Experimental study of the gas breakdown in a controlled nanometer scale electrode gap

Paschen's law is a convenient analytical empirical law allowing for predicting the breakdown voltage (Vb) of a gas to be estimated relatively precisely. It is based on several assumptions, such as a uniform electric field between two electrodes of infinite size. Practically, values of Vb are directly related to the product of the pressure with the electrodes distance (p∙d). Although this analytical approach has proven its usefulness for a large range of experimental conditions, the prediction of Vb is compromised for small inter-electrode distances, less than 1 µm. In other words, the pressure will no longer be able to compensate lower distances to keep the product p∙d constant for a given value of Vb. Numerous experimental, theoretical and simulation studieshighlight deviations from the Paschen's law for very small gap [1]. Consequently, this raises some concerns about the electrical insulation capabilities of gases for very short distances typically in the order of a micrometer and lower [2]. The experimental study follows previous work on the deviation of the Pashen’s law [3] and focuses on the statistical measurement of Vb in different gases (Argon, air, etc.) for inter-electrode gap ranging from 0.1 µm to 6 µm. The experimental setup consists of a silicon wafer coated with a thin film of gold (~500 nm). It is wired to the ground potential and acts as a cathode; A sharp needle with a tip radius curvature of 20 µm is used as an anode and is fully coated with gold. A piezoelectric actuator controls the inter-electrode gap. The experiments are carried out in a closed chamber to control the pressure, the humidity and gas purity. After showing clear deviations of Vb from the Pachen’s law prediction for several gases, a statistical approach will be presented in order to identify the different regime of the breakdown with regard to the interelectrode distance. The breakdown regime will also be study at different pressures to clarify the impact of this parameter with regard to the other experimental conditions.[1] D B Go and A Venkattraman 2014 J.Phys.D:Appl.Phys. 47 503001[2] C H Chen, J Andrew Yeh and P J Wang 2006 J. Micromech. Microeng. 16 1366–1373[3] A Peschot, N Bonifaci, O Lesaint, C Valadares and C. Poulain 2014 Appl. Phys. Lett. 105 123109