Design and Evaluation of Filterless RGB Sensor on Standard CMOS Process

Abstract

In this study, a color detection phenomenon that does not utilize color filters is evaluated via the standard CMOS process. The device comprises multiple pn-junctions stacked in the depth direction, which enable division of the light responses by different light absorptions with respect to wavelength. To eliminate the color filters, we use rectifiers to cut the reverse currents corresponding to the long-wavelength infrared (Ir) regions. Numerical simulations predict the dynamic range of the sensor as 160 dB after removal of the filters that can decrease this value. Applications based on the Internet of Things can be realized via mass production at low cost by eliminating the additional processes required to form the conventional color filters in front of the sensor. We evaluate the proposed device by both numerical simulation and experiment as well as clarify that the sensing phenomenon requires sufficient PWell thickness to separate the depletion regions for successful operation. The appropriate process parameters for the CMOS process are revealed, providing useful information for testing under a wide range of process conditions.

Bulk Carrier Contaminations and Their Effects on MOSFETs Under Energy Harvesting Systems

“…We defined d as the horizontal length between the illumination window and the transistor device location, and the generated carriers reached the transistor after undergoing d-length carrier transport. Quasi-stationary The standard CMOS process parameters are not the same as those of previous studies [20], [21]; however, this study reveals the effects of BCC on transistors, and therefore, these variations do not affect our evaluation. Additionally, the standard CMOS process parameters completely differ among various fabrication processes.…”

Standard CMOS Process Integrated Silicon-Based Ultraviolet-Infrared Complementary Sensor

“…The Ir sensing is based on RGB sensing scheme and eliminating the visible light response. Figure 5 shows the wavelength responses of current differences with 0.18 µm and 45 nm CMOS processes with the expansion of the reverse current region from the study on RGB sensor [12]. Considering the reverse current, the peaks moved to the Ir region, approximately 900-1,000 nm region, that is suitable for Ir sensing.…”

“…As we discussed in the previous work of RGB sensing [12], the sensor design must ensure the carrier separations by the multi-well structure. Too thin well thicknesses or too light doping induce the penetration of the depletion regions and generated carriers will pass through to the substrate region which this brings the malfunction.…”

“…The dynamic range is the important factor in sensing, and Fig. 7 shows every five colors of UV, Ir and RGB (from the previous work [12]) for each 0.18 µm and 45 nm CMOS process, respectively. The same high dynamic ranges of 160 dB are ensured both to UV and Ir which provide the high performances for sensing.…”

“…Recently, Si-based Ir sensor employing organic materials was proposed [11], which implies that Ir sensing with silicon-only technology without any filters remains challenging. A previous study proposed an RGB sensor designed using the standard CMOS process without any filters [12]. The concept of the sensor was based on utilizing the integration into an LSI block that provided several electronics devices with the same substrate.…”