Efficient plasma surface treatment with inverted fireballs

 

Have you ever considered higher energy efficiency in plasma processing?

A significantly higher plasma density can be achieved with so-called inverted plasma fireballs (IFBs). In an IFB, the plasma will be trapped in a small and appropriate volume due to the formation of a Faraday cage around a gridded anode. The high-density plasma is then trapped within this cage. Since the hollow anode is a Faraday cage, it is almost field free, which creates a very homogeneous plasma, even over large areas. The combination of high plasma density and homogeneity makes IFBs a versatile tool for all kinds of plasma surface treatment, from deposition to etching. It has been demonstrated in this recent paper that a 40 % increase in discharge energy leads to a tenfold increase in plasma density and, therefore, enhanced deposition.

 

Fig. 1 the difference between an ordinary rf plasma (left) and the same setup with the IFB turned on (right). It can be seen that the IFB confines the plasma where it is needed, inside the cage and close to the surface that is to be treated.

 

It was also demonstrated that IFBs can successfully cover large areas with highly homogeneous carbon films. For example, it has been shown that a 125 x 125 mm² could be covered evenly with an ultra-smooth carbon layer. The achieved growth rates were up to 20 nm/min at an overall input power of just 70 W. The lowest roughness was beyond 0.25 nm, which was actually too small to be detected with the AFM. The grown films showed good adhesion to the glass substrates. The only limitation of this technology is the need for gaseous precursors and a vacuum system. So far, it has very successfully been applied to deposit various carbon films, such as diamond-like carbon (DLC), amorphous carbon, carbon nanowalls and graphene.

 

As one can see, IFBs offer several important advantages, compared to standard PECVD technologies and other forms of surface treatment (such as etching, or surface activation):

 

Advantages of IFBs for Surface Treatment Technology:

1. Overall energy and process efficiency
2. It can be integrated into already existing low-pressure plasma systems
3. Long-term process stability
4. Large-area plasma treatment is feasible
5. High growth rates are achievable
6. The same setup can be used for different forms of surface treatment like coating, etching, or activation
7. An excellent tool for carbon film deposition on various surfaces
8. Less machine downtime

 

In order to get this new, exciting technology from pure research to market, we have formed the GET (grid enhance technology) consortium. This consortium consists of the Gruenwald Laboratories Gmbh, located in Austria and 4A-PLASMA, located in Germany.

 

Currently, we are looking for partners in the industrial and academic area. If you have any questions or want to work with us, just send us an email to:

 

info@get-plasma.tech, Eichenhofer@get-plasma.tech, or Gruenwald@get-plasma.tech

 

 

Here are some links to useful papers on the topic:

Links to scientific papers

¹Measurement of inverted n-hexane fireball properties with a Multipole Resonance Probe

^²Letter: Influence of inhomogeneous electrode biasing on the plasma parameters of inverted H2 fireballs

^³Diamond Like Carbon Deposition by Inverted Fireballs

⁴PECVD of carbon by inverted fireballs: From sputtering, bias enhanced nucleation to deposition

⁵Inverted fireball deposition of carbon films with extremely low surface roughness