JP2024127279A - Photodetector - Google Patents

Abstract

To provide a light detection device capable of reducing pixel size.SOLUTION: A light detection device includes an SPAD that amplifies carriers that occur in response to incident photons. The SPAD includes: a trench that is disposed on a substrate having a first surface located on a photon incident side and a second surface opposite to the first face, and that is formed from the second surface side toward the first surface side; a first semiconductor region of a first conduction type disposed along at least a portion of a bottom surface and side surfaces of the trench; and a second semiconductor region of a second conduction type, which is opposite to the first conduction type, disposed along at least a portion of the bottom surface and side surfaces of the trench with the first semiconductor region interposed therebetween.SELECTED DRAWING: Figure 1

Description

This disclosure relates to a light detection device.

Patent Document 1 discloses a single photon avalanche diode (hereinafter, simply referred to as a "SPAD") and a method for manufacturing the same. The pn junction between the anode region and the cathode region of this SPAD is formed in the vertical direction.
A specific manufacturing method is as follows. First, two trenches are formed in horizontally spaced regions of a p-type well region. One trench is filled with an electrically insulating material containing a p-type dopant. The other trench is filled with an electrically insulating material containing an n-type dopant. When annealing is performed, p-type impurities are diffused from the electrically insulating material filled in one trench into the p-type well region to form an anode region. Also, n-type impurities are diffused from the electrically insulating material filled in the other trench into the p-type well region to form a cathode region. The anode region and the cathode region come into contact with each other to form a pn junction.

U.S. Patent Application Publication No. 2019/0221704 A1

In the above-mentioned patent document 1, one SPAD is formed as one pixel, and a plurality of pixels are arranged in a matrix. In one pixel, the SPAD uses a plurality of trenches spaced apart in the horizontal direction, and impurities contained in an electrically insulating material filled in the trenches are diffused in the horizontal direction (lateral direction) to form an anode region and a cathode region.
This results in a large pixel size, and therefore there is a demand for the development of a SPAD that allows the pixel size to be reduced.

The photodetector according to the first embodiment of the present disclosure includes an avalanche diode that amplifies carriers generated by incident photons. The avalanche diode is disposed on a substrate having a first surface on which photons are incident and a second surface opposite to the first surface, and includes a trench formed from the second surface side toward the first surface side, a first semiconductor region of a first conductivity type disposed along at least a portion of the bottom and side surfaces of the trench, and a second semiconductor region of a second conductivity type opposite the first conductivity type disposed along at least a portion of the bottom and side surfaces of the trench with the first semiconductor region interposed therebetween.

The photodetector according to the second embodiment of the present disclosure is the photodetector according to the first embodiment, in which the substrate is provided with an element separator surrounding the side periphery of the avalanche diode. The substrate is made of a semiconductor. The element separator includes an isolation trench disposed from the first surface side toward the second surface side of the substrate, an isolation insulator disposed along the side of the isolation trench, and an isolation metal body embedded inside the isolation trench with the isolation insulator interposed therebetween.

In the photodetector according to the third embodiment of the present disclosure, a fixed charge film that fixes the charge near the first surface of the substrate is disposed along the first surface of the substrate in the photodetector according to the first or second embodiment.

FIG. 1 is a vertical cross-sectional configuration diagram showing a main part of a pixel of a photodetector according to a first embodiment of the present disclosure (a cross-sectional view taken along the line AA shown in FIG. 2). FIG. 2 is a plan view showing the configuration of a plurality of pixels of the photodetector shown in FIG. FIG. 3 is an energy band diagram in the horizontal direction of a pixel of the photodetector shown in FIG. 1 (an energy band diagram along line X1-X1 shown in FIG. 1). FIG. 4 is an energy band diagram in the vertical direction of a pixel of the photodetector shown in FIG. 1 (an energy band diagram along line Y1-Y1 shown in FIG. 1). FIG. 5 is a cross-sectional view illustrating a first step in the method for manufacturing the photodetector according to the first embodiment. FIG. 6 is a cross-sectional view illustrating a second step in the manufacturing method. FIG. 7 is a cross-sectional view illustrating a third step in the manufacturing method. FIG. 8 is a cross-sectional view illustrating a fourth step in the manufacturing method. FIG. 9 is a cross-sectional view illustrating a fifth step in the manufacturing method. FIG. 10 is a cross-sectional view illustrating a sixth step in the manufacturing method. FIG. 11 is a cross-sectional view illustrating a seventh step in the manufacturing method. FIG. 12 is a cross-sectional view illustrating an eighth step of the manufacturing method. FIG. 13 is a plan view illustrating the configuration of a plurality of pixels of a photodetection device according to a second embodiment of the present disclosure, corresponding to FIG. FIG. 14 is a plan view illustrating the configuration of a plurality of pixels of a photodetection device according to a first modified example of the second embodiment, the plan view corresponding to FIG. FIG. 15 is a plan view illustrating the configuration of a plurality of pixels of a photodetector according to a second modified example of the second embodiment, the plan view corresponding to FIG. FIG. 16 is a plan view illustrating the configuration of a plurality of pixels of a photodetector according to a third modified example of the second embodiment, the plan view corresponding to FIG. FIG. 17 is a plan view illustrating the configuration of a plurality of pixels of a photodetector according to a fourth modified example of the second embodiment, the plan view corresponding to FIG. FIG. 18 is a vertical cross-sectional configuration diagram corresponding to FIG. 1 and showing a main part of a pixel of a photodetector according to a third embodiment of the present disclosure. FIG. 19 is an energy band diagram in the horizontal direction of the pixel of the photodetector shown in FIG. 18 (an energy band diagram along line X2-X2 shown in FIG. 18). FIG. 20 is an energy band diagram in the vertical direction of the pixel of the photodetector shown in FIG. 18 (an energy band diagram taken along line Y2-Y2 shown in FIG. 18). FIG. 21 is a vertical cross-sectional configuration diagram showing a main part of a pixel of a photodetector according to a fourth embodiment of the present disclosure, and corresponds to FIG. FIG. 22 is a vertical cross-sectional configuration diagram corresponding to FIG. 1 and showing a main part of a pixel of a photodetector according to a fifth embodiment of the present disclosure. FIG. 23 is a vertical cross-sectional configuration diagram showing a main part of a pixel of a photodetector according to a sixth embodiment of the present disclosure, corresponding to FIG. FIG. 24 is a vertical cross-sectional configuration diagram showing a main part of a pixel of a photodetector according to a seventh embodiment of the present disclosure, corresponding to FIG. FIG. 25 is a vertical cross-sectional configuration diagram corresponding to FIG. 1 and showing a main part of a pixel of a photodetector according to an eighth embodiment of the present disclosure. 26 is a vertical cross-sectional configuration diagram corresponding to FIG. 1 and showing a main part of a pixel of a photodetector according to a ninth embodiment of the present disclosure. FIG. 27 is a vertical cross-sectional configuration diagram corresponding to FIG. 1 and showing a main part of a pixel of a photodetector according to a tenth embodiment of the present disclosure. FIG. 28 is a vertical cross-sectional configuration diagram corresponding to FIG. 1 and showing a main part of a pixel of a photodetector according to an eleventh embodiment of the present disclosure. FIG. 29 is a vertical cross-sectional configuration diagram corresponding to FIG. 1, showing a main part of a pixel of a photodetector according to a twelfth embodiment of the present disclosure. FIG. 30 is a vertical cross-sectional configuration diagram corresponding to FIG. 1 and showing a main part of a pixel of a photodetector according to a thirteenth embodiment of the present disclosure. FIG. 31 is a vertical cross-sectional configuration diagram corresponding to FIG. 1 and showing a main part of a pixel of a photodetector according to a fourteenth embodiment of the present disclosure. FIG. 32 is a vertical cross-sectional configuration diagram corresponding to FIG. 1 and showing a main part of a pixel of a photodetector according to a fifteenth embodiment of the present disclosure.

Hereinafter, embodiments of the present disclosure will be described in detail with reference to the drawings. The description will be made in the following order.
1. First embodiment In the first embodiment, a first example in which the present technology is applied to a SPAD that configures pixels of a photodetector will be described. In the first embodiment, a longitudinal sectional configuration and a planar configuration of the SPAD will be described. Furthermore, in the first embodiment, a manufacturing method of the SPAD will be described.
2. Second Embodiment In the second embodiment, a second example in which the planar configuration of the SPAD is changed in the photodetector according to the first embodiment will be described. In the second embodiment, a number of modified examples will also be described.
3. Third Embodiment In the third embodiment, a third example in which the configuration of the SPAD is changed in the photodetector according to the first embodiment will be described.
4. Fourth Embodiment In the fourth embodiment, a fourth example in which the configuration of the SPAD is changed in the photodetector according to the first embodiment will be described.
5. Fifth Embodiment In the fifth embodiment, a fifth example in which the configuration of the SPAD is changed in the photodetector according to the fourth embodiment will be described.
6. Sixth Embodiment In the sixth embodiment, a sixth example in which the configuration of the SPAD is changed in the photodetector according to the first embodiment will be described.
7. Seventh Embodiment In the seventh embodiment, a seventh example in which the configuration of the SPAD is changed in the photodetector according to the first embodiment will be described.
8. Eighth Embodiment In the eighth embodiment, an eighth example in which the configuration of the SPAD is changed in the photodetector according to the first embodiment will be described.
9. Ninth Embodiment In the ninth embodiment, a ninth example in which the configuration of the SPAD is changed in the photodetector according to the first embodiment will be described.
10. Tenth Embodiment In the tenth embodiment, a tenth example in which the configuration of the SPAD in the photodetector according to the sixth embodiment is changed will be described.
11. Eleventh Embodiment In the eleventh embodiment, an eleventh example in which the configuration of the SPAD is changed in the photodetector according to the tenth embodiment will be described.
12. Twelfth Embodiment In the twelfth embodiment, a twelfth example in which the configuration of the SPAD is changed in the photodetector according to the first embodiment will be described.
13. Thirteenth Embodiment In the thirteenth embodiment, a thirteenth example in which the configuration of the SPAD is changed in the photodetector according to the twelfth embodiment will be described.
14. Fourteenth Embodiment In the fourteenth embodiment, a fourteenth example in which the configuration of the SPAD is changed in the photodetector according to the first embodiment will be described.
15. Fifteenth Embodiment In the fifteenth embodiment, a fifteenth example in which the configuration of the SPAD is changed in the photodetector according to the first embodiment will be described.
16. Other embodiments

1. First embodiment
A photodetector 1 according to a first embodiment of the present disclosure and a method for manufacturing the same will be described with reference to FIGS.

Here, the arrow X direction shown as appropriate in the figure indicates one planar direction of the light detection device 1 placed on a flat surface for the sake of convenience. The arrow Y direction indicates another planar direction perpendicular to the arrow X direction. The arrow Z direction indicates the upward direction perpendicular to the arrow X and arrow Y directions. In other words, the arrow X direction, arrow Y direction, and arrow Z direction exactly coincide with the X-axis direction, Y-axis direction, and Z-axis direction, respectively, of a three-dimensional coordinate system.
Note that these directions are shown to facilitate understanding of the description and are not intended to limit the directions of the present technology.

[Configuration of photodetector 1]
(1) Schematic configuration of photodetection device 1 Fig. 1 shows an example of a vertical cross-sectional configuration of a main part of one pixel 10 of a photodetection device 1 according to a first embodiment. Fig. 2 shows an example of a planar configuration in which a plurality of pixels 10 shown in Fig. 1 are arranged.

The light detection device 1 according to the first embodiment is constructed as a sensor element or a sensor chip. This light detection device 1 can be used to construct, for example, a distance measurement system. In the distance measurement system, it is possible to measure the time of flight (ToF) of light emitted from a light source until it is reflected by an object to be measured and returns. For example, a laser light having excellent directionality and a peak wavelength in the infrared wavelength band can be used as the light source.

As shown in Fig. 1 and Fig. 2, the photodetector 1 includes a pixel 10. The pixel 10 includes a SPAD 11 as a light receiving element. One pixel 10 is shown in Fig. 1. As shown in Fig. 2, a plurality of pixels 10 are arranged. Here, a total of four pixels 10 are shown, arranged in a plurality in each of the directions of the arrow X and the arrow Y.

SPAD11 is a single-photon avalanche diode that amplifies (multiplies) carriers (electrons) generated by incident photons. SPAD11 operates in the nonlinear region (Geiger mode). In other words, SPAD11 operates with a reverse voltage that exceeds the breakdown voltage.

An anode power supply Va is connected to the anode region of the SPAD 11. The anode power supply Va supplies a large negative voltage that generates avalanche multiplication, in other words, a voltage equal to or greater than the breakdown voltage. Specifically, the anode power supply Va supplies a voltage of, for example, −20 V.
The cathode region of the SPAD 11 is connected to a readout circuit (not shown) via a protection circuit (not shown). A cathode voltage Vc clamped by the protection circuit is applied to the cathode region. The cathode voltage is, for example, a voltage of about 3 V, supplied from the operating power supply of the protection circuit or the readout circuit.

1 and 2 , in the photodetector 1, the SPAD 11 is disposed on a base 2. The SPAD 11 includes a trench 21, a first semiconductor region 22, and a second semiconductor region 23.
Furthermore, in the photodetector 1, an element separator 3 is disposed surrounding the side periphery of the SPAD 11. The element separator 3 surrounds the side periphery of one SPAD 11 and defines one pixel 10. The element separator 3 is disposed between adjacent pixels 10 in both the directions of the arrow X and the arrow Y, and electrically and optically separates the pixels 10 from each other.
The configuration of the SPAD 11 will be described in detail below.

1, the light detection device 1 is configured such that the photon incidence direction L is the side opposite to the direction of the arrow Z. The base 2 has a first surface 2A which is the photon incidence side, and a second surface 2B which faces the first surface 2A. For example, a single crystal silicon (Si) substrate into which n-type impurities with a low impurity density of 1014 cm-3 or more and 1016 cm-3 or less are introduced is used for the base 2.

Here, in the first, second, and fourth to fifteenth embodiments, the n-type will be described as the “second conductivity type”, and the p-type, which is the opposite conductivity type to the n-type, will be described as the “first conductivity type”. In the third embodiment, the n-type will be described as the “first conductivity type”, and the p-type will be described as the “second conductivity type”.
In other words, the SPAD 11 according to the present technology can be constructed by switching the conductivity type.

A well region 20 is disposed over the entire thickness of the substrate 2 in the region where the SPAD 11 and pixel 10 are formed. The well region 20 is set to the same conductivity type as the n-type impurity of the substrate 2, and is formed with an impurity density higher than the impurity density of the substrate 2, for example, 1017 cm-3 or more and 1018 cm-3 or less.

(2-2) Configuration of the Trench 21 The trench 21 is formed as one of the components that construct the multiplication region of the SPAD 11. The trench 21 is formed from the second surface 2B side toward the first surface 2A side of the base 2. The depth dimension Td of the trench 21 is set to be larger than the opening dimension Tw of the trench 21. In this case, the bottom surface Tb of the trench 21 is located at the middle part in the thickness direction of the base 2.
In the first embodiment, the trench 21 is formed to have a dimension in the depth direction (direction of the arrow Z) that is substantially the same as the opening dimension Tw. Note that, in the present technology, the trench 21 may be reduced in diameter in the depth direction.

When viewed in the direction of the arrow Z, i.e., the incident direction L (hereinafter simply referred to as "in a plan view"), the planar shape of the bottom surface Tb of the trench 21 is formed into a rectangular shape. Here, the planar shape of the bottom surface Tb of the trench 21 is formed into a square shape.

(2-3) Configuration of the first semiconductor region (anode region) 22 The first semiconductor region 22 is disposed along at least a portion of the bottom surface Tb and side surface Ts of the trench 21. Here, the first semiconductor region 22 is disposed along the entire area of the side surface Ts of the trench 21. The thickness dimension of the first semiconductor region 22 in a direction perpendicular to the bottom surface Tb (arrow Z direction) and the thickness dimension of the first semiconductor region 22 in a direction perpendicular to the side surface Ts of the first semiconductor region 22 (arrow X direction) are substantially the same.

As will be described in the manufacturing method, the first semiconductor region 22 is formed in an epitaxial growth layer or a deposition layer formed along the bottom surface Tb and the side surface Ts of the trench 21. The epitaxial growth layer is a Si layer formed by an epitaxial growth method. The deposition layer is a Si layer formed by a deposition method such as a chemical vapor deposition (CVD) method or an atomic layer deposition (ALD) method.
Here, the first semiconductor region 22 is a p-type semiconductor region and forms an anode region. The first semiconductor region 22 is formed to have an impurity density of, for example, 10 17 cm −3 or more and 10 18 cm −3 or less.

(2-4) Configuration of the second semiconductor region (cathode region) 23 The second semiconductor region 23 is disposed along at least a part of the bottom surface Tb and the side surface Ts of the trench 21, with the first semiconductor region 22 interposed therebetween. Here, the second semiconductor region 23 is substantially buried in the trench 21.

The second semiconductor region 23 is formed in an epitaxial growth layer or deposition layer separate from the epitaxial growth layer or deposition layer in which the first semiconductor region 22 is formed. As described above, the epitaxial growth layer is a Si layer formed by an epitaxial growth method. The deposition layer is a Si layer formed by a deposition method such as a CVD method or an ALD method.
Here, the second semiconductor region 23 is an n-type semiconductor region and forms a cathode region. The second semiconductor region 23 is formed to have an impurity density of, for example, 10 17 cm −3 or more and 10 18 cm −3 or less.

In the SPAD 11 configured in this manner, a first semiconductor region 22 serving as an anode region and a second semiconductor region 23 serving as a cathode region are disposed in one trench 21. At the contact portions between the first semiconductor region 22 and the second semiconductor region 23, a pn junction is formed, forming a multiplication region. Most of the pn junctions are formed in the vertical direction, which is the direction of the arrow Z.
When viewed in the direction of arrow Y (hereinafter simply referred to as "side view"), SPAD11 is formed in a columnar shape (here, a rectangular column shape) extending in the direction of arrow Z, with the first surface 2A side of the base 2 as the top surface and the second surface 2B side as the bottom surface.

1 and 2, a contact region 221 is disposed around the trench 21 on the second surface 2B side of the base 2 along the inner side of the element isolation body 3. Here, the contact region 221 is formed in a rectangular ring shape in a plan view.
The contact region 221 is formed of a p-type semiconductor region and has an impurity density higher than that of the first semiconductor region 22, for example, not less than 10 18 cm −3 and not more than 10 19 cm −3 .
A plug electrode 41 is electrically connected to the contact region 221, and an anode power supply Va is electrically connected through the plug electrode 41 or the like.

A contact region 231 is disposed in the center of the trench 21 on the second surface 2B side of the second semiconductor region 23. Here, the contact region 231 is formed in a rectangular shape in a plan view.
The contact region 231 is formed of an n-type semiconductor region and has an impurity density higher than that of the second semiconductor region 23, for example, not less than 10 18 cm −3 and not more than 10 19 cm −3 .
A plug electrode 41 is electrically connected to the contact region 231, and a cathode voltage Vc is supplied through the plug electrode 41 and the like.

1 and 2, the element isolator 3 surrounds the SPAD 11 and is disposed on the base 2. The element isolator 3 includes an isolation trench 31, an isolation insulator 32, and an isolation metal body 33. Furthermore, the element isolator 3 includes the base 2, which is a Si substrate as a semiconductor in this case.

In the first embodiment, the isolation trench 31 is disposed so as to penetrate substantially the entire area of the base 2 in the thickness direction from the first surface 2A side to the second surface 2B side of the base 2.
The isolation insulator 32 is disposed along the inner side surface of the isolation trench 31. The isolation insulator 32 is formed of, for example, a composite film of SiO2 and a high dielectric constant (High-k) insulator having a higher dielectric constant than SiO2.
The isolating metal body 33 is disposed in the isolating trench 31 with an isolating insulator 32 therebetween. The isolating insulator 32 is formed of a metal film such as tungsten (W) having excellent electrical conductivity and light blocking properties.

The element separator 3 and the substrate 2 form a metal-insulator-semiconductor (MIS) type structure, with the separating metal 33 as a metal, the separating insulator 32 as an insulator, and the substrate 2 as a semiconductor. In other words, an inversion layer I can be formed in the substrate 2 along the separating trench 31 due to the electric field effect from the element separator 3. The inversion layer I is used as a pinning region.

1, in the formation region of the SPAD 11 and the pixel 10, a fixed charge film 5 is disposed along the first surface 2A of the base 2. The fixed charge film 5 fixes charges in the vicinity of the first surface 2A of the base 2.
The fixed charge film 5 is formed of a composite film of SiO2 and a high dielectric constant insulator laminated on the SiO2, similar to, for example, the isolating insulator 32 of the element isolation body 3. When the fixed charge film 5 is disposed, an inversion layer I is formed in the vicinity of the first surface 2A of the base 2, so that the charge in this region is fixed.

(5) Configuration of Optical Lens 6 An optical lens 6 is disposed on the first surface 2A of the substrate 2 with a fixed charge film 5 interposed therebetween. In side view, the surface of the optical lens 6 on the arrow Z direction side is formed into a shape that curves in the opposite direction to the arrow Z direction for each pixel 10. In other words, the optical lens 6 is formed into a shape that focuses incident photons onto the SPAD 11.
The optical lens 6 is formed of, for example, a transparent resin material. Here, the optical lens 6 is formed as an on-chip lens.

(6) Configuration of Wiring Layer 4 On the second surface 2B side of the base 2, the base 2 is provided with a wiring layer 4. The wiring layer 4 includes a plug electrode 41, a wiring 42, and an inter-wiring insulator 43. The wiring layer 4 supplies an anode power supply Va and a cathode voltage Vc in the photodetector 1, and is also used for electrically connecting the photodetector 1 to a protection circuit and a readout circuit, both of which are not shown.

The plug electrodes 41 electrically connect between the SPAD 11 and the wiring 42, between the wirings 42, etc. The plug electrodes 41 are formed of a wiring material such as W, for example.
Here, the wiring 42 is formed in a plurality of layers and is made of a wiring material having excellent conductivity, such as copper (Cu) or aluminum (Al)-Cu.
The inter-wiring insulator 43 is actually formed of a plurality of insulating layers, and is configured to electrically isolate and protect the wirings 42, for example. The inter-wiring insulator 43 is formed of an insulating material such as SiO2.

(7) Configuration of Protection Circuit and Readout Circuit Although illustration and detailed description are omitted, each of the protection circuit and readout circuit is laminated on the second surface 2B of the base 2 with the wiring layer 4 interposed therebetween, on the opposite side to the direction of the arrow Z. In other words, each of the protection circuit and readout circuit is laminated on the photodetector 1, and this laminated structure can constitute, for example, the aforementioned distance measuring system.

(8) Energy Band Structure of the SPAD 11 and the Pixel 10 FIG. 3 shows an example of the horizontal energy band structure of the pixel 10 of the photodetector 1 shown in FIG.
3, the horizontal axis represents the substrate 2, well region 20, first semiconductor region (anode region) 22, second semiconductor region (cathode region) 23, and element isolation body 3, which are arranged in the horizontal direction. The vertical axis represents energy potential E, where Ec represents the conduction band and Ev represents the valence band.

As shown in FIG. 3, a doubling region is generated at the pn junction between the first semiconductor region 22 and the second semiconductor region 23 .
On the other hand, an MIS structure is formed in the portion of the substrate 2 in contact with the element isolator 3. For this reason, the valence band Ev is bent toward the Fermi level due to the electric field effect from the element isolator 3, and holes as minority carriers are gathered, forming an inversion layer I.

FIG. 4 shows an example of the vertical energy band structure of the pixel 10 of the photodetector 1 shown in FIG.
4, the horizontal axis represents each of the well region 20, the first semiconductor region (anode region) 22, the second semiconductor region (cathode region) 23, and the fixed charge film 5, which are arranged in the vertical direction. The vertical axis represents the energy potential E.

As shown in FIG. 4, a doubling region is generated at the pn junction between the first semiconductor region 22 and the second semiconductor region 23 .
On the other hand, in the portion of the substrate 2 in contact with the fixed charge film 5, the valence band Ev bends toward the Fermi level, and holes as minority carriers gather, forming an inversion layer I.

[Method of manufacturing the photodetector 1]
5 to 12 show an example of a cross section illustrating each step of the method for manufacturing the photodetector 1 according to the first embodiment. The manufacturing method is as follows.

First, a substrate 2 having a first surface 2 A and an opposing second surface 2 B is prepared. The substrate 2 may be, for example, a single crystal Si substrate (see FIG. 5).
A mask 8 is formed on the second surface 2B of the substrate 2 (see FIG. 5). The mask 8 has an opening 8H penetrating in the thickness direction in a region where the SPAD 11 is to be formed.
5, a mask 8 is used to remove a portion of the second surface 2B side of the base 2 exposed from the opening 8H to form a trench 21. To remove the base 2, anisotropic etching such as reactive ion etching (RIE) is used.

As shown in FIG. 6, a first semiconductor region 22 is formed in the substrate 2 along the bottom surface Tb and side surface Ts of the trench 21. The first semiconductor region 22 is formed by, for example, growing by selective epitaxial growth and comprising an epitaxial layer into which p-type impurities have been introduced.

As shown in FIG. 7, a second semiconductor region 23 is formed in the substrate 2 along the bottom surface Tb and side surface Ts of the trench 21, with the first semiconductor region 22 interposed therebetween. The second semiconductor region 23 is formed by, for example, growing by selective epitaxial growth and comprising an epitaxial layer into which n-type impurities have been introduced.

8, a contact region 231 is formed in the second semiconductor region 23. The contact region 231 is formed of an epitaxial layer into which n-type impurities are introduced, for example, by selective epitaxial growth, similar to the second semiconductor region 23. The impurity density of the contact region 231 is higher than the impurity density of the second semiconductor region 23.
At least one of the first semiconductor region 22, the second semiconductor region 23, and the contact region 231 may be formed by a deposition method.

Subsequently, unnecessary films on the second surface 2B of the substrate 2 are removed, and the second surface 2B is planarized by, for example, chemical mechanical polishing (CMP).
9, an insulating film 431 is formed on the planarized second surface 2B of the base 2. The insulating film 431 is made of an insulating material such as SiO 2 .

As shown in FIG. 10, a contact region 221 is formed on the second surface 2B side of the substrate 2 around the region where the SPAD 11 is formed and inside the region where the element isolator 3 is formed. The contact region 221 is formed by introducing a p-type impurity using, for example, an ion implantation method.

As shown in FIG. 11, an insulating film 432 of the inter-wiring insulator 43 is formed on an insulating film 431, and then the plug electrode 41 and the wiring 42 are formed. The insulating film 432, the plug electrode 41, and the wiring 42 are formed repeatedly to form the wiring layer 4 (see FIG. 1).

As shown in FIG. 12, an element isolator 3 and a fixed charge film 5 are sequentially formed on a substrate 2. The element isolator 3 is first formed as an isolation trench 31. The isolation trench 31 is formed by anisotropic etching such as RIE. Subsequently, an isolation insulator 32 is formed in the isolation trench 31, and then an isolation metal body 33 is formed in the isolation trench 31 with the isolation insulator 32 interposed therebetween.

As shown in FIG. 1 above, a fixed charge film 5 is formed on the first surface 2A of the substrate 2, and an optical lens 6 is formed on the fixed charge film 5. When this series of steps is performed, the manufacturing method is completed and the photodetector 1 according to the first embodiment is completed.

[Action and Effect]
As described above, the photodetector 1 according to the first embodiment includes the SPAD 11 that amplifies carriers generated by incident photons, as shown in Fig. 1 and Fig. 2. The SPAD 11 includes the trench 21, the first semiconductor region 22, and the second semiconductor region 23.
The trench 21 is disposed in a substrate 2 having a first surface 2A which is the photon incident side and a second surface 2B which faces the first surface 2A, and is formed from the second surface 2B side toward the first surface 2A side. The first semiconductor region 22 is disposed along at least a part of the bottom surface Tb and side surface Ts of the trench 21, and has a first conductivity type. The first semiconductor region 22 is used here as an anode region. The second semiconductor region 23 is disposed along at least a part of the bottom surface Tb and side surface Ts of the trench 21, with the first semiconductor region 22 interposed therebetween. The second semiconductor region 23 has a second conductivity type which is the opposite conductivity type to the first conductivity type. The second semiconductor region is used here as a cathode region.
In the SPAD 11 configured in this manner, the anode region and the cathode region are formed in one trench 21. That is, the planar size of the SPAD 11 can be reduced in the horizontal directions of the arrow X and arrow Y. Furthermore, since the SPAD 11 is formed using the trench 21 and can increase the pn junction area in the vertical direction of the arrow Z, the planar size can be reduced. Therefore, the planar size of the SPAD 11 can be reduced, and therefore the planar size of the pixel 10 can be reduced.

1 and 2, in the photodetector 1, the depth dimension Td of the trench 21 forming the SPAD 11 is greater than the opening dimension Tw of the trench 21. In addition, the bottom surface Tb of the trench 21 is located at the middle part in the thickness direction of the base 2. In other words, the trench 21 is dug down from the second surface 2B of the base 2 toward the first surface 2A side to the middle part in the thickness direction of the base 2. In other words, the SPAD 11 is formed in a columnar shape in a side view seen from the cross-sectional direction of the base 2.
Therefore, the SPAD 11 can increase the pn junction area in the vertical direction in accordance with the depth dimension Td, and therefore the planar size of the SPAD 11 can be reduced, and the planar size of the pixel 10 can be reduced.

In the photodetector 1, as shown in FIG. 1, at least one of the first semiconductor region 22 and the second semiconductor region 23 of the SPAD 11 is formed in an epitaxially grown layer or a deposition layer.
In the SPAD 11 configured in this manner, the manufacturing method does not require a high-temperature annealing step, and the first semiconductor region 22 and the second semiconductor region 23 can be formed in a narrow region in the trench 21. In other words, the spread of horizontal diffusion of impurities in each of the first semiconductor region 22 and the second semiconductor region 23 can be effectively suppressed or prevented.
Therefore, the planar size of the SPAD 11 can be reduced, and the planar size of the pixel 10 can be reduced.

1, in the photodetector 1, the SPAD 11 is formed in a columnar shape by utilizing the trench 21. That is, the distance between the first surface 2A of the base 2 and the SPAD 11 (the bottom surface Tb of the trench 21) is shortened.
For this reason, it is possible to omit the drift region 25 (see, for example, FIGS. 29 and 30) that relaxes the drift electric field in the base 2. In other words, it is possible to simplify the structure of the SPAD 11 and reduce the number of steps in the manufacturing method of the SPAD 11.

1 to 3, the photodetector 1 includes an element isolator 3 on the base 2, surrounding the side surface Ts of the SPAD 11. The base 2 is made of a semiconductor. The element isolator 3 includes an isolation trench 31, an isolation insulator 32, and an isolation metal body 33. The isolation trench 31 is disposed from the first surface 2A side toward the second surface 2B side of the base 2. The isolation insulator 32 is disposed along the side surface of the isolation trench 31. The isolation metal body 33 is embedded inside the isolation trench 31 with the isolation insulator 32 interposed therebetween.
Here, the element isolator 3 and the base 2 constitute an MIS type structure by the isolating metal body 33, the isolating insulator 32, and the semiconductor. That is, as shown in Figures 1 to 3, the element isolator 3 forms an inversion layer I in the base 2 along the isolating trench 31.
Therefore, compared to a pinning region formed through deep ion implantation and annealing processes, in the element separator 3, an inversion layer I is generated by an MIS structure to serve as a pinning region, so that it is possible to effectively reduce the horizontal extent of the element separator 3. In other words, it is possible to reduce the planar size of the element separator 3, and as a result, it is possible to reduce the planar size of the pixel 10.

Furthermore, in the light detection device 1, as shown in FIGS. 1 and 4, a fixed charge film 5 for fixing charges in the vicinity of the first surface 2A of the substrate 2 is disposed along the first surface 2A of the substrate 2.
Therefore, the charge in the vicinity of the first surface 2A of the base 2 can be easily fixed.

<2. Second embodiment>
13 to 17, a photodetector 1 according to a second embodiment of the present disclosure will be described. The photodetector 1 according to the second embodiment is an example in which any one of the configurations of the SPAD 11, the contact region 221, and the contact region 231 in the photodetector 1 according to the first embodiment is changed.
In addition, in the second embodiment and the subsequent embodiments, components that are the same as or substantially the same as the components of the photodetection device 1 according to the first embodiment are given the same reference numerals, and duplicated explanations are omitted.

[Configuration of photodetector 1]
FIG. 13 shows an example of a planar configuration in which a plurality of pixels 10 of the photodetector 1 according to the second embodiment are arranged.
13, the SPAD 11 of the light detection device 1 is formed in a circular shape in a plan view. In other words, the SPAD 11 is formed in a cylindrical shape.
More specifically, a bottom surface Tb of the trench 21 is formed in a circular shape in a plan view. A first semiconductor region 22 used as an anode region and a second semiconductor region 23 used as a cathode region are disposed along the bottom surface Tb and side surface Ts of the trench 21.
Moreover, the contact region 231 is formed in a circular shape in a plan view.

The components other than those described above are the same or substantially the same as the components of the light detection device 1 according to the first embodiment, so duplicated descriptions will be omitted.

[Action and Effect]
As described above, according to the photodetector 1 of the second embodiment, it is possible to obtain the same advantageous effects as those obtained by the photodetector 1 of the first embodiment.

[First Modification]
14 shows an example of a planar configuration in which a plurality of pixels 10 are arranged in the photodetector 1 according to a first modification of the second embodiment. The first to fourth modifications explain examples in which the configuration of the contact region 221 is changed.

As shown in FIG. 14, the SPAD 11 of the photodetector 1 has contact regions 221 arranged in regions facing the direction of the arrow Y in a plan view. The contact regions 221 extend in the direction of the arrow X along the element separator 3 extending in the direction of the arrow X. The contact regions 221 are not arranged in the regions facing the direction of the arrow X.

The components other than those described above are the same or substantially the same as the components of the photodetector 1 according to the second embodiment, so duplicated descriptions will be omitted.

[Action and Effect]
As described above, according to the photodetector 1 of the first modified example, it is possible to obtain the same advantageous effects as those obtained by the photodetector 1 of the second embodiment.

[Second Modification]
FIG. 15 shows an example of a planar configuration in which a plurality of pixels 10 are arranged in a photodetector 1 according to a second modified example of the second embodiment.
15 , the SPAD 11 of the photodetector 1 has contact regions 221 disposed in regions corresponding to the four corners of a rectangular pixel 10 in a plan view. The contact regions 221 have a rectangular planar shape. A total of four contact regions 221 are disposed in one pixel 10.

The components other than those described above are the same or substantially the same as the components of the photodetector 1 according to the second embodiment, so duplicated descriptions will be omitted.

[Action and Effect]
As described above, according to the photodetector 1 of the second modified example, it is possible to obtain the same advantageous effects as those obtained by the photodetector 1 of the second embodiment.

[Third Modification]
FIG. 16 shows an example of a planar configuration in which a plurality of pixels 10 are arranged in a photodetector 1 according to a third modified example of the second embodiment.
16 , in a plan view, the SPAD 11 of the photodetector 1 has contact regions 221 disposed in the middle of an area facing in the direction of the arrow X and in the middle of an area facing in the direction of the arrow Y. That is, four contact regions 221 are disposed in one pixel 10. Each contact region 221 extends along a part of the element separator 3.

The components other than those described above are the same or substantially the same as the components of the photodetector 1 according to the second embodiment, so duplicated descriptions will be omitted.

[Action and Effect]
As described above, according to the photodetector 1 of the third modified example, it is possible to obtain the same advantageous effects as those obtained by the photodetector 1 of the second embodiment.

[Fourth Modification]
FIG. 17 shows an example of a planar configuration in which a plurality of pixels 10 are arranged in a photodetector 1 according to a fourth modified example of the second embodiment.
17 , the SPAD 11 of the photo-detecting device 1 has contact regions 221 disposed in regions corresponding to the four corners of a rectangular pixel 10 in a plan view. The planar shape of the contact region 221 is formed into an L-shape. A total of four contact regions 221 are disposed in one pixel 10.

The components other than those described above are the same or substantially the same as the components of the photodetector 1 according to the second embodiment, so duplicated descriptions will be omitted.

[Action and Effect]
As described above, according to the photodetector 1 of the fourth modified example, it is possible to obtain the same advantageous effects as those obtained by the photodetector 1 of the second embodiment.

<3. Third embodiment>
18 to 20, a photodetector 1 according to a third embodiment of the present disclosure will be described. In the photodetector 1 according to the third embodiment, the conductivity type of the SPAD 11 and the like in the photodetector 1 according to the first embodiment is inverted, and the SPAD 11 is configured as a single-photon avalanche diode that amplifies (multiplies) carriers (holes) generated by incident photons.

[Configuration of photodetector 1]
(1) Configuration of SPAD 11 and Pixel 10 FIG. 18 shows an example of a vertical cross-sectional configuration of a main part of one pixel 10 of the photodetector 1 according to the third embodiment.
Although the basic configuration is the same as that of the photodetector 1 according to the first embodiment, the conductivity type is inverted in the photodetector 1 according to the third embodiment. That is, in the photodetector 1, the well region 20 is p-type (first conductivity type). The first semiconductor region 22 constituting the SPAD 11 is n-type (second conductivity type) and is used as a cathode region. The second semiconductor region 23 is p-type and is used as an anode region.
The fixed charge film 5 is made of a composite film in which, for example, SiO2, SiN, and SiO2 are laminated in this order.

(2) Energy Band Structure of the SPAD 11 and the Pixel 10 FIG. 19 shows an example of the horizontal energy band structure of the pixel 10 of the photodetector 1 shown in FIG.
19, the horizontal axis represents the respective regions arranged in the horizontal direction, that is, the base body 2, the well region 20, the first semiconductor region (cathode region) 22, the second semiconductor region (anode region) 23, and the element isolation body 3. The vertical axis represents the energy potential E.

As shown in FIG. 19, a doubling region is generated at the pn junction between the first semiconductor region 22 and the second semiconductor region 23 .
On the other hand, an MIS structure is formed in a portion of the base 2 in contact with the element isolator 3. For this reason, the valence band Ev is bent toward the Fermi level due to the electric field effect from the element isolator 3, electrons as minority carriers are gathered, and an accumulation layer A is formed.

FIG. 20 shows an example of the energy band structure in the vertical direction of the pixel 10 of the photodetector 1 shown in FIG.
20, the horizontal axis represents each of the well region 20, the first semiconductor region (cathode region) 22, the second semiconductor region (anode region) 23, and the fixed charge film 5, which are arranged in the vertical direction. The vertical axis represents the energy potential E.

As shown in FIG. 20, a doubling region is generated at the pn junction between the first semiconductor region 22 and the second semiconductor region 23 .
On the other hand, in the portion of the substrate 2 in contact with the fixed charge film 5, the valence band Ev is bent toward the Fermi level, electrons as minority carriers are gathered, and an accumulation layer A is formed.

The components other than those described above are the same or substantially the same as the components of the light detection device 1 according to the first embodiment, so duplicated descriptions will be omitted.

[Action and Effect]
As described above, according to the photodetector 1 of the third embodiment, it is possible to obtain the same advantageous effects as those obtained by the photodetector 1 of the first embodiment.

<4. Fourth embodiment>
A photodetector 1 according to a fourth embodiment of the present disclosure will be described with reference to Fig. 21. The photodetector 1 according to the fourth embodiment is an example in which the connection configuration between the second semiconductor region 23 and the contact region 231 of the SPAD 11 in the photodetector 1 according to the first embodiment is changed.

[Configuration of photodetector 1]
FIG. 21 shows an example of a vertical cross-sectional configuration of a main part of one pixel 10 of the photodetector 1 according to the fourth embodiment.
21 , in the SPAD 11 of the photodetector 1, a plug electrode 41 electrically connected to the second semiconductor region 23 used as a cathode region is disposed in the trench 21. To explain in detail, the plug electrode 41 extends into the trench 21, and the tip of the plug electrode 41 in the extending direction is electrically connected to the second semiconductor region 23. The connection portion of the second semiconductor region 23 is located exactly at the bottom surface Tb of the trench 21.

In the trench 21, an insulating film 45 is disposed between the side surface of the plug electrode 41 and the second semiconductor region 23. The insulating film 45 is made of at least one of SiO2 formed by thermal oxidation and CVD, for example.

The components other than those described above are the same or substantially the same as the components of the light detection device 1 according to the first embodiment, so duplicated descriptions will be omitted.

[Action and Effect]
As described above, according to the photodetector 1 of the fourth embodiment, it is possible to obtain the same advantageous effects as those obtained by the photodetector 1 of the first embodiment.

In addition, in the photodetector 1, as shown in FIG. 21, a plug electrode 41 is provided that extends into the trench 21 of the SPAD 11 and is electrically connected to the second semiconductor region (cathode region) 23.

When the trench 21 cannot be completely filled with the first semiconductor region 22 and the second semiconductor region 23, a void is formed in the trench 21. By providing the plug electrode 41, such a void can be effectively removed.

<5. Fifth embodiment>
A photodetector 1 according to a fifth embodiment of the present disclosure will be described with reference to Fig. 22. The photodetector 1 according to the fifth embodiment is an example in which a contact region 231 is provided instead of the plug electrode 41 extending into the trench 21 in the photodetector 1 according to the fourth embodiment.

[Configuration of photodetector 1]
FIG. 22 shows an example of a vertical cross-sectional configuration of a main part of one pixel 10 of the photodetector 1 according to the fifth embodiment.
As shown in FIG. 22, in the SPAD 11 of the photodetector 1, a contact region 231 electrically connected to the second semiconductor region 23 used as the cathode region is disposed in the trench 21.
More specifically, the contact region 231 is disposed on the side surface Ts of the trench 21 with the first semiconductor region 22 and the second semiconductor region 23 interposed therebetween. The contact region 231 is configured to extend just into the trench 21.

The contact region 231 is formed, for example, from polycrystalline Si formed by using a CVD method. The same n-type impurities as those in the second semiconductor region 23 are introduced into this polycrystalline Si, and the polycrystalline Si is formed with an impurity density higher than that of the second semiconductor region 23.

The components other than those described above are the same or substantially the same as the components of the photodetector 1 according to the fourth embodiment, so duplicated explanations will be omitted.

[Action and Effect]
As described above, according to the photodetector 1 of the fifth embodiment, it is possible to obtain the same advantageous effects as those obtained by the photodetector 1 of the fourth embodiment.

<6. Sixth embodiment>
A photodetector 1 according to a sixth embodiment of the present disclosure will be described with reference to Fig. 23. The photodetector 1 according to the sixth embodiment is an example in which the configuration of the contact region 231 in the photodetector 1 according to the first embodiment is changed.
FIG. 23 shows an example of a vertical cross-sectional configuration of a main part of one pixel 10 of a photodetector 1 according to the sixth embodiment.
23 , in the SPAD 11 of the photodetector 1, a first semiconductor region 22 and a second semiconductor region 23 are disposed in a trench 21, and a pn junction is reliably formed in the trench 21. Then, on the second surface 2B side of the base 2, a contact region 231 is disposed in the second semiconductor region 23.

To explain in more detail, the contact region 231 is formed in the manufacturing method by introducing n-type impurities from the second surface 2B side. The impurities are introduced using an ion implantation method.

The components other than those described above are the same or substantially the same as the components of the light detection device 1 according to the first embodiment, so duplicated descriptions will be omitted.

[Action and Effect]
As described above, according to the photodetector 1 of the sixth embodiment, it is possible to obtain the same advantageous effects as those obtained by the photodetector 1 of the first embodiment.

<7. Seventh embodiment>
A photodetector 1 according to a seventh embodiment of the present disclosure will be described with reference to Fig. 24. The photodetector 1 according to the seventh embodiment is an example in which the configuration of the contact region 231 in the photodetector 1 according to the first embodiment is changed.
FIG. 24 shows an example of a vertical cross-sectional configuration of a main part of one pixel 10 of the photodetector 1 according to the seventh embodiment.
24 , in the SPAD 11 of the photodetector 1, a first semiconductor region 22 and a second semiconductor region 23 are disposed in a trench 21, and a pn junction is reliably formed in the trench 21. Then, on the second surface 2B of the base 2, a contact region 231 is disposed in the second semiconductor region 23.

To explain in more detail, the contact region 231 is formed of, for example, single crystal Si or polycrystalline Si laminated on the second surface 2B. The contact region 231 is formed using a selective epitaxial growth method or a CVD method. In other words, the contact region 231 is a contact electrode. In addition, an n-type impurity is introduced into the contact region 231 at an impurity density higher than the impurity density of the n-type impurity in the second semiconductor region 23.

The components other than those described above are the same or substantially the same as the components of the photodetector 1 according to the sixth embodiment, so duplicated explanations will be omitted.

[Action and Effect]
As described above, according to the photodetector 1 of the seventh embodiment, it is possible to obtain the same advantageous effects as those obtained by the photodetector 1 of the sixth embodiment.

<8. Eighth embodiment>
A photodetector 1 according to an eighth embodiment of the present disclosure will be described with reference to Fig. 25. The photodetector 1 according to the eighth embodiment is an example in which an electric field relaxation region 26 is provided in the photodetector 1 according to the first embodiment.
FIG. 25 shows an example of a vertical cross-sectional configuration of a main part of one pixel 10 of the photodetector 1 according to the eighth embodiment.
As shown in Figure 25, in the SPAD 11 of the photodetector 1, an electric field relaxation region 26 that relaxes the electric field toward the second surface 2B side is arranged between the second surface 2B of the base 2 and the first semiconductor region 22 and the second semiconductor region 23.

The electric field relaxation region 26 is formed of an n-type semiconductor region having a lower impurity density than the second semiconductor region 23 and a higher impurity density than the well region 20. The peak of the n-type impurity density of the electric field relaxation region 26 is formed, for example, closer to the second surface 2B than the peak of the p-type impurity density of the contact region 221. In other words, the electric field relaxation region 26 has a shallow impurity density peak and is formed at a low impurity density.

The components other than those described above are the same or substantially the same as the components of the light detection device 1 according to the first embodiment, so duplicated descriptions will be omitted.

[Action and Effect]
As described above, according to the photodetector 1 of the eighth embodiment, it is possible to obtain the same advantageous effects as those obtained by the photodetector 1 of the first embodiment.

In addition, in the photodetector 1, as shown in FIG. 25, an electric field relaxation region 26 is disposed between the second surface 2B of the substrate 2 and the first and second semiconductor regions 22 and 23. This allows the electric field from the SPAD 11 to the second surface 2B to be relaxed.

<9. Ninth embodiment>
A photodetector 1 according to a ninth embodiment of the present disclosure will be described with reference to Fig. 26. The photodetector 1 according to the ninth embodiment is an example for describing an application example of the electric field relaxation region 26 in the photodetector 1 according to the eighth embodiment.
FIG. 26 shows an example of a vertical cross-sectional configuration of a main part of one pixel 10 of the photodetector 1 according to the ninth embodiment.
26, in the SPAD 11 of the photodetector 1, an electric field relaxation region 26 that relaxes the electric field toward the second surface 2B side is disposed between the second surface 2B of the base 2 and the first semiconductor region 22 and second semiconductor region 23, and further, a contact region 231 is disposed in the electric field relaxation region 26. In other words, the electric field relaxation region 26 and the contact region 231 are configured by a double diffusion structure.

The electric field relaxation region 26 is formed of an n-type semiconductor region having a lower impurity density than the second semiconductor region 23 and a higher impurity density than the well region 20. The contact region 231 is formed of an n-type semiconductor region having a higher impurity density than the second semiconductor region 23.

The components other than those described above are the same or substantially the same as the components of the light detection device 1 according to the eighth embodiment, so duplicated explanations will be omitted.

[Action and Effect]
As described above, according to the photodetector 1 of the ninth embodiment, it is possible to obtain the same advantageous effects as those obtained by the photodetector 1 of the eighth embodiment.

In addition, in the photodetector 1, as shown in FIG. 26, a contact region 231 is disposed in the electric field relaxation region 26. This allows the contact resistance between the contact region 231 and the plug electrode 41 to be reduced.

<10. Tenth embodiment>
A photodetector 1 according to a tenth embodiment of the present disclosure will be described with reference to Fig. 27. The photodetector 1 according to the tenth embodiment is an example in which the dielectric strength between electrodes in the photodetector 1 according to the sixth embodiment is increased.
FIG. 27 shows an example of a vertical cross-sectional configuration of a main part of one pixel 10 of the photodetector 1 according to the tenth embodiment.
27 , in the SPAD 11 of the photodetector 1, the contact region 221 is used as a first electrode, and the contact region 231 is used as a second electrode. The interelectrode insulator 7 is disposed between the contact region 221 and the contact region 231.

The interelectrode insulator 7 includes an insulating trench 71 formed from the second surface 2B toward the first surface 2A of the base 2, and an insulating filler 72 filled in the insulating trench 71.
The insulating trench 71 is formed deeper on the first surface 2A side than the peaks of the impurity concentrations of the contact regions 221 and 231, and shallower on the second surface 2B side than the trench 21. The insulating filler 72 is made of, for example, SiO2 deposited by a CVD method.

The components other than those described above are the same or substantially the same as the components of the light detection device 1 according to the first embodiment, so duplicated descriptions will be omitted.

[Action and Effect]
As described above, according to the photodetector 1 of the tenth embodiment, it is possible to obtain the same advantageous effects as those obtained by the photodetector 1 of the first embodiment.

In addition, in the photodetector 1, as shown in FIG. 27, an interelectrode insulator 7 is disposed between the contact region 221 (first electrode) and the contact region 231 (second electrode). Therefore, the interelectrode insulator 7 can improve the dielectric strength between the contact region 221 and the contact region 231.

<11. Eleventh embodiment>
A photodetector 1 according to an eleventh embodiment of the present disclosure will be described with reference to Fig. 28. The photodetector 1 according to the eleventh embodiment is an example in which the dielectric strength between electrodes in the photodetector 1 according to the tenth embodiment is further increased.
FIG. 28 shows an example of a vertical cross-sectional configuration of a main part of one pixel 10 of the photodetector 1 according to the eleventh embodiment.
28 , in the SPAD 11 of the photodetector 1, in the photodetector 1 according to the tenth embodiment, an interelectrode insulator 7 having a greater thickness in the thickness direction of the base 2 is provided. The basic configuration of the interelectrode insulator 7 is similar to the configuration of the interelectrode insulator 7 of the photodetector 1 according to the tenth embodiment.

The components other than those described above are the same or substantially the same as the components of the photodetector 1 according to the tenth embodiment, so duplicated explanations will be omitted.

[Action and Effect]
As described above, according to the photodetector 1 of the eleventh embodiment, it is possible to obtain the same advantageous effects as those obtained by the photodetector 1 of the tenth embodiment.

<12. Twelfth embodiment>
A photodetector 1 according to a twelfth embodiment of the present disclosure will be described with reference to Fig. 29. The photodetector 1 according to the twelfth embodiment is an example in which a drift region 25 is provided in the photodetector 1 according to the first embodiment.
FIG. 29 shows an example of a vertical cross-sectional configuration of a main part of one pixel 10 of a photodetector 1 according to the twelfth embodiment.
29, in the SPAD 11 of the photodetector 1, a drift region 25 that relaxes the drift electric field is provided in the photodetector 1 according to the first embodiment. The drift region 25 is provided between the first surface 2A of the substrate 2 and the bottom surface Tb of the trench 21, and relaxes the drift electric field to adjust the potential energy of photons. The drift region 25 is formed of an n-type semiconductor region or a p-type semiconductor region. Impurities in the drift region 25 are introduced by using an ion implantation method.

The components other than those described above are the same or substantially the same as the components of the light detection device 1 according to the first embodiment, so duplicated descriptions will be omitted.

[Action and Effect]
As described above, according to the photodetector 1 of the twelfth embodiment, it is possible to obtain the same advantageous effects as those obtained by the photodetector 1 of the first embodiment.

In addition, in the photodetector 1, a drift region 25 is provided as shown in FIG. 29. This allows the drift electric field to be alleviated.

<13. Thirteenth embodiment>
A photodetector 1 according to a thirteenth embodiment of the present disclosure will be described with reference to Fig. 30. The photodetector 1 according to the thirteenth embodiment is an example in which a plurality of drift regions 25 is provided in the photodetector 1 according to the twelfth embodiment.
FIG. 30 shows an example of a vertical cross-sectional configuration of a main part of one pixel 10 of a photodetector 1 according to the thirteenth embodiment.
As shown in FIG. 30, in the SPAD 11 of the photodetector 1 according to the twelfth embodiment, a plurality of drift regions 25 are arranged in the thickness direction of the base 2 .

The components other than those described above are the same or substantially the same as the components of the photodetector 1 according to the twelfth embodiment, so duplicated explanations will be omitted.

[Action and Effect]
As described above, according to the photodetector 1 of the thirteenth embodiment, it is possible to obtain the same advantageous effects as those obtained by the photodetector 1 of the twelfth embodiment.

<14. Fourteenth embodiment>
A photodetector 1 according to a fourteenth embodiment of the present disclosure will be described with reference to Fig. 31. The photodetector 1 according to the fourteenth embodiment is an example in which a SPAD 11 is constructed on a base 2 in which a plurality of semiconductor layers are stacked in the photodetector 1 according to the first embodiment.
FIG. 31 shows an example of a vertical cross-sectional configuration of a main part of one pixel 10 of a photodetector 1 according to the fourteenth embodiment.
As shown in FIG. 31, in the SPAD 11 of the photodetector 1, in the photodetector 1 according to the first embodiment, the base 2 is constructed by stacking a plurality of semiconductor layers 201 to 204.

The semiconductor layer 201 of the base 2 is disposed on the second surface 2B of the base 2. A well region 20 into which a p-type impurity is introduced at a low impurity density is disposed in the semiconductor layer 201. In this well region 20, a SPAD 11 constructed by a trench 21, a first semiconductor region 22, and a second semiconductor region 23 is disposed.
Furthermore, due to the electric field effect from the element isolator 3 , an accumulation layer A is formed in the semiconductor layer 201 along the element isolator 3 .

A semiconductor layer 202 is disposed on the semiconductor layer 201 on the first surface 2A side of the base body 2. An n-type impurity is introduced into the semiconductor layer 202 at a low impurity density.
Furthermore, due to the electric field effect from the element isolator 3 , an inversion layer I is formed in the semiconductor layer 202 along the element isolator 3 .

A semiconductor layer 203 is disposed on the semiconductor layer 202 on the first surface 2A side of the base body 2. A p-type impurity is introduced into the semiconductor layer 203 at a lower impurity density than that of the semiconductor layer 201.
Furthermore, due to the electric field effect from the element isolator 3 , an accumulation layer A is formed in the semiconductor layer 203 along the element isolator 3 .

A semiconductor layer 204 is disposed on the semiconductor layer 203 on the first surface 2A side of the base body 2. A p-type impurity is introduced into the semiconductor layer 204 at a lower impurity density than that of the semiconductor layer 203.
Furthermore, due to the electric field effect from the element isolator 3 , an accumulation layer A is formed in the semiconductor layer 204 along the element isolator 3 .

The components other than those described above are the same or substantially the same as the components of the photodetector 1 according to the thirteenth embodiment, so duplicated explanations will be omitted.

[Action and Effect]
As described above, according to the photodetector 1 of the fourteenth embodiment, it is possible to obtain the same advantageous effects as those obtained by the photodetector 1 of the first embodiment.

In addition, in the photodetector 1, as shown in FIG. 31, the base 2 is constructed by stacking multiple semiconductor layers 201 to 204. This allows the drift electric field and the electric field in the multiplication region to be adjusted uniformly.

<15. Fifteenth embodiment>
A photodetector 1 according to a fifteenth embodiment of the present disclosure will be described with reference to Fig. 32. The photodetector 1 according to the fifteenth embodiment is an example in which the configuration of the SPAD 11 in the photodetector 1 according to the first embodiment is changed.
FIG. 32 shows an example of a vertical cross-sectional configuration of a main part of one pixel 10 of a photodetector 1 according to the fourteenth embodiment.
31 , in the SPAD 11 of the photodetector 1 according to the first embodiment, the bottom surface Tb of the trench 21 is formed closer to the first surface 2A of the base 2 than the middle of the thickness direction of the base 2. Here, the bottom surface Tb of the trench 21 is formed at substantially the same position as the first surface 2A of the base 2. That is, the trench 21 is formed penetrating from the second surface 2B to the first surface 2A of the base 2.
In the fourteenth embodiment, the fixed charge film 5 is not required. A protective film 51 is disposed in place of the fixed charge film 5. The protective film 51 is made of, for example, SiO2.

The components other than those described above are the same or substantially the same as the components of the light detection device 1 according to the first embodiment, so duplicated descriptions will be omitted.

[Action and Effect]
As described above, according to the photodetector 1 of the fifteenth embodiment, it is possible to obtain the same advantageous effects as those obtained by the photodetector 1 of the first embodiment.

<16. Other embodiments>
The present technology is not limited to the above-described embodiment, and various modifications are possible without departing from the spirit and scope of the present technology.
For example, among the photodetection devices according to the first to fifteenth embodiments, two or more of the photodetection devices according to the first to fifteenth embodiments may be combined.

A photodetector according to a first embodiment of the present disclosure includes a SPAD for amplifying carriers generated by incident photons. The SPAD includes a trench, a first semiconductor region, and a second semiconductor region.
The trench is disposed in a substrate having a first surface on which photons are incident and a second surface opposite to the first surface, and is formed from the second surface side toward the first surface side. The first semiconductor region is disposed along at least a portion of the bottom surface and side surface of the trench, and has a first conductivity type. The first semiconductor region is used here as an anode region. The second semiconductor region is disposed along at least a portion of the bottom surface and side surface of the trench, with the first semiconductor region interposed therebetween. The second semiconductor region has a second conductivity type that is the opposite conductivity type to the first conductivity type. The second semiconductor region is used here as a cathode region.
In the SPAD configured in this manner, the anode region and the cathode region are formed in one trench. That is, the planar size of the SPAD can be reduced in the horizontal direction. Furthermore, the SPAD is formed using a trench, and the pn junction area can be increased in the vertical direction, so that the planar size can be reduced. Therefore, the planar size of the SPAD can be reduced, and therefore the planar size of the pixel can be reduced.

A photodetector according to a second embodiment of the present disclosure is the photodetector according to the first embodiment, further comprising an element isolator on a base surrounding a side periphery of the SPAD. The base is made of a semiconductor. The element isolator comprises an isolation trench, an isolation insulator, and an isolation metal body. The isolation trench is disposed from a first surface side toward a second surface side of the base. The isolation insulator is disposed along a side surface of the isolation trench. The isolation metal body is embedded inside the isolation trench with the isolation insulator interposed therebetween.
Here, the element isolator and the substrate form a MIS type structure, i.e. the element isolator forms an inversion or accumulation layer in the substrate along the isolating trench.
For this reason, in the element separator, the MIS structure or the accumulation layer is generated to form a pinning region, so that the horizontal extent of the element separator can be effectively reduced, that is, the planar size of the element separator can be reduced, and as a result, the planar size of the pixel can be reduced.

In a photodetector according to a third embodiment of the present disclosure, in the photodetector according to the first or second embodiment, a fixed charge film that fixes the charge on the first surface is disposed along the first surface of the substrate.
Therefore, the charge in the vicinity of the first surface of the substrate can be easily fixed.

<Configuration of this technology>
The present technology has the following configuration: According to the present technology having the following configuration, it is possible to reduce the pixel size in a light detection device.

(1)
an avalanche diode for amplifying carriers generated by incident photons;
The avalanche diode is
a trench disposed in a substrate having a first surface serving as a photon incidence side and a second surface opposing the first surface, the trench being formed from the second surface side toward the first surface side;
a first semiconductor region of a first conductivity type disposed along at least a portion of a bottom surface and a side surface of the trench;
a second semiconductor region of a second conductivity type opposite to the first conductivity type, the second semiconductor region being disposed along at least a portion of the bottom and side surfaces of the trench and with the first semiconductor region interposed therebetween.
(2)
The photodetector according to (1), wherein a depth dimension of the trench is greater than an opening dimension of the trench.
(3)
The photodetector according to any one of (1) to (2), wherein the bottom surface of the trench is located at a middle portion in a thickness direction of the base.
(4)
The photodetector according to any one of (1) to (2), wherein the bottom surface of the trench is located closer to the first surface side of the base than a middle point in a thickness direction of the base.
(5)
The photodetector according to any one of (1) to (4), wherein at least one of the first semiconductor region and the second semiconductor region is formed in an epitaxial growth layer or a deposition layer.
(6)
The first semiconductor region is an anode region or a cathode region,
The photodetector according to any one of (1) to (5), wherein the second semiconductor region is a cathode region or an anode region.
(7)
The photodetector device described in any one of (1) to (5), wherein the first semiconductor region and the second semiconductor region are formed in a rectangular or circular shape when viewed from the first surface side, and are formed in a columnar shape when viewed from the cross-sectional direction of the base.
(8)
the substrate includes an element isolation body surrounding a side surface of the avalanche diode;
The substrate is formed of a semiconductor,
The element isolator is
an isolation trench disposed from the first surface side toward the second surface side of the substrate;
an isolation insulator disposed along a side of the isolation trench;
The photodetector according to any one of (1) to (7), further comprising an isolating metal body buried inside the isolating trench with the isolating insulator interposed therebetween.
(9)
the element isolator and the base body form a metal-insulator-semiconductor type structure by the isolating metal body, the isolating insulator and the semiconductor,
The photodetector according to claim 8, wherein the element separator forms an accumulation layer or an inversion layer in the substrate along the isolation trench.
(10)
The photodetector according to any one of (1) to (9), wherein a fixed charge film that fixes charges near the first surface of the substrate is disposed along the first surface of the substrate.
(11)
The photodetector according to (10) above, further comprising an optical lens disposed on the first surface of the substrate, with the fixed charge film interposed therebetween, for focusing incident photons onto the avalanche diode.
(12)
The photodetector device according to any one of (1) to (11), wherein a plug electrode is disposed within the trench, with the first semiconductor region and the second semiconductor region interposed therebetween, and electrically connected to the second semiconductor region.
(13)
The photodetection device described in any one of (1) to (11), wherein a contact region is disposed within the trench, with the first semiconductor region and the second semiconductor region interposed therebetween, and electrically connected to the second semiconductor region.
(14)
The photodetector according to any one of (1) to (11), wherein a plug electrode or a contact electrode is electrically connected to the second semiconductor region.
(15)
The photodetector device described in any one of (1) to (14), wherein an electric field relaxation region that relaxes the electric field toward the second surface side is arranged between the second surface of the base body and the first semiconductor region and the second semiconductor region.
(16)
a first electrode disposed on the second surface side of the base body in at least a portion of the periphery of the first semiconductor region and electrically connected to the first semiconductor region;
a second electrode disposed on the second surface side of the base body and electrically connected to the second semiconductor region;
The photodetector according to any one of (1) to (11), further comprising an inter-electrode insulator disposed between the first electrode and the second electrode to electrically separate the first electrode and the second electrode.
(17)
The photodetector according to any one of (1) to (16), wherein a drift region that relaxes a drift electric field is disposed between the first surface of the substrate and the bottom surface of the trench.
(18)
The photodetector according to any one of (1) to (17), wherein the base is formed by stacking a plurality of semiconductor layers from the first surface side toward the second surface side.

1...photodetector, 10...pixel, 11...avalanche diode (SPAD), 2...substrate, 20...well region, 201-204...semiconductor layer, 21...trench, 22...first semiconductor region (anode region or cathode region), 221...contact region (first electrode), 231...contact region (second electrode), 23...second semiconductor region (cathode region or anode region), 25...drift region, 26...electric field relaxation region, 3...element separator, 31...separation trench, 32...separation insulator, 33...separation metal body, 4...wiring layer, 41...plug electrode, 42...wiring, 43...inter-wiring insulator, 5...fixed charge film, 6...optical lens, 7...inter-electrode insulator, 71...insulating trench, 72...insulating filler, I...inversion layer, A...accumulation layer.

Claims (18)

an avalanche diode for amplifying carriers generated by incident photons;
The avalanche diode is
a trench disposed in a substrate having a first surface serving as a photon incidence side and a second surface opposite to the first surface, the trench being formed from the second surface side toward the first surface side;
a first semiconductor region of a first conductivity type disposed along at least a portion of a bottom surface and a side surface of the trench;
a second semiconductor region of a second conductivity type opposite to the first conductivity type, the second semiconductor region being disposed along at least a portion of the bottom and side surfaces of the trench and with the first semiconductor region interposed therebetween. The photodetection device according to claim 1 , wherein a depth dimension of the trench is greater than an opening dimension of the trench. The photodetector according to claim 2 , wherein the bottom surface of the trench is located at a middle portion in a thickness direction of the base body. The light detection device according to claim 2 , wherein the bottom surface of the trench is located closer to the first surface side of the base than a middle point in a thickness direction of the base. The photodetector according to claim 1 , wherein at least one of the first semiconductor region and the second semiconductor region is formed in an epitaxially grown layer or a deposition layer. The first semiconductor region is an anode region or a cathode region,
The photodetector device according to claim 1 , wherein the second semiconductor region is a cathode region or an anode region. The photodetector according to claim 1 , wherein the first semiconductor region and the second semiconductor region are formed in a rectangular or circular shape when viewed from the first surface side, and are formed in a columnar shape when viewed from a cross-sectional direction of the base body. the substrate includes an element isolation body surrounding a side surface of the avalanche diode;
The substrate is made of a semiconductor,
The element isolator is
an isolation trench disposed from the first surface side toward the second surface side of the substrate;
an isolation insulator disposed along a side of the isolation trench;
2. The photodetector according to claim 1, further comprising an isolating metal body buried inside the isolating trench with the isolating insulator interposed therebetween. the element isolator and the base body form a metal-insulator-semiconductor type structure by the isolating metal body, the isolating insulator and the semiconductor,
9. The photodetector of claim 8, wherein the element isolation causes an accumulation or inversion layer to form in the substrate along the isolation trench. 2. The light detection device according to claim 1, further comprising a fixed charge film disposed along the first surface of the substrate for fixing charges in the vicinity of the first surface of the substrate. 11. The photodetector according to claim 10, further comprising an optical lens disposed on the first surface of the substrate, with the fixed charge film interposed therebetween, for focusing incident photons onto the avalanche diode. 2 . The photodetector according to claim 1 , wherein a plug electrode is disposed in the trench, with the first semiconductor region and the second semiconductor region interposed therebetween, and electrically connected to the second semiconductor region. The photodetector according to claim 1 , wherein a contact region is disposed in the trench, with the first semiconductor region and the second semiconductor region interposed therebetween, and electrically connected to the second semiconductor region. The photodetector according to claim 1 , wherein a plug electrode or a contact electrode is electrically connected to the second semiconductor region. The photodetector according to claim 1 , further comprising an electric field relaxation region that relaxes an electric field toward the second surface side, the electric field relaxation region being disposed between the second surface of the base body and the first and second semiconductor regions. a first electrode disposed on the second surface side of the base body in at least a portion of the periphery of the first semiconductor region and electrically connected to the first semiconductor region;
a second electrode disposed on the second surface side of the base body and electrically connected to the second semiconductor region;
The photodetector according to claim 1 , further comprising an inter-electrode insulator disposed between the first electrode and the second electrode to electrically separate them. The photodetector according to claim 1 , further comprising a drift region disposed between the first surface of the substrate and the bottom surface of the trench, the drift region relieving a drift electric field. The light detection device according to claim 1 , wherein the base body is formed by stacking a plurality of semiconductor layers from the first surface side toward the second surface side.

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