No abstract

a b s t r a c tWe report on the microfabrication and testing of a chip-scale plasma light source. The device consists of a stack of three anodically bonded Pyrex wafers, which hermetically enclose a gas-filled cavity containing interdigitated Aluminum electrodes. When the electrodes are powered through an impedance matching circuit, these devices have been used to generate stable millimeter-size RF plasma discharges operating continuously for over 24 h in He or Ar at pressures ranging from 10 to 500 mbar at RF powers of 300-1500 mW.

We present an experimental study of the DC breakdown voltage of MEMS interdigitated aluminum electrodes with gaps ranging from 10 to 500 µm. Unlike most research on MEMS electrodes that was done at atmospheric pressure, our work has focused on the effect of gas pressure and gas type on the breakdown voltage. A main goal was to identify geometries that favor the creation of low-voltage discharges. Helium, argon and nitrogen pressure was varied from 10 2 to 8.10 4 Pa (1 to 800 mbar). The breakdown voltage was plotted as a function of the Paschen reduced variable P red = p·d. For higher values of pressure, p or gap, d (high P red ), classical Paschen scaling was observed. For lower values of P red however, significant deviations were seen, particularly at low pressures. We attribute these differences not to field emission, but to the scale of the mean free path (which explains the higher than predicted voltages), and principally to the many length scales effectively present in our planar geometry (on-chip and even off-chip, that lead to the superposition of several Paschen curves). Guidelines are proposed for low-pressure operation of MEMS to avoid or to encourage breakdown.

Abstract. An experimental study of the dc breakdown voltage for planar MEMS interdigitated aluminum electrodes with gaps ranging from 10 to 500 m is presented. Unlike most research on the breakdown in MEMS electrodes that was performed at atmospheric pressure, this work focuses on the effect of gas pressure and gas type on breakdown voltage, because this is central for chip-scale plasma generation and for reliable operation in aerospace applications. The breakdown voltage is measured in helium, argon, and nitrogen atmospheres for pressures between 10 2 to 8.10 4 Pa ͑1 to 800 mbar͒. For higher values of the pressure P, or of the gap d ͑i.e., for high values of the Paschen reduced variable P red = P · d͒, classical Paschen scaling is observed. For lower values of P red , however, significant deviations are seen: the V bd versus. Pd curve shows an extended flat region rather than a narrow dip. These differences cannot be attributed to field emission, but are due to the many length scales effectively present in a planar geometry ͑on-chip and even off-chip͒ that leads to the superposition of several Paschen curves. Guidelines are formulated for low-pressure operation of MEMS to avoid or encourage breakdown.

We report on the fabrication and testing of a chip-scale plasma light source. The device consists of a stack of three anodically bonded Pyrex wafers, which hermetically enclose a gas-filled cavity in which electrodes are used to ignite a low power (<500 mW) RF plasma.