Advantages of Waveform Adaptability in Low Frequency PECVD Applications

Low frequency plasma enhanced chemical vapor deposition (LF-PECVD) is one of the commonly used methods for deposition antireflective (AR) coatings for Si-based solar cells. Although the solution is in mature condition the manufacturers continuously seek for improvements to increase system throughput and reduce the costs of ownership. To achieve these goals efforts are focused on optimization of the process parameters to increase the processing speed, coatings uniformity and repeatability of process conditions. An integral component of the system having an important influence on the process quality is the power supply used for plasma generation. In addition to long term stability, repeatability in cycle operation and high precision in power delivery it must enable redesign and process conditions adjustment to reach higher production ratings. In this contribution use of AC power supply with rectangular current and voltage waveform will be introduced as an alternative for standard sinus wave generators for LFPECVD. The deposition rates and process speed achievable with rectangular output will be discussed in detail. The analysis will be summarized with the comparison of the properties of the AR-coatings fabricated on a commercial PV system with rectangular and alternative waveform shapes of bipolar power supplies.