CUSTOM MATCHING NETWORKS
You don't find an impedance matching network that fits your need? We can make it.
Here are some examples of custom matchers we made.
Impedance Matching Network for a Large Area VHF CCP Reactor (13.56 to 81.36MHz)
We built for the LPP laboratory at Ecole Polytechnique in France a custom manual matching network for a large area capacitively coupled plasmas (CCP). The matching network should be able to perform the impedance matching up to 600W at four different RF frequencies: 13.56, 40.68, 60 and 81.36MHz.
The input impedance of the reactor (without discharge) was measured with a Vector Network Analyzer between 1 and 100MHz in order to design this optimized matching network.
The input and output RF ports, cooling air inlet and outlet were positioned to fit the customer needs. The series "tune"
inductor can be easily accessed at the back to modify its value before changing the excitation frequency.
Multi-frequency Impedance Matching Network for a Small Area CCP Reactor (13.56 + 27.12 + 40.68MHz)
Driving radio-frequency capacitively coupled plasmas (CCP) by (non-sinusoidal) tailored voltage waveforms has been shown to allow considerable control over various plasma properties for surface processing applications.
A tailored voltage waveform (such as a "peak" waveform illustrated on the right) is synthesized by exciting a single electrode with a group of harmonics. The impedance matching becomes therefore more complicated. Until now, this problem has been handled in research laboratories by using an oversized amplifier that can tolerate almost full power reflection without any impedance matching network, thus limiting the applicability of this technique to very small/low power laboratory systems (<50W).
To overcome this limitation a novel matching network has been invented by our customer. We built for the LPICM laboratory at Ecole Polytechnique in France two prototypes of a matching network (300W) able to match a CCP reactor simultaneously at 3 excitation frequencies (13.56, 27.12 and 40.68MHz). Two different prototypes have been built to equip two different CCP reactors.
A multi-frequency matching network is based on a network of 6 LC resonant circuits. The inductors are fixed air core copper coils, and the capacitors are variable vacuum capacitors. The 6 capacitors can be manually tuned from the front panel. A great attention was paid to the design and the placement of the various components to minimize the stray impedances and losses.
The effectiveness of such matching network was demonstrated experimentally (see reference below) on an Ar plasma excited by a three-frequency voltage waveform with a fundamental frequency of 13.56 MHz. Under the plasma conditions studied, the power coupling efficiency was increased from less than 40% (without impedance matching) to between 80% and 99% for the different exciting frequencies.
Source: Wang et al. Journal of Vacuum Science & Technology A 37, 021303 (2019) https://doi.org/10.1116/1.5056205