Chemical Vapor Deposition (CVD) is a semiconductor process used to deposit a thin film of material onto a substrate by chemical reaction in a gas phase. In CVD, the substrate is placed in a reaction chamber that is filled with a gas mixture containing the precursor chemicals. The precursor chemicals react to form a solid film on the surface of the substrate.
CVD is widely used in the semiconductor industry for depositing thin films of various materials, such as silicon dioxide (SiO2), silicon nitride (Si3N4), and metal films like aluminum, copper, and tungsten. The process is highly customizable, and the deposited film properties can be controlled by adjusting the reaction parameters such as temperature, pressure, and gas flow rates.
There are several types of CVD processes based on the method used for precursor delivery, such as atmospheric pressure CVD, low-pressure CVD, plasma-enhanced CVD, and metal-organic CVD.
The atmospheric pressure CVD process is the simplest form of CVD, where precursor gases are introduced into the reaction chamber at atmospheric pressure. This process is generally used for depositing thick films.
Low-pressure CVD (LPCVD) is a commonly used CVD process in the semiconductor industry, where the precursor gases are introduced into the reaction chamber at low pressure (typically 1 to 100 mTorr) and high temperature (500 to 1200°C). The low pressure facilitates gas-phase transport and helps to prevent gas-phase reactions that can lead to unwanted particle formation.
Plasma-enhanced CVD (PECVD) is a variant of the CVD process where a plasma is used to assist in the chemical reactions that occur in the gas phase. The plasma enhances the reactivity of the precursor gases, allowing for the deposition of films at lower temperatures and with better control over film properties.
Metal-organic CVD (MOCVD) is a specialized form of CVD used for depositing metal films and compound semiconductors such as gallium arsenide (GaAs) and indium phosphide (InP). The process uses organometallic precursor gases that are thermally decomposed in the gas phase to deposit thin films.
In summary, CVD is a versatile and widely used process in the semiconductor industry for depositing thin films of various materials with precise control over film.