A solid-state imaging apparatus of an APS structure is also called as a CMOS sensor, and is widely used for digital cameras and the like.
A conventional solid-state imaging apparatus has the problem of the following phenomena. To put it concretely, the phenomena are a blooming phenomenon, in which signal charges escape into an adjacent photoelectric converting portion, the color mixing, in which color reproducibility worsens by the blooming phenomenon, and the like. The generating mechanisms of these phenomena are severally as follows: the signal charges accumulated in a semiconductor region constituting a photoelectric converting portion for accumulating signal charges (N type semiconductor region in the case where the signal charges are electrons) become a saturation state, and overflowing signal charges go over an element isolation region to arrive at an adjacent pixel.
In order to settle the problem mentioned above, Japanese Patent Application Laid-Open No. 2004-266159 (hereinafter referred to as Patent Document 1) discloses the configuration in which a deep isolation injection layer is formed under the element isolation region. The Patent Document 1 describes the configuration of obstructing the effluences of signal charges from a photodiode.
Moreover, Japanese Patent Application Laid-Open No. 2005-229105 (hereinafter referred to as Patent Document 2) discloses the following configuration. That is, an overflow path region is formed under an element isolation insulation film, and the overflow path region is made to have a piece of potential lower than that of a P type well region constituting a photodiode. Thus, the photodiode overflows with signal charges, which are discharged to an N type silicon substrate, to suppress the blooming.
Moreover, in addition, also Japanese Patent Application Laid-Open No. 2006-024907 (hereinafter referred to as Patent Document 3) describes an element isolation structure suppressing the escaping of signal charges.
However, in the case of forming the diffusion layer for element isolation as the one disclosed in the Patent Document 1 mentioned above, since the element isolation diffusion layer having a sufficient width cannot obtained as the miniaturization of a pixel progresses, sufficient color mixing and blooming suppressing effects cannot be obtained sometimes.
Moreover, if the overflow path region disclosed in the Patent Document 2 mentioned above is formed, the signal charges generated by a photoelectric conversion at a deep part of a well are sometimes discharged when the P well constituting the photodiode is deeply formed, and the sensitivity of the photodiode does not sometimes become high.
Moreover, also by the element isolation structure disclosed in the Patent Document 3, the signal charge collecting efficiency cannot be said yet to be sufficient, and there is room for further examination.
USPTO Backgrounds
USPTO Backgrounds