JP2001272564A - Method for manufacturing semiconductor optical waveguide - Google Patents

Abstract

PROBLEM TO BE SOLVED: To manufacture an optical waveguide layer of a transverse width of about 0.5 μm by exposure with UV rays. SOLUTION: An (n) type InP buffer layer, an InGaAsP waveguide layer of about 0.4 μm in thickness, a glass layer and a photosensitive resin are laminated on a (n) type InP substrate (S1 to S3). The photosensitive resin is exposed with a pattern exposure device of a mercury lamp and is developed (S4) and the glass layer is etched by buffered hydrofluoric acid (S5). The photosensitive resin mask is removed (S6). The waveguide layer 14 is etched down to a depth of about 0.3 μm by a reactive ion etching method and the mask patterns of the glass mask 16a are transferred to the waveguide layer 14 (S7). The waveguide layer 14 is wet etched by a sulfuric acid-base etchant (S8). As a result, the waveguide of a section forming a trapezoidal shape of about 0.5 μm on the upper side and about 0.9 μm the lower side is obtained. A current block layer is grown alongside the waveguide by utilizing the overhanging of the glass mask (S9) and the glass mask is removed (S10). A non-doped InP clad layer and type InP clad layer 26 are grown over the entire part (S11).

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for manufacturing a semiconductor optical waveguide.

[0002]

2. Description of the Related Art In recent years, in the field of optical communication in which large capacity and high bit rate have been remarkably advanced, semiconductor optical amplifiers, semiconductor array waveguide gratings (AWG) and semiconductor optical add / drop elements (ADM) are representative. The importance of semiconductor optical function devices to be used is further increasing. In a semiconductor optical function device, a manufacturing technique for precisely controlling the shape of the optical waveguide layer is very important. In particular, it is necessary to reduce the dispersion of the element's complex propagation constant in the polarization direction by making the width of the optical waveguide layer approximately the same as its thickness (typically about 0.1 to 2 or 3 μm). In a semiconductor optical functional device such as a current injection type semiconductor optical amplifier and a wavelength conversion device using the same, it is preferable to reduce the thickness of the optical waveguide layer to 0.5 μm or less at the maximum in order to reduce resistance. Inevitably, an optical waveguide layer having a narrow width of 1 μm or less must be manufactured. That is, a pattern consisting of a straight line pattern or a substantially straight line and including a slight curve portion,
In the following, there is a need for a technique capable of manufacturing an optical waveguide layer having a lateral width of about 0.5 μm with good controllability and high reproducibility.

[0003]

In a photolithography using an ultraviolet exposure apparatus using a conventional ultraviolet lamp such as a mercury lamp or a xenon lamp as a light source, the line width that can be formed on the photosensitive resin mask is about 1.5 μm. It is difficult to form a pattern having a line width smaller than that.

[0004] The use of a shorter wavelength light source such as an excimer laser enables photolithography of 1 µm or less, but such deep ultraviolet light sources still have problems in stability and life, so running costs are low. Will be higher.
Further, such a deep ultraviolet exposure apparatus is considerably more expensive than a normal ultraviolet exposure apparatus.

On the other hand, recently, an electron beam drawing technique is sometimes used for such ultra-fine processing. However, since the electron beam lithography technology scans and exposes an electron beam, it can draw very fine lines, but has a low throughput. Further, since an expensive apparatus is required as compared with an ordinary ultraviolet exposure apparatus, it is not suitable as an apparatus for forming a pattern of about 0.5 μm.

In addition, there is an X-ray exposure apparatus as an exposure apparatus for directly forming a pattern of 1 μm or less. But,
This apparatus is also very large and has not yet been put to practical use due to problems such as the material of the mask material.

[0007] The present invention solves such problems,
It is an object of the present invention to provide a method for manufacturing an optical waveguide layer having a width of about 0.5 μm with good controllability and high reproducibility.

Another object of the present invention is to provide a method for manufacturing an optical waveguide layer having a lateral width of about 0.5 μm at a high throughput by using an inexpensive apparatus.

Another object of the present invention is to provide a method capable of manufacturing an optical waveguide having a width smaller than the mask width.

[0010]

According to the present invention, there is provided a method for manufacturing a semiconductor optical waveguide, comprising the steps of: manufacturing a primary wafer having a waveguide layer and a glass layer laminated on a lower clad; and forming the glass layer into a desired mask pattern. A mask forming step of forming a glass mask by processing, a transfer step of etching the waveguide layer according to the glass mask by a dry etching method, and transferring a pattern of the glass mask to the waveguide layer, a wet etching method A waveguide forming step of etching the waveguide layer so that the glass mask protrudes a predetermined length on both sides to form an optical waveguide having a desired cross-sectional shape from the waveguide layer; and forming a primary layer on both sides of the optical waveguide. A primary burying step of growing the buried layer to a height flush with the top surface of the waveguide; And a mask removal step of removing,
And a secondary embedding step of growing a secondary embedding layer on the optical waveguide and the primary embedding layer.

As described above, since both dry etching and wet etching are used, an optical waveguide having a lateral width smaller than the original mask width can be formed. Since wet etching is performed after the dry etching, a portion damaged by the dry etching can be removed, and growth defects can be reduced. By burying and growing the glass mask so as to protrude by a predetermined length in the lateral direction, a flat surface is obtained after the removal of the glass mask, and a high-quality upper cladding layer can be grown.

[0012] Preferably, a cap layer is laminated between the waveguide layer and the glass layer, and the waveguide forming step is such that the glass mask is placed on both sides by a first etchant for etching the waveguide layer. A first etching step of etching the waveguide layer so as to extend a predetermined length and forming an optical waveguide having a desired cross-sectional shape from the waveguide layer; and a second etching step of selectively etching a cap layer on the optical waveguide. A second etching step of etching the cap layer with an etchant to a width corresponding to the lateral width of the optical waveguide.

[0013] The cap layer protects the waveguide layer from damage during lamination of the glass layers and also prevents the waveguide from being exposed to the outside air during regrowth. Thereby, a high-quality optical waveguide can be obtained.

[0014] For example, the lower cladding layer and the cap layer comprises InP, the waveguide layer is _{In x Ga 1-x As y} P
_1-y (0 ≦ x <1, 0 <y ≦ 1).

The waveguide _{layer, (In x Ga 1-x} ) y Al
_{1-y As} y may consist (0 ≦ x ≦ 1,0 ≦ y ≦ 1).

[0016] By providing a step which is performed between the mask removing step and the secondary embedding step and etches a surface layer portion of the cap layer, a damaged portion which the cap layer has suffered during the lamination of the glass layer is provided. Remove. Thereby, a high-quality upper clad layer can be laminated.

For example, the lower cladding layer is made of InP.
And the waveguide layer is In_xGa _1-xAs_yP
_1-y(0 ≦ x <1, 0 <y ≦ 1).

The waveguide layer is (In _x Ga _{1 -x} ) _y Al
_{1-y As} y may consist (0 ≦ x ≦ 1,0 ≦ y ≦ 1).

In the mask forming step, for example, a photosensitive resin is coated on the glass layer of the primary wafer, the photosensitive resin is exposed and developed with the desired mask pattern, and the glass layer is etched with an etchant for glass to form the desired mask. It consists of processing into a pattern. That is, even when using a normal optical exposure apparatus such as an ultraviolet exposure apparatus,
An optical waveguide having a width of about 0.5 μm can be formed.

The dry etching method is, for example, a reactive ion etching method or a plasma etching method.

[0021]

Embodiments of the present invention will be described below in detail with reference to the drawings.

FIG. 1 is a flow chart of a first embodiment of the present invention applied to a semiconductor amplifier in the 1.55 μm band.
2 to 8 show schematic views of cross sections in each manufacturing step.

An n-type InP buffer layer 12 serving as a lower cladding layer is formed on an n-type InP substrate 10 by an organic metal growth method.
And a thickness of about _{0.4μm In x Ga 1-x As} y P
_{The 1-y} waveguide layer 14 is laminated (S1). FIG. 2 shows a schematic diagram of a cross section after step S1. Furthermore, plasma CV
The SiO ₂ glass layer 16 is formed on the waveguide layer 14 by the D method.
Are laminated (S2), and the photosensitive resin 1 is spin-coated.
8 is coated on the glass layer 16 (S3). FIG. 3 shows a schematic diagram of a cross section after step S3. As a result, a primary wafer is manufactured.

The photosensitive resin 18 of the primary wafer is exposed to a 1.5 μm-wide waveguide by a pattern exposure device of a mercury lamp and developed. Thereby, the width is about 1.5 μm
Is formed (S4). The SiO ₂ glass layer 16 is etched by dipping it in buffered hydrofluoric acid (a mixed solution of hydrofluoric acid: ammonium fluoride solution = 3: 20 in a volume mixing ratio), thereby changing the pattern of the photosensitive resin mask layer 18a to the SiO ₂ glass layer. 16 (S5). Thereby, the glass mask 1 having a desired pattern is formed.
6a is formed. FIG. 4 shows a schematic diagram of a cross section after step S5. At this time, if the etching time is 80 seconds, underetching in which the etchant goes under the photosensitive resin mask 18a occurs, and this effect causes
The width of the O ₂ glass mask 16a is reduced to about 1.0 μm.

After forming the SiO ₂ glass mask 16a, the photosensitive resin mask 18a is removed using a solvent for the photosensitive resin, for example, 2-butanone (S6).

Subsequently, the InGaAsP waveguide layer 14 is etched by a reactive ion etching (RIE) method to a depth of about 0.3 μm, and the mask pattern of the SiO ₂ glass mask 16a is transferred to the waveguide layer 14 ( S7). FIG. 5 shows a schematic diagram of a cross section after step S7. The width of the waveguide layer 14 obtained at this time is S
It is about 1.0 μm, which is almost the same as that of the iO ₂ glass mask 16a. Of course, in this dry etching, the waveguide layer 14 may be completely etched until it reaches the lower cladding layer 12.

If the waveguide layer 14 is etched by the RIE method and then buried and grown in the same shape, a layer called a surface damage layer remains on the etched surface due to ion bombardment during the RIE etching. Crystallinity remarkably deteriorates. However, in the present embodiment, as will be described later, since the damaged layer is completely removed by further performing wet etching, the deterioration of the crystallinity at the interface between the formed waveguide layer 14 and the regrown layer is reduced. Does not occur.

Subsequently, the InGaAsP waveguide layer 14 is wet-etched for about 25 seconds using a sulfuric acid-based etchant (concentrated sulfuric acid: hydrogen peroxide: water = 1: 8: 12 by volume mixing ratio) (S8). . In the case of the present embodiment, since the direction in which the normal mesa surface emerges matches the direction of the waveguide, InG
From the aAsP waveguide layer 14, a waveguide 14a having a trapezoidal cross section having an upper side of about 0.5 μm and a lower side of about 0.9 μm is obtained. FIG. 6 shows a schematic diagram of a cross section after step S8.
At this time, as shown in FIG. 6, the SiO ₂ glass mask 16a has a shape protruding about 0.25 μm to each side. This overhang plays an important role in the buried growth described later.

Immediately after the completion of the wet etching (S8), the wafer is introduced into a metal organic vapor phase epitaxy (MOVPE) apparatus to perform primary burying growth. In this embodiment, a current injection type semiconductor amplifier is manufactured.
A current blocking layer is formed by depositing a doped InP layer and an n-doped InP layer.

As the primary buried growth, the p-type In is grown next to the waveguide 14a so as to be aligned with the top surface of the waveguide 14a.
P current block layer 20 and n-type InP current block layer 2
2 is grown (S9). At this time, the overhang of the SiO ₂ glass mask 16a prevents the deposition of InP on the mask 16a. If there is no overhang, the InP layer 2
0 and 22 continue to grow so as to swell at the edge of the SiO ₂ mask 16a, and as a result, grow so as to cover the mask 16a. FIG.
9 shows a schematic view of the cross section after 9.

The SiO ₂ glass mask 16a is removed with buffered hydrofluoric acid (S10). The surface after removing the mask 16a is substantially flat.

Further, a non-doped InP having a thickness of 0.15 μm is used.
Cladding layer 24 and 2 μm thick p-type InP cladding layer 2
6 is grown by an organic metal vapor deposition method (S11). FIG.
Shows a schematic diagram of a cross section after step S11. Thereby, the waveguide of the semiconductor amplifier is completed.

In the case of a semiconductor amplifier, electrodes are formed thereafter by a known method. Since the process is very general and not directly related to this example,
Detailed description is omitted.

In this embodiment, since a normal ultraviolet exposure apparatus using a lamp as a light source can be used, a large area can be exposed at a time by a relatively inexpensive apparatus. Therefore, high throughput is obtained, running cost is low, and controllability and reproducibility are high. Since the surface damage layer by dry etching is removed by wet etching, generation of crystal defects at the interface of the regrown layer can be suppressed. Due to the under-etching effect at the time of wet etching, a waveguide narrower than the SiO ₂ glass mask 16a can be formed. Since the overhang of the SiO ₂ glass mask necessary for the primary burying regrowth is formed at the same time by wet etching, the number of steps can be reduced.

Although the RIE method has been exemplified as the dry etching method, another method, for example, a plasma etching method may be used.

In the embodiment shown in FIGS.
SiO 2 directly on the sP waveguide layer 14 ₂Glass mask layer 1
6 was deposited. However, semiconductors containing As are relatively oxidized.
Short time before the secondary burying growth.
However, exposure of the waveguide layer surface to the atmosphere is less preferred.
I don't. To prevent this, the primary wafer growth
Next, an InP cap layer is deposited on the InGaAsP waveguide layer.
You only have to stack them. In addition, SiO₂Directly under the glass mask
The semiconductor surface is exposed to plasma at the beginning of the glass mask deposition.
Takes some damage from exposure. This damage
Parts that have been affected are removed before secondary buried growth
Is preferred.

FIG. 9 shows a flowchart of the second embodiment in consideration of the above. 10 to 17 show schematic views of cross sections in each step.

An n-type InP buffer layer 1 serving as a lower cladding layer is formed on an n-type InP substrate 110 by an organic metal growth method.
12, a thickness of about _{0.4μm In x Ga 1-x As} y P
_{1- y} waveguide layer 114 and i-InP cap layer 116
Are laminated (S21). FIG. 10 shows a schematic view of a cross section after step S21. Furthermore, by the plasma CVD method,
The SiO ₂ glass layer 118 is laminated on the cap layer 116 (S22), and the photosensitive resin 120 is formed by spin coating.
Is coated on the glass layer 118 (S23). FIG.
Shows a schematic diagram of a cross section after step S23. As a result, a primary wafer is manufactured.

The photosensitive resin 120 of the primary wafer has a width
Mercury lamp pattern exposure device with 1.5 μm waveguide shape
And then develop. Thereby, the width is about 1.5 μm
Is formed (S24).
Buffered hydrofluoric acid (hydrofluoric acid by volume mixing ratio: ammonium fluoride
Solution (3:20 mixed solution). ₂
The glass layer 118 is etched, and the photosensitive resin
The pattern of the mask layer 120a is SiO₂Glass layer 118
(S25). As a result, the desired pattern
A lath mask 118a is formed. FIG. 12 shows the steps
The schematic diagram of the cross section after S25 is shown. At this time, etching
Assuming that the time is 80 seconds, the etchant
Under-etching that occurs under the metal 120a,
Due to this effect, SiO₂Width of glass mask 118a
Decreases to about 1.0 μm.

After forming the SiO ₂ glass mask 118a, the photosensitive resin mask 120a is replaced with a solvent for the photosensitive resin,
For example, it is removed using 2-butanone (S26).

Subsequently, the InGaAsP waveguide layer 114 is etched to a depth of about 0.3 μm by a reactive ion etching (RIE) method, and the mask pattern of the SiO ₂ glass mask 118 a is changed to the cap layer 11.
6 and transferred to the waveguide layer 114 (S27). FIG.
Shows a schematic diagram of a cross section after step S27. The lateral width of the waveguide layer 114 obtained at this time is about 1.0 μm, which is almost the same as that of the SiO ₂ glass mask 118a. Of course, in this dry etching, the waveguide layer 114 may be completely etched until the lower clad layer 112 is reached.

The InGaAsP waveguide layer 114 is formed using a sulfuric acid-based etchant (concentrated sulfuric acid: hydrogen peroxide solution: water =
1: 8: 12) for about 25 seconds (S28). In the case of the present embodiment, since the direction in which the normal mesa surface emerges matches the direction of the waveguide, InGaAsP
From the waveguide layer 114, a waveguide 114a having a trapezoidal cross section with an upper side of about 0.5 μm and a lower side of about 0.9 μm is obtained. InP cap layer 116 and InP clad layer 11
2 is not etched. FIG. 14 shows a schematic diagram of a cross section after step S28.

Next, the InP cap layer and the InP cladding layer 112 are etched with a hydrochloric acid-based etchant to such an extent that the width of the InP cap layer 116 matches the width of the waveguide 114a (S29). This allows I
The nP lower cladding layer 112 is somewhat thinner. FIG.
Shows a schematic diagram of a cross section after step S29. In this state, as in the case of the first embodiment, the SiO ₂ glass mask 118a has a shape protruding left and right by about 0.25 μm. This overhang plays an important role in the buried growth described later.

After the completion of the wet etching (S29),
Immediately, the wafer is introduced into an MOVPE apparatus to perform primary burying growth. The following process may be the same as in the first embodiment. Also in this embodiment, since a current injection type semiconductor amplifier is manufactured, a p-doped InP layer and an n-doped InP layer are deposited at the time of embedding to form a current blocking layer.

As the primary buried growth, the waveguide 114a
Next to the top of the cap layer 116.
The n-type InP current block layer 122 and the n-type InP current block layer 124 are grown (S30). At that time, SiO
₂ The overhang of the glass mask 118a
Prevents InP deposition on top. Without this overhang, InP layer 122, 124, SiO ₂ mask 118
The growth is continued so as to swell at the edge portion a, and as a result, it grows so as to cover the mask 118a. FIG. 16 shows a schematic diagram of a cross section after step S30.

The SiO ₂ glass mask 118a is removed with buffered hydrofluoric acid (S31). The surface after removing the mask 118a is substantially flat.

Further, a non-doped InP having a thickness of 0.15 μm is used.
A cladding layer 126 and a p-type InP cladding layer 128 having a thickness of 2 μm are grown by a metal organic vapor deposition method (S32). FIG. 17 shows a schematic diagram of a cross section after step S32. Thereby, the waveguide of the semiconductor amplifier is completed.

Thereafter, an electrode is formed by a known method.

In the embodiment shown in FIGS. 9 to 17, the InP
The addition of the cap layer 116 allows the waveguide 114
It is possible to prevent the top surface of “a” from being exposed to the outside air before being buried and regrown. In addition, since the waveguide layer 114 is not directly exposed to plasma at the start of the deposition of the glass mask, damage due to plasma can be avoided.

Although the InP cap layer 116 is finally left, after the glass mask 118a is removed and before the secondary growth, a part of the InP capping operation 116 is mainly made of hydrochloric acid. It may be removed with an etchant. As a result, a damaged portion received during lamination of the glass layer 118 is removed.

Although the case where the semiconductor optical amplifier for the 1.55 μm band is manufactured has been described, it is apparent that the present invention can be applied to the case where other semiconductor functional elements are manufactured.
For example, the present invention can be applied to a case where a 1.3 μm band optical waveguide layer is formed. However, since the waveguide layer contains a large amount of P (phosphorus), the shape of the waveguide layer after wet etching is not trapezoidal but rectangular. Even in such a case, the overhang of the SiO ₂ glass mask is still effective during the primary burying and regrowth. The wet etching time may be adjusted so that the overhang length of the SiO ₂ glass mask is an appropriate length.

Although the case where the n-type substrate is used has been described, the conductivity type may be reversed using a p-type substrate. In the case of a semiconductor AWG or ADM that does not normally inject a current, instead of a semiconductor amplifier, the conductivity type may be essentially any type.

The waveguide layers 14 and 114 are made of In _x Ga _{1-x
As y P 1-y (0} ≦ x <1,0 <y ≦ 1) has been described a case consisting _{of, (In x Ga 1-x} ) y Al 1-y A
The present invention can be applied to a case where s _y (0 ≦ x ≦ 1, 0 ≦ y ≦ 1).

[0054]

As can be easily understood from the above description, according to the present invention, the thickness is 1 μm or less, typically 0.5 μm.
An optical waveguide layer having a width of about m can be manufactured with good controllability and high reproducibility using a relatively inexpensive apparatus. Moreover,
It can be manufactured with high throughput.

[Brief description of the drawings]

FIG. 1 is a flowchart of a first embodiment of the present invention.

FIG. 2 is a schematic view of a cross section after step S1.

FIG. 3 is a schematic view of a cross section after step S3.

FIG. 4 is a schematic diagram of a cross section after step S5.

FIG. 5 is a schematic diagram of a cross section after step S7.

FIG. 6 is a schematic diagram of a cross section after step S8.

FIG. 7 is a schematic diagram of a cross section after step S9.

FIG. 8 is a schematic diagram of a cross section after step S11.

FIG. 9 is a flowchart of a second embodiment of the present invention.

FIG. 10 is a schematic diagram of a cross section after step S21.

FIG. 11 is a schematic diagram of a cross section after step S23.

FIG. 12 is a schematic diagram of a cross section after step S25.

FIG. 13 is a schematic diagram of a cross section after step S27.

FIG. 14 is a schematic view of a cross section after step S28.

FIG. 15 is a schematic view of a cross section after step S29.

FIG. 16 is a schematic diagram of a cross section after step S30.

FIG. 17 is a schematic diagram of a cross section after step S32.

[Explanation of symbols]

10: n-type InP substrate 12: n-type InP buffer layer (lower cladding layer) 14: waveguide layer 14a: waveguide 16: SiO ₂ glass layer 16a: glass mask 18: photosensitive resin 18a: photosensitive resin mask 20: p -Type InP current blocking layer 22: n-type InP current blocking layer 24: non-doped InP cladding layer 26: p-type InP cladding layer 110: n-type InP substrate 112: n-type InP buffer layer (lower cladding layer) 114: waveguide layer 114a : Waveguide 116: InP cap layer 118: SiO ₂ glass layer 118 a: glass mask 120: photosensitive resin 120 a: photosensitive resin mask 122: p-type InP current blocking layer 124: n-type InP current blocking layer 126: non-doped InP cladding layer 128: p-type InP cladding layer

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Masaji Usami 2-1-1-15 Ohara, Kamifukuoka-shi, Saitama Pref. Inside Kadeidi Research Institute, Inc. (72) Munefumi Tsuruzawa 2-chome, Ohara, Kamifukuoka-shi, Saitama No. 1-15 Inside Keididi Research Institute, Inc. (72) Inventor Haruhisa Sakata 2-chome, Ohara, Kamifukuoka City, Saitama Prefecture 1-115 Inside Keideidi Research Institute, Inc. (72) Inventor Shinsuke Tanaka 2-chome Ohara, Kamifukuoka City, Saitama Prefecture No. 1-15 F-term in K.D. Laboratory (reference) 2H047 KA04 PA05 PA06 PA12 PA14 PA24 QA02 TA05 TA42 TA43 5F045 AA04 AA08 AB12 AB18 AB32 AB40 AF20 BB08 DA53 DB05 EB20 HA13 HA14 5F073 AA13 CA12 CB02 DA05 DA25 DA

Claims (10)

[Claims] A step of manufacturing a primary wafer in which a waveguide layer and a glass layer are laminated on a lower clad; a mask forming step of processing the glass layer into a desired mask pattern to form a glass mask; Etching the waveguide layer in accordance with the glass mask, and transferring the pattern of the glass mask to the waveguide layer; and conducting the wet etching so that the glass mask extends to both sides by a predetermined length by wet etching. Etch the waveguide layer,
A waveguide forming step of forming an optical waveguide having a desired cross-sectional shape from the waveguide layer; a primary embedding step of growing a primary embedding layer on both sides of the optical waveguide to a height aligned with the top surface of the waveguide; A method for manufacturing a semiconductor optical waveguide, comprising: a mask removing step of removing a glass mask; and a secondary embedding step of growing a secondary embedding layer on the optical waveguide and the primary embedding layer. 2. The method according to claim 1, further comprising the step of forming a cap layer between the waveguide layer and the glass layer, wherein the step of forming the waveguide includes the step of forming the glass mask on both sides by a first etchant for etching the waveguide layer. A first etching step of etching the waveguide layer so as to protrude a predetermined length from the waveguide layer to form an optical waveguide having a desired cross-sectional shape from the waveguide layer; and selectively etching a cap layer on the optical waveguide. 2. The method for manufacturing a semiconductor optical waveguide according to claim 1, comprising: a second etching step of etching the cap layer to a width corresponding to a lateral width of the optical waveguide by two etchants. 3. The lower cladding layer and the cap layer are made of InP, and the waveguide layer is made of In _x Ga _1-x A.
_{s y P 1-y (0} ≦ x <1,0 <y ≦ 1) a method of manufacturing a semiconductor optical waveguide according to claim 2 comprising a. Wherein the waveguide layer is _{(In x Ga 1-x)} y
_{Al 1-y As y (0} ≦ x ≦ 1,0 ≦ y ≦ 1) a method of manufacturing a semiconductor optical waveguide according to claim 2 comprising a. 5. The method according to claim 2, wherein the first etchant comprises a sulfuric acid-based etchant, and the second etchant comprises a hydrochloric acid-based etchant. 6. The method according to claim 2, further comprising the step of etching a surface portion of the cap layer, which is performed between the mask removing step and the secondary filling step. 7. The lower cladding layer is made of InP,
The waveguide _{layer, In x Ga 1-x As} y P 1-y (0
2. The method of manufacturing a semiconductor optical waveguide according to claim 1, wherein ≦ x <1, 0 <y ≦ 1). 8. The waveguide layer is _{(In x Ga 1-x)} y
_{Al 1-y As y (0} ≦ x ≦ 1,0 ≦ y ≦ 1) a method of manufacturing a semiconductor optical waveguide according to claim 1 comprising a. 9. The mask forming step includes coating a photosensitive resin on the glass layer of the primary wafer, exposing and developing the photosensitive resin with the desired mask pattern, and exposing the glass layer with an etchant for glass. 3. The method according to claim 1, wherein the semiconductor optical waveguide is processed into a desired mask pattern. 10. The method of manufacturing a semiconductor optical waveguide according to claim 1, wherein the dry etching method is any one of a reactive ion etching method and a plasma etching method.