Image sensor

Abstract

The invention relates to the technical field of semiconductors and discloses an image sensor. A laminated layer formed by a first medium layer, a second medium layer and a third medium layer is taken as a side wall reflection layer around a medium layer above the surface of a photosensitive area, so that a light path is constructed; light is limited in a corresponding pixel photosensitive area to be prevented from being emitted into an adjacent pixel photosensitive area; and therefore, the cross-interference can be reduced, and the effective photosensitive efficiency of the photosensitive area can be improved. The image sensor has the beneficial effects that the incident light is limited on the basis of a refractive index difference between the first medium layer and the interlamination medium layer, and the second medium layer, namely the metal layer, only reflects the light transmitting through the first medium layer, so that the absorption effect of metal on the light is relieved to a certain extent; and furthermore, the laminated structure ensures a polishing effect during a subsequent chemical-mechanical polishing process, and the metal can be prevented from falling off and stripping.

Description

technical field [0001] The invention relates to the technical field of semiconductors, in particular to an image sensor with a light path. 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 charge-coupled device (Charge-Coupled Device, “CCD” for short) and complementary metal oxide semiconductor (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 and figure 2 are the photosensitive conditions in the image sensor structure under ideal conditions and actual condit...

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Problems solved by technology

[0006] However, in actual work, due to the extremely small size of the pixel unit compared to the external environment to be detected, the light-gathering effect of the microlens is limited. After a large amount of light enters the interlayer dielectric layer, it will not only enter the photosensitive area of ​​the corresponding pixel , will also enter adjacent pixels, causing crosstalk and reducing the effective photosensitive efficiency of the photosensitive area

[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, limiting 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, but the absorption effect of metal cannot be ignored

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