STRESS EVALUATION OF RADIO-FREQUENCY-BIASED PLASMA-ENHANCED CHEMICAL-VAPOR-DEPOSITED SILICON-NITRIDE FILMS

Stress is evaluated for silicon nitride films prepared by rf-biased pl asma-enhanced chemical vapor deposition. The total stress of the films shows a change from tensile to compressive with increasing applied rf bias during film deposition. The biaxial elastic moduli and linear th ermal expansion coefficients of the silicon nitride films are determin ed by measuring the temperature dependence of the total stress of film s deposited on two different substrate materials. Both the biaxial mod ulus and linear thermal expansion coefficient are dominantly related t o film density. The intrinsic stress of the silicon nitride films calc ulated using these values is very close to the total stress. The intri nsic tensile stress originates from spontaneous densification during f ilm growth, while the compressive stress results from incorporated ato ms that are accelerated and implanted into the films by rf-bias induce d plasma potential. (C) 1998 American Institute of Physics. [S0021-897 9(98)01207-9].