Image sensor having self-aligned and overlapped photodiode and method of making same

Abstract

An image sensing device includes a gate dielectric layer formed on a substrate and a transfer gate formed on the gate dielectric layer. A masking layer is formed on the transfer gate, the masking layer having a width smaller than a width of the transfer gate, such that a portion of the transfer gate protrudes laterally from under the masking layer. A photodiode is formed in the substrate to be self-aligned with the masking layer and to extending laterally under the transfer gate, that is, to overlap the transfer gate. Because of the overlap of the photodiode with the transfer gate, offset between the photodiode and the transfer gate is eliminated, such that an image lag phenomenon is eliminated.

Description

technical field [0001] The present invention relates to image sensors. Background technique [0002] An image sensor is a device that receives a light signal from an object and converts the light signal into an electrical signal. The electrical signal may then be transmitted for further processing, eg digitization, and subsequently stored in a storage device such as a memory or an optical or magnetic disk, or for display on a display, printing, etc. Image sensors are commonly used in devices such as digital still cameras, video cameras, printers, facsimile machines, and the like. [0003] There are generally two types of image sensors, namely, charge-coupled device (CCD) sensors and CMOS image sensors (CIS). CCD sensors generally have advantages including low noise operation and device uniformity. CIS devices are generally characterized by low power consumption and can operate at high speeds due to high frame rate capabilities. [0004] figure 1 is a schematic cross-sec...

AI Technical Summary

Problems solved by technology

The E2 group of charges remaining in the photodiode region causes the image delay phenomenon

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