Frontside illuminated charge-coupled device with high sensitivity to the blue, ultraviolet and soft X-ray spectral range

摘要

A CCD which is designed and processed so that most of each pixel is covered only with an ultra-thin gate electrode so that the CCD can be frontside illuminated and still achieve good sensitivity in the ultra- violet and soft x-ray spectral range. More specifically, in the present invention, the usual three gate structure and corresponding polysilicon layers 1, 2 and 3 of conventional thickness are reduced in width and supplemented by a fourth ultra-thin layer of polysilicon dubbed herein, poly 4, that is deposited over the entire array. This fourth layer, poly 4, makes contact with poly 3, so that when poly 3 is driven, it also drives poly 4, thus allowing charge to collect and transfer as in a normal three phase CCD. However, because the deposition thickness of the poly 4 layer is on the order of 400 Angsttoms, as opposed to conventional thicknesses of 2000 to 5000 Angsttoms, poly 4 is essentially transparent to photons and thereby allows achievement of high quantum efficiency.