Industrial CMOS technology for the integration of optical metrology systems (photo-ASICs)

Abstract

With ‘photo-ASICs’ comprising light-sensitive structures, light-emitting devices and analog and digital circuits, complete optical metrology systems can be integrated on a single chip. We report the realization of key components of such photo-ASICs using an industrual IC CMOS process. We achieve photodiodes with an external quantum efficiency of 50–80% in the visible spectrum and position-sensitive devices (PSDs) with a spatial non-linearity of around 0.3%. We demonstrate surface-channel CCDs with a charge-transfer efficiency of 99.8% at room temperature, as well as bucket-brigade devices (BBDs) with a lower charge-transfer efficiency of 96%. Light-emitting diodes (LEDs) are realized, emitting infrared light at 1160 nm (forward biased) and broadband visible yellow light with a spectral maximum at 640 nm (reverse biased). We discuss simple applications of passive photo-ASICs, such as a centroid detector, a 3-D camera, a motion detector and a focus sensor, used to obtain a relative measure for the local focus of an optically imaged scene, for example, in a photographic camera.