Low Power Photonic Demodulator

Abstract

A photodetector for detecting photons generated by received light is disclosed. The photodetector includes a semiconductor substrate, two or more guide regions, a light sensing region, and two or more detection regions. The semiconductor substrate and the guide regions are doped with a dopant of a first conductivity type. The light sensing region is disposed between the two or more guide regions for generating photocarriers from impact photons of received light. The detection region is doped with a dopant of a second conductivity type. The guide regions are respectively connected to a power supply to apply a potential on the guide regions to control the detection rate of the impact photons. A light sensing region is provided to form at least a reverse-biased pn junction between the guide regions to reduce or prevent a leakage path between the guide regions.

Description

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims the benefit of U.S. Provisional Patent Application No. 63 / 146,724, filed on February 8, 2021, the entire contents of which are incorporated herein by reference. Technical Field

[0003] The present invention relates broadly to a photon demodulator device, and more particularly to a photodetector for detecting impinging electromagnetic radiation from received light, which can be used in a TOF image sensor for distance measurement and 3D imaging. Background Art

[0004] TOF technology revolutionizes distance sensing by providing depth perception with high accuracy in real time. The distance between the sensor and the object is determined based on the time difference between the signal emission and the corresponding return signal. TOF image sensors can instantly detect the distance of the object surface based on the time it takes for the emitted light to be reflected and return to the source.

[0005] The most common type of TOF image sensor is the LiDAR sensor, which is often used in autonomous driving or ADAS vehicles. The TOF image sensor accurately determines the range information through the round-trip flight time from the source to the target. In other words, the TOF image sensor emits modulated ranging light (or emitted light, such as near-infrared light) during operation, and receives the return light (or received light) after the modulated ranging light encounters the object. The TOF image sensor can determine the distance of the captured scene by calculating the time difference between light emission and reflection, or by calculating the phase difference between the modulated ranging light pulse signal and the returned light pulse signal to generate depth information. Combined with traditional imaging technology, the TOF image sensor can obtain the three-dimensional topological structure of the object in the topological map, which is best represented by different colors to represent different distances. TOF technology has been widely used in three-dimensional vision, drones, facial recognition, robotics and other fields, and it will become one of the most important technologies to realize our future smart living environment.

[0006] TOF image sensors generally include ranging pixels and pixel circuits. Specifically, the ranging pixels in the TOF image sensor are used to modulate photogenerated charges, and the pixel circuits in the TOF image sensor are used to obtain image distance information, which is calculated based on the modulated charge information. FIG1 shows an embodiment of CAPD according to the prior art, which is generally used for photoelectric signal modulation for distance measurement. The basic concept of CAPD is described in detail in EP2,023,399B1. Compared with other technologies for the same purpose, CAPD can achieve high-speed demodulation to obtain more sensitive distance information. CAPD can also be easily integrated into existing IC manufacturing processes. However, CAPD suffers from very high power consumption due to the direct current at the substrate, making it difficult to use in battery-powered devices and equipment.

[0007] The conventional CAPD 100 forms two guide regions with one doping type (e.g., p-type) 140, 150 in the substrate 110 to achieve modulation of photogenerated charges. Typically, the conventional CAPD 100 requires an external power source to apply a voltage on the guide regions 140, 150 to generate a large current between the two guide regions 140, 150 associated with the electric field in the silicon substrate 110. An electromagnetic mask 50, such as a metal mask, may be deployed above the guide regions 140, 150 to shield and prevent the impact of electromagnetic radiation (e.g., light). When photons impact on the silicon substrate 110 between the electromagnetic masks 50, photogenerated charges will be generated at specific locations and guided by the electric field in the silicon substrate 110. The photogenerated charges will be collected by one of the two regions doped with a doping type opposite to the guide region (n-type) in the semiconductor substrate 110, which works as a detection node 120, 130. Since the total resistance between the two guide regions 140 and 150 is very small, when the conventional CAPD 100 modulates the photogenerated charges, there is a problem that a large current from an external power source flows into the silicon substrate 110 to form an auxiliary electric field. Therefore, the large current will cause a high power consumption problem of TOF image sensing.

[0008] US 9,716,121 B1 provides an existing measure to solve this problem. The photogenerated charge modulation device is characterized by rearranging the positions of the detection area and the guide area. The guide area is surrounded by the detection area to avoid leakage current in the substrate surface. However, there is still a leakage path in the silicon block, and the power consumption cannot be significantly reduced.

[0009] The disclosure of US10,141,369 B2 also attempts to solve the problem of high power consumption by reducing or preventing leakage current. The photodetector includes a blocking region disposed between the detection region and the protection region to block leakage current between the detection region and the protection region. However, the isolation still focuses on avoiding leakage current in the substrate surface without addressing the leakage path in the silicon body. Other examples of CAPD and TOF image sensors are shown in US 8,294,882 B2; US10,310,060 B2; US10,636,831 B2; and US10,690,753 B2.

[0010] Therefore, there is a need in the art for a CAPD structure that seeks to address at least some of the above-identified problems in TOF image sensors.Furthermore, other desirable features and characteristics will become apparent from the subsequent detailed description and the appended claims taken in conjunction with the accompanying drawings and this background of the disclosure. Summary of the invention

[0011] In view of the above background, an object of the present disclosure is to provide a low-power photodetector for detecting photons generated by received light and a TOF image sensor with significantly lower power consumption.

[0012] According to a first embodiment of the present disclosure, a photodetector includes a semiconductor substrate doped with a dopant of a first conductivity type, two or more guide regions, a light sensing region, and two or more detection regions. The two or more guide regions are formed in the semiconductor substrate and doped with a dopant of the first conductivity type. The light sensing region is arranged between the two or more guide regions for generating photocarriers from impact photons of received light. The two or more detection regions are formed in the semiconductor substrate and doped with a dopant of a second conductivity type. The two or more guide regions are respectively connected to a power supply to apply an electric potential to the two or more guide regions to control the detection rate of the impact photons. A light sensing region is provided to form at least a reverse-biased pn junction between the two or more guide regions to reduce or prevent a leakage path between the two or more guide regions.

[0013] According to another aspect of the present disclosure, the light sensing region is doped with a dopant of the second conductivity type.

[0014] According to yet another aspect of the present disclosure, the light sensing region includes three or more sub-regions, wherein any two adjacent sub-regions are doped with dopants of different conductivity types selected from the first and second conductivity types of dopants.

[0015] In one embodiment, three or more sub-regions are laterally alternately arranged to form a lateral sequence of doped regions.

[0016] In another embodiment, three or more sub-regions are vertically alternately arranged to form a vertical sequence of doped regions.

[0017] According to yet another aspect of the present disclosure, the photodetector further includes an isolation region arranged to surround the two or more guide regions and the two or more detection regions to isolate the two or more guide regions and the two or more detection regions from the semiconductor substrate.

[0018] According to another aspect of the present disclosure, the isolation region is doped with a dopant of the second conductivity type.

[0019] According to another aspect of the present disclosure, the two or more guide regions include a first guide region positioned adjacent to a first side of the light sensing region and a second guide region positioned adjacent to a second side of the light sensing region.

[0020] In one embodiment, the dopant of the first conductivity type is a p-type dopant and the dopant of the second conductivity type is an n-type dopant.

[0021] In another embodiment, the dopant of the first conductivity type is an n-type dopant and the dopant of the second conductivity type is a p-type dopant.

[0022] According to another aspect of the present disclosure, the two or more guide regions and the two or more detection regions are formed in a back side of a semiconductor substrate such that the photodetector has a BSI structure.

[0023] According to a second embodiment of the present disclosure, a TOF imaging system for performing distance measurement and 3D imaging is provided. The TOF imaging system includes a modulated light source for transmitting light pulses to a target object, a processor, and a receiving unit, the receiving unit including one or more phase-sensitive photodetectors for detecting photons generated by the received light reflected from the target object.

[0024] This Summary of the Invention is provided to introduce in a simplified form a selection of concepts that are further described below in the Detailed Description of the Invention. This Summary of the Invention is not intended to identify key features or essential features of the claimed subject matter, nor is it intended to be used as an aid in determining the scope of the claimed subject matter. Other aspects and advantages of the invention are disclosed as illustrated by the following Examples. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] The accompanying drawings include figures to further illustrate and clarify the above and other aspects, advantages and features of the present disclosure. It will be understood that these drawings depict only certain embodiments of the present disclosure and are not intended to limit the scope thereof. It will also be understood that these drawings are shown for simplicity and clarity and are not necessarily drawn to scale. The present disclosure will now be described and explained with additional specificity and detail through the use of the accompanying drawings, in which:

[0026] FIG1 depicts a cross-section of a conventional photodetector according to the prior art;

[0027] Figure 2 Depicts the operation of a TOF imaging system for performing distance measurement and 3D imaging of a target object according to certain embodiments of the present disclosure;

[0028] Figure 3 depicts a top view of a photodetector according to a first embodiment of the present disclosure;

[0029] Figure 4 Describes a first embodiment of the present disclosure along the line A-A' Figure 3 Cross section of a photodetector;

[0030] Figure 5 depicts a cross section of a photodetector according to a second embodiment of the present disclosure, wherein the light sensing region is a lateral sequence of alternating regions of opposite doping types;

[0031] Figure 6 depicts a cross section of a photodetector according to a third embodiment of the present disclosure, wherein the light sensing region is a vertical sequence of alternating regions of opposite doping types;

[0032] Figure 7 is a graph showing current collected at detection areas DA and DB of a conventional photodetector;

[0033] Figure 8 is a graph showing currents collected at detection areas DA and DB by the photodetector according to the first embodiment of the present disclosure;

[0034] Fig. 9 is a graph showing currents collected at detection areas DA and DB by a photodetector according to a second embodiment of the present disclosure;

[0035] Fig.10 is a graph showing leakage current between guide regions GA and GB of a conventional photodetector;

[0036] Fig.11 is a graph showing leakage current between guide regions GA and GB of the photodetector according to the first embodiment of the present disclosure;

[0037] Fig.12 is a graph showing leakage current between guide regions GA and GB of a photodetector according to a second embodiment of the present disclosure;

[0038] Fig.13 Depicts a cross section of a photodetector in a BIS structure according to a first embodiment of the present invention;

[0039] Fig.14 depicts a cross section of a BIS-structured photodetector according to a second embodiment of the present invention; and

[0040] Fig.15 A cross section of a BIS-structured photodetector according to a third embodiment of the present invention is depicted. DETAILED DESCRIPTION

[0041] The present disclosure generally relates to a photodetector device structure. More specifically, but not limitingly, the present disclosure relates to a photodetector device structure without leakage current between two guide regions and a substrate. One object of the present disclosure is to provide a TOF image sensor for depth perception with significantly lower power consumption.

[0042] The following detailed description is merely exemplary in nature and is not intended to limit the present disclosure or its application and / or use. It should be understood that there are a large number of variations. The detailed description will enable a person of ordinary skill in the art to implement the exemplary embodiments of the present disclosure without undue experimentation, and it will be understood that various changes or modifications may be made to the functions and structures described in the exemplary embodiments without departing from the scope of the present disclosure as set forth in the appended claims.

[0043] The use of the terms "one" and "an" and "the" and "at least one" and similar references in the context of describing the present invention (especially in the context of the following claims) is interpreted to cover both the singular and the plural, unless otherwise stated herein or clearly contradicted by the context. Unless otherwise stated, the terms "include", "have" and "include" will be interpreted as open terms (i.e., meaning "including but not limited to"). Unless otherwise stated, the use of any and all examples or exemplary language (e.g., "such as") provided herein is intended only to better illustrate the present invention without limiting the scope of the present invention. Any language in the specification should not be interpreted as indicating that any unclaimed element is essential to the practice of the present invention.

[0044] Benefits, advantages, solutions to problems, and any element(s) that may cause any benefit, advantage, or solution to occur or become more apparent are not to be construed as critical, required, or essential features or elements of any or all the claims. The invention is defined solely by the appended claims including any amendments made during the pendency of this application and all equivalents of those claims as issued.

[0045] As used throughout the specification, the symbols of n+, n, n- and p+, p, p- represent the relative levels of impurity concentrations in each conductivity type. That is, the n-type impurity concentration of n+ is relatively higher than the n-type impurity concentration of n, while the n-type impurity concentration of n- is relatively lower than the n-type impurity concentration of n. In addition, the p-type impurity concentration of p+ is relatively higher than the p-type impurity concentration of p, and the p-type impurity concentration of p- is relatively lower than the p-type impurity concentration of p. It should be noted that, for simplicity and clarity, there may be a case where n+ type and n- type are simply referred to as "n-type" and p+ type and p- type are simply referred to as "p-type".

[0046] These examples and other embodiments described in this disclosure can be implemented in a single die or in separate dies. Alternatively, the present invention can also be embedded in an integrated circuit with an intellectual property block. Various modes can be implemented according to the examples described in this disclosure. It will be readily understood by those of ordinary skill in the art after reading this disclosure that additional or other benefits can be obtained through various examples.

[0047] Unless otherwise defined, all terms (including technical and scientific terms) used in the embodiments of the present invention have the same meaning as commonly understood by one of ordinary skill in the art to which the present invention belongs.

[0048] Figure 2The operation of a TOF imaging system 300 for performing distance measurement and 3D imaging of a target object 40 or a scene is depicted. In a typical configuration, the TOF imaging system 300 includes a processor 310, a modulated light source 320, and a receiving unit 330. The TOF imaging system 300 is configured to analyze the time of flight of light to the target object 40. In particular, the modulated light source 320 has an illumination unit 321, such as a laser diode, a photodiode, a VCSEL, an LED array, which is configured to emit light pulses of a predetermined wavelength to the target object 40 and illuminate the field of view. In some embodiments, the modulated light source 320 may include a collimating lens 322, which is configured to collimate the light pulses to propagate to the target object 40. The light pulses are reflected back from the target object 40 and collected by the receiving unit 330. Depending on the distance between the target object 40 and the TOF imaging system 300, a time delay or phase shift between the light pulses from the modulated light source 320 and the received light reflected from the target object 40 received at the receiving unit 330 is measured. To achieve detection, the receiving unit 330 includes a lens 332 and one or more phase-sensitive photodetectors 331 for detecting photons generated by the received light reflected from the target object 40. In some embodiments, the one or more phase-sensitive photodetectors 331 can be implemented using CMOS technology. Therefore, it can be fully integrated in a standard IC manufacturing process, which can be arranged in an array and manufactured on a semiconductor substrate 110 together with other peripheral circuits. The array is essentially a 2D arrangement of pixels in rows and columns for representing the target object 40, and combined with the depth information of each pixel, a 3D model 30 can be obtained.

[0049] Without departing from the scope and spirit of the present disclosure, the TOF imaging system 300 may include other control circuits and / or optical elements. The processor 310 may be a general purpose processor or a dedicated processor configured to determine the characteristics of the target object 40 based on the received light. After the reflected light is received at the receiving unit 330, the determination of the phase difference may be performed by the CAPD. The phase difference Δφ may be determined for each pixel for deriving the 3D model 30 associated with the target object 40.

[0050] Figure 3 and Figure 4A CMOS photodetector 200 for modulating optical and electrical signals according to a first embodiment is shown. The photodetector 200, such as a CAPD, includes a semiconductor substrate 110 having a light receiving area 211, a light sensing area 210, two or more guide areas 140, 150, and two or more detection areas 120, 130. For simplicity and convenience, the subsequent disclosure describes the photodetector 200 including two guide areas 140, 150 and two detection areas 120, 130. It should be understood by those skilled in the art that the present invention does not exclude the photodetector 200 from having more than two guide areas and / or more than two detection areas. Therefore, it is obvious that the present invention is not limited to two guide areas and two detection areas, but should include all embodiments having two or more guide areas and / or two or more detection areas.

[0051] The two guide areas 140, 150 and the two detection areas 120, 130 are formed in the semiconductor substrate 110 outside the light receiving area 211. The light sensing area 210 is arranged on the semiconductor substrate 110 between the two guide areas 140, 150. On the left side of the light sensing area 210, the guide area GA 140 and the detection area DA 120 form a demodulation point, which can be referred to as a first tap. Similarly, on the right side of the light sensing area 210, the guide area GB 150 and the detection area DB 130 form another demodulation point, which can be referred to as a second tap. An electromagnetic mask 50, such as a metal mask, can be deployed to define the light receiving area 211 by shielding and preventing the impact of electromagnetic radiation.

[0052] The semiconductor substrate 110 may be a p-type substrate, which is referred to as being doped with a dopant of a first conductivity type. The light sensing region 210 may be an n-type region, which is referred to as being doped with a dopant of a second conductivity type. The light sensing region 210 may also include any combination of: N+, NWELL (n-well) or deep NWELL (deep n-well). On each side of the light sensing region 210 is a substrate or well of a first doping type, with two guide regions 140, 150. Optionally, the two guide regions 140, 150 include a first guide region and a second guide region, respectively, which are positioned adjacent to the first and second sides of the light sensing region 210. The two guide regions 140, 150 are doped with a dopant of the first conductivity type, such as p+ doping. The two guide regions 140, 150 may also include any combination of: P+, PWELL (p-well) or deep PWELL (deep p-well). A highly doped P+ is disposed on top of the guide region to form an ohmic contact.

[0053] The property of having two adjacent and oppositely doped regions can form a pn junction and produce a depletion region. The width of the depletion region in a semiconductor depends on the doping concentration. When the doping concentration in the light sensing region 210 is low enough, the entire light sensing region 210 is depleted and a large resistance is generated to avoid leakage between the guide regions 140, 150. Therefore, a light sensing region 210 is provided to form at least a pn junction between the two guide regions 140, 150 to achieve current isolation while allowing electric field propagation. The two guide regions 140, 150 are connected to an external voltage to generate an electric field in the light sensing region 210, which guides the photogenerated carriers to one of the detection regions 120, 130.

[0054] The two detection regions 120, 130 are doped with a second conductivity type dopant (e.g., n+ doping), which is opposite to the first conductivity type dopant. The detection regions 120, 130 may also include any combination of: N+, NWELL (n-well), or deep NWELL (deep n-well). A high doping N+ is provided on top of the detection region to form an ohmic contact.

[0055] A light sensing region 210 is provided to sense impact photons from received light by generating photocarriers. The two guide regions 140, 150 are respectively connected to a power source to apply a potential on the two guide regions 140, 150 so as to control the detection capability of the impact photons. When the applied potential has a higher voltage on the guide region GA 140 and a lower voltage on the guide region GB 150, the power source generates an electric field in the light sensing region 210, so that the impact photons can generate photocarriers (or minority carriers, such as electrons) and drift to the two detection regions 120, 130 near the higher bias guide region through the electric field. Advantageously, the light sensing region 210 (which is a depletion region with high resistance and lack of carriers) avoids leakage current between the two guide regions 140, 150, and effectively achieves low power consumption.

[0056] The two detection regions 120, 130 are placed near the two guide regions 140, 150, respectively. The two detection regions 120, 130 collect photocarriers generated by the received light in the light sensing region 210. The two guide regions 140, 150 generate majority carrier currents, which serve as guide currents for moving electrons. The two detection regions 120, 130 collect different amounts of photocarriers, depending on the direction of the electric field. And the different amounts of photocarriers provide phase information of the signal, which can be used to determine the distance at which the target object 40 reflects and transmits the received light to the photodetector 200.

[0057] In some embodiments, the light sensing region 210 is located between the first tap and the second tap. The photodetector 200 also includes an isolation region 220 (labeled as "ISO" in the figure), which is arranged to surround the two guide regions 140, 150 and the two detection regions 120, 130. Preferably, the isolation region 220 is doped with a dopant of the second conductivity type (e.g., n+ doping). The isolation region 220 may also include any combination of the following: N+, NWELL (n-well) or deep NWELL (deep n-well), so that the isolation region 220 is configured to cut off the leakage path between the two guide regions 140, 150 and the semiconductor substrate 110, and isolate the two guide regions 140, 150 and the two detection regions 120, 130 from the semiconductor substrate 110.

[0058] This illustrates the basic structure of the photodetector 200 according to the first embodiment of the present disclosure. Two variations will be discussed below in the subsequent disclosure, which are referred to as the second and third embodiments, respectively.

[0059] like Figure 5 As shown in, an alternative structure of the light sensing region 210 is disclosed. The light sensing region 210 includes three or more sub-regions 231, 232, 233, wherein any two adjacent sub-regions are doped with dopants of different conductivity types selected from dopants of the first and second conductivity types. For example, the first and third sub-regions 231, 233 are doped with dopants of the first conductivity type (e.g., p-type doping), while the second sub-region 232 is doped with dopants of the second conductivity type (e.g., n-type doping). The three or more sub-regions 231, 232, 233 are arranged alternately laterally to form a lateral sequence of doped regions with opposite doping types.

[0060] like Figure 6 As shown in, another alternative structure of the light sensing region 210 is disclosed. The light sensing region 210 includes three or more sub-regions 241, 242, 243, wherein any two adjacent sub-regions are doped with dopants of different conductivity types selected from dopants of the first and second conductivity types. For example, the first and third sub-regions 241, 243 are doped with dopants of the first conductivity type (e.g., p-type doping), while the second sub-region 242 is doped with dopants of the second conductivity type (e.g., n-type doping). The three or more sub-regions 241, 242, 243 are arranged alternately vertically to form a vertical sequence of doped regions with opposite doping types.

[0061] In the second and third embodiments, the light sensing region 210 includes a series of alternating sub-regions with opposite doping types to achieve current isolation between the two guide regions 140, 150 while allowing electric field propagation. The number of sub-regions should be greater than or equal to three to form at least two pairs of oppositely doped sub-regions. Each adjacent pair of oppositely doped sub-regions forms a pn junction and produces a depletion region. When all depletion regions in the oppositely doped sub-region pairs merge, the light sensing region 210 is completely depleted and produces a large resistance to avoid leakage between the two guide regions 140, 150.

[0062] Compared with conventional methods, the present disclosure provides the following advantages: (1) the photodetector 200 can be directly manufactured using existing commercial IC manufacturing processes in combination with other peripheral circuits; (2) the photodetector 200 can achieve fast switching to achieve more sensitive signal detection; and (3) the unnecessary direct current between the two guide regions 140, 150 is eliminated and minimized to achieve significant power reduction. Therefore, the present disclosure can be used to perform TOF imaging in portable devices.

[0063] Figure 7 The current collected at the detection areas DA and DB 120, 130 obtained from a conventional CAPD is shown as the voltage between the two guide areas GA and GB 140, 150 is increased. Figure 8-9 The current collected at the detection areas DA and DB 120, 130 obtained from the photodetector 200 of the first and second embodiments of the present disclosure when the voltage between the two guide areas GA and GB 140, 150 is increased is shown. The modulation contrast of the three cases can be compared. When the voltage between the two guide areas 140, 150 is increased, there is no significant difference in the current collected from the detection areas 120, 130.

[0064] Fig.10 FIG. 1 shows the leakage current between the two guide areas GA and GB 140, 150 when the voltage between the two guide areas GA and GB 140, 150 of the conventional CAPD increases. In contrast, Figure 11-12 The leakage current between the two guide areas GA and GB 140, 150 is shown when the voltage between the two guide areas GA and GB 140, 150 of the photodetector 200 related to the first and second embodiments of the present disclosure is increased. When the voltage difference increases to 0.3V, the leakage current in the conventional CAPD increases linearly to 8e - 3 A, while for the two exemplary photodetectors disclosed herein, the leakage current is greatly reduced. Fig.11 In the first embodiment shown in FIG. 1 , when the voltage is increased to 0.35 V, the leakage current is 2e -12 A is saturated. Similarly, Fig.12In the second embodiment shown, when the voltage increases to 0.4V, the leakage current is only 1.2e -12 A. Therefore, the leakage current in the photodetector 200 of the present disclosure is significantly reduced because the light sensing region 210 forms at least a reverse-biased pn junction between the two guide regions 140 , 150 , so as to reduce or prevent a leakage path between the two guide regions 140 , 150 .

[0065] Fig.13 A common variation of a CMOS photodetector is provided, in which the device is flipped upside down, with Figure 4 A structure similar to that of a photodetector of a semiconductor device 110. This is called a BSI structure. The back side of the substrate 110 is used as a sensing area with guide areas GA and GB 140, 150 and detection areas DA and DB 120, 130. A light receiving area 211 is provided on the front side of the substrate 110 to allow electromagnetic radiation to impinge into the light sensing area 210. The two guide areas 140, 150 and the two detection areas 120, 130 are still formed in the semiconductor substrate 110, outside the light receiving area 211, but on the back side. By flipping the photodetector 200, it can be bonded to another wafer from the back side. Therefore, the top surface can be thinned so that light can enter from the back side and reach the front side of the original structure.

[0066] Figure 14-15 Provides Figure 5-6 The photodetector is equivalent to the BSI structure of the photodetector.

[0067] The present disclosure provides a case where the dopant of the first conductivity type is p-type doping and the dopant of the second conductivity type is n-type doping. It is obvious to those skilled in the art that the present disclosure is also applicable to the case where the photodetector 200 with opposite doping polarity is formed in a similar manner. That is, the dopant of the first conductivity type is n-type doping and the dopant of the second conductivity type is p-type doping.

[0068] This illustrates the basic structure of a low power photodetector and TOF image sensor for detecting impinging electromagnetic radiation from received light according to the present disclosure. It will be apparent that variations and other features and functions disclosed above or alternatives thereof may be combined into many other different methods or devices. The modules, circuit blocks and components in the TOF image sensor are described in detail as examples illustrating the concepts and embodiments of the present disclosure and may be replaced with other general modules, components or circuit blocks throughout the specification. Therefore, the present embodiment is to be considered in all respects to be illustrative and not restrictive. The scope of the present disclosure is indicated by the appended claims rather than by the foregoing description, and therefore, all changes within the meaning and range of equivalents of the claims are intended to be included therein.

[0069] Abbreviations

[0070] 2D Two Dimensions

[0071] 3D

[0072] ADAS Advanced Driver Assistance

[0073] BSI Backside Illumination

[0074] CAPD Current Assisted Photon Demodulator

[0075] CMOS Complementary Metal Oxide Semiconductor

[0076] DA / DB Detection Area (A or B)

[0077] GA / GB Boot Area (A or B)

[0078] IC Integrated Circuit

[0079] ISO Isolation

[0080] LiDAR Light Detection and Ranging

[0081] LED Light Emitting Diode

[0082] NWELL n-well

[0083] PD Light Sensing

[0084] PWELL p-well

[0085] TOF Time of Flight

[0086] VCSEL Vertical Cavity Surface Emitting Laser

Claims

1. A photodetector for detecting photons generated by received light, the photodetector comprising: a semiconductor substrate doped with a dopant of a first conductivity type; two or more guide regions formed in the semiconductor substrate and doped with dopants of the first conductivity type; a light sensing region disposed between the two or more guide regions for generating photocarriers from impact photons of received light; and two or more detection regions formed in the semiconductor substrate and doped with a dopant of a second conductivity type, in: The two or more guide regions are respectively connected to power supplies to apply potentials on the two or more guide regions to control the detection rate of the impact photons; and providing the light sensing region to form at least a reverse biased pn junction between the two or more guide regions so as to reduce or prevent a leakage path between the two or more guide regions, The light sensing region includes three or more sub-regions, wherein any two adjacent sub-regions are doped with dopants of different conductivity types selected from the dopants of the first conductivity type and the dopants of the second conductivity type.

2. The photodetector according to claim 1, wherein The light sensing region is doped with a dopant of the second conductivity type.

3. The photodetector according to claim 1, wherein: The three or more sub-regions are laterally arranged alternately to form a lateral sequence of doped regions.

4. The photodetector according to claim 1, wherein The three or more sub-regions are vertically alternately arranged to form a vertical sequence of doped regions.

5. The photodetector according to claim 1, wherein An isolation region is also included, and the isolation region is arranged to surround the two or more guide regions and the two or more detection regions to isolate the two or more guide regions and the two or more detection regions from the semiconductor substrate.

6. The photodetector according to claim 5, wherein: The isolation region is doped with a dopant of the second conductivity type.

7. The photodetector according to any one of claims 1 to 6, characterized in that The two or more guide regions include a first guide region positioned adjacent to a first side of the light sensing region and a second guide region positioned adjacent to a second side of the light sensing region.

8. The photodetector according to any one of claims 1 to 6, characterized in that The first conductivity type dopant is a p-type dopant, and the second conductivity type dopant is an n-type dopant.

9. The photodetector according to any one of claims 1 to 6, characterized in that The first conductivity type dopant is an n-type dopant, and the second conductivity type dopant is a p-type dopant.

10. The photodetector according to any one of claims 1 to 6, characterized in that The two or more guide regions and the two or more detection regions are formed in a back side of the semiconductor substrate so that the photodetector has a back side illumination structure.

11. A time-of-flight imaging system for distance measurement and 3D imaging, comprising: A modulated light source for emitting light pulses toward a target object; processor; and A receiving unit, comprising one or more phase-sensitive photodetectors for detecting photons generated by the received light reflected from the target object, wherein each individual phase-sensitive photodetector comprises: a semiconductor substrate doped with a dopant of a first conductivity type; two or more guide regions formed in the semiconductor substrate and doped with dopants of the first conductivity type; a light sensing region disposed between the two or more guide regions for sensing impinging photons from received light by generating photocarriers; and two or more detection regions formed in the semiconductor substrate and doped with a dopant of a second conductivity type, in: The two or more guide regions are respectively connected to power supplies to apply potentials on the two or more guide regions to control the detection capability of the impact photons; and providing the light sensing region to form at least a reverse biased pn junction between the two or more guide regions to reduce or prevent a leakage path between the two or more guide regions, The light sensing region includes three or more sub-regions, wherein any two adjacent sub-regions are doped with dopants of different conductivity types selected from the dopants of the first conductivity type and the dopants of the second conductivity type.

12. The time-of-flight imaging system according to claim 11, characterized in that: The light sensing region is doped with a dopant of the second conductivity type.

13. The time-of-flight imaging system according to claim 11, wherein: The three or more sub-regions are laterally arranged alternately to form a lateral sequence of doped regions.

14. The time-of-flight imaging system according to claim 11, wherein: The three or more sub-regions are vertically arranged alternately to form a vertical sequence of doped regions.

15. The time-of-flight imaging system according to claim 11, wherein: The individual phase-sensitive photodetectors further include an isolation region arranged to surround the two or more guide regions and the two or more detection regions to isolate the two or more guide regions and the two or more detection regions from the semiconductor substrate.

16. The time-of-flight imaging system according to claim 15, characterized in that: The isolation region is doped with a dopant of the second conductivity type.

17. The time-of-flight imaging system according to any one of claims 11 to 16, characterized in that: The two or more guide regions include a first guide region positioned adjacent to a first side of the light sensing region and a second guide region positioned adjacent to a second side of the light sensing region.

18. The time-of-flight imaging system according to any one of claims 11 to 16, characterized in that: The first conductivity type dopant is a p-type dopant, and the second conductivity type dopant is an n-type dopant.

19. The time-of-flight imaging system according to any one of claims 11 to 16, characterized in that: The first conductivity type dopant is an n-type dopant, and the second conductivity type dopant is a p-type dopant.

20. The time-of-flight imaging system according to any one of claims 11 to 16, characterized in that: The two or more guide regions and the two or more detection regions are formed in a back side of the semiconductor substrate so that the photodetector has a back side illumination structure.

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