Development Of Control System Of Multi-Waveform Pulsed Bias Power Supply And Preparation Of CrN Films Using Magnetron Sputtering

Magnetron sputtering technology, which presents some incomparable advantages, such as low temperature and high efficiency, is an excellent physical vapor deposition technology and is well accepted in film deposition. During films preparation, negative bias voltage is usually applied to the substrate, and a number of studies have shown that the application of bias voltage to substrate can significantly improve the film performance. The previous investigations related to bias voltage concentrated on the influence of voltage amplitude, pulse frequency and pulse duration, while few researches about the effect of bias waveform shapes have been reported to the best of our knowledge.According to the circuit structure of solid state Marx pulsed high voltage modulator, the control system for the multi-waveform pulsed bias power supply is developed with microcontroller C8051F020 and programmable interval timer 8254 in this Paper, and then CrN films are deposited by DC magnetron sputtering deposition technology coupled with the multi-waveform bias power supply under four kinds of different pulsed bias waveform shapes. The microstructure, surface morphology, phase structure, micro-hardness, tribological and electrochemical properties of the coatings were characterized by scanning electronic microscope (SEM), atomic force microscope(AFM), X-ray diffraction (XRD), ball-on-disk tribometer, Vickers indenter, scratch tester and electrochemistry tester respectively. The influence of deposition Parameters, such as bias voltage,pulse frequency, on the macroscopic performance and microstructure of the films is analyzed, and the Parameters of bias voltage are also optimized.The results show that compared to the traditional rectangular shape of bias waveform, bias waveforms with discrete steps which are produced by controlling the rising and falling edge of pulsed bias can lead to better mechanical, electrochemical, tribological performance of the films. SEM analysis indicates that the surface morphology of CrN film is mainly featured by island-like structure, and with discrete step bias waveforms the grains are finer and more homogeneous. AFM results suggest that surface roughness of the films is greatly reduced with discrete steps bias waveforms. XRD results approve that the structure of the CrN films is found to be quite sensitive to the amplitude of the pulsed bias. The obtained films prepared by steps waveforms show single phase CrN with the preferential crystallographic orientation (200) and (111), while the preferential crystallographic orientation changes into only (200) with the traditional rectangular shape of bias waveform.The performance of the films fabricated using different bias voltage is evaluated that, the mechanical and electrochemical properties of obtained films become better with the bias voltage increasing. With the increasing of pulse frequency, the mechanical properties are promoted not so evidently compared to the effect of bias voltage.