LOW DIELECTRIC-CONSTANT, FLUORINE-DOPED SIO2 FOR INTERMETAL DIELECTRIC

Shrinking device geometry has produced a need for lower dielectric con stant materials for intermetal dielectric to reduce circuit RC time co nstants and intertrace ''cross-talk'' capacitance and reduce power con sumption at high frequency. One such material is F-doped SiO2. This st udy utilized an electron cyclotron resonance high-density oxygen plasm a source to produce SiO2 from a mixture of SiH4 and SiF4, O-2, and Ar. The total silicon gas flow was held constant and the ratio of SiH4 to SiF4 was varied from 0% to 100%. The fluorine content was measured us ing nuclear resonance analysis (NRA) with the reaction F-19(p,alpha ga mma)O-16. A comparison of the NRA data and the ratio of the Fourier tr ansform infrared Si-F absorbance near 934 cm(-1) to the Si-O peak near 1080 cm(-1) gives a proportionality constant of 144. The refractive i ndex and dielectric constant were determined as a function of fluorine content. The dielectric constant decreased linearly from 4.0 at zero F to 3.55 at 10.5 at. % F and the refractive index decreased from 1.47 4 to 1.417, Film stress, thermal stability, moisture absorption, and e lectrical breakdown were also measured. Film stress decreased from 150 to 70 MPa compressive as the F content increased. (C) 1996 American V acuum Society.