Image sensing device

Abstract

An image sensing device is provided, comprising a sensing region that converts incident light to receive the incident light and generate photocharge corresponding to the incident light, and a transistor region located on one side of the sensing region that reads out a pixel signal corresponding to the photocharge generated in the sensing region. The sensing region includes: a substrate having a first surface on which incident light is incident and a second surface opposite to the first surface, and including a photoelectric conversion region for converting the incident light into photocharge; and a first trench guide located on the second surface surrounding the photoelectric conversion region, and scattering reflected light into the substrate. The reflected light is a portion of the incident light and is transmitted through the substrate.

Description

Technical Field

[0001] The technology and implementation methods disclosed in this patent document generally relate to an image sensing device. Background Technology

[0002] Image sensors convert optical images into electrical signals. Recently, with advancements in industries such as computer and communications, the demand for image sensors has been increasing in various fields, including digital cameras, camcorders, personal communication systems (PCS), game consoles, security cameras, medical miniature cameras, and robotics.

[0003] To obtain a 3D image using an image sensor, information about color is needed, as well as information about the distance (or depth) between the target object and the image sensor.

[0004] One method for obtaining information about the distance between a target object and an image sensor is the time-of-flight (TOF) method. The TOF method calculates the distance between the target object and the image sensor by measuring the time it takes for light to travel from the target object to the image sensor after being reflected back from the target object. Summary of the Invention

[0005] One aspect of this disclosure provides a sensing device for improving photoelectric efficiency.

[0006] The technical problems to be solved by this disclosure are not limited to those described above. Those skilled in the art to which this disclosure pertains will clearly understand from the following description any other technical problems not mentioned herein.

[0007] According to one aspect of this disclosure, an image sensing device includes: a sensing region that converts incident light to receive the incident light and generate photocharge corresponding to the incident light; and a transistor region located on one side of the sensing region and reading out a pixel signal corresponding to the photocharge generated in the sensing region. The sensing region includes a substrate having a first surface on which incident light is incident and a second surface opposite to the first surface, and includes a photoelectric conversion region for converting the incident light into photocharge, and a first trench guide located on the second surface surrounding the photoelectric conversion region for scattering reflected light into the substrate. The reflected light is a portion of the incident light and is transmitted through the substrate.

[0008] According to another aspect of this disclosure, an image sensing device includes: a substrate layer including a substrate and a photoelectric conversion region located within the substrate, the substrate including a first surface and a second surface opposite to the first surface; a light incident layer located above the first surface and focusing incident light onto the substrate; and a wiring layer located below the second surface and including wiring. The substrate layer further includes a first trench guide that scatters reflected light incident on the second surface from the wiring layer into the substrate. Attached Figure Description

[0009] The above and other objects, features and advantages of this disclosure will become more apparent from the following detailed description taken in conjunction with the accompanying drawings:

[0010] Figure 1 This is a schematic diagram illustrating the configuration of an image sensing device based on some implementations of the disclosed technology.

[0011] Figure 2 It is shown Figure 1 A planar diagram of the planar structure of a single pixel in a pixel array.

[0012] Figure 3A It shows along Figure 2 A cross-sectional view of the pixel array intercepted by the line Y-Y'.

[0013] Figure 3B It shows along Figure 2 A cross-sectional view of the pixel array intercepted by line X-X'.

[0014] Figure 4 This is a diagram illustrating the structure of a first trench guide based on some implementations of the disclosed technology.

[0015] Figure 5 This is a plan view showing the structure of a first trench guide based on some implementations of the disclosed technology.

[0016] Figure 6 It is shown Figure 5 A cross-sectional view of the cross-sectional structure of the unit groove guide.

[0017] Figure 7 This is a diagram illustrating the structure of a first trench guide based on some implementations of the disclosed technology. Detailed Implementation

[0018] In the following, some embodiments of this disclosure will be described in detail with reference to the exemplary accompanying drawings. When adding reference numerals to the components in the various drawings, it should be noted that identical or equivalent components are designated by the same reference numerals even when they are shown in other drawings. Furthermore, in describing embodiments of this disclosure, detailed descriptions of well-known features or functions will be omitted to avoid unnecessarily obscuring the essential points of this disclosure.

[0019] Figure 1 This is a schematic diagram illustrating the configuration of an image sensing device based on some implementations of the disclosed technology.

[0020] Reference Figure 1The image sensing device ISD of this embodiment can use the time-of-flight (TOF) principle to measure the distance to the target object 1. The image sensing device ISD may include a light source 10, a lens module 20, a pixel array 30, and a control block 40.

[0021] Light source 10 can emit light toward target object 1 in response to a light modulation signal MLS from control block 40, which is a control signal. The light modulation signal MLS is fed into light source 10 to modulate the light emitted by light source 10 for illuminating target object 1. Light source 10 can be or can include a laser diode (LD) or light-emitting diode (LED), near-infrared laser (NIR), point light source, monochromatic light source with a combination of white lamp and monochromator, or other laser light source that emits light in a specific wavelength band (e.g., infrared, near-infrared, or visible light). For example, light source 10 can emit infrared light with a wavelength of 800 nm to 1000 nm. For ease of description, Figure 1 The image shows only one light source 10. However, multiple light sources can be arranged around the lens module 20.

[0022] Lens module 20 can collect light reflected from target object 1 and focus the collected reflected light onto unit pixels PX of pixel array 30. For example, lens module 20 may include a focusing lens with a glass or plastic surface or another cylindrical optical element. Lens module 20 may include multiple lenses aligned with the optical axis.

[0023] The pixel array 30 may include a plurality of unit pixels PX arranged in a two-dimensional structure (e.g., continuously arranged in the column and row directions). The unit pixel PX may be the smallest unit with the same shape repeatedly arranged on the pixel array 30.

[0024] Each unit pixel PX can be formed on a semiconductor substrate and can perform photoelectric conversion on light incident through lens module 20 to generate and output a pixel signal as an electrical signal corresponding to the incident light. The pixel signal can be a signal representing the distance to the target object 1, rather than a signal representing the color of the target object 1. Each unit pixel PX can be a current-assisted photonic demodulator (CAPD) type pixel, which uses the potential difference of the electric field to detect the photocharge (e.g., electrons) generated in the substrate by the incident light.

[0025] Each unit pixel PX may include a first trench guide formed on a second surface (rear surface) of a semiconductor substrate and a second trench guide formed on a first surface (front surface) opposite to the second surface. (Refer to the following...) Figure 2 The structure and function of the first groove guide and the second groove guide are described in the following figures.

[0026] The control block 40 can control the light source 10 to emit light toward the target object 1, and can drive the unit pixel PX of the pixel array 30 to process the pixel signal corresponding to the light reflected from the target object 1 in order to measure the distance to the surface of the target object 1.

[0027] The control block 40 may include a line driver 41, a demodulation driver 42, a light source driver 43, a timing controller 44, and a readout circuit 45.

[0028] The line driver 41 and the demodulation driver 42 can be collectively referred to as the control circuit.

[0029] The control circuit can drive the unit pixels PX of the pixel array 30 in response to a timing signal output from the timing controller 44. For example, the control circuit can generate a control signal that can select and control at least one row line among multiple row lines. The control signal may include a demodulation control signal that generates hole current in the substrate, a reset signal that controls a reset transistor, a transfer signal that controls a transfer transistor for transferring photocharge accumulated in the detection node, and a selection signal that controls a selection transistor. The row driver 41 can generate the reset signal, the transfer signal, and the selection signal, and the demodulation driver 42 can generate the demodulation control signal.

[0030] The light source driver 43 can generate an optical modulation signal MLS capable of driving the light source 10 based on the control of the timing controller 44. The optical modulation signal MLS can be a signal modulated at a predetermined frequency.

[0031] The timing controller 44 can generate timing signals to control the operation of the line driver 41, demodulation driver 42, light source driver 43 and readout circuit 45.

[0032] The readout circuit 45 can process the pixel signals output from the pixel array 30 under the control of the timing controller 44 to generate pixel data in the form of digital signals. To achieve this, the readout circuit 45 may include a correlated double sampler (CDS) for performing correlated double sampling on the pixel signals output from the pixel array 30.

[0033] Furthermore, the readout circuit 45 may include an analog-to-digital converter for converting the output signal from the correlated dual sampler into a digital signal. Additionally, the readout circuit 45 may include a buffer circuit for temporarily storing pixel data output from the analog-to-digital converter and outputting the pixel data to an external device under the control of the timing controller 44.

[0034] The light source 10 emits modulated light at a predetermined frequency toward the target object 1. The pixel array 30 detects the modulated light (e.g., incident light) reflected from the target object 1 and generates depth information for each unit pixel PX. A time delay exists between the modulated light and the incident light, depending on the distance between the image sensing device ISD and the target object 1. This time delay is represented by the phase difference between the signal generated by the image sensing device ISD and the light modulation signal MLS controlling the light source 10. An image processor (not shown) can generate a depth image including the depth information of each unit pixel PX by calculating the phase difference appearing in the signal output from the image sensing device ISD.

[0035] Figure 2 It is shown Figure 1 A planar diagram of the planar structure of a single pixel in a pixel array. Figure 3A and Figure 3B They are shown along Figure 2 A cross-sectional view of the pixel array intercepted by lines Y-Y' and X-X'.

[0036] Figure 2 It could be a diagram showing the unit pixel as viewed from above the second surface of the substrate.

[0037] Reference Figure 2 , Figure 3A and Figure 3B Each unit pixel PX may include a sensing region SA and a transistor region TA disposed on one side of the sensing region SA. In the example, the pixel array 30 may include a substrate layer 100 on which the unit pixels PX are formed, a light incident layer 200 formed above the substrate layer 100, and a wiring layer 300 formed below the substrate layer 100.

[0038] The sensing region SA can convert incident light to generate photocharge corresponding to the incident light. The sensing region SA can be formed in the substrate layer 100 and may include a substrate 110, a photoelectric conversion region 112, a first trench guide 120a, and a second trench guide 130. Figures 2 to 3B In the example shown, the first trench guide 120a and the second trench guide 130 are respectively disposed on opposite surfaces of the substrate 110 and are used to improve photoelectric efficiency.

[0039] Substrate 110 may include a semiconductor substrate having a first surface and a second surface opposite to the first surface. The first surface may be a surface in contact with the light incident layer 200, and the second surface may be a surface in contact with the wiring layer 300. For example, substrate 110 may be a silicon single crystal substrate. Substrate 110 may be a P-type or N-type bulk substrate, a substrate on which a P-type or N-type epitaxial layer is grown, or a substrate on which a P-type or N-type epitaxial layer is grown.

[0040] The photoelectric conversion region 112 may be formed within the substrate 110 and may convert light to generate photocharge. The photoelectric conversion region 112 may be located in the central portion of the sensing region SA and may include N-type impurities.

[0041] The first trench guide 120a improves the photoelectric efficiency of the unit pixel by scattering reflected light from the wiring layer 300 back to the substrate 110 into the substrate 110. The reflected light is a portion of the incident light that enters through the light incident layer 200 and is transmitted through the substrate 110. For example, when the image sensing device ISD of this embodiment is a sensing device for infrared (IR), infrared light has a longer wavelength than visible light and is therefore more likely to transmit through the substrate 110. The light transmitted through the substrate 110 can be reflected by the metal wiring 320 or other reflective structures in the wiring layer 300 and can return to the substrate 110. The first trench guide 120a scatters the reflected light from the second surface of the incident light that returns to the substrate 110 after being reflected from the wiring layer 300 into the substrate 110, thereby allowing the light to remain within the substrate 110 for a longer period, thus improving photoelectric efficiency.

[0042] The first trench guide 120a may include a plurality of pins 122 protruding from the surface of the substrate 110 and a trench 124 surrounding each of the plurality of pins 122. For example, the first trench guide 120a may be formed such that the second surface of the substrate 110 is etched to a certain depth, such that the plurality of pins 122 protruding in a pillar shape from the bottom surface of the trench 124 are positioned spaced apart from each other. Reflected light that has been reflected from the wiring layer 300 and propagates toward the first trench guide 120a may be scattered by the pins 122.

[0043] The trench 124 may extend in a first direction (e.g., the X direction) and a second direction intersecting the first direction (e.g., the Y direction) to have the same width in the edge region of the sensing region SA. For example, the trench 124 may be formed as a first trench region extending in the first direction in the edge region of the sensing region SA. Figure 2 The trench regions located above and below the photoelectric conversion region 112 and the second trench region extending in the second direction and having the same width as the first trench region. Figure 2 The trench regions located on the left and right sides of the photoelectric conversion region 112 are connected to each other to form a single square strip around the photoelectric conversion region 112. Multiple pins 122 may be arranged continuously in a line along the centerline of the trench 124 in a first and second direction. However, this is not a limitation; for optimal efficiency, the first trench guide 120a may be arranged in various ways.

[0044] although Figure 2An example is shown where pin 122 is formed in a square prism shape, but pin 122 can be formed in various prism shapes, such as cylinders and hexagonal prisms. Additionally, although... Figure 2 An example is shown where pins 122 are arranged in a line in the first and second directions, but depending on the size of pins 122 and the width of trench 124, pins 122 may be arranged in multiple rows along the center line of trench 124 in the first and second directions.

[0045] An insulating material (e.g., an oxide film) with a refractive index different from that of the substrate 110 may gap-fill the trench 124. For example, the interlayer insulating film 310 of the wiring layer 300 may gap-fill the trench 124 of the first trench guide 120a.

[0046] The first trench guide 120a may be formed on a portion of the second surface of the substrate 110 that does not overlap with the photoelectric conversion region 112. For example, on the second surface of the substrate 110, the first trench guide 120a may be formed in the edge region of the sensing region SA around the strip shape of the photoelectric conversion region 112. The first trench guide 120a may reflect and scatter light that does not propagate toward the photoelectric conversion region 112 but propagates toward the edge region of the sensing region SA after being reflected from the wiring layer 300 and returning to the substrate 110, thereby increasing the amount of light introduced into the photoelectric conversion region 112.

[0047] The second trench guide 130 may be formed on the first surface of the substrate 110 and may focus light incident on the first surface of the substrate 110 through the light incident layer 200 onto the photoelectric conversion region 112. The second trench guide 130 may include a structure in which an insulating material (e.g., an oxide film) with a refractive index different from that of the substrate 110 fills the gaps of trenches etched to a specific depth from the first surface of the substrate 110.

[0048] The width and depth of the second trench guide 130 can be adjusted to increase the refraction angle of light transmitted through the second trench guide 130, thereby enabling the corresponding light to be well focused on the photoelectric conversion region 112. In addition, the second trench guide 130 allows light entering the trench to propagate downwards while being continuously reflected from the inner wall of the trench, thereby increasing the propagation path of the incident light. Therefore, even if the corresponding light is incident, light with a long wavelength can be well focused on the photoelectric conversion region 112.

[0049] A transistor region TA may be located on one side of the sensing region SA in the substrate layer 100, and may include a pixel transistor for reading out a pixel signal corresponding to the photocharge generated in the sensing region SA. For example, the pixel transistor may include a transfer transistor TX for controlling the transfer of photocharge accumulated in the photoelectric conversion region 112, a drive transistor DX for amplifying the signal corresponding to the transferred photocharge, a selection transistor SX for outputting the signal from the drive transistor DX to a signal line, and a reset transistor RX for initializing the unit pixel PX to a pixel voltage. The pixel transistor may be formed on the second surface of the substrate 110.

[0050] A light incident layer 200 may be formed above the substrate layer 100 to focus incident light, after being reflected from the target object 1, onto the substrate 110. For example, the light incident layer 200 may be positioned to contact a first surface of the substrate 110 and to focus incident light onto a second trench guide 130. The light incident layer 200 may include a filter 220, an anti-reflective film 230, and a microlens 240.

[0051] A filter 220 may be formed above a first surface of the substrate 110 and selectively transmits light of a specific wavelength band (e.g., near-infrared or infrared light) from the incident light. A mesh structure 210 may be formed between filters 220 corresponding to adjacent unit pixels to prevent crosstalk of the incident light. A microlens 240 may be formed in a hemispherical shape above the filter 220 and may increase the light-gathering ability of the incident light to improve light reception efficiency. An anti-reflective film 230 may be formed below the microlens 240 to prevent diffuse reflection of the incident light. The anti-reflective film 230 may serve as a planarization layer to remove the steps caused by the filter 220.

[0052] Wiring layer 300 may be formed below substrate layer 100. Wiring layer 300 may be positioned to contact a second surface of substrate 110. Wiring layer 300 may include interlayer insulating film 310 and multiple layers of metal wiring 320 within interlayer insulating film 310. Interlayer insulating film 310 may be formed as a structure of multiple insulating film layers. Interlayer insulating film 310 may include at least one of oxide film and nitride film. Metal wiring 320 may include wiring for transmitting pixel signals read from transistor region TA of unit pixel PX and control signals required to generate pixel signals. Metal wiring 320 may include at least one of aluminum (Al), copper (Cu), or tungsten (W).

[0053] Figure 4 This is a diagram illustrating the structure of a first trench guide based on some implementations of the disclosed technology.

[0054] Reference Figure 4 The first trench guide 120b can be formed to completely cover the outer portion surrounding the photoelectric conversion region 112 in the sensing region SA.

[0055] In the above Figure 2 In the first trench guide 120a, the trench 124 extends in a first direction and a second direction to have the same width in the edge region of the sensing region SA. Figure 2 The first groove guide 120a is different. Figure 4 The trench 125 can be formed to completely cover the outer region surrounding the photoelectric conversion region 112 while surrounding the photoelectric conversion region 112. This outer region extends from the edge region of the sensing region SA to the region adjacent to the photoelectric conversion region 112. In this case, the pins 122 can be uniformly distributed within the trench 125. For example, the trench 125 can be positioned adjacent to the photoelectric conversion region 112 to surround the photoelectric conversion region 112 along the outer line of the photoelectric conversion region 112 on the second surface of the substrate 110, and the pins 122 can be completely uniformly distributed within the trench 125 to be spaced apart from each other at specific intervals.

[0056] Figure 5 This is a plan view illustrating the structure of a first trench guide based on some implementations of the disclosed technology. Figure 6 It is shown Figure 5 A cross-sectional view of the cross-sectional structure of the unit groove guide.

[0057] Reference Figure 5 and Figure 6 The first trench guide 120c may include a plurality of unit trench guides (UTGs) arranged around the photoelectric conversion region 112. Each unit trench guide (UTG) may include a pin 126 and a trench 128 surrounding the pin 126. The pin 126 may be located at the center of the corresponding trench 128. Figure 2 Unlike the first trench guide 120c which forms multiple pins inside the trench, each individual unit trench guide UTG is a self-contained structure with a single pin 126 located in the corresponding trench 128.

[0058] Multiple unit trench guides (UTGs) can be arranged to be spaced apart from each other at specific intervals in a first direction and a second direction in the edge region of the sensing region SA. For example, multiple unit trench guides (UTGs) can be arranged in the edge region of the sensing region SA around the strip shape of the photoelectric conversion region 112.

[0059] Figure 7 This is a diagram illustrating the structure of a first trench guide based on some implementations of the disclosed technology.

[0060] Reference Figure 7 The unit trench guide UTG can be formed to be completely distributed in the area of ​​the sensing area SA where the photoelectric conversion area 112 is not formed. For example, in the above... Figure 6In the process, the unit trench guide UTG is formed as a line arranged in the first and second directions in the edge region of the sensing area SA, but... Figure 7 In the process, the unit trench guide UTG can be uniformly arranged to completely cover the area in the sensing area SA that does not overlap with the photoelectric conversion area 112.

[0061] As described above, the embodiments of this disclosure enable incident light to remain within the substrate for an extended period, thereby improving the photoelectric efficiency of the image sensing device.

[0062] While this disclosure has been described above with reference to exemplary embodiments and accompanying drawings, it should be understood that numerous modifications or variations to the disclosed embodiments and other embodiments may be designed based on the content described and / or shown in this patent document.

[0063] Cross-reference and priority claims of related applications

[0064] This patent document claims priority and benefit to Korean Patent Application No. 10-2024-0197691, filed with the Korean Intellectual Property Office on December 26, 2024, the entire contents of which are incorporated herein by reference.

Claims

1. An image sensing device, the image sensing device comprising: A sensing area that receives incident light and generates photocharge corresponding to the incident light; as well as A transistor region, located on one side of the sensing region, reads out the pixel signal corresponding to the photocharge generated in the sensing region. The sensing area includes: A substrate having a first surface on which the incident light is incident and a second surface opposite to the first surface, the substrate including a photoelectric conversion region for converting the incident light into photocharge; and A first trench guide is located on the second surface surrounding the photoelectric conversion region and scatters reflected light into the substrate, the reflected light being a part of the incident light and transmitted through the substrate.

2. The image sensing device according to claim 1, wherein The sensing area also includes a second trench guide located on the first surface and focusing the incident light onto the photoelectric conversion area.

3. The image sensing device according to claim 1, wherein, The first trench guide includes: trenches; and Multiple pins are positioned spaced apart from each other and protrude in a columnar shape from the bottom surface of the trench.

4. The image sensing device according to claim 3, wherein, The trench is located in the edge region of the sensing region and has a first trench region extending in a first direction and a second trench region extending in a second direction intersecting the first direction, connected to each other to form a strip shape around the photoelectric conversion region, the second trench region having the same width as the first trench region.

5. The image sensing device according to claim 4, wherein, The plurality of pins are arranged in at least one line along the centerline of the trench in the first direction and the second direction.

6. The image sensing device according to claim 3, wherein, The trench completely covers the outer portion surrounding the photoelectric conversion area in the sensing area.

7. The image sensing device according to claim 6, wherein, The plurality of pins are distributed completely and evenly within the trench, spaced apart from each other at specific intervals.

8. The image sensing device according to claim 1, wherein, The first trench guide includes a plurality of unit trench guides arranged to be spaced apart from each other in a first direction and a second direction intersecting the first direction to surround the photoelectric conversion region.

9. The image sensing device according to claim 8, wherein, The plurality of unit trench guides are arranged in a line in the edge region of the sensing area in the first direction and the second direction.

10. The image sensing device according to claim 8, wherein, The plurality of unit trench guides are arranged to completely cover the outer portion surrounding the photoelectric conversion area in the sensing area.

11. The image sensing device according to claim 8, wherein, Each of the plurality of unit trench guides includes: pins; and A trench that surrounds the pin.

12. The image sensing device according to claim 1, further comprising: A light incident layer is located on the first surface and focuses the incident light onto the substrate; as well as A wiring layer located below the second surface, the wiring layer including wiring for transmitting the pixel signal read from the transistor region.

13. An image sensing device, the image sensing device comprising: A substrate layer, the substrate layer including a substrate and a photoelectric conversion region located within the substrate, the substrate including a first surface and a second surface opposite to the first surface; A light incident layer is located above the first surface and focuses the incident light onto the substrate; as well as A wiring layer, located below the second surface and comprising wiring, The substrate layer further includes a first trench guide, which scatters reflected light that is incident on the second surface after being reflected from the wiring layer into the substrate.

14. The image sensing device according to claim 13, wherein, The substrate layer further includes a second trench guide located on the first surface and focusing the incident light onto the photoelectric conversion region.

15. The image sensing device according to claim 13, wherein, The first trench guide is located on the second surface to contact the wiring layer.

16. The image sensing device according to claim 13, wherein, The first trench guide includes: A trench, formed around the photoelectric conversion region; and Multiple pins are positioned spaced apart from each other within the trench and protrude in a columnar shape from the bottom surface of the trench.

17. The image sensing apparatus according to claim 16, wherein, The trench has a first trench region extending in a first direction and a second trench region extending in a second direction intersecting the first direction to have the same width as the first trench region, connected to each other to form a strip shape surrounding the photoelectric conversion region.

18. The image sensing apparatus according to claim 16, wherein, The trench is located on the second surface to surround the photoelectric conversion region along the outer edge of the photoelectric conversion region.

19. The image sensing device according to claim 13, wherein, The first trench guide includes a plurality of unit trench guides arranged to be spaced apart from each other in a first direction and a second direction intersecting the first direction to surround the photoelectric conversion region.

20. The image sensing device according to claim 19, wherein, Each of the plurality of unit trench guides includes: pins; and A trench that surrounds the pin.

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