JPH11191657A - Growing method of nitride semiconductor and nitride semiconductor device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a growing method for nitride semiconductor of with good crystallinity. SOLUTION: A first protective film 11 is partly formed on a dissimilar substrate 1 consisting of a material different from that of a nitride semiconductor or on the surface of a nitride semiconductor layer 2 grown on the dissimilar substrate 1, and a first nitride semiconductor layer 3 is grown via the first protective film 11. The first nitride semiconductor 3 is selectively grown on the protective film 11 and continuously joined together with an adjacent nitride semiconductor on the protective film 11 as it continues to grow. The first nitride semiconductor 3 on the first protective film 11 has few lattice defects, so that a nitride semiconductor substrate of good crystallinity is obtained, when a thick nitride semiconductor film is grown via a protective film. A nitride semiconductor substrate is grown to a prescribed thickness, and when an element structure is formed thereon, a satisfactory element with improved characteristics is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a nitride semiconductor (In _XA).
The present invention relates to a method for growing l _Y Ga _{1 -XYN} , 0 ≦ X, 0 ≦ Y, X + Y ≦ 1), and particularly to a method for growing a substrate made of a nitride semiconductor.

[0002]

2. Description of the Related Art Generally, when a semiconductor is grown on a substrate,
It is known that when a substrate lattice-matched with a semiconductor to be grown is used, crystal defects of the semiconductor are reduced and crystallinity is improved. However, nitride semiconductors generally have sapphire,
Spinel is grown on a heterogeneous substrate that does not lattice match with a nitride semiconductor such as silicon carbide.

On the other hand, GaN lattice-matched with a nitride semiconductor
Attempts to fabricate bulk crystals have been made by various research institutions, but only reports of a few millimeters have been reported, which is far from practical use.

As a technique for manufacturing a GaN substrate, for example, Japanese Patent Application Laid-Open No. 7-202265 and Japanese Patent Application Laid-Open
No. 8 discloses a technique of forming a buffer layer made of ZnO on a sapphire substrate, growing a nitride semiconductor on the buffer layer, and then dissolving and removing the buffer layer. However, the crystallinity of a ZnO buffer layer grown on a sapphire substrate is poor, and it is difficult to obtain a good quality nitride semiconductor crystal even if a nitride semiconductor is grown on the buffer layer. Further, it is also difficult to continuously grow a thick nitride semiconductor serving as a substrate on a thin buffer layer made of ZnO.

[0005]

When a nitride semiconductor element used for various electronic devices such as an LED element, an LD element and a light receiving element is manufactured, if a substrate made of a nitride semiconductor can be manufactured, By growing a new nitride semiconductor on a substrate and growing a nitride semiconductor with few lattice defects, the crystallinity of these devices is dramatically improved, and devices that have not been realized before can be realized. Become. Accordingly, it is an object of the present invention to provide a method for growing a nitride semiconductor having good crystallinity, and more specifically, a method for growing a nitride semiconductor serving as a substrate, and a novel method including a nitride semiconductor substrate. It is to provide an element having a structure.

[0006]

That is, the present invention can achieve the object of the present invention by the following constitutions (1) to (22). (1) a first step of partially forming a first protective film on a nitride semiconductor grown on a heterogeneous substrate made of a different material from the nitride semiconductor; Growing the nitride semiconductor on the nitride semiconductor and growing the nitride semiconductor on the first protective film. (2) The nitride semiconductor according to (1), wherein the first protective film is formed to have a surface area larger than a surface area of a portion where the first protective film is not formed. Growth method. (3) A first protective film is partially formed on a heterogeneous substrate made of a material different from that of the nitride semiconductor so as to have a surface area larger than a surface area of a portion where the first protective film is not formed. A first step and, after the first step, a second step of growing a first nitride semiconductor on the heterogeneous substrate and growing the first nitride semiconductor on the first protective film. A method for growing a nitride semiconductor. (4) The first protective film is formed in a stripe shape, and the width of a portion (window portion) where the adjacent stripe-shaped first protective film is not formed is 5 μm or less. The method for growing a nitride semiconductor according to any one of the above (1) to (3). (5) The ratio (Ws / Ww) of the width (Ww) of the window portion to the width (Ws) of the stripe-shaped first protective film is 1 to 20, wherein (1) to (4). The method for growing a nitride semiconductor according to any one of the above items.

(6) The method for growing a nitride semiconductor according to any one of (1) to (5), wherein the heterogeneous substrate has a main surface off-angled from the main surface of the substrate. . (7) The method for growing a nitride semiconductor according to (6), wherein the heterogeneous substrate is off-angled in a step shape. (8) The heterogeneous substrate is sapphire having a (0001) plane = (C plane) as a main surface, and the first protective film is perpendicular to the (112-0) plane of the sapphire = (A plane). (1) to (1), characterized in that the
(7) The method for growing a nitride semiconductor according to any one of (7). (9) The heterogeneous substrate is sapphire having a (112-0) plane = (A plane) as a main surface, and the first protective film is formed on the (11-02) plane of the sapphire = (R plane). (1) characterized by having a vertical stripe shape.
The method for growing a nitride semiconductor according to any one of (7) to (7). (10) The heterogeneous substrate is a spinel whose main surface is a (111) plane, and the first protective film has a stripe shape perpendicular to the (110) plane of the spinel. The method for growing a nitride semiconductor according to any one of (1) to (7).

(11) After the second step, a third step of partially forming a second protective film on the first nitride semiconductor, and after the third step, a second nitride Semiconductors in the first
A fourth step of growing on the second protective film as well as growing on the nitride semiconductor of the above (1) to (10). Method of growing semiconductors. (12) The method for growing a nitride semiconductor according to (11), wherein the second protective film is formed on a crystal defect appearing on a surface of the first nitride semiconductor. (13) The device according to (1), wherein the second protective film has a stripe shape parallel to the first protective film.
The method for growing a nitride semiconductor according to 1) or 12).

(14) On the nitride semiconductor grown on a heterogeneous substrate made of a different material from the nitride semiconductor,
Is partially formed, a first nitride semiconductor is grown on the first protective film, and a nitride semiconductor having an element structure is laminated on the first nitride semiconductor. A nitride semiconductor device characterized by being produced. (15) The nitride semiconductor according to (14), wherein the first protective film is formed to have a surface area larger than a surface area of a portion where the first protective film is not formed. element. (16) A first protective film is partially formed on a heterogeneous substrate made of a material different from a nitride semiconductor, with a surface area larger than a surface area of a portion where the first protective film is not formed. A first nitride semiconductor is grown on the first protective film, and a nitride semiconductor having an element structure is stacked on the first nitride semiconductor. Semiconductor device. (17) The semiconductor device according to any one of (14) to (16), wherein the first nitride semiconductor has a total film thickness of 1 μm or more and 50 μm or less, and has the heterogeneous substrate. 2. The nitride semiconductor device according to claim 1. (18) The first nitride semiconductor has a total film thickness of 70 μm
The nitride semiconductor device according to any one of the above (14) to (16), having the above film thickness, wherein the heterogeneous substrate is removed. (19) The first nitride semiconductor has a window width of 5 μm.
m, wherein the first protective film is formed on a first protective film having a stripe shape of not more than m.
4) The nitride semiconductor device according to any one of the items (18) to (18). (20) The nitride according to any one of (14) to (19), wherein the nitride semiconductor having the element structure includes an n-side nitride semiconductor having a superlattice structure. Semiconductor device. (21) The (14), wherein an n-electrode is formed on the n-side nitride semiconductor having the superlattice structure.
The nitride semiconductor device according to any one of (1) to (20). (22) The width of the window (Ww) and the width of the protective film (Ws)
Wherein the ratio Ws / Ww of the nitride semiconductor device is 1 to 20.

That is, according to the growth method of the present invention, a first protective film is formed on a nitride semiconductor grown on a heterogeneous substrate (a method of the first embodiment), and the first nitride semiconductor is grown. By doing so, a nitride semiconductor with few crystal defects and good crystallinity can be obtained. Further, in the first embodiment of the present invention, the first protective film grown on the nitride semiconductor has a surface area larger than the surface area of the portion (window portion) where the first protective film is not formed. The formation is preferable because crystal defects are further reduced and the first nitride semiconductor is easily grown. According to another growth method of the present invention, a first protective film is formed on a heterogeneous substrate (the method of the second embodiment), and the surface area of the first protective film is not formed with the protective film. By having a surface area larger than the surface area of the window portion and growing the first nitride semiconductor on the first protective film, a nitride semiconductor with few crystal defects and good crystallinity can be obtained. In the growth method according to the second aspect, a first protective film is formed directly on a heterogeneous substrate,
When the first nitride semiconductor layer is grown from the exposed surface of the different substrate (the window where the protective film is not formed), relatively many crystal defects are generated, but the surface area of the first protective film and the window By adjusting the surface area of the portion, a first nitride semiconductor layer with few crystal defects can be obtained. When the surface area is further adjusted, the first nitride semiconductor starts to selectively grow on the window portion.

Further, in the method according to the first and second aspects of the present invention, since the heterogeneous substrate has a main surface that is off-angled (inclined) from the main surface of the heterogeneous substrate, the nitridation with a small number of crystal defects is reduced. It is preferable to form the semiconductor in a stepwise manner, as compared with the case where the off-angle is formed continuously, since crystal defects are reduced as compared with the case where the off-angle is formed continuously.

Further, in the methods of the first and second embodiments of the present invention, the number of crystal defects can be further reduced by specifying the plane orientation of the heterogeneous substrate and / or the shape of the first protective film. It is preferable because it can be performed.

Further, in the method according to the first and second aspects of the present invention, the first protective film is formed as a stripe having a width of the window (distance between the protective film and the protective film) of 5 μm or less. In this case, crystal defects generated at the interface between the heterogeneous substrate and the nitride semiconductor are less likely to be dislocated in the surface direction of the first nitride semiconductor, and crystal defects appearing on the surface of the first nitride semiconductor are reduced, which is preferable. Further, by adjusting the ratio Ws / Ww of the width (Ww) of the window portion to the width (Ws) of the protective film so as to be 1 to 20, the dislocation of crystal defects tends to be further reduced. This is preferable because crystal defects appearing on the surface of the nitride semiconductor are further reduced.

In the first and second embodiments of the present invention, preferably, after the second step, a second protective film is partially formed on the first nitride semiconductor. By growing the second nitride semiconductor on the second protective film, dislocation of crystal defects can be further suppressed,
This is preferable because crystal defects appearing on the surface of the second nitride semiconductor are further reduced. Further, it is preferable that the second protective film be formed on the crystal defect appearing on the surface of the first nitride semiconductor so as to cover the crystal defect, because dislocation of the crystal defect can be more favorably prevented.

Further, when the second protective film is formed so as to have a stripe shape parallel to the first protective film,
It is preferable to obtain the effects of the present invention. This is, for example, the first
When the protective film is provided in a direction perpendicular to the sapphire A surface, in a direction perpendicular to the sapphire R surface, and in a direction perpendicular to the spinel (110) surface, This means that the stripe of the first protective film and the stripe of the second protective film are provided in the same parallel direction.

The nitride semiconductor device of the present invention is formed by laminating a nitride semiconductor having an element structure on the first nitride semiconductor having few crystal defects obtained by the method of the first embodiment of the present invention. Since the nitride semiconductor device of the first embodiment is used, the crystallinity of the device structure is improved and the nitride semiconductor device has good performance. Further, in the nitride semiconductor device according to the first aspect of the present invention, the first protective film is formed so as to have a surface area larger than a surface area of a portion where the first protective film is not formed. It is preferable that the element structure is stacked on the nitride semiconductor because a crystal defect appearing on the surface of the first nitride semiconductor is small, so that a nitride semiconductor element having better performance can be obtained.

According to another nitride semiconductor device of the present invention, a nitride semiconductor having an element structure is laminated on a first nitride semiconductor having few crystal defects obtained by the method of the second embodiment of the present invention. (The nitride semiconductor device of the second embodiment), the crystallinity is improved and the nitride semiconductor device has good performance.

Further, in the nitride semiconductor device according to the first and second aspects of the present invention, the first protective film has a window width of 5 mm.
When the stripe shape is not more than μm, crystal defects of the first nitride semiconductor are further reduced, and device performance is further improved, which is preferable. An n-side nitride semiconductor having a superlattice structure is formed as a nitride semiconductor having an element structure, and an n-electrode is formed on the n-side nitride semiconductor having the superlattice structure.
Also, the ratio Ws / of the width (Ww) of the window and the width (Ws) of the protective film is obtained.
When Ww is 1 to 20, the effect of the present invention is more likely to be obtained more favorably.

[0019]

BEST MODE FOR CARRYING OUT THE INVENTION The growth method of the present invention will be described in more detail below by taking a specific schematic view of one embodiment of the growth method of the first embodiment of the present invention as an example. According to the growth method of the first mode and the growth method of the second mode of the present invention, the surface on which the first protective film is formed in the first step has a nitride semiconductor layer (for example, a buffer layer, GaN layer, etc.) (first mode) or a heterogeneous substrate surface (second mode)
Furthermore, when a protective film is formed on the surface of a heterogeneous substrate in the second embodiment, the surface area of the first protective film and the window portion are set in advance so that the first nitride semiconductor layer can be easily grown. The difference is that the size of the surface area is adjusted, but the others are almost the same. Also in the first embodiment, the first nitride semiconductor can be more favorably grown by adjusting the surface area of the first protective film and the width of the window. First, the growth method according to the first embodiment of the present invention will be described, and then the growth method according to the second embodiment of the present invention will be described.

FIGS. 1 to 6 are schematic sectional views showing the structure of a nitride semiconductor wafer obtained in each step of the growth method according to the first embodiment of the present invention. In the figure,
Reference numeral 1 denotes a heterogeneous substrate, 2 denotes a nitride semiconductor layer, 3 denotes a first nitride semiconductor layer, 4 denotes a second nitride semiconductor layer, 11 denotes a first protective film, and 12 denotes a second protective film.

According to the growth method of the first aspect of the present invention, the first
In the step, as shown in FIG. 1, a nitride semiconductor layer 2 is grown on the buffer layer grown on the heterogeneous substrate 1, and a first protective film 11 is partially formed on the nitride semiconductor layer 2. Formed. Dissimilar substrate 1 usable in the present invention
As it may be mentioned any substrate made of a material different from the nitride semiconductor, for example, other sapphire C plane, sapphire having the principal R-plane, A plane, spinel (MgA1 ₂ O ₄₎ Such an insulating substrate, SiC (6H,
4H, 3C), ZnS, ZnO, GaAs, S
A substrate material different from a conventionally known nitride semiconductor, such as i and an oxide substrate lattice-matched with a nitride semiconductor, can be used. Further, a substrate in which the main surface of the substrate material is off-angled, and more preferably a substrate in which the main surface is off-angled in a step shape, can be used. As described above, it is preferable that the main surface of the heterogeneous substrate be off-angle because crystal defects are further reduced.

As the buffer layer 2 formed on the heterogeneous substrate 1 shown in FIG. 1, for example, AlN, GaN, A
It is formed by growing lGaN, InGaN or the like at a temperature of 900 ° C. or less with a film thickness of several tens angstroms to several hundred angstroms. This buffer layer is formed in order to mitigate an irregular lattice constant between the heterogeneous substrate 1 and the nitride semiconductor layer 2, but may be omitted depending on the nitride semiconductor growth method, the type of the substrate, and the like. Further, the buffer layer is preferable for alleviating lattice mismatch between the heterogeneous substrate and the nitride semiconductor layer 2 and preventing generation of crystal defects.

In the growth method according to the first aspect of the present invention,
As the nitride semiconductor layer 2 grown after the first step,
Undoped (Undoped state, undop
e) GaN, GaN doped with n-type impurities, and S
GaN doped with i can be used. The nitride semiconductor 2 is heated at a high temperature, specifically, 900 ° C. to 1100 ° C.
It is grown on a heterogeneous substrate at a temperature of 10 ° C., preferably 1050 ° C., and the film thickness is not particularly limited. When the thickness of the nitride semiconductor layer 2 is in the above range, the total thickness of the nitride semiconductor layer 2 and the first nitride semiconductor can be suppressed, and the warpage of the wafer (warpage in a state having a heterogeneous substrate) can be prevented, which is preferable. .

As a material of the first protective film 11, a material having a property that a nitride semiconductor does not grow or hardly grows on the surface of the protective film is preferably selected. For example, silicon oxide (SiO _x ), silicon nitride ( Oxides such as Si _x N _y ), titanium oxide (TiO _x ), and zirconium oxide (ZrO _x ), nitrides, multi-layer films thereof, and metals having a melting point of 1200 ° C. or more can be used. These protective film materials have a nitride semiconductor growth temperature of 600 ° C. to 11 ° C.
It has the property of withstanding a temperature of 00 ° C. and preventing the nitride semiconductor from growing or hardly growing on its surface. 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.
Further, in order to partially (selectively) form, a photomask having a predetermined shape is manufactured by using a photolithography technique, and the material is vapor-phase-formed through the photomask. The first protective film 11 having a predetermined shape can be formed. The shape of the first protective film 11 is not particularly limited. For example, the first protective film 11 can be formed in a dot, stripe, or checkerboard shape. However, as described later, it is desirable to form the first protective film 11 in a stripe shape with a specific plane orientation. . Further, it is preferable that the surface area of the first protective film 11 is larger than the surface area of the window portion because the first nitride semiconductor 3 with less lattice defects can be easily obtained.

It is preferable that the first protective film 11 is formed such that the surface area of the first protective film is larger than the surface area of the portion (window portion) where the first protective film is not formed. When the surface area of the first protective film is increased as described above,
Dislocation of crystal defects generated at the interface between the heterogeneous substrate and the nitride semiconductor is suppressed by the first protective film, and crystal defects dislocated from the window portion are more likely to be interrupted in the middle, which is preferable. The adjustment of the surface area of the first protective film and the surface area of the window portion vary depending on the shape of the protective film. For example, when the protective film has a stripe shape, the width of the stripe of the protective film and the width of the window portion are adjusted. It can be done by doing. First protective film 1
Although the size of 1 is not particularly limited, for example, when formed in a stripe, a preferable stripe width is 0.5 to 100 μm.
m, more preferably about 1 μm to 50 μm, and the stripe pitch is desirably smaller than the stripe width. In other words, when the surface area of the protective film is larger than that of the window, a nitride semiconductor layer with less crystal defects can be obtained.

Further, as a preferable mode for adjusting the surface area of the protective film and the window portion, it is preferable that the first protective film 11 is formed in a stripe shape and the width of the window portion is adjusted to 5 μm or less, more preferably, the window portion. Of the width (Ww) of the stripe-shaped first protective film, Ws / Ww, is set to 1 to
The adjustment is performed so as to be 0. When the first nitride semiconductor is grown by adjusting the width and Ws / Ww of the first protective film 11 and the window as described above, a nitride semiconductor with very few crystal defects and good crystallinity can be obtained. Can be. The preferred value of the width of the window is 3 μm or less, more preferably 1 μm.
m or less, and the lower limit is 0.1 μm or more. By adjusting the width of the window in this way, a nitride semiconductor layer with less crystal defects can be obtained. The width of the striped protective film is
When the width of the window is 5 μm or less, it is 2 to 30 μm, preferably 5 to 20 μm.
m, more preferably 5 to 15 μm. Within this range, a nitride semiconductor layer with few crystal defects can be obtained, which is preferable. The thickness of the stripe-shaped protective film is not particularly limited, but is, for example, 0.01 to 5 μm, preferably 0.1 to 3 μm, and more preferably 0.1 to 2 μm.
μm. This range is preferable for obtaining the effect. The ratio Ws / Ww of the width (Ww) of the window to the width (Ws) of the protective film is 1 to 20, and preferably 1 to 10. When the number is 1 or less, crystal defects easily occur on the window portion and the protective film.
The nitride semiconductor does not completely adhere to each other, and a cavity is easily formed on the protective film.

Next, in the second step, as shown in FIG. 2, the first nitride semiconductor 3 is grown on the nitride semiconductor layer 2 on which the first protective film 11 has been formed. Nitride semiconductor layer 2
The first nitride semiconductor 3 grown thereon is not particularly limited, but is preferably undoped (undoped) GaN or GaN doped with an n-type impurity.

As shown in FIG. 2, the first nitride semiconductor layer 3 is formed on the nitride semiconductor layer 2 on which the first protective film 11 is formed.
Is grown, the first nitride semiconductor layer 3 does not grow on the first protective film 11, and the first nitride semiconductor layer 3 is selectively grown on the exposed nitride semiconductor layer 2. You. When the growth is further continued, the first nitride semiconductor layer 3 grows laterally on the first protective film 11 and is connected by the adjacent first nitride semiconductor layers 3 as shown in FIG. Then, it is as if the first nitride semiconductor layer 3 had grown on the first protective film 11.

The crystal defects (threading dislocations) appearing on the surface of the first nitride semiconductor layer 3 grown in this manner are much smaller than those of the conventional one. However, the upper portion of the window portion and the first protective film 11 in the initial stage of the growth of the first nitride semiconductor layer 3
The number of crystal defects at the top of each is significantly different. That is, the heterogeneous substrate 1 and the nitride semiconductor layer are added to the first nitride semiconductor layer 3 in the initial stage of growth grown on the portion (window) where the first protective film 11 is not formed on the heterogeneous substrate 1. (For example, a buffer layer in the case of FIG. 2), crystal defects are generated from the interface, and there is a tendency for dislocation to occur in the vertical direction. In the semiconductor layer 3, there is almost no crystal defect dislocation in the vertical direction.

For example, as shown in FIG. 3, a schematic diagram of threading dislocation due to a crystal defect of a nitride semiconductor crystal of a wafer is shown in FIG.
Crystal defects as shown by a plurality of fine lines from the heterogeneous substrate 1 toward the surface of the first nitride semiconductor layer 3;
It is thought that it is transposed. The crystal defects in the window shown in FIG. 3 are generated at the interface between the heterogeneous substrate 1 and the nitride semiconductor due to a mismatch in lattice constant between the heterogeneous substrate 1 and the nitride semiconductor.
It happens very often. Most of the crystal defects in the window portion are dislocated from the interface between the heterogeneous substrate 1 and the nitride semiconductor toward the surface during the growth of the first nitride semiconductor layer 3. However, as shown in FIG. 3, the crystal defects generated from the window continue to be dislocated in the initial growth of the first nitride semiconductor layer 3, but the first nitride semiconductor layer 3 does not grow. As the process continues, the number of crystal defects dislocations in the surface direction tends to decrease drastically, and the number of crystal defects dislocations up to the surface of the first nitride semiconductor layer 3 becomes extremely small. Further, the first nitride semiconductor layer 3 formed on the first protective film 11 is not the one grown from the heterogeneous substrate 1 but the one connected to the adjacent first nitride semiconductor layer 3 during growth. Therefore, the number of crystal defects is very small from the beginning of the growth, as compared with the portion of the first nitride semiconductor layer 3 grown on the nitride semiconductor layer 2 grown from the substrate. As a result, the surface of the first nitride semiconductor layer 3 after the growth is completed has very few dislocation crystal defects on the surface (the upper part of the protective film and the upper part of the window). Almost disappears. By using the first nitride semiconductor layer 3 having very few crystal defects as a growth substrate for a nitride semiconductor having an element structure, a nitride semiconductor element having better crystallinity than before can be realized. In addition, since the occurrence of crystal defects and the tendency of dislocation due to the growth of GaN of the present invention as described above are observed, it is preferable that the surface area of the window be smaller than the surface area of the protective film.

Although the number of crystal defects is reduced both in the window on the surface of the first nitride semiconductor layer 3 and in the upper portion of the protective film, the first nitride grown in the upper portion of the window having many crystal defects in the initial stage of growth. On the surface of the semiconductor layer 3, there is a tendency for crystal defects to be slightly larger than those grown on the protective film. This means
Probably, during the growth of the first nitride semiconductor layer 3, the dislocation of many crystal defects stopped, but the crystal defects that continue to be slightly dislocated tend not to be easily dislocated almost directly above the window portion. It is thought.

When the number of crystal defects due to the difference in the dislocations of the crystal defects is observed by a cross-sectional TEM, dislocations are observed only in the upper portion of the window, and almost no defects are observed in the upper portion of the protective film. In a preferred form, the crystal defect density of the window top, approximately 10 ⁶ / cm ² or less, in a preferred condition is 10 ⁵ / cm ² or less, the protective film upper,
Approximately 10 ⁵ / cm ² or less, preferably 10
⁴ / cm ² or less. Crystal defects can be measured, for example, by measuring the number of etch pits that appear on the etched surface when a nitride semiconductor is dry-etched.

The thickness of the first nitride semiconductor layer 3 is as follows.
Although it differs depending on the thickness and size of the first protective film formed earlier, the first nitride semiconductor layer is grown so as to cover the surface of the protective film. It is desirable to grow with a film thickness of 10 times or more, more preferably 50 times or more. Further, as described above, the thickness of the first nitride semiconductor is such that the dislocations of the crystal defects tend to decrease drastically during the growth of the first nitride semiconductor. It is preferable to adjust as described above. Furthermore, the first nitride semiconductor serves as a substrate on which a nitride semiconductor having an element structure is grown. To form the element structure, a heterogeneous substrate, a protective film, and the like are removed in advance. There is a case where the process is performed only with the nitride semiconductor of No. 1 and a case where the process is performed while leaving a heterogeneous substrate or the like. Further, the removal of the heterogeneous substrate or the like may be performed after the element structure is formed.
When an element structure is formed on the first nitride semiconductor, the thickness of the first nitride semiconductor affects the ease of forming the element structure depending on the presence or absence of a heterogeneous substrate. The thickness of the target semiconductor covers the first protective film, reduces dislocations of crystal defects, and further includes differences in manufacturing processes such as forming an element structure with or without removing a heterogeneous substrate or the like. It is desirable that the adjustment be made in consideration of the above.

When removing a heterogeneous substrate or a protective film, the first
Is grown to a thickness of more than 50 μm and about 1 mm or less, for example, preferably 70 to 500
μm, more preferably 100 to 300 μm, and still more preferably 100 to 250 μm. This range is preferable in terms of the growth of the nitride semiconductor having an element structure, and is preferable because even if the base layer and the protective film are removed by polishing, the first nitride semiconductor is hardly cracked and handling becomes easy. . Further, it is preferable to remove the heterogeneous substrate, since the nitride semiconductor substrate does not warp when forming the element structure, and an element structure with good crystallinity can be easily obtained. In the case where the formation is performed while leaving a heterogeneous substrate, a protective film, and the like, the thickness of the first nitride semiconductor is 1 to 50 μm, preferably 2 to 40 μm, more preferably 5 to 30 μm, and most preferably 10 to 2 μm.
0 μm. Within this range, warpage of the wafer due to a difference in thermal expansion coefficient between the heterogeneous substrate and the nitride semiconductor can be prevented, and a nitride semiconductor having an element structure can be favorably grown on the first nitride semiconductor as an element substrate. be able to.

When a nitride semiconductor is grown on a heterogeneous substrate, the entire wafer tends to be warped after growth due to a difference in thermal expansion coefficient between the heterogeneous substrate and the nitride semiconductor. It tends to increase as the film grows with a thicker film. When performing various processes on the nitride semiconductor layer of a wafer having a heterogeneous substrate to form an operating structure, it is difficult to process the nitride semiconductor when the wafer is warped. Therefore, when a nitride semiconductor device having a heterogeneous substrate is used, the thickness of the first nitride semiconductor layer is such that the film can be easily processed with the heterogeneous substrate attached even when the wafer warps, that is, a film thickness of 50 μm or less. desirable. Note that 1 μm indicates a limit value at which a nitride semiconductor can be grown on the protective film. In the case of a nitride semiconductor device having an element structure formed by leaving a heterogeneous substrate as it is, the first nitride semiconductor layer grown on the protective film is 1 ×
Most preferably, GaN is doped with an n-type impurity in the range of 10 ¹⁶ / cm ^{3 to} 5 × 10 ¹⁹ / cm ³ .

In the case of a nitride semiconductor device obtained by removing a heterogeneous substrate, the first nitride semiconductor is prevented from being cracked or chipped when the heterogeneous substrate is removed, and the handleability in a device process is improved. For this reason, the thickness of the first nitride semiconductor layer is preferably larger than 50 μm.
When the first nitride semiconductor has such a film thickness,
As described above, since the warpage of the wafer is more likely to increase, it is preferable to form the element structure on the first nitride semiconductor layer after removing the heterogeneous substrate. When the dissimilar substrate is removed in this manner, the first nitride semiconductor serving as a substrate for forming an element structure is not warped, and a nitride semiconductor having an element structure is easily formed. Also,
The upper limit of the thickness of the first nitride semiconductor layer is not particularly limited. However, if the thickness is too large, the thickness is preferably 1 mm or less from the viewpoint that the growth time is excessively required. In a nitride semiconductor device obtained by removing a heterogeneous substrate or the like, the heterogeneous substrate may be removed before or after forming an element structure on the first nitride semiconductor. An element structure is formed using the first nitride semiconductor layer as a nitride semiconductor substrate (GaN substrate). Polishing, etching, or the like is used as a method for removing the heterogeneous substrate. Also,
When the second protective film is formed, the element structure is formed on the second nitride semiconductor by removing only the second protective film when removing the heterogeneous substrate and using only the second nitride semiconductor. Alternatively, the element structure may be formed using the first nitride semiconductor and the second nitride semiconductor as a GaN substrate without removing the second protective film. Further, when growing a nitride semiconductor having an element structure on the nitride semiconductor substrate from which the heterogeneous substrate or the like has been removed, the element structure is grown on the surface opposite to the exposed surface by removing the heterogeneous substrate or the like. This is preferable since an element having good crystallinity can be obtained.

In the present invention, the thickness of the first nitride semiconductor layer is the thickness of the first nitride semiconductor layer 3 alone shown in FIGS. 6 and 8 or the thickness of the first nitride semiconductor layer. 3 and the total thickness of the second nitride semiconductor layer 4. That is, it refers to the film thickness of the nitride semiconductor layer grown on the first protective film 11 which is first grown on the substrate.

Next, as a preferred step, a third step and a fourth step are performed after the second step, whereby a nitride semiconductor substrate having an element structure can be obtained with good crystallinity.
First, in the third step of the present invention, as shown in FIG. 4, a portion where crystal defects are likely to appear on the surface of the first nitride semiconductor layer 3, for example, on the upper portion of the window portion or on the surface. A new protective film (second protective film 12) is provided to cover the crystal defects. In the present invention, the second protective film 12
The formation position of the first nitride semiconductor layer 3 is not particularly limited.
Is preferably partially formed on the surface of the first nitride semiconductor layer 3.
Is formed so as to cover the crystal defects appearing on the surface of the first nitride semiconductor layer 3, and more preferably above the window portion where the crystal defects exist in the initial growth of the first nitride semiconductor layer 3. By providing the second protective film 12 in this manner, it is possible to prevent further dislocation of crystal defects that have been displaced to the surface of the first nitride semiconductor layer 3. It is conceivable that the interrupted crystal defect may relocate to the active layer or the like during operation of the laser element or the like.

In FIG. 4, a flat surface is polished to reduce irregularities on the surface of the first nitride semiconductor layer 3 grown in FIG. A second protective film 12 may be formed on the surface of the semiconductor layer 3.

Preferably, the surface area of the second protective film 12 is not particularly limited. desirable. For example, when the first protective film 11 has a stripe shape, the second stripe-shaped second film having a width larger than the width of the window portion.
Is formed on the upper part of the window. Second protective film 12
Can be used as the material of the first protective film.

Next, in the fourth step of the present invention, the second
The second nitride semiconductor layer 4 is grown on the first nitride semiconductor layer 3 on which the protective film 12 is formed. As shown in FIG. 5, the second nitride semiconductor layer 4 does not grow on the second protective film 12 like the first nitride semiconductor layer 3 at first, and the first nitride semiconductor layer 3 does not grow. Selective growth only on the semiconductor layer 3. Then, the second nitride semiconductor layer 4 grown on the first nitride semiconductor layer 3 is the same nitride semiconductor,
Moreover, since the crystal is grown on the first nitride semiconductor layer 3 having few crystal defects, crystal defects due to mismatch of lattice constants are less likely to occur. Further, the second nitride semiconductor layer 4
Since the first nitride semiconductor layer 3 serving as the underlayer has few crystal defects, the number of dislocation crystal defects in the initial growth of the second nitride semiconductor layer 4 also decreases.

When the growth is further continued, as shown in FIG. 6, the adjacent second nitride semiconductor layers 4 are connected to each other at the upper part of the second protective film 12 so as to cover the second protective film 12. To grow. The second nitride semiconductor layer 4 thus grown grows with the first nitride semiconductor layer 3 having few crystal defects as a base layer, and thus becomes a nitride semiconductor having very few crystal defects. By using the second nitride semiconductor 4 as a growth substrate for a nitride semiconductor having an element structure, a nitride semiconductor element having extremely excellent crystallinity can be realized. Since the second protective film 12 is formed so as to cover the crystal defects appearing on the surface of the first nitride semiconductor 3, dislocation of the crystal defects can be suppressed. Further, even if a slight crystal defect continues dislocation in the early stage of the growth of the second nitride semiconductor 4, as in the case of the growth of the first nitride semiconductor 3, As the growth continues, dislocation of crystal defects tends to stop, and crystal defects appearing on the surface of the second nitride semiconductor 4 decrease. Since the second nitride semiconductor layer 4 thus obtained has fewer crystal defects than the first nitride semiconductor layer 3, when the element structure is formed on the second nitride semiconductor layer 4, the crystallinity becomes low. Good elements are more easily obtained.

Next, a growth method according to the second embodiment of the present invention will be described. 7 and 8 are schematic cross-sectional views showing the structure of a wafer in some steps according to one embodiment of the growth method according to the second embodiment of the present invention.

In the growth method according to the second embodiment of the present invention, as shown in FIG. 7, in a first step, a first protective film 11 is formed on a heterogeneous substrate 1 by forming the first protective film 11. Forming a partial layer having a surface area larger than the surface area of the portion (window portion) which is not formed, and then forming a buffer layer on the heterogeneous substrate 1 where the window portion is exposed in a second step; From above, the first nitride semiconductor layer 3 is grown as shown in FIG. In the growth method of the second embodiment, the buffer layer may be omitted in some cases. In the growth method according to the second embodiment, the first nitride semiconductor layer 3 is selectively grown from the window portion, similarly to the growth method according to the first embodiment.
Then, the first nitride semiconductor layer 3 is formed as shown in FIG. As shown in FIG. 8, the crystal defects generated at the interface between the heterogeneous substrate 1 and the nitride semiconductor (the buffer layer in the second embodiment) are the same as in the first embodiment. In the meantime, dislocations are generated from the window portion, but the dislocations are drastically reduced while the growth of the first nitride semiconductor layer 3 is continued, and further, crystal defects are hardly generated on the upper part of the first protective film 11. Crystal defects are reduced on the surface of the nitride semiconductor layer 3. Further, in the growth method of the second embodiment, as in the case of the growth method of the first embodiment, if the adjustment of the width of the protective film and the width of the window portion and the plane orientation of the heterogeneous substrate are specified, the better first Is obtained. Second
The different substrate, the protective film, the buffer layer, and the first nitride semiconductor layer 3 used in the growth method of the first embodiment may be the same as those used in the growth method of the first embodiment.

In the growth method according to the second embodiment of the present invention, the buffer layer and the first nitride semiconductor layer 3 grown on the buffer layer are also referred to as a first nitride semiconductor layer. That is, in the second step of claim 3, the first protective film 1 is grown continuously with the surface of the heterogeneous substrate 1 or continuously with the nitride semiconductor grown on the heterogeneous substrate.
All the nitride semiconductors grown to the upper part are defined as the first nitride semiconductor layer 3.

Further, in the growth method according to the second embodiment of the present invention, preferably, as in the case of the growth method according to the first embodiment, the surface of the first nitride semiconductor layer 3 is formed as a third step. The second protection is provided so as to cover the crystal defects appearing in the first region, at the portion where the crystal defects are likely to appear, and at the top of the window where the crystal defects are dislocated in the early stage of the growth of the first nitride semiconductor layer 3. The film 12 is formed, and subsequently, as a fourth step, the second nitride semiconductor layer 4 is grown on the first nitride semiconductor layer 3 on which the second protective film 12 has been formed. When the second protective film 12 is formed in this manner, similar to the growth method of the first embodiment,
It is possible to further suppress dislocations of crystal defects appearing on the surface of the first nitride semiconductor layer 3 and to prevent re-dislocation of crystal defects in which dislocations have been interrupted. The second nitride semiconductor 4 can be obtained as a nitride semiconductor substrate that can be formed. For example, as shown in FIG. 8, when the second protective film is formed above the window where the crystal defects are dislocated in the early stage of the growth of the first nitride semiconductor layer 3, re-dislocation of the crystal defects in which the dislocations are interrupted is performed. The second protective film 1 even if
2, dislocation to the second nitride semiconductor layer 4 can be prevented.

In the growth methods according to the first and second embodiments of the present invention, the third step and the fourth step can be performed repeatedly. That is, it is preferable to further form a new protective film on the portion of the nitride semiconductor layer where crystal defects are exposed, and grow a new nitride semiconductor on the protective film.

Next, a preferred embodiment of the heterogeneous substrate used in the present invention will be described. FIG. 9 is a unit cell diagram showing a crystal structure of a nitride semiconductor. Although the nitride semiconductor has a rhombohedral structure, it can be approximated in a hexagonal system. In the method of the present invention, preferably the C plane = (000
1) Sapphire having a main surface as a surface is used, and the first protective film has a stripe shape perpendicular to the sapphire A surface = (112-0) surface. For example, FIG. 10 is a plan view of a sapphire substrate on the main surface side. In this figure, the sapphire C surface is the main surface, and the orientation flat (orientation flat) surface is A
With the face. As shown in this figure, stripes of the first protective film are formed in a direction perpendicular to the A-plane and parallel to each other. As shown in FIG. 10, 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 the direction perpendicular to the A plane, the nitride semiconductors between the stripes are connected and grow easily, and the crystal growth as shown in FIGS. Become.

Similarly, when a sapphire substrate having the main surface A is used, for example, the orientation flat surface is set to the R surface =
Assuming the (11-02) plane, with respect to the direction perpendicular to the R plane,
By forming stripes parallel to each other, a nitride semiconductor tends to grow easily in the stripe width direction, so that a nitride semiconductor layer with few crystal defects can be grown.

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) and the orientation flat 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 having few crystal defects can be grown.
Although the above description is about the first protective film, when forming the second protective film, similarly, it is possible to form a stripe parallel to the first protective film on the surface of the second nitride semiconductor layer. desirable. The spinel is not shown in the figure because it is tetragonal.

Next, a heterogeneous substrate having a main surface off-angled from the main surface of the heterogeneous substrate will be described with reference to FIG. FIG. 15 is an enlarged schematic view showing a cross section of the sapphire substrate. The substrate off-angled in a step shape shown in FIG. 15 has a substantially horizontal terrace portion A and a step portion B. The surface irregularities of the terrace portion A are adjusted to about 0.5 angstroms on average and about 2 angstroms at maximum, and are formed almost regularly.
On the other hand, the height of the step is adjusted to about 15 angstroms. Although the off angle θ is exaggerated, it is inclined only 0.13 ° with respect to the horizontal plane of the growth surface. It is desirable that the step-like portion having such an off-angle is formed continuously over the entire substrate, but it may be particularly formed partially. The off angle θ indicates an angle between a straight line connecting the bottoms of a plurality of steps and the horizontal plane of the uppermost step as shown in FIG. Step difference is less than 30 angstroms,
More preferably, it is not more than 25 Å, most preferably not more than 20 Å. The lower limit is desirably 2 Å or more. In particular, sapphire C
When a plane is used, the off angle θ from the C plane is adjusted within 1 degree, preferably 0.8 degree or less, and more preferably 0.6 degree or less. In this embodiment, the step-shaped off-substrate is used. By using a heterosubstrate that is appropriately off-angled, the interatomic distance between the nitride semiconductor and the heterogeneous substrate is reduced, and a GaN substrate with less crystal defects can be obtained.

Next, the nitride semiconductor device of the present invention will be described. The nitride semiconductor device according to the first aspect of the present invention includes:
The layer is grown on a first nitride semiconductor which is a substrate of an element structure obtained by the growth method of the first embodiment. In addition, the nitride semiconductor device according to the second aspect of the present invention includes:
It is grown on a first nitride semiconductor which is a substrate of an element structure obtained by the growth method of the second embodiment. In the nitride semiconductor devices of the first and second embodiments of the present invention, the heterogeneous substrate may be removed or left without being removed. When a heterogeneous substrate is left, the total thickness of the first nitride semiconductor is 1 μm or more and 50 μm or less. When the heterogeneous substrate is removed, the total thickness of the first nitride semiconductor is 70 μm or more.

The device structure of the nitride semiconductor device of the present invention is not particularly limited, such as the layer structure, shape, electrodes, etc., and any of them may be used in combination. It is preferable that an n-side nitride semiconductor having a superlattice structure is formed as the n-side nitride semiconductor of the element structure. Such a superlattice layer is preferable because the element performance can be improved.
Further, it is preferable to form an n-electrode on the superlattice layer.
Even if the superlattice layer is doped with an n-type impurity in order to reduce the contact resistance with the electrode, the superlattice layer is preferable in that the crystallinity is improved. Further, as a preferred layer configuration of the element constituting the nitride semiconductor element, for example, having an active layer of a quantum well structure containing In, an active layer sandwiched between cladding layers having different band gap energies,
It is preferable from the viewpoint of improving the performance of the element such as the life characteristic. It is preferable to form an element structure having such a layer structure on the first nitride semiconductor having few crystal defects obtained by the growth method of the present invention because the element performance is further improved. One embodiment of the nitride semiconductor device according to the first and second embodiments of the present invention is specifically shown in Examples. However, the present invention is not limited to this. In the present invention, a method for growing a nitride semiconductor is not particularly limited, but may be an MOV.
All known methods for growing a nitride semiconductor, such as PE (organic metal vapor phase epitaxy), HVPE (halide vapor phase epitaxy), and MBE (molecular beam vapor phase epitaxy), can be applied. A preferred growth method is the MOVPE method, which allows the crystal to grow cleanly. However, MOVPE
Since the method requires time, it is preferable to perform the method in a short time when the film thickness is large.

[0054]

[Example 1] (Growth method of first mode) This example is directed to MOVPE (metal organic chemical vapor deposition), but the method of the present invention is not limited to MOVPE. Instead, any of the known methods for growing nitride semiconductors, such as HVPE (halide vapor phase epitaxy) and MBE (molecular beam vapor phase epitaxy), can be applied.

FIGS. 1 to 6 are schematic sectional views of a wafer in each step showing the first embodiment. A sapphire substrate 1 having a C surface as a main surface and an orientation flat surface as an A surface is set in a reaction vessel. A GaN buffer layer is grown on the sapphire substrate 1 to a thickness of 200 Å. After the growth of the buffer layer, only TMG was stopped, the temperature was raised to 1050 ° C., and when the temperature reached 1050 ° C., TMG,
Undoped GaN layer 2 using ammonia and silane gas
Is grown to a thickness of 5 μm. Buffer layer and GaN layer 2
A photomask in the form of a stripe is formed on the GaN layer 2 of the wafer in which the first and second layers are made of SiO _{2 having a} stripe width of 10 μm and a window of 8 μm by a CVD apparatus.
Is formed with a thickness of 0.1 μm (FIG. 1).
The stripe direction of the first protective film 11 is perpendicular to the sapphire A plane.

After the formation of the first protective film 11, the wafer is transferred to a reaction vessel, and at 1050 ° C., a first nitride semiconductor layer made of undoped GaN is formed to a thickness of 100 μm using TMG and ammonia as source gases. Grow (FIGS. 2 and 3).

Next, the wafer is taken out of the reaction vessel,
The surface of the first nitride semiconductor layer 3 is wrapped into a mirror-like surface, and a stripe width of 12 μm and an interval of 6 μm are formed on the surface of the first nitride semiconductor layer 3 in the same manner as the formation of the first protective film 11. The second protective film 12 made of Si ₃ N ₄ has a thickness of 0.1 μm.
A film thickness of m is formed so as to cover crystal defects (FIG. 4).

After the formation of the second protective film 12, the wafer is returned to the reaction vessel again, and a second nitride semiconductor layer 4 made of undoped GaN is grown to a thickness of 150 μm using TMG and ammonia as source gases. . After the growth of the second nitride semiconductor layer 4, the wafer was taken out of the reaction vessel and the surface was mirror-polished.

(Comparative Example) On the other hand, for comparison, a sapphire substrate having a C-plane as a main surface and an A-plane as an orientation flat surface was formed on a sapphire substrate.
GaN buffer layer of 200 Å was directly grown without forming the protective film 11 of Si, and 1 × 1 of Si was formed thereon.
A GaN doped with 0 ¹⁸ / cm ³ is grown to 100 μm.

The number of lattice defects per unit area of the second nitride semiconductor layer 4 obtained in Example 1 and the GaN layer obtained in Comparative Example was observed by a cross-sectional TEM and compared.
The nitride semiconductor of the present invention is 1/20 as compared with that of the comparative example.
It was reduced to 0 or less. When the surface of the first nitride semiconductor layer 3 was mirror-polished in a state where the second protective film 12 and the second nitride semiconductor layer 4 were not grown and the number of crystal defects was observed, the first The number of crystal defects in the nitride semiconductor layer 3 is 1/10 of the number of crystal defects in the GaN layer of the comparative example.
It was reduced to 0 or less.

Example 2 (Growth Method of Second Embodiment) A 2-inch φ, stripe-shaped photomask is formed on a sapphire substrate 1 having a C-plane as a main surface and an orientation flat surface as an A-plane. A first protective film 11 made of SiO _{2 having a} stripe width of 10 μm and a stripe interval (window portion) of 6 μm is formed with a thickness of 0.1 μm by an apparatus (FIG. 7). In addition,
The stripe direction is formed in a direction perpendicular to the orientation flat surface as shown in FIG.

After the formation of the protective film, the substrate is set in a reaction vessel, the temperature is set to 510 ° C., hydrogen is used as a carrier gas, ammonia and TMG (trimethylgallium) are used as source gases, and the first protective film 11 is formed. A buffer layer made of GaN is grown on the formed substrate 1 to a thickness of about 200 angstroms. (FIG. 7)

After the growth of the buffer layer, only TMG is stopped, and the temperature is raised to 1050 ° C. When the temperature reaches 1050 ° C., a first nitride semiconductor layer 3 made of GaN doped with 1 × 10 ¹⁸ / cm ^{3 of} Si is grown to a thickness of 100 μm using TMG, ammonia and silane gas as source gases (FIG. 8). reference).

After the growth of the first nitride semiconductor layer 3, the wafer is taken out of the reaction vessel, and the surface of the first nitride semiconductor layer 3 is lapped to a mirror surface to obtain a nitride semiconductor substrate made of Si-doped GaN. .

The number of lattice defects per unit area of the GaN layer obtained in Example 2 and the number of lattice defects per unit area of the GaN layer obtained in Comparative Example shown in Example 1 were observed and compared with a cross-sectional TEM. The nitride semiconductor layer was 1 compared with the comparative example.
/ 10 or less.

Example 3 A stripe-shaped mask was formed on the surface of the first nitride semiconductor layer 3 obtained in Example 2, and a stripe width of 10 μm and a window of 6 μm were formed by a CVD apparatus.
A second protective film 12 made of m ₃ Si ₃ N ₄ is formed to a thickness of 0.1 μm (FIG. 8). As shown in FIG. 8, the position of the second protective film 12 is mask-aligned so that the 10 μm stripe of the second protective film 12 is located on the crystal defect so as to cover the crystal defect. At the same time, a stripe parallel to the first protective film 11 is formed. After the formation of the second protective film 12, the wafer is returned to the reaction vessel again, and TMG, ammonia, silane gas is used as a source gas, and the Si is reduced to 1 ×.
A second nitride semiconductor layer 4 made of GaN doped with 10 ¹⁸ / cm ³ is grown to a thickness of 150 μm (FIG. 8). After the growth of the second nitride semiconductor layer 4, the wafer was taken out of the reaction vessel, and the surface was mirror-polished in the same manner as in Example 2 to determine the number of lattice defects per unit area by G in the comparative example.
As compared with the aN layer, the one of the present invention was reduced to 1/100 or less.

Fourth Embodiment In the second embodiment, sapphire having the A surface as the main surface and the orientation flat surface as the R surface is used for the substrate 1. On this sapphire substrate 1, the same first protective film 11 as in the second embodiment is formed. The first protective film 11
Is a stripe perpendicular to the R-plane. Thereafter, a first nitride semiconductor layer 3 made of Si-doped GaN was grown to a thickness of 100 μm in the same manner as in Example 2. As a result, a nitride semiconductor layer having almost the same crystal defects as in Example 2 grew. did it.

Embodiment 5 In Embodiment 5, the first nitride semiconductor layer 3 is grown by HVPE. First, (11
1) The plane is the main plane, and the orientation flat is the (110) plane.
A substrate 1 made of 1 inch φ spinel is prepared. A photomask is formed on the surface of the spinel substrate 1 in the same manner as in the second embodiment, and the first protective film 11 made of SiO ₂ is formed.
Are formed in a stripe shape perpendicular to the orientation flat surface. The stripe width is 12 μm and the stripe interval is 6
μm.

In the HVPE apparatus, a quartz boat containing Ga metal is installed inside a reaction vessel tube made of quartz.
Further, the above-mentioned substrate 1 inclined at an angle is set at a position away from the quartz boat. It should be noted that a halogen gas supply pipe is provided at a position close to the Ga metal in the reaction vessel, and an N source supply pipe is provided at a position close to the substrate separately from the halogen gas supply pipe.

A nitrogen carrier gas and mainly HCl gas are introduced from a halogen gas pipe. At this time, the Ga metal boat was heated to 900 ° C., and the spinel substrate side was heated to 1050 ° C. Then, HCl gas and Ga are reacted to form G
aCl ₃ is generated, and ammonia gas is also supplied mainly from the N source supply pipe close to the spinel substrate side, similarly to the nitrogen carrier gas. Further, silane gas is supplied together with the halogen gas, and the growth is performed at a growth rate of 50 μm / hr for 3 hours. And a Ga doped with 150 μm thick Si at 1 × 10 ¹⁸ / cm ^3.
Grow N.

After the growth, the wafer was taken out of the reactor, the GaN layer was wrapped to remove surface irregularities, and the lattice defect was measured. As a result, a nitride semiconductor layer almost equivalent to that of Example 2 was obtained. .

Example 6 In Example 2, a protective film 11 made of SiO ₂ having a stripe width of 10 μm and a stripe interval (window portion) of 5 μm was formed on the sapphire substrate 1 by 1 μm.
In the same manner except that the film is formed with a film thickness of 1 × 10 ¹⁸ /
cm ³ first nitride semiconductor layer 3 made of GaN doped
Is grown to a thickness of 100 μm. After the growth of the first nitride semiconductor layer 3, the wafer is taken out of the reaction vessel, and the surface of the first nitride semiconductor layer 3 is lapped to a mirror surface,
A nitride semiconductor substrate made of Si-doped GaN is obtained.

On the wafer of the GaN layer obtained in Example 6 and the GaN layer obtained in Comparative Example shown in Example 1 above,
Nine locations were arbitrarily selected in a range of 0 × 15 μm, the number of crystal defects per unit area was observed by a cross-sectional TEM, and the number of crystal defects was measured. In addition, as a method of measuring crystal defects, first, the GaN substrate is etched by about 1 μm by dry etching, and then observed by a cross-sectional TEM to count the crystal defects. As a result, the present invention shows that the number of crystal defects is about 1.3.
× 10 ⁶ / cm ² , and the comparative example was about 2.4 × 10 6
⁷ pieces / cm ² , and that of the present invention was 1/1 compared to the comparative example.
It was reduced to 0 or less. Further, as compared with Example 2, the number of crystal defects was further reduced.

Embodiment 7 The first embodiment is the same as the first embodiment except that a protective film 11 made of SiO ₂ having a stripe width of 10 μm and a window portion of 3 μm is formed on the undoped GaN layer 2 to a thickness of 1 μm. A nitride semiconductor layer 3 is grown to a thickness of 100 μm. After the growth of the first nitride semiconductor layer 3, the wafer is taken out of the reaction vessel, the back surface of the first nitride semiconductor layer 3 is wrapped and the sapphire substrate is removed to obtain a mirror-like nitride semiconductor made of Si-doped GaN. Obtain a substrate. When the number of crystal defects per unit area was measured in the same manner as in Example 6, the number was 1 × 10 ³ more than in Example 6.
A number / cm ^2, it was possible to obtain almost no nitride semiconductor substrate comprising an element substrate having a very good crystallinity of the crystal defects. Further, the seventh embodiment is the first embodiment of the first embodiment.
The number of crystal defects was further reduced as compared with that of the nitride semiconductor layer 3.

Example 8 A first protective film was formed on a sapphire substrate 1 in the same manner as in Example 6, except that sapphire having the A surface as the main surface and the orientation flat surface as the R surface was used. Then, a first nitride semiconductor layer 3 made of Si-doped GaN is grown to a thickness of 100 μm. Note that the shape of the first protective film 11 is a stripe perpendicular to the R plane. As a result, a nitride semiconductor layer with very few crystal defects almost equivalent to that of Example 6 could be grown.

[Embodiment 9] In the embodiment 5, the SiO ₂
The first protective film 11 made of
GaN doped with 150 μm of Si at a concentration of 1 × 10 ¹⁸ / cm ³ is grown in the same manner except that m, the window is 3 μm, and the thickness is 1 μm. After the growth, the wafer was taken out of the reaction vessel, the spinel substrate was wrapped and removed, and the number of crystal defects was measured. was gotten.

[Embodiment 10] FIG. 11 is a schematic cross-sectional view showing the structure of an LED device using a nitride semiconductor layer obtained by the growth method of the present invention as a substrate. Hereinafter, a tenth embodiment will be described with reference to FIG.

The sapphire substrate 1, the buffer layer, the first protective film 11, and a part of the first nitride semiconductor layer 3 of the wafer obtained in Example 2 were polished and removed, and the first nitride semiconductor layer was removed. 3 is exposed to form only the first nitride semiconductor layer 3. A wafer having the main surface of the first nitride semiconductor layer 3 (Si-doped GaN) is set in a reaction vessel of a MOVPE apparatus, and at 1050 ° C., the heterogeneous substrate 1 and the like of the first nitride semiconductor layer 3 are removed. Si on the surface opposite to the exposed surface
A second buffer layer 31 made of GaN doped with 1 × 10 ¹⁸ / cm ³ is grown. This second buffer layer 31
Is a nitride semiconductor single crystal layer which is normally grown at a high temperature of 900 ° C. or more, and is distinguished from the buffer layer 2 which is grown at a low temperature for alleviating lattice mismatch with the substrate.

Further, on the second buffer layer 31, In _0.4 G having a single quantum well structure and a thickness of 20 Å is formed.
An active layer 32 of a _0.6 N, a p-side cladding layer 33 of Mg-doped Al _0.2 Ga _0.8 N having a thickness of 0.3 μm, and a p-side contact layer 34 of Mg-doped GaN having a thickness of 0.5 μm are sequentially grown. .

The second buffer layers 31 to p having the element structure
After the growth of the side contact layer 34, the wafer is taken out of the reaction vessel and annealed at 600 ° C. in a nitrogen atmosphere to reduce the resistance of the p-side cladding layer 33 and the p-side contact layer 34. Thereafter, etching is performed from the p-side contact layer 34 side to expose the surface of the first nitride semiconductor layer 3. As described above, by exposing the nitride semiconductor layer below the active layer by etching and providing a “cut margin” at the time of cutting the chip, it becomes difficult to give an impact to the pn junction surface at the time of cutting, so that the yield is also reduced. An improved and highly reliable element can be obtained.

After etching, the translucent p-electrode 35 made of Ni / Au is formed on almost the entire surface of the p-side contact layer 34.
Is formed to a thickness of 200 angstroms, and a pad electrode 36 for bonding is formed on the p electrode 35 by 0.5.
It is formed with a film thickness of μm. FIG. 12 is a plan view of the chip after the formation of the p-electrode (a view from the pad electrode 36 side).

After the formation of the p-side electrode, an n-electrode 37 is formed to a thickness of 0.5 μm on the entire surface of the first nitride semiconductor layer 3 exposed by removing the sapphire substrate 1 and the like.

Then, scribe from the n-electrode side,
Is cleaved on the M-plane (101-0) of the nitride semiconductor layer 3 and a plane perpendicular to the M-plane to obtain a 300 μm square LED chip. This LED emits green light of 520 nm at 20 mA, and its output is twice or more and the electrostatic withstand voltage is twice or more as compared with that obtained by growing a nitride semiconductor device structure on a conventional sapphire substrate. It showed excellent properties.

[Embodiment 11] FIG. 13 is a schematic sectional view showing the structure of a laser device using a nitride semiconductor layer obtained by the growth method of the present invention as a substrate. Hereinafter, an eleventh embodiment will be described with reference to FIG.

The sapphire substrate 1, the buffer layer, the first protective film 11, the first nitride semiconductor layer 3, the second protective film 12, and the second nitride semiconductor layer 4 of the wafer obtained in Example 3.
Of the second nitride semiconductor layer 4 (Si-doped GaN) is set in a reaction vessel of the MOVPE apparatus at 1050 ° C. On the surface opposite to the surface exposed by removing the sapphire substrate 1 and the like, G doped with 1 × 10 ¹⁸ / cm ^{3 of} Si
A third buffer layer 41 of aN is grown. Third
Buffer layer 41 is a nitride semiconductor single crystal layer grown at a high temperature of 900 ° C. or higher, as in Example 10, and at a low temperature for reducing lattice mismatch between a conventionally grown substrate and the nitride semiconductor. It is distinguished from the buffer layer to be grown. In the case of manufacturing a laser device, the third buffer layer 41 is a strained superlattice formed by laminating nitride semiconductors having different thicknesses of 100 Å or less, more preferably 70 Å or less, and most preferably 50 Å or less. Preferably, it is a layer. When the strained superlattice layer is used, the crystallinity of the single nitride semiconductor layer is improved, so that a high-power laser element can be realized. LED
A strained superlattice layer may be applied to the cladding layer of the device.

(Crack Prevention Layer 42) Next, 5 × 1 of Si
0 ¹⁸ / cm ³ doped crack preventing layer 42 made of In _0.1 Ga _0.9 N and the is grown to the thickness of 500 angstroms. The crack prevention layer 42 is made of an n-type nitride semiconductor containing In, preferably InGaN, so that cracks can be prevented from entering the nitride semiconductor layer containing Al. The crack preventing layer is preferably grown to a thickness of 100 Å or more and 0.5 μm or less. If it is thinner than 100 Å, it is difficult to act as a crack prevention as described above.
If it is thicker than m, the crystals themselves tend to turn black. The crack prevention layer 42 can be omitted.

(N-side cladding layer 43) Next, Si was added to 5 ×
A first layer of 10 ¹⁸ / cm ³ doped n-type Al _0.2 Ga _0.8 N, 20 Å, and undoped
A superlattice structure having a total film thickness of 0.4 μm is formed by alternately laminating 100 second layers composed of GaN of pe) and 20 angstroms. The n-side cladding layer 43 functions as a carrier confinement layer and a light confinement layer, and is preferably a nitride semiconductor containing Al, preferably a superlattice layer containing AlGaN, and the total thickness of the superlattice layer is 100 Å or more. It is desirable that the growth be made at 2 μm or less, more preferably at 500 Å or more and 1 μm or less. When a superlattice layer is formed, a carrier confinement layer having good crystallinity without cracks can be formed.

(N-side light guide layer 44)
An n-type optical guide layer 44 of n-type GaN doped with × 10 ¹⁸ / cm ³ is grown to a thickness of 0.1 μm. This n-side light guide layer 44 acts as a light guide layer of the active layer,
It is desirable to grow GaN or InGaN, usually 100 Å to 5 μm, more preferably 2 Å.
It is desirable to grow with a film thickness of 00 Å to 1 μm. The n-side light guide layer 44 is usually made of Si, G
e is doped with an n-type impurity such as e to obtain an n-type conductivity type.
In particular, it can be undoped. When a superlattice is used, at least one of the first layer and the second layer may be doped with an n-type impurity or may be undoped.

(Active Layer 45) Next, undoped In
_A well layer of _0.2 Ga _0.8 N, 25 Å, and a barrier layer of undoped In _0.01 Ga _0.95 N,
Total thickness of 175 by alternately stacking 0 angstrom
An active layer 45 having an Angstrom multiple quantum well structure (MQW) is grown. The well layer and / or the barrier layer may be doped with Si, and the doping with Si is preferable because the threshold value is lowered.

(P-side Cap Layer 46) Next, p-type Al _0.3 doped with Mg at 1 × 10 ²⁰ / cm ³ , having a band gap energy larger than that of the p-side light guide layer 47 and larger than that of the active layer 45. A p-side cap layer 46 of Ga _0.9 N is grown to a thickness of 300 Å. Although the p-side cap layer 46 is p-type, the thickness is small, so that the i-type impurity is doped with n-type impurities to compensate for the carrier.
It may be of a type or undoped, and most preferably a layer doped with a p-type impurity. p-side cap layer 17
Is adjusted to 0.1 μm or less, more preferably 500 Å or less, and most preferably 300 Å or less. This is because if the layer is grown with a thickness greater than 0.1 μm, cracks are easily formed in the p-type cap layer 46, and a nitride semiconductor layer having good crystallinity is difficult to grow. When the composition ratio of Al is larger and the thickness of AlGaN is smaller, the LD element is more likely to oscillate. For example, if the Y value is 0.
In the case of two or more Al _Y Ga ₁ -YN, it is desirable to adjust the thickness to 500 Å or less. p-side cap layer 46
Although the lower limit of the film thickness is not particularly limited, it is desirable to form the film with a film thickness of 10 Å or more.

(P-side light guide layer 47) Next, the Mg band gap energy is smaller than that of the p-side cap layer 46.
A p-side light guide layer 47 made of p-type GaN doped with 1 × 10 ²⁰ / cm ³ is grown to a thickness of 0.1 μm. This layer functions as a light guide layer of the active layer, and is preferably made of GaN or InGaN, like the n-side light guide layer 44. This layer also functions as a buffer layer when growing the p-side cladding layer 48, and functions as a preferable light guide layer by growing with a film thickness of 100 Å to 5 μm, more preferably 200 Å to 1 μm. . This p-side light guide layer is usually doped with a p-type impurity such as Mg to have a p-type conductivity type, but it is not particularly necessary to dope the impurity. Note that this p
The light guide layer may be a superlattice layer. When a superlattice layer is formed, at least one of the first layer and the second layer may be doped with a p-type impurity or may be undoped.

(P-side cladding layer 48) Next, Mg was added to 1 ×
A first layer of p-type Al _0.2 Ga _0.8 N doped with 10 ²⁰ / cm ³ , 20 Å, and 1 × 10 ²⁰ Mg;
/ Cm ³ doped second layer of p-type GaN, 20 angstrom alternately laminated to a total film thickness of 0.4 μm
A p-side cladding layer 48 of m superlattice layers is formed.
This layer acts as a carrier confinement layer similarly to the n-side cladding layer 43, and acts as a layer for decreasing the resistivity on the p-type layer side by having a superlattice structure. This p
The thickness of the side cladding layer 48 is not particularly limited, but is not less than 100 Å and not more than 2 μm, and more preferably not more than 5 μm.
It is desirable to grow the film at a thickness of not less than 00 Å and not more than 1 μm. In this embodiment, the superlattice layer is also provided on the n-side cladding layer side. However, when the superlattice layer is provided on the p-side layer side rather than the n-side cladding layer side, the resistance value of the p-layer tends to decrease. Is preferable in lowering Vf.

In the case of a nitride semiconductor device having a double hetero structure having an active layer 45 having a quantum well layer, a thickness of 0.1 μm or less in contact with the active layer 45 and having a band gap energy larger than that of the active layer 45. A cap layer 46 made of a nitride semiconductor containing Al is provided, and a p-side light guide layer 47 having a smaller gap energy than the cap layer 46 is provided at a position farther from the active layer than the cap layer 46. It is extremely difficult to provide a p-side cladding layer 48 made of a superlattice layer containing a nitride semiconductor containing Al having a larger band gap than the p-side light guide layer 47 at a position farther from the active layer than the side light guide layer 47. Preferred. In addition, since the band gap energy of the p-side cap layer 46 is increased, the electrons injected from the n-layer are blocked by the cap layer 46, and the electrons do not overflow the active layer. Become.

(P-side contact layer 49) Finally, a p-side contact layer 49 of p-type GaN doped with Mg at 2 × 10 ²⁰ / cm ³ is grown to a thickness of 150 Å. The p-side contact layer has a thickness of 500 Å or less, more preferably 400 Å or less.
Adjust the film thickness to 0 Å or more.

After the reaction is completed, the wafer is annealed in a nitrogen atmosphere at 700 ° C.
The resistance of the mold layer is further reduced. After annealing, the wafer is taken out of the reaction vessel and, as shown in FIG.
The uppermost p-type contact layer 20 and the p-type cladding layer 19 are etched by a device into a ridge shape having a stripe width of 4 μm, and Ni / A is formed on the entire surface of the ridge surface.
A p electrode 51 made of u is formed. Next, as shown in FIG. 13, an insulating film 50 made of SiO ₂ is formed on the surface of the p-side cladding layer 48 and the contact layer 49 except for the p-electrode 51, and the p-electrode 51 is electrically connected to the p-electrode 51 via the insulating film 50. To form a p-pad electrode 52 connected to.

After forming the p-side electrode, the sapphire substrate 1 and the like of the wafer are polished and removed, and the entire surface of the second nitride semiconductor layer 4 having no exposed element structure is covered with an n-electrode made of Ti / Al. 53 is formed with a thickness of 0.5 μm, and Au / Sn is formed thereon for metallization with a heat sink.
And forming a thin film.

Then, scribe from the n-electrode side 53,
The second nitride semiconductor layer 4 is cleaved at the M-plane (11-00, a surface corresponding to the side surface of the hexagonal prism in FIG. 9) of the second nitride semiconductor layer 4, to form a resonance surface. SiO ₂ and TiO _{2 on the} resonance surface
A dielectric multilayer film was formed, and finally the bar was cut in a direction parallel to the p-electrode to form a laser chip. Next, the chip was placed face-up (in a state in which the substrate and the heat sink faced each other), and the p-pad electrode 52 was wire-bonded. Laser oscillation was attempted at room temperature. / Cm ² ,
At a threshold voltage of 4.0 V, continuous oscillation with an oscillation wavelength of 405 nm was confirmed, and a lifetime of 1000 hours or more was shown.

Embodiment 12 FIG. 14 is a schematic cross-sectional view showing the structure of an LED device using a nitride semiconductor layer obtained by the growth method of the present invention as a substrate, and shows the structure of the second nitride semiconductor layer 4. The element structure above the substrate is
0 has the same structure as the LED element. Example 1
Example 3 was used as the nitride semiconductor substrate of the LED element of Example 3.
The first nitride semiconductor layer 3 made of GaN doped with Si has a thickness of 25 μm and the second nitride semiconductor layer 4
Except that the film thickness of undoped GaN was 25 μm. On the second nitride semiconductor layer 4 of undoped GaN thus obtained, GaN doped with 1 × 10 ¹⁸ / cm ^{3 of} Si
A second buffer layer 31, a 20 angstrom thick film, an active layer 32 of In _0.4 Ga _0.6 N having a single quantum well structure, and a 0.3 μm thick Mg-doped Al _0.2 Ga _0.8 film.
N-side p-side cladding layer 33, 0.5 μm thick Mg
It has a structure in which a p-side contact layer 34 made of doped GaN is sequentially laminated, and a light-transmitting p-electrode 35 is provided on almost the entire surface of the p-side contact layer 34, and a bonding Are formed. Note that all of the substrate 1, the buffer layer 2, the first nitride semiconductor layer 3, the first protective film 11, the second protective film 12, and a part of the second nitride semiconductor layer 4 are the same as those of the tenth embodiment. In the same manner as in this embodiment, the n electrode and the p
A structure provided with electrodes may also be employed.

This device is different from the device of the tenth embodiment in that the second nitride semiconductor layer 4 having better crystallinity than the first nitride semiconductor layer 3 used as the nitride semiconductor substrate in the tenth embodiment. The element structure is formed thereon, and a p-electrode 35 and a negative electrode 37 are provided on the same surface side. In a nitride semiconductor device having a structure in which a nitride semiconductor layer (second buffer layer 31) doped with an n-type impurity is stacked on a second nitride semiconductor layer 4 made of undoped GaN, When an n-electrode is provided, providing an n-electrode in a nitride semiconductor layer doped with an n-type impurity tends to easily obtain an LED element having a low Vf and high luminous efficiency. This LED element was used in Example 10.
The output was improved about 1.5 times and the electrostatic withstand voltage was improved about 1.5 times as compared with the LED element of No. 1.

Example 13 As in Example 1, a GaN buffer layer of 200 Å and an undoped GaN layer 2 of 4 μm were formed on a sapphire substrate having a sapphire C surface as a main surface and an orientation flat surface as an A surface. A grown wafer was prepared, and a stripe width of 20 μm and a window of 5 μm were formed on the undoped GaN layer 2 using a CVD apparatus.
A wafer formed by forming a first protective film made of m ₂ SiO ₂ with a thickness of 0.1 μm is transferred to a MOVPE apparatus,
On the undoped GaN layer 2 and the first protective film, a first nitride semiconductor layer made of GaN doped with 1 × 10 ¹⁹ / cm ^{3 of} Si is grown to a thickness of 15 μm to grow an element structure. Is formed.

Thereafter, the first nitriding is performed in the same manner as in Example 12.
1 × 10 Si on the semiconductor layer ¹⁸/cm^ThreeDoped
GaN second buffer layer, 20 angstrom thick
ROHM, single quantum well structure In_0.4Ga_0.6Consisting of N
Active layer, 0.3 μm thick Mg-doped Al_0.2Ga_0.8N
P-side cladding layer, Mg-doped with a thickness of 0.5 μm
A p-side contact layer made of GaN is sequentially stacked. Soshi
To perform etching from the p-layer side,
Exposing the surface of the nitride semiconductor layer 3 to form an n-electrode
On the other hand, almost the entire surface of the p-side contact layer is transparent p-electrode.
Electrode and pad electrode for bonding on its p-electrode
Are formed, and the n-electrode and the p-electrode are formed from the same side as shown in FIG.
A structure with electrodes is provided. Finally, the thickness of the sapphire substrate
After polishing to a thickness of about 50 μm to make it thin,
Scribe into a 350 μm square element. This LED
The device has a first protective film formed on a GaN layer,
A first nitride semiconductor layer having a window portion of the first protective film of 5 μm;
Is formed, and a first protective film is formed on a heterogeneous substrate.
To form a first nitride semiconductor layer with a window of 6 μm
Better characteristics than the LED element of Example 10 performed
showed that.

Example 14 A 2-inch φ having an off-angle angle θ from the C plane of 0.13 °, a step height of about 15 Å, a terrace width W of about 56 Å, and an orientation flat surface as the A surface A sapphire substrate is prepared. FIG. 15 is an enlarged schematic view showing a cross section of the sapphire substrate. The substrate off-angled in the step shape shown in FIG.
And a step portion B. The surface irregularities of the terrace portion A are adjusted to about 0.5 angstroms on average and about 2 angstroms at maximum, and are formed almost regularly. On the other hand, the height of the step is adjusted to about 15 angstroms. Although the off-angle θ is exaggerated, the off-angle θ is set at 0.
It is only 13 ° inclined. It is desirable that the step-like portion having such an off-angle is formed continuously over the entire substrate, but it may be particularly formed partially. The off angle θ indicates an angle between a straight line connecting the bottoms of a plurality of steps and the horizontal plane of the uppermost step as shown in FIG. The step should be less than 30 angstroms, more preferably less than 25 angstroms, and most preferably less than 20 angstroms. The lower limit is desirably 2 Å or more. In particular, when a sapphire C-plane is used for the substrate, the off-angle θ from the C-plane
Is adjusted within 1 degree, preferably 0.8 degree or less, more preferably 0.6 degree or less. In this embodiment, the step-shaped off-substrate is used.
A normal off substrate may be used. By using a hetero-substrate with an appropriate off-angle, the interatomic distance between the nitride semiconductor and the hetero-substrate is reduced, step growth becomes possible, and a GaN substrate with even fewer crystal defects can be obtained.

A buffer layer made of GaN was formed on the off-angle surface of the sapphire substrate in the same manner as in the thirteenth embodiment.
After growing an Angstrom and undoped GaN layer by 4 μm, the undoped GaN layer is
SiO ₂ with a stripe width of 25 μm and a window of 5 μm on the layer
A first protective film is formed to a thickness of 0.1 μm.
Similarly, the stripe direction of the first protective film is perpendicular to the A-plane.

Next, this wafer was transferred to a MOVPE apparatus, and an S-doped GaN layer and a first protective film were deposited on the undoped GaN layer and the first protective film.
A first nitride semiconductor layer made of GaN doped with 1 × 10 ¹⁹ / cm ³ is grown to a thickness of 10 μm, and the first
A second buffer layer made of GaN doped with 1 × 10 ¹⁸ / cm ^{3 of} Si, a 20 angstrom thick film, an active layer made of In _0.4 Ga _0.6 N having a single quantum well structure, 0.3 μm thick Mg-doped Al _0.2 G
a p-side cladding layer of a _0.8 N, 0.5 μm thick M
A p-side contact layer made of g-doped GaN is sequentially stacked. Thereafter, in the same manner as in Example 13, the surface of the first nitride semiconductor layer is exposed by etching, and a structure is provided in which an n-electrode and a p-electrode are provided from the same surface side as shown in FIG. Then, after the sapphire substrate is polished to a thickness of about 50 μm and thinned, a device having a size of 350 μm square is obtained. This LED element improved the output by about 5% as compared with the LED element of Example 13.

[Embodiment 15] In the thirteenth embodiment, the Si
After the first nitride semiconductor layer made of GaN doped with 1 × 10 ¹⁹ / cm ^{3 is} grown to a thickness of 10 μm, the wafer is taken out of the reaction vessel, and is placed at a position corresponding to the window of the first protective film.
A second protective film having a stripe width of 15 μm is formed with a thickness of 0.1 μm. Then, the wafer is transferred to the MOVPE apparatus again, and a second nitride semiconductor layer made of GaN doped with 1 × 10 ¹⁹ / cm ^{3 of} Si is formed on the first nitride semiconductor layer and the second protective film. It is grown to a thickness of 15 μm.

Thereafter, the second nitriding is performed in the same manner as in the thirteenth embodiment.
1 × 10 Si on the semiconductor layer ¹⁸/cm^ThreeDoped
GaN second buffer layer, 20 angstrom thick
ROHM, single quantum well structure In_0.4Ga_0.6Consisting of N
Active layer, 0.3 μm thick Mg-doped Al_0.2Ga_0.8N
P-side cladding layer, Mg-doped with a thickness of 0.5 μm
A p-side contact layer made of GaN is sequentially stacked, and a second
By exposing the surface of the nitride semiconductor layer to form an n-electrode,
Almost the entire surface of the side contact layer is a translucent p-electrode and pad
An electrode was formed, and an n electrode and a p electrode were provided from the same surface side.
Structure. Finally, reduce the thickness of the sapphire substrate to about 50 μm.
After polishing to a thin degree, scribe the polished surface side
The element is a 350 μm square element. This LED element was used in Example 1.
2 showed better characteristics than the LED element.

[Example 16] In Example 10, a nitride semiconductor substrate forming an element structure was grown on the first nitride semiconductor layer 3 in the same manner as in Example 6, and the sapphire substrate 1 The buffer layer, the protective film 11 and the like are polished and removed, and the surface of the first nitride semiconductor layer 3 is exposed. Get chips. This LE
D showed very excellent characteristics as in Example 10, but Example 16 was better than Example 10 of the present invention.

[Embodiment 17] Embodiment 17 will be described below with reference to FIG. FIG. 16 is a schematic cross-sectional view showing the structure of one laser device using a nitride semiconductor layer obtained by the growth method of the present invention as a substrate.

The sapphire substrate 1, the buffer layer 2, and the protective film 11 of the wafer obtained in Example 6 were polished and removed, exposing the surface of the first nitride semiconductor layer 3, and removing the first nitride semiconductor layer. Use only 3

Next, a wafer having the first nitride semiconductor layer 3 (Si-doped GaN) as a main surface is set in a reaction vessel of a MOVPE apparatus, and a heterogeneous substrate of the first nitride semiconductor layer 3 is placed on the wafer. The following layers are formed on the surface opposite to the surface exposed by the removal.

(N-side cladding layer 43) Next, Si was added to 1 ×
A first layer of 10 ¹⁹ / cm ³ doped n-type Al _0.2 Ga _0.8 N, 20 Å, and undoped
A superlattice structure having a total film thickness of 0.4 μm is formed by alternately laminating 100 second layers composed of GaN of pe) and 20 angstroms.

(N-side light guide layer 44) Subsequently, 1
An n-type light guide layer 44 of x10 ¹⁷ / cm ³ doped n-type GaN is grown to a thickness of 0.1 μm.

(Active layer 45) Next, Si was added to 1 × 10 ¹⁷ /
A well layer of In _0.2 Ga _0.8 N doped with cm ³ , 25 Å, and I × 10 ¹⁷ / cm ³ doped with Si
An active layer 45 having a multiple quantum well structure (MQW) having a total film thickness of 175 Å is formed by alternately laminating barrier layers of n _0.01 Ga _0.95 N and 50 Å.

(P-side Cap Layer 46) Next, p-type Al _0.3 doped with Mg at 1 × 10 ²⁰ / cm ³ and having a band gap energy larger than that of the p-side light guide layer 47 and larger than that of the active layer 45 is used. A p-side cap layer 46 of Ga _0.9 N is grown to a thickness of 300 Å.

(P-side light guide layer 47) Next, Mg band gap energy is smaller than that of the p-side cap layer 46.
Is grown at a film thickness of 0.1 μm by p-type GaN doped with 1 × 10 ¹⁸ / cm ³ .

(P-side cladding layer 48) Next, Mg was added to 1 ×
A first layer of p-type Al _0.2 Ga _0.8 N doped with 10 ²⁰ / cm ³ , 20 Å, and 1 × 10 ²⁰ Mg;
/ Cm ³ doped second layer of p-type GaN, 20 angstrom alternately laminated to a total film thickness of 0.4 μm
A p-side cladding layer 48 of m superlattice layers is formed.

(P-side contact layer 49) Finally, a p-side contact layer 49 made of p-type GaN doped with Mg at 2 × 10 ²⁰ / cm ³ is grown to a thickness of 150 Å.

After the reaction, the wafer was annealed in a nitrogen atmosphere at 700 ° C.
The resistance of the mold layer is further reduced. After annealing, the wafer is taken out of the reaction vessel and, as shown in FIG.
The uppermost p-type contact layer 20 and the p-type cladding layer 19 are etched by a device into a ridge shape having a stripe width of 4 μm, and Ni / A is formed on the entire surface of the ridge surface.
A p electrode 51 made of u is formed. Next, as shown in FIG. 16, an insulating film 50 made of SiO ₂ is formed on the surfaces of the p-side cladding layer 48 and the contact layer 49 except for the p-electrode 51, and the p-electrode 51 is electrically connected to the insulating film 50 via the insulating film 50. To form a p-pad electrode 52 connected to.

After forming the p-side electrode, the first nitride semiconductor layer 3
Ti / Al over the entire surface on which the element structure of
An n-electrode 53 is formed with a thickness of 0.5 μm, and Au / S is formed on the n-electrode 53 for metallization with a heat sink.
A thin film made of n is formed.

Then, scribe from the n-electrode side 53,
The first nitride semiconductor layer 3 is cleaved at the M-plane (11-00, a surface corresponding to the side surface of the hexagonal prism in FIG. 9) of the first nitride semiconductor layer 3 to form a resonance surface. A dielectric multilayer film composed of SiO ₂ and TiO ₂ was formed on both or one of the resonance surfaces, and finally, the bar was cut in a direction parallel to the p-electrode to form a laser chip. Next, the chip is mounted on the heat sink face up (in a state where the substrate and the heat sink are opposed to each other), and the p-pad electrode 52 is wire-bonded.
When laser oscillation was attempted at room temperature, continuous oscillation at an oscillation wavelength of 405 nm was confirmed at room temperature at a threshold current density of 2.0 kA / cm ² and a threshold voltage of 4.0 V, indicating a life of 1000 hours or more.

[Embodiment 18] FIG. 17 is a schematic sectional view showing the structure of an LED device using a nitride semiconductor layer obtained by the growth method of the present invention as a substrate. The device structure above the active layer 32 has the same structure as the LED device of the sixteenth embodiment. As the nitride semiconductor substrate of the LED element of Example 18, undoped G
The first nitride semiconductor layer 3 made of aN is grown, and the sapphire substrate 1, the buffer layer, the nitride semiconductor layer 2, the first protective film 11 and the like of the wafer are removed, and only the first nitride semiconductor layer 3 is formed. Use the one that has been used. On the surface of the first nitride semiconductor layer 3 opposite to the surface exposed by removing the sapphire substrate 1 and the first protective film 11, an n-side cladding layer 51 having the following superlattice layer is formed. Let it grow. (N-side cladding layer 51) A first layer made of n-type Al _0.2 Ga _0.8 N doped with 1 × 10 ¹⁹ / cm ^{3 of} Si, 20 angstroms, and a second layer made of undoped GaN, 20 A superlattice structure having a total film thickness of 0.4 μm is formed by alternately laminating 100 Å and Å. When a superlattice layer is used, a clad layer with good crystallinity and good carrier confinement without cracks can be formed.

Next, on the formed clad layer 51, the active layer 32, the p-side clad layer 33,
It has a structure in which p-side contact layers 34 are sequentially stacked.
Etching is performed from the p-layer side to expose the surface of the n-side cladding layer 51 having a high impurity concentration to form an n-electrode. A pad electrode for bonding is formed on the n-electrode and the p-electrode from the same side as shown in FIG.
A structure with electrodes is provided. Finally, the sapphire substrate is polished to a thickness of about 50 μm to reduce the thickness, and then the polished surface side is scribed to form a 350 μm square device.

The obtained LED element exhibited good characteristics, and the output and the electrostatic breakdown voltage were improved by about 1.5 times and about 1.5 times, respectively, as compared with the LED element of Example 16.

[Example 19] A first nitride semiconductor to be a nitride semiconductor substrate in the same manner as in Example 7, except that the thickness of the first nitride semiconductor layer 3 made of undoped GaN was changed to 15 µm. Layer 3 is grown. An element structure is formed on the first nitride semiconductor layer 3 in the same manner as in Example 18 to obtain an LED element. The obtained LED element is
As in the case of the LED element of Example 18, good characteristics were exhibited.

[Embodiment 20] In the nineteenth embodiment, a sapphire substrate that is off-angled in a stepwise manner as in the fourteenth embodiment is used as the heterosubstrate in the same manner.
Obtain an ED element. This LED element is the LED of Example 19.
The output was improved by about 5% as compared with the device.

Example 21 Three kinds of nitride semiconductor substrates were formed in the same manner as in Example 7, except that the width of the window was changed to 5 μm, 3 μm, and 1 μm. As a result of measuring the number of defects and comparing the numbers relatively, the number of crystal defects was reduced by about 20% when the width of the window was 3 μm and 1 μm compared to when the width of the window was 5 μm.

[0127]

According to the present invention, despite the fact that nitride semiconductors are currently evaluated as ideal semiconductors, since nitride semiconductor substrates do not exist, nitride semiconductor devices with many lattice defects grown on heterogeneous substrates are used. Has been put to practical use. Therefore, when a device such as a laser device in which a crystal defect immediately affects the life is realized, the device is damaged in several tens of hours. However, according to the growth method of the present invention, a nitride semiconductor substrate that could not be grown conventionally can be obtained. Therefore, when a nitride semiconductor layer serving as an element structure is stacked on the nitride semiconductor substrate, very large lattice defects are generated. A small number of nitride semiconductor devices can be realized. For example, when a laser device is manufactured using the substrate of the present invention, a device that has almost reached the practical use level can be obtained. The fact that a nitride semiconductor substrate, which could not be obtained conventionally, can be obtained by the present invention has a great industrial value.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view showing the structure of a nitride semiconductor wafer obtained in each step of the method of the present invention.

FIG. 2 is a schematic cross-sectional view showing a structure of a nitride semiconductor wafer obtained in each step of the method of the present invention.

FIG. 3 is a schematic cross-sectional view showing a structure of a nitride semiconductor wafer obtained in each step of the method of the present invention.

FIG. 4 is a schematic sectional view showing the structure of a nitride semiconductor wafer obtained in each step of the method of the present invention.

FIG. 5 is a schematic sectional view showing the structure of a nitride semiconductor wafer obtained in each step of the method of the present invention.

FIG. 6 is a schematic sectional view showing the structure of a nitride semiconductor wafer obtained in each step of the method of the present invention.

FIG. 7 is a schematic sectional view showing the structure of a nitride semiconductor wafer obtained in each step of the method of the present invention.

FIG. 8 is a schematic sectional view showing the structure of a nitride semiconductor wafer obtained in each step of the method of the present invention.

FIG. 9 is a unit cell diagram showing the plane orientation of sapphire.

FIG. 10 is a plan view of the main surface of the substrate for explaining the stripe direction of the protective film.

FIG. 11 is a schematic cross-sectional view showing one structure of a nitride semiconductor LED element using a substrate according to the method of the present invention.

FIG. 12 is a plan view of the device of FIG. 11 as viewed from a p-electrode side.

FIG. 13 is a schematic sectional view showing one structure of a nitride semiconductor LD device using a substrate according to the method of the present invention.

FIG. 14 is a schematic cross-sectional view showing one structure of a nitride semiconductor LED element using a substrate according to the method of the present invention.

FIG. 15 is a schematic cross-sectional view showing a partial shape of one off-angled substrate.

FIG. 16 is a schematic cross-sectional view showing one structure of a nitride semiconductor LD device using a substrate according to the method of the present invention.

FIG. 17 is a schematic sectional view showing one structure of a nitride semiconductor LED element using a substrate according to the method of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Substrate 2 ... Buffer layer 3 ... 1st nitride semiconductor layer 4 ... 2nd nitride semiconductor layer 11 ... 1st protective film 12 ... ..Second protective film

 ──────────────────────────────────────────────────続 き Continued on the front page (31) Priority claim number Japanese Patent Application No. 9-201477 (32) Priority date Hei 9 (July 28, 1997) (33) Priority claim country Japan (JP) (31) Priority Claim No. 9-990097 (32) Priority date Hei 9 (1997) October 22 (33) Priority claiming country Japan (JP) (72) Inventor Shuji Nakamura 491-1, Okagaminakamachioka, Anan-shi, Tokushima Prefecture 100 Nichia Chemical Industry Co., Ltd.

Claims (22)

[Claims] 1. a first step of partially forming a first protective film on a nitride semiconductor grown on a heterogeneous substrate made of a material different from the nitride semiconductor, and after the first step, A second step of growing the first nitride semiconductor on the nitride semiconductor and growing the first nitride semiconductor on the first protective film. 2. The nitride according to claim 1, wherein the first protective film is formed to have a surface area larger than a surface area of a portion where the first protective film is not formed. Semiconductor growth method. 3. A method for forming a first protective film on a heterogeneous substrate made of a material different from that of a nitride semiconductor by partially forming a first protective film having a surface area larger than a surface area of a portion where the first protective film is not formed. A first step of forming; and, after the first step, a second step of growing a first nitride semiconductor on the heterogeneous substrate and growing on the first protective film. A method of growing a nitride semiconductor. 4. The first protective film is formed in a stripe shape, and the width of a portion (window portion) where an adjacent stripe-shaped first protective film is not formed is 5 μm or less. The method for growing a nitride semiconductor according to claim 1, wherein: 5. A ratio Ws / Ww of the width (Ww) of the window to the width (Ws) of the first protective film in a stripe form is 1 to 20.
The method for growing a nitride semiconductor according to claim 1, wherein: 6. A substrate according to claim 1, wherein said heterogeneous substrate has a main surface off-angled from a main surface of said substrate.
6. The method for growing a nitride semiconductor according to any one of 5. 7. The method for growing a nitride semiconductor according to claim 6, wherein the heterogeneous substrate is off-angled in a step shape. 8. The sapphire having the (0001) plane as a main surface, and the first protective film has a stripe shape perpendicular to the (112-0) plane of the sapphire. The method for growing a nitride semiconductor according to claim 1. 9. The different kind of substrate is sapphire whose main surface is a (112-0) plane, and the first protective film has a stripe shape perpendicular to the (11-02) plane of the sapphire. The method according to claim 1, wherein
Item 13. The method for growing a nitride semiconductor according to Item 1. 10. The different substrate is a spinel having a (111) plane as a main surface, and the first protective film has a stripe shape perpendicular to the (110) plane of the spinel. The method for growing a nitride semiconductor according to claim 1. 11. A third step of partially forming a second protective film on the first nitride semiconductor after the second step, and a second nitride semiconductor after the third step A fourth step of growing on the first nitride semiconductor and growing on the second protective film as well. A method for growing a nitride semiconductor. 12. The method according to claim 11, wherein the second protective film is formed on a crystal defect appearing on a surface of the first nitride semiconductor. 13. The method according to claim 11, wherein the second protection film has a stripe shape parallel to the first protection film. 14. A first protective film is partially formed on a nitride semiconductor grown on a heterogeneous substrate made of a material different from the nitride semiconductor, and the first protective film is partially formed on the first protective film. A nitride semiconductor device, comprising: growing a first nitride semiconductor; and stacking a nitride semiconductor having an element structure on the first nitride semiconductor. 15. The nitride according to claim 14, wherein the first protective film is formed to have a surface area larger than a surface area of a portion where the first protective film is not formed. Semiconductor element. 16. A first protective film partially having a surface area larger than a surface area of a portion where the first protective film is not formed on a heterogeneous substrate made of a material different from a nitride semiconductor. A first nitride semiconductor is grown on the first protective film, and a nitride semiconductor having an element structure is stacked on the first nitride semiconductor. Nitride semiconductor device. 17. The method according to claim 17, wherein the first nitride semiconductor has a total thickness of 1
The nitride semiconductor device according to any one of claims 14 to 16, wherein the nitride semiconductor device has a film thickness of not less than μm and not more than 50 μm, and has the different substrate. 18. The method according to claim 1, wherein the first nitride semiconductor has a total thickness of 7
The nitride semiconductor device according to any one of claims 14 to 16, wherein the nitride semiconductor device has a thickness of 0 µm or more and is obtained by removing the heterogeneous substrate. 19. The semiconductor device according to claim 19, wherein the first nitride semiconductor is grown on a stripe-shaped first protective film having a window width of 5 μm or less. 19. The nitride semiconductor device according to any one of 14 to 18. 20. A nitride semiconductor having the above element structure,
The nitride semiconductor device according to any one of claims 14 to 19, comprising an n-side nitride semiconductor having a superlattice structure. 21. The nitride semiconductor device according to claim 14, wherein an n-electrode is formed on the n-side nitride semiconductor having the superlattice structure. 22. The method according to claim 14, wherein a ratio Ws / Ww of the width (Ww) of the window to the width (Ws) of the protective film is 1 to 20. Nitride semiconductor device.