Fabrizio Siviero

Lifetime prediction in vacuum packaged MEMS provided with integrated getter film

Thin-film getter integration is one of the key technologies enabling the development of a wide class of MEMS devices, such as IR microbolometers and inertial sensors, where stringent vacuum requirements must be satisfied to achieve the desired performances and preserve them for the entire lifetime. Despite its importance, the question about lifetime prediction is still very difficult to answer in a reliable way. Here we present an experimental approach to the evaluation of lifetime, based on an accelerated life test performed varying both the storage conditions and the getter area. A test vehicle based on a resonator device was used. The hermeticity was evaluated by means of specific leak testing, while MEMS behavior during the ageing test was studied monitoring device functional parameters and by residual gas analysis (RGA). Unexpected results were observed leading to the discovery that methane is pumped by the getter below 100°C. These results served as the inputs of a suitable model allowing extrapolating the device lifetime in operating? conditions, and pointed out that RGA is an essential tool to correctly interpret the aging tests.

Use of non evaporable getter pumps to ensure long term performances of high quantum efficiency photocathodes

High quantum efficiency photocathodes are routinely used as laser triggered emitters in the advanced high brightness electron sources based on radio frequency guns. The sensitivity of “semiconductor” type photocathodes to vacuum levels and gas composition requires special care during preparation and handling. This paper will discuss the results obtained using a novel pumping approach based on coupling a 20 l s−1 sputter ion getter pump with a CapaciTorr® D100 non evaporable getter (NEG) pump. A pressure of 8⋅10−8 Pa was achieved using only a sputter ion pump after a 6 day bake-out. With the addition of a NEG pump, a pressure of 2⋅10−9 Pa was achieved after a 2 day bake-out. These pressure values were maintained without power due to the ability of the NEG to pump gases by chemical reaction. Long term monitoring of cathodes quantum efficiencies was also carried out at different photon wavelengths for more than two years, showing no degradation of the photoemissive film properties.

Fivefold enhancement in stability of organic light-emitting diodes with addition of non-evaporable getter pumps

We demonstrate a significant enhancement of the operational stability of organic light-emitting diodes (OLEDs) by fabricating the devices under ultrahigh-vacuum (UHV) conditions in the region of 10−10–10−11 Torr. The UHV condition is achieved by utilizing non-evaporable getter pumps together with regular turbo molecular pumps in an OLED deposition chamber. The short-term stability of the OLEDs is prolonged fivefold because of the removal of detrimental gases, especially water. We suggest that ultra-clean fabrication conditions are indispensable for revealing the true intrinsic degradation mode of OLEDs. Additionally, we analyze the effect of operating residual gas analyzers during the device fabrication.

Growth of microscopic cones on titanium cathodes of sputter-ion pumps driven by sorption of large argon quantities

Microscopic cones have been observed on titanium cathodes of sputter-ion pumps (SIPs) after pump operation. The cones were studied by means of scanning electron microscopy and energy dispersive x-ray analysis. Size and morphology of these cones are clearly correlated with the nature and the relative amount of each gas species pumped by each SIP during its working life. In particular, their growth was found to be fed by sputtering mechanisms, mostly during Ar pumping, and to be driven by the electromagnetic field applied to the Penning cells of each SIP. Experimental findings suggest that the formation and extent of such conic structures on cathode surfaces might play a leading role in the onset of phenomena typically related to the functioning of SIPs, e.g., the so-called argon instability.