Photodetectors, X-ray imaging sensors, and electronic equipment

Abstract

A light receiving element according to an embodiment of the present disclosure is provided with: a semiconductor substrate (11) including a photoelectric conversion region; a first first-conduction type region (13A) which is provided at an interface of one surface of the semiconductor substrate (11), and which is connected to a first electrode (16); a second first-conduction type region (13B) which is provided around the first first-conduction type region (13A) at the interface of said one surface, and which is connected to a second electrode (17); and a third first-conduction type region (13C) which is provided around the second first-conduction type region (13B) at the interface of said one surface, and which is in an electrically floating state.

Description

Technical Field

[0001] The present disclosure relates to a light receiving element suitable for X-ray imaging for medical use or non-destructive inspection, an X-ray imaging device including the same, and an electronic device.

Background Art

[0002] Solid imaging devices are used in various applications, such as imaging devices such as digital still cameras and video cameras, electronic devices such as portable terminal devices having an imaging function, or electromagnetic wave sensors that detect various wavelengths other than visible light. Among solid imaging devices, there is an APS (Active Pixel Sensor) provided with an amplification element for each pixel, and signal charges accumulated in a photodiode, which is a photoelectric conversion element, are read out through a MOS (Metal Oxide Semiconductor) transistor. A CMOS (complementary MOS) image sensor (CIS) is widely used.

[0003] In sensors for scientific applications that require highly sensitive measurement, a light receiving element (PIN photodiode) having a structure in which a photoelectric conversion region and a floating diffusion region (FD) are integrated is used (see, for example, Patent Document 1). Such a light receiving element is easy to manufacture from a simple structure. In addition, an arbitrary potential difference can be applied to the pn junction forming the photoelectric conversion region. Therefore, it is easy to increase the thickness of the photoelectric conversion region.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

[0005] ​Incidentally, in recent years, there has been a demand for the development of X-ray imaging sensors with high frame rates and low noise for scientific applications. To achieve this, it is necessary to reduce dark current, reduce capacitance, and improve readout speed.

[0006] It is desirable to provide a photodetector, an X-ray imaging sensor, and electronic equipment that can achieve a reduction in dark current, a reduction in capacitance, and an improvement in readout speed.

[0007] A light-receiving element in one embodiment of the present disclosure includes a semiconductor substrate including a photoelectric conversion region, a first first conductivity type region provided at the interface of one face of the semiconductor substrate and connected to a first electrode, a second first conductivity type region provided at the interface of one face around the first first conductivity type region and connected to a second electrode, and a third first conductivity type region provided at the interface of one face around the second first conductivity type region and in an electrically floating state. The first conduction type region comprises a second conduction type region embedded and formed within a semiconductor substrate, wherein the first conduction type region extends in the direction of the other plane opposite to one plane, and has an overhanging region that extends further horizontally on the other plane side than the second conduction type region. .

[0008] An X-ray imaging sensor according to one embodiment of the present disclosure comprises a plurality of photodetectors according to the above embodiment of the present disclosure, which generate signal charges based on X-rays.

[0009] An electronic device according to one embodiment of the present disclosure is equipped with an X-ray imaging sensor according to the above embodiment of the present disclosure.

[0010] In a photodetector, an X-ray image sensor, and an electronic device according to one embodiment of this disclosure, a first conductivity type region is provided at the interface of one face of a semiconductor substrate including a photoelectric conversion region, and a second conductivity type region connected to a second electrode and a third electrically floating conductivity type region are arranged in this order around a first conductivity type region connected to a first electrode. This allows dark current generated at the interface of one face of the semiconductor substrate to be discharged from the second conductivity type region, preventing it from reaching the first conductivity type region. Furthermore, the horizontal movement speed of signal charges generated within the semiconductor substrate 11 is improved. [Brief explanation of the drawing]

[0011] [Figure 1] This is a schematic cross-sectional view showing an example of the configuration of a photodetector according to the first embodiment of this disclosure. [Figure 2] This is a schematic cross-sectional view illustrating another example of the configuration of a photodetector according to the first embodiment of the present disclosure. [Figure 3] Figure 2 is a schematic diagram illustrating an example of the planar configuration of the p-type conductive region of the photodetector shown. [Figure 4] Figure 2 is a schematic diagram illustrating another example of the planar configuration of the p-type conductive region of the photodetector shown in Figure 2. [Figure 5] Figure 2 is a schematic diagram illustrating another example of the planar configuration of the p-type conductive region of the photodetector shown in Figure 2. [Figure 6] Figure 2 is a schematic diagram illustrating an example of power supply connection to the n-type conductive region of the photodetector shown. [Figure 7] Figure 2 is a schematic diagram illustrating another example of power supply connection to the n-type conductive region of the photodetector shown. [Figure 8] This is a schematic cross-sectional view showing the configuration of a photodetector according to a second embodiment of the present disclosure. [Figure 9] This is a schematic cross-sectional view showing the configuration of a photodetector according to the third embodiment of this disclosure. [Figure 10] This is a schematic cross-sectional view showing the configuration of a photodetector according to the fourth embodiment of this disclosure. [Figure 11] Figure 10 is a schematic diagram illustrating an example of the planar configuration of the p-type conductive region of the photodetector. [Figure 12] This is a schematic cross-sectional view showing the configuration of a photodetector according to the fifth embodiment of this disclosure. [Figure 13] Figure 12 is a schematic diagram illustrating an example of a planar configuration of an n-well photodetector. [Figure 14] This is a schematic diagram showing an example of a planar configuration of the p-type conductive region of a photodetector according to a modified example of the present disclosure. [Figure 15] This is a block diagram showing the configuration of an X-ray imaging sensor. [Figure 16] Figure 15 is a block diagram showing a detailed configuration example of the column selection section. [Modes for carrying out the invention]

[0012] Hereinafter, embodiments of the present disclosure will be described in detail with reference to the drawings. The following description is a specific example of the present disclosure, and the present disclosure is not limited to the following aspects. Also, the present disclosure is not limited to the arrangement, dimensions, dimensional ratios, etc. of each component shown in each figure. The order of description is as follows. 1. First Embodiment (Example of a Light-Receiving Element Having a Drain Provided between an Anode and a Guard Ring) 1-1. Configuration of the Light-Receiving Element 1-2. Manufacturing Method of the Light-Receiving Element 1-3. Operation and Effects 2. Second Embodiment (Example in Which the Anode is Extended in the Direction of the n-Type Conductive Layer) 3. Third Embodiment (Example in Which an Overhanging Portion of the Anode is Provided between the n-Type Conductive Layer and the Embedded Layer) 4. Fourth Embodiment (Example of a Light-Receiving Element in Which the Line Width and Spacing of a Plurality of Provided Guard Rings are Changed) 5. Fifth Embodiment (Example in Which an Embedded Layer Having a Concentration Distribution of Impurities is Provided) 6. Modification Example 7. Application Example

[0013] <1. First Embodiment> FIG. 1 shows a cross-sectional configuration of a light-receiving element (light-receiving element 10) according to a first embodiment of the present disclosure. The light-receiving element 10 is, for example, composed of a PIN (Positive Intrinsic Negative) type photodiode to which a reverse bias is applied between the front and back surfaces of a semiconductor substrate 11, and for example, it constitutes one pixel (pixel P) in a radiation imaging element (for example, an X-ray imaging element 1; see FIG. 15) or an electromagnetic wave detection device that reads information of a subject (images a subject) based on radiation (for example, α-rays, β-rays, γ-rays, X-rays, etc.).

[0014] (1-1. Configuration of the Light-Receiving Element) In the photodetector 10, for example, a p-type conductive region (first conductive region) 13 is partially formed at the interface of one surface (front surface S1) of an n-type semiconductor substrate 11, and an n-type conductive layer (second conductive layer) 12 is formed at the interface of the surface opposite to the front surface S1 (back surface S2). The p-type conductive region 13 is composed of multiple regions, and in the photodetector 10 of this embodiment, for example, it has a region constituting the anode 13A (first first conductive region), a region constituting the drain 13B (second first conductive region), and a region constituting the guard ring 13C (third first conductive region). Furthermore, in this embodiment, an n-type conductive region (second conductive region) is formed as an embedded layer 14 inside the semiconductor substrate 11. In addition, an insulating layer 15 is formed on the front surface S1 of the semiconductor substrate 11.

[0015] In this embodiment, we will describe the case in which hole carriers are read out as signal charges from the excitons (electron-hole pairs) generated by photoelectric conversion. In the figure, the "-" (minus) attached to "p" and "n" indicates a low concentration of p-type or n-type impurities, and the "+" (plus) indicates a high concentration of p-type or n-type impurities. The relative magnitudes of the p-type and n-type impurities are as follows: - <p<p + ,n - <n<n + That is the case.

[0016] The semiconductor substrate 11 is composed of, for example, an n-type, p-type, or i-type (intrinsic semiconductor) semiconductor. As described above, the semiconductor substrate 11 has a p-type conductivity region (first conductivity region) 13 formed at the interface on the surface S1 side, and has a pn junction or pin junction that becomes a photoelectric conversion region. In this embodiment, an example is shown in which the semiconductor substrate 11 is an n-type semiconductor substrate. The film thickness (hereinafter simply referred to as thickness) of the semiconductor substrate 11 in the stacking direction (Y-axis direction) is, for example, 10 μm or more and 700 μm or less.

[0017] The p-type conductive region 13 is a region containing p-type impurities (p-type impurity region), and multiple p-type conductive regions are formed at the interface on the surface S1 side of the semiconductor substrate 11. Specifically, the p-type conductive region 13 has three regions: a region constituting the anode 13A, a region constituting the drain 13B, and a region constituting the guard ring 13C. Each region is spaced apart from the others, the drain 13B is formed in a ring shape around the anode 13A, and the guard ring 13C is formed in a ring shape around the drain 13B. The thickness of the p-type conductive region 13 depends on the configuration of the pixel P, but for example, when the pitch of the pixel P is 10 μm or more and 100 μm or less, it is formed with a thickness of, for example, 2 μm to 3 μm from the interface of the surface S1 of the semiconductor substrate 11.

[0018] Anode 13A is an electrode to which a voltage is applied to read out, for example, hole carriers (h+) as signal charges from among the charge carriers generated by photoelectric conversion, and is connected to electrode 16 (first electrode), for example. Anode 13A is formed individually in the center of pixel P, for example. The planar shape of anode 13A is not particularly limited and may be circular (see Figure 3, for example) or polygonal. The size of anode 13A depends on the size of pixel P, but for example, when the pitch of pixel P is 10 μm or more and 100 μm or less, it is 0.100 μm or more and 10 μm or less.

[0019] Drain 13B is an electrode to which a voltage is applied to discharge the dark current generated at the interface of surface S1 when light is irradiated onto the semiconductor substrate 11, and is connected to, for example, electrode 17 (second electrode). Drain 13B is formed in a ring shape around anode 13A, so that the dark current generated at the interface of surface S1 when light is irradiated onto the semiconductor substrate 11 is constantly discharged from drain 13B and prevented from flowing into anode 13A. The planar shape of drain 13B is not particularly limited and may be annular or polygonal (see, for example, Figure 3).

[0020] The guard ring 13C is designed to mitigate electric field concentration at the drain 13B and simultaneously generate a horizontal electric field to assist horizontal signal carrier transport. The guard ring 13C is formed in a ring shape around the drain 13B, surrounding the anode 13A and the drain 13B. Unlike the anode 13A and the drain 13B, the guard ring 13C is electrically floating. The guard ring 13C may be formed as a single (single layer) around the drain 13B, as shown in Figure 1, or multiple guard rings may be formed. Figure 2 schematically shows another example of the cross-sectional configuration of the photodetector 10 of this embodiment, and Figure 3 schematically shows the planar configuration of the guard ring 13C of the photodetector 10 shown in Figure 2. In the photodetector 10 shown in Figures 2 and 3, the guard ring 13C has three p-type conductive regions and is formed in a triple layer (guard rings 13C1, 13C2, and 13C3) around the drain 13B. By providing multiple guard rings 13C in this way, it is possible to distribute the electric field concentration to multiple locations while simultaneously generating a horizontal electric field over a wide area.

[0021] When the drain 13B and guard ring 13C are formed in a polygonal shape (for example, rectangular), it is preferable to form the corners in a curved shape as shown in Figure 3. This reduces the concentration of the electric field at the corners. Also, although Figure 3 shows an example in which the drain 13B and guard ring 13C are continuously provided around the anode 13A, it is not limited to this. For example, the drain 13B and guard ring 13C may be partially cut, as shown in Figure 4, or they may be formed intermittently.

[0022] Furthermore, the line width of the rings constituting the drain 13B and guard ring 13C is preferably, for example, 0.100 μm or more and 10 μm or less. The distance between the drain 13B and the guard ring 13C is preferably 0.100 μm or more and 10 μm or less. However, the distance between the drain 13B and the guard ring 13C, and the line widths of the drain 13B and guard ring 13C do not necessarily have to be constant. For example, when the drain 13B and multiple guard rings 13C are each formed in a polygonal shape (for example, rectangular), as shown in Figure 5, it is preferable to form the distance between the drain 13B and the guard ring 13C and each guard ring 13C1, 13C2, 13C3 such that the corners (Wb) are wider than the straight sections (Wa). This further mitigates the concentration of the electric field at the corners.

[0023] The n-type conductive layer 12 is a region containing n-type impurities at a higher concentration than the n-type semiconductor substrate 11 (the n-type impurity region), and is formed at the interface on the back surface S2 side of the semiconductor substrate 11. The n-type conductive layer 12 is connected to a power supply VDD, and when, for example, hole carriers among the charge carriers generated by photoelectric conversion are read out as signal charges through the anode 13A, electron carriers (e-) can be discharged through this n-type conductive layer 12. The thickness of the n-type conductive layer 12 depends on the configuration of the pixel P, but for example, when the pitch of the pixel P is 10 μm or more and 100 μm or less, it is formed with a thickness of, for example, 1 μm from the interface on the back surface S2 of the semiconductor substrate 11.

[0024] Figures 6 and 7 show examples of methods for connecting a power supply to the n-type conductive layer 12, respectively. In Figure 6, a transparent electrode 18 is formed on the n-type conductive layer 12, and a power supply VDD is connected to it, applying a voltage from the back surface S2 side of the semiconductor substrate 11. In Figure 7, in the peripheral region 110B surrounding a pixel region 110A in which multiple pixels P are arranged, a neutral region 11N is formed outside the depletion region 11D formed on the semiconductor substrate 11, and a voltage is applied through this neutral region 11N via an n-type conductive region 19 provided at the interface of the surface S1 of the semiconductor substrate 11. In this case, as shown in Figure 7, it is preferable to form multiple high-voltage guard rings 13D between the pixels P formed in the pixel region 110A and the n-type conductive region 19 at the interface of the surface S1 of the semiconductor substrate 11 in the peripheral region 110B. Of the multiple high-voltage guard rings 13D, it is preferable that the high-voltage guard ring closest to the pixel region 110A is connected to ground GND.

[0025] The embedded layer 14 is intended to prevent charge carriers (in this case, hole carriers) generated in the semiconductor substrate 11 by photoelectric conversion from being transferred to the drain 13B and guard ring 13C. The embedded layer 14 is embedded inside the semiconductor substrate 11, specifically near the p-type conductivity region 13, and is an n-type conductivity region containing a higher concentration of n-type impurities than the n-type semiconductor substrate 11. More specifically, the embedded layer 14 is provided in the region of the p-type conductivity region 13 corresponding to the drain 13B and guard ring 13C, and has an opening in the region facing the anode 13A. This allows signal charges (hole carriers) generated in the semiconductor substrate 11 to be efficiently read out from the anode 13A. It is preferable that the embedded layer 14 is positioned so as not to be in direct contact with the drain 13B and guard ring 13C. The thickness of the embedded layer 14 varies depending on the magnitude of the reverse bias voltage applied between the front surface S1 and back surface S2 of the semiconductor substrate 11, but is, for example, between 0.100 μm and 10 μm.

[0026] The insulating layer 15 is formed on the surface S1 of the semiconductor substrate 11, and is formed using, for example, an inorganic insulating material. Examples of inorganic insulating materials include silicon nitride (SiN), aluminum oxide (Al2O3), silicon dioxide (SiO2), and hafnium oxide (HfO2). The insulating layer 15 is composed of at least one of these materials. Although not shown in the figures, a logic circuit or the like is formed on the insulating layer 15.

[0027] (1-2. Method for manufacturing photodetectors) The photodetector 10 can be manufactured, for example, as follows. First, an n-type conductive layer 12 is formed on the back surface S2 of the semiconductor substrate 11 using ion implantation technology. Next, a mask is formed in a predetermined area on the surface S1 of the semiconductor substrate 11, and then an n-type conductive region (embedded layer 14) is formed by doping with an n-type impurity (e.g., phosphorus (P)) using ion implantation technology. Next, a mask is formed in a predetermined area on the surface S1 of the semiconductor substrate 11, and then a p-type conductive region (anode 13A, drain 13B, and guard ring 13C) is formed by doping with a p-type impurity (e.g., boron (B)) using ion implantation technology. Finally, an insulating layer 15 is formed on the surface S1 of the semiconductor substrate 11, for example, using the CVD (Chemical Vapor Deposition) method. This completes the photodetector 10 shown in Figure 1. ru.

[0028] (1-3. Action / Effect) As mentioned above, solid-state imaging devices are used in a variety of applications, such as imaging devices in digital still cameras and video cameras, electronic devices such as mobile terminals with imaging capabilities, and electromagnetic wave sensors that detect various wavelengths other than visible light. CMOS image sensors, which read out the signal charge accumulated in a photodiode (a photoelectric conversion element) via a MOS transistor, are widely used in these solid-state imaging devices.

[0029] A unit pixel of a CMOS image sensor comprises, for example, a photodiode (PD) with a HAD (Hole Accumulated Diode) structure within a semiconductor substrate, and a floating diffusion region (FD) positioned on either side of the transfer gate relative to the photodiode. In addition to these, the unit pixel also includes, for example, a reset transistor, a select transistor, and an amplifier transistor.

[0030] Another configuration of the unit pixel in a CMOS image sensor is one in which the photoelectric conversion region and FD are integrated within the semiconductor substrate, without a HAD. This structure is simple and easy to manufacture, and allows for the application of any potential difference to the pn junction forming the photoelectric conversion region. Therefore, it is easy to increase the thickness of the photoelectric conversion region, and this advantage is utilized in sensors for scientific applications where high-sensitivity measurement is required.

[0031] Incidentally, in recent years, there has been a demand for the development of X-ray image sensors with high-speed drive and low-noise characteristics for scientific applications. Specifically, higher frame rates and improved resistance to high-energy inputs are required. However, the CMOS image sensor mentioned above as an alternative form had the problem that increasing the floppy disk (FD) increased the capacitance. On the other hand, decreasing the FD reduced the signal charge transfer rate, limiting the ability to increase the frame rate. Furthermore, in the CMOS image sensor mentioned above as an alternative form, because the surface of the semiconductor substrate is in contact with the depletion layer, for example, when fixed charges are generated on the insulating film or its interface on the semiconductor substrate due to the incidence of strong radiation, the capacitance and electric field fluctuate greatly, resulting in a problem of low resistance to high-energy inputs.

[0032] In contrast, in the photodetector 10 of this embodiment, an anode 13A is provided at the interface of the surface S1 of the n-type semiconductor substrate 11 that forms the photoelectric conversion region, and is composed of a p-type conductive region and connected to an electrode 16. Around the anode 13A, a drain 13B is provided, also composed of a p-type conductive region and connected to an electrode (electrode 17) different from the anode 13A. This makes it possible, for example, for dark current generated at the interface of the semiconductor substrate 11 during X-ray irradiation to be discharged by the drain 13B and prevented from reaching the anode 13A. Furthermore, a guard ring 13C is provided around the drain 13B, also composed of a p-type conductive region and in an electrically floating state. This makes it possible to improve the speed of movement of signal charges (in this case, hole carriers) generated in the semiconductor substrate 11 in the planar direction.

[0033] As described above, in this embodiment, a drain 13B connected to an electrode 17 different from the electrode 16 connected to the anode 13A is provided around the anode 13A located at the interface of the surface S1 of the semiconductor substrate 11, and a floating guard ring 13C is provided around the drain 13B. This improves the speed of movement of signal charges (in this case, hole carriers) generated in the semiconductor substrate 11 in the planar direction, making it possible to improve the signal charge transfer speed without increasing the size of the anode 13A. Furthermore, for example, when a dark current is generated at the interface of the semiconductor substrate 11 during X-ray irradiation, this dark current can be discharged by the drain 13B, improving resistance to high energy input. Thus, it is possible to achieve a reduction in dark current, a reduction in capacitance, and an improvement in readout speed.

[0034] Furthermore, in the photodetector 10 of this embodiment, a buried layer 14 with a high concentration of n-type impurities is formed inside the semiconductor substrate 11, specifically near the drain 13B and the guard ring 13C. This prevents signal charges (in this case, hole carriers) generated within the semiconductor substrate 11 from leaking into the drain 13B and the guard ring 13C. Thus, the transfer conversion efficiency can be further improved.

[0035] Next, the second to fifth embodiments and modified versions of the first embodiment described above will be explained. In the following, components similar to those in the first embodiment will be denoted by the same reference numerals, and their descriptions will be omitted as appropriate.

[0036] <2. Second Embodiment> Figure 8 shows a cross-sectional configuration of a light-receiving element (light-receiving element 20) according to the second embodiment of this disclosure. Similar to the first embodiment described above, the light-receiving element 20 consists of, for example, a PIN-type photodiode that applies a reverse bias between the front and back surfaces of a semiconductor substrate 11, and constitutes one pixel (pixel P) in a radiation image sensor (e.g., X-ray image sensor 1; see Figure 15) or an electromagnetic wave detection device that reads information about a subject (images a subject) based on radiation (e.g., alpha rays, beta rays, gamma rays, and X-rays, etc.).

[0037] The light-receiving element 20 has, for example, a p-type conductive region 23 formed at the interface of the surface S1 of an n-type semiconductor substrate 11, which includes, for example, an anode 23A, a drain 13B, and a guard ring 13C. An n-type conductive layer 12 is formed at the interface of the back surface S2 of the semiconductor substrate 11. In the light-receiving element 20 of this embodiment, the anode 23A has an extended portion 23X1 that extends toward the back surface S2, so that the lower end of the anode 13A is formed at a deeper position than the drain 13B and the guard ring 13C. Preferably, the extended portion 23X1 protrudes toward the back surface S2 side from, for example, the bottom surface of the embedded layer 14 formed below the drain 13B and the guard ring 13C.

[0038] As described above, in this embodiment, an extended portion 23X1 is provided on the anode 23A formed at the interface of the surface S1 of the n-type semiconductor substrate 11, and its tip is formed to protrude into the interior of the semiconductor substrate 11, specifically, on the back surface S2 side, beyond the bottom surface of the embedded layer 14 formed below the drain 13B and guard ring 13C. This provides the effect of further improving the transfer efficiency of signal charges (e.g., hole carriers) generated in the semiconductor substrate 11, in addition to the effects of the first embodiment described above.

[0039] <3. Third Embodiment> Figure 9 shows a cross-sectional configuration of a light-receiving element (light-receiving element 30) according to the third embodiment of this disclosure. Similar to the first embodiment described above, the light-receiving element 30 consists of, for example, a PIN-type photodiode that applies a reverse bias between the front and back surfaces of a semiconductor substrate 11, and constitutes one pixel (pixel P) in a radiation image sensor (e.g., X-ray image sensor 1; see Figure 15) or an electromagnetic wave detection device that reads information about a subject (images a subject) based on radiation (e.g., alpha rays, beta rays, gamma rays, and X-rays, etc.).

[0040] The light-receiving element 30 has, for example, a p-type conductive region 33 formed at the interface of the surface S1 of an n-type semiconductor substrate 11, which includes, for example, an anode 33A, a drain 13B, and a guard ring 13C. An n-type conductive layer 12 is formed at the interface of the back surface S2 of the semiconductor substrate 11. In the light-receiving element 30 of this embodiment, the anode 33A has an extended portion 33X1 that extends toward the back surface S2, and at its tip, an overhang portion 33X2 that extends in the planar direction (for example, the XZ plane direction) of the semiconductor substrate 11. This overhang portion 33X2 is provided in the lower layer of the embedded layer 14 formed below the drain 13B and the guard ring 13C. Preferably, the tip of the overhang portion 33X2 extends to the edge of the pixel P. Alternatively, it may be formed continuously with the overhang portions 33X2 of other adjacent pixels P.

[0041] As described above, in this embodiment, an extended portion 33X1 is provided on the anode 33A formed at the interface of the surface S1 of the n-type semiconductor substrate 11, and an extended portion 33X2 extending in the planar direction of the semiconductor substrate 11 is provided at its tip. This provides the effect of further improving the transfer efficiency of signal charges (e.g., hole carriers) generated within the semiconductor substrate 11, in addition to the effects of the second embodiment described above.

[0042] <4. Fourth Embodiment> Figure 10 shows a cross-sectional configuration of a photodetector (photodetector 40) according to the fourth embodiment of this disclosure. Figure 11 schematically shows the planar configuration of the p-type conductive region 43 of the photodetector 40 shown in Figure 10. The photodetector 40, similar to the first embodiment described above, consists of, for example, a PIN-type photodiode that applies a reverse bias between the front and back surfaces of a semiconductor substrate 11, and constitutes, for example, one pixel (pixel P) in a radiation image sensor (e.g., X-ray image sensor 1; see Figure 15) or an electromagnetic wave detection device that reads information about a subject based on radiation (e.g., alpha rays, beta rays, gamma rays, and X-rays, etc.) to capture an image of the subject.

[0043] The photodetector 40 has, for example, a p-type conductive region 33 formed at the interface of the surface S1 of an n-type semiconductor substrate 11, which includes, for example, an anode 43A, a drain 43B, and a guard ring 43C. An n-type conductive layer 12 is formed at the interface of the back surface S2 of the semiconductor substrate 11. In the photodetector 40 of this embodiment, the line width of the guard rings 43C1, 43C2, 43C3 and the spacing between the guard rings 43C1, 43C2, 43C3 are formed in a manner that increases towards the outer periphery.

[0044] As described above, in this embodiment, the line width of the guard rings 43C1, 43C2, and 43C3, and the spacing between the guard rings 43C1, 43C2, and 43C3 are formed to widen towards the outer circumference. This provides the effect of efficiently mitigating the concentration of the electric field between the guard rings 43C1, 43C2, and 43C3, in addition to the effects of the first embodiment described above.

[0045] Furthermore, as in the first embodiment described above, if the guard rings 13C1, 13C2, and 13C3 are arranged at equal intervals, the potential difference between the guard rings will decrease towards the outer edge, potentially weakening the transfer electric field (horizontal electric field). In contrast, as in this embodiment, by increasing the spacing between the guard rings 43C1, 43C2, and 43C3 towards the outer edge, the potential difference between the guard rings 43C1, 43C2, and 43C3 is equalized, resulting in the effect of equalizing the horizontal electric field directed toward the anode 43A within the pixel P.

[0046] <5. Fifth Embodiment> Figure 12 shows a cross-sectional configuration of a light-receiving element (light-receiving element 50) according to the fifth embodiment of this disclosure. Figure 13 schematically shows the planar configuration of the p-type conductive region 13 and the embedded layer 54 of the light-receiving element 50 shown in Figure 12. The light-receiving element 50, similar to the first embodiment described above, consists of, for example, a PIN-type photodiode that applies a reverse bias between the front and back surfaces of a semiconductor substrate 11, and constitutes, for example, one pixel (pixel P) in a radiation image sensor (e.g., X-ray image sensor 1; see Figure 15) or an electromagnetic wave detection device that reads information about an object based on radiation (e.g., alpha rays, beta rays, gamma rays, and X-rays, etc.) to capture an image of the object.

[0047] The photodetector 50 has, for example, a p-type conductive region 33 formed at the interface of the surface S1 of an n-type semiconductor substrate 11, which includes, for example, an anode 33A, a drain 13B, and a guard ring 13C. An n-type conductive layer 12 is formed at the interface of the back surface S2 of the semiconductor substrate 11. The photodetector 50 of this embodiment differs from the first embodiment in that the embedded layer 54 provided below the drain 13B and the guard ring 13C has a region with a locally high impurity concentration. Specifically, the embedded layer 54 has, for example, an impurity region 54a having n-type impurities of the same concentration as the embedded layer 14 in the first embodiment, and a high-impurity region 54b with a higher impurity concentration than the impurity region 54a. It is preferable to form this high-impurity region 54b in a region where leakage of signal charges (here, hole carriers) generated in the semiconductor substrate 11 into the drain 13B and guard ring 13C is likely to occur.

[0048] As described above, in this embodiment, a region with a locally high impurity concentration (high impurity region 54b) is formed in the embedded layer 54. This makes it possible to reinforce regions where signal charges generated in the semiconductor substrate 11 are prone to leaking into the drain 13B and guard ring 13C, and in addition to the effects of the first embodiment, it is possible to further improve the transfer efficiency of signal charges (e.g., hole carriers) generated in the semiconductor substrate 11.

[0049] <6. Variation> Figure 14 schematically shows the planar configuration of a p-type conductive region 63 in a photodetector (photodetector 60) according to a modified example of the first embodiment of this disclosure, together with other adjacent pixels P. Similar to the first embodiment, the photodetector 60 consists of, for example, a PIN-type photodiode that applies a reverse bias between the front and back surfaces of a semiconductor substrate 11, and constitutes one pixel (pixel P) in a radiation image sensor (e.g., X-ray image sensor 1; see Figure 15) or an electromagnetic wave detection device that reads information about a subject (images a subject) based on radiation (e.g., alpha rays, beta rays, gamma rays, and X-rays, etc.).

[0050] In the first embodiment described above, the p-type conductive region 13 is configured with an anode 13A placed at the center of the pixel P, and drains 13B and guard rings 13C arranged around it in that order, but the configuration is not limited to this. For example, as shown in Figure 14, an anode 63A may be formed at one corner of a rectangular pixel P. In that case, for example, as shown in Figure 14, four adjacent pixels P may be treated as a set, and an anode 63A may be formed in the center of each set. In that case, it is preferable that the drains 63B be formed to surround each anode 63A. This prevents the inflow of dark current into the anode 63A and improves resistance to high energy input. Guard rings 63C1, 63C2, and 63C3 are provided to surround the anode 63A and drains 63B provided for each of the four pixels P.

[0051] <7. Examples of Application> Figure 15 shows the functional configuration of the X-ray image sensor 1 using the element structure of the photodetector (e.g., photodetector 10) described in the first to fifth embodiments and modified examples above. The X-ray image sensor 1 reads information about a subject (images the subject) based on incident radiation Rrad (e.g., alpha rays, beta rays, gamma rays, X-rays, etc.). This X-ray image sensor 1 includes a pixel section (pixel area 110A), and the drive circuit (peripheral circuit section) for this pixel area 110A includes a row scanning section 121, an A / D conversion section 122, a column scanning section 123, and a system control section 124.

[0052] (Pixel area 110A) The pixel region 110A is equipped with multiple pixels (imaging pixels) P that generate signal charges based on radiation. The multiple pixels P are arranged in a matrix in two dimensions. As shown in Figure 1, the horizontal direction (row direction) within the pixel region 110A is defined as the "H" direction, and the vertical direction (column direction) is defined as the "V" direction.

[0053] (Row scanning unit 121) The row scanning unit 121 is composed of a shift register circuit and predetermined logic circuits, as described later, and is a pixel driving unit (row scanning circuit) that drives multiple pixels P in row units (horizontal line units) within the pixel area 110A (line sequential scanning). Specifically, imaging operations such as readout and reset operations of each pixel P are performed, for example, by line sequential scanning. This line sequential scanning is performed by supplying the aforementioned row scanning signal to each pixel P via the readout control line Lread.

[0054] (A / D conversion unit 122) The A / D conversion unit 122 has multiple column selection units 125, one for each of the multiple (four in this case) signal lines Lsig, and performs A / D conversion (analog-to-digital conversion) based on the signal voltage (voltage corresponding to the signal charge) input via the signal line Lsig. As a result, output data Dout (imaging signal) consisting of digital signals is generated and output to the outside.

[0055] Each column selection unit 125 includes, for example, a charge amplifier 172, a capacitive element (such as a capacitor or feedback capacitance element) C1, a switch SW1, a sample-and-hold (S / H) circuit 173, a multiplexer circuit (selection circuit) 174 including four switches SW2, and an A / D converter 175, as shown in Figure 16. Of these, the charge amplifier 172, capacitive element C1, switch SW1, S / H circuit 173, and switch SW2 are provided for each signal line Lsig. The multiplexer circuit 174 and A / D converter 175 are provided for each column selection unit 125. The charge amplifier 172, capacitive element C1, and switch SW1 constitute the charge amplifier circuit.

[0056] The charge amplifier 172 is an amplifier that converts the signal charge read from the signal line Lsig into a voltage (QV conversion). In this charge amplifier 172, one end of the signal line Lsig is connected to the negative (-) input terminal, and a predetermined reset voltage Vrst is input to the positive (+) input terminal. The output terminal and the negative input terminal of the charge amplifier 172 are connected via a parallel connection circuit of a capacitive element C1 and a switch SW1, creating a feedback connection. That is, one terminal of the capacitive element C1 is connected to the negative input terminal of the charge amplifier 172, and the other terminal is connected to the output terminal of the charge amplifier 172. Similarly, one terminal of the switch SW1 is connected to the negative input terminal of the charge amplifier 172, and the other terminal is connected to the output terminal of the charge amplifier 172. The on / off state of this switch SW1 is controlled by a control signal (ampretrieval control signal) supplied from the system control unit 124 via the ampretrieval control line Lcarst.

[0057] The S / H circuit 173 is located between the charge amplifier 172 and the multiplexer circuit 174 (switch SW2), and is a circuit for temporarily holding the output voltage Vca from the charge amplifier 172.

[0058] The multiplexer circuit 174 is a circuit that selectively connects or disconnects each S / H circuit 173 and the A / D converter 175 by sequentially turning on one of the four switches SW2 in accordance with the scanning drive by the column scanning unit 123.

[0059] The A / D converter 175 is a circuit that generates and outputs the output data Dout described above by performing A / D conversion on the output voltage from the S / H circuit 173, which is input via switch SW2.

[0060] (Column scanning unit 123) The column scanning unit 123 is configured to include, for example, a shift register and an address decoder (not shown), and sequentially drives each switch SW2 in the column selection unit 125 while scanning them. Through this selective scanning by the column scanning unit 123, the signals of each pixel P (the output data Dout) read out via each of the signal lines Lsig are sequentially output to the outside.

[0061] (System Control Unit 124) The system control unit 124 controls the operation of the row scanning unit 121, the A / D conversion unit 122, and the column scanning unit 123. Specifically, the system control unit 124 has a timing generator that generates the various timing signals (control signals) mentioned above, and controls the drive of the row scanning unit 121, the A / D conversion unit 122, and the column scanning unit 123 based on the various timing signals generated by this timing generator. Based on the control of the system control unit 124, the row scanning unit 121, the A / D conversion unit 122, and the column scanning unit 123 each perform imaging drive (line sequential imaging drive) for multiple pixels P within the pixel area 110A, thereby obtaining output data Dout from the pixel area 110A.

[0062] The first to fifth embodiments, modifications, and application examples have been described above, but the contents of this disclosure are not limited to the above embodiments, and various modifications are possible. For example, in the above embodiments, examples using hole carriers as signal charges were shown, but electron carriers may be used as signal charges. In that case, the conductivity types of each component will be the opposite conductivity types.

[0063] Furthermore, the layer configuration of the light-receiving element 10 described in the above embodiments is merely an example, and it may also have other layers. Moreover, the material and thickness of each layer are also merely examples and are not limited to those described above.

[0064] Furthermore, although the above example of application uses an X-ray imaging sensor 1, the light-receiving elements (for example, light-receiving element 10) described in the above embodiments can also be applied to radiation imaging sensors and electromagnetic wave detection devices that are not limited to X-rays.

[0065] Furthermore, the effects described herein are merely illustrative and not limiting, and other effects may also occur.

[0066] Furthermore, this disclosure can also take the following configuration. According to the technology with the following configuration, a second first conductivity type region connected to a second electrode is positioned between a first first conductivity type region connected to a first electrode and an electrically floating third conductivity type region, which are provided at the interface of one surface of the semiconductor substrate. As a result, the reach of dark current generated at the interface of one surface of the semiconductor substrate to the first first conductivity type region is reduced. In addition, the speed of movement of signal charge generated in the semiconductor substrate in the planar direction is improved. This makes it possible to reduce the size of the first first conductivity type region relative to the pixel area, thereby achieving a reduction in dark current, a reduction in capacitance, and an improvement in readout speed. (1) A semiconductor substrate including a photoelectric conversion region, A first conductivity type region is provided at the interface of one surface of the semiconductor substrate and connected to the first electrode, At the interface of the first surface, a second first conductivity region is provided around the first first conductivity region and connected to the second electrode, At the interface of the first surface, a third first conductivity region is provided around the second first conductivity region and is electrically floating. 、 The semiconductor substrate comprises a second conductivity type region embedded and formed within the semiconductor substrate, The first conductivity type region extends in the direction of the other surface opposite to the first surface, and has an overhanging region that extends further horizontally towards the other surface side than the second conductivity type region. Light-receiving element. (2) The photodetector according to (1), wherein the semiconductor substrate further has a second conductivity type layer at the interface of the other surface facing the first surface. (3) The photodetector according to either (1) or (2), wherein the third first conductivity type region is formed in a plurality around the second first conductivity type region. (4) The second first conductivity type region is provided continuously around the first first conductivity type region, and is a light-receiving element according to any one of (1) to (3) above. (5) The third first conductivity type region is provided continuously around the second first conductivity type region, and is a light-receiving element according to any one of (1) to (4) above. (6) The photodetector according to any one of (1) to (5), wherein the second first conductivity type region and the third first conductivity type region are arranged in this order with respect to the first first conductivity type region, and the photodetector has a polygonal planar shape with curved corners. (7 ) before The second conductivity type region has an opening at a position opposite to the first conductivity type region. Any of the above (1) to (6) The light-receiving element described above. (8) The second conductivity type region has regions with different impurity concentrations. Any of the above (1) to (7) The light-receiving element described. (9) The first first conductivity type region extends more in the other plane direction than the second first conductivity type region and the third first conductivity type region. The above (2) through (8) A light-receiving element as described in any of the following. (10) The third first conductivity type regions, which are formed in multiple locations around the second first conductivity type region, have different line widths from each other. The above (3) to (9) A light-receiving element as described in any of the following. (11) The line width of the third first conductivity type region, which is formed in multiple locations around the second first conductivity type region, is progressively wider as it moves away from the first first conductivity type region. The above (3) to (10) A light-receiving element as described in any of the following. (12) The spacing between the third first conductivity type regions, which are formed in multiple locations around the second first conductivity type region, is progressively wider towards the outside. The above (3) to (11) A light-receiving element as described in any of the following. (13) before The second conductivity type layer and the second conductivity type region have a higher impurity concentration than the semiconductor substrate. The above (1) to (12) A light-receiving element as described in any one of the following. (14) The aforementioned semiconductor substrate is composed of an intrinsic semiconductor. The above (1) to (13) A light-receiving element as described in any one of the following. (15) It comprises multiple photodetectors that generate signal charges based on X-rays, The aforementioned light-receiving element is A semiconductor substrate including a photoelectric conversion region, A first conductivity type region is provided at the interface of one surface of the semiconductor substrate and connected to the first electrode, At the interface of the first surface, a second first conductivity region is provided around the first first conductivity region and connected to the second electrode, At the interface of the first surface, a third first conductivity region is provided around the second first conductivity region and is electrically floating. 、 It has a second conductivity type region embedded and formed within the semiconductor substrate, The first conductivity type region extends in the direction of the other surface opposite to the first surface, and has an overhanging region that extends further horizontally towards the other surface side than the second conductivity type region. X-ray imaging sensor. (16) A pixel region in which multiple pixels are arranged, It has a peripheral region provided around the aforementioned pixel region, The semiconductor substrate has a depletion region in the pixel region and a neutral region in the peripheral region. (15) The X-ray imaging sensor described in [reference]. (17) The photodetector is a pn junction type photodetector provided for each of the plurality of pixels, which applies a reverse bias between one surface of the semiconductor substrate and another surface facing that surface. (16) The X-ray imaging sensor described in [reference]. (18) Equipped with an X-ray imaging sensor, The aforementioned X-ray imaging sensor has a plurality of photodetectors that generate signal charges based on X-rays, The aforementioned light-receiving element is A semiconductor substrate including a photoelectric conversion region, A first conductivity type region is provided at the interface of one surface of the semiconductor substrate and connected to the first electrode, At the interface of the first surface, a second first conductivity region is provided around the first first conductivity region and connected to the second electrode, At the interface of the first surface, a third first conductivity region is provided around the second first conductivity region and is electrically floating. 、 The semiconductor substrate comprises a second conductivity type region embedded and formed within the semiconductor substrate, The first conductivity type region extends in the direction of the other surface opposite to the first surface, and has an overhanging region that extends further horizontally towards the other surface side than the second conductivity type region. electronic equipment.

[0067] This application claims priority based on Japanese Patent Application No. 2021-075730, filed with the Japan Patent Office on 28 April 2021, and all contents of that application are incorporated herein by reference.

[0068] Those skilled in the art will understand that various modifications, combinations, subcombinations, and changes can be conceived depending on design requirements and other factors, and that these fall within the scope of the attached claims and their equivalents.

Claims

1. A semiconductor substrate including a photoelectric conversion region, A first conductivity type region is provided at the interface of one surface of the semiconductor substrate and connected to the first electrode, At the interface of the first surface, a second first conductivity region is provided around the first first conductivity region and connected to the second electrode, At the interface of the first surface, a third first conductivity region is provided around the second first conductivity region and is electrically floating, It comprises a second conductive region embedded and formed within the semiconductor substrate, The first conductivity type region extends in the direction of the other surface opposite to the first surface, and has an overhanging region that extends further horizontally towards the other surface side than the second conductivity type region. Light-receiving element.

2. The photodetector according to claim 1, wherein the semiconductor substrate further has a second conductivity type layer at the interface of the other surface facing the first surface.

3. The photodetector according to claim 1, wherein the third first conductivity type region is formed in a plurality around the second first conductivity type region.

4. The light-receiving element according to claim 1, wherein the second first conductivity type region is provided continuously around the first first conductivity type region.

5. The light-receiving element according to claim 1, wherein the third first conductivity type region is provided continuously around the second first conductivity type region.

6. The light-receiving element according to claim 1, wherein the second first conductivity type region and the third first conductivity type region are arranged in this order with respect to the first first conductivity type region, and the element has a polygonal planar shape with curved corners.

7. The photodetector according to claim 1, wherein the second conductivity type region has an opening at a position opposite to the first conductivity type region.

8. The photodetector according to claim 1, wherein the second conductivity type region has regions with different impurity concentrations.

9. The light-receiving element according to claim 2, wherein the first first conductivity type region extends in the other plane direction more than the second first conductivity type region and the third first conductivity type region.

10. The photodetector according to claim 3, wherein the third first conductivity type regions, which are formed in a plurality around the second first conductivity type region, have different line widths from each other.

11. The light-receiving element according to claim 3, wherein the line width of the third first conductivity type region, which is formed in a plurality around the second first conductivity type region, is progressively wider as it moves away from the first first conductivity type region.

12. The photodetector according to claim 3, wherein the spacing between the third first conductivity type regions, which are formed in a plurality around the second first conductivity type region, is progressively wider towards the outside.

13. The photodetector according to claim 2, wherein the second conductivity layer and the second conductivity region have a higher impurity concentration than the semiconductor substrate.

14. The photodetector according to claim 1, wherein the semiconductor substrate is made of an intrinsic semiconductor.

15. It is equipped with multiple photodetectors that generate signal charges based on X-rays, The aforementioned light-receiving element is A semiconductor substrate including a photoelectric conversion region, A first conductivity type region is provided at the interface of one surface of the semiconductor substrate and connected to the first electrode, At the interface of the first surface, a second first conductivity region is provided around the first first conductivity region and connected to the second electrode, At the interface of the first surface, a third first conductivity region is provided around the second first conductivity region and is electrically floating, It has a second conductivity type region embedded and formed within the semiconductor substrate, The first conductivity type region extends in the direction of the other surface opposite to the first surface, and has an overhanging region that extends further horizontally towards the other surface side than the second conductivity type region. X-ray imaging sensor.

16. A pixel region in which multiple pixels are arranged, It has a peripheral region provided around the aforementioned pixel region, The X-ray imaging sensor according to claim 15, wherein the semiconductor substrate has a depletion region in the pixel region and a neutral region in the peripheral region.

17. The X-ray imaging sensor according to claim 16, wherein the photodetector is provided for each of the plurality of pixels and is a pn junction type photodetector that applies a reverse bias between one surface of the semiconductor substrate and another surface facing the first surface.

18. Equipped with an X-ray imaging sensor, The aforementioned X-ray imaging sensor has a plurality of photodetectors that generate signal charges based on X-rays, The aforementioned light-receiving element is A semiconductor substrate including a photoelectric conversion region, A first conductivity type region is provided at the interface of one surface of the semiconductor substrate and connected to the first electrode, At the interface of the first surface, a second first conductivity region is provided around the first first conductivity region and connected to the second electrode, At the interface of the first surface, a third first conductivity region is provided around the second first conductivity region and is electrically floating, It comprises a second conductive region embedded and formed within the semiconductor substrate, The first conductivity type region extends in the direction of the other surface opposite to the first surface, and has an overhanging region that extends further horizontally towards the other surface side than the second conductivity type region. electronic equipment.

Images