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.
One of present EUVL challenges is to reduce as much as possible the organic compounds and water partial pressures
during the lithographic process.
These gases can in fact interact with sensitive surfaces and, in the presence of EUV radiation, decompose to generate
carbon-based films and oxides, which are detrimental to the optics, reducing its performance, lifetime and significantly
increasing the equipment total cost of ownership.
With this respect, use of Non Evaporable Getter (NEG) pumps seems particularly attractive. Getter pumps are very
clean, vibration-free, compact, able to deliver large pumping speed for all active gases, including water and hydrogen.
In the present paper, we report for the first time the results of specific tests aimed at measuring the pumping speed for
some selected organic compounds, namely toluene and decane (n-decane). The study shows that getter pumps can
effectively sorb these large organic molecules with high speed and capacity. Speed and capacity increases when
operating the getter cartridge at moderate temperature (e.g. 150-200°C), however remarkable sorption is achieved, even
at room temperature, without any power applied. When coupled with turbo-molecular pumps NEG pumps have therefore
the potential to improve the ultimate vacuum and mitigate the carbon/oxygen contamination in a UHV lithographic
In many MEMS applications the level of vacuum is a key issue as it directly affects the quality of the device, in terms
of response reliability. Due to the unavoidable desorption phenomena of gaseous species from the internal surfaces, the
vacuum inside a MEMS, after bonding encapsulation, tends to be degraded, unless a proper getter solution is applied.
The in situ getter film (PaGeWafer®) is recognised to be the most reliable way to get rid of degassed species, assuring
uniform, high quality performances of the device throughout the lifetime. Moreover, post process vacuum quality control
and reliability for hermetic bonding is extremely important for overall device reliability and process yield. In this paper
we will discuss the main factors that are critical in the attainment of vacuum and will present a novel calculation model
that enables the prediction of vacuum level after bonding, making also possible the estimate of the lifetime. Furthermore,
a new analytical method based on the residual gas analyses (RGA) will be presented that gives the main characteristics
of the materials. Modeling and simulation work support the process optimization and system design.
The need to reach high and stable values of the Q-factor is one of the most important issues of resonant MEMS in order to make high-performance sensors. The Q-factor is strongly influenced by the internal environment of the MEMS packaging, by total pressure and by gas composition. The most experienced and technically accepted way to keep the atmosphere stable in a hermetically sealed device is to use a getter material that is able to chemically absorb active gases under vacuum or in inert gas atmosphere for the lifetime of the devices. MEMS hermetically bonded devices such as gyroscopes, accelerometers, pressure and flow sensors, IR sensors, RF-MEMS and optical mirrors requires getter thin film solutions to work properly. Getter technical solution for wafer to wafer hermetically bonded MEMS systems is PaGeWafer, a silicon, glass or ceramic wafer ("cap wafer") with patterned getter film, few microns thick. In this paper, first the theoretical evaluation of Q-factor of a MEMS resonant structure in presence of a getter film is investigated and compared to the results of a Residual Gas Analysis of the same MEMS resonant structure and with the conventional measurement of Q-factor. Using getter thin film technology, total pressures down to 10<sup>-4</sup> mbar with corresponding high and stable Q-factors have been achieved in MEMS resonant structures. We were therefore able to confirm that getter films can provide high Q-values, stability of sensor signal, performances stability during the lifetime, removal of dangerous gases like H<sub>2</sub> and H<sub>2</sub>O in hermetically sealed MEMS resonant structures.