Aurion Anlagentechnik GmbH

High frequency matching networks

Application
The high frequency matching networks of the PRODIK series are used for fully automatic matching of a plasma impedance to the output impedance of an RF generator with a nominal frequency of 13.56 MHz. Different circuits allow the unproblematic and low-loss matching of diodes, magnetron cathodes and large planar electrodes for PECVD and etching (microelectronics, display technology, etc.).

The networks (matchboxes) are optimized for highest process stability and offer leading measurement and control technology. This results in optimal user friendliness and best process control.

Hardware
Our matching networks are manufactured in uncompromisingly high quality. High-quality vacuum and ceramic capacitors as well as silver-plated conductor parts made of solid copper at all highly stressed points guarantee high operational reliability and reproducibility. The housings are made of aluminum and all covers have copper beryllium spring contacts. This ensures extremely high quality RF shielding and yet allows easy opening and closing of the units through the use of a few quick release fasteners.

Measurement
2 voltages are recorded across a fixed capacitor at the matchbox input via capacitive voltage dividers. These are designed with low coupling, which suppresses crosstalk.

Currents are determined from the voltage differences, eliminating error-prone direct current measurements with inductive couplers.

The measured values are recorded by a logarithmic amplifier. This technology enables the highest precision with maximum dynamics.

The input impedances and (with lower accuracy) the load impedances are calculated from the measurement data. From this, a controller determines the optimum settings for the variable capacitors. Input and load impedance can be displayed or further processed by the system controller.

Furthermore, the DC bias potential is measured at the output of the matchbox and a plasma detection system detects whether the plasma has ignited.
Control concept
The PRODIK series convinces by innovative sensor technology and modern CAN bus technology with decentralized intelligence.

All measuring signals are A/D-converted immediately after acquisition and then transmitted digitally and thus without interference and loss via the bus.

The motor drives of the vacuum capacitors have their own electronics (CUB) with the motor drivers, the position acquisition and the CAN interface. The communication with the central controller uses a calibration directly in pF. This means that the entire pre-calibrated capacitor unit with drive can be completely replaced without the need for any calibration measures. All process parameters are directly reproducible.

The central controller, the ASC, has a RS232 interface and a Profibus as standard in addition to the CAN bus.

A universal analog/digital interface card (GCT) is available for the integration of an HF generator. via this the ASC can take over the complete control of the HF generator. This makes it possible, for example, to control the complete HF system including a non-profibus capable generator via the Profibus interface of the ASC.
Schematic representation of the control concept of AURION
For autotuning, as already mentioned, 2 voltages are measured across the input fixed capacitor. From this the input impedance is calculated, from which in turn the output or load impedance is derived with somewhat reduced accuracy. Optionally, it is possible to measure this output impedance directly and thus precisely control the coupled power.

Via the load impedance, it is possible to determine the reactive power, the output current and other process-relevant parameters.

These can be queried, displayed and evaluated via the ETHOS configuration software or further processed by the plant control system (e.g. PLC).

The complete modularization allows a fast and flexible, purely software-based adaptation of the control concept to a wide variety of requirements. For example, software variants are available for fast cycle time operation with sputter times in the range of seconds. Here, classic autotuning would not be applicable.

However, the AURION technology makes it possible to combine a stable short sputtering process with an automatic compensation of the drift between the processes, thus obtaining all the advantages.

The matching networks of the PRODIK series are designed according to the customer's plant requirements. Various circuits are available for this purpose