JPH07297140A - Fabrication of optical semiconductor device - Google Patents

Abstract

PURPOSE:To obtain a high quality crystal by growing a semiconductor crystal film selectively in stripe with uniform thickness over the entire length of required part and eliminating the influence of damage to an underlying layer at the time of forming a mask for selective growth. CONSTITUTION:The mask length LM is set equal to the length L at a laser part plus at least twice the diffusion length of material gas in metal organic CVD. Subsequently, mask M for selective growth having a stripe opening for exposing a selective growth region (width: W), e.g. a clad layer 2, an active layer 3 and a clad layer 4, on a semiconductor substrate 1 is formed. A semiconductor crystal layer constituting the laser part L and a semiconductor crystal layer constituting an optical waveguide part G having a different thickness are then formed simultaneously on the semiconductor substrate 1 including the selective growth region through the mask M for selective growth.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method suitable for manufacturing an optical semiconductor device in which, for example, a semiconductor light emitting device for optical communication and an optical waveguide are integrated.

Generally, in an optical semiconductor device, for example,
Many steps are required to fabricate a plurality of types of elements such as a light emitting element and an optical waveguide, and it is difficult to form a high quality element with good controllability. Therefore, such a problem must be resolved.

[0003]

2. Description of the Related Art At present, metal-organic vapor phase epitaxy (metalo)
organic vapor phase epitax
y: MOVPE) method is applied, and various masks for selective growth formed on the surface of a semiconductor substrate are used to make various Group III-Group 5 compound semiconductor devices.

That is, the width of the mask pattern for selective growth,
That is, it has been reported that the growth rate of the semiconductor crystal layer can be controlled depending on the opening width of the stripe formed on the mask, and a plurality of elements, for example, a light emitting element and an optical waveguide are formed in one growth step. Selective growth technology was realized.

The change in the growth rate is naturally associated with the change in the film thickness of the semiconductor crystal layer, and the quantum size effect appears that the change in the film thickness has a dramatic effect on the characteristic change. It has been reported that, when a multiple quantum well, which is one of the devices, is manufactured, 160 [nm] was obtained as the change width of the emission wavelength realized by changing the film thickness. Incidentally, when the film thickness is small, the emission wavelength becomes short.

At present, by applying the MOVPE method using the mask pattern for selective growth as described above,
DFB (distributed fedback)
A semiconductor device in which a laser and an optical modulator are integrated has been realized.

By the way, the selective growth mask pattern is manufactured by using an insulating film such as a Si oxide film or a Si nitride film as a material thereof and patterning it by a usual lithography technique.

FIG. 15 is a plan view of an essential part illustrating a selective growth mask, and a diagram showing the film thickness distribution of a semiconductor crystal film grown using the mask is added.

In the figure, W _M is the mask width, W _S is the selective growth region width, L _M is the mask length, and X is the direction.

In general, selective growth masks are often used in combination with those having a stripe pattern as shown in FIG. 15. Usually, the mask width W _M is
20 to 30 [μm] to 200 to 300 [μm], and the selective growth region width W _S is 2 to 3 [μm] to 20 to 3
It is 0 [μm]. Further, the mask length L _M is about 500 [μm], since two semiconductor light emitting elements including a semiconductor laser are manufactured at the same time from the viewpoint of productivity.
It is designed to be about 600 [μm].

Increasing the mask rate, that is, W _M / W _M + W _S , increases the growth rate of the selective growth film. Therefore, this property is utilized to, for example, the energy band gap of a plurality of quantum well structures. Control is taking place.

[0012]

When the selective growth technique is applied to realize a practical semiconductor device, for example, a semiconductor device in which a semiconductor laser and an optical waveguide are integrated, the resonator length is set along the stripe direction. It is an essential requirement that the laser active region can be formed while maintaining a constant thickness.

However, when the MOVPE method is applied to form a portion of the semiconductor device as described above by one-time selective growth, as shown in the diagram of FIG. 15, the distribution of thickness along the stripe direction is shown. Will occur. When the thickness of the laser active region is distributed, sufficient gain cannot be obtained.

Further, the selective growth mask is made of an insulating film as described above.
(Thermal chemical vapor d
The deposition method and the sputtering method are applied. Therefore, at that time, the surface of the semiconductor substrate is damaged, and thereafter, the selectively grown crystal is adversely affected.

With respect to this damage, at present, there is no proposal for effective countermeasures, and therefore, the technical development is carried out in the state where the above problems are still kept.

According to the present invention, when a semiconductor crystal film is selectively grown in stripes, the growth film thickness is made uniform over the entire length of a necessary portion, and the selective growth is performed when forming a selective growth mask. Eliminate the effect of damage given to the underlayer and obtain good quality crystals.

[0017]

In order to achieve the present invention,
Since we have done many experiments and collected data, we must first explain it.

FIG. 1 is an explanatory view showing a plane pattern, a selective growth mask, a film thickness distribution, etc. of an optical semiconductor element including a semiconductor laser and an optical waveguide, and the same symbols as those used in FIG. Or have the same meaning. The figure shows a case where two optical semiconductor elements are manufactured at the same time.

In the figure, M is a mask for selective growth made of SiO ₂ , L is a laser portion, G is an optical waveguide portion, W is a width of an optical semiconductor element, and ½W _M is an optical semiconductor element for selective growth. The width of the portion covered with the mask M, t ₁ is the grown film thickness of the semiconductor crystal layer in the region without the mask, t ₂ is the grown film thickness of the semiconductor crystal layer in the region with the mask, 1 is the semiconductor Substrates 2, clad layers, 3 active layers, and 4 clad layers, respectively.

When the selective growth region width W _S in the mask M is changed, the growth film thickness t ₂ of the semiconductor crystal layer in the region with the mask and the growth film thickness of the semiconductor crystal layer in the region without the mask are changed. The film thickness ratio with t ₁ can be controlled.

The width W of the optical semiconductor element is, for example, 300 [μ
m], and the selective growth region width W _S is, for example, 20 [μm]
, Then t ₂ / t ₁ is about 4, and 10 [μ
m], it becomes about 5.

The film thickness distribution of the crystal layer shown in FIG. 1 shows an ideal state. Actually, as described with reference to FIG. It is generated and its penetration length reaches the diffusion length of the source gas.

FIG. 2 is a diagram showing the mask size and the film thickness distribution for explaining the experiment in which the semiconductor crystal layer was selectively grown. The same symbols as those used in FIGS. Symbols represent the same part or have the same meaning. In addition, in the following description, it is preferable to refer to FIGS. 1 and 15.

In the figure, (A) is the size of the mask,
(B) shows the film thickness distribution, the vertical axis of (A) shows the length in the mask width direction, the horizontal axis shows the length in the mask length direction, and the vertical axis of (B) shows the film thickness. And the horizontal axis represents the length in the mask length direction. It should be noted that in the figure, a quarter is represented in consideration of symmetry.

As specific conditions for obtaining the data shown in FIG. 2, the selective growth region width W _S is 20 [μm].
In the case of 1/2, the mask width W _M is 280 [μm].
m], therefore, 140 [μm] at 1/2 W _M , the mask length L _M is 600 [μm], and therefore 300 at 1/2.
[Μm]. In the case of a laser of 1 [μm] band, the laser length is usually 300 [μm].

As can be seen from FIG. 2, the laser portion L
Has a fairly large film thickness distribution.
Of course, since the active layer also has a film thickness distribution, the laser cannot obtain a sufficient gain.

As a result of analyzing FIG. 2, the diffusion length of the source gas was 126 [μm] in the region with the mask M and 69 [μm] in the region without the mask M. That is, the diffusion length of the source gas is long on the mask M, and outside the mask M, the length required for the optical waveguide is 250.
It is much shorter than [μm].

On the basis of the above experimental results, in the present invention, the semiconductor crystal layer of the optical semiconductor element including the portion where the film thickness distribution needs to be reduced, such as the active layer in the laser, is provided once. to form in the selective growth, extended in mask length L _M to the selective growth mask M, to apply a diffusion length double minute length of at least a raw material gas to a length to cover the laser portion .

Based on the above-mentioned matters, the principle of the present invention will be described in the case of forming a semiconductor crystal layer for integrating a semiconductor laser and an optical waveguide by one-time selective growth.

FIG. 3 is an explanatory view showing a plane pattern, a selective growth mask, a film thickness distribution, etc. in an optical semiconductor element including a semiconductor laser and an optical waveguide for clarifying the principle of the present invention. The same symbols as those used in represent the same parts or have the same meanings. It should be noted that this figure also shows a case where two optical semiconductor elements are manufactured at the same time.

In the figure, L _M1 indicates a portion of the mask M extending in the same direction as the stripe.

In the present invention, the mask length L _M is at least “diffusion length of source gas × 2” in length of the laser portion L, that is, “length of mask extension portion L _M1 × 2”. Add the length of. In FIG. 3, since the number of optical semiconductor elements is two, the length of the laser portion L is double,
Even in this case, "the length of the mask extension L _M1 ×
The length of 2 "should be added.

The diffusion length of the source gas is trimethylindium (TMIn: In (CH ₃ ) ₃ ), triethylgallium (TEGa: Ga (C ₂ H ₅ ) ₃ ), phosphine (P
H ₃ ), arsine (AsH ₃ ) etc., pressure 50
When the temperature is set to 600 [° C.] under a reduced pressure of [Torr] to 80 [Torr], 100 [μm] to 140 [μm] in the portion where the mask is formed, and
60 [μm] to 70 [μm] in the area without the mask
Is.

Here, the total length of the optical semiconductor element in which the laser and the optical waveguide are integrated is 550 [μm], and the laser length is 3
When the optical waveguide length is 00 [μm] and the optical waveguide length is 250 [μm], the various semiconductor layers suitable for the optical semiconductor device having such dimensions are formed in consideration of the diffusion length of the raw material gas. It can be easily realized by one selective growth including the active layer having no distribution.

According to the above-mentioned principle of the present invention, the mask length L _M
Plays an important role, but if the length is “laser length + diffusion length of source gas × 2”, the objective can be sufficiently achieved, so it is not necessary to use a large mask. .

In accordance with the principles of the present invention described with reference to FIG.
The width W _S of the selective growth region of the stripe is constant over the entire mask length L _M and does not change. However, from the above description, by changing the selective growth region width W _S or appropriately changing the mask pattern,
It can be easily analogized that the film thickness distribution of the selectively grown layer can be controlled by controlling the growth rate of the semiconductor crystal.

FIGS. 4 and 5 are explanatory views showing a mask for selective growth, a film thickness distribution, etc. for clarifying the principle of the present invention. The same symbols as those used in FIGS. They represent the same part or have the same meaning.

In the figure, W _S1 is the width of the expanded portion of the selective growth region width W _S formed in the mask M, and O _M is the rectangular growth control opening formed near the center of the mask M. ing.

The masks M shown in FIGS. 4 and 5 both reduce the mask rate in the vicinity of the stripe center as compared with the vicinity of the stripe edges, and therefore the growth rate of the semiconductor crystal layer in the vicinity of the stripe center. Is decreasing.

As described above, by appropriately controlling the decrease in the growth rate depending on the mask rate, the film thickness distribution in the selective growth region, that is, the stripe portion can be made uniform. Of course,
In this case, the mask length L _M of the mask M may be any length as long as it covers the portion where the laser is formed, and as described with reference to FIG. 1, in principle, it is increased by “diffusion length of source gas × 2”. Is unnecessary. However, even better results can be obtained by using the technique of changing the mask pattern and the technique of changing the mask length described above, which will be described in detail later.

When forming the selective growth mask M described with reference to FIGS. 1 to 5, the film is formed by applying the thermal CVD method or the sputtering method. In such a case, the semiconductor crystal is formed. Since the substrate surface on which the layer is to be selectively grown is damaged, a good quality semiconductor crystal cannot be obtained.

In the present invention, the adverse effect on the selectively grown semiconductor crystal layer is removed by etching the damaged selectively grown region, and the flatness of each selectively grown semiconductor crystal layer deteriorates as it is. Further, since it also leads to the generation of the film thickness distribution, the recesses caused by the etching are flatly filled, and then the required semiconductor crystal layer is selectively grown.

In this case, as a semiconductor layer for filling the recess formed by removing the damaged layer in a flat manner, the group III-
Good results can be obtained by using a Group 6 element that acts as an n-type dopant to the Group 5 compound semiconductor, particularly one doped with Se in an amount of about 1 × 10 ¹⁹ [cm ⁻³ ].

From the above, in the method of manufacturing an optical semiconductor device according to the present invention, (1) the mask length in the stripe direction (mask length L _M : FIG. 3)
(See FIG. 3) has a device length that requires a particularly flat semiconductor crystal layer (for example, the length of the laser portion L: see FIG. 3) and is at least twice the diffusion length of the source gas in the metal-organic vapor phase epitaxy. The semiconductor crystal layer (clad layer 2) on the semiconductor substrate (semiconductor substrate 1: see FIG. 3) is set to a length obtained by adding the lengths.
A mask for selective growth (for selective growth) having a stripe opening for exposing the selective growth region (selective growth region having a width W _S : see FIG. 3) of the active layer 3, the clad layer 4, etc. Mask M: see FIG. 3),
Next, at least a thickness of the semiconductor crystal layer and the semiconductor crystal layer which are required to have a flatness on the semiconductor substrate including the selective growth region through the selective growth mask by applying the metal organic chemical vapor deposition method are at least thick. And a step of simultaneously growing different semiconductor crystal layers (the same semiconductor crystal layer as the laser portion L and existing in the optical waveguide portion G: see FIG. 3). Or

(2) In (1) above, the semiconductor crystal layer required to be flat is an active layer (active layer 3: see FIG. 3) and clad layers (clad layers 2 and 4: FIG. 3) sandwiching the active layer.
Semiconductor laser (laser part L: FIG. 3)
An optical waveguide (an optical waveguide portion G: a semiconductor crystal layer having a thickness different from that of the semiconductor crystal layer, which is a constituent element of the optical waveguide portion G:
(See FIG. 3), which is a semiconductor crystal layer forming a component, or

(3) In the above (1) or (2),
Mask length in stripe direction (mask length L _M : see FIG. 3)
To a length twice as long as the length of the device requiring a particularly flat semiconductor crystal layer (length of laser portion L: see FIG. 3) (length of two laser portions L: see FIG. 3). It is characterized in that the length is set to be a length obtained by adding at least twice the diffusion length of the source gas in the metal organic chemical vapor deposition method, or

(4) Selective growth mask having a stripe opening for exposing the selective growth region of the semiconductor crystal layer on the semiconductor substrate (selective growth region having width W _S : see FIGS. 7 and 8) (Selective growth mask M: see FIGS. 7 and 8) A pattern in which the mask ratio in the vicinity of the stripe center is lower than the mask ratio in the vicinity of the stripe edge (a structure having a widened portion having a width W _S1 : see FIG. 7, or , A structure having a growth control opening O _M : see FIG. 8), and then applying the metal organic chemical vapor deposition method to the semiconductor including the selective growth region through the selective growth mask. A semiconductor crystal layer (laser portion L:
7 and 8) and a semiconductor crystal layer having a thickness different from that of the semiconductor crystal layer (the same semiconductor crystal layer as the laser portion L and present in the optical waveguide portion G: FIGS. 7 and 8). (See reference), and the step of simultaneously growing

(5) In the above (4), the selective growth region (widened for reducing the mask ratio in the vicinity of the stripe center of the selective growth mask (selective growth mask M: see FIG. 7)) Area where the widening width is W _S1 : Fig. 7
Reference), or

(6) In the above (4), the selective growth mask is grown to reduce the mask rate in the vicinity of the stripe center of the selective growth mask (selective growth mask M: see FIG. 8). Control opening (growth control opening portion O _M :
(See FIG. 8) to selectively expose a part of the semiconductor substrate, or

(7) In (4), (5) or (6) above, a semiconductor crystal layer having a particularly flat mask length in the stripe direction (mask length L _M : see FIGS. 7 and 8) is required. The length of the element to be operated (the length of the laser portion L, or
Double the length thereof: see FIG. 7 and FIG. 8), or

(8) The mask length in the stripe direction is particularly equal to the length of the element requiring a flat semiconductor crystal layer (the length of the laser portion L: see FIG. 9) and the source gas used in the metal organic chemical vapor deposition method. The length is set to be a value obtained by adding at least twice the diffusion length of the pattern, and the mask ratio near the stripe center is lower than the mask ratio near the stripe edge (width W _S1
9) or a structure having an opening portion for growth control), and selective growth having a stripe opening for exposing the selective growth region of the semiconductor crystal layer on the semiconductor substrate. Mask (selective growth mask M:
(See FIG. 9), and then, a semiconductor crystal in which flatness is particularly required on the semiconductor substrate including the selective growth region through the selective growth mask by applying a metal organic chemical vapor deposition method. Layer (laser portion L: see FIG. 9) and a semiconductor crystal layer having a different thickness from the semiconductor crystal layer (the same semiconductor crystal layer as the laser portion L and present in the optical waveguide portion G: FIG. 9) (See reference), and the step of simultaneously growing

(9) In (8), the semiconductor crystal layer required to be flat is a semiconductor crystal layer which is a constituent element of a semiconductor laser including an active layer and a cladding layer sandwiching the active layer, and the semiconductor layer. A semiconductor crystal layer having a thickness different from that of the crystal layer is a semiconductor crystal layer forming a component of an optical waveguide integrated with the semiconductor laser, or

(10) In the above (8) or (9), the mask length in the stripe direction is the length of the element requiring a particularly flat semiconductor crystal layer (the length of the laser portion L: FIG. 9).
(Refer to FIG. 2) (the length of two laser portions L) plus at least twice the diffusion length of the source gas in the metalorganic vapor phase epitaxy method. Or

(11) In order to reduce the mask ratio in the vicinity of the stripe center of the selective growth mask (selective growth mask M: see FIG. 9) in the above (8), (9) or (10). Selective growth area (width W _S1
A structure having a widened portion (see FIG. 9) is formed, or

(12) In (8), (9), or (10), the mask ratio in the vicinity of the stripe center of the selective growth mask (selective growth mask M: see FIG. 9) is reduced. A growth control opening is formed in the selective growth mask to selectively expose a part of the semiconductor substrate, or

(13) The above (1) or (2) or (3) or (4) or (5) or (6) or (7) or (8) or (9) or (10) or (11) Alternatively, in (12), after the selective growth mask (selective growth mask 12: see FIG. 13) is formed,
Damaged semiconductor substrate (InP substrate 11: FIG. 13)
(Refer to FIG. 13), the step of removing the surface of the selective growth region (selective growth region 11A: see FIG. 13) of the semiconductor crystal layer is included.

(14) In (13) above, the recesses formed by removing the surface of the selectively grown region of the semiconductor crystal layer in the damaged semiconductor substrate are replaced by the impurity-containing semiconductor crystal layer (recess). Buried and n-side clad layer 13: FIG.
3), the step of flatly embedding is included, or

(15) In (13) or (14) above, an impurity that flatly fills the recess created by removing the surface of the selectively grown region of the semiconductor crystal layer in the damaged semiconductor substrate. The contained semiconductor crystal layer is a Group III-Group 5 compound semiconductor (n-InP: see FIG. 13) and the impurity is a Group 6 element (Se) of the periodic table, or

(16) In the above (13), (14) or (15), the sixth group element of the periodic table is Se.

[0060]

By adopting the above means, when the semiconductor crystal layer is selectively grown in stripes by using the selective growth mask, the film thickness of the semiconductor crystal layer is made uniform over the entire length of the necessary portion. Therefore, it is suitable for the case where semiconductor crystal layers in an optical semiconductor device in which a semiconductor laser and an optical waveguide are integrated are completed by a single selective growth, and a mask for selective growth is formed. In doing so, it is possible to easily eliminate the influence of the damage given to the underlayer of the selective growth and to selectively grow a high-quality semiconductor crystal layer. Therefore, an optical semiconductor device having high reliability and high performance can be manufactured in a small number of steps. It has become possible to make it happen.

[0061]

EXAMPLE FIG. 6 is a diagram showing the mask size and film thickness distribution for explaining the first example of the present invention. The symbols used in FIGS. The same symbol represents the same part or has the same meaning. In addition, in the following description, it is preferable to refer to FIGS. 1 to 5. Further, here, an optical semiconductor element in the 1 [μm] band, that is, an integrated semiconductor laser and an optical waveguide is targeted.

In the figure, (A) is the size of the mask,
(B) shows the film thickness distribution, the vertical axis of (A) shows the length in the mask width direction, the horizontal axis shows the length in the mask length direction, and the vertical axis of (B) shows the film thickness. And the horizontal axis represents the length in the mask length direction. In the figure, a quarter of the whole is shown in consideration of the symmetry in the case of manufacturing two optical semiconductor elements at the same time.

In general, a laser of 1 [μm] band has a laser length of 300 [μm], and if the length of the extended portion L _M1 of the mask length L _M is 100 [μm] on one side, 2 on both sides.
00 [μm]. Therefore, when two optical semiconductor elements are manufactured at the same time, the total mask length L _M is 800 [μm].
m]. If one optical semiconductor element is to be manufactured, the total length of the mask will be 500 [μm].

As specific conditions for obtaining the data of FIG. 6, the selective growth region width W _S is 20 [μm] (1/2 is 10 [μm]) and the mask width W _M is 280 [μm]. ]
(1/2 is 140 [μm]), the mask length L _M is 80
Although it is 0 [μm], the figure shows a quarter of the mask required to manufacture two optical semiconductor elements, so the mask length shown in the figure is 1 / 2L. _M is 4
It is 00 [μm].

As can be seen from FIG. 6, the laser portion L
Then, the large film thickness distribution is eliminated, a considerably uniform semiconductor crystal layer is obtained, and of course, the film thickness distribution of the active layer is also small, so that the laser can obtain a sufficient gain.

According to the present invention, as described with reference to FIGS. 4 and 5, the mask ratio in the vicinity of the stripe center of the mask M is compared with that in the vicinity of the stripe edge without extending the mask length L _M. It was clarified that the growth rate of the semiconductor crystal layer in the vicinity of the stripe center can be reduced by lowering it. Therefore, next, an example thereof will be described.

FIG. 7 is a diagram showing the mask size and film thickness distribution for explaining the second embodiment of the present invention, which is the same as the symbols used in FIGS. 1 to 6. Symbols represent the same part or have the same meaning. In addition, in the following description, it is preferable to refer to FIGS. 1 to 6. Also here, an optical semiconductor element in the 1 [μm] band, that is, an integrated semiconductor laser and an optical waveguide is targeted.

In the figure, (A) is the size of the mask,
(B) shows the film thickness distribution, the vertical axis of (A) shows the length in the mask width direction, the horizontal axis shows the length in the mask length direction, and the vertical axis of (B) shows the film thickness. And the horizontal axis represents the length in the mask length direction. In the figure, a quarter of the whole is shown in consideration of the symmetry in the case of manufacturing two optical semiconductor elements at the same time.

The feature of this embodiment is that the selective growth region width W _S near the center of the stripe is widened.

Also in the second embodiment, since the laser in the 1 [μm] band is the target, the laser length is 300 [μm], and therefore the mask length L _{M for} two optical semiconductor elements is 600 [μ].
m] (1/2 is 300 [μm]), the selective growth region width W _S is 40 [μm] near the center of the stripe (1/2 is 20 [μm]), and the other is 20 [μm].
(1/2 is 10 [μm]), the mask width W _M is 260 [μm] near the center (1/2 is 130 [μm]),
In addition, 280 [μm] (1/2 as 140
[Μm]).

Here, the selective growth region width W _S is 40 [μ
m], that is, the mask width W _M is 26.
The length of the portion which is narrowed to 0 [μm] (130 [μm] as 1/2) is 240 [μm], and therefore the length is 120 [μm] at 1/2, and the mask ratio in this case is the stripe ratio. It is 87 [%] near the center and 93 [%] outside the center. By the way, in the case of FIG. 2, the mask rate is 93% in all.

As can be seen from FIG. 7B, in the laser portion L, the large film thickness distribution is eliminated, and a considerably uniform semiconductor crystal layer is obtained. Therefore, since the thickness distribution of the active layer is also small, the laser can obtain a sufficient gain.

FIG. 8 is a diagram showing the mask size and film thickness distribution for explaining the third embodiment of the present invention, which is the same as the symbols used in FIGS. 1 to 7. Symbols represent the same part or have the same meaning. In addition, in the following description, it is preferable to refer to FIGS. 1 to 7. Also here, an optical semiconductor element in the 1 [μm] band, that is, an integrated semiconductor laser and an optical waveguide is targeted.

In the figure, (A) is the size of the mask,
(B) shows the film thickness distribution, the vertical axis of (A) shows the length in the mask width direction, the horizontal axis shows the length in the mask length direction, and the vertical axis of (B) shows the film thickness. And the horizontal axis represents the length in the mask length direction. In the figure, a quarter of the whole is shown in consideration of the symmetry in the case of manufacturing two optical semiconductor elements at the same time.

The feature of this embodiment is that a part of the mask, that is,
A growth control opening is formed near the center of the mask, and
The mask width W _M is partly narrowed.

Also in the third embodiment, since the laser in the 1 [μm] band is the target, the laser length is 300 [μm], and therefore the mask length L _{M for} two optical semiconductor elements is 600 [μ].
m] (1/2 is 300 [μm]), the selective growth region width W _S is 20 [μm] (1/2 is 10 [μm]) over the entire stripe length, and the mask width W _M is near the mask center. In that case, 160 [μm] (1/2 is 80 [μm]),
In addition, 280 [μm] (1/2 as 140
[Μm]).

Here, the overall size of the growth control opening is 120 [μm] in the mask width direction and 2 in the mask length direction.
00 [μm], therefore, with the size of ¼ shown in the drawing, 60 [μm] in the mask width direction and 100 [μ in the mask length direction.
m], and the mask ratio in this case is 53 [%] in the region where the growth control opening is present, and 93 in other places.
It is [%].

As can be seen from FIG. 8B, in the laser portion L, the large film thickness distribution is eliminated, and a considerably uniform semiconductor crystal layer is obtained. Therefore, since the thickness distribution of the active layer is also small, the laser can obtain a sufficient gain.

In the above-described first to third embodiments, the means for providing the mask extension portion in the selective growth mask is adopted, or the widened portion is formed in the stripe of the selective growth mask, or Although a means for reducing the mask ratio is adopted by forming a growth control opening in the selective growth mask, it is possible to more effectively eliminate the film thickness distribution by using these means together.

FIG. 9 is a diagram showing the mask size and film thickness distribution for explaining the fourth embodiment of the present invention, which is the same as the symbols used in FIGS. 1 to 8. Symbols represent the same part or have the same meaning. In addition, in the following description, it is preferable to refer to FIGS. 1 to 8. Also here, an optical semiconductor element in the 1 [μm] band, that is, an integrated semiconductor laser and an optical waveguide is targeted.

In the figure, (A) is the size of the mask,
(B) shows the film thickness distribution, the vertical axis of (A) shows the length in the mask width direction, the horizontal axis shows the length in the mask length direction, and the vertical axis of (B) shows the film thickness. And the horizontal axis represents the length in the mask length direction. In the figure, a quarter of the whole is shown in consideration of the symmetry in the case of manufacturing two optical semiconductor elements at the same time.

The feature of this embodiment is that the mask for selective growth is provided with a mask extension portion as in the first embodiment, and
Similar to the second embodiment, the width of the selective growth region near the center of the stripe is widened.

Also in the fourth embodiment, since the laser in the 1 [μm] band is the target, the laser length is 300 [μm], and the length of the extended portion L _M1 of the mask length L _M is 100 [μ on one side.
m] is 200 [μm] on both sides, and therefore the mask length L _{M for} two optical semiconductor elements is 800 [μm].
m] (1/2 is 400 [μm]), the selective growth region width W _S is 40 [μm] near the center of the stripe (1/2 is 20 [μm]), and the other is 20 [μm] (1
/ 10 [μm]), the mask width W _M is 260 [μm] near the center (1/2 is 130 [μm]), and the other is 280 [μm] (1/2 is 140 [μm]).
m]).

As can be seen from FIG. 9B, in the laser portion L, the film thickness distribution is eliminated over a long range,
A sufficiently uniform semiconductor crystal layer is obtained. Therefore, as compared with the first to third embodiments, the thickness distribution of the active layer is further reduced, so that the laser can obtain a sufficient gain.

In the first to fourth embodiments, the means for eliminating damage to the surface of the substrate when forming the selective growth mask M is not described, but as described as the principle of the invention, According to the present invention, the damage can be easily eliminated.

FIGS. 10 to 13 are front sectional views showing an essential part of an optical semiconductor device in the process steps for explaining the fifth embodiment of the present invention. Refer to these figures below. I will explain. Incidentally, here also, an optical semiconductor element in the 1 [μm] band, that is, an integrated semiconductor laser and an optical waveguide is targeted.

See FIG. 10. 10- (1) Sn-doped InP substrate 1 having a plane index (100)
After cleaning the surface of No. 1, a thermal CVD method is applied to form a SiO ₂ film having a thickness of, for example, 200 [nm] at a film forming temperature of about 600 [° C.].

When InP is heated, P is easily desorbed from the surface. Therefore, when the SiO ₂ film is formed as described above, the surface is damaged or a metamorphic layer is formed.

See FIG. 11 11- (1) By applying a normal lithography technique, the SiO ₂ film formed in the step 10- (1) is selectively etched to have a width of, for example, 20 [μm]. The selective growth mask 12 having the stripe openings 12A is formed. Here, the InP substrate 1 exposed in the stripe opening 12A
The stripe which is a part of 1 becomes the selective growth region 11A.

See FIG. 12 12- (1) Etch InP in the selective growth region 11A by applying a wet etching method using an etchant such as brommethanol, sulfuric acid type etching solution, phosphoric acid type etching solution. Then, a depth of about 0.5 [μm] is removed.

See FIG. 13 13- (1) By applying the MOVPE method, the recess filling and n
Side cladding layer 13, n-side SCH (separate c
onfinement heterostructure
e) Layer 14, strained multiple quantum well active layer 15, p-side SCH
The layer 16 and the p-side clad layer 17 are formed.

Here, the main data regarding the grown semiconductor layers are exemplified as follows. In addition, "PL" appearing in the following description is photoluminescence (photol).
Uminescience).

Recess Embedding and n-side Cladding Layer 13 Material: n-InP Impurity: Se Impurity concentration: 1 × 10 ¹⁹ [cm ⁻³ ] Thickness: 0.5 [μm]

Regarding the n-side SCH layer 14 Material: n-InGaAsP (PL wavelength 1.1 [μm] composition with lattice matching with InP) Impurity: Si Impurity concentration: 5 × 10 ¹⁷ [cm ⁻³ ] Thickness: 0 .1 [μm]

Strained Multiple Quantum Well Active Layer 15 Material: InGaAsP / InGaAsP (well layer has a thickness of 6 nm and a compressive strain of 1.0%)

Regarding the p-side SCH layer 16 Material: p-InGaAsP (PL wavelength 1.1 [μm] composition with lattice matching with InP) Impurity: Zn Impurity concentration: 5 × 10 ¹⁷ [cm ⁻³ ] Thickness: 0 .1 [μm]

About p-side clad layer 17 Material: p-InP Impurity: Zn Impurity concentration: 5 × 10 ¹⁷ [cm ⁻³ ] Thickness: 0.2 μm

Growth conditions Pressure: 76 [Torr] Temperature: 600 [° C.]

Raw material gas (carrier gas is hydrogen) In: trimethylindium (TMIn: In (C
H ₃ ) ₃ ) Ga: triethylgallium (TEGa: Ga (C
₂ H ₅ ) ₃ ) As: arsine (AsH ₃ ) P: phosphine (PH ₃ ) Zn: dimethylzinc (DMZn: Zn (CH ₃ ) ₂ ) Si: monosilane (SiH ₄ ) (n-type dopant) Se: H ₂ Se (n-type dopant)

13- (2) After that, by applying a usual technique, for example, current confinement,
Alternatively, a buried structure such as light confinement is formed,
A semiconductor laser is completed by forming a protective film and electrodes.

By the way, in the case of growing a semiconductor layer for filling the recess formed to remove the damage,
As the impurities to be doped into the semiconductor layer, necessary conductivity type impurities can be appropriately used. However, as described above, when Se is highly doped, the burying is performed particularly well and the excellent flatness is achieved. Sex is obtained. It is presumed that the reason is that the diffusion length of atoms becomes long due to the high doping of Se. Similar effects were confirmed with other Group 6 impurities, such as Te.

FIG. 14 shows the SEM (scanning electron) of the film thickness distribution of the semiconductor crystal layer in the optical axis direction (stripe direction of the selective growth mask) of the completed optical semiconductor element.
FIG. 4 is a diagram summarizing the results of measurement by ctron microscopy), in which the vertical axis represents the optical waveguide film thickness, and
The horizontal axis represents the position in the optical axis direction.

According to this data, the thickness is the strained multiple quantum well active layer 15 and the n-side SCH layer 14 and the p-side SC sandwiching it.
In the total of the H layers 16, the growth rate difference between the laser portion L and the optical waveguide portion G is three times at the maximum. Further, it has been confirmed that the room temperature PL intensity, which is an index of optical characteristics, is comparable to that produced on an ordinary flat substrate, and high quality is maintained.

The semiconductor laser incorporated in the optical semiconductor device has a threshold current of 15 [mA] and a CW (con)
tunable wave) oscillation and optical output 20 [m
W] was achieved, and due to the action of the optical waveguide coupled to the semiconductor laser, the narrow beam characteristic was also good, and 10 ° was obtained compared with the emission angle of 30 ° of the conventional one. . Such characteristics reduce complicated lens system,
It will be an important factor for reducing the cost of semiconductor lasers.

[0105]

In the method of manufacturing an optical semiconductor device according to the present invention, the mask length in the stripe direction is set to the length of the element such as a semiconductor laser, and the diffusion length of the source gas in the metal organic chemical vapor deposition method. Or double the length, or by changing the mask ratio by setting the length of the device as it is, the stripe opening for exposing the selectively grown region of the semiconductor crystal layer is formed. A selective growth mask having the same is formed, and a semiconductor crystal layer required for a semiconductor laser and a thickness different from that of the semiconductor crystal layer are formed on the semiconductor substrate including the selective growth region through the selective growth mask. A semiconductor crystal layer is grown at the same time.

By adopting the above structure, when the semiconductor crystal layer is selectively grown in stripes by using the selective growth mask, the film thickness of the semiconductor crystal layer is made uniform over the entire length of the necessary portion. Therefore, it is suitable for the case where semiconductor crystal layers in an optical semiconductor device in which a semiconductor laser and an optical waveguide are integrated are completed by a single selective growth, and a mask for selective growth is formed. In doing so, it is possible to easily eliminate the influence of the damage given to the underlayer of the selective growth and to selectively grow a high-quality semiconductor crystal layer. Therefore, an optical semiconductor device having high reliability and high performance can be manufactured in a small number of steps. It has become possible to make it happen.

[Brief description of drawings]

FIG. 1 is an explanatory view showing a plane pattern, a mask for selective growth, a film thickness distribution, etc. of an optical semiconductor element including a semiconductor laser and an optical waveguide.

FIG. 2 is a diagram showing a mask size and a film thickness distribution for explaining an experiment in which a semiconductor crystal layer is selectively grown.

FIG. 3 is an explanatory diagram showing a plane pattern, a mask for selective growth, a film thickness distribution, etc. in an optical semiconductor element including a semiconductor laser and an optical waveguide for clarifying the principle of the present invention.

FIG. 4 is an explanatory view showing a mask for selective growth, a film thickness distribution, etc. for clarifying the principle of the present invention.

FIG. 5 is an explanatory diagram showing a mask for selective growth, a film thickness distribution, etc. for clarifying the principle of the present invention.

FIG. 6 is a diagram showing a mask size and a film thickness distribution for explaining a first embodiment of the present invention.

FIG. 7 is a diagram showing a mask size and a film thickness distribution for explaining a second embodiment of the present invention.

FIG. 8 is a diagram showing a mask size and a film thickness distribution for explaining a third embodiment of the present invention.

FIG. 9 is a diagram showing a mask size and a film thickness distribution for explaining a fourth embodiment of the present invention.

FIG. 10 is a fragmentary front view showing an optical semiconductor element in a process essential part for explaining a fifth embodiment of the present invention.

FIG. 11 is a fragmentary front view showing an optical semiconductor element in a process key point for explaining a fifth embodiment of the present invention.

FIG. 12 is a fragmentary front view showing an optical semiconductor element in a process essential part for explaining a fifth embodiment of the present invention.

FIG. 13 is a fragmentary front view showing an optical semiconductor element in a process key point for explaining a fifth embodiment of the present invention.

FIG. 14 is a SEM (scanning electron) showing the film thickness distribution of the semiconductor crystal layer in the optical axis direction (stripe direction of the selective growth mask) of the completed optical semiconductor element.
It is the diagram which put together the result measured by microscopy).

FIG. 15 is a plan view of a principal part illustrating a selective growth mask.

[Explanation of symbols]

W _M Mask width W _S Selective growth region width L _M Mask length X direction M Selective growth mask L Laser part G Optical waveguide part W Optical semiconductor element width t ₁ Growth film thickness of semiconductor crystal layer in no mask region t ₂ Growth film thickness of semiconductor crystal layer in a region with mask 1 Semiconductor substrate 2 Cladding layer 3 Active layer 4 Cladding layer L _M1 Part formed in the same direction as the stripe in the mask M W _S1 mask M Widened part width of selective growth region width W _S O _M Rectangular growth control opening formed near the center of mask M 11 InP substrate 11A Selective growth region 12 Selective growth mask 12A Stripe opening 13 Concave filling and n Side clad layer 14 n-side SCH layer 15 Strained multiple quantum well active layer 16 p-side SCH layer 17 p-side clad layer

Front page continued (72) Haruhisa Kyoda, Inventor Haruhisa Kouda, 1015 Kamiodanaka, Nakahara-ku, Kawasaki, Kanagawa, Fujitsu Limited

Claims (16)

[Claims] 1. The mask length in the stripe direction is at least twice as long as the diffusion length of a source gas in the metal organic chemical vapor deposition method to the length of an element requiring a particularly flat semiconductor crystal layer. A step of forming a selective growth mask having stripe openings for setting the length to expose the selective growth region of the semiconductor crystal layer on the semiconductor substrate, and then applying a metal organic chemical vapor deposition method. A semiconductor crystal layer that requires particularly flatness and a semiconductor crystal layer having a thickness at least different from that of the semiconductor crystal layer are simultaneously grown on the semiconductor substrate including the selective growth region through the selective growth mask. And a step of manufacturing the optical semiconductor device. 2. A semiconductor crystal layer which is required to have flatness is a semiconductor crystal layer which is a constituent element of a semiconductor laser including an active layer and a cladding layer sandwiching the active layer, and has a thickness different from that of the semiconductor crystal layer. 2. The method of manufacturing an optical semiconductor device according to claim 1, wherein the semiconductor crystal layer is a semiconductor crystal layer that constitutes a constituent element of an optical waveguide integrated with the semiconductor laser. 3. The mask length in the stripe direction is twice as long as the length of an element requiring a particularly flat semiconductor crystal layer, and at least twice as long as the diffusion length of the source gas in the metal organic chemical vapor deposition method. 3. The method for manufacturing an optical semiconductor device according to claim 1, further comprising: 4. A pattern for a selective growth mask having a stripe opening for exposing a selective growth region of a semiconductor crystal layer on a semiconductor substrate, wherein the mask ratio near the stripe center is lower than the mask ratio near the stripe edge. And a semiconductor crystal layer that requires particularly flatness on the semiconductor substrate including the selective growth region through the selective growth mask by applying a metal organic chemical vapor deposition method and the semiconductor. A method of manufacturing an optical semiconductor device, comprising: simultaneously growing a semiconductor crystal layer having a thickness different from that of the crystal layer. 5. The method of manufacturing an optical semiconductor device according to claim 4, wherein a selective growth region widened to reduce the mask ratio near the stripe center of the selective growth mask is formed. 6. A growth control opening is formed in the selective growth mask in order to reduce the mask ratio in the vicinity of the stripe center of the selective growth mask to selectively expose a part of the semiconductor substrate. 5. The method for manufacturing an optical semiconductor device according to claim 4, wherein. 7. The method for manufacturing an optical semiconductor device according to claim 4, wherein the mask length in the stripe direction is set equal to the length of an element requiring a particularly flat semiconductor crystal layer. . 8. The mask length in the stripe direction is at least twice as long as the diffusion length of the source gas in the metal organic chemical vapor deposition method to the length of the device requiring a particularly flat semiconductor crystal layer. Along with the length, the mask rate near the stripe center is set lower than the mask rate near the stripe edge, and there is a stripe opening that exposes the selective growth region of the semiconductor crystal layer on the semiconductor substrate. A step of forming a selective growth mask, and then a semiconductor crystal which is required to have particularly flatness on the semiconductor substrate including the selective growth region through the selective growth mask by applying a metal organic chemical vapor deposition method. And a step of simultaneously growing a semiconductor crystal layer having a thickness different from that of the semiconductor crystal layer, the method of manufacturing an optical semiconductor device. 9. A semiconductor crystal layer required to have flatness is a semiconductor crystal layer which is a constituent element of a semiconductor laser including an active layer and a clad layer sandwiching the active layer, and has a thickness different from that of the semiconductor crystal layer. 9. The method of manufacturing an optical semiconductor device according to claim 8, wherein the semiconductor crystal layer is a semiconductor crystal layer forming a component of an optical waveguide integrated with the semiconductor laser. 10. A mask length in the stripe direction is twice as long as a length of an element requiring a particularly flat semiconductor crystal layer, and at least twice as long as a diffusion length of a source gas in the metal organic chemical vapor deposition method. 10. The method for manufacturing an optical semiconductor device according to claim 8 or 9, wherein the length is set to the sum of the above. 11. The optical semiconductor device according to claim 8, wherein the selective growth region is formed to be widened to reduce the mask ratio near the stripe center of the selective growth mask. Production method. 12. A growth control opening is formed in the selective growth mask to selectively expose a part of a semiconductor substrate in order to reduce the mask rate in the vicinity of the stripe center of the selective growth mask. 11. The method for manufacturing an optical semiconductor device according to claim 8, 9, or 10. 13. The method according to claim 1, further comprising the step of removing the surface of the selectively grown region of the semiconductor crystal layer in the damaged semiconductor substrate after forming the selective growth mask. Or 3 or 4 or 5 or 6
Alternatively, 7 or 8 or 9 or 10 or 11 or 12 is a method for manufacturing an optical semiconductor device. 14. A step of flatly filling a recess formed by removing a surface of a selectively grown region of a semiconductor crystal layer in a damaged semiconductor substrate with an impurity-containing semiconductor crystal layer. 14. The method for manufacturing an optical semiconductor device according to claim 13, which is characterized in that. 15. An impurity-containing semiconductor crystal layer that flatly fills a recess formed by removing a surface of a selectively grown region of a semiconductor crystal layer in a damaged semiconductor substrate is a Group III-V compound semiconductor. 15. The impurity is a Group 6 element of the periodic table, and the impurity is present.
A method for manufacturing the optical semiconductor device described. 16. The method for manufacturing an optical semiconductor device according to claim 13, 14 or 15, wherein the Group 6 element of the periodic table is Se.