Sang-Ho Seo

Highly and Variably Sensitive Complementary Metal Oxide Semiconductor Active Pixel Sensor Using P-Channel Metal Oxide Semiconductor Field Effect Transistor-Type Photodetector with Transfer Gate

In this paper, a new sensor using a p-channel metal oxide semiconductor field effect transistor (PMOSFET)-type photodetector with a transfer gate has been designed and fabricated by a 0.35 µm standard complementary metal oxide semiconductor (CMOS) process. The photodetector is composed of a floating gate connected to an n-well and a transfer gate. The transfer gate controls photocurrent flow by controlling the barrier for holes in the PMOSFET-type photodetector. The designed photodetector has similar IDS–VDS characteristics to a conventional PMOSFET when the incident light power instead of the gate voltage is varied. A unit pixel that uses this photodetector consists of a PMOSFET-type photodetector with a transfer gate and four n-channel metal oxide semiconductor field effect transistors (NMOSFETs). Its area is 7.2 ×8.1 µm2. It is confirmed that this photodetector, with a high and variable level of sensitivity, could be applied to an image acquisition system at a low illumination level.

Active Pixel Sensor Using a 1?16 Nano-Wire Photodetector Array for Complementary Metal Oxide Semiconductor Imagers

In this paper, a novel photodetector using an N-channel metal oxide semiconductor field effect transistor (NMOSFET) with a 30 nm-wide silicon nano-wire is described. The photodetector was fabricated on silicon-on-insulator (SOI) substrate and its wire was patterned by optical lithography, electron beam lithography and thermal oxidation. At room temperature, the device has similar IDS-VDS characteristics to a general NMOSFET when incident light is supplied instead of the gate voltage. A maximum responsivity of higher than 1×102 A/W and optical transient time of 80 µs have been obtained. Additionally, for the purpose of demonstrating the feasibility of the new device application, a 1×16 complementary metal oxide semiconductor (CMOS) active pixel sensor (APS) connected with the novel photodetector array was also designed and fabricated using 1-poly and 2-metal 1.5 µm CMOS technology. It is confirmed that this photodetector with high sensitivity as well as nano-scaled area could be applied to an image acquisition system for low illumination level.

Dynamic range extension of the n-well/gate-tied PMOSFET-type photodetector with a built-in transfer gate

We have designed and fabricated an active pixel sensor(APS) using an optimized n-well/gate-tied p-channel metal oxide semiconductor field effect transistor(PMOSFET)-type photodetector with a built-in transfer gate. This photodetector has a floating gate connected to n-well and a built-in transfer gate. The photodetector has been optimized by changing the length of the transfer gate. The APS has been fabricated using a 0.35 standard complementary metal oxide semiconductor(CMOS) process. It was confirmed that the proposed APS has a wider dynamic range than the APS using the previously proposed photodetector and a higher sensitivity than the conventional APS using a p-n junction photodiode.

Operation of a wide dynamic range CMOS image sensor based on dual sampling mechanism and its SPICE simulation

In this paper, a dynamic range(DR) extension technique based on a 3-transistor active pixel sensor(APS) and dual image sampling is proposed. The feature of the proposed APS is that the APS uses two or more photodiodes with different sensitivities, such as a high-sensitivity photodiode and a low-sensitivity photodiode. Compared with previously proposed wide DR(WDR) APS, the proposed approach has several advantages, such as no-external equipments or signal processing, no-additional time-requirement for additional charge accumulation, simple operation and adjustable DR extension by controlling parasitic capacitance and sensitivity of two photodiodes. Approximately 16 dB of DR extension was evaluated from the simulation for the situation of 10 times of sensitivity difference and the same size of parasitic capacitance between those two photodiodes.

Dynamic range expansion of active pixel sensor with output voltage feedback

In this paper, a wide dynamic range active pixel sensor(APS) with output voltage feedback structure has been designed by a 2-poly 4-metal 0.35 m standard CMOS technology. We presented a novel APS with output voltage feedback, which exhibits a wide dynamic range. The dynamic range increases at the cost of an additional diode and an additional MOSFET. The output voltage feedback structure enables the control of the output voltage level by itself, as incident light power varies. It is confirmed that the light level which the output voltage level of proposed APS is saturated is about 120,000 lux, which is higher than that of a conventional 3-transistor APS.

Detection of Zearalenone Using a Metal–Oxide–Semiconductor Field-Effect-Transistor-Based Biosensor Employing a Pt Reference Electrode

We have fabricated a metal–oxide–semiconductor field-effect-transistor (MOSFET)-based biosensor for the detection of zearalenone using a standard complementary metal–oxide–semiconductor (CMOS) process. Au was used as the gate metal to immobilize a self-assembled monolayer (SAM) made of mercaptohexadecanoic acid (MHDA). The SAM was used to immobilize anti-zearalenone antibody. The carboxyl group of the SAM was bound to the anti-zearalenone antibody. Anti-zearalenone antibody and zearalenone were bound by an antigen-antibody reaction. The measurements were performed in phosphate buffered saline (PBS; pH 7.4) solution. A Pt electrode was employed as a reference electrode. The gate voltage of the sensor was applied using the Pt reference electrode. The binding of the SAM, anti-zearalenone antibody, and zearalenone caused a variation in the drain current of the MOSFET-based biosensor. To verify the interaction among the SAM, anti-zearalenone antibody, and zearalenone, surface plasmon resonance (SPR) measurements were performed.

Dynamic range improvement of active pixel sensor using charge pump circuit

Wide dynamic range active pixel sensor(APS) using a charge pump circuit has been designed by using 2-poly 4-metal standard CMOS technology. The structure of the proposed APS is similar to the structure of the conventional 3-Tr APS. The proposed unit pixel consists of one photodiode and three MOSFETs. Using a charge pump circuit, the dynamic range of the proposed APS is increased, compared to the conventional 3-Tr APS.

Fabrication of silicon nano-wire MOSFET photodetector for high-sensitivity image sensor

We fabricated Si nano-wire MOSFET by using the conventional photolithography with a resolution. Si nano-wire was fabricated by using reactive ion etching (RIE), anisotropic wet etching and thermal oxidation on a silicon-on-insulator (SOI) substrate, and its width is 30 nm. Logarithmic circuit consisting of a NMOSFET and Si nano-wire MOSFET has been constructed for application to high-sensitivity image sensor. Its sensitivity was 1.12 mV/lux. The output voltage swing was 1.386 V.

A 2-stage CMOS operational amplifier with temperature compensation function for sensor signal processing

In this paper, we designed a 2-stage CMOS operational amplifier with temperature compensation function using 2-poly 4-metal 0.35 m standard CMOS technology. Using two bias circuits, the positive temperature coefficient(PTC) and the negative temperature coefficient(NTC) of the bias circuit are canceled out each other. When reference current circuit is simulated that it has a temperature coefficient of -150 ppm/ with a temperature change from 0 to 120 . Also the proposed circuit has a temperature coefficient of -0.011 dB/ of DC open loop gain with the same temperature range.

PMOSFET-Type Photodetector with High Responsivity for CMOS Image Sensor

In this paper, a new photodetector using a PMOSFET-type photodetector with a transfer gate has been designed and fabricated using a 0.35 mum standard CMOS technology. The photodetector is composed of a floating gate that is tied to an n-well and a transfer gate. The transfer gate controls the photocurrent flow by controlling the barrier for holes in the PMOSFET-type photodetector. The designed photodetector has similar Ids-Vds characteristics as those of a general PMOSFET when the incident light power, instead of the gate voltage, is varied. The area of the proposed photodetector is 3.8 mum times 5.7 mum and the responsivity is larger than 2.7 times 102 AAV at a wavelength of 632.8 nm.