JP4015849B2 - Manufacturing method of nitride semiconductor substrate - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for manufacturing a nitride semiconductor substrate used in a visible light emitting diode device or a blue-violet laser device.
[0002]
[Prior art]
Group III-V nitride semiconductors such as gallium nitride (GaN), indium nitride (InN) and aluminum nitride (AlN) are blue or green light emitting diode (LED) devices, blue semiconductor laser devices, or high-speed transistors capable of high-temperature operation It is suitable as a compound semiconductor material used for an apparatus or the like.
[0003]
By the way, conventionally, an insulating substrate made of sapphire as disclosed in, for example, Japanese Patent No. 3091593 is well known as a substrate on which a nitride semiconductor is grown.
[0004]
However, when a nitride semiconductor is grown on a different substrate made of sapphire or the like whose composition is different from that of the nitride semiconductor layer, the substrate warps due to a difference in thermal expansion coefficient between the growing nitride semiconductor and the substrate. It is known that the crystallinity of the nitride semiconductor deteriorates due to the occurrence of cracks or cracks.
[0005]
Therefore, in recent years, an attempt has been made to solve problems caused by different types of substrates by forming a substrate from a nitride semiconductor and forming an element structure made of the same type of nitride semiconductor on the substrate made of a nitride semiconductor. ing.
[0006]
For example, as an example of a method for manufacturing a nitride semiconductor substrate, a nitride semiconductor layer is grown relatively thick on a base substrate (base substrate), and the grown nitride semiconductor layer and the base substrate are Laser light is irradiated to the interface. A method of obtaining a nitride semiconductor substrate from a nitride semiconductor layer by examining the nitride semiconductor layer irradiated with laser light locally heated and sublimated and peeling the nitride semiconductor layer from the base material substrate has been studied. ing.
[0007]
[Problems to be solved by the invention]
However, in the conventional method for manufacturing a nitride semiconductor substrate, when the nitride semiconductor layer is peeled off from the base material substrate by laser light, the laser light is being scanned, that is, in the nitride semiconductor layer and the base material substrate. Only the interface irradiated with the laser light is peeled off, and the other portions remain bonded. At this time, there is a problem that stress concentrates on the joint portion between the nitride semiconductor layer and the base material substrate, and cracks are generated in the nitride semiconductor layer. As a result, it becomes difficult to manufacture a nitride semiconductor substrate with a high yield by irradiating laser light at about room temperature.
[0008]
In order to avoid this problem, a method of performing laser irradiation by raising the substrate temperature is also known. However, in such a method of raising the substrate temperature, it takes time each time the temperature of the substrate is raised and lowered. After all, it is inferior in mass productivity.
[0009]
In addition, when a nitride semiconductor is grown on a base material substrate, through defects due to lattice mismatch are introduced into the nitride semiconductor, so that there is a problem that a defect density in the obtained nitride semiconductor substrate is high.
[0010]
In addition, since the laser beam is condensed with a small beam diameter, it is necessary to efficiently irradiate the laser beam in order to peel off all the joint surfaces between the base material substrate and the nitride semiconductor layer. For example, in order to sublimate a nitride semiconductor, the optical density of laser light is about 0.1 J / cm. ² In order to obtain this light density, the laser beam is condensed with a small beam diameter. Therefore, since the beam diameter is smaller than the area of the substrate, it is necessary to scan the laser beam over the entire surface of the nitride semiconductor layer, and the productivity cannot be improved.
[0011]
An object of the present invention is to solve the above-mentioned conventional problems, and to reliably obtain a nitride half substrate having a low defect density and excellent productivity without generating cracks and the like.
[0012]
[Means for Solving the Problems]
In order to achieve the above object, the present invention has a configuration in which the main surface of the base material substrate on which the nitride semiconductor layer is grown is made uneven.
[0013]
Specifically, the method for manufacturing a nitride semiconductor substrate according to the present invention includes a first step of selectively forming a concavo-convex region on a main surface of a base material substrate, and a method for forming the concavo-convex region on the base material substrate. The semiconductor layer is irradiated with laser light on the interface between the second step of growing the semiconductor layer made of nitride and filling the concave portion of the uneven region and the upper surface thereof becomes flat, and the base material substrate in the semiconductor layer. A third step of forming the semiconductor substrate from the semiconductor layer by peeling the layer from the base material substrate.
[0014]
According to the method for manufacturing a nitride semiconductor substrate of the present invention, a concavo-convex region is formed on the main surface of the base material substrate, and then the concave portion of the concavo-convex region of the base material substrate is buried on the concavo-convex region and A semiconductor layer made of nitride is grown so that the upper surface is flat. Therefore, after that, when laser light is irradiated onto the interface of the semiconductor layer with the base material substrate, the stress of the portion irradiated with the laser light is a portion where the recess of the base material substrate is filled in the semiconductor layer made of nitride. And the other parts are opened by cleaving parallel to the substrate surface, so that cracks and cracks in the direction perpendicular to the substrate surface do not occur.
[0015]
In the method for manufacturing a nitride semiconductor substrate of the present invention, it is preferable that the third step irradiates at least the convex portion of the concavo-convex region of the base material substrate with laser light. In this case, it is not necessary to scan the entire surface of the semiconductor layer, so that the laser irradiation time can be shortened, and as a result, productivity can be improved.
[0016]
In this case, the first step forms a plurality of concave grooves extending in parallel with each other on the main surface of the base material substrate, and the third step sandwiches the laser light between the plurality of concave grooves on the base material substrate. Irradiation is preferably performed while scanning along the protruding portion. In this way, the convex portion sandwiched between the plurality of concave grooves becomes a so-called stripe shape, so that the laser beam can be scanned efficiently.
[0017]
In addition, the base material substrate is preferably made of sapphire whose principal plane is the {0001} plane, and the direction of the zone axis of each concave groove is preferably the <1-100> direction in the base material substrate.
[0018]
Further, in this case, the first step forms a plurality of island-shaped convex portions on the main surface of the base material substrate, and the third step generates a plurality of pulsed laser beams on the base material substrate. It is preferable to irradiate while scanning so as to synchronize with the convex portion. In this case, since the pulsed laser oscillation can easily increase the output, the semiconductor layer can be easily peeled off from the base material substrate, and the productivity is further improved.
[0019]
In this case, it is preferable that the third step simultaneously irradiates the plurality of convex portions of the concavo-convex region in the base material substrate with the laser beam. As described above, when a plurality of convex portions are irradiated at the same time, the irradiation time can be shortened, so that productivity is reliably improved.
[0020]
In the method for manufacturing a nitride semiconductor substrate of the present invention, in the first step, the area occupied by the protrusions is the area occupied by the recesses in the uneven area of the base material substrate. Of 5 More than 1 / min and One It is preferable to make it 00 times or less. In this way, when the semiconductor layer made of nitride is peeled off from the base material substrate, cracks and cracks can be prevented more reliably, and the entire surface of the semiconductor layer can be peeled off more reliably from the mother board. Become.
[0021]
In the method for manufacturing a nitride semiconductor substrate of the present invention, it is preferable that the third step irradiates laser light from a surface opposite to the main surface of the base material substrate.
[0022]
In the present specification, for the sake of convenience, instead of adding a bar on the Miller index, a negative sign “−” is added in front of the index to indicate its inversion.
[0023]
DETAILED DESCRIPTION OF THE INVENTION
(First embodiment)
A first embodiment of the present invention will be described with reference to the drawings.
[0024]
1 (a) to 1 (d) to 3 (a) to 3 (d) show cross-sectional structures in order of steps of the method for manufacturing a nitride semiconductor substrate according to the first embodiment of the present invention. Yes.
[0025]
First, as shown in FIG. 1A, a base substrate 11 made of sapphire (a single crystal of aluminum oxide) having a diameter of about 5.1 cm (2 inches) and a thickness of about 700 μm is prepared. The surface orientation of the main surface of the base material substrate 11 is the (0001) surface, and both the main surface and the opposite surface (back surface) are mirror-finished.
[0026]
Since sapphire has a band gap of 8.7 eV, it transmits light having a wavelength longer than 142.5 nm, which is a wavelength of energy corresponding to the band gap. Therefore, the KrF excimer laser light having a wavelength of 248 nm or the third harmonic light of the Nd: YAG laser having a wavelength of 355 nm passes through sapphire.
[0027]
(Base material substrate processing process)
Next, as shown in FIG. 1B, a striped resist pattern 12 having a thickness of about 2 μm, a width of about 10 μm, and a spacing of about 30 μm is formed on the main surface of the base substrate 11 by photolithography. Form. The stripe direction at this time is the <1-100> direction of the sapphire crystal zone axis.
[0028]
In the present specification, the <1-100> direction of the crystal zone axis refers to any one of the directions equivalent to the [1-100] direction of the crystal zone axis, and does not represent a specific one direction. . For example, directions equivalent to the <1-100> direction are [1-100], [-1100], [01-10], [0-110], [10-10], and [-1010]. Similarly, the {1-100} plane of the plane orientation refers to any one plane in a direction equivalent to the (1-100) plane of the plane orientation.
[0029]
Next, as shown in FIG. 1C, the base material substrate 11 is etched using the resist pattern 12 as a mask, for example, by reactive ion etching (RIE). The etching gas is chlorine (Cl ₂ ) Using gas, a plasma having an output value of about 200 W is generated at a pressure of about 5 Pa, etching is performed for about 1 hour, and a striped concave groove having a depth of about 1 μm is formed on the main surface of the base material substrate 11. 11a is formed.
[0030]
In this step, since plasma having an output of about 200 W is used, both sides of the resist pattern 12 are etched and rounded.
[0031]
Next, as shown in FIG. 1D, when the resist pattern 12 is removed, the base material substrate 11 having the concavo-convex region 20 whose main surface is concavo-convex can be obtained.
[0032]
Here, the detail of the uneven | corrugated-shaped area | region 20 is demonstrated using Fig.2 (a) and FIG.2 (b). FIG. 2A shows a planar configuration of the concavo-convex region 20, and FIG. 2B shows a cross-sectional configuration taken along line IIb-IIb in FIG.
[0033]
As shown in FIG. 2B, the width of the concave groove 11a is about 30 μm at the bottom, and the width of the convex region 11b sandwiched between the concave grooves 11a is about 10 μm at the bottom. Here, the side surfaces of the convex region 11b are side-etched so that the upper portion thereof is smaller by about 0.5 μm than the lower portion.
[0034]
Moreover, as shown to Fig.2 (a), the direction where the recessed groove | channel 11a, ie, the convex part area | region 11b extends, is the <1-100> direction of the sapphire crystal zone axis. Hereinafter, the direction in which the convex region 11b extends is referred to as a stripe direction.
[0035]
(Nitride semiconductor growth process)
Next, as shown in FIG. 3A, gallium chloride (GaCl) which is a group III source and ammonia (NH) which is a group V source. _Three The semiconductor layer 13 made of gallium nitride (GaN) is grown on the concavo-convex region 20 of the base substrate 11 by a hydride vapor phase epitaxy (HVPE) method. The group III source gallium chloride is produced by reacting metal gallium (Ga) and hydrogen chloride (HCl) under atmospheric pressure of about 900 ° C.
[0036]
Further, in order to increase the nucleation density of gallium nitride on the main surface of the base material substrate 11, the substrate temperature is kept at about 1000 ° C. and only gallium chloride is supplied for about 15 minutes before the semiconductor layer 13 is grown. (This process is hereinafter referred to as GaCl processing). In order to increase the nucleation density, a so-called low-temperature buffer layer made of gallium nitride and grown at a relatively low temperature of about 400 ° C. to 800 ° C. is provided on the base substrate 11 instead of GaCl treatment. In addition, the main surface of the base material substrate 11 may be nitrided with ammonia. Furthermore, a low-temperature buffer layer and nitriding treatment may be combined.
[0037]
Hereinafter, details of the growth of the semiconductor layer 13 will be described.
[0038]
After performing the GaCl treatment, gallium chloride and ammonia are introduced onto the base material substrate 11 to start growing the semiconductor layer 13 made of gallium nitride. Here, since the plane orientation of the main surface of the base material substrate 11 is the (0001) plane, the semiconductor layer 13 also grows with the (0001) plane as the main surface. When the growth temperature is about 1000 ° C., the growth rate on the other surface, that is, the side surface of the convex region 11b is larger than the growth rate on the (0001) plane. As a result, the growth rate in the direction parallel to the substrate surface, that is, the so-called lateral direction is increased to about 2 to 3 times, so that the concave groove 11a is gradually filled. In order to completely fill the concave groove 11a, the thickness of the semiconductor layer 13 is preferably equal to or larger than the width of the concave groove 11a.
[0039]
Further, the stripe direction is the <1-100> direction of the sapphire crystal zone axis constituting the base material substrate 11, and the sapphire and gallium nitride grow with the in-plane plane orientation shifted by 30 °. For this reason, the part located on the side surface of the concave groove 11a in the gallium nitride when the concave groove 11a is embedded becomes a flat {1-101} plane. For this reason, as the semiconductor layer 13 continues to grow, the concave groove 11a grows while being buried flat without causing defects such as pits.
[0040]
Subsequently, growth is performed until the thickness of the semiconductor layer 13 reaches about 200 μm on the convex region 11b even after the concave groove 11a is buried. Thereby, since the concave groove 11a of the uneven region 20 is filled with the semiconductor layer 13, the surface of the semiconductor layer 13 becomes flat. Thereafter, when the substrate temperature is lowered to around room temperature, the base material substrate 11 is warped as shown in FIG. 3A due to the difference in thermal expansion coefficient between the semiconductor layer 13 and the base material substrate 11.
[0041]
In the first embodiment, as compared with the case where the base material substrate 11 and the semiconductor layer 13 are joined in a planar state, the main surface of the base material substrate 11 is uneven, and thus the warping that occurs is reduced. For example, it has been confirmed that the radius of curvature in the stripe direction is about 80 cm and the radius of curvature in the direction perpendicular to the stripe direction in the substrate surface is about 1 m. For comparison, when the semiconductor layer 13 was grown without providing the concave-convex region 20 on the main surface of the base material substrate 11 and the curvature radius of the base material substrate 11 was examined, it was about 60 cm.
[0042]
(Laser irradiation process)
Laser irradiation to the semiconductor layer 13 uses a laser irradiation apparatus as shown in FIG.
[0043]
As shown in FIG. 4, the laser beam 10 emitted from the laser emitting unit 1 is scanned two-dimensionally by the scan lens 2 and is applied to the semiconductor layer 13. Here, the semiconductor layer 13 is irradiated with the laser beam 10 from a surface opposite to the main surface of the base material substrate 11. The beam diameter of the laser beam 10 on the semiconductor layer 13 can be adjusted by the plurality of condensing lenses 3 placed on the optical path of the laser beam 10. Further, the laser irradiation apparatus includes a mirror 4 having a high transmittance of the laser light 10 and a high reflectance of visible light, and an image recognition unit 5 that receives the visible light 10 a input through the mirror 4. . The image recognition unit 5 recognizes the laser irradiation position in the semiconductor layer 13 with the input visible light 10 a and controls the rotational position of the scan lens 2.
[0044]
In the first embodiment, the third harmonic of Nd: YAG having a wavelength of 355 nm is used for the laser light source. The pulse width is about 30 ns and the pulse period is about 50 kHz. By focusing the laser beam 10 into a circular beam having a diameter of about 20 μm, 1.0 J / cm ² A light density of the order is obtained. Since sapphire is transparent to the laser beam 10, as described above, the semiconductor layer 13 is irradiated with the laser beam 10 from the back surface side of the matrix substrate 11 through the matrix substrate 11.
[0045]
When irradiating the laser beam 10, since the semiconductor layer 13 is warped together with the base material substrate 11 as described above, the condenser lens 3 is adjusted to control the spot diameter of the laser beam 10 to be constant. Is preferably performed.
[0046]
In the first embodiment, the laser beam 10 is selectively irradiated along the interface with the convex region 11 b of the semiconductor layer 13. The scanning speed of the laser beam 10 is set to 50 cm / s so that the laser beam 10 is continuously irradiated along the interface with the convex region 11 b of the semiconductor layer 13. At this time, the center interval between the irradiation positions adjacent to each other in the scanning direction on the convex region 11b is about 10 μm. Accordingly, since the center interval of the irradiation positions is smaller than the beam diameter of the laser beam 10 of about 20 μm, the interface between the semiconductor layer 13 and the base material substrate 11 can be continuously irradiated even with pulsed irradiation. . In addition, the laser beam 10 can be continuously irradiated to the semiconductor layer 13 even if the irradiation is performed without stopping the scanning at the time of pulse irradiation, that is, with the optical axis being scanned.
[0047]
FIG. 3B shows a cross section of the base material substrate 11 in the middle of the irradiation process.
[0048]
The semiconductor layer 13 is heated by absorbing the laser light. Since the pulse width of the laser light is as short as 30 ns and the light density is high, the semiconductor layer 13 is locally heated at the portion irradiated with the laser light. By this heating, the irradiated portion of the laser light in the semiconductor layer 13 made of gallium nitride is thermally decomposed to generate the gallium layer 11c and nitrogen gas.
[0049]
In the first embodiment, since the beam diameter of the laser beam is larger than the width of the convex region 11b, a gallium layer 11c is also partially generated at the bottom of the concave groove 11a.
[0050]
Since the gallium layer 11c is a liquid at a temperature of 25 ° C. or higher and is a very soft material even at a temperature lower than 25 ° C., the bonding force between the base material substrate 11 and the semiconductor layer 13 through the gallium layer 11c is extremely small. As a result, stress due to the difference in thermal expansion coefficient concentrates on the joint portion between the base material substrate 11 and the semiconductor layer 13.
[0051]
Further, since nitrogen gas is generated by the thermal decomposition of the semiconductor layer 13, the thermal decomposition region of the semiconductor layer 13 and the vicinity thereof are brought into a state of extremely high pressure by the nitrogen gas.
[0052]
In the first embodiment, an uneven region 20 having an uneven shape is provided on the main surface of the base material substrate 11, and the semiconductor layer 13 made of gallium nitride is grown on the uneven region 20. Here, the stress applied to the semiconductor layer 13 at this time will be described with reference to FIG.
[0053]
When a semiconductor layer is grown on the exit surface of a base material substrate having a flat main surface as in the prior art, the base material substrate and the semiconductor layer are subjected to stress due to a difference in thermal expansion coefficient at the entire interface.
[0054]
In the first embodiment, stress concentrates on a region 30 that connects the upper surfaces of adjacent convex region 11 b of the base material substrate 11 in the semiconductor layer 13. In addition, since the semiconductor layer 13 has a small thermal expansion coefficient, if the base material substrate 11 having a larger thermal expansion coefficient than that of the semiconductor layer 13 is present at the interface, the first stress 31 is generated in the direction of expansion. On the other hand, the base material substrate 11 generates the second stress 32 in the direction in which it is contracted, and thereby the region embedded in the concave groove 11a of the base material substrate 11 in the semiconductor layer 13 is compressed. As a result, the first stress 31 and the second stress 32 act as a force for cutting the semiconductor layer 13 from the upper surface of the convex region 11b of the semiconductor layer 13 in a direction parallel to the main surface.
[0055]
As shown in FIG. 5, the first stress 31 and the second stress 32 may cause a crack 33 in the semiconductor layer 13 parallel to the substrate surface. However, since the semiconductor layer 13 and the base material substrate 11 are bonded to each other in the convex region 11b of the base material substrate 11 in the state after growth, the semiconductor layer 13 is not easily cut.
[0056]
Therefore, the laser irradiation causes the interface between the semiconductor layer 13 and the convex region 11b of the base material substrate 11 to be thermally decomposed, and the first stress 31 and the second stress 32, and further, the nitrogen generated by the thermal decomposition. The force with which the gas pushes the semiconductor layer 13 is concentrated on the upper portion of the concave groove 11 a of the semiconductor layer 13. In addition, since the plane direction of the main surface of the semiconductor layer 13 made of gallium nitride is the (0001) plane, it has the property of being easily cleaved in a plane parallel to the main surface.
[0057]
As a result, when the semiconductor layer 13 is thermally decomposed above the convex region 11b of the base material substrate 11 by laser irradiation, the stress is applied to the upper portion of the concave groove 11a of the base material substrate 11 in the semiconductor layer 13. The semiconductor layer 13 is cleaved along the (0001) plane of gallium nitride constituting the semiconductor layer 13 above the concave groove 11a. At the same time, high-pressure nitrogen gas is also diffused by cleaving the semiconductor layer 13 above the concave groove 11a.
[0058]
Furthermore, as will be described later, when the area ratio between the concave and convex portions in the concavo-convex region 20 of the base material substrate 11 is optimized, a single laser irradiation is performed on the convex region 11b of the base material substrate 11 so that the semiconductor More than half of the area embedded in the concave groove 11a of the layer 13 is cleaved. Therefore, when the laser irradiation to each convex region 11 b is repeated, the portion embedded in the concave groove 11 a of the semiconductor layer 13 can be completely separated (separated) from the base material substrate 11.
[0059]
In the first embodiment, since the laser beam is irradiated perpendicularly to the main surface of the substrate through the base material substrate 11 having the concavo-convex region 20, the irradiation intensity is increased on the side surface of the convex region 11b. As a result, the thermal decomposition of the semiconductor layer 13 does not occur completely.
[0060]
As described above, the second stress 32 in the upper portion of the convex region 11 b of the base material substrate 11 plays an important role in the peeling of the semiconductor layer 13. On the other hand, the thermal decomposition on the side surface of the convex region 11b does not greatly contribute to peeling. Rather, it is more effective to concentrate the second stress 32 generated in the upper part of the convex region 11b if the bonding is performed without peeling. For this reason, the angle of the side surface of the convex region 11b with respect to the substrate surface is preferably as close to vertical as possible, and may be 30 ° or more.
[0061]
By such a peeling mechanism, it has been confirmed that no cracks extending in a direction perpendicular to the main surface of the base material substrate 11 are generated in the semiconductor layer 13 during laser irradiation.
[0062]
Accordingly, as shown in FIG. 3C, the remaining portion 13a of the semiconductor layer 13 is formed in the concave groove 11a of the base material substrate 11 by irradiating all the interface with the convex region 11b of the semiconductor layer 13 with laser light. The semiconductor layer 13 is peeled off from the base material substrate 11 while remaining.
[0063]
Next, as shown in FIG. 3 (d), the gallium layer 11c is removed by hydrogen chloride, and then the concavo-convex portion of the bonding surface with the base material substrate 11 in the semiconductor layer 13 is polished and removed, thereby nitriding A nitride semiconductor substrate 13A is obtained from the semiconductor layer 13 made of gallium. At this time, the nitride semiconductor substrate 13A has a diameter of about 5.1 cm (2 inches), a thickness of about 180 μm, and has no cracks or lacking peripheral portions, and exists in a bulk state.
[0064]
As described above, according to the first embodiment, since laser irradiation is selectively performed only on the interface between the semiconductor layer 13 and the convex region 11b of the base material substrate 11, the entire surface of the semiconductor layer 13 is conventionally formed. Since the laser irradiation time can be reduced as compared with the case where the laser irradiation is performed, the throughput of the laser irradiation process can be improved.
[0065]
In the first embodiment, since the total area of the convex regions 11b in the base material substrate 11 is a quarter of the area of the substrate, the irradiation time of the laser light can be at least a quarter. Actually, when irradiating the entire surface of the substrate, the laser irradiation position is irradiated so that a part of the laser irradiation position overlaps the part irradiated last time. Less than one quarter.
[0066]
Specifically, when the laser beam having a beam diameter of 20 μm is irradiated so that the irradiation positions overlap each other by 10 μm, in the first embodiment, the semiconductor layer 13 having a diameter of 2 inches is about 4 minutes. Irradiation with the laser beam ends. On the other hand, when the irradiation is performed so that the entire surface of the semiconductor layer 13 is overlapped by 10 μm as in the prior art, the laser light irradiation process requires about 30 minutes.
[0067]
Further, in the first embodiment, since the convex region 11b of the base material substrate 11 extends in a stripe shape on the concave / convex region 20, the scanning of the optical axis of the laser beam is simplified, which is efficient. Can be irradiated.
[0068]
In the first embodiment, since the semiconductor layer 13 made of gallium nitride is embedded and grown on the base material substrate 11 having the concavo-convex region 20 on the main surface, as shown in FIG. 13, the penetrating defect 33 extends toward the vicinity of the center of the concave groove 11 a in the upper portion of the concave groove 11 a of the base material substrate 11, and the plurality of penetrating defects 33 are coupled to each other, thereby reducing the number of penetrating defects 33. To do. For this reason, the density of penetrating defects on the surface of the semiconductor layer 13 is approximately 1 × 10 10 above the concave groove 11a. ⁶ cm ^-2 It is.
[0069]
Therefore, when an element is formed using the obtained nitride semiconductor substrate 13A, it is preferable to provide a functional part of the element in a region where the through defects 33 are reduced. The through defects 33 in regions other than the concave groove 11a are provided with a concave portion on the convex region 11b in the semiconductor layer 13 to newly provide a concave / convex region, and gallium nitride is again grown on the new concave / convex region. This can be reduced.
[0070]
By the way, the defect density in a semiconductor layer made of gallium nitride grown on a conventional substrate made of sapphire is 1 × 10 5. ⁹ cm ^-2 Degree.
[0071]
As described above, according to the first embodiment, it is possible to reliably obtain the nitride semiconductor substrate 13A in which the irradiation time of the laser beam can be significantly reduced to a quarter or less and the defect density is also reduced.
[0072]
In the first embodiment, the RIE method is used as a method for forming the concave / convex region 20 on the main surface of the base material substrate 11. However, the present invention is not limited to this, and the formation conditions and the formation method of the concave / convex region 20 are used. Is not particularly limited, and for example, an ion milling method or an ECR etching method can be used. Furthermore, physical means such as sand blasting or polishing may be used, or a deposition method such as selective growth may be used.
[0073]
In addition, when the base material substrate 11 has a multilayer structure, the uneven region 20 may be provided in at least one layer on the surface thereof.
[0074]
In the first embodiment, the depth of the concave groove 11a of the base material substrate 11 is about 1 μm. However, if the depth is too shallow, the stress (second stress) applied to the semiconductor layer 13 embedded in the concave groove 11a. 32) becomes smaller, and the semiconductor layer 13 is less likely to be cleaved along the (0001) plane. Accordingly, the depth of the concave groove 11a is preferably deep, and is preferably 0.1 μm or more.
[0075]
In the first embodiment, the stripe direction is the <1-100> direction of the sapphire crystal zone axis. However, depending on the material used for the base material substrate 11, a semiconductor made of the base material substrate 11 and gallium nitride is used. The relationship of the plane orientation with the layer 13 may be different. In that case, it is preferable that the <11-20> direction of the gallium nitride crystal zone axis coincides with the stripe direction. For example, when silicon carbide (SiC) or aluminum nitride (AlN) is used as the base material substrate 11, the plane orientation of gallium nitride coincides with that of the base material substrate 11, so that the stripe direction is the crystal band of gallium nitride. It is preferable to be in the <11-20> direction of the axis.
[0076]
In the first embodiment, the growth temperature of the semiconductor layer 13 is about 1000 ° C., but there is a preferable temperature range for embedding the concave groove 11 a of the base material substrate 11 flatly, and the temperature is 900 ° C. or higher. It is preferable. In addition, the higher the temperature, the easier the recessed groove 11a is embedded. On the other hand, if the temperature is extremely high, sublimation is dominant over the growth of gallium nitride and the semiconductor layer 13 does not grow. Therefore, under the growth conditions of the first embodiment, the growth temperature of the semiconductor layer 13 is 1500 ° C. The following is preferable.
[0077]
In the first embodiment, the width of the concave groove 11a of the base material substrate 11 is about 30 μm and the width of the convex region 11b is about 10 μm. However, there is a preferable range for the area ratio of the concave portion and the convex portion. is there. That is, the upper limit of the area occupied by the width of the concave groove 11a is that cleaving occurs along the (0001) plane of the gallium nitride plane by irradiation only on the convex region 11b, and the entire semiconductor layer 13 is formed on the base substrate 11. It is a condition that it peels from. Therefore, from this condition, the area occupied by the width of the concave groove 11a is preferably about 100 times or less the area occupied by the width of the convex region 11b. On the other hand, if the area occupied by the width of the concave groove 11a is too small, the stress (second stress 32) when laser light irradiation is performed is not released, so that the semiconductor layer 13 has a direction perpendicular to the substrate surface. A crack is generated, and the desired nitride semiconductor substrate 13A cannot be obtained. Therefore, it is preferable that the area occupied by the width of the concave groove 11a is 1/5 or more of the area occupied by the width of the convex region 11b.
[0078]
In the first embodiment, the light density of the laser light is about 1.0 J / cm. ² However, there is a lower limit to the light density of the laser light, and a light density higher than that capable of decomposing the semiconductor layer 13 is required. The light density necessary for decomposing gallium nitride is about 0.1 mJ / cm when the semiconductor layer 13 is directly irradiated. ² That's it. At the time when the laser light reaches the semiconductor layer 13, of the incident laser light due to reflection and scattering at the surface of the base material substrate 11 and reflection and scattering at the interface between the base material substrate 11 and the semiconductor layer 13. Dozens of percent is considered to be reduced.
[0079]
In the first embodiment, the convex region 11b is a stripe pattern. However, it is preferable that other patterns be a linearly continuous pattern because the scanning of the optical axis of the laser beam is simplified. Further, a one-stroke pattern such as a spiral shape is preferable because the entire semiconductor layer 13 can be irradiated with laser in one scan. Even in this case, it is more preferable that the side surface of the pattern of the convex region 11b is provided so as to coincide with the {1-101} plane of gallium nitride.
[0080]
In the first embodiment, the resist pattern 12 is used as an etching mask. However, the mask material is not limited to a resist, and other materials may be used as long as the etching selectivity with sapphire is not extremely small. be able to. For example, instead of resist, silicon oxide (SiO 2 ₂ ), A dielectric film made of silicon nitride (SiN), or a metal film such as nickel (Ni), gold (Au), or tungsten (W).
[0081]
(Second Embodiment)
Hereinafter, a second embodiment of the present invention will be described with reference to the drawings.
[0082]
7 (a) to 7 (c) to 9 (a) to 9 (c) show cross-sectional structures in order of steps of the method for manufacturing a nitride semiconductor substrate according to the second embodiment of the present invention. Yes.
[0083]
In the second embodiment, the shape of the convex portion in the concavo-convex region 20 is replaced with a stripe pattern and is a dot pattern. Here, the same components as those in the first embodiment are denoted by the same reference numerals.
[0084]
First, as shown in FIG. 7A, a base material substrate 11 made of sapphire having a diameter of about 5.1 cm (2 inches) and a thickness of about 700 μm is prepared. The surface orientation of the main surface of the base material substrate 11 is the (0001) surface, and both the main surface and the opposite surface (back surface) are mirror-finished.
[0085]
(Base material substrate processing process)
Next, as shown in FIG. 7B, a dot pattern having a diameter of about 10 μm and a center position between adjacent portions of about 30 μm is formed on the main surface of the base substrate 11 by photolithography. A resist pattern 12A is formed.
[0086]
As shown in the plan view of FIG. 8, the resist pattern 12 </ b> A is arranged at the apex position of each equilateral triangle when equilateral triangles with sides of 30 μm are closely packed. Patterning is performed so that one side of the equilateral triangle coincides with the {1-100} plane of the sapphire plane orientation. Note that if the dot pattern is missing at the peripheral portion of the base material substrate 11, the semiconductor layer 13 may not grow well at the lacked portion, and therefore the dot pattern is not disposed at the peripheral portion of the base material substrate 11. I am doing so.
[0087]
Next, as shown in FIG. 7C, the base substrate 11 is etched using the resist pattern 12A as a mask by RIE under the same conditions as in the first embodiment. Is formed to a depth of about 1 μm. Thereafter, by removing the resist pattern 12A, the resist pattern 12A is transferred, and a plurality of convex portions 11e each having a dot shape are formed. The cross-sectional shape of the convex portion 11e is almost the same as that in FIG. 2B, and the width of the convex portion 11e is about 10 μm. The side surface of the protrusion 11e is subjected to side etching in which the upper diameter is about 0.5 μm smaller than the lower diameter. Further, the distance between the center positions of the adjacent convex portions 11e is about 30 μm.
[0088]
(Nitride semiconductor growth process)
Next, as shown in FIG. 9A, by the HVPE method using ammonia and gallium chloride as raw materials, under the same conditions as in the first embodiment, on the uneven region 20 of the base material substrate 11, A semiconductor layer 13 made of gallium nitride is grown.
[0089]
The planar shape of the convex portion 11e is a circle (dot), but the growth rate of the {1-101} plane of gallium nitride is relatively small. Therefore, when the semiconductor layer 13 having a thickness of about 1 μm is grown, The side surface of the portion 11e is covered with gallium nitride surrounded by six {1-101} planes and the (0001) plane of the main surface. In addition, since the arrangement of the protrusions 11e is set as shown in FIG. 7C and FIG. 8, the gallium nitride protruding from the adjacent protrusions 11e is united on the {1-101} plane, As a result, the low part 11d is embedded flat. Even after the low part 11d is buried by the semiconductor layer 13, the semiconductor layer 13 is grown until the thickness of the semiconductor layer 13 is about 200 μm above the convex part 11e. Thereby, the low part 11d of the uneven region 20 is filled with the semiconductor layer 13, and the surface of the semiconductor layer 13 becomes flat. Thereafter, when the substrate temperature is lowered to around room temperature, the base material substrate 11 is warped as shown in FIG. 9A due to the difference in thermal expansion coefficient between the semiconductor layer 13 and the base material substrate 11. The warp generated at this time hardly depends on the direction on the substrate surface, and the radius of curvature is about 1 m.
[0090]
(Laser irradiation process)
Also in the second embodiment, the laser irradiation apparatus shown in FIG. 4 is used. The irradiation conditions are also equivalent. For example, the beam diameter of the laser light is about 20 μm, and the pulse period of the laser light emission is about 50 kHz. At this time, since the diameter of the convex portion 11e is about 10 μm and smaller than the beam diameter of about 20 μm, one convex portion 11e can be irradiated by one pulse irradiation.
[0091]
As a feature of the second embodiment, the laser light emission period is irradiated in synchronization with the formation position of the convex portion 11e. Specifically, as described above, the distance between the center positions of the adjacent convex portions 11e is about 30 μm and the pulse frequency is 50 kHz. Therefore, by setting the scanning speed to 150 cm / s, the dot-like shape is obtained. Pulse irradiation can be performed in synchronization with the positions of the convex portions 11e arranged in a row. At this time, it is preferable to feed back the position information from the image recognition unit 5 shown in FIG. 4 to the scan lens 2 and irradiate the laser beam while finely adjusting the irradiation position.
[0092]
As described above, the semiconductor layer 13 is heated by absorbing the irradiated laser beam. Since the pulse width of the laser light is as short as about 30 ns and the light density is high, the semiconductor layer 13 is locally heated at the portion irradiated with the laser light. By this heating, the irradiated portion of the laser light in the semiconductor layer 13 is thermally decomposed to generate the gallium layer 11c and nitrogen gas.
[0093]
In the second embodiment, since the low portion 11d is formed around the convex portion 11e that is the laser irradiation position of the base material substrate 11, the same effect as that of the first embodiment can be obtained. . That is, when the vicinity of the convex portion 11e in the semiconductor layer 13 is thermally decomposed by laser light irradiation, the stress toward the contraction of the upper portion of the convex portion 11e causes the upper portion of the low portion 11d in the semiconductor layer 13 to It is released by cleaving in the (0001) plane of the plane orientation of gallium nitride constituting the layer 13. Further, high-pressure nitrogen gas generated by thermal decomposition is also emitted when the semiconductor layer 13 is peeled off from the base material substrate 11.
[0094]
With such a peeling mechanism, in the second embodiment, cracks that extend in a direction perpendicular to the main surface of the base material substrate 11 do not occur in the semiconductor layer 13 during laser irradiation.
[0095]
Therefore, as shown in FIG. 9B, the remaining portion 13a of the semiconductor layer 13 is formed on the lower portion 11d of the base material substrate 11 by irradiating all the interfaces with the convex portions 11e of the semiconductor layer 13 with laser light. The semiconductor layer 13 is peeled off from the base material substrate 11 while leaving
[0096]
Next, as shown in FIG. 9 (c), the gallium layer 11c is removed by hydrogen chloride, and then the concavo-convex portion of the bonding surface with the base material substrate 11 in the semiconductor layer 13 is removed by polishing, thereby nitriding. A nitride semiconductor substrate 13A is obtained from the semiconductor layer 13 made of gallium. At this time, the nitride semiconductor substrate 13A has a diameter of about 5.1 cm (2 inches), a thickness of about 180 μm, and has no cracks or lacking peripheral portions, and exists in a bulk state.
[0097]
As described above, according to the second embodiment, the laser irradiation is selectively performed only on the interface with the convex portion 11e of the semiconductor layer 13, so that the entire surface of the semiconductor layer 13 is irradiated as in the conventional case. Compared with the above, since the laser irradiation time can be reduced, the throughput of the laser irradiation process can be improved.
[0098]
In addition, since the dot-like projections 11e are arranged in a dispersed manner, by irradiating one projection 11e with one laser pulse, the interface of the semiconductor layer 13 with the projection 11e is locally localized. Is peeled off by heating. As a result, since it is not necessary to irradiate the laser irradiation positions so as to overlap each other, the laser light irradiation time can be further shortened as compared with the first embodiment.
[0099]
Specifically, in the second embodiment, laser light having a beam diameter of about 20 μm is used, and the irradiation of the laser light is completed in only about 1 minute 30 seconds with respect to the semiconductor layer 13 having a diameter of 2 inches. Can do. On the other hand, in the conventional irradiation method, as described above, the laser light irradiation process requires about 30 minutes, and the manufacturing method according to the second embodiment can significantly shorten the laser irradiation process. To do.
[0100]
In the second embodiment, since the convex portion 11e has a periodic dot pattern, the scanning of the optical axis of the laser light is simplified, so that laser irradiation can be performed efficiently.
[0101]
In the second embodiment, the semiconductor layer 13 made of gallium nitride is embedded and grown on the main surface of the base material substrate 11 having the concavo-convex region 20 on the main surface. The penetration defect density is approximately 1 × 10 10 above the lower part 11d. ⁶ cm ^-2 It is.
[0102]
As described above, according to the second embodiment, the laser irradiation time for the semiconductor layer 13 can be remarkably reduced to about 1 minute 30 seconds, and the nitride semiconductor substrate 13A having a region in which the defect density is remarkably reduced is obtained. be able to.
[0103]
In the second embodiment, the planar shape of each convex portion 11e is circular, but the planar shape is not limited as long as it is within the beam diameter of the laser beam.
[0104]
Further, more preferably, the arrangement pattern of the convex portions 11e is such that the direction of the side where the convex portions 11e are arranged coincides with the {1-101} plane of the gallium nitride surface orientation, as shown in FIG. It is good to configure.
[0105]
In the second embodiment, the arrangement pattern of the convex portions 11e is the apex position of each equilateral triangle when the equilateral triangles are closely packed, but laser irradiation is performed even in other arrangement patterns. Thus, the laser irradiation process can be shortened.
[0106]
Further, in this case, as described above, it is preferable to arrange the convex portion 11e so that the {1-101} planes of the growing gallium nitride are combined. In this case, it is more preferable to simplify the scanning of the optical axis of the laser light by periodically arranging the convex portions 11e.
[0107]
(Third embodiment)
Hereinafter, a third embodiment of the present invention will be described with reference to the drawings.
[0108]
10 (a) to 10 (c) and FIGS. 11 (a) to 11 (c) show cross-sectional structures in order of steps of the method for manufacturing a nitride semiconductor substrate according to the third embodiment of the present invention. Yes.
[0109]
In the third embodiment, the laser irradiation method for the dot pattern constituting the concavo-convex region 20 in the base material substrate is changed. Here, the same components as those of the second embodiment are denoted by the same reference numerals.
[0110]
First, as shown in FIG. 10A, a base material substrate 11 made of sapphire having a diameter of about 5.1 cm (2 inches) and a thickness of about 700 μm is prepared. The surface orientation of the main surface of the base material substrate 11 is the (0001) surface, and both the main surface and the opposite surface (back surface) are mirror-finished.
[0111]
(Base material substrate processing process)
Next, as shown in FIG. 10B, a dot pattern having one diameter of about 10 μm and a center position distance between adjacent portions of about 30 μm is formed on the main surface of the base substrate 11 by photolithography. A resist pattern 12A is formed. The planar shape of the dot pattern at this time is the same as the pattern shown in FIG.
[0112]
Next, as shown in FIG. 10 (c), the base substrate 11 is etched using the resist pattern 12A as a mask by the RIE method under the same conditions as in the second embodiment. Is formed to a depth of about 1 μm. Thereafter, by removing the resist pattern 12A, a plurality of dot-shaped convex portions 11e each formed by transferring the resist pattern 12A are formed. The cross-sectional shape of the convex portion 11e is almost the same as that shown in FIG. 2A, and the width of the convex portion 11e is about 10 μm. The side surface of the protrusion 11e is subjected to side etching in which the upper diameter is about 0.5 μm smaller than the lower diameter. Further, the distance between the center positions of the adjacent convex portions 11e is about 30 μm.
[0113]
(Nitride semiconductor growth process)
Next, as shown in FIG. 11 (a), by the HVPE method using ammonia and gallium chloride as raw materials, on the uneven region 20 of the base material substrate 11 under the same conditions as in the second embodiment, The semiconductor layer 13 made of gallium nitride is grown until the thickness is about 200 μm above the protrusion 11e. Thereby, the low part 11d of the uneven region 20 is filled with the semiconductor layer 13, and the surface of the semiconductor layer 13 becomes flat. Thereafter, when the substrate temperature is lowered to around room temperature, the base material substrate 11 is warped as shown in FIG. 11A due to the difference in thermal expansion coefficient between the semiconductor layer 13 and the base material substrate 11. The warp generated at this time hardly depends on the direction on the substrate surface, and the radius of curvature is about 1 m.
[0114]
(Laser irradiation process)
In the third embodiment, the output value of the laser emitting unit 1 in the laser irradiation apparatus shown in FIG. 4 is increased. As the laser light, the third harmonic of an Nd: YAG laser having a wavelength of 355 nm is used. Since the laser beam has a high output, even if the beam diameter of the laser beam is increased to about 5 mm, it is about 2.0 J / cm. ² Can be obtained. However, the pulse period is small because of high output, and is about 10 Hz. The pulse width is about 10 ns, which is sufficient to locally heat the interface between the base material substrate 11 and the semiconductor layer 13.
[0115]
Here, as in the first and second embodiments, since sapphire is transparent to the laser beam, the semiconductor layer 13 is irradiated with the laser beam from the rear surface side of the matrix substrate 11 through the matrix substrate 11. .
[0116]
Irradiation of the laser light to the semiconductor layer 13 requires irradiation of at least the interface of the semiconductor layer 13 with the convex portion 11e. Specifically, the irradiation is sequentially performed from the periphery of the base material substrate 11 toward the inside so that the irradiated portions overlap each other by 2 mm. Note that the irradiation position can be overlapped by 2 mm by setting the linear velocity at the time of scanning with the laser light to about 30 cm / s. That is, laser irradiation is performed along the outer edge portion of the base material substrate 11, and when the laser irradiation for one round is finished, the irradiation position is shifted to the inside of the base material substrate 11 by 3 mm, thereby setting the irradiation position in the radial direction by 2 mm. Can be stacked.
[0117]
As described above, the semiconductor layer 13 is heated by absorbing the irradiated laser beam. Since the pulse width of the laser light is as short as about 10 ns and the light density is high, the semiconductor layer 13 is locally heated at the portion irradiated with the laser light. By this heating, the irradiated portion of the laser light in the semiconductor layer 13 is thermally decomposed to generate the gallium layer 11c and nitrogen gas.
[0118]
In the third embodiment, since the low portion 11d is formed at the laser irradiation position of the base material substrate 11, the same effect as that of the second embodiment can be obtained. That is, when the interface portion with the base material substrate 11 in the semiconductor layer 13 is thermally decomposed by the laser beam irradiation, the stress toward the contraction of the upper portion of the convex portion 11 e is not irradiated with the laser beam in the semiconductor layer 13. The upper portion of the low portion 11d is released by cleaving on the (0001) plane of the gallium nitride constituting the semiconductor layer 13. Further, high-pressure nitrogen gas generated by thermal decomposition is also emitted when the semiconductor layer 13 is cleaved on the (0001) plane.
[0119]
By such a peeling mechanism, in the third embodiment, cracks that extend in a direction perpendicular to the main surface of the semiconductor layer 13 during laser irradiation do not occur. In the third embodiment, by irradiating the entire surface of the interface of the semiconductor layer 13 with the base material substrate 11, the gallium layer 11 c is generated on the almost entire surface of the interface of the semiconductor layer 13 with the base material substrate 11. Also, about 2.0 J / cm ² Since the laser light intensity is high, the gallium layer 11 c is also formed on the side surface of the convex portion 11 e of the base material substrate 11. Since the bonding force of the gallium layer 11c is very small, as shown in FIG. 11B, the semiconductor layer 13 can be easily separated from the base substrate 11 simply by lifting the semiconductor layer 13. At this time, a remaining portion 13 a that is cleaved by a crack on the (0001) plane in the semiconductor layer 13 may occur on the lower portion 11 d of the base material substrate 11.
[0120]
Next, as shown in FIG. 11 (c), the gallium layer 11c is removed by hydrogen chloride, and then the concavo-convex portions of the bonding surface with the base material substrate 11 in the semiconductor layer 13 are polished and removed, thereby nitriding A nitride semiconductor substrate 13A is obtained from the semiconductor layer 13 made of gallium. At this time, the nitride semiconductor substrate 13A has a diameter of about 5.1 cm (2 inches), a thickness of about 180 μm, and has no cracks or lacking peripheral portions, and exists in a bulk state.
[0121]
As described above, according to the third embodiment, the plurality of convex portions 11e are formed in the concavo-convex region 20 of the base material substrate 11 at intervals of about 30 μm. Since the beam diameter is as large as 5 mm, it is possible to irradiate about 10,000 or more convex portions 11e at a time, so that the irradiation time can be significantly reduced. Specifically, in the third embodiment, laser irradiation can be completed in only about 1 minute for the semiconductor layer 13 having a diameter of 2 inches.
[0122]
In the third embodiment, there is a case where the laser light is irradiated only on a part of the convex portion 11e of the base material substrate 11 during laser irradiation, and the semiconductor layer 13 in the vicinity thereof is thermally decomposed. Even in this case, the semiconductor layer 13 does not crack in the direction perpendicular to the main surface of the base substrate 11, and the upper portion of the lower portion 11 d in the semiconductor layer 13 is (0001) in the plane orientation of the semiconductor layer 13. Cleave along the plane. For this reason, even if the beam diameter of the pulse irradiation is increased, it is possible to prevent the contraction stress of the base material substrate 11 from being concentrated and the semiconductor layer 13 from being cracked or cracked.
[0123]
Also in the third embodiment, the semiconductor layer 13 made of gallium nitride is embedded and grown on the main surface of the base material substrate 11 having the concavo-convex region 20 on the main surface. The penetration defect density is approximately 1 × 10 10 above the lower part 11d. ⁶ cm ^-2 It is.
[0124]
As described above, by increasing the beam diameter of the laser beam, the laser irradiation time can be remarkably reduced, and a nitride semiconductor substrate 13A having a region in which the defect density is significantly reduced without cracks and cracks can be obtained. Can do.
[0125]
In the third embodiment, the entire surface of the semiconductor layer 13 is irradiated with laser light. However, at least the interface portion of the semiconductor layer 13 with the convex portion 11e of the base material substrate 11 may be irradiated. . In that case, the irradiation time of the laser light can be shortened compared with the case where the entire surface of the semiconductor layer 13 is irradiated.
[0126]
(Fourth embodiment)
The fourth embodiment of the present invention will be described below.
[0127]
In the fourth embodiment, an optimal dot pattern arrangement is obtained by changing the interval between the convex portions 11e in the concavo-convex region 20 according to the second embodiment.
[0128]
Here, in the concavo-convex region 20 shown in FIG. 7 (c), the base material substrate 11 and the semiconductor layer 13 are peeled by changing the ratio of the area occupied by the convex portion 11e and the area occupied by the low portion 11d. Check out.
[0129]
For example, as a first example, when the area occupied by the low portion 11d in the concavo-convex region 20 is less than about one-fifth of the area occupied by the convex portion 11e, the semiconductor layer 13 is irradiated with laser light. When a part of the semiconductor layer 13 is thermally decomposed, a region where the semiconductor layer 13 is cleaved by the (0001) plane of the plane orientation becomes insufficient, and thus a crack extending in the surface direction of the semiconductor layer 13 is generated.
[0130]
In addition, when the area of the low part 11d is set to about one fifth of the area of the convex part 11e, the convex parts 11e are connected to each other, and the low part 11d is scattered in a concave section in the convex part 11e. It has become.
[0131]
As a second example, if the area occupied by the low portion 11d in the concavo-convex region 20 is about one-fifth or more of the area occupied by the convex portion 11e, cracks generated in the semiconductor layer 13 in the plurality of prepared samples In some cases, a bulk substrate made of gallium nitride having a diameter of about 5.1 cm (2 inches) that does not extend in the surface direction of the semiconductor layer 13 may be obtained.
[0132]
Therefore, more preferably, by setting the area occupied by the low portion 11d to be one-half or more of the area occupied by the convex portion 11e, a bulk substrate made of gallium nitride of 2 inches at almost all points of a plurality of samples is formed. Obtainable.
[0133]
As a third example, a case where the area occupied by the low part 11d is larger than the area occupied by the convex part 11e will be verified.
[0134]
When the area occupied by the low portion 11d exceeds about 100 times the area occupied by the convex portion 11e, the region where the semiconductor layer 13 is cleaved on the (0001) plane is low even if all the convex portions 11e are irradiated with laser light. The entire interface with the portion 11d cannot be reached. For this reason, the semiconductor layer 13 cannot be peeled from the base material substrate 11. In order to reliably peel the semiconductor layer 13 from the base material substrate 11, the area occupied by the low part 11d needs to be 100 times or less the area occupied by the convex part 11e.
[0135]
More preferably, by making the area occupied by the low portion 11d in the uneven region 20 20 times or less than the area occupied by the convex portion 11e, a bulk shape made of gallium nitride of 2 inches at almost all points of the plurality of samples prepared. Substrate can be obtained.
[0136]
When the semiconductor layer 13 cannot be peeled off from the base substrate 11 because the area occupied by the low portion 11d is too large, laser beam irradiation is performed on the bonding region between the base substrate 11 and the semiconductor layer 13. It goes without saying that the entire surface of the semiconductor layer 13 can be peeled by performing again.
[0137]
In the fourth embodiment, when the arrangement of the protrusions 11e is extremely biased on the uneven area 20, for example, all the protrusions 11e are concentrated in a half area on the main surface of the base material substrate 11. Needless to say, the results described above do not apply to such cases. However, for example, when the density of the protrusions 11e is examined in a region including several tens of protrusions 11e in the uneven region 20, and the density is substantially uniform, the above-described result can be used. .
[0138]
【The invention's effect】
According to the method for manufacturing a nitride semiconductor substrate according to the present invention, since the concavo-convex region is formed on the main surface of the base material substrate, the stress of the portion irradiated with the laser light is applied to the base material substrate in the semiconductor layer made of nitride. Since the portion filled with the recess and the other portion are cleaved in parallel with the substrate surface, cracks and cracks in the direction perpendicular to the substrate surface do not occur.
[Brief description of the drawings]
FIGS. 1A to 1D are cross-sectional structural views showing a manufacturing method of a nitride semiconductor substrate according to a first embodiment of the present invention.
FIGS. 2A and 2B show a method of manufacturing a nitride semiconductor substrate according to the first embodiment of the present invention, FIG. 2A is a plan view of an uneven region, and FIG. It is sectional drawing in the IIb-IIb line | wire of a).
FIGS. 3A to 3D are structural cross-sectional views in order of steps showing a method for manufacturing a nitride semiconductor substrate according to the first embodiment of the present invention. FIGS.
FIG. 4 is a schematic configuration diagram of a laser emitting device used in the method for manufacturing a nitride semiconductor substrate according to the first embodiment of the present invention.
FIG. 5 is a cross-sectional view schematically showing stress generated at an interface between a base material substrate and a semiconductor layer in the method for manufacturing a nitride semiconductor substrate according to the first embodiment of the present invention.
FIG. 6 is a cross-sectional view schematically showing through defects generated in a semiconductor layer grown on a base material substrate in the method for manufacturing a nitride semiconductor substrate according to the first embodiment of the present invention.
7A to 7C are structural cross-sectional views in order of steps showing a method for manufacturing a nitride semiconductor substrate according to a second embodiment of the present invention.
FIG. 8 is a plan view showing a resist pattern for forming a dot pattern in the method for manufacturing a nitride semiconductor substrate according to the second embodiment of the present invention.
FIGS. 9A to 9C are cross-sectional views in order of steps showing a method for manufacturing a nitride semiconductor substrate according to the second embodiment of the present invention. FIGS.
FIGS. 10A to 10C are cross-sectional structural views in order of steps showing a method for manufacturing a nitride semiconductor substrate according to a third embodiment of the present invention. FIGS.
FIGS. 11A to 11C are structural cross-sectional views in order of steps showing a method for manufacturing a nitride semiconductor substrate according to a third embodiment of the present invention. FIGS.
[Explanation of symbols]
1 Laser emission part
2 Scan lens
3 Condensing lens
4 Mirror
5 Image recognition unit
10 Laser light
10a Visible light
11 Base material substrate
11a concave groove
11b Convex area
11c Gallium layer
11d low part
11e Convex
12 resist pattern
12A resist pattern
13 Semiconductor layer
13a remaining
13A Nitride semiconductor substrate
20 Uneven region
31 First stress
32 Second stress
33 penetration defect

Claims (8)

A first step of selectively forming a concavo-convex region on the main surface of the base material substrate;
A second step of growing a semiconductor layer made of nitride so as to fill the concave portion of the concave-convex region on the concave-convex region of the base material substrate and to flatten the upper surface thereof;
A third step of forming a semiconductor substrate from the semiconductor layer by irradiating a laser beam on the interface of the semiconductor layer with the base material substrate and peeling the semiconductor layer from the base material substrate. A method for producing a nitride semiconductor substrate, comprising: 2. The method of manufacturing a nitride semiconductor substrate according to claim 1, wherein the third step irradiates at least a convex portion of the concavo-convex region in the base material substrate with a laser beam. The first step forms a plurality of concave grooves extending in parallel to each other on the main surface of the base material substrate,
3. The nitride according to claim 2, wherein the third step irradiates the laser beam while scanning along a convex portion sandwiched between the plurality of concave grooves in the base material substrate. A method for manufacturing a semiconductor substrate. The base material substrate is made of sapphire whose principal surface has a {0001} plane.
4. The method for manufacturing a nitride semiconductor substrate according to claim 3, wherein a direction of a crystal zone axis of each concave groove is a <1-100> direction in the base material substrate. In the first step, a plurality of island-shaped convex portions are formed on the main surface of the base material substrate,
3. The nitride semiconductor substrate according to claim 2, wherein in the third step, pulsed laser light is irradiated while scanning in synchronization with the plurality of convex portions in the base material substrate. Production method. 3. The method of manufacturing a nitride semiconductor substrate according to claim 2, wherein the third step irradiates a plurality of convex portions of the concavo-convex region of the base material substrate with a laser beam simultaneously. The first step is the one of the irregular region in the base substrate, claims, characterized in that the following且one 00 times 5 minutes 1 times or more of the area occupied by the convex portion and the area occupied by the recesses The manufacturing method of the nitride semiconductor substrate of any one of 1-6. The nitride semiconductor substrate according to any one of claims 1 to 7, wherein the third step irradiates a laser beam from a surface opposite to the main surface of the base material substrate. Production method.

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