Low-capacitance CCD image sensor with thin single-layer structure

CCD is a continuum of MOS capacitors, so its big capacitance becomes one of the major disadvantages compared with CMOS image sensor, that cause not only large power dissipation but also other problems, such as generating an electro magnetic interference. We have developed a CCD linear image sensor with thin single-layer electrodes for the purpose of reducing the CCD capacitance. A two phase pulse drive CCD is fabricated with single layer poly Si electrode that has narrow electrode gaps and thinner electrode thickness. At the sensor that has 2.625um pitch 10k pixel linear array with a single sided CCD register, the coupling capacitance has been reduced to totally less than 40% compared to the conventional two layer CCD electrode structure, due to non electrode overlapping and thin thickness of the CCD electrodes. The total power consumption for CCD drive is reduced to 45% of conventional CCD and high transfer efficiency (>99%) is obtained at 20MHz. Moreover, the size of the area around CCD for the contact between electrode and clock applying wire is reduced by eliminating second layer electrode. The flatness above the silicon surface is also improved for better image quality.