Deposition and characterization of polysilicon films deposited by rapid thermal processing
- North Carolina State Univ., Raleigh, NC (United States)
Low-pressure chemical vapor deposition (LPCVD) of polycrystalline silicon in a cold-wall, lamp-heated, rapid-thermal processor was investigated. Blanket polysilicon films were obtained by the pyrolysis of a 10% silane-argon gas mixture onto (100) Si wafers which were capped with a thermal SiO{sub 2} layer. The depositions were performed at a total pressure ranging from 1 to 5 Torr and in a temperature range from 575 to 850{degrees}C. It was found that the deposition of films was controlled by a surface limited reaction at temperatures below {approximately}780{degrees}C, and an activation energy of 39{+-}2 kcal/mol was measured for this reaction. Above 780{degrees}C, a decrease in activation energy was observed. To meet the throughput requirement of single wafer processing, deposition temperatures higher than 700{degrees}C are needed. In this temperature range, deposition rates exceed 1000 {angstrom}/min as compared to 20-300 {angstrom}/min in conventional LPCVD furnaces. The structural characteristics of the films were assessed by ultraviolet surface reflectance, Raman spectroscopy, and transmission electron microscopy. The transition temperature from amorphous silicon to polycrystalline silicon occurs at {approximately}600{degrees}C. Processing windows, which result in smooth films with a root-mean-square roughness of less than 100 {angstrom}, are defined. Polysilicon films ({approximately}2500 {angstrom} in thickness) have a columnarlike grain structure, and the grains span distances as little as {approximately}100 {angstrom} near the SiO{sub 2} interface to {ge}1000 {angstrom} as they approach the upper surface. A correlation between average projected grain size and surface roughness is demonstrated. Oxygen levels were derived from secondary ion mass and Auger electron spectroscopic data.
- OSTI ID:
- 68542
- Journal Information:
- Journal of Vacuum Science and Technology. B, Microelectronics Processing and Phenomena, Journal Name: Journal of Vacuum Science and Technology. B, Microelectronics Processing and Phenomena Journal Issue: 3 Vol. 10; ISSN 0734-211X; ISSN JVTBD9
- Country of Publication:
- United States
- Language:
- English
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