Chemical Vapor Deposition - Types

Types

A number of forms of CVD are in wide use and are frequently referenced in the literature. These processes differ in the means by which chemical reactions are initiated (e.g., activation process) and process conditions.

• Classified by operating pressure:
  • Atmospheric pressure CVD (APCVD) – CVD process at atmospheric pressure.
  • Low-pressure CVD (LPCVD) – CVD process at sub-atmospheric pressures. Reduced pressures tend to reduce unwanted gas-phase reactions and improve film uniformity across the wafer.
  • Ultrahigh vacuum CVD (UHVCVD) – CVD process at very low pressure, typically below 10−6 Pa (~10−8 torr). Note that in other fields, a lower division between high and ultra-high vacuum is common, often 10−7 Pa.

Most modern CVD processes are either LPCVD or UHVCVD.

• Classified by physical characteristics of vapor:
  • Aerosol assisted CVD (AACVD) – A CVD process in which the precursors are transported to the substrate by means of a liquid/gas aerosol, which can be generated ultrasonically. This technique is suitable for use with non-volatile precursors.
  • Direct liquid injection CVD (DLICVD) – A CVD process in which the precursors are in liquid form (liquid or solid dissolved in a convenient solvent). Liquid solutions are injected in a vaporization chamber towards injectors (typically car injectors). The precursor vapors are then transported to the substrate as in classical CVD process. This technique is suitable for use on liquid or solid precursors. High growth rates can be reached using this technique.
• Plasma methods (see also Plasma processing):
  • Microwave plasma-assisted CVD (MPCVD)
  • Plasma-Enhanced CVD (PECVD) – CVD process that utilizes plasma to enhance chemical reaction rates of the precursors. PECVD processing allows deposition at lower temperatures, which is often critical in the manufacture of semiconductors.
  • Remote plasma-enhanced CVD (RPECVD) – Similar to PECVD except that the wafer substrate is not directly in the plasma discharge region. Removing the wafer from the plasma region allows processing temperatures down to room temperature.
• Atomic layer CVD (ALCVD) – Deposits successive layers of different substances to produce layered, crystalline films. See Atomic layer epitaxy.
• Combustion Chemical Vapor Deposition (CCVD) – Combustion Chemical Vapor Deposition or flame pyrolysis is an open-atmosphere, flame-based technique for depositing high-quality thin films and nanomaterials.
• Hot wire CVD (HWCVD) – also known as catalytic CVD (Cat-CVD) or hot filament CVD (HFCVD), this process uses a hot filament to chemically decompose the source gases.
• Hybrid Physical-Chemical Vapor Deposition (HPCVD) – This process involves both chemical decomposition of precursor gas and vaporization of a solid source.
• Metalorganic chemical vapor deposition (MOCVD) – This CVD process is based on metalorganic precursors.
• Rapid thermal CVD (RTCVD) – This CVD process uses heating lamps or other methods to rapidly heat the wafer substrate. Heating only the substrate rather than the gas or chamber walls helps reduce unwanted gas-phase reactions that can lead to particle formation.
• Vapor phase epitaxy (VPE)