JP2013115313A - Crystal growth apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a vapor phase growth apparatus of horizontal system in which generation and adhesion of by-products are prevented by dissipating radiation heat from a susceptor efficiently, and a high quality crystal layer can be grown even if crystal growth is carried out repeatedly.SOLUTION: A material gas supply section defining a material gas passage is disposed on the upstream side of the material gas passage for a substrate holding section, and has a material gas supply guide composed of a material transmitting infrared rays radiated from the substrate holding section. The material gas supply guide has an infrared ray exit part consisting of an uneven structure formed on a surface different from a surface defining the material gas passage.

Description

  The present invention relates to a vapor phase growth apparatus, and more particularly to a horizontal (horizontal) MOCVD (Metal-Organic Chemical Vapor Deposition) apparatus.

  Conventionally, vapor phase growth such as MOCVD has been widely used as a semiconductor single crystal growth method in industrial fields such as laser diodes (LD), light emitting diodes (LEDs), and electronic devices. The growth apparatus using the MOCVD method includes a method in which a material gas flow (gas flow) is flowed vertically (vertical method) and a method in which it is flowed horizontally (horizontal method) with respect to the growth surface of the substrate. A method suitable for the target device and the like is selected. In a conventional horizontal type (hereinafter referred to as horizontal type) vapor phase growth apparatus, for example, as disclosed in Patent Document 1, growth reproducibility is lost due to by-products adhering to the flow channel. It is disclosed that an adverse effect is suppressed by providing a cooling water circulation type cooling mechanism on the upstream side of the flow. Patent Document 2 discloses that a cooling mechanism made of stainless steel is provided to suppress a gas phase reaction of a material gas. In Patent Document 3, a horizontal partition plate is provided in the upstream portion of the flow channel, two upper and lower gas flow paths are formed, a material gas is supplied to the lower gas flow path, and the upper gas flow path is provided. A structure is disclosed in which purge gas is supplied and cooling means capable of adjusting the temperature of the lower surface of the flow channel is provided upstream of the susceptor. Patent Document 4 discloses a substrate holder provided with a cooling means and a configuration in which helium gas or the like flows along the back surface of the substrate. Patent Document 5 discloses a barrel type reactor in which a cooling gas is allowed to flow in a space provided between a heating means and a susceptor.

Japanese Patent Laid-Open No. 2001-23902 JP 2002-246323 A Japanese Unexamined Patent Publication No. 2000-1000072 JP-A 64-17424 Japanese Utility Model Publication No. 03-102727

  As described above, in the conventional growth apparatus, a cooling mechanism including a water cooling jacket or the like is provided on the upstream side of the flow so as to prevent the accumulation of by-products. However, in the structure in which the cooling device is arranged in the vicinity of the outer periphery of the susceptor that holds the substrate, there is a problem that the temperature of the outer peripheral portion of the susceptor is lowered and the film thickness is not uniform or the composition is not uniform. Further, in the crystal growth of a crystal system in which the growth temperature is high, for example, a GaN crystal, the substrate temperature (that is, the susceptor temperature) is 1000 ° C. or higher. A refractory metal that can be used in a cooling device in such a high temperature range is expensive. Processing is also difficult, advanced manufacturing techniques are required, and processing costs are high. Therefore, there is a problem that the manufacturing cost of the apparatus becomes high. In addition, there is a problem that the adhesion of reaction by-products hinders the crystal growth process and leads to a decrease in crystal quality.

  The present invention has been made in view of such a point, and an object of the present invention is to efficiently dissipate radiant heat from the susceptor and prevent the formation and adhesion of by-products without giving temperature fluctuation to the susceptor. It is an object of the present invention to provide a horizontal type vapor phase growth apparatus capable of performing the above-mentioned. Another object of the present invention is to provide a horizontal type vapor phase growth apparatus capable of growing a high-quality crystal layer even when crystal growth is repeatedly performed.

A vapor phase growth apparatus according to the present invention includes a substrate holding unit that holds a substrate, a material gas supply unit that defines a material gas flow path that supplies a material gas to a growth surface of the substrate, and heating that heats the substrate holding unit. And comprising
The material gas supply unit is disposed on the upstream side of the material gas flow path with respect to the substrate holding unit, and has a material gas supply guide made of a material transmissive to infrared rays emitted from the substrate holding unit. The supply guide is characterized in that it has an infrared emitting portion made of a concavo-convex structure formed on a surface different from the surface defining the material gas flow path.

It is the upper side figure (upper stage) and sectional drawing (lower stage) of a MOCVD apparatus. It is an expanded sectional view of the material gas supply guide in the section containing the cylinder central axis of the susceptor of Example 1. FIG. 3 is a partially enlarged cross-sectional view showing a portion near the susceptor of the infrared emission window of FIG. It is sectional drawing explaining the structure of an infrared emission window, and is a figure which illustrates typically the transmission maximum inclination angle ((theta) mx) of a 1st inclined surface. It is sectional drawing explaining the structure of an infrared radiation window, and is a figure which illustrates typically the transmission minimum inclination angle ((theta) mn1) of a 1st inclined surface. It is sectional drawing explaining the structure of an infrared emission window, and is a figure which illustrates typically the minimum inclination angle ((theta) mn2) of a 1st inclined surface. It is an expanded sectional view in the field containing the cylinder central axis of a susceptor of the material gas supply guide of Example 2. It is a figure for demonstrating the course of the waveguide infrared rays in case the mirror is not provided in the 2nd inclined surface. It is sectional drawing which shows typically the structure of the growth layer of Examples 1, 2 and a comparative example. It is sectional drawing explaining the modification of an infrared rays emission part.

  Hereinafter, a horizontal type vapor phase growth apparatus will be described in detail with reference to the drawings. In the following, preferred embodiments of the present invention will be described, but these may be appropriately modified and combined. In the drawings described below, substantially the same or equivalent parts will be described with the same reference numerals.

  FIG. 1 schematically shows the configuration of a crystal growth apparatus 10 of the present invention. The apparatus configuration of the crystal growth apparatus 10 will be described in detail below.

[Device configuration]
FIG. 1 shows a top view (upper stage) and a sectional view (lower stage) of a crystal growth apparatus (MOCVD apparatus) 10, and the top view is a top view when the substrate side is viewed along line VV in the sectional view. is there. As shown in FIG. 1, the MOCVD apparatus 10 includes a reaction vessel 11, a flow channel body 12, a flow channel floor plate 13, a material gas supply guide 15, a flow channel exhaust pipe 17, and a columnar susceptor that holds and holds a substrate 20. 22, a heater 24 that heats the susceptor 22 (that is, heats the substrate 20), and a substrate rotation mechanism 25 that rotates the susceptor 22 (that is, rotates the substrate 20).

  The flow channel body 12 includes a top plate, side walls, and a partition plate 12A. The flow channel portion (material gas supply portion) includes the flow channel body 12, the flow channel floor plate 13, and the material gas supply guide 15 and the flow channel 14A and the flow channel 14B. Is configured. The surfaces of the flow channel floor plate 13, the material gas supply guide 15, the substrate 20, and the susceptor 22 are configured to be in the same horizontal plane. A material channel is supplied to the flow channel 14A, which is a flow channel on the side close to the substrate 20 and the susceptor 22 (that is, a lower flow), via a gas supply pipe 12C, and the flow is an upper flow channel of the flow channel 14A. Gas is supplied to the channel 14B via the gas supply pipe 12D.

  The material gas supply guide 15 is disposed on the upstream side of the material gas with respect to the susceptor 22, and an infrared emission window 15 </ b> A which is an infrared emission portion described later is formed on the back surface of the material gas supply guide 15. In addition, a cooling gas passage 16 through which cooling gas flows is provided on the back side of the material gas supply guide 15, and the material gas supply guide 15 is cooled. Cooling gas is supplied to the cooling gas passage 16 via a cooling gas supply pipe 16A. Further, a water cooling jacket 18 is provided along the cooling gas flow path 16, and cooling water is supplied and discharged from a cooling water supply pipe 18A and a cooling water discharge pipe 18B, respectively.

Further, the MOCVD apparatus 10 is provided with a heat shield plate 26 for shutting off the heat of the heater 24, and a heater chamber partition cylinder 27 that partitions the heater chamber outside the heat shield plate 26. A heater chamber gas supply pipe 27A is connected to the heater chamber, and purge gas is supplied. Nitrogen gas, hydrogen gas, argon gas or the like is used as the purge gas. A reaction vessel purge gas supply pipe 11A is connected to the reaction vessel 11 so that an inert gas (N ₂ or the like) can flow so that a material gas or the like diffused into the reaction vessel can be exhausted. The cooling gas may be a gas that does not corrode the susceptor 22, the heater 24, and the heat shield plate 26. Specifically, nitrogen gas, hydrogen gas, argon gas, or the like may be used. However, a mixed gas of hydrogen: nitrogen = 0: 1 to 3: 1 is preferable for cooling the material gas supply guide 15.

[Material gas supply guide and infrared emission window]
The configuration of the material gas supply guide 15 will be described with reference to FIGS. 1 and 2. FIG. 2 is an enlarged cross-sectional view of the material gas supply guide 15 in a cross section including the cylindrical central axis of the susceptor 22. For example, a cross section of a vertical plane including the radial direction OM (O: the center of the cylinder of the susceptor 22) in the plan view of FIG. 1 is shown.

  As schematically shown in the plan view of FIG. 1, the surface 15F of the material gas supply guide 15 is arranged so as to be in the same horizontal plane as the surfaces of the substrate 20 and the susceptor 22, and a flow channel 14A (material gas flow path). The bottom surface is defined. Then, an infrared emission window 15A (shown by a broken line) is formed on the back surface 15R of the material gas supply guide 15 which is a surface different from the surface (surface 15F) defining the material gas flow path. . The material gas supply guide 15 is made of a material that is transparent to infrared rays emitted from the susceptor 22, for example, quartz, and guides infrared rays (IR) emitted from the susceptor 22, and guides the guided light (infrared rays). ) From the infrared emission window 15A which is the emission part.

  More specifically, in the present embodiment, the surface 15F of the material gas supply guide 15 defines the bottom surface of the flow channel 14A. For example, it is formed as a parallel plate shape having a back surface parallel to the surface 15F on the flow channel 14A side. The infrared emission window 15A of the material gas supply guide 15 is carved on the back surface 15R of the material gas supply guide 15, that is, the surface opposite to the surface defining the flow channel 14A. The material gas supply guide 15 is disposed with a slight gap G between the end surface 15E of the material gas supply guide 15 and the susceptor 22. The infrared emission window 15 </ b> A has serrated irregularities including triangular grooves (recesses) in the cross section. More specifically, as shown in FIG. 2, the triangular recess 31 of the infrared emission window 15 </ b> A is arranged in order from the susceptor 22 to the first inclined surface 31 </ b> A (that is, the side closer to the susceptor 22) in the upstream direction of the material gas flow. And the second inclined surface 31B inclined with respect to the first inclined surface 31A (that is, the inclined surface far from the susceptor 22), and the triangular recess 31 is continuously formed. Thus, an infrared emission window 15A having a sawtooth concavo-convex structure is formed. As shown in the plan view of FIG. 1, the infrared emission window 15 </ b> A is engraved on the back surface of the material gas supply guide 15 concentrically with the susceptor 22 in a plane (or a horizontal plane) perpendicular to the cylinder central axis of the susceptor 22. (Shown with a broken line). In other words, both the first inclined surface 31A and the second inclined surface 31B are inclined curved surfaces having a truncated cone side surface shape coaxial with the cylindrical central axis of the susceptor 22.

  FIG. 3 is a partial enlarged cross-sectional view showing a portion near the susceptor 22 (part U shown by a broken line) of the infrared emission window 15A of FIG. The recess 31 has a shape of a triangle PQR composed of vertices P, Q, R and a base PR, and the first inclined surface 31A has an inner angle θ1 with respect to the base PR of the triangle PQR (ie, with respect to the back surface 15R). (0 <θ1 <90 °, hereinafter also referred to as a first inclination angle). The second inclined surface 31B has an inner angle of θ2 (0 <θ2 <90 °, below) with respect to the base PR. , Also referred to as a second inclination angle). That is, generally, the first inclined surface 31A and the second inclined surface 31B are surfaces perpendicular to the cylinder central axis of the susceptor 22 (broken lines in the figure) in a cross section including the cylinder central axis of the susceptor 22. That is, it corresponds to the two sides of the triangular recess 31 inclined by the inner angles θ1 and θ2, respectively, with respect to the base PR of the triangle PQR.

  As schematically shown in FIG. 3, the light (infrared ray) IR0 incident on the material gas supply guide (quartz) 15 is incident on the interface (15F, 15R) between the quartz and the gas phase at a higher angle than the critical angle α. In this case, the light is guided into the material gas supply guide 15 (guided light or guided infrared light), and is emitted into the gas phase when incident at a lower angle than the critical angle α. A portion of the guided light is absorbed by the quartz while propagating through the quartz and converted into heat. That is, quartz is heated by the guided light. In the vicinity of the susceptor 22, infrared rays radiated from the susceptor 22 or the heater 24 are dominant. Therefore, if the infrared rays can be removed, heating of the flow channel can be suppressed. The guided light IR incident on the first inclined surface 31A is directly emitted to the outside or emitted from the first inclined surface 31A and then reflected to the outside by the second inclined surface 31B depending on the incident angle. Or enters the material gas supply guide (quartz) 15 again from the second inclined surface 31B. That is, the first inclined surface 31A functions as an infrared emission inclined surface, and the second inclined surface 31B emits infrared rays that are emitted from the first inclined surface 31A to the outside of the material gas supply guide 15 and are incident at a critical angle or more. It functions as an infrared reflecting inclined surface that reflects.

  In the following, guided light for efficiently emitting infrared IR incident from the susceptor 22 into the material gas supply guide 15 from the guided light exit window 15A and removing heat from the vicinity of the susceptor 22 to suppress heating of the flow channel. The structure of the exit window 15A will be described in detail.

[Structure of infrared emission window]
1. Maximum transmission inclination angle (θmx) of the first inclined surface 31A
FIG. 4 is a cross-sectional view illustrating the structure of the infrared emission window 15A as in FIG. 3, and is a diagram schematically illustrating the maximum transmission inclination angle (θmx) of the first inclined surface 31A. In the following description, it is assumed that the clockwise direction is positive (plus) and the counterclockwise direction is negative (minus).

The transmission maximum inclination angle θmx (that is, the maximum value of the first inclination angle) of the first inclined surface 31A (that is, the infrared emission inclined surface) for taking out infrared rays out of the material gas supply guide 15 is the material gas supply guide. The traveling direction line LM of the infrared IR (arrow in the figure) of the minimum reflection angle (equal to the critical angle α) reflected at the interface I (15F) between the gas layer 15 and the gas layer (flow channel) is the first inclined surface 31A. This corresponds to the case where the angle formed with respect to the normal line HO coincides with the maximum transmission angle on the plus side (that is, equal to the critical angle α) (or the normal line HO is closer to the horizontal direction than the traveling direction line LM). (See FIG. 4). Therefore, θmx is given by the following equation.
θmx = α + α = 2α (Formula 1)

Therefore, the inclination angle θ1 (first inclination angle) of the first inclined surface 31A is
θ1 ≦ 2α (Formula 2)
If it is. For example, when the material gas supply guide 15 is made of quartz and the wavelength of infrared rays is assumed to be 1 μm, the refractive index of quartz is 1.451 and the critical angle α = 43.6 °, so θ1 ≦ 2 × 43.6 ° = 87.2 °.

2. Minimum transmission inclination angle (θmn1) of first inclined surface 31A
FIG. 5 is a cross-sectional view illustrating the structure of the infrared emission window 15A as in FIG. 4, and is a diagram schematically illustrating the minimum transmission inclination angle (θmn1) of the first inclined surface 31A. The transmission minimum inclination angle (θmn1) of the first inclined surface 31A for the infrared rays to be taken out of the material gas supply guide 15 without being totally reflected by the first inclined surface 31A is the maximum reflection reflected by the interface I. The angle formed by the traveling direction line LO of the infrared ray IR (an arrow in the figure) with an angle (that is, 90 °) with respect to the normal line HO of the first inclined surface 31A is equal to the negative maximum transmission angle (the critical angle α). ) (See FIG. 5). Accordingly, θmn1 is given by the following equation.
θmn1 = 90−α (Formula 3)

Therefore, the inclination angle θ1 of the first inclined surface 31A is
θ1 ≧ 90−α (Formula 4)
If it is. For example, assuming that the material gas supply guide 15 is made of quartz and the wavelength of infrared rays is 1 μm, θ1 ≧ 90 ° −43.6 ° = 46.4 °.

3. Minimum inclination angle (θmn2) of first inclined surface 31A
FIG. 6 is a cross-sectional view illustrating the structure of the infrared emission window 15A, and schematically illustrates the minimum inclination angle (θmn2) of the first inclined surface 31A. The minimum inclination angle (θmn2) of the first inclined surface 31A for taking out infrared rays out of the material gas supply guide 15 is infrared IR (maximum reflection angle (ie, 90 °) reflected by the interface I (indicated by an arrow in the figure)). ) And the first inclined surface 31A, and the traveling direction line OT of the reflected light IQ toward the interface I at a critical angle, ∠TOQ = ∠LOP = θmn2. Accordingly, the minimum inclination angle θmn2 of the first inclined surface 31A is given by the following expression.
90 ° + α-2θmn2 = 180 °
θmn2 = (90 ° −α) / 2 (Formula 5)

Therefore, the inclination angle θ1 of the first inclined surface 31A is
θ1 ≧ (90 ° −α) / 2 (Formula 6)
If it is. For example, assuming that the material gas supply guide 15 is made of quartz and the wavelength of infrared rays is 1 μm, θ1 ≧ (90 ° −43.6 °) /2=23.2°.

4). Inclination Angle of First Inclined Surface 31A As described above, the maximum transmission inclination angle (θmx) of the first inclined surface 31A, which is an infrared emitting inclined surface, is the interface between the material gas supply guide 15 and air (or vacuum). Θmx = 2α, where α is the critical angle of infrared rays at α. The minimum inclination angle is θmn2 = (90 ° −α) / 2. Furthermore, the minimum transmission tilt angle of the first inclined surface 31A for taking out the infrared rays from the material gas supply guide 15 without being totally reflected by the first inclined surface 31A is θmn1 = 90−α. Therefore, the inclination angle θ1 of the first inclined surface 31A may be (90 ° −α) / 2 ≦ θ1 ≦ 2α, and 90 ° −α ≦ θ1 in terms of the extraction efficiency to the outside of the material gas supply guide 15. It is preferable that ≦ 2α. Further, from the viewpoint of processing the material gas supply guide 15 such as quartz, 45 ° to 60 ° is preferable because it can be easily processed. In particular, when the incident light from the positive angle side is increased, the re-incident on the second inclined surface 31B can be reduced, so 60 ° is optimal.

  The depth of the infrared emission window 15A, that is, the height of the recess 31 is preferably equal to or greater than the infrared insensitive size. Specifically, the depth D (see FIG. 3) of the infrared emission window 15A is preferably 0.2 to 0.5 mm, and is 1/10 to 1/3 of the thickness of the material gas supply guide 15. Preferably there is. The angle formed by the first inclined surface 31A and the second inclined surface 31B is preferably 90 ± 5 °. If it is smaller than this, the light incident on the second inclined surface 31B and reflected in the material gas supply guide 15 increases. On the other hand, if it is larger than this, the groove width of the concave portion 31 (the triangular base) expands and the interval between the first inclined surfaces 31A increases, so that the extraction efficiency decreases.

  FIG. 7 is an enlarged cross-sectional view of the surface of the material gas supply guide 15 according to the second embodiment including the cylindrical central axis of the susceptor 22. The material gas supply guide 15 has the same configuration as that of the first embodiment except that the mirror 33 is provided on the second inclined surface 31B.

  FIG. 8 is a diagram for explaining the path of guided light (that is, guided infrared light) when the mirror 33 is not provided on the second inclined surface 31B. An angle measured clockwise with respect to the normal of the inclined surface is called a positive angle, and an angle measured counterclockwise is called a negative angle. The guided light in the material gas supply guide 15 includes reflected light reflected by the interface I and reflected light reflected by the interface II. In the figure, a light beam a is light reflected by the interface II and incident on the first inclined surface 31A. The incident angle is larger than the critical angle and is reflected by the first inclined surface 31A toward the interface I (reflected light a '). If the incident angle to the interface I of the light ray a 'is less than the critical angle, it is emitted to the gas phase, and if it is greater than the critical angle, it becomes reflected light (guided light). The light ray b is light that is reflected by the interface I and is incident on the first inclined surface 31A. Since the incident angle is smaller than the critical angle, the light beam b is emitted from the first inclined surface 31A and is incident on the second inclined surface 31B. To do. If the incident angle to the second inclined surface 31B is larger than the critical angle, it is reflected by the second inclined surface 31B and emitted to the outside of the material gas supply guide 15 (reflected light b ′), and if it is smaller than the critical angle, the material gas is supplied. The light enters the guide 15 (incident light b ″). In addition, the light ray c reflected at the interface I and incident on the second inclined surface 31B in the material gas supply guide 15 has an incident angle on the second inclined surface 31B larger than the critical angle. It is reflected by 31B and heads for the next first inclined surface 31A. If the incident angle to the next first inclined surface 31A is smaller than the critical angle, it is emitted (ray c '), and if it is larger than the critical angle, it is reflected. The guided light of the material gas supply guide 15 is taken out by the optical path described above.

  As described above, depending on the incident angle, the light emitted from the first inclined surface 31A may enter the material gas supply guide 15 again (refractive intrusion). In the second embodiment, since the mirror 33 that reflects the light emitted from the first inclined surface 31A is provided on the second inclined surface 31B, re-incident into the material gas supply guide 15 can be prevented, and the guided light is transmitted. The efficiency of taking out the material gas supply guide 15 is improved, and the heating of the material gas supply guide 15 can be suppressed.

  The mirror 33 can be formed by evaporating rhodium (Rh) on the second inclined surface 31B, for example. Rhodium (Rh) has a high reflectance up to the infrared region, and at the same time has a very high corrosion resistance, so it can maintain a high reflection performance even in a high temperature atmosphere. The rhodium film thickness is preferably 50 to 200 nm. The mirror 33 is not limited to rhodium, and a material having a high reflectance with respect to infrared rays can be used.

[Evaluation of grown crystal]
(1) Crystal growth Crystal growth was performed using the MOCVD apparatus provided with the material gas supply guide 15 of Example 1 and Example 2, and the grown crystal was evaluated. Further, except that the material gas supply guide is not provided with the infrared emission window 15A, crystal growth is performed using a MOCVD apparatus having the same configuration as that of Example 1 and Example 2 as a comparative example, and Examples 1, 2, and The grown crystals were compared using the apparatus of the comparative example. FIG. 9 is a cross-sectional view schematically showing the structures of the growth layers of Examples 1 and 2 and the comparative example. The crystal growth of Examples 1 and 2 and the comparative example were all carried out under the same procedure and conditions. The crystal growth procedure and conditions will be described below. Specifically, a GaN crystal was grown by the following procedure using the following organometallic compound material gas and hydride material gas. As the substrate 20, a c-plane sapphire (α-alumina), circular (2 inches) substrate having a growth surface inclined by 0.5 ° in the m-axis direction (0.5 ° off) was used. TMG (trimethylgallium) was used as the organometallic material gas, and NH ₃ (ammonia) was used as the hydride gas. The organometallic material gas and the hydride gas were mixed and supplied from the gas supply pipe 12C, and a gas mixed with hydrogen: nitrogen = 1: 1 was supplied from the gas supply pipe 12D at a flow rate of 28 L / min. In addition to the material gas (organometallic compound gas and hydride gas), hydrogen (H ₂ ) gas was supplied as a carrier gas to the gas supply pipe 12C. The total flow rate was adjusted to 6 L / min together with the material gas. Further, a mixed gas of hydrogen: nitrogen = 1: 1 is supplied to the cooling gas supply pipe 16A at a flow rate of 10 L / min, and a mixed gas of hydrogen: nitrogen = 1: 1 is supplied to the heater chamber gas supply pipe 27A at 8 L / min. The flow rate was. Further, normal temperature (room temperature) water was passed through the water cooling jacket 17 at a flow rate of 3 L / min.

  First, the substrate 20 was heat-treated. Hydrogen gas is supplied from the gas supply pipe 12C at a flow rate of 6 L / min and hydrogen gas / nitrogen = 1: 1 from the gas supply pipe 12D at a flow rate of 28 L / min. The temperature of the susceptor 22 is 1000 ° C. and the pressure is 100 kPa (Pa: The sapphire substrate 20 was annealed for 10 minutes.

Next, after the temperature of the susceptor 22 (ie, the substrate 20) is set to 550 ° C. and the pressure is set to 100 kPa, TMG is supplied from the gas supply pipe 12C at 30 μmol / min and NH ₃ is supplied at 4 L / min. The grown GaN layer 41 was grown with a layer thickness of 10 nm. Next, the temperature of the susceptor 22 was 1050 ° C., the pressure was 100 kPa, and the low-temperature grown GaN layer 41 was annealed for 7 minutes.

Next, after setting the temperature of the susceptor 22 to 1030 ° C. and the pressure to 100 kPa, 45 μmol / min of TMG and 4 L / min of NH ₃ were supplied, and the high-temperature growth GaN layer 42 was grown on the low-temperature growth GaN layer 41 for 1 hour. .

(2) Evaluation results of growth crystal Table 1 shows the evaluation results of the structures of the growth layers of the samples of Examples 1 and 2 and the comparative example. The layer thickness was measured using a reflection interferometer using a white light source. Since the refractive index of the sapphire substrate is different from 1.7 and the refractive index of the GaN crystal is 2.4, the layer thickness can be measured by measuring the reflection interference. The layer thickness was measured at 5 points (including the center) at 5 mm intervals from the center of the 2-inch substrate, and the average value is shown in Table 1. The layer thickness increase rate was based on the layer thickness of the comparative example (ie, 1.0). The maintenance frequency interval was defined as the number of times that the flow channel floor plate on the upstream side of the susceptor, that is, the deposit in the vicinity of the susceptor on the upper surface of the material gas supply guide peeled and swollen.

  As shown in Table 1, the average layer thickness of the comparative example was 3.2 μm, but a significant effect of increasing the layer thickness was found to be 4.1 μm in Example 1 and 4.6 μm in Example 2. The layer thickness increase rate at this time was 1.28 times in Example 1 and 1.44 times in Example 2. The number of maintenance intervals was 23 times in the comparative example, 26 times in Example 1, and 31 times in Example 2, and the effect of increasing the number of maintenance intervals was recognized.

  The improvement in the layer thickness increase rate in Examples 1 and 2 can be considered as the improvement in material use efficiency. As described above, since the flow rates of the material gases used in Examples 1 and 2 and the comparative example are the same, when the material usage efficiency of the comparative example is set to 100%, in Example 1, the material usage efficiency is improved by 28%. In Example 2, it can be said that it improved by 44%. In other words, if the stacked structure of semiconductor elements such as LED elements is the same, the amount of material gas used can be reduced by an amount corresponding to the improvement in material gas use efficiency, so that the manufacturing cost can be reduced. In addition, since the manufacturing time can be shortened at the same time, productivity can be improved and manufacturing cost can be reduced.

  The dirt (sediment) from the susceptor near end on the upper surface of the material gas supply guide up to the maintenance to the inner end of the heater chamber partition wall is clearly yellow after growing several times in the comparative example. As it overlapped, it gradually became dark brown, and the peeling of the deposits started about 20 times. On the other hand, in Example 1, the dirt (sediment) on the inner end side of the heater chamber partition wall is a light brown color after several growths, obviously the degree of dirt is reduced, and the exfoliation of the deposit is about 26 times. I didn't get up. In Example 2, the adhesion tendency of dirt (sediment) was further reduced, and as a result, peeling did not occur until about 31 times of growth. As described above, the usable number of times until the flow channel portion is cleaned can be increased due to the effect of reducing the contamination of the flow channel portion. In other words, the manufacturing cost can be reduced because the semiconductor element can be manufactured by the shortened cleaning time in the same period.

  As described above, in the conventional structure in which the cooling device is disposed near the outer periphery of the susceptor, the temperature of the outer periphery of the susceptor is reduced, resulting in nonuniform layer thickness and nonuniform composition. The heat in the vicinity of the susceptor can be dissipated without giving temperature fluctuation to such a susceptor (that is, the substrate). Further, the vicinity of the susceptor that cannot be cooled by the water-cooled jacket type or the like can be cooled. Furthermore, the manufacturing cost of the device is also low.

  In the horizontal type MOCVD apparatus, the material gas is added to the horizontal gas flow layer and conveyed to the substrate. Therefore, the material gas diffuses in the stagnation layer immediately above the substrate and reaches the substrate. The material gas becomes a semiconductor crystal through a thermochemical reaction accompanied by migration on the substrate. In other words, the higher the ideal condition is found in the MOCVD apparatus, the higher the quality of the epitaxial crystal growth film, that is, the higher the orientation and the lower the number of dislocations and defects. However, if the deposit on the upstream side of the substrate is deposited thickly, it peels off due to an increase or decrease in the growth temperature (susceptor temperature), disturbing the gas flow and hindering the crystal growth process via the thermochemical decomposition reaction, leading to a decrease in crystal quality. . According to the present invention, adhesion of deposits (by-products) in the upstream portion of the substrate can be suppressed, so that a high-quality epitaxial crystal growth layer can be obtained.

  As described above, according to the present invention, the radiant heat in the flow channel floor plate upstream of the susceptor, that is, in the vicinity of the susceptor of the material gas supply unit, is dissipated to the outside of the material gas supply unit (the back side of the material gas supply guide). Since the temperature rise of the material gas supply guide is suppressed, it is possible to prevent the material gas from being decomposed and consumed unnecessarily, and to prevent the material gas supply part from being contaminated and deposits (by-products). It can be prevented. Therefore, the use efficiency of the material gas can be improved and the maintenance frequency of the apparatus can be reduced. In particular, the growth temperature is very high, for example, gallium nitride (GaN) -based MOCVD growth is highly effective. Furthermore, a high quality epitaxial crystal can be grown.

[Modification example]
In the first and second embodiments described above, the case where the susceptor has a cylindrical shape and the concave portion of the infrared emitting portion is formed concentrically on a surface perpendicular to the central axis of the cylinder has been described as an example. Absent. For example, the shape of the susceptor is not limited to a cylindrical shape. In addition, the concave portion of the infrared emitting portion is not limited to being formed concentrically, and the concave portion of the infrared emitting portion is guided in accordance with the direction of infrared radiation from the susceptor and the waveguide direction in the material gas supply guide. What is necessary is just to have the structure which has the output surface arrange | positioned so that infrared rays may be radiate | emitted outside.

  Moreover, although the infrared radiation | emission part (emission window) 15A demonstrated to the example the case where it was comprised from the continuation of the recessed part dented from the back surface of the material gas supply guide 15, it does not restrict to this. For example, as shown in FIG. 10, the material gas supply guide 15 may be configured as an infrared emission window 15 </ b> B protruding from the back surface. For example, the infrared emission window 15 </ b> B is configured by serrated irregularities in which triangular concave portions 35 are continuously formed, and the irregular structures protrude from the back surface of the material gas supply guide 15. Also in this case, the triangular recess 35 includes a first inclined surface 35A on the side close to the susceptor 22 and a second inclined surface 35B on the far side. The first inclined surface 35A and the second inclined surface 35B are inclined with respect to a plane (or a horizontal plane) perpendicular to the center axis of the cylinder of the susceptor 22 (that is, inner angles of the triangle) are θ1, θ2 respectively. (0 <θ1, θ2 <90 °).

  Moreover, although the case where the cross section of the infrared emitting portion is a triangular concave portion has been described as an example, it is not limited to a triangular shape. For example, the first inclined surface which is an infrared emitting surface has a convex shape, or the second inclined surface has a concave shape so as to efficiently reflect infrared rays emitted from the first inclined surface. Also good. Furthermore, the above-described embodiments and modifications may be appropriately combined and changed. The above numerical values, materials, etc. are merely examples.

DESCRIPTION OF SYMBOLS 10 Vapor growth apparatus 15 Material gas supply guide 20 Substrate 22 Susceptor 14A, 14B Flow channel 15A, 15B Infrared radiation | emission part 31 Recessed part 31A 1st inclined surface 31B 2nd inclined surface 33 Mirror

Claims (9)

A substrate holder for holding the substrate;
A material gas supply section for defining a material gas flow path for supplying a material gas to the growth surface of the substrate;
A heating unit for heating the substrate holding unit,
The material gas supply unit is disposed upstream of the material gas flow path with respect to the substrate holding unit, and has a material gas supply guide made of a material that is transmissive to infrared rays emitted from the substrate holding unit. And
The vapor deposition apparatus according to claim 1, wherein the material gas supply guide includes an infrared emitting portion having an uneven structure formed on a surface different from a surface defining the material gas flow path. The substrate holding part has a cylindrical shape,
The infrared emitting section has a first inclined surface inclined with respect to a plane perpendicular to the cylindrical center axis and a first inclined surface in a cross section in a plane including the cylindrical central axis of the substrate holding portion. 2. The vapor phase growth apparatus according to claim 1, further comprising a concave portion including an inclined second inclined surface.   The vapor deposition apparatus according to claim 2, wherein the infrared emitting portion is formed by unevenness in which a plurality of the concave portions are continuously formed.   4. The vapor phase growth apparatus according to claim 2, wherein the concave portion of the infrared emitting portion is a concave portion having a triangular cross section in a plane including a cylindrical central axis of the substrate holding portion.   The material gas supply guide is composed of a plate-like member whose surface is arranged so as to define the material gas flow path, and the infrared emitting part is provided on the back surface of the material gas supply guide. The vapor phase growth apparatus according to any one of claims 1 to 4.   6. The vapor phase growth apparatus according to claim 2, wherein the first inclined surface has a truncated conical side surface shape that is coaxial with a cylindrical central axis of the substrate holding portion. The first inclined surface is an inclined surface closer to the substrate holding portion than the second inclined surface in the concave portion, and is perpendicular to the cylindrical central axis of the substrate holding portion of the first inclined surface. When the inclination angle with respect to the surface is θ1 (0 <θ1 <90 °) and the critical angle of the infrared ray at the interface with the vacuum of the material gas supply guide is α,
(90 ° -α) / 2 ≦ θ1 ≦ 2α
The vapor phase growth apparatus according to claim 2, wherein: The first inclined surface is an inclined surface closer to the substrate holding portion than the second inclined surface in the concave portion, and is perpendicular to the cylindrical central axis of the substrate holding portion of the first inclined surface. When the inclination angle with respect to the surface is θ1 (0 <θ1 <90 °) and the critical angle of the infrared ray at the interface with the vacuum of the material gas supply guide is α,
90 ° -α ≦ θ1 ≦ 2α
The vapor phase growth apparatus according to claim 2, wherein:   9. The vapor phase growth apparatus according to claim 2, wherein the infrared reflection inclined surface includes a mirror portion.

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