JP2006093442A - Photodiode, photodiode array, method for manufacturing the same and spectroscope - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To have a fast optical responsive speed in low noises, and to provide a photodiode having a high light sensitivity, a photodiode array provided with a plurality of photodiodes, a spectroscope which uses this photodiode array as a light detecting means, and a method for manufacturing the photodiode array. <P>SOLUTION: In the photodiode 10, a low density buried layer 2 containing second conductive impurities of a low density is formed inside a substrate 1 containing first conductive impurities, a high density layer 3 containing the second conductive impurities of a high density is formed inside the low density buried layer 2, and a drawing part 4 exposed to the surface of the substrate 1 is formed in the high density layer 3 so as to contain the second conductive impurities of the high density. The high density layer 3 is electrically connected to an electrode 6. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a photodiode, a photodiode array including a plurality of photodiodes, a spectroscope using the photodiode array as a light detection means, and a method for manufacturing the photodiode.

A photodiode widely used in a spectroscope or the like has, for example, a Si layer in which a PN junction is formed, and a SiO ₂ layer formed as an insulating layer on the surface of the Si layer. In this Si layer, an N-type (or P-type) semiconductor layer (Si layer) as a light-sensitive region where light enters is embedded in the surface of a P-type (or N-type) semiconductor layer (Si layer) as a substrate. Formed as follows. Thereby, a PN junction is formed in the Si layer. When light is incident on the depletion layer generated around the interface of the PN junction or the periphery thereof, carrier charges are generated in the depletion layer. Incident light is detected by extracting the carrier charge. As a technique related to such a photodiode, for example, those disclosed in Patent Documents 1 and 2 below are known.
JP 2000-232233 A Japanese Patent Laid-Open No. 2001-237452

By the way, dark current caused by electron-pair defects of molecular bonds is generated as noise at the interface between the Si layer and the SiO ₂ layer. In particular, when the concentration of impurities contained in the photosensitive region is low, a depletion layer formed at the interface of the PN junction spreads in the photosensitive region. Then, when the depletion layer spreading in the photosensitive region further spreads to the interface between the Si layer and the SiO ₂ layer, a charge is generated in the SiO ₂ layer 48 according to the incident light, and the above-mentioned Dark current due to electron-pair defects in molecular bonds is further increased, resulting in large noise. Therefore, for example, when applying a photodiode to a spectroscope that requires high photosensitivity, the impurity concentration of the photosensitive region must be set low in order to increase the photosensitivity of the photodiode. The increase in dark current becomes a large noise. Furthermore, if the impurity concentration in the photosensitive region is low, the electrical resistance increases accordingly, and the optical response speed also decreases. For this reason, it is difficult to realize a photodiode that has a high light sensitivity that can be used for a spectroscope (and a photodiode array used in the spectroscope), while having a low noise and a high light response speed.

  SUMMARY OF THE INVENTION An object of the present invention is to provide a photodiode having low noise and high optical response speed, and having high photosensitivity, a photodiode array including a plurality of the photodiodes, and a spectrometer using the photodiode array as a light detection means. And a method of manufacturing the photodiode.

  The photodiode according to the present invention includes a base made of a semiconductor containing a first conductivity type impurity, and a semiconductor formed inside the base and containing a second conductivity type impurity different from the first conductivity type. And a high concentration formed of a semiconductor formed in a region continuous to the low concentration buried layer and containing the second conductivity type impurity in a higher concentration than the low concentration buried layer. And a region extending from the surface of the substrate to the high-concentration layer and bonded to the high-concentration layer, and the second conductivity type impurity is formed in a higher concentration than the low-concentration buried layer. And a lead portion made of a semiconductor contained in the substrate.

  Further, according to the method of manufacturing a photodiode of the present invention, a region containing a second conductivity type impurity different from the first conductivity type is embedded in a substrate constituted by a semiconductor containing the first conductivity type impurity. A method of manufacturing a photodiode, comprising: implanting the second conductivity type impurity ions into a first region inside the substrate and a second region continuous with the first region. In this ion implantation step, the second region is ion-implanted so that the impurity concentration is higher than that of the first region. In this case, the ion implantation step includes the step of ion-implanting the second conductivity type impurity ions into the first region and the second conductivity type impurity ions from the first region. And the step of implanting ions into the second region so that the impurity concentration of the second conductivity type is substantially the same as that of the second region. It is preferable that the method further includes a step of ion-implanting into a third region communicating with the second region.

According to the photodiode of the present invention and the method for manufacturing the photodiode, the low-concentration buried layer (first region) containing the second conductive type (N-type or P-type) impurity at a low concentration is used as the first conductive type. Since it is formed inside a substrate containing a type (P-type or N-type) impurity, the depletion layer formed at the interface between the substrate and the low-concentration buried layer does not reach the surface of the substrate. Can be formed. For this reason, when the SiO ₂ layer is formed on the surface of the substrate as the Si layer, a dark current is generated at the interface between the Si layer and the SiO ₂ layer, but the depletion layer does not reach this interface. Therefore, increase in dark current can be suppressed. Since the high-concentration layer (second region) containing impurities higher in concentration (low resistance) than the low-concentration buried layer is provided in a region continuous with the low-concentration buried layer, the low-concentration buried layer is provided. Even if the impurity concentration of the layer is low, a high light response speed can be realized. Since the impurity concentration of the low-concentration buried layer is low, a depletion layer is formed not only around the low-concentration buried layer but also over the entire region occupied by the low-concentration buried layer. For this reason, high photosensitivity is realizable over a wide wavelength region.

  In the present invention, the low concentration buried layer preferably has a substantially rectangular shape formed by two long sides and two short sides in a plan view. Thereby, when applied to a spectroscope, a plurality of photodiodes can be arranged with high density in a state where long sides are adjacent to each other on the substrate surface, so that high wavelength resolution can be realized.

  In the present invention, it is preferable that the high concentration layer is formed in a shape including one or a plurality of regions extending along the long side direction of the low concentration buried layer in a plan view. As a result, even if the carrier charge is generated in any part of the depletion layer around the low-concentration buried layer that is long in the long side direction, the high-concentration layer having a high impurity concentration (low electrical resistance) Since it is formed in the vicinity of the carrier generation site, this carrier charge can be moved at high speed via the high concentration layer. Therefore, the optical response speed can be further improved.

  In the present invention, the high-concentration layer may be formed in a planar shape in which a region extending along the long side direction of the low-concentration buried layer is substantially parallel to the surface of the substrate in plan view. Further, the high concentration layer may be formed in a linear shape with a region extending along the long side direction of the low concentration buried layer in plan view. As a result, the region occupied by the low-concentration buried layer is expanded, and the region where the depletion layer is formed is expanded accordingly, thereby further improving the photosensitivity.

  Furthermore, the photodiode array of the present invention is characterized in that a plurality of the photodiodes are arranged on the substrate surface. Therefore, according to the photodiode array of the present invention, since the photodiode having the above-described low noise, high photosensitivity and fast optical response speed is used, a highly functional photodiode array can be realized. In particular, when the photodiode has a long and narrow rectangular shape formed by two long sides and two short sides in plan view, a plurality of photodiodes are adjacent to each other on the substrate surface of the photodiode array. Therefore, high wavelength resolution can be realized.

  Furthermore, the spectroscope of the present invention is characterized by comprising spectroscopic means for splitting incident light and the photodiode array for converting the amount of incident light after splitting into an electric signal. According to the spectrometer of the present invention, the photodiode array as the light detection means has a high wavelength resolution and a fast optical response speed while maintaining high photosensitivity, so that a highly accurate spectrometer can be realized.

  According to the present invention, a photodiode having low noise and high optical response speed, and further having high photosensitivity, a photodiode array including a plurality of the photodiodes, a spectroscope using the photodiode array as a light detection means, And a method for manufacturing a photodiode.

  Hereinafter, with reference to the drawings, a photodiode, a photodiode array, a spectrometer, and a method for manufacturing the photodiode according to the present embodiment will be described. In the following description of the drawings, the same reference numerals are given to the same elements, and duplicate descriptions are omitted.

  First, the configuration of the photodiode according to the present embodiment will be described with reference to FIGS. 1 and 2. FIG. 1A is a plan view of the photodiode according to the present embodiment, and FIG. 1B is a diagram showing a cross-sectional structure in the direction of the arrow I-I shown in FIG. These are figures which show the cross-section of the II-II arrow direction shown to the figure (a). And FIG. 2 is a figure for demonstrating the aspect of the depletion layer formed in the photodiode which concerns on this embodiment. Here, FIG. 2 represents a cross-section in the direction of the arrow I-I shown in FIG.

First, the configuration of the photodiode 10 will be described with reference to FIG. The photodiode 10 includes a base 1, a low-concentration buried layer 2 (first region) embedded in the base 1, and a high-concentration layer 3 (embedded further in the low-concentration buried layer 2 ( 2nd area | region) and the drawer | drawing-out part 4 (3rd area | region) exposed to the surface of the base | substrate 1 while being joined to this high concentration layer 3. The photodiode 10 is further formed on a surface of the silicon thermal oxide film 5 and a silicon thermal oxide film layer (SiO ₂ ) 5 formed on the surface of the substrate 1 on the side where the lead portion 4 is exposed. And an electrode 6 that penetrates through the silicon thermal oxide film 5 and is joined to the lead portion 4, and an electrode 7 that is formed on the surface opposite to the surface on which the silicon thermal oxide film 5 is formed. ing.

The substrate 1 has a first conductivity type impurity in the silicon (Si) layer (here, arsenic or the like when the first conductivity type is N type, boron or the like when the first conductivity type is P type, and so on). It is a contained semiconductor layer. The impurity concentration contained in the substrate 1 is about 10 ¹³ to 10 ¹⁵ cm ⁻³ .

The low concentration buried layer 2 is a semiconductor layer in which a second conductivity type impurity different from the first conductivity type is contained in a silicon (Si) layer at a low concentration. The impurity contained in the low concentration buried layer 2 The concentration is about 10 ¹⁴ to 10 ¹⁶ cm ⁻³ .

  Here, the above-mentioned “first conductivity type” and “second conductivity type” mean different conductivity types (N type, P type). That is, when the first conductivity type is P type, the second conductivity type is N type, and when the first conductivity type is N type, the second conductivity type is P type.

  The low-concentration buried layer 2 has an elongated, substantially rectangular shape formed by two long sides and two short sides in plan view. The low-concentration buried layer 2 is formed so as to be substantially parallel to the surface of the substrate 1 and embedded in the substrate 1 with a thickness of about 1.0 μm at a depth of about 1.5 μm from the surface. Has been.

The high concentration layer 3 is a semiconductor layer in which a second conductivity type impurity is contained at a high concentration in a silicon (Si) layer, and the impurity concentration contained in the high concentration layer 3 is about 10 ¹⁸ to 10 ¹⁹ cm ^−3. It has become. The high-concentration layer 3 is formed in a substantially rectangular shape that is substantially parallel to the surface of the substrate 1 and extends from one short side of the low-concentration buried layer 2 to the other short side in plan view. Has been.

The lead portion 4 is a semiconductor layer containing a high concentration of the second conductivity type impurity, and the impurity concentration contained in the lead portion 4 is about 10 ¹⁹ cm ⁻³ . The lead portion 4 is formed along with the electrode 6 on one short side of the low-concentration buried layer 2 in plan view. The lead portion 4 is joined to the high concentration layer 3 so as to communicate the high concentration layer 3 with the surface of the substrate 1.

  Here, the impurity concentration of the substrate 1, the low concentration buried layer 2, the high concentration layer 3 and the lead portion 4, the buried position and thickness of the low concentration buried layer 2, the buried position of the high concentration layer 3, and The thickness is set in detail so that the depletion layer formed around the interface (PN junction surface) between the substrate 1 and the low-concentration buried layer 2 has a desired shape. Specifically, as shown in FIG. 2, in order to reduce the dark current, the depletion layer A formed around the interface between the substrate 1 and the low concentration buried layer 2 is formed of the substrate 1 and the silicon thermal oxide film. 5 is set in detail so as to be formed in a region widely including the low-concentration buried layer 2 so as not to reach the interface with 5. Furthermore, it is preferable to improve the photosensitivity so that the depletion layer A is formed not only around the low concentration buried layer 2 but also inside the low concentration buried layer 2. In practice, the depletion layer A does not include the region occupied by the high concentration layer 3.

  In the photodiode 10 configured as described above, when light is incident on the depletion layer A with a voltage applied between the electrodes 6 and 7, carriers corresponding to the incident light are generated in the depletion layer A. The carriers move through the high concentration layer 3 and the lead portion 4 to reach the electrode 6, and charges are extracted by the electrode 6.

  As described above, according to the photodiode according to the present embodiment, the depletion layer A does not reach the interface between the substrate 1 and the silicon thermal oxide film 5, and therefore an increase in dark current (noise) generated in the vicinity of this interface. Can be suppressed. A high concentration layer 3 containing impurities of the same conductivity type as the low concentration buried layer 2 at a high concentration (low electric resistance) is formed inside the low concentration buried layer 2. For this reason, even when the low-concentration buried layer 2 is provided in an elongated and substantially rectangular shape as in the present embodiment, carriers generated according to incident light are generated by the high-concentration layer 3 and the lead-out portion having a low electrical resistance. 4 can be moved to reach the electrode 6, the phenomenon of moving a long distance (for example, a distance corresponding to the length of the long side) inside the low-concentration buried layer 2 having a high electrical resistance is less likely to occur. For this reason, improvement in the optical response speed is achieved. Moreover, since the impurity concentration contained in the low-concentration buried layer 2 is low, the depletion layer A is not only around the low-concentration buried layer 2 but also inside the low-concentration buried layer 2 (low-concentration buried layer). When the high-concentration layer 3 is included in the layer 2, the region occupied by the high-concentration layer 3 is excluded). For this reason, high photosensitivity can be realized over a wide wavelength region. That is, according to the photodiode 10 according to the present embodiment, it is possible to realize a photodiode having low noise and high optical response speed and further having high photosensitivity.

  Next, the photodiode array according to the present embodiment will be described. The basic configuration of the photodiode array according to the present embodiment includes a plurality of the photodiodes 10 described above, and the photodiodes 10 are arranged on the substrate surface so that the long sides forming the planar shape of the low concentration buried layer 2 are adjacent to each other. It is arranged in parallel with the density. In this case, since the electrodes 6 for extracting the carrier charges generated in the photodiode 10 are provided on one short side in the planar shape of the low concentration buried layer 2, a large number of photodiodes 10 have a high density. Is arranged.

  FIG. 3 shows four types of photodiode arrays having the above basic configuration. 3A to 3D are all plan views showing the photodiode array according to the present embodiment.

  The photodiode array 21 shown in FIG. 3A is a monolithic type, and a plurality of photodiodes 10 connected to the shift register 20b are arranged so that the long sides forming the planar shape of the low concentration buried layer 2 are adjacent to each other. Are arranged in parallel on the surface of the substrate 20a. The photodiode array 22 shown in FIG. 3B is also of a monolithic type, and a plurality of photodiodes 10 connected to the shift register 20b are adjacent to each other in the long side forming the planar shape of the low concentration buried layer 2. In this way, a plurality of rows (two rows in the example shown in FIG. 3) arranged in parallel on the surface of the substrate 20a are provided.

  The photodiode array 23 shown in FIG. 3C has a separate chip structure, and a plurality of photodiodes 10 connected to the readout circuit 20c have long sides forming the planar shape of the low concentration buried layer 2 mutually. These are arranged in parallel on the surface of the substrate 20a so as to be adjacent to each other. The photodiode array 24 shown in FIG. 3 (d) has a separate chip structure, but has a plurality of substrates 20a (two in the example shown in FIG. 3). A plurality of photodiodes 10 connected to the circuit 20c are arranged in parallel in a row so that the long sides forming the planar shape of the low concentration buried layer 2 are adjacent to each other.

  Here, the monolithic type includes a shift register 20b on a substrate 20a, and the shift register 20b can output the amount of light received by the photodiode 10 as digital data. On the other hand, the chip-separated structure is a photodiode array having a configuration in which a semiconductor chip (in this case, a read circuit 20c including the shift register 20b) is provided separately from the substrate 20a. The circuit 20c and each photodiode 10 provided on the substrate 20a are electrically connected by a wire 20d.

  According to the photodiode arrays 21 to 24, the photodiodes 10 can be arranged on the substrate 20a with high density, so that high wavelength resolution can be realized.

  Next, the spectrometer 30 according to the present embodiment will be described with reference to FIG. FIG. 4 is a perspective view showing the spectrometer according to the present embodiment.

  As shown in the figure, the spectroscope 30 includes an optical fiber 31, an incident part 32, a diffraction grating part 33, a mirror 34, a base 35, a light detection means 36, and the like. The incident part 32 fixes the end of the optical fiber 31, the diffraction grating part 33 as a spectroscopic means diffracts the light incident through the optical fiber 31, and the mirror 34 causes the light incident from the optical fiber 31 to enter the diffraction grating part 33. The light reflected by the diffraction grating portion 33 is reflected toward the light detection means 36. The light detection means 36 is for converting the amount of light diffracted by the diffraction grating section 33 into an electrical signal for each wavelength, and any one of the photodiode arrays 21 to 24 according to the present embodiment is used. . The incident portion 32, the diffraction grating portion 33, the mirror 34, and the light detection means 36 are installed on the base 35.

  As described above, in the spectroscope 30 using the photodiode arrays 21 to 24 according to the present embodiment as the light detection means, the light detection means 36 (that is, any one of the photodiode arrays 21 to 24) has the plurality of photodiodes 10 high. Further, the photodiode 10 has a low dark current (low noise), high photosensitivity, and fast photoresponse speed, so that it becomes a highly accurate spectroscope having high wavelength resolution.

  Next, a method for manufacturing the photodiode 10 according to the present embodiment will be described with reference to FIG. FIG. 5 is a view for explaining the photodiode manufacturing method according to this embodiment. FIGS. 5A to 5C are cross-sectional views of the photodiode in the long side direction in plan view. ) To (f) are diagrams showing impurity concentration profiles in the respective manufacturing steps shown in FIGS. (A) to (c), in which the horizontal axis indicates the logarithmic value of the impurity concentration, The axis indicates the depth from the surface.

  First, as shown in FIG. 5A, an opening 8a corresponding to a region where the low-concentration buried layer 2 is to be formed is formed on the silicon thermal oxide film 5a formed on the surface of the substrate 1 by a method such as etching. Form. Then, a first impurity implantation condition including an impurity implantation energy, an impurity beam current, and an irradiation time of the beam current for specifying the shape, formation position, and impurity concentration of the low concentration buried layer 2 Then, the second conductivity type impurity is implanted from the opening 8a using the ion implantation method. Thereafter, annealing is performed to form the low concentration buried layer 2, and the silicon thermal oxide film 5a is removed.

Here, FIG. 5D shows a first impurity concentration profile implanted using the first impurity implantation condition. The impurity concentration profile shown in FIG. 5D is an impurity concentration profile for a cross section including the low concentration buried layer 2 perpendicular to the surface of the substrate 1. As shown in FIG. 5D, the impurity concentration implanted using the first impurity implantation condition is within the range corresponding to the formation region of the low-concentration buried layer 2 inside the substrate 1 (for example, 0. For example, a substantially constant value B1 of about 10 ¹⁴ to 10 ¹⁶ cm ^{−3 is} obtained at a depth of about 5 to 1.5 μm (between depths A11 and A12).

  Next, as shown in FIG. 5B, an opening 8b corresponding to a region where the high-concentration layer 3 is to be formed by etching or the like with respect to the silicon thermal oxide film 5b newly formed on the surface of the substrate 1. Form. The second impurity implantation conditions including the impurity implantation energy, the impurity beam current, and the irradiation time of the beam current for specifying the shape, formation position and impurity concentration of the high concentration layer 3 are also obtained. Then, a second conductivity type impurity is implanted from the opening 8b by using an ion implantation method, and then annealed to form the high concentration layer 3. Then, the silicon thermal oxide film 5b is removed.

Here, FIG. 5E shows a second impurity concentration profile implanted using the second impurity implantation condition. The profile shown in FIG. 5E is an impurity concentration profile for a cross section including the high concentration layer 3 perpendicular to the surface of the substrate 1. As shown in FIG. 5E, the impurity concentration implanted using the second impurity implantation condition is in a range corresponding to the formation region of the high-concentration layer 3 in the low-concentration buried layer 2 (for example, 0 for each). A substantially constant value B2 of about 10 ¹⁸ to 10 ¹⁹ cm ⁻³ , for example, between depths A 21 and A 22 of about 7 to 1.2 μm. This value B2 is larger than the above-described value B1. According to the second impurity concentration profile, the high concentration layer 3 is formed inside the low concentration buried layer 2 with a higher impurity concentration than the low concentration buried layer 2.

  Next, as shown in FIG. 5C, an opening 8c corresponding to a region where the extraction portion 4 is to be formed is formed on the silicon thermal oxide film 5c newly formed on the surface of the substrate 1 by a method such as etching. Form. Then, under the third impurity implantation conditions including the impurity implantation energy, the impurity beam current, and the irradiation time of the beam current for specifying the shape, formation position, and impurity concentration of the lead portion 4. Then, impurities of the second conductivity type are implanted from the opening 8c using an ion implantation method, and then annealed to form the lead portion 4. Thereafter, the electrode 6 is formed on the surface of the silicon thermal oxide film 5c and in the region including the opening 8c. In this case, the electrode 6 is formed so as to be electrically connected to the lead portion 4 through the opening 8c. Further, the electrode 7 is formed on the other surface of the base 1. Thus, the photodiode 10 is formed.

Here, FIG. 5F shows a third impurity concentration profile implanted using the third impurity implantation condition. The profile shown in FIG. 5F is an impurity concentration profile for a cross section including the lead portion 4 perpendicular to the surface of the substrate 1. As shown in FIG. 5F, the impurity concentration implanted using the third impurity implantation condition is within a range corresponding to the region where the lead portion 4 is formed in the substrate 1 (from the surface of the substrate 1 in the figure). A substantially constant value B3 of, for example, about 10 ¹⁹ cm ⁻³ is taken within a range of, for example, a depth of about 0.7 to 1.2 μm shown in A3. The value B3 is substantially the same as the value B2 described above. According to the third impurity concentration profile, the lead portion 4 reaches the high concentration layer 3 from the surface of the substrate 1 at substantially the same concentration as the high concentration layer 3 and at a higher impurity concentration than the low concentration buried layer 2. It is formed in the area up to.

  The present invention is not limited to the manufacturing method of the photodiode 10, the photodiode arrays 21 to 24 and the spectroscope 30 and the photodiode 10 according to the above-described embodiment, and the detailed configuration, detailed operation, and detailed manufacturing process are not limited. It can be changed. For example, the low-concentration buried layer 2 may be a plurality of planar high-concentration layers embedded in the low-concentration buried layer 2 so as to be substantially parallel to each other. Further, the planar shape of the low-concentration buried layer 2 is not limited to the above-described rectangular shape, and may be another shape such as an elongated ellipse.

<Modifications related to photodiodes>
Further, photodiodes 10a to 10c shown in FIGS. 6 to 8 may be used in place of the photodiode 10. Here, FIG. 6A is a plan view showing a photodiode as a first modification according to the present embodiment, and FIG. 6B is a cross section taken along the direction of the arrow III-III shown in FIG. It is a figure which shows a structure, The figure (c) is a figure which shows the cross-section of the IV-IV arrow direction shown to the figure (a).

  FIG. 7A is a plan view showing a photodiode as a second modification according to the present embodiment, and FIG. 7B is a cross-sectional structure in the direction of arrows V-V shown in FIG. FIG. 10C is a diagram showing a cross-sectional structure in the direction of the arrow VI-VI shown in FIG. FIG. 8A is a plan view showing a photodiode as a third modification according to the present embodiment, and FIG. 8B is a cross-sectional structure in the direction of arrow VII-VII shown in FIG. (C) is a figure which shows the cross-section of the VIII-VIII arrow direction shown to the same figure (a).

  First, the photodiode 10a shown in FIG. 6 has a high-concentration layer 3a formed in a shape having one linear region extending in the long-side direction at the approximate center of the low-concentration buried layer 2 in plan view. Except for this point, the configuration is the same as that of the photodiode 10 according to the present embodiment. Further, the photodiode 10b shown in FIG. 7 has a high concentration layer 3b formed in a shape having two linear regions extending along two long sides of the low concentration buried layer 2 in a plan view. Except for this point, the configuration is the same as that of the photodiode 10 according to the present embodiment. Further, the photodiode 10c shown in FIG. 8 has two linear regions extending along each of the two long sides of the low-concentration buried layer 2 and a long portion substantially at the center of the low-concentration buried layer 2 in plan view. The high-concentration layer 3c is formed so as to include one linear region extending in the side direction. Except for this point, the configuration is the same as that of the photodiode 10 according to the present embodiment.

  Therefore, according to the photodiodes 10a to 10c, the high concentration layers 3a to 3c are formed in a shape having one to three linear regions extending in the long side direction. The region occupied by the concentration layer 3a is reduced as compared with the region occupied by the high concentration layer 3 of the photodiode 10 described above. For this reason, since the region occupied by the depletion layer in the low concentration buried layer 2 is enlarged as compared with the case of the photodiode 10, higher photosensitivity can be realized over a wide wavelength region. Further, for the photodiodes 10b and 10c, the high-concentration layers 3b and 3c are respectively formed in a shape having two or three linear regions, so that the high-concentration layer 3a is formed in comparison with the photodiode 10a. The number of carriers that move through the network increases. As a result, a higher light response speed can be realized while maintaining high light sensitivity over a wide wavelength region.

  Note that the number of the linear regions described above is not limited to one to three, and may be four or more. In particular, if the cross-sectional diameter of the linear region is set small, a larger number of linear regions can be formed without increasing the volume occupied by the entire linear region in the low concentration buried layer 2, that is, the volume occupied by the high concentration layer. It is also possible to provide it. By providing such a large number of linear regions evenly in the low concentration buried layer 2, carrier charges generated in the depletion layer in the low concentration buried layer 2 can more easily reach the high concentration layer 3. Become. For this reason, a faster optical response speed can be realized.

  As shown in FIG. 11, in the photodiode according to the present invention, a high concentration layer 3 is formed on the surface of the substrate 1 (near the interface between the substrate 1 and the silicon thermal oxide film 5). Alternatively, the low-concentration buried layer 2 may be formed in a state of being bonded to the high-concentration layer 3. Here, FIG. 11 shows a cross section of the photodiode. Even in such a configuration, the depletion layer A is not formed in the dark current generation region in the vicinity of the surface of the substrate 1 because the high concentration layer 3 containing high concentration impurities is formed on the surface of the substrate 1. For this reason, an increase in dark current can be suppressed. In this case, in order to improve the sensitivity to incident light in a wide wavelength region, the thickness of the high concentration layer 3 is made as thin as possible, and a depletion layer (in this case, a depletion layer formed inside the low concentration buried layer 2) is formed. It is preferable to form it as close as possible to the interface with the silicon thermal oxide film 5.

<First Modification Related to Manufacturing Method>
Further, any one of the other two manufacturing methods shown in FIGS. 9 and 10 may be used instead of the manufacturing method of the photodiode 10 described above. FIGS. 9A to 9F are views for explaining a first modification example relating to a method for manufacturing a photodiode, and FIGS. 10A to 10D explain a second modification example. FIG. 9A to 9D and FIGS. 10A to 10D each represent a cross section of a photodiode.

  First, based on FIGS. 9A to 9F, a first modification example relating to a method for manufacturing a photodiode will be described. As shown in FIG. 9A, a silicon thermal oxide film 5a is formed on the surface of the substrate layer 1a, and the silicon thermal oxide film 5a is formed on the low-concentration buried layer 2a (low in the formation process) by a method such as etching. Opening 8a corresponding to the formation planned region (representing concentration buried layer 2) is formed, and low concentration buried layer 2a is formed on the surface of substrate layer 1a using thermal diffusion or ion implantation. Form. Here, the substrate layer 1 a is a silicon layer that constitutes the base 1 and contains impurities of the same conductivity type and the same concentration as the base 1. When the low-concentration buried layer 2 is formed by an ion implantation method, the impurity implantation energy, the impurity beam current, and the impurity current for specifying the shape, formation position, and impurity concentration of the low-concentration buried layer 2a, Under the fourth impurity implantation conditions including the irradiation time of the beam current, the second conductivity type impurity is implanted from the opening 8a using the ion implantation method, and then annealed to fill the low concentration. The embedded layer 2a is formed. Thereafter, the silicon thermal oxide film 5a is removed.

  Here, FIG. 9E shows a fourth impurity concentration profile implanted using the fourth impurity implantation condition. The impurity concentration profile shown in FIG. 9E is an impurity concentration profile for a cross section including the low-concentration buried layer 2 a perpendicular to the surface of the substrate 1. As shown in FIG. 9E, the impurity concentration implanted using the fourth impurity implantation condition is within a range corresponding to the formation region of the low-concentration buried layer 2a in the substrate layer 1a (the substrate layer 1a The above-mentioned substantially constant value B1 is taken in the range from the surface to a depth A4 of about 0.5 μm, for example. According to the fourth impurity concentration profile, the low concentration buried layer 2a is formed in a region from the surface of the substrate layer 1a to the depth A4.

  Next, as shown in FIG. 9B, a silicon thermal oxide film 5b is newly formed on the surface of the substrate layer 1a, and the high concentration layer 3d (formation) is formed on the silicon thermal oxide film 5b by a method such as etching. The opening 8b corresponding to the formation planned region of the high-concentration layer 3 in the middle) is formed, and the high-concentration layer is formed on the surface of the low-concentration buried layer 2a using the thermal diffusion method or the ion implantation method 3d is formed. When the high concentration layer 3d is formed by the ion implantation method, the impurity implantation energy for specifying the shape, formation position and impurity concentration of the high concentration layer 3d is the same as in the manufacturing process of the photodiode 10 described above. Then, a second conductivity type impurity is implanted from the opening 8b using an ion implantation method under a fifth impurity implantation condition including an impurity beam current and an irradiation time of the beam current. Thereafter, annealing is performed to form the high concentration layer 3d. Thereafter, the silicon thermal oxide film 5b is removed.

  Here, FIG. 9F shows a fifth impurity concentration profile implanted using the fifth impurity implantation condition. The profile shown in FIG. 9F is an impurity concentration profile for a cross section including the high concentration layer 3 d perpendicular to the surface of the substrate 1. As shown in FIG. 9 (f), the impurity concentration implanted using the fifth impurity implantation condition is within the range corresponding to the formation region of the high concentration layer 3d in the low concentration buried layer 2a (low concentration implantation). The above-mentioned substantially constant value B2 is taken in the range from the surface of the buried layer 2a to the depth A5 of about 0.2 μm, for example. According to the fifth impurity concentration profile, the high concentration layer 3d is formed inside the low concentration buried layer 2a with a higher impurity concentration than the low concentration buried layer 2a.

  Next, as shown in FIG. 9C, epitaxial growth is performed on the surface of the substrate layer 1a to form an epitaxial layer 1b having the same conductivity type and containing the same concentration of impurities as the substrate layer 1a. In the formation process, the ion implantation method described with reference to FIGS. 9A and 9B is repeatedly used to form the low concentration buried layer 2 and the high concentration layer 3 buried therein. The substrate 1 is composed of the substrate layer 1a and the epitaxial layer 1b. Thereafter, in the same manner as in the method of manufacturing the photodiode 10 according to the above-described embodiment (see FIGS. 5C and 5F), the lead portion 4 is formed as shown in FIG. Electrodes 6 and 7 are formed. Thus, the photodiode 10 is formed.

<Second Modification Related to Manufacturing Method>
Next, based on FIGS. 10A to 10D, a second modification example relating to a method for manufacturing a photodiode will be described. First, as in the case of the first modification described above (see FIGS. 9A and 9E), as shown in FIG. 10A, a low concentration buried layer is formed on the surface of the substrate layer 1a. 2a is formed. Next, epitaxial growth is performed on the surface of the substrate layer 1a to form an epitaxial layer 1b having the same conductivity type and the same concentration of impurities as the substrate layer 1a. The low concentration buried layer 2 is formed by repeatedly using the ion implantation method described with reference to FIG. The substrate 1 is composed of the substrate layer 1a and the epitaxial layer 1b.

  Next, in the same manner as the manufacturing method of the photodiode 10 described above (see FIGS. 5B and 5E), the high concentration layer 3 is formed inside the low concentration buried layer 2 as shown in FIG. 10C. After that, the silicon thermal oxide film 5b is removed. Then, in the same manner as the manufacturing method of the photodiode 10 described above (see FIGS. 5C and 5F), the lead portion 4 is formed as shown in FIG. Form. Thus, the photodiode 10 is formed.

It is a figure which shows the photodiode which concerns on this embodiment. It is a figure for demonstrating the mode of the depletion layer formed in the photodiode which concerns on this embodiment. It is a top view which shows the photodiode array which concerns on this embodiment. It is a perspective view which shows the spectrometer which concerns on this embodiment. It is a figure for demonstrating the manufacturing method of the photodiode which concerns on this embodiment. It is a figure which shows the modification of the photodiode which concerns on this embodiment. It is a figure which shows the modification of the photodiode which concerns on this embodiment. It is a figure which shows the modification of the photodiode which concerns on this embodiment. It is a figure for demonstrating the modification of the manufacturing method of the photodiode which concerns on this embodiment. It is a figure for demonstrating the modification of the manufacturing method of the photodiode which concerns on this embodiment. It is a figure which shows the modification of the photodiode which concerns on this embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Base | substrate, 1a ... Substrate layer, 1b ... Epitaxial layer, 2, 2a ... Low concentration buried layer, 3, 3a, 3b, 3c, 3d ... High concentration layer, 4 ... Lead-out part, 5, 5a-5c ... Silicon Thermal oxide film, 6, 7 ... Electrode, 10, 10a-10c ... Photodiode, 20a ... Substrate, 20b ... Shift register, 20c ... Read circuit, 20d ... Wire, 21-24 ... Photodiode array, 30 ... Spectroscope, 31 ... Optical fiber, 32... Incident part, 33... Diffraction grating part, 34... Mirror, 35.

Claims (9)

A substrate made of a semiconductor containing an impurity of the first conductivity type;
A low-concentration buried layer made of a semiconductor formed inside the substrate and containing an impurity of a second conductivity type different from the first conductivity type;
A high-concentration layer formed of a semiconductor formed in a region continuous with the low-concentration buried layer and containing the second conductivity type impurity in a higher concentration than the low-concentration buried layer;
The region extending from the surface of the substrate to the high concentration layer and formed so as to be bonded to the high concentration layer, and containing the second conductivity type impurity in a higher concentration than the low concentration buried layer. A photodiode having a lead portion made of a semiconductor.   2. The photodiode according to claim 1, wherein the low concentration buried layer has a substantially rectangular shape formed by two long sides and two short sides in a plan view.   3. The photodiode according to claim 2, wherein the high concentration layer is formed in a shape including one or a plurality of regions extending along a long side direction of the low concentration buried layer in a plan view.   The high-concentration layer is formed in a planar shape in which a region extending along a long side direction of the low-concentration buried layer is substantially parallel to the substrate surface in plan view. Photodiodes.   4. The photodiode according to claim 3, wherein the high-concentration layer has a linear region extending in a long side direction of the low-concentration buried layer in a plan view.   6. A photodiode array, wherein a plurality of the photodiodes according to claim 1 are arranged on a substrate surface.   A spectroscope comprising: a spectroscopic unit that splits incident light; and the photodiode array according to claim 6 that converts an amount of incident light after the splitting into an electric signal. A method of manufacturing a photodiode, wherein a region containing a second conductivity type impurity different from the first conductivity type is embedded in a substrate composed of a semiconductor containing a first conductivity type impurity,
An ion implantation step of ion-implanting the second conductivity type impurity ions into a first region inside the substrate and a second region formed continuously with the first region; In the process, a method of manufacturing a photodiode, wherein the second region is ion-implanted so that the impurity concentration is higher than that of the first region. The ion implantation step includes
Ion-implanting impurity ions of the second conductivity type into the first region;
Ion-implanting the second conductivity type impurity ions into the second region such that the impurity concentration is higher than that of the first region;
Ion-implanting the second conductivity type impurity ions into the third region communicating with the second region from the surface of the base so that the impurity concentration is substantially the same as that of the second region;
A method for producing a photodiode, further comprising:

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