Chemical Vapour Deposition (CVD) is a process where the chemical reactions of gaseous radicals form solid molecules which are deposited on a surface. In Plasma-Enhanced CVD (PECVD), a plasma contributes to the production of radicals from gas (or vapour) precursors which react to form the solid molecules that are deposited on a (typically) heated surface. The advantages of the plasma are that it reduces the required temperature of the surface and modulation of the plasma density can be used as a tool to change the structure of the deposited film. CVD-based processes are conformal coating processes and allow deposition on structures having 3D topography.
CVD-based reactors are configured as "Hot Wall" or "Cold Wall" reactors. Controlling the wall temperature allows for the prevention or minimization of vapour condensation on reactor walls. The substrate or the workpiece holders are heated to sufficiently high temperature to optimize the molecular disintegration of gases and vapours and reactive formation of solid coatings.
Metal-Organic CVD (MOCVD) reactors use Metalorganic precursors as the main reactive source in the CVD process.
Atomic Layer Deposition (ALD) is essentially a pulsed CVD process in which the reaction typically takes place as result of two subsequent pulses of two reactive precursors and gases or vapors. This allows for mono-layer control accuracy.
PECVD and PE-ALD Reactors
PECVD reactors, like their CVD counterparts are configured as "Hot Wall" or "Cold Wall" reactors. Depending on the application, inductively or capacitively coupled plasmas are used to assist in breaking down the precursor molecules. The substrate or the workpiece holders are typically heated to a sufficiently high temperature (which is lower than in a standard CVD system due to the plasma's contricbution to radical formation) and biased (in the case of a capacitively coupled plasma) to optimize the molecular disintegration of gases and vapors and reactive formation of solid coatings.