Solid-state imaging device

Abstract

The solid-state imaging device includes a first set of units disposed in a substrate. The first set of units includes a first pixel unit, a second pixel unit, and a third pixel unit arranged in sequence, and these pixel units each have a photoelectric conversion element. This solid-state imaging device further includes a metal gate structure disposed above the first set of units. The metal gate structure includes a first portion disposed between the first pixel unit and the second pixel unit, and a second portion disposed between the second pixel unit and the third pixel unit. The first portion has a first width, and the second portion has a second width greater than the first width.

Description

Technical Field

[0001] Embodiments of the present invention relate to a solid-state imaging device, and more particularly to a microlens-free solid-state imaging device. Background Art

[0002] An image sensor is a semiconductor device that converts photons into electrical signals. Image sensors are generally categorized as charge-coupled devices (CCDs) and complementary metal-oxide-semiconductor (CMOS) image sensors. CMOS sensors consist of photodiodes that detect incident light and convert it into electrical signals, as well as logic circuits that transmit and process these signals.

[0003] In recent years, phase detection autofocus (PDAF) technology has been introduced into electronic products such as digital single-lens reflex cameras (DSLRs), digital still cameras (DSCs), and smartphone cameras. Its principle is to provide a pair of semi-shielded green pixels with microlenses mounted on them. The signal difference between these two green pixels creates the phase detection autofocus (PDAF) function. However, because the formation of microlenses on the pixels limits the thickness of the pixel's color filter, it is difficult to improve the color purity of the incident light irradiating the pixel's photoelectric conversion element.

[0004] Therefore, it is highly anticipated to develop a novel image sensing structure that does not require microlenses. Summary of the Invention

[0005] In solid-state imaging devices, incident light strikes non-central areas of the pixel array at an oblique angle, greater than the normal angle of the incident light striking the central area of the pixel array. The incident angle is the angle between the normal to the light-receiving surface of the solid-state imaging device and the incident light. Consequently, crosstalk between pixel cells is higher in non-central areas than in the central area, reducing the sensitivity of the phase detection autofocus (PDAF) pixels in these non-central areas.

[0006] According to an embodiment of the present disclosure, the metal gate structure of a solid-state imaging device includes a metal gate disposed on one side of a phase detection autofocus (PDAF) pixel unit near the center of the pixel array. The width of the metal gate is greater than the width of a metal gate disposed between two image-capture pixels. This reduces crosstalk between the pixels and improves the sensitivity of the PDAF pixels.

[0007] An embodiment of the present invention provides a solid-state imaging device, which includes a first set of units disposed in a substrate. The first set of units includes a first pixel unit, a second pixel unit, and a third pixel unit arranged in sequence, and these pixel units have their respective photoelectric conversion elements. The solid-state imaging device further includes a metal gate structure disposed above the first set of units. The metal gate structure includes a first portion disposed between the first pixel unit and the second pixel unit, and a second portion disposed between the second pixel unit and the third pixel unit. The first portion has a first width, and the second portion has a second width greater than the first width.

[0008] In conjunction with the accompanying drawings, it will be described in detail through the following embodiments. Description of the Drawings

[0009] Through the following detailed description in conjunction with the accompanying drawings, the content of the embodiments of the present invention can be better understood. It should be emphasized that, according to the standard practice in the industry, many components (features) are not drawn to scale. In fact, for the sake of clear discussion, the sizes of various components may be arbitrarily increased or decreased.

[0010] Figure 1A is a top view schematic diagram showing a solid-state imaging device according to some embodiments of the present invention;

[0011] Figure 1B-1 、 Figure 1B-2 and Figure 1B-3 are cross-sectional schematic diagrams showing parts of the solid-state imaging device shown in Figure 1A according to some embodiments of the present invention;

[0012] Figure 1C-1 、 Figure 1C-2 and Figure 1C-3 are cross-sectional schematic diagrams showing parts of the solid-state imaging device according to other some embodiments of the present invention;

[0013] Figure 2A is a top view schematic diagram showing a solid-state imaging device according to other some embodiments of the present invention;

[0014] Figure 2B are cross-sectional schematic diagrams showing parts of the solid-state imaging device shown in Figure 2A according to some embodiments of the present invention;

[0015] Figure 3 is a chart of angular response curves (ARC) according to some embodiments of the present invention, which illustrates the simulation results of the relationship between the sensitivity of the phase detection autofocus (PDAF) pixel units in the central area of the pixel array and the incident angle of the incident light on the phase detection autofocus (PDAF) pixel units;

[0016] Figure 4 It is a diagram of an angle response curve (ARC) according to some embodiments of the present invention, which illustrates the simulation results of the relationship between the sensitivity of the phase detection autofocus (PDAF) pixel units in the central region of the pixel array and the incident angle of the incident light on the phase detection autofocus (PDAF) pixel units.

[0017] Among them, the reference numerals are explained as follows:

[0018] 100, 200 Solid-state imaging device

[0019] 102 Substrate

[0020] 104 Array region

[0021] 105 Light-shielding region

[0022] 106, 1061, 1062, 1063, 1064 Phase detection autofocus (PDAF) pixel units

[0023] 108, 1081, 1082, 1083, 1084, 1085, 1086, 1087, 1088, 1089, 10810, 10811 Image capture pixel units

[0024] 109 Pixel array

[0025] 109C Central region

[0026] 109O Non-central region

[0027] 110 Metal gate structure

[0028] 112C, 112E, 112M, 112F, 142C, 142E, 142M First part

[0029] 114C, 114E, 114M, 114F, 144C, 144E, 144M Second part

[0030] 115C, 115E, 115M, 115F, 145C, 145E, 145M Third part

[0031] 120 Isolation structure

[0032] 122, 123 Photoelectric conversion element

[0033] 124 High-k dielectric film

[0034] 126 Buffer layer

[0035] 128 Passivation layer

[0036] 130 dielectric grid structure

[0037] 132, 133 Color Filters

[0038] 134 planarization layer

[0039] 136 Low refractive index oxide layer

[0040] 300, 400 charts

[0041] 301A, 301B, 302A, 302B, 303A, 303B, 401A, 402A curves

[0042] C Center

[0043] C1 First Central Line

[0044] C2 Second Central Line

[0045] D1 First direction

[0046] D2 Second direction

[0047] E1, E2 edge

[0048] T Thickness

[0049] W1C, W1E, W1M First width

[0050] W2C, W2E, W2M Second width

[0051] W3C, W3E, W3M Third width

[0052] W4C, W4E fourth width

[0053] W5C, W5E fifth width

[0054] W6C, W6E Sixth width DETAILED DESCRIPTION

[0055] The following content provides many different embodiments or examples for implementing different components of the embodiments of the present invention. Specific embodiments or examples of components and configurations are described below to simplify the embodiments of the present invention. Of course, these are merely examples and are not intended to limit the embodiments of the present invention. For example, if the description mentions that a first component is formed on a second component, it may include an embodiment in which the first and second components are in direct contact, and it may also include an embodiment in which an additional component is formed between the first and second components so that the first and second components are not in direct contact. In addition, the embodiments of the present invention may repeat component symbols and / or letters in many examples. These repetitions are for the purpose of simplicity and clarity and do not in themselves represent a specific relationship between the various embodiments and / or configurations discussed.

[0056] Some variations of some embodiments are discussed below. In the various schematic diagrams and illustrated embodiments, the same elements are denoted by the same reference numerals. It should be understood that additional steps may be provided before, during, and after the described methods, and some of the described steps may be replaced or omitted for some other method embodiments.

[0057] Please refer to Figure 1A , Figure 1A , which is a top - view schematic diagram showing a solid - state imaging device 100 according to some embodiments of the present invention. The solid - state imaging device 100 includes a substrate 102, a pixel array 109 disposed in the substrate 102, and a metal gate structure 110 disposed above the pixel array 109.

[0058] The substrate 102 includes an array region 104 and a light - shielding region 105 surrounding the array region 104. The pixel array 109 is located in the array region 104. The pixel array 109 includes phase - detection autofocus (PDAF) pixel units 106 and image - capture pixel units 108 (represented by dashed squares), and the phase - detection autofocus (PDAF) pixel units 106 and image - capture pixel units 108 are arranged in a first direction D1 and a second direction D2, and the second direction D2 is perpendicular to the first direction D1.

[0059] The first direction D1 is parallel to the length direction of the rectangular shape of the pixel array 109, and the second direction D2 is parallel to the width direction of the rectangular shape of the pixel array 109. The first direction D1 is a direction extending from the center C of the pixel array 109 towards the edge E1, and the second direction D2 is a direction extending from the center C of the pixel array 109 towards the edge E2.

[0060] The pixel array 109 has a first central line C1 parallel to the first direction D1 and a second central line C2 parallel to the second direction D2. The first central line C1 intersects the second central line C2 at the center C of the pixel array 109. The pixel array 109 includes a central region 109C and a non - central region 109O surrounding the central region 109C. The center C of the pixel array 109 is located within the central region 109C. In some embodiments, the central region 109C may have a rectangular shape or a circular shape. In some embodiments, the central region 109C may include a region extending 15% of the length (or width) of the pixel array 109 from the center C of the pixel array 109 towards the edge.

[0061] The phase - detection autofocus (PDAF) pixel units 106 and image - capture pixel units 108 each include a respective photoelectric conversion element (not shown) formed in the substrate 102 Figure 1A)。The distance to an object is determined by the phase difference of light incident on paired phase detection autofocus (PDAF) pixel units 106, and phase detection autofocus (PDAF) can be used to quickly focus on the object.

[0062] A metal gate structure 110 is formed on a substrate 102. The metal gate structure 110 includes a horizontal portion extending along a first direction D1 and a vertical portion extending along a second direction D2. These portions of the metal gate structure 110 are correspondingly disposed at the boundaries between pixel units. Specifically, a part of the metal gate structure 110 is disposed at the boundary between two adjacent image capture pixel units 108, which is defined as the first part 112. A part of the metal gate structure 110 is disposed at the boundaries between a phase detection autofocus (PDAF) pixel unit 108 and its two adjacent image capture pixel units 108, which are defined as the second part 114 and the third part 115, where the second part 114 is disposed on the side of the phase detection autofocus (PDAF) pixel unit 106 close to the center C of the pixel array, and the third part 115 is disposed on the other side of the phase detection autofocus (PDAF) pixel unit 106 close to the edge E1 (or E2) of the pixel array.

[0063] For example, a group of units is disposed in the central region 109C of the pixel array 109. This group of units includes an image capture pixel unit 1081, an image capture pixel unit 1082, a phase detection autofocus (PDAF) pixel unit 1061, and an image capture pixel unit 1083 arranged in sequence along the first direction D1. The first part 112 C is disposed between the image capture pixel unit 1081 and the image capture pixel unit 1082. The second part 114 C is disposed between the image capture pixel unit 1082 and the phase detection autofocus (PDAF) pixel unit 1061. The third part 115 C is disposed between the phase detection autofocus (PDAF) pixel unit 1061 and the image capture pixel unit 1083.

[0064] For example, a group of units is disposed in the middle region of the pixel array 109. This group of units includes an image capture pixel unit 1084, an image capture pixel unit 1085, a phase detection autofocus (PDAF) pixel unit 1062, and an image capture pixel unit 1086 arranged in sequence along the first direction D1. The first part 112 M is disposed between the image capture pixel unit 1084 and the image capture pixel unit 1085. The second part 114 M is disposed between the image capture pixel unit 1085 and the phase detection autofocus (PDAF) pixel unit 1062. The third part 115 MIt is located between the phase detection auto focus (PDAF) pixel unit 1062 and the image capture pixel unit 1086 .

[0065] For example, a group of units is disposed in the edge region of the pixel array 109. The group of units includes an image capture pixel unit 1087, an image capture pixel unit 1088, a phase detection auto focus (PDAF) pixel unit 1063, and an image capture pixel unit 1089, which are sequentially arranged in the first direction D1. E The second portion 114 is disposed between the image capturing pixel unit 1087 and the image capturing pixel unit 1088. E It is located between the image capture pixel unit 1088 and the phase detection auto focus (PDAF) pixel unit 1063. E It is located between the phase detection auto focus (PDAF) pixel unit 1063 and the image capture pixel unit 1089 .

[0066] For example, a group of units is disposed in a corner area of the pixel array 109. The group of units includes image capture pixel units 108 sequentially arranged in the second direction D2. 10 , phase detection auto focus (PDAF) pixel unit 1064, and image capture pixel unit 108 11 Part 2 114 F Set in the image capture pixel unit 108 10 and the phase detection auto focus (PDAF) pixel unit 1064. The third portion 115 F Set in the phase detection auto focus (PDAF) pixel unit 1064 and the image capture pixel unit 108 11 between.

[0067] For clarity and brevity, Figure 1A Only the above components are shown, the rest can be seen in Figure 1B-1 、 Figure 1B-2 and Figure 1B-3 .

[0068] Please refer to Figure 1B-1 、 Figure 1B-2 and Figure 1B-3 , Figure 1B-1 、 Figure 1B-2 and Figure 1B-3 Schematic cross-sectional views of portions of the solid-state imaging device 100 at the central region, middle region, and edge region are shown, respectively. In one embodiment, the substrate 102 may be a silicon substrate. In some embodiments, the substrate 102 may be a silicon germanium substrate, a gallium arsenide substrate, or the like. In some embodiments, the substrate 102 may be a germanium substrate or a semiconductor-on-insulator substrate, such as a silicon-on-insulator (SOI) substrate.

[0069] The solid-state imaging device 100 further includes an isolation structure 120 disposed in the substrate 102. The isolation structure 120 defines phase detection autofocus (PDAF) pixel units 108 and image capture pixel units 106 in the substrate 102. In other words, the isolation structure 120 is formed at the boundaries between the phase detection autofocus (PDAF) pixel units 106 and the image capture pixel units 108, and at the boundaries between two adjacent image capture pixel units 108. In some embodiments, the isolation structure 120 may be or include silicon oxide, silicon nitride, silicon oxynitride, or a combination of the foregoing, and may be formed by a patterning process and a deposition process.

[0070] Photoelectric conversion elements 122 and 123 (such as photodiodes) are disposed in the substrate 102, where the photoelectric conversion element 122 is disposed in the image capture pixel unit 108, and the photoelectric conversion element 123 is disposed in the phase detection autofocus (PDAF) pixel unit 106. The isolation structure 120 separates the photoelectric conversion elements 122 from each other and separates the photoelectric conversion element 122 from the photoelectric conversion element 123. In some embodiments, a single photoelectric conversion element 122 is formed in a single image capture pixel unit 108, and four photoelectric conversion elements 123 are formed in a single phase detection autofocus (PDAF) pixel unit 106. The photoelectric conversion elements 122 and 123 are configured to sense incident light and generate intensity signals according to the intensity of the incident light irradiated on the photoelectric conversion elements.

[0071] In some embodiments, the photoelectric conversion elements 122 and 123 are disposed adjacent to the back surface of the substrate 102. The front surface of the substrate 102 generally has a wiring layer of various circuits (not shown) required for the solid-state imaging device 100 formed thereon. In some embodiments shown in FIGS. 1A to 1B-3, the solid-state imaging device 100 is a backside illumination (BSI) imaging device. In a backside illumination imaging device, the back surface of the substrate 102 on which the photoelectric conversion elements 122 and 123 are formed is close to the incident light receiving surface of the solid-state imaging device 100. The front surface of the substrate 102 on which the wiring layer is formed is away from the incident light receiving surface of the solid-state imaging device 100.

[0072] In some other embodiments, the solid-state imaging device 100 may be a front-side illumination (FSI) imaging device. In a front-side illumination imaging device, the front surface of the substrate 102 on which the wiring layer is formed is close to the incident light receiving surface of the solid-state imaging device 100, and the back surface of the substrate 102 on which the photoelectric conversion elements 122 and 123 are formed is away from the incident light receiving surface of the solid-state imaging device 100.

[0073] The solid-state imaging device 100 further includes a high-k (high-dielectric constant) film 124 and a buffer layer 126. The high-k film 124 is disposed on the substrate 102 and covers the photoelectric conversion elements 122 and 123. The buffer layer 126 is disposed on the high-k film 124. In some embodiments, the high-k film 124 may be or include hafnium oxide (HfO2), hafnium tantalum oxide (HfTaO), hafnium titanium oxide (HfTiO), hafnium zirconium oxide (HfZrO), tantalum pentoxide (Ta2O5), a combination of the foregoing, or a similar material, and the high-k film 124 can be formed by a deposition process. The buffer layer 126 may be or include silicon oxide, silicon nitride, or silicon oxynitride, and can be formed by a deposition process.

[0074] A metal gate structure 110 including a first portion 112, a second portion 114, and a third portion 115 is disposed on the buffer layer 126. The metal gate structure 110 is configured for optical isolation between adjacent pixel units to increase sensitivity (e.g., quantum efficiency (QE)) and reduce crosstalk between pixel units. In some embodiments, the metal gate structure 110 may be or include tungsten (W), copper (Cu), or aluminum copper (AlCu), and can be formed by a deposition process or electroplating, followed by a patterning process.

[0075] The solid-state imaging device 100 further includes a passivation layer 128. The passivation layer 128 is disposed on the upper surface of the buffer layer 126 and covers the metal gate structure 110. The passivation layer 128 fills the openings in the metal gate structure 110. The passivation layer 128 has a flat top surface. In some embodiments, the passivation layer 128 may be or include silicon oxide, silicon nitride, silicon oxynitride, a combination of the foregoing, or a similar material, and can be formed by a deposition process. In some other embodiments, the passivation layer 128 may not be formed. The thickness of the passivation layer 128 may be from about 0 micrometers (μm) to about 0.3 micrometers, for example, from about 0.05 micrometers to about 0.3 micrometers.

[0076] The solid-state imaging device 100 further includes a dielectric gate structure 130, color filters 132 and 133 disposed on the upper surface of the passivation layer 128. The dielectric gate structure 130 defines openings filled by the color filters 132 and 133. The color filter 132 is correspondingly disposed above the image capture pixel unit 108, and the color filter 133 is correspondingly disposed above the phase detection autofocus (PDAF) pixel unit 106. In some embodiments, the dielectric gate structure 130 is disposed on the metal gate structure 110 and is aligned with the metal gate structure 110. When viewed from a top view angle, the dielectric gate structure 130 has the same or similar shape as the metal gate structure 110.

[0077] A portion of the dielectric grating structure 130 is disposed between two adjacent image capture pixel units 108, which is defined as the first portion 142. A portion of the dielectric grating structure 130 is disposed between the phase detection autofocus (PDAF) pixel unit 106 and two adjacent image capture pixel units 108, which is defined as the second portion 144 and the third portion 145. The second portion 144 is disposed on a side of the phase detection autofocus (PDAF) pixel unit 106 closer to the center C of the pixel array. The third portion 145 is disposed on the other side of the phase detection autofocus (PDAF) pixel unit 106 closer to the edge E1 (or E2) of the pixel array.

[0078] In some embodiments, the dielectric grating structure 130 may be a light-transmissive material, and its refractive index is less than the refractive indices of the color filters 132 and 133. Due to the low refractive index of the dielectric grating structure 130, the incident light in the color filters 132 and 133 undergoes total internal reflection, and thus the dielectric grating structure 130 serves as a light guide to guide the incident light through the color filters 132 and 133 to the photoelectric conversion elements 122 and 123. In some embodiments, the dielectric grating structure 130 may be or include a dielectric, such as silicon oxide (e.g., SiO2) or hafnium oxide (e.g., HfO2), and may be formed by a deposition process and a patterning process. The color filters 132 and 133 are specified for the corresponding colors or wavelengths of the incident light, and are configured to filter all incident light other than the specified colors or wavelengths.

[0079] The solid-state imaging device 100 further includes a planarization layer 134 and a low-refractive-index (low-n) oxide layer 136. The planarization layer 134 is disposed on the dielectric grating structure 130 and the color filters 132 and 133. In some embodiments, the refractive index of the planarization layer 134 is less than 1.6. The low-refractive-index oxide layer 136 is an antireflection layer, and it has a refractive index ranging from about 1.2 to about 1.5. In some embodiments, the low-refractive-index oxide layer 136 may be or include silicon oxide (e.g., SiO2), and may be formed by a deposition process or a coating process.

[0080] In the embodiments of the present invention, no microlens is formed on the solid-state imaging device 100. In other words, the solid-state imaging device 100 does not include a microlens formed on the low-refractive-index layer 136. Since the microlenses corresponding to the pixel units 106 and 108 will focus the incident light on the focal point, the thickness of the color filter is limited. Compared with the case of forming a microlens on the solid-state imaging device 100, in the embodiments without a microlens, the thickness of the color filter can be increased. For example, the thickness of the color filters iced filter 132 and 133 of 1B-1 to 1B-3 can be about 0.85 micrometers to about 1.3 micrometers. In the embodiments of the present invention, the thicker color filters 132 and 133 improve the color purity of the incident light, resulting in an enhancement of the performance of the solid-state imaging device.

[0081] However, the incident light irradiates on the non-central region of the pixel array at an oblique angle, which is greater than the normal angle at which the incident light irradiates on the central region of the pixel array. The incident angle is the angle between the normal of the light receiving surface of the solid-state imaging device and the incident light. Therefore, the crosstalk of the pixel units in the non-central region is higher than that in the central region, which reduces the sensitivity of the phase detection autofocus (PDAF) pixel units in the non-central region. Embodiments of the present invention utilize a metal gate structure 110, which is disposed on a side of the phase detection autofocus (PDAF) pixel unit 106 close to the center C of the pixel array. The width of this metal gate is greater than the width of the metal gate disposed between two adjacent image capture pixel units 108, which reduces the crosstalk between the pixel units and increases the sensitivity of the phase detection autofocus (PDAF) pixel units. This part will be described in detail later.

[0082] Referring back to Figure 1A , Figure 1A FIG. shows three groups of pixel units arranged in the first direction D1 to illustrate the width variation of the metal gate structure 110, where these three groups of pixel units are located in the central region 109C, the middle region, and the edge region of the pixel array 109, respectively, and each includes a phase detection autofocus (PDAF) pixel unit 106 and several image capture pixel units 108. The above-mentioned middle region and edge region are located in the non-central region 109O of the pixel array 109, and the middle region is between the central region 109C and the edge region.

[0083] Please refer to FIGS. 1A to 1B-3. When measured from the first direction D1, the first part 112 has respective first widths W1, and the first widths W1 are consistent from the center C to the edge E1 of the pixel array 109. In some embodiments, the first width W1 can be from about 0.06 micrometers to about 0.2 micrometers. For example, the first part 112 of the edge region of the pixel array 109 E of the first width W1 E is the same as the first part 112 of the middle region of the pixel array 109 M of the first width W1 M and the first part 112 of the central region of the pixel array 109 C of the first width W1 C is the same.

[0084] When measured from the first direction D1, the second part 114 has respective second widths W2, and the second widths W2 increase from the center C of the pixel array 109 towards the edge E1. For example, the second width W2 of the second part 114 of the edge region of the pixel array 109 E of the second width W2 E is greater than the second width W2 of the second part 114 of the middle region of the pixel array 109 MThe second width W2 M In the second part 114 of the middle region of the pixel array 109 M The second width W2 M is greater than that of the second part 114 in the central region 109C of the pixel array 109 C The second width W2 C .

[0085] When measured from the first direction D1, the third part 115 has respective third widths W3, and the third widths W3 decrease from the center C of the pixel array 109 towards the edge E1. For example, in the third part 115 of the edge region of the pixel array 109 E The third width W3 E is less than that of the third part 115 in the middle region of the pixel array 109 M The third width W3 M In the third part 115 of the middle region of the pixel array 109 M The third width W3 M is less than that of the third part 115 in the central region 109C of the pixel array 109 C The third width W3 C . In some embodiments, the second width W2 and the third width W3 can be in the range of about 0.11 micrometers to about 0.65 micrometers.

[0086] Furthermore, in the central region 109C, the first width W1 of the first part 112 C is equal to the second width W2 of the second part 114 C and the third width W3 of the third part 115 C C C C . Therefore, in the non - central region 109O, the second width W2 of the second part 114 is greater than the first width W1 of the first part 112, and the first width W1 of the first part 112 is greater than the third width W3 of the third part 115.

[0087] Furthermore, in some embodiments, the second width W2 M plus the third width W3 M is equal to twice the first width W1 M E E E The second width W2plus the third width W3is equal to twice the first width W1 E E .

[0088] Please refer to FIG. 1B - 1. In the central region 109C, half of the second part 114 C is located in the image capture pixel unit 108, and the second part 114 C ​The other half is located in the phase detection autofocus (PDAF) pixel unit 106. Referring to FIGS. 1B-2 and 1B-3, in the non-central region 109O, more than half of the second portion 114 is located in the phase detection autofocus (PDAF) pixel unit 106, and less than half of the second portion 114 is located in the image capture pixel unit 108.

[0089] It is noted that since the second portion 114 has an increased second width W2 in the phase detection autofocus (PDAF) pixel unit 106, the second portion 114 can advantageously block the penetration of incident light between adjacent pixel units, which reduces crosstalk between pixel units and increases the sensitivity of the phase detection autofocus (PDAF) pixel unit 106.

[0090] Continuing to refer to Figure 1A , when measured from the second direction D2, the first portion 112 has respective fourth widths W4 that are uniform from the center of the pixel array 109 towards the edge E2. When measured from the second direction D2, the second portion 114 has respective fifth widths W5 that increase from the center of the pixel array 109 towards the edge E2. When measured from the second direction D2, the third portion 115 has respective sixth widths W6 that decrease from the center of the pixel array 109 towards the edge E2. Furthermore, the fourth width W4 of the first portion 112 C is equal to the fifth width W5 of the second portion 114 C and the sixth width W6 of the third portion 115 C .

[0091] According to the embodiment shown in FIGS. 1A to 1B-3, in the non-central region of the pixel array, the second portion of the metal gate structure is disposed on the first side close to the center of the array in the phase detection autofocus (PDAF) pixel unit, and its thickness is greater than the thickness of the first portion of the metal gate structure disposed between two image capture pixel units, so as to provide a good balance between the color purity of incident light and crosstalk.

[0092] Figures 1C-1 to 1C-3 is a cross-sectional schematic diagram according to some other embodiments of the present invention, which shows some parts of the solid-state imaging device 100 in the central region, the intermediate region, and the edge region, where the same elements as Figures 1B-1 to 1B-3 are denoted by the same symbols and their descriptions are omitted. Figures 1C-1 to 1C-3 The embodiment of Figures 1B-1 to 1B-3 differs from the embodiment of Figures 1C-1 to 1C-3 in that, in the embodiment of Figures 1B-1 to 1B-3 , the passivation layer 128 as shown in

[0093] In addition, the metal gate structure 110 contacts the dielectric gate structure 130. The metal gate structure 110 and the dielectric gate structure 130 together define an opening filled with color filters 132 and 133. Thus, this can further increase the thickness of the color filters 132 and 133. For example, the thickness of the color filters 132 and 133 can range from about 0.85 micrometers to about 1.3 micrometers. Therefore, the color purity of the incident light is improved, thereby enhancing the performance of the solid-state imaging device.

[0094] Figure 2A and Figure 2B are top view and cross-sectional schematic diagrams showing the solid-state imaging device 200 according to some other embodiments of the present invention, where the same elements as Figures 1A to 1B-3 are denoted by the same symbols and their descriptions are omitted.

[0095] Figure 2A Shows three groups of pixel units arranged in the first direction D1 to illustrate the width variation of the metal gate structure 110, where these three groups of pixel units are located in the central region 109C, the intermediate region, and the edge region of the pixel array 109, respectively, and each includes a phase detection autofocus (PDAF) pixel unit 106 and several image capture pixel units 108. The above-mentioned intermediate region and the edge region are located in the non-central region 109O of the pixel array 109, and the intermediate region is between the central region 109C and the edge region. FIG. 2B shows a cross-sectional schematic diagram of a part of the solid-state imaging device 200 in the edge region.

[0096] Please refer to Figure 2A and Figure 2B , when measured from the first direction D1, the first part 112 has respective first widths W1, and the first widths W1 are consistent from the center C to the edge E1 of the pixel array 109. In some embodiments, the first width W1 can be between about 0.06 micrometers and about 0.2 micrometers. For example, the first part 112 of the edge region of the pixel array 109 E has the first width W1 E which is the same as the first part 112 of the intermediate region of the pixel array 109 M has the first width W1 M and the first part 112 of the central region of the pixel array 109 C has the first width W1 C which is the same.

[0097] When measured from the first direction D1, the second part 114 has respective second widths W2, and the second widths W2 are consistent from the center C to the edge E1 of the pixel array 109. For example, the second part 114 of the edge region of the pixel array 109 E has the second width W2 E which is the same as the second part 114 of the intermediate region of the pixel array 109M The second width W2 M and the second part 114 of the central region of the pixel array 109 C The second width W2 C is the same.

[0098] When measured from the first direction D1, the third part 115 has respective third widths W3, and the third widths W3 are consistent from the center C to the edge E1 of the pixel array 109. For example, the third part 115 of the edge region of the pixel array 109 E The third width W3 E is the same as the third part 115 of the intermediate region of the pixel array 109 M The third width W3 M and the third part 115 of the central region of the pixel array 109 C The third width W3 C is the same. In some embodiments, the second width W2 and the third width W3 may be from about 0.11 micrometers to about 0.65 micrometers.

[0099] Furthermore, in the central region 109C and the non - central region 109O, the second width W2 of the second part 114 may be equal to the third width W3 of the third part 115 and greater than the first width W1 of the first part 112.

[0100] Referring to FIG. 2B, the second part 114 E more than half is located in the phase - detection autofocus (PDAF) pixel units 106, while the second part 114 E less than half is located in the image - capture pixel units 108.

[0101] Notably, since the second part 114 has an increased second width W2 in the phase - detection autofocus (PDAF) pixel units 106, the second part 114 can advantageously block the penetration of incident light between adjacent pixel units, which reduces crosstalk between pixel units and increases the sensitivity of the phase - detection autofocus (PDAF) pixel units.

[0102] Similarly, when measured from the second direction D2, the first part 112 has respective fourth widths W4, and the fourth widths W4 are consistent from the center of the pixel array 109 towards the edge E2. The second part 114 has respective fifth widths W5, and the fifth widths W5 are consistent from the center of the pixel array 109 towards the edge E2. The third part 115 has respective sixth widths W6, and the sixth widths W6 are consistent from the center of the pixel array 109 towards the edge E2. In the embodiment as Figure 2A shown, the fifth width W5 is equal to the sixth width W6 and greater than the third width W4.

[0103] According to Figure 2A and Figure 2B In the non - central region of the pixel array, for the second part of the metal gate structure, it is disposed on the side closer to the array center of the phase - detection autofocus (PDAF) pixel unit, and its thickness is greater than the thickness of the first part of the metal gate structure disposed between two image - capture pixel units, so as to provide a good balance between the color purity and crosstalk of the incident light.

[0104] Furthermore, in some embodiments, the width of the dielectric gate structure 130 can be different from the width of the metal gate structure 110, as Figure 2B shown. For example, the second part 144 of the dielectric gate structure 130 can be narrower than the second part 114 of the metal gate structure 110. The third part 145 of the dielectric gate structure 130 can be narrower than the third part 115 of the metal gate structure 110.

[0105] In addition, embodiments of the present invention provide a method for adjusting the sensitivity characteristics of phase - detection autofocus (PDAF) pixel units without micro - lenses.

[0106] Figure 3 and Figure 4 are graphs 300 and 400 of the angular response curve (ARC) according to some embodiments of the present invention, which illustrate the simulation results of the relationship between the sensitivity of the phase - detection autofocus (PDAF) pixel units in the central region of the pixel array and the incident angle of the incident light on the phase - detection autofocus (PDAF) pixel units. The curves ending with A (e.g., 301A) show the sensitivity characteristics of the phase - detection autofocus (PDAF) pixel unit 106 collected via the photoelectric conversion element 123 closer to the right side, while the curves ending with B (e.g., 301B) show the sensitivity characteristics of the phase - detection autofocus (PDAF) pixel unit 106 collected via the photoelectric conversion element 123 closer to the left side.

[0107] Please refer to Figure 3 , curves 301A - 303B show the sensitivity characteristics of the phase - detection autofocus (PDAF) pixel unit 106 as Figure 2B shown, where curves 303A - B, 302A - B, 301A - B respectively represent that the second width W2 of the second part 114 is high, medium, and low.

[0108] Graph 300 shows that a second part 114 with a higher second width W2 results in a higher sensitivity slope. Therefore, in the case of no micro - lens, by adjusting the width of the second part of the metal gate structure, the sensitivity characteristics of the phase - detection autofocus (PDAF) pixel unit 106 can be adjusted.

[0109] Please refer to Figure 4, curves 401A and 402B show the sensitivity characteristics of the phase detection autofocus (PDAF) pixel unit 106 as Figure 1B-1 shown, where curve 401A represents that the thickness T of the passivation layer 128 is 0 microns (i.e., not formed), and curve 402A represents that the thickness T of the passivation layer 128 is 0.4 microns. Chart 400 shows that a passivation layer 128 with a higher thickness T results in higher sensitivity characteristics. Therefore, in the absence of a microlens, the sensitivity characteristics of the phase detection autofocus (PDAF) pixel unit 106 can be adjusted by adjusting the thickness of the passivation layer.

[0110] According to an embodiment of the present invention, the solid-state imaging device does not include a microlens formed on the solid-state imaging device. Therefore, the thickness of the color filter can be increased, which improves the color purity of the incident light and thus enhances the performance of the solid-state imaging device.

[0111] Furthermore, in the non-central region of the pixel array, the second part of the metal gate structure is disposed on the side of the phase detection autofocus (PDAF) pixel unit closer to the center of the array, and its thickness is greater than the thickness of the first part of the metal gate structure disposed between two image capture pixel units, to provide a good balance between the color purity of the incident light and crosstalk.

[0112] Although the present invention has been described by way of example and in terms of a preferred embodiment, it should be understood that the invention is not limited to the disclosed embodiments. On the contrary, it encompasses various modifications and similar arrangements (which are obvious to those skilled in the art to which the invention pertains). Therefore, the scope of the appended claims should be given the broadest interpretation to include all such modifications and similar arrangements.

Claims

1. A solid-state imaging device, comprising: A first group of units, disposed in a pixel array of a substrate, including a first pixel unit, a second pixel unit, a third pixel unit, and a fourth pixel unit arranged in sequence in a direction from the center of the pixel array towards an edge of the pixel array, and the first pixel unit, the second pixel unit, the third pixel unit, and the fourth pixel unit each have a photoelectric conversion element, wherein the first pixel unit, the second pixel unit, and the fourth pixel unit are image capture pixel units, and the third pixel unit is a phase detection autofocus pixel unit; And A metal gate structure, disposed on the first group of units, including: A first portion, disposed between the first pixel unit and the second pixel unit, and having a first width; A second portion, disposed between the second pixel unit and the third pixel unit, and having a second width, the second width being greater than the first width; A third portion, the third portion being disposed between the third pixel unit and the fourth pixel unit, and having a third width, the third width being less than the first width, and the second width plus the third width being equal to twice the first width; A dielectric gate structure, disposed on the metal gate structure; and A passivation layer, disposed between the metal gate structure and the dielectric gate structure, wherein the passivation layer fills the metal gate structure.

2. The solid-state imaging device according to claim 1, further comprising: A second group of units, disposed in the substrate, including a fifth pixel unit, a sixth pixel unit, and a seventh pixel unit arranged in sequence, and the fifth pixel unit, the sixth pixel unit, and the seventh pixel unit each have a photoelectric conversion element, wherein the fifth pixel unit and the sixth pixel unit are image capture pixel units, and the seventh pixel unit is a phase detection autofocus pixel unit; Wherein the metal gate structure further includes: A fourth portion, disposed between the fifth pixel unit and the sixth pixel unit, and having a fourth width; and A fifth portion, disposed between the sixth pixel unit and the seventh pixel unit, and having a fifth width, the fifth width being equal to the fourth width.

3. The solid-state imaging device according to claim 2, further comprising: A third group of units, disposed in the substrate, including an eighth pixel unit, a ninth pixel unit, and a tenth pixel unit arranged in sequence, and the eighth pixel unit, the ninth pixel unit, and the tenth pixel unit each have a photoelectric conversion element, wherein the eighth pixel unit and the ninth pixel unit are image capture pixel units, and the tenth pixel unit is a phase detection autofocus pixel unit; Wherein the metal gate structure further includes: A sixth portion, disposed between the eighth pixel unit and the ninth pixel unit, and having a sixth width; and A seventh portion, disposed between the ninth pixel unit and the tenth pixel unit, and having a seventh width, the seventh width being greater than the sixth width.

4. The solid-state imaging device according to claim 3, wherein The seventh width is greater than the second width, and the second width is greater than the fifth width.

5. The solid-state imaging device according to claim 3, wherein: The first group of units, the second group of units, and the third group of units are arranged in the array, and the second group of units, the first group of units, and the third group of units are arranged in this order in this direction.

6. The solid-state imaging device according to claim 3, wherein: The second group of units further includes an eleventh pixel unit, wherein the seventh pixel unit is located between the sixth pixel unit and the eleventh pixel unit, and the eleventh pixel unit is an image capture pixel unit; The third group of units further includes a twelfth pixel unit, wherein the tenth pixel unit is located between the ninth pixel unit and the twelfth pixel unit, and the twelfth pixel unit is an image capture pixel unit; Wherein the metal gate structure further includes: An eighth portion, disposed between the seventh pixel unit and the eleventh pixel unit, and having an eighth width; and A ninth portion, disposed between the tenth pixel unit and the twelfth pixel unit, and having a ninth width, the ninth width being less than the eighth width.

7. The solid-state imaging device according to claim 1, further comprising: An isolation structure, disposed in the substrate, wherein the isolation structure defines the first group of units; A high-k dielectric film, disposed on the substrate; And A buffer layer, disposed between the high-k dielectric film and the metal gate structure, Wherein the thickness of the passivation layer ranges from 0.05 micrometers to 0.3 micrometers.

8. The solid-state imaging device according to claim 1, further comprising: A plurality of color filters, disposed in the dielectric gate structure, and the color filters are further disposed in the metal gate structure; A planarization layer, disposed on the dielectric gate structure and the color filters; and A low-refractive-index oxide layer, disposed on the planarization layer, Wherein the dielectric gate structure includes: A first portion, disposed on the first portion of the metal gate structure, and the opposite sidewalls of the first portion of the dielectric gate structure are aligned with the opposite sidewalls of the first portion of the metal gate structure; and A second portion, disposed on the second portion of the metal gate structure, and the opposite sidewalls of the second portion of the dielectric gate structure are aligned with the opposite sidewalls of the second portion of the metal gate structure.

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