Apparatus and method for protecting integrated circuit charge storage elements from photo-induced currents

摘要

An apparatus and a method for protecting charge storage elements from photo-induced currents in silicon integrated circuits are provided. In order to protect against photo-induced currents that are generated outside the storage node circuits themselves, an n-well guard ring is placed as closely as possible to the transistors and other elements in the storage node circuits. As a result there is a minimum of exposed silicon area in which light can produce current in areas next to the storage node circuits, and the n-well guard ring captures photo-induced currents that are generated outside the storage node circuits. In order to protect against the photo-induced currents that are generated inside the storage node circuits, an aluminum interconnect layer is placed on top of the storage node circuit, separated by an insulating layer of silicon dioxide. This creates a shield against the light and protects the storage node circuit by reflecting light away.