JPH10270786A - Etching method of compound semiconductor, manufacture of compound semiconductor, and semiconductor laser - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an etching method by which two or more compound semiconductor layers composed of different materials can be etched at a time. SOLUTION: A stripe-like ridge waveguide 9 having a flat section 5a of 0.4 μm in thickness and a stripe section 5b of 3 μm in width in a p-type A GaInP clad layer 5 is formed by etching (at an etching rate of about 140 Å/sec) a compound semiconductor layer composed of a p-type GaAs protective layer 7, a p-type GaInP layer 6, and the clad layer 5 at a time through a mask layer 8 by using an etchant prepared by mixing 75 vol.% hydraulic acid (containing 47% HBr), 50 vol.% phosphoric acid (containing 85-87% H3 PO4 ), and 1 vol.% hydrogen peroxide (containing 35% H2 O) with each other and maintained at 10 deg.C.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of etching a compound semiconductor which can improve the efficiency of an etching process, a method of manufacturing a compound semiconductor device using the etching method, and a semiconductor laser.

[0002]

2. Description of the Related Art Compound semiconductor crystals are widely used in semiconductor lasers and electronic devices. Hereinafter, a conventional technique will be described using a red semiconductor laser as an example.

FIG. 7 is a process chart of a conventional semiconductor laser using a GaInP-based semiconductor crystal and an AlGaInP-based semiconductor crystal.

[0004] First, as shown in FIG.
an n-type GaInP buffer layer 66 on an aAs substrate 65;
n-type AlGaInP cladding layer 67, undoped Al
GaInP active layer 68, p-type AlGaInP cladding layer 69, p-type G for making good ohmic contact
aInP cap layer 70 and p-type GaAs protective layer 7 for preventing oxidation of this p-type GaInP cap layer 70
1 is continuously grown by metal organic chemical vapor deposition (MOCVD) or molecular beam epitaxy (MBE).

[0005] Next, as shown in FIG.
After a SiO ₂ mask layer 72 is formed on the As protective layer 71 in a stripe shape by an electron beam evaporation method and a photolithographic technique, as shown in FIG. 7C, the p-type GaAs protective layer 71 is interposed via the mask layer 72. Is selectively etched with a phosphoric acid-based etchant to form a striped p-type GaAs protective layer 73. Further, as shown in FIG. 7D, the p-type GaInP
Cap layer 70 and p-type AlGaInP clad layer 6
9 is selectively etched with hydrobromic acid containing 47% of hydrogen bromide (HBr) to form a stripe portion 69a and a flat portion 69b on the p-type AlGaInP cladding layer 69, thereby forming a stripe-shaped ridge 74.

After that, as shown in FIG. 7E, an n-type GaAs current confinement layer (block layer) 75 is formed on the flat portion 69b via the mask layer 72 by MOCVD or MBE. 72 is removed with a hydrofluoric acid-based etchant. Next, on the block layer 75 and in the stripe p
A p-type GaAs cap layer 76 on the
After being formed by the VD method or the MBE method, a p-type electrode and an n-type electrode are formed on the p-type cap layer 76 and the lower surface of the n-type substrate 65, respectively.
A mold electrode (neither is shown) is formed using a vapor deposition method and a heat treatment.

FIG. 8 is a manufacturing process diagram of a self-pulsation type semiconductor laser using a conventional GaInP-based semiconductor crystal and AlGaInP-based semiconductor crystal.

[0008] First, as shown in FIG.
An n-type GaInP buffer layer 78, n
AlGaInP cladding layer 79, undoped AlG
aInP active layer 80, p-type AlGaInP cladding layer 8
1. A p-type GaInP cap layer 82 and a p-type GaAs protective layer 83 are continuously grown by MOCVD or MBE.

Next, SiO 2 is deposited by electron beam evaporation._Twolayer
Resist pattern by photolithographic technology
Pattern 84 is formed in a stripe shape, and the resist pattern 84 is formed.
Through SiO_TwoSelect layer with hydrofluoric acid-based etchant
Chinged striped SiO _TwoA layer 85 is formed. Change
Next, as shown in FIG._Twolayer
A phosphoric acid-based etch through the p-type GaAs protective layer
Selective etching with a stripping solution to maintain a striped p-type GaAs
A protective layer 86 is formed.

Next, as shown in FIG. 8C, the stripe-shaped SiO ₂ layer 85 is subjected to side etching with a hydrofluoric acid-based etchant to reduce its size.
After the O ₂ mask layer 87 is formed and the side portions on the upper surface of the striped p-type GaAs protective layer 86 are exposed, the photoresist 84 is removed by a dedicated removing solution. And
As shown in FIG. 8D, the p-type GaInP cap layer 82 and the p-type AlGaInP clad layer 81 are selectively etched with hydrobromic acid via the striped p-type GaAs protective layer 86 to form a p-type AlGaInP clad layer. A stripe-shaped ridge waveguide 88 having a stripe portion 81a and a flat portion 81b is formed on 81.

Thereafter, as shown in FIG. 8E, an n-type GaAs current confinement layer (block layer) 89 is formed on the flat portion 81b and a part of the surface of the protection layer 86 via the mask layer 87.
After being formed by the CVD method or the MBE method, the mask layer 87 is removed with a hydrofluoric acid-based etchant as shown in FIG. Next, a p-type GaAs cap layer 90 is formed on the block layer 89 and the protective layer 86 by MOCVD or MBE.
After the formation, a p-type electrode and an n-type electrode (both not shown) are formed on the p-type cap layer 90 and on the lower surface of the n-type substrate 77 by vapor deposition and heat treatment, respectively.

[0012]

As described above, when forming the stripe-shaped ridge waveguide 88, the p-type GaAs protective layer 83 is first etched with a phosphoric acid-based etchant via the stripe-shaped SiO ₂ mask layer 87. And a GaInP cap layer 82 and an AlG
A method is used in which the aInP cladding layer 81 is etched in a stripe shape using a hydrobromic acid-based etchant.

Therefore, the stripe-shaped ridge waveguide 88
Has become disadvantageous in that the formation process of the semiconductor laser becomes complicated, and the change in the pattern size in each etching process affects, for example, the occurrence of variations in the optical characteristics of the semiconductor laser and the reduction in reliability.

The present invention provides a compound semiconductor crystal containing at least Ga and As, a compound semiconductor crystal containing at least Zn and Se, a compound semiconductor crystal containing at least In and As, or a compound semiconductor containing at least In and P. An object of the present invention is to provide a method of etching a compound semiconductor composed of any one or more of crystals, a method of manufacturing a compound semiconductor device using the etching method, and a semiconductor laser.

[0015]

The method of etching a compound semiconductor according to the present invention comprises a first compound semiconductor crystal containing at least Ga and As, a second compound semiconductor crystal containing at least Zn and Se, or In and As. A compound semiconductor having at least one of the at least one third compound semiconductor crystal is etched using a mixed solution containing hydrobromic acid and aqueous hydrogen peroxide.

The method of etching a compound semiconductor according to the present invention includes a first compound semiconductor crystal containing at least Ga and As, a second compound semiconductor crystal containing at least Zn and Se, and a third compound semiconductor containing at least In and As. Using a mixed solution containing hydrobromic acid, aqueous hydrogen peroxide, and phosphoric acid, a compound semiconductor having at least either a compound semiconductor crystal or a fourth compound semiconductor crystal containing at least In and P And etching.

Further, the method of etching a compound semiconductor according to the present invention includes a first compound semiconductor crystal containing at least Ga and As, a second compound semiconductor crystal containing at least Zn and Se, and a third compound semiconductor containing at least In and As. A compound semiconductor having at least one of a compound semiconductor crystal or a fourth compound semiconductor crystal containing at least In and P is prepared by using a mixed solution containing hydrobromic acid, aqueous hydrogen peroxide, and hydrochloric acid. It is characterized by etching.

Further, the method of etching a compound semiconductor according to the present invention includes a first compound semiconductor crystal containing at least Ga and As, a second compound semiconductor crystal containing at least Zn and Se, and a third compound semiconductor containing at least In and As. A compound semiconductor comprising at least either a compound semiconductor crystal or a fourth compound semiconductor crystal containing at least In and P is mixed with hydrobromic acid, aqueous hydrogen peroxide, phosphoric acid, and hydrochloric acid. The etching is performed using a liquid.

The method of etching a compound semiconductor according to the present invention may further comprise a first compound semiconductor crystal containing at least Ga and As, a second compound semiconductor crystal containing at least Zn and Se, and a third compound semiconductor crystal containing at least In and As. A compound semiconductor having at least one of a compound semiconductor crystal or a fourth compound semiconductor crystal containing at least In and P is formed using a mixed solution containing hydrobromic acid, aqueous hydrogen peroxide, and water. It is characterized by etching.

The first containing at least Ga and As
The compound semiconductor crystal is an AlGaAs-based semiconductor crystal, Ga
It may be an As-based semiconductor crystal or a laminate thereof. Further, the second compound semiconductor crystal containing at least Zn and Se is a ZnSeS-based semiconductor crystal, ZnSe
A system semiconductor crystal or a laminate thereof may be used. Further, the third compound semiconductor crystal containing at least In and As is an InGaAs-based semiconductor crystal, InAlAs
A system semiconductor crystal, an InGaAlAs system semiconductor crystal, or a laminate thereof may be used. Further, the fourth compound semiconductor crystal containing at least In and P is GaInP.
-Based semiconductor crystal, AlInP-based semiconductor crystal, AlGaIn
It may be a P-based semiconductor crystal or a laminate thereof.

The compound semiconductor is a GaAs semiconductor substrate, G
aInP semiconductor crystal layer, AlGaInP crystal layer, GaI
The stacked body includes the nP semiconductor crystal layer and the GaAs semiconductor crystal layer in this order, and the stacked body may be etched using any of the above-described etching methods.

Here, a mixed solution containing hydrobromic acid and aqueous hydrogen peroxide, a mixed solution containing hydrobromic acid, phosphoric acid and aqueous hydrogen peroxide, and a mixed solution containing hydrobromic acid, hydrochloric acid and aqueous hydrogen peroxide A mixed liquid, a mixed liquid containing hydrobromic acid, phosphoric acid, hydrochloric acid, and hydrogen peroxide water,
In addition, a mixed solution containing hydrobromic acid, water and aqueous hydrogen peroxide is used as an etchant. These etchants include the above-described various compound semiconductor crystals (including the case of a layer; the same applies hereinafter) and the like. Is very small in selectivity to the stacked body, so that a ridge waveguide stripe pattern can be formed in a single etching step.

This is because hydrogen bromide (HBr) contained in hydrobromic acid and hydrogen peroxide (H ₂
Since HBrO generated by the reaction of O ₂ ) acts as an etching group, it is considered that the selectivity to various compound semiconductor crystals (crystal layers) and their laminates becomes extremely small.

That is, H, which is a compound in an extremely unstable state,
BrO oxidizes the object to be etched to form an oxide,
It is considered that the etching proceeds because the HBr that is decomposed and regenerated immediately reduces the oxide. In order to obtain a uniform etching depth in the plane of the compound semiconductor (wafer), it is necessary to circulate the etching solution. From this, the etching is H
It is expected that this is due to the diffusion control of BrO.

The mixed solution containing hydrobromic acid and aqueous hydrogen peroxide etches various compound semiconductor crystals (crystal layers) by the above-described action.
By mixing phosphoric acid and hydrochloric acid, or water, it is possible to control the etching rate, control the etching cross-sectional shape, or provide etching selectivity,
The composition of the etching solution can be selected according to each purpose.

In the case of etching various compound semiconductor crystals (crystal layers) and a laminate thereof, for example, when etching is performed using a SiO ₂ layer or a photoresist as a mask, a mixed solution containing hydrobromic acid and hydrogen peroxide is used. liquid,
Alternatively, a mixed solution containing hydrobromic acid, phosphoric acid, and hydrogen peroxide, or a mixed solution containing hydrobromic acid, hydrochloric acid, and hydrogen peroxide, or a mixed solution containing hydrobromic acid, phosphoric acid, hydrochloric acid, and hydrogen peroxide By using a mixed solution containing, it is also possible to perform etching in which side etching which is usually observed in the case of chemical etching does not occur at all.

Further, a method of manufacturing a compound semiconductor device according to the present invention is characterized in that it has a step of using the above-described method of etching a compound semiconductor.

In the semiconductor laser according to the present invention, the current confinement layer has substantially the same width as the uppermost compound semiconductor crystal layer of the stripe-shaped ridge waveguide, and extends from both ends of the uppermost compound semiconductor layer to the vicinity thereof. It is characterized in that it is formed substantially directly above. In addition, the current confinement layer is formed with a width smaller than that of the stripe-shaped ridge waveguide, and side regions parallel to both the upper surface and the lower surface of the uppermost compound semiconductor crystal layer of the stripe-shaped ridge waveguide are formed. It is characterized by being.

[0029]

BEST MODE FOR CARRYING OUT THE INVENTION

(Embodiment 1) A method for manufacturing a semiconductor laser using the compound semiconductor etching method of this embodiment will be described with reference to FIG.

First, as shown in FIG.
An n-type Ga layer having a thickness of 0.3 μm is formed on an aAs substrate 1._0.5In
_0.5P buffer layer 2, n-type (Al_0.7
Ga _0.3)_0.5In_0.5P clad layer 3, thickness 0.1μ
m undoped (Al_xGa _1-x)_0.5In_0.5P activity
Layer 4, p-type (Al_0.7Ga_0.3)_{0. Five}
In_0.5P cladding layer 5, p-type Ga having a layer thickness of 0.1 μm
_0.5In_0.5P cap layer 6 and 0.3 μm thick p
Type GaAs protective layer 7 is formed by metal organic chemical vapor deposition (MOCVD).
Method) or molecular beam epitaxial method (MBE method).
Continue to grow.

Next, as shown in FIG.
A stripe-shaped layer having a thickness of 0.2 μm and a width of 2.0 μm on the layer 7
SiO_TwoThe mask layer 8 is formed by electron beam evaporation and photolithography.
After forming by sograph technology or the like, it is shown in FIG.
As described above, the p-type GaAs protective layer 7
GaInP cap layer 6, p-type AlGaInP
Layer 5 is treated with hydrobromic acid (containing 47% HBr) at a temperature of 10 ° C.
Existence): Phosphoric acid (H_ThreePO _Four85-87%): Peracid
Hydrogen water (H_TwoO_Two= 35: 50: 1)
Etching with etching solution (volume ratio)
Is about 140 ° / sec) and the p-type cladding layer 5 has a thickness
0.4 μm flat portion 5 a and 3 μm width stripe portion 5
A striped ridge waveguide 9 having b is formed.

Thereafter, as shown in FIG. 1B, the n-type GaAs current confinement layer 10 is
1E, the mask layer 8 is removed with a hydrofluoric acid-based etchant, and then the p-type GaAs cap layer 12 is removed by MOCVD or MBE.
After the formation by the E method, a p-type electrode and an n-type electrode (both not shown) are formed on the p-type GaAs cap layer 12 and the lower surface of the n-type substrate 1, respectively.

[0033] As can be seen from this example, p-type GaAs protective layer 7 through the SiO ₂ mask layer 8, p-type GaIn
In the etching of the P cap layer 6 and the p-type AlGaInP cladding layer 5 with hydrobromic acid: phosphoric acid: hydrogen peroxide solution, the pattern of the stripe-shaped ridge waveguide 9 can be formed in one etching step. Since side etching does not occur, the n-type GaAs current confinement layer 10 is grown from both ends 6a of the p-type GaInP cap layer 6, which is the uppermost layer of the ridge waveguide 9, along the side surfaces of the mask layer 8. Become. That is, in the semiconductor laser manufactured by this method, the current confinement layer has substantially the same width as the uppermost compound semiconductor crystal layer of the stripe-shaped ridge waveguide, and
The uppermost compound semiconductor layer is formed almost directly above from both ends thereof in the vicinity thereof. With such a method, the spread angle of the laser light can be easily controlled by controlling the size of the mask layer 8, and the laser light is accurately controlled in the semiconductor laser having the structure.

In the etching solution of this embodiment, the etching rate increases as the mixing ratio of the aqueous hydrogen peroxide increases, and the etching rate decreases as the mixing ratio of the phosphoric acid increases. The temperature of the solution or the solution can be arbitrarily selected according to the purpose, but in practice, the ratio of hydrobromic acid: hydrogen peroxide solution is 50: 1 to 300: 1.
And the ratio of hydrobromic acid: phosphoric acid is desirably 3: 1 to 1: 3. Further, the temperature is preferably 5 to 50C.

(Embodiment 2) A method of manufacturing a semiconductor laser using the compound semiconductor etching method of this embodiment will be described with reference to FIG.

First, as shown in FIG.
An n-type Ga _0.5 I layer having a thickness of 0.3 μm is formed on an aAs substrate 13.
n _0.5 P buffer layer 14, n-type (Al
_0.7 Ga _0.3 ) _0.5 In _0.5 P clad layer 15, undoped (Al _x Ga _{1 -x} ) _0.5 In with a layer thickness of 0.1 μm
_0.5 P active layer 16, p-type (Al _0.7 G
a _0.3 ) _0.5 In _0.5 P clad layer 17, layer thickness 0.1 μm
p-type m Ga _0.5 In _{0. 5} P cap layer 18, and the layer thickness 0.3 [mu] m p-type GaAs protective layer 19 a metal organic chemical vapor deposition (MOCVD) or molecular beam epitaxy (M
(BE method).

Next, as shown in FIG.
After forming a stripe-shaped SiO ₂ mask layer 20 having a thickness of 0.2 μm and a width of 3.0 μm on the As protective layer 19 by an electron beam evaporation method and a photolithographic technique, FIG.
As shown in FIG. 3C, the p-type GaAs is
s protective layer 19, p-type GaInP cap layer 18, p-type A
The 1GaInP cladding layer 17 is made of hydrobromic acid (containing 47% of HBr) at a temperature of 30 ° C .: hydrogen peroxide solution (H ₂ O ₂ is
(Containing 5%): water = 1: 1: 30 (volume ratio) by etching (etching rate: about 50 ° / sec) to form a p-type AlGaInP cladding layer 17 having a thickness of 0.4 μm.
m flat portion 17a and stripe portion 1 having a lower width of 3 μm
The stripe-shaped ridge waveguide 21 having 7b is formed.

Thereafter, as shown in FIG.
₂ n-type GaAs current confinement layer 22 via mask layer 20
Is formed by MOCVD or MBE, and FIG.
As shown in (e), the mask layer 20 is removed with a hydrofluoric acid-based etchant, and then the p-type GaAs cap layer 23 is
After being formed by OCVD or MBE, p-type GaAs
A p is formed on each of the s cap layer 23 and the n-type substrate 13
A mold electrode and an n-type electrode (both not shown) are formed.

[0039] As can be seen from this example, p-type GaAs protective layer 19 through the SiO ₂ mask layer 20, p-type Ga
In the etching of the InP cap layer 18 and the p-type AlGaInP cladding layer 17 with hydrobromic acid: hydrogen peroxide solution: water, it is possible to form a pattern of the stripe-shaped ridge waveguide 21 in one etching step and to perform side etching. Control of the amount is also possible. For example, when the etching time is 140 seconds to 200 seconds, the etching depth is about 0.6 μm.
m, while the side etching amount is 1.
This is because it changes from 0 to 1.3 μm.

The mixing ratio and temperature of the etching solution can be arbitrarily selected according to the purpose, but practically, hydrobromic acid: hydrogen peroxide solution is 1: 1 to 100: 1, and It is desirable that the ratio of hydrofluoric acid: water is 1: 1 to 1:50. Further, the temperature is preferably 5 to 50C.

(Embodiment 3) A method of manufacturing a semiconductor laser using the compound semiconductor etching method of this embodiment will be described with reference to FIG.

First, as shown in FIG.
On an aAs substrate 24, an n-type Ga _0.5 I layer having a thickness of 0.3 μm is formed.
n _0.5 P buffer layer 25, n-type (Al
_0.7 Ga _0.3 ) _0.5 In _0.5 P clad layer 26, undoped (Al _x Ga _1-x ) _0.5 In layer 0.1 μm thick
_0.5 P active layer 27, p-type (Al _0.7 G
a _0.3 ) _0.5 In _0.5 P clad layer 28, thickness 0.1 μm
p-type m Ga _0.5 In _{0. 5} P cap layer 29, and the layer thickness 0.3 [mu] m p-type GaAs protective layer 30 and metal organic chemical vapor deposition (MOCVD) or molecular beam epitaxy (M
(BE method).

Next, as shown in FIG.
After a stripe-shaped SiO ₂ mask layer 31 having a thickness of 0.2 μm and a width of 2.0 μm is formed on the As protective layer 30 by an electron beam evaporation method, a photolithographic technique, or the like, FIG.
As shown in, p-type Ga through the SiO ₂ mask layer 31
The As protective layer 30, the p-type GaInP cap layer 29, and the p-type AlGaInP cladding layer 28 are formed at a temperature of 10 ° C. with hydrobromic acid (containing 47% of HBr): phosphoric acid (H ₃ PO ₄ is 85
８７87%): etching with an etching solution of hydrogen peroxide solution (containing 35% of H ₂ O ₂ ) = 75: 50: 1 (volume ratio) (etching rate: about 140 ° / sec);
A stripe-shaped ridge waveguide 32 having a flat portion 28a having a thickness of 0.4 μm and a stripe portion 28b having a lower width of 3.0 μm is formed on the mold cladding layer 28.

Thereafter, as shown in FIG.
A side etching portion 33 is formed on the aAs protective layer 30 using a phosphoric acid-based etchant, and further, as shown in FIG. 3E, an n-type Al _0.5 In _0.5 P current confinement layer 34 is formed by MOCV.
It is formed by the D method or the MBE method. Next, as shown in FIG. 3F, the SiO ₂ mask layer 31 is removed with a hydrofluoric acid-based etchant, and the p-type GaAs cap layer 35 is removed by MOCVD.
After the formation by the MBE method or the MBE method, the p-type electrode and the n-type electrode are formed on the p-type GaAs cap layer 35 and the lower surface of the n-type substrate 24, respectively.
Forming electrodes (both not shown) are formed.

The semiconductor laser obtained by the manufacturing method of this embodiment has a two-stage current confinement layer (block layer) structure. Then, an n-type AlInP current confinement layer (block layer)
Reference numeral 34 denotes a p-type GaAs protection layer 3 which is formed to have a width smaller than that of the stripe-shaped ridge waveguide 32 and is an uppermost compound semiconductor crystal layer of the stripe-shaped ridge waveguide 32.
0 has both side convex regions 34a parallel to the upper and lower surfaces. Thereby, the p-type Ga shown in FIG.
The formation of unevenness in the As cap layer 90 is eliminated, and the p-type GaAs cap layer 35 having a flat surface is formed.

The semiconductor laser device manufactured by such a method has an oscillation threshold current of about 40 mA,
Self-excited oscillation stably from about mW to about 10 mW indicates that a high-performance semiconductor laser device has been obtained.

(Embodiment 4) A method of manufacturing a semiconductor laser using the compound semiconductor etching method of this embodiment will be described with reference to FIG.

First, as shown in FIG.
An n-type Ga layer having a thickness of 0.3 μm is formed on an aAs substrate 36._0.5I
n_0.5P buffer layer 37, 1.2 μm thick n-type (Al
_0.7Ga_0.3)_0.5In_0.5P cladding layer 38, layer thickness
0.1 μm undoped (Al _xGa_1-x)_0.5In
_0.5P active layer 39, 0.6 μm thick p-type (Al_0.7G
a _0.3)_0.5In_0.5P clad layer 40, layer thickness 0.1μ
p-type Ga_0.5In_0.5P cap layer 41 and layer thickness
A 0.3 μm p-type GaAs protective layer 42 is
Long method (MOCVD method) or molecular beam epitaxial method (M
(BE method).

Next, as shown in FIG.
After forming a stripe-shaped SiO ₂ mask layer 43 having a thickness of 0.2 μm and a width of 3.0 μm on the As protective layer 42 by an electron beam evaporation method and a photolithographic technique, FIG.
As shown in (c), the p-type GaAs is formed via the mask layer 43.
s protective layer 42, p-type GaInP cap layer 41, p-type A
The 1GaInP cladding layer 40 is formed at a temperature of 30 ° C. with hydrobromic acid (containing 47% of HBr): hydrogen peroxide solution (H ₂ O ₂ is 3%).
(Containing 5%): water = 1: 1: 30 (volume ratio) by an etching solution (etching rate: about 50 ° / sec) to form a p-type AlGaInP cladding layer 40 having a layer thickness of 0.4 μm.
A stripe-shaped ridge waveguide 44 having an m flat portion 40a and a stripe portion 40b having a lower width of 3.0 μm is formed.

Thereafter, as shown in FIG.
After performing side etching 45 on the aAs protective layer 42 with a phosphoric acid-based etchant, an n-type GaAs current confinement layer 46 is formed by MOCVD or MBE as shown in FIG. As shown in FIG. 4F, the SiO ₂ mask layer 43 is removed with a hydrofluoric acid-based etchant, and
After the As cap layer 47 is formed by MOCVD or MBE, a p-type electrode and an n-type electrode (both not shown) are formed on the p-type GaAs cap layer 47 and on the lower surface of the n-type substrate 36, respectively.

The semiconductor laser obtained by the manufacturing method of this embodiment has a two-stage current confinement layer (block layer) structure. Then, an n-type AlInP current confinement layer (block layer)
Reference numeral 46 denotes a p-type GaAs protective layer 4 which is formed to have a width smaller than that of the stripe-shaped ridge waveguide 44 and is the uppermost compound semiconductor crystal layer of the stripe-shaped ridge waveguide 44.
2 has a side convex region 46a parallel to both the upper and lower surfaces. Thereby, the p-type Ga shown in FIG.
The formation of irregularities in the As cap layer 90 is eliminated, and the p-type GaAs cap layer 47 having a flat surface is formed.

The characteristics of the semiconductor laser device manufactured by such a method are as follows.
It has stable self-sustained pulsation characteristics from about A to about 10 mA, indicating that a high-performance semiconductor laser has been obtained.

(Embodiment 5) A method for manufacturing a semiconductor laser using the method for etching a compound semiconductor according to this embodiment will be described with reference to FIG.

First, an n-type Ga _0.5 In _0.5 P buffer layer 49 having a thickness of 0.3 μm is formed on an n-type GaAs substrate 48.
N-type (Al _0.7 Ga _0.3 ) _0.5 In with a layer thickness of 1.2 μm
_0.5 P cladding layer 50, undoped (Al _x Ga _{1 -x} ) _0.5 In _0.5 P active layer 51 with a layer thickness of 0.1 μm, p-type (Al _0.7 Ga _0.3 ) _0.5 In _0.5 P with a layer thickness of 0.8 μm
Cladding layer 52, p-type Ga _0.5 In with a thickness of 0.1 μm
_0.5 P cap layer 53, 0.3 μm thick p-type GaAs
The protective layer 55 is continuously grown by metal organic chemical vapor deposition (MOCVD) or molecular beam epitaxy (MBE).

Next, after a stripe of thickness 0.2μm on the p-type GaAs protective layer 55, the SiO ₂ mask layer 54 of width 3.0μm was formed by electron beam evaporation and photolithography, the SiO ₂ mask Through layer 54,
Hydrobromic acid at a temperature of 30 ° C. (containing 47% of HBr): aqueous hydrogen peroxide (containing 35% of H ₂ O ₂ ): water = 5: 1: 20
By performing etching (etching rate is about 30 ° / sec) with an etching solution of 0 (volume ratio), p-type Ga
Only the As protective layer 55 is selectively etched away.

In the case of the above-mentioned hydrobromic acid: hydrogen peroxide solution: water etching solution, the mixing ratio of water: hydrobromic acid is 1:40.
Or less, and the mixing ratio of hydrobromic acid: hydrogen peroxide solution is 5: 1
In the following cases, a GaAs compound semiconductor crystal or G
An etching effect is exerted on the aAs-based compound crystal laminate, but not on the InP-based compound semiconductor crystal or the InP-based compound semiconductor crystal laminate. The practical temperature in this case is 5 to 50C.

(Embodiment 6) A method of manufacturing a semiconductor laser using the compound semiconductor etching method of this embodiment will be described with reference to FIG.

On an n-type GaAs substrate 56, an n-type Ga _0.5
In _0.5 P layer 57, n-type (Al _0.7 Ga _0.3 ) _0.5 In
_0.5 P layer 58, undoped (Al _x Ga _{1 -x} ) _0.5 In
_0.5 P layer 59, p-type (Al _0.7 Ga _0.3 ) _0.5 In _0.5
A P-type layer 60, an n-type GaAs layer 61, and a p-type GaAs layer 62 are formed on a p-type GaAs layer 62 of a wafer formed by metal organic chemical vapor deposition (MOCVD) or molecular beam epitaxy (MBE). A photoresist pattern 63 is formed by a lithographic technique or the like.

Next, the p-type GaAs is
The temperature ranging from the s layer 62 to the n-type GaAs substrate 56 is 3
Hydrobromic acid at 0 ° C. (containing 47% of HBr): hydrochloric acid (HC
l 35% content): phosphoric acid (H ₃ PO ₄ is from 85 to 87%
(Contained): hydrogen peroxide solution (containing 35% of H ₂ O ₂ ) = 7
By etching with an etching solution of 5: 50: 50: 1 (volume ratio) (etching rate is about 1 μm / min),
An element is isolated by forming an etching groove 64.

Here, by mixing hydrochloric acid and phosphoric acid,
For example, the non-uniform state of etching, which is observed when an off-substrate having been subjected to off-polishing (polishing so that the wafer surface has an arbitrary crystal plane) is greatly improved.

The mixing ratio and temperature of the above-mentioned etching solution can be arbitrarily selected according to the purpose, but practically, hydrobromic acid: hydrogen peroxide solution is 50: 1 to 150: 1, Hydrofluoric acid: hydrochloric acid: phosphoric acid 1: 2: 2 to 4: 1: 1
And the temperature is preferably 10 to 50 ° C.

(Embodiment 7) A method for manufacturing a semiconductor laser using the compound semiconductor etching method of this embodiment will be described.

Although not shown, for example, n-type GaAs
An n-type GaAs buffer layer and an n-type Al _0.45 G
a _0.55 As cladding layer, undoped Al _0.14 Ga _0.86 A
After an s active layer, a p-type Al _0.45 Ga _0.55 As clad layer, and a p-type GaAs contact layer are sequentially formed by MOCVD or MBE, a desired SiO ₂ mask pattern is formed by electron beam evaporation and photolithography.

Thereafter, through a mask pattern, hydrobromic acid (containing 47% of HBr): phosphoric acid (containing 85 to 87% of H ₃ PO ₄ ): aqueous hydrogen peroxide (containing HBr at a temperature of 10 ° C.)
₂ O ₂ 35% content) = 75: 50: 1 ( p -type AlG from p-type GaAs contact layer with an etching solution volume ratio)
By etching a part of the aAs cladding layer (etching rate is about 100 ° / sec), a pattern of a stripe-shaped ridge waveguide can be formed.

(Embodiment 8) A method of etching a compound semiconductor according to this embodiment will be described.

Although not shown in the figure, for example, n-type Ga
Z formed on MO substrate by MOCVD or MBE
The temperature of the nSe layer is 30 ° C. through the photoresist pattern.
Hydrobromic acid (containing 47% HBr): phosphoric acid (H ₃ P
Etching with an etching solution of O ₄ : 85-87%): hydrogen peroxide solution (H ₂ O ₂ : 35%) = 75: 50: 1 (volume ratio) (etching rate: about 300 ° / sec)
By doing so, a desired pattern can be obtained.

(Embodiment 9) A method of etching a compound semiconductor of this embodiment will be described.

Although not shown in the drawing, for example, an InAs layer formed on an InP substrate by MBE is formed by etching a hydrobromic acid (HBr 4) at a temperature of 10 ° C. through a photoresist pattern.
7% contained): containing phosphoric acid (H ₃ PO ₄ is from 85 to 87%): hydrogen peroxide (H ₂ O ₂ 35% content) = 75:
A desired pattern can be obtained by etching with an etchant of 50: 1 (volume ratio) (etching rate is about 50 ° / sec).

(Embodiment 10) A method for etching a compound semiconductor of this embodiment will be described.

Although not shown in the figure, for example, n-type GaAs
An n-type GaAs buffer layer and an n-type Al _0.45 G
a _0.55 As cladding layer, undoped Al _0.14 Ga _0.86 A
After an s active layer, a p-type Al _0.45 Ga _0.55 As clad layer, and a p-type GaAs contact layer are sequentially formed by MOCVD or MBE, a desired SiO ₂ mask pattern is formed by electron beam evaporation and photolithography.

Thereafter, through a mask pattern, hydrobromic acid (containing 47% of HBr): hydrogen peroxide (containing 35% of H ₂ O ₂ ) at a temperature of 30 ° C. = 75: 1 (volume ratio) Etching with an etching solution (etching rate is about 10
(00 ° / sec), it is possible to etch from the p-type GaAs contact layer to the p-type Al _0.45 Ga _0.55 As clad layer, and the pattern of the stripe-shaped ridge waveguide is formed in one etching step. It is.

(Embodiment 11) A method for etching a compound semiconductor of this embodiment will be described.

Although not shown in the figure, for example, n-type Ga
On an As substrate, an n-type Ga _0.5 In _0.5 P layer and an n-type (Al
_0.7 Ga _0.3 ) _0.5 In _0.5 P layer, undoped (Al _x Ga
_{1-x) 0. 5 In 0.5} P layer, p-type (Al _0.7 Ga _{0.3) 0.5} In
_0.5 P layer, n-type GaAs layer and p-type GaAs layer are MOCV
P-type GaAs of wafer formed by D method or MBE method
A desired photoresist pattern is formed on the s layer by a photolithographic technique or the like.

After that, a process to reach the p-type GaAs substrate through the photoresist pattern at a temperature of 30 ° C. of hydrobromic acid (containing 47% of HBr): hydrogen peroxide solution (H ₂ O ₂₎
35%): hydrochloric acid (35% HCl) = 75:
By performing etching with an etchant of 1: 2.5 (volume ratio) (etching rate is about 1000 ° / sec), an element isolation groove is formed.

Incidentally, hydrobromic acid: phosphoric acid: water = 1: 1:
Various compound semiconductors were heated at a temperature of 3 using an etching solution of 30.
Etching can be performed at 0 ° C. (etching rate is about 40 ° / sec in the case of ZnSe).

In the embodiment described above, an example of manufacturing a semiconductor laser using a compound semiconductor crystal (crystal layer) has been described. However, the same applies to a method of manufacturing another compound semiconductor element (electronic device). Can be used. Further, in addition to the above-described compound semiconductor crystal (crystal layer) and a laminate thereof, a similar effect can be obtained when used for a compound semiconductor crystal (crystal layer) having an ionized bond.

[0077]

As described above, according to the etching method of the present invention using the mixed solution containing hydrobromic acid and hydrogen peroxide, the GaAs compound semiconductor crystal (crystal layer),
InP-based compound semiconductor crystal (crystal layer), ZnSe-based compound semiconductor crystal (crystal layer), InAs-based compound semiconductor crystal (crystal layer), or these compound semiconductor crystals (crystal layer)
It is possible to form a pattern with good controllability by a single etching step on the laminate composed of. On the other hand, by mixing phosphoric acid, hydrochloric acid, phosphoric acid and hydrochloric acid, or water in the mixed solution, it is possible to control the etching rate, control the etching cross-sectional shape, or impart etching selectivity, It is also possible to easily select the composition of the etching solution according to each purpose. According to the semiconductor laser of the present invention, it is easy to control the divergence angle of the laser beam, and to easily form the semiconductor laser having the two-stage current confinement layer structure and to improve the characteristics thereof. This has the effect that it can be performed.

[Brief description of the drawings]

FIG. 1 is a manufacturing process diagram of a semiconductor laser according to a first embodiment of the present invention.

FIG. 2 is a manufacturing process diagram of a semiconductor laser according to a second embodiment of the present invention.

FIG. 3 is a manufacturing step diagram of a semiconductor laser according to a third embodiment of the present invention.

FIG. 4 is a manufacturing process diagram of a semiconductor laser according to a fourth embodiment of the present invention.

FIG. 5 is a manufacturing step diagram of a semiconductor laser according to a fifth embodiment of the present invention.

FIG. 6 is a schematic diagram illustrating etching of a compound semiconductor crystal layer according to a sixth embodiment of the present invention.

FIG. 7 is an example of a manufacturing process diagram of a conventional semiconductor laser.

FIG. 8 is an example of a manufacturing process diagram of a conventional semiconductor laser.

DESCRIPTION OF SYMBOLS 1 On n-type GaAs substrate 1 2 n-type GaInP buffer layer 3 n-type AlGaInP cladding layer 4 undoped AlGaInP active layer 5 p-type AlGaInP cladding layer 6 p-type GaInP cap layer 7 p-type protection layer 8 SiO ₂ mask Layer 9 Striped ridge waveguide 10 n-type GaAs current confinement layer 12 p-type GaAs cap layer

Claims (13)

[Claims] 1. A first compound semiconductor crystal containing at least Ga and As, and a second compound semiconductor crystal containing at least Zn and Se.
A compound semiconductor having at least either a compound semiconductor crystal or a third compound semiconductor crystal containing at least In and As is etched using a mixed solution containing hydrobromic acid and aqueous hydrogen peroxide. A method for etching a compound semiconductor, comprising: 2. A first compound semiconductor crystal containing at least Ga and As, and a second compound semiconductor containing at least Zn and Se.
A compound semiconductor having at least one of a compound semiconductor crystal, a third compound semiconductor crystal containing at least In and As, or a fourth compound semiconductor crystal containing at least In and P is treated with hydrobromic acid and A method for etching a compound semiconductor, comprising etching using a mixed solution containing hydrogen oxide water and phosphoric acid. 3. A first compound semiconductor crystal containing at least Ga and As, and a second compound semiconductor crystal containing at least Zn and Se.
A compound semiconductor having at least one of a compound semiconductor crystal, a third compound semiconductor crystal containing at least In and As, or a fourth compound semiconductor crystal containing at least In and P is treated with hydrobromic acid and A method for etching a compound semiconductor, comprising etching using a mixed solution containing hydrogen oxide water and hydrochloric acid. 4. A first compound semiconductor crystal containing at least Ga and As, and a second compound semiconductor containing at least Zn and Se.
A compound semiconductor having at least one of a compound semiconductor crystal, a third compound semiconductor crystal containing at least In and As, or a fourth compound semiconductor crystal containing at least In and P is treated with hydrobromic acid and A method for etching a compound semiconductor, comprising etching using a mixed solution containing hydrogen oxide water, phosphoric acid, and hydrochloric acid. 5. A first compound semiconductor crystal containing at least Ga and As, and a second compound semiconductor crystal containing at least Zn and Se.
A compound semiconductor having at least one of a compound semiconductor crystal, a third compound semiconductor crystal containing at least In and As, or a fourth compound semiconductor crystal containing at least In and P is treated with hydrobromic acid and A method for etching a compound semiconductor, comprising etching using a mixed solution containing hydrogen oxide water and water. 6. The first compound semiconductor crystal containing at least Ga and As is an AlGaAs-based semiconductor crystal,
The method for etching a compound semiconductor according to claim 1, wherein the method is an aAs-based semiconductor crystal or a laminate thereof. 7. The second compound semiconductor crystal containing at least Zn and Se is a ZnSeS-based semiconductor crystal, Zn
The method for etching a compound semiconductor according to claim 1, wherein the etching method is a Se-based semiconductor crystal or a stacked body thereof. 8. The third compound semiconductor crystal containing at least In and As is an InGaAs-based semiconductor crystal,
6. The compound semiconductor etching method according to claim 1, wherein the compound semiconductor is an nAlAs-based semiconductor crystal, an InGaAlAs-based semiconductor crystal, or a laminate thereof. 9. The fourth material containing at least In and P.
Compound semiconductor crystal is GaInP-based semiconductor crystal, AlI
The method for etching a compound semiconductor according to claim 2, wherein the compound semiconductor is an nP-based semiconductor crystal, an AlGaInP-based semiconductor crystal, or a stacked body thereof. 10. A compound semiconductor comprising: a GaAs semiconductor substrate, a GaInP semiconductor crystal layer, an AlGaInP crystal layer,
A compound semiconductor comprising a GaInP semiconductor crystal layer and a GaAs semiconductor crystal layer in this order, and the stacked body is etched using the etching method according to any one of claims 1 to 5. Etching method. 11. A method for manufacturing a compound semiconductor device, comprising the step of using the method for etching a compound semiconductor according to claim 1. Description: 12. A current confinement layer having substantially the same width as the uppermost compound semiconductor crystal layer of the stripe-shaped ridge waveguide, and being formed almost directly above both ends of the uppermost compound semiconductor layer and in the vicinity thereof. A semiconductor laser, comprising: 13. A current confinement layer having a width smaller than that of a stripe-shaped ridge waveguide, and a side region parallel to both upper and lower surfaces of an uppermost compound semiconductor crystal layer of the stripe-shaped ridge waveguide. A semiconductor laser characterized by being formed.