Crystalline Deposition
Semiconductor fabrication process that deposits a thin layer of single crystal material onto a single crystal substrate. High quality epitaxial growth maintains the lattice orientation of the underlying wafer while allowing for different doping levels or material compositions. It creates the active regions for transistors and light emitting diodes where the bulk wafer acts as a physical support.
Thermal Mechanism
Chemical vapor deposition provides the primary method for achieving precise layer formation. In a typical reactor, precursor gases flow over a heated substrate to trigger a surface reaction that builds the atomic structure layer by layer. High temperatures are required to give the atoms enough mobility to find their correct lattice positions.
Any mismatch in the thermal expansion coefficients between the substrate and the new layer can introduce strain or defects.
Device Performance
Purity levels in the deposited film exceed those of the base wafer. By using epitaxial growth, designers can create sharp doping profiles that are impossible to achieve through diffusion or ion implantation. Rapid transitions between layers enable the construction of high electron mobility transistors.
The thickness of the layer directly influences the breakdown voltage and switching speed of power devices. Selective growth allows for the formation of features only in specific windows opened in an oxide mask.
