Sub-Torr Chip-Scale Sputter-Ion Pump Based on a Penning Cell Array Architecture

This paper investigates a miniaturized, chip-scale Penning cell array for sputter-ion pumping. In a 2.5 cm³ package, a 0.2 cm³ pump architecture with 1.5 mm diameter cells in a 4 × 2 array reduces pressure from 1 Torr (133.3 Pa) to <; 200 mTorr (26.6 Pa) in about 10 h, and from 115 mTorr (15.3 Pa) to <; 10 mTorr (1.33 Pa) in 4 h. The rate of molecular removal in this range of pressures is 0.09 ×10¹³ to 1.17 ×10¹³ molecules/s. Experiments show that the architecture is capable of igniting and sustaining the plasma required for operating at a pressure at least as low as 1.5 μTorr (200 nPa). The advantage of the Penning cell architecture reported here in comparison to other chip-scale ion pump architectures is the drastically reduced operating pressures that can be achieved and maintained. The microdischarge requires 450-600 V applied across the device and consumes 100-250 mW. The Penning cell array architecture shows significant promise for power efficient high-vacuum pumping in chip-scale and smaller systems.