JP3823775B2 - Manufacturing method of nitride semiconductor substrate - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a nitride semiconductor (In_xAl_yGa_1-xyN, 0 ≦ X, 0 ≦ Y, X + Y ≦ 1), and more particularly, to a method for growing a nitride semiconductor that can be a single substrate.
[0002]
[Prior art]
In recent years, a single substrate made of a nitride semiconductor obtained by growing a nitride semiconductor on a heterogeneous substrate having a lattice constant different from that of a nitride semiconductor such as sapphire, spinel, or silicon carbide, and then removing the heterogeneous substrate has been developed. Attention has been paid. This is because a single substrate made of a nitride semiconductor has less warpage and can be easily cleaved than a nitride semiconductor substrate having a different kind of substrate.
[0003]
For example, there is a method of manufacturing a single substrate by growing gallium nitride or the like on a sapphire substrate which is a different substrate, and then removing the different substrate by lapping. As a method of separating sapphire from a nitride semiconductor other than wrapping, the sapphire is irradiated with a Krf pulse excimer laser to separate the sapphire from the common surface in contact with the sapphire and the nitride semiconductor. A method has been reported. In this method, the nitride semiconductor absorbs the laser beam on the common surface with which the sapphire is in contact by laser irradiation, the nitride semiconductor is decomposed, and sapphire can be separated.
[0004]
[Problems to be solved by the invention]
However, with the polishing removal method described above, when a nitride semiconductor is grown on a heterogeneous substrate such as a sapphire substrate, the sapphire substrate has a high hardness, and thus a large stress is applied during polishing. Therefore, it is difficult to form a single substrate of a nitride semiconductor such as gallium nitride because the nitride semiconductor is chipped or cracked due to the stress at the time of lapping.
[0005]
In addition, when a nitride semiconductor is grown on a substrate by a vapor phase growth method such as a hydride vapor phase growth method or a metal organic vapor phase growth method, specifically, if a film thickness of 100 μm or more is grown, the strain increases. It is difficult to grow a thick film because chipping or cracking occurs in a physical semiconductor.
[0006]
In the case of a substrate removal method by laser irradiation, for example, when forming a single substrate of gallium nitride, sapphire breaks due to the gas pressure of nitrogen gas generated by decomposition of gallium nitride, and this crack causes contact with sapphire. Defects occur on the gallium nitride surface. If such a flaw is present on the surface of gallium nitride or the like, a minute crack called a microcrack may occur. When such a crack occurs, it is considered that the lifetime characteristics and the yield of the light emitting element formed on the nitride semiconductor substrate are reduced.
[0007]
Accordingly, an object of the present invention is to enable a nitride semiconductor thick film growth in a nitride semiconductor substrate fabricated by utilizing lateral growth, and further to crack the nitride semiconductor grown on the support substrate. It is to provide a single substrate by easily removing the support substrate without causing chipping. It is another object of the nitride semiconductor single substrate obtained here to be a nitride semiconductor having low dislocations and good crystallinity.
[0008]
[Means for Solving the Problems]
That is, the object of the present invention can be achieved by the configurations of the present invention shown in the following (1) to (8).
(1) A step of forming a protective film having a periodic stripe-like, lattice-like, or island-like window on a supporting substrate, and a first nitride semiconductor on the protective film from the exposed portion of the supporting substrate. Forming a first nitride semiconductor having a T-shaped cross section periodically arranged by lateral growth and stopping the protective film without covering the protective film; and forming the protective film on the first nitride semiconductor T Forming a space below the first nitride semiconductor laterally grown by removing the support substrate until it is exposed on both sides of the letter-shaped pillar portion, and an upper surface of the first nitride semiconductor. Or a method of manufacturing a nitride semiconductor substrate, comprising: a step of growing a second nitride semiconductor from the upper surface and a side surface that is a laterally grown portion to cover the entire surface of the support substrate; and a step of separating and removing the support substrate.
(2) The method for manufacturing a nitride semiconductor substrate according to (1), wherein a third nitride semiconductor is grown on the second nitride semiconductor.
(3) The method for manufacturing a nitride semiconductor substrate according to (2), wherein the film thickness of the third nitride semiconductor is 300 μm or more.
(4) The method for manufacturing a nitride semiconductor substrate according to (1), wherein the method of removing the protective film is etching.
(5) The nitride semiconductor substrate according to (1), wherein the protective film is silicon oxide, silicon nitride, titanium oxide, zirconium oxide, a multilayer film thereof, or a refractory metal film having a melting point of 1200 ° C. or higher. Production method.
(6) The nitride semiconductor substrate manufacturing method according to (1), wherein the support substrate has a buffer layer on a different substrate.
(7) The method for manufacturing a nitride semiconductor substrate according to (6), wherein the buffer layer is a gallium nitride layer or an indium gallium nitride layer.
(8) The method for manufacturing a nitride semiconductor substrate according to (2) or (3), wherein the third nitride semiconductor is doped with an n-type impurity.
[0009]
The nitride semiconductor substrate of the present invention grows laterally starting from a supporting substrate and a periodic stripe-like, lattice-like, or island-like portion on the surface of the supporting substrate, and grows laterally before bonding to each other. The first nitride semiconductor having a T-shaped cross section periodically arranged by stopping and the upper surface of the first nitride semiconductor, or the upper surface and the laterally grown side surface are grown as nuclei, and the entire surface of the support substrate is grown. A second nitride semiconductor to be covered; and a third nitride semiconductor having a thickness of 300 μm or more on the second nitride semiconductor layer, wherein the second nitride semiconductor is below a portion where the second nitride semiconductor is bonded to each other It is preferable that the support substrate is separated and removed from the formed space.
Thus, the first nitride semiconductor in contact with the support substrate has a T-shaped cross section, and the entire surface of the support substrate is covered with the second nitride semiconductor by regrowth, thereby reducing threading dislocations and flattening the surface. It can be made. Furthermore, a single substrate can be obtained by growing the third nitride semiconductor on the third layer. This is because the contact area between the first nitride semiconductor and the supporting substrate is only a T-shaped column portion, and this column portion is not reduced in threading dislocation and has poor crystallinity. For this reason, if the third nitride semiconductor is grown at 300 μm or more, the supporting substrate can be removed and separated by lapping or applying a thermal shock to the contact interface. This is because a difference in thermal expansion occurring at the contact interface between the nitride semiconductor and the support substrate can be increased by growing a nitride semiconductor of 300 μm or more. Furthermore, the contact interface between the first nitride semiconductor having a T-shaped cross section and the support substrate in the present invention has a space and a smaller contact area than a nitride semiconductor substrate formed by the ELO method. Therefore, the support substrate can be easily removed by lapping or the like. If the thickness of the third nitride semiconductor is 300 μm or less, the stress caused by the difference in thermal expansion is not sufficient to remove the support substrate. For this reason, it is necessary to rely on physical stress such as lapping, so that the nitride semiconductor is cracked or chipped. Further, if the third nitride semiconductor is grown at 1 mm or more, the support substrate can be peeled and removed naturally due to the high-temperature growth of the nitride semiconductor at 1000 ° C. or higher and the difference in thermal expansion that occurs during cooling. In order to perform this peeling and removal, the mechanical strength of the nitride semiconductor is required. For this purpose, it is necessary to grow the third nitride semiconductor at 1 mm or more, more preferably 2 mm or more.
[0010]
In the nitride semiconductor substrate having such a structure, for example, a protective film having a stripe-shaped, lattice-shaped, or island-shaped window portion is formed on a support substrate, and a first film is formed on the protective film from the support substrate exposed portion. A nitride semiconductor is laterally grown and stopped without covering the protective film, and the protective film is removed to form a space below the laterally grown first nitride semiconductor, and then the first nitride It can be manufactured by growing the second nitride semiconductor from the upper surface of the physical semiconductor or from the upper surface and the side surface which is a laterally grown portion.
[0011]
In addition, when the first nitride semiconductor is grown on the support substrate via the protective film, a stripe-shaped, lattice-shaped or island-shaped window is formed in the protective film. It is preferable to form a part. By making the window portion into a lattice shape or an island shape, the growth direction of the first nitride semiconductor becomes multidirectional, and the support substrate can be more easily separated. Moreover, it is preferable that the shape of the protective film which forms the grid | lattice-like window part and is enclosed by the window part is made into a polygon or a circle. Since the second nitride semiconductor grows from the periphery of the polygonal or circular protective film toward the center by making the shape of the protective film polygonal or circular, the junction of the second nitride semiconductor is the protective film. Thus, the area of the junction where dislocations are concentrated can be minimized.
[0012]
Here, the support substrate may be a heterogeneous substrate such as sapphire or a nitride semiconductor layer grown on the entire surface of the heterogeneous substrate. When a heterogeneous substrate such as sapphire is directly used as the support substrate, it is preferable to grow a low-temperature growth buffer layer on the heterogeneous substrate before growing the first nitride semiconductor in order to reduce lattice mismatch. Specifically, a gallium nitride layer or an indium gallium nitride layer can be used as the buffer layer. This is because a nitride semiconductor containing indium is relatively soft and thus has an effect of suppressing the occurrence of cracks in the nitride semiconductor.
[0013]
On a support substrate, a nitride semiconductor substrate having a nitride semiconductor layer grown laterally starting from a periodic stripe-like or lattice-like portion of the substrate surface was grown laterally from each growth starting point. Nitride semiconductors are not bonded to each other but are arranged with a gap. As described above, the lateral growth on the protective film is stopped before the first nitride semiconductors are bonded to each other, and thereafter, the second nitride semiconductor is grown on the gap in which the second nitride semiconductors are arranged and bonded to each other. Thus, a nitride semiconductor that does not form voids on the crystal surface can be grown even if the protective film is formed widely. In addition, since the second nitride semiconductor travels in space, it is possible to suppress the stress generated when the second nitride semiconductor is grown from the side of the first nitride semiconductor. Further, since there is no tilt phenomenon of the crystal growth surface as it proceeds on the protective film, the concentration of dislocations at the junction is alleviated.
[0014]
The third nitride semiconductor is characterized by being doped with n-type impurities. After removing the support substrate, the nitride semiconductor on the side of the contact surface with the support substrate has irregularities on the surface, and this is flattened to a mirror surface by polishing. If the planarized third nitride semiconductor is doped with an n-type impurity, a semiconductor light-emitting element or light-receiving element having an electrode on the counter electrode surface can be formed. Thereby, improvement in efficiency efficiency and life characteristics can be expected.
[0015]
As the protective film, silicon oxide, silicon nitride, titanium oxide, zirconium oxide, a multilayer film thereof, or a refractory metal film having a melting point of 1200 ° C. or higher is used. These protective film materials are preferable for laterally growing a nitride semiconductor on the protective film because the nitride semiconductor does not grow or hardly grow on the surface.
[0016]
Of the present inventionIn the method for manufacturing a nitride semiconductor substrate, a protective film having a stripe-shaped, lattice-shaped, or island-shaped window portion is formed on a support substrate, and the first nitride semiconductor is formed on the protective film from the exposed portion of the support substrate. The protective film is grown in a lateral direction and stopped without covering, and the protective film is removed to form a space under the laterally grown first nitride semiconductor, and then the first nitride semiconductor is removed. A second nitride semiconductor is grown from the upper surface or from the upper surface and the side surface which is a laterally grown portion to cover the entire surface of the support substrate, and then a third nitride having a thickness of 300 μm or more is formed on the second nitride semiconductor. Growing physical semiconductors and separating and removing support substratesIs preferred.
[0017]
Although the protective film is removed after the growth of the first nitride semiconductor, the protective film may be removed so as to form a space at least below the junction of the second nitride semiconductor. If the protective film is removed until the supporting substrate is exposed, SiO₂It is possible to suppress problems caused by decomposition of a protective film such as a nitride semiconductor grown on the protective film, that is, problems such as abnormal growth of the nitride semiconductor and deterioration of crystallinity.
[0018]
As a method for removing the protective film, dry etching or wet etching can be used, and both methods can remove the protective film without reducing the crystallinity of the nitride semiconductor. Furthermore, the dry etching can easily control the depth at which the protective film is removed.
[0019]
That is, in the nitride semiconductor substrate according to the present invention, laterally grown nitride semiconductors are not joined to each other but arranged with gaps, and a nitridation semiconductor layer having a space is formed by regrowth. The support substrate is removed after a thick nitride semiconductor is formed thereon. The inventors of the present invention have disclosed a nitride semiconductor having a T-shaped first nitride semiconductor wing grown in the lateral direction and a space having a width of 10 μm to 50 μm, preferably 10 μm to 30 μm, at the lower part of the junction. By using the substrate, even if a thick film of 300 μm or more is formed as the third nitride semiconductor, cracks and the like do not occur. By forming this space, the contact area between the support substrate and the nitride semiconductor is reduced, so that the support substrate can be easily removed by lapping or natural peeling after the thick film growth at the contact interface. Moreover, since this space has an effect as an air gap and can suppress warpage and the like, a thick film can be grown. Moreover, since epitaxial growth is started in the absence of dislocation-concentrated junctions, there is no pit generation due to nitrogen desorption at the time of substrate temperature rise, which has been a problem in the past, but rather flatter and superior in crystallinity than before. It has been found that the element layer can be grown.
[0020]
The third nitride semiconductor is a nitride semiconductor layer having a low dislocation density as a whole by growing a thick nitride semiconductor layer by halide vapor phase epitaxy (hereinafter referred to as “HVPE”) to disperse dislocations. A single substrate is obtained.
[0021]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the present invention will be described in more detail with reference to the drawings. In the present embodiment, a nitride semiconductor substrate according to the first invention will be described. FIG. 1A to FIG. 1F are schematic views showing an example of a method of manufacturing a nitride semiconductor substrate according to the first invention step by step.
[0022]
FIG. 1A is a schematic cross-sectional view in which a step of growing a nitride semiconductor on the support substrate 1 and further forming a stripe of a protective film is performed. As this support substrate 1, sapphire or spinel (MgAl) whose main surface is any one of the C-plane, R-plane, and A-plane.₂O₄An insulating substrate such as SiC (6H, 4H, 3C), ZnS, ZnO, GaAs, Si, and an oxide substrate lattice-matched with a nitride semiconductor can be used. The thickness of these supporting substrates is not particularly limited, and the film thickness is 100 μm or more, preferably 400 μm or more. Moreover, when an off angle is formed in the support substrate, for example, the off angle can be set to 0.01 ° to 0.5 °.
[0023]
Before growing the protective film 2 formed on the support substrate 1, a buffer layer (not shown) may be formed on the support substrate 1 as long as it is a thin film. As the buffer layer, AlN, GaN, AlGaN, InGaN or the like is used. The buffer layer is grown at a temperature of 300 ° C. to 900 ° C. with a film thickness of 10 Å to 5 μm, preferably 10 Å to 0.5 μm. Further, the buffer layer may be grown as a multilayer film. This buffer layer has the effect of a buffer layer that relaxes the lattice constant difference between the support substrate 1 and the first nitride semiconductor 3. Therefore, this buffer layer may be grown between the support substrate and the first nitride semiconductor, and a protective film may be grown, and after the opening is formed in this protective film, the buffer layer may be grown. .
[0024]
Next, as the protective film 2 partially formed on the support substrate 1, a material having a property that a nitride semiconductor does not grow or is difficult to grow on the surface of the protective film is selected. Preferably, silicon oxide (SiO_x), Silicon nitride (Si_xN_y), Titanium oxide (TiO_x), Zirconium oxide (ZrO)_xOr the like, or a multilayer film thereof can be used. In addition to the above, a metal having a melting point of 1200 ° C. or higher, for example, a material such as tungsten or molybdenum can be used.
[0025]
As a method for forming this protective film, CVD, sputtering, and vapor deposition are used. First, the protective film 2 is formed, and further, a resist is applied, and the protective film is formed into a stripe or lattice having a predetermined shape by photolithography. Etching into a shape. By etching the protective film in a stripe shape or a lattice shape, a stripe-shaped or island-shaped window portion is formed in the protective film. Conversely, a lattice-like window may be formed in the protective film 2 while leaving the protective film 2 in an island shape. The stripe width and the lattice width of the protective film having a predetermined shape are not particularly limited, but when formed with stripes, the stripe width is preferably 5 to 30 μm. Further, it is desirable that the window portion where the protective film 2 is not formed be narrower than the stripe width. When the protective film is formed in a lattice shape, the lattice width is preferably 10 to 20 μm. When the lattice-shaped window is formed while leaving the protective film 2 in an island shape, the width of the island-shaped protective film is 10 μm or less, preferably 5 μm or less, and the width of the lattice-shaped window is 10 to 30 μm, preferably It is desirable to set it as 10-20 micrometers. The width of the protective film is 5 to 50 μm in the case of the stripe width, and the width of the opening is also 5 to 50 μm. Furthermore, the protective film is removed after growing the first nitride semiconductor 3 in a later step, and becomes a space. Therefore, the film thickness of the protective film needs to be a film thickness that can form this space, and is 0.05 μm to 10 μm.
[0026]
On the other hand, when the lattice-shaped window is formed by leaving the protective film 2 in an island shape, the shape of the protective film may be a polygon (triangle, square, hexagon, etc.) or a circle. The protective films 2 are preferably arranged so as to be as dense as possible with a constant interval. Hexagonal protective films are arranged in a honeycomb shape (arranged so that each hexagon is adjacent to each other and one side is surrounded by six hexagons). Triangles are arranged so that adjacent triangles face each other, and six triangles form one hexagon, and the hexagons are arranged in a honeycomb shape. According to these arrangements, the distance between the protective films 2 (= the width of the window portion) can be made constant, and the density of the protective film 2 can be increased.
[0027]
Further, in order to leave the protective film in an island shape and form a lattice-like window portion, the junction of the second nitride semiconductor 4 that grows later is only one point in the center of the protective film 2, There is an advantage that the area of the joint portion where dislocations are easily concentrated can be minimized.
[0028]
When the protective film is formed in a stripe shape, if the support substrate is a sapphire substrate, the orientation flat surface is the sapphire A surface, and θ = 0 ° to 2 on either side of the vertical axis of the orientation flat surface. When stripes are formed with a shift of [deg.], Preferably [theta] = 0.01 [deg.] To 1 [deg.], The growth surface of the second nitride semiconductor is not roughened, and a good crystal with a flat growth surface can be obtained.
[0029]
As shown in FIG. 1B, the first nitride semiconductor 3 formed on the substrate 1 is undoped, doped with n-type impurities such as Si, Ge, Sn and S, or Mg. Those doped with p-type impurities can be used. The growth temperature is 900 ° C. to 1100 ° C., and the film thickness of 1.5 μm or more is preferable in that a mirror surface with few pits can be formed on the crystal surface. Also, as the first nitride semiconductor, GaN and Al_xGa_{1 - x}Stacked with N (0 <x <1, preferably 0 <x ≦ 0.5), or GaN and In_yGa_{1- y}A stack with N (0 <y ≦ 1) may be used. By using these, GaN layer and Al_xGa_{1 - x}Stress caused by the difference in thermal expansion coefficient between the N layer and In_yGa_{1- y}The support substrate 1 can be easily removed by using the low film strength of N. GaN, Al in this case_xGa_{1 - x}N or In_yGa_{1- y}N may be undoped or doped with n-type impurities or p-type impurities. The preferred film thickness of the first nitride semiconductor 3 varies depending on the film thickness and size of the protective film 2. Since the surface of the protective film needs to have a portion with good crystallinity grown in the lateral direction, the first nitride semiconductor 3 is at least 1.5 times the thickness of the protective film, It is preferable to grow the film with a thickness of 0 to 10 μm. When the first nitride semiconductor 3 is grown from the growth starting point, which is a junction with the support substrate 1, threading dislocations initially grow in the vertical direction. Thereafter, threading dislocations also change the growth direction during the growth of the T-shaped blades of the first nitride semiconductor 3. This threading dislocation is grown in a direction other than the longitudinal direction, preferably in the lateral direction, so that the threading dislocation is bent in the growth direction and reaches the sides of the T-shaped blades.
[0030]
Next, as shown in FIG. 1C, the first nitride semiconductor 3 is laterally grown on the protective film 2, and the protective film is removed while the growth is stopped halfway. Etching can be used as a method for removing the protective film, and the etching means is not particularly limited, and includes dry etching or wet etching. If it is isotropic dry etching, the etching can be controlled easily.
[0031]
By removing the protective film, a space can be formed below the portion of the first nitride semiconductor that has grown in the lateral direction and has few crystal defects. Therefore, in the nitride semiconductor grown on the first nitride semiconductor, stress generated between the first nitride semiconductor and the protective film during growth from the side surface formed by lateral growth of the first nitride semiconductor is suppressed. Can do. By removing the protective film completely until the nitride semiconductor is exposed, SiO 2 is grown when the reaction element is grown on the substrate.₂It is possible to prevent the protective film such as the like from decomposing and diffusing at a temperature of 1000 ° C. or higher and entering the nitride semiconductor on the protective film. Therefore, decomposed SiO₂It is possible to solve the problems such as entering the nitride semiconductor to lower the crystallinity and causing abnormal growth. Further, when the second nitride semiconductor grows from the upper surface of the first nitride semiconductor in a later step, the protection having a space as shown in FIGS. 2 and 3 is possible without completely removing the protective film. If the film shape is adopted, the second nitride semiconductor is bonded in space, so that a nitride semiconductor having a flat and mirror surface can be formed. As shown in FIG. 3, protective films may be left on both sides of the T-shaped column portion of the first nitride semiconductor 3. In the case where there are protective films on both sides of the column portion, a space is formed below the T-shaped wings, so that the same effect as described above is obtained. Further, the protective film remaining on the side surface of the pillar also has an effect as a base for suppressing decomposition and deterioration during the reaction of the first nitride semiconductor 3.
[0032]
Next, as shown in FIG. 1 (d), the second nitride semiconductor 4 is grown on the first nitride semiconductor 3 from which the protective film 2 has been removed, from the top and side surfaces of the first nitride semiconductor 3. Let The second nitride semiconductor is not only growth on the first nitride semiconductor but also growth on the space portion. For this reason, the ELO method for forming a flat surface of a nitride semiconductor by continuous growth on a protective film cannot be used due to low selectivity._xGa_1-xN (0 ≦ X <1) can also be used.
[0033]
Examples of the second nitride semiconductor 4 include undoped, GaN doped with n-type impurities such as Si, Ge, Sn, and S, or those doped with p-type impurities such as Mg, and n-type impurities and p-type impurities. Can be used as well. The second nitride semiconductor 4 is grown at 900 to 1100 ° C. Among them, it is preferable to dope Mg to grow the second nitride semiconductor 4 because the second nitride semiconductor easily extends in the lateral direction and easily fills the gaps in the first nitride semiconductor 3. On the other hand, when undoped, the electrical characteristics are stabilized. In addition, since the second nitride semiconductor grows on the space, Al cannot be used because the selectivity on the growth on the protective film is low._xGa_1-xN (0 <x <1) can also be used. The film thickness of the second nitride semiconductor is desirably 3 to 30 μm, preferably 5 to 20 μm in the case of GaN._xGa_1-xIn the case of N, 2 to 15 μm is preferable.
[0034]
Furthermore, an appropriate multilayer film may be used as the second nitride semiconductor. The number of layers and the film thickness of the multilayer film are not particularly limited, and may be a superlattice obtained by laminating two pairs of bulks or laminating many thin films. The thickness of each layer is preferably 10 to 2 μm.
[0035]
Here, since the second nitride semiconductor is grown from the upper surface and the side surface of the first nitride semiconductor having good crystallinity obtained by lateral growth, the second nitride semiconductor grows on the portion where the protective film has been formed. The nitride semiconductor of No. 2 has no crystal defects, and the crystal defects remain only in the nitride semiconductor grown on the upper portion of the window of the protective film. FIG. 1D shows an example in which the second nitride semiconductor grows using the top surface of the first nitride semiconductor and the laterally grown side surface as nuclei. It may be grown only from the upper surface of one nitride semiconductor. Under the second nitride semiconductor, the propagation of crystal defects from a nitride semiconductor with many remaining space defects can be suppressed. Even if the protective film remains as a thin film, if there is a space below both T-shaped blades, the effect of alleviating strain between the support substrate and the nitride semiconductor is obtained.
[0036]
Next, as shown in FIG. 1E, a third nitride semiconductor 5 is grown on the second nitride semiconductor 4, and then the support substrate is separated. Further, the surface separated from the support substrate is polished to be flat and mirror surface.
[0037]
Here, since the third nitride semiconductor 5 is grown as a thick film, it is preferably grown by the HVPE method. An n-type impurity such as Si may be doped, and the film thickness is set to 300 μm or more which facilitates lapping. Further, if the thickness of the third nitride semiconductor 5 is 1 mm or more, more preferably 2 mm or more, the support substrate can be naturally peeled.
[0038]
By performing thick film growth of the third nitride semiconductor 5, a nitride semiconductor substrate having a lower dislocation density can be obtained. The third nitride semiconductor is advantageously thicker from the viewpoint of more uniformly dispersing defects. If it is preferably 400 μm or more, defects can be dispersed.
[0039]
Next, if the third nitride semiconductor 5 is 300 μm or more, the support substrate 1 is removed from the nitride semiconductor substrate by lapping, and then the grindstone and the substrate wafer are rotated and pressed against each other to support the nitride semiconductor substrate. The substrate side is ground. Lapping is performed after the surface side of the second nitride semiconductor 4 of the nitride semiconductor substrate obtained in the above step is bonded to a base and fixed. Wax, metal, epoxy resin, or the like is used for the adhesive used for the bonding.
[0040]
Further, if the third nitride semiconductor 5 is grown with a film thickness of 1 mm or more, lapping or the like is not required, and the support substrate can be naturally removed.
[0041]
Further, the nitride semiconductor single substrate obtained in the above step is subjected to surface polishing so that the surface of the nitride semiconductor from which the supporting substrate is removed is further flattened with a mirror, as shown in FIG. A single substrate is used. The single substrate of the nitride semiconductor obtained here has a threading dislocation density of 1 × 10 in CL measurement.⁷Piece / cm²The film thickness can be obtained from a thin film to a thick film substrate of 2 mm or more. According to the present invention, it can be expected that a nitride semiconductor of an ingot is obtained alone..
[0042]
According to the nitride semiconductor substrate in the present embodiment, the concentration of dislocations at the junction of the nitride semiconductor is relaxed, the recognition of the junction is easy, and the warpage is also suppressed. Manufacture of a physical semiconductor device is facilitated. Further, if the nitride semiconductor substrate can be obtained as a single substrate having a flat surface, cleavage can be facilitated, and a light emitting element or the like having an n-side electrode formed on the back surface can be provided. When manufacturing a semiconductor laser device, the stripe structure for controlling the transverse mode of the semiconductor laser device has a region in which an active region in which current and / or light is confined becomes a growth starting point of the first nitride semiconductor 3, 2 is preferably formed so as to be located between the two nitride semiconductors 4 (the defect density between them is 1 × 10 6).⁷Piece / cm²And can be: This is because the region where the first nitride semiconductor 4 grown in the lateral direction becomes the growth starting point, that is, the region of the window portion of the protective film has a high dislocation density, and the portion where the second nitride semiconductors are joined is also conventional. This is because the dislocation density is higher than that in other regions, although the dislocations are greatly suppressed. For example, a ridge portion is formed in the case of a ridge waveguide type semiconductor laser, and a buried stripe portion is formed in the case of a buried hetero semiconductor laser, and the region where the first nitride semiconductor 3 is grown and the second The nitride semiconductor 4 is formed so as to be located between them, avoiding the junction of the nitride semiconductor 4. Since the concentration of dislocations at the junction between the second nitride semiconductors 4 is relaxed to a greater extent than before, the stripe structure of the semiconductor laser element can be formed closer to the junction. In addition, the lifetime of the laser element is improved.
[0043]
In the present invention, the general formula of a nitride semiconductor is In_xAl_yGa_1-xyN (0 ≦ X <1, 0 ≦ Y <1, 0 ≦ X + Y <1). Further, B can be used as a group III element, or a mixed crystal in which a part of N which is a group V element is substituted with As and P can be used.
[0044]
Further, as the n-type impurity used during the growth of the nitride semiconductor, specifically, a group IV or group VI element such as Si, Ge, Sn, S, O, Ti, Zr can be used. Examples include Be, Zn, Mn, Cr, Mg, and Ca. In addition, when the second nitride semiconductor layer is grown, it is necessary to ensure good ohmic properties in order to obtain n-type conductivity. For that, n-type impurities are 5 × 10¹⁶/ Cm³~ 5x10²¹/ Cm³It is preferable to dope in the range of.
[0045]
In the method for manufacturing a nitride semiconductor substrate of the present invention, a method for growing a nitride semiconductor such as the buffer layer, the first nitride semiconductor 3 and the second nitride semiconductor 4 is not particularly limited, but MOVPE ( Methods such as metal organic chemical vapor deposition), HVPE (halide vapor deposition), MBE (molecular beam epitaxy), MOCVD (metal organic chemical vapor deposition) can be applied.
[0046]
With such a method of manufacturing a nitride semiconductor, threading dislocations from the support substrate can be bent in both wings when the T-shaped first wing semiconductor is grown in the T-shaped first nitride semiconductor. This bent threading dislocation proceeds to the sides of the T-shaped wings. Therefore, threading dislocations at least in the bent range do not grow in the vertical direction. That is, since the threading dislocation does not extend in the second nitride semiconductor grown on the upper part of the T-shaped blades, a low dislocation region is formed. Furthermore, if the third nitride semiconductor is grown with a thickness of 300 μm or more, the support substrate can be easily removed by lapping. Further, if the third nitride semiconductor is grown at 1 mm or more, the support substrate can be naturally peeled without lapping or the like. Further, since the space is formed under the T-shaped blades by removing the protective film, the support substrate and the nitride semiconductor can be relaxed, and the support substrate can be removed without causing cracks or chips. In addition, the contact interface with the support substrate, which is the growth starting point of the first nitride semiconductor, has poor crystallinity and is more fragile than a single crystal. If the support substrate is removed by lapping from a nitride semiconductor grown on the support substrate through a buffer layer, a nitride semiconductor grown by ELO, or other thick film grown, the support substrate and The interface with the nitride semiconductor is adhered to the entire surface, and the warpage of the substrate is large. Therefore, stress is applied to the nitride semiconductor grown thereon, causing cracks and the like. For this reason, if lapping is continued, cracks extend to the surface side of the nitride semiconductor before the single substrate made of the nitride semiconductor is formed, and the single substrate is dispersed. However, in the present invention, the contact interface with the support substrate is only the T-column portion of the first nitride semiconductor, and the stress on the bonding surface between the support substrate and the nitride semiconductor is less than that of the nitride semiconductor. The space formed below the T-shaped wings has the effect of an air gap, can reduce the warpage of the substrate, and facilitate the removal of the support substrate.
[0047]
【Example】
Although the Example of this invention is shown below, this invention is not limited to this.
[Example 1] Using a sapphire substrate 1 having a C-plane as a main surface and an orientation flat surface as an A-plane, by MOCVD, the temperature is 510 ° C, the carrier gas is hydrogen, the source gas is ammonia, and TMG (trimethylgallium) Then, a buffer layer made of GaN is grown on the sapphire substrate 1 to a thickness of 200 angstroms.
[0048]
After growing the buffer layer, SiO is deposited thereon by CVD.₂A protective film is formed to a thickness of 0.5 μm, a striped photomask is formed, and etching is performed to form a SiO 2 film having a stripe width of 14 μm and a window portion of 6 μm.₂A protective film 2 is formed. The stripe direction of the protective film 2 is a direction perpendicular to the sapphire A plane.
[0049]
Next, the first nitride semiconductor 3 made of GaN is grown to a thickness of 2 μm by MOCVD at a temperature of 1050 ° C. under reduced pressure conditions, using TMG and ammonia as source gases. At this time, the first nitride semiconductor 3 is made of SiO.₂Growing from the opening of the protective film and laterally growing on the protective film, the first nitride semiconductor is completely SiO 2₂Stop growth before covering the protective film. The gap between adjacent first nitride semiconductors is about 2 μm.
[0050]
Next, by isotropic etching, which is dry etching, at a temperature of 120 ° C., oxygen and CF are used as an etching gas.₄Using SiO₂The protective film 2 is completely removed.
[0051]
Further, from the side and top surfaces of the first nitride semiconductor grown in the lateral direction, the temperature is raised to 1050 ° C. by MOCVD at normal pressure, TMG and ammonia are used as source gases, and the second nitride semiconductor made of GaN. 4 is grown to a film thickness of 15 μm. Note that the second nitride semiconductor 4 may be grown not under normal pressure but under reduced pressure.
[0052]
When the surface of the obtained second nitride semiconductor 4 was observed by CL (cathode luminescence), crystal defects were observed in the upper part of the opening of the protective film, but it grew on the upper part where the protective film was formed. The surface of the second nitride semiconductor 4 thus formed has good crystallinity with almost no crystal defects. The number of crystal defects is about 6 × 10⁶cm^-2Met.
[0053]
Thereafter, a third nitride semiconductor 5 is formed on the second nitride semiconductor 4 by HVPE. First, a boat containing Ga metal is installed in the HVPE apparatus, and the nitride semiconductor substrate obtained in the previous step is installed at a position away from the boat. Next, HCl gas, which is a halogen gas to be reacted with Ga metal, and an N source supply pipe are provided separately from the halogen gas supply pipe, and ammonia gas is flowed as the N source. Thus, undoped GaN is formed with a film thickness of 2 mm.
[0054]
Next, the support substrate is peeled and removed by natural peeling by cooling the nitride semiconductor substrate after completion of the reaction. From the above, a single crystal substrate of GaN with good crystallinity can be obtained with a film thickness of 2 mm.
[0055]
[Example 2] In Example 1, only TMG was stopped on the substrate, the temperature was raised to 1050 ° C, and when it reached 1050 ° C, TMG and ammonia were used as source gases, and a nitride semiconductor made of undoped GaN was made. An underlayer is grown to a thickness of 2.5 μm.
[0056]
[Embodiment 3] The same procedure as in Embodiment 1 is performed except that the etching is stopped to the extent that the first nitride semiconductor is not exposed, and the second nitride semiconductor is grown. As a result, good results are obtained in substantially the same manner as in Example 1.
[0057]
[Embodiment 4] A nitride semiconductor substrate is grown in the same manner as in Embodiment 1 except that the protective film 2 is left on both sides of the T-shaped column as shown in FIG. As a result, the surface of the second nitride semiconductor layer grown on the upper portion where the protective film has been formed has good crystallinity.
[0058]
[Example 5] In Example 1, as shown in FIG. 4, a second nitride semiconductor is grown by HVPE. The film thickness of the second nitride semiconductor is 2 mm. Thus, a single substrate of GaN separated from the support substrate can be obtained with a film thickness of 2 mm.
[0059]
【The invention's effect】
According to the nitride semiconductor substrate of the present invention, the generation of pits due to the concentration of dislocations at the junction of the nitride semiconductor layer grown in the lateral direction is suppressed, and the recognition of the junction in the element formation process is facilitated. Thus, a single substrate of a nitride semiconductor having a thick film grown can be obtained.
[Brief description of the drawings]
FIGS. 1A to 1F are cross-sectional views schematically showing a manufacturing process of a nitride semiconductor substrate according to the first invention.
FIG. 2 is a cross-sectional view schematically showing another embodiment of the nitride semiconductor substrate according to the first invention.
FIG. 3 is a cross-sectional view schematically showing still another aspect of the nitride semiconductor substrate according to the first invention.
FIG. 4 is a cross-sectional view schematically showing another aspect of the nitride semiconductor substrate according to the first invention.

Claims (8)

On a supporting substrate, a periodic striped, lattice-shaped, or island-like forming a protective film having a window portion, the first nitride semiconductor laterally grown on the support substrate exposed portion from the protective film forming a first nitride semiconductor having a T-shaped cross section which are arranged periodically by stopping Rukoto in a state of not covering the protective layer by, the protective layer of the first nitride semiconductor of the T Forming a space below the first nitride semiconductor laterally grown by removing the support substrate until it is exposed on both sides of the pillar portion ; and an upper surface of the first nitride semiconductor, or top and lateral and growth portion in which the Hare covering a than the second support substrate whole surface by a nitride semiconductor grown side step, nitride semiconductor substrate having a step of separating and removing the support substrate, comprising the Manufacturing method. The method for manufacturing a nitride semiconductor substrate according to claim 1, wherein a third nitride semiconductor is grown on the second nitride semiconductor. 3. The method for manufacturing a nitride semiconductor substrate according to claim 2, wherein the film thickness of the third nitride semiconductor is 300 [mu] m or more.   The method for manufacturing a nitride semiconductor substrate according to claim 1, wherein the method for removing the protective film is etching.  2. The nitride semiconductor according to claim 1, wherein the protective film is silicon oxide, silicon nitride, titanium oxide, zirconium oxide, a multilayer film thereof, or a refractory metal film having a melting point of 1200 ° C. or higher. A method for manufacturing a substrate.  The method for manufacturing a nitride semiconductor substrate according to claim 1, wherein the support substrate has a buffer layer on a different substrate.  The method for manufacturing a nitride semiconductor substrate according to claim 6, wherein the buffer layer is a gallium nitride layer or an indium gallium nitride layer.  4. The method for manufacturing a nitride semiconductor substrate according to claim 2, wherein the third nitride semiconductor is doped with an n-type impurity.

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