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 plasma-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 thermal expansion coefficients of the silicon nitride films are determined by measuring the temperature dependence of the total stress of films deposited on two different substrate materials. Both the biaxial modulus and linear thermal expansion coefficient are dominantly related to film density. The intrinsic stress of the silicon nitride films calculated using these values is very close to the total stress. The intrinsic tensile stress originates from spontaneous densification during film growth, while the compressive stress results from incorporated atoms that are accelerated and implanted into the films by rf-bias induced plasma potential. (C) 1998 American Institute of Physics. [S0021-8979(98)01207-9].