A 1024 element linear CCD sensor with a new photodiode structure

Abstract

Recently, interest in silicon sensors has been increasing for facsimile reader, optical character recognition and other page scanning applications, because of its reliability and low cost. There are two types of Si imaging sensors, an MOS sensor( 1,2) and a CCD sensor(3,4). The linear MOS sensor consists of MOS shift registers and a p-n junction diode array. This type of device offers advantages of low dark current and high blue sensitivity. However, it continues to suffer from signal non-uniformity caused by threshold voltage variations in shift registers. On the other hand, the CCD linear sensor features large output signals and high packing density. However, this device has not been put into practical use because of signal non-uniformity induced by variations in poly-Si photo gate thickness. A novel 1024 element linear CCD sensor, w7131, has been developed. This provides a new photodiode structure, which combines the advantages of the CCD sensor and the MOS sensor, and eliminates the nonuniformity of the earlier devices.