RESISTIVITY OF LPCVD POLYCRYSTALLINE-SILICON FILMS

The resistivity of low pressure polysilicon films doped with phosphorus, primarily from a POCl3 source, has been investigated and compared with that of higher temperature, atmospheric pressure polysilicon films. The resistivity of the low pressure films is markedly higher than that of the atmospheric pressure films at moderate doping levels but approaches that of the atmospheric pressure films at higher doping levels. The behavior is consistent with the higher number of traps expected in the low pressure films because of their lower deposition temperature. At high doping levels, the resistivity of the two types of polysilicon is virtually identical and appears to be limited by the solid solubility of phosphorus in silicon, indicating a fundamental limitation on the sheet resistance which can be obtained in polysilicon films used in integrated-circuit applications. The mobility in these heavily doped films is about half that in single-crystal silicon at similar high dopant concentrations. © 1979, The Electrochemical Society, Inc. All rights reserved.