Solid State Imaging Techniques. On-chip Inner-Layer Lens Technology for an Improvement in Photo-sensitive Characteristics of a CCD Image Sensor.

An on-chip inner-layer lens has been developed to improve the photo-sensitivity and smear of CCD image sensors. The inner-layer lens structure consists of a boron-phospho-silicate-glass (BPSG) layer and a heat melting transparent resin. The refractive indices for the inner-layer lens was higher than the BPSG layer and the planarization layer. Taking the incident angle into account, we have applied a new three dimentional simulation to the inner-layer lens to investigate the optical pass. We fabricate a 1/4-type IT-CCD image sensor with an inner-layer lens. This fabricated results of an image sensor has been explained well by the new three dimentional optical simulation. The increase of photo-sensitivity using the inner-layer lens technology is 16% without deterioration in the CCD characteristics. Furthermore using the inner-layer lens reduces the smear value by 70%.