This study presents a novel gas bio-sensor in the form of a micro-machined resonator and its readout circuit. The resonator has the structure of a clamped-clamped beam with thermal actuation and piezo-resistive sensing that supports a plate capable of being attached with test gas molecules to detect gas concentration. The purpose of this study is to design and fabricate the micro-scaled inertial beam with its readout circuit in a system-on-chip package. The circuit includes a driver, a front-end converter, a feed-trough reduction unit, a square-wave converter and a phase detector. In the process of signal reading, the sensor is first driven by a DDS module and power amplifier, and then sense the vibrations by piezo-resistivity. The piezo-resistivity is detected by a Wheatstone bridge circuits. The carried signal of modulation is processed by a Wheatstone bridge circuits. An instrumentation amplifier adjusts the gain to the appropriate amplitude. The circuit with reduction on feed-through noise increases the SNR. Square wave conversion circuit and PFD process the signal and the driver reference signal to detect phase difference. The data of phase difference is counted into a microcontroller dsPIC4011 and then the data being transmitted to the computer by RS232 to a USB adapter. Finally, the whole circuit is implemented by using TSMC 0.35 2P4M process and one-step postprocessing.

No abstract

This study aims to develop a novel CMOS-MEMS logic gate via commercially available CMOS process (TSMC, 2P4M ). Compared to existing CMOS MEMS designs, which uses foundry processes, the proposed design imposes several new challenges including: carrying two voltage levels on a non-warping suspended plate, metalto-metal contact, and etc. Different combinations of oxide-metal films and post-CMOS process are investigated to achieve a non-warping suspended structure layer. And different wet etchants are investigated to remove sacrificial layers without attacking structure layers and features. In a prototype design, the selected structure layer is metal-3 and oxide film; the device is released using AD-10 and titanium etchant; the device is 250 μm long, 100 μm wide, and 1.5 μm gap. The experimental results show that the suspended plate slightly curls down 0.485 μm. This device can be actuated by 10/0 V with a moving distance 50nm. The resonant frequency is measured at 36 kHz. Due to the damage of the tungsten plugs, the logic function can only be verified by its mechanical movements instead of electrical readouts for now.

No abstract

A CMOS temperature sensor with a highly linear proportional-to-absolute-temperature (PTAT) output current is presented. A common-source circuit with a source-degeneration poly-crystalline silicon (Poly-Si) resistor is biased by a PTAT voltage generator. The current flowing through the resistor exhibits a PTAT characteristic with high linearity of 99.999% at least for a temperature range from 0 to 125ºC. The PTAT gate voltage can be adjusted by a bias voltage V b and hence the PTAT current can also be adjusted. The PTAT current is mirrored to an added current controlled oscillator which output pulse frequencies have also a PTAT characteristic. Under the V b of 1V and 1.13V, the plots of measured pulse frequencies against temperature exhibit the sensitivity of 2.30 and 2.28 kHz/ºC or so with linearity up to 99.994% and 99.993%, respectively.