JP5612407B2 - Semiconductor light receiving element and method for manufacturing semiconductor light receiving element - Google Patents

Description

  The present invention relates to a semiconductor light receiving element and a method for manufacturing the same.

Conventionally, as a light receiving element, a semiconductor light receiving element made of a laminate is known (for example, see Patent Document 1). The semiconductor light receiving element described in Patent Document 1 is a semiconductor light receiving element having a pin structure in which a non-doped layer is arranged between doped layers, and is produced by the following method. First, on an n-type semiconductor substrate (n-InP), an n-type optical confinement layer (n-AlInGaAs), an i-type light absorption layer (non-doped AlInGaAs), a p-type optical confinement layer (p-AlInGaAs), a p-type cladding layer After sequentially stacking (p-InP) and a p-type contact layer (p-GaInAsP), the n-type optical confinement layer is etched to form a mesa stripe. Then, the exposed surface of the semiconductor layer containing Al exposed on the side surface of the mesa stripe is oxidized and converted into an Al _x Oy region. As described above, in the semiconductor light-receiving element described in Patent Document 1, the Al _x O _y region having high electrical resistance is formed in the longitudinal direction of the mesa stripe side surface or the circumferential direction of the mesa post side surface, and dark current (leakage current) is generated. Is suppressed.

Japanese Patent Laid-Open No. 11-330531

However, in the semiconductor light receiving element described in Patent Document 1, since the light receiving portion (pin junction region) having a pin structure is formed by mesa etching, the exposed surface of the pin junction portion on the side surface of the mesa stripe or the side surface of the mesa post is etched. Crystal defects may occur. For this reason, even when the Al _x O _y region is formed, the leakage current may not be sufficiently suppressed.

  Accordingly, the present invention has been made to solve such a technical problem, and an object of the present invention is to provide a semiconductor light receiving element capable of suppressing leakage current and a method for manufacturing the semiconductor light receiving element. .

  That is, a semiconductor light receiving element according to the present invention is formed by laminating a first conductivity type substrate, a first conductivity type first semiconductor layer laminated on the substrate, and the first semiconductor layer or the first semiconductor layer. A second conductivity type second semiconductor layer containing Al and laminated on the non-doped light absorption layer; and a cap layer laminated on the second semiconductor layer, wherein a part of the cap layer is a second semiconductor. Etching is performed so as to expose the layer, and a part of the second semiconductor layer is oxidized from the exposed surface of the second semiconductor layer to the interface on the substrate side, whereby the second surrounded by the oxide region containing Al oxide. A conductive semiconductor region is formed.

  In the semiconductor light receiving element according to the present invention, a second conductive type second semiconductor layer containing Al and a cap layer are sequentially stacked on the first semiconductor layer or the light absorption layer so as to expose the second semiconductor layer. In addition, a part of the cap layer is etched, and the exposed second semiconductor layer is oxidized from the exposed surface to the interface on the substrate side. Thus, in the semiconductor light receiving element according to the present invention, the pn junction surface or the pi junction surface can be covered with the oxidized region without exposing the pn junction surface or the pi junction surface by etching. Then, the light receiving portion can be formed by surrounding the semiconductor region with the oxidized region. For this reason, since it can suppress that the crystal defect resulting from an etching generate | occur | produces in a pn junction surface or a pi junction surface, it becomes possible to aim at suppression of a leakage current.

  Here, the cap layer is preferably a second conductivity type semiconductor layer. With this configuration, the cap layer can function as a light receiving unit. The interface on the substrate side of the semiconductor region may be configured as a pn junction surface or a pi junction surface.

  Moreover, it is preferable that the semiconductor light receiving element has an electrode portion disposed on the upper surface side of the cap layer and in a position overlapping with the cap layer in the semiconductor lamination direction. By comprising in this way, it can avoid that an electrode part peels.

  A semiconductor light receiving element according to the present invention is laminated on a first conductive type substrate, a first conductive type first semiconductor layer laminated on the substrate, and on the first semiconductor layer or the first semiconductor layer. And a second conductive type second semiconductor layer containing Al, which is laminated on the non-doped light absorption layer, and the second semiconductor layer includes an oxidation region formed by oxidizing the contained Al, and an oxidation It is characterized by having a semiconductor region of the second conductivity type surrounded by the region and joined as a pn junction surface or a pi junction surface with the first semiconductor layer or the light absorption layer.

  According to the semiconductor light receiving element of the present invention, since the periphery of the second conductivity type semiconductor region is surrounded by the oxidized region formed by oxidizing the contained Al, etching for exposing the pn junction surface or the pi junction surface is performed. The light receiving portion can be formed without doing so. For this reason, since it can suppress that the crystal defect resulting from an etching generate | occur | produces in a pn junction surface or a pi junction surface, it becomes possible to aim at suppression of a leakage current.

  The method for manufacturing a semiconductor light receiving element according to the present invention includes a first semiconductor layer stacking step of stacking a first conductive type first semiconductor layer on a first conductive type substrate, and the first semiconductor layer stacking step. A second semiconductor layer stacking step of stacking a second conductivity type second semiconductor layer containing Al on the non-doped light absorption layer stacked on the semiconductor layer; and a cap layer on the second semiconductor layer. A cap layer stacking step, an etching step for etching a part of the cap layer so as to expose the second semiconductor layer, and a part of the second semiconductor layer from the exposed exposed surface of the second semiconductor layer to the interface on the substrate side And an oxidation step for oxidizing the material.

  In the method for manufacturing a semiconductor light receiving element according to the present invention, in the first semiconductor layer forming step, the first conductive type first semiconductor layer is stacked on the first conductive type substrate, and in the second semiconductor layer stacking step, A second conductivity type second semiconductor layer containing Al is laminated on the first semiconductor layer or the non-doped light absorption layer laminated on the first semiconductor layer, and the second semiconductor layer is formed on the second semiconductor layer in the cap layer lamination step. A cap layer is stacked on the substrate, and in the etching step, a part of the cap layer is etched to expose the second semiconductor layer, and in the oxidation step, the second semiconductor layer is exposed from the exposed surface of the second semiconductor layer to the interface on the substrate side. 2 A part of the semiconductor layer is oxidized. Thus, in the manufacturing method according to the present invention, the pn junction surface or the pi junction surface can be covered with the oxidized region without exposing the pn junction surface or the pi junction surface by etching. Therefore, for example, by forming the oxidized region in a ring shape, a semiconductor region surrounded by the oxidized region can be formed, so that the light receiving portion can be formed in the oxidizing step. For this reason, since it can suppress that the crystal defect resulting from an etching generate | occur | produces in a pn junction surface or a pi junction surface, it becomes possible to aim at suppression of a leakage current.

  The cap layer may be a second conductivity type semiconductor layer. By configuring in this way, it can function as a light receiving unit without removing the cap layer, so that it can be efficiently manufactured.

  According to the present invention, it is possible to suppress leakage current in a semiconductor light receiving element.

It is a top view which shows the structure of the semiconductor light receiving element which concerns on 1st Embodiment. It is a sectional side view in the II-II line of the semiconductor light receiving element of FIG. It is a schematic diagram explaining the manufacturing process of the semiconductor light receiving element of FIG. It is a schematic diagram explaining the manufacturing process of the semiconductor light receiving element of FIG. It is a schematic diagram explaining the manufacturing process of the semiconductor light receiving element of FIG. It is a schematic diagram explaining the oxidation area | region in case etching depth differs. It is a top view which shows the structure of the semiconductor light receiving element which concerns on 2nd Embodiment. FIG. 8 is a side sectional view of the semiconductor light receiving element of FIG. 7 taken along line VIII-VII. It is a schematic diagram explaining the manufacturing process of the semiconductor light receiving element of FIG. It is a schematic diagram explaining the manufacturing process of the semiconductor light receiving element of FIG. It is a schematic diagram explaining the manufacturing process of the semiconductor light receiving element of FIG. It is a top view which shows the structure of the modification of the semiconductor light receiving element which concerns on embodiment. It is a top view which shows the structure of the modification of the semiconductor light receiving element which concerns on embodiment.

  Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. In the description of the drawings, the same elements are denoted by the same reference numerals, and redundant description is omitted. Further, the dimensional ratios in the drawings do not necessarily match those described.

(First embodiment)
FIG. 1 is a top view showing a configuration of a semiconductor light receiving element according to an embodiment of the present invention, and FIG. 2 is a side sectional view taken along line II-II of the semiconductor light receiving element shown in FIG. The semiconductor light-receiving element 1 shown in FIGS. 1 and 2 is a compound semiconductor light-receiving element having a pin junction, and is suitably employed as a single element of, for example, a light receiver or a photodetector.

  As shown in FIG. 1, the semiconductor light receiving element 1 is a light receiving element formed of a stacked body having a semiconductor junction inside the element, and includes a light receiving unit 20. The light receiving unit 20 is formed in a mesa shape with a circular horizontal section, receives light from the upper surface side of the mesa unit, and makes the light enter the element. Here, a pin-junction laminate is employed as the semiconductor junction, and a photocurrent can be output by light incident inside the device. An oxide region 15 surrounding the periphery of the light receiving unit 20 is formed on the side of the light receiving unit 20.

  As shown in FIG. 2, the light receiving unit 20 is formed on the substrate 10. The substrate 10 is a semiconductor substrate, and for example, an n-type InAs substrate is used. Further, on one main surface of the substrate 10, there are a first semiconductor layer 11 having the same conductivity type as the substrate 10, a non-doped light absorption layer 12, and a second semiconductor layer 13 having a conductivity type different from that of the substrate 10. They are sequentially stacked. For example, n-type InAsSb is used as the first semiconductor layer 11, and i-type (non-doped) InAsSb is used as the light absorption layer 12, for example. The second semiconductor layer 13 is a group III-V compound semiconductor layer in which one of the elements constituting the semiconductor layer is Al. As the second semiconductor layer 13, for example, p-type AlInAsSb is used.

A part of the second semiconductor layer 13 is converted into an oxidized region 15 in which the contained Al is oxidized to increase the resistance. The oxidation region 15 containing Al _x O _y is formed in a ring shape, and a semiconductor region 13a that is pi-junctioned with the light absorption layer 12 is formed on the inner peripheral side of the oxidation region. That is, the region surrounded by the oxidized region 15 is the semiconductor region 13a. The semiconductor region 13a is one of the semiconductor layers constituting the light receiving unit 20 formed in a mesa shape, and is located on the lowermost side in the semiconductor layer constituting the light receiving unit 20. The oxidized region 15 is annularly etched so that a part of the cap layer 14 stacked on the second semiconductor layer 13 is exposed, and the substrate 10 side is exposed from the exposed surface of the second semiconductor layer 13. The second semiconductor layer 13 is formed by being oxidized up to the interface. The cap layer 14 is a semiconductor layer having the same conductivity type as the second semiconductor layer 13, and for example, p-type InPSb is used.

On the cap layer 14, an AR layer (Anti-Reflection coat) 16 for preventing reflection of incident light is formed. For example, SiN / Al ₂ O ₃ is used as the AR layer. The semiconductor region 13a, the cap layer 14, and the AR layer 16 described above constitute a mesa-shaped light receiving unit 20. As shown in FIGS. 1 and 2, an upper electrode portion 17 is formed on the upper surface side of the semiconductor light receiving element 1. The upper electrode portion 17 includes an annular electrode member 17a formed so as to surround the light receiving portion 20, and a bonding pad (electrode pad) 17b electrically connected to the electrode member 17a. The light receiving window portion 20a is formed on the upper surface side of the mesa portion by the annular electrode member 17a. The light receiving window portion 20 a is an opening having a circular horizontal cross section, and the radius thereof is smaller than the radius of the light receiving portion 20. Further, a lower electrode portion 18 is formed on the back surface which is the other main surface of the substrate 10. For example, Ti / Pt / Au is used as the upper electrode portion 17, and AuGe / Ni / Au is used as the lower electrode portion 18, for example.

  Next, effects of the semiconductor light receiving element 1 according to the present embodiment will be described. A voltage is applied to the semiconductor light receiving element 1 shown in FIG. 2 via the upper electrode portion 17 and the lower electrode portion 18 to apply a reverse bias to the pin junction of the semiconductor region 13a, the light absorption layer 12, and the first semiconductor layer 11. Thus, the depletion layer of the light absorption layer 12 is enlarged. In this state, when light enters the light receiving unit 20 and reaches the light absorption layer 12, an electron-hole pair is formed in the depletion layer and a photocurrent is generated. Here, the outer edge of the light receiving unit 20 is formed by an oxidation region 15 formed in an annular shape. That is, by forming the semiconductor layer 13 containing Al on the light absorption layer 12, the outer edge of the light receiving unit 20 is not physically formed by etching, but the chemical reaction causes the second semiconductor layer 13. The outer edge of the light receiving portion 20 can be formed by converting a part of the oxide region 15 to function as an insulating layer and electrically isolating the semiconductor region 13a. Therefore, the pn junction surface or the pi junction surface can be covered with the oxidized region 15 without exposing the pn junction surface or the pi junction surface by etching. The light receiving unit 20 can be formed by surrounding the semiconductor region 13 a with the oxidized region 15. For this reason, since it can suppress that the crystal defect resulting from an etching generate | occur | produces in a pn junction surface or a pi junction surface, it becomes possible to aim at suppression of a leakage current.

  Next, a method for manufacturing the semiconductor light receiving element 1 according to this embodiment will be described. 3 to 5 are side sectional views showing manufacturing steps of the semiconductor light receiving element 1 shown in FIG.

  First, as shown in FIG. 3A, a semiconductor layer forming step (first semiconductor stacking step, second semiconductor stacking step, cap layer stacking step) is performed. A pin junction structure is formed on the substrate 10 by an epitaxial growth technique. Epitaxial growth is performed by, for example, metal organic chemical vapor deposition (MOCVD) excellent in film thickness control or molecular beam epitaxy (MBE).

  When used as a substrate 10 having an n-type conductivity type, an n-type first semiconductor layer 11, an i-type light absorption layer 12, a p-type second semiconductor layer 13 containing Al, p on the substrate 10. The cap layer 14 of the mold is grown epitaxially in order. As described above, the second semiconductor layer 13 containing Al having a wide band gap is formed between the light absorption layer 12 and the cap layer 14. The composition and film thickness are, for example, that the substrate 10 is n-type InAs, 250 μm, the first semiconductor layer 11 is n-type InAsSb, 1.5 μm, the light absorption layer 12 is i-type InAsSb, 8.0 μm, and the second semiconductor layer. 13 is 0.1 μm of p-type AlInAsSb, and the cap layer 14 is 0.1 μm of p-type InPSb.

  Next, as shown in FIG. 3B, a mesa portion forming step (etching step) is performed. At least the cap layer 14 is etched so that the second semiconductor layer 13 is exposed on the upper surface, thereby forming a cylindrical mesa portion of the light receiving portion 20. At this time, as shown in the drawing, a part of the second semiconductor layer 13 may be etched together with the cap layer 14. First, a pattern of the light receiving unit 20 is created by a photowork, a resist is applied, and then etching and resist removal are performed, so that an annular opening 14 a is formed in the cap layer 14 and an annular opening 13 b is formed in the second semiconductor layer 13. Then, a mesa portion composed of the second semiconductor layer 13 and the cap layer 14 is formed. In order to form the mesa portion with good uniformity, a dry etching method is preferably used for the etching. Further, it may be performed by a wet etching method. Note that, by not removing the second semiconductor layer 13 and the cap layer 14 other than the mesa portion, it is possible to prevent peeling of the upper electrode portion 17 formed in a later step. That is, the second semiconductor layer 13 and the cap layer 14 that overlap the upper electrode portion 17 in the stacking direction are left without being removed.

  Next, as shown in FIG. 3C, an oxidation step (oxidation step) is performed. For example, by supplying water vapor in a high temperature atmosphere, the exposed second semiconductor layer 13 is oxidized to form the oxidized region 15. Here, the details of the oxidized region 15 will be described with reference to FIG. FIG. 6 is a schematic diagram showing the form of the oxidized region 15 when the etching depths are different. FIG. 6A shows that the exposed second semiconductor layer 13 is oxidized by etching only the cap layer 14. FIG. 6B shows a case where the exposed second semiconductor layer 13 is oxidized by etching a part of the second semiconductor layer 13 together with the cap layer 14. As shown in FIGS. 6A and 6B, in either case, the second semiconductor layer 13 is exposed from the exposed surface to the interface on the substrate 10 side (here, the interface with the light absorption layer 12). 2 A part of the semiconductor layer 13 is oxidized. Thus, the oxidized region 15 can reach the pi junction interface, and the inside of the oxidized region 15 can be used as the pi junction interface. For this reason, it becomes possible to suppress generation | occurrence | production of leak current.

Next, as shown in FIG. 4D, an AR layer forming step is performed. The composition and film thickness of the AR layer 16 are, for example, 0.8 μm with SiN / Al ₂ O ₃ . Next, as shown in FIG. 4E, a through hole forming step is performed. First, a resist is applied, an annular through-hole pattern is formed by photowork, and then etching and resist removal are performed to form the annular through-hole 16a so that a part of the cap layer 14 is exposed on the upper surface. Form. Next, as shown in FIG. 4F, an upper electrode forming step is performed. The upper electrode film is deposited by vapor deposition, and the annular electrode member 17a and the bonding pad 17b are formed by the lift-off method to form the upper electrode portion 17. Thereby, the light receiving window portion 20a of the light receiving portion 20 is formed. The composition and film thickness of the upper electrode part 17 are, for example, 1.2 μm for Ti / Pt / Au.

  Next, as shown in FIG. 5G, a substrate back surface polishing step is performed. The back surface 10a side of the substrate 10 is polished. Then, as shown in FIG. 5H, the lower electrode portion 18 is formed by vapor deposition on the polished back surface 10a side. The composition and film thickness of the lower electrode portion 18 are 0.7 μm, for example, AuGe / Ni / Au.

  3 to 5, the second semiconductor layer 13 containing Al is oxidized and reaches the pi junction interface without exposing the pi junction interface when the mesa portion of the light receiving unit 20 is formed. To do. Compared with the case where the pi junction surface and the ni junction surface are formed by etching, the damage to the pi junction surface and the ni junction surface is lower when the oxidized region 15 is formed. And since it can avoid that a crystal defect generate | occur | produces in a pi junction surface and a ni junction surface by an etching, it becomes possible to suppress a leak current appropriately. Thus, since the light receiving portion 20 can be formed by shallower etching than in the prior art, it is particularly effective when the semiconductor light receiving element 1 is employed as a single element that does not need to be isolated.

  As described above, in the method of manufacturing the semiconductor light receiving element 1 according to the first embodiment, in the semiconductor layer forming step, the n-type first semiconductor layer 11, the non-doped light absorption layer 12, and Al are formed on the n-type substrate 10. P-type second semiconductor layer 13 containing p-type and p-type cap layer 14 are sequentially stacked, and a part of cap layer 14 is etched so that second semiconductor layer 13 is exposed on the upper surface side in the mesa portion forming step. In the oxidation step, a part of the second semiconductor layer 13 is oxidized from the exposed exposed surface of the second semiconductor layer 13 to the interface on the substrate 10 side. Thus, the pn junction surface or the pi junction surface can be covered with the oxidized region 15 without exposing the pn junction surface or the pi junction surface by etching. Then, by forming the oxidized region 15 in an annular shape, the semiconductor region 13a surrounded by the oxidized region 15 can be formed, so that the light receiving portion 20 can be formed in the oxidizing step. For this reason, since it can suppress that the crystal defect resulting from an etching generate | occur | produces in a pn junction surface or a pi junction surface, it becomes possible to aim at suppression of a leakage current.

(Second Embodiment)
Next, a second embodiment of the present invention will be described. FIG. 7 is a top view showing the configuration of the semiconductor light receiving element according to the embodiment of the present invention, and FIG. 8 is a side sectional view of the semiconductor light receiving element shown in FIG. The semiconductor light receiving element 2 shown in FIGS. 7 and 8 is configured in substantially the same manner as the semiconductor light receiving element 1 according to the first embodiment, and is mainly different in the shape of the upper electrode portion 17 and the material of the semiconductor layer. In the following, in consideration of the ease of understanding, the description overlapping with the semiconductor light receiving element 1 is omitted, and the description will focus on the differences.

  As shown in FIGS. 7 and 8, the semiconductor light receiving element 2 is a light receiving element made of a laminated body having a semiconductor junction inside the element, and the light receiving part 20 is formed on the substrate 10. An oxide region 15 surrounding the periphery of the light receiving unit 20 is formed on the side of the light receiving unit 20. Similar to the semiconductor light receiving element 1, a first semiconductor layer 11, a non-doped light absorption layer 12, and a second semiconductor layer 13 containing Al are sequentially stacked on one main surface of the substrate 10. For example, n-type InP is used as the substrate 10, n-type InP is used as the first semiconductor layer 11, and i-type InGaAs is used as the light absorption layer 12, for example. As the layer 13, for example, p-type InAlAs is used.

A part of the second semiconductor layer 13 is converted into an oxidized region 15 in which the contained Al is oxidized to increase the resistance. The oxidized region 15 containing Al _x O _y is formed so as to surround a circular region along the pattern of the light receiving portion 20, and a semiconductor region 13 a that is surrounded by the oxidized region 15 and pi-junction with the light absorption layer 12 is formed. Is formed. The semiconductor region 13a is one of the semiconductor layers constituting the light receiving unit 20 formed in a mesa shape, and is located on the lowermost side in the semiconductor layer constituting the light receiving unit 20. The oxidized region 15 is etched so that a part of the cap layer 14 laminated on the second semiconductor layer 13 exposes the second semiconductor layer 13, and the interface from the exposed surface of the second semiconductor layer 13 to the substrate 10 side is etched. The second semiconductor layer 13 is formed by being partially oxidized. The cap layer 14 is a semiconductor layer having the same conductivity type as that of the second semiconductor layer 13, and for example, p-type InP is used.

An AR layer 16 for preventing reflection of incident light is formed on the cap layer 14. The semiconductor region 13a, the cap layer 14, and the AR layer 16 described above constitute a mesa-shaped light receiving unit 20. Further, an upper electrode portion 17 is formed on the upper surface side of the semiconductor light receiving element 1. The upper electrode portion 17 is formed so as to surround the light receiving portion 20, and a light receiving window portion 20a is formed on the upper surface side of the mesa portion. Further, a lower electrode portion 18 is formed on the back surface which is the other main surface of the substrate 10. For example, SiN / Al ₂ O ₃ is used as the AR layer 16, Ti / Pt / Au is used as the upper electrode portion 17, and AuGe / Ni / Au is used as the lower electrode portion 18, for example.

  The operational effects of the semiconductor light receiving element 2 according to the present embodiment are the same as those of the semiconductor light receiving element 1 according to the first embodiment.

  Next, a method for manufacturing the semiconductor light receiving element 2 according to this embodiment will be described. 9 to 11 are side cross-sectional views showing manufacturing steps of the semiconductor light receiving element 2 shown in FIG.

  First, as shown in FIG. 9A, a semiconductor layer forming step (first semiconductor stacking step, second semiconductor stacking step, cap layer stacking step) is performed. This process is the same as that described in the first embodiment, and only the material of the semiconductor layer is different. The composition and film thickness are, for example, that the substrate 10 is n-type InP, 250 μm, the first semiconductor layer 11 is n-type InP, 1.5 μm, the light absorption layer 12 is i-type InGaAs, 8.0 μm, and the second semiconductor layer. 13 is 0.1 μm of p-type InAlAs, and the cap layer 14 is 0.1 μm of p-type InP.

  Next, as shown in FIG. 9B, a mesa portion forming step (etching step) is performed. At least the cap layer 14 is etched so that the second semiconductor layer 13 is exposed on the upper surface, thereby forming a cylindrical mesa portion of the light receiving portion 20. At this time, as shown in the drawing, a part of the second semiconductor layer 13 may be etched together with the cap layer 14. First, a resist is applied, a pattern of the light receiving portion 20 is created by a photowork, and then a mesa portion including the second semiconductor layer 13 and the cap layer 14 is formed by performing etching and resist removal.

Next, as shown in FIG. 9C, an oxidation step (oxidation step) is performed. This step is performed in the same manner as described in the first embodiment. Next, as shown in FIG. 10D, an AR layer forming step is performed. The composition and film thickness of the AR layer 16 are, for example, 0.8 μm with SiN / Al ₂ O ₃ . Next, as shown in FIG. 10E, a through hole forming step is performed. This step is performed in the same manner as described in the first embodiment. Next, as shown in FIG. 10F, an upper electrode forming step is performed. The upper electrode film is laminated by vapor deposition, and the upper electrode portion 17 is formed by a lift-off method. Thereby, the light receiving window portion 20a of the light receiving portion 20 is formed. The composition and film thickness of the upper electrode part 17 are, for example, 1.2 μm for Ti / Pt / Au.

  Next, as shown in FIG. 11G, a substrate back surface polishing step is performed. This step is performed in the same manner as described in the first embodiment. Then, as shown in FIG. 10H, the lower electrode portion 18 is formed by vapor deposition on the polished back surface 10a side. The composition and film thickness of the lower electrode portion 18 are 0.7 μm, for example, AuGe / Ni / Au.

  9 to 11, the second semiconductor layer 13 containing Al is oxidized and reaches the pi junction interface without exposing the pi junction interface when the mesa portion of the light receiving unit 20 is formed. To do. Compared with the case where the pi junction surface and the ni junction surface are formed by etching, the damage to the pi junction surface and the ni junction surface is lower when the oxidized region 15 is formed. And since it can avoid that a crystal defect generate | occur | produces in a pi junction surface and a ni junction surface by an etching, it becomes possible to suppress a leak current appropriately. As described above, since the light receiving portion 20 can be formed by shallower etching than in the prior art, it is particularly effective when the semiconductor light receiving element 2 is employed as a single element that does not need to be isolated.

  As described above, in the method of manufacturing the semiconductor light receiving element 2 according to the second embodiment, as in the semiconductor light receiving element 1 according to the first embodiment, the pn junction surface or the pi junction surface is not exposed by etching. The junction surface or the pi junction surface can be covered with the oxidized region 15. Therefore, since the semiconductor region 13a surrounded by the oxidized region 15 can be formed, the light receiving portion 20 can be formed in the oxidizing step. For this reason, since it can suppress that the crystal defect resulting from an etching generate | occur | produces in a pn junction surface or a pi junction surface, it becomes possible to aim at suppression of a leakage current.

  In addition, embodiment mentioned above shows an example of the semiconductor light receiving element which concerns on this invention. The semiconductor light receiving element according to the present invention is not limited to the semiconductor light receiving element according to each embodiment, and the semiconductor light receiving element according to each embodiment may be modified or applied to other ones.

  For example, in the above-described embodiment, the semiconductor light receiving element in which the shape of the light receiving unit 20 is a cylindrical shape has been described. However, the horizontal cross section of the light receiving unit 20 is not limited to a circular shape. For example, FIG. A rectangular shape may be used like the light receiving portion 20 of the semiconductor light receiving elements 3 and 4 shown.

  In the above-described embodiment, an example in which the upper electrode portion 17 has an electrode shape surrounding the light receiving portion 20 has been described. However, the embodiment is not limited to the electrode shape. The electrode shape in which the upper electrode portion 17 surrounds the light receiving portion 20 is desirable from the viewpoint of uniformity.

  In the above-described embodiment, an example in which a semiconductor layer is used as the cap layer 14 has been described. However, the cap layer 14 may not be a semiconductor layer as long as it is removed after the oxidation step.

  In the above-described embodiment, the semiconductor light receiving element having a pin junction has been described. However, for example, a p-type second semiconductor that does not include the light absorption layer 12 and contains Al on the n-type first semiconductor layer 11. A semiconductor light receiving element having a pn junction surface in which the layer 13 is directly laminated may be used. Even in such a configuration, it is possible to suppress the leakage current by forming the oxidized region 15.

  In the above-described embodiment, the example in which the second semiconductor layer is the second conductivity type has been described. However, not all the thickness directions may be the second conductivity type. For example, the portion close to the light absorption layer of the second semiconductor layer may be non-doped as long as the depletion layer has a thickness that reaches the light absorption layer. In this case, it is preferable because no band discontinuity occurs.

  Furthermore, in the above-described embodiment, the semiconductor light-receiving element using the n-type substrate 10 has been described. However, in the semiconductor light-receiving element configured by switching the n-type and the p-type of the embodiment using the p-type substrate. Even in the case of application, leakage current can be suppressed.

  DESCRIPTION OF SYMBOLS 1 ... Semiconductor light receiving element, 10 ... Board | substrate, 11 ... 1st semiconductor layer, 12 ... Light absorption layer, 13 ... 2nd semiconductor layer, 13a ... Semiconductor region, 14 ... Cap layer, 15 ... Oxidation region, 20 ... Light-receiving part.

Claims (7)

A semiconductor light receiving element,
A first conductivity type substrate;
A first semiconductor layer of a first conductivity type stacked on the substrate;
A second conductive type second semiconductor layer containing Al and laminated on the first semiconductor layer or a non-doped light absorption layer laminated on the first semiconductor layer;
A cap layer laminated on the second semiconductor layer;
With
A portion of the cap layer is etched to expose the second semiconductor layer, and a portion of the second semiconductor layer is oxidized from the exposed surface of the second semiconductor layer to the interface on the substrate side, A second conductivity type semiconductor region surrounded by an oxide region containing Al oxide is formed;
A semiconductor light receiving element characterized by the above.   The semiconductor light receiving element according to claim 1, wherein the cap layer is a second conductivity type semiconductor layer.   The semiconductor light receiving element according to claim 1, wherein an interface of the semiconductor region on the substrate side is configured as a pn junction surface or a pi junction surface. Having an electrode portion disposed on the upper surface side of the cap layer and in a position overlapping the cap layer in the semiconductor lamination direction;
The semiconductor light receiving element according to claim 1, wherein A semiconductor light receiving element,
A first conductivity type substrate;
A first semiconductor layer of a first conductivity type stacked on the substrate;
A second conductive type second semiconductor layer containing Al and laminated on the first semiconductor layer or a non-doped light absorption layer laminated on the first semiconductor layer;
With
The second semiconductor layer is surrounded by an oxidized region in which contained Al is oxidized and the oxidized region, and is joined to the first semiconductor layer or the light absorbing layer as a pn junction surface or a pi junction surface. Having a semiconductor region of two conductivity types;
A semiconductor light receiving element characterized by the above. A method of manufacturing a semiconductor light receiving element,
A first semiconductor layer laminating step of laminating a first conductive type first semiconductor layer on a first conductive type substrate;
A second semiconductor layer stacking step of stacking a second conductive type second semiconductor layer containing Al on the first semiconductor layer or on the non-doped light absorption layer stacked on the first semiconductor layer;
A cap layer stacking step of stacking a cap layer on the second semiconductor layer;
An etching step of etching a part of the cap layer so as to expose the second semiconductor layer;
An oxidation step of oxidizing a part of the second semiconductor layer from the exposed exposed surface of the second semiconductor layer to the interface on the substrate side;
A method for manufacturing a semiconductor light-receiving element.   The method of manufacturing a semiconductor light receiving element according to claim 6, wherein the cap layer is a second conductivity type semiconductor layer.

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