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HCD-P 100


 

Features:

  • operation over an extended power and pressure range
  • no mode jumps
  • high plasma and radical species densities with excellent
    radial homgeneity
  • compatible with chemical reactive and non-reactive gases
  • cw and pulsed power operation
  • low contamination



Applications:

  • plasma-enhanced chemical vapor deposition (PE-CVD)
  • plasma polymerisation
  • surface modification
  • plasma cleaning
  • plasma etching
  • reactive and non-reactive ion etching
  • material science (in general)

Concept of the HCD-P100

Hollow cathode discharges represent a relatively simple means for the efficient production of high density, low temperature plasmas. The plasma source HCD-P 100 employs the hollow cathode effect. Basically, the source consists of a hexagonal matrix of 48 hollow cathode discharges. The inner hollow cylinders are rf-powered enclosing the primary plasma; the outer part of the source is electrically grounded.
An hexagonal array of orifices is drilled into the housing and the hollow cylinders allowing plasma jets to be extracted after the primary plasma has been excited in the hollow cathode. A proprietary compact gas distribution system for the primary gas and the monomer gas featuring fractal geometry gas channels plus a proprietary internal cathode structure guaranties a homogenous jet formation over extended source dimensions.
The material used is all-aluminium important for a good thermal conductivity and reduced surface loss rates when working with radicals and excited species. Depending on the technological needs the whole system can be operated isothermally by adjusting the cooling/heating water-temperature.

 

Performance

There are two major parameters controlling the performance and technical applicability of hollow cathode plasma sources such as the HCD -P. These are the working pressure range of the hollow cathode (primary) discharge and the rf-power required for plasma breakdown, i.e. ignition.

 

Homogeneity Issues

The achievable film homogeneity and quality in plasma polymerisation is controlled by the substrate distance to the monomer inlet and jet-orifices (primary plasma). Another important influence relates to the total gas flow patterns. Detailed experimental investigations have shown that a distance of about 60 mm between the plasma jet outlets and the substrate is a good compromise between the desired film homogeneity and achievable deposition rates.
As an example for a low-temperature PE-CVD process with the HCD-P DLC-deposition on a substrate has been performed. High quality DLC films were grown at room temperature with a film uniformity better than 4 % across a 4" Si-wafer (substrate bias at 400 V). In summary, the HCD-P yields excellent homogeneities in plasma-induced surface modifications/activations as well as in plasma polymerised thin films.

 

Contamination

It is commonly said that HCD's are prone to unwanted parasitic sputtering of the source electrodes. Due to its proprietary and patented excitation geometry PlasmaConsult's hollow cathode plasma sources HCD enclose the plasma completely with the exception of the plasma jet holes. Any possible contamination must have its origin in the inner cylinder or at the jet orifices.

From the source geometry it is highly unlikely that contaminants (in this case aluminium) will leave the inner source and are deposited e.g. on a substrate.

In fact, after two hours of operation (300 sccm Ar, 1 mbar, 400 W), the surface concentration of aluminium on a Si-wafer was found to be 0,25 % of the Si concentration only.

Lifetime


The HCD-P is manufactured using exclusively aluminium and ceramic parts for electrical insulation. No quartz windows etc. are necessary. Since all ceramic parts are shielded from direct plasma interaction and sputtering the source is extremely robust and offers extended lifetimes often superior to those of inductively and microwave excited plasmas.

 

 

Technical data

RF-Power:                1 - 700 W  13.56 MHz

Mounting flanges:    DN 250 ISO-K or larger, CF flange optionally

Cooling:                   water

Pressure range:       5 - 1000 Pa

Gas flow rates:         5 - 500 sccm (primary gas)

                                 4 - 100 sccm (monomer / precursor gas )

 

Application note: