Fully embedded color filter array for image sensor

Abstract

This application relates to a fully embedded color filter array for image sensors. An image sensor includes a substrate. An array of photodiodes is disposed in the substrate. A plurality of spacers is arranged in a spacer pattern. At least one spacer of the plurality of spacers has an aspect ratio of 18:1 or greater. A buffer layer is disposed between the substrate and the spacer pattern. A color filter array is disposed in the spacer pattern.

Description

[0001] This application is a divisional application of the Chinese invention patent application with the invention name “Image sensor and manufacturing method thereof”, application number 202010805617.6, and application date of August 12, 2020. Technical Field

[0002] The present invention relates generally to color filters and, more particularly, to color filter arrays for image sensors. Background Art

[0003] A color image sensor includes a color filter array. Each filter in the color filter array can only allow light of one color to pass through to the sensor. The color filter array can include sidewalls between adjacent filters, isolating each filter from adjacent filters in the color filter array. However, these sidewalls can take up a significant amount of space and compromise the density of the color filter array. Summary of the Invention

[0004] In one aspect, the present application provides an image sensor comprising: a substrate in which a photodiode array is disposed; a plurality of spacers arranged in a spacer pattern, wherein at least one spacer of the plurality of spacers has an aspect ratio of at least 18:1; a buffer layer disposed between the substrate and the spacer pattern; and a color filter array disposed in the spacer pattern.

[0005] In another aspect, the present application further provides an image sensor comprising: a substrate, wherein a photodiode array is disposed in the substrate; a plurality of spacers arranged into a spacer pattern; a buffer layer disposed between the spacer pattern and the substrate; a color filter array disposed in the spacer pattern; and a support material pattern defining a grid, the support material pattern being disposed between the spacer pattern and the buffer layer. BRIEF DESCRIPTION OF THE DRAWINGS

[0006] Non-limiting and non-exhaustive embodiments of the present invention are described with reference to the following figures, wherein like reference numerals refer to like parts throughout the various views unless otherwise specified.

[0007] Figures 1A-1I Examples of cross-sectional views of a fully buried color filter array at different steps in forming the color filter array according to the teachings of the present invention are shown.

[0008] Figures 2A-2H Examples of cross-sectional views of a fully buried color filter array at different steps in forming the color filter array according to the teachings of the present invention are shown.

[0009] Figures 3A-3CAn exemplary top-down view of a fully-embedded color filter array at different steps of forming the color filter array in accordance with the teachings of this disclosure is shown.

[0010] Figure 4 is a flowchart illustrating process steps of one example of fabricating a fully-embedded color filter array device in accordance with the teachings of this disclosure.

[0011] Figure 5 is a diagram illustrating one example of an imaging system having a fully-embedded color filter array in accordance with the teachings of this disclosure.

[0012] In the several views of the drawings, corresponding reference characters indicate corresponding components. A person skilled in the art will understand that the elements in the drawings are not necessarily to scale and are presented for purposes of illustration and explanation only. For example, some elements in the drawings can be exaggerated in scale, while others can be omitted or simplified in order to better illustrate various aspects of the present disclosure. Furthermore, elements of a business practical embodiment of the present disclosure will frequently be described in terms of functions that they are capable of performing or in terms of the results they are capable of producing, rather than in terms of their specific structural or compositional characteristics. DETAILED DESCRIPTION

[0013] Examples related to color filter arrays and methods of fabricating the color filter arrays using sacrificial replacement layers are disclosed herein. In the following description, numerous specific details are set forth to provide a thorough understanding of the examples. One skilled in the relevant art will recognize, however, that the technology described herein can be practiced without one or more of the specific details, or with other methods, components, materials, etc. In other instances, well-known structures, materials, or operations are not shown or described in detail in order to avoid obscuring the certain aspects.

[0014] In this specification, reference can be made to "one example" or "one embodiment," meaning that a particular feature, structure, or characteristic described in connection with the example is included in at least one example of the disclosure. The appearance of the phrases "in one example" or "in one embodiment" in various places in the specification are not necessarily all referring to the same example. In addition, the particular features, structures, or characteristics can be combined in any suitable manner in one or more examples.

[0015] In this specification, several technical terms are used. Such terms are used in their ordinary sense in the field to which the disclosure belongs unless specifically defined herein or the context of their use clearly dictates otherwise. It should be noted that in this document, element names and notations can be used interchangeably (e.g., Si and silicon); however, both have the same meaning.

[0016] A color filter array with good photodiode isolation allows for more precise placement of the photodiodes beneath the color filter array. Sidewalls that isolate the individual color filters in the color filter array allow the color filter array to have good photodiode isolation. However, sidewalls formed using standard photolithography can take up a significant amount of space and compromise the footprint density of the color filter array.

[0017] Figures 1A-1I Examples of cross-sectional views of a fully buried color filter array at different steps in forming the color filter array according to the teachings of the present invention are shown. Figure 1A An image sensor device is shown having a substrate 110, which includes a plurality of photodiodes 115 and a buffer layer 120 disposed on substrate 110. Substrate 110 may be a semiconductor material, such as a silicon substrate or a silicon substrate doped with impurities, for example, a p-type doped silicon substrate or an n-type doped silicon substrate. Photodiodes 115 may be formed in substrate 110. In one embodiment, photodiodes 115 may be n-type doped photodiodes formed by implanting and / or diffusing n-type impurities (e.g., arsenic or phosphorus), while substrate 110 may be a p-type doped silicon substrate. In another embodiment, photodiodes 115 may be p-type doped photodiodes formed by implanting and / or diffusing p-type impurities (e.g., boron), while substrate 110 may be an n-type doped silicon substrate. Buffer layer 120 may be an oxide, such as silicon dioxide, or another material transparent to light in the visible spectrum. Each of photodiodes 115 may generate light-induced charge in response to received incident light.

[0018] Figure 1B Shown Figure 1A A device, wherein a sacrificial material layer 130 is formed on the buffer layer 120. The sacrificial material layer 130 can be formed by chemical vapor deposition. In one embodiment, the sacrificial material layer 130 can be flattened by a chemical mechanical polishing (CMP) process. The sacrificial material can be a material that can be removed by a wet etching process, including but not limited to carbon-based materials, oxide materials, nitride materials, and silicon-based materials. The sacrificial material can be a material that can be patterned by a dry etching process. Figure 1BAs shown, the sacrificial material layer 130 can be formed as a flat layer of uniform thickness. The sacrificial material layer 130 should be made of a material that does not cause the buffer layer 120 to be substantially removed when removed by a wet etching process. For example, if the buffer layer 120 is silicon dioxide, the sacrificial material layer 130 should also not be silicon dioxide. To reiterate, the buffer layer 120 and the sacrificial material layer 130 can be made of different materials, wherein the sacrificial material has an etching selectivity to the buffer layer 120. In other words, the material used to form the sacrificial material layer 130 can be selected from a material having a different etching rate than the material used to form the buffer layer 120. In one embodiment, the sacrificial material layer can be made of a nitride material, and the buffer layer 120 can be made of silicon dioxide.

[0019] Figure 1C Shown Figure 1B A device in which portions of the sacrificial material layer 130 are removed to form a sacrificial material pattern 135. As will be described in more detail below, the sacrificial material pattern 135 may be a "checkerboard" pattern. According to the "checkerboard" pattern, the sacrificial material pattern 135 may be formed by patterning and dry etching the sacrificial material layer 130. In an embodiment, the sacrificial material pattern 135 may form sacrificial material blocks 136. Each of the sacrificial material blocks 136 may have a rectangular prism shape, such that the sacrificial material block has four sides of approximately equal length. Figure 1C As shown, the sacrificial material blocks 136 are spaced apart in one direction by approximately the length of one of the sides of the sacrificial material block 136. In other embodiments, the sacrificial material blocks 136 may have four sides of unequal length. The shape and size of the sacrificial material blocks may depend on the desired size and shape of the spacers and color filters of the imaging sensor device. Each sacrificial material block 136 may cover one photodiode 115 and be centered on the respective photodiode 115. Alternatively, each sacrificial material block may cover multiple photodiodes 115. The thickness or height of the sacrificial material blocks 136 may be configured based on the desired thickness or height of the spacers.

[0020] Figure 1D Shown Figure 1Cdevice 100 of FIG. 1, where the spacer pattern 140 is formed on the sides of the sacrificial material blocks 136. The spacer pattern 140 can be formed from individual spacers 145 formed on a single side of the sacrificial material blocks 136, for example, by atomic layer deposition (ALD) or chemical vapor deposition (CVD). In one embodiment, the spacers 145 can be formed as a continuous grid of spacers. In one embodiment, the width of each individual spacer 145 can be in a range between 0.01-0.1 pm. The width of the spacers 145 can be defined by the spacing between the sacrificial material blocks 136 and can be thinner than the minimum critical dimension (CD) of a photolithographic patterning and etching process. In one embodiment, the thickness of the individual spacers 145 can be less than or equal to 0.05 pm. The individual spacers 145 can touch each other at points between the corners of the sacrificial material blocks 136. The spacer pattern 140 can be thicker than 0.05 pm at the corners where the spacers 145 connect. Restated, the aspect ratio (height to width ratio) of the spacers 145 can be as high as 18: 1 or even greater.

[0021] The spacer pattern 140 is made of a spacer material that is etch selective to the sacrificial material and the buffer layer 120. The spacer material can also have a refractive index as low as 1.3 or even lower. The material used to form the spacers 145 can be selected based on the application of the image sensor device or the optical performance required of the image sensor device. In one embodiment, each of the spacers 145 can be a single or multi-layer stack structure. In one embodiment, the material used to form the spacers 145 can be an oxide material, a nitride material, or a material with a low refractive index (e.g., a material with a refractive index lower than 1.3). In another embodiment, the material used to form the spacers 145 can be a material with a high reflectivity, such as a metal. In one embodiment, the spacers can be formed from a combination of a metal and a dielectric material, for example, a metal material (e.g., tungsten or aluminum) surrounded by a layer of a dielectric material (e.g., silicon oxide).

[0022] In an embodiment, the process of forming the spacers 145 (discussed below) causes the first side of the spacers 145 facing away from the sacrificial material pattern to have a sloped portion near the top of the spacers 145 that is not perfectly vertical and is sloped towards the sacrificial material blocks. Thus, the first side has a first slope. The second side of the spacers 145 facing the sacrificial material blocks will be more vertical or can be slightly sloped away from the vertical portion of the spacers 145. Thus, the second side has a second slope that is different from the first slope. Restated, the second side of the spacers 145 facing the sacrificial material blocks can conform to the shape of the sacrificial material blocks and have a different slope than the first side of the spacers 145 facing away from the sacrificial material blocks.

[0023] Figure 1E It is shown that Figure 1DThe apparatus of FIG. 1 is shown with the sacrificial material pattern 135 removed. When the sacrificial material is removed, a self-supporting spacer pattern 140 is retained. As will be further explained below, the self-supporting spacer pattern 140 defines first openings 148 and second openings 149 between four spacers 145. Each of the first openings 148 is defined by four first sides of the spacers 145. Each of the second openings 149 is defined by four second sides of the spacers 145. To reiterate, the first openings 148 are adjacent only the first sides of the spacers 145, and the second openings 149 are adjacent only the second sides of the spacers 145. Based on the geometry of the top of the spacers 145, the first openings 148 will allow slightly more light in than the second openings 149.

[0024] Figure 1F The apparatus of FIG. 1 is shown with the sacrificial material pattern 135 removed. When the sacrificial material is removed, a self-supporting spacer pattern 140 is retained. As will be further explained below, the self-supporting spacer pattern 140 defines first openings 148 and second openings 149 between four spacers 145. Each of the first openings 148 is defined by four first sides of the spacers 145. Each of the second openings 149 is defined by four second sides of the spacers 145. To reiterate, the first openings 148 are adjacent only the first sides of the spacers 145, and the second openings 149 are adjacent only the second sides of the spacers 145. Based on the geometry of the top of the spacers 145, the first openings 148 will allow slightly more light in than the second openings 149. Figure 1E The apparatus of FIG. 1 is shown with the sacrificial material pattern 135 removed. When the sacrificial material is removed, a self-supporting spacer pattern 140 is retained. As will be further explained below, the self-supporting spacer pattern 140 defines first openings 148 and second openings 149 between four spacers 145. Each of the first openings 148 is defined by four first sides of the spacers 145. Each of the second openings 149 is defined by four second sides of the spacers 145. To reiterate, the first openings 148 are adjacent only the first sides of the spacers 145, and the second openings 149 are adjacent only the second sides of the spacers 145. Based on the geometry of the top of the spacers 145, the first openings 148 will allow slightly more light in than the second openings 149.

[0025] Figure 1G The apparatus of FIG. 1 is shown with the sacrificial material pattern 135 removed. When the sacrificial material is removed, a self-supporting spacer pattern 140 is retained. As will be further explained below, the self-supporting spacer pattern 140 defines first openings 148 and second openings 149 between four spacers 145. Each of the first openings 148 is defined by four first sides of the spacers 145. Each of the second openings 149 is defined by four second sides of the spacers 145. To reiterate, the first openings 148 are adjacent only the first sides of the spacers 145, and the second openings 149 are adjacent only the second sides of the spacers 145. Based on the geometry of the top of the spacers 145, the first openings 148 will allow slightly more light in than the second openings 149. Figure 1FThe apparatus of FIG. 1, where a microlens array 160 is formed on the color filter array 150. The microlenses 160 are configured to focus incident light to the corresponding photodiodes 115. In one embodiment, the microlenses 160 can be made of a microlens material, such as a polymer. The microlenses 160 can be hemispherical, or otherwise shaped to operate as a lens based on the difference in refractive index from air to the microlens material. The curvature of each microlens can be configured based on the desired optical performance (e.g., focal length) of the corresponding photodiode 115.

[0026] Figure 1G An image sensor apparatus with a fully embedded color filter array is shown. A substrate 110 has an array of photodiodes 115 disposed in the substrate 110. A buffer layer 120 is formed on the substrate 110. Spacers 145 form a spacer pattern 140. The spacer pattern 140 is formed on the buffer layer 120 such that the buffer layer 120 is between the spacers 145 and the substrate 110. A color filter array 150 is disposed within the first openings 148 and the second openings 149 of the spacer pattern 140 such that the color filter array 150 is disposed in the spacer pattern 140.

[0027] The height of the spacers 145 can be configured based on the desired optical performance of the color filter and microlens array. In one embodiment, the height of the spacers 145 is configured to be less than the height of the color filters in the color filter array 150. In another embodiment, the height of the spacers 145 is configured to be the same as the height of the color filters in the color filter array 150. In yet another embodiment, the height of the spacers 145 is configured to be greater than the height of the color filters in the color filter array 150. Figure 1G In one embodiment, the color filters in the color filter array 150 can have a height that is less than the height of the spacers 145. In another embodiment, the color filters in the color filter array 150 can have a height that is the same as the height of the spacers 145, as shown in FIG. 2. In yet another embodiment, the color filters in the color filter array 150 can have a height that is greater than the height of the spacers 145, as shown in FIG. 3. Figure 1H Figure 1I

[0028] As pixels continue to shrink, the area used to ensure color filter isolation becomes more important. Examples in accordance with the teachings of the present disclosure provide significant advantages in both color filter isolation and density. The spacers 145 provide improved color filter isolation for the color filter array 150. In one example, the spacers 145 are formed of a material that has a lower refractive index than each of the color filters of the color filter array 150. This material property of the spacers 145 and the color filter array 150 causes photons to reflect off the spacers 145 instead of passing through the spacers 145. As a result, the color filters are better isolated from light passing through adjacent color filters, and color filter isolation is improved even with thin spacers 145.

[0029] ​​An advantage of the image sensor device is that it can have high and thin spacers 145 between the color filters that prevent light from directions other than the top side of the device from being directed into the photodiodes 115. Thus, the spacers 145 prevent corruption of the photodiode output. The thin spacers 145 also provide the advantage of not occupying too much area of the fully buried color filter array when viewed from above. The photodiodes 115 require a minimum amount of light to properly sense the incoming light source. Thus, the photodiodes 115 require an amount of area to collect light using the microlenses 160 in order to properly operate. The amount of area required depends on the lighting conditions and other factors. The small area of the spacers 145 allows more photons to pass through the microlenses 160 to the photodiodes 115, rather than colliding with the spacers 145, and thus allows the color filter array 150 and photodiodes 115 to occupy the maximum effective area of the array and have better quantum efficiency when viewed from above. The height of the spacers 145 and the isolation effect also provide better angular response by the image sensor.

[0030] Figures 2A-2H Another example of a cross-sectional view of a fully buried color filter array at different times during the fabrication of the fully buried color filter array according to the teachings of the present disclosure is shown. Figure 2A An image sensor device similar to that of Figure 1A is shown. Figure 2A A pattern of support material 205 disposed on a buffer layer 220 is shown. The buffer layer 220 is disposed on a substrate 210 containing a plurality of photodiodes 215.

[0031] The pattern of support material 205 can be a metal or metalloid, such as tungsten or aluminum. The pattern of support material 205 should be a material that is etch selective to the buffer layer 220 and the sacrificial material layer 230 (discussed below). In one embodiment, the support material 205 can further direct incident light to the individual photodiodes 205 by reflection or refraction, such that optical cross-talk between adjacent photodiodes can be suppressed.

[0032] Figure 2B An image sensor device of Figure 2A is shown, where an adhesive layer 208 is located on the pattern of support material 205. The adhesive layer 208 can be titanium nitride (TiN). The adhesive layer 208 can cover the top surface of the pattern of support material 205. The adhesive layer should be etch selective to the buffer layer 220 and the sacrificial material layer 230 (discussed below).

[0033] Figure 2C An image sensor device of Figure 2BAn image sensor device as in The sacrificial material layer 230 can be made of the same materials as discussed with respect to the sacrificial material layer 130 and formed by the same processes as discussed.

[0034] Figure 2D An image sensor device as in Figure 2C The sacrificial material pattern 235 can include sacrificial material blocks 236. Each sacrificial material block 236 can be centered in an opening of the grid formed by the support material pattern 205. Thus, each sacrificial material block 236 is in contact with four portions of the grid formed by the support material pattern 205, which define the opening in the support material pattern 205. Each sacrificial material block 236 can cover about half of the four portions of the support material pattern 205 and the adhesive layer on top of the four portions of the support material pattern 205.

[0035] Figure 2E An image sensor device as in Figure 2D The spacer pattern 240 can be disposed on top of the adhesive layer 208 with the support material pattern 205 in the middle of the adhesive layer. The spacers 245 form the spacer pattern 240, which can be made of the same materials as disclosed above with respect to the spacer pattern 140, have the same properties as it, and be formed in the same way as it, except that the spacer pattern 240 is formed on the adhesive layer 208. In one embodiment, the spacer pattern 240 can be in the form of a continuous pattern, thus the spacers 245 can be formed as a continuous grid of spacers.

[0036] The height of the spacer pattern 240 can be limited by the strength of the material used to form the spacer pattern 240 and / or the process used to form the spacers 245. By forming the spacer pattern 240 on the adhesive layer 208 on top of the support material pattern 205 instead of directly on the buffer layer 220, the height of the first and second openings 248, 249 formed by the combination of the support material pattern 205, the adhesive layer 208, and the spacer pattern 240 can extend farther from the buffer layer 220 than the first and second openings 148, 149 in the spacer pattern 140 extend from the buffer layer 120.

[0037] Figure 2F An image sensor device as in Figure 2Ean image sensor device of Figure 1 1 1, wherein the pattern of sacrificial material 235 is removed. The pattern of sacrificial material 235 can be removed by the same process described below with respect to the pattern of sacrificial material 135.

[0038] Figure 2G An image sensor device of Figure 1 1 1 is shown. Figure 2F An image sensor device of Figure 1 1 1 is shown, wherein a color filter array 250 is disposed in the first openings 248 and the second openings 249. Each color filter 250 is formed between two adjacent spacers 245. The color filter array 250 can be formed from the same material as the color filter array 150, have the same properties as it, and be formed in the same manner as it, except that the color filter array 250 can have a height that is less than, equal to, or greater than the height of the spacers 245. Thus, the color filter array 250 will have a height that is greater than or less than or equal to the combined height of the spacers 245, the adhesive layer 208, and the pattern of support material 205. Restated, the pattern of spacers 240 on the adhesive layer 208 and the pattern of support material 205 can extend farther from the buffer layer 220 than the color filter array 250.

[0039] Figure 2H An image sensor device of Figure 1 1 1 is shown. Figure 2G An image sensor device of Figure 1 1 1 is shown, wherein a microlens 260 is formed on the color filter array 250. The microlens 260 can be formed from the same material as the microlens 160, have the same properties as it, and be formed in the same manner as it. The focal length of each microlens 260 can depend on the height of the color filter 250. As such, the height of the color filter array 250 can be configured based on the desired optical performance of the image sensor device.

[0040] Figure 2H An image sensor device having a fully embedded color filter array is shown. A substrate 210 has an array of photodiodes 215 disposed in the substrate 210. A buffer layer 220 is formed on the substrate 210. A pattern of support material 205 is formed on the buffer layer 220 such that the buffer layer 220 is between the pattern of support material 205 and the substrate 210. An adhesive layer is formed on the pattern of support material 205 such that the pattern of support material and the buffer layer 220 are between the adhesive layer 208 and the substrate 210. Spacers 245 form a pattern of spacers 240. The pattern of spacers 240 is formed on the buffer layer such that the buffer layer 220, the pattern of support material 205, and the adhesive layer 208 are between the spacers 245 and the substrate 210. A color filter array 250 is disposed within the first openings 248 and the second openings 249 of the pattern of spacers 240 such that the color filter array 150 is disposed in the pattern of spacers 240 and the pattern of support material 205.

[0041] Figure 2H The embodiments shown in Figure 1 1 1 provide a greater fill factor than Figure 1GThe embodiments shown in FIG. 1 1 provide even greater color filter isolation while providing similar color filter array occupancy density. Some photo image sensors can require very high color filter isolation and large color filter occupancy density. However, the height of the spacer 145 given a thickness of the spacer material can be limited by the strength of the spacer material such that the spacer height required for color filter isolation needs to be too great of a spacer thickness for the required color filter array occupancy density. This problem can be solved by placing the spacer 245 on the support material pattern 205 and the adhesive layer 208. This increases the distance that the spacer 245 extends from the buffer layer 220 without increasing the area that the spacer occupies at the top of the color filter array 250. The microlens 260 focuses light toward the middle of the color filter to the photodiode 215 disposed below the middle of the base of the color filter. Thus, the additional area that the support material pattern 205 occupies at the bottom of the color filter has little effect on the photodiode 215 and the color filter array 250 can maintain the same density as the color filter array 150 shown in FIG. 1 1. Figure 1G The color filter array 150 shown in FIG. 1 1 can have a density that is the same as the color filter array 250 shown in FIG. 1 1.

[0042] Figures 3A-3C Example top-down views of the fully-embedded color filter array at different times during the manufacture of the fully-embedded color filter array are shown. Figure 3A Example views of the sacrificial material pattern 335 and the additional sacrificial material pattern 338 are shown. Figure 1C may be Figure 3A Example of the device along line la-la'. The additional sacrificial material pattern 338 can be made of the same material as the sacrificial material pattern 335, have the same properties as it, and be formed in a similar manner as it. The sacrificial material blocks 336 that make up the sacrificial material pattern 335 can form a "checkerboard" pattern. The spaces between the sacrificial material blocks 336 that form the sacrificial material pattern 335 can have about the same size and dimensions as the sacrificial material blocks 336. The additional sacrificial material pattern 338 can be formed to assist in forming the spacers 345 on the periphery of the spacer pattern 340. The additional sacrificial material pattern 338 need not form blocks of the same size as the sacrificial material blocks 336 that form the sacrificial material pattern 335, but only need to define the sidewalls on which the spacers 345 can be formed in order to complete the spacer pattern 340. Thus, the sacrificial material blocks 339 that form the additional sacrificial material pattern 338 can have a different shape than the sacrificial material blocks 336 that form the sacrificial material pattern 335.

[0043] Figure 3B Example views of the sacrificial material pattern 335 and the additional sacrificial material pattern 338 are shown, where the spacer pattern 340 is formed on the sides of the sacrificial material pattern 335. The spacer pattern 340 can form a continuous grid of spacers. Figure 1D may be Figure 3Ban example of a device along line Ib-Ib' of FIG. 1B. Spacers 345 can be formed on the sides of additional sacrificial material pattern 338 in the same manner that spacers 345 are formed on the sidewalls of sacrificial material pattern 335.

[0044] Figure 3C An example view of spacer pattern 340 is shown, where sacrificial material pattern 335 and additional sacrificial material pattern 338 are removed. Figure 1E Figure 3C an example of a device along line Ic-Ic' of FIG. 1C.

[0045] Figure 4 is a flowchart illustrating process steps for one example of fabricating a fully- embedded color filter array device according to the teachings of this disclosure. Figure 4 The process of FIG. 4 can be performed on a device such as the device shown in FIG. 1A. Figure 1A Process block 410 illustrates that the process can begin by forming support material pattern 205 and adhesive layer 208 on the device.

[0046] Support material pattern 205 can be formed by depositing a support material and then etching away some of the support material. For example, the support material can be deposited as an aluminum blanket layer, which can then be etched to form support material pattern 205. The support material pattern can define a square or rectangular grid matching the spacer pattern 340 shown in FIG. 3, but with wider "lines" in the grid. Figures 3B-3C

[0047] In an embodiment, adhesive layer 208 can be formed on top of support material pattern 205 by a vapor deposition process. A nitride hard mask is formed on adhesive layer 208 on top of support material pattern 205, and an etch process can remove adhesive material deposited at locations not covered by the nitride hard mask. The nitride hard mask can then be removed. Adhesive layer 208 can also be formed by any other process that deposits adhesive layer 208 on top of support material pattern 205 instead of on buffer layer 220. Forming support material pattern 205 and adhesive layer 208 is optional, and can not be performed.

[0048] Process block 420 illustrates forming sacrificial material pattern 135 or 235. If support material pattern 205 and adhesive layer 208 are formed on the device, then sacrificial material layer 230 can be formed on top of support material pattern 205, adhesive layer 208, and buffer layer 220. Otherwise, sacrificial material layer 130 can be formed on buffer layer 120.

[0049] ​​The sacrificial material layer 130 or 230 can be formed by deposition, for example, by chemical vapor deposition (CVD). In one embodiment, a chemical mechanical polishing or planarization process can be applied after the deposition of the sacrificial material layer 130 or 230 to smooth or planarize the surface of the sacrificial material layer 230. The sacrificial material layer 130 or 230 can be etched by a dry etching process to form the sacrificial material pattern 135. The sacrificial material pattern 235 can be etched by using the same process described with respect to the sacrificial material pattern 135.

[0050] Process block 430 illustrates that a spacer pattern 140 or 240 is formed on the sidewalls of the sacrificial material. The spacer pattern 140 or 240 can be formed from a single spacer 145 or 245 that is formed on a single side of the sacrificial material block 136 or 236 of the sacrificial material pattern 135 or 235 and also on a side of the sacrificial material block 339 of the additional sacrificial material pattern 338. A spacer material is deposited on the sides of the sacrificial material blocks 136 that make up the sacrificial material pattern 135 or 235, and then the excess spacer material is etched away from the top surface of the buffer layer and the sacrificial material blocks, thereby forming the spacer pattern 140. The deposition can be performed by a vapor phase chemical process, such as atomic layer deposition. The etching can be performed by an anisotropic dry etching process. The etching process can be such that the side of the spacer 145 or 245 that is facing away from the sacrificial material block has a sloped portion that is sloped toward the sacrificial material block. Each of the formed spacers 145 or 245 can have an aspect ratio of up to 18: 1 or more.

[0051] Process block 440 illustrates that the sacrificial material pattern 135 or 235 is removed. The sacrificial material pattern 135 or 235 can be removed by a wet etching process. The removal of the sacrificial material pattern 135 or 235 causes the second openings 149 or 249 to be open. Both the dry etching process and the wet etching process performed on the sacrificial material should be substantially free of etching the spacers 145 or 245, the adhesive layer 208, the support material pattern 205, or the buffer layer 120 or 220.

[0052] Process block 450 illustrates that a color filter array 150 or 250 and a microlens 160 or 260 are formed. The color filter array 150 or 250 can be formed in the first openings 148 or 248 and the second openings 149 or 249. The microlens 160 or 260 can be formed on the color filter array 150 or 250.

[0053] Figure 5is a diagram illustrating one example of an imaging system including a fully embedded color filter array in accordance with the teachings of this disclosure. As shown in the depicted example, the imaging system 500 includes a pixel array 505 coupled to control circuitry 535 and readout circuitry 515 coupled to functional logic 525.

[0054] The pixel array 505 is a two-dimensional ("2D") array of pixels 507 (e.g., pixels Pl, P2,..., Pn). In one embodiment, each pixel is a complementary metal-oxide-semiconductor ("CMOS") imaging pixel. The pixel array 505 can be implemented as a front-side illuminated image sensor array or a back-side illuminated image sensor array. In one embodiment, the pixel array 505 includes a fully embedded color filter array, such as the fully embedded color filter array depicted in FIGS. 1H or 2H. The fully embedded color filter array includes a plurality of embedded color filters for the pixels 507. The fully embedded color filter array can be arranged with a pattern, such as: a Bayer pattern or mosaic of red, green, and blue additive filters (e.g., RGB, RGBG, or GRGB); a filter pattern of cyan, magenta, yellow, and key (black) subtractive filters (e.g., CMYK); a combination of both; or other. As shown, each pixel is arranged in rows (e.g., rows Rl through Ry) and columns (e.g., columns Cl through Cx) to capture image data of a person, place, or object, which can then be used to render a 2D image of the person, place, or object. Figure 1G

[0055] In one embodiment, after each pixel has captured its image data or image charge, the image data is read out by the readout circuitry 515 and transmitted to the functional logic 525. The readout circuitry 515 can include amplification circuitry (e.g., differential amplifier circuitry), analog-to-digital ("ADC") conversion circuitry, or other.

[0056] The functional logic 525 can include logic and memory for storing image data or for manipulating the image data even by applying post-image effects (e.g., cropping, rotating, removing red-eye, adjusting brightness, adjusting contrast, or other). In one example, the readout circuitry 515 can read out one row of image data at a time along a readout column line (as illustrated), or can read out the image data using various other techniques (such as serial readout or all pixels read out simultaneously and in full parallel).

[0057] ​The control circuit 535 is coupled to the pixel array 205. The control circuit 535 can include logic and memory for controlling the operational characteristics of the pixel array 505. For example, the control circuit 535 can generate shutter signals for controlling image acquisition. In one embodiment, the shutter signals are global shutter signals that are used to simultaneously enable all of the pixels 507 within the pixel array 505 to capture their respective image data at a single acquisition window. In an alternative embodiment, the shutter signals are rolling shutter signals whereby each row, column, or group of pixels are sequentially enabled during successive acquisition windows.

[0058] The description of the embodiments of the application presented above, including that described in the abstract, is not intended to be exhaustive or to be limited to the precise form disclosed. While specific embodiments and examples of the application are described herein for illustrative purposes, various equivalent modifications are possible within the scope of the application, as those skilled in the relevant art will recognize. Indeed, it is understood that specific voltages, currents, frequency, power range values, times, etc. are provided for illustrative purposes only and other values can be utilized in other embodiments and examples in accordance with the teachings of the present application.

[0059] These modifications can be made in the instance of the application as described above. The terms used in the following claims should not be construed to limit the application to the specific embodiments disclosed in the specification and the claims. Rather, the scope of the application is to be determined entirely by the appended claims, which are to be construed in accordance with the established doctrine of claim interpretation according to 35 U.S.C. § 112(6). Thus, the specification and drawings are to be regarded as illustrative only and not restrictive in nature.

Claims

1. An image sensor comprising: a substrate, wherein an array of photodiodes is disposed in the substrate; a plurality of spacers arranged in a spacer pattern to form a grid of spacers that defines first openings; a buffer layer disposed between the substrate and the spacer pattern; a color filter array disposed in the spacer pattern, wherein the plurality of spacers directly contact color filters included in the color filter array; and a pattern of support material structured to form a grid of support material that defines second openings that overlap the first openings defined by the grid of spacers, wherein the pattern of support material is disposed between the spacer pattern and the buffer layer, wherein the first openings of the grid of spacers are wider than the second openings of the grid of support material such that there is a lateral separation distance between edges of individual spacers included in the plurality of spacers and corresponding edges in the pattern of support material, wherein the individual spacers interface with the pattern of support material, wherein proximal portions of the individual spacers included in the plurality of spacers extend from near the pattern of support material, wherein distal portions of the individual spacers extend from the proximal portions, respectively, and wherein each of the distal portions narrows to form a single distal end, a width of the single distal end having less than a corresponding uniform width of the proximal portions.

2. The image sensor of claim 1, wherein the spacer pattern extends further from the buffer layer than the color filter array extends from the buffer layer.

3. The image sensor of claim 1, wherein at least one spacer included in the plurality of spacers has an aspect ratio of at least 18:

1.

4. The image sensor of claim 1, wherein a thickness of each of the plurality of spacers is less than or equal to 0.05 pm.

5. The image sensor of claim 1, wherein each of the color filters included in the color filter array is disposed in the first and second openings that are aligned, respectively.

6. The image sensor of claim 1, wherein each of the plurality of spacers is composed of a spacer material having a lower refractive index than a refractive index of each color filter included in the color filter array.

7. The image sensor of claim 1, wherein a combined height of the spacer pattern and the pattern of support material is greater than a height of the color filter array.

8. The image sensor of claim 1, wherein a portion of support material included in the pattern of support material and disposed between two adjacent second openings included in the second openings has a first width that is greater than a second width of individual spacers included in the plurality of spacers.

9. The image sensor of claim 1, wherein the pattern of support material further includes an adhesive layer disposed between the plurality of spacers included in the pattern of spacers and support material included in the pattern of support material to provide adhesion between the support material and the pattern of spacers.

10. The image sensor of claim 9, wherein the adhesive layer directly contacts the color filters included in a color filter array.

11. The image sensor of claim 1, further comprising a microlens array, wherein each microlens included in the microlens array extends at least partially into a respective opening included in the first openings of the pattern of spacers, wherein the color filter array is disposed between the buffer layer and the microlens array, and wherein the distal end of the individual spacers is disposed between corresponding adjacent microlenses included in the microlens array.

12. An image sensor comprising: a substrate, wherein an array of photodiodes is disposed in the substrate; a plurality of spacers arranged in a pattern of spacers to form a grid of spacers that defines first openings; a buffer layer disposed between the pattern of spacers and the substrate; a color filter array disposed in the pattern of spacers; and a pattern of support material structured to form a grid of support material that defines second openings, wherein the pattern of support material is disposed between the pattern of spacers and the buffer layer, wherein the first openings of the grid of spacers are wider than the second openings of the grid of support material such that there is a lateral separation distance between an edge of an individual spacer included in the plurality of spacers and a corresponding edge in the pattern of support material, wherein the individual spacer interfaces with the pattern of support material, and wherein the first and second openings define a cavity that is at least partially filled by a color filter included in the color filter array, wherein a proximal portion of the individual spacer included in the plurality of spacers extends from near the pattern of support material, wherein a distal portion of the individual spacer extends from the proximal portion, respectively, and wherein each of the distal portions narrows to form a single distal end having a width that is less than a corresponding uniform width of the proximal portion.

13. The image sensor of claim 12, wherein the pattern of support material further includes an adhesive layer disposed between the plurality of spacers included in the pattern of spacers and support material included in the pattern of support material, wherein the plurality of spacers directly contact the color filters included in the color filter array.

14. The image sensor of claim 12, wherein at least one spacer included in the plurality of spacers has an aspect ratio of at least 18: 1, and wherein a thickness of the individual spacer included in the plurality of spacers is less than or equal to 0.05 pm. ​ 15. The image sensor of claim 12, wherein each of the second openings is positioned to overlap a corresponding one of the first openings formed by the plurality of spacers included in the spacer pattern.

16. The image sensor of claim 15, further comprising a microlens array, wherein each microlens included in the microlens array extends at least partially into a respective one of the first openings included in the spacer pattern, wherein the color filter array is disposed between the buffer layer and the microlens array, and wherein a combined height of the spacer pattern and the support material pattern is greater than a height of the color filter array such that the distal ends of the individual spacers are disposed between corresponding adjacent microlenses included in the microlens array.

17. The image sensor of claim 12, wherein the support material pattern further includes an adhesive layer disposed between the plurality of spacers included in the spacer pattern and a support material included in the support material pattern, wherein both the adhesive layer and the support material have an etch selectivity with respect to the buffer layer.

18. The image sensor of claim 12, wherein the support material pattern directly contacts the color filters included in the color filter array.

19. The image sensor of claim 12, wherein the plurality of spacers are composed of a spacer material having a refractive index of 1.3 or lower.

20. The image sensor of claim 12, wherein a first pair of distal ends of a first pair of spacers included in the plurality of spacers adjacent to each other are tilted with respect to each other.

Images