Characterization of low dielectric constant plasma enhanced chemical vapor deposition fluorinated silicon oxide films as intermetal dielectric materials

Abstract

The characteristics of fluorinated silicon oxide films prepared by plasma enhanced chemical vapor deposition are discussed. The deposition of these films was carried out in the temperature range of 80–220 °C in a conventional parallel plate plasma reactor with <±3% uniformity across 4 in. wafer by flowing 2 sccm of disilane, 100 sccm of nitrous oxide and 20 sccm of tetrafluoromethane. As the deposition temperature increased from 80 to 220 °C, the deposition rate of the films increased from 16.7 to 18.4 nm/min; meanwhile, the etch rate decreased from 2.69 to 1.48 nm/s. The refractive index was 1.46 regardless of the deposition temperature. The Fourier transform infrared spectra of the films showed a decreasing Si–O stretching wave number with an increasing full width at half maximum as the deposition temperature increased. The high frequency capacitance–voltage measurements of the metal–oxide–semiconductor (MOS) capacitors fabricated using the films showed increasing effective oxide charge density and decreasing dielectric constant with increasing deposition temperature. A deposition temperature of 180 °C resulted in films with the smallest dielectric constant of 3.75. These films showed an average breakdown strength of 9.14 MV/cm with 77.5% of the MOS capacitors having breakdown field strengths ⩾9.5 MV/cm.