Image sensor and preparation method thereof

Abstract

The invention relates to the technical field of semiconductors, and discloses an image sensor and a preparation method thereof. In the image sensor, a plurality of columnar through holes are distributed in a dielectric layer above a photosensitive device of each photosensitive area to form a light guide area which is used for guiding light into a photosensitive device, and incident light can be bound in the light guide area to prevent light rays from being shot into adjacent pixel photosensitive areas during propagation to cause light crosstalk, so that the propagation route of the incident light in the light guide area is improved; and the transmission characteristics of the light guide area can be adjusted by controlling the parameters such as the pore size, the dielectric material, the distribution density and the like of the through holes in the light guide area, and controlling the arrangement mode of the through holes, so that an effect of improving the light intensity of the light shot into the light guide area is achieved. Moreover, based on the conventional image sensor circuit, a plurality of through holes are formed in the dielectric layer above the photosensitive area by using an etching and mat accumulation process, so that the image sensor is easy and convenient to operate and easy for mass production.

Description

technical field [0001] The invention relates to the technical field of semiconductors, in particular to an image sensor with a light guide area. Background technique [0002] As we all know, an image sensor is a semiconductor device that converts an optical image into an electrical signal. Image sensors can be roughly classified into two types: Charge-Coupled Device (CCD for short) and Complementary Metal Oxide Semiconductor (CMOS for short) image sensors. [0003] According to its readout method, the existing CMOS image sensors can be roughly divided into passive pixel sensor (Passive Pixel Sensor, referred to as "PPS"), active pixel sensor (Active Pixel Sensor, referred to as "APS") and digital pixel sensor There are three types of sensors (Digital Pixel Sensor, referred to as "DPS"). [0004] figure 1 with figure 2 are the photosensitive conditions in the image sensor structure under ideal conditions and actual conditions, respectively. [0005] Such as figure 1 As...

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Problems solved by technology

[0007] In the prior art, it has been proposed that an air hole is formed by etching around the dielectric layer above the photosensitive area, thereby forming a waveguide-like optical path above the photosensitive area, and confining most of the incident light to be transmitted in this path, but This method has limited restrictions on light, especially the dielectric layer above the photosensitive area is usually a low dielectric constant material, and the refractive index is usually low (generally about 1.5); in addition, it has also been proposed that the dielectric layer above the photosensitive area Around, a continuous metal layer is used as a reflective layer to prevent the impact of incident light on adjacent pixels, but metal has a certain absorption effect on electromagnetic waves. With the further shrinking of the size of CMOS image sensors, for certain limit wavelengths of light, It can be regarded as an electromagnetic wave approximately, and the absorption effect of metal cannot be ignored

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