(Dielectric Science & Technology Division Thomas D. Callinan Award) Boron Carbon Nitride Thin Films for Low-k Dielectric Interconnect and Optical Applications

New microprocessor CMOS technologies require interlayer dielectric materials with lower dielectric constant than those used in current technologies to meet RC delay goals and to minimize cross-talk. Silicon oxide or fluorinated silicon oxide (SiOF) materials having dielectric constant in the range of 3.6 to 4 have been used for many technology nodes. In order to meet the aggressive RC delay goals, new technologies require dielectric materials with k < 3. Boron carbide nitride (BCN) shows promise as a low dielectric constant material with good mechanical strength suitable to be used in newer CMOS technologies. BCN ternary system exhibits exceptional properties and attract much attention from mechanical, optical and electronic perspectives. BCN thin films contain interesting phases such as diamond, cubic BN (c-BN), hexagonal boron nitride (h-BN), B₄C, β-C₃N₄. Attempts have been made to form a material with semiconducting properties between the semi metallic graphite and the insulating h-BN, or to combine the cubic phases of diamond and c-BN (BC₂N heterodiamond) in order to merge the higher hardness of the diamond with the advantages of c-BN, in particular with its better chemical resistance to iron and oxygen at elevated temperatures.

For optical applications, the deposition of BCN coatings on polymers is a promising method for protecting the polymer surface against wear and scratching. BCN films have high optical transparency and thus can be used as mask substrates for X-ray lithography.

In this work, the deposition and characterization of amorphous thin films of boron carbon nitride (BCN) are reported. The BCN thin films were deposited by radio frequency (rf) magnetron sputtering technique. The BCN films were deposited by sputtering from a high purity B₄C target with the incorporation of nitrogen gas in the sputtering ambient. Films of different compositions were deposited by varying the ratios of argon and nitrogen in the sputtering ambient. Investigation of the oxidation kinetics of these materials was performed to study high temperature compatibility of the material. Both the dielectric and optical properties seem to be sensitive to carbon and nitrogen content in the films.