JP2013183075A - Vapor growth device - Google Patents

Abstract

【the purpose】
Provided is a vapor phase growth apparatus that is excellent in temperature controllability and reproducibility and can grow a high-quality crystal layer even when crystal growth is repeatedly performed.
[Solution]
A substrate holding unit that holds the substrate, a heater that is coated to heat the substrate holding unit, and a heater chamber that surrounds the heater and shields radiant heat from the heater are provided. The inner wall surface of the heater chamber facing the heater is provided with a coating having the same thermal emissivity as the heater coating.
[Selection] Figure 2

Description

  Vapor phase growth such as MOCVD is widely used as a semiconductor single crystal growth method in industrial fields such as semiconductor elements such as light emitting diodes (LEDs), laser diodes (LD), 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.

  The organometallic material used for MOCVD growth is thermally decomposed from about 350 ° C. Further, when the organometallic material gas and the hydride gas are mixed, the hydride is easily decomposed by the thermal decomposition of the organometallic material to generate crystals.

  In a conventional MOCVD apparatus for growing an AlGaAs-based semiconductor or an AlGaInP-based semiconductor, heat radiation is suppressed by partitioning with a heat shield plate or a heater chamber partition in order to block radiant heat from the heater. For example, Patent Document 1 describes the soaking of the susceptor in the crystal growth apparatus and the heat (heat extraction) escaping from the heating apparatus. However, for example, in the crystal growth of a group III nitride semiconductor based on GaN (gallium nitride), the growth temperature is about 1000 ° C. or higher, and the growth temperature is 200-300 ° C. as compared to the case of the AlGaAs semiconductor described above. High and the amount of radiant heat is very large.

In addition, in the conventional MOCVD apparatus, an inert gas (nitrogen: N ₂ ) or the like is introduced as a purge gas into the heater chamber in order to protect the heater terminal and the rotary introducer and prevent material gas from entering the heater chamber. It has been broken. In the GaN-based semiconductor MOCVD apparatus, NH ₃ used as a material gas corrodes graphite used for a susceptor and a heater. Therefore, the graphite surface is generally coated with SiC, PBN (Pyrolytic Boron Nitride) or the like for protection.

  As a device for extending the life of the heater against the corrosive gas, a heater member, a coating member, a structure in which the corrosive gas is not brought into contact with the heater, and the like have been studied (for example, Patent Documents 2 and 3).

JP 2009-302223 A JP-A-11-67427 JP 2009-194045 A

  As described above, in the conventional growth apparatus, the heater is coated with SiC or the like for protection from the corrosive gas. However, particularly in high-temperature growth of a GaN-based semiconductor or the like, the heater is coated around the coating material. Scattering is intense. The scattered coating material adheres to the surface of the heater indoor wall such as the back surface of the susceptor and the heat shield (for example, BN). The adhesion of the coating material changes the thermal emissivity of the back surface of the susceptor, heat shield, etc., and the actual temperature (actual temperature growth rate) of the substrate placed on the susceptor changes even if the control temperature is constant. I found out that

  When growing the semiconductor device described above, it is necessary to control the susceptor (substrate) temperature accurately and with good reproducibility in controlling the crystal composition, layer thickness, doping concentration, and the like of the growth layer. In particular, when a light emitting diode (LED) is grown, the band gap changes depending on the crystal composition of the light emitting layer, and the emission wavelength changes.

  However, as described above, even if the control temperature is kept constant, the actual temperature of the substrate changes due to the change in the thermal emissivity around the heater, and the reproducibility of the emission wavelength, internal quantum efficiency, operating voltage, etc. decreases in the LED However, there are problems that the characteristics are deteriorated, the manufacturing yield is reduced, and the cost is increased.

  The present invention has been made in view of such points, and its purpose is to suppress the change of the thermal emissivity in the apparatus and to maintain the initial thermal environment for a long time, and is excellent in temperature controllability and reproducibility thereof. It is to provide a vapor phase growth apparatus. That is, an object of the present invention is to provide a vapor phase growth apparatus capable of growing a high-quality crystal layer with high temperature controllability even when crystal growth is repeatedly performed.

The vapor phase growth apparatus of the present invention is
A substrate holder for holding the substrate;
A heater that is coated and heats the substrate holder;
A heater chamber that surrounds the heater and shields radiant heat from the heater;
The inner wall surface of the heater chamber facing the heater is provided with a coating having the same thermal emissivity as the heater coating.

It is the top view (upper stage) and sectional drawing (lower stage) which show typically the composition of the crystal growth device of the present invention. It is an expanded sectional view which expands and shows the surrounding part (part W shown with a broken line in FIG. 1) of the heater chamber of FIG. It is sectional drawing which shows typically the structure of the growth layer of Example 1 and a comparative example. It is a figure which compares and shows the time-dependent change of the temperature measurement result at the time of GaN layer growth at the time of using the MOCVD apparatus of Example 1, and the MOCVD apparatus of a comparative example. It is a figure which compares and shows the time-dependent change of the temperature measurement result at the time of InGaN layer growth at the time of using the MOCVD apparatus of Example 1, and the MOCVD apparatus of a comparative example.

  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 cross-sectional view (lower stage) of a horizontal type crystal growth apparatus (MOCVD apparatus) 10, and the top view shows a case where the substrate side is viewed along line VV in the cross-sectional view. FIG. 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. (Substrate holding part) 22, provided on the back side of the susceptor 22, the susceptor 22 is rotated by the heater 24 and the rotating shaft 29 (substrate rotating mechanism) that heat the susceptor 22 (that is, heats the substrate 20) (that is, the substrate). A motor 25 that rotates 20). Further, a thermocouple for measuring the temperature of the susceptor 22 is provided on the back surface side of the susceptor 22 in order to control the growth temperature.

  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 arranged on the upstream side of the material gas with respect to the susceptor 22. On the back side of the material gas supply guide 15, a cooling gas flow path 16 is provided through which the cooling gas flows through the cooling gas supply pipe 16 </ b> A, and the material gas supply guide 15 is cooled.

Further, the MOCVD apparatus 10 includes a heat shield part 26 composed of one or more heat shield plates for shutting off the heat of the heater 24 and preventing heat removal, and a heater chamber 27R outside the heat shield part 26. A heater chamber partition wall 27 is defined. In the following, a case where the heat shield 26 is composed of a plurality of heat shield plates will be described as an example. A heater chamber gas supply pipe 27A is connected to the heater chamber partition wall 27, and purge gas is supplied into the heater chamber 27A. Nitrogen gas, hydrogen gas, argon gas or the like is used as the purge gas. In addition, 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 be flowed so that a material gas or the like diffused into the reaction vessel can be exhausted. The heater chamber partition wall 27 has a notch in a part in the downstream direction of the material gas, and has a structure capable of exhausting the heater chamber purge gas and the cooling gas.

  The cooling gas may be any gas that does not corrode the susceptor 22, the heater 24, and the heat shield 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.

  FIG. 2 is an enlarged cross-sectional view showing a portion around the heater chamber 27R (a portion W indicated by a broken line in FIG. 1). In Example 1, the surface of the heater 24 which is a heating unit is coated (coated) with SiC (silicon carbide). A heat shield portion 26 composed of a plurality of heat shield plates is provided on the side and below the heater 24. Then, the heat shield 26F facing the heater 24, the rotating shaft (rotating mechanism) 29, and the back surface of the susceptor 22 in the heat shield 26 are directly radiated from the heater 24 and heated. In other words, the heat shield plate 26F facing the heater 24, the rotary shaft 29, and the back surface of the susceptor 22 define the inner wall of the heater chamber 27R. The constituent elements of the heater chamber 27R that define the inner wall of the heater chamber 27R are not limited to these. In short, the component facing the heater 24 among the components of the heater chamber 27R defines the inner wall of the heater chamber 27R.

  In Example 1, the surface facing the heater 24 of the inner wall surface of the heater chamber 27R is coated with the same material (SiC) as the coating material on the surface of the heater 24. That is, among the heat shield plates of the heat shield section 26, SiC coating is applied to the surface of the heat shield plate 26 </ b> F facing the heater 24, the surface of the rotating shaft 29, and the back surface of the susceptor 22. More specifically, the heat shield plate coating 26C is provided on the surface of the portion where the heat shield plate 26F faces the heater 24, and the coating 29C is provided on the surface of the portion where the rotary shaft 29 faces the heater 24, A coating 22 </ b> C is provided on the back surface (bottom surface) of the susceptor 22.

  The coating was performed by coating SiC twice with a film thickness of 30 μm (total film thickness: 60 μm). The coating film thickness is preferably 10 μm or more, which is the thermal emissivity of a thick film (so-called bulk) that exhibits the thermal emissivity of the coating material itself. Moreover, since it may peel off with a thermal expansion difference when too thick, 100 micrometers or less are preferable.

  Further, although SiC has been described as an example of the coating material for the inner wall surface of the heater chamber, for example, PBN, TaC, TiC, or the like can be used as long as it is the same material as the coating material for the heater. Or even if it uses a different coating material, the coating which has the same thermal emissivity as the coating of a heater should just be given. For example, the coating film thickness may be adjusted with respect to the base material of the inner wall of the heater chamber so as to have the same thermal emissivity.

[Crystal growth]
Crystal growth was performed using the MOCVD apparatus 10 of Example 1, and evaluation was performed. In addition, crystal growth was performed using a MOCVD apparatus having the same configuration as the MOCVD apparatus of Example 1 except that the inner surface of the heater chamber 27R was not coated. More specifically, in the MOCVD apparatus of the comparative example, the heat shield plate and the rotating mechanism were not coated with SiC, and BN (boron nitride) as a base material thereof was exposed on the surface.

  FIG. 3 is a cross-sectional view schematically showing the structure of the growth layer of Example 1 and the comparative example. In addition, all the crystal growth using the MOCVD apparatus of Example 1 and a comparative example was implemented on 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. A circular (2 inch) c-plane sapphire (α-alumina) substrate was used as the growth substrate 20. As an organic metal material gas TMG (trimethyl gallium), TMI (trimethyl indium), TMA (trimethyl aluminum), with Cp ₂ Mg (bis-cyclopentadienyl magnesium), NH ₃ (ammonia) as the hydride gas, SiH ₄ (Monosilane) was used.

  The organometallic material gas and the hydride gas were supplied from the supply pipe 12C at a total flow rate of 10 L / min together with the carrier gas in which hydrogen and nitrogen were mixed. Further, a carrier gas mixed with hydrogen and nitrogen was supplied from the gas supply pipe 12D at a flow rate of 30 L / min.

  First, the substrate 20 was heat-treated. A hydrogen gas is supplied from the gas supply pipe 12C at a flow rate of 6 L / min, and a gas mixture of hydrogen: nitrogen = 1: 1 is supplied from the gas supply pipe 12D at a flow rate of 30 L / min, and the temperature of the susceptor 22 is set to 1000 ° C. Annealed for a minute.

Next, the temperature of the susceptor 22 (that is, the substrate 20) is set to 530 ° C., the carrier gas is hydrogen, TMG and NH ₃ are supplied as material gases from the gas supply pipe 12C, and the low temperature growth GaN layer is formed on the sapphire substrate 20. 41 was grown with a layer thickness of 30 nm. A carrier gas in which hydrogen was mixed at a rate of 15 L / min and nitrogen was mixed at a rate of 15 L / min was supplied from the gas supply pipe 12D. Next, the temperature of the susceptor 22 was set to 1050 ° C., and the low-temperature grown GaN layer 41 was annealed for 10 minutes.

Next, the temperature of the susceptor 22 is set to 1030 ° C., hydrogen is used as the carrier gas, TMG, NH _3, and SiH ₄ are supplied from the gas supply pipe 12 C as material gases, and the n-type GaN layer 42 is formed on the low-temperature grown GaN layer 41. Was grown with a layer thickness of 6 μm. A carrier gas in which hydrogen was mixed at a rate of 15 L / min and nitrogen was mixed at a rate of 15 L / min was supplied from the gas supply pipe 12D.

Next, a light emitting layer 43 having a quantum well structure was grown. More specifically, the temperature of the susceptor 22 was set to 760 ° C., the carrier gas was nitrogen, TMG and NH ₃ were supplied as material gases, and a GaN layer was grown as a barrier layer with a layer thickness of 8 nm. Next, nitrogen was used as a carrier gas, TMG, TMI and NH ₃ were supplied as material gases, and an InGaN layer was grown as a well layer with a layer thickness of 3 nm. After the barrier layer and the well layer were alternately grown in the above-described procedure, the barrier layer was grown and the light emitting layer 43 was grown. In the growth of the barrier layer and the well layer, only nitrogen was supplied at 30 L / min as a carrier gas from the gas supply pipe 12D.

Next, the temperature of the susceptor 22 is set to 900 ° C., the carrier gas is hydrogen, TMA, TMG, NH ₃ and Cp ₂ Mg are supplied from the gas supply pipe 12C as material gases, and the p-type AlGaN layer is formed on the light emitting layer 43. 44 was grown with a layer thickness of 30 nm. A carrier gas in which hydrogen was mixed at a rate of 15 L / min and nitrogen was mixed at a rate of 15 L / min was supplied from the gas supply pipe 12D.

Next, the temperature of the susceptor 22 is set to 900 ° C., the carrier gas is hydrogen, TMG, NH ₃ and Cp ₂ Mg are supplied as material gases from the gas supply pipe 12C, and the p-type GaN layer is formed on the p-type AlGaN layer 44. 45 was grown with a layer thickness of 100 nm.

[Substrate surface temperature during growth]
The substrate surface temperature during growth was measured by a radiation thermometer installed above the growth substrate 20. FIG. 4 and FIG. 5 show the change over time in the temperature measurement results when the MOCVD apparatus of Example 1 and the MOCVD apparatus of the comparative example are used. That is, the horizontal axis indicates the number of times of growth, and the vertical axis indicates the temperature change (° C.) based on the temperature at the start of use of the apparatus (the number of times of growth is the first time). 4 shows the measurement result of the surface temperature during the growth of the n-type GaN layer 42, and FIG. 5 shows the measurement result of the surface temperature during the growth of the light emitting layer 43 (InGaN). In addition, the average value of the surface temperature in the wafer surface is shown.

  In the case of using the MOCVD apparatus of the comparative example, in the initial stage of use (about 30 to 40 times), the maximum surface temperature is 40 ° C. (FIG. 4) for GaN growth and about 20 ° C. (FIG. 5) for InGaN growth. Declined. On the other hand, when the MOCVD apparatus of Example 1 is used, the temperature change is within a range of about ± 5 ° C. even if the growth is performed 700 to 800 times.

  When GaN is grown in a state where the temperature is deviated, the surface morphology of the growth layer changes, which adversely affects the crystal quality of the light emitting layer grown on the GaN layer. For example, electrical characteristics such as emission wavelength, light output-current characteristic (LI) characteristic, and forward voltage (Vf) change. If growth is performed at a temperature shifted by 40 ° C., pits are formed on the surface, causing current leakage, or conversely, a structure (protrusion) called hillock is formed. The production yield decreases due to the deterioration of the adhesiveness. Further, in the growth of InGaN, the temperature shift directly affects the composition. For example, the problem is that the In composition of the light emitting layer is shifted and the emission wavelength is greatly shifted.

  In the MOCVD apparatus of the comparative example, SiC as a heater coating material was scattered and adhered to the surface of the heat shield plate made of BN and the back surface of the susceptor, and the emissivity of heat from the inner wall of the heat shield plate and the back surface of the susceptor decreased. It is considered a thing. When the emissivity of heat changes, the heat dissipation path changes, and it is considered that the actual growth temperature of the substrate disposed on the susceptor has greatly changed even at the same control temperature.

  On the other hand, according to the MOCVD apparatus of Example 1, since the inner wall of the heat shield plate and the back surface of the susceptor are coated with the same material as the coating material of the heater, the thermal emissivity does not change even if the coating material adheres. Therefore, it was found that the heat radiation state at the start of use of the apparatus (or immediately after the maintenance) can be maintained, and the change in the actual growth temperature with time can be prevented.

  By the way, the temperature control of the susceptor is generally performed by a thermocouple installed inside the susceptor. In view of the reproducibility of the growth temperature, a position as close as possible to the growth substrate is desirable, but in practice, it is difficult to install a thermocouple at a position in contact with the growth substrate in order to realize rotation and conveyance of the growth substrate. Therefore, the thermocouple is placed at a distance from the growth substrate, and the temperature at that position is controlled. Although it is conceivable to control the temperature on the growth substrate by measuring with a radiation thermometer, since the reaction product of the material gas accumulates in the reaction chamber, the contamination is not a ratio around the heater, but is transparent. Even if the temperature of the substrate is observed through the quartz part, the quartz part is immediately contaminated, and accurate measurement is difficult. Even if maintenance is performed frequently, if the maintenance frequency increases, the production throughput of the crystal growth wafer decreases, which causes an increase in cost.

  In the MOCVD apparatus, the influence of radiation is large in heat transfer. In particular, the growth temperature of gallium nitride (GaN) -based semiconductors is as high as about 1,000 ° C., so the influence of radiation by components around the heater is very large. Specifically, the heat generated by the heater is dissipated not only in the direction of the substrate but also in all directions due to radiation. At this time, if the thermal emissivity of the components around the heater changes, the heat dissipation due to radiation changes, and the ratio of the heat transmitted to the growth substrate changes. If the distance from the heat source to the growth substrate and the thermal conductivity are constant and the amount of heat transmitted in the direction of the growth substrate changes, the temperature difference between the heat source and the growth substrate also changes accordingly.

  As described above, in MOCVD growth, particularly, for example, growth of GaN-based crystals, the growth temperature is as high as about 1,000 ° C., and the scattering of coating materials such as SiC for protecting the heater from corrosive gas is remarkable. Yes, it adheres to the heater room wall facing the heater. Then, the emissivity of heat from the wall surface of the heater room such as the inner wall of the heat shield plate and the back surface of the susceptor to which the coating material is attached changes, and the actual growth temperature of the substrate disposed on the susceptor changes greatly even at the same control temperature.

  According to the present invention, the surface of the member facing the heater, ie, the lower surface of the susceptor, and the inner wall surface of the heater chamber facing the heater are coated with the same material as the coating material of the heater. Therefore, even if the heater coating material scatters from the heater and adheres to the inner wall surface of the heater chamber, the thermal emissivity of the inner wall surface does not change, and the thermal emissivity at the start of use of the device or immediately after maintenance does not change. In addition, changes in the actual growth temperature with time can be prevented. Therefore, the maintenance frequency of the apparatus can be reduced and a highly reproducible vapor phase growth apparatus can be provided. In other words, even when crystal growth is repeatedly performed, the temperature controllability is high, and therefore the controllability and reproducibility of the semiconductor layer composition, layer thickness, doping concentration, etc. are high, and vapor phase growth capable of growing a high-quality crystal layer. An apparatus can be provided.

  In addition, although the case where the heater indoor wall surface such as the inner wall of the heat shield plate or the back surface of the susceptor is coated with the same material as the heater coating material has been described, the present invention is not limited thereto, and a different coating material may be used. For example, the thermal emissivity of the inner wall surface of the heater chamber varies depending on the coating film thickness and the base material of the inner wall of the heater chamber, but the coating film thickness is adjusted for the base material of the inner wall so as to have the same thermal emissivity. It may be coated.

  In the above-described embodiments, the flow channel type MOCVD apparatus has been described as an example. However, the present invention is not limited to this, and the present invention can also be applied to a two-flow type MOCVD apparatus. Further, the present invention can be applied to a vertical MOCVD apparatus and other vapor phase growth apparatuses.

DESCRIPTION OF SYMBOLS 10 Vapor growth apparatus 20 Substrate 22 Susceptor 24 Heater 26 Heat shield part 26F Heat shield plate 29 Rotating mechanism 22C, 26C, 29C Coating

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

  Vapor phase growth such as MOCVD is widely used as a semiconductor single crystal growth method in industrial fields such as semiconductor elements such as light emitting diodes (LEDs), laser diodes (LD), 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.

  The organometallic material used for MOCVD growth is thermally decomposed from about 350 ° C. Further, when the organometallic material gas and the hydride gas are mixed, the hydride is easily decomposed by the thermal decomposition of the organometallic material to generate crystals.

  In a conventional MOCVD apparatus for growing an AlGaAs-based semiconductor or an AlGaInP-based semiconductor, heat radiation is suppressed by partitioning with a heat shield plate or a heater chamber partition in order to block radiant heat from the heater. For example, Patent Document 1 describes the soaking of the susceptor in the crystal growth apparatus and the heat (heat extraction) escaping from the heating apparatus. However, for example, in the crystal growth of a group III nitride semiconductor based on GaN (gallium nitride), the growth temperature is about 1000 ° C. or higher, and the growth temperature is 200-300 ° C. as compared to the case of the AlGaAs semiconductor described above. High and the amount of radiant heat is very large.

In addition, in the conventional MOCVD apparatus, an inert gas (nitrogen: N ₂ ) or the like is introduced as a purge gas into the heater chamber in order to protect the heater terminal and the rotary introducer and prevent material gas from entering the heater chamber. It has been broken. In the GaN-based semiconductor MOCVD apparatus, NH ₃ used as a material gas corrodes graphite used for a susceptor and a heater. Therefore, the graphite surface is generally coated with SiC, PBN (Pyrolytic Boron Nitride) or the like for protection.

  As a device for extending the life of the heater against the corrosive gas, a heater member, a coating member, a structure in which the corrosive gas is not brought into contact with the heater, and the like have been studied (for example, Patent Documents 2 and 3).

JP 2009-302223 A JP-A-11-67427 JP 2009-194045 A

  As described above, in the conventional growth apparatus, the heater is coated with SiC or the like for protection from the corrosive gas. However, particularly in high-temperature growth of a GaN-based semiconductor or the like, the heater is coated around the coating material. Scattering is intense. The scattered coating material adheres to the surface of the heater indoor wall such as the back surface of the susceptor and the heat shield (for example, BN). The adhesion of the coating material changes the thermal emissivity of the back surface of the susceptor, heat shield, etc., and the actual temperature (actual temperature growth rate) of the substrate placed on the susceptor changes even if the control temperature is constant. I found out that

  When growing the semiconductor device described above, it is necessary to control the susceptor (substrate) temperature accurately and with good reproducibility in controlling the crystal composition, layer thickness, doping concentration, and the like of the growth layer. In particular, when a light emitting diode (LED) is grown, the band gap changes depending on the crystal composition of the light emitting layer, and the emission wavelength changes.

  However, as described above, even if the control temperature is kept constant, the actual temperature of the substrate changes due to the change in the thermal emissivity around the heater, and the reproducibility of the emission wavelength, internal quantum efficiency, operating voltage, etc. decreases in the LED However, there are problems that the characteristics are deteriorated, the manufacturing yield is reduced, and the cost is increased.

  The present invention has been made in view of such points, and its purpose is to suppress the change of the thermal emissivity in the apparatus and to maintain the initial thermal environment for a long time, and is excellent in temperature controllability and reproducibility thereof. It is to provide a vapor phase growth apparatus. That is, an object of the present invention is to provide a vapor phase growth apparatus capable of growing a high-quality crystal layer with high temperature controllability even when crystal growth is repeatedly performed.

The vapor phase growth apparatus of the present invention is
A substrate holder for holding the substrate;
A heater that is coated and heats the substrate holder;
A heater chamber that surrounds the heater and shields radiant heat from the heater;
The inner wall surface of the heater chamber facing the heater is provided with a coating having the same thermal emissivity as the heater coating.

It is the top view (upper stage) and sectional drawing (lower stage) which show typically the composition of the crystal growth device of the present invention. It is an expanded sectional view which expands and shows the surrounding part (part W shown with a broken line in FIG. 1) of the heater chamber of FIG. It is sectional drawing which shows typically the structure of the growth layer of Example 1 and a comparative example. It is a figure which compares and shows the time-dependent change of the temperature measurement result at the time of GaN layer growth at the time of using the MOCVD apparatus of Example 1, and the MOCVD apparatus of a comparative example. It is a figure which compares and shows the time-dependent change of the temperature measurement result at the time of InGaN layer growth at the time of using the MOCVD apparatus of Example 1, and the MOCVD apparatus of a comparative example.

  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 cross-sectional view (lower stage) of a horizontal type crystal growth apparatus (MOCVD apparatus) 10, and the top view shows a case where the substrate side is viewed along line VV in the cross-sectional view. FIG. 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. (Substrate holding part) 22, provided on the back side of the susceptor 22, the susceptor 22 is rotated by the heater 24 and the rotating shaft 29 (substrate rotating mechanism) that heat the susceptor 22 (that is, heats the substrate 20) (that is, the substrate). A motor 25 that rotates 20). Further, a thermocouple for measuring the temperature of the susceptor 22 is provided on the back surface side of the susceptor 22 in order to control the growth temperature.

  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 arranged on the upstream side of the material gas with respect to the susceptor 22. On the back side of the material gas supply guide 15, a cooling gas flow path 16 is provided through which the cooling gas flows through the cooling gas supply pipe 16 </ b> A, and the material gas supply guide 15 is cooled.

Further, the MOCVD apparatus 10 includes a heat shield part 26 composed of one or more heat shield plates for shutting off the heat of the heater 24 and preventing heat removal, and a heater chamber 27R outside the heat shield part 26. A heater chamber partition wall 27 is defined. In the following, a case where the heat shield 26 is composed of a plurality of heat shield plates will be described as an example. A heater chamber gas supply pipe 27A is connected to the heater chamber partition wall 27, and purge gas is supplied into the heater chamber 27A. 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 heater chamber partition wall 27 has a notch in a part in the downstream direction of the material gas, and has a structure capable of exhausting the heater chamber purge gas and the cooling gas.

  The cooling gas may be any gas that does not corrode the susceptor 22, the heater 24, and the heat shield 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.

  FIG. 2 is an enlarged cross-sectional view showing a portion around the heater chamber 27R (a portion W indicated by a broken line in FIG. 1). In Example 1, the surface of the heater 24 which is a heating unit is coated (coated) with SiC (silicon carbide). A heat shield portion 26 composed of a plurality of heat shield plates is provided on the side and below the heater 24. Then, the heat shield 26F facing the heater 24, the rotating shaft (rotating mechanism) 29, and the back surface of the susceptor 22 in the heat shield 26 are directly radiated from the heater 24 and heated. In other words, the heat shield plate 26F facing the heater 24, the rotary shaft 29, and the back surface of the susceptor 22 define the inner wall of the heater chamber 27R. The constituent elements of the heater chamber 27R that define the inner wall of the heater chamber 27R are not limited to these. In short, the component facing the heater 24 among the components of the heater chamber 27R defines the inner wall of the heater chamber 27R.

  In Example 1, the surface facing the heater 24 of the inner wall surface of the heater chamber 27R is coated with the same material (SiC) as the coating material on the surface of the heater 24. That is, among the heat shield plates of the heat shield section 26, SiC coating is applied to the surface of the heat shield plate 26 </ b> F facing the heater 24, the surface of the rotating shaft 29, and the back surface of the susceptor 22. More specifically, the heat shield plate coating 26C is provided on the surface of the portion where the heat shield plate 26F faces the heater 24, and the coating 29C is provided on the surface of the portion where the rotary shaft 29 faces the heater 24, A coating 22 </ b> C is provided on the back surface (bottom surface) of the susceptor 22.

  The coating was performed by coating SiC twice with a film thickness of 30 μm (total film thickness: 60 μm). The coating film thickness is preferably 10 μm or more, which is the thermal emissivity of a thick film (so-called bulk) that exhibits the thermal emissivity of the coating material itself. Moreover, since it may peel off with a thermal expansion difference when too thick, 100 micrometers or less are preferable.

  Further, although SiC has been described as an example of the coating material for the inner wall surface of the heater chamber, for example, PBN, TaC, TiC, or the like can be used as long as it is the same material as the coating material for the heater. Or even if it uses a different coating material, the coating which has the same thermal emissivity as the coating of a heater should just be given. For example, the coating film thickness may be adjusted with respect to the base material of the inner wall of the heater chamber so as to have the same thermal emissivity.

[Crystal growth]
Crystal growth was performed using the MOCVD apparatus 10 of Example 1, and evaluation was performed. In addition, crystal growth was performed using a MOCVD apparatus having the same configuration as the MOCVD apparatus of Example 1 except that the inner surface of the heater chamber 27R was not coated. More specifically, in the MOCVD apparatus of the comparative example, the heat shield plate and the rotating mechanism were not coated with SiC, and BN (boron nitride) as a base material thereof was exposed on the surface.

  FIG. 3 is a cross-sectional view schematically showing the structure of the growth layer of Example 1 and the comparative example. In addition, all the crystal growth using the MOCVD apparatus of Example 1 and a comparative example was implemented on 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. A circular (2 inch) c-plane sapphire (α-alumina) substrate was used as the growth substrate 20. As an organic metal material gas TMG (trimethyl gallium), TMI (trimethyl indium), TMA (trimethyl aluminum), with _Cp 2 Mg (bis-cyclopentadienyl magnesium), NH ₃ (ammonia) as the hydride gas, SiH ₄ (Monosilane) was used.

  The organometallic material gas and the hydride gas were supplied from the supply pipe 12C at a total flow rate of 10 L / min together with the carrier gas in which hydrogen and nitrogen were mixed. Further, a carrier gas mixed with hydrogen and nitrogen was supplied from the gas supply pipe 12D at a flow rate of 30 L / min.

  First, the substrate 20 was heat-treated. A hydrogen gas is supplied from the gas supply pipe 12C at a flow rate of 6 L / min, and a gas mixture of hydrogen: nitrogen = 1: 1 is supplied from the gas supply pipe 12D at a flow rate of 30 L / min, and the temperature of the susceptor 22 is set to 1000 ° C. Annealed for a minute.

Next, the temperature of the susceptor 22 (that is, the substrate 20) is set to 530 ° C., the carrier gas is hydrogen, TMG and NH ₃ are supplied as material gases from the gas supply pipe 12C, and the low-temperature growth GaN layer is formed on the sapphire substrate 20. 41 was grown with a layer thickness of 30 nm. A carrier gas in which hydrogen was mixed at a rate of 15 L / min and nitrogen was mixed at a rate of 15 L / min was supplied from the gas supply pipe 12D. Next, the temperature of the susceptor 22 was set to 1050 ° C., and the low-temperature grown GaN layer 41 was annealed for 10 minutes.

Next, the temperature of the susceptor 22 is set to 1030 ° C., hydrogen is used as the carrier gas, TMG, NH ₃ and SiH ₄ are supplied from the gas supply pipe 12 C as material gases, and the n-type GaN layer 42 is formed on the low-temperature grown GaN layer 41. Was grown with a layer thickness of 6 μm. A carrier gas in which hydrogen was mixed at a rate of 15 L / min and nitrogen was mixed at a rate of 15 L / min was supplied from the gas supply pipe 12D.

Next, a light emitting layer 43 having a quantum well structure was grown. More specifically, the temperature of the susceptor 22 was set to 760 ° C., the carrier gas was nitrogen, TMG and NH ₃ were supplied as material gases, and a GaN layer was grown as a barrier layer with a layer thickness of 8 nm. Next, nitrogen was used as a carrier gas, TMG, TMI, and NH ₃ were supplied as material gases, and an InGaN layer was grown as a well layer with a layer thickness of 3 nm. After the barrier layer and the well layer were alternately grown in the above-described procedure, the barrier layer was grown and the light emitting layer 43 was grown. In the growth of the barrier layer and the well layer, only nitrogen was supplied at 30 L / min as a carrier gas from the gas supply pipe 12D.

Next, the temperature of the susceptor 22 is set to 900 ° C., the carrier gas is hydrogen, TMA, TMG, NH ₃ and Cp ₂ Mg are supplied from the gas supply pipe 12C as material gases, and the p-type AlGaN layer is formed on the light emitting layer 43. 44 was grown with a layer thickness of 30 nm. A carrier gas in which hydrogen was mixed at a rate of 15 L / min and nitrogen was mixed at a rate of 15 L / min was supplied from the gas supply pipe 12D.

Next, the temperature of the susceptor 22 is set to 900 ° C., the carrier gas is hydrogen, TMG, NH ₃ and Cp ₂ Mg are supplied as material gases from the gas supply pipe 12 C, and the p-type GaN layer is formed on the p-type AlGaN layer 44. 45 was grown with a layer thickness of 100 nm.

[Substrate surface temperature during growth]
The substrate surface temperature during growth was measured by a radiation thermometer installed above the growth substrate 20. FIG. 4 and FIG. 5 show the change over time in the temperature measurement results when the MOCVD apparatus of Example 1 and the MOCVD apparatus of the comparative example are used. That is, the horizontal axis indicates the number of times of growth, and the vertical axis indicates the temperature change (° C.) based on the temperature at the start of use of the apparatus (the number of times of growth is the first time). 4 shows the measurement result of the surface temperature during the growth of the n-type GaN layer 42, and FIG. 5 shows the measurement result of the surface temperature during the growth of the light emitting layer 43 (InGaN). In addition, the average value of the surface temperature in the wafer surface is shown.

  In the case of using the MOCVD apparatus of the comparative example, in the initial stage of use (about 30 to 40 times), the maximum surface temperature is 40 ° C. (FIG. 4) for GaN growth and about 20 ° C. (FIG. 5) for InGaN growth. Declined. On the other hand, when the MOCVD apparatus of Example 1 is used, the temperature change is within a range of about ± 5 ° C. even if the growth is performed 700 to 800 times.

  When GaN is grown in a state where the temperature is deviated, the surface morphology of the growth layer changes, which adversely affects the crystal quality of the light emitting layer grown on the GaN layer. For example, electrical characteristics such as emission wavelength, light output-current characteristic (LI) characteristic, and forward voltage (Vf) change. If growth is performed at a temperature shifted by 40 ° C., pits are formed on the surface, causing current leakage, or conversely, a structure (protrusion) called hillock is formed. The production yield decreases due to the deterioration of the adhesiveness. Further, in the growth of InGaN, the temperature shift directly affects the composition. For example, the problem is that the In composition of the light emitting layer is shifted and the emission wavelength is greatly shifted.

  In the MOCVD apparatus of the comparative example, SiC as a heater coating material was scattered and adhered to the surface of the heat shield plate made of BN and the back surface of the susceptor, and the emissivity of heat from the inner wall of the heat shield plate and the back surface of the susceptor decreased. It is considered a thing. When the emissivity of heat changes, the heat dissipation path changes, and it is considered that the actual growth temperature of the substrate disposed on the susceptor has greatly changed even at the same control temperature.

  On the other hand, according to the MOCVD apparatus of Example 1, since the inner wall of the heat shield plate and the back surface of the susceptor are coated with the same material as the coating material of the heater, the thermal emissivity does not change even if the coating material adheres. Therefore, it was found that the heat radiation state at the start of use of the apparatus (or immediately after the maintenance) can be maintained, and the change in the actual growth temperature with time can be prevented.

  By the way, the temperature control of the susceptor is generally performed by a thermocouple installed inside the susceptor. In view of the reproducibility of the growth temperature, a position as close as possible to the growth substrate is desirable, but in practice, it is difficult to install a thermocouple at a position in contact with the growth substrate in order to realize rotation and conveyance of the growth substrate. Therefore, the thermocouple is placed at a distance from the growth substrate, and the temperature at that position is controlled. Although it is conceivable to control the temperature on the growth substrate by measuring with a radiation thermometer, since the reaction product of the material gas accumulates in the reaction chamber, the contamination is not a ratio around the heater, but is transparent. Even if the temperature of the substrate is observed through the quartz part, the quartz part is immediately contaminated, and accurate measurement is difficult. Even if maintenance is performed frequently, if the maintenance frequency increases, the production throughput of the crystal growth wafer decreases, which causes an increase in cost.

  In the MOCVD apparatus, the influence of radiation is large in heat transfer. In particular, the growth temperature of gallium nitride (GaN) -based semiconductors is as high as about 1,000 ° C., so the influence of radiation by components around the heater is very large. Specifically, the heat generated by the heater is dissipated not only in the direction of the substrate but also in all directions due to radiation. At this time, if the thermal emissivity of the components around the heater changes, the heat dissipation due to radiation changes, and the ratio of the heat transmitted to the growth substrate changes. If the distance from the heat source to the growth substrate and the thermal conductivity are constant and the amount of heat transmitted in the direction of the growth substrate changes, the temperature difference between the heat source and the growth substrate also changes accordingly.

  As described above, in MOCVD growth, particularly, for example, growth of GaN-based crystals, the growth temperature is as high as about 1,000 ° C., and the scattering of coating materials such as SiC for protecting the heater from corrosive gas is remarkable. Yes, it adheres to the heater room wall facing the heater. Then, the emissivity of heat from the wall surface of the heater room such as the inner wall of the heat shield plate and the back surface of the susceptor to which the coating material is attached changes, and the actual growth temperature of the substrate disposed on the susceptor changes greatly even at the same control temperature.

  According to the present invention, the surface of the member facing the heater, ie, the lower surface of the susceptor, and the inner wall surface of the heater chamber facing the heater are coated with the same material as the coating material of the heater. Therefore, even if the heater coating material scatters from the heater and adheres to the inner wall surface of the heater chamber, the thermal emissivity of the inner wall surface does not change, and the thermal emissivity at the start of use of the device or immediately after maintenance does not change. In addition, changes in the actual growth temperature with time can be prevented. Therefore, the maintenance frequency of the apparatus can be reduced and a highly reproducible vapor phase growth apparatus can be provided. In other words, even when crystal growth is repeatedly performed, the temperature controllability is high, and therefore the controllability and reproducibility of the semiconductor layer composition, layer thickness, doping concentration, etc. are high, and vapor phase growth capable of growing a high-quality crystal layer. An apparatus can be provided.

  In addition, although the case where the heater indoor wall surface such as the inner wall of the heat shield plate or the back surface of the susceptor is coated with the same material as the heater coating material has been described, the present invention is not limited thereto, and a different coating material may be used. For example, the thermal emissivity of the inner wall surface of the heater chamber varies depending on the coating film thickness and the base material of the inner wall of the heater chamber, but the coating film thickness is adjusted for the base material of the inner wall so as to have the same thermal emissivity. It may be coated.

  In the above-described embodiments, the flow channel type MOCVD apparatus has been described as an example. However, the present invention is not limited to this, and the present invention can also be applied to a two-flow type MOCVD apparatus. Further, the present invention can be applied to a vertical MOCVD apparatus and other vapor phase growth apparatuses.

DESCRIPTION OF SYMBOLS 10 Vapor growth apparatus 20 Substrate 22 Susceptor 24 Heater 26 Heat shield part 26F Heat shield plate 29 Rotating mechanism 22C, 26C, 29C Coating

Claims (5)

A substrate holder for holding the substrate;
A heater that is coated and heats the substrate holder;
A heater chamber that surrounds the heater and shields radiant heat from the heater;
A vapor phase growth apparatus characterized in that the inner wall surface of the heater chamber facing the heater is provided with a coating having the same thermal emissivity as the coating of the heater.   The vapor phase growth apparatus according to claim 1, wherein the surface of the substrate holding part facing the heater is coated with a coating having the same thermal emissivity as that of the coating of the heater.  It has a rotation mechanism which rotates the said substrate holding part, The coating which has the same thermal emissivity as the coating of the said heater is given to the surface which faces the said heater of the said rotation mechanism. Item 3. The vapor phase growth apparatus according to Item 1 or 2.   The gas phase according to any one of claims 1 to 3, wherein the coating having the same thermal emissivity as the coating of the heater is a coating using the same material as the coating material of the heater. Growth equipment.   5. The vapor phase growth apparatus according to claim 1, wherein the coating of the heater includes any one of SiC, PBN, TaC, and TiC. 6.

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