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This paper presents a MEMS Resonant Pressure Transducers (RPT) that is produced using a flexible fabrication route to allow pressure ranges from 1bar to 700bar in fully oil isolated hermetic packages without compromising sensor performance. The fabrication method makes use of silicon fusion bonding (SFB) and deep reactive ion etching (DRIE) to build up a three-layer die, with the middle layer consisting of a strain sensitive resonator. The key aspects of the fabrication process and sensor design that make this possible are presented, along with data showing long-term stability of better than 100ppm drift per year.

To support the manufacture of complex products made of multiple micro-parts, a traceable and accurate 3D-measurement system with sub-micron accuracy is required. This paper investigates the use of a micro electro mechanical system (MEMS) tactile-micro-probe for 3D-coordinate metrology on the micro-scale. It will show that probe-tip contamination may be a significant source of error for such tactile-probing systems. Even in a clean-room environment, there are many types of contaminants that may affect dimensional measurement accuracy. These mainly come from repeated contact between probe tip and artefact material. To address this issue a number of cleaning methods were utilized to remove contaminants from the MEMS tactile-micro-probe sensor. Scanning electron microscopy was used to assess the efficacy of each cleaning method. Initial findings on different cleaning methods including ultrasonic, plasma, micro-beam melting, electron beam melting and cryogenic cleaning have shown that the latter is a feasible process.

When designing micro-scale tactile probes, a design trade-off must be made between the stiffness and flexibility of the probing element. The probe must be flexible enough to ensure sensitive parts are not damaged during contact, but it must be stiff enough to overcome attractive surface forces, ensure it is not excessively fragile, easily damaged or sensitive to inertial loads. To address the need for a probing element that is both flexible and stiff, a novel micro-scale tactile probe has been designed and tested that makes use of an active suspension structure. The suspension structure is used to modulate the probe stiffness as required to ensure optimal stiffness conditions for each phase of the measurement process. In this paper, a novel control system is presented that monitors and controls stiffness, allowing two probe stiffness values (“stiff” and “flexible”) to be defined and switched between. During switching, the stylus tip undergoes a displacement of approximately 18 µm, however, the control system is able ensure a consistent flexible mode tip deflection to within 12 nm in the vertical axis. The overall uncertainty for three-dimensional displacement measurements using the probing system is estimated to be 58 nm, which demonstrates the potential of this innovative variable stiffness micro-scale probe system.