317,844 3/1982 Carlson ............................... 437/101 OTHER PUBLICATIONS J. Electrochem. Soc.: Solid State Science and Technol ogy, Oct. 1987, pp. 2541-2545, "The Effect of Low Pressure on the Structure of LPCVD Polycrystalline Silicon Films,' P. Joubert et al. Primary Examiner-Olik Chaudhuri Assistant Examiner-G. Fourson Attorney, Agent, or Firm-John T. Rehberg 57 ABSTRACT A process for the formation of material layers such as amorphous silicon is disclosed. When a precursor gas such as silane is utilized to form amorphous silicon, silicon crystals are often formed on top of the amor phous silicon layer. The crystals are created by the presence of low pressure silane in the reactor at the end of the deposition cycle. Formation of crystals is inhib ited by lowering the temperature before silane flow is terminated.