Flare reduction image sensor

Abstract

A flare reduction image sensor is provided. The flare reduction image sensor includes a plurality of N P pixels and a plurality of N ML microlenses, where each of the plurality of microlenses is aligned with a respective pixel of the plurality of pixels such that N P =N ML . The flare reduction image sensor also includes a plurality of N L phase shift layers, where each phase shift layer is aligned with a respective microlens of the plurality of microlenses, where N L is less than or equal to N ML .

Description

Technical Field

[0001] This invention relates to a flare reduction image sensor. Background Technology

[0002] Camera modules in commercial products such as standalone digital cameras, mobile devices, automotive parts, and medical devices include image sensors with pixel arrays. A pixel array comprises multiple pixels arranged in a two-dimensional periodic array. Many image sensors include microlens arrays formed by multiple microlenses, each aligned with a corresponding pixel. The periodicity of the pixel array and the microlens array on it causes the image sensor to resemble a reflective two-dimensional diffraction grating. A portion of the light incident on the image sensor is diffracted onto the camera's imaging lens. Various elements of the camera, such as the cover glass, infrared cutoff filter, and the surface of the imaging lens, reflect this diffracted light back to the image sensor, producing image artifacts known as petal flares. Summary of the Invention

[0003] The embodiments disclosed herein reduce petal flares.

[0004] In a first aspect, the present invention provides a flare reduction image sensor. The flare reduction image sensor comprises N... P Multiple pixels and a number of N ML Multiple microlenses, each of which is aligned with a corresponding pixel in a plurality of pixels, such that N P =N ML Flare reduction image sensors also include N L Multiple phase-shifting layers, wherein each phase-shifting layer is aligned with a corresponding microlens in a plurality of microlenses, wherein N L Less than or equal to N ML .

[0005] In some embodiments, the pixel array has a pixel pitch P in the respective orthogonal directions x and y. x and P y Each of the orthogonal directions x and y is parallel to the top surface of the semiconductor substrate; and the average spacing between each phase-shifting layer is D in directions x and y, respectively. x and D y It satisfies at least one of the following: (i) D x More than P x and (ii)D y More than P y .

[0006] In some embodiments, the average spacing D x and D y The pixel pitch is greater than the specified value in both the x and y directions, such that Dx More than P x And D y More than P y .

[0007] In some embodiments, the average spacing between any two closest phase-shifting layers is Where n is a positive integer.

[0008] In some embodiments, the distance between any two closest microlenses without an accompanying phase-shift layer is Where n is a positive integer.

[0009] In some embodiments, the phase-shifting layer is The average spacing is diagonally adjacent.

[0010] In some embodiments, alternating rows of microlenses in the x or y direction are accompanied by a phase-shifting layer.

[0011] In some embodiments, the pixel pitches in the orthogonal directions x and y are equal, such that P x =P y .

[0012] In some embodiments, the average spacing between the phase-shifting layers in the orthogonal directions x and y is equal, such that D x =D y .

[0013] In some embodiments, the average spacing between any two closest phase-shifting layers is Where n is a positive integer.

[0014] In some embodiments, the total number of phase-shifting layers is equal to half the number of microlenses, such that N L =1 / 2N ML .

[0015] In some embodiments, the average spacing between any two closest phase-shifting layers is mP. x , where m is an integer greater than 1.

[0016] In some embodiments, the total number of phase-shifting layers is equal to one-quarter of the number of microlenses, such that N L =1 / 4N ML .

[0017] In some embodiments, the distance between any two closest microlenses without accompanying phase-shift layers is mP. x , where m is an integer greater than 1.

[0018] In some embodiments, the total number of phase-shifting layers is equal to three-quarters of the number of microlenses, such that N L =3 / 4N ML .

[0019] In some embodiments, each microlens has an upper surface and a lower surface between the upper surface and the semiconductor substrate, wherein for each of the plurality of phase shift layers and the corresponding microlens aligned therewith, the phase shift layer is above the upper surface of the microlens.

[0020] In some embodiments, the phase-shifting layer is formed of oxide.

[0021] In some embodiments, the optical thickness of the phase-shifting layer is a quarter-wavelength at a wavelength between 620 nm and 750 nm.

[0022] In some embodiments, the wavelength is 630 nm. Attached Figure Description

[0023] Figure 1 A camera for imaging a scene according to an embodiment is depicted.

[0024] Figure 2 This is a schematic diagram of the pixel array of a flare reduction image sensor. A flare reduction image sensor is... Figure 1 An example of an image sensor.

[0025] Figure 3 A pixel array having a phase-shifting layer aligned with a set of microlenses is shown according to an embodiment.

[0026] Figure 4 This is a diagram illustrating the arrangement of the phase-shifting layer array according to an embodiment.

[0027] Figure 5 Five examples of pixel subarrays are shown, each with a different arrangement of phase shift layers.

[0028] Figure 6 It shows Figure 5 The graph shows the measurement results of the second-order diffraction intensity of five examples of pixel subarrays shown. Detailed Implementation

[0029] Petal flares occur when light is scattered from one lens within an image sensor onto another, distorting the image. For example, light can interfere with nearby lenses when it is reflected, diffracted, or incident on them. One aspect of this embodiment includes the understanding that the primary source of petal flares is light incident on and focused by lenses or microlenses of adjacent pixels. Embodiments of this disclosure reduce petal flares by adding a phase-shifting layer to the microlenses.

[0030] Microlenses can be lenses with widths ranging from 10 micrometers to 1 millimeter. The phase-shifting layer can be a chemical vapor deposition (CVD) oxide layer on the microlens, with a thickness equivalent to a quarter-wavelength of the red wavelength.

[0031] Figure 1 An image sensor 100 is shown, which includes a pixel array 154. Figure 1 In the depicted scenario, image sensor 100 is incorporated into camera 190, which images the scene. Camera 190 includes image sensor 100, which includes pixel array 154. Image sensor 100 may be part of a chip-scale package or an on-board chip package.

[0032] Figure 2 This is a schematic cross-sectional view of a flare reduction image sensor 200, which is an example of an image sensor 100. Figure 2 The cross section shown in the figure is orthogonal to the plane formed by the orthogonal directions 298X and 298Y (hereinafter referred to as the xy plane), each of which is orthogonal to the direction 298Z. Figure 2 The cross-sectional plane depicted is parallel to the yz plane. In this text, the xy plane is formed by orthogonal directions 298X and 298Y, and the plane parallel to the xy plane is referred to as the transverse plane. Unless otherwise stated, the height of an object in this text refers to the extent of the object in direction 298Z or in a direction 180° opposite to direction 298Z.

[0033] The flare reduction image sensor 200 includes a semiconductor substrate 210, a plurality of pixels 220 formed therein, a plurality of microlenses 260, and a plurality of phase shift layers 270. The technical benefit of the phase shift layers 270 is to prevent the aforementioned petal-like flares within the image sensor 200. The plurality of pixels 220 form a pixel array 220A, and the plurality of microlenses 260 form a microlens array 260A.

[0034] In one embodiment, the flare reduction image sensor 200 includes an intermediate layer 205 between a microlens 260 and a semiconductor substrate 210. The intermediate layer 205 may include at least one of a spectral filter and a buffer oxide layer.

[0035] Semiconductor substrate 210 has a top substrate surface 219, which can be perpendicular to direction 298Z. Multiple pixels 220 form a pixel array 220A, which has a pixel pitch P in corresponding orthogonal directions x and y. x and P y And by N P It consists of N pixels, where N PIt is a positive integer. Multiple pixels 220 include pixels 220(1) to 220(N). P ).

[0036] Microlens 260 has an optical axis 262, which can be perpendicular to the top substrate surface 219. Microlens 260 has an upper surface 269 and a lower surface 261. The lower surface 261 of microlens 260 can be flat in a plane parallel to the xy plane. The upper surface 269 of microlens 260 has a radius R around the optical axis 262. m The convex curved portion. The flare reduction image sensor 200 may include a plurality of microlenses 260 forming a microlens array 260A. In an embodiment, the microlens array 260A has N... P Each microlens 260 is aligned with a corresponding pixel 220.

[0037] Each phase-shifting layer 270 is aligned with a corresponding microlens 260 to form a phase-shifting layer array. The phase-shifting layer array consists of N L It consists of 270 phase-shifting layers, of which N L Equal to or less than N P In one embodiment, the phase-shifting layer 270 has the same dimensions and curvature as the upper surface 269 of the microlens 260. The phase-shifting layer has a thickness 274, which can be between 100 and 200 nanometers. In another embodiment, the phase-shifting layer 270 is a conformal coating on the upper surface 269.

[0038] In this embodiment, the optical thickness of the phase-shifting layer 270 is equal to a quarter-wavelength at a wavelength between 600 nm and 750 nm, wherein the optical thickness at the free-space wavelength λ0 is the product of the geometric thickness of the phase-shifting layer 270 and the refractive index of the phase-shifting layer 270 at the free-space wavelength λ0. For example, the free-space wavelength λ0 can be 630 nm. In this embodiment, the quarter-wavelength optical thickness is applicable to red, blue, and green wavelengths, respectively, or one of 600 nm to 750 nm, 400 nm to 525 nm, and 475 nm to 560 nm.

[0039] The phase-shifting layer 270 may be a CVD oxide layer fabricated as part of the microlens 260 or deposited on top of the microlens 260. A photoresist layer may be used to protect the phase-shifting layer 270 during the etching process to form the microlens 260.

[0040] Figure 3 This is an unfolded diagram of the flare reduction image sensor 200. Figure 3 The cross section shown in the diagram is orthogonal to the xy plane and is perpendicular to it. Figure 2 The cross sections are on the same plane.

[0041] Figure 3 The section 395 is indicated. Section 395 is Figure 4 The cross section is parallel to the xy plane. Figure 4 This is a plan view of the flare reduction image sensor 200, viewed from plane 395. Figure 4 This indicates the direction 298X′, which is orthogonal to 298Z and lies in the plane formed by 298X and 298Y. Direction 298X′ forms a 45° angle with both directions 298X and 298Y in the xy-plane. It is best to refer to the following description together. Figure 3 and Figure 4 .

[0042] Figure 3 The flare reduction image sensor 200 includes a filter layer 390, multiple pixels 220, multiple microlenses 260, and multiple phase shift layers 270. The filter layer 390 may be an infrared cutoff filter.

[0043] exist Figure 3 In the illustrated example, the flare reduction image sensor 200 has a phase-shifting layer 270 on a microlens 260, and adjacent microlenses of the microlens 260 do not have accompanying phase-shifting layers, such that the total number of phase-shifting layers 270 is N. L The total number N of 260 microlenses ML Half of, or N L =1 / 2N ML .

[0044] Pixel array 220A has pixel pitch P in the corresponding directions x and y. x and P y In this embodiment, the pixel pitch can be between 0.5 μm and 3 μm in the x and y directions. Each phase-shifting layer 270 can be separated from the adjacent phase-shifting layer by a distance D in the respective x and y directions. x and D y In the embodiment, D x Greater than P x And D y Greater than P y .exist Figure 3 and Figure 4 In the example shown, P x and P y The phase shift layers are equal in length, or of length *a*, and the phase shift layer 270 is periodic in the direction of 298X′, with a phase shift layer pitch of *b*.

[0045] In the example of the flare reduction image sensor 200, the microlens array 260A has the same pitch as the pixel array 220A. In an embodiment, the microlens array 260A with a pitch of 264 acts as a diffraction grating for the reflected light 330, d sinθ m =m iλ, where d represents the pitch of the microlens array 260A (264), and θ m The angle of the reflected light is 335°, m i λ is the order of the maximum intensity, and λ is the wavelength of the incident light. In the maximum intensity of the reflected light at 330°, the second order or m... i =2, causing image flare when reflected light 330 is absorbed or detected in image sensor 200. After its phase is shifted by half a wave by phase shift layer 270, the phase-shifted reflected light 332 can produce destructive interference at the second-order intensity maximum, resulting in reduced image flare. In this embodiment, the angle of the reflected light at the second-order intensity maximum is between 30° and 40°.

[0046] Figure 4 The periodicity of the phase-shifting layer 270 shown in the example can be represented by a repeating pattern of an N×N array of pixels or microlenses, where N is a positive number in the x and y directions. For example, N can be 2, and the possible patterns of a 2×2 array are as follows: Figure 5 The image shows pixel subarrays 510, 520, 530, 540, and 550. Figure 5 In the diagram, shaded circles (such as 515 and 526) indicate the location of the phase-shifting layer, while uncovered circles (such as 525 and 536) indicate the location of the microlens without an accompanying phase-shifting layer. Figure 5 Each square (such as 511 or 522) in the diagram illustrates the pixel aligned with the corresponding microlens (such as 515 or 526).

[0047] When repeating (e.g., tiling) a 2×2 array pattern under any multiple 90° rotations around the z direction in the xy plane, Figure 5 Each pixel subarray in the array produces the same configuration of phase-shifting layers. For example, pixel subarray 550 includes a microlens 558 aligned with the phase-shifting layers. When the 2×2 array pattern is tiled, the pitch of the phase-shifting layers is twice the pitch of the pixel array or microlens array, and the total number of phase-shifting layers is one-quarter of the total number of pixels. When the 2×2 array pattern is rotated about a 298Z direction, the pitch and total number of phase-shifting layers aligned with the corresponding microlenses do not change.

[0048] In the pixel subarray 510, each pixel (511, 512, 513, and 514) aligned with the corresponding microlens (515, 516, 517, and 518) includes a phase-shifting layer aligned with the corresponding microlens. In fact, in the case of a 2×2 tiled pattern of the pixel subarray 510, the phase-shifting layer is aligned with each microlens of the image sensor, and thus with each pixel of the image sensor. In this pixel subarray 510, the number of phase-shifting layers is equal to each of the number of pixels in the pixel array and the number of microlenses, N. L =N ML=N P And the pixel pitch is the same as the pitch of the phase-shifting layer: P x =D x and P y =D y .

[0049] In the pixel subarray 520, three of the four microlenses (526, 527, and 528) shown in the 2×2 array have phase-shifting layers aligned with the microlenses. In the case of a tiled pattern of the 2×2 array of the pixel subarray 520, the number of microlenses with aligned phase-shifting layers is three-quarters of the total number of microlenses, such that N L =3 / 4N ML =3 / 4N P In this embodiment, the distance between any two closest microlenses without an accompanying phase-shift layer is mP. x , where m is an integer greater than 1.

[0050] In the pixel subarray 530, microlenses 537 and 538 in the second row parallel to the 298X direction both have aligned phase-shifting layers. In the case of this 2×2 array tiling pattern, each row parallel to the 298X direction or each column parallel to the 298Y direction has all microlenses aligned with the phase-shifting layers, while adjacent rows or columns have all microlenses without phase-shifting layers. The total number of phase-shifting layers is half the total number of pixels, such that N L =1 / 2N ML =1 / 2N P In an embodiment, alternating rows of microlenses in the x or y direction are accompanied by a phase-shifting layer.

[0051] Pixel subarray 540 is equivalent to Figure 3 and Figure 4 The example shown has a total number of phase-shifting layers that is half the number of pixels in the pixel array: N L =1 / 2N ML =1 / 2N P In the 298X′ direction, if P x =P y =a, then the phase-shifting layer array has or The pitch. In embodiments, the pitch of the phase-shifting layer array can be an integer multiple of the base pitch: Where n is a positive integer.

[0052] In the pixel subarray 550, one of the four microlenses 558 shown in the 2×2 array has a phase-shifting layer aligned with the microlens. The total number of microlenses with aligned phase-shifting layers is one-quarter of the total number of microlenses, such that N L=1 / 4N ML =1 / 4N P When tiling a 2×2 array pattern, the pitch of the phase-shifting layer array is equal to twice the pixel array pitch: or D x =D y =2P x =2P y =2a. In an embodiment, the pitch of the phase-shifting layer array can be an integer multiple of the base pitch: b = na, where n is a positive integer.

[0053] Figure 6 Graph 600 shows the second-order diffraction intensity of light in the wavelength range of 400 nm to 700 nm. Graph 600 includes curves corresponding to... Figure 5 Diffraction measurements were performed on pixel subarrays 510, 520, 530, 540, and 550, respectively. The diffraction results show that pixel subarrays 520–550 perform better in reducing second-order diffraction intensity at lower wavelengths compared to pixel subarray 510. Among pixel subarrays 510–550, pixel subarray 540 exhibits the best performance in reducing second-order diffraction intensity over a wider wavelength range.

[0054] Feature combination

[0055] The features described above and those in the following claims can be combined in various ways without departing from the scope of the invention. The examples listed below illustrate some possible, non-limiting combinations.

[0056] (A1) A flare reduction image sensor comprising N components in a semiconductor substrate. P Multiple pixels and a number of N ML Multiple microlenses, multiple pixels forming a pixel array, each microlens being aligned with a corresponding pixel in the array, and the multiple microlenses forming a microlens array, N ML equals N P Flare reduction image sensors also include N L Multiple phase-shifting layers, each of which is aligned with a corresponding microlens in the microlens array, N L Less than or equal to N P .

[0057] (A2) In the embodiment of the image sensor (A1), the pixel array has a pixel pitch P in the corresponding orthogonal directions x and y. x and P y Each of the orthogonal directions x and y is parallel to the top surface of the semiconductor substrate. The average spacing between each phase-shifting layer is D in directions x and y, respectively. x and Dy It satisfies at least one of the following: (i) D x More than P x and (ii)D y More than P y .

[0058] (A3) In an embodiment of the image sensor (A1), each microlens has an upper surface and a lower surface between the upper surface and the semiconductor substrate. For each of the plurality of phase-shifting layers and the corresponding microlens aligned thereto, the phase-shifting layer is above the upper surface of the microlens.

[0059] (A4) In an embodiment of the image sensor (A1), the phase shift layer is formed of oxide.

[0060] (A5) In an embodiment of the image sensor (A1), the optical thickness of the phase-shifting layer is a quarter-wavelength at a wavelength between 620 nm and 750 nm.

[0061] (A6) In the embodiment of the image sensor (A5), the wavelength is 630 nm.

[0062] (A7) In any of the embodiments of the image sensors (A2)–(A6), the average spacing D x and D y It is greater than the pixel pitch in both the x and y directions, making D x More than P x And D y More than P y .

[0063] (A8) In the embodiment of the image sensor (A7), the phase-shifting layer is used to... The average spacing is diagonally adjacent.

[0064] (A9) In any embodiment of the image sensor (A2)–(A7), the average spacing between any two closest phase-shifting layers is Where n is a positive integer.

[0065] (A10) In any embodiment of the image sensor (A2)–(A7), the distance between any two closest microlenses without an accompanying phase-shift layer is Where n is a positive integer.

[0066] (A11) In any of the image sensors (A2)–(A7), alternating rows of microlenses in the x or y direction are accompanied by a phase-shifting layer.

[0067] (A12) In any embodiment of the image sensor (A2)–(A7), the pixel pitch is equal in the orthogonal directions x and y, such that P x =P y .

[0068] (A13) In the embodiment of the image sensor (A12), the average spacing between each phase-shifting layer in the orthogonal directions x and y is equal, such that D x =D y .

[0069] (A14) In the embodiment of the image sensor (A13), the average spacing between any two closest phase-shifting layers is Where n is a positive integer.

[0070] (A15) In the embodiment of the image sensor (A14), the total number of phase-shifting layers is equal to half the number of microlenses, such that N L =1 / 2N ML .

[0071] (A16) In the embodiment of the image sensor (A13), the average spacing between any two closest phase-shifting layers is mP. x , where m is an integer greater than 1.

[0072] (A17) In the embodiment of the image sensor (A16), the total number of phase-shifting layers is equal to one-quarter of the number of microlenses, such that N L =1 / 4N ML .

[0073] (A18) In the embodiment of the image sensor (A13), the distance between any two closest microlenses without an accompanying phase-shift layer is mP. x , where m is an integer greater than 1.

[0074] (A19) In the embodiment of the image sensor (A18), the total number of phase-shifting layers is equal to three-quarters of the number of microlenses, such that N L =3 / 4N ML .

[0075] Modifications to the above methods and systems may be made without departing from the scope of the embodiments of the present invention. Therefore, it should be noted that the content contained in the above specification or shown in the accompanying drawings should be understood as illustrative rather than restrictive. In this document, unless otherwise stated, the phrase "in embodiments" is equivalent to the phrase "in some embodiments" and does not refer to all embodiments. The following claims are intended to cover all general and specific features described herein, as well as all statements regarding the scope of the methods and systems of the present invention, and linguistically, can be said to be somewhere in between.

Claims

1. A flare reduction image sensor, comprising: a number N of pixels, the number N of pixels being in a semiconductor substrate and forming a pixel array having a pixel pitch P P and P x and P y in respective orthogonal directions x and y, each of the orthogonal directions x and y being parallel to a top surface of the semiconductor substrate; a number N ML of microlenses, each microlens of the number of microlenses being aligned with a respective one of the number of pixels and the number of microlenses forming a microlens array, N ML being equal to N P ; and a number N L of phase shift layers, each of the number N L of phase shift layers aligned with a respective one of the microlens array and having an optical thickness equal to a quarter wave at a wavelength between 620 nm and 750 nm, N P , an average spacing between the respective phase shift layers in the directions x and y being D x and D y , respectively, that satisfies at least one of (i) D x exceeds P x and (ii) D y exceeds P y .

2. The flare reduction image sensor of claim 1, wherein the average pitch D x and D y are greater than the pixel pitch in both directions x and y, such that D x exceeds P x and D y exceeds P y .

3. The flare reduction image sensor of claim 1, wherein an average spacing between any two closest phase shift layers is where n is a positive integer.

4. The flare reduction image sensor of claim 1, wherein the distance between any two nearest micro lenses without an accompanying phase shift layer is where n is a positive integer.

5. The flare reduction image sensor of claim 4, wherein the phase shift layers are diagonally adjacent with an average spacing of 1.5 microns.

6. The flare reduction image sensor of claim 1, wherein alternating rows of microlenses in a direction x or y are accompanied by a phase shift layer.

7. The flare reduction image sensor of claim 1, wherein the pixel pitch in orthogonal directions x and y are equal, such that P x = P y .

8. The flare reduction image sensor of claim 7, wherein the average spacing between respective phase shift layers in orthogonal directions x and y is equal, such that D x = D y .

9. The flare reduction image sensor of claim 8, wherein an average spacing between any two closest phase shift layers is where n is a positive integer.

10. The flare reduction image sensor of claim 9, wherein a total number of the phase shift layers is equal to half of a number of the microlenses, such that N L = 1 / 2N ML .

11. The flare reduction image sensor of claim 8, wherein the average spacing between any two closest phase shift layers is mP x where m is an integer greater than 1.

12. The flare reduction image sensor of claim 11, wherein a total number of the phase shift layers is equal to one quarter of a number of the microlenses, such that N L = 1 / 4N ML .

13. The flare reduction image sensor of claim 8, wherein the distance between any two nearest micro lenses without an accompanying phase shift layer is mP x where m is an integer greater than 1.

14. The flare reduction image sensor of claim 13, wherein a total number of the phase shift layers is equal to three quarters of a number of the microlenses, such that N L = 3 / 4N ML .

15. The flare reduction image sensor of claim 1, wherein each microlens has an upper surface and a lower surface between the upper surface and the semiconductor substrate, for each phase shift layer of the plurality of phase shift layers and a respective microlens of the plurality of microlenses aligned therewith, the phase shift layer is over the upper surface of the microlens.

16. The flare reduction image sensor of claim 1, wherein each phase shift layer of the plurality of phase shift layers is formed from an oxide.

17. A flare reduction image sensor, comprising: a number N P of pixels, the number N of pixels being in a semiconductor substrate and forming a pixel array; a number N ML of microlenses, each microlens of the number of microlenses being aligned with a respective one of the number of pixels and the number of microlenses forming a microlens array, N ML being equal to N P ; and The quantity is N L Multiple phase-shifting layers, each of the multiple phase-shifting layers (i) being aligned with a corresponding microlens in the microlens array, N L Less than N P (ii) and has an optical thickness equal to a quarter-wavelength at wavelengths between 620 nm and 750 nm.

18. The flare reduction image sensor of claim 17, wherein the wavelength is 630 nm.

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