JP2022175859A - Light detector - Google Patents

Abstract

To provide a light detector that is suitable for measuring light with a long wavelength and is easily manufactured.SOLUTION: A light detector 10 comprises: a substrate 11 made of a p-type semiconductor or an n-type semiconductor; a light-shielding layer 12 that covers part or all of one surface of the substrate 11; a light introduction part 121 that is provided at a position other than a range covered by the light-shielding layer 12 on the one surface of the substrate 11 or provided on a side surface of the substrate 11; a charge capture part 13 that at the one surface and under the light-shielding layer 12, is provided apart from the light introduction part 121 and is made of a semiconductor of a type opposite to that of the substrate 11; and a measurement part 14 electrically connected to the charge capture part 13.SELECTED DRAWING: Figure 1

Description

The present invention relates to a photodetector, and more particularly to a device that uses semiconductors to detect light having a wavelength within a specific range.

2. Description of the Related Art Conventionally, a photodetector has been used that includes a pn junction semiconductor device in which a p-layer made of a p-type semiconductor and an n-layer made of an n-type semiconductor are joined. For example, in the photodetector disclosed in Patent Document 1, a p-layer made of a p-type semiconductor is formed on a part of the surface of the n-layer by diffusing impurities from the surface of the n-layer made of an n-type semiconductor, thereby forming a pn layer. Semiconductor devices with junctions are described.

When light enters such a semiconductor device from the surface (incident surface) of the p-layer or n-layer, the light is gradually absorbed as it travels through the semiconductor. Assuming that the intensity of light on the plane of incidence is I ₀ and the depth from the plane of incidence is x, the intensity of light I(x) at depth x is given by the Beer-Lambert law: I(x)=I ₀ exp( -αx). Here, α is an absorption coefficient, and the shorter the wavelength of light, the larger the absorption coefficient α. Therefore, the longer the wavelength of light, the more likely it is that light will be absorbed at a deeper position from the plane of incidence.

When light is absorbed in a semiconductor, electron-hole pairs are created. Among these electrons and holes, those generated within the depletion layer of the pn junction or within a predetermined distance (diffusion distance) from the depletion layer move to the n layer and the holes move to the p layer. produce a photocurrent. By detecting this photocurrent, it is possible to detect that light has entered the semiconductor device. Since the above relationship exists between the wavelength of light and the depth at which light is absorbed, a pn junction is provided. The deeper the location, the longer the wavelength of light detected.

JP-A-55-017461

In order to detect long-wavelength light in the photodetector described in Patent Document 1, it is necessary to increase the thickness of the p-layer so as to deepen the position of the pn junction. However, it is difficult to increase the thickness of the p-layer because the range of depth that impurities can reach by diffusion is limited in actual manufacturing.

A problem to be solved by the present invention is to provide a photodetector that is suitable for measuring long-wavelength light and that is easy to manufacture.

A photodetector according to the present invention, which has been made to solve the above problems,
a) a substrate made of a p-type or n-type semiconductor;
b) a light shielding layer covering part or all of one surface of said substrate;
c) a light introduction part provided at a position other than the range covered with the light shielding layer on one surface of the substrate or on the side surface of the substrate;
d) on the one surface below the light-shielding layer and spaced from the light introduction portion, or on the other surface of the substrate and spaced from a position facing the light introduction portion on the other surface; a charge trapping portion made of a semiconductor of a type opposite to that of the substrate;
e) a measuring section electrically connected to the charge trapping section.

The "semiconductor of the type opposite to that of the substrate" in the charge trapping portion refers to an n-type semiconductor when the semiconductor constituting the substrate is a p-type semiconductor, and the semiconductor constituting the substrate is an n-type semiconductor. Sometimes refers to p-type semiconductors.

The light to be measured that has entered the substrate from the light introduction portion is gradually absorbed by the semiconductor of the substrate as it travels through the substrate, generating pairs of holes and electrons. Among the generated holes and electrons, the charges, which are minority carriers in the semiconductor of the substrate (electrons when the semiconductor of the substrate is p-type and holes when it is n-type), move within the substrate. Among these minority carriers, those generated within a predetermined range from the charge trapping portion are captured by the charge trapping portion. The measurement unit measures the current generated between the substrate and the charge trapping portion when the charge trapping portion traps charges or the voltage of the charge trapping portion (the potential of the charge trapping portion, or the voltage between the reference position and the charge trapping portion). to measure.

If r is the distance from the position where the light is incident on the substrate (incident position), the intensity of the light to be measured traveling through the substrate is I(r)= It is represented by I ₀ ·exp(-αr). As described above, the shorter the wavelength of light, the larger the absorption coefficient α. Therefore, almost no light with a wavelength shorter than a certain wavelength reaches a position a certain distance from the incident position in the optical path in the substrate, and only light with a longer wavelength reaches the position. Absorption of light occurs and pairs of holes and electrons are generated. As a result, the distance between the light introducing portion and the charge trapping portion (when the charge trapping portion is provided on the one surface) or the distance between the position facing the light introducing portion on the other surface and the charge trapping portion (the charge trapping portion Light having a wavelength longer than a predetermined wavelength is detected, depending on the case where the portion is provided on the other surface. When lights with different wavelengths are incident at the same intensity, the longer the wavelength, the smaller the degree of attenuation of the light, and the higher the detection intensity in the charge trapping section. Therefore, the wavelength of the detected light is specified. be able to.

As described above, with conventional photodetectors, the wavelength of light to be detected depends on the depth of the pn junction from the surface of the semiconductor layer. there were. In contrast, according to the present invention, since the charge trapping portion is provided on the surface of the substrate and the light introducing portion is provided at a different position, the distance between the light introducing portion and the charge trapping portion can be set arbitrarily. Therefore, a photodetector suitable for measuring long-wavelength light can be easily manufactured. In addition, the photodetector according to the present invention has the effect of facilitating manufacturing even when measuring light with a relatively short wavelength.

The charge trapping portion may be provided on the side of the substrate on which the light shielding layer is provided (the one surface), or may be provided on the opposite surface (the other surface). In the case where the light introduction part is provided on the one surface and light is introduced in a direction inclined with respect to the substrate, when measuring light with a long wavelength, the position where the charge is generated by moving long in the substrate is measured. is closer to the other surface than to the one surface. In such a case, it is preferable to provide the charge trapping portion on the other surface side because the strength of charge detection can be increased.

In the photodetector according to the present invention, rather than covering only a part of the substrate surface with the light shielding layer and providing the light introduction portion in the non-light shielding portion, the entire surface of the substrate is covered with the light shielding layer, and then the side portion of the substrate is covered with the light shielding layer. Although a light introducing portion is provided, it becomes easy to introduce light into the substrate at an angle close to parallel to the substrate. As the optical path in the substrate becomes more parallel to the substrate, the length of the optical path in the substrate can be increased, so that measurements at longer wavelengths are possible.

In the photodetector according to the present invention, the charge trapping portions are arranged on the one surface below the light shielding layer or on the other surface of the substrate at a position facing the light shielding layer. It is preferable that at least two are provided so that the distances from the introduction part are different.

Since at least two charge trapping portions are provided at different distances from the light introducing portion, light of two or more wavelengths can be distinguished and detected as follows. As described above, the light to be measured that has entered the substrate from the light introducing portion is gradually absorbed by the semiconductor of the substrate as it travels through the substrate, generating pairs of holes and electrons. Charges, which are minority carriers among the generated holes and electrons, move in the substrate and are captured in the charge trapping portion closest to the position where the charges were generated. The measurement section measures the current generated between the substrate and each charge trapping section when each charge trapping section traps the charge, or the voltage of each charge trapping section (the potential of the charge trapping section, or the voltage between the reference position and the charge trapping section). voltage). As described above, the shorter the wavelength, the more rapidly the light intensity I(r) attenuates. The value of the current or voltage in the capture section rapidly attenuates with distance from the incident position as the wavelength of the light to be detected becomes shorter. Therefore, light of two or more wavelengths can be distinguished and detected based on the value of current or voltage in each of these charge trapping portions.

For example, a preliminary experiment may be performed for a plurality of lights with known wavelengths but different wavelengths from each other to determine the degree of attenuation for each wavelength. Find the wavelength of the light Based on this principle, when the light to be measured is monochromatic light, the wavelength can be specified based on the degree of attenuation described above. In addition, when the light to be measured is light of multiple wavelengths superimposed, the sum of the data obtained in the preliminary experiment for each wavelength is calculated for multiple examples with different intensity ratios (weighting) for each wavelength. It can be obtained by comparing each of the plurality of examples with the measurement result of the light to be measured.

In Patent Document 1, an n-layer is formed by epitaxial growth on a substrate made of a p-type semiconductor, and then an impurity is diffused into the n-layer to form a p-layer. describes fabricating a photodetector with two pn junctions. In contrast, in the photodetector according to the present invention, two or more charge trapping portions are arranged on one or the other surface of the substrate, so that the two or more charge trapping portions can be produced in one step. Thus, the photodetector according to the present invention also has the effect of simplifying the process of manufacturing two or more charge trapping portions.

The at least two charge trapping portions are typically arranged side by side in one direction. Accordingly, it is possible to suitably detect the light traveling in the one direction or one direction inclined from the one direction to the direction perpendicular to the substrate.

Moreover, the at least two charge trapping portions may be arranged side by side in two or more directions. In this configuration, by detecting the light traveling in the two or more directions or in a direction tilted from each of the two or more directions to the direction perpendicular to the substrate, the detection sensitivity is reduced when the intensity of each light is weak. can be raised. Alternatively, in this case, if the distance between the position where light is incident on the substrate and each charge trapping portion is set to a different value for each direction in which the charge trapping portions are arranged, the relationship between this distance and the detection intensity can be obtained at finer intervals. Therefore, it is possible to improve the measurement accuracy.

As described above, the at least two charge trapping portions can be arranged side by side in at least one direction.

Alternatively, the at least two charge trapping portions may be arranged without being aligned in one or more directions. For example, the charge trapping section may be arranged spirally around the light introducing section.

On the other hand, even when only one wavelength of light is measured, two or more charge trapping portions can be provided. Two or more may exist. If the incident position is point-shaped, a plurality of charge trapping portions are present on the circumference at a predetermined distance from the incident position. A plurality of charge trapping portions exist on the line. By using two or more charge trapping units in this way, it is possible to improve the measurement accuracy.

In addition, the photodetector according to the present invention can have the following additional features regardless of the number of charge traps.

When only a part of the substrate surface is covered with a light shielding layer and the light introduction part is provided in the non-light shielding part of the surface, the light introduction part further includes a sunken part where a part of the substrate sinks from the surface. can be provided. According to the photodetector provided with such a sunken portion, by making light enter the substrate from the side wall of the sunken portion on the side of the charge trapping portion, the light can be introduced into the substrate at an angle closer to parallel to the substrate. , which allows measurements at longer wavelengths.

In the photodetector having the sunken portion, the sunken portion may further include a reflecting portion for reflecting light. By properly setting the angle of the reflecting portion, it is possible to appropriately set the angle of the light incident on the substrate from the side wall of the depressed portion.

In the photodetector according to the present invention, the light introducing section may include an incident direction adjusting section for selectively passing light incident on the substrate from a predetermined direction. As a result, electric charges are generated only on the optical path of the light incident from the predetermined direction, and unnecessary electric charges are prevented from being generated at various positions in the substrate due to light incident on the substrate from various directions. Therefore, it is possible to improve the measurement accuracy.

In the photodetector according to the present invention, some of the minority carriers generated in the substrate are not located in the charge trapping section but on both sides of the charge trapping section (between the charge trapping section and the light introduction section, or in the light introduction section when viewed from the charge trapping section). opposite side). Such charge may be captured by the charge trapping section even though it should not be captured by the charge trapping section. In addition, when two or more charge trapping portions are provided, not only the charge trapping portion closest to the position where the hole-electron pair is generated, but also the charge that should not be trapped in the neighborhood Minority carriers may also be trapped in the trapping section. When minority carriers are trapped in the charge trapping portion that should not be trapped in this way, it causes a decrease in resolution.

Therefore, in the photodetector according to the present invention, a semiconductor of the same type as the semiconductor of the charge trapping portion is provided between the charge trapping portion and the light introducing portion and/or on the opposite side of the light introducing portion when viewed from the charge trapping portion. If the charge trapping portion is made of an n-type semiconductor, the trap portion can be made of an n-type semiconductor, and if the charge trap portion is made of a p-type semiconductor, a p-type semiconductor. When two or more charge trapping portions are provided, a trap portion can be provided between two adjacent charge trapping portions. By providing such a trapping section, the trapping section can remove minority carriers that have reached the position of the trapping section rather than the position of the charge trapping section and should not be trapped by the charge trapping section, thereby improving the measurement accuracy. can be higher.

On the other hand, it is also possible to increase the detection intensity by moving the charges that have reached both sides of the charge trapping portion, rather than the charge trapping portion, toward the charge trapping portion. Therefore, in the photodetector according to the present invention, a substrate of the same type as the semiconductor of the substrate is provided between the charge trapping portion and the light introducing portion and/or on the opposite side of the light introducing portion when viewed from the charge trapping portion. A block portion made of a semiconductor having an impurity concentration higher than that of the semiconductor may be provided. When two or more charge trapping portions are provided, a block portion may be provided between two adjacent charge trapping portions. By providing such a block portion, charges, which are minority carriers in the semiconductor of the substrate, are subjected to a repulsive force from the block portion toward the charge trapping portion side by the potential generated by the block portion, and are thereby trapped in the charge trapping portion. charge increases. As a result, measurement accuracy can be improved.

According to the present invention, it is possible to obtain a photodetector that is suitable for measuring long-wavelength light and that is easy to manufacture.

1 is a schematic configuration diagram showing a first embodiment of a photodetector according to the present invention; FIG. 4A and 4B are diagrams showing the operation of the photodetector according to the first embodiment; FIG. FIG. 4 is a diagram schematically showing the intensity of short-wavelength light and long-wavelength light in a substrate; FIG. 4 is a diagram schematically showing an example of measured intensities of short-wavelength light and long-wavelength light; The figure which shows the modification of the photon detection apparatus of 1st Embodiment. FIG. 5 is a partial enlarged view showing another modification of the photodetector of the first embodiment, which has a translucent member. FIG. 10 is a view showing another modification of the photodetector of the first embodiment, which has an incident direction selection filter; FIG. 10 is a view showing another modification of the photodetector of the first embodiment, which has a plurality of light introducing portions; FIG. 2 is a schematic configuration diagram showing a second embodiment of a photodetector according to the present invention; FIG. 10 is a diagram showing the operation of the photodetector of the second embodiment; FIG. 3 is a schematic configuration diagram showing a third embodiment of a photodetector according to the present invention; FIG. 10 is a diagram showing the operation of the photodetector of the third embodiment; FIG. 4 is a schematic configuration diagram showing a fourth embodiment of a photodetector according to the present invention; The figure which shows the operation|movement of the photon detection apparatus of 4th Embodiment. The figure which shows the modification of the photon detection apparatus of 4th Embodiment. FIG. 5 is a schematic configuration diagram showing a fifth embodiment of a photodetector according to the present invention; The figure which shows the operation|movement of the photon detection apparatus of 5th Embodiment. The figure which shows the modification of the photon detection apparatus of 5th Embodiment. FIG. 6 is a schematic configuration diagram showing a sixth embodiment of a photodetector according to the present invention; The figure which shows the operation|movement of the photon detection apparatus of 6th Embodiment. FIG. 11 is a schematic configuration diagram showing a seventh embodiment of a photodetector according to the present invention; The figure which shows the operation|movement of the photon detection apparatus of 7th Embodiment. FIG. 5 is a diagram showing an example of a photodetector that is a modification of the first embodiment and that includes only one charge trapping unit, and its operation. The figure which shows the example which further modified the modification of 1st Embodiment provided with one charge trapping part. The figure which shows the example which has an incident direction selection filter in the modification of 1st Embodiment provided with one charge trapping part. FIG. 10 is a diagram showing an example of a photodetector further modified from the modification of the first embodiment, which is provided with a plurality of light introducing portions and includes only one charge trapping portion per light introducing portion. FIG. 10 is a diagram showing an example of a photodetector that is a modification of the second embodiment and that includes only one charge trapping unit, and its operation. FIG. 11 is a diagram showing an example of a photodetector that is a modification of the third embodiment and that includes only one charge trapping unit, and its operation. FIG. 11 is a diagram showing an example of a photodetector that is a modification of the fourth embodiment and that includes only one charge trapping unit, and its operation. The figure which shows the example which further modified the modification of 4th Embodiment provided with one charge trapping part. FIG. 12 is a diagram showing an example of a photodetector that is a modification of the fifth embodiment and that includes only one charge trapping unit, and its operation. FIG. 11 is a diagram showing an example of a further modification of the modification of the fifth embodiment, an example of a photodetector provided with a plurality of light introducing portions and only one charge trapping portion per light introducing portion, and the operation thereof. FIG. 14 is a diagram showing an example of a photodetector that is a modification of the sixth embodiment and that includes only one charge trapping unit, and its operation. FIG. 12 is a diagram showing an example of a photodetector that is a modification of the seventh embodiment and that includes only one charge trapping unit, and its operation.

An embodiment of a photodetector according to the present invention will be described with reference to FIGS. 1 to 34. FIG. Although the terms "upper" and "lower" are used in the following description, these terms are used for the sake of convenience to indicate the relative positional relationship of components within the photodetector. It does not limit the direction of use of the detection device.

(1) First embodiment
(1-1) Configuration of Photodetector of First Embodiment As shown in FIG. 14.

Substrate 11 is made of a p-type semiconductor. As the p-type semiconductor of the substrate 11, for example, a well-known material obtained by adding a trivalent impurity to Si or Ge can be used.

The light shielding layer 12 is formed on the surface (upper surface) of the substrate 11 . However, there is a region (non-light-shielding portion) where the light-shielding layer 12 is not provided on part of the surface of the substrate 11 , and this region serves as the light introducing portion 121 . Metals such as Al, Au, and Cu, resins such as polyimide, and the like are used for the material of the light shielding layer 12 . Although not shown in FIG. 1, the light shielding layer 12 may be provided on the side surface and the bottom surface of the substrate 11 as well. Accordingly, it is possible to prevent erroneous detection due to incident light from the side surface or the bottom surface of the substrate 11 that is different from the light introducing portion 121 . On the other hand, when light is prevented from entering from the side or bottom surface of the substrate 11 by placing a shield on the side or bottom of the substrate 11 when the photodetector 10 is used, the light shielding layer 12 can be formed on the side or bottom surface of the substrate 11 . No need to set.

The charge trapping portions 13 are made of an n-type semiconductor, and are arranged side by side in one direction on the surface of the substrate 11 between the surface and the portion of the light shielding layer 12 other than the light introduction portion 121 . That is, each charge trapping portion 13 is arranged apart from the light introduction portion 121 . In addition to the charge trapping portion 13 arranged apart from the light introducing portion 121 , the charge trapping portion 13 may be provided on the surface of the substrate 11 facing the light introducing portion 121 . Although five charge trapping portions 13 are shown in FIG. 1, the number of charge trapping portions 13 is not particularly limited as long as it is two or more. As the n-type semiconductor of the charge trapping portion 13, for example, a well-known material obtained by adding a pentavalent impurity to Si or Ge can be used.

In this embodiment, the substrate 11 made of a p-type semiconductor and the charge trapping portion 13 made of an n-type semiconductor are used. may be used. In any case, a semiconductor having a polarity opposite to that of the substrate 11 is used for the charge trapping portion 13 .

One measurement unit 14 is electrically connected to each of the plurality of charge trapping units 13 . In this embodiment, the measurement unit 14 is an ammeter that detects the current that flows between the substrate 11 and each charge trapping unit 13 and is introduced into the measurement unit 14 . A voltmeter that measures the potential of the charge trapping portion 13 or the voltage between the charge trapping portion 13 and another reference position may be used as the measuring portion 14 instead of the ammeter. The potential or voltage of the charge trapping portion 13 is generated by charges flowing into and being accumulated in the charge trapping portion 13 . Alternatively, each integrated transistor used in an image sensor or the like may be used as the measurement unit 14 . It is not essential that the measurement unit 14 exists in the vicinity of the substrate 11, and the charge may be transferred to the measurement unit 14 arranged at a distant position for measurement. Various examples of the measuring unit 14 described here can also be applied to measuring units in second to seventh embodiments described later.

(1-2) Operation of Photodetector of First Embodiment The operation of the photodetector 10 of the first embodiment will be described with reference to FIGS. 2 to 4. FIG. When the photodetector 10 is used, the light L to be measured is made incident on the light introducing portion 121 in a direction inclined by a predetermined angle θ (<90°) from the surface of the substrate 11 . As a result, the light L is refracted on the surface of the substrate 11 and travels through the substrate 11 at an angle inclined with respect to the surface of the substrate 11 . Meanwhile, the light L is gradually absorbed by the semiconductor of the substrate 11, thereby generating charges C consisting of electron-hole pairs.

Assuming that the intensity of the light L on the surface of the substrate 11 is I ₀ , and the distance traveled by the light L within the substrate 11 is x, the intensity I(x) of the light at the distance x is expressed by Lambert-Beer's equation using the absorption coefficient α. It is represented by I(x)=I ₀ ·exp(-αx) according to the law. For example, when the p-type (or n-type) semiconductor constituting the substrate 11 is Si doped with an impurity, the absorption coefficient α is 10000 cm ⁻¹ for green light with a wavelength of about 500 nm and red light with a wavelength of about 650 nm. is 3000 cm ^-1 for near-infrared light with a wavelength of about 800 nm, and 1000 cm ^-1 for near-infrared light. Using these absorption coefficients α, the distance x ₉₀ at which the intensity of the incident light is attenuated by 90% (10% of the intensity on the surface of the substrate 11) is found to be approximately 2.4 μm when α=10000 cm ⁻¹ . , about 8 μm when α=3000 cm ⁻¹ and about 24 μm when α=1000 cm ⁻¹ . That is, the shorter the wavelength of the light L, the more rapidly the light L is attenuated. On the other hand, as the wavelength of the light L becomes longer, the attenuation becomes gentler, and the absorption of the light L occurs not only at positions close to the light introduction part 121 but also at positions far from the light introduction part 121 .

The charge C generated by the absorption of light diffuses in the substrate 11, and among the charges C, the minority carriers of the substrate 11 (electrons if the substrate 11 is made of a p-type semiconductor, and ) are trapped in the charge trapping portion 13 closest to the position where it was generated (light is absorbed). The charge transfer from the substrate 11 to the charge trapping section 13 is detected as current or voltage by the measuring section 14 connected to the charge trapping section 13 .

The light L to be measured traveling through the substrate 11 is rapidly absorbed by the semiconductor of the substrate 11 and attenuated as the wavelength becomes shorter, and as the wavelength becomes longer, the light L is gradually absorbed by the semiconductor of the substrate 11 and reaches farther. (See Figure 3). Therefore, the charge generated by light absorption in the semiconductor of the substrate 11 decreases as the distance from the light introducing portion 121 increases, and almost no electric charge is generated at a position distant from the light introducing portion 121 to some extent. Therefore, the number of charges captured by the charge trapping portion 13 and the value of the current or voltage of each charge trapping portion 13 measured by the measuring portion 14 decrease as the distance from the charge trapping portion 13 closer to the light introduction portion 121 increases. (See Figure 4). This decrease becomes more rapid as the wavelength of the light to be measured becomes shorter. Therefore, light of two or more wavelengths can be distinguished and detected based on the current or voltage values of the plurality of charge trapping portions 13 . The wavelength of the light L can be determined, for example, by comparing it with the results of a preliminary experiment using light with a known wavelength.

In the conventional photodetector described in Patent Document 1, the wavelength of light to be detected depends on the depth of the pn junction from the surface of the semiconductor layer, so it is difficult to fabricate when the wavelength of the light to be measured is long. Met. On the other hand, the photodetector 10 of the present embodiment is easy to manufacture because the charge trapping portion 13 is provided on the surface of the substrate 11 regardless of the wavelength of light to be detected.

In addition, the photodetector 10 of the present embodiment can be easily manufactured in that a plurality of charge trapping portions 13 can be simultaneously manufactured by using an impurity diffusion method, for example.

(1-3) Modification of the Photodetector of the First Embodiment In the example shown in FIG. A trapping portion 13 is formed. On the other hand, as shown in FIG. 5, the upper surface of the substrate 11 and the lower surface of the charge trapping portion 13 may be flush with each other by forming the charge trapping portion 13 directly on the upper surface of the substrate 11 . Such a charge trapping portion 13 can be produced, for example, by an epitaxial growth method, and can be suitably applied particularly when the material of the charge trapping portion 13 is a compound semiconductor.

As shown in FIG. 6, the light introduction part 121 may be provided with a translucent member 15 made of a material that allows the light to be measured to pass therethrough. Since the translucent member 15 has a higher refractive index than air, the light L is refracted at the boundary between the outside and the translucent member 15 (light introducing portion 121). As a result, the angle of the light L with respect to the normal to the substrate 11 is larger at the angle θ ₂ inside the translucent member 15 than at the angle θ ₁ before entering the translucent member 15 . As a result, the amount of light L that collides with the side wall of the light introduction part 121 and does not enter the substrate 11 (see x in FIG. Since the intensity of the light L taken in can be increased, the resolution is improved. SiO ₂ , SiN, various resins, and the like can be used as the material of the translucent member 15 .

Further, as shown in FIG. 7, an incident direction adjusting section 16 may be provided on the upper side of the light introduction section 121 (on the side opposite to the substrate 11). The incident direction adjusting portion 16 shown in FIG. 7 has a hole inclined in a specific direction with respect to the surface of the substrate 11, and only light incident in a direction that can pass through this hole is allowed to pass through the light introducing portion. 121 is an incident direction selection filter. The incident direction adjusting unit 16 generates electric charge only on the optical path of the light L incident from the above direction, and the light is incident on the substrate from various directions, thereby generating unnecessary electric charge at various positions within the substrate. Since it is possible to prevent this, measurement accuracy can be improved. Instead of the incident direction selection filter, a lens may be arranged and the angle thereof changed to adjust the traveling direction of light.

As shown in FIG. 8, a plurality of light introducing portions (non-light-shielding portions) are provided on the surface of the substrate (two light introducing portions 1211 and 1212 in the example shown in the figure), and each light introducing portion A plurality of charge trapping portions 13 may be provided in at least one direction from there. In the example of FIG. 8, the distance between the adjacent charge trapping portions 13 is a, the distance between the first light introducing portion 1211 and the charge trapping portion 13 closest thereto is b, the second light introducing portion 1212 and the charge trapping portion 13 closest thereto is The distance from the charge trapping portion 13 is set to b+0.5a. Accordingly, charges generated by light incident from the first light introducing portion 1211 are captured by the charge capturing portions 13 separated from the first light introducing portion 1211 by the distances b, b+a, and b+2a, and are captured by the second light introducing portion 1211 . Charges generated by light incident from the light introducing portion 1211 are captured by the charge capturing portions 13 separated from the second light introducing portion 1211 by distances b+0.5a, b+1.5a, and b+2.5a. As a result, the same measurement as when the charge trapping portions 13 are arranged at intervals of 0.5a can be performed. Resolution can be made higher than when they are arranged side by side.

(2) Second embodiment
(2-1) Configuration of Photodetector of Second Embodiment FIG. 9 shows a photodetector 20 of the second embodiment. The photodetector 20 includes a substrate 21 , a light shielding layer 22 , a charge capture section 23 and a measurement section 24 . The configurations of the substrate 21 and the light shielding layer 22 are the same as those of the substrate 11 and the light shielding layer 12 in the first embodiment, and the light shielding layer 22 is provided with the light introducing portion 221 . A plurality of charge trapping portions 23 are provided on the surface (rear surface 212) of the substrate 21 opposite to the surface 211 provided with the light shielding layer 22, at a position facing the light shielding layer 22 (the portion without the light introducing portion 221). arranged side by side. Therefore, each charge trapping portion 23 is spaced apart from the region facing the light introduction portion 221 on the rear surface 212 . The charge trapping portion 23 is formed by diffusing impurities from the front surface (back surface 212) of the substrate 21, like the charge trapping portion 13 of the first embodiment. It should be noted that the charge trapping portion 23 may be produced by an epitaxial growth method or the like, as in the modification of the first embodiment. A measurement unit 24 similar to that of the first embodiment is connected to each charge trapping unit 23 .

(2-2) Operation of Photodetector of Second Embodiment The operation of the photodetector 20 of the second embodiment will be described with reference to FIG. When using the photodetector 20 , the light L to be measured is directed in a direction inclined with respect to the surface 211 of the substrate 21 and made incident on the light introduction section 221 . As a result, the light L travels through the substrate 21 in a direction inclined with respect to the surface 211 of the substrate 21 , so that the depth from the surface 211 increases. The light L is gradually absorbed as it travels through the substrate 21, thereby generating charges C consisting of electron-hole pairs. Among the generated electrons and holes, the minority carriers (electrons in the example of FIG. 10) of the substrate 21 are captured by the charge trapping portion 23 closest to the position where they were generated. As in the first embodiment, the current or voltage generated by this charge trapping is measured by the measuring unit 24, and light of two or more wavelengths can be distinguished and detected based on the values of these currents or voltages.

In the photodetector 20 of the second embodiment, the charge trapping section 23 is provided at a position deep from the rear surface 212 of the substrate 21, that is, the front surface 211 on which the light L is incident. is suitable for trapping the charge generated after has traveled some long distance. By detecting the light L that has traveled a long distance in this way, it is possible to distinguish and detect light with longer wavelengths. On the other hand, by thinning the substrate 21 in the configuration of the second embodiment, relatively short-wavelength light (for example, visible light) may be measured.

(3) Third embodiment
(3-1) Configuration of Photodetector of Third Embodiment FIG. 11 shows a photodetector 30 of the third embodiment. The photodetector 30 includes a substrate 31 , a light shielding layer 32 , a charge trapping portion 33 and a measuring portion 34 , and a side portion of the substrate 31 serves as a light introducing portion 321 .

The substrate 31 is made of a p-type or n-type semiconductor (the former in FIG. 11) as in the first embodiment. The same p-type or n-type semiconductor as the substrate 11 and the charge trapping portion 13 of the first embodiment can be used. The light shielding layer 32 covers the entire one surface of the substrate 31 . When the substrate 31 is made of a p-type semiconductor, the charge trapping portion 33 is made of an n-type semiconductor, and when the substrate 31 is made of an n-type semiconductor, the charge trapping portion 33 is made of a p-type semiconductor. The same material as the light shielding layer 12 of the first embodiment can be used for the light shielding layer 32 .

A plurality of charge trapping portions 33 are provided on the surface of the substrate 31 so as to be aligned in one direction. Although FIG. 11 shows an example in which five charge trapping portions 33 are provided, the number of charge trapping portions 33 is not particularly limited as long as it is two or more. In addition, although the upper surface of the substrate 31 and the upper surface of the charge trapping section 33 are set to the same height in FIG. 11, the upper surface of the substrate 31 and the lower surface of the charge trapping section 33 may be set to the same height. Furthermore, in FIG. 11, the charge trapping portion 33 is provided on the surface of the substrate 31 on the light shielding layer 32 side, but it may be provided on the opposite surface (rear surface) of the substrate 31 . One measurement unit 34 is provided for each of the plurality of charge trapping units 33 .

(3-2) Operation of Photodetector of Third Embodiment The operation of the photodetector 30 of the third embodiment will be described with reference to FIG. When using the photodetector 30 , the light L to be measured is directed from the side of the substrate 31 in a direction parallel to the surface of the substrate 31 and made incident on the light introduction portion 321 . As a result, the light L travels through the substrate 31 in a direction parallel to the surface of the substrate 31 . The point that the charge C is generated while the light L travels in the substrate 31, the point that the minority carriers of the substrate 31 among the generated charges C are trapped in the charge trapping portion 33 closest to the position where the charge C is generated, The point that the movement of the electric charge C is detected as current or voltage by the measurement unit 34, and the point that light with two or more wavelengths can be distinguished and detected based on the values of these currents or voltages are the same as in the first embodiment. is the same as the photodetector 10 in FIG.

Since the photodetector 30 of the third embodiment can cause the light L to travel in a direction parallel to the surface of the substrate 31, the optical path of the light L can be lengthened. Therefore, according to the photodetector 30 of the second embodiment, the wavelength discrimination resolution can be increased.

(4) Fourth embodiment
(4-1) Configuration of Photodetector of Fourth Embodiment FIG. 13 shows a photodetector 40 of the fourth embodiment. The photodetector 40 includes a substrate 41 , a light shielding layer 42 , a charge trapping section 43 and a measuring section 44 . The substrate 41 is provided with a depressed portion 420 in which a portion of the upper surface is dug downward. The light shielding layer 42 is provided in a region of the upper surface of the substrate 41 closer to the charge trapping section 43 than the sinking section 420 . As the material of the light shielding layer 42, the same material as the light shielding layer in the first and second embodiments can be used. The configurations of the charge trapping section 43 and the measuring section 44 are the same as those of the first and second embodiments. A side wall of the depressed portion 420 closer to the charge trapping portion 43 functions as a light introducing portion 421 . In the present embodiment, the vertical cross-sectional shape of the sunken portion 420 is trapezoidal, and the lower base of the trapezoid is shorter than the upper base (bottom closer to the surface of the substrate 41). For the substrate 41 and the charge trapping portion 43, p-type and n-type semiconductors similar to those of the substrate and the charge trapping portion in the first and second embodiments can be used.

(4-2) Operation of Photodetector of Fourth Embodiment The operation of the photodetector 40 of the fourth embodiment will be described with reference to FIG. When the photodetector 40 is used, the light L to be measured is irradiated from the upper side of the substrate 41 to the side wall of the recessed portion 420 , which is the light introduction portion 421 , near the charge trapping portion 43 . The light L is refracted by the side walls and enters the substrate 41 . As a result, the light L travels in a direction closer to parallel to the surface of the substrate 41 than the optical path outside the substrate 41 inside the substrate 41 . The point that the charge C is generated while the light L travels in the substrate 41, the point that the minority carriers of the substrate 41 among the generated charges C are captured in the charge trapping portion 43 closest to the position where the charge C is generated, The point that the movement of the charge C is detected as a current or voltage by the measurement unit 44, and the point that light with two or more wavelengths can be distinguished and detected based on the values of these currents or voltages are the same as in the first embodiment. is the same as the photodetector 10 in FIG.

According to the photodetector 40 of the fourth embodiment, the light L can be caused to travel in a direction closer to parallel to the surface of the substrate 41 than the optical path outside the substrate 41 inside the substrate 41, so that the optical path of the light L can be It can be lengthened, and the wavelength discrimination resolution can be increased.

(4-3) Modification of Photodetector of Fourth Embodiment In the example shown in FIG. 13, the shape of the longitudinal section of the sunken portion 420 is trapezoidal, but the shape of the sunken portion is not limited to this. For example, as shown in FIG. 15, a subsidence portion 420A having a triangular vertical cross section may be provided on the surface of the substrate 41 . In this case, the oblique side of the triangle of the sunken portion 420A becomes the light introducing portion 421A. In addition, in FIG. 15, the shape of the longitudinal section of the subsidence portion 420A is a right-angled triangle, but it may be a triangle other than that.

In addition, as in the first embodiment, the upper surface of the substrate 41 and the lower surface of the charge trapping section 43 may be flush with each other. may provide an incident direction selection filter above the sunken portions 420 and 420A.

(5) Fifth embodiment
(5-1) Configuration of Photodetector of Fifth Embodiment FIG. 16 shows a photodetector 50 of the fifth embodiment. The photodetector 50 includes a substrate 51 , a light shielding layer 52 , a charge trapping section 53 and a measuring section 54 . The substrate 51 is provided with a depressed portion 520 in which a portion of the upper surface is dug downward. The configurations (including materials) of the substrate 51, the light shielding layer 52, the charge trapping section 53, and the measuring section 54 are the same as those of the fourth embodiment. The sinking portion 520 has a right-angled triangular vertical cross section, the side near the charge trapping portion 53 being perpendicular to the surface of the substrate 51, and the side opposite to the charge trapping portion 53 being an oblique side. A side wall of the sunken portion 520 corresponding to the side of the right triangle near the charge trapping portion 53 functions as a light introduction portion 521 . Note that the side wall, which is the light introducing portion 521 , may be slightly inclined from the direction perpendicular to the surface of the substrate 51 . A reflecting portion 522 coated to reflect light is formed on the oblique side of the right-angled triangle opposite to the charge trapping portion 53 .

(5-2) Operation of Photodetector of Fifth Embodiment The operation of the photodetector 50 of the fifth embodiment will be described with reference to FIG. When the photodetector 50 is used, the light L to be measured is irradiated from the upper side of the substrate 51 onto the reflecting portion 522 in the sunken portion 520 . The light L applied to the reflecting portion 522 is reflected by the reflecting portion 522 , enters the light introduction portion 521 , and enters the substrate 51 from the light introduction portion 521 . As a result, the light L travels in a direction closer to parallel to the surface of the substrate 51 than the optical path outside the substrate 51 inside the substrate 51 . Furthermore, by adjusting the angle of the reflecting portion 522 or the angle at which the light L is incident on the reflecting portion 522, it is possible to make the optical path in the substrate 51 parallel to the surface of the substrate 51 as shown in FIG. be. In the example of FIG. 17, the reflecting surface of the reflecting portion 522 is inclined at 45° with respect to the surface of the substrate 51, so that the light L incident on the reflecting portion 522 in the direction perpendicular to the surface of the substrate 51 is It is caused to advance in a direction parallel to the surface of the substrate 51 . The traveling direction of the light L in the substrate 51 may be slightly inclined with respect to the surface of the substrate 51 depending on the angle of the reflecting portion 522 .

The point that the charge C is generated while the light L travels in the substrate 51, the point that the minority carriers of the substrate 51 among the generated charges C are trapped in the charge trapping portion 53 closest to the position where the charge C is generated, The point that the movement of the charge C is detected as a current or voltage by the measurement unit 54, and the point that light with two or more wavelengths can be distinguished and detected based on the values of these currents or voltages are the same as in the first embodiment. is the same as the photodetector 10 in FIG.

According to the photodetector 50 of the fifth embodiment, the light L can be caused to travel in the direction parallel to or close to the surface of the substrate 51 within the substrate 51, so that the optical path of the light L can be lengthened and the wavelength It is possible to increase the discrimination resolution of

(5-3) Modification of Photodetection Device of Fifth Embodiment FIG. 18 shows a photodetection device 50A that is a modification of the photodetection device of the fifth embodiment. The photodetector 50A has a sunken portion 520A in which a portion of the upper surface of the substrate 51 is dug downward. The longitudinal section of the subsidence portion 520A has an inverted M shape obtained by reversing the letter M of the alphabet upside down. One reflecting portion is provided on each of the two slopes in the inverted M-shaped longitudinal section. Here, one reflecting portion is called a first reflecting portion 522A, and the other reflecting portion is called a second reflecting portion 522B. In the inverted M-shaped longitudinal section, the side wall facing the first reflecting portion 522A is the first light introducing portion 521A, and the side wall facing the second reflecting portion 522B is the second light introducing portion 521B.

On the surface (upper surface) of the substrate 51, a plurality of charge trapping portions 53 are arranged side by side in two directions from the sinking portion 520A. Specifically, on the side of the first light introducing portion 521A than the sinking portion 520A, a plurality of charge trapping portions 53 are arranged in one direction away from the sinking portion 520A, and the second light introducing portion 521A is located closer to the sinking portion 520A. On the 521B side, a plurality of charge trapping portions 53 are arranged in a direction opposite to the charge trapping portions 53 on the first light introduction portion 521A side (a direction different by 180°) so as to be separated from the subsidence portion 520A. On the first light introduction portion 521A side, the charge trapping portion 53 closest to the first light introduction portion 521A is located at the center (hereinafter simply referred to as “center”) with respect to the direction in which the plurality of charge trapping portions 53 are arranged, and the first light introduction portion 521A. It is arranged at a position where the distance of the portion 521A is _L0 . On the side of the second light introduction portion 521B, the charge trapping portion 53 closest to the second light introduction portion 521B is arranged at a position where the distance between the center thereof and the second light introduction portion 521B is (L ₀ +L ₁ /2). ing. The distance between the centers of adjacent charge capturing portions 53 on the first light introduction portion 521A side and the second light introduction portion 521B _side is L1. Therefore, when the first light introduction portion 521A side and the second light introduction portion 521B side are combined, the distance from the light introduction portion (the first light introduction portion 521A or the second light introduction portion 521B) is L. A plurality of charge trapping portions 53 differing by _1/2 are provided.

The light-shielding layer 52 is provided on the surfaces of the substrate 51 and the charge trapping section 53, and the charge trapping section 53 is provided with the measurement section 54, which are the same as the above-described embodiments. . Also, the materials of the substrate 51, the charge trapping portion 53, and the light shielding layer 52 are the same as those in each of the embodiments described so far.

According to the photodetector 50A of this modified example, by irradiating the light L to be measured from the upper side of the substrate 51 onto the first reflecting portion 522A and the second reflecting portion 522B in the sunken portion 520A, the light L It is reflected by the first reflecting portion 522A or the second reflecting portion 522B. The light reflected by the first reflecting portion 522A enters the substrate 51 from the first light introducing portion 521A, and the light reflected by the second reflecting portion 522B enters the substrate 51 from the second light introducing portion 521B. It travels through the substrate 51 in a direction parallel to or close to . The principle of detecting the light L is the same as that of the photodetector 50 of the fifth embodiment.

In the photodetector 50A of this modified example, as described above, by arranging the plurality of charge trapping portions 53 on both the _first light introduction portion 521A side and the second light introduction portion 521B side at intervals L1, Since the distance between each of the plurality of charge trapping portions 53 and the light introduction portion (the first light introduction portion 521A or the second light introduction portion 521B) differs by L ₁ /2, only one light introduction portion is provided and a plurality of light introduction portions is provided. , the wavelength discrimination resolution can be made higher than in the case where the charge trapping portions 53 are arranged at _intervals of L1.

In this modified example, the distance between the charge trapping portion 53 and the first light introduction portion 521A and the second light introduction portion 521B and the distance between the charge trapping portions 53 are shown, but these are only examples and are measured. It can be changed as appropriate according to the wavelength of light. Also, it is not essential that the intervals between the charge trapping portions 53 are equal.

For example, the distance between the first light introducing portion 521A and the charge trapping portion 53 closest thereto and the distance between the second light introducing portion 521B and the charge trapping portion 53 closest thereto are made equal, and furthermore, the adjacent charge trapping portions 53 The distances between may be equal. As a result, the light reflected by the first reflecting section 522A and the light reflected by the second reflecting section 522B can be measured under the same conditions, and the measurement accuracy can be increased by combining them.

The direction in which the charge trapping portions 53 are arranged is not limited to one direction in each of the embodiments and modifications other than the modification shown in FIG. 18 and two directions in the modification of FIG. For example, a polygonal pyramidal protrusion such as a triangular pyramid or a square pyramid is erected in the subsidence, and the plurality of pyramidal surfaces possessed by the polygonal pyramid (three surfaces for a triangular pyramid, four surfaces for a square pyramid, etc.) ), and then the charge trapping portions can be arranged side by side in a direction away from each pyramidal surface. Thereby, a plurality of charge trapping portions are arranged side by side in three or more directions. Alternatively, a conical convex portion is erected at the center of the cylindrical depressed portion, a reflecting portion is provided on the conical surface of the convex portion, and a plurality of circular charge trapping portions are formed concentrically with the cylinder of the depressed portion. may be placed side by side.

Furthermore, a plurality of charge trapping portions may be spirally arranged after a conical convex portion is erected at the center of the cylindrical depressed portion and a reflecting portion is provided on the conical surface of the convex portion. . Thereby, each charge trap is arranged at a different distance from the side wall of the depression. In this case, the charge traps need not be arranged in one direction or in multiple directions.

(6) Sixth embodiment
(6-1) Configuration of Photodetector of Sixth Embodiment FIG. 19 shows a photodetector 60 of the sixth embodiment. The photodetector 60 includes a substrate 61 , a light shielding layer 62 , a charge trapping section 63 , a measuring section 64 and a trap section 65 . The configurations of the substrate 61, the light shielding layer 62, the charge capturing section 63 and the measuring section 64 are the same as those of the first embodiment. Further, as in the first embodiment, there is a region where the light shielding layer 62 is not provided on a part of the surface of the substrate 61, and this region becomes the light introducing portion 621. FIG. The trap section 65 is made of the same type of semiconductor as the semiconductor of the charge trapping section 63 (n-type semiconductor in this example), and is provided between adjacent charge trapping sections 63 . Moreover, the trapping portion 65 is located outside the range in which a plurality of the charge trapping portions 63 are arranged, specifically, between the charge trapping portion 63 closest to the light introducing portion 621 and the light introducing portion 621, and from the light introducing portion 621. It is also provided on the opposite side of the light introducing portion 621 when viewed from the farthest charge trapping portion 63 . The measuring section 64 is not connected to the trap section 65 . Note that some of the plurality of trap units 65 shown in this example may be omitted. In order to prevent the charge C (described later) trapped in the trap section 65 from overflowing to the substrate 61 side, the trap section 65 may be provided with discharge means for discharging the charge (for example, means for grounding the trap section 65). .

(6-2) Operation of Photodetector of Sixth Embodiment The operation of the photodetector 60 of the sixth embodiment will be described with reference to FIG. As in the photodetector 10 of the first embodiment, the light L to be measured is caused to enter the light introduction portion 621 in a direction inclined by a predetermined angle from the surface of the substrate 61, so that the light L enters the substrate 61. is gradually absorbed by the semiconductor of the substrate 61 while advancing. This absorption of light produces a charge C consisting of electron-hole pairs.

The charge C generated by the absorption of light in this way moves (diffuses) in the substrate 61 with a certain spread. Therefore, part of the charge C may be introduced into other charge trapping portions 63 instead of the charge trapping portion 63 (closest charge trapping portion) closest to the position where the light is absorbed. If part of the charge C is introduced into such an adjacent charge trapping portion 63, it causes a decrease in measurement accuracy. Therefore, in the photodetector 60 of the sixth embodiment, by providing the trapping portion 65 between the adjacent charge trapping portions 63, the charge trapping portion 63 moves closer to the charge trapping portion 63 adjacent thereto than the nearest charge trapping portion. The charge C is trapped by the trap section 65 . As a result, introduction of the charge C into the charge trapping portion 63 other than the closest charge trapping portion can be suppressed, and the wavelength discrimination resolution can be increased.

(7) Photodetector of the seventh embodiment
(7-1) Configuration of Photodetector of Seventh Embodiment FIG. 21 shows a photodetector 70 of the seventh embodiment. This photodetector 70 has a substrate 71, a light shielding layer 72, a light introducing portion 721, a charge trapping portion 73, and a measuring portion 74, which are similar to those of the photodetector 60 of the sixth embodiment. In the photodetector 70, instead of the trap section 65 in the photodetector 60 of the sixth embodiment, the semiconductor of the substrate 71 (p-type semiconductor in the example shown in FIG. 21) is of the same type and has a higher impurity concentration. A block portion 75 made of a high semiconductor (p-type semiconductor) is provided. Further, the block portion 75 is provided outside the range in which a plurality of the charge trapping portions 73 are arranged, specifically, between the charge trapping portion 73 closest to the light introducing portion 721 and the light introducing portion 721, and from the light introducing portion 721. It is also provided on the opposite side of the light introducing portion 721 when viewed from the farthest charge trapping portion 73 . The measuring section 74 is not connected to the block section 75 . Note that some of the plurality of block units 75 shown in this example may be omitted.

(7-2) Operation of Photodetector of Seventh Embodiment The operation of the photodetector 70 of the seventh embodiment will be described with reference to FIG. As in the photodetector 60 of the sixth embodiment, the light L to be measured is caused to enter the light introduction portion 721 in a direction inclined by a predetermined angle from the surface of the substrate 71 , so that the light L enters the substrate 11 . is gradually absorbed by the semiconductor of the substrate 71 while proceeding. This absorption of light produces a charge C consisting of electron-hole pairs.

As in the case of the sixth embodiment, the charge C generated by the absorption of light moves (diffuses) in the substrate 71 with a certain amount of spread, so that part of the charge C is transferred to the nearest charge trapping portion. Instead, it may be introduced into another charge trapping portion 73 . Therefore, in the photodetector 70 of the seventh embodiment, by providing the block portion 75 between the adjacent charge trapping portions 73, when the minority carriers in the substrate 71 approach the block portion 75, the minority carriers are to act as a repulsive force. As a result, introduction of the charges C into the charge trapping portions 73 other than the closest charge trapping portion can be suppressed, and the wavelength discrimination resolution can be increased.

Some of the plurality of trap portions 65 and block portions 75 shown in the sixth and seventh embodiments may be omitted.

(8) Example in which only one charge trapping portion is provided In each of the embodiments and modifications described so far, a plurality of charge trapping portions are provided. Only one part may be provided.

For example, a photodetector 10A shown in FIG. 23 has only one charge trapping section 13 and only one measuring section 14 in the photodetector 10 of the first embodiment.

When using the photodetector 10A, the light L to be measured is tilted from the surface of the substrate 11 by a predetermined angle θ (<90°), as in the photodetector 10 of the first embodiment. The light is incident on the light introducing portion 121 in the direction. As a result, the light L is refracted on the surface of the substrate 11 and travels through the substrate 11 at an angle oblique to the surface of the substrate 11. In the meantime, the light L is gradually absorbed by the semiconductor of the substrate 11, thereby electrons A charge C consisting of a pair of a and a hole is generated. The generated charges C diffuse within the substrate 11 , and among them, minority carriers generated within a predetermined range from the charge trapping portion 13 are captured by the charge trapping portion 13 . The measurement unit 14 measures current or voltage generated between the substrate 11 and the charge trapping unit 13 by the charge trapping unit 13 trapping the charge.

As described in the first embodiment, the electric charge generated by light absorption in the semiconductor of the substrate 11 decreases as the distance from the light introducing portion 121 increases, and is almost generated at a position distant from the light introducing portion 121 to some extent. Therefore, the number of charges captured by the charge trapping portion 13 and the value of the current or voltage of each charge trapping portion 13 measured by the measuring portion 14 decrease as the distance from the charge trapping portion 13 closer to the light introducing portion 121 increases. continue to do This decrease becomes more rapid as the wavelength of the light to be measured becomes shorter. Therefore, only charges generated by light having a relatively long wavelength are captured by the charge capture section 13 spaced apart from the light introduction section 121 by a predetermined distance. As a result, only light within a wavelength range longer than a predetermined wavelength can be detected according to the distance between the light introducing portion 121 and the charge trapping portion 13 . The distance between the light introducing portion 121 and the charge trapping portion 13 (the above-mentioned predetermined distance) is determined by It can be defined by the distance to the nearest point. Alternatively, this distance may be defined by the distance between the center of gravity of the region of the light introducing portion 121 and the center of gravity of the region of the charge trapping portion 13, or the like.

Although this photodetector 10A cannot distinguish between two or more wavelengths of light and detect any of them, it detects light within a wavelength range longer than a predetermined wavelength and detects light with a shorter wavelength than the predetermined wavelength. It can be detected separately from light. According to the photodetector 10A, since the charge trapping portion 13 is provided on the surface of the substrate 11 regardless of the wavelength of light to be detected, manufacturing is facilitated.

Preliminary experiments are performed using light within the wavelength range to be detected and light within a wavelength range shorter than that, and the predetermined distance may be determined so that the former is detected and the latter is (almost) not detected. . In this preliminary experiment, as shown in FIG. 1, a plurality of charge trapping portions 13 are arranged side by side in a direction away from the light introducing portion 121, and one measurement portion 14 is provided for each charge trapping portion 13. It is preferable to select an optimum one from the combination of the plurality of charge trapping units 13 and measuring units 14 .

As in the first embodiment, when the upper surface of the substrate 11 and the lower surface of the charge trapping portion 13 are made to be the same height by forming the charge trapping portion 13 directly on the upper surface of the substrate 11 (see FIG. 24), the light introducing portion Even when the incident direction adjusting section 16 is provided in 121 (see FIG. 25), only one charge capturing section 13 and one measuring section 14 may be provided.

Further, as shown in FIG. 26, a plurality of light introduction portions (non-light-shielding portions) are provided on the surface of the substrate 11 (first light introduction portion 1211 and second light introduction portion 1212 in the example of FIG. 26), and each light introduction portion , one set of the charge trapping portion 13 may be provided correspondingly. In this case, the distance c between the first light introducing portion 1211 and the corresponding charge trapping portion 13 and the distance d between the second light introducing portion 1212 and the corresponding charge trapping portion 13 are set to different values. , the two charge trapping portions 13 detect light within different wavelength ranges.

Furthermore, in the photodetectors according to the second to seventh embodiments, the number of charge trapping portions can be reduced to only one. For example, as in the photodetector 20A shown in FIG. 27, only one charge capturing portion 23 may be provided on the back surface 212 of the substrate 21, which is the surface opposite to the surface 211 provided with the light shielding layer 22. (corresponding to the second embodiment). In this case, the charge trapping portion 23 has a wavelength range longer than a predetermined wavelength according to the distance between the charge trapping portion 23 and the region (opposing region 222 ) facing the light introducing portion 221 on the back surface 212 . Only light can be detected. This distance can be defined by the distance between the point of the opposing region 222 that is closest to the charge trapping portion 23 and the point of the region of the charge trapping portion 23 that is closest to the opposing region 222 . Alternatively, this distance may be defined by the distance between the center of gravity of the opposing region 222 and the center of gravity of the region of the charge trapping section 23, or the like.

Also, as in the photodetector 30A shown in FIG. 28, in the case where the side portion of the substrate 31 serves as the light introducing portion 321, only one charge capturing portion 33 may be provided (corresponding to the third embodiment).

Alternatively, as in a photodetector 40A shown in FIG. A side wall near the portion 43 may be used as the light introducing portion 421 (corresponding to the fourth embodiment). The shape of the sunken portion is not limited to the example shown in FIG. 29. For example, as shown in FIG. good too.

In addition, as in the photodetector 50B shown in FIG. 31, in an example in which a reflecting portion 522 having a reflecting surface inclined at 45° with respect to the surface of the substrate 51 is provided in the depressed portion 520, the substrate facing the reflecting surface Only one charge trapping portion 53 may be provided on the surface of 51 (corresponding to the fifth embodiment). As a result, the light L incident on the reflecting portion 522 in the direction perpendicular to the surface of the substrate 51 is reflected by the reflecting portion 522 , so that the light can travel in the direction parallel to the surface of the substrate 51 within the substrate 51 . Alternatively, as shown in FIG. 32, one reflecting portion (first reflecting portion 522A and second reflecting portion 522B) is provided on each of the two slopes of the sunken portion 520A having an M-shaped vertical cross section, and this One charge trapping portion 53 may be provided on each side of the inverted M shape.

In the photodetector 60A (corresponding to the sixth embodiment) using the trap section 65 shown in FIG. 33 and the photodetector 70A (corresponding to the seventh embodiment) using the block section 75 shown in FIG. Only one capturing portion 63, 73 can be provided. In these cases, the trap section 65 and/or the block section 75 are positioned closer to the light introducing sections 621 and 721 than the charge trapping sections 63 and 73 and/or closer to the light introducing sections 621 and 721 than the charge trapping sections 63 and 73 are. set on the opposite side.

The present invention is not limited to the above-described embodiments and modifications, and the configurations of the embodiments and modifications can be appropriately combined or further modified.

10, 10A, 20, 20A, 30, 30A, 40, 40A, 50, 50A, 50B, 50C, 60, 60A, 70, 70A... Photodetector 11, 21, 31, 41, 51, 61, 71... Substrate 211: one surface of the substrate 212: the other surface (back surface) of the substrate
12, 22, 32, 42, 52, 62, 72... Light shielding layers 121, 221, 321, 421, 421A, 521, 621, 721... Light introduction part (non-light shielding part)
Reference numerals 13, 23, 33, 43, 53, 63, 73... Charge trapping parts 14, 24, 34, 44, 54, 64, 74... Measuring part 15... Translucent member 16... Incident direction adjusting parts 420, 420A, 520 , 520A... subsidence parts 1211, 521A, 6211... first light introducing parts 1212, 521B, 6212... second light introducing part 222... facing area 522... reflecting part 522A... first reflecting part 522B... second reflecting part 65... trap Part 75 ... block part

Claims (9)

a) a substrate made of a p-type or n-type semiconductor;
b) a light shielding layer covering part or all of one surface of said substrate;
c) a light introduction part provided at a position other than the range covered with the light shielding layer on one surface of the substrate or on the side surface of the substrate;
d) on the one surface below the light-shielding layer and spaced from the light introduction portion, or on the other surface of the substrate and spaced from a position facing the light introduction portion on the other surface; a charge trapping portion made of a semiconductor of a type opposite to that of the substrate;
e) a measurement unit electrically connected to the charge trapping unit; The charge trapping portion is located on the one surface below the light shielding layer, or on the other surface of the substrate at a position facing the light shielding layer so that the distances from the light introducing portion are different from each other. 2. The photodetector according to claim 1, wherein at least two are provided. 3. The photodetector according to claim 2, wherein the charge traps are arranged in at least one direction. The light introducing portion is provided in a non-light-shielding portion that is a position other than the range covered with the light-shielding layer,
4. The photodetector according to any one of claims 1 to 3, wherein the non-light-shielding portion further includes a sunken portion in which a portion of the substrate sinks from the surface. 5. The photodetector according to claim 4, further comprising a reflecting section within the subsidence section. 4. The photodetector according to claim 1, wherein one surface of said substrate is entirely covered with said light shielding layer. 7. The method according to any one of claims 1 to 6, wherein the light introduction section further comprises an incident direction selection filter for selectively passing light incident on the substrate from directions within a predetermined range. 3. The photodetector according to . A trap section made of the same type of semiconductor as that of the charge trapping section is provided between the charge trapping section and the light introducing section and/or on the opposite side of the light introducing section as viewed from the charge trapping section. The photodetector according to any one of claims 1 to 7. Between the charge trapping portion and the light introducing portion and/or on the opposite side of the light introducing portion as viewed from the charge trapping portion, an impurity of the same type as the semiconductor of the substrate and having a higher impurity concentration than the semiconductor of the substrate is provided. 9. The photodetector according to any one of claims 1 to 8, comprising a block portion made of a tall semiconductor.

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