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Patent Issued for Image Sensor and Method for Fabricating the Same

August 20, 2014



By a News Reporter-Staff News Editor at Electronics Newsweekly -- A patent by the inventor Lim, Youn-Sub (Gyeonggi-do, KR), filed on January 17, 2012, was published online on August 5, 2014, according to news reporting originating from Alexandria, Virginia, by VerticalNews correspondents.

Patent number 8796799 is assigned to Hynix Semiconductor Inc. (Gyeonggi-do, KR).

The following quote was obtained by the news editors from the background information supplied by the inventors: "Exemplary embodiments of the present invention relate to a technology for fabricating a semiconductor device, and more particularly, to an image sensor including a lightguide and a method for fabricating the same.

"An image sensor is a device for converting an optical image into an electrical signal. As design rules of devices shrinks, the unit pixel size of image sensors also decreases and causes a decrease in sensitivity of image sensors. Here, such a decrease in sensitivity may increase a signal-to-noise ratio (SNR) and thus degrade the quality of an image acquired through image sensors.

"To address such features, a front-side-illumination (FSI) image sensor may use a lightguide. Hereafter, referring to FIG. 1, an image sensor including a lightguide will be described.

"FIG. 1 is a cross-sectional view of a conventional image sensor.

"Referring to FIG. 1, the conventional image sensor includes a substrate 11 having a plurality of unit pixel regions and a plurality of light receiving elements 13 formed in respective unit pixel regions. The respective light receiving elements 13 are isolated by an isolation layer 12. An interlayer dielectric layer 14 including multilayer metal interconnections 16 is formed on the substrate 11. The interlayer dielectric layer 14 includes a lightguide 15 formed for respective light emitting elements 13. A color filter 17 having an RGB structure is formed on the interlayer dielectric layer 14 so as to cover the unit pixel regions, and a planarization layer 18 is formed on the color filter 17. On the planarization layer 18, a hemispheric lens 19 is formed for respective light receiving elements 13.

"In the conventional image sensor, the opening area of the lightguide 15 is limited by the metal interconnections 16 formed in the interlayer dielectric layer 14. Therefore, the conventional image sensor has physical limits in focusing light.

"Furthermore, in order to secure an incident angle which satisfies a total reflection condition of light incident on the lightguide 15, adjacent hemispheric lenses 19 are formed to be spaced apart from each other. However, since there are physical limits in securing an incident angle to satisfy the total reflection condition, it is difficult to obtain appropriate margins for the lens 19. Furthermore, light incident between adjacent lens 19 may not reach the light receiving element 13 and be lost.

"Meanwhile, when uniform properties are not secured at the edges of each unit pixel region even when adjacent lenses 19 are formed to contact each other, there are physical limits in focusing light incident obliquely with respect to the lens 19 to a target unit pixel region. Thus, optical shading effects may be distorted.

"In order to obtain lens 19 which satisfies the light focusing ability and the total reflection condition despite the limited opening area of the lightguide 15, the lightguide 15 is formed of a high refractive index material. In this case, production costs of image sensors may increase."

In addition to the background information obtained for this patent, VerticalNews journalists also obtained the inventor's summary information for this patent: "An embodiment of the present invention is directed to an image sensor capable of improving a light focusing ability of a lightguide and a method for fabricating the same.

"Another embodiment of the present invention is directed to an image sensor capable of securing a lens design margin and a method for fabricating the same.

"Another embodiment of the present invention is directed to an image sensor capable of reducing production costs and a method for fabricating the same.

"In accordance with an embodiment of the present invention, an image sensor includes: a substrate having a unit pixel region; a light receiving element formed in the substrate of each unit pixel region; an interlayer dielectric layer formed over the substrate; a lightguide formed in the interlayer dielectric layer for the light receiving element; a light focusing pattern formed over the interlayer dielectric layer at the pixel region; a planarization layer formed over the substrate and covering the light focusing pattern; and a lens formed over the planarization layer at the pixel region.

"In accordance with yet another embodiment of the present invention, a method for fabricating an image sensor includes: forming a plurality of light receiving elements in the substrate at a plurality of unit pixel regions, respectively; forming an interlayer dielectric layer over the substrate; forming a plurality of lightguides through the interlayer dielectric layer for the plurality of light receiving elements, respectively; forming a plurality of light focusing patterns over the interlayer dielectric layer at the plurality of unit pixel regions, respectively; forming a planarization layer over the entire upper surface of the substrate such that the planarization layer covers the plurality of light focusing patterns; and forming a plurality of lenses over the planarization layer at the plurality of unit pixel regions, respectively."

URL and more information on this patent, see: Lim, Youn-Sub. Image Sensor and Method for Fabricating the Same. U.S. Patent Number 8796799, filed January 17, 2012, and published online on August 5, 2014. Patent URL: http://patft.uspto.gov/netacgi/nph-Parser?Sect1=PTO1&Sect2=HITOFF&d=PALL&p=1&u=%2Fnetahtml%2FPTO%2Fsrchnum.htm&r=1&f=G&l=50&s1=8796799.PN.&OS=PN/8796799RS=PN/8796799

Keywords for this news article include: Electronics, Hynix Semiconductor Inc..

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Source: Electronics Newsweekly


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