Atmospheric Pressure Plasma CVD

Atmospheric Pressure Plasma CVD (APCVD) offers a number of advantages, particularly for online, continuous processes such as glass, steel or textile manufacture. The costs and operating difficulties associated with high vacuum equipment are avoided and the coating may be a continuous, rather than a batch process, avoiding the need to interrupt the line.

The large-scale use of atmospheric pressure discharges is well established A wide range of different technologies have been explored. CVD Technologies has focused onto Glow Discharge Dielectric Barrier plasmas, which offer some of the lowest thermal loads, and is a readily scalable process technology. Furthermore, the capital costs of APGD plasmas are much lower than alternative approaches.

A variant is provided by either remote or in-situ AP Plasma use. In the latter the substrate sits within the plasma allowing for direct plasma activation of both the substrate and the growing film. The combination of a parallel plate type configuration, along with an in-situ plasma (which CVD Technologies uses) has attractions for film growth and for scalability of the technology

These non equilibrium, or "cold" plasmas have significant advantage in that the energy of the electrons is used to create reactive and charged species without significantly raising the gas temperature. For deposition, a homogeneous glow discharge is preferred to the filamentary dielectric barrier discharge normally associated with operation at atmospheric pressure. The homogenous glow regime may be obtained by optimising the system parameters and the choice of discharge gas

The use of helium has been found to facilitate this condition due to the relatively long lifetime of its meta-stable excited state, although other gases such as argon and nitrogen can be employed and are used in our processes

We have demonstrated the capability to deposit silica, titania, aluminium oxide, and metal composite films using this technology. Growth rates can be very high (some tens of nm per second).