WO2016194931A1 - In-situ observation device of substrate warpage and crystal growth apparatus - Google Patents

In-situ observation device of substrate warpage and crystal growth apparatus Download PDF

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Publication number
WO2016194931A1
WO2016194931A1 PCT/JP2016/066135 JP2016066135W WO2016194931A1 WO 2016194931 A1 WO2016194931 A1 WO 2016194931A1 JP 2016066135 W JP2016066135 W JP 2016066135W WO 2016194931 A1 WO2016194931 A1 WO 2016194931A1
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substrate
crystal
crystal growth
light
base substrate
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PCT/JP2016/066135
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French (fr)
Japanese (ja)
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憲次朗 池尻
英雄 会田
浩司 小山
聖祐 金
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並木精密宝石株式会社
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Publication of WO2016194931A1 publication Critical patent/WO2016194931A1/en

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    • C—CHEMISTRY; METALLURGY
    • C30—CRYSTAL GROWTH
    • C30B—SINGLE-CRYSTAL GROWTH; UNIDIRECTIONAL SOLIDIFICATION OF EUTECTIC MATERIAL OR UNIDIRECTIONAL DEMIXING OF EUTECTOID MATERIAL; REFINING BY ZONE-MELTING OF MATERIAL; PRODUCTION OF A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; SINGLE CRYSTALS OR HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; AFTER-TREATMENT OF SINGLE CRYSTALS OR A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; APPARATUS THEREFOR
    • C30B25/00—Single-crystal growth by chemical reaction of reactive gases, e.g. chemical vapour-deposition growth
    • C30B25/02—Epitaxial-layer growth
    • C30B25/16—Controlling or regulating
    • C—CHEMISTRY; METALLURGY
    • C30—CRYSTAL GROWTH
    • C30B—SINGLE-CRYSTAL GROWTH; UNIDIRECTIONAL SOLIDIFICATION OF EUTECTIC MATERIAL OR UNIDIRECTIONAL DEMIXING OF EUTECTOID MATERIAL; REFINING BY ZONE-MELTING OF MATERIAL; PRODUCTION OF A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; SINGLE CRYSTALS OR HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; AFTER-TREATMENT OF SINGLE CRYSTALS OR A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; APPARATUS THEREFOR
    • C30B35/00—Apparatus not otherwise provided for, specially adapted for the growth, production or after-treatment of single crystals or of a homogeneous polycrystalline material with defined structure
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01B—MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
    • G01B11/00—Measuring arrangements characterised by the use of optical techniques
    • G01B11/24—Measuring arrangements characterised by the use of optical techniques for measuring contours or curvatures

Definitions

  • the present invention relates to an in-situ observation apparatus and a crystal growth apparatus for substrate warpage.
  • Warpage of the semiconductor substrate finally taken out after completion of the semiconductor process can be measured with a non-destructive and non-contact dedicated measuring device.
  • the semiconductor process performs processing with complicated temperature changes continuously, it is not enough to measure the semiconductor substrate after the process is completed.
  • In-situ observation of warpage changes due to stress changes during the semiconductor process ( Hereinafter, it is important to follow in-situ observation).
  • in-situ observation is very important for semiconductor crystal growth with large temperature changes.
  • various stresses are generated in the semiconductor substrate due to differences in growth methods and differences in characteristics from the base substrate. Specifically, the stress caused by the difference in thermal expansion due to the temperature distribution in the thickness direction of the underlying substrate, the lattice relaxation and coalescence of hetero growth, the stress due to the difference in thermal expansion coefficient, and the lattice generated due to the difference in growth method of homoepitaxial growth Stress generated due to the constant difference is generated.
  • These stresses cause warping in the growing semiconductor substrate. This warpage due to stress causes uneven temperature during growth, and not only causes poor quality of the semiconductor crystal but also causes cracks and breaks in the semiconductor crystal.
  • In-situ observation in the field of crystal growth includes in-situ observation for obtaining surface thin film information typified by ellipsometry, film thickness measurement by laser reflection (Non-Patent Document 1), in-warp of a semiconductor substrate. There is in situ observation (Non-Patent Document 2).
  • a conventional apparatus observes the surface of a growing semiconductor crystal and performs complex measurement including warping.
  • MOCVD Metal-Organic-Chemical-Vapor-Deposition
  • MOCVD Metal-Organic-Chemical-Vapor-Deposition
  • warping during growth as shown in Patent Document 1 is in- Situ observation is performed. Based on the obtained information, optimization of the base substrate and feedback to growth conditions are performed, and warpage is controlled.
  • the crystal growth surface is directly observed. Therefore, the in-situ observation is restricted by the morphology and thickness uniformity of the crystal growth surface, and accurate information cannot be obtained. For example, in the MOCVD nucleation phase, the signal drops due to surface roughness, so no information on warpage can be obtained.
  • the present invention has been made in view of the above circumstances, and it is an object of the present invention to provide an apparatus and a crystal growth apparatus that enable in-situ observation of the warping behavior of a crystal growth substrate.
  • the apparatus of the present invention includes at least a substrate, a light source that emits laser light, and a light receiving unit that receives the laser light, and at least one of the surfaces of the substrate is a crystal growth surface, The back surface is a reflecting surface, the laser light emitted from the light source is reflected by the reflecting surface, and the reflected light is received by the light receiving unit, and in-situ observation of the warpage of the substrate is performed. To do.
  • the laser light is two parallel separated lights separated before incidence of the reflecting surface, and an optical path difference occurs between the separated lights due to reflection on the back surface.
  • the wavelength of the laser light is preferably in the visible light range.
  • the wavelength of the laser light is preferably in the range of 620 nm to 660 nm.
  • the surface roughness Ra of the reflecting surface is preferably 20 nm or less.
  • the surface roughness Ra of the reflecting surface is preferably 1 nm or less.
  • the surface roughness Ra of the reflecting surface is preferably 0.1 nm or less.
  • the crystal growth apparatus of the present invention is provided with the apparatus described in any one of (1) to (7) above, and grows a crystal on the surface of the crystal growth surface.
  • the crystal grows any one of a nitride semiconductor, diamond, and SiC.
  • the apparatus and the crystal growth apparatus of the present invention it is possible to observe in-situ observation of the warp behavior of a crystal growth substrate on the back surface without being restricted by the morphology and thickness uniformity of the crystal growth surface. It becomes.
  • FIG. 6 is a partial cross-sectional explanatory view schematically showing the state of crystal growth by vertical HVPE and in-situ observation of substrate warpage on the back surface.
  • FIG. 6 is a partial cross-sectional explanatory view schematically showing the state of crystal growth by horizontal HVPE and in-situ observation of substrate warpage on the back surface.
  • FIG. 2 is a partial cross-sectional explanatory view schematically showing a schematic configuration of a microwave CVD apparatus, which is an example of a crystal growth apparatus for a diamond single crystal, and an in-situ observation state of substrate warpage on the back surface.
  • a microwave CVD apparatus which is an example of a crystal growth apparatus for a diamond single crystal, and an in-situ observation state of substrate warpage on the back surface.
  • It is a CCD observation image which shows the laser spot image of a semiconductor laser beam in an Example.
  • the first feature of the present embodiment is that the apparatus includes at least a substrate, a light source that emits laser light, and a light receiving unit that receives the laser light, and at least one of the surfaces of the substrate is a crystal growth surface.
  • the back surface is a reflecting surface, the laser light emitted from the light source is reflected by the reflecting surface, and the reflected light is received by the light receiving unit, and in-situ observation of the warpage of the substrate is performed. It was decided.
  • the warping behavior of the growth substrate (the substrate) during the film formation of the crystal is not limited by the morphology and thickness uniformity of the crystal growth surface, In-situ observation is possible from the back side.
  • a crystal is formed (growth) on a substrate when the crystal is formed so as to be in contact with the substrate, or a crystal is formed on the substrate via one or more layers. It is meant to include being done.
  • the back surface refers to a surface of the substrate on which the crystal is not grown or is not formed.
  • a second feature is that the laser light is two parallel separated lights separated before incidence on the reflecting surface, and an optical path difference occurs between the separated lights due to reflection on the back surface, and the optical path. Due to the difference, the in-situ observation of the warp was performed. According to this configuration, the optical path between the two reflected lights (separated light) reflected on the back surface is in a non-parallel state, and an optical path difference corresponding to the shape of the back surface (the warp shape and warpage amount of the substrate) occurs In-situ observation of the warpage of the substrate can be performed.
  • the third feature is that the wavelength of the laser beam is in the visible light range. According to this configuration, in-situ observation can be visually observed using a CCD or the like.
  • the fourth feature is that the wavelength of the laser beam is in the range of 620 nm to 660 nm. This configuration is optimal for in-situ observation because it has the lowest loss when reflected on the back surface of the substrate and does not absorb light even if there is a light transmissive part in the propagation optical path.
  • the fifth feature is that the surface roughness Ra of the reflecting surface is 20 nm or less. According to this configuration, scattering of laser light can be prevented.
  • the sixth feature is that the surface roughness Ra of the reflecting surface is 1 nm or less. According to this configuration, it is possible to further prevent laser light from being scattered and further prevent the laser light signal from dropping.
  • the seventh feature is that the surface roughness Ra of the reflecting surface is 0.1 nm or less. According to this configuration, it is possible to further prevent laser light from being scattered and further prevent the laser light signal from dropping.
  • the eighth feature is that the apparatus according to any one of the above is provided and a crystal growth apparatus for growing a crystal on the surface of the crystal growth surface.
  • the warping behavior of the growth substrate (the substrate) during the film formation of the crystal is not limited by the morphology and thickness uniformity of the crystal growth surface, In-situ observation is possible from the back side. Therefore, the warping behavior of the substrate can be optimally controlled.
  • the ninth feature is that the crystal grows a nitride semiconductor, diamond, or SiC crystal. According to this configuration, in-situ observation on the back surface of various crystals becomes possible.
  • FIG. 1 is an explanatory view schematically showing a schematic configuration of a vertical hydride vapor phase epitaxy (HVPE) apparatus suitable for a method for manufacturing a nitride semiconductor crystal.
  • the HVPE apparatus according to the present invention may be either a vertical type or a horizontal type.
  • the HVPE apparatus of FIG. 1 includes a reactor (reaction chamber) 1, a susceptor (substrate mounting portion) 3 for supporting a base substrate 4, which is a substrate disposed in the reactor 1, on a support surface, and a heater 2. .
  • the base substrate 4 is a substrate for growing an epitaxial growth film made of a GaN-based material on one surface 4a.
  • a total of five introduction pipes are installed: a pipe 8 for the carrier gas G 1, a pipe 9 for the group 3 source gas G 4, and a pipe 10 for the group 5 source gas G 3.
  • an exhaust pipe 6 is installed below the reactor 1 so that the gas flow is guided from above to below.
  • the apparatus according to the present invention includes a warp measuring apparatus 7 to be described later.
  • illustration of a vacuum device is abbreviate
  • a container 11 containing Ga liquid which is a Group 3 raw material of nitride semiconductor is disposed, and the Group 3 source gas G4 introduced into the reactor 1 is combined with the Ga liquid in the container 11.
  • a Group 3 metal chloride gas G2 is generated and introduced into the crystal growth surface of the base substrate 4.
  • a nitride semiconductor crystal 5 is grown as an epitaxially grown single crystal film on the underlying substrate 4.
  • the base substrate 4 is a substrate in which at least one side 4a on the crystal growth surface side of the nitride semiconductor crystal 5 is mirror-polished. Therefore, in the growth step of the nitride semiconductor crystal 5 described later, the nitride semiconductor crystal 5 is grown and formed on the mirror-polished surface. If necessary, a base substrate whose both surfaces are mirror-polished may be used. In this case, any one surface can be arbitrarily used as the crystal growth surface of the nitride semiconductor crystal 5.
  • the mirror polishing may be performed so that the nitride semiconductor crystal 5 is smooth enough to grow on at least one side 4a.
  • the surface roughness Ra is preferably 1 nm or less, preferably 0.8 nm or less. More preferably, it is 0.7 nm or less. If the Ra of the single side 4a exceeds 1 nm, the quality of the nitride semiconductor crystal 5 grown on the single side 4a is deteriorated. Furthermore, as a measure of the extent to which the nitride semiconductor crystal 5 can be epitaxially grown, it is preferable that the surface roughness Ra be 0.1 nm or less. Ra can be determined by measuring surface irregularities with a surface roughness measuring machine or an atomic force microscope (AFM). It is assumed that there is no crack on one side 4a on which nitride semiconductor crystal 5 is formed.
  • AFM atomic force microscope
  • the surface roughness Ra of the back surface (reflecting surface) is preferably such that the laser light 7b is not scattered as described above, and is specifically set to 20 nm or less.
  • the surface roughness Ra of the back surface (reflection surface) when using a base substrate that has been mirror-polished on both sides is preferably 1 nm or less, and more preferably 0.1 nm or less.
  • the formation of the nitride semiconductor crystal 5 on the base substrate 4 means that the nitride semiconductor crystal 5 is formed so as to be in contact with the base substrate 4, or one or more layers on the base substrate 4. It is assumed that the nitride semiconductor crystal 5 is formed via
  • the concave surface of the one side 4 a is caused by the temperature difference between the upper and lower surfaces of the base substrate 4.
  • the shape becomes stronger and the curvature changes greatly.
  • the temperature is lowered to about 500 to 600 ° C. and (b) the low temperature buffer layer is grown, the concave shape of the base substrate 4 is weakened and the curvature is slightly reduced.
  • the temperature is raised to about 1000 ° C., and (c) at the stage where the n-GaN layer is grown as a kind of the nitride semiconductor crystal 5, due to the lattice constant difference between the n-GaN layer and the base substrate 4,
  • the concave shape of the base substrate 4 is strengthened and the curvature is increased. Further, as the film formation proceeds and the thickness increases, the curvature increases.
  • the temperature is lowered to about 700 to 800 ° C.
  • the thickness of the InGaN-based active layer and the In composition in the InGaN Since the uniformity affects the in-plane uniformity of the emission wavelength, it affects the production yield of LED chips and the like. Since the thickness and In composition of the InGaN layer are affected by the film formation temperature, it is ideal that the curvature of the base substrate 4 during film formation be as close to 0 as possible in order to improve temperature uniformity within the substrate surface. is there. Finally, when the base substrate 4 is cooled down (e), the base substrate 4 is greatly warped again due to the difference in coefficient of thermal expansion, so that the curvature of the base substrate 4 after a series of film forming steps is large. Become.
  • the back surface refers to the surface of the base substrate 4 on which the nitride semiconductor crystal 5 is not grown or not formed.
  • the warpage measuring device 7 includes an optical element (preferably a semiconductor laser) which is a light source (not shown) inside and is connected to the HVPE device.
  • the laser beam 7 a emitted from the optical element is emitted from one emission port of the warpage measuring device 7 and is incident on the back surface of both surfaces of the base substrate 4. That is, the back surface of the base substrate 4 becomes a reflection surface of the laser light 7a.
  • the laser beam 7 a is reflected on the back surface of the base substrate 4. Further, the reflected reflected light (laser light 7b) is incident on the warp measuring device 7 again and received by a light receiving unit (not shown) inside the device 7, thereby forming the nitride semiconductor crystal 5 of the base substrate 4. Changes in the warp shape and warpage amount in the film are observed in-situ.
  • the laser beam 7a Before the laser beam 7a is incident on the reflecting surface of the base substrate 4, as shown in FIG. 2, the laser beam 7a is already separated into two separated light beams 7a1 and 7a2 having optical paths parallel to each other. Examples of the separation operation include birefringence.
  • the two parallel separated lights 7a1 and 7a2 have optical paths parallel to each other before entering the back surface, and the optical path difference (optical path length difference) between them is set to zero.
  • the separated lights 7a1 and 7a2 are reflected so that their optical paths are separated by reflection, and become reflected lights 7b1 and 7b2, respectively. Therefore, regardless of the concave shape or the convex shape, the optical path between the reflected lights 7b1 and 7b2 reflected on the back surface is in a non-parallel state, and between the reflected lights 7b1 and 7b2, the shape of the back surface (that is, the warped shape and warpage of the base substrate 4). An optical path difference corresponding to the amount is generated. The reflected light 7b1 and 7b2 are received by the light receiving unit and the optical path difference is observed, whereby in-situ observation of the warpage of the base substrate 4 is performed by the optical path difference.
  • the wavelength of the laser beam 7b is preferably a visible light region as a wavelength region that can be visually observed using a CCD (Charge-Coupled Device) or the like, and is specifically set to 360 nm to 830 nm. Further, in the visible light range, the wavelength range of 620 nm to 660 nm is the lowest loss when reflected on the back surface of the base substrate 4 and is not absorbed even if there is a light transmissive part in the propagation optical path. Since it is a wavelength, it is preferable.
  • the warp measuring device 7 can detect the laser light 7b reflected from the back surface without being scattered. Accordingly, the signal of the laser beam 7b does not drop (the laser beam 7b is scattered and cannot be detected by the warp measuring device 7), and the warp shape and warp during the film formation of the nitride semiconductor crystal 5 on the base substrate 4 are avoided. The amount can be observed in-situ.
  • the nitride semiconductor crystal 5 may be subjected to another process such as etching, polishing, or slicing.
  • the warping behavior of the base substrate 4 that causes the base substrate 4 or the crystal (nitride semiconductor crystal 5) to be broken or cause quality or performance failure is determined by the laser beam on the back surface. Reflection enables in-situ observation.
  • the warpage behavior of the base substrate 4 is the warpage behavior (change in warpage shape and amount of warpage) of the base substrate 4 during the growth of the nitride semiconductor crystal 5. Since the back surface of the substrate 4 is warped in-situ, the back surface can be observed in-situ without being limited by the morphology and thickness uniformity of the crystal growth surface (single surface 4a). Therefore, the warping behavior of the base substrate 4 can be optimally controlled.
  • FIG. 3 is an explanatory view schematically showing a schematic configuration of a horizontal HVPE apparatus suitable for the method for producing a nitride semiconductor crystal of the present invention.
  • the same number is attached
  • a total of three introduction pipes that is, a pipe 8 for the carrier gas G 1, a pipe 9 for the group 3 source gas G 4, and a pipe 10 for the group 5 source gas G 4 are installed horizontally.
  • Each introduction pipe extends toward the center of the reactor 1. The illustration of the vacuum device is omitted.
  • the reactor 1 is formed in a cylindrical shape, and is arranged in a laid-down state so as to face each other with the upper surface and the bottom surface standing in a direction perpendicular to the horizontal plane. Furthermore, a heater 2 is disposed around the reactor 1.
  • the susceptor 3 is disposed in a cantilevered manner on the other end side of the reactor 1 where the introduction pipe is installed, and the mounting surface of the base substrate 4 is in a horizontal plane. They are arranged in parallel.
  • the carrier gas G1, the group 3 source gas G4, and the group 5 source gas G3 pass through the pipes 8 to 10 in the reactor 1 to form the base substrate. 4 is introduced horizontally.
  • a container 11 containing Ga liquid as shown in FIG. 1 is arranged inside the pipe 9 (not shown in FIG. 3), and the Group 3 source gas G4 introduced from one end side of the pipe 9 is provided.
  • the Group 3 source gas G4 introduced from one end side of the pipe 9 is provided.
  • a Group 3 metal chloride gas G 2 is generated and introduced into the crystal growth surface of the base substrate 4.
  • N 2 gas G1 and GaCl gas G2 and NH 3 gas G3 are formed on one surface 4a of the base layer or the base substrate 4.
  • the nitride semiconductor crystal 5 (especially the GaN film) is grown over a predetermined time while introducing.
  • the laser beam 7a is emitted from the warp measuring device 7 during the formation of the nitride semiconductor crystal 5, is incident on and reflected from the back surface of the base substrate 4, and reflected light 7b1, 7b2 as shown in FIG. Observe the optical path difference. Such observation enables in-situ observation of changes in the warp shape and the warp amount during the formation of the nitride semiconductor crystal 5 on the base substrate 4.
  • the warpage shape and the warpage amount are not limited by the morphology and thickness uniformity of the crystal growth surface (single surface 4a).
  • the change can be observed in-situ on the back surface. Therefore, the warping behavior of the base substrate 4 can be optimally controlled.
  • FIG. 4 is a perspective view showing an example of the base substrate 4 according to the third embodiment.
  • FIG. 5 is an explanatory view schematically showing a schematic configuration of a microwave CVD (Chemical Vapor Deposition) apparatus suitable for the method for producing a diamond single crystal of the present invention.
  • the same number is attached
  • a base substrate 4 is prepared.
  • the material of the base substrate 4 include magnesium oxide (MgO), aluminum oxide ( ⁇ -Al 2 O 3 : sapphire), Si, quartz, platinum, iridium, and strontium titanate (SrTiO 3 ).
  • the base substrate 4 is a mirror whose at least one side 4a is mirror-polished.
  • the diamond single crystal growth step which will be described later, the diamond single crystal is grown and formed on the mirror-polished surface side (on the surface of the one surface 4a). If necessary, a base substrate whose both surfaces are mirror-polished may be used. In this case, any one surface can be arbitrarily used as a growth surface of the diamond single crystal.
  • the mirror polishing may be performed so as to be smooth to the extent that a diamond single crystal can be grown on at least one side 4a.
  • a guideline it is preferable to polish the surface to a surface roughness Ra of 10 nm or less. If the Ra of the single side 4a exceeds 10 nm, the quality of the diamond single crystal grown on the single side 4a is deteriorated. Furthermore, it is assumed that there is no crack on one side 4a. Ra may be measured with a surface roughness measuring machine.
  • a diamond single crystal is grown on one side 4a of the base substrate 4.
  • the method for growing the diamond single crystal is not particularly limited, but in this embodiment, a microwave plasma CVD apparatus 12 (hereinafter referred to as apparatus 12) as shown in FIG. 5 is used.
  • a water cooling holder 20 equipped with a heating body such as a heater and a water flow device is disposed in a chamber 15 provided with a gas introduction pipe 13 and a gas discharge pipe.
  • a microwave power source 16 is connected to the microwave introduction window 18 via the waveguide 17 so that plasma can be generated in the chamber 15.
  • a water flow device (not shown) is mounted inside the water cooling holder 20 and cools the base substrate 4 and a diamond single crystal 19 described later with a water flow.
  • a diamond single crystal 19 which is a film-like crystal is heteroepitaxially grown for a predetermined time (about 10 hours).
  • the laser beam 7 a is emitted from the warpage measuring device 7 during the film formation of the diamond single crystal 19, propagates through the optical window 21 provided in the water-cooled holder 20, and laser is applied to the back surface of the base substrate 4.
  • the light 7a is incident and reflected, and the optical path difference between the reflected lights 7b1 and 7b2 is observed as shown in FIG. By such observation, it becomes possible to observe in-situ changes in the warp shape and the warp amount during the film formation of the diamond single crystal 19 on the base substrate 4.
  • the warp measuring device 7 can detect the laser light 7b reflected from the back surface without being scattered. Therefore, the signal of the laser beam 7b does not drop (the laser beam 7b is scattered and cannot be detected by the warp measuring device 7), and the warp shape and the warp amount during the film formation of the diamond single crystal 19 on the base substrate 4 are reduced. Can be observed in-situ.
  • the surface roughness Ra of the back surface (reflective surface) is preferably such that the laser beam 7b is not scattered as described above, and is specifically set to 20 nm or less.
  • the surface roughness Ra of the back surface (reflection surface) when using a base substrate that has been subjected to mirror polishing on both sides is preferably 1 nm or less, and most preferably 0.1 nm or less.
  • the warpage behavior (change in warpage shape and amount of warpage) of the base substrate 4 during the growth of the diamond single crystal 19 is reflected by the laser light reflection on the back surface. -Situ observation is possible.
  • the warping behavior causes destruction of the base substrate 4 and the crystal (diamond single crystal 19), or quality and performance defects. Since the back surface of the substrate 4 is warped in-situ, the back surface can be observed in-situ without being limited by the morphology and thickness uniformity of the crystal growth surface (single surface 4a). Therefore, the warping behavior of the base substrate 4 can be optimally controlled.
  • the in-situ observation target process of the base substrate 4 is not limited to the film forming process of the nitride semiconductor crystal 5 and the diamond single crystal 19, In-situ observation of the warping behavior of the base substrate 4 in the annealing process performed before and after the film formation may be performed. In this case as well, in-situ observation may be performed by reflecting the semiconductor laser light from the warp measuring device 7 on the back surface of the base substrate 4.
  • the nitride semiconductor crystal 5 to be epitaxially grown may be a single crystal of AlN or BN in addition to the above embodiments.
  • the crystal to be epitaxially grown on the base substrate may be a SiC single crystal in addition to the nitride semiconductor crystal or diamond.
  • a metal film may be formed on the back surface, and the separated lights 7a1 and 7a2 may be reflected on the metal film.
  • the surface roughness Ra of the metal film surface serving as a reflecting surface for reflecting the separated lights 7a1 and 7a2 is preferably such that the laser light 7b is not scattered, and is specifically set to 20 nm or less.
  • the metal film material is preferably Pt, Ir, or Ta, but is not limited thereto.
  • the vertical HVPE apparatus shown in FIG. 1 is used for the apparatus according to the present embodiment, the substrate has a thickness of 0.43 mm, the planar shape is circular, the diameter is 2 inches, the crystal growth surface and the back surface are ( A sapphire single crystal substrate set with a (0001) plane was used.
  • the (0001) plane was mirror-polished to have a surface roughness Ra of 1 nm or less.
  • GaN was grown as a nitride semiconductor crystal 5 with a thickness of 200 ⁇ m.
  • the container 11 contains Ga liquid, and the carrier gas G1 is N 2 gas, the Group 3 source gas G4 is HCl, the Group 3 metal chloride gas G2 is GaCl, and the Group 5 source gas G3 is ammonia (NH 3 ). .
  • the sapphire substrate after the growth of GaN was annealed at 1020 ° C., and the semiconductor laser light was reflected on the back surface of the sapphire substrate, and the warpage behavior of the sapphire substrate in the annealing treatment was observed in-situ.
  • the semiconductor laser light was set to conditions in the wavelength range of 620 nm to 660 nm.
  • FIG. 6 shows a laser spot image of the semiconductor laser light obtained by reflection from the back surface of the sapphire substrate during the in-situ observation.
  • the portion surrounded by a square frame is a laser spot image of the semiconductor laser light detected during in-situ observation.
  • an elliptical semiconductor laser beam was detected during in-situ observation, and it was confirmed that the warping behavior of the sapphire substrate can be observed in-situ.
  • the same sapphire single crystal substrate and HVPE apparatus as in the example were prepared, and the semiconductor laser light was reflected on the (0001) plane of the crystal growth surface opposite to the back surface.
  • the configuration of the HVPE apparatus was the same as that of the above example except that the reflection surface of the semiconductor laser light was changed to a crystal growth surface.
  • the sapphire single crystal substrate after the growth of GaN was heated to 1020 ° C., and in-situ observation of the warpage behavior of the sapphire substrate was attempted, and a semiconductor laser obtained by reflection from the crystal growth surface of the sapphire substrate The light is shown in FIG.
  • the portion surrounded by the square frame is the semiconductor laser light detected during annealing.
  • the semiconductor laser light was detected as a turbulent spot image.
  • the disorder of the semiconductor laser light seems to be due to the deterioration of the surface morphology of the crystal growth surface due to the growth by the HVPE method. Further, it was confirmed that the warping behavior of the sapphire substrate could not be observed in-situ due to the disturbance of the semiconductor laser light.

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Abstract

[Problem] To provide a device which is capable of in-situ observation of warpage behavior of a crystal growth substrate, and a crystal growth apparatus. [Solution] This device includes at least a substrate, a light source that emits a laser light, and a light reception unit that receives the laser light. Warpage of the substrate is observed in-situ by the laser light emitted from the light source being reflected off of a reflective surface which is the back surface of the substrate, and the reflected light being received at the light reception unit. The laser light is two parallel separated lights separated before entering the reflective surface. The reflection from the back surface generates an optical path difference between the separated lights and the warpage is observed in-situ by this optical path difference. Further, this device is provided on the crystal growth apparatus in which crystal is grown on a crystal growth surface of the substrate.

Description

基板の反りのｉｎ－ｓｉｔｕ観察装置及び結晶成長装置In-situ observation apparatus and crystal growth apparatus for substrate warpage
　本発明は、基板の反りのｉｎ－ｓｉｔｕ観察装置及び結晶成長装置に関するものである。 The present invention relates to an in-situ observation apparatus and a crystal growth apparatus for substrate warpage.
　半導体の高度化に伴い、半導体基板にかかる応力による反り測定の重要度が増しており、非破壊及び非接触での反り測定法が数多く開発されている。その理由として、半導体基板の反り測定に関して破壊を伴う場合、破壊時に応力緩和が生じ、測定結果が実際の応力を反映しないおそれがあるためである。また接触式の反り測定は、基板表面の状態を重視する半導体プロセスに適用することは望ましくない。そのため、非破壊及び非接触での反り測定法が望まれている。 With the advancement of semiconductors, the importance of warpage measurement due to stress applied to a semiconductor substrate has increased, and many non-destructive and non-contact warpage measurement methods have been developed. The reason for this is that when the semiconductor substrate warpage is accompanied by breakage, stress relaxation occurs at the time of breakage, and the measurement result may not reflect actual stress. Moreover, it is not desirable to apply contact-type warpage measurement to a semiconductor process that places importance on the state of the substrate surface. Therefore, non-destructive and non-contact warpage measurement methods are desired.
　非破壊及び非接触の専用測定装置により、半導体プロセス終了後に最終的に取り出した半導体基板の反りを測ることが出来る。しかし、半導体プロセスは複雑な温度変化を伴った処理を連続で行うため、プロセス終了後の半導体基板の測定だけでは不十分であり、半導体プロセス中の応力変化による反り変化を、随時その場観察（以下、ｉｎ－ｓｉｔｕ観察と記載）で追うことが重要である。 専 用 Warpage of the semiconductor substrate finally taken out after completion of the semiconductor process can be measured with a non-destructive and non-contact dedicated measuring device. However, since the semiconductor process performs processing with complicated temperature changes continuously, it is not enough to measure the semiconductor substrate after the process is completed. In-situ observation of warpage changes due to stress changes during the semiconductor process ( Hereinafter, it is important to follow in-situ observation).
　特に大きな温度変化を伴う半導体結晶成長では、ｉｎ－ｓｉｔｕ観察の重要性は大きい。下地基板を用いた半導体結晶体成長では、成長法の違いや下地基板との特性の違いにより様々な応力が半導体基板に発生する。具体的には、下地基板の厚み方向における温度分布による熱膨張量の差からくる応力、ヘテロ成長の格子緩和やコアレッセンス、熱膨張係数差による応力、ホモエピタキシャル成長の成長方法の違いから発生する格子定数差により生じる応力などが発生する。これらの応力は成長中の半導体基板に反りを生じさせる。この応力による反りは成長時の温度の不均一の原因ともなり、半導体結晶の品質不良の要因となるだけでなく、半導体結晶にクラックや破断をもたらす原因となる。 In particular, in-situ observation is very important for semiconductor crystal growth with large temperature changes. In semiconductor crystal growth using a base substrate, various stresses are generated in the semiconductor substrate due to differences in growth methods and differences in characteristics from the base substrate. Specifically, the stress caused by the difference in thermal expansion due to the temperature distribution in the thickness direction of the underlying substrate, the lattice relaxation and coalescence of hetero growth, the stress due to the difference in thermal expansion coefficient, and the lattice generated due to the difference in growth method of homoepitaxial growth Stress generated due to the constant difference is generated. These stresses cause warping in the growing semiconductor substrate. This warpage due to stress causes uneven temperature during growth, and not only causes poor quality of the semiconductor crystal but also causes cracks and breaks in the semiconductor crystal.
　このため成長中の半導体基板の反りを、ｉｎ－ｓｉｔｕ観察する装置が開発されてきた。結晶成長分野におけるｉｎ－ｓｉｔｕ観察は、エリプソメトリ法に代表される表面薄膜情報を得るためのｉｎ－ｓｉｔｕ観察や、レーザ反射による膜厚測定(非特許文献１)、半導体基板の反りのｉｎ－ｓｉｔｕ観察(非特許文献２)がある。従来の装置は成長中の半導体結晶の表面を観察し、反りを含めた複合的な測定を行うようにしている。 Therefore, an apparatus for in-situ observation of warping of a growing semiconductor substrate has been developed. In-situ observation in the field of crystal growth includes in-situ observation for obtaining surface thin film information typified by ellipsometry, film thickness measurement by laser reflection (Non-Patent Document 1), in-warp of a semiconductor substrate. There is in situ observation (Non-Patent Document 2). A conventional apparatus observes the surface of a growing semiconductor crystal and performs complex measurement including warping.
　例えば３族窒化物半導体系の成長のひとつである気相エピタキシャル成長法の有機金属気相成長法（MOCVD：Metal Organic Chemical Vapor Deposition）では、特許文献１に示されるような成長中の反りのｉｎ－ｓｉｔｕ観察が行われている。得られた情報を基に、下地基板の最適化や成長条件へのフィードバックが行われ、反りの制御が行われている。 For example, in metalorganic vapor phase epitaxy (MOCVD: Metal-Organic-Chemical-Vapor-Deposition), which is one of the growth methods of Group III nitride semiconductors, warping during growth as shown in Patent Document 1 is in- Situ observation is performed. Based on the obtained information, optimization of the base substrate and feedback to growth conditions are performed, and warpage is controlled.
　このような半導体基板の結晶成長面を観察する反りのｉｎ－ｓｉｔｕ観察は、結晶成長面を直接観察するので、正確な情報を得ようとすると結晶成長面のモフォロジーや厚みの均一性に制約されてしまう。例えばMOCVD法の核生成段階において表面荒れにより信号が落ちてしまう（非特許文献３）。 In-situ observation of the warp for observing the crystal growth surface of the semiconductor substrate directly observes the crystal growth surface, so that obtaining accurate information is limited by the morphology and thickness uniformity of the crystal growth surface. End up. For example, the signal drops due to surface roughness in the nucleation stage of the MOCVD method (Non-patent Document 3).
米国特許第７５０５１５０号明細書US Pat. No. 7,505,150
　このような結晶成長面を観察する反りのｉｎ－ｓｉｔｕ観察は結晶成長面を直接観察する。従って前記ｉｎ－ｓｉｔｕ観察は、結晶成長面のモフォロジーや厚み均一性に制約されてしまい、正確な情報が得られない。例えばMOCVDの核生成フェーズにおいては表面荒れにより信号が落ちてしまうため、反りの情報が得られない。 In such in-situ observation of the warp for observing the crystal growth surface, the crystal growth surface is directly observed. Therefore, the in-situ observation is restricted by the morphology and thickness uniformity of the crystal growth surface, and accurate information cannot be obtained. For example, in the MOCVD nucleation phase, the signal drops due to surface roughness, so no information on warpage can be obtained.
　従って、従来の観察手法は、モフォロジーや厚み均一性の悪化が生じる表面状態では有効に機能せず、反りのｉｎ－ｓｉｔｕ観察が困難であった。本発明は上記の事情を鑑みてなされたものであり、結晶の成長用基板の反り挙動をｉｎ－ｓｉｔｕ観察することが可能となる装置と結晶成長装置の提供を課題とする。 Therefore, the conventional observation method does not function effectively in the surface state where the morphology and thickness uniformity deteriorate, and it is difficult to observe the warp in-situ. The present invention has been made in view of the above circumstances, and it is an object of the present invention to provide an apparatus and a crystal growth apparatus that enable in-situ observation of the warping behavior of a crystal growth substrate.
　前記課題は、以下の本発明により達成される。即ち、
　（１）本発明の装置は、少なくとも、基板、レーザ光を放射する光源、及びレーザ光を受光する受光部を備え、基板はその両面のうち、少なくとも一方の面が結晶成長面であると共に、その裏面が反射面であり、光源から放射されたレーザ光が反射面で反射され、反射された反射光が受光部で受光されて、基板の反りのｉｎ－ｓｉｔｕ観察が行われることを特徴とする。 The above-mentioned subject is achieved by the following present invention. That is,
(1) The apparatus of the present invention includes at least a substrate, a light source that emits laser light, and a light receiving unit that receives the laser light, and at least one of the surfaces of the substrate is a crystal growth surface, The back surface is a reflecting surface, the laser light emitted from the light source is reflected by the reflecting surface, and the reflected light is received by the light receiving unit, and in-situ observation of the warpage of the substrate is performed. To do.
　（２）本発明の装置の一実施形態は、レーザ光が、反射面の入射前に分離されている２つの平行な分離光であり、裏面での反射によって分離光の間に光路差が発生し、その光路差により反りのｉｎ－ｓｉｔｕ観察が行われることが好ましい。 (2) In one embodiment of the apparatus of the present invention, the laser light is two parallel separated lights separated before incidence of the reflecting surface, and an optical path difference occurs between the separated lights due to reflection on the back surface. In addition, it is preferable to perform in-situ observation of warpage due to the optical path difference.
　（３）本発明の装置の他の実施形態は、レーザ光の波長が可視光域であることが好ましい。 (3) In another embodiment of the apparatus of the present invention, the wavelength of the laser light is preferably in the visible light range.
　（４）本発明の装置の他の実施形態は、レーザ光の波長が、620ｎｍ以上660ｎｍ以下の範囲であることが好ましい。 (4) In another embodiment of the apparatus of the present invention, the wavelength of the laser light is preferably in the range of 620 nm to 660 nm.
　（５）本発明の装置の他の実施形態は、反射面の表面粗さRaが、20ｎｍ以下であることが好ましい。 (5) In another embodiment of the apparatus of the present invention, the surface roughness Ra of the reflecting surface is preferably 20 nm or less.
　（６）本発明の装置の他の実施形態は、反射面の表面粗さRaが、１ｎｍ以下であることが好ましい。 (6) In another embodiment of the apparatus of the present invention, the surface roughness Ra of the reflecting surface is preferably 1 nm or less.
　（７）本発明の装置の他の実施形態は、反射面の表面粗さRaが、0.1ｎｍ以下であることが好ましい。 (7) In another embodiment of the apparatus of the present invention, the surface roughness Ra of the reflecting surface is preferably 0.1 nm or less.
　（８）また、本発明の結晶成長装置は、前記（１）～（７）の何れかに記載の装置が備えられると共に、結晶成長面の面上に結晶を成長することを特徴とする。 (8) Further, the crystal growth apparatus of the present invention is provided with the apparatus described in any one of (1) to (7) above, and grows a crystal on the surface of the crystal growth surface.
　（９）本発明の結晶成長装置の他の実施形態は、結晶が、窒化物半導体、ダイヤモンド、SiCの何れかの結晶を成長させることが好ましい。 (9) In another embodiment of the crystal growth apparatus of the present invention, it is preferable that the crystal grows any one of a nitride semiconductor, diamond, and SiC.
　本発明に係る装置及び結晶成長装置に依れば、結晶の成長用基板の反り挙動を、結晶成長面のモフォロジーや厚み均一性に制約されること無く、裏面によりｉｎ－ｓｉｔｕ観察することが可能となる。 According to the apparatus and the crystal growth apparatus of the present invention, it is possible to observe in-situ observation of the warp behavior of a crystal growth substrate on the back surface without being restricted by the morphology and thickness uniformity of the crystal growth surface. It becomes.
縦型HVPEによる結晶成長と、裏面での基板の反りのｉｎ－ｓｉｔｕ観察の状況を模式的に示す部分断面説明図である。FIG. 6 is a partial cross-sectional explanatory view schematically showing the state of crystal growth by vertical HVPE and in-situ observation of substrate warpage on the back surface. (a) 基板の裏面が凹状に反っている場合のｉｎ－ｓｉｔｕ観察の原理の一例を模式的に示す説明断面図である。(b) 基板の裏面が凸状に反っている場合のｉｎ－ｓｉｔｕ観察の原理の一例を模式的に示す説明断面図である。(a) It is explanatory sectional drawing which shows typically an example of the principle of in-situ observation in case the back surface of a corrugated board is warped concavely. (b) It is explanatory sectional drawing which shows typically an example of the principle of in-situ observation in case the back surface of a corrugated substrate is curving in convex shape. 横型HVPEによる結晶成長と、裏面での基板の反りのｉｎ－ｓｉｔｕ観察の状況を模式的に示す部分断面説明図である。FIG. 6 is a partial cross-sectional explanatory view schematically showing the state of crystal growth by horizontal HVPE and in-situ observation of substrate warpage on the back surface. 第３の実施形態に係る下地基板の一例を示す、斜視図である。It is a perspective view which shows an example of the base substrate which concerns on 3rd Embodiment. ダイヤモンド単結晶の結晶成長装置の一例である、マイクロ波CVD装置の概略構成と、裏面での基板の反りのｉｎ－ｓｉｔｕ観察の状況を模式的に示す部分断面説明図である。FIG. 2 is a partial cross-sectional explanatory view schematically showing a schematic configuration of a microwave CVD apparatus, which is an example of a crystal growth apparatus for a diamond single crystal, and an in-situ observation state of substrate warpage on the back surface. 実施例における、半導体レーザ光のレーザスポット像を示すCCD観察像である。It is a CCD observation image which shows the laser spot image of a semiconductor laser beam in an Example. 比較例における、半導体レーザ光を示すCCD観察像である。It is a CCD observation image which shows a semiconductor laser beam in a comparative example.
　本実施の形態の第一の特徴は、装置が少なくとも、基板、レーザ光を放射する光源、及びレーザ光を受光する受光部を備え、基板はその両面のうち、少なくとも一方の面が結晶成長面であると共に、その裏面が反射面であり、光源から放射されたレーザ光が反射面で反射され、反射された反射光が受光部で受光されて、基板の反りのｉｎ－ｓｉｔｕ観察が行われることとした。
　この構成に依れば、結晶の成膜中における成長用基板（前記基板）の反り挙動（反り形状や反り量の変化）を、結晶成長面のモフォロジーや厚み均一性に制約されること無く、裏面によりｉｎ－ｓｉｔｕ観察することが可能となる。従って、基板の反り挙動を最適に制御することが出来る。
　なお本発明において、基板の上に結晶が形成（成長）されるとは、基板に接するように結晶が形成されること、或いは基板の上に、単数又は複数の何らかの層を介して結晶が形成されることを包含する事とする。
　また本発明において裏面とは、基板の両面の内、結晶の結晶成長が成されていない、或いは成されない面を指すものとする。 The first feature of the present embodiment is that the apparatus includes at least a substrate, a light source that emits laser light, and a light receiving unit that receives the laser light, and at least one of the surfaces of the substrate is a crystal growth surface. In addition, the back surface is a reflecting surface, the laser light emitted from the light source is reflected by the reflecting surface, and the reflected light is received by the light receiving unit, and in-situ observation of the warpage of the substrate is performed. It was decided.
According to this configuration, the warping behavior of the growth substrate (the substrate) during the film formation of the crystal (change in warping shape and warping amount) is not limited by the morphology and thickness uniformity of the crystal growth surface, In-situ observation is possible from the back side. Therefore, the warping behavior of the substrate can be optimally controlled.
In the present invention, a crystal is formed (growth) on a substrate when the crystal is formed so as to be in contact with the substrate, or a crystal is formed on the substrate via one or more layers. It is meant to include being done.
In the present invention, the back surface refers to a surface of the substrate on which the crystal is not grown or is not formed.
　第二の特徴は、前記レーザ光が、前記反射面の入射前に分離されている２つの平行な分離光であり、前記裏面での反射によって分離光の間に光路差が発生し、その光路差により前記反りのｉｎ－ｓｉｔｕ観察が行われることとした。
　この構成に依れば、裏面で反射された２つの反射光（分離光）間の光路は非平行状態となり、裏面の形状（基板の反り形状や反り量）に応じた光路差が発生して、基板の反りのｉｎ－ｓｉｔｕ観察を行うことが可能となる。 A second feature is that the laser light is two parallel separated lights separated before incidence on the reflecting surface, and an optical path difference occurs between the separated lights due to reflection on the back surface, and the optical path. Due to the difference, the in-situ observation of the warp was performed.
According to this configuration, the optical path between the two reflected lights (separated light) reflected on the back surface is in a non-parallel state, and an optical path difference corresponding to the shape of the back surface (the warp shape and warpage amount of the substrate) occurs In-situ observation of the warpage of the substrate can be performed.
　第三の特徴は、前記レーザ光の波長が、可視光域であることとした。この構成に依れば、ｉｎ－ｓｉｔｕ観察を、CCD等を使用して目視により観察可能となる。 The third feature is that the wavelength of the laser beam is in the visible light range. According to this configuration, in-situ observation can be visually observed using a CCD or the like.
　第四の特徴は、前記レーザ光の波長が、620ｎｍ以上660ｎｍ以下の範囲であることとした。この構成に依れば、基板の裏面での反射時に最も低損失であると共に、伝搬光路に光透過性の部品があったとしても光吸収されないため、ｉｎ－ｓｉｔｕ観察に最適である。 The fourth feature is that the wavelength of the laser beam is in the range of 620 nm to 660 nm. This configuration is optimal for in-situ observation because it has the lowest loss when reflected on the back surface of the substrate and does not absorb light even if there is a light transmissive part in the propagation optical path.
　第五の特徴は、前記反射面の表面粗さRaが、20ｎｍ以下であることとした。この構成に依れば、レーザ光の散乱を防止することが出来る。 The fifth feature is that the surface roughness Ra of the reflecting surface is 20 nm or less. According to this configuration, scattering of laser light can be prevented.
　第六の特徴は、前記反射面の表面粗さRaが、１ｎｍ以下であることとした。この構成に依れば、レーザ光の散乱をより防止して、レーザ光の信号の落ちを更に防止することが可能となる。 The sixth feature is that the surface roughness Ra of the reflecting surface is 1 nm or less. According to this configuration, it is possible to further prevent laser light from being scattered and further prevent the laser light signal from dropping.
　第七の特徴は、前記反射面の表面粗さRaが、0.1ｎｍ以下であることとした。この構成に依れば、レーザ光の散乱をより防止して、レーザ光の信号の落ちを更に防止することが可能となる。 The seventh feature is that the surface roughness Ra of the reflecting surface is 0.1 nm or less. According to this configuration, it is possible to further prevent laser light from being scattered and further prevent the laser light signal from dropping.
　第八の特徴は、前記何れかに記載の装置が備えられると共に、前記結晶成長面の面上に結晶を成長する結晶成長装置とした。この構成に依れば、結晶の成膜中における成長用基板（前記基板）の反り挙動（反り形状や反り量の変化）を、結晶成長面のモフォロジーや厚み均一性に制約されること無く、裏面によりｉｎ－ｓｉｔｕ観察することが可能となる。従って、基板の反り挙動を最適に制御することが出来る。 The eighth feature is that the apparatus according to any one of the above is provided and a crystal growth apparatus for growing a crystal on the surface of the crystal growth surface. According to this configuration, the warping behavior of the growth substrate (the substrate) during the film formation of the crystal (change in warping shape and warping amount) is not limited by the morphology and thickness uniformity of the crystal growth surface, In-situ observation is possible from the back side. Therefore, the warping behavior of the substrate can be optimally controlled.
　第九の特徴は、前記結晶が、窒化物半導体、ダイヤモンド、SiCの何れかの結晶を成長させることとした。この構成に依れば、様々な結晶の裏面によるｉｎ－ｓｉｔｕ観察が可能となる。 The ninth feature is that the crystal grows a nitride semiconductor, diamond, or SiC crystal. According to this configuration, in-situ observation on the back surface of various crystals becomes possible.
　次に、上記特徴を有する実施形態を、図面に基づいて説明する。 Next, an embodiment having the above features will be described with reference to the drawings.
＜第１の実施形態＞
　以下、図１を参照して、本発明に係る基板の反りのｉｎ－ｓｉｔｕ観察装置における第１の実施形態を詳細に説明する。図１は、窒化物半導体結晶の製造方法に好適な、縦型のハイドライド気相成長（HVPE：Hydride Vapor Phase Epitaxy）装置の概略構成を模式的に示す説明図である。本発明に係るHVPE装置は、縦型又は横型のどちらを用いても良い。 <First Embodiment>
Hereinafter, a first embodiment of an in-situ observation apparatus for warping of a substrate according to the present invention will be described in detail with reference to FIG. FIG. 1 is an explanatory view schematically showing a schematic configuration of a vertical hydride vapor phase epitaxy (HVPE) apparatus suitable for a method for manufacturing a nitride semiconductor crystal. The HVPE apparatus according to the present invention may be either a vertical type or a horizontal type.
　図１のHVPE装置は、リアクター（反応室）１と、リアクター１内に配置され基板である下地基板４を支持面上に支持するためのサセプター（基板装着部）３と、ヒーター２とを備える。下地基板４は、その片面4aの面上にGaN系材料から成るエピタキシャル成長膜を成長させるための基板である。リアクター１の上方には、キャリアガスG1用の配管８、３族原料ガスG4用の配管９、及び５族原料ガスG3用の配管10の計５本の導入管が設置されている。また、リアクター１の下方には、ガスの流れが上方から下方に誘導されるように、排気管６が設置されている。更に本発明に係る装置では、後述する反り測定装置７を備えている。なお、真空装置の図示は省略している。 The HVPE apparatus of FIG. 1 includes a reactor (reaction chamber) 1, a susceptor (substrate mounting portion) 3 for supporting a base substrate 4, which is a substrate disposed in the reactor 1, on a support surface, and a heater 2. . The base substrate 4 is a substrate for growing an epitaxial growth film made of a GaN-based material on one surface 4a. Above the reactor 1, a total of five introduction pipes are installed: a pipe 8 for the carrier gas G 1, a pipe 9 for the group 3 source gas G 4, and a pipe 10 for the group 5 source gas G 3. Further, an exhaust pipe 6 is installed below the reactor 1 so that the gas flow is guided from above to below. Furthermore, the apparatus according to the present invention includes a warp measuring apparatus 7 to be described later. In addition, illustration of a vacuum device is abbreviate | omitted.
　更に、リアクター１内には、窒化物半導体の３族原料であるGa液体を収容した容器11が配置されており、リアクター１内に導入された３族原料ガスG4が容器11内のGa液体と反応して、３族金属塩化物ガスG2が生成され、下地基板４の結晶成長面に導入される。 Further, in the reactor 1, a container 11 containing Ga liquid which is a Group 3 raw material of nitride semiconductor is disposed, and the Group 3 source gas G4 introduced into the reactor 1 is combined with the Ga liquid in the container 11. By reacting, a Group 3 metal chloride gas G2 is generated and introduced into the crystal growth surface of the base substrate 4.
　下地基板４上に、エピタキシャル成長単結晶膜として窒化物半導体結晶５を成長させる。 A nitride semiconductor crystal 5 is grown as an epitaxially grown single crystal film on the underlying substrate 4.
　また下地基板４は、少なくとも窒化物半導体結晶５の結晶成長面側の片面4aが、鏡面研磨されたものを用いる。従って、後述する窒化物半導体結晶５の成長工程において、窒化物半導体結晶５は鏡面研磨された面上に成長形成される。なお、必要に応じて両面が鏡面研磨された下地基板を用いても良く、この場合何れか一方の面を窒化物半導体結晶５の結晶成長面として任意に利用できる。 Further, the base substrate 4 is a substrate in which at least one side 4a on the crystal growth surface side of the nitride semiconductor crystal 5 is mirror-polished. Therefore, in the growth step of the nitride semiconductor crystal 5 described later, the nitride semiconductor crystal 5 is grown and formed on the mirror-polished surface. If necessary, a base substrate whose both surfaces are mirror-polished may be used. In this case, any one surface can be arbitrarily used as the crystal growth surface of the nitride semiconductor crystal 5.
　鏡面研磨は、少なくとも片面4a上で窒化物半導体結晶５が成長可能な程度まで平滑となるように行われれば良く、目安としては表面粗さRaで１ｎｍ以下であることが好ましく、0.8ｎｍ以下であることがより好ましく、0.7ｎｍ以下であることが更に好ましい。片面4aのRaが１ｎｍを超えると、片面4a上に成長させる窒化物半導体結晶５の品質悪化を招いてしまう。更に、窒化物半導体結晶５がエピタキシャル成長可能な程度の目安としては、表面粗さRaが0.1nm以下に形成することが好ましい。Raは、表面粗さ測定機や原子間力顕微鏡（AFM：Atomic Force Microscopy）により表面の凹凸を測定することにより求めることが出来る。窒化物半導体結晶５を形成する片面4a上にはクラックが無いものとする。 The mirror polishing may be performed so that the nitride semiconductor crystal 5 is smooth enough to grow on at least one side 4a. As a guideline, the surface roughness Ra is preferably 1 nm or less, preferably 0.8 nm or less. More preferably, it is 0.7 nm or less. If the Ra of the single side 4a exceeds 1 nm, the quality of the nitride semiconductor crystal 5 grown on the single side 4a is deteriorated. Furthermore, as a measure of the extent to which the nitride semiconductor crystal 5 can be epitaxially grown, it is preferable that the surface roughness Ra be 0.1 nm or less. Ra can be determined by measuring surface irregularities with a surface roughness measuring machine or an atomic force microscope (AFM). It is assumed that there is no crack on one side 4a on which nitride semiconductor crystal 5 is formed.
　一方、裏面（反射面）の表面粗さRaは、前記の通りレーザ光7bが散乱しない程度であることが好ましく、具体的には20ｎｍ以下に設定される。前記の通り、鏡面研磨を両面に施した下地基板を用いる場合の裏面（反射面）の表面粗さRaは、１ｎｍ以下であることが好ましく、更に0.1ｎｍ以下が最も好ましい。裏面が鏡面研磨された下地基板４を用いることで、よりレーザ光7bの散乱が抑えられ、レーザ光7bの信号の落ち（レーザ光7bが散乱して反り測定装置７で検出不可能になること）を更に防止することが可能となる。 On the other hand, the surface roughness Ra of the back surface (reflecting surface) is preferably such that the laser light 7b is not scattered as described above, and is specifically set to 20 nm or less. As described above, the surface roughness Ra of the back surface (reflection surface) when using a base substrate that has been mirror-polished on both sides is preferably 1 nm or less, and more preferably 0.1 nm or less. By using the base substrate 4 whose back surface is mirror-polished, the scattering of the laser beam 7b is further suppressed, and the signal of the laser beam 7b falls (the laser beam 7b is scattered and cannot be detected by the warp measuring device 7). ) Can be further prevented.
　下地基板４の上に窒化物半導体結晶５が形成されるとは、下地基板４に接するように窒化物半導体結晶５が形成されること、或いは下地基板４の上に、単数又は複数の何らかの層を介して窒化物半導体結晶５が形成されることを包含する事とする。 The formation of the nitride semiconductor crystal 5 on the base substrate 4 means that the nitride semiconductor crystal 5 is formed so as to be in contact with the base substrate 4, or one or more layers on the base substrate 4. It is assumed that the nitride semiconductor crystal 5 is formed via
　反りのｉｎ－ｓｉｔｕ観察対象である、下地基板４の反り形状や反り量は、窒化物半導体結晶５の成膜中に時々刻々と変化している。具体的な一例としては、（ａ）窒化物半導体結晶５の形成前段階工程である下地基板４のサーマルクリーニング段階では、下地基板４の上下面での温度差に起因して、片面4aの凹面形状が強まり、曲率が大きく変化する。続いて、500～600℃程度に温度を下降し、（ｂ）低温バッファ層を成長させる場合には、下地基板４の凹面形状が弱まり、曲率はやや小さくなる。続いて、1000℃程度に温度を上昇し、（ｃ）窒化物半導体結晶５の一種としてn-GaN層成長を行う段階では、n-GaN層と下地基板４の格子定数差に起因して、下地基板４の凹面形状が強まり曲率は大きくなる。更に成膜が進行し、厚みが大きくなるほど曲率が大きくなる。続いて、温度を700～800℃程度に下降して、（ｄ）窒化物半導体結晶５の更なる一種として、InGaN系活性層の成長段階では、InGaN系活性層の厚みとInGaN中のIn組成の均一性が、発光波長の面内均一性に影響するため、LEDチップ等の製造歩留まりに影響する。InGaN層の厚みやIn組成は成膜温度に影響を受けることから、基板面内の温度均一性を向上させるために、成膜中の下地基板４の曲率はできるだけ０に近づけるのが理想的である。最終的に、下地基板４を（ｅ）クールダウンする段階で、再び熱膨張係数差によって下地基板４は再び大きく反るため、一連の成膜工程終了後の下地基板４の曲率は大きなものとなる。 The warp shape and warpage amount of the base substrate 4, which are the in-situ observation targets of the warp, change every moment during the formation of the nitride semiconductor crystal 5. As a specific example, (a) in the thermal cleaning stage of the base substrate 4 which is a pre-formation step of the nitride semiconductor crystal 5, the concave surface of the one side 4 a is caused by the temperature difference between the upper and lower surfaces of the base substrate 4. The shape becomes stronger and the curvature changes greatly. Subsequently, when the temperature is lowered to about 500 to 600 ° C. and (b) the low temperature buffer layer is grown, the concave shape of the base substrate 4 is weakened and the curvature is slightly reduced. Subsequently, the temperature is raised to about 1000 ° C., and (c) at the stage where the n-GaN layer is grown as a kind of the nitride semiconductor crystal 5, due to the lattice constant difference between the n-GaN layer and the base substrate 4, The concave shape of the base substrate 4 is strengthened and the curvature is increased. Further, as the film formation proceeds and the thickness increases, the curvature increases. Subsequently, the temperature is lowered to about 700 to 800 ° C., and (d) As a further kind of the nitride semiconductor crystal 5, in the growth stage of the InGaN-based active layer, the thickness of the InGaN-based active layer and the In composition in the InGaN Since the uniformity affects the in-plane uniformity of the emission wavelength, it affects the production yield of LED chips and the like. Since the thickness and In composition of the InGaN layer are affected by the film formation temperature, it is ideal that the curvature of the base substrate 4 during film formation be as close to 0 as possible in order to improve temperature uniformity within the substrate surface. is there. Finally, when the base substrate 4 is cooled down (e), the base substrate 4 is greatly warped again due to the difference in coefficient of thermal expansion, so that the curvature of the base substrate 4 after a series of film forming steps is large. Become.
　なお、裏面とは、下地基板４の両面の内、窒化物半導体結晶５の結晶成長が成されていない、或いは成されない面を指すものとする。 It should be noted that the back surface refers to the surface of the base substrate 4 on which the nitride semiconductor crystal 5 is not grown or not formed.
　反り測定装置７は、その内部に図示しない光源である光素子（望ましくは半導体レーザ）を備えており、HVPE装置に連結されて備えられている。その光素子から出射されたレーザ光7aが、反り測定装置７の一方の出射口から放射され、下地基板４の両面のうち裏面上に入射される。即ち、下地基板４の裏面がレーザ光7aの反射面となる。レーザ光7aは下地基板４の裏面上で反射される。更に、反射された反射光（レーザ光7b）は、再度反り測定装置７内に入射され、装置７内部の図示しない受光部で受光されることで、下地基板４の窒化物半導体結晶５の成膜中における反り形状や反り量の変化がｉｎ－ｓｉｔｕ観察される。 The warpage measuring device 7 includes an optical element (preferably a semiconductor laser) which is a light source (not shown) inside and is connected to the HVPE device. The laser beam 7 a emitted from the optical element is emitted from one emission port of the warpage measuring device 7 and is incident on the back surface of both surfaces of the base substrate 4. That is, the back surface of the base substrate 4 becomes a reflection surface of the laser light 7a. The laser beam 7 a is reflected on the back surface of the base substrate 4. Further, the reflected reflected light (laser light 7b) is incident on the warp measuring device 7 again and received by a light receiving unit (not shown) inside the device 7, thereby forming the nitride semiconductor crystal 5 of the base substrate 4. Changes in the warp shape and warpage amount in the film are observed in-situ.
　反射光であるレーザ光7bによる、下地基板４の反りのｉｎ－ｓｉｔｕ観察原理について、図２を参照して、更に詳述する。レーザ光7aは下地基板４の反射面に入射される前に、図２に示すように、既に２つの互いに平行な光路を有する、分離光7a1、7a2に分離されている。分離動作としては、複屈折などが挙げられる。この２つの平行な分離光7a1及び7a2は、裏面に入射する前までは互いに平行な光路を有すると共に、互いの光路差（光路長差）は０に設定されている。 The in-situ observation principle of warping of the base substrate 4 by the reflected laser beam 7b will be described in more detail with reference to FIG. Before the laser beam 7a is incident on the reflecting surface of the base substrate 4, as shown in FIG. 2, the laser beam 7a is already separated into two separated light beams 7a1 and 7a2 having optical paths parallel to each other. Examples of the separation operation include birefringence. The two parallel separated lights 7a1 and 7a2 have optical paths parallel to each other before entering the back surface, and the optical path difference (optical path length difference) between them is set to zero.
　ここで図２(a)又は図２(b)に示すように、下地基板４が窒化物半導体結晶５の成膜中に発生する反りによって裏面が凹状又は凸状に反っていると、裏面での反射によって分離光7a1、7a2の間に光路差が発生する。図２(a)に示すように裏面が凹状に反っている場合は、分離光7a1、7a2は反射により互いの光路が近づくように反射されて、それぞれ反射光7b1、7b2となる。一方、図２(b)に示すように裏面が凸状に反っている場合は、分離光7a1、7a2は反射により互いの光路が離れるように反射され、それぞれ反射光7b1、7b2となる。従って凹状又は凸状に関わらず、裏面で反射された反射光7b1、7b2間の光路は非平行状態となり、反射光7b1、7b2間には裏面の形状（即ち、下地基板４の反り形状や反り量）に応じた光路差が発生する。その反射光7b1、7b2を前記受光部で受光し光路差を観察することで、光路差により下地基板４の反りのｉｎ－ｓｉｔｕ観察が行われる。 Here, as shown in FIG. 2 (a) or FIG. 2 (b), when the back surface is warped in a concave or convex shape due to the warp generated during the formation of the nitride semiconductor crystal 5, the back surface Due to the reflection, an optical path difference is generated between the separated lights 7a1 and 7a2. As shown in FIG. 2 (a), when the back surface is warped in a concave shape, the separated lights 7a1 and 7a2 are reflected so as to approach each other by reflection and become reflected lights 7b1 and 7b2, respectively. On the other hand, when the back surface is warped as shown in FIG. 2 (b), the separated lights 7a1 and 7a2 are reflected so that their optical paths are separated by reflection, and become reflected lights 7b1 and 7b2, respectively. Therefore, regardless of the concave shape or the convex shape, the optical path between the reflected lights 7b1 and 7b2 reflected on the back surface is in a non-parallel state, and between the reflected lights 7b1 and 7b2, the shape of the back surface (that is, the warped shape and warpage of the base substrate 4). An optical path difference corresponding to the amount is generated. The reflected light 7b1 and 7b2 are received by the light receiving unit and the optical path difference is observed, whereby in-situ observation of the warpage of the base substrate 4 is performed by the optical path difference.
　レーザ光7bの波長は、CCD（Charge-Coupled Device：電荷結合素子）等を使用して目視により観察可能な波長域として可視光域が好ましく、具体的には360ｎｍ～830ｎｍに設定する。更にその可視光域の中でも、620ｎｍ以上660ｎｍ以下の波長範囲が、前記下地基板４の裏面での反射時に最も低損失であると共に、伝搬光路に光透過性の部品があったとしても光吸収されない波長であるため、好ましい。 The wavelength of the laser beam 7b is preferably a visible light region as a wavelength region that can be visually observed using a CCD (Charge-Coupled Device) or the like, and is specifically set to 360 nm to 830 nm. Further, in the visible light range, the wavelength range of 620 nm to 660 nm is the lowest loss when reflected on the back surface of the base substrate 4 and is not absorbed even if there is a light transmissive part in the propagation optical path. Since it is a wavelength, it is preferable.
　下地基板４の裏面は、窒化物半導体結晶５が形成されない面なので、窒化物半導体結晶膜５の成膜に伴う表面荒れの発生や、表面荒れの進行が発生しない。従って、裏面上から反射されたレーザ光7bが散乱すること無く、反り測定装置７で検出可能となる。よってレーザ光7bの信号が落ちること無く（レーザ光7bが散乱して反り測定装置７で検出不可能になること無く）、下地基板４の窒化物半導体結晶５の成膜中における反り形状や反り量をｉｎ－ｓｉｔｕ観察することが出来る。 Since the back surface of the base substrate 4 is a surface on which the nitride semiconductor crystal 5 is not formed, the occurrence of surface roughness accompanying the formation of the nitride semiconductor crystal film 5 and the progress of surface roughness do not occur. Therefore, the warp measuring device 7 can detect the laser light 7b reflected from the back surface without being scattered. Accordingly, the signal of the laser beam 7b does not drop (the laser beam 7b is scattered and cannot be detected by the warp measuring device 7), and the warp shape and warp during the film formation of the nitride semiconductor crystal 5 on the base substrate 4 are avoided. The amount can be observed in-situ.
　更に、窒化物半導体結晶５の成長後、窒化物半導体結晶５にエッチングや研磨、スライシング等の別工程を実施しても良い。 Furthermore, after the nitride semiconductor crystal 5 is grown, the nitride semiconductor crystal 5 may be subjected to another process such as etching, polishing, or slicing.
　以上、本実施形態に係るHVPE装置に依れば、下地基板４や結晶（窒化物半導体結晶５）の破壊或いは品質や性能不良の原因となる下地基板４の反り挙動を、裏面でのレーザ光反射によりｉｎ－ｓｉｔｕ観察することが可能となる。前記下地基板４の反り挙動とは、窒化物半導体結晶５の成長中の下地基板４の反り挙動（反り形状や反り量の変化）である。裏面により下地基板４の反りをｉｎ－ｓｉｔｕ観察しているため、結晶成長面（片面4a）のモフォロジーや厚み均一性に制約されること無く、裏面によりｉｎ－ｓｉｔｕ観察することが可能となる。従って、下地基板４の反り挙動を最適に制御することが出来る。 As described above, according to the HVPE apparatus according to the present embodiment, the warping behavior of the base substrate 4 that causes the base substrate 4 or the crystal (nitride semiconductor crystal 5) to be broken or cause quality or performance failure is determined by the laser beam on the back surface. Reflection enables in-situ observation. The warpage behavior of the base substrate 4 is the warpage behavior (change in warpage shape and amount of warpage) of the base substrate 4 during the growth of the nitride semiconductor crystal 5. Since the back surface of the substrate 4 is warped in-situ, the back surface can be observed in-situ without being limited by the morphology and thickness uniformity of the crystal growth surface (single surface 4a). Therefore, the warping behavior of the base substrate 4 can be optimally controlled.
＜第２の実施形態＞
　以下、図３を参照して、本発明に係る基板の反りのｉｎ－ｓｉｔｕ観察装置における第２の実施形態を詳細に説明する。図３は、本発明の窒化物半導体結晶の製造方法に好適な横型のHVPE装置の概略構成を模式的に示す説明図である。なお、前述の図１のHVPE装置と同一箇所には同一番号を付し、重複する説明は省略又は簡略化して記述する。 <Second Embodiment>
Hereinafter, with reference to FIG. 3, a second embodiment of the in-situ observation apparatus for warping of a substrate according to the present invention will be described in detail. FIG. 3 is an explanatory view schematically showing a schematic configuration of a horizontal HVPE apparatus suitable for the method for producing a nitride semiconductor crystal of the present invention. In addition, the same number is attached | subjected to the same location as the HVPE apparatus of the above-mentioned FIG. 1, and the overlapping description is abbreviate | omitted or simplified and described.
　リアクター１の一端側には、キャリアガスG1用の配管８、３族原料ガスG4用の配管９、及び５族原料ガスG4用の配管10の計３本の導入管が水平に設置されている。各導入管はリアクター１の中央部に向かって延設されている。なお真空装置の図示は省略している。 At one end of the reactor 1, a total of three introduction pipes, that is, a pipe 8 for the carrier gas G 1, a pipe 9 for the group 3 source gas G 4, and a pipe 10 for the group 5 source gas G 4 are installed horizontally. . Each introduction pipe extends toward the center of the reactor 1. The illustration of the vacuum device is omitted.
　リアクター１は円筒状に形成されており、上面及び底面が水平面に対して垂直方向に立設された状態で互いに向かい合うような横倒しの状態で配置されている。更にリアクター１の周囲には、ヒーター２が配置されている。 The reactor 1 is formed in a cylindrical shape, and is arranged in a laid-down state so as to face each other with the upper surface and the bottom surface standing in a direction perpendicular to the horizontal plane. Furthermore, a heater 2 is disposed around the reactor 1.
　更に、リアクター１内部の前記導入管が設置された一端側の他端側には、サセプター３が片持ち状に支持された状態で配置されており、下地基板４の装着面は水平面に対して平行に配置されている。 Furthermore, the susceptor 3 is disposed in a cantilevered manner on the other end side of the reactor 1 where the introduction pipe is installed, and the mounting surface of the base substrate 4 is in a horizontal plane. They are arranged in parallel.
　従って、図３のHVPE装置を用いてエピタキシャル成長膜を成長する際は、キャリアガスG1と、３族原料ガスG4と、５族原料ガスG3は、各配管８～10を通して、リアクター１内で下地基板４に向かって水平方向に導入される。 Therefore, when the epitaxial growth film is grown using the HVPE apparatus of FIG. 3, the carrier gas G1, the group 3 source gas G4, and the group 5 source gas G3 pass through the pipes 8 to 10 in the reactor 1 to form the base substrate. 4 is introduced horizontally.
　配管９の内部には、図１で図示したようなGa液体を収容した容器11が配置されており（図３では図示せず）、配管９の一端側から導入された３族原料ガスG4が容器11内のGa液体と反応して、３族金属塩化物ガスG2が生成され、下地基板４の結晶成長面に導入される。 A container 11 containing Ga liquid as shown in FIG. 1 is arranged inside the pipe 9 (not shown in FIG. 3), and the Group 3 source gas G4 introduced from one end side of the pipe 9 is provided. By reacting with the Ga liquid in the container 11, a Group 3 metal chloride gas G 2 is generated and introduced into the crystal growth surface of the base substrate 4.
　下地基板４をHVPE装置のサセプター３に装着し、所定の反応温度に昇温した後、下地層又は下地基板４の片面4a上に、N2ガスG1及びGaClガスG2と、NH3ガスG3とを導入しながら、窒化物半導体結晶５（特にGaN膜）を所定時間に亘って成長させる。 After the base substrate 4 is mounted on the susceptor 3 of the HVPE apparatus and heated to a predetermined reaction temperature, N 2 gas G1 and GaCl gas G2 and NH 3 gas G3 are formed on one surface 4a of the base layer or the base substrate 4. The nitride semiconductor crystal 5 (especially the GaN film) is grown over a predetermined time while introducing.
　本実施形態においても、窒化物半導体結晶５の成膜中に反り測定装置７からレーザ光7aを出射し、下地基板４の裏面上に入射及び反射させ、図２のように反射光7b1、7b2の光路差を観察する。このような観察により、下地基板４の窒化物半導体結晶５の成膜中における反り形状や反り量の変化がｉｎ－ｓｉｔｕ観察可能となる。 Also in the present embodiment, the laser beam 7a is emitted from the warp measuring device 7 during the formation of the nitride semiconductor crystal 5, is incident on and reflected from the back surface of the base substrate 4, and reflected light 7b1, 7b2 as shown in FIG. Observe the optical path difference. Such observation enables in-situ observation of changes in the warp shape and the warp amount during the formation of the nitride semiconductor crystal 5 on the base substrate 4.
　以上、本実施形態に係るHVPE装置に依れば、第１の実施形態と同様に、結晶成長面（片面4a）のモフォロジーや厚み均一性に制約されること無く、前記反り形状や反り量の変化を裏面によりｉｎ－ｓｉｔｕ観察することが可能となる。従って、下地基板４の反り挙動を最適に制御することが出来る。 As described above, according to the HVPE apparatus according to the present embodiment, as in the first embodiment, the warpage shape and the warpage amount are not limited by the morphology and thickness uniformity of the crystal growth surface (single surface 4a). The change can be observed in-situ on the back surface. Therefore, the warping behavior of the base substrate 4 can be optimally controlled.
＜第３の実施形態＞
　以下、図４又は図５を参照して、本発明に係る基板の反りのｉｎ－ｓｉｔｕ観察装置における第３の実施形態を詳細に説明する。図４は第３の実施形態に係る下地基板４の一例を示す、斜視図である。図５は、本発明のダイヤモンド単結晶の製造方法に好適な、マイクロ波CVD（Chemical Vapor Deposition）装置の概略構成を模式的に示す説明図である。なお、前述の図１又は図３のHVPE装置と同一箇所には同一番号を付し、重複する説明は省略又は簡略化して記述する。 <Third Embodiment>
Hereinafter, a third embodiment of the in-situ observation apparatus for warping of a substrate according to the present invention will be described in detail with reference to FIG. 4 or FIG. FIG. 4 is a perspective view showing an example of the base substrate 4 according to the third embodiment. FIG. 5 is an explanatory view schematically showing a schematic configuration of a microwave CVD (Chemical Vapor Deposition) apparatus suitable for the method for producing a diamond single crystal of the present invention. In addition, the same number is attached | subjected to the same location as the HVPE apparatus of the above-mentioned FIG. 1 or FIG. 3, and the overlapping description is abbreviate | omitted or simplified and described.
　まず図４に示すように下地基板４を用意する。下地基板４の材質は、例えば、酸化マグネシウム（MgO）、酸化アルミニウム（α－Al2O3：サファイア）、Si、石英、白金、イリジウム、チタン酸ストロンチウム（SrTiO3）等が挙げられる。 First, as shown in FIG. 4, a base substrate 4 is prepared. Examples of the material of the base substrate 4 include magnesium oxide (MgO), aluminum oxide (α-Al 2 O 3 : sapphire), Si, quartz, platinum, iridium, and strontium titanate (SrTiO 3 ).
　また下地基板４は、少なくとも片面4aが鏡面研磨されたものを用いる。後述するダイヤモンド単結晶の成長工程において、ダイヤモンド単結晶は鏡面研磨された面側（片面4aの面上）に成長形成される。なお、必要に応じて両面が鏡面研磨された下地基板を用いても良く、この場合何れか一方の面をダイヤモンド単結晶の成長面として任意に利用できる。 Also, the base substrate 4 is a mirror whose at least one side 4a is mirror-polished. In the diamond single crystal growth step, which will be described later, the diamond single crystal is grown and formed on the mirror-polished surface side (on the surface of the one surface 4a). If necessary, a base substrate whose both surfaces are mirror-polished may be used. In this case, any one surface can be arbitrarily used as a growth surface of the diamond single crystal.
　鏡面研磨は、少なくとも片面4a上でダイヤモンド単結晶が成長可能な程度まで平滑となるように行われれば良く、目安としては表面粗さRaで10ｎｍ以下まで研磨することが好ましい。片面4aのRaが10ｎｍを超えると、片面4a上に成長させるダイヤモンド単結晶の品質悪化を招いてしまう。更に、片面4a上にはクラックが無いものとする。Raの測定は、表面粗さ測定機により行えば良い。 The mirror polishing may be performed so as to be smooth to the extent that a diamond single crystal can be grown on at least one side 4a. As a guideline, it is preferable to polish the surface to a surface roughness Ra of 10 nm or less. If the Ra of the single side 4a exceeds 10 nm, the quality of the diamond single crystal grown on the single side 4a is deteriorated. Furthermore, it is assumed that there is no crack on one side 4a. Ra may be measured with a surface roughness measuring machine.
　次に、下地基板４の片面4a上に、ダイヤモンド単結晶を成長形成する。ダイヤモンド単結晶の成長方法は特に限定されないが、本実施形態では、図５に示すようなマイクロ波プラズマCVD装置12（以下、装置12と表記）を用いる。この装置12は、ガス導入管13とガス排出管14を備えたチャンバー15内に、ヒーター等の加熱体や水流装置が装着された水冷ホルダ20が配置されている。そして、チャンバー15内にプラズマを発生できるように、マイクロ波電源16が導波管17を介してマイクロ波導入窓18に接続されている。水冷ホルダ20の内部には、図示しない水流装置が搭載されており、下地基板４及び後述するダイヤモンド単結晶19を水流により冷却する。膜状の結晶であるダイヤモンド単結晶19を所定時間（約10時間）ヘテロエピタキシャル成長させる。 Next, a diamond single crystal is grown on one side 4a of the base substrate 4. The method for growing the diamond single crystal is not particularly limited, but in this embodiment, a microwave plasma CVD apparatus 12 (hereinafter referred to as apparatus 12) as shown in FIG. 5 is used. In this apparatus 12, a water cooling holder 20 equipped with a heating body such as a heater and a water flow device is disposed in a chamber 15 provided with a gas introduction pipe 13 and a gas discharge pipe. A microwave power source 16 is connected to the microwave introduction window 18 via the waveguide 17 so that plasma can be generated in the chamber 15. A water flow device (not shown) is mounted inside the water cooling holder 20 and cools the base substrate 4 and a diamond single crystal 19 described later with a water flow. A diamond single crystal 19 which is a film-like crystal is heteroepitaxially grown for a predetermined time (about 10 hours).
　本実施形態においても、ダイヤモンド単結晶19の成膜中に反り測定装置７からレーザ光7aを出射し、水冷ホルダ20に設けた光学窓部21を伝搬させて、下地基板４の裏面上にレーザ光7aを入射及び反射させ、図２のように反射光7b1、7b2の光路差を観察する。このような観察により、下地基板４のダイヤモンド単結晶19の成膜中における反り形状や反り量の変化がｉｎ－ｓｉｔｕ観察可能となる。 Also in this embodiment, the laser beam 7 a is emitted from the warpage measuring device 7 during the film formation of the diamond single crystal 19, propagates through the optical window 21 provided in the water-cooled holder 20, and laser is applied to the back surface of the base substrate 4. The light 7a is incident and reflected, and the optical path difference between the reflected lights 7b1 and 7b2 is observed as shown in FIG. By such observation, it becomes possible to observe in-situ changes in the warp shape and the warp amount during the film formation of the diamond single crystal 19 on the base substrate 4.
　下地基板４の裏面は、ダイヤモンド単結晶19が形成されない面なので、ダイヤモンド単結晶19の成膜に伴う表面荒れの発生や、表面荒れの進行が発生しない。従って、裏面上から反射されたレーザ光7bが散乱すること無く、反り測定装置７で検出可能となる。よってレーザ光7bの信号が落ちること無く（レーザ光7bが散乱して反り測定装置７で検出不可能になること無く）、下地基板４のダイヤモンド単結晶19の成膜中における反り形状や反り量をｉｎ－ｓｉｔｕ観察することが出来る。 Since the back surface of the base substrate 4 is a surface on which the diamond single crystal 19 is not formed, the occurrence of surface roughness accompanying the film formation of the diamond single crystal 19 and the progress of surface roughness do not occur. Therefore, the warp measuring device 7 can detect the laser light 7b reflected from the back surface without being scattered. Therefore, the signal of the laser beam 7b does not drop (the laser beam 7b is scattered and cannot be detected by the warp measuring device 7), and the warp shape and the warp amount during the film formation of the diamond single crystal 19 on the base substrate 4 are reduced. Can be observed in-situ.
　裏面（反射面）の表面粗さRaは、前記の通りレーザ光7bが散乱しない程度であることが好ましく、具体的には20ｎｍ以下に設定される。鏡面研磨を両面に施した下地基板を用いる場合の裏面（反射面）の表面粗さRaは、１ｎｍ以下であることが好ましく、更に0.1ｎｍ以下が最も好ましい。裏面が鏡面研磨された下地基板４を用いることで、よりレーザ光7bの散乱が抑えられ、レーザ光7bの信号の落ち（レーザ光7bが散乱して反り測定装置７で検出不可能になること）を更に防止することが可能となる。 The surface roughness Ra of the back surface (reflective surface) is preferably such that the laser beam 7b is not scattered as described above, and is specifically set to 20 nm or less. The surface roughness Ra of the back surface (reflection surface) when using a base substrate that has been subjected to mirror polishing on both sides is preferably 1 nm or less, and most preferably 0.1 nm or less. By using the base substrate 4 whose back surface is mirror-polished, the scattering of the laser beam 7b is further suppressed, and the signal of the laser beam 7b falls (the laser beam 7b is scattered and cannot be detected by the warp measuring device 7). ) Can be further prevented.
　以上、本実施形態に係るマイクロ波プラズマCVD装置に依れば、ダイヤモンド単結晶19の成長中の下地基板４の反り挙動（反り形状や反り量の変化）を、裏面でのレーザ光反射によりｉｎ－ｓｉｔｕ観察することが可能となる。反り挙動は、下地基板４や結晶（ダイヤモンド単結晶19）の破壊、或いは品質や性能不良の原因となる。裏面により下地基板４の反りをｉｎ－ｓｉｔｕ観察しているため、結晶成長面（片面4a）のモフォロジーや厚み均一性に制約されること無く、裏面によりｉｎ－ｓｉｔｕ観察することが可能となる。従って、下地基板４の反り挙動を最適に制御することが出来る。 As described above, according to the microwave plasma CVD apparatus according to the present embodiment, the warpage behavior (change in warpage shape and amount of warpage) of the base substrate 4 during the growth of the diamond single crystal 19 is reflected by the laser light reflection on the back surface. -Situ observation is possible. The warping behavior causes destruction of the base substrate 4 and the crystal (diamond single crystal 19), or quality and performance defects. Since the back surface of the substrate 4 is warped in-situ, the back surface can be observed in-situ without being limited by the morphology and thickness uniformity of the crystal growth surface (single surface 4a). Therefore, the warping behavior of the base substrate 4 can be optimally controlled.
　なお、本発明はその技術的思想に基づいて種々変更可能であり、例えば下地基板４のｉｎ－ｓｉｔｕ観察対象工程を、前記窒化物半導体結晶５やダイヤモンド単結晶19の成膜工程だけで無く、成膜前後に行うアニール工程での下地基板４の反り挙動をｉｎ－ｓｉｔｕ観察しても良い。この場合も、反り測定装置７からの半導体レーザ光を、下地基板４の裏面上で反射させてｉｎ－ｓｉｔｕ観察を行えば良い。 The present invention can be variously modified based on its technical idea. For example, the in-situ observation target process of the base substrate 4 is not limited to the film forming process of the nitride semiconductor crystal 5 and the diamond single crystal 19, In-situ observation of the warping behavior of the base substrate 4 in the annealing process performed before and after the film formation may be performed. In this case as well, in-situ observation may be performed by reflecting the semiconductor laser light from the warp measuring device 7 on the back surface of the base substrate 4.
　また、エピタキシャル成長させる窒化物半導体結晶５としては、前記各実施形態の他にAlN又はBNの単結晶でも良い。また、下地基板上にエピタキシャル成長させる結晶は、窒化物半導体結晶やダイヤモンド以外にSiCの単結晶でも良い。 The nitride semiconductor crystal 5 to be epitaxially grown may be a single crystal of AlN or BN in addition to the above embodiments. The crystal to be epitaxially grown on the base substrate may be a SiC single crystal in addition to the nitride semiconductor crystal or diamond.
　また、前記裏面上に金属膜を成膜し、その金属膜上で分離光7a1、7a2を反射させても良い。分離光7a1、7a2を反射させる反射面となる金属膜表面の表面粗さRaは、レーザ光7bが散乱しない程度であることが好ましく、具体的には20ｎｍ以下に設定される。また金属膜の材料としては、Pt、Ir、Taが好ましいが、これらに限定されるものではない。 Further, a metal film may be formed on the back surface, and the separated lights 7a1 and 7a2 may be reflected on the metal film. The surface roughness Ra of the metal film surface serving as a reflecting surface for reflecting the separated lights 7a1 and 7a2 is preferably such that the laser light 7b is not scattered, and is specifically set to 20 nm or less. The metal film material is preferably Pt, Ir, or Ta, but is not limited thereto.
　以下に本発明の実施例を説明するが、本発明は以下の実施例にのみ限定されるものではない。 Examples of the present invention will be described below, but the present invention is not limited to the following examples.
　本実施例に係る装置には図１に示す縦型のHVPE装置を用いると共に、基板には厚み0.43ｍｍ、平面方向の形状が円形状で直径が２インチであり、結晶成長面及び裏面を(0001)面と設定したサファイア単結晶基板を用いた。その(0001)面には鏡面研磨を施し、表面粗さRaで１ｎｍ以下とした。 The vertical HVPE apparatus shown in FIG. 1 is used for the apparatus according to the present embodiment, the substrate has a thickness of 0.43 mm, the planar shape is circular, the diameter is 2 inches, the crystal growth surface and the back surface are ( A sapphire single crystal substrate set with a (0001) plane was used. The (0001) plane was mirror-polished to have a surface roughness Ra of 1 nm or less.
　窒化物半導体結晶５としてGaNを200μｍの厚みで結晶成長させた。容器11にはGa液体を収容し、更にキャリアガスG1はN2ガス、３族原料ガスG4はHCl、３族金属塩化物ガスG2はGaCl、５族原料ガスG3はアンモニア（NH3）とした。 GaN was grown as a nitride semiconductor crystal 5 with a thickness of 200 μm. The container 11 contains Ga liquid, and the carrier gas G1 is N 2 gas, the Group 3 source gas G4 is HCl, the Group 3 metal chloride gas G2 is GaCl, and the Group 5 source gas G3 is ammonia (NH 3 ). .
　次にGaNの成長後のサファイア基板に1020℃でアニール処理を施し、更にサファイア基板の裏面上に半導体レーザ光を反射させ、アニール処理におけるサファイア基板の反り挙動をｉｎ－ｓｉｔｕ観察した。半導体レーザ光は、620ｎｍ以上660ｎｍ以下の波長域の条件に設定した。そのｉｎ－ｓｉｔｕ観察時に、サファイア基板の裏面から反射によって得られた半導体レーザ光のレーザスポット像を、図６に示す。 Next, the sapphire substrate after the growth of GaN was annealed at 1020 ° C., and the semiconductor laser light was reflected on the back surface of the sapphire substrate, and the warpage behavior of the sapphire substrate in the annealing treatment was observed in-situ. The semiconductor laser light was set to conditions in the wavelength range of 620 nm to 660 nm. FIG. 6 shows a laser spot image of the semiconductor laser light obtained by reflection from the back surface of the sapphire substrate during the in-situ observation.
　図６より四角枠で囲んだ部分が、ｉｎ－ｓｉｔｕ観察時に検出された半導体レーザ光のレーザスポット像である。図６に示すように、楕円状の半導体レーザ光がｉｎ－ｓｉｔｕ観察時に検出され、サファイア基板の反り挙動がｉｎ－ｓｉｔｕ観察可能となることが確認された。 In FIG. 6, the portion surrounded by a square frame is a laser spot image of the semiconductor laser light detected during in-situ observation. As shown in FIG. 6, an elliptical semiconductor laser beam was detected during in-situ observation, and it was confirmed that the warping behavior of the sapphire substrate can be observed in-situ.
比較例Comparative example
　次に比較例として、実施例と同一のサファイア単結晶基板及びHVPE装置を用意すると共に、半導体レーザ光を裏面とは反対側の結晶成長面の(0001)面上で反射させた。半導体レーザ光の反射面を結晶成長面に変更した以外は、前記実施例と同一のHVPE装置構成とした。 Next, as a comparative example, the same sapphire single crystal substrate and HVPE apparatus as in the example were prepared, and the semiconductor laser light was reflected on the (0001) plane of the crystal growth surface opposite to the back surface. The configuration of the HVPE apparatus was the same as that of the above example except that the reflection surface of the semiconductor laser light was changed to a crystal growth surface.
　前記実施例と同じく、GaNの成長後のサファイア単結晶基板を1020℃に加熱し、サファイア基板の反り挙動のｉｎ－ｓｉｔｕ観察を試みると共に、サファイア基板の結晶成長面から反射によって得られた半導体レーザ光を図７に示す。 As in the previous example, the sapphire single crystal substrate after the growth of GaN was heated to 1020 ° C., and in-situ observation of the warpage behavior of the sapphire substrate was attempted, and a semiconductor laser obtained by reflection from the crystal growth surface of the sapphire substrate The light is shown in FIG.
　図７より、四角枠で囲んだ部分が、アニール時に検出された半導体レーザ光である。図７に示すように、半導体レーザ光は乱れたスポット像で検出された。半導体レーザ光の乱れの原因として、HVPE法による成長によって結晶成長面の表面のモフォロジーが悪化したためと思われる。更に、半導体レーザ光の乱れによりサファイア基板の反り挙動をｉｎ－ｓｉｔｕ観察出来ないことが確認された。 From FIG. 7, the portion surrounded by the square frame is the semiconductor laser light detected during annealing. As shown in FIG. 7, the semiconductor laser light was detected as a turbulent spot image. The disorder of the semiconductor laser light seems to be due to the deterioration of the surface morphology of the crystal growth surface due to the growth by the HVPE method. Further, it was confirmed that the warping behavior of the sapphire substrate could not be observed in-situ due to the disturbance of the semiconductor laser light.
　以上により、結晶成長面となるサファイア単結晶基板の表面は、GaNの成長によりモフォロジーが悪化するため、反り挙動のｉｎ－ｓｉｔｕ観察が不可能であることが判明した。一方HVPE成長されないサファイア単結晶基板の裏面はモフォロジーの悪化が防止されるため、結晶成長面のモフォロジーに制約されること無く、半導体レーザ光による反り挙動をｉｎ－ｓｉｔｕ観察することが可能であることが判明した。 From the above, it has been found that in-situ observation of the warping behavior is impossible because the morphology of the surface of the sapphire single crystal substrate that becomes the crystal growth surface deteriorates due to the growth of GaN. On the other hand, the backside of the sapphire single crystal substrate on which HVPE is not grown prevents the morphology from deteriorating, so it is possible to observe in-situ warping behavior by semiconductor laser light without being restricted by the morphology of the crystal growth surface. There was found.
　　　１　　　　　リアクター
　　　２　　　　　ヒーター
　　　３　　　　　サセプター
　　　４　　　　　下地基板
　　　4a　　　　　下地基板の片面
　　　５　　　　　窒化物半導体結晶
　　　６　　　　　排気管
　　　７　　　　　反り測定装置
　　　7a、7b　　　レーザ光
　　　G1　　　　　キャリアガス
　　　G2　　　　　３族金属塩化物ガス
　　　G3　　　　　５族原料ガス
　　　G4　　　　　３族原料ガス
　　　８　　　　　キャリアガス用の配管
　　　９　　　　　３族原料ガス用の配管
　　　10　　　　　５族原料ガス用の配管
　　　11　　　　　Ga液体を収容した容器
　　　12　　　　　マイクロ波プラズマCVD装置
　　　13　　　　　ガス導入管
　　　14　　　　　ガス排出管
　　　15　　　　　チャンバー
　　　16　　　　　マイクロ波電源
　　　17　　　　　導波管
　　　18　　　　　マイクロ波導入窓
　　　19　　　　　ダイヤモンド単結晶
　　　20　　　　　水冷ホルダ
　　　21　　　　　光学窓部 DESCRIPTION OF SYMBOLS 1 Reactor 2 Heater 3 Susceptor 4 Ground substrate 4a One side of ground substrate 5 Nitride semiconductor crystal 6 Exhaust pipe 7 Warpage measuring device 7a, 7b Laser beam G1 Carrier gas G2 Group 3 metal chloride gas G3 Group 5 source gas G4 Group 3 source Gas 8 Pipe for carrier gas 9 Pipe for Group 3 source gas 10 Pipe for Group 5 source gas 11 Container containing Ga liquid 12 Microwave plasma CVD equipment 13 Gas inlet pipe 14 Gas exhaust pipe 15 Chamber 16 Microwave power source 17 Waveguide 18 Microwave introduction window 19 Diamond single crystal 20 Water-cooled holder 21 Optical window

Claims (9)

  1. 　装置は少なくとも、基板、レーザ光を放射する光源、及びレーザ光を受光する受光部を備え、
    　基板はその両面のうち、少なくとも一方の面が結晶成長面であると共に、その裏面が反射面であり、光源から放射されたレーザ光が反射面で反射され、反射された反射光が受光部で受光されて、基板の反りのｉｎ－ｓｉｔｕ観察が行われることを特徴とする装置。     The apparatus includes at least a substrate, a light source that emits laser light, and a light receiving unit that receives the laser light,
    The substrate has at least one of its both surfaces as a crystal growth surface and its back surface as a reflection surface. The laser light emitted from the light source is reflected by the reflection surface, and the reflected light reflected by the light receiving unit. An apparatus characterized by receiving light and performing in-situ observation of substrate warpage.
  2. 　前記レーザ光は、前記反射面の入射前に分離されている２つの平行な分離光であり、前記裏面での反射によって分離光の間に光路差が発生し、その光路差により前記反りのｉｎ－ｓｉｔｕ観察が行われることを特徴とする請求項１記載の装置。 The laser light is two parallel separated lights separated before incidence on the reflecting surface, and an optical path difference occurs between the separated lights due to reflection on the back surface, and the warping in is caused by the optical path difference. Device according to claim 1, characterized in that -situ observation is performed.
  3. 　前記レーザ光の波長が、可視光域であることを特徴とする請求項１又は２に記載の装置。 The apparatus according to claim 1 or 2, wherein the wavelength of the laser beam is in a visible light range.
  4. 　前記レーザ光の波長が、620ｎｍ以上660ｎｍ以下の範囲であることを特徴とする請求項１～３の何れかに記載の装置。 The apparatus according to any one of claims 1 to 3, wherein a wavelength of the laser beam is in a range of 620 nm to 660 nm.
  5. 　前記反射面の表面粗さRaが、20ｎｍ以下であることを特徴とする請求項１～４の何れかに記載の装置。 The apparatus according to any one of claims 1 to 4, wherein a surface roughness Ra of the reflecting surface is 20 nm or less.
  6. 　前記反射面の表面粗さRaが、１ｎｍ以下であることを特徴とする請求項１～５の何れかに記載の装置。 6. The apparatus according to claim 1, wherein a surface roughness Ra of the reflecting surface is 1 nm or less.
  7. 　前記反射面の表面粗さRaが、0.1ｎｍ以下であることを特徴とする請求項１～６の何れかに記載の装置。 The apparatus according to any one of claims 1 to 6, wherein the reflection surface has a surface roughness Ra of 0.1 nm or less.
  8. 　請求項１～７の何れかに記載の装置が備えられると共に、前記結晶成長面の面上に結晶を成長することを特徴とする結晶成長装置。 A crystal growth apparatus comprising the apparatus according to any one of claims 1 to 7 and growing a crystal on the surface of the crystal growth surface.
  9. 前記結晶が、窒化物半導体、ダイヤモンド、SiCの何れかの結晶を成長させることを特徴とする請求項８記載の結晶成長装置。 The crystal growth apparatus according to claim 8, wherein the crystal grows a crystal of any one of a nitride semiconductor, diamond, and SiC.
PCT/JP2016/066135 2015-06-02 2016-06-01 In-situ observation device of substrate warpage and crystal growth apparatus WO2016194931A1 (en)

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JPH09126913A (en) * 1995-10-30 1997-05-16 Hitachi Ltd Stress measuring device and semiconductor manufacturing apparatus
JPH10146753A (en) * 1996-11-15 1998-06-02 Nec Corp Method and device for polishing substrate
JP2003014446A (en) * 2001-07-02 2003-01-15 Misawa Homes Co Ltd Camber measuring apparatus
JP2005197621A (en) * 2004-01-09 2005-07-21 Nec Saitama Ltd Csp removal device and method therefor
JP2007217216A (en) * 2006-02-15 2007-08-30 Sumitomo Electric Ind Ltd GaN CRYSTAL SUBSTRATE AND ITS MANUFACTURING METHOD AS WELL AS MANUFACTURING METHOD OF SEMICONDUCTOR DEVICE
JP2011246749A (en) * 2010-05-25 2011-12-08 Tokuyama Corp Aluminum-based group iii nitride production apparatus and method for producing aluminum-based group iii nitride

Patent Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPH09126913A (en) * 1995-10-30 1997-05-16 Hitachi Ltd Stress measuring device and semiconductor manufacturing apparatus
JPH10146753A (en) * 1996-11-15 1998-06-02 Nec Corp Method and device for polishing substrate
JP2003014446A (en) * 2001-07-02 2003-01-15 Misawa Homes Co Ltd Camber measuring apparatus
JP2005197621A (en) * 2004-01-09 2005-07-21 Nec Saitama Ltd Csp removal device and method therefor
JP2007217216A (en) * 2006-02-15 2007-08-30 Sumitomo Electric Ind Ltd GaN CRYSTAL SUBSTRATE AND ITS MANUFACTURING METHOD AS WELL AS MANUFACTURING METHOD OF SEMICONDUCTOR DEVICE
JP2011246749A (en) * 2010-05-25 2011-12-08 Tokuyama Corp Aluminum-based group iii nitride production apparatus and method for producing aluminum-based group iii nitride

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