JP2002344002A - Light-receiving element and mounting body thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a light-receiving element having wavelength pass-band characteristics in which a high sensitivity rate is obtained, even in a thin filter layer, and the depth of impurity diffusion in a light-receiving part is equivalent to that of conventional pin photodiodes. SOLUTION: A filter layer 3 and a buffer layer 4 are successively laminated on a first main face 2 of a semiconductor substrate 1, and island-shaped light- absorbing layer 5 and window layer 6 are laminated on the buffer layer 4. A diffusion region 7, where p-type impurity is diffused, is formed in the window layer 6. An n-side electrode 8 is formed on the buffer layer 4, and a p-side electrode 9 is formed on the diffusion area 7. Also, a light incident part 10 is formed on the buffer layer 4, where the light-absorbing layer 5 is not formed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a light receiving element and a light receiving element mounting body. In particular, the present invention relates to a light receiving element that selectively receives signal light having a long wavelength (longer wavelength side) when a plurality of signal lights having different wavelengths are incident.

[0002]

2. Description of the Related Art At present, a pin photodiode made of a compound semiconductor is widely used as a light receiving element for optical fiber communication.

[0003] In this pin photodiode, a window structure is employed in order to increase the light receiving sensitivity. This is because a light absorption layer having a small forbidden band width (long absorption edge wavelength) is formed on a semiconductor substrate, and a filter layer (window layer) having a large forbidden band width (short absorption end wavelength) is formed on the light absorption layer. With this structure, light having an absorption edge wavelength in the light absorption layer and the filter layer can be efficiently received.

[0004] As a general pin photodiode, there is one made of InGaAs / InP, and InGaAs is used as a material of a light absorbing layer and InP is used as a material of a filter layer. In this case, signal light having a wavelength in a range from the absorption edge wavelength of InP of 0.9 μm to the absorption edge wavelength of InGaAs of 1.65 μm can be received with high sensitivity. The structure of this pin photodiode is disclosed in, for example, Japanese Patent Application Laid-Open No. 1-238070.

Hereinafter, a conventional pin photodiode will be described with reference to FIG. FIG. 10 is a sectional view of a conventional pin photodiode.

[0006] As shown in FIG. 10, ⁿ on the substrate 101 of n ⁺ -InP - carrier blocking layer -InP (buffer ^layer) 102, n - -InGaAs optical absorption layer 103, n ^-
-AlAsSb carrier blocking layer 104 and n ^-- I
The nP filter layers 105 are sequentially laminated. Here, the forbidden band width of AlAsSb is larger than the forbidden band width of InP, and its absorption edge wavelength is 0.67 μm.

[0007] Filter layer 105 and carrier blocking layer 10
4, a p ⁺ diffusion region 106 in which Zn is diffused is formed, and a surface protective film 107 is formed thereon. Further, a ring-shaped anode electrode 108 is formed on the diffusion region 106, and
The cathode electrode 109 is formed on the back surface of the substrate 1.

In the pin photodiode shown in FIG. 10, since the carrier blocking layer 104 is formed,
The sensitivity to signal light having a wavelength of 0.9 μm or less can be improved as compared with a pin photodiode in which the carrier blocking layer 104 is not formed.

The reason is as follows. Signal light having a wavelength of 0.9 μm or less is absorbed by the filter layer 105 to generate electron-hole pairs, but the pin photodiode without the carrier blocking layer 104 is formed. In the case of the above, a part of the electrons generated in the filter layer 105 flows into the light absorption layer 103 to generate a photocurrent, whereas when the carrier blocking layer 104 is provided, the interface between the filter layer 105 and the carrier blocking layer 104 This is because electrons are blocked by the hetero barrier and do not become photocurrent.

[0010] Also, a pass band type PIN photodiode having sensitivity to light in a narrower wavelength range has been developed. For example, when performing wavelength division multiplexing communication using signal light having a wavelength of 1.3 μm and signal light having a wavelength of 1.55 μm, a passband type pin photodiode having sensitivity only to each wavelength is useful.

Here, a pin having a short wavelength passband characteristic that has sufficient sensitivity to signal light having a wavelength of 1.3 μm but has little sensitivity to signal light having a wavelength of 1.55 μm. The photodiode is InGa
It can be easily realized by using InGaAsP having an absorption edge wavelength of 1.4 μm as the material of the light absorption layer of the above-mentioned pin photodiode composed of As.

On the other hand, in order to obtain a long-wavelength passband characteristic that the signal light having a wavelength of 1.55 μm has sufficient sensitivity but the signal light having a wavelength of 1.3 μm has almost no sensitivity. , The material of the carrier blocking layer 104 is InP,
The material of the filter layer 105 is made of I having an absorption edge wavelength of 1.4 μm.
This can be realized by using nGaAsP. The relationship that the forbidden bandwidth of the carrier blocking layer 104 is larger than the forbidden bandwidth of the filter layer 105 is maintained.

[0013]

However, in a conventional pin photodiode having passband characteristics,
To increase the difference in sensitivity between the signal light on the long wavelength side and the signal light on the short wavelength side, it is necessary to increase the thickness of the filter layer 105.

Here, in order to realize a pin photodiode having a long wavelength pass band characteristic, the filter layer 105 is required.
As described above, it is necessary to use InGaAsP as a material, but when InGaAsP is grown epitaxially thick, there is a problem that the composition of InGaAsP tends to fluctuate.

On the other hand, planar type pi in which impurities such as Zn are diffused into the filter layer 105 in an island shape to form a diffusion region.
In an n-photodiode, the thickness of the carrier blocking layer 104 is 1 to 2 μm, and the impurity diffusion is usually performed to this depth.

That is, in the conventional pin photodiode, even if the material of the filter layer 105 is InGaAsP and the filter layer 105 can be grown epitaxially thick, there is a problem that it is difficult to perform impurity diffusion deeply and with good control. . The carrier blocking layer 10
4 and the filter layer 105 are doped with p-type in advance, and if a mesa-type pin photodiode is used to separate elements by etching, there is no need for island-like partial impurity diffusion, but in particular, InGaAs / InP
In the system, a mesa-type pin photodiode has a large dark current, and its reliability is lower than that of a planar-type photodiode manufactured by impurity diffusion.

The present invention has been made to solve the above-mentioned problem, and a high sensitivity ratio can be obtained even with a thin filter layer.
A main object of the present invention is to provide a light receiving element having a long wavelength pass band characteristic equivalent to that of an n photodiode.

[0018]

A first light receiving element according to the present invention comprises a semiconductor substrate, a filter layer formed on a first main surface of the semiconductor substrate, and an island formed on the filter layer. And a light incident portion formed on a portion of the filter layer where the light absorption layer is not formed, wherein the absorption edge wavelength of the filter layer is the absorption edge wavelength of the semiconductor substrate. Longer than the absorption edge wavelength of the light absorption layer.

According to the first light receiving element, the incident light obliquely incident from the light incident portion formed on the first main surface side of the semiconductor substrate is reflected by the second main surface and incident on the light absorbing layer. ,
The incident light transmits twice through the filter layer formed between the semiconductor substrate and the light absorbing layer. That is, the thickness of the filter layer can be substantially doubled with respect to the light receiving element having a structure in which the incident light passes through the filter layer once.

Further, the first light receiving element preferably has a reflection film formed on the second main surface of the semiconductor substrate.

Further, the first light receiving element includes a carrier blocking layer formed between the filter layer and the light absorbing layer and made of a material having a larger bandgap than the filter layer; And a wide band gap layer having an impurity diffusion region formed thereon.

According to this structure, since the filter layer is between the light absorbing layer and the semiconductor substrate, a wide band gap layer is stacked on the light absorbing layer, and the light receiving portion is formed by impurity diffusion. Since the thickness of the filter layer can be substantially doubled, the depth of impurity diffusion can be made equal to that of a conventional pin photodiode. Further, if a carrier blocking layer made of a material having a larger forbidden band width than the filter layer is inserted between the filter layer and the light absorption layer, it is possible to prevent carriers generated in the filter layer from flowing into the light absorption layer. it can.

Further, in the first light receiving element, the semiconductor substrate, the filter layer and the carrier blocking layer are of a first conductivity type, and the impurity diffusion region is of a second conductivity type. A first electrode formed on at least one of a layer and the carrier blocking layer; a second electrode formed on the impurity diffusion region; and at least one of the semiconductor substrate, the filter layer, and the carrier blocking layer. It is preferable to have a pad portion formed thereon with an insulating film interposed therebetween, and a wiring for electrically connecting the second electrode and the pad portion.

With this configuration, both the p-side and n-side electrodes can be formed on the first main surface side of the semiconductor substrate, and flip chip bonding can be easily performed. Also, by forming a pad for bonding the p-side electrode to the mounting substrate outside the island-shaped light absorbing layer, the difference in size between the light absorbing layer mesa and the diffusion region can be reduced, so that the area other than the lower part of the diffusion region can be reduced. Tail current generated when incident light enters the light absorption layer can be suppressed.

The second light receiving element according to the present invention, in the first light receiving element, further includes an inclined portion for reflecting the incident light incident on the semiconductor substrate and causing the incident light to enter the light absorbing layer. The semiconductor device is formed on a second main surface of the semiconductor substrate.

According to this configuration, the incident light perpendicularly incident on the first main surface can be reflected by the inclined portion.
Even when the incident light is vertically incident, the incident light can be incident on the light absorbing layer.

A third light receiving element according to the present invention is a semiconductor substrate, a filter layer formed on a second main surface of the semiconductor substrate, and an island formed on the first main surface of the semiconductor substrate. A light incident layer formed on a portion of the first main surface where the light absorbing layer is not formed, wherein an absorption edge wavelength of the filter layer is an absorption edge of the semiconductor substrate. It is longer than the wavelength and shorter than the absorption edge wavelength of the light absorbing layer.

Also in this configuration, similarly to the first light receiving element, incident light obliquely incident from a light incident portion formed on the first main surface side of the semiconductor substrate is reflected by the second main surface to absorb light. Before entering the layer, the incident light passes through the filter layer formed between the semiconductor substrate and the light absorbing layer twice. That is, the thickness of the filter layer can be substantially doubled with respect to the light receiving element having a structure in which the incident light passes through the filter layer once.

Furthermore, it is preferable that the third light receiving element has a wide band gap layer having an impurity diffusion region formed on the light absorbing layer.

A fourth light receiving element according to the present invention is the third light receiving element, further comprising an inclined portion on the first main surface of the semiconductor substrate, wherein a light incident portion is on the inclined portion. is there.

According to this configuration, the incident light perpendicularly incident on the first main surface can be refracted by the inclined portion.
In the case of normal incidence, incident light can be made to enter the light absorbing layer.

Further, in each of the first to fourth light receiving elements, it is preferable that the light incident from the light incident portion is transmitted through the filter layer at least twice before being incident on the light absorbing layer.

According to a fifth aspect of the present invention, there is provided a light receiving element comprising: a semiconductor substrate; a filter layer formed on a first main surface side or a second main surface side of the semiconductor substrate;
A light absorbing layer formed in an island shape on the main surface side, a reflective film formed on the first main surface side of the semiconductor substrate, and a light incident portion formed on the second main surface side of the semiconductor substrate Wherein the absorption edge wavelength of the filter layer is longer than the absorption edge wavelength of the semiconductor substrate and shorter than the absorption edge wavelength of the light absorption layer.

With this configuration, incident light is incident from the light incident portion formed on the second main surface side of the semiconductor substrate, but is directly absorbed on the first main surface side like a normal back illuminated pin photodiode. Instead of being incident on the layer, the light can be reflected by the reflective film formed on the first main surface side and further reflected by the second main surface and then be incident on the light absorbing layer. In this case, since the incident light passes through the filter layer three times, the thickness of the filter layer through which the incident light passes can be substantially tripled.

Further, in the fifth light receiving element, it is preferable that the light incident from the light incident portion is transmitted through the filter layer at least three times before being incident on the light absorbing layer.

In a sixth light receiving element according to the present invention, the filter layer and the carrier blocking layer are formed in one or a plurality of islands, the semiconductor substrate is semi-insulating, and the filter layer and the carrier A carrier blocking layer of a first conductivity type, the impurity diffusion region of a second conductivity type, a first electrode formed on the filter layer or the carrier blocking layer in an island having the light absorbing layer, A second electrode formed on the impurity diffusion region, and a pad portion formed on the filter layer or the carrier blocking layer on the semiconductor substrate or on an island other than the island on which the first electrode is formed, And a wiring for electrically connecting the second electrode and the pad portion.

With this configuration, by using a semi-insulating semiconductor substrate, it is possible to prevent the pad capacitance of the p-side electrode from being added to the element capacitance.

According to the present invention, there is provided a light receiving element mounting body, comprising: a mounting substrate; an optical waveguide formed in the mounting substrate; and a deflection device for deflecting a path of incident light propagating through the optical waveguide toward a surface of the mounting substrate. A light-receiving element mounting body having an element and a light-receiving element disposed on the mounting substrate, wherein the light-receiving element is a semiconductor substrate and at least one of a first main surface side and a second main surface side of the semiconductor substrate. A light absorbing layer formed on the first main surface side of the semiconductor substrate in an island shape, and a light incident portion formed on the first main surface side of the semiconductor substrate. Wherein the light receiving element is disposed (or fixed) with the first main surface side on which the light incident portion is formed facing a mounting substrate.

With this configuration, the light receiving element can be flip-chip bonded and optically coupled easily from the mounting substrate side, so that the parasitic capacitance associated with mounting is reduced as compared with the case where wire bonding is performed, and high-speed operation becomes possible. To
Since the optical coupling is completed at the time of bonding, a mounting step for optical coupling is not required.

Further, in the light receiving element mounting body, the optical waveguide is an optical fiber embedded in a groove formed on the mounting substrate, and the deflecting element cuts the optical fiber so as to cut the optical fiber. It is a reflection plate inserted in a slit formed above, and it is preferable that the light receiving element is disposed (or fixed) on the mounting substrate across the groove.

[0041]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a light receiving element and a light receiving element mounting body according to an embodiment of the present invention will be described with reference to the drawings. In the following drawings, components having substantially the same function are denoted by the same reference numeral for simplification of description. Note that the present invention is not limited to the following embodiments.

(First Embodiment) Hereinafter, a light receiving element according to a first embodiment of the present invention will be described with reference to FIG. FIG. 1A is a plan view of the light receiving element according to the first embodiment, and FIG. 1B is a plan view of X in FIG. 1A.
FIG. 1C is a cross-sectional view along the X-ray, and FIG.
3 is a sectional view taken along line YY in FIG.

The light receiving element of this embodiment is a semiconductor substrate 1
A filter layer 3 formed on the first main surface 2 of the semiconductor substrate 1 and a light absorbing layer 5 formed in an island shape on the filter layer 3
And Here, the absorption edge wavelength of the filter layer 3 is longer than the absorption edge wavelength of the semiconductor substrate 1, and the light absorption layer 5
Shorter than the absorption edge wavelength. Then, a light incident portion 10 is formed on a portion of the filter layer 3 where the light absorbing layer 5 is not formed. Preferably, a carrier blocking layer (buffer layer) 4 made of a material having a larger forbidden band width than that of the filter layer 3 is formed between the filter layer 3 and the light absorption layer 5.

The light receiving element shown in FIG.
This is an InP-based pin photodiode. In the configuration of the present embodiment, as shown in FIG. 1B, the absorption edge wavelength is 1.4 on the first main surface 2 of the semiconductor substrate 1 made of n-type InP.
filter layer 3 of n-type InGaAsP
A carrier blocking layer (buffer layer) 4 made of n-type InP is sequentially laminated, and a light absorption layer 5 made of island-like low-concentration n-type InGaAs and a wide band gap made of low-concentration n-type InP are formed on the carrier blocking layer 4. The layer (window layer) 6 is laminated. Like the carrier blocking layer 4, the wide band gap layer 6 is also made of a material having a larger forbidden band width than the filter layer 3. Wide band gap layer 6
A diffusion region 7 in which a p-type impurity (for example, Zn or Be) is diffused is formed in the central portion of FIG. Also,
A circular n-side electrode 8 is formed on the carrier blocking layer 4, and a ring-shaped p-side electrode 9 is formed on the diffusion region 7.

As shown in FIG. 1C, a circular light incident portion 1 is formed on the carrier blocking layer 4 apart from the light absorbing layer 5.
0 is formed, and an antireflection film 11 made of SiN is deposited inside the light incident portion 10 and the p-side electrode 9.
The antireflection film 11 is also formed on the diffusion region 7.

Further, as shown in FIGS. 1A and 1B, the exposed surface of the carrier blocking layer 4 is made of SiN and SiO ₂ except for the scribe lane 12 around the light receiving element.
Are covered with an insulating film 13 formed by stacking. A pad (pad electrode) 14 which is a conductor formed on the insulating film 13 is electrically connected to the p-side electrode 9 via a wiring 15. In the present embodiment, the pads 14 and n
The side electrode 8 is formed at a position symmetrical with respect to a line connecting the light incident part 10 and the center of the light absorbing layer 5. The n-side electrode 8, the p-side electrode 9, the pad 14, and the wiring 15 are formed of, for example, a laminated metal film of Ti / Pt / Au, and these patterns are collectively formed by one vapor deposition and lift-off process. It is also possible to form it.

The second principal surface 16 of the semiconductor substrate 1 has
A reflection film 17 for reflecting incident light is formed. Although the reflection film 17 may be composed of only a metal film, a higher reflectivity can be obtained by using a laminated structure of a dielectric and a metal, for example, SiN and Al. This is because if a metal film is directly formed on the semiconductor substrate 1, an alloy reaction occurs between the two, and an appropriate reflection surface may not be formed. Of course, if a metal that does not easily react with the alloy is used, the problem can be avoided. However, a metal that does not easily react often has poor adhesion, and therefore forms a metal film via a dielectric layer. It is desirable.

In the light receiving element according to the first embodiment, FIG.
As shown in (c), when the incident light 18 is obliquely incident from the light incident part 10, the incident light 18 is reflected on the second main surface 16 of the semiconductor substrate 1 and is incident on the light absorbing layer 5. Therefore, the incident light 18 is emitted twice before entering the semiconductor substrate 1 and before entering the light absorbing layer 5.
It passes through the filter layer 3. That is, the thickness of the filter layer 3 through which the incident light 18 passes can be substantially doubled.

Next, the light receiving element according to the first embodiment of the present invention, in which the incident light is transmitted twice through the filter layer, will be further described in comparison with the conventional light receiving element in which the incident light is transmitted once through the filter layer. I do.

When signal light having different wavelengths of the short wavelength and the long wavelength enters, the signal light on the short wavelength side is absorbed by the filter layer before reaching the light absorption layer. The amount of light absorption of the signal light on the short wavelength side by the filter layer is 1 when the thickness of the filter layer is d and the absorption coefficient for the signal light on the short wavelength side is α.
-Exp (-αd).

For example, in order to obtain a sensitivity ratio of 20 dB in the conventional light receiving element, the absorption amount in the filter layer must be 99%, the absorption coefficient α is set to 1 μm ^−1, and these are substituted into the above equation. When the thickness d of the filter layer is determined, it is understood that the thickness d of the filter layer needs to be about 4.6 μm.

However, in the light receiving element according to the first embodiment of the present invention, if the thickness of the filter layer 3 is set to 2.3 μm, the incident light passes through the filter layer 3 twice, so that the incident light 18 Is about twice 2.3 μm, that is, about 4.
The light passes through a filter layer having a thickness of 6 μm.
A sensitivity ratio of 20 dB can be obtained between the signal light having a wavelength of 55 μm and the signal light having a wavelength of 1.3 μm. As a result, the epitaxial growth of InGaAsP more than necessary is no longer necessary, so that the composition of InGaAsP can be prevented from fluctuating.

Further, between the filter layer 3 and the light absorbing layer 5,
Since the carrier blocking layer 4 made of a material having a larger forbidden band width than that of the filter layer 3 is inserted, the carrier generated by the filter layer 3 does not flow into the light absorption layer 5 and the sensitivity ratio does not decrease.

Here, the filter function of the filter layer 3 and the carrier blocking function of the carrier blocking layer 4 will be described.

First, the filter layer 3 will be described. Since InGaAsP constituting the filter layer 3 has different absorption edge wavelengths depending on its composition, by changing the composition, it is possible to select a wavelength of light to be transmitted or light not to be transmitted. That is, InGaAsP
The layer 3 composed of can function as a filter.

[0056] InGaAsP _{is, In 1-x Ga x As} y P
_1-y and y = 2.12x between x and y
There is a relationship. That is, there is freedom of the one-dimensional in the composition of _{In 1-x Ga x As y} P, when defining the values of composition x or y, InGaAsP having a predetermined absorption edge wavelength is uniquely determined. In other words, the composition of InGaAsP can be expressed by the absorption edge wavelength of InGaAsP.

FIG. 2 is a graph showing the relationship between the wavelength and the light absorption of InGaAsP. In this specification, In _1-x G
a _x As _y P _1-y light in (0 ≦ x ≦ 1,0 ≦ y ≦ 1) is defined as the absorption edge wavelength of the maximum wavelength to be absorbed. As shown in FIG. 2, InP containing no Ga and As
In the case of (x = 0, y = 0), the absorption edge wavelength is 0.93 μm
The absorption edge wavelength is the smallest among InGaAsP-based materials. On the other hand, In _1-x Ga _x A containing no P
At s (y = 1), the absorption edge wavelength is larger than 1.6 μm, and the absorption edge wavelength is largest in the InGaAsP-based material. The absorption edge wavelength of the InGaAsP-based material is represented by the compositions x and y
Can be set to an arbitrary value between the upper end and the lower end.

[0058] _{In 1-x Ga x As y} P 1-y absorption edge wavelength λg of
And the relationship between the composition x and y are shown in Table 1 below. The forbidden band width Eg is also shown for reference.

[0059]

[Table 1]

Thus, by determining the values of the compositions x and y, for example, 1.0 μm, 1.30 μm, 1.5 μm
An InGaAsP layer having an absorption edge wavelength such as m can be obtained.

Next, the carrier blocking layer 4 will be described. The carrier blocking layer 4 located between the filter layer 3 and the light absorbing layer 5 has a function of preventing carriers generated in the filter layer 3 from diffusing into the light absorbing layer 5. Therefore, the holes of the electron-hole pairs photoexcited by the filter layer 3 can be prevented from diffusing into the light absorbing layer 5 by the carrier blocking layer 4. FIG. 3 schematically shows the band gap of each layer (1, 3, 4, 5, and 6) of the light receiving element of the present embodiment, where black circles represent electrons and white circles represent holes.

In the case of the light receiving element of the present embodiment, since light is reflected by the second main surface 16 of the semiconductor substrate 1 and enters the light absorbing layer 5, the incident light is different from the conventional case of surface incidence.
Before the light absorption layer 5, the light reaches the filter layer 3 first. Since InP constituting the semiconductor substrate 1 has a relatively large band gap, it transmits light having a wavelength of 1.3 μm or 1.55 μm for optical fiber communication (see FIG. 2 and Table 1). In the filter layer 3 having a small gap, photoexcitation may be caused by incident light to generate electron-hole pairs. In order to prevent the holes of the electron-hole pairs from diffusing into the light absorbing layer 5, an InP carrier blocking layer having a larger band gap than the filter layer 3 is provided between the filter layer 3 and the light absorbing layer 5. 4 has been inserted. In this configuration, the holes of the electron-hole pairs generated in the filter layer 3 cannot be diffused into the light absorption layer 5 and recombine in the filter layer 3 as they are, so that no photocurrent is generated.

In the case of front incidence as in the conventional example, the wide band gap layer 6 can function as a window layer (window layer). In the case where light is reflected by the second main surface 16 and enters the light absorbing layer 5, the wide band gap layer 6 does not function as a window layer but reduces the reverse leakage current of the pn junction. It plays a role exclusively. More specifically, InGaAs / In
In a P-type pin photodiode, the light absorption layer 5 of I
It is known that when a pn junction is exposed on the surface of an nGaAs layer, a leak current increases. However, InG
When the InP wide band gap layer 6 is provided on the aAs layer 5, a pn junction is exposed on the surface of the wide band gap layer 6, and a pn junction is formed on the surface of the InGaAs layer 5. Since it is not exposed, the leakage current can be reduced as compared with the case where the wide band gap layer 6 is not provided.

In the configuration of the present embodiment, although the incident light 18 does not directly enter the light absorbing layer 5 formed on the first main surface 2 side of the semiconductor substrate 1, the light incident portion 10 is on the first main surface 2 side. Therefore, the light receiving element of the present embodiment is of a front-illuminated type. The light receiving element of the present embodiment is of a planar type in which a wide band gap layer 6 is stacked on a light absorbing layer 5 and a light receiving portion is formed by impurity diffusion. Since it is located between the semiconductor substrates 1, the depth of impurity diffusion is equivalent to that of a conventional planar pin photodiode. Therefore, without deepening the impurity diffusion,
The sensitivity ratio can be improved. Furthermore, since both the p-side and n-side electrodes are formed on the first main surface 2 side of the semiconductor substrate 1, flip-chip bonding can be easily performed. Further, since the insulating film 13 covers the wide band gap layer 6 where the impurity is not diffused, the tail current generated when the incident light 18 is incident on the light absorbing layer 5 other than below the diffusion region 7 is suppressed. be able to.

The reason why the antireflection film 11 is deposited inside the p-side electrode 9 in the light receiving element according to the first embodiment is that light is directly incident from above the light absorbing layer 5 in the inspection step. This is to prevent light incident on the light source from being reflected. However, depending on the configuration of the light receiving element mounting body, the scattered light of the incident light 18 may be incident from above the light absorbing layer 5 to deteriorate the sensitivity ratio. In this case, the p-side electrode 9 is not ring-shaped. It is more desirable to use a circular shape instead of a light absorbing layer to block incident light from above the light absorbing layer. In the light receiving element according to the first embodiment, the n-side electrode 8 and the pad 14 are formed on the carrier blocking layer 4.
It may be formed on the semiconductor substrate 1. The filter layer 3 has a smaller forbidden band width than the carrier blocking layer 4,
This is because, in many cases, the semiconductor substrate 1 has a higher carrier concentration than the carrier blocking layer 4, so that forming an n-side electrode thereon may reduce the contact resistance. Also, when performing flip chip bonding,
Since it is better that the heights of the n-side electrode 8 and the pad 14 are the same, it is desirable that the pad 14 be formed on the same semiconductor layer as the n-side electrode 8.

The other conditions of the light receiving element according to the present embodiment are exemplified as follows. Note that the present invention is not limited to these conditions, and suitable conditions can be set as appropriate.

The thickness of the semiconductor substrate (InP substrate) 1 is 1
It is about 50 to 200 μm. The height of the island-shaped structure (light receiving portion mesa) including the wide band gap layer 6 including the impurity diffusion region 9 and the light absorbing layer 5 is about 2.5 to 5 μm. In this specification, “island-like” means a shape composed of a certain area surrounded in a plane area, and exclusively means the shape of the convex island structure shown in FIG. In addition, it includes the shape of the structure in which a part or the whole is embedded.

The thickness of the filter layer 3 is about 2 to 3 μm, and the thickness of the carrier blocking layer 4 is about 1 to 2 μm. The thickness of the light absorbing layer 5 is about 1.5 to 3 μm,
The mesa shape is a circle having a diameter of 100 to 140 μm. The thickness of the wide band gap layer 6 is 1 to 2 μm, and the mesa shape is a circle having a diameter of 100 to 140 μm. The shape of the diffusion region 7 in the wide band gap layer 6 is a circle having a diameter of 80 to 120 μm. Reflective film 17
Has a thickness of about 0.2 to 0.4 μm. Each shape is a shape viewed from the normal direction of the substrate (above the light receiving element).

Further, the relationship of the carrier concentration is shown. The carrier blocking layer 4 (or the filter layer 3) (n ⁺ layer) has a high carrier concentration, while the light absorbing layer 5 (n ⁻ layer or i layer) has a high carrier concentration. The carrier concentration is low. In the present embodiment, the wide band gap layer 6 is formed from a layer (n ⁻ layer) having a low carrier concentration, but the carrier concentration of the wide band gap layer 6 is not particularly limited.

(Second Embodiment) Next, a light receiving element according to a second embodiment of the present invention will be described with reference to FIG. FIG. 4A is a plan view of a light receiving element according to the second embodiment, and FIG.
FIG. 4C is a cross-sectional view taken along line X-ray, and FIG.
3 is a sectional view taken along line YY in FIG. Here, FIG.
(D) shows an inclined portion 1 when the semiconductor substrate 1 is viewed from the back surface.
It is a rear view which shows the shape of 9 places.

The light receiving element according to the second embodiment is different from the light receiving element according to the first embodiment in that, as shown in FIG. This is the point that a concave portion having the inclined portion 19 is formed, and the reflective film 20 is formed on the second main surface 16 of the semiconductor substrate 1 having the inclined portion 19. Since the incident light 18 enters the inclined portion 19, the reflection film 20 may be formed only on the inclined portion 19. The inclined portion 19 is located at a position facing the light incident portion 10, and the inclination angle of the inclined portion 19 with respect to the semiconductor substrate 1 is:
The incident light 18 is formed so as to be reflected by the inclined portion 19 and enter the light absorbing layer 5. The tilt angle may be set to a suitable value within a range of, for example, 15 to 35 degrees. If the inclined portion 19 is formed such that a predetermined crystal plane is exposed, the inclination angle can be set with high accuracy and easily.

For simplification of the description, the same components as those of the light receiving element according to the first embodiment are denoted by the same reference numerals, and the description thereof will be omitted.

In the light receiving element according to the second embodiment, the first
The incident light 18 perpendicularly incident on the main surface 2 is perpendicularly incident on the semiconductor substrate 1 from the light incident part 10 and then the inclined part 19.
And is incident on the light absorbing layer 5.

The light receiving element according to the second embodiment is different from the light receiving element according to the first embodiment, and can be used when perpendicular incidence is more suitable according to the mounting form of the light receiving element. In the light receiving element according to the second embodiment, as in the light receiving element according to the first embodiment, since the incident light 18 passes through the filter layer 3 twice, the filter having a thickness twice as large as that of the filter according to the first embodiment is used. It goes without saying that there is an effect of transmitting through the layer.

(Third Embodiment) Next, a light receiving element according to a third embodiment of the present invention will be described with reference to FIG. FIG. 5A is a plan view of a light receiving element according to the third embodiment, and FIG. 5B is a plan view of X in FIG. 5A.
FIG. 5C is a cross-sectional view taken along line X-ray, and FIG.
3 is a sectional view taken along line YY in FIG.

The light receiving element according to the third embodiment is different from the light receiving element according to the first embodiment in that a filter is provided on a first main surface 2 of a semiconductor substrate 1 as shown in FIG. Layer 3
Is not formed, but the filter layer 21 is formed on the second main surface 16 of the semiconductor substrate 1, and the reflection film 17 is formed on the filter layer 21. Further, no carrier blocking layer is formed.

For simplification of description, the same components as those of the light receiving element according to the first embodiment are denoted by the same reference numerals, and the description thereof will be omitted.

In the light receiving element according to the third embodiment, similarly to the light receiving element according to the first embodiment, the incident light 18 is filtered twice before and after being reflected by the second main surface 16 of the semiconductor substrate 1. 21. That is, the thickness of the filter layer 21 through which the incident light 18 passes can be substantially doubled.

Further, since the incident light 18 is incident from the light incident portion 10 formed on the first main surface 2 side of the semiconductor substrate 1, it is of a surface incident type. Further, since the filter layer 21 is on the second main surface 16 of the semiconductor substrate 1, the light receiving portion in which the wide band gap layer 6 is laminated on the light absorbing layer 5 is a planar pin photodiode formed by impurity diffusion. This is easy, and the depth of impurity diffusion is
It is equivalent to a photodiode. Further, in the light receiving element according to the third embodiment, since the semiconductor substrate 1 itself has a role of preventing the carriers generated in the filter layer 21 from flowing into the light absorbing layer 5, the carrier blocking layer is particularly used. No need to provide.

Note that a configuration in which the light receiving element according to the third embodiment and the light receiving element according to the first embodiment are combined, that is, a filter is provided on both the first main surface 2 and the second main surface 16 of the semiconductor substrate 1. It is also possible to form a layer. In this structure, the upper and lower filter layers can pass through the filter layer twice, that is, four times, so that the thickness of the filter layer can be made substantially four times as thick, and substantially four times. Can be obtained. InG to be a filter layer
As described above, when the aAsP layer is grown epitaxially thick, the composition tends to fluctuate. However, the filter layer having a thickness of 2.3 μm on the first main surface 2 and the second main surface 16 of the semiconductor substrate 1. Is easy to form.
In this case, the incident light passes through the filter layer having a thickness of about 9.2 μm, and a sensitivity ratio of about 40 dB can be obtained as a sensitivity ratio between the signal light having the wavelength of 1.55 μm and the signal light having the wavelength of 1.3 μm.

(Fourth Embodiment) Next, a light receiving element according to a fourth embodiment of the present invention will be described with reference to FIG. FIG. 6A is a plan view of a light receiving element according to the fourth embodiment, and FIG. 6B is a plan view of X in FIG. 6A.
FIG. 6C is a cross-sectional view along the X-ray, and FIG.
3 is a sectional view taken along line YY in FIG.

The light receiving element according to the fourth embodiment is different from the light receiving element according to the third embodiment in that, as shown in FIG. This is a point where a concave portion having a groove 22 is formed.

For the sake of simplicity, the same components as those of the light receiving element according to the third embodiment are denoted by the same reference numerals, and the description thereof is omitted here.

The light incident part 10 is formed on the inclined part 22, and the incident light 18 incident from the light incident part 10 is refracted by the inclined part 22, enters the semiconductor substrate 1, and then enters the second main surface. The light is reflected by 16 and enters the light absorption layer 5. Unlike the light receiving element according to the third embodiment, there is no inclined portion 22,
In the case of a light receiving element having a structure in which the first main surface 2 and the second main surface 16 are parallel to each other, it is necessary to make the incident light 18 obliquely enter in order to make the incident light 18 enter the light absorbing layer 5. However, like the light receiving element according to the fourth embodiment, the second main surface 1
6, an inclined portion 22 is formed.
If the light 8 is refracted, the incident light 18 perpendicularly incident on the first main surface 2 can be incident on the light absorbing layer 5.
The light receiving element according to the fourth embodiment is similar to the light receiving element according to the third embodiment in that the incident light 18
Needless to say, since 1 is transmitted twice, there is an effect of transmitting the filter layer substantially twice as thick.

(Fifth Embodiment) Next, a light receiving element according to a fifth embodiment of the present invention will be described with reference to FIG. FIG. 7A is a plan view of a light receiving element according to the fifth embodiment, and FIG. 7B is a plan view of X in FIG. 7A.
FIG. 7C is a cross-sectional view taken along line X-ray, and FIG.
3 is a sectional view taken along line YY in FIG. Here, FIG.
(D) shows an inclined portion 1 when the semiconductor substrate 1 is viewed from the back surface.
It is a rear view which shows the shape of 9 places.

The light receiving element according to the fifth embodiment is different from the light receiving element according to the first embodiment, as shown in FIG. Face 16
The second point is that the second reflection film 24 is formed on the carrier blocking layer 4 on the first main surface 2. The reflection film 17 is not formed on the portion of the second main surface 16 where the light incident portion 23 is formed.

For the sake of simplicity, the same components as those of the light receiving element according to the first embodiment are denoted by the same reference numerals, and description thereof is omitted here.

According to the light receiving element according to the fifth embodiment,
The incident light that has entered from the light incident portion 23 formed on the second main surface 16 is reflected by the reflection film 24 on the first main surface 2 and further reflected by the reflection film 17 on the second main surface 16. Later, the light enters the light absorption layer 5. In this case, the incident light 18 passes through the filter layer 3 three times before reaching the light absorption layer 5.
For example, if the thickness of the filter layer 3 is set to 2.3 μm,
The incident light 18 is transmitted through the filter layer having a thickness of 6.9 μm, and the signal light having a wavelength of 1.55 μm and the signal light having a wavelength of 1.3 μm are transmitted.
30 dB can be obtained as the sensitivity ratio of the signal light.
This configuration is particularly effective in the case of a light receiving element that is desirably a back illuminated type, and the thickness of the filter layer 3 through which the incident light 18 passes can be substantially tripled.

By increasing the distance between the light incident portion 23 and the light absorbing layer 5 and increasing the size of the reflective film 24 or providing a plurality of reflective films 24, the number of filter layers is 5 or 2n + 1 (n is 2 It is possible to realize a light receiving element having a configuration of transmitting light by the above (natural number) times. In addition, by forming the light incident portion 24 as a surface incident type light receiving element having a configuration in which the light incident portion 24 is formed on the first main surface 2 side of the semiconductor substrate 1, the incident light 18 reaches the light absorbing layer 5 four times or 2n. (N is a natural number of 2 or more) can realize a light receiving element configured to transmit through the filter layer.

(Sixth Embodiment) Next, a light receiving element according to a sixth embodiment of the present invention will be described with reference to FIG. FIG. 8A is a plan view of a light receiving element according to the sixth embodiment, and FIG. 8B is a plan view of X in FIG. 8A.
FIG. 8C is a cross-sectional view taken along line X-ray, and FIG.
3 is a sectional view taken along line YY in FIG.

As shown in FIG. 8B, semi-insulating InP
On a first main surface 26 of a semiconductor substrate 25 formed of a semiconductor substrate 25, two islands in which a filter layer 27 made of n-type InGaAsP having an absorption edge wavelength of 1.4 μm and a carrier blocking layer 28 made of n-type InP are stacked, A mesa 29 and a second mesa 30 are formed. On the first mesa 29, an island-like low-concentration n-type In
A light absorption layer 31 made of GaAs and a wide band gap layer 32 made of low-concentration n-type InP are stacked.
In the center of the wide band gap layer 32, p such as Zn
There is a diffusion region 33 in which the type impurity is diffused, and the first mesa 2
An n-side electrode 34 is formed on the carrier blocking layer 28 and a p-side electrode 35 is formed on the diffusion region 33. n-side electrode 3
4 is formed so as to occupy the first mesa 29.

As shown in FIGS. 8A and 8C,
In the first mesa 29, a light incident portion 36 is formed on the carrier blocking layer 28 apart from the light absorbing layer 31, and the light incident portion 36 is formed.
Is deposited with an antireflection film 37 made of SiN.

Further, as shown in FIGS. 8A and 8B, the exposed surface of the semiconductor layer is covered with the insulating film 3 on which SiN and SiO ₂ are laminated except for the peripheral scribe lane 38.
9 and an insulating film 39 on the second mesa 30.
The pad 40 formed through the P-side electrode 35 and the wiring 4
1 connected. n-side electrode 34, p-side electrode 3
5, the pad 40 and the wiring 41 are, for example, Ti / Pt / A
It is made of a laminated metal film of u, and can be formed collectively by one evaporation and lift-off process.

Further, on the second main surface 42 of the semiconductor substrate 25, a reflection film 43 for reflecting light is formed. The reflection film 43 may be composed of only a metal film.
For example, if a laminated structure of SiN and Al is used, higher reflectance can be obtained.

The light receiving element according to the sixth embodiment is similar to the light receiving element according to the first embodiment in that the incident light 44
5 and twice through the filter layer 27 before entering the light absorbing layer 31. That is, the thickness of the filter layer 27 through which the incident light 44 passes can be substantially doubled. Further, since the carrier blocking layer 28 made of a material having a larger bandgap than the filter layer 27 is inserted between the filter layer 27 and the light absorption layer 31, the carriers generated in the filter layer 27 are And the sensitivity ratio does not decrease.

The incident light 44 is applied to the first
Although the light does not directly enter the light absorbing layer 31 formed on the main surface 26 side, since the light incident portion 36 is on the first main surface 26 side, the light receiving element according to the sixth embodiment is of a front-illuminated type. The light receiving element according to the sixth embodiment is of a planar type in which a wide band gap layer 32 is stacked on a light absorbing layer 31 and a light receiving portion is formed by impurity diffusion. Since it is between the layer 31 and the semiconductor substrate 25, the depth of impurity diffusion is the same as that of the light receiving element according to the first embodiment. Further, the first main surface 26 of the semiconductor substrate 25
Since the p-side and n-side electrodes are both formed on the side, flip-chip bonding can be easily performed.

The above effects are the same as those of the light receiving element according to the first embodiment. However, the light receiving element according to the sixth embodiment uses a semi-insulating semiconductor substrate 25 and a p-side electrode 35.
Of the pad 40 and the portion of the light absorbing layer 31 are separated in a mesa shape (island shape). If not,
Since an n-type substrate is used to form a pad for a p-side electrode via an insulating film, a MIS (Metal Insul) is formed.
ator semiconductor) structure,
The pad capacitance is added to the element capacitance, and the pad capacitance may affect the entire light receiving element. On the other hand, in the light receiving element according to the sixth embodiment, the n-type layer (the first mesa 29) on which the n-side electrode 34 is formed.
Since the pad 40 is formed on a mesa (the second mesa 30) different from the above, there is an original effect that the pad capacitance is not added to the element capacitance.

In the light-receiving element according to the sixth embodiment, the p-side electrode 35 is formed in a circular shape, not a ring shape, so as to block incident light from above the light absorbing layer 31. This is to prevent the scattered light of the incident light 44 from being incident from above the light absorbing layer 31 and deteriorating the sensitivity ratio. However, when the incident light is directly incident from above the light absorbing layer 31 in the inspection step, the p-side electrode 35 may be formed in a ring shape. Further, in the light receiving element according to the sixth embodiment, the n-side electrode 34 is formed on the carrier blocking layer 28, but may be formed on the filter layer 27. The filter layer 27 has a smaller forbidden band width than the carrier blocking layer 28, and the contact resistance may be reduced by forming an n-side electrode thereon.
The pad 40 may be formed on the second mesa 30 including only the filter layer 27, or may be formed on the semiconductor substrate 25. However, in any case, it is desirable to interpose the insulating film 39. This is because even a semi-insulating substrate has some conductivity, and if the pad 40 is formed directly on the semiconductor layer, a leak current is generated between the pad 40 and the n-side electrode.

(Seventh Embodiment) In the seventh embodiment,
A light receiving element mounting body in which the light receiving element according to the first embodiment of the present invention is electrically or optically mounted on an optical member will be described with reference to FIG. FIG. 9 is a cross-sectional view of a light receiving element mounted body according to the seventh embodiment of the present invention.

A guide groove 46 is formed on a mounting substrate 45 made of quartz glass or a semiconductor such as Si or GaAs, and an optical fiber 47 is placed in the guide groove 46. The guide groove 46 is filled with a resin (not shown).

A slit 48 is formed in the mounting substrate 45 so as to cut the optical fiber 47 obliquely.
8, a reflection plate 49 is inserted. Also, the mounting board 45
A light receiving element 50 is flip-chip bonded across the guide groove 46 on the surface of the substrate. The light receiving element 50
The light incident part 51 of the light receiving element 50 is bonded to the mounting substrate 45.

The incident light 52 propagating through the optical fiber 47 from the right side of the drawing sheet is reflected by the reflection plate 49 and enters the light incident portion 51 of the light receiving element 50. As described in the first embodiment, the incident light 52 incident on the light receiving element 50 is reflected by the second main surface of the semiconductor substrate and is incident on the light absorbing layer. Therefore, the incident light 52 passes through the filter layer twice before entering the semiconductor substrate and before entering the light absorbing layer. That is, the thickness of the filter layer through which the incident light 52 passes can be substantially doubled.

In the light receiving element mounted body according to the seventh embodiment, since the light receiving element 50 is flip-chip bonded to the mounting substrate 45, the parasitic capacitance associated with the wire is reduced as compared with the case where the wire bonding is performed, and the speed is increased. Operation becomes possible. In particular, when the mounting substrate is a dielectric material such as glass or a semi-insulating semiconductor substrate, the effect of reducing the parasitic capacitance is increased. Further, by using a light receiving element obliquely incident on the light incident portion, the incident light 52 from the mounting substrate 45 side can be used.
Is directly incident on the light incident portion 51 of the light receiving element 50 and optically coupled, so that the optical coupling is completed when the light receiving element 50 is bonded to the mounting substrate 45, thereby eliminating a mounting process for optical coupling. Become.

Although not shown, the optical fiber 4
If a semiconductor laser is placed on the emission side of 7 (the left end side of the optical fiber 47 in FIG. 9) and the reflecting plate 49 is a half mirror, a light receiving and emitting module can be easily formed.

The light receiving element 50 may be the light receiving element according to the second to sixth embodiments. However, when the light is incident obliquely on the light incident part 51 as shown in FIG. The light receiving element according to the sixth embodiment is preferable.
, That is, the reflection plate 49 passes the incident light 5
In the case where the light receiving element is provided at an angle of 45 degrees with respect to the traveling direction 2, the light receiving elements according to the second and fourth embodiments are preferable.

[0106]

According to the light receiving element of the present invention, the incident light from the light incident portion is reflected by the first principal surface or the second principal surface and is incident on the light absorbing layer until the incident light enters the light absorbing layer. Since the light is transmitted twice or more through the filter layer formed between the substrate and the light absorbing layer, the thickness of the filter layer is substantially reduced by 2 to the light receiving element having a structure in which the incident light is transmitted once through the filter layer. It can be more than double. As a result, the long wavelength (1.55
For example, a sensitivity ratio of 20 dB or more can be obtained as the sensitivity ratio between the signal light on the μm side and the signal light on the short wavelength (1.3 μm) side.

On the other hand, according to the light receiving element mounted body of the present invention,
Since the light-receiving element can be easily flip-chip bonded to the mounting board, the parasitic capacitance associated with mounting is reduced compared to the case of wire bonding, high-speed operation is possible, and optical coupling is completed at the time of bonding. A mounting process for optical coupling is not required.

[Brief description of the drawings]

FIG. 1 (a) is a plan view of a light receiving element according to a first embodiment of the present invention. FIG. 1 (b) is a cross-sectional view taken along line XX in FIG. 1 (a). Sectional view

FIG. 2 is a graph showing a relationship between wavelength and absorption of InGaAsP.

FIG. 3 is a graph showing a band gap of each layer.

4A is a plan view of a light receiving element according to a second embodiment of the present invention. FIG. 4B is a cross-sectional view taken along line XX in FIG. Sectional view (d) Back view showing a part of the back face of the light receiving element of the present embodiment

5 (a) is a plan view of a light receiving element according to a third embodiment of the present invention. FIG. 5 (b) is a cross-sectional view taken along line XX in FIG. 5 (a). Sectional view

6A is a plan view of a light receiving element according to a fourth embodiment of the present invention. FIG. 6B is a cross-sectional view taken along line XX in FIG. 6A. FIG. 6C is a sectional view taken along line YY in FIG. Sectional view

FIG. 7A is a plan view of a light receiving element according to a fifth embodiment of the present invention. FIG. 7B is a cross-sectional view taken along line XX in FIG. Sectional view (d) Back view showing a part of the back face of the light receiving element of the present embodiment

8A is a plan view of a light receiving element according to a sixth embodiment of the present invention. FIG. 8B is a cross-sectional view taken along line XX in FIG. Sectional view

FIG. 9 is a sectional view of a light receiving element mounted body according to a seventh embodiment of the present invention.

FIG. 10 is a cross-sectional view of a conventional pin photodiode having a long wavelength passband characteristic.

[Explanation of symbols]

 1, 25 Semiconductor substrate 2, 26 First main surface 3, 21, 27 Filter layer 4, 28 Carrier blocking layer (buffer layer) 5, 31 Light absorption layer 6, 32 Wide band gap layer (window layer) 7, 33 Diffusion Regions 8, 34 n-side electrode 9, 35 p-side electrode 10, 23, 36, 51 light incident portion 11, 37 antireflection film 12, 38 scribe lane 13, 39 insulating film 14, 40 pad (pad electrode) 15, 41 Wiring 16, 42 Second main surface 17, 20, 24, 43 Reflective film 18, 44, 52 Incident light 19, 22 Inclined portion 29 First mesa 30 Second mesa 45 Mounting board 46 Guide groove 47 Optical fiber 48 Slit 49 Reflection Plate 50 Light receiving element

Claims (16)

[Claims] A semiconductor substrate; a filter layer formed on a first main surface of the semiconductor substrate; a light absorption layer formed in an island shape on the filter layer; and the light absorption on the filter layer A light incident portion formed in a portion where the layer is not formed, wherein the absorption edge wavelength of the filter layer is longer than the absorption edge wavelength of the semiconductor substrate and shorter than the absorption edge wavelength of the light absorption layer. A light receiving element characterized by the above-mentioned. 2. The light receiving device according to claim 1, wherein a reflection film is formed on a second main surface of the semiconductor substrate. 3. A carrier blocking layer formed between the filter layer and the light absorbing layer, the carrier blocking layer being made of a material having a larger bandgap than the filter layer, and an impurity formed on the light absorbing layer. The light receiving element according to claim 1, further comprising a wide band cap layer having a diffusion region. 4. The semiconductor substrate, the filter layer, and the carrier blocking layer are of a first conductivity type, the impurity diffusion region is of a second conductivity type, and the semiconductor substrate, the filter layer, and the carrier blocking layer are of a first conductivity type. A first electrode formed on at least one of them, a second electrode formed on the impurity diffusion region, and at least one of the semiconductor substrate, the filter layer and the carrier blocking layer via an insulating film The light receiving element according to claim 3, further comprising: a pad portion formed by the step (c), and a wiring for electrically connecting the second electrode and the pad portion. 5. An inclined portion for reflecting incident light incident on the semiconductor substrate and causing the incident light to enter the light absorbing layer is formed on a second main surface of the semiconductor substrate. The light receiving element according to claim 1. 6. A semiconductor substrate; a filter layer formed on a second main surface of the semiconductor substrate; a light absorbing layer formed in an island shape on a first main surface of the semiconductor substrate; A light incident portion formed on a portion of the main surface where the light absorption layer is not formed, wherein an absorption edge wavelength of the filter layer is longer than an absorption edge wavelength of the semiconductor substrate; A light receiving element having a wavelength shorter than the absorption edge wavelength. 7. The light receiving element according to claim 6, wherein a wide band gap layer having an impurity diffusion region is formed on the light absorbing layer. 8. The light-receiving element according to claim 7, wherein the first main surface of the semiconductor substrate has an inclined portion, and the light incident portion is on the inclined portion. 9. At least two filter layers are formed before light incident from the light incident part enters the light absorbing layer.
9. The light receiving element according to claim 1, wherein the light is transmitted once. 10. A semiconductor substrate, a filter layer formed on a first main surface side or a second main surface side of the semiconductor substrate, and light formed in an island shape on the first main surface side of the semiconductor substrate. An absorption layer, a reflection film formed on the first main surface side of the semiconductor substrate, and a light incident portion formed on the second main surface side of the semiconductor substrate; and an absorption end of the filter layer. A light receiving element, wherein a wavelength is longer than an absorption edge wavelength of the semiconductor substrate and shorter than an absorption edge wavelength of the light absorption layer. 11. The light-receiving element according to claim 10, wherein the light incident from the light incident portion passes through the filter layer at least three times before entering the light absorbing layer. 12. The filter layer and the carrier blocking layer are formed in one or a plurality of islands, the semiconductor substrate is semi-insulating, and the filter layer and the carrier blocking layer are of a first conductivity type. A first electrode formed on the filter layer or the carrier blocking layer in an island having the light absorbing layer; and a first electrode formed on the impurity diffusion region. A second electrode; a pad portion formed on the semiconductor substrate or on the filter layer or the carrier blocking layer forming an island other than the island on which the first electrode is formed; and the second electrode and the pad portion The light receiving element according to claim 3, further comprising: a wiring for electrically connecting the light receiving element to the light receiving element. 13. A light receiving element having a filter layer formed between a semiconductor substrate and a light absorbing layer, wherein light incident from a first main surface side of the semiconductor substrate is applied to a second main surface of the semiconductor substrate. A light-receiving element that passes through the filter layer at least twice before being reflected by the light absorption layer and absorbed by the light absorption layer. 14. The light receiving element according to claim 13, wherein an absorption edge wavelength of said filter layer is longer than an absorption edge wavelength of said semiconductor substrate and shorter than an absorption edge wavelength of said light absorption layer. 15. A mounting substrate, an optical waveguide formed in the mounting substrate, a deflecting element for deflecting a path of incident light propagating through the optical waveguide toward a surface of the mounting substrate, and disposed on the mounting substrate. A light receiving element mounting body, comprising: a semiconductor substrate; and a filter layer formed on at least one of a first main surface side and a second main surface side of the semiconductor substrate. And a light absorbing layer formed in an island shape on the first main surface side of the semiconductor substrate; and a light incident portion formed on the first main surface side of the semiconductor substrate. A light-receiving element mounting body, wherein the first main surface side on which the light incident portion is formed is arranged facing a mounting substrate. 16. The optical waveguide, wherein the optical waveguide is an optical fiber embedded in a groove formed on the mounting substrate, and wherein the deflecting element is formed on the mounting substrate so as to cut the optical fiber. The light-receiving element mounting body according to claim 15, wherein the light-receiving element is disposed on the mounting substrate across the groove.