JP2011198940A - Vapor deposition apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a vapor deposition apparatus which can improve thickness uniformity of a grown crystal layer on a substrate and can provide high yields.SOLUTION: The vapor deposition apparatus includes: a susceptor for holding, heating and rotating the substrate; and a nozzle for supplying a material gas flow on an upper surface of the substrate. The nozzle blows out the material gas flow radially from a gas radiation center inside thereof along an entire surface of the substrate.

Description

  The present invention relates to a vapor phase growth apparatus that performs epitaxial growth of a semiconductor crystal such as a two-flow reactor.

  A crystal growth apparatus that performs epitaxial growth (vapor phase growth) is a compound or its solid solution that undergoes a thermal decomposition reaction on a heated substrate (wafer) of a reaction gas (material gas) introduced into the reaction vessel (reactor). This is a vapor phase growth apparatus in which a single crystal layer having the same crystal plane is grown on the substrate while maintaining the crystal plane orientation of the substrate.

  In the two-flow reactor of the vapor phase growth reaction apparatus, a film forming gas flow is formed by a synthetic flow of a material gas laminar flow and a holding gas flow on the wafer, and the material gas is flowed in parallel and directly above the substrate. (See Patent Document 1). The holding gas flow is made perpendicular to the material gas flow or at an angle inclined to about 40 ° from the vertical (see Patent Document 2). As a result, the material gas flows so as to be pressed against the substrate. With these two gas flow (flow) configurations, for example, even when a material gas reaches a high temperature of about 1000 ° C. on the substrate and a volume expansion of about 4.5 times occurs in GaN crystal growth, a stable material on the substrate Gas flow is maintained.

  FIG. 1 is a schematic cross-sectional view showing an example of an internal structure of a reaction vessel (not shown) that can be evacuated in a conventional two-flow reactor. In the figure, 9 is a holding gas ejector for supplying a holding gas for suppressing the laminar flow of the material gas, 10 is a nozzle for supplying the laminar flow of the material gas horizontally, and 13 is for guiding the material gas horizontally. A flow auxiliary plate, 14 is a susceptor arranged rotatably, 15 is a semiconductor substrate, 16 is a heat shield, 17 is a heater for radiantly heating the susceptor, and 20 is a water-cooled jacket. It is.

Japanese Patent Laid-Open No. 04-284623 JP 2003-173981 A

  According to, for example, metal organic chemical vapor deposition (MOCVD) method using a two-flow reactor, when a material gas is flowed along the substrate 15 as shown in FIG. A slow flow boundary layer (stagnation layer) is formed on the substrate surface under the flow layer. In crystal growth, material gas molecules are supplied from a fast-flowing layer to the boundary layer, diffused in the boundary layer, and accompanied by thermal decomposition, leading to crystal growth on the substrate.

  The concentration of the material gas is high in the upstream portion near the nozzle, and is low by the amount consumed in the remote downstream portion. Therefore, in the epitaxial layer on the substrate, the film thickness of the upstream part on the front side of the nozzle is thick, and the film thickness of the downstream part far from the nozzle is thin. That is, the film thickness of the epitaxial layer depends on the concentration of the material gas in the material gas flow flowing on the boundary layer. Therefore, the substrate is rotated to make the film thickness uniform. However, the film thickness is not uniform between the central portion of the substrate and the peripheral portion of the substrate only by rotating the substrate. The reason will be described below.

In the crystal growth apparatus in which the material gas flow is flowed horizontally with respect to the substrate surface, as shown in FIG. 2, the gas temperature of the boundary layer (stagnation layer) is downstream from the upstream side near the nozzle. Is heated toward. The temperature gradient becomes about 200 ° C. on the auxiliary flow plate 13, reaches a high temperature of 400 ° C. to 600 ° C. at the periphery of the susceptor 14, and becomes equal to the susceptor temperature (substrate temperature) and becomes saturated. Here, the material gas (for example, TMGa and NH ₃ ) starts thermal decomposition at 400 to 450 ° C. as a boundary. The distribution line of the temperature at which the material gas starts thermal decomposition is called a material gas decomposition heat isothermal line (it may be abbreviated as an isothermal line).

  Here, when a circular substrate is used as a growth substrate as shown in FIG. 3, the susceptor 14 and the heater 17 are formed in a circular shape because of the ease of making the substrate soaking. In this case, the isothermal line has an arc shape along the shape of the heater 17.

  Here, the film thickness distribution in this case is examined. For example, as the GaN-based crystal film thickness on the material gas channel, as shown in FIG. 4A, the material gas channel F1 from the nozzle 10 (center of the substrate 15), F2 (first radial position from the center of the substrate 15). , F3 (second radial position farther from the first than the center of the substrate 15). Gas material decomposition is started by the gas material decomposition heat isotherm (cp1, cp2, cp3). The closer to the both ends of the substrate diameter in the material gas laminar flow (material gas flow paths F2 and F3), the closer to the isothermal line on the center line CL of the substrate area. For this reason, both end sides are deposited thick because the material gas is not consumed. Therefore, as a result of the rotation, the peripheral portion of the substrate becomes thicker than the center of the substrate. Specifically, the thicknesses of the intersections CL1, CL2, CL3 passing through the substrate center line CL and the flow paths F1, F2, F3 are thicker toward the both ends of the flow path as shown in the graph of FIG. (T (CL)). The concave film thickness distribution of the GaN layer may differ by about 10% between the central portion and the peripheral portion. 4 (a), 4 (b), and 4 (c) show the film thickness distributions (t (cp1), t (cp2), and t (t) on the material gas flow paths F1, F2, and F3 when the substrate does not rotate. cp3)). The film thickness at the upstream side of the flow channel on the nozzle side is large, and the film thickness at the downstream side is thin. However, when the substrate rotates, the upstream side and the downstream side are switched at every rotation, so that the film thickness is averaged (t (CL1), t (CL2), t on the circumference around the rotation axis of the substrate). (CL3)). However, since the isothermal lines are arcuate, the film thickness on the material gas flow paths F1, F2, and F3 increases in this order (t (CL1) <t (CL2) <t (CL3)). As a result, when the isothermal line has an arc shape, the film thickness is not uniform even when the substrate is rotated (see Patent Document 2). When a semiconductor light emitting element is formed by such a conventional method, for example, the film thickness distribution of the crystal growth layer is concentric with a 2-inch substrate size, and the forward current (Vf) distribution and light emission of the element obtained from the same substrate. Generates non-uniformity in wavelength distribution and output distribution.

  In the technique disclosed in Patent Document 2, as a solution to make the film thickness uniform, the film thickness distribution is reduced by injecting the second gas at a position farther from the nozzle than the half of the substrate and diluting the source gas. Has proposed. However, the material gas flow (laminar flow) ejected from the nozzle is disturbed to hinder a good two-dimensional crystal growth process. Further, since the substrate surface temperature of the sprayed portion is lowered by the gas blown to the substrate from the second injection port, the substrate surface temperature periodically changes when attention is paid to a certain point on the substrate. There is a problem that decreases.

  Therefore, the present invention can improve the film thickness uniformity of the grown crystal layer in which the difference in the concave film thickness distribution of the GaN layer hardly appears between the central portion and the peripheral portion, and the yield of the semiconductor light emitting device having a predetermined characteristic is high. An object is to provide a vapor phase growth apparatus.

  The vapor phase growth apparatus according to the present invention includes a susceptor that holds a substrate and heats and rotates the substrate, a nozzle that supplies a material gas flow to the upper surface of the substrate, and directs the material gas flow over the entire surface of the substrate and the susceptor. The nozzle presses the material gas flow radially from the center of the gas emission inside thereof along the entire surface of the substrate. With this configuration, the material gas flow is ejected radially, and the film thickness distribution resulting from the bending of the temperature line of the material gas decomposition heat is offset, and the film thickness uniformity can be improved.

  In the conventional vapor phase growth apparatus, as a result of the material gas decomposition heat isotherm being curved concavely toward the material gas traveling flow direction, the film thickness on the center line of the substrate orthogonal to the material gas flow becomes concave ( (See FIG. 4). As a result of the experiment, the inventor made the nozzle ejection portion for the material gas, for example, a fan-shaped inner surface, and ejected the material gas radially onto the substrate, so that the film thickness equidistant line Lt ( As a result of bending (see FIG. 7), it was found that the film thickness on the center line of the substrate orthogonal to the material gas flow becomes convex. Applying this phenomenon, it is possible to make the thickness of the epitaxial layer uniform by the vapor phase growth apparatus of the present invention that offsets the effect of “relaxing effect of material gas decomposition heat isotherm” by the effect of “radial material gas ejection” Yes.

It is a schematic sectional drawing which shows the internal structure of the conventional 2 flow reactor. It is a schematic sectional drawing of the susceptor and a board | substrate in the conventional 2 flow reactor. It is a schematic top view which shows the relationship between the susceptor and nozzle of the conventional 2 flow reactor. It is a figure for demonstrating the isothermal line and film thickness distribution on a susceptor and a board | substrate in the conventional 2 flow reactor. It is a schematic sectional drawing which shows the internal structure of 2 flow reactor of embodiment by this invention. It is a schematic top view which shows the relationship between the susceptor and nozzle of 2 flow reactor of embodiment by this invention. It is a figure for demonstrating the isothermal line and film thickness distribution on a susceptor and a board | substrate in 2 flow reactor of embodiment by this invention. It is a schematic perspective view of the fan-shaped nozzle used for the Example by this invention. It is a schematic perspective view of the flat nozzle used for the comparative example. It is the general | schematic fragmentary sectional view planarly viewed from the nozzle height direction which shows the modification of the nozzle of the vapor phase growth apparatus of this invention. It is a perspective view for demonstrating the upper flow press plate which is a modification of the gas press apparatus of the vapor phase growth apparatus of this invention.

  Hereinafter, an apparatus according to an embodiment of the present invention will be described with reference to the drawings.

  FIG. 5 is a schematic cross-sectional view showing the internal structure of the two-flow reactor of the embodiment configured as a horizontal growth furnace. In the same figure, except for the nozzle 11 and the pressing gas jetting device 12, it is the same as the conventional vapor phase growth apparatus, so these will be described first. As for the nozzle 11 and the holding gas ejector 12, the nozzle 11 has a fan-shaped inner surface and material gas is ejected radially, and the material gas intrusion side of the opening of the holding gas ejector 12 is aligned with a radial arc in which the material gas spreads. The shape will be described later.

  A reaction vessel (not shown) that can be evacuated in the two-flow reactor is configured as a horizontal growth furnace, and the reaction vessel has a structure capable of blocking the atmosphere.

  A disc-shaped susceptor 14 is rotatably disposed in the center of the reaction vessel, and a growth substrate 15 is placed on the susceptor 14 so as to be flush with the susceptor (examples described later). Then, the thickness t3 of the susceptor 14 holding the substrate 15 is 3 mm, and the diameter φ is 70 mm). A thin film is formed on the substrate 15 set on the susceptor 14 by epitaxial growth. The susceptor 14 has a disk shape, has a rotation shaft at the center, and can rotate at 10 times / min to 30 times / min. The susceptor 14 is made of a carbon material, and is coated with a material that does not pollute the gas in the reaction furnace when heated and does not react with the atmospheric gas, such as silicon carbide.

  The flow auxiliary plate 13 is attached to the susceptor 14 and rotates together. (In the embodiment described later, the diameter φ of the flow auxiliary plate 13 is 150 mm). The heater 17 is attached to the lower surface of the susceptor, and is slightly larger than the susceptor. . A thermocouple (not shown) is installed in the vicinity of the heater 17, and a control system (not shown) for controlling the temperature based on the output and heating the susceptor 14 to a set temperature is provided.

  The heat shield plate 16 is located on the outer periphery of the heater 17 and blocks the nozzle 11 from being heated by the radiant heat of the heater. In addition, the water-cooling jacket 20 is provided in the outer periphery of the heat insulation board 16, and the heat insulation is further improved. Further, the upper end of the water cooling jacket 20 is extended to just below the auxiliary flow plate 13. However, a slight gap is provided so as not to prevent the rotation of the flow auxiliary plate 13.

The nozzle 11 for injecting a material gas onto the substrate 15 is installed in a state that is horizontal or inclined several degrees from the horizontal with respect to the substrate on the susceptor. The nozzle 11 away from the susceptor blows and supplies a laminar flow of material gas from the ejection opening 11 c toward the flow direction F, that is, the center of the substrate 15 along the entire surface of the substrate 15. Specifically, the material gas includes nitrogen (N ₂ ), hydrogen (H ₂ ), ammonia gas (NH ₃ ), n-type dopant gas (monosilane gas (SiH ₄ ), disilane gas (Si ₂ H ₆ )), organic metal Gas (TMGa (trimethylgallium), TEGa (triethylgallium), TMAl (trimethylaluminum), TMIn (trimethylindium), Cp2Mg (cyclopentadienylmagnesium)).

  A holding gas ejector 12 as a gas pressing device is provided above the central portion of the substrate 15. The holding gas ejector 12 is arranged so that the opening of the ejector becomes a predetermined height t1 of 10 mm to 30 mm in the nozzle height direction T from the substrate 15 (in the example described later, t1 = 20 mm). Has been.

The holding gas ejector 12 blows and supplies a holding gas for suppressing the laminar flow of the material gas to the entire surface of the susceptor 14 and the substrate 15 toward the entire surface of the substrate 15. Specifically, H ₂ , N ₂ or a mixed gas thereof is used as the holding gas.

  The holding gas flux of the cross-sectional area covering the substrate 15 is an angle θ slightly inclined from the substrate normal direction or from the substrate normal direction (in the range of 0 ° <θ <40 °, in the examples described later, θ = 15 °), the material gas is sprayed in a state inclined in the downstream direction F.

(Nozzle 11)
As shown in FIGS. 5 and 6, the tip position of the ejection opening 11 c of the nozzle 11 is located outside the susceptor 14 and on the flow auxiliary plate 13. For example, the nozzle 11 can be disposed so that the position of the tip thereof is the same as the inner peripheral end of the water cooling jacket 17 (in the embodiment described later, the distance Le from the center of the substrate 15 to the tip of the opening of the nozzle 11 is 40 mm. is there). By disposing at this position, overheating of the nozzle 11 due to the radiant heat of the heater 17 can be prevented. This is because, when the radiant heat of the heater 17 is applied to the nozzle 11, the material gas is decomposed inside the nozzle 11 and clogs the nozzle 11. The nozzle 11 is preferably made of quartz. This is because quartz transmits infrared radiation and can suppress overheating of the nozzle 11.

  As shown in FIG. 6, the nozzle 11 ejects the material gas from the gas radiation center X in a radial manner in the nozzle width direction W. In the nozzle 11, the gas emission center X is a distance of n × R (where n is a distance coefficient and R is a radius of the substrate 15) from the rotation center of the substrate 15, and the distance coefficient is n = 2. It arrange | positions so that it may exist in the position which satisfy | fills 5-5. The distance Lc from the center of the substrate 15 to the radiation center X of the material gas flow is preferably 2.5 × R to 5 × R. If it is 5R or more, the curvature of the iso-thickness line Lt (see FIG. 7) becomes small, and it becomes impossible to cancel out the film thickness concave curvature derived from the material gas decomposition heat isotherm. Moreover, if it is less than 2.5 × R, it is difficult to manufacture the nozzle 11. From the experimental results, about 3 × R or more is appropriate. In the examples described later, Lc = 3 × R (76.2 mm).

  The radiation angle of the material gas is determined by the distance relationship between the nozzle and the substrate. First, the material gas covering angle θw with which the material gas covers the entire surface of the substrate 15 is obtained by (Equation 1).

θw = 2 × tan ⁻¹ (R / (n × R)) (Formula 1)
However, R shows the radius of the board | substrate 15 and n is a distance coefficient (n = 2.5-5).

  The total radiation angle θa of the material gas is obtained by (Expression 2).

θa = 2 × tan ⁻¹ ((Wp / 2) / (n × R)) (Expression 2)
However, Wp is the width of the cross section of the pressed gas flux in the nozzle width direction W.

  In the examples described later, the radiation angle θw = 36.9 ° covering the substrate 15 is set, and the pressing gas width (Wp = 80 mm) is the maximum radiation angle, so θa = 55.4 °.

  The ejection opening 11c of the nozzle 11 is formed so that, for example, T / W ≦ 0.1 in the nozzle width direction W and the nozzle height direction T so that the width parallel to the substrate is larger than the height. ing. This is because the gas is uniformly spread on the surface of the substrate with the holding gas.

(Presser gas ejector 12)
In order for the material gas flow to be maintained in a laminar flow over the entire surface of the substrate, the holding gas has a shape covering the material gas flow path. Therefore, the opening shape of the pressing gas ejector can be considered as a cross-sectional shape on the substrate of the pressing gas flow to be blown out (corresponding to the opening as a substantially rectangular effective surface in FIG. 6). By changing the ejection opening of the holding gas ejector 12 from a circular shape to a substantially rectangular shape, a loss loss of the material gas ejected from the material gas nozzle to the outside of the substrate can be reduced. Furthermore, as shown in FIG. 6, the intrusion surface side of the material gas flow ejected radially from the ejection opening of the holding gas ejector is a concave arc 12a. In the case of a concave arc that matches the radial arc in which the material gas spreads, the angle at which the material gas flow enters the holding gas flow is almost a right angle on the arc, and the material gas can go straight, so it can be pushed out. Is prevented. That is, in order to maintain the curvature of the equal film thickness line Lt (see FIG. 7), it is desirable that the pressed gas jet shape is also a concave arc. As shown in FIG. 6, it is preferable to arrange the center of curvature of the concave circular arc 12a on the axis center line of the nozzle 11 on the entrance surface side of the material gas flow at the ejection opening of the holding gas ejector. It can be.

The holding gas ejector 12 has a holding gas outlet having a structure in which the holding gas has a concave arc 12a with respect to the holding gas so that the holding gas is orthogonal to the radial material gas traveling direction. As a result, the traveling direction of the material gas ejected radially and the material gas intrusion surface of the pressing gas are perpendicular to each other, so that the material gas flow can continue straight in the pressing gas flow while maintaining the radial shape. Incidentally, when the shape of the holding gas ejector 12 is circular as before, the penetration angle of the material gas into the holding gas becomes oblique, the direction of travel of the material gas is bent outward, and the material gas on the surface of the substrate 15 is. The density is low and the film thickness is thin. In the examples described later, the opening of the blowing portion of the holding gas diffuser 12 is Lp = 80 mm and Wp = 80 mm (Lp: length in the flow direction F, Wp: length in the nozzle width direction W), and the area is 6400 mm. ² . In the blowing part of the holding gas diffuser, the entire pressing gas that hits the material gas flow may be concave.

(Constant film thickness line Lt of crystal growth derived from radially progressing material gas)
The film thickness distribution in this embodiment will be examined. For example, as the film thickness of the GaN-based crystal on the material gas channel, as shown in FIG. 7A, the material gas channel F1 from the gas radiation center X of the fan-shaped nozzle 11 (the channel passing through the center of the substrate 15), F2 Consider (flow path flowing at a first angle from the radiation center X) and F3 (flow path flowing at a second angle from the radiation center X). The graphs of FIGS. 7A, 7B, and 7C show film thickness distributions (straight lines passing through black circles) on the material gas flow paths F1, F2, and F3 when the substrate does not rotate. In addition, the film thickness distribution (straight line passing through the white circles) on the same material gas flow paths F1, F2, and F3 when a conventional nozzle is used is shown. Further, the graph of FIG. 7D shows changes in the film thickness of the intersections CL1, CL2, and CL3 with the flow paths F1, F2, and F3 through the substrate center CL when the substrate is rotated and grown.

  As shown in FIG. 4A, when the material gas flows (in one direction) with the conventional nozzle, the intersections of the flow paths F1, F2, and F3 and the isothermal lines are in the downstream direction in the order of cp1, cp2, and cp3. It is greatly shifted. As a result, as shown in FIG. 4D, the film thicknesses of the intersections CL1, CL2, CL3 with the substrate center line CL are t (CL1), t (CL2), t ( It becomes thicker in the order of CL3). When the film thickness change is plotted in FIG. 7D, a film thickness curve tA is obtained.

  Next, as in the present embodiment shown in FIG. 7A, when the material gas is ejected radially to the substrate (center), the intersection points cp1, cp2, and cp3 of the flow paths F1, F2, and F3 and the isothermal lines are as follows. Then, cp2 and cp3 are closer to the cp1 side than the conventional example (FIG. 4A) (the white circle moves to the position of the black circle for cp3). That is, when the material gas is ejected radially, the deviation in the downstream direction of the isothermal lines of the flow paths F1, F2, and F3 is reduced. As a result, as shown in FIGS. 7A, 7B, and 7C, the film thicknesses of the intersections CL1, CL2, and CL3 with the substrate PC center line CL shift from the white circle to the black circle in the conventional example. That is, the phenomenon that the film thickness in the circumferential direction from the substrate center increases can be suppressed. This is called the “relaxing effect of the material gas decomposition heat isothermal line”, and when this point is plotted in FIG. 7D, a film thickness curve tAb is obtained.

  Further, as in the present embodiment shown in FIG. 7A, a phenomenon in which the film thickness distribution on the substrate center line CL becomes convex due to the radial ejection of the material gas flow paths F1, F2, and F3. explain. The radiation center of the material gas flow is assumed to be X, and the material gas decomposition heat isothermal line is assumed to have an arc shape passing through cp1 with the radiation center X as a reference. In this case, the equal film thickness line Lt on the substrate has an arc shape with the radiation center X as a reference. Therefore, the film thickness equivalent to the substrate center CL <b> 1 moves to the upstream side as the end of the substrate 15. In other words, the thicknesses of the intersections CL1, CL2, CL3 of the substrate center line CL and the material gas flow paths F1, F2, F3 become thinner in this order. This is called a “convex film thickness effect”, and when this point is plotted in FIG. 7D, a film thickness curve tB is obtained.

  By canceling the film thickness curve tAb due to the “relaxation effect of the material gas decomposition heat isothermal line” and the film thickness curve tB due to the “convex film thickness effect”, the film thickness curve at the substrate center CL becomes tC and becomes uniform. This canceling effect is obtained when the distance from the substrate center CL1 to the radiation center X is 2R to 5R (R: radius of the substrate). If the film thickness of the substrate center line CL is made uniform, the upstream side and the downstream side are switched in the material gas flow by rotating the substrate, and as a result, a flat GaN crystal layer is obtained.

  A GaN crystal was grown by the two-flow reactor apparatus of the above embodiment.

(substrate)
As a growth substrate, a 2-inch φ c-plane sapphire single crystal substrate, a thickness t = 0.43 mm, and a 0.05 ° off-substrate whose plane orientation is inclined by 0.05 ° in the <10-10> direction, so-called ( [0001] 0.05 ° off to <10-10> substrate was used.

(Fan-shaped nozzle)
FIG. 8 is a schematic perspective view of the fan-shaped nozzle 11 used in the embodiment.

  The opening area of the ejection opening 11c of the fan-shaped nozzle 11 was a cross-sectional area where the ejection linear velocity was the same as that of a nozzle of a comparative example described later. For comparison of the effect, the opening size of the fan-shaped nozzle 11 was made equal to that of the comparative example. Therefore, the nozzle shape of a comparative example is also demonstrated here. FIG. 9 shows a schematic perspective view of the flat nozzle 10 used in the comparative example.

  8 and 9, Wn represents a length in the nozzle width direction W, and Tn represents a length in the nozzle height direction T.

The ejection opening 11c of the flat nozzle 10 used in the comparative example had a nozzle width Wn of 80 mm and a nozzle height Tn of 1 mm. The ejection opening area Sn of the flat nozzle 10 used in the comparative example was 80 mm ² because Sn = Wn × Tn.

The opening size of the fan-shaped nozzle 11 of the embodiment can be obtained by the following equation.
tan (θa / 2) = (Wp / 2) / (3 × R−Le)
= 0.525
Wp: Holding gas area width (80mm)
Le: Distance from the center of the substrate 15 to the tip of the nozzle 11 (40 mm)
R: substrate radius (25.4 mm)
Therefore, the nozzle width Wn of the fan-shaped nozzle 11 is obtained as follows.
Wn = 2 × tan (θa / 2) × (3 × R−Le)
= 2 × 0.525 × (76.2-40)
= 38mm
The nozzle height Tn of the fan-shaped nozzle 11 can be calculated by dividing the opening area of the flat nozzle 10 used in the comparative example by the nozzle width Wn of the fan-shaped nozzle 11.
Tn = 80/38 = 2.1mm
Therefore, in the embodiment, the ejection opening 11c of the fan-shaped nozzle 11 has a nozzle width Wn of 38 mm and a nozzle height Tn of 2.1 mm.

  As described above, the angle θa = 55.4 ° opening from the radiation center X to both side edges of the opening of the fan-shaped nozzle 11 and the radiation angle θw = 36.9 ° (supply area on the substrate 15). It was.

(Pressure gas flow rate)
For comparison of the effect, the flow rate of the holding gas was made equal to that of the comparative example. Therefore, the flow rate of the holding gas of the comparative example will be described here.

In the holding gas of the comparative example, as a holding gas flux, a holding gas ejector having a circular cross section was used. In the embodiment, since the holding gas ejector 12 is substantially rectangular (having a concave arc portion on the intrusion surface side of the radial material gas flow), the gas ejection area has been increased, so that only the amount corresponding to the increase in area has been implemented. In the example it was increased. By this operation, the effect of the holding gas was made the same. Specifically, in the case of a circular substrate (radius r), the area is πr ² = 50.3 (cm ² ), and in the case of a rectangle, Wp × Lp. The amount was increased to 1.3 times (≈ (2r) ² / πr ² ) = 64 (cm ² ) with respect to the gas flow.

(growth)
As a substrate heat treatment process, H ₂ (hydrogen) was supplied from a nozzle at a rate of 10 L / min, H ₂ (hydrogen) + N ₂ (nitrogen) was supplied as a holding gas at a mixing ratio of 1: 1 at 39 L / min, and heat treatment was performed at 1000 ° C. for 10 minutes. did.

As a buffer layer forming step, TMGa (trimethylgallium) was added from a nozzle at 20 μmol / min, NH ₃ (ammonia) 2 L / min, and H ₂ (hydrogen) was added and flowed so that the total amount was 10 L / min. As a holding gas, H ₂ (hydrogen) + N ₂ (nitrogen) was supplied at a mixing ratio of 1: 1 at 39 L / min and grown at a growth temperature of about 550 ° C. for 10 minutes to grow a low-temperature GaN layer.

As a heat treatment process for the buffer layer, H ₂ (hydrogen) was flowed from the nozzle at 10 L / min, and H ₂ (hydrogen) + N ₂ (nitrogen) was flowed at 39 L / min at a mixing ratio of 1: 1 as a hold-down gas at 10 ° C. The low temperature GaN layer was heat treated by partial heat treatment.

Next, as a high temperature GaN layer formation step, TMGa (trimethylgallium) is added from a nozzle at 40 μmol / min, NH ₃ (ammonia) 4 L / min, and H ₂ (hydrogen) is added so that the total amount is 10 L / min. did. As a holding gas, H ₂ (hydrogen) + N ₂ (nitrogen) was supplied at a mixing ratio of 1: 1 at 39 L / min. Growth was performed at a growth temperature of about 1050 ° C. for 2 hours to form a GaN layer having a thickness of about 7 μm.

(Comparative Example 1)
A GaN crystal was grown in a two-flow reactor which was the same as in Example 1 except for the difference between the fan-shaped nozzle 11 and the flat nozzle 10 and the difference in the flow rate of the pressing gas.

(Result: Comparison of film thickness distribution)
Table 1 shows a comparison of the film thickness distributions of the GaN layers obtained by the two-flow reactors of Comparative Example 1 and Example 1.

＊上記の膜厚は中央部（膜厚中心値）と周囲部（基板外周より１．５ｍｍより内側（膜厚周囲値））で比較した。差異は（式１）に基づき％で記載した。
＊差異（％）＝｛｜（周囲部−中央部）｜／（周囲部と中央部のうち薄い側の膜厚）｝×１００・・・（式１）。

* The above film thicknesses were compared at the central portion (film thickness central value) and the peripheral portion (inner than the outer periphery of the substrate from 1.5 mm (film thickness peripheral value)). Differences are stated in% based on (Equation 1).
* Difference (%) = {| (peripheral part−central part) | / (thickness on the thinner side of the peripheral part and the central part)} × 100 (Formula 1).

  In Example 1, the film thickness center value was 3.45 μm, the ambient value was 3.51 μm, the difference was 1.74%, and the uniformity was very high. If the area is converted, the distribution becomes narrower.

  On the other hand, in Comparative Example 1, the peripheral value was 3.49 μm at the film thickness center value of 3.23 μm, and the periphery was thick with a difference of 8.0%. The distribution was concentric concave.

  A semiconductor layer was grown by the two-flow reactor device of the above embodiment to produce an MQW structure light emitting element, that is, a nitride semiconductor light emitting device.

  Since the process up to the heat treatment of the buffer layer is the same as that of the first embodiment, the description thereof is omitted.

As a process for forming the n-type GaN layer, the thickness of the n-type GaN layer is 4.5 μm, and SiH ₄ (monosilane) has a Si impurity density of about 6 × 10 ¹⁸ (pieces / cm ³ ) in order to form the n-type GaN layer. The process was the same as the process for forming the GaN layer of Example 1, except that the addition was performed.

Next, the formation process of the light emitting layer of MQW structure was performed as follows. From the same nozzle as in Example 1, NH ₃ (ammonia) was 4 L / min, and N ₂ (nitrogen) was added and flowed so that the total amount was 10 L / min, and the growth temperature was lowered to about 800 ° C. N ₂ (nitrogen) was passed through the holding gas at 30 L / min. When the temperature is reached, first, TEGa (triethylgallium) is 5.5 μmol / min, NH ₃ (ammonia) 4 L / min, and the total amount is 10 L / min from the nozzle to grow the barrier layer (GaN). N ₂ (nitrogen) was added to the solution and allowed to flow. N ₂ (nitrogen) was passed through the holding gas at 39 L / min. Growth was performed at a growth temperature of 800 ° C. for 3 minutes to form a GaN crystal layer having a thickness of 18 nm.

Next, after forming the barrier layer, TEGa is 5.5 μmol / min, TMIn (trimethylindium) is 6.5 μmol / min, NH ₃ is 4 L / min, and the total amount is from the nozzle to grow the well layer (InGaN). N ₂ was added and flowed so as to be 10 L / min. The holding gas was supplied with N ₂ at 39 L / min. Growth was performed at a growth temperature of 800 ° C. for 25 seconds to form an InGaN crystal layer having a thickness of 3 nm.

  These barrier layer and well layer pair forming steps were repeatedly grown in six cycles to form an MQW structure as a light emitting layer. And the barrier layer (GaN) was grown as a cap layer, and it was set as the light emitting layer.

Next, as a block layer forming step, H ₂ is adjusted so that TMGa is 3.5 μmol / min, TMAl (trimethylaluminum) is 0.4 μmol / min, NH ₃ is 4 L / min, and the total amount is 10 L / min. (Hydrogen) was added and flushed. The holding gas was supplied with N ₂ at 39 L / min. The growth was performed at a growth temperature of 950 ° C. for 5 minutes to form an AlGaN crystal layer having a thickness of 20 nm.

Next, as a step of forming the p-type GaN layer, H ₂ (hydrogen) was added and flowed from a nozzle so that TMGa was 12 μmol / min, NH ₃ was 4 L / min, and the total amount was 10 L / min. The holding gas was supplied with 39 L / min of H ₂ and N ₂ at a mixing ratio of 1: 1. Growth was carried out at a growth temperature of about 950 ° C. for 15 minutes to form a GaN layer having a thickness of about 0.15 μm.
Note that Cp2Mg (cyclopentadienylmagnesium) was added to a Mg impurity density of about 5 × 10 ¹⁹ (pieces / cm ³ ) in order to form a p-type GaN layer.

(Nozzle deformation example)
FIG. 10 is a schematic partial sectional view in plan view from the nozzle height direction T showing a modification of the vapor phase growth apparatus of the present invention, in particular, a modification of the nozzle. This modification is the same as the configuration shown in FIG. 5 except for the nozzle.

  The nozzle 11 includes an inflow portion 11a (constant area rectangular cross section) serving as an inflow passage through which the material gas flows, and a fan-shaped inner surface 11b having an outflow port communicating with the inflow portion 11a.

  The fan-shaped inner surface 11b is composed of a fan-shaped wall portion 11bb that faces each other in parallel and expands in the nozzle width direction W, and a guide wall 11bc that connects the fan-shaped wall portion in the nozzle height direction T, and defines a gas flow path. Yes. Since the guide walls 11bc on both sides expand in the width direction W at a predetermined angle with respect to the central axis of the nozzle 11, the cross-sectional area of the gas flow path gradually increases from the inflow portion 11a to the ejection opening 11c. As shown in FIG. 10, the extension planes of the inner surfaces of the guide walls 11bc on both sides converge to the radiation center X of the material gas. Since the inflowing material gas is regulated by the fan-shaped wall portion 11bb and the guide wall 11bc, the injected material gas is prevented from diffusing in the nozzle height direction T, and the injection width (nozzle width direction W) is expanded. Therefore, the fan-shaped inner surface 11 b of the nozzle 11 can eject the material gas flow from the gas radiation center X of the inflow portion 11 a radially along the entire surface of the substrate 15.

  Further, as a further modification of the nozzle 11, as shown by a one-dot chain line in FIG. 10, the partition plate 11d is arranged radially from the radiation center X near the inflow portion 11a at the back from the ejection opening 11c of the fan-shaped inner surface 11b. Thus, a plurality of radiation channels CH can be provided.

  The material gas from the inflow part 11a flows into each radiation channel CH arrange | positioned radially, and is injected from the fan-shaped inner surface 11b. At this time, since the material gas injected from the outlet of the radiation channel CH is regulated by the guide wall 11bc, the injected material gas is prevented from diffusing in the nozzle height direction T, and the concentration distribution is widened. Can contribute to widening the injection width.

  In addition, each radiation channel is arranged radially from the center axis of the flow path as the starting point (radiation center X), that is, the focal point of each axis of each radiation channel is located at the center axis, so that the material gas flows from the inflow portion 11a. Can flow evenly into each radiation channel. Furthermore, since each radiation channel has substantially the same inner width and channel length, the flow rate passing through each radiation channel is substantially the same, and each radiant channel is uniformly rectified in each radiation channel, so that the entire radial gas flow is obtained. The concentration distribution can be made uniform.

(Modification of gas pressing device)
A modified example in which the upper flow pressing plate is used as a gas pressing device in place of the pressing gas ejector for supplying and supplying the pressing gas for pressing the laminar flow of the material gas to the entire surface of the susceptor 14 and the substrate 15 will be described.

  FIG. 11 is a perspective view illustrating the relationship between the flow auxiliary plate 13, the susceptor 14, the substrate 15, and the nozzle 11 for explaining the upper flow pressing plate 121. Since the modified example of this growth apparatus is the same as the structure shown in FIG. 5 except that the upper flow pressing plate 121 is used instead of the holding gas ejector, its essential part will be described. The upper flow pressing plate 121 has an inclined plane toward the substrate 15 at a pitch angle θt from above the nozzle 11 to above the central portion of the substrate 15 so as to cover all of the injected radial material gas flow. The upper flow pressing plate 121 is disposed at a predetermined height from the substrate 15 so as not to contact the flow auxiliary plate 13, the susceptor 14, and the substrate 15.

  Since the gap between the flow auxiliary plate 13, the susceptor 14 and the substrate 15 and the inclined surface of the upper flow pressing plate 121 becomes narrower along the direction in which the material gas flow proceeds, the inclined plane of the upper flow pressing plate 121 causes the material gas flow to flow. The pressure is applied to the substrate 15. The laminar flow of the material gas is pressed against the substrate 15 by the upper flow pressing plate 121 by an amount corresponding to the decrease in the concentration of the material gas molecules consumed in the stagnation layer on the substrate surface under the radial material gas flow layer. The thickness of the laminar flow is reduced to maintain the concentration of material gas molecules, and supply and diffusion to the stagnation layer are promoted.

DESCRIPTION OF SYMBOLS 11 Nozzle 12 Holding gas ejector 13 Flow auxiliary | assistant board 14 Susceptor 15 Board | substrate 16 Heat shield board 20 Water-cooling jacket 17 Heater

Claims (4)

A susceptor that holds the substrate and heats and rotates the substrate, a nozzle that supplies a material gas flow to the upper surface of the substrate, and a gas pressing device that presses the material gas flow toward the entire surface of the substrate and the susceptor And including
The nozzle is a vapor phase growth apparatus characterized in that the material gas flow is ejected radially along the entire surface of the substrate from a gas radiation center in the nozzle.   In the nozzle, the gas emission center is a distance of n × R (where n is a distance coefficient and R is a radius of the substrate) from the rotation center of the substrate, and the distance coefficient is n = 2.5. The vapor phase growth apparatus according to claim 1, wherein the vapor phase growth apparatus is disposed so as to exist at a position satisfying .about.5. 3. The vapor phase growth apparatus according to claim 2, wherein the nozzle has a fan-shaped inner surface structure such that a gas radiation angle θw satisfies a relationship of at least θw = 2 × tan ⁻¹ (1 / n). The gas pressing device is a pressing gas ejector that is provided above the susceptor and supplies a pressing gas that presses the material gas flow onto the susceptor and the upper surface of the substrate.
The presser gas ejector includes a presser gas jet outlet having a structure in which a concave arc is formed with respect to the presser gas so that the presser gas is orthogonal to a radial material gas traveling direction. 4. The vapor phase growth apparatus according to any one of 1 to 3.

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