Abstract
An industrial size plasma reactor of 5 m3 volume was used to study the deposition of silica-like coatings by the plasma-enhanced chemical vapor deposition (PECVD) method. The plasma was sustained by an asymmetrical capacitively coupled radio-frequency discharge at a frequency of 40 kHz and power up to 7 kW. Hexamethyldisilioxane (HMDSO) was introduced continuously at different flows of up to 200 sccm upon pumping with a combination of roots and rotary pumps at an effective pumping speed between 25 and 70 L/s to enable suitable gas residence time in the plasma reactor. The deposition rate and ion density were measured continuously during the plasma process. Both parameters were almost perfectly constant with time, and the deposition rate increased linearly in the range of HMDSO flows from 25 to 160 sccm. The plasma density was of the order of 1014 m−3, indicating an extremely low ionization fraction which decreased with increasing flow from approximately 2 × 10−7 to 6 × 10−8. The correlations between the processing parameters and the properties of deposited films are drawn and discussed.
Highlights
A widely used method for deposition of thin coatings onto solid materials at low temperatures is plasma-enhanced chemical vapor deposition (PECVD)
The plasma density was of the order of 1014 m−3, indicating an extremely low ionization fraction which decreased with increasing flow from approximately 2 × 10−7 to 6 × 10−8
The deposition kinetic was measured by optical interferometry using a custom-designed miniature fiber-optics sensor, whereas the structure of the deposited films was determined after the treatment by secondary ion mass spectrometry (SIMS) depth profiling
Summary
A widely used method for deposition of thin coatings onto solid materials at low temperatures is plasma-enhanced chemical vapor deposition (PECVD). A precursor is leaked into a plasma reactor where it is partially ionized and dissociated, and the resulting species stick to a surface to form a thin and often compact coating. Various precursors can be used to deposit films of appropriate properties. Organosilicon precursors are suitable for deposition of coatings containing silica. Films of various properties are deposited from almost pure silicon dioxide to a polymer-like coating resembling polydimethylsiloxane. The following literature survey presents important results obtained by various authors using various discharge configurations
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