Yuki Maruyama

A Time-Resolved, Low-Noise Single-Photon Image Sensor Fabricated in Deep-Submicron CMOS Technology

We report on the design and characterization of a novel time-resolved image sensor fabricated in a 130 nm CMOS process. Each pixel within the 3232 pixel array contains a low-noise single-photon detector and a high-precision time-to-digital converter (TDC). The 10-bit TDC exhibits a timing resolution of 119 ps with a timing uniformity across the entire array of less than 2 LSBs. The differential non-linearity (DNL) and integral non-linearity (INL) were measured at ±0.4 and ±1.2 LSBs, respectively. The pixel array was fabricated with a pitch of 50 μm in both directions and with a total TDC area of less than 2000 μm2. The target application for this sensor is time-resolved imaging, in particular fluorescence lifetime imaging microscopy and 3D imaging. The characterization shows the suitability of the proposed sensor technology for these applications.

A novel filterless fluorescence detection sensor for DNA analysis

A new method is presented of on-chip optical spectroscopy, functioning without the need for a bandpass filter or grating. The principle of optical spectroscopy is based on the difference of optical absorption coefficients with wavelength. The optical intensity is calculated from the different penetration depths in Si. The key to the new spectrometer is the use of a photogate active pixel providing the selective control of photo-generated charge using the gate voltage. To demonstrate this spectrometer, a novel filterless fluorescence detection sensor has been fabricated in our laboratory, using standard 5-/spl mu/m CMOS silicon integrated circuit technology. The SYBR-Green label fluoresces at 520 nm when exited by 470-nm radiation. In a simulation experiment using two LEDs, the fluorescent intensity detected was 1/300 of the excitation light intensity (intensity of fluorescence was 1 /spl mu/W/cm/sup 2/, while the excitation illumination was 300 /spl mu/W/cm/sup 2/). In an experiment using actual DNA solution containing SYBR-Green, it was confirmed that the fluorescence detection sensor successfully detected the fluorescent label without the need for a filter.

Label free CMOS DNA image sensor based on the charge transfer technique

This paper describes a label free and fully electronic 32x32 CMOS DNA image sensor fabricated in a 1-poly 1-metal CMOS technology, suitable for inexpensive and highly integrated applications. The pixel operates using the charge transfer technique. DNA immobilization and hybridization on the silane-coated surface are detected, as well as variations in the silane coating. Significant output voltages of 76.4+/-16.5 mV and 64.5+/-15.7 mV were measured after immobilization and hybridization of DNA molecules containing 22 bases. From these results, the immobilized and hybridized DNA densities were estimated. These were 6.3+/-1.4x10(8) cm(-2) and 5.3+/-1.3x10(8) cm(-2), respectively. The DNA detection limit was calculated to be approximately 2.7x10(7) cm(-2) molecules (22 bases). Thanks to its potentiometric detectability, the DNA immobilization and hybridization was successfully verified.

Photon-Counting Arrays for Time-Resolved Imaging

The paper presents a camera comprising 512 × 128 pixels capable of single-photon detection and gating with a maximum frame rate of 156 kfps. The photon capture is performed through a gated single-photon avalanche diode that generates a digital pulse upon photon detection and through a digital one-bit counter. Gray levels are obtained through multiple counting and accumulation, while time-resolved imaging is achieved through a 4-ns gating window controlled with subnanosecond accuracy by a field-programmable gate array. The sensor, which is equipped with microlenses to enhance its effective fill factor, was electro-optically characterized in terms of sensitivity and uniformity. Several examples of capture of fast events are shown to demonstrate the suitability of the approach.

Multiwavelength Photosensor for On-Chip Real-Time Monitoring of Fluorescence and Turbidity

In this paper, we report simultaneous detection of fluorescence and turbidity using a multiwavelength photosensor. The multiwavelength photosensor is fabricated in a 5 µm 1-poly 1-metal p-well complementary metal oxide semiconductor (CMOS) technology. First, to confirm the basic characteristics of the multiwavelength photosensor, the linearity of irradiated intensity and photocurrent, fluorescence detection capability, and turbidity detection capability were separately observed. Then, in the fluorescence detection measurement using a fluorescent dye, a detection limit of DNA concentration of 49.8 nM was determined. Then, the turbidity detection performance was compared with that of a Si photodiode. Finally, the sensor was used for real-time monitoring of DNA amplification using the loop-mediated isothermal amplification (LAMP) method. Owing to its multiwavelength detection, simultaneous changes in fluorescence and turbidity were successfully observed using a single sensor.

A Wide Dynamic Range Photogate-Type Active Pixel Sensor Using a Self-Regulation Principle

A wide dynamic range photogate-type active pixel image sensor based on a self-regulation principle is reported. A 5 ×5 element prototype sensor was fabricated using a 5 µm single-poly, single-metal negative channel metal oxide semiconductor (NMOS) silicon integrated circuit technology. The key techniques are based on the feedback of a floating diffusion (FD) potential to the photogate applied voltage and on the control of the sub-threshold characteristic of the photogate using an ion implantation process. The proposed sensor makes it possible to automatically adjust the sensitivity of each pixel using only three transistors. The conversion of the irradiated light to the output voltage is linear under low-light conditions, while it is nonlinear under bright light. The photo-electric conversion characteristics are similar to those of a linear-logarithmic image sensor. The dynamic range can be expanded without the need for an additional capacitor, an analog-to-digital (A/D) converter or any complex circuitry. Compared with a conventional photogate-type image sensor that was fabricated on the same chip, the dynamic range was expanded by 28 dB.

On - Chip Multi Wavelength Detection Sensor for Real Time Monitoring of Fluorescence and Opacity

In this paper simultaneous detection of fluorescence and turbidity using on-chip multi wavelength detection sensor was reported. The sensor was fabricated in 5 mum, single-poly, double-metal, p-well CMOS technology. At first, the capability of fluorescence and turbidity were confirmed. In the experiment of fluorescence detection, concentrations down to 37.5 nM have reliably been measured. In the experiment of turbidity detection, the comparable results with Si photodiode were detected. Finally, the sensor was applied for real time monitoring of a loop-mediated isothermal amplification method (LAMP). The fluorescence and turbidity change were successfully observed.