JP2000277437A - Growth method for nitride semiconductor and element thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a growth method for a nitride semiconductor wherein such nitride semiconductor substrate is provided as, when a device structure is formed with a nitride semiconductor as a substrate, no chipping or cracking occurs with the substrate even if a resonance surface is formed by beveling, for better life characteristics while dislocation is so reduced as to improve reliability of an element at actual use, and to provide a nitride semiconductor element which is excellent in such element characteristics as life characteristics with the one provided by that growth method for nitride the semiconductor as a substrate. SOLUTION: A first nitride semiconductor 2 is grown on a nitride semiconductor substrate 1 by such method as dislocation is reduced by using the lateral growth of a nitride semiconductor (method for forming a first protective film 11 or first rough 13). A device structure is formed to grow a nitride semiconductor element on the first nitride semiconductor 2 thus provided.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a nitride semiconductor (In).
_{X Al Y Ga 1-XY N} , 0 ≦ X, 0 ≦ Y, relates to a method of growing X + Y ≦ 1), in particular a method for the growth of small nitride semiconductor dislocation. Further, the present invention provides a nitride semiconductor (In _x Al _Y Ga _1- ) used for a light emitting element such as a light emitting diode or a laser diode, or a light receiving element such as a solar cell or an optical sensor using the substrate made of the nitride semiconductor. _XY N, 0 ≦
X, 0 ≦ Y, and X + Y ≦ 1).

[0002]

2. Description of the Related Art In recent years, blue and blue-green light emitting diodes (LEDs) and laser diodes (L
D) has been put to practical use or has become practical.

[0003] For example, the present inventors have proposed that Applide Physics L
Vol.73, Number6 (1998) pp.832-834 describes that a 0.1 μm thick GaN layer was grown on sapphire to a thickness of 2 μm by metal organic chemical vapor deposition (MOCVD).
a protective film made of SiO _{2 having} a thickness of m
After that, GaN is again MOCVD on the surface having the protective film.
Is grown to a film thickness of 20 μm (ELOG growth), followed by hydride vapor phase epitaxy (HVPE).
GaN having a thickness of about 0 μm is grown, and then the sapphire substrate is removed by polishing.
An N substrate is obtained, a device structure is formed on the GaN substrate, and the M plane of the GaN substrate [a hexagonal side surface;
-100 ° etc.] and a nitride semiconductor device formed by forming a resonance surface. The reported laser element has a good far-field pattern of laser light from the resonance surface formed by cleavage, and has an operating current adjusted so as to have an output of 5 mW.
Continuous oscillation for 0 hours becomes possible.

[0004]

However, the above Ap
The nitride semiconductor device reported to pl.Phys.Lett.
Although there is a possibility of practical use of a laser element, the life characteristics are not sufficiently satisfactory for practical use.
The above reported laser device can continuously oscillate at a high temperature for a considerably long time. I can guess.

As a result of various studies for further improving the life characteristics, the present inventors have found that the surface of a nitride semiconductor substrate on which a device structure is grown has a substantially uniform surface according to a surface transmission electron microscope (surface TEM) observation. 1 × 10 ⁷ pieces / cm ²
A degree of dislocation was confirmed, and it was considered that this dislocation might deteriorate the life characteristics. Although the above dislocation density is considerably reduced as compared with the case where GaN is grown on a conventional sapphire substrate, the life characteristics are further improved in order to ensure sufficient reliability of the device in practical use. There is a need.

The reason why dislocations are observed almost uniformly on the surface of the nitride semiconductor substrate is that HVPE is used to improve the physical strength at the time of cleavage and to prevent chipping or cracking.
In the process of growing the nitride semiconductor to a thickness of m, the dislocations seen above the portion where the protective film is not formed (window portion)
It can be inferred that it spreads uniformly with the growth of the nitride semiconductor.

By the way, when a nitride semiconductor is grown to a thickness of 20 μm by MOCVD after forming the protective film,
Almost 1 × 10 ⁹ dislocations / cm ² are observed in the upper part of the window, while almost no dislocations are observed in the upper part of the protective film. Suppose the device structure,
In particular, when a ridge-shaped stripe is formed, the life characteristics are improved. However, in order to remove sapphire from a 20 μm-thick nitride semiconductor and form a resonance surface by cleavage, a 20 μm-thick nitride semiconductor substrate does not have sufficient physical strength and causes chipping or cracking. Yield decreases.
Further, the physical strength of the nitride semiconductor substrate is also required when forming a device structure. As described above, removing the sapphire and forming the device structure on the nitride semiconductor-only substrate enables a simple method of cleavage capable of obtaining a mirror-like resonance surface. The film must be grown to a thickness that provides sufficient physical strength at the time of the device process. For this reason, almost no dislocations obtained by ELOG growth are lost from the surface of the nitride semiconductor substrate. As described above, in order to improve the life characteristics of a laser element, it is desired to further reduce the dislocation density of a nitride semiconductor substrate for forming a device structure.

Therefore, an object of the present invention is to provide a nitride semiconductor substrate, in which a chip is not chipped or cracked even when a device structure is formed or a resonance surface is formed by cleavage. Another object of the present invention is to provide a method of growing a nitride semiconductor, which can provide a nitride semiconductor substrate with reduced dislocations, which can improve the life characteristics and improve the reliability of the element in practical use. It is a further object of the present invention to provide a nitride semiconductor device having good device characteristics such as lifetime characteristics, using a nitride semiconductor obtained by the nitride semiconductor growth method of the present invention as a substrate.

[0009]

That is, the present invention can achieve the object of the present invention by the following constitutions (1) to (16). (1) A first step of growing a first nitride semiconductor on a nitride semiconductor substrate by a method of reducing dislocations by utilizing lateral growth of the nitride semiconductor (E in the first step)
LOG growth). (2) The first step is a step in which the first step is performed on a nitride semiconductor substrate.
(1) The method for growing a nitride semiconductor according to (1), wherein the first protective film is partially formed, and then the first nitride semiconductor is grown on the surface on which the first protective film is formed. . (3) The first protective film is formed in the M-axis direction of the nitride semiconductor substrate, <1-100>, <10-10>, and <01-1.
0>, wherein the nitride semiconductor layer has a stripe shape formed in a direction parallel to any of the M-axis directions. (4) In the first step, first irregularities are formed on the surface of the nitride semiconductor substrate, and then the first nitride semiconductor is grown on the surface having the first irregularities. (1) The method for growing a nitride semiconductor according to (1). (5) The first unevenness is in the M-axis direction of the nitride semiconductor substrate, <1-100>, <10-10>, and <01-10.
<4> The method for growing a nitride semiconductor according to the item (4), wherein the stripe shape is formed in a direction parallel to the M-axis direction. (6) The nitride semiconductor substrate has a surface with a dislocation density of 10 ¹⁰ / cm ² or less (1).
3. The method for growing a nitride semiconductor according to item 1. (7) The nitride semiconductor substrate has a thickness of 50 to 1000 μm.
The method for growing a nitride semiconductor according to any one of (1) to (6), having a film thickness of: (8) The dislocation using a lateral growth of the nitride semiconductor at a growth rate of 10 μm / hour or less and 0.5 μm / hour or more, wherein the nitride semiconductor substrate is formed on a heterogeneous substrate made of a material different from the nitride semiconductor. Step of Growing a Second Nitride Semiconductor by the Method of Reducing the ELO (ELO of the Second Step)
G growth) and, after the second step, a third film having a growth rate of not more than 500 μm / hour and not less than 10 μm / hour on the second nitride semiconductor and having a thickness larger than the thickness of the second nitride semiconductor. It is characterized by comprising a third nitride semiconductor obtained by a third step of growing a nitride semiconductor and, after the third step, at least a fourth step of removing a heterogeneous substrate (1).
The method for growing a nitride semiconductor according to any one of (1) to (7). (9) After the fourth step, the nitride semiconductor substrate has a growth rate of 500 μm / hour or less of 10 μm or less on a surface opposite to a surface from which the heterogeneous substrate of the third nitride semiconductor is removed.
The nitride according to (8), comprising at least a third nitride semiconductor and a fourth nitride semiconductor obtained by a fifth step of growing a fourth nitride semiconductor at a rate of not less than / hour. Method of growing semiconductors. (10) In the second step, a second protective film is partially formed on the nitride semiconductor grown on the heterogeneous substrate, and then the second protective film is formed on the surface having the second protective film. (8)-characterized by a step of growing a nitride semiconductor.
The method for growing a nitride semiconductor according to any one of (9). (11) The second protective film formed in the second step is formed in a manner such that the M-axis direction of the nitride semiconductor substrate is <1-100.
>, <10-10> or any one of <01-10>
It is a stripe shape formed so as to be parallel to the axial direction, and is formed so as to be parallel to the first protective film or the first unevenness formed in the first step. The method for growing a nitride semiconductor according to (10), wherein (12) The second step forms second irregularities on the nitride semiconductor grown on the heterogeneous substrate, and then grows the second nitride semiconductor on the surface having the second irregularities. The method for growing a nitride semiconductor according to any one of (8) to (9), which is a step. (13) The second unevenness formed in the second step is:
M-axis direction of the nitride semiconductor substrate, <1-100>, <
10-10> and <01-10>, a stripe shape formed so as to be parallel to the M-axis direction of any one of the first unevenness or the first unevenness formed in the first step. (12) The method for growing a nitride semiconductor according to (12), wherein the nitride semiconductor is formed so as to be parallel to the protective film. (14) A nitride semiconductor having reduced dislocations obtained by the method for growing a nitride semiconductor according to any one of (1) to (13) is used as a substrate, and at least n is formed on the nitride semiconductor substrate. A nitride semiconductor device, comprising: a device structure having a p-type nitride semiconductor, an active layer, and a p-type nitride semiconductor. (15) The nitride semiconductor device according to (14), wherein the nitride semiconductor element has a stripe-shaped first protective film or a ridge-shaped stripe formed of stripe-shaped first irregularities parallel to the stripe direction. The nitride semiconductor device as described in the above. (16) The ridge-shaped stripe of the nitride semiconductor element is formed on the upper part of the stripe-shaped first protective film or on the upper part of the concave part of the stripe-shaped first unevenness (14). Or the nitride semiconductor device according to (15).

In other words, according to the growth method of the present invention, dislocation on the surface is reduced by performing ELOG growth in the first step on a nitride semiconductor substrate having a film thickness large enough to form a device structure as described above. In particular, by growing the first nitride semiconductor having a portion where dislocations are hardly observed on the surface, chipping and cracking hardly occur even when cleaved,
In addition, since there is a portion having almost no dislocation, it is possible to provide a good substrate which can prevent deterioration of the element and improve the life characteristics. The substrate is a substrate for forming a device structure. In the present invention, the substrate including the nitride semiconductor substrate in the first step and the first nitride semiconductor with reduced dislocations has a device structure. A substrate to be formed. Hereinafter, it may be simply referred to as the substrate of the present invention.

Conventionally, as shown in the above-mentioned problem, an attempt to reduce dislocations is to suppress the propagation of dislocations before a step of growing a nitride semiconductor into a thick film as a substrate for forming a device structure. Various attempts have been made to turn it off or on.

On the other hand, according to the present invention, on the basis of conventional knowledge, the manufacturing process is seemingly complicated and requires a long time on a nitride semiconductor substrate grown to a thickness large enough to form a device structure. The above problem can be solved by performing ELOG growth that seems to exist. The first nitride semiconductor obtained by performing ELOG growth on the nitride semiconductor substrate has a portion where the dislocation density is reduced and further, there is almost no dislocation. The substrate of the present invention comprising the nitride semiconductor substrate and the first nitride semiconductor,
When a thick nitride semiconductor substrate provides physical strength, and when a device structure is formed on the first nitride semiconductor of the substrate of the present invention, the life characteristics can be improved. Although the method of the present invention seems to complicate the manufacturing process at a glance as described above, the life characteristics can be improved by using the substrate of the present invention, and cracking and chipping are prevented. The yield can be improved, and when the manufacturing process is comprehensively considered, the manufacturing efficiency is improved.

An object of the present invention is to provide a laser device comprising a thick nitride semiconductor with reduced dislocations as a substrate and a device structure formed thereon, as reported in Appl. Phys. Lett. However, the achievement of continuous oscillation for a considerably long time has been newly found as a problem that must be solved in order to achieve practical use and improve reliability. For this reason, even if a nitride semiconductor device obtained by forming a device structure on a nitride semiconductor substrate cannot be used for a long time, It is difficult to find a new subject of the present invention such as how the dislocation of the semiconductor affects the life characteristics.

Still further, in the present invention, a method for reducing dislocations by utilizing the lateral growth of the nitride semiconductor in the first step (hereinafter sometimes referred to as ELOG growth in the first step). However, when a first protective film is partially formed on a nitride semiconductor substrate, and then the first nitride semiconductor is grown on a surface on which the first protective film is formed, dislocation progress is prevented. Preferred for Still further, in the present invention, the first protective film may be formed in a manner that:
A stripe shape formed in a direction parallel to the M-axis direction of any one of <00>, <10-10>, and <01-10> can promote the lateral growth of the nitride semiconductor and propagate the dislocation. It is preferable to suppress Further, when the first protective film is formed in parallel with the second protective film in the form of a stripe or the second unevenness in the form of a stripe described later, the lateral growth of the first nitride semiconductor becomes better. In addition, it is possible to favorably obtain on the first nitride semiconductor, and it is also preferable to reduce dislocations.

Still further, according to the present invention, the ELOG growth in the first step only forms the first irregularities on the surface of the nitride semiconductor substrate, and the first irregularities are formed on the surface having the first irregularities.
It is preferable to grow a nitride semiconductor of the above in that propagation of dislocations is suppressed. In this case, the first protective film as described above is not used. Still further, in the present invention, the first unevenness is in the direction of the M axis of the nitride semiconductor substrate, <1-100>, <1.
When the stripe shape is formed in a direction parallel to the M-axis direction of any one of <10-10> and <01-10>, lateral growth of the nitride semiconductor can be promoted and propagation of dislocations can be suppressed. Preferred.

Furthermore, in the present invention, if the dislocation density of the surface of the nitride semiconductor substrate used in the first step is 10 ¹⁰ / cm ² or less, ELOG growth is performed on the nitride semiconductor substrate. This is preferable for reducing dislocations appearing on the surface of the first nitride semiconductor obtained by the above method. Still further, in the present invention, the nitride semiconductor substrate has a thickness of 50 μm.
When the thickness is from m to 1000 μm, the physical strength in the device step or the cleavage step becomes good, chipping or cracking of the nitride semiconductor substrate is prevented, and it is preferable from the viewpoint of improving the yield when mass-producing elements. .

Further, in the present invention, when the nitride semiconductor substrate is made of at least the third nitride semiconductor obtained from the second to fourth steps, the surface of the third nitride semiconductor Since dislocations have already been reduced to some extent, dislocations are preferably further reduced on the surface of the first nitride semiconductor obtained by performing ELOG growth on this third nitride semiconductor. When growing the third nitride semiconductor by a method of growing at a high rate,
Even if the third nitride semiconductor is grown into a thick film, abnormal growth hardly occurs. Here, the first step in the first step
Is grown on the surface opposite to the surface of the third nitride semiconductor from which the dissimilar substrate has been removed.

Further, in the present invention, the nitride semiconductor substrate may include a third nitride semiconductor obtained through a fifth step after the fourth step, and a fourth nitride semiconductor grown thereon. It is preferable that the substrate be made of, since warpage is reduced and ELOG growth in the first step is performed. That is, when the heterogeneous substrate is removed, the surface state of the growth surface of the third nitride semiconductor is different from the surface state of the removed surface. When the fourth nitride semiconductor is grown on the growth surface of the nitride semiconductor (the surface opposite to the surface on which the heterogeneous substrate is removed), the warpage of the third nitride semiconductor is reduced. By growing the fourth nitride semiconductor after removing the heterogeneous substrate, the physical strength of the nitride semiconductor substrate can be reinforced.

Further, in the present invention, the EL in the second step
OG growth is a step of partially forming a second protective film on a nitride semiconductor grown on a heterogeneous substrate to grow the second nitride semiconductor, or a nitride grown on a heterogeneous substrate. In the step of forming the second unevenness on the semiconductor and growing the second nitride semiconductor, the dislocation of the nitride semiconductor substrate can be reduced, and the first nitride semiconductor having few dislocations can be grown. preferable. Further, in the present invention, the second protective film or the second unevenness formed in the second step is formed by the <1-100>, <10-10>, and <0> of the nitride semiconductor substrate.
1-10> is a stripe shape formed so as to be parallel to any of the M-axis directions, and
Is formed so as to be parallel to the first protective film or the first unevenness formed in the step, the lateral growth of the nitride semiconductor is further promoted and the dislocation of the nitride semiconductor substrate is reduced. In addition, the lateral growth of the first nitride semiconductor grown on the nitride semiconductor substrate in the first step is further improved, which is preferable in terms of reducing dislocations.

Here, when the first protective film and the like are formed, the second protective film and the like have already been removed, but the dislocation distribution does not appear on the surface of the nitride semiconductor substrate from which the heterogeneous substrate has been removed. Observed in a stripe shape, a first protection or the like is formed along the dislocation distribution in the stripe shape. By forming in this manner, the first protective film and the second protective film, or the first protective film and the second unevenness, the first unevenness and the second protective film,
And the second unevenness are parallel to the M-axis direction of the nitride semiconductor. In addition, the orientation flat surface (orientation flat surface) is perpendicular to the M-axis direction of the nitride semiconductor, and by using this orientation flat surface as a reference, the protective film and unevenness used in the first and second steps are reduced. It can be formed as a stripe shape in the parallel direction.

In the present invention, a nitride semiconductor (comprising a nitride semiconductor substrate and a first nitride semiconductor) having reduced dislocations obtained by the method for growing a nitride semiconductor of the present invention is used as a substrate. On this substrate, at least n
When a device structure including a p-type nitride semiconductor, an active layer, and a p-type nitride semiconductor is formed, a nitride semiconductor device having good device characteristics such as life characteristics can be provided. Still further, in the present invention, the nitride semiconductor element
When the first protective film in the form of a stripe or the first unevenness in the form of a stripe has a ridge-shaped stripe formed in parallel to the stripe direction, the nitride semiconductor substrate is cleaved in a plane perpendicular to the M-axis direction. It is preferable because a good mirror-like resonance surface is obtained and the far-field pattern becomes good. Still further, in the present invention, when the ridge-shaped stripe of the nitride semiconductor element is formed on the first protective film or on the concave portion of the first unevenness, the first nitride film is formed on these portions. Since the dislocation on the surface of the product semiconductor tends to be minimized, deterioration of the element is prevented, which is preferable from the viewpoint of improving the life characteristics.

In the present invention, the term “undoped” in the following description refers to a layer formed without intentionally doping an impurity. Even if it is a mixed layer, it is an undoped layer if an impurity is not intentionally doped.

[0023]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail with reference to FIGS. First, FIGS. 1A to 1D are schematic sectional views of a substrate for forming a device structure obtained by the nitride semiconductor growth method of the present invention. With reference to FIG. 1, a method for growing a nitride semiconductor having the first step of the present invention will be described.

The method for growing a nitride semiconductor according to the present invention comprises:
In the step (1), dislocations are reduced on the nitride semiconductor substrate 1 by utilizing lateral growth of the nitride semiconductor (first method).
ELOG growth in the first step), the first
Can be obtained. In the first step, the ELOG growth in the first step of growing the first nitride semiconductor 2 is not particularly limited as long as it is a method of reducing dislocations by utilizing lateral growth of the nitride semiconductor. At any stage of the growth, there is a method in which the lateral growth rate of the nitride semiconductor is promoted with respect to the vertical growth rate of the nitride semiconductor, and the propagation of dislocations is suppressed. It is not clear how dislocations propagate,
Dislocations tend to propagate along the direction of growth of the nitride semiconductor. If the lateral growth of the nitride semiconductor is promoted, the dislocations propagate in the lateral direction. It seems that it tends to be difficult. as a result,
It is estimated that the first nitride semiconductor with reduced dislocations can be grown.

As the ELOG growth in the first step, a conventionally known ELOG growth performed in a step before growing a thick nitride semiconductor substrate may be used. Flat 10-77245, same 10-2
75826, 10-119377, 10-1328
31, 11-37827, 11-37826, 1
EL described in the specification etc. of each item of No. 0-146431
OG growth or the like can be used. However, these E
LOG growth is performed on a heterogeneous substrate, whereas ELOG growth in the first step of the present invention is performed on a thick nitride semiconductor substrate, but is performed in substantially the same manner. be able to.

As a preferred specific example of the ELOG growth in the first step of the present invention, a first material made of a material in which a nitride semiconductor is difficult to grow on a nitride semiconductor substrate or which does not grow is used.
And a method of forming the first unevenness 13 on the nitride semiconductor substrate.
When the first protective film 11 and the first unevenness 13 are formed as described above, and the first nitride semiconductor 2 is grown on the formation surface, any one of the steps of the growth process of the first nitride semiconductor 2 As compared with the vertical growth of the nitride semiconductor, the lateral growth of the nitride semiconductor is promoted, and the dislocations progress in the horizontal direction together with the lateral growth of the nitride semiconductor, and it is difficult to progress in the vertical direction again. As a result, it is considered that the first nitride semiconductor 2 with reduced dislocations can be obtained.

The average dislocation density on the surface of the first nitride semiconductor 2 obtained in this manner is reduced to about 1/100 or less of the average dislocation density on the surface of the nitride semiconductor substrate, which is preferable. Under the conditions, dislocations are hardly observed on the surface of the first nitride semiconductor 2. Further, the distribution of dislocations on the surface of the first nitride semiconductor 2 is such that the dislocations in the upper portion of the first protective film 11 or in the concave portions of the first irregularities 13 are extremely dislocations as compared with other portions (the upper portion of the window or the upper portion of the convex portion). And dislocations are hardly observed according to the observation of the surface TEM, the cathode luminescence (CL) and the like. If the average dislocation density of the first nitride semiconductor 2 decreases as described above, it is possible to improve the life characteristics of an element formed on the first nitride semiconductor 2, and further, to a portion having almost no dislocation, When the ridge-shaped stripe of the element is formed, the life characteristics of the element can be significantly improved. The dislocation density on the surface of the first nitride semiconductor 2 is determined by ELOG performed in the first step.
Depending on the type of growth, the average dislocation density is 1 × 1
0 ⁵ / cm ³ or less, preferably 1 × 10 ⁴ / c
m ³ or less, more preferably 1 × 10 ³ / cm ³ or less under more preferable conditions. Also, the dislocation density above the first protective film 11 and the dislocation above the concave portion of the first unevenness 13 tend to be hardly observed. The upper part of the window and the first irregularities 1
The dislocation density at the top of the convex part of No. ³ is 1 × 10 ⁷ / cm ³ or less,
Under preferable conditions, it is 1 × 10 ⁶ / cm ³ or less, and under more preferable conditions, it is 1 × 10 ⁵ / cm ³ or less. In the present invention, the dislocation density is measured by surface TEM or CL.

In the following, the nitride semiconductor substrate 1 obtained by one embodiment of the case where the ELOG growth is performed using the first protective film 11 and the case where the first unevenness 13 is formed is performed. FIG. 1 is a schematic cross-sectional view of a substrate forming a device structure composed of the first nitride semiconductor 2 and FIG.
This will be described in more detail with reference to (a) to (d). FIG.
(A) to (c) show a mode in which the first protective film 11 is used, and FIG. 1 (d) shows a mode in which the first unevenness 13 is formed. In some cases, the first protective film 11 is used to form concavities and convexities, and a protective film is formed on the bottom of the concave portion and / or on the upper portion of the convex portion. This is described below. First, Figure 1
1A is a schematic cross-sectional view in which a first protective film 11 is formed on a nitride semiconductor substrate 1 and a first nitride semiconductor 2 is grown on the surface on which the first protective film 11 is formed. FIG. 1 (b) shows an example in which unevenness is formed on a nitride semiconductor substrate 1, a first protective film 11 is formed on the bottom of the concave portion and on the upper portion of the convex portion, and a first nitride semiconductor 2 is grown on the formed surface. It is a typical sectional view made to do. FIG. 1 (c) shows a case where irregularities are formed on a nitride semiconductor substrate 1, a first protective film 11 is formed only on the protrusions, and a first nitride semiconductor 2 is grown on the formed surface. FIG. FIG. 1D is a schematic cross-sectional view in which the first unevenness 13 is formed on the nitride semiconductor substrate 1 and the first nitride semiconductor 2 is grown on the formed surface. FIG. 1D shows an embodiment in which the process is performed without using a protective film.

The first nitride semiconductor 2 obtained by the above-described ELOG growth is not particularly limited, but is preferably a nitride semiconductor made of GaN. The first nitride semiconductor 2 may be undoped or doped with impurities. Undoped is preferable in terms of crystallinity.
During LOG growth, p-type impurities (Be, Zn, Mn, Cr
And Mg), and at least one of n-type impurities (Si, Ge and Sn), preferably at least one or more p-type impurities, more preferably at least one or more p-type impurities and at least one of n-type impurities Doping with at least one kind, most preferably Mg and Si, promotes the lateral growth of the nitride semiconductor, which is preferable in terms of reducing dislocations and preventing generation of voids. The doping amount of the impurity is preferably 1
× 10 ¹⁷ / cm ³ to 1 × 10 ¹⁹ / cm ³ , more preferably 1 × 10 ¹⁷ / cm ³ to 1 × 10 ¹⁹ / cm ³ , still more preferably 5 × 10 ¹⁷ / cm ^{3 to} 5 × 10 ¹⁹ / cm. cm ³ . When the impurity concentration is within the above range, lateral growth of the nitride semiconductor can be favorably promoted as compared with vertical growth, which is preferable in terms of suppressing propagation of crystal defects and preventing generation of voids. In the case of doping with a p-type impurity and an n-type impurity, doping is performed with appropriate adjustment so that the sum of the concentrations of the two becomes the doping amount in the above range. In this case, the ratio of the concentration of the p-type impurity to the concentration of the n-type impurity is appropriately adjusted depending on the type of the impurity used so that voids and dislocations can be favorably prevented. When an n-electrode is formed in the first nitride semiconductor 2, doping amounts of the n-type impurity and the p-type impurity, such as doping the n-type impurity or doping the n-type impurity more than the p-type impurity, are used. To adjust.

The thickness of the first nitride semiconductor 2 is not particularly limited, but is preferably 5 μm to 50 μm, and more preferably 10 μm to 35 μm. When the thickness of the first nitride semiconductor 2 is within the above range, the first protective film 11 and the first unevenness 1 formed on the nitride semiconductor substrate 1 are formed.
3 can be satisfactorily covered, the dislocation density on the surface of the first nitride semiconductor 2 becomes lower than the dislocation density on the surface of the nitride semiconductor substrate 1, and the dislocation distribution on the surface of the first nitride semiconductor 2 In particular, the upper part of the first protective film 11 and the first irregularities 13
Almost no dislocation is seen in the upper part of the concave portion.

As a material of the first protective film 11 shown in FIGS. 1A to 1C, a material having a property in which a nitride semiconductor does not grow or hardly grows on the surface of the first protective film 11 is preferable. For example, oxides and nitrides such as silicon oxide (SiO _x ), silicon nitride (Si _x N _y ), titanium oxide (TiO _x ), zirconium oxide (ZrO _x ), and multilayer films of these, and 1200 ° C. or higher And the like having a melting point of. These protective film materials have the property of withstanding the growth temperature of the nitride semiconductor of 600 ° C. to 1100 ° C. and preventing the nitride semiconductor from growing or hardly growing on the surface thereof. In order to form the protective film material on the surface of the nitride semiconductor, for example, a vapor deposition technique such as vapor deposition, sputtering, or CVD can be used.

First, the first protective film 1 in the case of FIG.
The forming method, shape, and the like of No. 1 will be described. In order to partially (selectively) form the first protective film 11 on the nitride semiconductor substrate 1, a photomask having a predetermined shape is manufactured using a photolithography technique, and the photomask is formed through the photomask. The first protective film 11 having a predetermined shape can be formed by vapor-phase deposition of the above material. The shape of the first protective film 11 is not particularly limited, and may be, for example, any one of a dot, a stripe, and a grid shape, preferably a stripe shape. When the first protective film 11 has a stripe shape, the first
It is preferable because the nitride semiconductor 2 can be favorably formed.

The first protective film 11 is formed by adjusting the surface area of the first protective film 11 so as to be larger than the surface area of the portion (window portion) where the first protective film 11 is not formed. Preferably. The adjustment of the surface area of the first protective film 11 and the surface area of the window portion vary depending on the shape of the protective film. Can be performed.

The size of the first protective film 11 is not particularly limited. For example, when the first protective film 11 is formed of a stripe, the preferable stripe width is 0.5 to 100 μm, and more preferably 1.
μm to 50 μm, more preferably 2 to 25 μm.
Further, the stripe pitch (the width of the window portion where the first protective film 11 is not formed) is desirably smaller than the stripe width. Preferably it is 0.8 to 2 μm.

As described above, when the surface area of the first protective film 11 is increased, the propagation of dislocations is suppressed by the first protective film 11, and the propagation of dislocations propagating from the window is further reduced in the lateral direction. It tends to be difficult to propagate in the vertical direction again, and a portion of the surface region of the first nitride semiconductor 2 above the first protection film 11 where dislocations are scarcely observed (a surface-to-surface vicinity) is widely observed. It is preferable because it can be obtained. Further, the surface of the first nitride semiconductor 2 tends to be mirror-like, which is preferable.

The thickness of the first protective film 11 is not particularly limited. However, a thinner protective film 11 is preferable since the first nitride semiconductor 2 having a mirror-like surface and less dislocations can be obtained in a shorter time. For example, although it depends on the material of the protective film, the thickness is, for example, 0.01 to 5 μm, preferably 0.02 to 3 μm.
μm, and more preferably 0.05 to 2 μm.
Within this range, dislocations can be favorably prevented from propagating in the vertical direction, dislocations can be reduced, and the surface of the first nitride semiconductor 2 is preferably mirror-finished. The thickness of the protective film is
Although it depends on the material of the protective film, the first nitride semiconductor 2 can cover the protective film in a shorter time as the thinner, as long as the film quality such as pinholes does not occur even if the film thickness is reduced. It is preferable to obtain a mirror-shaped first nitride semiconductor 2.

Next, as shown in FIG. 2B, in the first step, the unevenness is formed on the nitride semiconductor substrate 1 and the first protective film 11 is formed on the bottom of the concave portion and the upper portion of the convex portion. Will be described.

As a method of forming the unevenness on the nitride semiconductor substrate 1, any method may be used as long as the nitride semiconductor substrate 1 can be partially removed, and examples thereof include etching and dicing. Etching. By etching, nitride semiconductor substrate 1
In the case where the unevenness is partially (selectively) formed, a stripe-like or checkerboard-like photomask is produced using mask patterns of various shapes in photolithography technology, and the resist pattern is changed to a nitride semiconductor substrate. 1 and etched. When dicing is performed, for example, it can be formed in a stripe shape or a grid shape.

In the case where the unevenness is formed on the nitride semiconductor substrate 1 by etching, the etching method is as follows.
There are methods such as wet etching and dry etching, and dry etching is preferably used to form a smooth surface. The dry etching includes, for example, reactive ion etching (RIE), reactive ion beam etching (RIBE), and electron cyclotron etching (E
There are devices such as CR) and ion beam etching, all of which can etch a nitride semiconductor by appropriately selecting an etching gas. For example, a specific nitride semiconductor etching means described in Japanese Patent Application Laid-Open No. H8-17803 previously filed by the present applicant can be used.

When the unevenness is formed by etching, the etched surface has a shape in which the side surface of the recess is substantially perpendicular to the nitride semiconductor substrate 1 as shown in FIG.
Alternatively, the shape may be a normal mesa shape or a reverse mesa shape, or a shape formed so that the side surface of the concave portion of the nitride semiconductor substrate 1 is stepped. As shown in FIG. 1B, when the first protective film 11 is formed on the upper part of the convex part and the bottom part of the concave part as shown in FIG. This is preferable because it is easy to cover, and it is easy to remove the protective film material on the side surface of the concave portion. In the case of FIG.
From the beginning of the OG growth, the first protective film 11 is formed on the bottom of the recess and the top of the projection so that substantially all of the nitride semiconductor growth starts from the lateral growth, and the first nitride film is formed only from the side of the recess. The object semiconductor 2 is grown. Such a reduction in dislocations by adjusting the growth direction is because once a dislocation propagates in the horizontal direction, it tends to be difficult to propagate again in the vertical direction.

The shape of the concavities and convexities in the case of FIG. 1B, that is, the depth and width of the concave portion are shown below. The depth of the concave portion is not particularly limited, but is not less than 500 Å, preferably about 0.5 to 5 μm. When the depth of the concave portion is within the above range, ELOG growth is stable, and the surface of the first nitride semiconductor 2 tends to be mirror-like. When the unevenness is in the form of a stripe, for example, the width of the upper part of the protrusion is the same as the width of the first protective film in the case where the unevenness is not formed, and the width of the opening of the concave part (window) is as follows. Although not particularly limited, it is 2 to 5 μm.

The method of forming the first protective film 11 on the bottom of the concave portion and the upper portion of the convex portion is slightly different depending on whether the method of forming the irregularities is etching or dicing. First, in the case of forming irregularities by etching, after forming a protective film material on the nitride semiconductor substrate 1, a resist film is formed thereon, the pattern is transferred, exposed, and developed to partially form the first.
After the formation of the protective film 11, the nitride semiconductor substrate 1 is etched to form irregularities. Subsequently, on the nitride semiconductor substrate 1 on which the unevenness is formed, that is, the first protective film 1
1. A protective film material is further formed on the top and the bottom of the recess, and CF ₄
The protective film on the side surface of the concave portion of the nitride semiconductor substrate 1 is removed by dry etching using O ₂ gas and O ₂ gas to expose the side surface of the concave portion. As shown in FIG. And formed on the upper part of the projection. When formed in this manner, for example, in FIG. 1B, the first protective film 11 is illustrated as a single layer, but a further protective film is formed on the first protective film 11 above the convex portion, and two layers are formed. It is in a state where the protective films are stacked. Here, before forming the first protective film 11 on the bottom of the concave portion, the first protective film 11 on the upper portion of the convex portion is formed.
After the removal, the protective film material may be simultaneously formed on the convex portion upper portion and the concave portion bottom portion.

Next, when forming irregularities by dicing,
Irregularities are formed on the nitride semiconductor substrate 1 from above by a dicing saw using a dicing saw, and then a protective film is formed thereon, and the concave side surfaces are exposed by dry etching with CF ₄ and O ₂ gas. As described above, the first protective film 11 is formed in a desired shape and position by removing the protective film by etching.

The thickness of the first protective film 11 formed on the upper and lower portions of the convex portions of the concave and convex portions is not particularly limited. It is preferable that the film thickness is such that the side surfaces can be exposed by removing the film and that the bottom surface of the concave portion can be covered. The thickness of the first protective film 11 is
It is preferable that the first nitride semiconductor 2 is adjusted so as to grow easily in the lateral direction. In some cases, the thickness of the first protective film 11 at the bottom of the concave portion and the upper portion of the convex portion may be different.

The state of the first nitride semiconductor 2 by ELOG growth in the case of FIG. 1B will be described. First, the first nitride semiconductor 2 starts growing laterally from the exposed side surface of the concave portion where the first protective film 11 is not formed. And the first grown from the side surface of the adjacent concave portion
Nitride semiconductor 2 continues to grow while being bonded so as to cover the first protective film 11 at the bottom of the concave portion. When the nitride semiconductor 2 grows at substantially the same height as the first protective film 11, the nitride semiconductor 2 Thus, the first nitride semiconductor 2 as shown in FIG. 1B can be grown by covering the first protective film 11 by growing in the direction. In the process of the ELOG growth, the dislocation propagates in the lateral direction along with the lateral growth of the nitride semiconductor. Therefore, the dislocation propagating in the vertical direction is drastically reduced. I can't see it.

Next, as shown in FIG. 1 (c), a case where the first protective film 11 is formed only on the upper portions of the uneven portions formed on the nitride semiconductor substrate 1 will be described. In this case, as in the case of FIG. 1B described above, the method of forming the irregularities is formed by dicing or etching, and the shape of the side surface of the concave portion is also the same.

As shown in FIG. 1C, the side surface and the bottom surface of the concave portion of the nitride semiconductor substrate 1 are exposed as surfaces on which the growth is possible, and the first protective film 11 is formed on the upper surface of the convex portion. The growth of the nitride semiconductor from above is suppressed. When the first nitride semiconductor 2 is grown in such a state, it is considered that the growth starts from the side surface of the concave portion and the bottom portion of the concave portion at the start of the growth. However, as the semiconductor grows, the growth of the nitride semiconductor that has started to grow vertically from the bottom of the recess is blocked by the nitride semiconductor that has grown laterally from the side surface of the recess. As a result, the nitride semiconductor that has grown laterally on the first protective film 11 and covers the first protective film 11 is the nitride semiconductor that has started to grow laterally from the side surface of the concave portion, as shown in FIG. Thus, the first nitride semiconductor 2 having a thick film is obtained. In the first nitride semiconductor 2 obtained, propagation of dislocations is favorably suppressed as described above.

In the case where the first protective film 11 is not formed on the bottom of the concave portion shown in FIG. 1C, the size of the concave and convex shape is such that the growth of the nitride semiconductor on the side surface of the concave portion of the nitride semiconductor substrate 1 depends on the bottom of the concave portion. It is formed so as to be prioritized with respect to the growth in. 1C, preferably, the length of the side surface of the nitride semiconductor substrate 1 on the concave side [d in FIG. 1C] and the width of the opening of the concave [FIG.
(C) is formed by adjusting w], more preferably, the nitride semiconductor substrate 1 with the uneven shape exposed.
The relationship between the length (d) of the side surface of the concave portion and the width (w) of the opening of the concave portion, w / d is 0 <w / d ≦ 5, more preferably 0 <
When formed so as to satisfy w / d ≦ 3, most preferably 0 <w / d ≦ 1, the growth rate can be controlled well, and the growth from the side surface of the concave portion of the nitride semiconductor substrate 1 can be further promoted. As a result, the growth of the nitride semiconductor from the bottom of the concave portion is easily interrupted, and the first nitride semiconductor 2 with few dislocations is easily obtained.

The shape of the surface on which the first protective film 11 is formed above the convex portions of the formed concavities and convexities is not particularly limited. The shape of the formed nitride semiconductor substrate 1 as viewed from above may be formed in a random depression, stripe, grid, dot, or the like, and is preferably a stripe. For example, when the unevenness is in the form of a stripe, the width of the stripe at the upper part of the protrusion is 10 to 10 as the shape of the stripe.
20 μm, stripe interval (opening of concave portion) 2 to 5 μm
It may be m.

Next, as shown in FIG. 1D, a case where only the first unevenness 13 is formed and the first protective film 11 is not formed will be described. 1D, the first unevenness 13 is formed by dry etching, dicing, or the like as in the case of forming the unevenness in FIGS. 1B and 1C. The shape of the side surface of the concave portion is the same as above. However, the case of FIG. 1D is different from the above in that the protective film is not formed, and that point is described below. First, when the first irregularities 13 are formed by etching,
It can be formed by preparing a stripe-shaped or grid-shaped photomask using mask patterns of various shapes in the photolithography technique, forming a resist pattern on the first nitride semiconductor 2, and etching.
Then, after forming the irregularities by etching, the photomask above the convexities is removed, and only the first irregularities 13 can be formed on the nitride semiconductor substrate 1. In the case of performing dicing, a photomask is not used as in the case of etching, so that unevenness can be formed in the same manner as in FIG. 1B and the like.

The shape of the first unevenness 13 is not particularly limited, and may be a random depression, a stripe shape, a grid shape, a dot shape, or the like, as in FIGS. 1B and 1C. In order to promote the lateral growth of the nitride semiconductor and reduce dislocations, it is preferable to use a stripe shape.
The size of the shape of the first irregularities 13, that is, the length of the side surface of the concave portion, the width of the upper portion of the convex portion, and the width of the bottom portion of the concave portion are not particularly limited. It is preferable that the first nitride semiconductor 2 growing from a portion to a thick film is adjusted so as to grow laterally from the side surface of the concave portion. When the shape of the first unevenness 13 is a stripe shape, the stripe shape is, for example, a stripe width (width of the upper portion of the convex portion) of 3 to 20 μm and a stripe interval (width of the lower portion of the concave portion) of 3 to 20 μm. can do. Increasing the portion of the first nitride semiconductor 2 that grows from the opening of the concave portion can be achieved by increasing the width of the bottom portion of the concave portion and decreasing the width of the upper portion of the convex portion. In this manner, dislocations are reduced. Can be more. When the width of the bottom of the recess is increased, it is preferable to increase the depth of the recess in order to prevent the growth in the vertical direction that may grow from the bottom of the recess.

In the case of FIG. 1D, the first nitride semiconductor 2
Starts growing from the top of the first uneven portion 13 and the bottom of the concave portion, but the lateral growth from the side surface of the concave portion is promoted as compared with the vertical growth from the vertical direction from the bottom of the concave portion.
What has grown from the side surface inside the recess joins to suppress growth from the bottom. As a result, dislocations are hardly observed at the upper portion of the opening of the concave portion. On the other hand, the first nitride semiconductor 2 growing from the upper portion of the convex portion tends to grow vertically and laterally toward the opening of the concave portion. In the vertical growth, propagation of dislocations is difficult to be suppressed, but in growth toward the opening of the concave portion, the propagation of dislocations tends to be suppressed since the dislocations propagate in the horizontal direction. As a result, the dislocation of the first nitride semiconductor 2 on the protrusion is also reduced. In the case of FIG. 1D, almost no dislocations are found in the upper portion of the concave portion, but it is slightly larger in the upper portion of the convex portion depending on conditions (for example, growth conditions such as dislocation density and reaction conditions of the nitride semiconductor substrate 1). Since dislocations are seen in the ridge, it is preferable to form a ridge-shaped stripe above the opening of the concave portion from the viewpoint of life characteristics. Alternatively, the ELOG growth in FIG. 1D is performed again on the first nitride semiconductor 2, in which case the first nitride semiconductor substrate 1 is formed such that the first concave portion formed on the nitride semiconductor substrate 1 has a convex portion. It is preferable to form irregularities on the nitride semiconductor 2 from the viewpoint of reducing dislocations.

The EL shown in FIGS. 1 (a), 1 (b) and 1 (c)
In the case of OG growth, EL is again formed on the first nitride semiconductor 2.
OG growth may be performed. When ELOG growth is performed again, the position where a new protective film is formed is the first nitride semiconductor 2
When dislocations appear on the surface of the substrate, it is preferable to form dislocations on such portions, for example, on the surface of the upper portion of the window where the first protective film 11 is not formed, from the viewpoint of reducing dislocations. Such ELOG growth may be repeated two or more times. Dislocations tend to be able to further suppress the propagation of dislocations by repeating ELOG growth.

In the first step, the method for growing the first nitride semiconductor 2 is not particularly limited.
OVPE (metalorganic vapor phase epitaxy), HVPE (hydride vapor phase epitaxy), MBE (molecular beam epitaxy),
All known methods for growing nitride semiconductors, such as MOCVD (metal organic chemical vapor deposition), can be applied. As a preferable growth method, when the film thickness is 50 μm or less, the growth rate is easily controlled by using the MOCVD method. When the film thickness is 50 μm or less, HVPE has a high growth rate and is difficult to control.

The substrate for forming a device structure composed of the nitride semiconductor substrate 1 and the first nitride semiconductor 2 obtained in the first step has few dislocations, and particularly has an upper portion of the first protective film 11 and a lower portion. It is hardly seen above the concave portion of the first unevenness 13, and the life characteristics of the element can be improved. Further, when cleavage is performed perpendicularly to the M-axis direction of the nitride semiconductor, a good cleavage plane is obtained, and at the time of cleavage, chipping or cracking of the substrate hardly occurs, and the yield can be improved.

Further, the first protective film 11 and the first unevenness 13 in FIGS. 1 (a), 1 (b), 1 (c) and 1 (d) are shown.
Is a stripe shape, and the stripe is in the M-axis direction of the nitride semiconductor substrate 1, <1-100>,
When formed in a direction parallel to the M-axis direction of either <10-10> or <01-10>, it is preferable to promote the lateral growth of the nitride semiconductor and to suppress the propagation of dislocations. . In addition, as described above, almost no dislocations are found on the first protective film 11 and on the first nitride semiconductor surface above the concave portions of the first unevenness 13. It is preferable to form a ridge-shaped stripe in the non-existing portion to improve the life characteristics. Further, when the ridge-shaped stripe is formed as described above, even when the resonance surface is formed by cleavage, it can be cleaved perpendicularly to the M-axis direction of the nitride semiconductor substrate 1, and a good mirror surface can be obtained. This is preferable because a resonance surface can be easily obtained.

Next, the nitride semiconductor substrate 1 for growing the first nitride semiconductor 2 by ELOG growth in the first step will be described. In the present invention, the nitride semiconductor substrate 1 is not particularly limited. However, after forming the first nitride semiconductor 2, when forming a device structure on this formation surface, or when forming a resonance surface by cleavage, or the like, It is preferable that the first nitride semiconductor 2 has a physical strength and a film thickness to the extent that chipping, cracking, and the like are not easily generated, and easily reduces the dislocation of the first nitride semiconductor 2 obtained in the first step. Specifically, a preferable nitride semiconductor substrate 1 is one having a dislocation density of 10 ¹⁰ / cm ³ or less, more preferably 10 ⁹ / cm ³ or less, on the surface on which the first nitride semiconductor is grown. When the dislocation density is in the above range, it is preferable to reduce the dislocation of the first nitride semiconductor 2 grown by ELOG growth on the nitride semiconductor substrate. Further, when the dislocation is small, the physical strength is also improved, which is preferable in terms of preventing chipping and cracking.
The nitride semiconductor substrate 1 preferably has a thickness of 50
μm to 1000 μm, more preferably 80 μm to
It is 500 μm. With such a thickness, the physical strength of the nitride semiconductor substrate 1 is improved, which is preferable in terms of yield and the like. The composition of the nitride semiconductor substrate 1 is not particularly limited, but a nitride semiconductor made of GaN is exemplified. The nitride semiconductor substrate 1 may be undoped or doped with impurities. When the n-electrode is formed on the nitride semiconductor substrate 1, the nitride semiconductor substrate 1
Is doped with an n-type impurity to have ohmic contact. It is preferable that the nitride semiconductor substrate 1 is undoped from the viewpoint of crystallinity.

In the present invention, a method for forming the nitride semiconductor substrate 1 is not particularly limited, but a method including a method for reducing dislocations by utilizing lateral growth of the nitride semiconductor is preferable. For example, as a specific method, a method for obtaining a substrate having at least a third nitride semiconductor preferably obtained in the second to fourth steps is mentioned, and more preferably obtained in the second to fifth steps. At least third
To obtain a substrate having the nitride semiconductor and the fourth nitride semiconductor. When removing the heterogeneous substrate, the second nitride semiconductor may be removed from the buffer layer or may remain, but is preferably removed from the viewpoint of warpage and cleavage.

If the nitride semiconductor substrate 1 of the present invention is a third nitride semiconductor, it becomes a nitride semiconductor substrate 1 with reduced dislocations and good crystallinity. It is preferable in terms of reduction of crystallinity and improvement of crystallinity. Further, when the nitride semiconductor substrate 1 is a third and a fourth nitride semiconductor, there is a tendency that warpage occurs because the surface states of the removed surface and the growth surface of the third nitride semiconductor are different. By growing a fourth nitride semiconductor on the above-mentioned nitride semiconductor, the warpage can be reduced, which is preferable in that the ELOG growth in the first step is favorably performed. After the fifth step,
The third nitride semiconductor may be polished from the side from which the third nitride semiconductor has been removed, and the nitride semiconductor substrate 1 may be made only of the fourth nitride semiconductor. If only the fourth nitride semiconductor is used, the third and fourth nitride semiconductors may be used. Since the cause of an adverse effect on the device characteristics due to an oxide film or the like that may be formed at the boundary with the semiconductor can be removed, it is preferable from the viewpoint of improving the device characteristics.

The second step will be described below in order with reference to FIGS. In the second step, as shown in FIG. 2, the lateral growth of the nitride semiconductor is performed at a growth rate of 10 μm / hour or less and 0.5 μm / hour or more on a heterogeneous substrate 21 made of a material different from the nitride semiconductor. This is a step of growing the second nitride semiconductor 22 by using a method of reducing dislocations (ELOG growth in the second step). The growth rate for growing the second nitride semiconductor 22 is 10 μm as described above.
0.5 μm / hour or less, preferably 7 μm or less
/ Hr or less 1 μm / hr or more, more preferably 5 μm / hr
The time is 1.5 μm / hour or less. When the growth rate is within the above range, the propagation of dislocations can be favorably suppressed during the ELOG growth in the second step, and the second nitride semiconductor 22
It is preferable to adjust the thickness of the film. A specific growth method having such a growth rate is, for example, MOCVD.

In the second step, the heterogeneous substrate 21 may be any substrate as long as it is made of a material different from that of the nitride semiconductor. For example, the main surface is a C surface, an R surface, or an A surface. sapphire insulating substrate such as spinel (MgA1 ₂ O _4), (including 6H, 4H, and 3C) SiC, ZnS, ZnO, GaAs, Si, and the oxide substrate or the like to the nitride semiconductor and the lattice matching, conventionally known A substrate material capable of growing the nitride semiconductor used can be used. Further, a substrate in which the main surface of the dissimilar substrate 21 is off-angled, more preferably, a substrate in which the main surface is off-angled in a step shape, can be used. As described above, when the main surface of the heterogeneous substrate is off-angle, the number of dislocations is further reduced.

[0062] The second nitride semiconductor 22 is not particularly limited, but is preferably a nitride semiconductor made of GaN. The second nitride semiconductor 22 may be undoped or doped with impurities. The second nitride semiconductor 22 is preferably undoped from the viewpoint of crystallinity. Further, when the p-type impurity and / or the n-type impurity are doped at the time of the ELOG growth in the second step, similarly to the case of the ELOG growth in the first step, the lateral growth of the nitride semiconductor is increased. It is promoted and is preferable in terms of reduction of dislocations and prevention of generation of voids at a junction between adjacent nitride semiconductors. The thickness of the second nitride semiconductor 22 is not particularly limited, and is not less than a thickness capable of covering at least the first protective film 11 and the first unevenness 13.
Preferably 1 to 50 μm, more preferably 2 to 40 μm
m, more preferably 7 to 20 μm. When the thickness is in the above range, the first protective film 11 and the like can be covered well, which is preferable in terms of suppressing the propagation of dislocations.

In the second step, the ELOG growth in the second step of growing the second nitride semiconductor 22 includes:
There is no particular limitation, and any method may be used as long as the growth rate in the lateral direction of the nitride semiconductor is promoted relative to the growth rate in the vertical direction of the nitride semiconductor. For example, conventionally known ELOG growth and a nitride semiconductor growth method described in the specification already filed by the present applicant can be mentioned. The applicants have filed, for example, Japanese Patent Application Nos. 10-77245 and 10-27.
5826, 10-119377, 10-13283
1, 11-37827, 11-37826, 10
ELO described in the specification of each item of 146431
G growth or the like can be used.

In the second step, one embodiment of the specific example of the ELOG growth is described in each of the above-mentioned specifications. For example, the case where the second protective film 12 shown in FIG. In the case where the second unevenness 14 is formed,
An embodiment of the ELOG growth in the step (1) will be described below. 2A to 2D show the second protective film 12 or the second unevenness 14 on the heterogeneous substrate 21 in the second step.
FIG. 1 is a schematic cross-sectional view of one embodiment showing a second nitride semiconductor 22 and the like obtained by ELOG growth using GaN. First, FIG. 2A shows that a thin nitride semiconductor 25 is grown on a heterogeneous substrate 21, a second protective film 12 is partially formed on the surface thereof, and the second protective film 12 is formed. FIG. 4 is a schematic cross-sectional view showing a state where a second nitride semiconductor 22 is grown on the surface which has been made. In FIG. 2A, the thin-film nitride semiconductor 25 is grown on the heterogeneous substrate 21, but the thin-film nitride semiconductor 25 may be omitted. To reduce dislocations,
It is preferable to form a thin nitride semiconductor 25. FIG. 2B shows a thin nitride semiconductor 2 on a heterogeneous substrate 21.
5 is grown, irregularities are formed on the nitride semiconductor 25 of the thin film, a second protective film 12 is formed on the bottom of the concave portion and on the convex portion, and a second protective film 12 is formed on the surface on which the second protective film 12 is formed. 2 is a schematic cross-sectional view obtained by growing a second nitride semiconductor 22. FIG.
FIG. 2C shows that a thin nitride semiconductor 25 is grown on a heterogeneous substrate 21, irregularities are formed on the thin nitride semiconductor 25, and a second protective film 12 is formed only on the convex portions. FIG. 4 is a schematic cross-sectional view showing a second nitride semiconductor 22 grown from above. FIG. 2D shows that a thin nitride semiconductor 25 is grown on the heterogeneous substrate 21, and the second unevenness 14 is formed on the thin nitride semiconductor 25.
FIG. 4 is a schematic cross-sectional view in which a second nitride semiconductor 22 is grown on the surface on which No. 4 is formed.

The thin film nitride semiconductor 25 is not particularly limited, but includes a nitride semiconductor made of GaN. The thin film nitride semiconductor 25 may be undoped or doped with impurities, but is preferably undoped from the viewpoint of crystallinity. The thin film nitride semiconductor 25
It is grown on the heterogeneous substrate 21 at a high temperature, specifically about 900 ° C. to 1100 ° C., preferably 1050 ° C. The thickness of the thin nitride semiconductor 25 is not particularly limited.
It is desirable to form the layer with a thickness of at least 00 Å, preferably about 1 to 10 μm, and more preferably 1 to 5 μm. Since the thickness of the thin nitride semiconductor 25 becomes a base layer for forming the second protective film 12 and the second irregularities 14, it is appropriately adjusted depending on whether the protective film and the irregularities are formed, When the film thickness is in the above range, adjustment becomes easy.

In the second step, as shown in FIG. 2A, before growing the thin nitride semiconductor 25 on the heterogeneous substrate 21 (the thin nitride semiconductor 25 is not grown). In this case, before forming the second protective film 12)
Then, a low-temperature growth buffer layer may be grown. AlN, GaN, AlGaN, InGaN
Are used. The buffer layer is 900 ° C or less and 300 ° C
At the above temperature, the film is grown with a film thickness of 0.5 μm to 10 Å. When the buffer layer is formed on the heterogeneous substrate 21 at a temperature of 900 ° C. or lower in this way, the lattice constant between the nitride semiconductor grown in contact with the heterogeneous substrate 21 and the heterogeneous substrate 21 is reduced, and the second nitride semiconductor No. 22 dislocations tend to be reduced.

In the second step, the formation method, shape and size of the second protective film 12 and the formation method, shape and size of the second unevenness 14 are described in detail in the nitride semiconductor substrate in the first step. The method, shape, size, and the like of the first protective film 11 and the first unevenness 13 formed on the substrate 1 are the same. However, in the first step, the first
The difference is that the protective film 11 or the first unevenness 13 is formed on the thin film nitride semiconductor 25 grown on the heterogeneous substrate 21 in the second step.

Here, the ELO of the first step is placed on the nitride semiconductor substrate 1 obtained by the ELOG growth of the second step.
G growth is performed, but the first step ELOG growth and the second step
The process may be the same or different from the ELOG growth. For example, the ELOG growth in the second step is performed as shown in FIG.
In the first step, the ELOG growth in the first step is the method in FIG. 1D, or in the second step, the method shown in FIG.
In the above method, the first step may be performed in various combinations such as the method shown in FIG. The selection of the ELOG growth in the first step and the second step is selected in consideration of the condition that the dislocation is easily reduced and the condition that the yield hardly decreases in mass production. When the first protective film 11 or the first irregularities 13 and the second protective film 12 or the second irregularities 14 have a stripe shape, the stripe shape of the stripe formed in the first step is the same. The first protective film 11 and the first irregularities 13 are formed in parallel with the stripe-shaped second protective film 12 and the second irregularities 14 formed in the second step, and they are formed of a nitride semiconductor. Substrate 1
Is preferably formed in a direction parallel to the M-axis direction. If the protective film and the like in the first step and the second step are formed parallel to the same M-axis direction among the three types of M-axis directions of the nitride semiconductor substrate 1 as described above. The lateral growth of the first nitride semiconductor 2 grown by ELOG growth in the first step is favorably promoted,
It is preferable in terms of reducing dislocations and preventing generation of voids.

Since the GaN crystal forming the nitride semiconductor substrate 1 is point-symmetric, it is formed in a stripe shape in the first step so as to be parallel to any of the three types of M-axis directions for easy cleavage. It is presumed that similar results can be obtained even if a protective film or the like is formed. However, when it is actually performed, the protective film and the protective film in the first and second steps are parallel to the same M-axis direction among the three types of M-axis directions of the nitride semiconductor substrate 1. When irregularities are formed, the first
There is a tendency that the ELOG growth in the step (1) is good and the growth of the first nitride semiconductor 2 with reduced dislocation is good.

A method in which the first protective film or the first irregularities and the second protective film or the second irregularities are parallel to the same M-axis direction of the nitride semiconductor substrate 1. According to the dislocation distribution observed by CL or the like on the surface of the nitride semiconductor substrate 1 from which the dissimilar substrate 21 and the like have been removed, the dislocation distribution is observed in a stripe shape. A protection or the like is formed, or an orientation flat surface (orientation flat surface) is made perpendicular to the M-axis direction of the nitride semiconductor, and the protection used in the first step and the second step is based on the orientation flat surface. The film and the irregularities are formed as stripes in the parallel direction. By forming in this manner, the first protective film and the second protective film,
Alternatively, the first protective film and the second unevenness, the first unevenness and the second protective film, the first unevenness and the second unevenness, and the like are respectively parallel to the M-axis direction of the nitride semiconductor.

As described above, as the heterogeneous substrate 21 used in the second step, a substrate in which the main surface of the material to be the heterogeneous substrate is off-angled, and a substrate in which the stepped off-angle is further used. More preferred. When a substrate with an off-angle is used, three-dimensional growth is not observed on the surface, and step growth appears, so that the surface tends to be flat. Further, the direction (step direction) along the steps of the sapphire substrate that is off-angled in a step shape is A
When formed perpendicular to the surface, the step surface of the nitride semiconductor coincides with the cavity direction of the laser, and laser light is less likely to be irregularly reflected due to surface roughness, which is preferable.

More preferred heterogeneous substrates include (000
1) Sapphire whose main surface is plane [C-plane], (112-0)
Sapphire whose main surface is the [A-plane] or spinel whose main surface is the (111) plane. Here, the heterogeneous substrate is (00
01) When the sapphire is a sapphire having the [C-plane] as a main surface, the protective film formed on the nitride semiconductor 25 or the like of the thin film or the stripe shape of the unevenness is (112-0) of the sapphire.
It is preferable to have a stripe shape perpendicular to the plane [A-plane] [to form a stripe in a direction parallel to the (101-0) [M-plane] of the nitride semiconductor]. The off angle θ (θ shown in FIG. 8) is preferably 0.1
° to 0.5 °, more preferably 0.1 to 0.2 °.

In the case of sapphire having the (112-0) plane [A-plane] as the main surface, the stripe shape of the protective film and the unevenness is perpendicular to the (11-02) -plane [R-plane] of the sapphire. It is preferable to have a simple stripe shape,
In the case of a spinel having a (111) plane as a main surface, it is preferable that the uneven stripe shape has a stripe shape perpendicular to the (110) plane of the spinel. Here, the case where the protective film and the concavities and convexities are stripe-shaped has been described. However, in the present invention, the nitride semiconductor easily grows in the lateral direction on the A-plane and R-plane of sapphire and the (110) plane of spinel. It is preferable to consider the formation of the protective film and the unevenness so that the end face of the first nitride semiconductor is formed first.

The heterogeneous substrate 21 used in the present invention will be described in more detail with reference to the drawings. FIG. 6 is a unit cell diagram showing the crystal structure of sapphire. First, a case will be described in which sapphire whose main surface is the C surface is used, and the unevenness is a stripe shape perpendicular to the sapphire A surface. For example, FIG. 7 is a plan view of a sapphire substrate on the main surface side. In this figure, the sapphire C plane is the main surface, and the orientation flat (orientation flat) surface is the A surface.
As shown in this figure, the protective film and the uneven stripes are formed in parallel to each other in the direction perpendicular to the A-plane. As shown in FIG. 7, when a nitride semiconductor is selectively grown on a sapphire C plane, the nitride semiconductor tends to grow in a direction parallel to the A plane in the plane and hard to grow in a direction perpendicular to the A plane. It is in. Therefore, when the stripes are provided in a direction perpendicular to the A-plane, the nitride semiconductors between the stripes are connected to each other, and the nitride semiconductors are easily grown.
It is thought that G growth can be easily performed, but the details are not clear.

Next, when a sapphire substrate having the A surface as the main surface is used, as in the case where the C surface is the main surface, for example, if the orientation flat surface is an R surface, the orientation flat surface is perpendicular to the R surface. By forming stripes parallel to each other, a nitride semiconductor tends to grow in the stripe width direction, so that a nitride semiconductor layer with few dislocations can be grown.

Next, also with respect to spinel (MgAl ₂ O ₄ ), the growth of the nitride semiconductor is anisotropic, and the growth surface of the nitride semiconductor is (111) plane, and the orientation flat surface is (11).
When the plane is the 0) plane, the nitride semiconductor tends to grow in a direction parallel to the (110) plane. Therefore, (11
When a stripe is formed in a direction perpendicular to the 0) plane, the nitride semiconductor layer and the adjacent nitride semiconductor are connected to each other at the upper portion of the protective film, and a crystal with few dislocations can be grown. The spinel is not shown in the figure because it is tetragonal.

Next, in the growth method of the present invention, as shown in FIG. 3, in the third step, the ELO of the second step is performed.
On the second nitride semiconductor 22 formed by G growth,
The third nitride semiconductor 23 is grown at a growth rate of 500 μm / hour or less and 10 μm / hour or more. In the third step, the growth rate for growing the third nitride semiconductor 23 is:
As described above, it is not more than 500 μm / hour and not less than 10 μm / hour, preferably not more than 100 μm / hour and not less than 50 μm / hour. When the growth rate of the third nitride semiconductor 23 is within the above range, abnormal growth can be prevented when growing the third nitride semiconductor 23 to the above film thickness, and furthermore, the third nitride semiconductor 23 is preferable because the growth surface is clean. For example, HVPE or the like can be cited as a specific method in which the growth rate falls within the above range.

The third nitride semiconductor 23 grown in the third step is not particularly limited, but a nitride semiconductor made of GaN is preferable from the viewpoint of crystallinity and the like. Further, the third nitride semiconductor 23 may be undoped or doped with impurities, but is preferably undoped from the viewpoint of crystallinity.

The third nitride semiconductor 23 is grown to be thicker than the second nitride semiconductor 22. Third
The thickness of the nitride semiconductor 23 is not particularly limited, but may be a physical value such as when performing the first step or forming a device structure after at least the heterogeneous substrate 21 is removed in the fourth step described later. It is desirable that the film thickness is not less than the film thickness that can withstand the mechanical strength and does not easily cause chipping or cracking, and is in a range where the size of the apparatus and the operation are easy. For example, the specific thickness of the third nitride semiconductor 23 is preferably 50 μm to 1000 μm.
m, more preferably 80 μm to 500 μm. When the film thickness is in such a range, when the third nitride semiconductor 23 is used as the nitride semiconductor substrate 1, operability is good and chipping, cracking, and the like can be prevented, which is preferable.

Next, as shown in FIG. 4, in a fourth step, after growing the third nitride semiconductor 23 in the third step,
At least the dissimilar substrate 21 is removed to obtain the nitride semiconductor substrate 1 having at least the third nitride semiconductor 23 and used in the first step. As a portion to be removed in the fourth step, it is sufficient that at least the heterogeneous substrate 21 is removed, and the buffer layer, the nitride semiconductor 25 of the thin film, the second protective film 13 and the like shown in FIG. Also, a resonance surface can be formed by cleavage. It is preferable to remove the heterosubstrate 21 to the second nitride semiconductor 22 from the viewpoint of reducing the warpage of the third nitride semiconductor 23, and furthermore, there is a possibility that a void may be generated on the protective film. When the second nitride semiconductor 22 is removed, the cleavability becomes better. In addition, the part to be removed in the fourth step may be removed to a part of the third nitride semiconductor in consideration of operability in a manufacturing step, warpage, and the like. As a method for removing the heterogeneous substrate 21 and the like from the third nitride semiconductor 23, for example, a method such as polishing is given. When the third nitride semiconductor 23 is used as the nitride semiconductor substrate 1 in the first step, the third nitride semiconductor 2
3 on the surface opposite to the surface from which the different substrate
The ELOG growth of the step is performed.

Next, a case having the fifth step will be described. As shown in FIG. 5, after the fourth step, the fifth step
In the step, the heterogeneous substrate 2 of the third nitride semiconductor 23 is formed.
On the surface opposite to the surface from which 1 etc. has been removed, a growth rate of 500
The fourth nitride semiconductor is grown at a rate of 10 μm / hour or less and 10 μm / hour or less. In the case where the fifth step is provided, the nitride semiconductor substrate 1 in the first step is composed of at least a third nitride semiconductor and a fourth nitride semiconductor, preferably the third and fourth nitride semiconductors. It consists of semiconductor only.

When the growth method of the present invention includes the fifth step, the third nitride semiconductor is removed after growing the fourth nitride semiconductor 24, and the nitride semiconductor used in the first step is removed. As the substrate 1, a substrate composed of only the fourth nitride semiconductor 24 may be used. After the fifth step, the third
Is removed, and the fourth nitride semiconductor 2 is removed.
When only 4 is used, the boundary between the third and fourth nitride semiconductors is removed, so that an oxide film which is considered to be formed at the boundary can be removed, which is preferable in terms of improvement in element characteristics (lifetime characteristics and the like). When the nitride semiconductor substrate 1 using only the fourth nitride semiconductor in the first step is used, the thickness of the fourth nitride semiconductor is not particularly limited, but may be, for example, 80 to 500 μm. It is preferable in terms of physical strength.

The fourth nitride semiconductor 24 is not particularly limited, but may be the same nitride semiconductor as the third nitride semiconductor 23 described above. The growth rate of the fourth nitride semiconductor is 500 μm / hour or less as described above.
μm / hour or more, and is preferably the same as the case where the third nitride semiconductor 23 is grown. After removing the heterogeneous substrate 21 in this manner, when the fourth nitride semiconductor 24 is grown on the growth surface of the third nitride semiconductor 23, the third
Of the nitride semiconductor 23 is reduced, and the first step, the device step, and the like can be favorably performed. When the fourth nitride semiconductor 24 is grown, the crystallinity is further improved. When the first step is performed on the fourth nitride semiconductor 24, the dislocation of the first nitride semiconductor 2 can be reduced. It is preferable from the viewpoint of improving crystallinity.

The thickness of the fourth nitride semiconductor 24 is not particularly limited. The thicker the thickness of the fourth nitride semiconductor 24 is, the better the warpage is reduced and the better the crystallinity is. In this case, the operability or the like is reduced or the size of the device is limited, so that the total thickness of the third nitride semiconductor 23 and the fourth nitride semiconductor 24 is 1000 μm or less, preferably 800 μm or less, preferably Is preferably 400 μm or less, and at least the thickness of at least the third and fourth nitride semiconductors is preferably 80 μm or more. It is preferable that the film thickness is in this range in terms of physical strength, operability, and the like. In this case, the thickness of the third nitride semiconductor 23 is adjusted such that the total thickness of the third and fourth nitride semiconductors is 1000 μm or less within the above range.

Next, a nitride semiconductor device having a device structure formed on the substrate of the present invention obtained by the method for growing a nitride semiconductor of the present invention will be described. The nitride semiconductor device of the present invention has at least an n-type nitride on the substrate of the nitride semiconductor obtained by the method of the present invention (on the first nitride semiconductor 2 grown on the nitride semiconductor substrate 1). An element in which a device structure having a semiconductor, an active layer, and a p-type nitride semiconductor is formed is exemplified. There is no particular limitation on the n-type nitride semiconductor or the like constituting the above-described element, and a conventionally known device structure can be appropriately used. As one embodiment of the device structure, there is a device structure described in an example described later. However, the present invention is not limited to this. The shape of the electrodes and the elements is not particularly limited, and various known ones can be used. That is, since the substrate obtained by the method for growing a nitride semiconductor of the present invention is a good substrate with reduced dislocations, the life characteristics can be improved although it varies depending on the type of device structure. . Further, since the substrate is made of a nitride semiconductor, it can be cleaved favorably on a plane perpendicular to the M-axis direction of the nitride semiconductor.

In the present invention, a preferable nitride semiconductor device is, for example, a laser device in which a light emitting region is a ridge-shaped stripe in view of device characteristics such as life characteristics. As a more preferable element, a ridge-shaped stripe is formed in parallel with the stripe direction of the first protective film 11 and the first unevenness 13 having the stripe shape formed in the first step, and more preferably the stripe shape is formed. It is preferable that the first protective film 11 be formed above the protective film of the first protective film 11 and the concave portion of the first unevenness 13 in order to improve the life characteristics. ELOG of the first step
Although there is a difference in the average dislocation density on the surface of the first nitride semiconductor 2 depending on the type of growth, dislocations are hardly seen in the upper portion of the first protective film 11 and the upper portion of the concave portion of the first unevenness 13. If a light emitting region, for example, a ridge-shaped stripe as described above is formed in this portion, propagation of dislocations can be prevented during operation of the laser element or the like, element deterioration can be suppressed, and life characteristics can be improved.

[0087]

The present invention will be described in more detail with reference to the following examples, which are embodiments of the present invention. However, the present invention is not limited to this.

[Example 1] A process for manufacturing a nitride semiconductor substrate composed of the nitride semiconductor substrate 1 and the first nitride semiconductor 2 shown in FIG. (Refer to FIGS. 2 to 4 for the second to fourth steps.)

[Manufacture of Nitride Semiconductor Substrate 1] (Second Step) As the heterogeneous substrate 21, the C-plane is a main surface,
Using a sapphire substrate 21 having an orientation flat surface as an A surface, this sapphire substrate 21 is set in a MOCVD reaction vessel, the temperature is set to 510 ° C., hydrogen is used as a carrier gas, and ammonia and TMG (trimethylgallium) are used as source gases. Is used to grow a GaN buffer layer on the sapphire substrate 21 to a thickness of 200 angstroms.

After the growth of the buffer layer, only TMG is stopped, the temperature is increased to 1050 ° C., and when the temperature reaches 1050 ° C.,
Using TMG, ammonia, and silane gases as source gases, a thin film of nitride semiconductor 25 made of undoped GaN is formed in a thickness of 5 μm.
It is grown to a thickness of m. A stripe-shaped photomask is formed on the thin-film nitride semiconductor 25 of the wafer in which the buffer layer and the thin-film nitride semiconductor 25 are stacked, and C
S with a stripe width of 18 μm and a window of 2 μm using a VD device
A _second protective film 12 made of iO ₂ is formed with a thickness of 0.5 μm. Note that the stripe direction of the second protective film 12 is a direction perpendicular to the sapphire A surface, that is, a direction perpendicular to the orientation flat surface as shown in FIG. When formed in this way, the direction perpendicular to the A-plane of sapphire
The direction is parallel to the M-axis direction of the nitride semiconductor.

After forming the second protective film 12, the wafer is
GaN doped with Si and Mg impurities at 5 × 10 ¹⁷ / cm ³ at 1050 ° C. using TMG, ammonia, silane gas, and Cp ₂ Mg (cyclopentadienyl magnesium) as source gases at 1050 ° C. The second nitride semiconductor 22 composed of
It is grown to a thickness of m. The impurities of Si and Mg are doped simultaneously with the growth of the second nitride semiconductor 22. However, the growth rate of the second nitride semiconductor 22 was 3 μm / hour.

When the surface of the obtained second nitride semiconductor 22 is observed by CL (cathode luminescence), almost no crystal defects are found on the upper portion of the second protective film 12, and 8 × 10 ^{5 on the} upper portion of the window portion. / Cm ² was observed. The dislocation density may be slightly different depending on the observed part.

(Third Step) Next, a third nitride semiconductor 23 made of undoped GaN is grown on the second nitride semiconductor 22 to a thickness of 200 μm by an HVPE apparatus. However, the growth rate of the third nitride semiconductor 23 is:
50 μm / hour.

(Fourth Step) Next, after growing the third nitride semiconductor 23, the sapphire substrate 21 to the second nitride semiconductor 22 are removed by polishing to remove only the third nitride semiconductor 24. The nitride semiconductor substrate 1 is obtained. On the surface of the obtained third nitride semiconductor 24 from which the sapphire substrate or the like has been removed, there are a stripe-like portion having almost no dislocations and a slightly more dislocation portion. On the other hand, the growth surface of the third nitride semiconductor 24 has an average dislocation density of 1 × 10
There are about ⁷ / cm ² .

[Manufacture of Substrate of the Present Invention] (First Step) On the nitride semiconductor substrate 1 made of the third nitride semiconductor 23 described above, a striped surface of the removal surface of the third nitride semiconductor 23 is formed. In the direction parallel to the M-axis direction of the nitride semiconductor which is parallel to the dislocation distribution, the first protective film 11 is placed on the growth surface of the third nitride semiconductor 23 (the surface opposite to the removal surface), Second protective film 1 formed in the second step
2 is formed. After forming the first protective film 11, the first
Is grown to a film thickness of 15 μm using a MOCVD apparatus. Regarding the dislocation density on the surface of the first nitride semiconductor 2, slight dislocations are seen on the surface above the window portion, but almost dislocations are found on the surface of the first nitride semiconductor 2 above the first protective film 11. Can not be seen.

[Embodiment 2] In Embodiment 1, the thickness of the third nitride semiconductor 23 grown in the third step is set to 150.
Then, a substrate for forming a device structure is manufactured in the same manner except that a fifth step is added after the fourth step. (Fifth step) On the growth surface of the third nitride semiconductor 23 from which the sapphire substrate or the like has been removed, a fourth nitride semiconductor 24 made of undoped GaN is applied by an HVPE apparatus.
It is grown to a thickness of 200 μm (FIG. 5).

On the nitride semiconductor substrate 1 composed of the obtained third nitride semiconductor 23 and fourth nitride semiconductor 24, the first
The ELOG growth of the step is performed. Third nitride semiconductor 2
When the fourth nitride semiconductor 24 is grown on the growth surface of No. 3, warpage is reduced, and ELOG growth in the first step is performed in the first embodiment.
Thus, the first nitride semiconductor 2 with better dislocation and reduced dislocation can be obtained.

[Embodiment 3] A process for manufacturing a nitride semiconductor substrate composed of the nitride semiconductor substrate 1 and the first nitride semiconductor 2 shown in FIG. (Refer to FIGS. 2 to 5 for the second to fifth steps.)

(Second Step) As a heterogeneous substrate 21, a sapphire substrate 21 having a 2-inch φ, C surface as a main surface and an orientation flat surface as an A surface is set in a MOCVD reaction vessel.
The temperature was set to 510 ° C., and a buffer layer (not shown) made of GaN was formed on the sapphire substrate 21 with a thickness of about 200 Å using hydrogen as the carrier gas, ammonia and TMG (trimethylgallium) as the source gas. Let it grow.

After growing the buffer layer, only TMG is stopped.
Increase temperature to 1050 ° C. When the temperature reaches 1050 ° C., a thin nitride semiconductor 25 made of undoped GaN is grown to a thickness of 2 μm using TMG and ammonia as source gases.

After growing the nitride semiconductor 25 as a thin film, a stripe-shaped photomask is formed, and a stripe width of 15 μm and a stripe interval (opening of a concave portion) are formed by a sputtering apparatus.
0.5 μm of the second protective film 12 made of 3 μm SiO ₂
Then, the recessed side surface of the thin-film nitride semiconductor 25 is exposed by etching the nitride semiconductor 25 in the middle of the thin film using an RIE apparatus to form irregularities. The stripe direction is as shown in FIG.
It is formed in a direction perpendicular to the orientation flat surface. When the growth is performed in the direction perpendicular to the orientation flat surface, the direction perpendicular to the orientation flat surface is parallel to the M-axis direction of the nitride semiconductor.

After forming irregularities on the thin nitride semiconductor 25, a protective film material is formed on the surface of the thin nitride semiconductor 25 having the irregularities by a sputtering apparatus, and the irregularities are formed by CF ₄ and O ₂ gas. The protective film on the side surface of the concave portion of the second nitride semiconductor 22 formed by the formation is removed by etching to expose the side surface of the concave portion, and the second protective film 12 is formed on the upper portion of the convex portion and the lower portion of the concave portion.

After the second protective film 12 is formed, it is set in a MOCVD reaction vessel at a temperature of 1050 ° C., using TMG, ammonia, silane gas and Cp ₂ Mg as source gases, and simultaneously growing Si and Mg at the same time. 5 × 10 ¹⁷ / cm of impurities
^A second nitride semiconductor 22 made of ^3- doped GaN is grown to a thickness of 15 μm using a MOCVD apparatus. However, the growth rate of the second nitride semiconductor 22 was set at 2 μm / hour.

When the surface of the obtained second nitride semiconductor 22 is observed by CL (cathode luminescence), dislocation is extremely reduced. However, on the surface of the second nitride semiconductor 22, a slight distribution of dislocations is seen parallel to the stripe direction of the second protective film 12. This distribution of dislocations is a case where the distribution is relatively compared with other portions where almost no dislocations are observed.

(Third Step) Next, a third nitride semiconductor 23 made of undoped GaN is grown on the second nitride semiconductor 22 to a thickness of 100 μm by an HVPE apparatus. However, the growth rate of the third nitride semiconductor 23 is:
50 μm / hour.

(Fourth Step) Next, after growing the third nitride semiconductor 23, the sapphire substrate 21 to the second nitride semiconductor 22 are removed by polishing to remove only the third nitride semiconductor 23. I do. On the surface from which the third nitride semiconductor 23 has been removed, a dislocation distribution almost similar to that slightly distributed on the surface of the second nitride semiconductor 23 can be seen.

(Fifth Step) Next, on the growth surface of the third nitride semiconductor 23, a fourth nitride semiconductor 24 made of undoped GaN was deposited at 250 μm using an HVPE apparatus.
It grows with the film thickness of. Obtained third nitride semiconductor 23
On the surface of the nitride semiconductor substrate [FIG. 2 (b)] composed of the first and fourth nitride semiconductors 24, slight dislocations are seen almost uniformly.

(First Step) On the nitride semiconductor substrate 1 composed of the third nitride semiconductor 23 and the fourth nitride semiconductor 24, a striped surface of the removal surface of the third nitride semiconductor 23 is formed. The first protective film 11 is placed on the growth surface of the fourth nitride semiconductor 24 in a direction parallel to the M-axis direction of the nitride semiconductor so as to be parallel to a very slight dislocation distribution. The second protective film 1 after the formation of the irregularities
As in the case of forming No. 2, the first protective film 11 is formed on the bottom of the concave portion and the upper portion of the convex portion. After the formation of the first protective film 11, the first nitride semiconductor 2 is grown to a thickness of 15 μm using a MOCVD apparatus. Dislocations on the surface of the first nitride semiconductor 2 are:
Hardly seen overall. Then, a substrate 1 composed of the nitride semiconductor substrate 1 and the first nitride semiconductor 2 [FIG.
In (b)], dislocations are scarcely observed, and chipping and cracking hardly occur.

[Embodiment 4] A method of manufacturing the substrate of FIG. 1C will be described below. (Second step) As a heterogeneous substrate 1, a sapphire substrate 1 having a 2-inch φ, C surface as a main surface and an orientation flat surface as an A surface is set in a reaction vessel. Ammonia and TMG (trimethylgallium) are used as hydrogen and source gas, and GaN is formed on the sapphire substrate 1.
A buffer layer (not shown) is grown to a thickness of about 200 Å.

After growing the buffer layer, only TMG is stopped.
Increase temperature to 1050 ° C. When the temperature reaches 1050 ° C., a thin nitride semiconductor 25 made of undoped GaN is grown to a thickness of 2 μm using TMG and ammonia as source gases.

After growing the nitride semiconductor 25 as a thin film, a stripe-shaped photomask is formed, and a stripe width of 15 μm and a stripe interval (opening of a concave portion) are formed by a sputtering apparatus.
The second protective film 11 made of ₂ μm SiO ₂ has a thickness of 0.5 μm.
m, and then etching the thin film nitride semiconductor 25 by an RIE apparatus until the sapphire substrate 1 is exposed to form irregularities, thereby exposing the concave side surfaces of the thin film nitride semiconductor 25. As a result, the second protective film 12 is formed only on the upper part of the protrusion. The width d of the side surface of the concave portion is approximately 2 μm. As shown in FIG. 7, the stripe direction is a direction perpendicular to the orientation flat surface and parallel to the M-axis direction of the nitride semiconductor.

After the second protective film 12 is formed, the film is set in a reaction vessel at a temperature of 1050 ° C., using TMG, ammonia, silane gas and Cp ₂ Mg as a source gas. 5 × 10 ¹⁷ / cm ³ doped G
A second nitride semiconductor 22 made of aN is grown to a thickness of 15 μm by a MOCVD apparatus. The growth rate of second nitride semiconductor 22 is 2 μm / hour.

(Third Step) Next, the second nitride semiconductor 2
A third nitride semiconductor 23 made of undoped GaN is grown on the substrate 2 to a thickness of 150 μm using an HVPE apparatus. The growth rate is 50 μm / hour.

(Fourth Step) After the growth of the third nitride semiconductor 23, the portion from the sapphire substrate to the second nitride semiconductor 22 is removed, leaving only the third nitride semiconductor 23. Third
On the surface from which the nitride semiconductor 23 has been removed, slight dislocations
Are distributed in a stripe shape in parallel with the protective film 12.

(Fifth Step) On the growth surface of the third nitride semiconductor 23, a fourth nitride semiconductor 24 made of undoped GaN is grown to a thickness of 200 μm by an HVPE apparatus. The growth rate is 50 μm / hour. Through the above steps, the nitride semiconductor substrate 1 including the third nitride semiconductor 23 and the fourth nitride semiconductor 24
[FIG. 2 (c)] can be obtained. Dislocations of about 1 × 10 ⁷ / cm ² are observed on the surface of the obtained nitride semiconductor substrate 1.

(First Step) Next, a stripe-shaped photomask is formed on the surface of the nitride semiconductor substrate 1 composed of the third nitride semiconductor 23 and the fourth nitride semiconductor 24, and sputtering is performed. A first protective film 11 made of SiO _{2 having a} stripe width of 15 μm and a stripe interval (width w of the opening of the concave portion) of 2 μm is formed with a thickness of 0.5 μm by an apparatus.
Subsequently, the width d of the side surface of the concave portion is approximately 2 μm by the RIE device.
The first protective film 11 is formed only on the upper part of the protrusion by etching to a depth of 3. The stripe direction of the formed first protective film 11 is the same as that of the second protective film 1.
The direction is parallel to the same M-axis direction among the three types of M-axis directions of the nitride semiconductor substrate 1 so as to be parallel to the two stripe directions.

After forming the first protective film 11 only on the upper portion of the convex portion as described above, the first nitride semiconductor 2 is reduced to 30 μm.
It grows with the film thickness of. The dislocations on the surface of the first nitride semiconductor 2 are slightly distributed in the form of stripes on the upper surface of the window portion. Substrate composed of the object semiconductor 2 [FIG.
(C)] can be obtained.

[Embodiment 5] Hereinafter, an embodiment of a method for manufacturing the substrate shown in FIG. 1D will be described.
(Refer to FIG. 2D to FIG. 5 for the second to fifth steps.) (Second step) As the heterogeneous substrate 21, the 2 inch φ, the C surface is the main surface, and the orientation flat surface is the A surface. Sapphire substrate 2
1 was set in a reaction vessel, the temperature was set to 510 ° C., and a buffer layer (not shown) made of GaN was formed on a sapphire substrate 21 using hydrogen as a carrier gas, ammonia and TMG (trimethylgallium) as a source gas. ) About 2
It is grown to a thickness of 00 Å.

After growing the buffer layer, only TMG is stopped.
Increase temperature to 1050 ° C. When the temperature reaches 1050 ° C., a thin film nitride semiconductor layer 25 of GaN doped with 1 × 10 ¹⁸ / cm ^{3 of} Si is grown to a thickness of 2 μm using TMG, ammonia, and silane gas as source gases.

After growing the thin nitride semiconductor layer 25, a stripe-shaped photomask is formed, and the stripe width (the part to be the top of the projection) is 5 μm and the stripe interval (the part to be the bottom of the depression) is 10 μm by a sputtering apparatus. A patterned SiO ₂ film is formed, and then the thin film nitride semiconductor layer 25 in a portion where the SiO ₂ film is not formed is etched halfway by an RIE apparatus to such an extent that the thin film nitride semiconductor 25 remains. Is formed, thereby exposing the thin nitride semiconductor 25 on the side surface of the concave portion. After forming the irregularities, the second irregularities 14 are formed by removing the SiO ₂ above the convex portions. The stripe direction of the second unevenness 14 is formed in a direction perpendicular to the orientation flat surface, as shown in FIG.

Next, it was set in a reaction vessel, and the temperature was set at 10
At 50 ° C., a second nitride semiconductor layer 22 made of undoped GaN is grown to a thickness of 15 μm by MOCVD using TMG, ammonia and silane gas as source gases. The growth rate is 2 μm / hour.

(Third Step) The Second Nitride Semiconductor 2
On the second substrate 2, a third nitride semiconductor 23 made of undoped GaN is grown with a HVPE apparatus to a thickness of 100 μm. The growth rate is 50 μm / hour.

(Fourth Step) After the growth of the third nitride semiconductor 23, the steps from the sapphire substrate 1 to the second nitride semiconductor are removed to form a single third nitride semiconductor 23.

(Fifth Step) The third step obtained in the fourth step
Undoped GaN on the growth surface of the nitride semiconductor 23
Is grown with an HVPE apparatus to a thickness of 200 μm. The growth rate is 50
μm / hour.

Through the above steps, a nitride semiconductor substrate including the third nitride semiconductor 23 and the fourth nitride semiconductor 24 is obtained. Obtained fourth nitride semiconductor 2
On the four surfaces, dislocations of about 5 × 10 ⁶ / cm ² were observed. In addition, dislocation distribution is hardly observed on the surface from which the third nitride semiconductor 23 has been removed and dislocations are hardly observed in the portion grown from the opening of the concave portion, but 1 × 1 in the portion grown from the upper portion of the convex portion.
0 ⁷ / cm ² of about dislocations are distributed in parallel to the stripe direction of the second concave-convex 13.

(First Step) Next, the substrate shown in FIG. 1C is grown. The first unevenness 13 is formed on the nitride semiconductor substrate 1 composed of the third nitride semiconductor 23 and the fourth nitride semiconductor 24 in the same manner as the second unevenness 14 formed in the second step. Form. However, the stripe direction of the first unevenness 13 is parallel to the stripe-shaped dislocation distributed on the removal surface of the third nitride semiconductor 23 so that the stripe direction of the first unevenness 13 is parallel to the stripe direction of the second unevenness 14. By forming so as to be, the direction becomes parallel to the M-axis direction of the nitride semiconductor. An undoped G layer having the first unevenness 13
A first nitride semiconductor 2 made of aN is grown to a thickness of 20 μm. On the surface of the obtained substrate composed of nitride semiconductor substrate 1 and first nitride semiconductor 2, almost no dislocation was observed in the portion grown from the opening of the concave portion, and no dislocation was observed in the portion grown from the upper portion of the convex portion. Is slightly visible.
Further, the substrate has a thickness such that chipping or the like is prevented.

Example 6 In Example 5, the fourth nitride semiconductor 24 was grown to a thickness of 300 μm in the fifth step, and then the third nitride semiconductor 23 was polished and removed. A substrate of the present invention is manufactured in the same manner except that the fourth nitride semiconductor 24 having a thickness of 250 μm is used as the nitride semiconductor substrate 1 used in the first step. In the obtained substrate of the present invention, dislocations are reduced as in Example 5, and dislocations are hardly observed particularly on the surface of the upper portion of the concave portion.

The following is an example of a nitride semiconductor device as an embodiment of the nitride semiconductor device of the present invention using the substrate of the present invention obtained by the method for growing a nitride semiconductor of the present invention. Is shown. However, the present invention is not limited to this. [Embodiment 7] The following device structures are sequentially arranged on a substrate obtained by growing the first nitride semiconductor 2 on the nitride semiconductor substrate made of the third nitride semiconductor 23 obtained in Embodiment 1. Let it grow.

(Undoped n-type contact layer) [not shown in FIG. 9] On the nitride semiconductor substrate, 105
At 0 ° C., TMA (trimethylaluminum)
Undoped Al _0.05 G using TMG and ammonia gas
a An n-type contact layer made of _0.95 N is grown to a thickness of 1 μm. (N-type contact layer 72) Next, at the same temperature, TMA, TMG and ammonia gas are used as source gases, silane gas (SiH ₄ ) is used as impurity gas, and
^An n-type contact layer 72 of ¹⁸ / cm ³ doped Al _0.05 Ga _0.95 N is grown to a thickness of 3 μm.

(Crack prevention layer 73)
0 ° C and TMG, TMI (trimethyl ether)
Silane and ammonia as impurity gas
5 × 10 Si using gas ¹⁸/ Cm^ThreeDoped In
_0.08Ga_0.92The crack preventing layer 73 made of N is 0.15
It is grown to a thickness of μm.

(N-type cladding layer 74)
The temperature was raised to 50 ° C., and TMA, TMG and ammonia were used as raw material gases, and A made of undoped Al _0.14 Ga _0.86 N
A layer is grown to a thickness of 25 Å, followed by
Stop TMA and use silane gas as impurity gas.
A B layer made of GaN doped with i at 5 × 10 ¹⁸ / cm ³ is grown to a thickness of 25 Å. And
This operation is repeated 160 times to laminate the A layer and the B layer, and grow the n-type cladding layer 74 composed of a multilayer film (superlattice structure) having a total film thickness of 8000 angstroms.

(N-type guide layer 75) Next, at the same temperature, using TMG and ammonia as source gases, an n-type guide layer 75 of undoped GaN was formed to a thickness of 0.075 μm.
It grows with the film thickness of.

(Active Layer 76) Next, the temperature was raised to 800 ° C., and TMI, TMG and ammonia were used as raw material gases.
Using silane gas as an impurity gas, Si is 5 × 10 ¹⁸
A barrier layer made of In _0.01 Ga _0.99 N doped with / cm ³ is grown to a thickness of 100 Å. Subsequently, the silane gas was stopped, and undoped In _0.11 Ga _0.89
A well layer made of N is grown to a thickness of 50 angstroms. This operation is repeated three times, and finally, an active layer 76 of a multiple quantum well structure (MQW) having a total film thickness of 550 angstroms, on which a barrier layer is laminated, is grown.

(P-type electron confinement layer 77) Next, at the same temperature, TMA, TMG and ammonia are used as source gases, Cp ₂ Mg (cyclopentadienyl magnesium) is used as an impurity gas, and Mg is reduced to 1 ×. A p-type electron confinement layer 77 made of 10 ¹⁹ / cm ³ doped Al _0.4 Ga _0.6 N is grown to a thickness of 100 Å.

(P-type guide layer 78) Next, the temperature was set to 105
0 ° C, using TMG and ammonia as raw material gas,
The p-type guide layer 78 made of undoped GaN is
It is grown to a thickness of 75 μm. This p-type guide layer 78
Is grown as undoped, but the Mg concentration is 5 × 10 ¹⁶ due to the diffusion of Mg from the p-type electron confinement layer 77.
/ Cm ³ , indicating p-type.

(P-type cladding layer 79) Next, at the same temperature, using TMA, TMG and ammonia as the source gas,
An A layer made of undoped Al _0.1 Ga _0.9 N is grown to a thickness of 25 Å, followed by stopping TMA, using Cp ₂ Mg as an impurity gas, and adding 5 × 1 Mg.
A B layer of GaN doped with 0 ¹⁸ / cm ³ is grown to a thickness of 25 Å. This operation is repeated 100 times to stack the A layer and the B layer, thereby growing the p-type cladding layer 79 composed of a multilayer film (superlattice structure) having a total film thickness of 5000 angstroms.

(P-type contact layer 80) Next, at the same temperature, TMG and ammonia are used as source gases, Cp ₂ Mg is used as an impurity gas, and Mg is 1 × 10 ²⁰ / cm ^3.
The p-type contact layer 80 made of doped GaN is
It is grown to a thickness of 0 Å.

After the reaction, the wafer is annealed in a nitrogen atmosphere at 700 ° C. in the reaction vessel to further reduce the resistance of the p-type layer. After annealing, the wafer is taken out of the reaction vessel, a protective film made of SiO ₂ is formed on the surface of the uppermost p-side contact layer, and is etched by SiCl ₄ gas using RIE (reactive ion etching). As shown, the surface of the n-side contact layer 2 where the n-electrode is to be formed is exposed. Next, as shown in FIG. 10A, almost all of the uppermost p-side contact layer 80 is coated with a Si oxide (mainly SiO 2) by a PVD apparatus.
₂ ) After forming a first protective film 61 of 0.5 μm in thickness, a mask of a predetermined shape is applied on the first protective film 61 to form a third protective film 63 of photoresist. ,
It is formed with a stripe width of 1.8 μm and a thickness of 1 μm. Next, as shown in FIG. 10B, after the formation of the third protective film 63, the RIE (reactive ion etching) device
The first protective film is etched into a stripe shape using F ₄ gas and using the third protective film 63 as a mask. Thereafter, the photoresist is removed by treating with an etchant, thereby forming a first 1.8 μm stripe width on the p-side contact layer 80 as shown in FIG.
Can be formed.

Further, as shown in FIG. 10D, after forming the first protective film 61 in the form of a stripe, the p-side contact layer 10 and the p-side cladding layer 89 are again formed by RIE using SiCl ₄ gas. By etching, a ridge-shaped stripe having a stripe width of 1.8 μm is formed. However, as shown in FIG.
It is formed so as to avoid the central portion of the first protective film 11 above the first protective film 11 formed during the LOG growth. After the formation of the ridge stripe, the wafer is transferred to a PVD apparatus, and a second protective film 62 made of Zr oxide (mainly ZrO ₂ ) is placed on the first protective film 61 as shown in FIG. , P exposed by etching
It is formed continuously on the side cladding layer 79 with a thickness of 0.5 μm. The formation of the Zr oxide in this way is preferable because the pn plane is insulated and the transverse mode can be stabilized. Next, the wafer was immersed in hydrofluoric acid, and FIG.
As shown in (f), the first protective film 61 is removed by a lift-off method.

Next, as shown in FIG. 10 (g), a p-electrode made of Ni / Au is formed on the surface of the p-side contact layer exposed by removing the first protective film 61 on the p-side contact layer 80. 20 is formed. However, the p-electrode 20 has a stripe width of 100 μm and is formed over the second protective film 62 as shown in FIG. After the formation of the second protective film 62, an n-electrode 21 made of Ti / Al is formed on the exposed surface of the n-side contact layer 72 in a direction parallel to the stripe as shown in FIG.

As described above, the n-electrode and the p-electrode are formed.
The resulting wafer is oriented perpendicular to the striped electrodes.
Then, the substrate is cleaved in a bar shape from the substrate side, and the cleavage plane (11-00)
Resonance on the plane, the plane corresponding to the side of the hexagonal columnar crystal = M plane)
Make a vessel. SiO on the resonator surface _TwoAnd TiO_TwoInvitation
A dielectric multilayer film is formed, and finally, in a direction parallel to the p-electrode,
Then, the laser device is cut as shown in FIG. Get
Place the laser elements on a heat sink and
Attempt laser oscillation at room temperature by wire bonding the poles
saw. As a result, the threshold value at room temperature is 2.5 kA / c.
m^TwoWith a threshold voltage of 5 V and an oscillation wavelength of 400 nm
Oscillation has been confirmed and shows a life of 10,000 hours or more at room temperature. Change
Then, when forming the device structure or forming the resonance surface by cleavage,
Chipping and cracking are prevented, and a good resonance surface is obtained.
Further, the yield is improved.

Example 8 A laser device was fabricated in the same manner as in Example 7, except that the substrates of Examples 2 to 6 were used as nitride semiconductor substrates. The obtained five kinds of laser elements have a very small number of dislocations on the surface of a substrate for forming a device structure, and further have a portion in which almost no dislocations are observed, similarly to the seventh embodiment. As a result, the life characteristics are good, and chipping and cracking are prevented when a device structure is formed or when a resonance surface is formed by cleavage, and good results can be obtained.

[0143]

According to the present invention, even when a device structure is formed using a nitride semiconductor as a substrate or a resonance surface is formed by cleavage, no chipping or cracking occurs in the substrate. It has reduced dislocations on the surface, and especially has a portion with almost no dislocations on the surface of the growth surface, so that device characteristics such as life characteristics can be improved and reliability in practical use can be improved. It is possible to provide a method for growing a nitride semiconductor in which a substrate made of such a nitride semiconductor is obtained. Further, the present invention can provide a nitride semiconductor device having good device characteristics such as life characteristics, using a nitride semiconductor obtained by the nitride semiconductor growth method of the present invention as a substrate.

[Brief description of the drawings]

FIG. 1 is a schematic cross-sectional view of a substrate as an embodiment of a nitride semiconductor substrate for forming a device structure according to the present invention.

FIG. 2 is a schematic cross-sectional view of a wafer as one embodiment of a step of growing a nitride semiconductor to be a nitride semiconductor substrate in a first step of the present invention.

FIG. 3 is a schematic cross-sectional view of a wafer as an embodiment of a step of growing a nitride semiconductor to be a nitride semiconductor substrate in a first step of the present invention.

FIG. 4 is a schematic cross-sectional view of a wafer as an embodiment of a step of growing a nitride semiconductor to be a nitride semiconductor substrate in a first step of the present invention.

FIG. 5 is a schematic cross-sectional view of a wafer as an embodiment of a step of growing a nitride semiconductor to be a nitride semiconductor substrate in a first step of the present invention.

FIG. 6 is a unit cell diagram showing a plane orientation of sapphire.

FIG. 7 is a plan view of the main surface of the substrate for explaining the stripe direction of the protective film.

FIG. 8 is a schematic cross-sectional view showing a partial shape of an off-angled dissimilar substrate.

FIG. 9 is a schematic cross-sectional view showing a nitride semiconductor laser device according to one embodiment of the present invention.

FIG. 10 is a schematic cross-sectional view showing a partial structure of a wafer in each step of a method according to an embodiment for forming a ridge-shaped stripe.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Nitride semiconductor substrate 2 ... 1st nitride semiconductor substrate 11 ... 1st protective film 12 ... 2nd protective film 13 ... 1st unevenness 14 ... 2. Unevenness 21 ... heterogeneous substrate 22 ... second nitride semiconductor 23 ... third nitride semiconductor 24 ... fourth nitride semiconductor 25 ... thin film nitride semiconductor

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 5F041 AA40 AA43 CA05 CA23 CA34 CA40 CA46 CA64 CA65 CA74 CA75 CA77 CB04 5F045 AA04 AB14 AC01 AC03 AC08 AC09 AC12 AD14 AF04 AF09 AF13 BB16 CA11 CA13 DA53 DA67 DB02 5F051 AA08 CB10CB GA03 5F073 AA07 AA13 AA45 AA74 AA83 CA07 CB05 CB07 DA04 DA05 DA25 DA32 DA35 EA29 5F088 AB07 BA13 CB04 CB07 CB14 GA02

Claims (16)

[Claims] 1. A method for reducing dislocations by utilizing lateral growth of a nitride semiconductor on a nitride semiconductor substrate,
A method for growing a nitride semiconductor, comprising a first step of growing a first nitride semiconductor. 2. The first step partially forms a first protective film on a nitride semiconductor substrate, and thereafter grows a first nitride semiconductor on a surface on which the first protective film is formed. 2. The method for growing a nitride semiconductor according to claim 1, wherein said method is performed. 3. The method according to claim 1, wherein the first protective film is formed in the direction of the M-axis of the nitride semiconductor substrate, <1-100>, <10-10> and <0.
3. The method for growing a nitride semiconductor according to claim 2, wherein the nitride semiconductor has a stripe shape formed in a direction parallel to the M-axis direction of any one of 1-10>. 4. The method according to claim 1, wherein the first step includes forming first irregularities on the surface of the nitride semiconductor substrate, and thereafter, growing the first nitride semiconductor on the surface having the first irregularities. The method for growing a nitride semiconductor according to claim 1, wherein: 5. The method according to claim 1, wherein the first unevenness is in the M-axis direction of the nitride semiconductor substrate, <1-100>, <10-10>, and <01.
10. A stripe shape formed in a direction parallel to any one of the M-axis directions of -10>.
3. The method for growing a nitride semiconductor according to item 1. 6. The method for growing a nitride semiconductor according to claim 1, wherein the dislocation density of the surface of the nitride semiconductor substrate is 10 ¹⁰ / cm ² or less. 7. The semiconductor device according to claim 1, wherein said nitride semiconductor substrate is 50 to 100.
7. The method for growing a nitride semiconductor according to claim 1, having a thickness of 0 [mu] m. 8. A nitride semiconductor substrate having a growth rate of 10 μm on a heterogeneous substrate made of a material different from a nitride semiconductor.
at a rate of 0.5 μm / hour or less and 0.5 μm / hour or less by a method of reducing dislocations by utilizing lateral growth of a nitride semiconductor.
A second step of growing a nitride semiconductor, and after the second step, a film of the second nitride semiconductor on the second nitride semiconductor at a growth rate of 500 μm / hour or less and 10 μm / hour or more A third step of growing a third nitride semiconductor having a thickness larger than the thickness; and a third step of removing at least a foreign substrate after the third step. The method for growing a nitride semiconductor according to claim 1. 9. The growth rate of the nitride semiconductor substrate is set to 500 μm / hour or less on the surface opposite to the surface from which the heterogeneous substrate of the third nitride semiconductor is removed after the fourth step.
9. The semiconductor device according to claim 8, comprising at least a third nitride semiconductor and a fourth nitride semiconductor obtained by a fifth step of growing a fourth nitride semiconductor at a rate of not less than μm / hour. A method for growing a nitride semiconductor. 10. The second step includes forming a second protective film partially on a nitride semiconductor grown on a heterogeneous substrate, and then forming a second protective film on a surface having the second protective film. The method for growing a nitride semiconductor according to any one of claims 8 to 9, wherein the method is a step of growing the nitride semiconductor of (2). 11. The method according to claim 1, wherein the second protective film formed in the second step is formed in a direction along the M-axis of the nitride semiconductor substrate, <1-10.
0>, <10-10>, and <01-10> in a stripe shape formed in a direction parallel to the M-axis direction, and a first shape formed in the first step.
The method for growing a nitride semiconductor according to claim 10, wherein the nitride semiconductor is formed so as to be parallel to the protective film or the first unevenness. 12. The method according to claim 12, wherein the second step forms second irregularities on the nitride semiconductor grown on the heterogeneous substrate.
The method for growing a nitride semiconductor according to claim 8, wherein the method is a step of growing a second nitride semiconductor on a surface having the second unevenness. 13. The method according to claim 1, wherein the second unevenness formed in the second step is in the M-axis direction of the nitride semiconductor substrate, <1-100.
>, <10-10> or any one of <01-10>
It is a stripe shape formed so as to be parallel to the axial direction, and is formed so as to be parallel to the first unevenness or the first protective film formed in the first step. The method for growing a nitride semiconductor according to claim 12, wherein: 14. A nitride semiconductor having reduced dislocations obtained by the method for growing a nitride semiconductor according to claim 1 as a substrate, and at least n is formed on the nitride semiconductor substrate. A nitride semiconductor device, comprising: a device structure having a p-type nitride semiconductor, an active layer, and a p-type nitride semiconductor. 15. The nitride semiconductor device according to claim 1, wherein the nitride semiconductor element has a stripe-shaped first protective film or a ridge-shaped stripe of the stripe-shaped first unevenness formed in parallel with the stripe direction. 15. The nitride semiconductor device according to 14. 16. A ridge-shaped stripe of the nitride semiconductor device, wherein the ridge-shaped stripe is formed on a stripe-shaped first protective film,
16. The nitride semiconductor device according to claim 14, wherein the nitride semiconductor device is formed above a concave portion of the stripe-shaped first unevenness.