Strategies for Defect-Free and Deep Wet Etching of Pyrex 7740

In this paper, two aspects in the wet glass etching, the pre-annealing of the glass and the mask process, are taken into consideration to achieve the deep and defect-free wet etching of Pyrex glass. Compared with the conventional strategies, i.e.,HFsolution component and mask kinds, our experiment results prove the pre-annealing is another key role to obtain theoretical isotropy character in wet etching. Besides, the high temperature pre-annealing dramatically improves the structure profiles and reduces the notching defects. Additionally, a novel multilayer mask process is proposed. With 1.5μmPR/ 100nmAu/ 100 nmAu/ 20 nmCrmask and > 450 °C pre-annealing, > 150 μm deep and non-pin-holes Pyrex glass structures are achieved and the roughness of etched surface is lower than 1 nm.

The Design and Implementation of High Pressure Rectangular Diaphragm Sensor Based on MEMS Technology

This paper describes the design and fabrication of a piezoresistive high-pressure rectangular sensor which will be used in the petrochemical industry field. The stress distribution of the piezoresistance on the membrane was analyzed by the Finite Element Method through the ANSYS software. The piezoresistance was fabricated on SOI wafers by the MEMS bulk-micromachining technology and the silicon substrate was bonded with the Pyrex 7740# glass by the anodic bonding technology. The linearity, sensitivity, repeatability and accuracy of the fabricated result were 0.3%, 1.109mV/MPa, 0.41% and 0.57%, respectively. This type of microstructure sensor has advantages of high sensitivity, linearity and accuracy. Meanwhile, the sensor has a wide measurement range because of the rectangular membrane. The piezorsistive high pressure rectangular diaphragm sensor offers several advantages such as, high sensitivity, linearity and accuracy, and additionally, the wide measurement range of the sensor will guarantee its great applications in the petrochemical industry fields.

Gas Permeation in Polydimethylsiloxane In Situ Monitoring by Silicon Pressure Sensors

This paper proposes a new way to detect the gas-leakage through PDMS. We use PDMS instead of Pyrex #7740 glass to seal the backside V-grooves of silicon pressure sensors. We put the packaged sensor into a pressurized chamber with CO2 at 300 psi. By observing the output voltage of the pressure sensor, the time history for CO2 permeating into the sensor cavity was easily found. In experiments, we use several PDMS membranes with different thickness, from 45 to 2000 μm, to package the pressure sensors and investigate the gas-leakage of PDMS. The gas leaking through PDMS is shown to be governed by diffusion mechanism, and the diffusion coefficients derived from CO2 leaking history is 2.2×10-9 m2/sec, matched with the previous work.

A Bulk Micromachined Si-on-Glass Tunneling Accelerometer

A bulk micromachined tunneling accelerometer on Pyrex 7740 substrate is reported in this paper, which is intended for the applications in highly sensitive inertia measurements, such as those in microgravity environments and self-contained navigation. The tunneling tip is defined by an isotropic wet etching followed by a maskless wet thermal oxidation for the sharpening of the tip. Unlike the process ever reported by other facilities, an ICP etching on the side of the Si wafer with the tip is utilized to partially define the suspension and the proof mass before the anodic bonding of the Si wafer with the glass substrate, and an addition maskless ICP etching is used to release the whole movable structure after the bonding. Fabricated samples have displayed the effectiveness of the process proposed, which is relatively simple and may guarantee the yield of mass production. The theoretical analysis and design of the closed loop architecture of the device are demonstrated. Capable of sensing out-of-plane acceleration, this device has demonstrated a high resolution of 0.015mg/rtHz (@ 1∼100Hz) and a nonlinearity of less than 1% over ±1g input range.