Giora Yahav

A Fast-Gated CMOS Image Sensor With a Vertical Overflow Drain Shutter Mechanism

This paper presents a fast-gated CMOS image sensor (CIS) with a vertical overflow drain (VOD) shutter mechanism. The prototype imager includes two novel features: 1) the adaptation of the VOD shutter structure into a 0.18-μm CIS process and 2) the application of the VOD shutter for the purposes of time-resolved imaging with down to 5-ns pulsewidth. A 360-pixel × 180-pixel array with several 5.4-μm × 5.4-μm pixel types was implemented and tested, demonstrating 2-ns shutter rise/fall times and the 1:20 shutter contrast ratio for 850-nm pulsed illumination. These parameters, together with the uniformity of the shutter and the large full-well capacity of the pixel, are on par with the state-of-the-art of indirect time-of-flight and time-resolved imagers. The device structure and the special mode of operation that enables a fast gating are studied through the TCAD simulations and experimental results. Important design features that affect the pixel performance are illustrated in detail.

Development of a ToF Pixel With VOD Shutter Mechanism, High IR QE, Four Storages, and CDS

In this paper we discuss the development of an indirect time-of-flight (ToF) pixel in the 0.11-μm CMOS image sensor technology. The pixel design is based on a pinned-photodiode structure with a novel vertical overflow drain (VOD) shutter mechanism used for fast modulation. We present the second generation of the pixel, with a greatly improved VOD structure that enables a fast shutter efficiency better than 1:100 and a deeper photodiode collection depth for better quantum efficiency in the near-infrared wavelengths. We present a new 6.7-μm pixel design with four pinned storage diodes (SDs) that feature in-pixel complete charge transfer and enable correlated-double-sampling readout as well as an almost simultaneous global shutter exposure of up to four interleaved frames to be used for the scene depth computation. The novel design features a low readout noise of 7.5e-and a full-well-capacity of 9500eper SD (a total of 38000eper pixel).

Dynamic Multispectral Imaging Using the Vertical Overflow Drain Structure

Multispectral imaging enables discrimination of spectra beyond the 3-D spectral space of human vision. Most multispectral systems are complex and bulky, and simpler monolithic designs usually require several pixels in order to generate one multispectral data point. Here, we use the vertical overflow drain (VOD) structure to enable monolithic multispectral imaging in a single pixel. We show that by controlling the substrate bias voltage it is possible to change the effective depth of the photodiode, thus enabling dynamic tuning of the pixels spectral response. A small voltage change (<;5 V) is shown experimentally to reduce the red light quantum efficiency by ~ 40 %, while the blue light quantum efficiency is reduced by <;10%. Using this effect, we demonstrate an ability to discriminate between different monochromatic illumination sources with 20-nm spectral resolution in a single pixel. In addition, we present an RGB image taken using an off-the-shelf charge coupled devices with no color filters by relying solely on the VOD mechanism. Finally, we present process and device simulations suggesting that this mechanism can be implemented in any pinned photodiode pixel with a VOD barrier, including in CMOS image sensors fabricated on n-type starting material.