JP2012101977A - Method for manufacturing nitride semiconductor substrate, and method for manufacturing nitride semiconductor self-standing substrate - Google Patents

Abstract

A method of manufacturing a nitride semiconductor substrate and a method of manufacturing a nitride semiconductor self-supporting substrate capable of suppressing warpage (plane orientation distribution) of a nitride semiconductor single crystal and performing homogeneous crystal growth are provided.
A method of manufacturing a nitride semiconductor substrate includes a GaN film formed on a substrate having a GaN thin film and a stripe mask while maintaining a substantially uniform temperature distribution in a crystal growth region in a quartz reactor in an HVPE furnace. While the thick film 5 is grown, the control temperature of the heater 8 for heating the HVPE furnace 20 is changed so that the warpage of the growing GaN thick film 5 falls within a predetermined range.
[Selection] Figure 1

Description

  The present invention relates to a method for manufacturing a nitride semiconductor substrate and a method for manufacturing a nitride semiconductor free-standing substrate.

  Conventionally, group III nitride semiconductors such as gallium nitride (GaN), indium gallium nitride (InGaN), and gallium aluminum nitride (AlGaN) have attracted attention as materials for blue light emitting diodes (LEDs) and laser diodes (LDs). Yes. Furthermore, since group III nitride semiconductors have the characteristics of good heat resistance and environmental resistance, application development for electronic device elements has also begun. Hereinafter, GaN will be described as a representative example of a group III nitride semiconductor.

  A substrate for GaN growth that is currently in wide use is sapphire. As a growth method of a GaN single crystal film, a method of epitaxial growth on a single crystal sapphire substrate by metal organic vapor phase epitaxy (MOVPE method) or the like is generally used.

  However, since the sapphire substrate has a lattice constant different from that of GaN, a single crystal film of GaN cannot be directly grown on the sapphire substrate. For this reason, a method has been devised in which an AlN or GaN buffer layer is once grown on a sapphire substrate at a low temperature to reduce lattice distortion and a GaN single crystal film is grown thereon.

  By using the low-temperature grown nitride layer as a buffer layer, the GaN single crystal film can be epitaxially grown, but the lattice deviation between the substrate and the crystal is not completely eliminated. Has innumerable defects. Defects in the GaN single crystal film may be an obstacle to manufacturing GaN-based LDs and high-brightness LEDs.

  Therefore, the emergence of a GaN free-standing substrate has been strongly desired. However, GaN is difficult to pull up a large ingot from the melt like Si and GaAs. Therefore, various methods such as an ultra-high temperature and high pressure method, a flux method, a hydride vapor phase epitaxy method (HVPE method) have been tried. The HVPE method GaN substrate is the most developed among the above methods. Currently, distribution to the market has begun, and there are great expectations not only for LD applications but also for high-brightness LEDs.

  Although a GaN substrate by the HVPE method has been put into practical use, there is still much room for improvement in the characteristics of the GaN substrate manufactured by the HVPE method. The problem here is the warpage (or plane orientation distribution) of the GaN substrate. The warpage can be obtained as a difference in height between the center portion and the outer edge portion of the back surface of the substrate. Further, if the thickness distribution is known, it can also be obtained from the difference in height between the center portion and the outer edge portion of the substrate surface.

  In general, a GaN single crystal grown by heteroepitaxy is warped even after the base substrate is removed. The self-standing GaN single crystal substrate from which the base substrate has been removed can be flattened as a mechanical shape by polishing both surfaces of the substrate, but has an in-plane distribution of crystal orientations.

  In epitaxial growth of devices, it is necessary to grow a mixed crystal such as AlGaN or InGaN on a GaN single-crystal free-standing substrate. However, even under the same growth conditions, the mixed crystal composition changes depending on the plane orientation, and thus has an orientation distribution. The mixed crystal thin film grown on the substrate has an in-plane distribution of the composition. For example, although InGaN is used for the active layer of the LED, if the composition of InGaN varies within the plane, the emission wavelength varies, and the device yield decreases. Since the variation in the plane orientation is caused by the warp before the processing of the crystal, it is important to reduce the warp in the as-grown in order to reduce the variation in the plane orientation.

  As a technique for suppressing the warpage of the GaN single crystal in such as-grown, a technique for reducing the warpage by performing annealing after crystal growth is disclosed (for example, see Patent Document 1). However, there is a concern that the manufacturing cost increases because additional steps are added after crystal growth.

  In addition, a technique for suppressing warpage of a GaN single crystal by doping an appropriate impurity so as to correct distortion is disclosed (for example, see Patent Document 2). However, generally, the addition of impurities becomes a factor that impairs other characteristics.

  Therefore, there has been a demand for a warpage control method that does not incur extra costs and does not impair other characteristics.

  In response to the above problems, heaters that can be controlled independently are installed on the front and back sides of the substrate, while controlling the temperature gradient in the vertical direction and feeding back the warping during growth in situ. A controllable nitride semiconductor manufacturing apparatus is disclosed (for example, see Patent Document 3).

  In the apparatus described in Patent Document 3, the thermocouple is disposed close to the substrate surface, the substrate surface temperature can be accurately measured, and the temperature of the substrate surface measured by the thermocouple is adjusted so as to be constant. By controlling the heater output, the warpage of the GaN single crystal can be brought close to zero.

JP 2004-165564 A Patent 4529846 JP 2009-295658 A

  However, in the method for manufacturing a nitride semiconductor substrate described in Patent Document 3, if the thermocouple is disposed close to the substrate surface, crystals are deposited on the thermocouple itself, preventing accurate measurement, There is a problem of disturbing the flow. On the other hand, in order not to disturb the flow of the source gas, if the thermocouple is installed in a part away from the substrate surface at the expense of the accuracy of the measurement result, the infrared absorption amount of the crystal grows. Even if the substrate temperature changes slightly, the change cannot be detected or there is a high possibility of underestimation, and accurate feedback control becomes difficult.

  When the change in the substrate temperature cannot be detected, the upper and lower heaters are controlled to generate a temperature gradient in the vertical direction in the furnace in order to suppress warpage while keeping the temperature of the thermocouple constant. As a result, an unexpected temperature gradient is generated, and as described in Patent Document 3, an unexpected convection of the raw material gas is generated, which causes a hindrance to homogeneous crystal growth. In addition, the apparatus becomes complicated and causes cost increase.

  Accordingly, an object of the present invention is to provide a nitride semiconductor substrate manufacturing method and a nitride semiconductor free-standing substrate manufacturing method capable of suppressing warpage (plane orientation distribution) of a nitride semiconductor single crystal and performing uniform crystal growth. Is to provide.

In order to solve the above-mentioned problems, the present invention provides a method for producing a nitride semiconductor single crystal by heteroepitaxy,
While maintaining a substantially uniform temperature distribution in the crystal growth region in the crystal growth apparatus by vapor phase growth, a nitride semiconductor single crystal is grown on the substrate,
There is provided a method for manufacturing a nitride semiconductor substrate, wherein the control temperature of a heater for heating the crystal growth apparatus is changed so that the warpage of the growing nitride semiconductor single crystal is within a predetermined range. The

In the method for manufacturing a nitride semiconductor substrate, the nitride semiconductor single crystal is grown on the substrate having a larger linear expansion coefficient than the nitride semiconductor single crystal,
It is preferable to lower the control temperature at a predetermined rate so that the warpage falls within a predetermined range.

In the method for manufacturing a nitride semiconductor substrate, the nitride semiconductor single crystal is grown on the substrate having a smaller linear expansion coefficient than the nitride semiconductor single crystal,
It is preferable to raise the control temperature at a predetermined rate so that the warpage falls within a predetermined range.

  In the method for manufacturing a nitride semiconductor substrate, the warp is preferably detected during crystal growth by optical means, and the control temperature is preferably feedback-controlled so that the detected warp falls within a predetermined range. .

  In the method for manufacturing a nitride semiconductor substrate, it is preferable to use sapphire, SiC, GaAs, ZnO, or Si as the substrate.

  In the method for manufacturing a nitride semiconductor substrate, the method for growing the nitride semiconductor single crystal is preferably an HVPE method.

  In addition, after the nitride semiconductor single crystal is grown by the method described above, a nitride semiconductor single crystal substrate is obtained by removing the substrate to provide a nitride semiconductor single crystal substrate. The

  The predetermined ratio is preferably determined by predicting in advance a change in temperature of the substrate with respect to the crystal growth time.

  Further, the predetermined ratio is determined by the method of detecting the warp during crystal growth by optical means and performing feedback control of the control temperature so that the detected warp falls within a predetermined range. It is preferable to manufacture the semiconductor substrate and record the data of the control temperature during the growth and determine that the same nitride semiconductor substrate can be obtained based on the data.

  According to the method for manufacturing a nitride semiconductor substrate and the method for manufacturing a nitride semiconductor free-standing substrate according to the present invention, it is possible to suppress the warpage (plane orientation distribution) of the nitride semiconductor single crystal and perform uniform crystal growth. .

1A to 1F are cross-sectional views illustrating an example of a manufacturing process of a nitride semiconductor substrate according to an embodiment. FIG. 2 is a partial cross-sectional view showing an example of the structure of the HVPE furnace according to the embodiment. FIG. 3 is a graph showing an example of the thickness dependence of warpage during growth of the sample according to Example 1. FIG. 4 is a graph showing an example of the thickness dependence of warpage during the growth of the sample according to Example 2. FIG. 5 is a graph showing an example of thickness dependence of warpage during growth of a sample according to Example 3. FIG. 6 is a graph showing an example of thickness dependence on warpage during growth of a sample according to a comparative example. FIG. 7 is a graph showing an example of the doping concentration dependency on the warpage of the GaN free-standing crystal according to the comparative example.

[Summary of embodiment]
The main point of this embodiment is that, in the growth of a GaN single crystal by heteroepitaxy, a crystal growth apparatus using a vapor phase method in which the temperature distribution in the crystal growth area is maintained substantially uniform is used to control the crystal growth area during crystal growth. The purpose is to reduce the warpage of the GaN single crystal by the thermal stress caused by the difference in linear expansion coefficient between the substrate and the epi layer by changing the temperature while maintaining the uniformity of the temperature distribution.

  First, in describing embodiments of the present invention, main causes (a) to (c) of warpage remaining after removal of a base substrate of a GaN crystal generated by heteroepitaxy will be described.

(A) Warpage due to surface tension during island bonding of Volmer-Weber type growth mechanism Generally, growth of GaN crystals by heteroepitaxy follows a growth process of Volmer-Weber type. That is, in the initial stage of growth, the crystal is in the form of discrete islands, and as the growth proceeds, the islands are joined together to form a flat surface and shift to two-dimensional growth.

  It is considered that the bonding between crystal islands proceeds because the surface energy decreases due to the bonding. That is, the islands attract each other due to surface tension. However, since the position of the GaN island on the base substrate is constrained by the base substrate, the two water droplets do not slide on the glass plate to complete the binding like the water droplets on the glass plate, Stress is generated that bends the substrate into a concave surface.

(B) Defect density distribution in the thickness direction After the transition to the two-dimensional growth, the increase in stress due to the surface tension as described in (a) disappears, but the increase in stress continues due to other causes. The reason why the stress continues is thought to be the reduction of the surplus half-lattice plane due to the annihilation of dislocations.

  It has been found that the warp caused by the above (a) and (b) can be reduced to some extent by controlling the island density of the GaN crystal, for example, in the initial growth process. However, the inventors have first clarified the method of generating and reducing the warp caused by (c) described below.

(C) Thermal stress due to unexpected temperature change during growth If the substrate temperature changes for some reason during the growth of the GaN crystal, warping due to the difference in linear expansion coefficient between GaN and the underlying substrate occurs. Usually, the substrate temperature is monitored by a thermocouple installed in the vicinity of the susceptor on which the substrate is placed, and the heater output is feedback-controlled so that the monitored temperature becomes constant at the set temperature (control temperature). However, the temperature monitored by the thermocouple (the temperature controlled to be the same as the control temperature) is not necessarily equal to the true substrate temperature. In particular, in the case of a material such as GaN whose transparency to infrared rays is not so small, an error tends to occur between the control temperature and the true substrate temperature. This is because the main heating mechanism of the transparent substrate is heat conduction from the susceptor, and the true substrate temperature is likely to change depending on the contact state between the substrate and the susceptor.

  In the growth of GaN crystals by heteroepitaxy, warpage occurs due to the causes described in (a) and (b), so that the contact state between the substrate and the susceptor tends to change, and there is an error between the control temperature and the true substrate temperature. Is likely to occur. In such a situation, for example, when the infrared absorption coefficient of the GaN crystal changes, the monitor value of the control temperature hardly appears, the true substrate temperature changes, and warpage due to thermal stress occurs. Newly grown GaN on the surface of the warped GaN crystal has a defect arrangement that minimizes the energy in that state (plastic deformation), so that warping remains even after the substrate is removed after growth. Will do. Here, the cause of the increase in the infrared absorption coefficient of the GaN crystal includes, for example, an increase in free carrier absorption due to doping, coloring due to other point defects, and the like.

  In order to suppress the warpage of the GaN crystal caused by the above (c), in principle, the heater control may be performed so that the true substrate temperature becomes constant. However, accurate monitoring of the true substrate temperature is difficult. If the change in the infrared absorption coefficient can be estimated from the growth conditions, it is conceivable to perform heater control in accordance with the change in the infrared absorption coefficient, but in practice, accurate estimation is not easy. Therefore, it is effective to monitor the warpage of the GaN crystal and feedback control the control temperature so that the monitored warpage becomes a constant value.

  Here, the feedback control is ideally set so that the warpage of the GaN crystal is zero. However, when the warpage due to (a) and (b) is large, if the control is performed so that the warpage of the GaN crystal becomes zero, the true substrate temperature may change. If the true substrate temperature is changed too much, the GaN crystal will crack due to excessive thermal stress, or it will be out of the temperature range where good crystallinity can be obtained, so feedback control is performed within a range where these can be avoided. preferable.

[Embodiment]
First, a method for manufacturing a nitride semiconductor substrate and a method for manufacturing a nitride semiconductor free-standing substrate according to an embodiment of the present invention will be described with reference to FIGS.

  1A to 1F are cross-sectional views illustrating an example of a manufacturing process of a nitride semiconductor substrate according to an embodiment.

  First, as shown in FIG. 1A, a substrate 1 is prepared. The substrate 1 is a c-plane sapphire substrate having a diameter of 3 inches, for example.

  Next, as shown in FIG. 1B, an undoped GaN thin film 2 having a thickness of 1.5 μm, for example, is grown on the surface of the substrate 1 by using the MOVPE method.

Next, as shown in FIG. 1C, a SiO ₂ film 3 having a thickness of 100 nm, for example, is deposited on the template substrate having the substrate 1 and the GaN thin film 2 by using a thermal CVD method.

Next, using a standard photolithography technique, a SiO ₂ stripe mask 4 is formed as shown in FIG. The stripe mask 4 has a stripe pattern mask width of 5 μm and an opening width of 4 μm, for example.

Next, a template having the stripe mask 4 is set as a sample 19 in an HVPE furnace shown in FIG. 2 described later, and a GaN thick film 5 is grown as shown in FIG. The above-mentioned GaCl and NH ₃ are used as raw materials for HVPE growth of GaN. Further, Si doping is performed by supplying SiH ₂ Cl ₂ together with GaCl and NH ₃ . The growth pressure is atmospheric pressure.

  FIG. 2 is a partial cross-sectional view showing an example of the structure of the HVPE furnace according to the embodiment.

The HVPE furnace (vapor phase growth furnace) 20 includes a quartz reactor 7, an external heater 8, a susceptor 9, a laser light source 10, a detector 13, a thermocouple 14, an HCl supply pipe 15, and an NH ₃ supply. A pipe 17 and a SiH ₂ Cl ₂ supply pipe 18 are provided.

  The quartz reactor 7 is a transparent reactor formed of quartz, and is a hot wall type in which the temperature of the crystal growth region is made substantially uniform by being heated by the external heater 8.

  The external heater 8 is, for example, a resistance overheating heater. Hereinafter, the temperature set in the external heater 8 is referred to as “control temperature”.

  The susceptor 9 is made of graphite or the like, and has a disk-shaped table for installing the sample 19. The susceptor 9 is installed inside the quartz reactor 7, and the surface of the base is coated with SiC and installed horizontally. The sample 19 is a template having the stripe mask 4 and is arranged on the susceptor 9 with a so-called face-up. The susceptor 9 rotates at a speed of, for example, 10 rpm with the rotation of the rotating shaft 90 during the growth of the GaN thick film 5.

  The laser light source 10 is installed on the susceptor 9 and makes the laser beam 11 incident on the sample 19.

  The detector 13 detects the reflected light 12 reflected by the sample 19 from the laser beam 11. The detector 13 monitors the amount of warpage of the sample 19 from the position where the reflected light 12 is detected.

  The thermocouple 14 is made of platinum rhodium or the like, and is installed on the back surface of the susceptor 9 to monitor the control temperature.

  The HCl supply pipe 15 is a pipe for supplying HCl. By supplying HCl to a Ga melt 16 provided in the middle of the pipe, the HCl supply pipe 15 reacts with each other to generate GaCl, and supplies GaCl into the quartz reactor 7. .

The NH ₃ supply pipe 17 supplies NH ₃ into the quartz reactor 7.

The SiH ₂ Cl ₂ supply pipe 18 supplies SiH ₂ Cl ₂ into the quartz reactor 7.

  In the HVPE furnace 20 having the configuration described above, the warp of the sample 19 is monitored, and the control temperature is feedback-controlled by the external heater 8 so that the warp of the GaN thick film 5 becomes a constant value.

  Next, after the growth of the GaN thick film 5 described above, as shown in FIG. 1 (f), the substrate 1 is removed using laser peeling to obtain a GaN free-standing crystal 6 having a c-plane with a diameter of 3 inches and GaN.

(Effect of embodiment)
According to the above-described embodiment, in the heteroepitaxial growth of nitride crystal, the temperature in the quartz reactor 7 is changed as a whole while keeping the temperature of the crystal growth region substantially uniform, resulting in a temperature gradient. Generation of convection is suppressed, warpage due to an unexpected temperature change is suppressed, and a GaN free-standing crystal 6 having a small plane orientation distribution can be manufactured.

Similar to the embodiment, a sample 19 with a SiO ₂ stripe mask 4 was prepared and set in an HVPE furnace 20 to grow a GaN thick film 5 having a thickness of about 500 μm. The GaN thick film 5 was undoped up to a thickness of 100 μm, and thereafter, a predetermined amount of SiH ₂ Cl ₂ was supplied together with the source gas so that the Si concentration in GaN was about 3 × 10 ¹⁸ cm ⁻³ .

  Further, the warp of the sample 19 was detected using the laser light source 10 and the detector 13 during the growth, and the external heater 8 was controlled so that the amount of warp during the growth became substantially zero.

  FIG. 3 is a graph showing an example of the thickness dependence of warpage during growth of the sample according to Example 1.

  For comparison, the data of a comparative example to be described later are shown in FIG. The comparative example is a case where growth was performed under the same Si concentration as in Example 1 and a constant control temperature. The right axis shows the transition of control temperature by feedback. Due to the feedback control to make the warp substantially zero, the control temperature, which was initially 1090 ° C., was finally reduced to about 1025 ° C.

  After the growth of the GaN thick film 5 was completed, the substrate 1 was removed by laser peeling to obtain a GaN free-standing crystal 6 having a diameter of 3 inches. When the warpage of the GaN free-standing crystal 6 was measured with a laser displacement meter, it was found that the warpage was 5 μm or less.

First, a c-plane SiC substrate having a diameter of 3 inches was prepared as the substrate 1. Next, an undoped GaN thin film having a thickness of 1.5 μm was grown on the surface of the c-plane SiC substrate by using the MOVPE method. Thereafter, in the same manner as in the embodiment, a c-plane GaN template with a SiO ₂ stripe mask was prepared and set in the HVPE furnace 20 to grow a GaN thick film 5 having a thickness of about 500 μm. The GaN thick film 5 was undoped up to a thickness of 100 μm, and thereafter, a predetermined amount of SiH ₂ Cl ₂ was supplied together with the source gas so that the Si concentration in GaN was about 3 × 10 ¹⁸ cm ⁻³ . The control temperature at the start of growth was 1010 ° C.

  Further, the warp of the sample 19 was detected using the laser light source 10 and the detector 13 during the growth, and the external heater 8 was controlled so that the amount of warp during the growth became substantially zero.

  FIG. 4 is a graph showing an example of the thickness dependence of warpage during the growth of the sample according to Example 2.

  For comparison, the same data is shown in the figure when the growth is performed under the condition that the Si concentration is the same and the control temperature is constant (1010 ° C.). The right axis shows the transition of control temperature by feedback.

  When grown at a constant control temperature, the warpage in the positive direction due to (a) and (b) increases up to a thickness of about 100 μm, but when doping starts, it causes (c) Negative warping that seems to be increasing.

  On the other hand, when feedback control is performed, almost no warping occurs. Further, the control temperature, which was initially 1010 ° C., was finally increased to about 1085 ° C. by feedback control.

  After the growth of the GaN thick film 5 was completed, the substrate 1 was removed by laser peeling to obtain a GaN free-standing crystal 6 having a diameter of 3 inches. When the warpage of the GaN free-standing crystal 6 was measured with a laser displacement meter, it was found that the warpage was 5 μm or less. .

First, a (111) A-plane GaAs substrate having a diameter of 3 inches was prepared. Next, an undoped GaN thin film having a thickness of 1.5 μm was grown on the surface of the A-plane GaAs substrate by using the MOVPE method. Thereafter, in the same manner as in the embodiment, a c-plane GaN template with a SiO ₂ stripe mask was prepared and set in the HVPE furnace 20 to grow a GaN thick film 5 having a thickness of about 500 μm. The GaN thick film 5 was undoped up to a thickness of 100 μm, and thereafter, a predetermined amount of SiH ₂ Cl ₂ was supplied together with the source gas so that the Si concentration in GaN was about 3 × 10 ¹⁸ cm ⁻³ . The control temperature at the start of growth was 1090 ° C.

  Further, the warp of the sample 19 was detected using the laser light source 10 and the detector 13 during the growth, and the external heater 8 was controlled so that the amount of warp during the growth became substantially zero.

  FIG. 5 is a graph showing an example of thickness dependence of warpage during growth of a sample according to Example 3.

  For comparison, the same data is shown in the figure when the growth is performed under the condition that the Si concentration is the same and the control temperature is constant (1010 ° C.). The right axis shows the transition of control temperature by feedback.

  When growing at a constant control temperature, GaAs and GaN have similar linear expansion coefficients, so the slope of the increase in warpage did not increase suddenly even when doping was started, but the warpage increased with the thickness. When the thickness was 500 μm, it exceeded 50 μm. This seems to be caused by (a) and (b).

  On the other hand, when feedback control is performed, almost no warping occurs. In addition, the control temperature, which was initially 1090 ° C., was finally lowered to about 1020 ° C. by feedback control.

  After the growth of the GaN thick film 5 was completed, the substrate 1 was removed by laser peeling to obtain a GaN free-standing crystal 6 having a diameter of 3 inches. When the warpage of the GaN free-standing crystal 6 was measured with a laser displacement meter, it was found that the warpage was 5 μm or less. .

[Other variations]
In Examples 1 to 3 described above, only the case of a GaN free-standing crystal has been described, but the same effect can be expected for other group III nitride semiconductors such as AlN and AlGaN. In addition to the HVPE method, the present invention may be applied to other vapor phase growth methods such as the MOVPE method and the sublimation method.

[Comparative Example 1]
Next, a comparative example will be described with reference to FIGS.

The manufacturing process of the comparative example was the same as that described in Example 1 except that the control temperature was kept constant at 1090 ° C., and the partial pressures of GaCl and NH ₃ were 1.5 kPa and 40 kPa. The growth of the GaN thick film 5 was performed for several concentrations of SiH ₂ Cl ₂ . The growth pressure is atmospheric pressure. The growth rate at this time was about 300 μm / h.

  FIG. 6 is a graph showing an example of thickness dependence on warpage during growth of a sample according to a comparative example.

  The warpage increases with the thickness of the GaN thick film 5, but increases particularly remarkably after the start of doping (thickness of 100 μm or more). It was also found that the increase in warpage was greater as the doping concentration was higher.

  After the growth of each GaN thick film 5 was completed, the substrate 1 was removed by laser peeling to obtain a GaN free-standing crystal 6 having a diameter of 3 inches. These GaN free-standing crystals 6 had a concave warp when the surface was turned up.

  FIG. 7 is a graph showing an example of the doping concentration dependency on the warpage of the GaN free-standing crystal according to the comparative example.

The warpage of each GaN free-standing crystal 6 monotonously increased with the Si concentration in the crystal. In a conductive GaN substrate, a Si concentration (carrier) concentration of 1 × 10 ¹⁸ cm ⁻³ or more is usually required, but as shown in FIG. 7, warpage at an Si concentration of 1 × 10 ¹⁸ cm ⁻³ is about 200 μm. I found that it was very big.

DESCRIPTION OF SYMBOLS 1 Substrate 2 GaN thin film 3 SiO ₂ film 4 Stripe mask 5 GaN thick film 5 Thick film 6 Free-standing crystal 7 Quartz reactor 8 External heater 9 Susceptor 10 Laser light source 11 Laser light 12 Reflected light 13 Detector 14 Thermocouple 15 HCl supply tube 16 Ga melt 17 NH ₃ supply pipe 18 SiH ₂ Cl ₂ supply pipe 19 Sample 20 HVPE furnace

Claims (7)

A method for producing a nitride semiconductor single crystal by heteroepitaxy, comprising:
While maintaining a substantially uniform temperature distribution in the crystal growth region in the crystal growth apparatus by vapor phase growth, a nitride semiconductor single crystal is grown on the substrate,
A method of manufacturing a nitride semiconductor substrate, wherein a control temperature of a heater for heating the crystal growth apparatus is changed so that the warpage of the growing nitride semiconductor single crystal is within a predetermined range. Growing the nitride semiconductor single crystal on the substrate having a larger linear expansion coefficient than the nitride semiconductor single crystal;
The method for manufacturing a nitride semiconductor substrate according to claim 1, wherein the control temperature is decreased at a predetermined rate so that the warpage falls within a predetermined range. Growing the nitride semiconductor single crystal on the substrate having a smaller linear expansion coefficient than the nitride semiconductor single crystal;
The method for manufacturing a nitride semiconductor substrate according to claim 1, wherein the control temperature is increased at a predetermined rate so that the warpage falls within a predetermined range.   The nitride according to claim 1, wherein the warp is detected during crystal growth by optical means, and the control temperature is feedback-controlled so that the detected warp falls within a predetermined range. A method for manufacturing a semiconductor substrate.   5. The method of manufacturing a nitride semiconductor substrate according to claim 1, wherein any one of sapphire, SiC, GaAs, ZnO, and Si is used as the substrate.   The method for manufacturing a nitride semiconductor substrate according to claim 1, wherein a method of crystal growth of the nitride semiconductor single crystal is an HVPE method.   A method for manufacturing a nitride semiconductor free-standing substrate, comprising: growing the nitride semiconductor single crystal by the method according to claim 1, and then removing the substrate to obtain a nitride semiconductor single crystal substrate.

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