Research On A New Type Of Light Shielding Technology For Interline Transfer CCD

Charge coupled device(CCD)has been invented for more than 40 years,it has made great development,especially in the field of solid imaging technology.Interline-transfer CCD(IT-CCD)has many advantages,such as simple structure,no alone store region,smaller area than frame-transfer CCD,few vertical smearing problem under normal illumination.But the IT-CCD has a drawback,because of the structure,a small amount of irradiated light can enter the vertical CCD,this affects the imaging quality.In this paper,shading technology for vertical CCD is the research object.Discuss the problem of using aluminum as light shading technology,studying new process and integrated technology of new shading material to reduce the light leakage rate.1.IT-CCD process was studied,we discussed device's design,process and flow,analyzed the leakage reason of IT-CCD,and the problem of using metal aluminum as a shading process,to guide the development of new shading technology.2.A new process technology for shading layer was studied,we contrasted the shading performance of different materials.Finally,tungsten was used as a shading material.The tungsten deposition for light shading layer was developed from the aspects of the deposition mode,inhomogeneity,resistivity and stress.Compared with different etching systems,the etching of tungsten was developed from the aspects of etching rate,etch inhomogeneity,etching selection ratio and line width.3.The integration technology of the new shading layer was studied,and the process scheme was proposed.Adjusting the shading layer process sequence to reduced the distance between the shading layer and the vertical CCD;Adjusting the structure of the device under the shading layer to solve the problem of etching residue;The structure of metal wire was adjusted,tungsten was used as a shading layer,and aluminum was used as a wire layer to solve the RC delay and high frequency performance.4.The evaluation of shading performance was studied.Combining foreign light leakage evaluation methods,we put forward the evaluation method.We contrasted the new shading technology and aluminum shading process by using this evaluation method,The light leakage rate of vertical CCD reduced to 0.06%,this got a breakthrough in this field.