Papers by Author: Shu Jung Chen

Abstract: This paper proposes a new vacuum sensor with CMOS Metal-N-Poly thermoelectric materials which works for both thermoelectric sensing and resistive heating. A new method of vacuum measurement with self-heating is proposed based on the dual phases of heating and sensing for the same element which is realized with CMOS thermoelectric sensor. Using the TSMC 0.35 μm CMOS-MEMS process, the proposed thermoelectric sensor is designed and fabricated with standard CMOS materials of the 4th metal and N-polysilicon to form 64 pairs of central-symmetrical thermocouples. There is an air convection-sensing area at the center of membrane and is filled with array of micro-through-holes to enhance the effect of heat convection. When the air molecules move through the array of hole, the heat exchange will take away the heat to cause a temperature drop of sensing area which gives a weak voltage between the cold and hot end of the thermocouples. The heating of thermopile itself is designed at the first phase and sensing the output voltage at the second phase subsequently. According to a careful investigation of the measurement with a wide range of 10m~10k torr, our proposed sensing scheme based on a thermoelectric type sensor is proved for practical vacuum detection and most of all it is proved as a new approach to use a commercial thermopile without heater, which is easier to include than a special custom design.

Abstract: A new modified infrared tracking sensor array with spatial filter is proposed, which identifies the locations and sizes of thermal object efficiently with the winner-take-all (WTA) circuit and a low offset correlated double sampling (CDS) circuit. The winner-take-all (WTA) circuit is used in combination with active readout circuit for thermopile array. In this circuit, thermal image intensity has been chosen for the input saliency map. The removal process is performed by zeroing the values of the thermal image background intensity levels, so only the potential thermal objects of interest are compared by the WTA. The offset reduction with CDS technique enhances the sensitivity of winner-take-all (WTA) circuit and shows a sharp selectivity which makes it possible to pick up only one winner pixel from each thermal object. In order to simulate and present the infrared thermal sensor array in this paper, the sensor array is integrated by using a 2P4M 0.35μm standard CMOS technology. This proposed architecture shows a high resolution with two orders higher than the circuits without CDS. The results have shown that integrated thermopile array with WTA and CDS can approach a high level of development, reliability and easy for high accuracy infrared tracking applications.

Abstract: A new idea of improving complementary metal-oxide-semiconductor (CMOS) thermopile performance is introduced to reduce the thermal conductance by leading the microcracks into structure of thermopile, which greatly increases the heat flow barrier. A highly sensitive infrared detector requires a low thermal conductance to maximize the temperature change and signal induced by incident IR radiation. Several designs of infrared microsensors are proposed to study influential parameters from microcrack for improving performance of thermopile. To that end, by using some adequate designs of polysilicon architecture, we can greatly reduce the heat flow from the main stream without introducing further electric resistance, which is related with noise. Firstly we develop such a structure of thermopile with low thermal conductance and high performance by using CMOS compatible process which can be easily and exactly fabricated. The suspended structure of infrared sensors is used in this study to provide ideal, thermally isolated, structures for support of the thin film detector. We also simulate the heat flow of the new structures. The results show good match with our original idea.

Abstract: A new modified CMOS buffer amplifier with rail-to-rail input and output range is proposed by TSMC 0.35μm 2P4M process at 3.3V supply. The technique adds dummy pairs to sense the common mode range of the input differential pair and adjusts the output current accordingly. The amplifier provides high gain for a wider range of output voltages. Design considerations for reducing the impact of the additional circuitry on the core are provided. The technique described can be adapted for use with traditional fully-differential rail-to-rail amplifiers, which performs 86.9dB ~92dB dc gain, 15 MHz unit-gain bandwidth, high driving ability with high slew rate under a 100pF capacitance and a 3kΩ series resistance loading. The simulation results indicate that the settling times of rising and falling edge are within 3.5μs. It is effective for a high resolution and high speed LCD driver.

Abstract: Conventionally the accelerometer behaves like a spring – mass system and its structures involve solid proof mass, which is allowed to move under acceleration conditions. In this paper, we design and fabrication a novel thermal-bubble-based micromachined accelerometer with advantages of minimum solid thermal conductance and high sensitivity successfully. The proposed accelerometer based on thermal convection creates a tiny heated air bubble hermetically sealed inside the sensor package cavity. Four thermopiles around the center heater serve as the temperature sensors to detect two-dimension motion of the chip and also are adequately applied to the technology of inclinometers, anemometers and flow meters. A new micro-link structure is also proposed to enhance the construction of accelerometer with the micro heater and two pairs of thermopiles floating over an etched cavity. The heater and the thermopiles are connected by network-like structure of micro-links, which enhance the structure and greatly reduce the solid heat flow from the heater to the hot junctions of thermopiles. The samples are fabricated by TSMC 0.35μm 2P4M CMOS process which is provided by CIC with outstanding strong structures and uniform quality. Our design is proved to be adequate for commercial batch production. We measure the output signal by inclining the sensor to evaluate the performance of this accelerometer.