IMAGE SENSOR CHARGE DIRECTION STRUCTURES AND METHODS

Abstract

A system for handling static charges can include an array of photodiodes, a metal grid coupled to the array of photodiodes, and a set of metal protrusions extending away from the metal grid. The set of metal protrusions can be configured to conduct charge from an electrostatic discharge or a static charge into the metal grid.

Description

BACKGROUND 1. Technical field

[0001] Aspects of this document generally relate to image sensor devices, such as devices for monitoring electromagnetic radiation. 2. Background

[0002] Packages for semiconductor devices have been developed that enable electrical signal routing from a semiconductor die to a printed circuit board or motherboard to which the package is coupled. Various semiconductor packages have been developed that protect the semiconductor die from moisture or mechanical stress. SUMMARY

[0003] A static charge management system may include an array of photodiodes, a metal grid coupled to the array of photodiodes, and a set of metal protrusions extending from the metal grid. The set of metal protrusions may be configured to conduct charge from an electrostatic discharge or a static charge into the metal grid.

[0004] Implementations of a static charge management system may include one, all, or any of the following: The set of metal projections may be located on one side of the metal grid, opposite the array of photodiodes. The set of metal projections may each be arranged at a set of intersection points of the metal grid. The set of metal protrusions may be arranged in a layer of passivation material coupled to the metal grid.

[0005] The array of photodiodes may be incorporated into a backlight sensor.

[0006] The set of metal projections may include one of a rectangular prism, a cylinder, or a triangular prism.

[0007] The set of metal projections may include one of a square-based cone, a triangular-based cone, a cone, or a truncated cone.

[0008] Implementations of a static charge management system may include an array of photodiodes, a metal grid coupled on a first side of the array of photodiodes, and a set of metal protrusions coupled on a side of the metal grid opposite the first side of the array of photodiodes and extending away from the metal grid.

[0009] Implementations of a static charge management system may include one, all, or any of the following: The set of metal projections may each be arranged at a set of intersection points of the metal grid.

[0010] The set of metal projections can be arranged along the metal grid.

[0011] The set of metal protrusions may be disposed in a layer of passivation material coupled to the side of the metal grid opposite the first side of the array of photodiodes.

[0012] The array of photodiodes may be incorporated into a backlight sensor.

[0013] The set of metal projections may include one of a rectangular prism, a cylinder, or a triangular prism.

[0014] The set of metal projections may include one of a square-based cone, a triangular-based cone, a cone, or a truncated cone.

[0015] Implementations of a method for handling charge may include providing an array of photodiodes having a first side to which a metal grid may be coupled, and a set of metal protrusions coupled to the metal grid on a side of the metal grid opposite the first side of the array of photodiodes and extending away from the metal grid, and capturing electrical charge into the set of metal protrusions. The method may also include conducting the electrical charge into the metal grid.

[0016] Implementations of a cargo handling method may include one, all, or any of the following: The method may include where the metal grid is grounded and further include conducting the electrical charge to ground using the metal grid.

[0017] Receiving electrical charge may further include receiving electrical charge from a passivation layer.

[0018] The set of metal protrusions can be formed in a passivation layer.

[0019] The electrical charge can come from an electrostatic discharge or static electricity.

[0020] The array of photodiodes may be incorporated into a backlight sensor.

[0021] The foregoing and other aspects, features and advantages will be apparent to those skilled in the art from the DESCRIPTION and DRAWINGS, as well as from the CLAIMS. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Implementations are described below in conjunction with the accompanying drawings, wherein like reference numerals denote like elements and wherein: Fig. Figure 1 is a plan view of an implementation of a metal grid over an array of photodiodes; Fig. 2 is a cross-sectional view of a first implementation of a metal grid and metal projections and a second implementation of a metal grid and metal projections; and Fig. Figure 3 is a tabular representation of various shapes of different implementations of metal protrusions. DESCRIPTION

[0023] This disclosure, its aspects, and implementations are not limited to the specific components, assembly procedures, or method elements disclosed herein. Many other components, assembly procedures, and / or method elements known in the art that are consistent with the contemplated image sensor charge direction structures and methods will be apparent from this disclosure for use with particular implementations.Accordingly, for example, although particular implementations are disclosed, such implementations and implementing components may include any shape, size, style, type, model, version, dimension, concentration, material, quantity, process element, step, and / or the like known in the art for such image sensor charge direction structures, and implementing components and methods consistent with the intended operation and methods.

[0024] Image sensor devices may exhibit image artifacts caused by an electrical charge generating an electric field that breaks electrical insulation between individual pixels in a pixel array (array of photodiodes), causing "charge sharing" in pixel clusters. In the image generated by an image sensor device, these image artifacts may take on the appearance of a water droplet or blob, appearing like defects in the image. In some implementations, the electrical charge is caused by an electrostatic discharge (ESD) event that traps electrical charge in a layer of passivation material incorporated within the image sensor device, particularly on the backside of the image sensor device. In other implementations, the electrical charge may be static charge accumulated on the image sensor device / backside of the image sensor device.

[0025] This image artifact effect, which occurs due to charge storage, is observed where the array of photodiodes is incorporated into a back-illuminated sensor (BSI). However, the ability of electrical charge to generate image artifacts using this mechanism can occur in a variety of image sensor types.

[0026] In various image sensor systems, a grid made of a metallic material (metal grid) is used to aid in the management of the electrical charge that builds up on the array of photodiodes that form the pixel array of an image sensor device. The metal grid may be coupled to one side of the photodiode array. In some image sensor implementations, the metal grid is coupled to a lower side of the photodiode array or to a side of the photodiode array opposite where other devices such as microlenses, color filter arrays, or a light-transmitting cover are adjacent to or coupled to the photodiode array. However, in other implementations, the metal grid may be coupled to the side of the photodiode array facing the image sensor device itself.In some implementations, the metal grid is attached to an electrical ground (grounded); in other implementations, the metal grid is electrically floating with respect to the ground. It has been found that the metal grid, on its own, promotes a reduction in image artifacts due to electrical charge, but does not eliminate them in certain situations and / or with certain types of image sensor devices because the electrical charges cannot reach the metal grid from the materials surrounding the metal grid / photodiode array.

[0027] Referring to Fig. 1 illustrates part of an implementation of an image sensor 2 including an array of photodiodes (pixel array) 4 over which a metal grid 6 is coupled. It is understood that in Fig. 1 only a small section of the array of photodiodes is illustrated and the structure of the metal grid 6 is repeated over the entire, a substantial majority, a majority or a section of the array of photodiodes 4. While the sections of the metal grid in Fig. 1 as if they were located in the same layer, the metal grid in some implementations may include components that physically cross each other while being held in electrical contact with each other. In Fig. 1 illustrates a set of metal protrusions 8 extending upward from the paper. The metal protrusions 8 collect and conduct electrical charge into the metal grid 6 during operation of the image sensor device. As previously explained, the electrical charges collected by the metal protrusions 8 may originate from an ESD event and / or may be static charge accumulated on / in the array of photodiodes. In this way, the charge collection and conduction function of the metal protrusions 8 can be compared to the function of lightning rods, albeit at a microscopic level.However, the operation of metal protrusions 8 and lightning rods differ in one important respect, as lightning rods are designed to both receive charge from lightning and act as point sources, releasing ionized molecules into the surrounding air during a thunderstorm to help reduce the likelihood of a lightning strike. In contrast, the metal protrusions 8 operate by collecting electrical charge and conducting it down into the metal grid, thus notably not releasing electrical charge during operation of the image sensor device.

[0028] In the Fig. 1, each of the set of metal protrusions 8 is illustrated in this implementation as being located at an intersection 10 of the metal grid 6. In this implementation, each intersection 10 includes a metal protrusion 8 coupled thereto. In other implementations, the ratio of metal protrusions to intersections may be less than 1:1, such as, by way of non-limiting example, 1:2, 1:3, 1:5, 1:10, or another desired ratio to achieve a particular / desired / required effect in electrical charge management. The ratio may also be achieved in various ways, with a 1:2 ratio having a metal protrusion 8 coupled at every other intersection 10, or in a pattern where a metal protrusion is coupled at two adjacent intersections 10, followed by skipping two adjacent intersections.A variety of patterns or even random patterns for locating metal protrusions at intersections can be used in different system implementations.

[0029] While the Fig. While the implementation illustrated in Figure 1 shows each of the set of metal protrusions 8 located at an intersection 10 of the metal grid 6, in other implementations, the metal protrusions may be located at other locations along the metal grid, such as along one or both sets of intersecting metal tracks that form the metal grid 6. In this way, the set of metal protrusions is located along the metal grid rather than at the intersections of the metal grid. In these implementations, concentrations of metal protrusions at specific locations on the pixel array / array of photodiodes may be employed to promote the distribution of charge away from known, particularly electrostatically sensitive locations on the device.The use of concentrations of metal protrusions can also be used to promote faster conduction of electrical charges away from certain areas in the array, or to move electrical charges more quickly to the metal layer (like electrical traces across the face of the pixel array, but instead consisting of closely spaced metal protrusions).

[0030] Referring to Fig. 2 illustrates a first implementation of a metal grid 12 including two metal protrusions 14 coupled thereto. In the cross-sectional view in this implementation, the metal grid 12 is coupled to a portion of the photodiode array 16. In this implementation, the side 18 of the photodiode array 16 to which the metal layer 12 is coupled is the backside of the photodiode array 16 or the side opposite the side that receives electromagnetic radiation and may include microlenses, a color filter array, or areas with a light-transmitting cover. As illustrated in this implementation, the two metal protrusions 14 are freestanding, or in other words, they extend from the metal layer 12 without being surrounded by any other support / encapsulation material.In this implementation, the use of the metal protrusions 14 increases the overall surface area of ​​the metal layer 12 and also creates focused points on the metal layer 12 that help collect / getter static electrical charges adjacent to the metal layer 12 to conduct them into the material of the metal layer 12.

[0031] Referring again to Fig. 2 illustrates a second implementation of a metal grid 20 including metal protrusions 22 extending therefrom. This metal grid 20 is coupled to the backside 26 of the photodiode array 24, similar to the previously described implementation. In this implementation, the metal protrusions 22 are located within a layer of passivation material 28. Since the backside passivation material is the location where electrical charge storage has been observed following an ESD event, the ability of the metal protrusions 22 to directly contact the layer of passivation material 28 on the backside 26 of the photodiode array 24 can assist in the collection / gettering of the electrical charge into the metal protrusions 22 and then down into the metal grid 20.While in this implementation the metal protrusions 22 are illustrated as completely penetrating the material of the passivation material 28, in other implementations the metal protrusions 22 may extend only partially into the thickness of the layer of passivation material 28, with the ends remaining covered by the layer of passivation material.

[0032] Because the metal protrusions 14, 22 are exposed or located only within the layer of passivation material 28, the metal protrusions 14, 22 are not involved in the process of collecting the photon-generated charge within the silicon substrate / photodiode array 16, 24 itself. Thus, the function of the metal protrusions 14, 22 is to assist in the management of electrical charge in the form of static charge or stored charge from an ESD event, rather than providing / collecting electrical charge used by photodiodes / image sensors to create an image resulting from electromagnetic radiation.A wide range of wavelengths of electromagnetic radiation may be employed in the various image sensor implementations disclosed herein, such as, by way of non-limiting example, infrared light, ultraviolet light, visible light, microwaves, radio waves, x-rays, or any other type of electromagnetic radiation to which the array of photodiodes is responsive.

[0033] Referring to Fig. 2, the freestanding metal protrusions 14 could be formed using a subtractive process in which a patterned layer is formed on a metal layer. The patterned layer can be formed using a photolithography process with a patterned photoresist or by a hard mask process in which a photolithography / etching process is used to etch an oxide / nitride pattern, which is subsequently used to etch away the metal layer except where the pattern is present, leaving a set of metal pillars that form the metal protrusions 14. In this process implementation, the metal etching can be performed using a dry or wet etching process. In various implementations where a patterned photoresist is used, the photoresist is typically removed after the metal protrusions 14 are etched.In various implementations, the hard mask material may be left on the metal protrusions 14 or may be removed, depending on the desired electrical conductivity of the metal protrusions 14. In various methods and structure implementations, the metal material used for the metal protrusions 14 may be the same as the metal material of the metal layer 12; in other cases, the metal materials used for the metal protrusions 14 and the metal layer 12 may be different.

[0034] In another process implementation, a damascene or additive process may be used to form the metal protrusions, in which a layer of oxide, nitride, or passivation material is deposited over the metal layer and then has openings formed therein into which metal is deposited using a chemical vapor deposition process (such as when using tungsten) or an electroplating process (such as when using copper). A chemical mechanical planarization (CMP) process may then be used to bring the deposited metal down to the surface of the oxide, nitride, or passivation material layer and electrically isolate the top surfaces of the metal protrusions from each other. The remaining oxide, nitride, or passivation material is then etched away, leaving the freestanding metal protrusions 14.

[0035] The above Damascus process can also be used to Fig. 2, except that the passivation material 28 is not etched away, leaving the metal protrusions 22 within the passivation material 28, as illustrated. In some implementations, a damascene process may be used to form the metal layer 20 and the metal protrusions 22 in two different steps. A variety of method implementations for forming the metal protrusions may be constructed using the principles disclosed herein.

[0036] Referring to Fig. Figure 3 illustrates a diagram of various possible shapes for metal protrusions. In the left column, the side cross-sectional view shows a prism (constant or substantially constant cross-section for the metal protrusion) and a cone (tapered cross-section for the metal protrusion). Although not illustrated in the side cross-sectional view, frustoconical shapes can also be used for the side cross-sections of various metal protrusions in various implementations. Three non-limiting examples of cross-sectional shapes for the metal protrusions are shown in the diagram of Fig. 3 illustrates a circle, a square, and a triangle. If the cross-section is a circle and the side cross-section view is a prism, the resulting shape would be a cylinder. If the cross-section is a square / rectangle and the side cross-section view is a prism, the resulting shape would be a cube / cuboid. If the cross-section is a triangle and the side cross-section view is a prism, the resulting shape would be a triangular prism.

[0037] Similarly, if the cross-section of the cone base is a circle or an ellipsoid, the resulting shape of the metal projection is a cone. If the cross-section is a square or a rectangle, the result is a square-based pyramid. If the cross-section is a triangle, the result is a triangular-based pyramid.

[0038] While the side cross-sectional views in Fig.3 as having straight sides, in various implementations the sides may be curved or rounded, forming a prism with a curved or rounded side surface. Furthermore, while a circle / ellipsoid, a square / rectangle, and a triangle are illustrated, the cross-sectional shape of the metal protrusion may take any of a variety of shapes, including, by way of non-limiting example, a parallelogram, a pentagon, a hexagon, an octagon, or another closed shape. In this manner, a prism or a cone may be formed from a variety of cross-sectional shapes using the principles disclosed herein.

[0039] The image sensor charge direction structures disclosed herein may be incorporated into a backlight sensor.

[0040] The image sensor charge direction structures disclosed herein may be located on a side of the metal grid opposite the array of photodiodes.

[0041] The image sensor charge direction structures disclosed herein may include a rectangular prism, a cylinder, a triangular prism, a square-based cone, a triangular-based cone, a cone, or a truncated cone.

[0042] The image sensor charge direction structures disclosed herein may include where the set of metal protrusions is formed in a passivation layer.

[0043] The image sensor charge direction structures disclosed herein may include where the electrical charge originates, from an electrostatic discharge event or static electricity.

[0044] It should be readily understood that where the foregoing description refers to particular implementations of image sensor charge direction structures and methods, as well as implementing components, subcomponents, methods, and submethods, a number of modifications may be made without departing from the spirit thereof, and that these implementations, implementing components, subcomponents, methods, and submethods may also be applied to other image sensor charge direction structures and associated methods.

Claims

[1] A static charge handling system comprising: an array of photodiodes; a metal grid coupled to the array of photodiodes; and a set of metal protrusions extending from the metal grid, the set of metal protrusions configured to conduct charge from one of an electrostatic discharge or a static charge into the metal grid. [2] The system of claim 1, wherein the set of metal projections is each arranged at a set of intersection points of the metal grid. [3] The system of claim 1, wherein the set of metal protrusions is disposed in a layer of passivation material coupled to the metal grid. [4] The system of claim 1, wherein the set of metal projections comprises one of a rectangular prism, a cylinder, a triangular prism, a square-based cone, a triangular-based cone, a cone, or a conical truncated cone. [5] A static charge handling system comprising: an array of photodiodes; a metal grid coupled to a first side of the array of photodiodes; and a set of metal projections coupled to one side of the metal grid opposite the first side of the array of photodiodes and extending away from the metal grid. [6] The system of claim 5, wherein the set of metal projections is each arranged at a set of intersections of the metal grid or each along the metal grid. [7] The system of claim 5, wherein the set of metal protrusions is located in a layer of passivation material coupled to the side of the metal grid opposite the first side of the array of photodiodes. [8] A method for handling electrical charge, comprising: Providing an array of photodiodes having a first side to which a metal grid is coupled, and a set of metal protrusions coupled to the metal grid on a side of the metal grid opposite the first side of the array of photodiodes and extending away from the metal grid; Receiving electrical charge into the set of metal projections; and Conducting the electrical charge into the metal grid. [9] The method of claim 8, further comprising where the metal grid is grounded and conducting the electrical charge to ground using the metal grid. [10] The method of claim 8, wherein receiving electrical charge further comprises receiving electrical charge from a passivation layer.

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