JPH11330501A - Semiconductor photodetecting element and its manufacture - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the light emitting efficiency, by a method wherein a multiple reflecting film separates an element layer from a semiconductor substrate also reflecting the transmission beams transmitting semiconductor photodetecting element in the element layer on the interface between the reflecting film and the element layer, so that the reflected beams may be repeatedly entered into the semiconductor photodetecting element. SOLUTION: A multireflecting film 16 wherein SiO2 films 14 having the first refractive index and polysilicon films 15 having the second refractive index are laminated with one another is formed on a semiconductor substrate 1. This multiple reflecting film 16 insulates the semiconductor substrate 1 and an element layer 2 with each other and simultaneously almost perfectly reflects the incident beams from the incident surface 13 of photodetecting elements 3 formed on the element region so as to repeatedly enter the reflected beams into the photodetecting elements 3. Through these procedures, the incident beams can repeatedly pass through the element layer 2 even if the thickness of the element layer 2 is within the range of 10 μm-20 μm, so that photodetecting efficiency is raised up to the level equivalent to double the thickness of the element layer.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor light receiving device, and more particularly to a semiconductor light receiving device having high light receiving efficiency in an infrared region and a method of manufacturing the same.

[0002]

2. Description of the Related Art Conventionally, in a single photodetector formed on a silicon substrate, the silicon substrate is made sufficiently thick to generate electron-hole pairs in the silicon substrate so that the energy of incident light can be absorbed by the silicon substrate with high efficiency. To obtain high light receiving efficiency.

However, for example, when an array of light receiving elements is arranged on a silicon substrate or an optical integrated circuit is formed by integrating a light receiving element and a transistor for amplifying an optical signal on the same substrate, an element isolation technique is required. The introduction of is indispensable.

Usually, a pn junction isolation which is easy to form is often used as an element isolation method for an integrated circuit. However, in the case of an optical integrated circuit, if light enters the pn junction for element isolation, the reverse-biased pn junction exhibits photoconductivity, and thus cannot play the role of element isolation. Therefore, for element isolation of an optical integrated circuit, it was necessary to use a dielectric isolation method that surrounds an element region on a silicon substrate with an insulating film such as SiO ₂ .

In recent years, silicon wafer bonding technology has been developed,
The silicon substrates can be bonded to each other via the SiO ₂ film. The silicon wafer bonding technology and the dielectric separation method of embedding the dielectric film in the trench or V-groove are used to insulate the element region into islands. Separation methods have been developed.

However, in this method, the depth of the trench or the V-shaped groove has a certain limitation due to a problem in processing technology, so that the thickness of the element layer cannot be made sufficiently large, and dielectric isolation is possible. The thickness of the element layer was limited to a range of at most 10 μm to 20 μm.

FIG. 6 is a sectional view of a semiconductor light receiving element for an optical integrated circuit using a conventional silicon wafer bonding technique. The semiconductor light receiving element shown in FIG. 6 includes a silicon substrate 1, an element layer 2 for forming an element, an element region 3 for forming a light receiving element on this element layer, and an element region 4 for forming a transistor for amplifying a light receiving signal. ing. Hereinafter, 3 and 4 are collectively referred to as an element region.

The dielectric isolation region 5 between the element regions 3 and 4
Is formed by embedding polysilicon 6 in a V groove via a SiO ₂ film 7 or the like as a dielectric. In this dielectric separation, it is not always necessary to use a V-groove, but a method of forming a trench or the like and embedding a dielectric such as SiO ₂ therein may be used.

The light receiving element is formed by using the n ⁻ layer 8, the p type layer 9 of the element layer 2, and the n ⁺ layer 10 for making a contact on the n side. The pn ⁻ −n ⁺ structure including 9, 8, and 10 constitutes a pin type light receiving element. In the element region 4 where the transistor is formed, the n ⁺ layer 10 is used as a contact layer for the emitter diffusion layer and the collector, the p-type layer 9 is used as a base region, and the n ⁻ -type layer 8 is used as a collector region. Can be

11 is a light receiving element and an electrode of a transistor,
Reference numeral 12 denotes a passivation film that covers these electrodes and the wiring connecting them. Note that the passivation film can also serve as an antireflection film on the light receiving surface 13.

In the conventional optical integrated circuit shown in FIG. 6, the silicon substrate 1 and the element layer 2 are bonded via a dielectric film such as a SiO ₂ film 14, and after the bonding, a manufacturing process using a normal dielectric separation is performed. Is applied as it is to form light receiving elements and transistors in the element regions 3 and 4 of the element layer 2, respectively.

As described above, at this time, the thickness of the element layer is limited to the range of 10 μm to 20 μm due to the restriction on the dielectric isolation. 13 enters the element layer 2
Are not sufficiently absorbed, and pass through the SiO ₂ film 14, and are absorbed by the thick silicon substrate 1 to generate electron-hole pairs.

The electron-hole pairs generated in the silicon substrate 1 are blocked by the SiO ₂ film 14 and cannot reach the light receiving element, so that they disappear without being converted into electric energy. Therefore, in order to increase the light receiving efficiency of the light receiving element, it is necessary to increase the thickness of the element layer and increase the light absorption of the element layer.

Here, the wavelength dependence of the light absorption of silicon will be discussed with reference to FIG. The horizontal axis in the figure is the depth from the surface of silicon, the vertical axis is the light absorptivity of silicon, and the parameter of each curve shown in the lower part of the figure is the wavelength of light. Visible wavelength 6
At 60 nm, the absorptance of silicon having a thickness of 10 μm or more exceeds 95%, so that the light-receiving element formed in the element layer having a thickness of 10 μm to 20 μm exhibits high light-receiving efficiency, but has a wavelength of 9 μm.
It can be seen that in the infrared region of 50 nm or more, sufficient light absorption cannot be obtained with an element layer having a thickness of 10 μm.

For example, as a typical infrared light emitting device in the infrared region, Ga which exhibits high luminous efficiency at a wavelength of 940 nm is used.
When an As light emitting element is used as a light source, the thickness of the element layer is 2
Even if the thickness is increased to 0 μm, the light absorption rate by silicon is 30
FIG. 7 shows that most of the incident light is transmitted through the SiO ₂ film 14 and absorbed by the silicon substrate 1, and the light receiving efficiency of the light receiving element is greatly reduced.

[0016]

As described above, in the conventional light receiving device using the silicon wafer bonding technique, the device regions are separated from each other by a dielectric isolation method in which a dielectric is buried in a V-groove or a trench. Layer thickness of 10 μm to 20
There is a problem that the light receiving efficiency must be significantly reduced in the infrared region.

The present invention has been made to solve the above problems, and provides a light-receiving element which exhibits sufficiently high luminous efficiency in the infrared region even when the thickness of the element layer is in the range of 10 μm to 20 μm. The purpose is to do.

[0018]

According to the present invention, there is provided a semiconductor light receiving element formed on an element layer on a semiconductor substrate, wherein the element layer has a first refractive index at an interface with the semiconductor substrate. And a multi-reflection film in which a film having a second refractive index is alternately laminated. The multi-reflection film insulates and separates the element layer and the semiconductor substrate, and forms a semiconductor light-receiving layer formed on the element layer. Light transmitted through the element is reflected at the interface, and the reflected light is incident on the semiconductor light receiving element again.

Further, the semiconductor light receiving element of the present invention includes a plurality of element regions in which the element layers are separated from each other by a dielectric film on a semiconductor substrate, and the plurality of element regions are provided at an interface with the semiconductor substrate. A multi-reflection film in which a film having a refractive index of 2 and a film having a second refractive index are alternately stacked, wherein the multi-reflection film insulates and separates the element region and the semiconductor substrate from each other, and Reflecting the transmitted light transmitted through the semiconductor light receiving element formed in the region at the interface,
The reflected light is incident on the semiconductor light receiving element again.

Preferably, the dielectric film separating the element regions from each other is a multiple reflection film in which films having a first refractive index and films having a second refractive index are alternately laminated. And

More preferably, the film having the first refractive index is made of a polycrystalline semiconductor, and the film having the second refractive index is made of a dielectric. More preferably, the polycrystalline semiconductor is made of any one of silicon and germanium, and the dielectric is made of SiO ₂ , Si ₃ N ₄ ,
SiO _x (1 ≦ x ≦ 2), SiN _x (1 ≦ x ≦ 1), S
iO _x N _y (1 ≦ x + y ≦ 2), PSG, BSG, BP
SG, Al ₂ O ₃ , AlN, (Ba, Sr) TiO ₃ ,
It is characterized by being made of any one of TiO ₂ and Ta ₂ O ₃ .

Preferably, the films having the first and second refractive indices are SiO ₂ , Si ₃ N ₄ , SiO _x (1
≦ x ≦ 2), SiN _x (1 ≦ x ≦ 1), SiO _x N _y
(1 ≦ x + y ≦ 2), PSG, BSG, BPSG, Al
₂ O ₃ , AlN, (Ba, Sr) TiO ₃ , TiO ₂ ,
The film made of any one of Ta ₂ O ₃ and having the second refractive index is made of a material different from the film having the first refractive index.

According to the method of manufacturing a semiconductor light receiving element of the present invention, a multiple reflection film is formed by alternately laminating an SiO ₂ film and a polycrystalline silicon film on one main surface of a first silicon substrate. One principal surface of the silicon substrate and the surface of the SiO ₂ film or the polycrystalline silicon film which is the final film of the multiple reflection film are joined in clean air, and the joining strength is increased by heat treatment of the joining. The method is characterized by including a step of removing the other main surface of the second silicon substrate having undergone the above process by a predetermined thickness, and further polishing the surface to form an element layer having a predetermined thickness.

Further, in the method of manufacturing a semiconductor light receiving element according to the present invention, the multiple reflection film is formed by alternately laminating an SiO ₂ film and a polycrystalline silicon film on one main surface of the first silicon substrate. The surface of the polycrystalline silicon film, which is the final film of the multiple reflection film, is polished, and one main surface of a second silicon substrate and the surface of the polycrystalline silicon film are joined in clean air. Heat treatment to increase the bonding strength, remove the other main surface of the second silicon substrate having undergone the above process by a predetermined thickness, and further polish the surface to form an element layer of a predetermined thickness. It is characterized by including.

In the method of manufacturing a semiconductor light receiving element according to the present invention, a first multiple reflection film is formed by alternately stacking a SiO ₂ film and a polycrystalline silicon film on one main surface of a first silicon substrate. Then, a second multiple reflection film is formed by alternately stacking a SiO ₂ film and a polycrystalline silicon film on one main surface of the second silicon substrate, and a final film of the first multiple reflection film is formed. An SiO ₂ film; a polycrystalline silicon film as a final film of the second multiple reflection film; joining a surface of the SiO ₂ film and a surface of the polycrystalline silicon film in clean air; By doing so, the bonding strength is increased, the other main surface of the first or second silicon substrate that has undergone the above process is removed by a certain thickness, and the surface is further polished to obtain an element layer having a predetermined thickness. It is characterized by including a step. Preferably, the surface of the polycrystalline silicon film forming the final film is polished.

[0026]

Embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 1 is a view showing the structure of the silicon light receiving element according to the first embodiment of the present invention. Parts corresponding to those in FIG. 6 are denoted by the same reference numerals, and detailed description is omitted.

The difference from the conventional structure is that the SiO ₂ film 14 and the polysilicon film 1 are provided between the silicon substrate 1 and the element layer 2.
5 are alternately stacked to form a multiple reflection film 16. Here, it is desirable that no impurity be added to the polysilicon film 15 in order to avoid light absorption by free electrons or holes.

As described above, the element layer 2 forming the light receiving element
A multi-reflection film 16 is formed between the silicon substrate 1 and the SiO ₂ film 14 with respect to the wavelength of the incident light from the light receiving surface 13.
If the thickness of the polysilicon film 15 is optimized, the element layer 2
Can be reflected almost 100% by the multiple reflection film 16. When light is perpendicularly incident on the multiple reflection film 16, the reflectance R _{2N + 1} of the multiple reflection film is given by the following equation (1).

[0029]

(Equation 1)

Here, N is the number of repetitions of a double film made of SiO ₂ and polysilicon, n ₁ is the refractive index of silicon forming the element layer 2, and n ₂ and n ₃ are SiO ₂ film 14 and polysilicon film 15, respectively. And n _l is the refractive index of the silicon substrate 1.

If the thicknesses of n ₁ and n _l are infinite, the thicknesses of n ₂ and n ₃ are d ₂ and d ₃ , and the wavelength of incident light in air is λ ₀ , then n ₂ · d ₂ = n ₃ ·
d ₃ = SiO like relationship lambda _0/4 holds ₂ film 14
And the thickness of the polysilicon film 15 are set respectively. From the result of equation (1), it is understood that the reflectance R _{2N + 1} approaches 100% as N increases and the refractive index ratio n 2 / n 3 of the double film constituting the multiple reflection film decreases.

For the multiple reflection film 16 composed of the SiO ₂ film 14 and the polysilicon film 15, the number of repetitions N and the reflectance R
FIG. 2 shows the result of _obtaining the relationship with _{2N + 1} . For example, SiO
If the thickness of the layers is optimized by a total of five layers of three layers of _two films and two layers of polysilicon films, a reflectance of 90% or more can be obtained. Note that N
= 2, that is, the reflectivity does not reach 90% with two layers of SiO ₂ and polysilicon, but the reflectivity becomes 90% or more with three layers of SiO ₂ film.

As shown in FIG. 6, in the conventional light receiving element using the silicon wafer bonding technique, the SiO ₂ film 14 is provided merely to insulate the element layer 2 and the silicon substrate 1 from each other. The transmitted light transmitted through the element layer from the light receiving surface 13 was further transmitted through the SiO ₂ film 14 and absorbed by the silicon substrate 1, and the reflection by the SiO ₂ film 14 was negligibly small.

As shown in the first embodiment, the conventional
As shown in FIG. 1, the insulating film composed of the SiO ₂ film 14 is replaced with a multiple reflecting film 16 in which three SiO ₂ films and two polysilicon films are alternately laminated.
The fact that the reflectance of No. 6 can be made 90% or more can be said to be an unexpectedly large effect.

It should be noted that the step of laminating the SiO ₂ film and the polysilicon film has a sufficient track record in the process of manufacturing a semiconductor integrated circuit, and is a great advantage in that it does not involve any problems in the steps.

With this configuration, the transmitted light that enters the light receiving element from the incident surface 13 and passes through the element layer 2 is almost completely reflected by the multiple reflection film 16 and passes through the element layer 2 again. Therefore, the same effect of improving the light receiving efficiency as when the thickness d of the element layer becomes 2d is produced.

Further, since the improvement in the light receiving efficiency is due to the reflection of light, not only the effect of simply doubling the thickness of the element layer, but also the generation of electron-hole pairs due to reflected light is doubled. Since the irradiation is performed near the depletion layer of the light receiving element as compared with the case where light is incident on the element layer, the time required for diffusion of electron / hole pairs into the depletion layer can be greatly reduced.

That is, by interposing the multiple reflection film 16 of the present invention between the silicon substrate 1 and the element layer 2,
It is extremely noticeable that the improvement of the light receiving efficiency and the operation speed of the integrated silicon light receiving element are simultaneously achieved.

With respect to the improvement of the light receiving efficiency, for example, the wavelength 94
When a GaAs infrared light emitting device of 0 nm is used as a light source, when the thickness of the element layer is 20 μm, the light is effectively absorbed by the light of the reciprocating 40 μm silicon. Rate can be improved to about 70%. That is, the light receiving efficiency can be extremely easily doubled or more as compared with the related art.

As described above, at this time, the operation speed of the light receiving element is greatly improved. Therefore, if the multiple reflection film 16 of the present invention is used between the silicon substrate 1 and the element layer 2, the light receiving element and the amplifying transistor Can greatly improve the gain bandwidth product of the light receiving system of the optical integrated circuit including:

When a GaAlAs light emitting device having a wavelength of 880 nm is used as a light source, the absorptance of the light receiving device using the conventional silicon wafer bonding technique shown in FIG. 6 is about 60 when the thickness of the device layer 2 is 20 μm. However, if the structure of the light receiving element having the multiple reflection film 16 of the present invention shown in FIG. 1 is used, the light absorptance can be improved to about 90%.

Next, a method of manufacturing a silicon photodetector according to a second embodiment of the present invention will be described with reference to FIG.
The structure of the light receiving element of the present invention is characterized in that the silicon substrate 1 and the element layer 2 are bonded through the multiple reflection film 16, and after the good bonding is performed, the conventional V-groove or trench is used. Since the existing dielectric separation step can be used as it is, the following embodiment will be described in detail focusing on this bonding step alone.

As shown in FIG. 3A, the silicon substrate 1
SiO ₂ film 14 by thermal oxidation and CVD (Chem
ical vapor deposition) and a polysilicon film 15 are alternately deposited. As mentioned earlier, the thickness of the film at this time differs depending on the wavelength range of use of the light receiving element, and the product of the film thickness and the refractive index is set so that each product is 1/4 of the wavelength of light in air. Is done.

As a method of growing a film, M having high controllability of film thickness is used.
OCVD (Metal-Organic Chemical Vapor Deposition)
Needless to say, better results can be obtained by using the MBE (Molecular Beam Epitaxy) method or the MBE method.

When growing the SiO ₂ film 14 on the silicon substrate 1, it is desirable to clean the surface of the silicon substrate 1. However, the polished surface of a wafer purchased in a normal specification as a silicon wafer for a mass production process is simply used as it is. Good results can be obtained if used.

The element layer 2 shown in FIG. 3A is a silicon wafer before bonding and has a polished surface 2a of a wafer having the same specifications as the silicon substrate 1. Then, the SiO ₂ bonding surface 14 a of the final SiO ₂ film 14 formed in the above step and the polished surface 2 a of the element layer 2 are joined to face each other. At this time,
The polished surface 2a of the element layer 2 serving as a bonding surface is a hydrophobic etching solution, and the bonding surface 14a of the SiO ₂ film 14 on the substrate 1 is used.
Good results can be obtained if a is washed with a hydrophilic etching solution.

As shown in FIG. 3B, the silicon substrate 1 and the silicon wafer to be the element layer 2 are joined in a clean environment of class 10 or less. Here, class 10 or less means
The number of debris of 0.5 μm or less at 1 ft ³ is a cleanliness of 10 or less, and good results can be obtained by working in a clean bench placed in a normal semi-clean room. Here, the term “joining” refers to simply bringing the joining surfaces into close contact with each other without particularly applying pressure.

After bonding the silicon substrate 1 and the silicon wafer serving as the element layer 2 via the multiple reflection film 16, the bonding is performed at 800 ° C. to 110 ° C. in an oxidizing atmosphere to increase the bonding strength.
Heat treatment at a temperature of 0 ° C. for 1 hour or more. Here, the oxidizing atmosphere refers to a mixed gas of oxygen and nitrogen, or a hydrogen-burning oxidizing atmosphere in which hydrogen is slightly mixed in oxygen.

If an oxidizing atmosphere is used, the surface opposite to the bonding surface between the silicon substrate 1 and the element layer 2 is
Since the O ₂ film 14b is formed, the stress generated on the front and back of each wafer during the heat treatment is balanced, and the warpage of the wafer can be significantly reduced even when a large wafer is used.

Since the bonding state shown in FIG. 3B thus bonded is extremely strong, an unnecessary thickness portion of the silicon wafer serving as the element layer 2 is cut by a grinder using a grinder. It is possible to easily scrape down to 17.

The cut surface 17 of the glider contains many scratches and defects, and a semiconductor element cannot be formed on the surface. Therefore, the surface is further subjected to CMP (Chemical-Mechanical).
Polishing) to remove up to the CMP polished surface 18.
Thus, the multiple reflection film 16 on the silicon substrate 1
An element layer 2 having a thickness of 10 μm to 20 μm is formed thereon.

Subsequently, in the process of forming the dielectric isolation region 5 in the element layer 2 and forming the light receiving element and the transistor for amplifying the optical signal, the manufacturing process of the semiconductor integrated circuit by the ordinary dielectric isolation technology is used as it is. Can be implemented.

Next, a method for manufacturing a silicon photodetector according to a third embodiment of the present invention will be described with reference to FIG. The third embodiment is characterized in that the uppermost layer of the multiple reflection film formed on the silicon substrate is a thick polysilicon film, and the thick polysilicon film and the element layer are bonded.

That is, a multiple reflection film 16 composed of a three-layer SiO ₂ film 14 and a two-layer polysilicon film 15 is formed on the silicon substrate 1 as in the first embodiment. Subsequently, a polysilicon film 19 as a final layer thicker than the polysilicon film 15 is formed.

When a polysilicon film is formed by using the CVD method, the surface is usually lost in smoothness during the polycrystallization process, and it is likely to have an extremely fine uneven surface (cloudy surface). If the polysilicon film 15 including such fine irregularities and the SiO ₂ film 14 are stacked, the surface smoothness of the SiO ₂ film 14 may be lost depending on the growth conditions.

At this time, as shown in FIG. 3A, the element layer bonding surface 2a and the final SiO ₂ bonding surface
If a is bonded, voids may be generated at the interface, which adversely affects the yield of the bonding process.

In order to avoid this problem, as shown in FIG. 4, in the third embodiment, a thick polysilicon film 19 is formed as a final layer, and fine irregularities are removed by using a CMP polishing method.

The thus polished CMP polished surface 20
And an adhesive surface 2a of the element layer 2 are subjected to a surface treatment with a hydrophilic or hydrophobic cleaning solution, and then joined in a clean atmosphere,
If heat treatment is performed at 800 ° C. to 1100 ° C. for 1 hour or more, a strong adhesive state can be obtained.

At this time, since there is no difference in the refractive index between the final polysilicon film 19 and the element layer 2 made of single crystal silicon, the thickness of the polysilicon film 19 is reduced to the multiple reflection film 16.
The difference from the thickness of the polysilicon film 15 does not affect the reflectivity of the multiple reflection film 16 at all. For example, C
Even if a slight error occurs in the parallelism between the CMP polished surface 20 and the multiple reflection film 16 due to the MP polishing, no problem occurs.

Next, a method for manufacturing a silicon photodetector according to a fourth embodiment of the present invention will be described with reference to FIG. In the fourth embodiment, since a multiple reflection film having a higher reflectance is formed between the silicon substrate 1 and the element layer 2, there is an advantage in increasing the number of layers of the multiple reflection film. .

For example, when forming a total of seven multi-reflection films composed of four SiO ₂ films and three poly-silicon films, if all of them are formed on the silicon substrate 1, the distortion caused by the multi-reflection film will occur. Is excessive, and the silicon substrate 1 may be warped, and the yield of bonding with the element layer 2 may be reduced.

[0062] As shown in FIG. 5 this time, divided into the polishing surface of the lower portion of the silicon wafer forming the polishing surface and the element layer 2 of the top of the silicon substrate 1 to form respectively a multiple reflection film, SiO ₂ film in the central portion Is bonded to the CMP polished surface 23 of the polysilicon film 15 cleaned and polished by CMP, the problem of the warpage is greatly reduced.

At this time, due to an error occurring in the CMP polished surface 23, the final polysilicon film 15 formed on the element layer 2 is formed.
Thickness may deviate from the design value of the multiple reflection film,
At this time, for a total of five layers of the multiple reflection film shown in FIG.
In FIG. 5, an additional polysilicon film 21 and an additional SiO ₂
The addition of the film 22 makes it possible to increase the overall reflectance.

The present invention is not limited to the above embodiment. For example, in the first embodiment, the structure in which the multiple reflection film 16 is formed between the silicon substrate 1 and the element layer 2 has been described, but the present invention is not necessarily limited to this. If the SiO ₂ film 7 in the element isolation region 5 is also a multiple reflection film, when scattered light enters from the incident surface 13, it can be used as a part of the reflection surface.

In the second to fourth embodiments, the method of forming a multiple reflection film composed of a SiO ₂ film and a polysilicon film mainly by the CVD method has been described. However, if the MOCVD method or the MBE method is used, The accuracy of the film thickness is improved, and the smoothness of the multiple reflection film can be improved.
Further, if the polysilicon film is made amorphous by using a plasma technique and measures are taken such as using it as a component of a multi-reflection film, the smoothness of the polysilicon film is further improved, and the CMP polishing step of the bonding surface is eliminated. be able to.

Further, in the first to fourth embodiments, the structure in which the polysilicon film is used as the film having a large refractive index has been described. However, the present invention is not necessarily limited to the polysilicon film. For example, as shown in Table 1, a germanium film can be used similarly, and a film made of a compound semiconductor material having various band gaps for a wider wavelength region can be widely used for the same purpose. Can be used. At this time, the silicon substrate 1 and the element layer 2 may be made of germanium or a compound semiconductor.

In the first to fourth embodiments, the film having a large refractive index is not necessarily limited to a semiconductor material. For example, as shown in Table 1, Si ₃ N ₄ , A
l ₂ O ₃ , TiO ₂ , Ta ₂ O ₅ , (Ba, Sr) Ti
O _3, etc., which has a small refractive index S
iO ₂ and PSG (Phospho-Silicate-Glass) , BSG (Bor
o-Silicate-Glass) may be combined.

Other dielectric materials that can be used for this purpose include SiO _x (1 ≦ x ≦ 2), SiN _x
(1 ≦ x ≦ 1), SiO _x N _y (1 ≦ x + y ≦ 2) BP
SG (Boro-Phospho-Silicate-Glass), AlN, etc. are included.

Although the present invention has been described with reference to the case where the present invention is applied to a pin type light receiving element, the present invention is also applicable to a normal pn junction type light receiving element, a phototransistor, or a photoconductive element having no pn junction. Needless to say, In addition, various modifications can be made without departing from the spirit of the present invention.

[0070]

[Table 1]

[0071]

As described above, when an integrated semiconductor light receiving element is to be formed by using a silicon wafer bonding technique, conventionally, a silicon substrate and an element layer are bonded via an SiO ₂ film. In order to form a light receiving element or the like in an element layer, it is necessary to separate element regions in which these elements are formed from each other by using a dielectric isolation method in which a dielectric is buried in a V-groove or a trench. Therefore, the thickness of the element layer is set to 10 μm.
Therefore, there is a problem that the light receiving efficiency of the integrated semiconductor light receiving element is significantly reduced in an infrared region where the light absorption coefficient of silicon is reduced.

According to the semiconductor light receiving element and the method of manufacturing the same of the present invention, for example, a polysilicon film and an SiO ₂ film are alternately used instead of the SiO ₂ film conventionally used as the insulating film between the silicon substrate and the element layer. To form a multiple reflection film laminated on
The silicon substrate and the element layer are adhered to each other through the multi-reflection film, and the two are insulated from each other. At the same time, the incident light of the light receiving element formed in the element layer is reflected by the multi-reflection film, and the thickness of the element layer is effectively reduced. By doubling the thickness, it is possible to obtain a light receiving element exhibiting sufficiently high luminous efficiency in the infrared region even when the thickness of the element layer is in the range of 10 μm to 20 μm.

[Brief description of the drawings]

FIG. 1 is a sectional view showing a structure of an integrated semiconductor light receiving element according to a first embodiment of the present invention.

FIG. 2 is a diagram showing the relationship between the number of repetitions of the multiple reflection film of the present invention and the reflectance.

FIG. 3 is a diagram showing a silicon wafer bonding method used for forming a semiconductor light receiving element according to a second embodiment of the present invention.

FIG. 4 is a view showing a silicon wafer bonding method used for forming a semiconductor light receiving element according to a third embodiment of the present invention.

FIG. 5 is a view showing a silicon wafer bonding method used for forming a semiconductor light receiving element according to a fourth embodiment of the present invention.

FIG. 6 is a sectional view showing the structure of a conventional integrated semiconductor light receiving element.

FIG. 7 is a diagram showing the relationship between the depth from the surface of silicon and the light absorptance using wavelength as a parameter.

[Explanation of symbols]

1 ... silicon substrate 2 ... element layer 2a ... element layer bonding surface 3 ... element region (light receiving elements) 4 ... device region (transistor) 5 ... dielectric isolation region 6 ... polysilicon 7 ... SiO ₂ film 8 ... n ^- layer 9 ... p-type layer 10 ... n ⁺ layer 11 ... electrode 12 ... passivation film 13 ... light receiving surface 14 ... SiO ₂ film 14a ... SiO ₂ bonding surface 14b ... SiO ₂ film 15 ... polysilicon film 16 ... multiple reflection film 17 ... grinding Surfaces 18, 20, 23: CMP polished surface 19: Thick polysilicon film 21: Additional polysilicon film 22: Additional SiO ₂ film

Claims (10)

[Claims] 1. A semiconductor light receiving element formed on an element layer on a semiconductor substrate, wherein the element layer has a first refractive index film and a second refractive index film at an interface with the semiconductor substrate. A multi-reflection film alternately laminated, wherein the multi-reflection film insulates and separates the element layer and the semiconductor substrate, and transmits transmitted light transmitted through a semiconductor light receiving element formed on the element layer to the interface. And the reflected light is incident on the semiconductor light receiving element again. 2. A semiconductor light receiving element formed on an element layer on a semiconductor substrate, wherein the element layer includes a plurality of element regions separated from each other by a dielectric film on the semiconductor substrate. The first region is formed at the interface with the semiconductor substrate.
A multi-reflection film in which a film having a refractive index of 2 and a film having a second refractive index are alternately stacked. The multi-reflection film insulates the element region from the semiconductor substrate, and A semiconductor light receiving element, wherein the transmitted light transmitted through the semiconductor light receiving element formed in the element region is reflected at the interface, and the reflected light is incident on the semiconductor light receiving element again. 3. The dielectric film according to claim 2, wherein the dielectric film comprises a multiple reflection film in which a film having a first refractive index and a film having a second refractive index are alternately stacked. Semiconductor light receiving element. 4. The film according to claim 1, wherein the film having the first refractive index is made of a polycrystalline semiconductor, and the film having the second refractive index is made of a dielectric. A semiconductor light receiving element according to one of the above. 5. The polycrystalline semiconductor is made of one of silicon and germanium, and the dielectric is made of Si
O ₂ , Si ₃ N ₄ , SiO _x (1 ≦ x ≦ 2), SiN _x
(1 ≦ x ≦ 1), SiO _x N _y (1 ≦ x + y ≦ 2), P
SG, BSG, BPSG, Al ₂ O ₃ , AlN, (B
_{a, Sr) TiO 3, TiO} 2, Ta 2 semiconductor photodetector according to claim 4, characterized in that from one of O _5. 6. The film having the first and second refractive indexes,
SiO ₂ , Si ₃ N ₄ , SiO _x (1 ≦ x ≦
2), SiN _x (1 ≦ x ≦ 1), SiO _x N _y (1 ≦ x
+ Y ≦ 2), PSG, BSG, BPSG, Al ₂ O ₃ ,
AlN, (Ba, Sr) TiO 3, TiO 2, Ta 2 O
_5. The film according to claim 1, wherein the film having the second refractive index is made of a material different from that of the film having the first refractive index. The semiconductor light receiving element according to any one of the above. 7. A method according to claim 1, wherein one of the main surfaces of the first silicon substrate is made of Si.
An O ₂ film and a polycrystalline silicon film are alternately laminated to form a multi-reflection film, and the one main surface of the second silicon substrate and the SiO ₂ film or the poly film forming the final film of the multi-reflection film are formed. The surface of the crystalline silicon film is bonded in clean air, and the bonding is heat-treated to increase the bonding strength. The other main surface of the second silicon substrate that has undergone the above-described process is removed by a certain thickness. And a step of polishing the surface to form an element layer having a predetermined thickness. 8. The method according to claim 1, wherein one of the main surfaces of the first silicon substrate is made of Si.
A multi-reflection film is formed by alternately laminating an O ₂ film and a polycrystalline silicon film, and the surface of the polycrystalline silicon film, which is the final film of the multi-reflection film, is polished. One principal surface and the surface of the polished polycrystalline silicon film are joined in clean air, and the joining is heat-treated to increase the joining strength. A method for manufacturing a semiconductor light-receiving element, comprising a step of removing a main surface by a predetermined thickness and further polishing the surface to form an element layer having a predetermined thickness. 9. A method according to claim 1, wherein one of the main surfaces of the first silicon substrate is made of Si.
The first multiple reflection film is formed by alternately laminating the O ₂ film and the polycrystalline silicon film, and the SiO ₂ film and the polycrystalline silicon film are alternately laminated on one main surface of the second silicon substrate. To form a second multi-reflection film, a final film of the first multi-reflection film is an SiO ₂ film, a final film of the second multi-reflection film is a polycrystalline silicon film, and the SiO ₂ film And the surface of the polycrystalline silicon film are bonded in clean air, and the bonding strength is increased by performing a heat treatment on the bonding. The other main surface of the first or second silicon substrate having undergone the above-described process A method of manufacturing a semiconductor light receiving element, comprising: removing a layer having a predetermined thickness and polishing the surface to form an element layer having a predetermined thickness. 10. The method according to claim 9, wherein the surface of the polycrystalline silicon film forming the final film is polished.