The investigation of Casimir force using micromachined structures

Casimir force is one of the elusive forces in nature. Most of the experimental efforts to estimate the Casimir force were not successful. The successful experiments were affected by the artifacts and the anomalies This work explores a novel platform to investigate the Casimir force.;The fabrication process development of the MEMS chip required eight masks. It was implemented on glass and SOI substrates. The glass substrate provides the fixed plate whereas the DRIE structures released in the SOI substrate provide the moveable plate. Electroplated gold posts on the glass substrate define the initial gap between the plates. Thermocompression flip chip bonding of the glass and SOI chips was performed in order to obtain a single chip parallel plate MEMS device.;The micromachined structures were characterized using AFM in order to estimate the spring constant. Capacitance measurements of the electrostatic actuators have shown the dissimilar behavior of the electrostatic actuators. Further, optical interferometry measurements have shown the tilt in the moveable plate thereby making the non viability of the parallel plate geometry for the Casimir force measurements.;An alternate method to estimate the Casimir force in the parallel plate geometry was also implemented. For this purpose, a one mask process step was implemented on the SOI wafers with different buried oxide thicknesses. Parallel silicon boundaries with different gaps were obtained by the removal of the buried oxides using anhydrous HF vapor. After the buried oxide etch, the dynamic behavior of the 200 mum thick silicon device layer was observed. It was concluded that, at 40 nm gap, electrostatic repulsive forces arising from the H+ terminated parallel silicon boundaries was more when compared to the Casimir force.;A novel microelectromechanical systems (MEMS) device to estimate the Casimir force between the parallel boundaries was developed. The device has a fixed gold plate and a moveable silicon plate with the sputtered gold. The moveable plate is supported by the separate electrostatic actuators which control the gap between the plates. Mathematical analysis of the device has shown that a measureable capacitance shift can be obtained due to the Casimir force. Results from the electromechanical simulations show that the moveable plate is parallel to the fixed plate even under 1mum separation.;Stiction observed at 13 nm gap between the parallel silicon boundaries is attributed to the combination of the Casimir force and the electrostatic force. However, no stiction was observed at 40 nm gap. This is due to the electrostatic repulsive force.