Three-dimensional integrated sensors

Integration of sensing devices and associated signal processing devices is a way to intelligent sensors, and great efforts have so far been devoted in this direction. The sensing organs in animals are the most sophisticated intelligent sensors and have to be learnt. Most sensing organs in animal are of three-dimensional structure, a retina being the typical, in which signals from the receptor cells are most effectively and efficiently processed. The new challenge is to make an artificial retina with three-dimensional integrated circuits, where thousands of elements are integrated not only on a plane but also in the depth direction. Three-dimensional ICs have vertical connections between elements on each level, rather like the elevators or escalators in a building. In this paper, outline of the research and recent technical achievements are introduced and future prospect is discussed.