Compounds in the Si-O-N-B and Si-B-C-N systems are important materials because of their outstanding thermal, chemical and mechanical stability as well as superior and technologically important dielectric properties. SiO2 is a classical refractory material and the most common gate dielectric in microelectronic devices. Its structure is made up of SiO4 tetrahedra in which each oxygen forms two bonds with neighboring Si atoms. Recently, the challenge to create smaller dimensions in microelectronic devices has demanded the use of thinner silicon oxide layers for the gate dielectric or a higher dielectric constant material. In recent years nitride-oxides (silicon oxynitrides) have been widely investigated as possible substitutes because of their higher stability and durability, their ability to prevent boron diffusion, and their higher dielectric constant. The introduction of three-coordinate nitrogen in SiO2 increases the crosslinking in the structure resulting in higher density, strength, and hardness in comparison to the pure oxide. Most of the reported Si-O-N systems are amorphous and appear to have a higher dielectric constant than the pure oxide.Synthesis of crystalline phases of these compounds is desirable because they would exhibit superior mechanical and electrical properties. Silicon oxynitride Si2N2O is a refractory material with all the aforementioned desirable properties. Related Si-B-O compounds could potentially crystallize with highly-dense diamond-like structures in which all the constituent elements are tetrahedrally coordinated leading to even superior properties such as superhardness and high stability at extreme conditions. Such materials would be alternatives to diamond in high performance applications. An alternative to 3D diamond-like structures would be stoichiometric, non-oxide compounds in the Si-B-C-N system. In general, silicon-boron-carbon-nitride ceramics are considered as "ultrahigh temperature" materials, which combine extreme thermal stability and remarkable resistance to oxidation.Researchers at Arizona State University have synthesized unimolecular precursors composed of light elements (B, C, N, O, and Si) for preparation of superhard thin films and coatings as well as superior dielectric materials by chemical vapor deposition (CVD). New systems with compositions Si2B2O, SiB2O, and SiBCN have been synthesized as thin films on Si(100) substrates. A new and practical method for deposition of thin films and coatings of the refractory, dielectric nitride Si2N2O and related Si-O thin oxide layers has also been developed at low temperatures. This technology also represents an ideal method for development of Si nanoparticles (quantum dots) that are embedded in a SiO2 matrix. This would lead to construction of light emitting devices on Silicon.
|Original language||English (US)|
|Publication status||Published - Feb 28 2001|