What Is Silane?
Silane (monosilane, SiH4) is a colorless gas with a distinct odor at room temperature and pressure.
Silane is a silicon hydride. Monosilane, disilane, and trisilane refer to compounds with one, two, or three silicon atoms, respectively. Due to its low polarity, silane dissolves in common organic solvents.
Silane is classified as a hazardous substance requiring name labeling and notification, a substance for risk assessment, a flammable gas, and a known mutagenic chemical.
Uses of Silane
Silane (SiH4) serves as a highly reactive inorganic compound in various applications, notably in the semiconductor industry.
Chemical vapor deposition (CVD) involves injecting a special gas at atmospheric pressure to create a film. Techniques vary, including energy application to the gas or gas interaction. In silane-based CVD, a film forms when electrical energy is applied to the injected silane.
Applications include silicon wafer fabrication and the development of gate oxide films for MOS devices. Besides, silane supports research and development for new uses.
Handling silane requires caution due to its spontaneous combustion in the air.
Properties of Silane
Silane, the simplest silane form, consists of silicon and hydrogen (SiH4), with a molecular weight of 32.12 g/mol. It is colorless, odorless, and gaseous at room temperature and pressure but has a very low boiling point (-112°C) and melting point (-185°C). Silane is nearly water-insoluble and exhibits nonpolar characteristics.
Its high reactivity and instability mean it ignites spontaneously upon contact with the air and reacts violently with water, producing silicon dioxide and hydrogen gas.
SiH4 + 2H2O → SiO2 + 4H2
Due to its reactivity, flammability, and explosive nature, silane must be handled carefully. It poses health risks upon inhalation or skin contact. Silane is a key gas source for silicon deposition in the semiconductor industry CVD processes and amorphous silicon production in solar cell manufacturing.
Structure of Silane
Silane features a tetrahedral structure with a central silicon atom surrounded isotropically by four hydrogen atoms. Each silicon atom bonds to a hydrogen atom via a sigma bond, with Si-H bond angles close to 109.5° and a bond length of approximately 1.48 Å. This structure renders silane a nonpolar molecule due to the electronegativity balance.
Other Information on Silane
Production Methods for Silane
While several methods exist to produce silane, the prevalent industrial approach involves silicon powder mixed with sodium or potassium to enhance surface area and reaction speed. Passing hydrochloric acid gas through this mixture produces silane.
Si + 4HCl + 4Na → SiH4 + 4NaCl
After formation, silane is separated and purified as a gas. Another method involves reacting silicon with hydrogen under high temperatures and pressures, though it is less common due to its inefficiency and high energy demands.