Carbon-nitride and diamond-like-carbon films were deposited by electron cyclotron resonance chemical vapor deposition (ECR-CVD) using carbon precursors in either a nitrogenor an argon-high-density plasma. The carbon precursors were tetrachloroethylene (C 2C14), ethylene (C2H4) and neopentane (C5H12). Electron spectroscopy for chemical analysis (ESCA) and Fourier transform infrared (FTIR) spectroscopy showed three distinct chemical compositions: chlorine-doped carbon nitride (CNx:Cl), hydrogenated carbon nitride (CNx:H) and hydrogenated amorphous carbon (a-C:H). FTIR spectroscopy revealed a fourth composition: chlorine-doped amorphous carbon (a-C:Cl). ESCA analysis of the a-C:Cl film was not performed. Microstructures ranging from amorphous to microcrystalline were observed using differential interference contrast (DIC) optical microscopy and atomic force microscopy (AFM). Plasma etching of the substrate prior to film growth and biasing of the stage during film growth strongly influence the resulting microstructure. 100-μm-size, stacked, pyramidal CNx:Cl crystallites were deposited onto a glass microscope slide through a combination of substrate preetching and rf-biasing of the stage during film growth. In later experiments, pulsed-dc-highvoltage biasing of the stage during the growth process resulted in the deposition of 1-jim-size, rectangular- and triangular-shaped CNx:Cl crystallites onto fused silica.
Chlorinated instead of hydrogenated precursors were used to eliminate hydrogen incorporation during the growth of the ECR-CVD carbon nitride films. Chlorinated hydrocarbon precursors like trichloroethylene (C2HC13) and C2C14 reduce the amount of hydrogen in the plasma and make the formation of CN bonds more favorable. The results also show that doublebonded CC precursors are needed for N2 to react with carbon. However, when a hydrogenated precursor like C2H4 is used with a N2 plasma, hydrogen reacts with the CC double bond to form CH and NH bonds faster than N2 can react to form double- and single-bonded CN. The disadvantages of using chlorinated-carbon precursors are that the resulting CNx:Cl films contain a small amount of chlorine (Cl), are porous and are unstable with respect to moisture incorporation.
It is much easier to obtain stable, dense films using chlorinated precursors if more conventional materials are deposited. Silicon dioxide (SiO2) and silicon nitride (Si3N4) films were deposited by ECR-CVD using trichlorosilane (SiHC13). The films showed no degradation or moisture incorporation after several months.