Dark Current and Clock-Induced Charges in a Fully Depleted Charge Domain CDTI-Based CCD-on-CMOS Image Sensor

The charge-coupled device (CCD) is an essential image sensor for spaceborne scientific applications, high-resolution Earth observation, and low-light imaging due its charge transfer feature yielding intrinsically a high dynamic range. To create a high-performance image sensor that can integrate with CMOS technology, a new design of CCDs using advanced CMOS manufacturing has been developed. In this article, a charge domain fully depleted CCD-on-CMOS image sensor built with capacitive deep trench isolation (CDTI) is described and characterized. Dark current and clock-induced charges (CICs) are investigated through their dependence on operational parameters, such as biasing, clocking, and temperature. The contributions of each charge generation source are separated, identified, and quantified to provide an accurate depiction of the device behavior in multipinned phase (MPP) charge transfer mode. In the light of the physical phenomena at play, involving interface state charge generation and impact ionization, an optimization on the device's clocking is proposed as the best trade-off on CICs and dark current. Perspectives aiming at further enlarging the applicative field of this image sensor are discussed.