JP2002305149A - Growing method for nitride semiconductor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To accelerate lateral growth by suitably controlling growth conditions and to reduce the curvature of a semiconductor by suppressing the film thickness of a grown nitride semiconductor. SOLUTION: The growing method for the nitride semiconductor comprises a process of growing a 1st nitride semiconductor layer, on a heterogeneous substrate made of a material different from the nitride semiconductor, a process of forming a protective film which is formed partially on the surface of the 1st nitride semiconductor layer and is hard to have the nitride semiconductor grown on its surface, and a process of growing a continuous 2nd nitride semiconductor layer on the protective film and a baser layer by heating the 1st nitride semiconductor layer and the base layer formed of the protective film and supplying the gas from a nitrogen source and the gas from group-III, together with the a carrier gas. The density of the gas of the nitrogen source is 5 to 6 slm and the concentration of the gas of the group-III source is 80 to 130 sccm.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a method for growing a nitride semiconductor.

[0002]

2. Description of the Related Art Semiconductor light emitting devices are expected to be applied in various fields, and have been actively researched and developed in recent years.
In particular, nitride-based semiconductor elements are used for light-emitting elements such as light-emitting diodes (LEDs), laser diodes (LDs), solar cells, light sensors, and the like, light-receiving elements, and electronic devices such as transistors and power devices.

In order to obtain such a semiconductor light emitting device,
Nitride semiconductor (In _X Al _Y Ga as a general formula)
_1- XYN, represented by 0 ≦ X, 0 ≦ Y, X + Y ≦ 1) on a substrate. In order to obtain an excellent semiconductor light emitting device, it is necessary to grow a nitride semiconductor having few crystal defects. In general, it is known that, when a semiconductor is grown on a substrate, using a substrate lattice-matched with the semiconductor to be grown reduces crystal defects of the semiconductor and improves crystallinity. However, since a nitride semiconductor does not have a lattice-matching substrate at present, it is generally grown on a heterogeneous substrate such as sapphire, spinel, or silicon carbide that does not lattice-match with the nitride semiconductor.

[0004] Under such circumstances, various methods for growing a nitride semiconductor have been studied in order to obtain a good nitride semiconductor device. In particular, a method of forming a protective film and selectively growing a nitride semiconductor has been studied.

[0005] The selective growth means that a stripe-like, circular pattern-like or lattice-like protective film made of SiO ₂ , SiN, or the like is partially formed on a GaN layer grown on sapphire, for example, and the protective film is formed on the protective film. Then, GaN is again grown by a vapor phase growth method such as metal organic chemical vapor deposition (MOVPE), whereby the growth starts from the window portion where the protective film is not formed (hereinafter referred to as “window portion”), and gradually. Lateral growth of GaN occurs at the top of the protective film, and GaN grown laterally from adjacent windows joins on the protective film and continues to grow to obtain a nitride semiconductor with extremely few crystal defects. is there. A method of growing a nitride semiconductor using the lateral growth of the nitride semiconductor after forming such a protective film is described in Epitaxially Lateral Overgrowth (hereinafter referred to as “ELOG”).
Is called).

When a substrate having a selective growth layer as described above is used for, for example, a laser device, the state of the substrate greatly affects the characteristics of the finally obtained device. For this reason, it is important to improve the crystallinity and surface morphology by improving the substrate, which leads to improvement in device characteristics.

[0007] The selective growth layer obtained by selective growth has a different crystallinity because the growth mechanism differs between the upper part of the protective film and the upper part of the window. As described above, the selective growth layer grows in the lateral direction above the protective film and is formed by combining the selective growth layers. Therefore, on the surface of the selective growth layer, the crystallinity is different between the upper part of the protective film and the upper part of the window located between the protective film and the protective film, and regions having different crystallinity are distributed on the substrate surface. Become.

[0008] In a portion grown vertically from a lower GaN layer in the upper part of the window, lattice defects of the GaN layer propagate and are inherited, so that the grown GaN layer also has poor crystallinity.

On the other hand, the portion grown above the protective film by the lateral growth is generally a region having relatively few lattice defects because the dislocation density is not generally grown in the horizontal direction at the same density as the vertical direction.

Therefore, the upper portion of the protective film can be used as a region having excellent crystallinity which is preferable for forming an element. If this area can be increased, many high-quality elements can be formed and the efficiency can be improved.

[0011]

However, when the area of the protective film is increased in order to increase the ratio of a region favorable for element formation, lateral growth is insufficient as shown in FIGS. 1 (a) to 1 (c). As a result, there arises a problem that a gap 6 is generated above the protective film 1. This is due to the limited rate of lateral growth,
G that grows laterally from the windows adjacent to both sides on the protective film 1
This is because aNs cannot be bonded to each other on the protective film 1, and as a result, a gap 6 is formed between the aN and the protective film 1 at the joint of the selective growth layer. As the width of the protective film 1 becomes wider, the rate of lateral growth becomes slower, and the generation of the voids 6 on the protective film 1 tends to increase. Since the presence of such a gap 6 may adversely affect the substrate, the formation of the gap 6 must be suppressed in order to form a good substrate.

As a method for suppressing the generation of voids, the present applicant sets the stripe direction of the protective film 1 to θ = 0.1 to 0.4 ° from the direction perpendicular to the crystal plane (dashed line) as shown in FIG.
A method for selective growth with shift has been developed (JP-A-2000-2000)
-294827). In this method, since lateral growth is promoted, it is possible to suppress generation of voids and control selective growth to a preferable state.

However, when an element is formed from the nitride semiconductor layer grown by this method, the protection film 1 provided in a stripe pattern on the substrate is not perpendicular to the C plane, so that the characteristics of the cleavage plane deteriorate. There is.

On the other hand, if the stripes forming the protective film 1 are selectively grown perpendicularly to the orientation flat surface 3 (hereinafter, referred to as the “orientation flat surface”) to prevent this, the characteristics of the element are improved. However, in this case, since the rate of lateral growth is not promoted, there is a problem in that the growth surfaces of the nitride semiconductors laterally grown from both sides on the protective film 1 are not coupled to each other as described above, and voids are generated. .

If the growth is carried out for a sufficient time so that no voids are formed, the growth in the lateral direction is promoted and the growth in the vertical direction is promoted.
Will be. When a nitride semiconductor is grown on a substrate such as sapphire that does not lattice match, warpage occurs as shown in FIG. Since this warp increases as the growth layer becomes thicker, it is not desirable to make the nitride semiconductor layer thicker.

The present invention has been made to solve such a problem. An important object of the present invention is to reduce the thickness of the nitride semiconductor layer by promoting lateral growth,
Another object of the present invention is to provide a nitride semiconductor growth method capable of obtaining a device having excellent characteristics by growing the protective film while keeping the protective film perpendicular to the cleavage plane.

[0017]

Means for Solving the Problems In order to achieve the above object, a method for growing a nitride semiconductor according to the present invention has the following features. The method for growing a nitride semiconductor according to claim 1, wherein a first nitride semiconductor layer is grown on a heterogeneous substrate made of a material different from that of the nitride semiconductor; Forming a protective film partially formed on the surface of the semiconductor layer and having a property on the surface on which a nitride semiconductor is unlikely to grow; and forming an underlayer composed of the first nitride semiconductor layer and the protective film on the surface. Heating, supplying a nitrogen source gas and a group 3 source gas together with a carrier gas to the surface of the underlayer to grow a continuous second nitride semiconductor layer on the protective film and the underlayer; Consists of Further, in this nitride semiconductor growing method, the concentration of the nitrogen source gas is 5%.
６6 slm, the concentration of the gas of the group 3 source is 80 to 130 s
ccm.

According to a second aspect of the present invention, in the method of growing a nitride semiconductor, in addition to the features of the first aspect, the gas of the Group 3 source is trimethylgallium. .

Furthermore, a nitride semiconductor growth method according to a third aspect of the present invention is characterized in that, in addition to the features described in the first aspect, the nitrogen source gas is ammonia.

Further, in the method for growing a nitride semiconductor according to claim 4 of the present invention, in addition to the features described in any one of claims 1 to 3, the concentration of the nitrogen source gas is set to 5. 6 slm, the gas concentration of the group 3 source is 100 scc
m.

Further, in the method for growing a nitride semiconductor according to claim 5 of the present invention, a step of growing a first nitride semiconductor layer on a heterogeneous substrate made of a material different from that of the nitride semiconductor; Forming a stripe-shaped protective film partially formed on the surface of the first nitride semiconductor layer and having a property that a nitride semiconductor is unlikely to grow on the surface, perpendicular to the orientation flat surface of the heterogeneous substrate; A base layer composed of the first nitride semiconductor layer and the protective film is heated, and a nitrogen source gas having a concentration of 5 to 6 slm and a group III gas having a concentration of 80 to 130 sccm are formed on the surface of the base layer. Supplying a source gas together with a carrier gas to grow a continuous second nitride semiconductor layer on the protective film and the underlayer.

Further, in the method for growing a nitride semiconductor according to claim 6 of the present invention, in addition to the features described in any one of claims 1 to 5, the supply of the carrier gas may be 2 or more.
-3 sccm, and the second nitride semiconductor layer is grown on the protective film so that the film thickness is 10 μm or less.

According to a seventh aspect of the present invention, in addition to the feature of the fifth or sixth aspect, the protective film has a stripe width of 10 μm.
It is characterized by the above.

Further, in the method of growing a nitride semiconductor according to claim 8 of the present invention, in addition to the features of claim 7, the stripe width Ws of the protective film and the window portion without the protective film are provided. The ratio Ww / Ws to the width Ww is in the range of 0.2 to 0.5.

According to a ninth aspect of the present invention, in addition to the feature of any one of the first to eighth aspects, it is preferable that the carrier gas is a hydrogen gas. Features.

According to a tenth aspect of the present invention, there is provided a method for growing a nitride semiconductor according to any one of the first to ninth aspects, wherein the different substrate is made of sapphire, spinel or silicon carbide. It is characterized by being.

Further, according to the method for growing a nitride semiconductor according to the eleventh aspect of the present invention, in addition to the feature according to any one of the first to tenth aspects, the warpage of the substrate of the nitride semiconductor is set to 100 μm. It is characterized by the following.

Further, according to a method for growing a nitride semiconductor according to a twelfth aspect of the present invention, in addition to the features described in any one of the first to eleventh aspects, the method further comprises the step of: The growth time is 300 minutes or less.

Furthermore, the method of growing a nitride semiconductor according to claim 13 of the present invention, in addition to the features of any of claims 1 to 12, further comprises a nitride semiconductor substrate grown by the method. In addition, another nitride semiconductor substrate is grown by using the above method.

According to the method for growing a nitride semiconductor of the present invention, the growth in the lateral direction is promoted by adjusting the reaction conditions, the growth in the vertical direction is suppressed by eliminating voids in a short time, and a high quality thin film is obtained. It is intended to provide a simple nitride semiconductor. According to the present invention, since the growth rate in the lateral direction is improved, even if the vertical growth is thin, in other words, even if the second nitride semiconductor layer is thinned, the lateral growth can be sufficiently achieved on the protective film. Thus, the generation of voids can be suppressed. And since the film thickness is thin, the warpage of the nitride semiconductor substrate can be reduced. Furthermore, since a sufficient growth rate can be ensured, the protective film can be grown without being shifted from the C plane while being kept at a right angle, so that the light emitting characteristics of the semiconductor element are improved and the yield in cleavage is improved.

[0031]

Embodiments of the present invention will be described below with reference to the drawings. However, the embodiments described below exemplify a nitride semiconductor growth method for embodying the technical idea of the present invention, and the present invention specifies the nitride semiconductor growth method as follows. do not do.

Further, in this specification, in order to make it easy to understand the scope of the claims, the numbers corresponding to the members described in the embodiments are appended to the members indicated in the column of "Means for Solving the Problems". are doing. However, the members described in the claims are not limited to the members of the embodiments. Also, the size and positional relationship of the members shown in each drawing are
Sometimes exaggerated for clarity.

In this specification, the term “the protective film is perpendicular to the crystal plane of the substrate” means that the crystal plane is A when the substrate is sapphire.
Plane, C plane, M plane, or R plane, or (110) plane when the substrate is spinel or silicon carbide, which means perpendicular to these planes.

The present invention realizes the manufacture of a nitride semiconductor having few crystal defects that can be used as a substrate. Nitride semiconductors are used for light-emitting elements such as light-emitting diodes (LEDs), laser diodes (LDs), solar cells, light sensors, light-receiving elements, transistors, and electronic devices such as power devices.

The general formula of the n-type layer described in this specification
Al_XGa_1-XAl of N and p-type layers _XGa_1-XN etc.
Is merely a general formula, and the n-type
X of the layer and X of the p-type layer do not indicate the same value.
Similarly, the same applies to the Y value used in other general formulas.
Not necessarily the same value in the general formula
Absent.

Further, in this specification, gallium nitride (GaN) means an alloy containing another metal, for example, AlGaN, InGaN, AlInGa
N and the like.

Gallium nitride has been extensively studied for microelectronic devices. Microelectronic devices include, but are not limited to, transistors, field emitters, optoelectronic devices, and the like.

In the present invention, the gas of the nitrogen source corresponds to a hydride gas such as ammonia or hydrazine.
Organic Ga gas such as (trimethylgallium) and TEG (triethylgallium), and in the case of HVPE, a hydrogen halide gas that reacts with a group III source such as HCl, or a gallium halide (particularly GaCl ₃ ) that reacts with a hydrogen halide gas And the like correspond to the gas of the Ga source.

In the present invention, growth conditions are set so as to promote lateral growth. In particular, the flow rates of the nitrogen source gas and the group 3 source gas as the source gas were adjusted. As a means for adjusting these ratios, a method of changing one or both of a nitrogen source gas and a group III source gas is considered.
In the embodiment of the present invention, basically, the supply amount of the gas of the nitrogen source is fixed and the supply amount of the gas of the group 3 source is changed.

In the step of growing the second nitride semiconductor layer 5, when supplying the nitrogen source gas and the group III source gas together with the carrier gas, it is preferable to supply these gases at any ratio. There are various ways to determine this. For example,
There are a method of determining the ratio of the gas of the nitrogen source and the gas of the group 3 source by a molar ratio, and a method of individually adjusting the flow rates and setting the optimum conditions. The optimum conditions may be determined by changing the reaction conditions in various ways. In the present invention, in order to set the reaction conditions, the supply amount of the gas of the Group 3 source is fixed to a constant value,
A method of setting the supply amount of each source gas by adjusting the supply amount of the nitrogen source gas so as to obtain an optimum result is adopted. As a result of the experiment, TM
When the supply amount of G gas was fixed at 100 sccm and the supply amount of ammonia was adjusted to 5.6 slm, it was found that lateral growth was promoted and ELOG having good characteristics was realized.

As a result of an experiment using the method of the present invention, the time required to obtain sufficient lateral growth was reduced to about half as compared with the case where an ELOG substrate was grown by the conventional method. Therefore, the thickness of the second nitride semiconductor film can be reduced to about half, and the warpage caused by the thick film is suppressed. The detailed principle that the growth rate in the vertical direction is greatly increased without increasing or suppressing the growth in the vertical direction is not clear, but growth is increased by increasing the supply of ammonia. It is presumed that this promotes lateral growth.

[0042]

EXAMPLE When a nitride semiconductor is selectively grown on a heterogeneous substrate 2, a second nitride semiconductor layer 5 is formed as a selectively grown layer in various forms depending on the conditions. FIG. 1 shows how a nitride semiconductor grows by selective growth.
In the selective growth, a part of the substrate is covered with a protective film 1 that does not react with the nitride semiconductor (FIG. 1A), and the nitride semiconductor is grown from a part of the substrate surface where the protective film 1 is not covered. (FIGS. 1B and 1C). ELOG growth, which has been focused on as the nitride semiconductor substrate described above, generally forms a stripe-shaped protective film 1 on a substrate and grows a nitride semiconductor from a window where the protective film 1 is not provided. Adjacent second nitride semiconductor layers 5 are formed by being combined with each other above the protective film 1 (FIG. 1). However, when the second nitride semiconductor layers 5 are bonded to each other, voids shown in FIGS. 1 and 2 are formed. The present invention controls such a gap, and this point will be described in detail below.

[Example 1] An example in which a nitride semiconductor is grown using MOVPE (metal organic chemical vapor deposition) will be described below. However, the method of the present invention is not limited to the MOVPE method, for example, HVPE (halide vapor phase epitaxy), MBE
All methods known for growing nitride semiconductors, such as (molecular beam vapor deposition), can be applied.

FIG. 1 is a schematic sectional view of a wafer in each of the following steps. The foreign substrate 2 in the present invention, sapphire _{(A1 2 0} 3), spinel (MgAl
₂ 0 _4), a single crystal substrate of silicon carbide (SiC).
In this example, a 2 inch φ sapphire substrate is used as the heterogeneous substrate 2. Main surface is C surface, orientation flat surface 3
A sapphire substrate having A as a surface is set in a MOVPE reaction vessel. At a temperature of 500 ° C., a buffer layer made of GaN was formed on the sapphire substrate 11 by using hydrogen as a carrier gas, ammonia (NH ₃ ) and trimethylgallium (Ga (CH ₃ ) ₃ : TMG) as a source gas, and forming a 200 ° film on the sapphire substrate 11. Grow in thickness.

(First Nitride Semiconductor Layer 4) After the growth of the buffer layer, the temperature is set to 1050 ° C., and the first nitride semiconductor layer 4 also made of GaN is grown to a thickness of 5 μm.
It is desirable that the first nitride semiconductor layer 4 is formed by growing Al _X Ga _1-X N (0 ≦ X ≦ 0.5) having an Al mixed crystal ratio X value of 0.5 or less. If it exceeds 0.5, cracks tend to occur in the crystal itself rather than crystal defects,
The crystal growth itself tends to be difficult. Further, it is desirable that the film is grown to a thickness larger than that of the buffer layer and adjusted to a thickness of 10 μm or less. As a type of the substrate, it is known to grow a nitride semiconductor such as SiC, ZnO, spinel, and GaAs in addition to sapphire, and a material different from the nitride semiconductor can be used.

After the growth of the first nitride semiconductor layer 4, the wafer is taken out of the reaction vessel, and the first nitride semiconductor layer 4 is removed.
Form a striped photomask on the surface of
The protective film 1 made of SiO ₂ having a stripe width of 14.0 μm and a stripe interval (window portion) of 6 μm was formed by a D apparatus at 1 μm.
(FIG. 1A). The shape of the protective film 1 may be any shape such as a stripe shape, a dot shape, a grid shape, and the like. However, when the area of the protective film 1 is larger than that of the window portion, the second nitride having less crystal defects can be used. The semiconductor layer 5 grows easily.

As a material of the protective film 1, a material having a property in which a nitride semiconductor does not grow or hardly grows on the surface of the protective film is preferably selected. For example, silicon oxide (Si)
O _X ), silicon nitride (Si _X N _Y ), titanium oxide (Ti
O _X), an oxide such as zirconium oxide (ZrO _X),
In addition to a nitride, a multilayer film, and a metal having a melting point of 1200 ° C. or more, a metal film or the like can be used. These protective film materials have a nitride semiconductor growth temperature of 600 ° C. to 110 ° C.
It withstands a temperature of 0 ° C., and has a property that a nitride semiconductor does not grow or hardly grows on its surface. To form a protective film material on a nitride semiconductor surface, for example, evaporation,
A vapor phase film forming technique such as sputtering or CVD can be used. Further, in order to partially (selectively) form, a photomask having a predetermined shape is manufactured using photolithography technology, and the material is formed into a film through the photomask. Thereby, a protective film having a predetermined shape can be formed. As shown in FIG. 2, the stripe direction of the protective film 1 is a direction of θ = 0 ° with respect to a direction AA perpendicular to the sapphire A surface (orientation flat surface 3).

(Second Nitride Semiconductor Layer 5) After the formation of the protective film 1, the wafer is set again in the MOVPE reaction vessel, the temperature is set at 1050 ° C., and ammonia is added for 0.27 m 2.
ol / min and TMG at 225 μmol / min (V /
III ratio = 1200) and a second layer made of undoped GaN
Is grown to a thickness of 7 μm (FIG. 1B). The second nitride semiconductor layer 5 grows in the vertical direction with respect to FIG. 1 to a certain thickness, then grows in the horizontal direction (FIG. 1B), and grows from the adjacent window. The nitride semiconductor layers 5 are bonded together to form a film (FIG. 1).
(C)).

The second nitride semiconductor layer 5 can be grown by using a halide vapor phase epitaxy (HVPE).
In this manner, it can be grown by the MOVPE method. The second nitride semiconductor layer 5 is made of G containing no In or Al.
It is most preferable to grow aN. As a gas at the time of growth, in addition to TMG, triethylgallium (Ga (C ₂
H ₅ ) ₃ : using an organic gallium compound such as TEG),
Most preferably, ammonia or hydrazine is used as the nitrogen source.

When the second nitride semiconductor layer 5 is basically in an undoped state, the second nitride semiconductor layer 5 tends to have the lowest crystal defects, the highest mobility, and the lowest carrier concentration. However, growth may be performed by doping n-type impurities to increase the carrier concentration. In particular, the heterogeneous substrate 2,
When an electrode is formed on the surface of the second nitride semiconductor layer 5 by removing the first nitride semiconductor layer 4, the protective film, and the like,
The second nitride semiconductor layer 5 is doped with an n-type impurity such as Si or Ge to increase the carrier concentration to, for example, 1 × 10 ¹⁷ /
It is desirable to adjust ^{cm 3 ~5 × 10 19 / cm} 3.

Under the above conditions, the pressure was set to 400 Torr and the growth was performed for 250 minutes to obtain a second nitride semiconductor layer 5 having a thickness of 7 μm. The warp of the obtained nitride semiconductor substrate is 10
It was 0 μm or less. This nitride semiconductor exhibited good crystallinity, and the shape of the voids was formed almost uniformly in the stripe direction of the protective film 1, and good selective growth was achieved. Therefore, the surface of the obtained nitride semiconductor has good uniformity and serves as a good substrate for forming a nitride semiconductor element. According to this method, the growth time can be reduced to about half that of the conventional method, so that there is an advantage that the growth speed is greatly improved. This also allows the protection film 1 to be formed even when the growth in the vertical direction is small.
The upper gap is filled. Therefore, the advantage that the entire film thickness can be suppressed and the warpage of the substrate can be reduced can be enjoyed. Furthermore, since the stripe of the protective film 1 can be parallel to the M plane of the sapphire substrate, that is, the axis shift can be made 0 °, the characteristics of the device obtained from the grown nitride semiconductor can be improved and the yield can be improved. .

Under the conventional conditions, the stripe of the protective film is M
When the nitride semiconductor layer was grown at a right angle to the plane, that is, with a deviation of 0 °, the gap on the protective film was not completely filled even when the nitride semiconductor layer was grown at 15 μm. If one waits until the semiconductor layer is buried on the protective film, the film thickness becomes several tens μm, and the warpage of sapphire and GaN increases.
The present applicant has developed a method of laminating a stripe shape of SiO _{2 serving} as a protective film with a deviation of ± 0.1 to 0.5 ° from a plane orientation M plane of a sapphire substrate in order to promote lateral growth. However, although the growth of the nitride semiconductor layer itself can be successfully performed by this method, it is extremely difficult to obtain a mirror surface of GaN, and there is a problem that the characteristics of an element obtained from the grown semiconductor layer are deteriorated due to the above-mentioned deviation. Was.

In the method of the present invention, by optimally adjusting the reaction conditions for growing ELOG on the protective film,
A low defect ELOG substrate can be obtained even in a state where the layers are stacked at 7.5 microns. At this time, the stripe of the protective film is M
Even if the axis deviation is set to almost 0 ° so as to be perpendicular to the plane, sufficient lateral growth can be obtained, the voids are filled on the protective film, and a high-quality semiconductor growth layer can be obtained. In particular, since there is no axis deviation of the protective film, the quality in the element structure is improved, the yield is improved, and in the case of a semiconductor laser, the beam characteristics are improved.

In the above method, the bonding between GaN on the protective film is much faster than in the conventional ELOG growth.
The gap becomes thin. The photolithography recognition at the time of forming the ridge, which has been caused by this, has been improved and almost completely performed.

Also, in the growth method (T-ELOG) in which the growth rate of the reaction is reduced, it is possible to obtain a mirror-finished substrate surface with the axis shift set to 0 °.

[Example 2] Further, the method of the present invention
An example of application to ELOG growth (second ELOG) on a single body will be described. After growing the second nitride semiconductor layer 5 in the first embodiment, as shown in FIG.
1 to form a third nitride semiconductor layer 45 which is a selective growth layer. As shown in FIG. 4A, a protective film 41 is provided on the surface of the second nitride semiconductor layer 5 so as to cover the window of the first semiconductor layer 4 which is the underlying layer, and the third nitride A semiconductor layer 45 was grown. At this time, the stripe direction of the protective film 41 was formed parallel to the protective film 1 formed first, and the stripe width was 14 μm and the width of the window was 6 μm.

The obtained nitride semiconductor has good crystallinity similarly to the first embodiment, and also takes a good growth form during its selective growth. Was almost uniform. According to this method, the cavity can be cleaved in the cleavage step (M
Surface), beam characteristics, yield, and the like of an element obtained from a nitride semiconductor are dramatically improved.

As described above, in the present invention, the second nitride semiconductor layer 5 may be formed twice or more times. At this time, the second formed already as in the above embodiment is used.
It is preferable to form the protective film 1 so as to cover the window portion of the nitride semiconductor layer 5 because the propagation of crystal defects from the window portion having relatively poor crystallinity can be prevented. Further, in the present invention, since the width of the protective film 1 that can be formed can be widened, as shown in FIG.
May be formed to an extent sufficient to cover the window underneath, and the width of the protective film 1 may be narrower than the first time.

Embodiment 3

Using the nitride semiconductor obtained in Example 1 as a substrate, layers described below are laminated to form a laser device shown in FIG.

The selective growth layer formed on the heterogeneous substrate 101 in Example 1 is used as a nitride semiconductor substrate 102 of each layer to be formed below. First, undoped GaN 104 is grown to a thickness of 15 μm thereon, which is also used as a nitride semiconductor substrate.

(N-side contact layer 105) Next, using ammonia and TMG, and silane gas as an impurity gas, Si
An n-side contact layer 105 made of GaN doped with 10 ¹⁸ / cm ³ is grown to a thickness of 4 μm.

(Crack preventing layer 106) Next, TMG,
Using TMI (trimethylindium) and ammonia,
The temperature was set to 800 ° C. and the In ₀ . ₀₆ Ga ₀ . _A crack preventing layer 106 made of 94N is grown to a thickness of 0.15 μm. The crack prevention layer can be omitted.

(N-side cladding layer 107)
At 0 ° C., using TMA (trimethylaluminum), TMG and ammonia, undoped Al ₀ . ₁₆ Ga ₀ . ₈₄
A layer of N is grown to a thickness of 25 ° followed by TMA
Is stopped, silane gas is flowed, and Si is reduced to 1 × 10 ¹⁹ / c.
m ³ doped with n-type made of GaN layer is grown to the thickness of 25 Å. These layers are alternately stacked to form a superlattice layer, and an n-side cladding layer 107 made of a superlattice having a total film thickness of 1.2 μm is grown.

(N-side light guide layer 108) Subsequently, the silane gas is stopped, and n
The side light guide layer 108 is grown to a thickness of 0.1 μm.
The n-side light guide layer 108 may be doped with an n-type impurity.

(Active Layer 109) Next, the temperature was raised to 800 ° C.
And Si-doped In₀.₀₅Ga₀.₉₅Consisting of N
A barrier layer is grown to a thickness of 100 ° followed by the same temperature
And undoped In₀. ₂Ga₀.₈Well layer made of N
Is grown to a thickness of 40 °. Two times for the barrier layer and the well layer
Alternately stacked, finally ending with a barrier layer, total thickness 380Å
Of an active layer having a multiple quantum well structure (MQW).
The active layer may be undoped as in this embodiment, or
An n-type impurity and / or a p-type impurity may be doped.
Impurities may be doped into both the well layer and the barrier layer.
One of them may be doped. Here, n is applied only to the barrier layer.
Doping with a type impurity tends to lower the threshold value.

(P-side cap layer 110)
Raise to 050 ° C, TMG, TMA, ammonia, Cp ₂
Using Mg (cyclopentadienyl magnesium), p
P-type A doped with 1 × 10 ²⁰ / cm ^{3 of} Mg, which has a larger band gap energy than the side light guide layer 111
l ₀ . ₃ Ga ₀ . _A p-side cap layer 107 of 7N is grown to a thickness of 300 °.

(P-side light guide layer 111) Subsequently, Cp ₂ M
g, TMA is stopped, and at 1050 ° C., a p-side optical guide layer 111 made of undoped GaN having a band gap energy smaller than that of the p-side cap layer 110 is grown to a thickness of 0.1 pm.

(P-side cladding layer 112)
At 0 ° C., undoped Al ₀ . ₁₆ Ga ₀ . _A layer of 84N is grown to a thickness of 25 ° followed by Cp ₂ Mg, TM
A is stopped, a layer of undoped GaN is grown to a thickness of 25 °, and a p-side cladding layer 112 of a superlattice layer having a total thickness of 0.6 μm is grown. p-side cladding layer 112
In the case where a superlattice in which at least one includes a nitride semiconductor layer containing Al and the bandgap energies are different from each other is formed using a superlattice, one of the layers is heavily doped with impurities, so-called modulation doping. , The crystallinity tends to be improved. However, both may be doped in the same manner. The p-side cladding layer 112
1, preferably a nitride semiconductor layer containing AI _x Ga _1-x
It is desirable to have a superlattice structure including N (0 <X <1), and more preferably a superlattice structure in which GaN and AIGaN are stacked. When the p-side cladding layer 112 has a superlattice structure, the Al mixed crystal ratio of the entire cladding layer can be increased. This reduces the refractive index of the cladding layer itself and further increases the band gap energy, which is very effective in lowering the threshold value. Further, by using the superlattice, the number of bits generated in the cladding layer itself is reduced as compared with the case where the superlattice is not used.

(P-side contact layer 113) Finally, 10
At 50 ° C., 1 × 1 Mg was added on the p-side cladding layer 109.
A p-side contact layer 113 made of p-type GaN doped with 0 ²⁰ / cm ³ is grown to a thickness of 150 °. p-side contact layer of p-type _{In X Al Y Ga 1-X} -Y N (0
.Ltoreq.X, 0.ltoreq.Y, and X + Y.ltoreq.1). Preferably, the p-electrode 12
The most favorable ohmic contact with 0 is obtained. Since the contact layer 113 is a layer for forming an electrode, 1 × 10
It is desirable to have a high carrier concentration of ¹⁷ / cm ³ or more. If it is lower than 1 × 10 ¹⁷ / cm ^3, it tends to be difficult to obtain an electrode and a preferable ohmic. Further, when the composition of the contact layer is GaN, it becomes easy to obtain a preferable ohmic material with the electrode material.

The wafer on which the nitride semiconductor has been grown as described above is taken out of the reaction vessel, and a protective film made of SiO ₂ is formed on the surface of the uppermost p-side contact layer.
Etching is performed by SiCl ₄ gas using RIE (reactive ion etching) to expose the surface of the n-side contact layer 105 where the n-electrode is to be formed. In order to etch a nitride semiconductor deeply, SiO ₂ is optimal as a protective film.

Next, a ridge stripe having a width of 2 μm is formed in the stripe-shaped waveguide region by etching so that the thickness of the p-side cladding layer becomes 0.01 μm.
At this time, as described above, the second nitride semiconductor layer has a crystallinity distribution in a direction perpendicular to the stripe of the protective film, and the waveguide region is formed on the protective film having relatively good crystallinity. By being formed, the element has good element durability. In the case where the second nitride semiconductor layer has a gap at the time of bonding, it is preferable to form a waveguide region so as to avoid the upper part of the gap, whereby crystal defects extending from the gap can be prevented. .

After the formation of the ridge stripe, a protective film made of ZrO ₂ is formed on the side surfaces of the ridge and on the exposed surface of the p-side cladding layer, and over this, a p-electrode made of Ni / Au is formed on the surface of the p-side contact layer 113. 120 is formed. n
On the surface of the side contact layer 105, n made of Ti / Al
The electrode 121 is formed in a direction parallel to the stripe.

As described above, the sapphire substrate of the wafer on which the n-electrode and the p-electrode have been formed is polished to 70 μm, and then cleaved in a bar shape from the substrate side in a direction perpendicular to the stripe-shaped electrodes. A resonator is formed on a cleavage plane ((11-00) plane, a plane corresponding to a hexagonal side surface = M plane). A dielectric multilayer film made of SiO ₂ and TiO ₂ is formed on the resonator surface, and finally, the bar is cut in a direction parallel to the p-electrode to obtain a laser device as shown in FIG. The resonator length at this time was 800 μm.

The obtained laser device had good device characteristics, had little variation in device characteristics on the wafer, and greatly improved the yield.

Although the semiconductor laser device has been described in the above embodiments, the present invention is not limited to a semiconductor laser.
The present invention can be applied to other nitride semiconductor light emitting devices such as an LED device and a super luminescent diode.

[0077]

According to the method for growing a nitride semiconductor of the present invention, it is possible to obtain a substrate with less warpage and to realize a feature of growing a semiconductor substrate capable of obtaining a device having good characteristics with a high yield. . This is because, in the nitride semiconductor growth method of the present invention, the lateral growth is promoted by controlling the reaction conditions, and the growth layers on the protective film can be joined to fill the void in a short time. That is, a sufficient lateral growth can be obtained at a stage where the growth in the vertical direction is thinner by increasing the growth speed as compared with the related art, so that it is possible to reduce the thickness of the substrate and suppress the warpage. Further, since sufficient lateral growth can be obtained even when the protective film is grown without any misalignment of the protective film, the characteristics of the element obtained from the grown nitride semiconductor are also high in quality and the yield can be improved. You can enjoy the advantage. Thus, the present invention improves the production efficiency by shortening the process and improving the yield by optimizing the conditions for selectively growing a nitride semiconductor on a heterogeneous substrate, and at the same time, adopts a laser or the like. It is also possible to improve the quality at the time.

Further, the method of the present invention can be applied to a method of growing ELOG on GaN alone, that is, a method of further performing second ELOG growth on ELOG. E for multiple
In the case of LOG growth, in the first ELOG growth as well as in the second ELOG growth, the shift of the protective film is eliminated and the second ELOG is grown on 0 ° and grown thereon.
At this time, the lateral growth is promoted and the voids are easily filled.
According to this method, it is possible to cleave the M-plane of GaN perpendicularly to the resonator in the cleavage step, so that it is possible to realize the merit of dramatically improving the beam characteristics, yield, and the like when this is used as an element.

[Brief description of the drawings]

FIG. 1 is a schematic cross-sectional view showing a step of selectively growing a nitride semiconductor.

FIG. 2 is a schematic view showing a state in which a protective film is formed on a heterogeneous substrate.

FIG. 3 is a side view showing a state in which a grown nitride semiconductor is warped.

FIG. 4 is a schematic cross-sectional view showing a step of growing a nitride semiconductor according to one embodiment of the present invention.

FIG. 5 is a schematic cross-sectional view showing a main structure of a laser device according to one embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Protective film 2 ... Different kind of substrate 3 ... Orientation flat surface 4 ... 1st nitride semiconductor layer 5 ... 2nd nitride semiconductor layer 6 ... Void 41 ... Protective film 45: third nitride semiconductor layer 101: heterogeneous substrate 102: nitride semiconductor substrate 104: GaN 105: n-side contact layer 106: crack preventing layer 107 N-side cladding layer 108 n-side light guide layer 109 active layer 110 p-side cap layer 111 p-side light guide layer 112 p-side cladding layer 113 p Side contact layer 120 ... p electrode 121 ... n electrode

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 5F045 AA04 AB14 AC08 AC12 AF02 AF09 BB11 DA53 DB02 EE12 5F073 AA13 AA74 CA07 CA17 CB05 DA05 DA07 DA32

Claims (13)

[Claims] A step of growing a first nitride semiconductor layer on a heterogeneous substrate made of a material different from a nitride semiconductor; and forming a first nitride semiconductor layer partially on a surface of the first nitride semiconductor layer.
Forming a protective film having a property on the surface of which the nitride semiconductor is unlikely to grow, heating a base layer composed of the first nitride semiconductor layer and the protective film, and forming a nitrogen source on the surface of the base layer. And supplying a group 3 source gas together with a carrier gas to grow a continuous second nitride semiconductor layer on the protective film and the underlayer. The method for growing a nitride semiconductor, wherein the nitrogen source gas has a concentration of 5 to 6 slm and the group 3 source gas has a concentration of 80 to 130 sccm. 2. The method for growing a nitride semiconductor according to claim 1, wherein the gas of the Group 3 source is trimethylgallium. 3. The method for growing a nitride semiconductor according to claim 1, wherein said nitrogen source gas is ammonia. 4. The concentration of the nitrogen source gas is 5.6 sl.
The method for growing a nitride semiconductor according to any one of claims 1 to 3, wherein m and the concentration of the gas of the Group 3 source are 100 sccm. 5. A step of growing a first nitride semiconductor layer on a heterogeneous substrate made of a material different from a nitride semiconductor; and forming a first nitride semiconductor layer partially on a surface of the first nitride semiconductor layer;
Forming a stripe-shaped protective film having a property on which a nitride semiconductor is unlikely to grow on the surface perpendicular to the orientation flat surface of the heterogeneous substrate; and forming a protective film composed of the first nitride semiconductor layer and the protective film. The formation layer is heated, and the surface of the underlayer has a concentration of 5 to 6 slm.
Supplying a gas of a nitrogen source and a gas of a group 3 source having a concentration of 80 to 130 sccm together with a carrier gas to grow a continuous second nitride semiconductor layer on the protective film and the underlayer. And a method for growing a nitride semiconductor. 6. The supply of the carrier gas is 2-3 scc.
m, the thickness of the second nitride semiconductor layer is 1 μm to 1
2. The method according to claim 1, wherein the layer is grown to a thickness of 0 μm.
Or the method for growing a nitride semiconductor according to 5. 7. The method for growing a nitride semiconductor according to claim 5, wherein a stripe width of the protective film is 10 μm or more. 8. The ratio Ww / Ws of the stripe width Ws of the protective film to the width Ww of the window without the protective film is 0.2 to 0.2.
8. The method for growing a nitride semiconductor according to claim 7, wherein the range is 0.5. 9. The method for growing a nitride semiconductor according to claim 1, wherein the carrier gas is a hydrogen gas. 10. The method for growing a nitride semiconductor according to claim 1, wherein the heterogeneous substrate is sapphire, spinel, or silicon carbide. 11. The method for growing a nitride semiconductor according to claim 1, wherein the warpage of the entire substrate of the manufactured nitride semiconductor is suppressed to 100 μm or less. 12. The method for growing a nitride semiconductor according to claim 1, wherein the time for growing said second nitride semiconductor layer is 300 minutes or less. 13. The nitride semiconductor device according to claim 1, wherein another nitride semiconductor substrate is further grown on said nitride semiconductor substrate grown by said method using said method. Method of growing semiconductors.