JP2002009399A - Method for manufacturing semiconductor light-emitting element, and semiconductor laser - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for manufacturing a semiconductor element whereby warpage of a wafer is reduced to a degree not causing a problem on device characteristics and handling of the wafer when a semiconductor layer is selectively grown on a mask by ELO growth, and a semiconductor laser by which warpage of the wafer is reduced in the case of LD while a dislocation density of a stripe light-emitting part is reduced. SOLUTION: When a nitride compound semiconductor layer is selectively grown on a wafer substrate by ELO growth and a semiconductor layer is stacked thereon so as to form a light-emitting layer forming part, a mask for selective growth in a horizontal direction is formed such that openings for exposing seeds entirely on the surface of the wafer substrate are not arranged only in a single direction successively. Further, in the case of LD, a mask is formed such that openings are not arranged only in a single direction successively while a part not having a dislocation density is formed in a stripe shape.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention uses a nitride-based compound semiconductor (compound semiconductor of a group III element and nitrogen, etc.) and is required for an optical disk memory having a high storage density and a high definition of a laser beam printer. The present invention relates to a method for manufacturing a semiconductor light emitting device including a semiconductor laser and a light emitting diode capable of emitting light in a blue region. More specifically, a method of manufacturing a semiconductor light emitting device capable of preventing warpage in a wafer while lowering the threading dislocation density of a nitride compound semiconductor layer using lateral growth, and reducing the dislocation density in the light emitting layer as much as possible. And a semiconductor laser capable of improving oscillation characteristics.

[0002]

2. Description of the Related Art Conventional light emitting diodes (LEDs) and laser diodes (LDs) that emit light in the blue region include a group III nitride compound semiconductor formed on a sapphire substrate by a metal organic chemical vapor deposition method.
This is realized by sequentially laminating the layers by MOCVD.

For example, as shown in FIG. 8, a semiconductor laser that oscillates in CW in a blue region is one in which a group III nitride compound semiconductor is sequentially laminated on a sapphire substrate 21 by MOCVD, and a GaN buffer layer 22, n Contact layer 23 made of n-type GaN, n-type cladding layer 24 made of Al _0.12 Ga _0.88 N, n-type light guide layer 2 made of GaN
5. Active layer 26 having a multiple quantum well structure of InGaN-based compound semiconductor, p-type light guide layer 2 of p-type GaN
7. p-type cladding layer 2 made of p-type Al _0.12 Ga _0.88 N
8. A p-type contact layer 29 made of p-type GaN is sequentially laminated, and a part of the laminated semiconductor layer is etched by dry etching or the like as shown in FIG. N-side electrode 3 on the surface
1. The p-side electrode 30 is formed on the p-type contact layer 29 described above. And
A portion of the p-side electrode 30 along the stripe is used as a light emitting unit.

[0004] However, when growing nitride compounds,
The via substrate has a lattice constant with nitride compound semiconductors.
Growing nitride compounds with significantly different coefficients of thermal expansion
Threading Dislocation (TD) in the semiconductor layer
Density is 1 × 10⁸~ 1 × 10 ^Tencm^-2About red
1 of a compound semiconductor layer grown on a color-based GaAs substrate
× 10^Twocm^-2Significantly higher dislocation density than
ing. In semiconductor lasers, the dislocation density is particularly large
And the threshold current value increases, and the light emitting diode (L
It is demanded that the dislocation density be lower than ED). Only
In addition to sapphire, industrially suitable substrates have been found
Not in.

[0005] On the other hand, as a method of reducing TD, for example, Sasaoka et al.
As shown in “aNELO growth” (Journal of the Japan Society for Crystal Growth, Vol. 25, No. 8, 1998, pp. 99-105), crystal growth utilizing ELO (Epitaxial Lateral Overgrowth) has attracted attention. As this method, a seed of a semiconductor layer of SiO ₂ mask is provided, exposed from the opening window with an open window on the example semiconductor layer, SiO ₂
By growing the mask in the horizontal direction on the mask, the TD is eliminated by utilizing the fact that the nitride-based compound grows more easily in the horizontal direction than in the vertical direction.

However, in the case of the ELO growth, as shown in FIG. 7, the second GaN layer is successively arranged in the lateral direction from openings 44 on both sides provided at regular intervals in the mask layer 43 on the first GaN layer 42. 45 grows so as to match at the center of the mask layer 43, but the dislocation density increases at the matching portion, particularly at the center where the growth layer from the four openings of the quadrilateral joins. The density becomes very large. In the growth layer on the opening 44, the threading dislocation density of the first GaN layer continues in the vertical direction, and the dislocation density is large. Therefore, it is preferable that the mask layer 43 be formed as wide as possible in order to reduce the overall dislocation density. However, as the width of the mask layer increases, the uniform semiconductor layer must be formed unless the semiconductor layer epitaxially grown is made thicker. In addition to the above, problems such as an increase in dislocation density due to other factors occur.

However, in the semiconductor laser, as shown in FIG. 8, for example, the light emitting portion is formed only in a partial region of a stripe shape. It is assumed that the increase in the threshold current value and the deterioration of the conduction characteristics of the LD can be suppressed. In this case, as shown in FIG. 6, it is efficient to alternately form the linear openings 43 and the mask layer 44 in one direction. However, both ends and the center of the mask width are formed as described above. The dislocation density increases and half of the mask width
It is preferable to use the portion excluding the both ends for a light emitting region having a stripe width of an LD, for example. Therefore, L
Even if the stripe width of D is about 4 μm, the mask width M must be at least 10 to 15 μm or more. In this case, the GaN layer grown on the mask must be thicker than the mask width, that is, about 15 to 20 μm or more. is there.

[0008]

As described above, in order to make a device having few crystal defects by using only the light emitting portion of the semiconductor laser, it is necessary to provide an opening portion of the mask along the stripe direction forming the light emitting portion of the device. FIG. 6
As shown in (2), the opening of the mask is formed only in one direction. On the other hand, the mask width is small and Ga
Although there is no problem with a laminated structure in which the N layer is as thin as about 5 μm, when the mask width becomes 10 μm or more and the thickness of the semiconductor layer laminated thereon becomes 15 μm or more, the difference in the thermal expansion coefficient between the semiconductor layer and the substrate becomes larger. , The warp of the wafer becomes remarkable. When wafer warpage occurs, uniform processing cannot be performed within the wafer during the wafer process, the stripe width cannot be made uniform, cracks are likely to occur when wrapping the wafer, and stress is applied to the device due to the warpage. Problems such as the fact that the working characteristics are likely to fluctuate occur.

On the other hand, if the thickness of the substrate is increased from the conventional value of about 330 μm to about 700 μm, there will be no problem during the wafer process. Then, warpage occurs and the above-described problem occurs. Also, JP-A-11-186178
In order to prevent the warpage of the wafer due to the difference in thermal expansion coefficient from the substrate, the above-mentioned publication utilizes the above-mentioned ELO growth and forms a growth region in an island shape without epitaxially growing a semiconductor layer over the entire surface of the substrate. Thus, a method for preventing wafer warpage by disposing a large mask in a non-growth region to prevent the wafer from growing is disclosed. However, this method has a problem in that more than half of the wafer is a non-growth region even in the case of the embodiment, and the waste is greatly increased.

The present invention has been made in view of such a situation, and when a semiconductor layer is selectively grown on a mask by ELO growth, the threading dislocation density as a whole wafer is reduced by increasing the mask width. However, it is an object of the present invention to provide a method of manufacturing a semiconductor light emitting device capable of reducing the warpage of a wafer to such an extent that device characteristics and wafer handling are not hindered even when a semiconductor layer grown thereon becomes thicker.

Another object of the present invention is to reduce the dislocation density of the active layer in at least the stripe-shaped light-emitting region when the light-emitting region can be limited to a stripe-shaped portion as in a semiconductor laser, and to reduce the threshold current. Lower the value,
An object of the present invention is to provide a semiconductor laser having a structure capable of preventing wafer warpage while obtaining high output.

[0012]

In order to selectively grow a nitride-based compound semiconductor layer on a mask layer in the lateral direction (grow by ELO), the present inventor increases the mask width and grows on the mask layer. In order to eliminate the effect of wafer warpage caused by increasing the thickness of the nitride-based compound semiconductor layer,
As a result of intensive studies, if the openings in the mask layer are formed continuously in only one direction, the direction of the warp will be warped in a certain direction in relation to the direction of the openings, and conversely most of the openings will be Even if the growth layer is thickened by widening the mask width or a long linear opening is formed, warping can be significantly reduced unless the openings are scattered or the openings are continuous only in one direction. I found what I could do.

According to the method of manufacturing a semiconductor light emitting device of the present invention, a mask layer on which a nitride compound semiconductor layer does not grow directly is formed directly on the surface of a wafer-like substrate or on a layer provided on the substrate. An opening for exposing a seed for growing a nitride-based compound semiconductor layer in the mask layer is formed so as not to be only continuous in a single direction over the entire surface of the wafer-like substrate. A nitride-based compound semiconductor layer is provided on the entire surface of the wafer-like substrate by selectively growing laterally on the mask layer from the portion, and a nitride is formed so as to form a light-emitting layer on the nitride-based compound semiconductor layer. Forming a semiconductor laminated portion made of a base compound semiconductor,
The wafer-shaped substrate is formed into chips.

Here, the nitride compound semiconductor is G
a, Al, In and other Group III elements and N or N and other V
It means a semiconductor made of a compound with a group element. Therefore, in addition to GaN, A in which the composition ratio of Al and Ga is changed
It refers to a compound semiconductor containing N in which the mixed crystal ratio of a group III element or the mixed crystal ratio of a group V element is appropriately changed, such as an lGaN-based compound or an InGaN-based compound in which the composition ratio of In and Ga is changed. Further, the mask layer means a layer made of a material such as SiO ₂ , which cannot be directly epitaxially grown on the surface of a nitride-based compound semiconductor layer even if the nitride-based compound semiconductor layer is to be epitaxially grown.

According to this method, since the openings in the mask layer are not formed continuously in only one direction, the stress based on the difference in thermal expansion coefficient between the substrate and the semiconductor layer to be grown does not act in only one direction. , Evenly in all directions, and no extreme warpage occurs in one direction. As a result, it is possible to prevent non-uniformity of processing in the wafer process, cracking of the wafer, and the like, and the quality is greatly improved.

Most of the openings are formed so that the plane shape is a quadrangle or a hexagon, so that if the shape is a quadrangle, the rate of crystal growth in the horizontal direction is M and the direction perpendicular to the A-plane. Even if the direction differs from the direction perpendicular to the plane, it is easy to adjust the length in the growth direction, and if it is hexagonal, the growth rate in each direction is the same because the GaN-based compound is hexagonal. So that the lateral growth can be uniform. Here, the majority of the opening means that a linear opening can be provided in a part, for example, in the vicinity of the stripe light emitting part of the LD.

A semiconductor laser according to the present invention comprises a substrate, a mask layer provided directly on the substrate or on a layer laminated on the substrate and having an opening, and a mask layer provided on the mask layer from the opening. A semiconductor laminated portion in which a nitride-based compound semiconductor layer selectively grown in a lateral direction and a nitride-based compound semiconductor layer are laminated so as to form a light-emitting layer having a stripe-shaped light-emitting portion on the nitride-based compound semiconductor layer The mask layer extends over the entire length of the chip without crossing the opening below the stripe-shaped light-emitting portion, and the openings are scattered in portions other than below the stripe-shaped light-emitting portion. It is formed.

According to this structure, the stripe-shaped light-emitting portion of the semiconductor laser is formed only of a portion having very few crystal defects, and the opening of the mask layer is not formed in only one direction. Warpage can be suppressed very small, the yield can be improved, and a high-performance semiconductor laser with a small threshold current value can be obtained.

Specifically, the opening of the mask layer is formed linearly along the stripe-shaped light-emitting portion in a portion adjacent to the stripe-shaped light-emitting portion, and is formed in a matrix shape in portions other than the stripe-shaped light-emitting portion. Or a pattern in which the mask layer is formed randomly or the mask layer has a linear opening,
3 formed by superimposing a pattern rotated by 20 °
By being formed into a symmetrical shape, without having a continuous opening in only one direction, the stripe-shaped light emitting portion,
A semiconductor laser having a semiconductor layer with a low dislocation density over the entire stripe-shaped light emitting portion without crossing the opening can be obtained.

[0020]

Next, a method for manufacturing a semiconductor light emitting device and a semiconductor laser according to the present invention will be described with reference to the drawings. The method for manufacturing a semiconductor light emitting device according to the present invention is a method for selectively growing a nitride-based compound semiconductor layer by ELO growth on a wafer-like substrate, and laminating a semiconductor layer thereon so as to constitute a light emitting layer forming portion. As shown in FIG. 1, an example of a mask for performing selective growth in one direction is a mask pattern according to an embodiment of the present invention. It is characterized in that most of the openings are formed so as to be n-fold (n is an integer of 2 or more) symmetrical (n-fold symmetrical structure during 180 ° rotation). Using such a mask, a nitride-based compound semiconductor layer is provided over the entire surface of the wafer-like substrate by selectively growing in a lateral direction on the mask layer from the opening, and a light-emitting layer is formed thereon. A semiconductor laminated portion is formed by laminating nitride compound semiconductor layers, and a semiconductor substrate is manufactured by breaking a wafer-like substrate into chips.

The example shown in FIG. 1 is an example of a pattern formed by laminating three patterns formed by opening openings on a straight line and three patterns obtained by rotating the patterns by 60 ° and 120 °, respectively. An example of a three-fold symmetry is shown. As a result, as shown in the enlarged view of FIG. 1B, the openings are scattered in a hexagonal shape, are formed side by side at intervals of 60 °, and are not openings that are continuous only in one direction. .

As described above, the present inventor has found that when a thick nitride semiconductor layer having a thickness of, for example, about 10 μm or more is grown on a sapphire substrate by ELO growth, the wafer is likely to be warped, causing characteristic fluctuations and damage during handling. Therefore, as a result of intensive studies to prevent the wafer from warping even when a thick semiconductor layer is grown, it has been found that there is a relationship with the direction of the opening for forming a seed provided on the mask.

That is, even in a semiconductor layer grown by ELO growth, a threading dislocation still exists at the opening thereof because the threading dislocation of the lower layer is inherited as it is. Also, a junction part grown from both directions also exists in the center of the mask. It is known that the dislocation density becomes large, and it is not necessary to emit light in the entire chip as in a semiconductor laser. It is preferable not to include a portion having a large dislocation density in the opening or the junction. From such a viewpoint, as shown in FIG. 6, when the opening 44 is formed only in one direction with respect to the wafer,
2 inch wafer of thick sapphire substrate, 24
When a GaN layer having a thickness of μm is grown by ELO, the warpage of the upper portion and the center (T-C) and the lower portion and the center (B-C) shown in FIG. ) And right and center (RC) are each 40
μm, and it was found that the direction of the opening was very closely related to the warpage.

In the case of ELO growth of 4 μm, the warpage is about 40 μm in any direction. If the substrate thickness is 700 μm even if the growth thickness is 24 μm, the warpage in the above-mentioned directions is 50 μm and 20 μm, respectively. However, before the final chip was formed, the substrate was thinned to 300 μm.
Due to the thinning to the extent, the same warpage as described above occurred. On the other hand, using a mask having the pattern shown in FIG.
As a result of the ELO growth of a thick GaN semiconductor layer, the (T
-C, BC) and (LC, RC) directions are 60
μm. That is, when the mask layer having the openings of the pattern shown in FIG. 1 is used, the warpage slightly increases, but the warpage can be significantly suppressed as compared with the conventional structure in which the openings are provided only in one direction. I understand.

As shown in FIG. 1A, the pattern shown in FIG. 1A has a linear opening having a width of 10 to 20 μm and a width of 20 to 20 μm.
A pattern in which a pattern having a width P of 30 μm is formed periodically (in the figure, P is smaller than Q, but in order to clearly show the opening, P is actually about 1 to 3 times Q) , 6
The opening 3a has a hexagonal shape as shown in FIG. 1B, which is formed by superimposing a pattern rotated by 0 ° and a pattern rotated by 120 °. (It is not necessary to form a hexagon.) Since the nitride-based compound semiconductor that grows laterally on the mask 3 from the opening 3a is hexagonal, a certain percentage of the hexagonal opening is formed in any direction from the opening. Can be formed to grow. As a result, the junction of the semiconductor layer which grows laterally from the plurality of openings becomes a point, and the dislocation density at the junction hardly increases. Therefore, as shown by S in FIG. 1A, by forming a stripe-shaped light emitting portion in a half region avoiding the center of the mask width P, the dislocation density can be reduced without crossing the opening 3a. A small stripe-shaped light emitting portion can be formed.

FIG. 2 is a sectional explanatory view of a semiconductor laser chip (LD) in which a stripe-shaped light emitting portion is formed in such a portion having a very low dislocation density. That is, in the semiconductor laser according to the present invention, a first nitride-based compound semiconductor layer 2 is provided directly on a substrate 1 or laminated on the substrate, and a mask layer 3 having an opening 3a is provided thereon. A second nitride-based compound semiconductor layer 4 selectively grown laterally from the opening 3a on the mask layer 3; and a nitride stacked to form a light-emitting layer having a stripe-shaped light-emitting portion. A semiconductor laminated portion 15 made of a system compound semiconductor layer is provided. The mask layer 3 extends over the entire length of the chip without crossing the opening below the stripe-shaped light-emitting portion, and has openings 3a scattered in portions other than below the stripe-shaped light-emitting portion. ing. In FIG. 2, the mask layer 3 is shown only on the lower side of the light emitting layer forming portion, but is actually formed on the lateral side thereof (in the drawing, the stripe portion is shown in an enlarged manner). ing).

The substrate 1 is, for example, a sapphire (Al ₂ O ₃ single crystal) substrate that can withstand high temperatures, but is not limited to sapphire, and other semiconductor substrates such as Si and Ge can be used. Whatever material is used, G
Although the lattice constant of aN does not match with that of aN, lattice matching cannot be achieved. However, by performing lateral selective growth through the mask layer, a semiconductor layer having a low dislocation density can be grown on the mask layer.

The first nitride-based compound semiconductor layer 2 has a thickness of, for example, about 4 μm,
It is formed by a normal epitaxial growth method such as an OCVD method, and is used as a seed when a second nitride-based compound semiconductor layer 4 described later is selectively grown. However, even if the first nitride-based compound semiconductor layer is not provided, it may be omitted if the nitride-based compound semiconductor layer can be grown using a semiconductor substrate such as Si or a sapphire substrate as a seed.

The mask layer 3 is made of, for example, SiO ₂ , Si ₃ N
_{4. A material} such as W, on which a semiconductor layer cannot be directly epitaxially grown, is formed to a thickness of about 200 nm by sputtering or the like. The mask layer 3 prevents the second semiconductor layer from growing directly on the surface of the substrate 1 or on the first GaN layer 2. It is difficult and preferable. The mask layer 3 is provided on the entire surface of the first nitride-based compound semiconductor layer 2 in a wafer state, and is then patterned into the pattern shown in FIG. 1 to form an opening 3a. Further, in the example shown in FIG. 2, a concave portion 3b is formed on the surface side of the remaining mask layer 3 leaving a width of about 2 μm from the opening. When manufacturing the semiconductor laser shown in FIG.
The width M of the mask layer 3 in the direction along the stripe is 10 to 1
It is formed to about 5 μm. The mask width M is the minimum width required for the LD that emits light in a stripe shape as described above, and can be further increased.

Depression 3b formed on the surface of mask layer 3
After the opening 3a is formed, a mask is formed again with a resist film, and etching is performed using an HF-based aqueous solution, so that the thickness is about half the thickness of the mask layer 3, that is, 100%.
It is formed to a depth of about nm. Therefore, a concave portion 3b is formed on the inner surface of the mask layer 3 except for a width of about 2 μm from both ends. The reason why the thickness is set to about 2 μm is to prevent the concave portion from being exposed to the opening side due to variations in manufacturing conditions. The concave portion 3b prevents the contact stress from acting on the second semiconductor layer 4 growing in the lateral direction and grows straight in the lateral direction.

The second nitride-based compound semiconductor layer 4 is, for example, a non-doped GaN layer having a thickness of about 20 μm. The semiconductor layer 4 begins to grow using the first GaN layer 2 exposed from the opening 3a of the mask layer 3 as a seed, and when the semiconductor layer 4 reaches the surface of the mask layer 3, is selectively grown in the lateral direction. That is, since the GaN layer grows faster and more crystallographically in the lateral direction than in the vertical direction, even if the mask layer 3 is provided with the recess 3b, it hardly grows below. , Grows laterally while forming a gap 3c between the mask layer 3 and slightly grows upward, and finally in the lateral direction from the opening in three directions around the center of the mask layer 3. The grown semiconductor layer matches. After the surface of the mask layer 3 is completely buried, it grows upward, and the second GaN layer (semiconductor layer) 4 also grows completely on the mask layer 3. The second GaN layer 4 has good crystallinity except for both ends (parts in contact with the openings 3a) and a part where the center part matches on the mask layer 3, and has a low dislocation density.

Semiconductor laminated portion 15 on second GaN layer 4
Is a semiconductor lamination part that constitutes a normal semiconductor laser.
ing. That is, for example, when Si is 5 × 10¹⁸cm^-3About
N-type contact layer made of heavily doped n-type GaN
5 is about 0.5 μm, for example, Si is 5 × 10¹⁸cm^-3
Moderately doped n-type Al_0.08Ga_0.92N consisting of N
The shape cladding layer 6 is about 0.4 μm, for example, Si is 1 ×
10¹⁸cm^-3A n-type GaN that is heavily doped
1 is approximately 0.2 μm, for example, Si
Doped In_0.01Ga_0.99A second n-type gas consisting of N
The thickness of the nitride layer 8 is about 50 nm,_0.1Ga_0.9C consisting of N
Well layer with a thickness of about 5 nm._0.02Ga_0.98Bali made of N
A layer in which five well layers are alternately laminated by about 5 nm each
50 n of the active layer 9 having a quantum well (MQW) structure
m, for example, Mg-doped Al _0.2Ga_0.8From N
The p-type cap layer 10 having a thickness of about 20 nm, for example, Mg
Is 1 × 10¹⁸cm^-3Consists of moderately doped GaN
The p-type guide layer 11 has a thickness of about 0.1 μm,
× 10¹⁷cm^-3Moderately doped Al_0.08Ga_0.92N
The p-type cladding layer 12 made of
If Mg is 3 × 10¹⁸cm^{- Three}Lightly doped GaN
P-type contact layer 13 of about 0.1 μm
It is formed by successively laminating.

The structure of the semiconductor laminated portion 15 and the material of each layer are as follows:
The present invention is not limited to this example, and the active layer 9 may have a bulk structure other than the quantum well structure. The active layer 9 made of a material determined by a desired emission wavelength may be a clad layer 6 made of a material having a larger band gap. , 12 are formed. When a semiconductor laser is configured as in the example shown in FIG. 2, the active layer 9 is formed of a material having a higher refractive index than the cladding layers 6 and 12. By doing so, light can be confined in the active layer 9, but when the active layer 9 is too thin to confine light sufficiently, as in the example shown in FIG.
Light guide layers 7, 8, 11 having a refractive index between the cladding layers 6, 12 and the active layer 9 are provided. However, if light is sufficiently confined by the active layer 9, the light guide layers 7, 8, 1
It is not necessary to provide 1.

The uppermost p-type contact layer 13 of the semiconductor laminated portion 15 is subjected to mesa etching and a part of the semiconductor laminated portion 15 is etched to expose the n-type contact layer 5, and the entire surface thereof is exposed. A protective film 14 is formed by depositing SiO _{2 on the} substrate. Then, a p-side electrode 16 made of Ni—Au and an n-side electrode 17 made of Ti—Al connected to the n-type contact layer are formed on the mesa portion of the p-type contact layer 13 through the contact hole of the protective film 14. Each is formed. The cavity is cleaved so that the cavity length (length in the direction perpendicular to the paper) is about 500 μm, and the LD chip shown in FIG. 2 is formed.

In this laminated structure, the stripe-shaped mesa-shaped portion of the p-type contact layer 13 becomes a current injection region (even if the contact layer 13 is not mesa-shaped, the p-side electrode is formed in a stripe shape). If this is done, a stripe-shaped current injection region is formed), and the mask layer 3 and the p-side electrode 16 are positioned under the lower layer so that the width is equal to or less than half the width of the stripe-shaped recess 3b provided in the mask layer 3. It is formed.

Next, a method of manufacturing the semiconductor laser will be described. For example, using an epitaxial growth apparatus such as MOCVD, the substrate temperature is set to about 1100 ° C. and H
Perform thermal cleaning in ₂ atmospheres. Then, Ga
Triethyl gallium (TEG) as a source gas for N
Ammonia (NH ₃ ) as a raw material gas is introduced, and the non-doped first GaN layer 2 is grown to about 4 μm.
Next, the substrate is taken out of the growth apparatus, and a SiO ₂ film is formed to a thickness of about 200 nm using, for example, a sputtering apparatus. Thereafter, a resist film is provided on the SiO ₂ film, patterned, and the SiO ₂ film is etched using an HF aqueous solution, thereby opening the opening 3a as shown in FIG.
Is formed, and a three-fold symmetric mask layer 3 is formed. further,
A resist film is provided on the entire surface and patterned, and H
By etching with the F aqueous solution, the concave portions 3b are formed in a stripe shape (perpendicular to the paper surface).

Thereafter, the wafer is again put into a growth apparatus such as a MOCVD apparatus, and as a source gas, in addition to the above-mentioned gases, Al
Trimethylaluminum (TMA), trimethylindium (TMIn) of In, and S as an n-type dopant
iH ₄ , cyclopentadienyl magnesium (Cp ₂ Mg) or dimethyl zinc (DMZ) as a p-type dopant
The necessary gas of n) is introduced together with hydrogen of the carrier gas, and the second nitride compound semiconductor layer 4 and each semiconductor layer of the semiconductor laminated portion 15 are grown to the above-mentioned thicknesses.
In this case, the substrate temperature is 1 until the first n-type guide layer 7.
The second n-type guide layer 8 and the active layer 9 are grown at a substrate temperature of about 770 ° C., and the subsequent layers are grown again at a substrate temperature of about 1050 ° C.

After the growth of each semiconductor layer is completed, the substrate is taken out of the growth apparatus, a resist mask is provided on the surface, and reactive ion beam etching (RIBE) is performed.
As shown in FIG. 3A, a part of the semiconductor lamination portion 15 is etched with a 200 μm width in a part of a 400 μm period by using the apparatus to expose a part of the n-type contact layer 5.
Further, the resist mask is removed, a resist mask is provided again, and mesa etching is performed by the same apparatus so that the p-type contact layer 13 remains in a width of about 4 μm as shown in FIG. Thereafter, using a film forming apparatus such as a plasma CVD method, a protective film 14 such as SiO ₂ is formed on the entire surface to a thickness of about 200 nm, and the electrode formation portion is etched with an HF-based etchant to form a contact hole. To form

Next, as the p-side electrode 16,
0 nm and 200 nm of Au were deposited by a vacuum deposition apparatus, and 100 n of Ti was used as the n-side electrode 17.
m and Al are deposited to a thickness of 200 nm, and electrodes 16 and 17 are formed.
Is formed, and the back surface of the substrate 1 is ground to a thickness of about 60 μm, and then cleaved so that the resonator length becomes about 500 μm, thereby forming an LD chip.

According to the present invention, the nitride compound semiconductor layer portion having a small dislocation density is grown linearly without crossing the opening while eliminating the warpage of the wafer without forming a continuous opening in only one direction. In addition, since the semiconductor lamination portion is formed so as to have a stripe-shaped light emitting portion in a portion having a low dislocation density, the stripe-shaped resonator portion for emitting the semiconductor laser has excellent crystallinity and flatness. The semiconductor lamination part of the resonator part also grows with good crystallinity, and a high-performance semiconductor laser with a small threshold current value can be obtained. Moreover, the entire surface of the wafer can be used, and more than half of the substrate is not wasted. In addition, since the concave portion is formed on the surface of the mask layer, the contact stress between the mask layer and the semiconductor layer does not work during growth, and the crystal axis of the growing semiconductor layer is not bent by the stress,
A flat semiconductor layer grows over a long width.

In the above example, the p-type contact layer 1
Although the semiconductor laser 3 has a stripe structure in which only a mesa-type stripe shape is used, only the electrodes may be formed in a stripe shape without etching the semiconductor layer. Well, and
A proton implantation type in which protons or the like are implanted can also be used. Further, a refractive index waveguide structure in which the current limiting layer is embedded may be employed.

FIGS. 4 and 5 show mask patterns for suppressing the warpage of the wafer while forming a light emitting region having a low dislocation density over the entire area without crossing a portion having a high dislocation density in the stripe light emitting portion of the LD. Another example is shown. That is, FIG. 4 shows that a portion where the stripe-shaped light emitting portion S is formed has a linear mask layer 3 sandwiched between linear openings 3d.
In other portions, the mask layer 3 is formed in a lattice shape, and the square openings 3a are formed in a matrix shape. As a result, also in the wafer, in the stripe-shaped light emitting portion S, the linear opening penetrates the wafer, but in other portions, since the openings 3a are provided at the same interval in both the vertical and horizontal directions, only one direction is provided. No warpage occurs, and warpage in the wafer can be suppressed. In FIG. 4, the intervals (mask width) of the rectangular openings 3a are written at the same vertical and horizontal intervals, but the intervals can be adjusted according to the difference in the growth rate. Further, another linear mask portion is formed adjacent to the stripe-shaped light-emitting portion S. This is for increasing the rate in the horizontal direction near the light-emitting portion. Only one may be used.

The above-described example is an example in which the pattern of one chip is repeated in the same shape in the wafer (only the pattern for one chip is shown in FIG. 4).
This is an example in which a pattern for interrupting continuity is formed between patterns of each chip. That is, although one chip has a structure in which an opening is provided in parallel with the stripe-shaped light emitting portion S, the mask portion 3 and the opening J are used in a region J used as a chip and an adjacent region K not used as a chip. The pattern is such that the portion 3e is reversed. When a chip is formed from the wafer, an LD chip is manufactured from the region J by cleaving at the broken line H in the figure, and the region K is formed.
Is to be discarded. Even with this pattern, since the openings were not continuous in a straight line, the warpage of the wafer could be suppressed. It is preferable that the region K is shorter in the portion to be discarded. However, even if the region K is shorter than the length of the region J by about half, the warpage of the wafer is not affected. In the case of an LED, since it is not necessary to cleave the LED, it can be used also in the region K.
There is no waste at all.

[0044]

According to the present invention, since the opening of the mask layer is not formed by an opening continuous only in one direction, the mask width is increased, and the growth thickness of the semiconductor layer grown thereon is reduced. Even if the thickness needs to be increased, the wafer does not warp.
As a result, a high quality semiconductor light emitting device can be obtained at low cost without adversely affecting handling in a wafer process or device characteristics.

Further, according to the semiconductor laser of the present invention,
The stripe-shaped light-emitting portion has no portion having a large dislocation density at all, and has a semiconductor layer portion with few crystal defects over the entire stripe-shaped light-emitting portion. There is no opening, and even if a thick nitride-based compound semiconductor layer is grown, warpage does not become a problem in the state of the wafer. In addition, the substrate can be effectively used, and the manufacturing cost can be reduced. As a result, a high-performance semiconductor laser having a small threshold current value can be obtained at low cost.

[Brief description of the drawings]

FIG. 1 is a diagram showing an example of a mask pattern used in a method for manufacturing a semiconductor light emitting device according to the present invention.

FIG. 2 is an explanatory cross-sectional view of one embodiment of a semiconductor laser according to the present invention.

FIG. 3 is an explanatory diagram of a pattern example in which a laminated portion is etched after laminating semiconductors.

FIG. 4 is another example of a mask pattern suitable for a semiconductor laser according to the present invention.

FIG. 5 is yet another example of a mask pattern suitable for a semiconductor laser according to the present invention.

FIG. 6 is a diagram illustrating an example of a preferable pattern for growing a semiconductor layer having a low dislocation density over the entire stripe-shaped light emitting portion of an LD, and a state of warpage in that case.

FIG. 7 is a diagram illustrating a problem when a semiconductor layer is grown by ELO growth.

FIG. 8 is an explanatory sectional view showing an example of a conventional blue semiconductor laser.

[Explanation of symbols]

 Reference Signs List 3 mask layer 3a opening 4 second nitride-based compound semiconductor layer 9 active layer 15 semiconductor lamination

 ──────────────────────────────────────────────────続 き Continued on the front page F-term (reference)

Claims (5)

[Claims] A mask layer on which a nitride-based compound semiconductor layer does not directly grow is formed directly on the surface of a wafer-like substrate or on a layer provided on the substrate. An opening for exposing a seed for growing a nitride-based compound semiconductor layer is formed so as not to be continuous only in a single direction over the entire surface of the wafer-like substrate, and a horizontal portion is formed on the mask layer from the opening. A semiconductor laminated portion made of a nitride-based compound semiconductor such that a nitride-based compound semiconductor layer is provided on the entire surface of the wafer-like substrate by selectively growing in the direction, and a light-emitting layer is formed on the nitride-based compound semiconductor layer. And forming the wafer-like substrate into chips. 2. The method for manufacturing a semiconductor light emitting device according to claim 1, wherein most of the opening is formed so that the planar shape becomes a square or a hexagon. 3. A substrate, a mask layer having an opening provided directly on the substrate or on a layer laminated on the substrate, and selectively growing laterally from the opening on the mask layer. A nitride-based compound semiconductor layer, and a semiconductor laminated portion on which the nitride-based compound semiconductor layer is laminated so as to form a light-emitting layer having a stripe-shaped light-emitting portion on the nitride-based compound semiconductor layer, The mask layer extends over the entire length of the chip without crossing the opening below the stripe-shaped light-emitting portion, and the openings are formed scattered in portions other than below the stripe-shaped light-emitting portion. Semiconductor laser. 4. An opening of the mask layer is formed linearly along the stripe-shaped light-emitting portion in a portion adjacent to the stripe-shaped light-emitting portion, and is formed in a matrix or randomly in a portion other than the stripe-shaped light-emitting portion. 4. The semiconductor laser according to claim 3, which is formed. 5. A three-fold symmetrical shape wherein the mask layer is formed by superposing a pattern having a linear opening, a pattern obtained by rotating the pattern by 60 °, and a pattern obtained by rotating the pattern by 120 °. 4. The semiconductor laser according to claim 3, wherein the semiconductor laser is formed.