JP2010030846A - Method for producing nitride material - Google Patents

Abstract

The present invention provides a method for manufacturing a nitride object that suppresses the warping of the growth substrate that occurs when the nitride object is grown on the substrate and improves the quality and reproducibility of the nitride object of the nitride object on the substrate.
A method for manufacturing a nitride object using a holder 1 that holds a substrate for growing a nitride object, wherein: (1) non-growth of a main surface of the growth substrate 3 on a side on which the nitride object is not grown A step of holding the growth substrate 3 by the holding body 1 so that the entire main surface is not in close contact with the holding body 1, and (2) a step of growing a nitride body on the held substrate 3 by vapor phase growth. Are provided.
[Selection] Figure 1

Description

  The present invention relates to a method for manufacturing a nitride object in which a nitride object (nitride single crystal) such as GaN, AlN, or AlGaN is grown on the surface of a substrate, and in particular, light emission from a light emitting diode (LED), a semiconductor laser (LD), or the like. The present invention relates to a method of manufacturing a nitride object applied to an electronic element such as a power device such as an element, a transistor, or a power FET (Field Effect Transistor).

  Nitride objects such as GaN and AlGaN are suitable for use in light-emitting elements such as light-emitting diodes (LEDs) and semiconductor lasers (LDs), and their use is expected to expand in the future.

In recent years, GaN single crystals have been produced by vapor phase epitaxy (see, for example, Patent Document 1).
Japanese Patent Laid-Open No. 2000-12900

  However, in the content of Patent Document 1, since the entire surface of the growth substrate for producing a single crystal has a structure in contact with the holder, for example, when the substrate is warped due to a temperature rise, the nitride object of the substrate The temperature distribution on the growth surface becomes non-uniform. Due to this non-uniform temperature distribution, there are problems that crystal defects (dislocations), the quality reproducibility of the grown nitrided body is reduced, and the nitrided body or the substrate is cracked.

  Accordingly, the present invention has been completed in view of the above-described conventional problems, and the object of the present invention is when a growth substrate is warped when a nitride object is grown on the substrate, or originally a growth substrate. It is an object of the present invention to provide a method for manufacturing a nitride object that maintains the quality and reproducibility of the nitride object on the substrate even when there is warpage.

  The present invention is a method for manufacturing a nitride object using a holder for holding a growth substrate for growing a nitride object, and (1) non-growth in which the nitride object is not grown on the main surface of the growth substrate. A step of holding the growth substrate by the holding body so that only the outer peripheral portion of the side main surface is in close contact with the holding body; and (2) growing a nitride object on the held substrate by vapor deposition. And a method for producing a nitride body comprising:

  The vapor phase growth method in the step (2) is preferably a hydride vapor phase growth method.

  The nitride body is preferably composed of a GaN single crystal, an AlN single crystal, or a mixed crystal thereof.

  It is preferable that the holding body has a recess and the growth substrate is provided so as to cover the recess.

  It is preferable that a protrusion for holding the growth substrate is provided on the inner wall surface of the concave portion of the holding body.

  It is preferable that a step for holding the growth substrate is provided on the inner wall surface of the concave portion of the holding body.

  The holding body is preferably graphite coated with at least one selected from the group consisting of SiC, BN and TaC.

  Since the nitride body manufacturing method of the present invention is such that only the outer peripheral portion of the main surface of the growth substrate on which the nitride body is not grown is in close contact with the holder, the growth substrate 3 and The contact of the holding body 1 is limited to the outer peripheral portion, and the entire surface of the substrate excluding the outer peripheral portion has a uniform temperature, which is the conventional problem of crystal defects (dislocations) and the quality reproducibility of the grown nitrided object, the nitrided object or the substrate Cracking can be suppressed.

  Further, the holding body is graphite coated with at least one selected from the group consisting of SiC, BN and TaC, so that the corrosiveness of ammonia or hydrogen chloride gas used for growth can be improved.

  In the method for producing a nitride single crystal of the present invention, preferably, the nitride body is composed of a GaN single crystal, an AlN single crystal, or a mixed crystal thereof, so that a light emitting diode (LED), a semiconductor laser (LD), and the like The light emitting element, the transistor, and a power object such as a power FET (Field Effect Transistor) are nitrided objects that are suitably used for electronic elements.

  In the nitride object manufacturing method of the present invention, the substrate is preferably made of a GaN single crystal, an AlN single crystal, or a mixed crystal thereof, so that the substrate and the nitride object grown on the surface thereof are of the same type. be able to. As a result, it is possible to suppress the occurrence of dislocations in the nitrided object due to the difference in lattice constant and thermal expansion coefficient from the substrate generated at the initial growth interface of the nitrided object, and to produce a nitrided object with high crystal quality. it can.

  A method for manufacturing a nitride object according to the present embodiment will be described below.

  The method for manufacturing a nitride object according to the present embodiment is performed using a holder 1 that holds a substrate 3 for growing a nitride object. Here, examples of the nitride object include gallium nitride compound semiconductors such as GaN and AlGaN, and AlN. When the nitride body is a GaN single crystal, examples of the growth substrate 3 include sapphire, SiC, GaN single crystal, AlN single crystal, or a mixed crystal of GaN single crystal and AlN single crystal. Among these, GaN single crystals, AlN single crystals, or mixed crystals of GaN single crystals and AlN single crystals are preferably used. The growth substrate has a thickness of about 0.3 to 0.6 mm. The growth substrate has a diameter of 20 mm to 60 mm.

  The production of a specific nitride object is shown. In FIG. 1, S is a vapor phase growth apparatus, 1 is a holding body, 2 is a space, 3 is a growth substrate, 4a and 4b are heaters, 5a is a group V source gas, 5b is a group III source gas, and 6 is a carrier gas. , 8 indicates a quartz tube.

  The method for manufacturing a nitride object according to the present embodiment includes a step (1) of holding the growth substrate 3 by the holding body 1 and a step (2) of growing the nitride object on the held growth substrate 3. Is done.

(Process 1)
In step (1), only the outer peripheral side of the non-growth main surface (referred to as the main surface of the growth substrate 3 facing the holding body 1) on the side where the nitrided object is not grown out of the main surface of the growth substrate 3 is present. It should be in close contact with the holder 1.

  Although graphite is used for the holding body 1, since corrosive ammonia and hydrogen chloride are used, it is necessary to use the holding body 1 in which one or more selected from the group consisting of SiC, BN and TaC is coated on the graphite surface. preferable. Examples of the coating method include a CVD method and a sputtering method. Thereby, the corrosion resistance of the holder 1 is improved. PBN is preferable among BN. PBN means pyrogenic boron nitride (pyrolytic BN (p-BN)).

  The non-growth main surface of the growth substrate 3 is in close contact with the holder 1 only on the outer peripheral side of the non-growth main surface. As a result, the contact between the growth substrate 3 and the holding body 1 is limited to the outer peripheral side of the non-growth main surface, and the entire surface of the substrate excluding the outer peripheral portion has a uniform temperature, and crystal defects (dislocations) and It is possible to suppress the quality reproducibility of the grown nitride object and the cracking of the nitride object or the substrate. Here, when the non-growth main surface is circular, the outer peripheral portion of the non-growth main surface refers to a region of 1 to 6% from the outside of the non-growth surface with respect to the diameter of the circle.

  The holding body 1 preferably has a recess 9. By holding the growth substrate 3 on such a holder 1, the space 2 is formed, and since the region on the space 2 in the growth substrate 3 is not in contact with the holder 1, the temperature becomes uniform and crystal defects occur. In addition, it is possible to suppress the quality reproducibility of the grown nitride object and the cracking of the nitride object or the substrate.

  The depth of the recess 9 is 0.1 to 1 mm. For example, a GaN single crystal having an outer diameter of 52 mm is used as the growth substrate 3, and a recess 9 having a depth of 0.2 mm is provided in a cylindrical holder 1 having an outer diameter of 60 mm.

  As shown in FIG. 2, a step 7 for holding the growth substrate 3 is preferably provided on the inner wall surface of the recess 9 of the holder 1. For example, a GaN single crystal having an outer diameter of 52 mm is used as the growth substrate 3, and a recess 9 having a depth of 0.4 mm is provided in a cylindrical holder 1 having an outer diameter of 60 mm.

  As shown in FIG. 2C, the step width is 0.2 mm at the outer periphery as shown in FIG. 2A so that the depth 21 of the space 2 is 0.2 mm. 72 forms a ring-shaped step 7 of 2 mm. Then, as shown in FIG. 2C, the growth substrate 3 is mounted on the step 7 and fixed.

  Further, as another embodiment, as shown in FIG. 3A, it is preferable that a protrusion 10 for holding the inside 9 of the holding body 1 is provided. According to this, as shown in FIG. 3B, the structure is not limited to a structure in which the outer peripheral side of the non-growth main surface of the growth substrate 3 is brought into contact with the step 7 for providing the space 2. It is sufficient that three or more protrusions are provided, and thereby the same effect as that obtained when the step 7 is provided can be obtained.

  The protrusion 10 protrudes laterally from the inner wall surface of the holder 1. The tip of the protrusion preferably protrudes from the inner wall surface by 0.5 to 3 mm. For example, a GaN single crystal having an outer diameter of 52 mm is used as the growth substrate 3, and a recess 9 having a depth of 0.4 mm is provided in a cylindrical holder 1 having an outer diameter of 60 mm. Then, the protrusion 10 is set so that the depth of the space 2 is 0.2 mm.

(Process 2)
This is a step of growing a nitride object on the held growth substrate 3 by vapor phase growth. A hydride vapor phase growth method is preferably used as the method for manufacturing the nitride object of the present embodiment. Other examples of vapor phase growth include metal organic vapor phase epitaxy (MOVPE) and sublimation, but hydride vapor phase growth is possible because of its high growth rate, good quality, and the ease of producing nitrided bodies. The method is preferred.

  Actually, a method for producing a nitride object on the growth substrate 3 by vapor phase growth will be described below.

  As shown in FIG. 1, a growth substrate 3 is placed in a vapor phase growth apparatus 2 while being supported by a holder 1. Then, the heater 4b is heated to 700 ° C. or more, and the nitride gas is grown by introducing the carrier gas 6 together with the source gases 5a and 5b.

  The source gas 5a or 5b uses group V ammonia and group III trimethylgallium or gallium chloride, and the carrier gas 6 uses nitrogen, hydrogen, or a mixed gas thereof. When gallium chloride is used as a Group III raw material, gallium chloride is produced by filling metal gallium into a quartz container 11 and setting the heater 4a to about 800 ° C. to cause hydrogen chloride gas to flow and react. It is preferable to heat the holder 1 and the substrate 3 by setting the heater 4b to 700 to 1000 ° C. when forming a low-temperature buffer layer or the like and 1000 to 1300 ° C. when growing a single crystal. In this case, the low temperature buffer layer is formed with a thickness of 10 to 100 nm. The gas composition is the same even when the low temperature buffer layer is formed.

The source gas supplied into the vapor phase growth apparatus S for growing a nitride body is ammonia (NH ₃ ) gas, gallium chloride (GaCl) gas, hydrogen chloride (HCl) gas, or the like, and also nitrogen (N ₂ ) gas. , Hydrogen (H ₂ ) gas, silane (SiH ₄ ) gas, or the like may be included.

  When hydrogen chloride gas is used, hydrogen chloride is reacted with gallium metal at a temperature of about 800 ° C. in the vapor phase growth apparatus S, and supplied from the source gas 5b as gallium chloride (GaCl) gas. Ammonia gas is supplied from the source gas 5 a and mixed therewith and supplied to the growth substrate 3, thereby growing a GaN single crystal on the surface of the substrate 3. The flow rate ratio of ammonia gas to hydrogen chloride gas is such that the flow rate of ammonia gas is about 15 to 30 times the flow rate of hydrogen chloride gas. By setting it to about 15 to 30 times, it is possible to increase the growth rate of the GaN single crystal, and to suppress the growth of columnar crystals and the increase of dislocations in the GaN single crystal.

  The material of the vapor phase growth apparatus S is quartz or the like, and the shape of the vapor phase growth apparatus S is a cylindrical body such as a cylindrical shape or a rectangular tube shape.

  A GaN single crystal can be obtained by performing crystal growth of the GaN single crystal under the above conditions.

  In the above method, it is not specified whether the growth substrate 3 is a GaN substrate or a sapphire substrate. However, when a GaN substrate is used instead, it is performed under the same conditions except that the low-temperature buffer layer is not necessary.

  As described above, a nitride object made of GaN single crystal or the like suitable for epitaxial growth of a gallium nitride compound semiconductor applied to an optical element and an electronic element can be manufactured.

Note that the present invention is not limited to the above-described embodiment, and various modifications may be made without departing from the scope of the present invention. For example, a growth substrate 3 made of AlN single crystal is used, aluminum is used instead of gallium, high frequency induction heating coils are used as the heaters 4a and 4b, and ammonia (NH ₃ ) gas and hydrogen chloride (HCl) gas are mainly used. By supplying a raw material gas as a component, it is possible to grow an AlN single crystal. The same applies to the case where trimethylaluminum, an organic metal gas, is used instead of metal aluminum instead of hydrogen chloride, which is a raw material gas.

  As described above, the case where the growth surface of the GaN single crystal body on the growth substrate 3 is described has been described. However, the growth substrate 3 is fixed so as not to fall down even if the growth surface is held downward. In some cases, the same effect can be obtained. Further, the vapor phase growth apparatus S is not limited to the horizontal type as shown in FIG. 1, but can be applied to an apparatus for growing a nitride body in the vapor phase, and the source gas is also limited to the materials shown in the embodiments. First, it can be applied to a source gas capable of growing a nitride body.

  Although the example in which the space 2 is formed by placing the growth substrate 3 is shown as the holder 1 used in the method for growing a nitride object according to the present invention, the present invention is limited to forming the space 2. Instead, only the outer peripheral side of the non-growth main surface of the main surface of the growth substrate 3 on the side on which the nitrided body is not grown needs to be in close contact with the holder.

  Examples of the method for manufacturing a nitride object will be described below.

  In this example, a GaN single crystal was manufactured using the manufacturing apparatus of FIG. 1, and the obtained GaN single crystal was evaluated (Examples 1-2 and Comparative Examples 1-2).

  First, as the growth substrate 3, a disk-shaped single crystal growth substrate having a diameter of 52 mm and a thickness of 0.4 mm was used. The growth substrate 3 was fixed to a holding body 1 installed in a quartz tube 8 which is a vapor phase growth apparatus.

  The growth substrate 3 of Example 1 and Comparative Example 1 was made of sapphire, and the growth substrate 3 of Example 2 and Comparative Example 2 was made of GaN.

  The holding body 1 in Examples 1-2 and Comparative Examples 1-2 showed an outer diameter of 60 mm and a thickness of 20 mm. A commercially available SiC-coated graphite was used.

  As shown in FIG. 2 (a), both the holding body 1 of Example 1 and Example 2 are attached to the holding body 1 from the holding body 1 to the concave portion 9 (depth 0.5 mm) and the growth substrate 3. A step 7 (depth 0.3 mm) was provided.

  On the other hand, neither the recessed part 9 nor the level | step difference 7 was provided in the holding body of Comparative Example 1 and Comparative Example 2. 4A shows the holding body 81 of Comparative Examples 1 and 2, and FIG. 4B shows the holding body 81 holding the growth substrate 83 of Comparative Examples 1 and 2.

  Next, the group V source gas 5a and the group III source gas 5b were simultaneously supplied to the growth substrate 3. In addition, as the V group source gas 5a, ammonia gas was used and supplied in an amount of 750 cc / min. Further, as the group III source gas 5b, hydrogen chloride gas is supplied in an amount of 30 cc / min, and gallium chloride is generated by heating the metal gallium filled in the quartz container 11 while controlling the heater 4a at 800 ° C. And supplied. At this time, 50% of nitrogen and hydrogen were supplied as carrier gas 6 in a total amount of 5000 cc / min.

  Further, the temperature of the growth substrate 3 was controlled to 1000 ° C. by the heater 4b. Thereby, the growth of the GaN single crystal was started while rotating the holder 1 at 20 rpm. In Example 1 and Comparative Example 1, GaN growth was started after 50 nm of the buffer layer was grown at a low temperature of 500 ° C. to 700 ° C. before the growth was started.

  After growing the GaN single crystal, the quartz tube 8 was opened, and the GaN single crystal having a total thickness of 1 mm was taken out from the vapor phase growth apparatus S. The growth substrate 3 was removed by grinding 0.5 mm using a diamond grindstone. The remaining GaN single crystal is ground with a diamond grindstone to an outer diameter of 50.8 mm, then lapped with # 800 diamond abrasive grains, and then mirror-finished with a colloidal silica abrasive. It was. As described above, GaN single crystals of Examples 1 and 2 and Comparative Examples 1 and 2 having an outer diameter of 50.8 mm and a thickness of 0.4 mm and polished on both sides were produced.

The surfaces of the GaN single crystals of Examples 1 and 2 and Comparative Examples 1 and 2 were observed with X-ray topographic images. The average dislocation density (cm ⁻² ), dislocation density in-plane variation (cm ⁻² ), and dislocation density lot The variation σ (cm ⁻² ) and the crack occurrence rate (%) were derived.

The average dislocation density (cm ⁻² ) was derived by counting the number of dislocation lines in the X-ray topographic image and converting it to a density per unit area.

Dislocation density in-plane variation (cm ^-2 ) is calculated by measuring the dislocation density derived from the above X-ray topographic image at five points in the diameter direction passing through the center in the crystal growth plane and calculating the standard deviation. Was derived by

Furthermore, dislocation density lot-to-lot variation σ (cm ⁻² ) is calculated by calculating the dislocation density from the X-ray topographic image of the central part of the crystals of five different growth lots grown under the same conditions, and calculating the standard deviation. Was derived by

  The crack generation rate (%) was derived by visually inspecting crystals of 10 different growth lots grown under the same conditions and confirming the presence or absence of cracks.

  The results are shown in Table 1.

  From Table 1, the GaN single crystal substrate of Example 1 obtained using the holding body 1 provided with the space 2 between the growth substrate 3 was obtained using the holding body 1 not provided with the space 2. It was found that the dislocation density is lower than that of the GaN single crystal substrate of Comparative Example 1 and is superior. Moreover, the same thing was understood also about Example 2 compared with Comparative Example 2.

  Further, in Example 1, dislocation density in-plane variation and dislocation density lot-to-lot variation were lower than in Comparative Example 1, and it was confirmed that the dislocation density decreased, in-plane variation decreased, and lot-to-lot variation decreased. The result similar to Example 1 was obtained also about Example 2 compared with the comparative example.

It is sectional drawing of the vapor phase growth apparatus S used for the manufacturing method of the nitride body of this Embodiment. (A) is sectional drawing of embodiment of the holding body 1, (b) is a perspective view of one embodiment of the holding body 1, (c) is sectional drawing of embodiment of the holding body 1 holding the growth substrate 3. is there. (A) is sectional drawing of one Embodiment of the holding body 1, (b) is a top view of the holding body 1, (c) is sectional drawing of one Embodiment of the holding body 1 holding the growth substrate 3. FIG. . (A) is sectional drawing of one Embodiment of the holding body 81 of a comparative example, (b) is sectional drawing of 1 embodiment of the holding body 81 holding the growth substrate 83 of a comparative example.

Explanation of symbols

S: Vapor growth apparatus 1, 81: Holding body 2: Space 3, 83: Growth substrate 4a, 4b: Heater 5a: Group V source gas 5b: Group III source gas 6: Carrier gas 7: Step 8: Quartz tube 9: Recess 10: Protrusion 11: Quartz container 21: Depth of space 2

Claims (7)

A method of manufacturing a nitride object using a holder for holding a growth substrate for growing the nitride object,
(1) a step of holding the growth substrate such that only the outer peripheral portion of the non-growth side main surface that does not grow a nitride body among the main surfaces of the growth substrate is in close contact with the holder;
(2) growing a nitride body on the held substrate by vapor deposition;
A method for manufacturing a nitride object comprising:   The method for producing a nitride object according to claim 1, wherein the vapor phase growth method in the step (2) is a hydride vapor phase growth method.   The method for manufacturing a nitride object according to claim 1 or 2, wherein the nitride object is composed of a GaN single crystal, an AlN single crystal, or a mixed crystal thereof.   The method for manufacturing a nitride object according to any one of claims 1 to 3, wherein the holding body has a recess, and the growth substrate is provided so as to cover the recess.   The method for manufacturing a nitride object according to claim 4, wherein a protrusion for holding the growth substrate is provided on an inner wall surface of the concave portion of the holding body.   The method for manufacturing a nitride object according to claim 4, wherein a step for holding the growth substrate is provided on an inner wall surface of the concave portion of the holding body. The method for manufacturing a nitride object according to any one of claims 1 to 6, wherein the holding body is graphite coated with at least one selected from the group consisting of SiC, BN, and TaC.