JP2021027321A - Light-receiving element unit - Google Patents

Abstract

To provide a light-receiving element unit in which two light-receiving elements are stacked to be miniaturized.SOLUTION: A light-receiving element unit 1 includes a first light-receiving element 10 having a first light-receiving region on a main surface side of a first semiconductor substrate, a second light-receiving element 20 having a second light-receiving region on a main surface side of a second semiconductor substrate, and a support substrate 2 having wiring for electrically connecting the first light-receiving element and the second light-receiving element to the outside. Of the first light-receiving element and the second light-receiving element, one of them has a recess 16 formed in a concave shape from a back side opposite to the light-receiving region toward the light-receiving region side, and the other one is housed in the recess.SELECTED DRAWING: Figure 3

Description

The present invention relates to a light receiving element unit having two types of light receiving elements that convert light in different wavelength ranges into an electric signal in order to detect light having a wide range of wavelengths.

Conventionally, in order to detect light having a wide range of wavelengths and convert it into an electric signal, a light receiving element unit having a plurality of light receiving elements having different wavelengths to be detected has been used. Such a light receiving element unit is formed by arranging a plurality of light receiving elements on a support substrate, for example, and the incident axis of the incident light is different for each light receiving element. In optical communication using an optical fiber, optical signals having different wavelengths are transmitted via the same optical fiber and emitted from the receiving end of the optical fiber. When the above-mentioned light receiving element unit is used for this optical communication, it is separated by wavelength and incident on the corresponding light receiving element.

A light receiving element unit having a plurality of light receiving elements has a large width (area) when the light receiving elements are arranged side by side, and a mechanism for spectroscopy is also required. .. Therefore, for example, as in Patent Documents 1 and 2, there is known a technique in which two light receiving elements are superposed so that light transmitted through one light receiving element is incident on the other light receiving element.

Japanese Unexamined Patent Publication No. 2011-192873 Japanese Unexamined Patent Publication No. 2019-12713

However, as in Patent Documents 1 and 2, when two light receiving elements are overlapped, the thickness increases, so that the light receiving element unit also becomes large. Therefore, it is conceivable to suppress an increase in the thickness when the two light receiving elements, which have been thinned by processing such as polishing, are overlapped with each other.

Here, when two light receiving elements are overlapped, the light transmitted through the first light receiving element on the incident side of the light is converted into an electric signal by the second light receiving element on the opposite side to the incident side. The light receiving element for a wavelength longer than that of the first light receiving element becomes the second light receiving element. That is, the first light receiving element is a light receiving element for a short wavelength range of the light receiving wavelength range of the light receiving element unit, and the second light receiving element is for a long wavelength range that is transmitted without being absorbed by the first light receiving element. It is a light receiving element of.

For example, when a silicon substrate is used for the first light receiving element and an indium phosphide substrate is used for the second light receiving element, or a gallium nitride based substrate is used for the first light receiving element, the second light receiving element is used. May use a silicon substrate. As a result, the first light receiving element receives the incident light on the short wavelength side, and the second light receiving element receives the incident light on the long wavelength side transmitted through the first light receiving element.

A light receiving element using an indium phosphide substrate or a gallium nitride based substrate has a higher manufacturing cost than a light receiving element using a silicon substrate, and therefore it is desired to reduce the size (area). On the other hand, since there is a high possibility that a defect such as a crack may occur in the light receiving element due to the thinning process of thinning the substrate, it is required that one of the first and second light receiving elements is not thinned very much or at all. In some cases. In this case, even if the first and second light receiving elements are stacked, the thickness cannot be sufficiently suppressed, so that it is not easy to reduce the size.

An object of the present invention is to provide a light receiving element unit in which two light receiving elements are overlapped and miniaturized.

The light receiving element unit of the invention of claim 1 has a first light receiving element having a first light receiving region on the main surface side of the first semiconductor substrate, and a second light receiving element having a second light receiving region on the main surface side of the second semiconductor substrate. In a light receiving element unit including the light receiving element, the first light receiving element, and a support substrate that supports the second light receiving element, one of the first light receiving element and the second light receiving element is the same. It has a recess formed concavely from the back surface opposite to the main surface toward the first or second light receiving region side, the other is housed in the recess, and the first light receiving region is light in the first wavelength region. The second light receiving region is characterized by converting a signal into an electric signal and converting an optical signal in a second wavelength region different from the first wavelength region into an electric signal.

According to the above configuration, the light receiving element unit has a first light receiving element and a second light receiving element, and one of them is a concave portion formed in a concave shape from the back surface opposite to the main surface toward the light receiving region. The other is housed in the recess, the first light receiving region of the first light receiving element converts an optical signal in the first wavelength region into an electric signal, and the second light receiving region of the second light receiving element is the second. An optical signal in a second wavelength region different from the one wavelength region is converted into an electric signal.
Therefore, in order to receive light in a wide wavelength range including the first and second wavelength regions, two light receiving elements are overlapped, and the thickness can be suppressed by the recesses to reduce the size of the light receiving element unit.

In the invention of claim 1, the light receiving element unit of the second aspect of the invention is the first light receiving element and the second light receiving element, the light transmitted through the first light receiving region of the first light receiving element is the light transmitted through the first light receiving region. It is characterized in that it is arranged so as to be incident on the second light receiving region of the second light receiving element.
According to the above configuration, the light receiving element unit can receive incident light having different wavelengths without being separated, so that the light receiving element unit can be miniaturized.

The light receiving element unit of the invention of claim 3 is characterized in that, in the invention of claim 2, the first light receiving element has antireflection layers on the inlet side and the outlet side of the incident light, respectively.
According to the above configuration, the reflection of the incident light of the first light receiving element on the inlet side is suppressed to secure the light receiving amount of the first and second light receiving elements, and the exit of the incident light transmitted through the first light receiving element. It is possible to suppress the reflection of light on the side and secure the amount of light received by the second light receiving element.

In the invention of any one of claims 1 to 3, the light receiving element unit of the invention of claim 4 has the recess, and the recess side is fixed to the support substrate. The second light receiving element has an electrode on the main surface side of the second semiconductor substrate, and the electrode is fixed to a wiring formed on the support substrate by a solidified conductive member.
According to the above configuration, the second light receiving element can be accommodated in the recess of the first light receiving element to reduce the size of the light receiving element unit, and at the same time, the second light receiving element is fixed to the support substrate. Since it is electrically connected to the wiring formed on the support substrate, the formation of the light receiving element unit can be facilitated.

According to the light receiving element unit of the present invention, the light receiving element unit is miniaturized by stacking the first and second light receiving elements by accommodating the other in the recess formed in one of the first and second light receiving elements. be able to.

It is a perspective view of the light receiving element unit which concerns on Examples 1 and 2 of this invention. It is a top view of the light receiving element unit which concerns on Example 1. FIG. FIG. 2 is a sectional view taken along line III-III of FIG. It is a top view of the light receiving element unit which concerns on Example 2. FIG. FIG. 5 is a sectional view taken along line VV of FIG. It is a perspective view of the light receiving element unit which concerns on Example 3 of this invention. It is a top view of the light receiving element unit which concerns on Example 3. FIG. FIG. 7 is a cross-sectional view taken along the line VIII-VIII of FIG.

Hereinafter, embodiments for carrying out the present invention will be described based on examples.

FIG. 1 shows the appearance of the light receiving element unit 1, FIG. 2 shows a main part of the light receiving element unit 1 as viewed from the direction in which light is incident, and FIG. 3 shows a cross section of the main part of the light receiving element unit 1. As shown in FIGS. 1 to 3, the light receiving element unit 1 has a support substrate 2, a first light receiving element 10, and a second light receiving element 20 housed in a recess 16 of the first light receiving element 10. A plurality of wirings 3a to 3c for electrically connecting the first light receiving element 10 and the second light receiving element 20 to the outside are formed on the support substrate 2, and each of these wirings 3a to 3c is connected to the outside. Pad portions 4a to 4c for connection are formed. The incident light is incident on the first light receiving element 10 from the side opposite to the support substrate 2.

The first light receiving element 10 will be described.
The first light receiving element 10 has a first light receiving region 12 on the main surface side of, for example, a silicon substrate (hereinafter abbreviated as Si substrate) 11 as a first semiconductor substrate, and is a photo that mainly receives incident light in the visible light region. It is a diode. The Si substrate 11 is, for example, n-type, and a p-type diffusion region 12a doped with boron, for example, is formed on the main surface side of the n-type Si substrate 11 which is the inlet side of the incident light, and the main surface is predetermined. It is covered with an antireflection layer 13 having a thickness (for example, a silicon nitride film or a silicon oxide film having a thickness of 160 nm). The material and thickness of the antireflection layer 13 are appropriately set.

An electrode material mainly containing, for example, aluminum or gold is selectively deposited in a predetermined region including an opening formed in the antireflection layer 13 so as to communicate with the p-type diffusion region 12a to form the first anode electrode 14. Has been done. The exposed back surface of the n-type Si substrate 11 opposite to the main surface serves as the first cathode electrode 15. The first anode electrode 14 is connected to the corresponding wiring 3b of the support substrate 2 by, for example, a gold wire 5 (conductive wire). The first cathode electrode 15 is fixed to the corresponding wiring 3c of the support substrate 2 by a conductive member 17 (for example, a conductive adhesive containing silver particles, eutectic solder, gold bumps, etc.) solidified by drying or cooling. And is also electrically connected.

Although not shown, the first cathode electrode 15 may be doped with phosphorus, for example, to reduce the resistance on the back surface side of the Si substrate 11, and is formed by mainly adhering an electrode material containing aluminum or gold. You may be. Further, although not shown, the first cathode electrode connected to the main surface of the n-type Si substrate 11 outside the p-type diffusion region 12a via the opening formed in the antireflection layer 13 is gold. It may be connected to the corresponding wiring 3c by a wire or the like.

The vicinity of the pn junction formed by the n-type Si substrate 11 and the p-type diffusion region 12a is the first light receiving region 12, and the incident light (optical signal) is converted into electric charges. This electric charge is transmitted to the outside as an electric current (electrical signal) via the first anode electrode 14 and the first cathode electrode 15. The vertical and horizontal widths of the first light receiving region 12 are, for example, about 2000 μm and the depth is about 10 μm, which are appropriately set. Further, the first light receiving element 10 is formed into a rectangle having a side of, for example, about 3 mm, and its thickness is, for example, about 250 to 400 μm without being thinned too much or at all.

The main surface of the Si substrate 11 is the Si (100) surface. The Si substrate 11 is provided with a recess 16 formed in a concave shape inward of the Si substrate 11 from a surface (back surface) opposite to the p-type diffusion region 12a toward the first light receiving region 12 side. An antireflection layer 18 having a predetermined thickness (for example, a silicon nitride film or a silicon oxide film having a thickness of 250 nm) is also formed on the inner surface of the recess 16 on the outlet side of the incident light transmitted through the first light receiving element 10. Has been done. These antireflection layers 13 and 18 also function as an insulating protective layer.

The recess 16 is formed by selectively etching a region corresponding to the first light receiving region 12 from the back surface of the Si substrate 11. Although not shown, an etching mask having an opening in a region corresponding to the first light receiving region 12 is formed on the back surface of the Si substrate 11, and Si is used as an etching solution using an alkaline aqueous solution (for example, a KOH aqueous solution or a TMAH aqueous solution). It is formed by etching the substrate 11.

At this time, the back surface of the Si substrate 11 is a Si (100) surface, and as the etching progresses, the Si (100) surface inside the Si substrate 11 is exposed. On the other hand, in the vicinity of the boundary with the region covered by the etching mask, the Si (111) surface, which has a slower etching rate than the Si (100) surface, is exposed as the etching progresses, and the peripheral wall of the recess 16 becomes inclined. .. The recess 16 is formed in a quadrangular pyramid shape by anisotropic etching utilizing the difference in etching rate. The recess 16 is formed to a depth of, for example, about 200 μm, and this depth is easily controlled by the etching time.

The second light receiving element 20 will be described.
The second light receiving element 20 has a second light receiving region 22 on the main surface side of, for example, an indium phosphide substrate (hereinafter, abbreviated as InP substrate) 21 as a second semiconductor substrate, and the first light receiving element 10 of the first light receiving element 10. It is a photodiode that receives incident light in the infrared light region that has passed through the light receiving region 12. The vertical and horizontal widths of the second light receiving element 20 are smaller than the vertical and horizontal widths of the recess 16 of the first light receiving element 10, and the thickness thereof is smaller than the depth of the recess 16. The second light receiving element 20 is housed in the recess 16. For example, the second light receiving element 20 is formed in a rectangular shape having a side of about 1 mm and is thinned to have a thickness of about 150 μm.

The InP substrate 21 is, for example, n-type, and a p-type region 22a mainly composed of, for example, InGaAs is formed on the main surface side of the InP substrate 21. This main surface is covered with an antireflection layer 23 having a predetermined thickness (for example, a silicon nitride film or a silicon oxide film having a thickness of 250 nm), and the back surface opposite to the main surface is also covered with the same antireflection layer 28. ing.

An opening is provided in each of the antireflection layers 23 so as to communicate with the second light receiving region 22 and the InP substrate 21 outside the second light receiving region 22, and an electrode material mainly containing, for example, aluminum or gold is provided in each predetermined region including the opening. The second anode electrode 24 and the second cathode electrode 25 are formed by being selectively deposited.

The second anode electrode 24 and the second cathode electrode 25 are supported by a conductive member 27 (for example, a conductive adhesive containing silver particles, eutectic solder, gold bumps, etc.) solidified by drying or cooling. It is fixed to the corresponding wires 3a and 3c. As a result, the second light receiving element 20 is fixed to the support substrate 2 and electrically connected. Since physical fixing and electrical connection are performed at the same time, the light receiving element unit 1 can be easily formed. Although not shown, the back surface side of the second light receiving element 20 is fixed to the support substrate 2 with an adhesive or the like, and the second anode electrode 24 and the second cathode electrode 25 are connected to the corresponding wirings 3a and 3c with gold wires. It may be connected by such as.

The vicinity of the pn junction formed by the n-type InP substrate 21 and the p-type region 22a is the second light receiving region 22, and the incident light is converted into electric charges. This electric charge is transmitted to the outside as an electric current (electrical signal) via the second anode electrode 24 and the second cathode electrode 25. The vertical and horizontal widths of the second light receiving region 22 are, for example, about 800 μm, and the depth is about 10 μm, which are appropriately set. The second light receiving element 20 may be a PIN photodiode.

The support substrate 2 will be described.
The support substrate 2 is, for example, a ceramic substrate or a printed circuit board, and a plurality of exposed wirings 3a to 3c are formed in portions where the electrodes of the first and second light receiving elements 10 and 20 are fixed. These plurality of wirings 3a to 3c can be easily electrically connected to the first and second anode electrodes 14 and 24 and the first and second cathode electrodes 15 and 25 of the first and second light receiving elements 10 and 20 from the outside. It is formed so that it can be connected, and is provided with pad portions 4a to 4c for connection with the outside.

The second light receiving element 20 is fixed to the support substrate 2, the first light receiving element 10 is fixed to the support substrate 2 so as to accommodate the second light receiving element 20 in the recess 16, and the light receiving element unit 1 is It is formed. As a result, the first light receiving element 10 and the second light receiving element 20 are arranged so that the light transmitted through the first light receiving region 12 is incident on the second light receiving region 22.

In the light receiving element unit 1, light is incident on the first light receiving element 10 from the side opposite to the support substrate 2, and in the first light receiving element 10, for example, the wavelength in the visible light region to the infrared light region is 400 to 1000 nm. Light in the region (optical signal in the first wavelength region) is converted into an electric current and transmitted to the outside as an electric signal. Then, light that passes through the first light receiving element 10, for example, in a wavelength region of 1000 to 1600 nm (optical signal in the second wavelength region) is incident on the second light receiving element 20, and this light is emitted by the second light receiving element. At 20, it is converted into an electric current and transmitted to the outside as an electric signal.

That is, the light receiving element unit 1 converts the incident signals contained in the incident light having significantly different wavelengths into electric signals without separation or filtering. Since the second light receiving element 20 is housed in the recess 16 of the first light receiving element 10, the light receiving element unit 1 is downsized to the same size as the light receiving unit having only the first light receiving element 10. In addition, the second light receiving element 20 can be made smaller to reduce the manufacturing cost of the light receiving element unit 1. The light receiving element unit 1 is housed in a case (not shown) provided with a plurality of terminals connected to a plurality of pad portions 4a to 4c of the support substrate 2, a window for light incident, and the like. Used for optical communication, etc.

The second embodiment, which is a partial modification of the first embodiment, will be described with reference to FIGS. 1, 4, and 5. FIG. 4 shows a main part of the light receiving element unit 1 as viewed from the direction in which light is incident, and FIG. 5 shows a cross section of the main part of the light receiving element unit 1. Since the first and second light receiving elements 10 and 20 are the same light receiving elements as those in the first embodiment, they are designated by the same reference numerals as those in the first embodiment and the description thereof will be omitted. In the first light receiving element 10, the second anode electrode 24 and the second cathode electrode 25 of the second light receiving element 20 are provided on the inner surface of the recess 16 and the back surface of the Si substrate 11, and the corresponding wiring 3a of the supporting substrate 2 is provided. Two intermediate wires 31 and 32 for connecting to each of the 3c are formed. The intermediate wirings 31 and 32 are formed by selectively depositing a wiring material mainly containing, for example, aluminum or gold on the antireflection layer 18.

The second anode electrode 24 and the second cathode electrode 25 of the second light receiving element 20 are fixed to the corresponding intermediate wirings 31 and 32 of the first light receiving element 10 by the conductive member 27, respectively. As a result, the second light receiving element 20 is fixedly accommodated in the recess 16 of the first light receiving element 10 and is electrically connected to the intermediate wirings 31 and 32. Further, the light transmitted through the first light receiving region 12 is arranged so as to enter the second light receiving region 22.

The first cathode electrode 15 of the first light receiving element 10 in which the second light receiving element 20 is housed in the recess 16 is electrically fixed to the corresponding wiring 3c of the support substrate 2 by the conductive member 17. Be connected. At this time, the intermediate wirings 31 and 32 are also fixed to the corresponding wirings 3a and 3c by the conductive member 17, and are electrically connected to each other.

Then, the first anode electrode 14 of the first light receiving element 10 is connected to the corresponding wiring 3b of the support substrate 2 by, for example, a gold wire 5, to form the light receiving element unit 1. Since the second light receiving element 20 is housed in the recess 16 of the first light receiving element 10, the light receiving element unit 1 is downsized to the same size as the light receiving unit having only the first light receiving element 10. In addition, the second light receiving element 20 can be made smaller to reduce the manufacturing cost of the light receiving element unit 1.

FIG. 6 shows the appearance of the light receiving element unit 101, FIG. 7 shows a main part of the light receiving element unit 101 as viewed from the direction in which light is incident, and FIG. 8 shows a cross section of the main part of the light receiving element unit 101. As shown in FIGS. 6 to 8, the light receiving element unit 101 has a support substrate 102, a first light receiving element 110, and a second light receiving element 120 in which the first light receiving element 110 is housed in the recess 126. A plurality of wirings 103a to 103c for connecting to the first light receiving element 110 and the second light receiving element 120 are formed on the support substrate 102, and each of these wirings 103a to 103c has a pad portion for connecting to the outside. 104a to 104c are formed. The incident light is incident on the first light receiving element 110 from the side opposite to the support substrate 102.

The first light receiving element 110 will be described.
The first light receiving element 110 is a photodiode having a first light receiving region 112 on the main surface side of, for example, a Si substrate 111 as a first semiconductor substrate, and mainly receives incident light in the visible light region. The Si substrate 111 is, for example, n-type, and a p-type diffusion region 112a doped with boron, for example, is formed on the main surface side of the n-type Si substrate 111 which is the inlet side of the incident light.

The vertical and horizontal widths of the first light receiving element 110 are smaller than the vertical and horizontal widths of the recess 126 of the second light receiving element 120, and the thickness thereof is smaller than the depth of the recess 126. The first light receiving element 110 is housed in the recess 126. For example, the first light receiving element 110 is formed in a rectangular shape having a side of about 1 mm, and is thinned to have a thickness of about 150 μm.

The main surface on the inlet side of the incident light and the back surface on the outlet side of the incident light transmitted through the first light receiving element 110 are antireflection layers 113, 118 having a predetermined thickness (for example, a silicon nitride film having a thickness of 160 nm or silicon oxidation). It is covered with a film, etc.). These antireflection layers 113 and 118 also function as an insulating protective layer. The materials and thicknesses of the antireflection layers 113 and 118 are appropriately set.

An opening is provided in each of the antireflection layer 113 so as to communicate with the p-type diffusion region 112a and the Si substrate 111 on the outside thereof. An electrode material mainly containing, for example, aluminum or gold is selectively deposited in each predetermined region including these openings to form a first anode electrode 114 and a first cathode electrode 115.

The vicinity of the pn junction formed by the n-type Si substrate 111 and the p-type diffusion region 112a is the first light receiving region 112, and the incident light (optical signal) is converted into electric charges. This electric charge is transmitted to the outside as a current (electrical signal) via the first anode electrode 114 and the first cathode electrode 115. The vertical and horizontal widths of the first light receiving region 112 are, for example, about 800 μm and the depth is about 10 μm, which are appropriately set.

The second light receiving element 120 will be described.
The second light receiving element 120 has, for example, a second light receiving region 122 on the main surface side of the InP substrate 121 as the second semiconductor substrate, and is an infrared light region transmitted through the first light receiving region 112 of the first light receiving element 110. It is a photodiode that receives the incident light of. The thickness of the second light receiving element 120 is formed to be larger than the thickness of the first light receiving element 110 without being thinned too much or at all. Then, in order to suppress the thickness when the first and second light receiving elements 110 and 120 are stacked, the recess 126 for accommodating the first light receiving element 110 is provided, and the vertical direction of the second light receiving element 120 is provided. And the horizontal width is larger than the vertical and horizontal widths of the first light receiving element 110. For example, the second light receiving element 20 is formed in a rectangular shape having a side of about 3 mm and a thickness of about 250 to 400 μm.

The InP substrate 121 is, for example, n-type, and a p-type region 122a mainly composed of, for example, InGaAs is formed on the main surface side of the InP substrate 121. This main surface is covered with an antireflection layer 123 having a predetermined thickness (for example, a silicon nitride film or a silicon oxide film having a thickness of 250 nm).

The InP substrate 121 includes a recess 126 formed in a concave shape inward of the InP substrate 121 from the back surface opposite to the p-type region 122a toward the second light receiving region 122. The recess 126 is formed on the back surface of the InP substrate 121 so as to include a region corresponding to the second light receiving region 122 by, for example, machining, and has a width of about 1.2 to 1.5 mm and a length of the second light receiving element. A groove equal to 120 vertical or horizontal lengths. This groove is preferably formed so that the second semiconductor substrate extends in a direction in which it is difficult to cleave.

The recess 126 is formed to a depth of, for example, about 200 μm, and the bottom thereof is subjected to a flattening treatment such as polishing in order to prevent scattering of incident light. An antireflection layer 128 having a predetermined thickness (for example, a silicon nitride film having a thickness of 250 nm, a silicon oxide film, or the like) is formed on the inner surface of the recess 126 and the back surface of the InP substrate 121. The antireflection layer 128 and the antireflection layer 123 on the main surface side also function as an insulating protective layer. Intermediate wirings 131 and 132 for connecting to the first anode electrode 114 and the first cathode electrode 115 of the first light receiving element 110 are formed on the antireflection layer 128 on the back surface side of the InP substrate 121.

The antireflection layer 123 on the main surface side of the InP substrate 121 is provided with an opening so as to communicate with the second light receiving region 122 and the InP substrate 121 on the outside thereof. An electrode material mainly containing, for example, aluminum or gold is selectively deposited in each predetermined region including these openings to form a second anode electrode 124 and a second cathode electrode 125. The second anode electrode 124 and the second cathode electrode 125 are supported by a conductive member 127 (for example, a conductive adhesive containing silver particles, eutectic solder, gold bumps, etc.) solidified by drying or cooling. By fixing to the corresponding wirings 103a and 103c of 102, respectively, the second light receiving element 120 is fixed to the support substrate 102 and is also electrically connected.

The vicinity of the pn junction formed by the n-type InP substrate 121 and the p-type region 122a is the second light receiving region 122, and the incident light (optical signal) is converted into a charge. This electric charge is transmitted to the outside as an electric current (electrical signal) via the second anode electrode 124 and the second cathode electrode 125. The vertical and horizontal widths of the second light receiving region 122 are, for example, about 1500 μm and the depth is about 10 μm, which are appropriately set.

The support substrate 102 will be described.
The support substrate 102 is, for example, a ceramic substrate or a printed circuit board, and a plurality of wirings 103a to 103c are formed in which the portions where the first and second light receiving elements 110 and 120 are electrically connected are exposed. These plurality of wirings 103a to 103c can be easily electrically connected to the first and second anode electrodes 114 and 124 and the first and second cathode electrodes 115 and 125 of the first and second light receiving elements 110 and 120 from the outside. Pad portions 104a to 104c are provided for connection with the outside so that they can be connected.

The side of the second light receiving element 120 opposite to the recess 126 (main surface side) is fixed to the support substrate 102, and the first light receiving element 110 is fixed so as to be accommodated in the recess 126 of the second light receiving element 120. The light receiving element unit 101 is formed. As a result, the light transmitted through the first light receiving region 112 is arranged so as to enter the second light receiving region 122. The second light receiving element 120 in which the first light receiving element 110 is fixed in the recess 126 may be fixed to the support substrate 102.

The back surface side of the first light receiving element 110 is fixed to the recess 126 by the adhesive 117. The adhesive 117 contains, for example, an epoxy resin as a main component and is transparent to the incident light transmitted through the first light receiving element 110. The adhesive is applied only to the outer edge of the back surface of the first light receiving element 110 so that the incident light transmitted through the first light receiving element 110 enters the second light receiving element 120 without passing through the adhesive 117. May be fixed.

The first anode electrode 114 and the first cathode electrode 115 of the first light receiving element 110 are respectively connected to the corresponding intermediate wires 131 and 132 on the back surface of the second light receiving element 120 by, for example, gold wires 105 and 106. The intermediate wirings 131 and 132 are connected to the corresponding wirings 103b and 103c of the support substrate 102 by, for example, gold wires 107 and 108, respectively.

Light is incident on the first light receiving element 110 from the side opposite to the support substrate 102 to the light receiving element unit 101, and in the first light receiving element 110, for example, the wavelength in the visible light region to the infrared light region is 400 to 1000 nm. Light in the region (optical signal in the first wavelength region) is converted into an electric current and transmitted to the outside as an electric signal. For example, light in a wavelength region of 1000 to 1600 nm (light signal in a second wavelength region) transmitted through the first light receiving element 110 is incident on the second light receiving element 120, and this light is emitted in the second light receiving element 120. It is converted into an electric current and transmitted to the outside as an electric signal.

Since the first light receiving element 110 is housed in the recess 126 of the second light receiving element 120, the light receiving element unit 101 formed in this way is downsized to the same size as the light receiving unit of only the second light receiving element 120. Will be done. The light receiving element unit 101 is housed in a case (not shown) provided with a plurality of terminals connected to a plurality of pad portions 104a to 104c of the support substrate 102, respectively, and a window for light incident, and optical communication or the like. Used for. A gallium nitride-based substrate is used for the first semiconductor substrate, and a silicon substrate or an indium phosphide substrate is used for the second semiconductor substrate so as to receive ultraviolet light and visible light or ultraviolet light and infrared light. May be good.

The actions and effects of the light receiving element unit 1 according to the first and second embodiments and the light receiving element unit 101 according to the third embodiment will be described.
The light receiving element unit 1 includes a first light receiving element 10 and a second light receiving element 20, and is mounted on a first semiconductor substrate of the first light receiving element 10 from the back surface to the main surface side opposite to the first light receiving region 12. It has a recess 16 formed in a concave shape toward the first light receiving region 12. On the other hand, the light receiving element unit 101 includes a first light receiving element 110 and a second light receiving element 120, and is a main surface on the second semiconductor substrate of the second light receiving element 120 from the back surface opposite to the second light receiving region 122. It has a recess 126 formed in a concave shape toward the second light receiving region 122 on the side. A second light receiving element 20 is housed in the recess 16, and a first light receiving element 110 is housed in the recess 126. In other words, one of the first light receiving element and the second light receiving element has a recess, and the other is housed in the recess.

Therefore, in order to receive light in a wide wavelength range, the first light receiving element 10 and the second light receiving element 20 can be overlapped with each other, and the thickness can be suppressed to reduce the size of the light receiving element unit 1. Further, the first light receiving element 110 and the second light receiving element 120 can be overlapped with each other, and the thickness can be suppressed to reduce the size of the light receiving element unit 101.

The first light receiving element 10 and the second light receiving element 20 are arranged so that the light transmitted through the first light receiving region 12 is incident on the second light receiving region 22. Further, the first light receiving element 110 and the second light receiving element 120 are arranged so that the light transmitted through the first light receiving region 112 is incident on the second light receiving region 122. Therefore, since the light receiving element units 1, 101 can receive the incident light having different wavelengths without being separated, the light receiving element units 1, 101 can be miniaturized.

The first light receiving element 10 has antireflection layers 13 and 18 on the inlet side and the outlet side of the incident light, respectively. Further, the first light receiving element 110 has antireflection layers 113 and 118 on the inlet side and the outlet side of the incident light, respectively. Therefore, the reflection of the incident light of the first light receiving elements 10 and 110 on the inlet side is suppressed to secure the light receiving amount of the first light receiving elements 10 and 110 and the light receiving amount of the second light receiving elements 20 and 120. It is possible to secure the amount of light received by the second light receiving elements 20 and 120 by suppressing the reflection of light on the outlet side of the incident light transmitted through the light receiving elements 10 and 110 of 1.

In the first embodiment, the first light receiving element 10 has a recess 16 and the recess 16 side is fixed to the support substrate 2, and the second light receiving element 20 housed in the recess 16 is the second light receiving element 20 on the main surface side. The anode electrode 24 and the second cathode electrode 25 are fixed to the corresponding wirings 3a and 3c of the support substrate 2 by the conductive member 27, respectively. Therefore, the second light receiving element 20 can be accommodated in the recess 16 of the first light receiving element 10 to reduce the size of the light receiving element unit 1, and the second light receiving element 20 is fixed to the support substrate 2. Since they are electrically connected at the same time, the formation of the light receiving element unit 1 can be facilitated.

In the second embodiment, the first light receiving element 10 has a recess 16 and intermediate wirings 31 and 32 connected to the corresponding wirings 3a and 3c of the support substrate 2 on the recess 16 side, and the recess 16 side supports the recess 16. It is fixed to the substrate 2. Then, in the second light receiving element 20 housed in the recess 16, the second anode electrode 24 and the second cathode electrode 25 on the main surface side are connected by the conductive member 27 to the corresponding intermediate wiring 31 of the first light receiving element 10. It is fixed to 32 respectively. Therefore, the second light receiving element 20 can be accommodated in the recess 16 of the first light receiving element 10 to reduce the size of the light receiving element unit 1, and the first light receiving element 20 to which the second light receiving element 20 is fixed can be miniaturized. Since the 10 is fixed to the support substrate 2 and electrically connected at the same time, the formation of the light receiving element unit 1 can be facilitated.

In the third embodiment, the second light receiving element 120 has a recess 126, and the side opposite to the recess 126 (main surface side) is fixed to the support substrate 102. The first light receiving element 110 receives a second light from the gold wires 105 and 106 in which the first anode electrode 114 and the first cathode electrode 115 on the main surface side are conductive, with the back surface side fixed to the recess 126. It is connected to the corresponding intermediate wires 131 and 132 formed on the element 120, respectively. Therefore, the light receiving element unit 101 can be miniaturized by accommodating the first light receiving element 110 in the recess 126 of the second light receiving element 120.

The first semiconductor substrate is a silicon substrate (Si substrates 11, 111), and the second semiconductor substrate is an indium phosphide substrate (InP substrates 21, 121). Therefore, the first light receiving elements 10 and 110 mainly receive the incident light in the visible light region without splitting the incident light, and the second light receiving elements 20 and 120 transmit the red light transmitted through the first light receiving elements 10 and 110. The incident light in the external light region can be received, and the light receiving element units 1, 101 can be miniaturized.

In addition, a person skilled in the art can carry out the embodiment with various modifications added to the embodiment without departing from the spirit of the present invention, and the present invention also includes such modifications.

1,101: Light receiving element unit 2,102: Support substrate 3a to 3c, 103a to 103c: Wiring 4a to 4c, 104a to 104c: Pad 5,105 to 108: Gold wire (conductive wire)
10,110: First light receiving element 11,111: Si substrate (first semiconductor substrate)
12,112: First light receiving region 12a, 112a: p-type diffusion region 13,18,113,118: Antireflection layer 14,114: First anode electrode 15,115: First cathode electrode 16: Recessed 17,27, 127: Conductive adhesive 20, 120: Second light receiving element 21, 121: InP substrate (second semiconductor substrate)
22,122: Second light receiving region 22a, 122a: p-type region 23,28,123,128: Antireflection layer 24,124: Second anode electrode 25,125: Second cathode electrode 31,32,131,132: Intermediate wiring 117: Adhesive 126: Recess

Claims (4)

A first light receiving element having a first light receiving region on the main surface side of the first semiconductor substrate, a second light receiving element having a second light receiving region on the main surface side of the second semiconductor substrate, and the first light receiving element. In the light receiving element unit provided with the support substrate that supports the second light receiving element.
Of the first light receiving element and the second light receiving element, one has a concave portion formed in a concave shape from the back surface opposite to the main surface toward the first or second light receiving region side, and the other. Is housed in the recess
The first light receiving region is characterized by converting an optical signal in the first wavelength region into an electric signal, and the second light receiving region is characterized by converting an optical signal in a second wavelength region different from the first wavelength region into an electric signal. Light receiving element unit. The first light receiving element and the second light receiving element are arranged so that the light transmitted through the first light receiving region of the first light receiving element is incident on the second light receiving region of the second light receiving element. The light receiving element unit according to claim 1. The light receiving element unit according to claim 1 or 2, wherein the first light receiving element has antireflection layers on the inlet side and the outlet side of the incident light, respectively. The first light receiving element has the recess, and the recess side is fixed to the support substrate.
The second light receiving element has an electrode on the main surface side of the second semiconductor substrate, and the electrode is fixed to a wiring formed on the support substrate by a solidified conductive member. The light receiving element unit according to any one of claims 1 to 3.