Synthesis and characterization of LPCVD SiC films using novel precursors

Author

Mahalingam Bhaskaran, New Jersey Institute of Technology

Document Type

Dissertation

Date of Award

Fall 1-31-1997

Degree Name

Doctor of Philosophy in Electrical Engineering - (Ph.D.)

Department

Electrical and Computer Engineering

First Advisor

Roland A. Levy

Second Advisor

Roy H. Cornely

Third Advisor

Kenneth Sohn

Fourth Advisor

Durgamadhab Misra

Fifth Advisor

James M. Grow

Abstract

A unique low pressure chemical vapor deposition (LPCVD) process has been developed to synthesize amorphous and crystalline SiC films using environmentally benign chemicals. The interrelationships governing the process variables, compositions and select properties of the resulting films were established. Such films can be used to produce high quality mask membrane for x-ray lithography. These films can also be used in fabricating high power electrical devices, and hetrojunction devices in conjunction with silicon.

Amorphous SiC films were synthesized using a single precursor, ditertiarybutylsilane, at temperatures below 850°C. Compositional analysis performed on these deposits revealed that, in the deposition temperature range of 625 to 750°C, the composition of the deposits changed progressively from slightly silicon rich (55% Si) to slightly carbon rich (51%C). Above 750°C, there was a rapid increase in the carbon content from the near stoichiometric value to about 75%-C at 850°C. The stoichiometric films exhibited high stress values of 700 ± 50 MPa. Attempts to reduce the stress values resulted in films with excess carbon content of about 60%-C. From the high frequency C-V characterization, the dielectric constant for these films was estimated to be 10.1 ± 0.5. Temperature bias stressing studies revealed a trapped charge density of 0.869 X 107 CM-2 within the bulk.

Crystalline silicon carbide films were grown on silicon substrates using dichlorosilane and acetylene as precursors, in the temperature range of 950°C to 1050"C. The carbon content in the film was found to be increasing with the deposition temperature, when the flow ratio of precursors was one. The carbon composition was also found to be sharply dependent on acetylene flow, for constant deposition temperature and pressure. Stoichiometric films were achieved for dichlorosilane to acetylene flow ratio of 4:1. X-ray diffraction studies confirmed the growth of β-SiC with orientation in all the cases. The voltage-current relationship for Si-film-metal structure showed a diode behavior with an ideality factor of 4.03 in the diffusion current dominating regime.