JP3135814B2 - Manufacturing method of high reflectance reflector - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a high-reflectance mirror used for a surface-emitting type semiconductor laser or a resonant photodetector.

[0002]

2. Description of the Related Art Conventionally, techniques in such a field include:
For example, "ST Ho and others" High index
contrast mirror for optic
almicavities ”, Applied
Physics Letters, vol. 57 (1
4), 1 October 1990, p. 1387 "
There was what was described in.

FIG. 5 is a sectional view showing a manufacturing process of the conventional high-reflectance mirror disclosed in the above-mentioned document. In general, a surface emitting laser or a resonant photodetector requires a reflecting mirror having a high reflectance of more than 99%. For that purpose, it is necessary to stack layers having different refractive indexes so as to satisfy a phase condition. is there. At this time, the higher the difference in refractive index between the materials to be laminated, the higher the reflectance can be obtained with a smaller number of layers.

In the example shown in FIG. 5, an AlGaAs semiconductor layer (refractive index: up to 3.5) and an air layer (refractive index: 1) are used as laminating materials in order to increase the refractive index difference.
Air is the material with the smallest refractive index and can be said to be the most suitable material for obtaining a large refractive index difference. Hereinafter, a method of manufacturing the high-reflectance mirror will be described.

[0005] First, as shown in FIG.
On a substrate 1, a molecular beam epitaxy method (MBE method)
Al _0.28 Ga _0.72 As layers 2, 4, 6 and Al _0.6 Ga
_{The 0.4} As layers 3, 5, and 7 are alternately and repeatedly grown.
After that, as shown in FIG.
Only the _0.6 Ga _0.4 As layers 3, 5, and 7 are selectively etched, and the Al _0.28 Ga _0.72 As layers 2, 4, 6 and the air layer 1 are selectively etched.
A stacked structure of 1, 12, and 13 is obtained. Where Al _0.28 G
The thickness of each of the a _0.72 As layers 2, 4, 6 and the air layers 11, 12, 13 is set to ~ 0.3 in order to satisfy the phase condition.
μm (5 / 4λ thickness) and ~ 0.15 μm (1 / 4λ thickness)
(Where λ is the wavelength of light). With this combination of materials, a reflectance of about 99% can be obtained with (Al _0.28 Ga _0.72 As / air) × 3 pairs. In addition, 8 is a cladding layer, and 9 is an active layer.

[0006]

However, in the above-mentioned conventional high-reflectance reflecting mirror, (1) the thickness of the AlGaAs layer sandwiched between the air is .about.0.3.
Since it is as thin as μm, it is very fragile and difficult to manufacture. (2) As a high refractive index layer (here, an AlGaAs layer),
Since a layer made by crystal growth is used, the material is limited to a material having the same lattice constant as the substrate (here, GaAs), and there is no degree of freedom of the material. For example, when a reflecting mirror is formed on another substrate such as Si, the AlG used here is used.
aAs cannot be used, and it is difficult to obtain a suitable high refractive index layer.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems and to provide a high-reflectance reflective film that can be easily manufactured by 99% or more by combining an air layer and any other material on an arbitrary substrate by using a direct bonding method. It is an object to provide a method for manufacturing a mirror.

[0008]

According to the present invention, there is provided a method of manufacturing a high-reflectance mirror, comprising the steps of: (A) forming an Au film (22) on a Si substrate (21); And an InGaAsP layer (2) on an InP substrate (23).
Forming an InGaAsP layer (24);
And selectively bonding an InGaAsP layer (24) to the Au film (22) on the Si substrate (21) by a direct bonding method to form an air layer (25) at a selective etching portion of the InGaAsP layer (24). And a forming step.

(B) An Au film (2) is formed on a Si substrate (21).
2) forming an Al film on a GaAs substrate (26);
A step of forming a GaAs layer (27);
selectively etching the s layer (27); and forming the AlGaAs layer (2) on the Au film (22) of the Si substrate (21).
7) using the direct bonding method to form the AlGaAs layer (27).
Forming an air layer (25) at the selective etching portion of (1).

(C) An Au film (2) is formed on a Si substrate (21).
Forming 2) and forming SiO ₂ on the Si substrate (28).
Forming a layer (29), and forming the SiO ₂ layer (29)
And selectively bonding the SiO ₂ layer (29) to the Au film (22) of the Si substrate (21) by a direct bonding method to form an air layer (25) on the selectively etched portion of the SiO ₂ layer (29). Is formed.

(D) SiO ₂ / S on Si substrate (31)
i) forming a multilayer film (32);
3) forming an InGaAsP layer (34) thereon;
A step of selectively etching the InGaAsP layer (34); and a step of directly bonding the InGaAsP layer (34) to the SiO ₂ / Si multilayer film (32) of the Si substrate (31) by a direct bonding method. Forming an air layer (35) at the selective etching site.

(E) a step of forming a Si substrate (41); a step of forming an InGaAsP / InP multilayer film (43) on an InP substrate (42);
Forming an InP layer (44) on the InP multilayer film (43), selectively etching the InP layer (44), and bonding the InP layer (44) to the Si substrate (41) by a direct bonding method. Forming an air layer (45) at a selective etching portion of the InP layer (44).

[0013]

[Action]

(A) According to the method for manufacturing a high-reflectance mirror according to any one of claims 1 to 5, an air layer and any other material are combined and integrated on an arbitrary substrate using a direct bonding method. Therefore, a reflector having a high reflectance of 99% or more can be realized on an arbitrary substrate.

Further, since the thin semiconductor layer does not include a structure sandwiched between the air layers, there is no problem that the semiconductor layer is easily broken, and a high-reflectance mirror can be realized by an easy process. (B) According to the method for manufacturing a high-reflectance mirror according to claims 1 to 3, Au and an air layer deposited on a certain substrate are combined and integrated using a direct bonding method. A reflector having a high reflectance of 99% or more can be realized on an arbitrary substrate.

(C) According to the method for manufacturing a high-reflectance mirror according to the fourth aspect, the direct bonding method is used to form the S
Since a four-layer film of iO ₂ / Si / SiO ₂ / Si was formed and combined with an air layer to integrate them,
A reflecting mirror having a high reflectance of 99% or more on a Si substrate can be realized. (D) According to the method for manufacturing a high-reflectance mirror according to claim 5, a Si substrate is formed, and an InGaAsP is formed on an InP substrate.
/ InP multilayer film is formed, and this InGaAsP / InP
An InP layer is formed on the multilayer film, the InP layer is selectively etched, and the InP layer is directly bonded to the Si substrate by a direct bonding method, and an air layer is formed at a selectively etched portion of the InP layer to thereby achieve high reflectance. I realized that
A reflecting mirror having a high reflectance of 99% or more on a Si substrate can be realized.

[0016]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a cross-sectional view of a high-reflectance mirror according to a first embodiment of the present invention. FIG. 2 is a cross-sectional view of a manufacturing process of the high-reflectance mirror according to the first embodiment of the present invention. In FIG.
Is a Si substrate, and A deposited on the Si substrate 21
By combining the u film 22 and the air layer 25, 9
A high reflectance of 9% or more can be obtained. Here, 23 is an InP substrate, 24 is an InGaAsP layer, and 30 is an active layer.

Hereinafter, a method for manufacturing the high-reflectance mirror will be described. (1) First, as shown in FIG. 2A, an Au film 22 (thickness> 1000 °) is formed on a Si substrate 21 by a normal vapor deposition method.
Is deposited. (2) On the other hand, as shown in FIG.
First, a wafer having an InGaAsP layer 24 having a mirror-finished surface is prepared. The thickness of the InGaAsP layer 24 is set to be equal to the thickness of the air layer required to satisfy a phase condition described later. Here, In
The GaAsP layer 24 is required to have two characteristics such that the surface is a mirror surface and only the layer laminated thereon can be removed by etching without etching the substrate. Here, if the InGaAsP layer 24 illustrated is crystal-grown in a state of being lattice-matched to the InP substrate 23 by, for example, a metal organic chemical vapor deposition method, a mirror surface can be obtained.

(3) Next, as shown in FIG. 2C, for example, H
Using a mixed solution of NO ₃ : H ₂ O: HF = 3: 2: 1,
The InGaAsP layer 24 is etched. This etching is preferable because only the InGaAsP layer 24 can be selectively removed without etching the InP substrate 23.

[0019] (4) Thereafter, FIG. 2 and the wafer obtained in (a), the surface of the H ₂ S of the wafer obtained in FIG. 2 (c)
O ₄ : H ₂ O: H ₂ O ₂ = 3: 1: 1 with a mixture of 5 to 5
After treating for about 10 seconds and washing with water, both wafers are spin-dried, and the mirror surfaces of both substrates are brought together at room temperature by 5 to 10 kg / cm.
Apply pressure of about ² to adhere. When left in this state for about 15 minutes, both substrates are integrated by van der Waals force or hydrogen bonding between OH groups adsorbed on the surface. Furthermore, if it is necessary to increase the adhesion strength, 40
Heat treatment can be performed at a temperature of 0 ° C. or less.

In this way, as shown in FIG. 2D, a high-reflectance mirror on which the air layer 25 is formed can be manufactured. Next, a second embodiment of the present invention will be described. In this embodiment, the InP in the first embodiment is used.
The difference is that a GaAs substrate is used in place of the substrate 23 and the InGaAsP layer 24, and an AlGaAs layer is grown on the GaAs substrate.

Hereinafter, a second embodiment of the present invention will be described in detail with reference to FIG. (1) First, as shown in FIG. 3A, an Au film 22 (thickness> 1000 °) is formed on a Si substrate 21 by a normal vapor deposition method.
Is deposited. (2) Next, as shown in FIG. 3B, a GaAs substrate 26 is used, and an AlGaAs layer 27 is grown on the GaAs substrate 26 by crystal growth.

(3) Next, as shown in FIG. 3C, for example, using a photoresist or the like as an etching mask,
The lGaAs layer 27 is formed using a selective etchant of HF.
As in the case of FIG. 2C, a portion is selectively removed. (4) Then, the wafer obtained in FIG.
The surface of the wafer obtained in (c) was treated with H ₂ SO ₄ : H ₂ O:
After treatment with a mixed solution of H ₂ O ₂ = 3: 1: 1 for about 5 to 10 seconds, washing with water, spin drying of both wafers, and mirror surfaces of both substrates at room temperature to about 5 to 10 kg / cm ² . Apply pressure to adhere.

When left in this state for about 15 minutes, both substrates are subjected to van der Waals force or OH adsorbed on the surface.
They are integrated by hydrogen bonding between groups. Further, when it is necessary to increase the adhesion strength, heat treatment can be performed at a temperature of 400 ° C. or lower. Thus, FIG.
As shown in (d), a high-reflectance mirror in which the air layer 25 is formed can be manufactured.

Next, a third embodiment of the present invention will be described in detail with reference to FIG. (1) First, as shown in FIG. 4A, an Au film 22 (thickness> 1000 °) is formed on a Si substrate 21 by a normal vapor deposition method.
Is deposited. (2) Next, as shown in FIG.
Then, an SiO ₂ film 29 is formed on the Si substrate 28 by thermal oxidation.

(3) Next, as shown in FIG. 4C, for example, using a photoresist or the like as an etching mask,
The iO ₂ layer 29 was formed using a selective etchant of HF as shown in FIG.
As in (c), partial removal is performed selectively. (4) Then, the wafer obtained in FIG.
The surface of the wafer obtained in (c) was treated with H ₂ SO ₄ : H ₂ O:
After treatment with a mixed solution of H ₂ O ₂ = 3: 1: 1 for about 5 to 10 seconds, washing with water, spin drying of both wafers, and mirror surfaces of both substrates at room temperature to about 5 to 10 kg / cm ² . Apply pressure to adhere.

When left in this state for about 15 minutes, both substrates are subjected to van der Waals force or OH adsorbed on the surface.
They are integrated by hydrogen bonding between groups. Further, when it is necessary to increase the adhesion strength, heat treatment can be performed at a temperature of 400 ° C. or lower. Thus, FIG.
As shown in (d), a high-reflectance mirror in which the air layer 25 is formed can be manufactured.

Next, the reflectance of the high reflectance mirror shown in FIG. 1 will be described. First, the amplitude reflectance r ₀ from the surface of the Au film 22 is

[0028]

(Equation 1)

[0029] (wherein, n _a: the refractive index of air = 1, n _g
-Ik _g : Au complex refractive index = 0.403-8.25
i), and the reflectance R≡ | r ₀ | ² is 97.7% (r
₀ = 0.9884). Therefore, the Au film 22 alone does not reach the required reflectance of 99%.
Therefore, when the air layer 25 is combined, the InP substrate 23
The amplitude reflectance r ₁ at the interface of the air layer _{25, r 1 = (n InP -n} a) / (n InP + n a) ... (2) ( where the refractive index = 3 n _InP is InP substrate 23 .2)
In response to the impact, if the phase condition is satisfied, the amplitude reflectivity r _t of _{total, r t = (r 0 +} r 1) / (1 + r 0 r 1) ... (3) , and this time, the total reflectance R _t = | r _t | ²
= 99.3%, and a reflectance exceeding 99% can be realized.

In order to satisfy the phase condition, assuming that the thickness of the air layer is d, it suffices to satisfy 4π (d / λ) + θ = 2π (4) (λ: wavelength of light). Now, in the case of the Au film 22, since θ = 2.9091 is obtained from the equation (1), for example, if λ = 1.3 μm, d is obtained from the equation (4).
= 0.35 μm.

Therefore, the thickness of the InGaAsP layer 24 described in the manufacturing method of FIG.
It can be seen that μm is sufficient. FIG. 6 is a configuration diagram of a high-reflectance mirror according to a fourth embodiment of the present invention. In this embodiment, as in the first embodiment, instead of depositing Au on the Si substrate, a multilayered film 32 of SiO ₂ / Si is deposited on the Si substrate 31 and combined with the air layer 35. Achieve high reflectivity.

First, a SiO ₂ / Si multilayer film 32, for example, SiO ₂ / Si / SiO ₂ / Si, is formed on a Si substrate 31 by electron beam evaporation or sputtering.
Is formed so as to have a thickness satisfying the phase condition (λ / 4n: λ is the wavelength of light and n is the refractive index of each layer).
At this time, R _O = | r _O | ² = 96.6%, and by combining and integrating the air layer 35 thereon, a reflectance of 99% or more can be obtained as in the previous example. Other processes are the same as in the first embodiment. In FIG. 6, 33
Denotes an InP substrate, 34 denotes an InGaAsP layer, and 36 denotes an active layer.

A method for manufacturing a high-reflectance mirror according to a fourth embodiment of the present invention will be described. (1) SiO ₂ / Si / SiO ₂ / S on Si substrate 31
The four-layer film 32 of i is formed. (2) An InGaAsP layer 34 is formed on the InP substrate 33. (3) The InGaAsP layer 34 is selectively etched.

(4) SiO ₂ / S on the Si substrate 31
The InGaAsP is formed on the four-layer film 32 of i / SiO ₂ / Si.
The InGaAsP layer 34 is connected to the layer 34 by a direct bonding method.
An air layer 35 is formed at the selective etching portion of FIG. FIG. 7 is a configuration diagram of a high-reflectance mirror according to a fifth embodiment of the present invention. In this embodiment, instead of forming a multilayer film of Au or SiO ₂ / Si on a Si substrate as in the first and second embodiments, InGaAsP / In
By forming a P multilayer film 43 and combining this with the air layer 45, a high reflectance is realized.

In this case, for example, when an InGaAsP layer is lattice-matched to InP and has a composition having an energy gap wavelength of 1.45 μm by a metal organic chemical vapor deposition method, the InGaAsP / InGaAsP layer is formed on the InP. I
41 layers in the order of nP (the last layer is therefore InGaAs
By forming the P layer) and combining this with the air layer 45, a reflectance of 99% or more can be obtained.

In this case, the process corresponds to the InGaAsP layer 24 in the step of FIG.
If HCl is used as a selective etchant using the InP layer 44 (HCl is etched by InP,
GaAsP is not etched), and the high-reflectance mirror shown in FIG. 7 can be manufactured by the same process as in the first embodiment. Reference numeral 46 denotes an active layer.

A method for manufacturing a high-reflectance mirror according to the fifth embodiment of the present invention will be described. (1) The Si substrate 41 is formed. (2) An InGaAsP / InP multilayer film 43 is formed on the InP substrate 42. (3) The InGaAsP / InP multilayer film 43 has In
A P layer 44 is formed. (4) The InP layer 44 is selectively etched.

(5) The InP layer 4 is formed on the Si substrate 41.
Then, an air layer 45 is formed at a selective etching portion of the InP layer 44 by a direct bonding method. It should be noted that the present invention is not limited to the above embodiment, and various modifications can be made based on the gist of the present invention, and these are not excluded from the scope of the present invention.

[0039]

As described above, according to the present invention, the following effects can be obtained. (1) According to the first to fifth aspects of the present invention, the air layer and any other material are combined and integrated on an arbitrary substrate by using a direct bonding method. Thus, a reflecting mirror having a high reflectance of 99% or more can be realized.

Further, since a structure in which a thin semiconductor layer is sandwiched between air layers is not included, there is no problem that the semiconductor layer is easily broken, and a high-reflectance mirror can be realized by an easy process. (2) According to the first to third aspects of the present invention, Au and an air layer deposited on a certain substrate are combined and integrated by using a direct bonding method.
A reflecting mirror having a high reflectance of 9% or more can be realized.

(3) According to the invention described in claim 4, SiO ₂ / Si / SiO _{2 is formed} on the Si substrate by using the direct bonding method.
_{Since a two-} layer film of ₂ / Si is deposited and combined with the air layer to integrate them, a reflecting mirror having a high reflectance of 99% or more on the Si substrate can be realized. (4) According to the fifth aspect of the present invention, the Si substrate is formed by using the direct bonding method, and the InGaAsP is formed on the InP substrate.
/ InP multilayer film is formed, and this InGaAsP / InP
An InP layer is formed on the multilayer film, the InP layer is selectively etched, and the InP layer is directly bonded to the Si substrate by a direct bonding method, and an air layer is formed at a selectively etched portion of the InP layer to thereby achieve high reflectance. I realized that
A reflecting mirror having a high reflectance of 99% or more on a Si substrate can be realized.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of a high-reflectance mirror showing a first embodiment of the present invention.

FIG. 2 is a cross-sectional view illustrating a manufacturing process of the high-reflectance mirror according to the first embodiment of the present invention.

FIG. 3 is a cross-sectional view illustrating a manufacturing process of a high-reflectance mirror according to a second embodiment of the present invention.

FIG. 4 is a sectional view showing a manufacturing process of a high-reflectance mirror according to a third embodiment of the present invention.

FIG. 5 is a sectional view showing a manufacturing process of a conventional high-reflectance mirror.

FIG. 6 is a configuration diagram of a high-reflectance mirror according to a fourth embodiment of the present invention.

FIG. 7 is a configuration diagram of a high-reflectance mirror according to a fifth embodiment of the present invention.

[Explanation of symbols]

21,28,31,41 Si substrate 22 Au film 23,33,42 InP substrate 24, 34 InGaAsP layer 25, 35, 45 air layer 26 GaAs substrate 27 AlGaAs layer 29 SiO ₂ film 30,36,46 active layer 32 SiO ₂ / Si multilayer film 43 InGaAsP / InP multilayer film 44 InP layer

──────────────────────────────────────────────────続 き Continuation of front page (72) Inventor Ken Kamijo 1-7-12 Toranomon, Minato-ku, Tokyo Oki Electric Industry Co., Ltd. (56) References JP-A-5-323109 (JP, A) JP Hei 1-255802 (JP, A) (58) Field surveyed (Int. Cl. ⁷ , DB name) G02B 5/08-5/10

Claims (5)

(57) [Claims] (A) a step of forming an Au film on a Si substrate; (b) a step of forming an InGaAsP layer on an InP substrate; (c) a step of selectively etching the InGaAsP layer; ) The Au film on the Si substrate is coated with the InG
forming an air layer at a selective etching portion of the InGaAsP layer by directly joining the aAsP layer. (A) a step of forming an Au film on a Si substrate; (b) a step of forming an AlGaAs layer on a GaAs substrate; (c) a step of selectively etching the AlGaAs layer; ) The AlGa film on the Si substrate has the AlGa
Forming an air layer in a selective etching portion of the AlGaAs layer by directly bonding the As layer to the AlGaAs layer. 3. A step of (a) forming an Au film on a Si substrate, and (b) a step of forming an SiO ₂ layer on a Si substrate.
(C) selectively etching the SiO ₂ layer;
The (d) the SiO ₂ layer directly Au film on the Si substrate bonding method, the to selective etching portions of the SiO ₂ layer of a high reflectance reflector and said applying and forming an air layer Production method. 4. A process of (a) forming a multilayer film of SiO ₂ / Si on a Si substrate, and (b) a process of forming InGaAs on an InP substrate.
forming an sP layer; (c) selectively etching the InGaAsP layer; and (d) forming an S on the Si substrate.
forming an air layer at a selectively etched portion of the InGaAsP layer by directly bonding the InGaAsP layer to the iO ₂ / Si multilayer film. 5. The method according to claim 1, wherein (a) a step of forming a Si substrate; and (b)
(E) forming an InGaAsP / InP multilayer film on the InP substrate; (c) forming an InP layer on the InGaAsP / InP multilayer film; (d) selectively etching the InP layer; The InP is applied to the Si substrate.
Forming a layer of air at a selectively etched portion of the InP layer by a direct bonding method.