- About Plasma Products
- RF Generators
- Matching Networks
- Signal Sources / Filter / Switches
- Customized Designs
- Repair Service
In plasma physics radio frequency amplifiers and generators must sometimes cope with extreme load mismatch conditions. Especially with broadband stages this is a challenge that we are happy to rise to. Our robust final amplifier stages meet the demands with appropriate dimensioning and intelligent protection circuits.
The radio frequency generators apply start of the art and efficient amplifier stages. Both features – the robustness and the efficiency – we have carefully balanced.
The RF generators and the MatchingCubes are equipped with micro controllers in order to control them safely and reliably in every minute. The devices come with a whole bunch of helpful features or can selected as option:
– internal and external pulsing
– external oscillator
– automatical matching
– serial and analog interface, and Profibus
– frequency shift tuning (FST)
Hence, our RF generators, MatchingCubes, filters, RF switches are suitable for a wide variety of applications:
– capacitively coupled plasma (CCP)- inductively coupled plasma (ICP)
– plasma enhanced chemical vapor deposition (PECVD)
– plasma polymerization
– surface activation
– plasma sterilization
– plasma etching
For the application of the electrical asymmetry effect we have a number of especially optimized devices.
Electrical Asymmetry Effect
If the electrodes of a plasma chamber are different in its mechanical dimensions a dc voltage – the DC bias – is generated. Hence, its origin is a mechanical asymmetry.
Now, one can use not only one signal source but two or three, with the second source working on two times the fequency of the first and the third source working on three time the frequency of the first. Then also a DC bias between the electrodes of the plasma chamber appears. If the frequencies are phase locked the DC bias can be controlled by the phase relationships. This is called the electrical asymmetry effect. This is a powerful tool to optimize plasma processes.
A collection of scientific articles you can find here.
Frequency Shift Tuning
In the vast majority of applications a matching network takes care of the matching of the plasma chamber to the RF generator. Usually the match contains two variable capacitors. Its capacitances are varied by tuning through motors. The mechanical tuning of the capacitors takes time.
Another approach is to work with fixed capacitors and then to vary the frequency. Because then no electro mechanical components are involved the matching can be much faster. Another advantage is that fixed capacitors are cheaper than variable capacitors. This brings the disadvantage however that the matching condition can be a little worse. This is because there is only one variance: the frequency.
13,56 MHz Generators
All 13.56MHz generators RFG-13-xxx we have designed as robust and efficient generators that come in different cabinets depending on their respective power levels. The generators meet the special requirements to use the electrical asymmetry effect.
Our broadband generators provide with the frequency an additional degree of freedom to optimize your application. Optionally the generators can be equipped with the option “frequency shift tuning”. This allows to work with a cost-saving fixed match.
The vast majority of all radio frequency ignited plasma applications work at 13.56MHz. Sometimes higher or lower frequencies can bring advantages for the plasma process. Therefore we offer generators that work on one of the other ISM frequencies (industrial, scientific, medical): 27.12MHz and 40.68MHz but even above and below. The modular design allows to change the working frequency without much effort.
The generators can deliver a pulsed rf signal. The pulse length and the periode length can be adjusted. Moreover it is possible to use an external signal for pulsing the rf. For this the device must be equipped with the option External Pulsing.
With the option External Oscillator the generators can adopt a TTL signal from an external source. Alternatively an external sinusoidal signal can be used.
All generators have a serial interface. With it the devices can be perfectly controlled. The interface support two protocols: an ASCII protocol and a binary protocol. A proprietary software for remote control of the generators is available.
An Analog Interface is optionally available.
A Profibus Interface will be optionally available shortly.
The MatchingCube is a matching network in L configuration. It is suitable for use with capacitively coupled plasma (CCP) and inductively coupled plasma (ICP).
Both capacitances of both capacitors can be varied with step motors. If it is not possible to find a matching condition the inductance can be modified. Therefore windings can be removed or added. Here winding are not just shortened or left open because this would still affect the matching condition.
The MatchingCube measures the at its output applied dc voltage: the DC bias. Its value can be requested via the remote control interface.
A matching network is limited by its electric strength of the employed capacitors and the maximum current that the coil and the capacitors can conduct. Often the question arises if a matching network is suitable for a certain RF power. The element that correlates the RF power with the current and voltage is the load impedance. The load impedance of a plasma chamber is determined by a number of details of its design, e.g. the dimension of the electrodes and the distance between the electrodes. If you can estimate the load impedance we can run a simulation to determine which MatchingCube will fit best to your plasma system.
The MatchingCube can be equipped with a AutoMatch Function. Is the device equipped with this option it supports to find the matching condition automatically. It may be necessary to adjust some parameters for this. Using the remote control software this is easy to do.
During the design process we made sure that the AutoMatch function works well also with small RF power levels.
The MatchingCube has a serial interface. This interface can be connected either to a barthel RF generator or with a PC. If the MatchingCube is connected with a barthel RF generator the most important MatchingCube settings can be done via the generator’s front panel or via the generator’s remote control software. If the MatchingCube is connected to a PC all settings can be done via it’s remote control software. A LabVIEW-VI (National Instruments) we can provide.
Optionally an Analog Interface is available.
Certainly you can use the MatchingCube self-sustained without any remote control.
Multi Channel Signal Generator PHS
The Chassis of the multi channel signal generator PHS can host and control up to four respectively eight PlugIns. Each PlugIn generates a signal with a specific frequency. The phase relationships between the respective signals are adjustable; that is not only with identical frequencies but also with two times, three time, n-times frequencies. With this feature the PHS is perfectly suitable to be used for systems that apply the electrical asymmetry effect.
In plasma physics filters are necessary when different frequencies are used; in the broader sense this is true for a DC generator that is used together with an RF generator. We can offer a bunch of different filters:
- high voltage DC / RF
- built in RF filters
- stand alone RF filters
barthel RF generators and MatchingCubes can be equipped with built in RF filters in order to optimize them for systems that apply the electrical asymmetry effect.
If you want to connect an RF generator selectively with different plasma chambers we can provide suitable coaxial switches for this.
Sometimes even flexible products with a whole bunch of options are insufficient to realize an optimum solution. In this case we are happy to think about a highly customized solution that we design according to the problem specifications and in close cooperation with our customer.
Please contact us.
Besides the design and production of state of the art equipment we also offer repair service for products from other manufacturers (e.g. AMT Herley, Dressler).