176 / 2018-08-25 22:45:18

Investigation on the Microscale Breakdown Characteristics under Repetitive Nanosecond Pulses

microscale breakdown, repetitive nanosecond pulses, pin-sphere electrode

The improvement of micro and nano processing technology has greatly promoted the revolutionary of microelectronic components into miniaturization and high integration. Nowadays, microelectronic mechanical system (MEMS) has been more and more widely used in industry and daily life. However, as the size of the devices get smaller, those microelectronic components may suffer from high voltage while working, which could produce extremely high electric field strength between the metal structures inside the components and cause discharge. The discharge between metal electrodes through the gas medium may lead to micro-gap breakdown, resulting in the performance failure and even permanent physical damage of the devices and systems. As a result, higher requirements are proposed in the insulation structure design of microelectronic components. The breakdown characteristics of metal structures under high field strength are worthy of great attention. It is of great significance to study the micro-gap breakdown law and the discharge mechanism of insulation structure design in micro-electronic components.
According to the breakdown characteristics of micro-gap, an electrical test and optical diagnostic experimental system for micro-gap breakdown under repetitive nanosecond pulses was established. Firstly, through the high-voltage DC source and the semiconductor high-speed switch, we established the nanosecond pulse power supply, which can output adjustable nanosecond pulses voltage with the frequency of 0-1000 Hz and amplitude of 0-3 kV. Meanwhile, the pin electrodes with a radius of curvature of 5 μm and the sphere electrodes with the radius of 70 μm were prepared by electrochemical etching and Joule melting methods. The effects of different voltage frequencies, different electrode spacing and different polarities on the pin-sphere electrodes breakdown characteristics were studied. The typical waveform of breakdown voltage and current is analyzed, and the breakdown mechanism under micro-gap is explored.
Experiments were conducted to investigate the breakdown characteristics of the pin-sphere electrodes at single pulse and different frequency repetitive pulses. The results of 1~20μm gap shows that the breakdown voltage generally increases with the increase of the electrode spacing at the same frequency. The experimental values of breakdown voltage at the same pitch are larger than the theoretical values, and the average breakdown field strength decreases with the increase of the gap, but both are higher than the average breakdown field strength of the macro spacing. Under repetitive pulses, the breakdown voltage at the same pitch is significantly higher than that at the single pulse; and as the frequency increases, the breakdown voltage has a tendency to decrease.
The study of the breakdown characteristics of the pin-sphere electrodes with different polarity between 1-20μm gaps shows that when the pin electrode is the anode, the breakdown voltage is higher than that of the cathode electrode. This is exactly the opposite of the polarity effect of macroscopic electrode gas breakdown. Field electron emission plays a decisive role in the process of microscale breakdown, and the initial electrons are mainly generated by field-electron emission. The electric field of the pin-sphere electrode system is extremely uneven, and the field enhancement coefficient near the pin electrode is extremely large, leading to the highest field strength. Therefor when applied as a cathode, due to the higher field strength the pin electrode is more likely to emit electrons into the gap to become initial electrons, resulting in lower breakdown voltages.