Light sensors having dielectric optical coating filters

Abstract

A light sensor includes a photodetector sensor region formed in a semiconductor substrate. To shape the spectral response of the light sensor, a dielectric optical coating filter covers the photodetector sensor region and a circumferential region of the substrate that surrounds the photodetector sensor region. In accordance with specific embodiments, the dielectric optical coating filter has chamfered corners to improve the thermal reliability of the dielectric optical coating covering the photodetector sensor region. Methods for making such a light sensor are also disclosed.

What is claimed is: 
     
         1 . A light sensor, comprising:
 a photodetector sensor region formed in a semiconductor substrate; and   a dielectric optical coating filter covering the photodetector sensor region and covering a circumferential region of the substrate that surrounds the photodetector sensor region;   wherein the dielectric optical coating filter has one or more chamfered corners.   
     
     
         2 . The light sensor of  claim 1 , wherein the one or more chamfered corners of the dielectric optical coating filter comprises four chamfered corners. 
     
     
         3 . The light sensor of  claim 2 , wherein the dielectric optical coating filter further comprises four peripheral sides connected by the four chamfered corners. 
     
     
         4 . The light sensor of  claim 1 , wherein:
 the one or more chamfered corners of the dielectric optical coating filter comprises four chamfered corners;   the photodetector sensor region has a photodetector footprint;   the dielectric optical coating filter has a filter footprint that is larger than and encompasses the photodetector footprint; and   the filter footprint includes four peripheral sides connected by the four chamfered corners.   
     
     
         5 . The light sensor of  claim 4 , wherein each of the chamfered corners has a 45 degree angle relative to an adjacent one of the peripheral sides. 
     
     
         6 . The light sensor of  claim 1 , wherein:
 the photodetector sensor region include first, second, third and fourth peripheral sides that collective define a rectangular photodetector footprint;   the dielectric optical coating filter has a filter footprint including first, second, third and fourth peripheral sides that are parallel, respectively, to the first, second, third and fourth peripheral sides of the photodetector sensor region; and   the one or more chamfered corners of the dielectric optical coating filter comprises four chamfered corners;   a first one of the chamfered corners connects the first and second peripheral sides of the dielectric optical coating filter;   a second one of the chamfered corners connects the second and third peripheral sides of the dielectric optical coating filter;   a third one of the chamfered corners connects the third and fourth peripheral sides of the dielectric optical coating filter; and   a fourth one of the chamfered corners connects the fourth and first peripheral sides of the dielectric optical coating filter.   
     
     
         7 . The light sensor of  claim 1 , wherein the dielectric optical coating filter comprises a stack of dielectric films. 
     
     
         8 . The light sensor of  claim 1 , wherein the dielectric optical coating filter comprises one or more of the following dielectric materials: silicon dioxide (SiO2), silicon hydride (SixHy), silicon nitride (SixNy), silicon oxynitride (SixOzNy), tantalum oxide (TaxOy), gallium arsenide (GaAs), or gallium nitride (GaN). 
     
     
         9 . A light sensor, comprising:
 a photodetector sensor region formed in a semiconductor substrate and having a photodetector footprint; and   a dielectric optical coating filter covering the photodetector sensor region and having a filter footprint that is larger than and encompasses the photodetector footprint;   wherein an outer circumference of the dielectric optical coating filter footprint is defined by a plurality of straight line segments, adjacent pairs of which are non-orthogonal.   
     
     
         10 . The light sensor of  claim 8 , wherein the dielectric optical coating filter comprises a stack of dielectric films any one of which is selected from the group consisting of: a silicon dioxide (SiO2) film, a silicon hydride (SixHy) film, a silicon nitride (SixNy) film, a silicon oxynitride (SixOzNy) film, a tantalum oxide (TaxOy) film, a gallium arsenide (GaAs) film, or a gallium nitride (GaN) film. 
     
     
         11 . A method for fabricating a light sensor, comprising:
 (a) covering a surface of a semiconductor substrate, which includes a photodetector sensor region, with photoresist;   (b) performing photolithography using a photomask to define a pattern surrounding the photodetector sensor region that includes chamfered corners;   (c) using a developer, removing a portion of the photoresist that covered the photodetector sensor region and covered a circumferential region surrounding the photodetector sensor region, wherein the portion of the photoresist that is removed and a portion of the photoresist that remains depends on that pattern defined at step (b);   (d) depositing a dielectric optical coating over the photodetector sensor region, over the circumferential region, and over the photoresist not covering the photodetector sensor region that remained after the removing at step (c); and   (e) lifting off a portion of the dielectric optical coating that is over the remaining photoresist not covering the photodetector sensor region, so that the a remaining portion of the dielectric optical coating covers the photodetector sensor region and the circumferential region;   wherein because of the chamfered corners included in the pattern defined by the photomask used at step (b), following the lifting off at step (e), a portion of the dielectric optical coating that extends beyond the photodetector sensor region includes chamfered corners.   
     
     
         12 . The method of  claim 11 , wherein step (d) includes depositing a stack of dielectric films over the photodetector sensor region. 
     
     
         13 . The method of  claim 11 , wherein step (d) includes depositing one or more of the following dielectric materials over the photodetector sensor region: silicon dioxide (SiO2), silicon hydride (SixHy), silicon nitride (SixNy), silicon oxynitride (SixOzNy), tantalum oxide (TaxOy), gallium arsenide (GaAs), or gallium nitride (GaN). 
     
     
         14 . The method of  claim 11 , wherein the pattern defined by the photomask used at step (b) includes four peripheral sides connected to one another by four chamfered corners. 
     
     
         15 . The method of  claim 11 , wherein the pattern defined by the photomask used at step (b) includes a plurality of straight line segments, adjacent pairs of which are non-orthogonal.