Plasma-enhanced chemical vapor deposition

These energetic electrons can induce many processes that would otherwise be very improbable at low temperatures, such as dissociation of precursor molecules and the creation of large quantities of free radicals.

Ionized atoms or molecules that diffuse to the edge of the sheath region feel an electrostatic force and are accelerated towards the neighboring surface.

Excitation frequencies in the low-frequency (LF) range, usually around 100 kHz, require several hundred volts to sustain the discharge.

Thus one can adjust the chemistry and ion bombardment in the deposition by changing the frequency of excitation, or by using a mixture of low- and high-frequency signals in a dual-frequency reactor.

Capacitive plasmas are usually very lightly ionized, resulting in limited dissociation of precursors and low deposition rates.

High density plasmas can also be generated by a DC discharge in an electron-rich environment, obtained by thermionic emission from heated filaments.

The voltages required by the arc discharge are of the order of a few tens of volts, resulting in low energy ions.

Working at Standard Telecommunication Laboratories (STL), Harlow, Essex, R C G Swann discovered that RF discharge promoted the deposition of silicon compounds onto the quartz glass vessel wall.

[5] Swann attending to his original prototype glow discharge equipment in the laboratory at STL Harlow, Essex in the 1960s.

High-density plasma deposition of silicon dioxide from silane and oxygen/argon has been widely used to create a nearly hydrogen-free film with good conformality over complex surfaces, the latter resulting from intense ion bombardment and consequent sputtering of the deposited molecules from vertical onto horizontal surfaces[citation needed].