Takumi Yamaguchi

1/4-inch 2-mpixel MOS image sensor with 1.75 transistors/pixel

This paper presents new MOS image sensor technologies that realize ultra-small pixel size, i.e., 2.25/spl times/2.25 /spl mu/m/sup 2/, with high sensitivity and low supply voltage. A 1/4-inch 2-Mpixel MOS image sensor has been developed by a new pixel configuration and by a new pixel design with a 0.25-/spl mu/m CMOS process. In the new pixel configuration, a unit pixel consists of one photodiode (PD), one transfer transistor, and an amplifier circuit with three transistors which are shared by four pixels. As a result, the unit pixel has 1.75 transistors. High sensitivity has been achieved by a high aperture ratio of 25%. In the new pixel design, the low supply voltage of 2.5 V has been realized by optimizing both the potential profile in the PD and the gate length of the transfer transistor.

A 2.0-/spl mu/m pixel pitch MOS image sensor with 1.5 transistor/pixel and an amorphous Si color filter

In this paper, an ultrafine pixel size (2.0/spl times/2.0 /spl mu/m/sup 2/) MOS image sensor with very high sensitivity is developed. The key technologies that realize the MOS image sensor are a newly developed pixel circuit configuration (1.5 transistor/pixel), a fine 0.15-/spl mu/m design rule, and an amorphous Si color filter (Si-CF). In the new pixel circuit configuration, a unit pixel consists of one photodiode, one transfer transistor, and an amplifier circuit with two transistors that are shared by four neighboring pixels. Thus, the unit pixel has only 1.5 transistors. The fine design rule of 0.15 /spl mu/m enables reduction of wiring area by 40%. As a result, a high aperture ratio of 30% is achieved. A newly developed Si-CF realizes the 1/10 thickness of that of the conventional organic-pigment CF, giving rise to high light-collection efficiency. With these three technologies combined, a high sensitivity of 3400 electrons/lx/spl middot/s is achieved even with a pixel size of 2.0/spl times/2.0 /spl mu/m/sup 2/.

A 1/4in 2M pixel CMOS image sensor with 1.75 transistor/pixel

A 2.5V CMOS image sensor using a pixel configuration of four photodiodes in one unit sharing seven transistors is presented. This image achieves a 2.25/spl mu/m pixel pitch with 25% aperture ratio in a 0.25/spl mu/m IP2M CMOS process.

Degradation-free MOS image sensor with photonic crystal color filter

This letter demonstrates a long-term reliable MOS image sensor equipped with a novel photonic crystal color filter (PC-CF). PCs are periodically structured dielectric media, generally possessing a photonic band gap. In the newly developed PC-CF, it is clarified that the desirable spectral property, i.e., peak wavelength and spectral passband, can be achieved by modifying the thicknesses of the defect layers, which act just like a defect in a PC. The spectral characteristics with the peak wavelengths at 450 (blue), at 530 (green), and at 610 nm (red) are realized in this letter. Moreover, the fabricated image sensor guarantees high reliability of longer than 200 000 h and heat resistance of above 300 /spl deg/C.

A 2.0 /spl mu/m pixel pitch MOS image sensor with an amorphous Si film color filter

A CMOS image sensor with an amorphous Si film color filter is implemented on a standard Si process. The color filter thickness is less than 100 nm. The sensor achieves a 30% aperture ratio by a 1.5 transistor/pixel architecture and a 0.15 /spl mu/m design rule.

A MOS Image Sensor with Microlenses Built by Sub-Wavelength Patterning

A MOS image sensor has digital-microlenses implemented by sub-wavelength patterning of concentric SiO2 ring walls. The sensitivity at the periphery of the imager is 3000e-/1x-s. In comparison, the sensitivity at the periphery of a conventional imager is 1300e/1x-s. Thus, extremely uniform brightness throughout the reproduced image is demonstrated even with an angle of incidence > 45deg.

Solid State Imaging Techniques. A 1/4-inch High-resolution CCD Image Sensor with Electronic Image Stabilizing Function.

A 1/4-inch format 560 k pixel IT-CCD image sensor was developed with a high-resolution electronic image stabilizing system that uses a driving method and novel process technology. The new pixel design, process, and on-chip color filter technology keeps almost the same characteristics as the conventional 1/3-inch format 360 k pixel IT-CCD image sensor, in spite of the new sensors reduced pixel-size.