JP2011138895A - Method of manufacturing crystal, and method of manufacturing light-emitting element - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of manufacturing a crystal which uniformizes the thickness of In<SB>x</SB>Al<SB>y</SB>Ga<SB>(1-x-y)</SB>N crystal (0≤x<1, 0≤y<1, 0<x+y≤1), and improving the growth speed, and to provide a method of manufacturing a light-emitting element. <P>SOLUTION: In a process of growing an InAlGaN crystal, a first source gas supply unit 11a, which is positioned at a side near a main surface, in a direction vertical to a main surface 20a of a substrate 20, supplies a first source gas G1 including a group V element material onto the main surface 20a of the substrate 20; a second gas supply unit 11b, which is positioned at a side farther from the main surface 20a than the first gas supply unit 11a in the direction vertical to the main surface 20a of the substrate 20, supplies a second source gas G2 including an organic metal, namely, a raw material of a plurality of group III elements, onto the main surface 20a of the substrate 20; and the flow velocity of the first source gas G1 is not less than 0.5 and not more than 0.8 of that of the second source gas G2; and a pressure inside a reaction vessel 3 is set to not less than 20 kPa and less than 60 kPa. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

The present invention relates to a method of manufacturing a manufacturing method and light-emitting element of the crystal, and more specifically, within the reaction vessel _{In x Al y Ga (1-} xy) N ( indium aluminum gallium nitride) crystal (0 ≦ x <1 , 0 ≦ y <1, 0 <x + y ≦ 1), and a method for manufacturing a light-emitting element including the crystal.

Metal organic chemical vapor deposition (MOCVD: Metal Organic Chemical Vapor deposition ) method, typical _{In x Al y Ga (1-} xy) N crystal is one of the production method (hereinafter, also referred to as InAlGaN crystal), for example, In this method, a group III organic metal is vaporized, thermally decomposed on the substrate surface, and reacted with a group V gas to form a film. Since this method is excellent in productivity, it is widely used as a film forming technique when manufacturing a semiconductor device.

  An MOCVD apparatus used for the MOCVD method includes a chamber, a susceptor disposed in the chamber, and a passage for flowing a reaction gas to the surface of the substrate. In the MOCVD apparatus, a substrate is placed on a susceptor, the substrate is heated to an appropriate temperature, and an organic metal gas is introduced into the substrate surface through a passage to form a film. Here, in order to make the thickness of the film to be formed uniform, the MOCVD apparatus is required to flow the reaction gas uniformly along the substrate surface. In the MOCVD apparatus, various passage shapes have been proposed in order to flow the reaction gas uniformly along the substrate surface.

As a conventional MOCVD apparatus, for example, Japanese Unexamined Patent Application Publication No. 2008-16609 (Patent Document 1) discloses a MOCVD apparatus including a susceptor for placing a substrate and a passage for introducing a reaction gas into the substrate. ing. The passage is a horizontal three-layer flow system and extends in parallel to the mounting surface of the susceptor. A purge gas such as hydrogen (H ₂ ) gas or nitrogen (N ₂ ) gas is used at a position farthest from the substrate in the passage, and trimethyl gallium (TMG), trimethyl indium (TMI), and trimethyl aluminum are positioned closer to the substrate. A mixed gas of an organometallic gas containing a group III element such as (TMA) and a carrier gas such as H ₂ gas or N ₂ gas is used, and ammonia (at a position closer to the substrate, that is, a position closest to the substrate). A mixed gas of a gas containing a group V element such as NH ₃ ) and a carrier gas such as H ₂ gas or N ₂ gas is used. When these gases are introduced into the MOCVD apparatus, the reaction gases mixed with each other are introduced and diffused parallel to the mounting surface in the susceptor and heated by the susceptor. The organometallic gas contained in the mixed gas is decomposed by heating to become an intermediate reactant, and reacts with NH ₃ gas to become InAlGaN crystals. As a result, an InAlGaN crystal is formed on the surface of the substrate.

JP 2008-16609 A

  However, in the MOCVD apparatus disclosed in Patent Document 1, the conditions of the reaction gas supplied on the upstream side and the downstream side of the susceptor are different. For this reason, the problem that the thickness of the crystal manufactured is not uniform has arisen.

_{Further, In x Al y Ga (1} -xy) N (0 ≦ x <1,0 ≦ y <1,0 <x + y ≦ 1) to produce the crystal, TMG, 2 kinds of TMI and TMA Or three types need to be used. For this reason, there has been a problem that the growth rate of the produced crystal is slow under the conditions for producing the InAlGaN crystal.

  Accordingly, an object of the present invention is to provide a method for manufacturing a crystal and a method for manufacturing a light-emitting element, in which the thickness of the InAlGaN crystal is made uniform and the growth rate is improved.

  As a result of earnest research on the cause of the non-uniform thickness of the InAlGaN crystal, the present inventor found that the organometallic gas of the group III material hardly diffuses in the source gas layer of the group V material on the upstream side of the susceptor. We found out that it was caused by difficulty in reaching the substrate.

  In addition, as a result of intensive studies on the cause of the slow growth rate of InAlGaN crystals, the present inventor has produced two or more of TMG, TMI and TMA, for example, to produce a ternary or quaternary InAlGaN crystal. Although it is necessary to use three types, it has been found that TMG, TMI and TMA are easily vapor-phase reacted with each other under the conditions for producing InAlGaN crystals.

Therefore, the production method of the crystal of the present invention, a method of manufacturing the _{In x Al y Ga (1-} xy) N crystal (0 ≦ x <1,0 ≦ y <1,0 <x + y ≦ 1) in a reaction vessel And the following steps are provided. A substrate having a main surface is prepared. While supplying the raw material gas in a direction along the main surface of the substrate, growing _{In x Al y Ga (1-} xy) N crystal on the main surface of the substrate by heating the substrate. The _{In x Al y Ga (1-} xy) growing a N crystals, containing raw materials of Group V element from the first gas supply portion located closer to the main surface in a direction perpendicular to the main surface of the substrate first A source gas is supplied onto the main surface of the substrate, and a plurality of III groups are supplied from the second gas supply unit located on the side farther from the main surface than the first gas supply unit in the direction perpendicular to the main surface of the substrate. A second source gas containing an organic metal that is an elemental raw material is supplied onto the main surface of the substrate, and the flow rate of the first source gas is set to 0.5 to 0.8 of the flow rate of the second source gas, The pressure is set to 20 kPa or more and less than 60 kPa.

  According to the method for producing a crystal of the present invention, by setting the flow rate of the first source gas that is the source of the group V element to 0.5 to 0.8 of the second source gas that is the source of the group III element, It was found that the second source gas diffuses the first source gas and reaches the upstream side of the substrate. For this reason, for example, by rotating the susceptor, the first and second source gases can be made to flow uniformly along the main surface of the substrate, so that the thickness of the crystal to be manufactured can be made uniform.

  Further, it has been found that by making the pressure in the reaction vessel 20 MPa or more and less than 60 kPa, it is possible to suppress a plurality of Group III element source gases from undergoing a gas phase reaction with each other. For this reason, since the group III element source gas can reach the main surface of the substrate, the growth rate of the InAlGaN crystal containing two or three group III elements can be improved.

In the foregoing method of producing a crystal in the _{In x Al y Ga (1-} xy) growing a N crystals, the flow rate of the first source gas below 0.18 m / s or more 0.35 m / s.

  By reducing the flow rate of the first source gas containing the group V element as described above, the second source gas can more easily diffuse the first source gas. For this reason, the crystal | crystallization which has more uniform thickness can be manufactured.

The method for manufacturing a light emitting device of the present invention includes a step of growing an In _x Al _y Ga _(1-xy) N crystal on a main surface of a substrate by the above-described crystal manufacturing method, and In _x Al _y Ga _(1-xy). Forming an electrode on the N crystal.

  According to the method for manufacturing a light-emitting element of the present invention, since the InAlGaN crystal is manufactured by the above-described crystal manufacturing method, the light-emitting element can be manufactured with a uniform thickness and an improved growth rate.

  According to the crystal manufacturing method and the light emitting element manufacturing method of the present invention, the thickness of the InAlGaN crystal can be made uniform and the growth rate can be improved.

It is sectional drawing which shows schematically the epitaxial film in Embodiment 1 of this invention. It is sectional drawing which shows roughly the manufacturing apparatus of the crystal | crystallization in Embodiment 1 of this invention. It is sectional drawing which shows roughly the epitaxial film in Embodiment 2 of this invention. It is sectional drawing which shows schematically the light emitting element in Embodiment 3 of this invention. It is a figure which shows the relationship between the distance from the center of a susceptor in Example 1, and a growth rate. FIG. 3 is a diagram showing a relationship between a distance from the center of the susceptor and an In composition ratio in Example 1. It is a figure which shows the relationship between the distance from the center of a susceptor in Example 1, and the composition ratio of Al. It is a figure which shows the relationship between the distance from the center of the susceptor in Example 5 of this invention of Example 2, and a growth rate. It is a figure which shows the relationship between the distance from the center of the susceptor in Example 5 of this invention of Example 2, and the composition ratio of In. It is a figure which shows the relationship between the distance from the center of a susceptor in Example 5 of this invention of Example 2, and the composition ratio of Al.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the following drawings, the same or corresponding parts are denoted by the same reference numerals, and description thereof will not be repeated.

(Embodiment 1)
With reference to FIG. 1, the epitaxial film in the present embodiment will be described. As shown in FIG. 1, the epitaxial film 25 includes a substrate 20 having a main surface 20a, a buffer layer 21 formed on the main surface 20a of the substrate 20, and an InAlGaN layer 22 formed on the buffer layer 21. I have.

The substrate 20 is, for example, a sapphire (Al ₂ O ₃ ) substrate, a gallium nitride (GaN) substrate, or the like. The substrate 20 has a main surface 20a of, for example, 2 inches or more.

  The buffer layer 21 is, for example, a GaN layer. Note that the buffer layer 21 may be omitted.

The InAlGaN layer 22 is an In _x Al _y Ga _(1-xy) N crystal (0 ≦ x <1, 0 ≦ y <1, 0 <x + y ≦ 1). That, InAlGaN layer 22, In _x Al _y N crystal (0 <x <1,0 <y <1, x + y = 1), In x Ga (1-x) N crystal (0 <x <1), and A ternary crystal of Al _y Ga _(1-y) N crystal (0 <y <1) or an In _x Al _y Ga _(1-xy) N crystal (0 <x <1, 0 <y <1, Any of quaternary crystals of 0 <x + y <1).

  The variation in the thickness of the InAlGaN layer 22 is within 6%, preferably within 4%, and more preferably within 2%. When the variation in thickness is within 6%, if this InAlGaN layer 22 is used as a cladding layer of a light emitting element, the distribution of light confinement can be made uniform, so that the yield of light emitting elements such as a semiconductor laser that can sufficiently confine light is obtained. Can be improved. If it is within 4%, the yield of the light emitting elements can be further improved, and if it is within 2%, the yield of the light emitting elements can be further improved.

  Here, the variation in thickness means that the largest thickness, the smallest thickness, and the median value of thicknesses are measured in the InAlGaN layer 22, and the variation is {largest thickness−smallest thickness) / median value} × 100. The value of This can also be measured by measuring the maximum value, the minimum value, and the median value of the growth rate and determining the distribution from the median value when the InAlGaN layer 22 is grown. The median is a value located at the center when, for example, five points are measured.

  The InAlGaN layer 22 may be a ternary crystal or a quaternary crystal, but is preferably a quaternary crystal. In the case of a quaternary crystal, the composition ratio x of indium (In) is preferably 1% or more and 4% or less, and the composition ratio y of aluminum (Al) is preferably 10% or more and 30% or less. In this case, the InAlGaN layer 22 can be suitably used as a cladding layer.

  Further, the quaternary InAlGaN crystal can provide a lattice constant d (InAlGaN) closer to the lattice constant d (GaN) of GaN than the lattice constant d (AlGaN) of AlGaN having the same band gap as that of InAlGaN. The quaternary InAlGaN crystal can provide a lattice constant d (InAlGaN) closer to the lattice constant d (GaN) of GaN than the lattice constant d (AlGaN) of AlGaN having the same refractive index as that of InAlGaN.

  In the InAlGaN layer 22, the diameter of the surface in the direction parallel to the main surface 20a of the substrate 20 is, for example, 2 inches or more.

  Next, with reference to FIG. 2, the crystal manufacturing apparatus in the present embodiment will be described. In this embodiment, an MOCVD apparatus is used as a crystal manufacturing apparatus.

  As shown in FIG. 2, the MOCVD apparatus 1 includes a reaction vessel 3, a susceptor 5, a heater 9, and a source gas supply unit 11. A susceptor 5, a heater 9, and a source gas supply unit 11 are disposed in the reaction vessel 3. The source gas supply unit 11 extends in the horizontal direction in FIG. 2, and the mounting surface (upper surface in FIG. 2) of the susceptor 5 faces inside the source gas supply unit 11.

  The susceptor 5 is disposed inside the reaction vessel 3. The susceptor 5 has a disk shape and is disposed on a heater 9 having a disk shape. A rotating shaft 13 serving as a rotating mechanism is attached to the lower part of the susceptor 5, so that the susceptor 5 can rotate with the mounting surface facing the inside of the source gas supply unit 11. A plurality of grooves 7 having a circular shape when viewed in plan are formed on the mounting surface of the susceptor 5. Each of the substrates 20 having the main surface 20a is placed in each of the grooves 7, whereby the substrate 20 is heated. For example, seven grooves 7 are formed on the mounting surface of the susceptor 5, and a circular substrate 20 is mounted in each of these grooves 7. The heater 9 heats the substrate 20 via the susceptor 5.

  The source gas supply unit 11 supplies the reaction vessel 3 with the first and second source gases G1 and G2 and the gas G3 as a subflow from the direction along the main surface 20a of the substrate 20. That is, the source gas supply unit 11 is a passage for flowing a reaction gas composed of the first and second source gases G1, G2 and the gas G3 to the main surface 20a of the substrate 20. The source gas supply unit 11 of the present embodiment extends parallel to the mounting surface of the susceptor 5 and is rectangular when viewed in a plane perpendicular to the source gas flow direction (the direction from the left side to the right side in FIG. 2). The cross-sectional shape is as follows. The source gas supply unit 11 is a horizontal three-layer flow system, and the first gas supply unit 11a, the second gas supply unit 11b, and the third gas supply unit 11c are arranged on the upstream side (left side in FIG. 2). Including.

  The first gas supply unit 11 a is located on the side close to the main surface 20 a in the direction D perpendicular to the main surface 20 a of the substrate 20. The second gas supply unit 11b is located on the side farther from the main surface 20a than the first gas supply unit 11a in the direction D perpendicular to the main surface 20a of the substrate 20. The third gas supply unit 11 c is located on the side farther from the main surface 20 a than the second gas supply unit 11 b in the direction D perpendicular to the main surface 20 a of the substrate 20. That is, in the direction D perpendicular to the mounting surface of the susceptor 5, the first gas supply unit 11a, the second gas supply unit 11b, and the third gas supply unit 11c are closer to the mounting surface of the susceptor 5 in this order.

  The positions of the outlets of the first and second source gases G1, G2, and gas G3 of the first to third gas supply units 11a to 11c are the directions along the main surface 20a of the substrate 20, that is, the first and second As shown in FIG. 2, the two raw material gases G1, G2 and the gas G3 may be different or the same in the flow direction.

The first gas supply unit 11 a supplies the first source gas G <b> 1 containing the group V element source to the reaction vessel 3. As the first source gas G1, for example, a mixed gas of a gas containing a group V element such as NH ₃ gas and a carrier gas such as H ₂ gas or N ₂ gas can be used.

The second gas supply unit 11b supplies a second source gas G2 containing a plurality of organic metals, which are group III element sources, to the reaction vessel. As the second source gas G2, a mixed gas of two or more kinds of organometallic gases containing a group III element such as TMG, TMI, or TMA and a carrier gas such as H ₂ gas or N ₂ gas can be used. In addition, as a gallium (Ga) source, an Al source, and an In source, other materials (for example, triethylgallium (TEG), triethylamine (TEA), triethylindium (TEI)) or the like can be used instead of or in addition to the above materials. It may be used.

The 3rd gas supply part 11c supplies gas G3 which does not contain a raw material. As the gas G3, a purge gas that suppresses the reaction between the first and second source gases G1 and G2 is preferably used. As the gas G3, a carrier gas such as H ₂ gas or N ₂ gas can be used.

  In the MOCVD apparatus 1, the third gas supply unit 11c may be omitted. In this case, crystals are deposited by supplying the source gases G1 and G2 to the surface (upper wall in FIG. 2) facing the main surface 20a (mounting surface of the susceptor 5) of the substrate 20 in the reaction vessel 3. It is preferable that a means such as a purge mechanism for suppressing the above is provided.

  Further, in the MOCVD apparatus 1 of the present embodiment, the susceptor 5 is a face-up type arranged below the reaction vessel, but is not particularly limited thereto. The MOCVD apparatus may be a face-down type in which the susceptor 5 is disposed above the reaction vessel.

  Next, with reference to FIG. 1 and FIG. 2, a method for manufacturing a crystal in the present embodiment will be described. In the present embodiment, the epitaxial film 25 shown in FIG. 1 is manufactured by MOCVD using the MOCVD apparatus 1 shown in FIG.

  First, the substrate 20 having the main surface 20a is prepared. The substrate 20 to be prepared is not particularly limited. For example, a sapphire substrate, a GaN substrate, or the like can be used. In this step, for example, in the MOCVD apparatus 1, the substrate 20 is placed on the placement surface of the susceptor 5, and the substrate 20 is held by the susceptor 5.

  Next, the buffer layer 21 is grown on the main surface 20 a of the substrate 20 by heating the substrate 20 while supplying the source gas in a direction along the main surface 20 a of the substrate 20.

  In the step of growing the buffer layer 21, the first source gas G1 containing the group V element source from the first gas supply unit 11a located on the side close to the main surface 20a in the direction D perpendicular to the main surface 20a of the substrate 20. On the main surface 20a of the substrate 20, and from the second gas supply unit 11b located on the side farther from the main surface 20a than the first gas supply unit 11a in the direction D perpendicular to the main surface 20a of the substrate 20. , A second source gas G2 containing a group III element is supplied onto the main surface 20a of the substrate 20. Further, a gas G3 that does not include a raw material is supplied from a third gas supply unit 11c that is located farther from the main surface 20a than the second gas supply unit 11b in the direction D perpendicular to the main surface 20a of the substrate 20.

  Specifically, in the MOCVD apparatus 1, the susceptor 5 is heated by the heater 9 while the substrate 20 is placed on the placement surface of the susceptor 5, and the susceptor 5 is rotated by the rotation shaft 13. And gas which does not comprise source gas from 1st and 2nd source gas G1 and G2 which constitute source gas from each of the 1st and 2nd gas supply parts 11a and 11b, and the 3rd gas supply part 11c G3 is introduced. The source gas flows from the upstream side to the downstream side (right direction in FIG. 2). For the first and second source gases G1 and G2, for example, the materials described above can be used. When each of these source gases G1, G2 and G3 is introduced into each of the first to third gas supply parts 11a to 11c, they are introduced and diffused in parallel to the mounting surface on the susceptor 5 and heated. The susceptor 5 is heated. The gas having a group III element contained in the second source gas G2 is decomposed by heating to become an intermediate reactant, and similarly reacted with the intermediate reactant of the gas having a group V element contained in the first source gas G1 decomposed by heating. GaN crystal. As a result, a GaN crystal is formed on the main surface 20 a of the substrate 20.

  Next, an InAlGaN crystal (on the buffer layer 21 in the present embodiment) is heated on the substrate 20 by supplying the source gas in a direction along the main surface 20a of the substrate 20 to heat the substrate 20. In this embodiment, an InAlGaN layer 22) is grown. In the step of growing the InAlGaN layer 22, the flow rate of the first source gas G1 is set to 0.5 or more and 0.8 or less of the flow rate of the second source gas G2, and the pressure in the reaction vessel 3 is set to 20 kPa or more and less than 60 kPa.

  Specifically, the reaction vessel 3 is supplied from the first and second gas supply units 11a and 11b so that the flow rate of the first raw material gas G1 is 0.5 to 0.8 of the flow rate of the second raw material gas G2. The flow rates of the first and second source gases G1 and G2 supplied to are adjusted. In addition, the pressure in the reaction vessel 3 is adjusted by introducing, purging, or the like the gas G3 so that the pressure in the reaction vessel 3 is 20 kPa or more and less than 60 kPa.

  By setting the flow rate of the first source gas G1 to 0.5 or more of the flow rate of the second source gas G2, a high growth rate can be maintained and the surface morphology of the grown InAlGaN layer 22 can be improved. By setting the flow rate of the first source gas G1 to 0.8 or less of the flow rate of the second source gas G2, the second source gas G2 containing a plurality of organometallic gases that are a source of a plurality of group III elements becomes a group V The first raw material gas G <b> 1 is easily diffused and reaches the upstream side of the substrate 20. For this reason, the first and second source gases G1 and G2 can be made to flow uniformly along the main surface 20a of the substrate 20 by rotating the susceptor 5 by the rotating shaft 13, so that the main surface 20a of the substrate 20 is flown. Since the growth rate in the vertical direction can be made uniform, the thickness of the manufactured InAlGaN layer 22 can be made uniform.

  By setting the pressure in the reaction vessel to 20 kPa or more and less than 60 kPa, it is possible to suppress a gas phase reaction between two or more kinds of organometallic gases that are the raw materials of the group III element in the second raw material gas G2. For this reason, since the group III element source gas can reach the main surface of the substrate, the growth rate of the InAlGaN crystal containing two or three group III elements can be improved.

  In the step of growing the InAlGaN layer 22, the flow rate of the first source gas G1 is preferably set to 0.18 m / s or more and 0.35 m / s or less. When the flow rate of the first source gas G1 is reduced in this way, the second source gas G2 becomes easier to diffuse the first source gas G1, and thus the growth rate distribution of the InAlGaN layer 22 can be improved uniformly. For this reason, the InAlGaN layer 22 having a more uniform thickness can be manufactured.

  In the step of growing the InAlGaN layer 22, the InAlGaN layer 22 is preferably grown at 870 ° C. or higher and 940 ° C. or lower. When the temperature is 870 ° C. or higher, the morphology of the InAlGaN layer 22 can be improved. When the temperature is 940 ° C. or lower, the incorporation of In is good when the InAlGaN layer 22 containing In is grown.

  In this step, an InAlGaN layer 22 is grown on the buffer layer 21 as in the step of growing the buffer layer 21. Specifically, for example, the above-described materials can be used for the first and second source gases G1 and G2. When each of these source gases G1, G2 and G3 is introduced into each of the first to third gas supply parts 11a to 11c, they are introduced and diffused in parallel to the mounting surface on the susceptor 5 and heated. The susceptor 5 is heated. The gas having a plurality of group III elements contained in the second source gas G2 is decomposed by heating to become an intermediate reactant, and the intermediate reactant of the gas having group V elements contained in the first source gas G1 decomposed by heating in the same manner. Reacts with InAlGaN crystals. As a result, an InAlGaN layer 22 made of InAlGaN crystal is formed on the buffer layer 21.

  In the step of growing the buffer layer 21 and the step of growing the InAlGaN layer 22, the dopant is supplied by supplying the dopant gas to the main surface 20a of the substrate 20 simultaneously with the first and second source gases G1 and G2. The containing layer can also be grown.

  By performing the above steps, the epitaxial film 25 shown in FIG. 1 can be manufactured. Although the manufacturing method of the epitaxial film 25 including the buffer layer 21 has been described in the present embodiment, the buffer layer 21 may be omitted. Further, when the step of growing the buffer layer 21 is performed, the buffer layer 21 may be grown in the same manner as the step of growing the InAlGaN layer 22.

As described above, according to the manufacturing method of the crystal in the present embodiment, the reaction vessel _{3 In x Al y Ga (1} -xy) N crystal (0 ≦ x <1,0 ≦ y <1,0 <X + y ≦ 1) is a method of manufacturing a substrate 20 having a main surface 20a, and heating the substrate 20 while supplying a source gas in a direction along the main surface 20a of the substrate 20. A step of growing an In _x Al _y Ga _(1-xy) N crystal (InAlGaN layer 22) on the main surface 20a of the substrate 20, and a step of growing an In _x Al _y Ga _(1-xy) N crystal The first source gas G1 containing the group V element source material is supplied onto the main surface 20a of the substrate 20 from the first gas supply unit 11a located on the side close to the main surface 20a in the direction perpendicular to the main surface 20a of the substrate 20. Supply direction and a direction perpendicular to the main surface 20a of the substrate 20 In the substrate 20, the second source gas G2 containing an organic metal which is a source of a plurality of group III elements is supplied from the second gas supply unit 11b located farther from the main surface 20a than the first gas supply unit 11a. Supplyed onto the main surface 20a, the flow rate of the first source gas G1 is set to 0.5 to 0.8 of the flow rate of the second source gas G2, and the pressure in the reaction vessel 3 is set to 20 kPa and less than 60 kPa.

  According to the crystal manufacturing method of the present embodiment, the flow rate of the first source gas G1 that is the source of the group V element is set to 0.5 to 0.8 of the second source gas G2 that is the source of the group III element. As a result, it was found that the second source gas G2 diffuses the first source gas G1 and reaches the upstream side of the substrate 20. For this reason, by rotating the susceptor 5, a crystal having a uniform thickness can be manufactured.

  Further, it has been found that by making the pressure in the reaction vessel 20 MPa or more and less than 60 kPa, it is possible to suppress the gas phase reaction of the two or three group III element source gases. For this reason, since the second source gas G2 that is a group III element source gas can reach the main surface 20a of the substrate 20, the growth rate of the InAlGaN crystal containing two or three group III elements can be improved. . In particular, in the conventional large reaction vessel, the growth rate was significantly reduced on the downstream side, but in this embodiment, the growth rate is effectively reduced by controlling the pressure in the reaction vessel 3 even in the large reaction vessel. Can be suppressed.

  Therefore, according to the crystal manufacturing method of the present embodiment, it is possible to manufacture a crystal that makes the thickness of the InAlGaN crystal uniform and improves the growth rate.

(Embodiment 2)
With reference to FIG. 3, the epitaxial film 30 in the present embodiment will be described. The epitaxial film 30 includes a substrate 20, an n-type buffer layer 32, an n-type cladding layer 33, undoped light guide layers 34 and 36, an active layer 35, a p-type electron blocking layer 37, and a p-type cladding layer 38. And a p-type contact layer 39.

  The substrate 20 is, for example, a GaN substrate. N-type buffer layer 32 is formed on main surface 20a of substrate 20 and is, for example, an n-type GaN layer. The n-type cladding layer 33 is formed on the n-type buffer layer 32 and is, for example, an n-type InAlGaN layer. The undoped light guide layer 34 is formed on the n-type cladding layer 33 and is, for example, an InGaN layer. The active layer 35 is formed on the undoped light guide layer 34 and has a multiple quantum well structure including, for example, a well layer made of InGaN and a barrier layer made of GaN. The active layer 35 may be made of a single semiconductor material. The undoped light guide layer 36 is formed on the active layer 35 and is made of, for example, InGaN. The p-type electron block layer 37 is formed on the undoped light guide layer 36 and is made of, for example, AlGaN. The p-type cladding layer 38 is formed on the p-type electron block layer 37 and is, for example, p-type AlGaN. The p-type contact layer 39 is formed on the p-type cladding layer 38 and is, for example, p-type GaN.

  In the present embodiment, the n-type cladding layer 33, the undoped light guide layer 34, the well layer, the p-type electron blocking layer 37, and the p-type cladding layer 38 are the same as the InAlGaN layer 22 of the first embodiment.

  Then, the manufacturing method of the epitaxial film 30 in this Embodiment is demonstrated. Epitaxial film 30 in the present embodiment is manufactured using MOCVD apparatus 1 described in the first embodiment.

  Specifically, first, as in the first embodiment, a substrate 20 having a main surface 20a is prepared.

  Next, on the substrate 20, an n-type buffer layer 32, an n-type cladding layer 33, an undoped light guide layer 34, an active layer 35, an undoped light guide layer 36, a p-type electron blocking layer 37, p A mold cladding layer 38 and a p-type contact layer 39 are grown in this order. In this step, for example, in the MOCVD apparatus 1 shown in FIG. 2, each layer is grown by changing the type of the second source gas G2.

  The step of growing the InAlGaN crystal in each layer is performed in the same manner as the step of growing the InAlGaN layer 22 of the first embodiment. That is, in the present embodiment, when the n-type cladding layer 33, the undoped light guide layer 34, the well layer, the p-type electron blocking layer 37, and the p-type cladding layer 38 are grown, the flow rate of the first source gas G1 is set. The flow rate of the second source gas G2 is set to 0.5 or more and 0.8 or less, and the pressure in the reaction vessel is set to 20 kPa or more and less than 60 kPa. Further, when a binary layer such as GaN is grown, it may be performed in the same manner as the step of growing the InAlGaN layer 22 of the first embodiment.

  By performing the above steps, the epitaxial film 30 shown in FIG. 3 can be formed.

  As described above, according to the method of manufacturing the epitaxial film 30 including the InAlGaN crystal of the present embodiment, the flow rate of the first source gas G1 that is the source of the group V element is set to the second source that is the source of the group III element. The InAlGaN crystal is grown with the gas G2 being 0.5 to 0.8. Therefore, since the second source gas G2 diffuses the first source gas G1 and reaches the upstream side of the substrate 20, for example, by rotating the susceptor, the thickness of each layer constituting the epitaxial film 30 is made uniform. Can be.

  Moreover, the pressure in the reaction vessel is set to 20 kPa or more and less than 60 kPa. Therefore, it is possible to suppress the gas phase reaction between the two or three group III element source gases in the second source gas G2, so that the group III element source gas reaches the main surface 20a of the substrate 20. Therefore, the growth rate of each layer of InAlGaN crystal containing two or three group III elements can be improved. Therefore, the growth rate of the epitaxial film 30 can be improved.

(Embodiment 3)
With reference to FIG. 4, a semiconductor laser 40 as an example of a light emitting element in the present embodiment will be described. The semiconductor laser 40 includes the epitaxial film 30 of the second embodiment shown in FIG. 3, an insulating film 41, a p-type electrode 42, and an n-type electrode 43. The insulating film 41 has an opening, is formed on the p-type contact layer 39, and is made of, for example, silicon dioxide (SiO ₂ ). The p-type electrode 42 is formed in contact with the p-type contact layer 39 exposed from the opening of the insulating film 41, and is made of, for example, nickel (Ni) / gold (Au). N-type electrode 43 is formed on the back surface of substrate 20 and is made of, for example, titanium (Ti) / Al.

  Next, a method for manufacturing the semiconductor laser 40 in the present embodiment will be described. First, the epitaxial film 30 is manufactured according to the method for manufacturing the epitaxial film 30 of the second embodiment.

  Next, an insulating film 41 having an opening is formed on the p-type contact layer 39 of the epitaxial film 30 by photolithography.

  Next, a p-type electrode 42 is formed so as to fill the opening of the insulating film 41, and an n-type electrode 43 is formed on the back surface of the substrate 20. Although the formation method of the p-type electrode 42 and the n-type electrode 43 is not specifically limited, For example, it can form by a vapor deposition method.

  By performing the above steps, the semiconductor laser 40 shown in FIG. 4 can be manufactured.

  As described above, according to the method of manufacturing semiconductor laser 40 in the present embodiment, epitaxial film 30 in which the thickness of each layer is made uniform and the growth rate is improved is used. Since each thickness is made uniform, the yield is improved and the growth rate is improved, so that the semiconductor laser 40 with reduced manufacturing cost can be manufactured.

  In the present embodiment, the semiconductor laser is described as an example of the light emitting element. However, the present invention is not limited to the semiconductor laser, and the present invention can also be applied, for example, a light emitting diode (LED).

  In this example, the effect of setting the flow rate of the first source gas to 0.5 to 0.8 that of the second source gas and setting the pressure in the reaction vessel to 20 kPa to less than 60 kPa was examined.

(Sample 1)
For sample 1, epitaxial film 25 shown in FIG. 1 was manufactured according to Embodiment 1 using MOCVD apparatus 1 shown in FIG.

  Specifically, first, a sapphire substrate was prepared as the substrate 20. The pressure in the reaction vessel of the MOCVD apparatus 1 was set to 40 kPa, and the temperature of the susceptor 5 was set to 900 ° C. by the heater 9. Further, the susceptor 5 was not rotated. In this state, GaN was formed as the buffer layer 21 on the main surface 20 a of the substrate 20.

The state in the MOCVD apparatus 1 was similarly maintained, and quaternary InAlGaN was grown on the buffer layer 21 under the following conditions. Ammonia and nitrogen were used as the first source gas G1, and TMG, TMA, TMI and nitrogen were used as the second source gas G2. The flow rate of the first source gas G1 was 0.18 m / s, and the flow rate of the second source gas G2 was 0.34 m / s. The molar concentrations of TMG, TMA, and TMI as the second source gas G2 were 1.75 × 10 ⁻⁴ , 1.00 × 10 ⁻⁴ , and 2.21 × 10 ⁻⁴ . Further, nitrogen having a flow rate of 0.77 m / s was used as the gas G3 supplied from the third gas supply unit 11c.

By performing the above steps, an epitaxial film of Sample 1 was manufactured.
(Sample 2)
The epitaxial film of sample 2 was basically manufactured in the same manner as the epitaxial film of sample 1, but was different only in that the flow rate of the first source gas G1 was set to 0.34 m / s in the step of forming the InAlGaN layer. It was.

(Evaluation methods)
For the epitaxial films of Sample 1 and Sample 2, the growth rate of the InAlGaN layer 22 was measured. The result is shown in FIG.

Furthermore, the InAlGaN layer 22 of the epitaxial film of Sample 1 and Sample 2, the _{In x Al y Ga (1-} xy) N crystal in the In composition ratio x and the Al composition ratio y was measured by SIMS. The results are shown in FIGS.

  5 to 7, the horizontal axis L indicates the distance from the center of the susceptor when the center of the susceptor is 0, and the positive value is relative to the first to third gas supply units 11a to 11c. The negative value is a direction closer to the first to third gas supply units 11a to 11c. That is, the smaller the value of L, the closer to the first to third gas supply units 11a to 11c, and the larger the absolute value of L, the closer to the outer periphery of the susceptor.

(Evaluation results)
As shown in FIG. 5, in the sample 1 in which the pressure in the reaction vessel is 40 kPa and the flow rate of the first raw material gas is 0.5, which is the flow rate of the second raw material gas, the flow rate of the first raw material gas is the second raw material gas. Compared to the sample 2 with a gas flow rate of 1.0, the organometallic gas of the second source gas G2 can easily reach the substrate 20 on the upstream side, the growth rate on the upstream side increases, and the growth rate distribution is It turned out that it was linear.

  Further, as shown in FIGS. 6 and 7, in the sample 1 in which the flow rate of the first source gas is 0.5, which is the flow rate of the second source gas, the flow rate of the first source gas is 1 of the flow rate of the second source gas. It was found that the uptake of Al and In increased on the upstream side compared to Sample 2 set to 0.0, and the uptake of Al and In was linear.

  Sample 1 and sample 2 grew without rotating the susceptor 5, but these results showed that the growth rate in the direction along the main surface 20a of the substrate 20 could be made uniform by rotating the susceptor 5. . For this reason, it was found that an InAlGaN crystal having a uniform thickness can be manufactured by rotating the susceptor 5.

  On the other hand, since the growth rate distribution of Sample 2 is convex, even when the susceptor 5 is rotated, the thickness on the outer peripheral side becomes smaller than the thickness at the center, and becomes an InAlGaN crystal with variations in thickness. I understood it.

  As described above, according to the present example, the first raw material gas flow rate is 0.5 or more and 0.8 or less of the second raw material gas flow rate, and the pressure in the reaction vessel is 20 kPa or more and less than 60 kPa. It was confirmed that the speed could be made uniform.

  In this example, the effect of setting the flow rate of the first source gas to 0.5 to 0.8 that of the second source gas and setting the pressure in the reaction vessel to 20 kPa to less than 60 kPa was examined.

(Invention Examples 1 to 5)
In inventive examples 1 to 5, the epitaxial film 25 shown in FIG. 1 was manufactured according to the first embodiment using the MOCVD apparatus 1 shown in FIG.

  Specifically, first, a sapphire substrate was prepared as the substrate 20. Then, the pressure in the reaction vessel of the MOCVD apparatus 1 was set to 20 kPa or 40 kPa described in Table 1 below, and the temperature of the susceptor 5 was set to 900 ° C. Further, the susceptor 5 was rotated. In this state, GaN was formed as the buffer layer 21 on the main surface 20 a of the substrate 20.

  The quaternary InAlGaN was grown on the buffer layer 21 while maintaining the same state in the MOCVD apparatus 1. Ammonia and nitrogen were used as the first source gas G1, and TMG, TMA, TMI and nitrogen were used as the second source gas G2. The flow rates and flow rates of the first and second source gases G1 and G2 were set as shown in Table 1 below. Further, as the second source gas G2, the molar concentrations of TMG, TMA, and TMI are as shown in Table 1 below. Further, the flow rate and flow rate of the gas G3 that does not include the raw material supplied from the third gas supply unit 11c are as shown in Table 1 below.

By implementing the above process, the epitaxial film of the invention examples 1-5 was manufactured.
(Comparative Examples 1-4)
The epitaxial films of Comparative Examples 1 to 4 were basically manufactured in the same manner as the epitaxial films of Invention Examples 1 to 5, but the flow rate of the first raw material was set to the flow rate of the second raw material gas in the step of forming the InAlGaN layer. The difference was that the pressure outside the range of 0.5 to 0.8 and / or the pressure in the reaction vessel was 60 kPa.

(Evaluation methods)
The InAlGaN layer of the epitaxial film of the present invention Examples 1 to 5 and Comparative Examples 1 to 4, growth rate, and _{In x Al y Ga (1-} xy) N Example 1 In composition ratio x and the Al composition ratio y of the crystal It measured similarly. The results of Example 5 of the present invention are shown in FIGS.

  8 to 10, the horizontal axis L indicates the distance from the center of the susceptor when the center of the susceptor is 0. The smaller the value of L, the first to third gas supply units 11a. It means that it is close to ~ 11c and located on the outer peripheral side.

  As shown in FIG. 8, by measuring the growth rate, the distribution from the maximum value, the minimum value, and the median value of the growth rate can be measured. In this way, the growth rates from the maximum value, the minimum value, and the median value of the InAlGaN layers of the epitaxial films of Invention Examples 1 to 5 and Comparative Examples 1 to 4 were examined. The results are shown in Table 1 below.

  In Table 1, the median is the value when 5 points are measured linearly from the susceptor center to the outer periphery of the susceptor (5 points of 0 mm, ± 10 mm, and ± 20 mm when the wafer center coordinates are 0). The value was between the maximum value and the minimum value. The median distribution was (maximum thickness-minimum thickness) / median.

(Evaluation results)
As shown in Table 1, Invention Examples 1 to 5 in which the flow rate of the first source gas was set to 0.5 to 0.8 of the flow rate of the second source gas, and the pressure in the reaction vessel was set to 20 kPa to less than 60 kPa. In the InAlGaN layer 22 of the epitaxial film, the distribution from the median growth rate was 0.074 or less, and it was found that the growth rate in the direction perpendicular to the main surface 20a of the substrate 20 was uniform. For this reason, it turned out that the thickness of an InAlGaN layer can be made uniform. Furthermore, the minimum value of the growth rate of the InAlGaN layers 22 of Invention Examples 1 to 5 was 0.41 μm / h or more, and it was found that the three kinds of organometallic gases could be prevented from reacting with each other. For this reason, it was found that the growth rate of the InAlGaN layer can be improved.

  In the InAlGaN layers 22 of Invention Examples 2 to 5 in which the flow rate of the first source gas G1 was 0.18 m / s or more and 0.35 m / s or less, the distribution from the median growth rate was 0.052 or less. The minimum growth rate was 0.50 μm / h or more. From this, it was found that the thickness can be made more uniform and the growth rate can be further improved by setting the flow rate of the first source gas to 0.18 m / s or more and 0.35 m / s or less.

  On the other hand, in Comparative Example 1 and Comparative Example 2 in which the flow rate of the first raw material gas was 1.0, which is the flow rate of the second raw material gas, the flow rate of the first raw material gas was high, so the organometallic gas in the second raw material gas However, since the first raw material gas could not be sufficiently diffused, the variation in growth rate was larger than those of Examples 1 to 5 of the present invention.

  In Comparative Example 3 in which the pressure in the reaction vessel was 60 kPa and the flow rate of the first raw material gas was 1.0, which was the flow rate of the second raw material gas, the organometallic gases reacted with each other. It was lower than Examples 1-5.

  In Comparative Example 4 in which the pressure in the reaction vessel was 60 kPa, the variation in the growth rate was larger than those of Invention Examples 1 to 5, and the minimum value of the growth rate was lower than that of Invention Examples 1 to 5. A low growth rate means that the growth rate of the InAlGaN crystal is low.

  As described above, according to this example, the flow rate of the first source gas is set to 0.5 to 0.8 that of the second source gas, and the pressure in the reaction vessel is set to 20 kPa to less than 60 kPa. It was confirmed that the crystal thickness can be made uniform and the growth rate can be improved.

  It should be understood that the embodiments and examples disclosed herein are illustrative and non-restrictive in every respect. The scope of the present invention is shown not by the embodiments and examples described above but by the scope of claims for patent, and is intended to include all modifications within the meaning and scope equivalent to the scope of claims for patent.

  DESCRIPTION OF SYMBOLS 1 MOCVD apparatus, 3 reaction container, 5 susceptor, 7 groove | channel, 9 heater, 11 source gas supply part, 11a 1st gas supply part, 11b 2nd gas supply part, 11c 3rd gas supply part, 13 rotating shaft , 20 substrate, 20a main surface, 21 buffer layer, 22 InAlGaN layer, 25, 30 epitaxial film, 32 n-type buffer layer, 33 n-type cladding layer, 34, 36 undoped light guide layer, 35 active layer, 37 p-type electron Block layer, 38 p-type cladding layer, 39 p-type contact layer, 40 semiconductor laser, 41 insulating film, 42 p-type electrode, 43 n-type electrode, G1 first source gas, G2 second source gas, G3 gas.

Claims (3)

In a reaction vessel an _{In x Al y Ga (1-} xy) N crystal (0 ≦ x <1,0 ≦ y <1,0 <x + y ≦ 1) a method for producing a,
Preparing a substrate having a main surface;
While supplying the raw material gas in a direction along the main surface of the substrate, a step of growing the _{In x Al y Ga (1-} xy) N crystal on the major surface of the substrate by heating the substrate With
In the _{In x Al y Ga (1-} xy) growing a N crystal,
A first source gas containing a group V element source is supplied onto the main surface of the substrate from a first gas supply unit located on the side close to the main surface in a direction perpendicular to the main surface of the substrate; An organic metal that is a raw material for a plurality of group III elements from a second gas supply unit located on a side farther from the main surface than the first gas supply unit in a direction perpendicular to the main surface of the substrate Supplying a second source gas onto the main surface of the substrate;
The flow rate of the first source gas is 0.5 to 0.8 that of the second source gas,
A method for producing a crystal, wherein the pressure in the reaction vessel is 20 kPa or more and less than 60 kPa. In the _{In x Al y Ga (1-} xy) growing a N crystals, the flow rate of said first material gas below 0.18 m / s or more 0.35 m / s, according to claim 1 crystals Production method. The method for producing a crystal according to claim 1 or 2, a step of growing the _{In x Al y Ga (1-} xy) N crystal on the main surface of said substrate,
It said In _x Al _y Ga and a step of forming an electrode on _(1-xy) N crystal, method of manufacturing the light emitting device.

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