Silicon oxynitride is a compound made up of silicon, oxygen, and nitrogen. It is a ceramic substance with the chemical composition SiOxNy. While the composition of amorphous forms can constantly change between SiO2 (silica) and Si3N4 (silicon nitride), the only known intermediate crystalline phase is Si2N2O. It is sometimes abbreviated as SiOxNy, with x and y representing the different amounts of oxygen and nitrogen in the molecule.
It exists in nature as the rare mineral sinoite in some meteorites and may be produced in a laboratory. The particular composition can be modified to get the desired material qualities. This compound is a ceramic substance having qualities that make it valuable in a variety of applications, particularly those involving electronics and optics.
Properties
Silicon oxynitride’s properties can be modified by varying the composition during the fabrication process, making it a versatile material for a wide range of technical applications. The compound’s unusual combination of electrical, optical, and thermal properties makes it widely used in a variety of fields. It is renowned for its superior dielectric characteristics. It is commonly used as a dielectric material in microelectronics and semiconductor devices to insulate and separate conducting layers.
- Chemical formula: N2OSi2
- Molar mass: 100.183 g·mol−1
- Appearance: Colorless crystals
- Density: 2.81 g·cm−3
- Crystal structure: Orthorhombic
Synthesis
Polycrystalline silicon oxynitride ceramics are primarily produced by nitridation of a mixture of Si and silicon dioxide at a temperature above melting point of silicon (1414 °C), in the range 1420–1500 °C:
3 Si + SiO2 + 2 N2 → 2 Si2N2O
Silicon oxynitride materials with diverse stoichiometries can also form as a result of pyrolysis of preceramic polymers, such as polysilanes and polyethoxysilsesquiazane. The resulting SiON materials are known as polymer-derived ceramics (PDCs). Using preceramic polymers, thick or porous Si oxynitride ceramics in complicated shapes can be created using shaping procedures more commonly used for polymers.
Silicon oxynitride has excellent thermal stability, allowing it to tolerate high temperatures without substantial damage. This characteristic is useful in applications requiring materials to withstand high heat conditions.
Applications
Thin films of silicon oxynitride can be formed on silicon using a variety of plasma deposition processes and employed in microelectronics as a dielectric layer alternative to silicon dioxide and silicon nitride, offering low leakage currents and good thermal stability. Because these films have an amorphous form, their chemical composition varies greatly from Si2N2O. Changing the nitrogen/oxygen ratio in these films allows for continual tuning of the refractive index between ~1.45 for silicon dioxide and ~2.0 for silicon nitride. This characteristic is beneficial for gradient-index optical components like graded-index fibers.
