High-temperature vapor phase growth apparatus and method for growing semiconductor crystal film

Abstract

To solve the problem that under a growth condition of a high temperature exceeding 1,200°C above a substrate for growth of aluminum nitride, for example, a raw material gas reacts in vapor phase not above the substrate so that the amount of a raw material reaching above the substrate decreases, and then raw material gas use efficiency decreases and a device also deteriorates owing to the high temperature.SOLUTION: There is provided a lateral type vapor-phase growth device that has a raw material gas jetting part for jetting a raw material gas and a susceptor surface for heating a substrate arranged in parallel, and can be heated up to 1,200°C or higher, wherein at least one gas jet member having a plurality holes for jetting an inert gas toward the raw material gas is arranged between the raw material gas jetting part and susceptor.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a high-temperature vapor phase growth apparatus and a method for growing semiconductor crystal films, which are optimal for growing nitride semiconductor crystal films such as aluminum nitride and aluminum gallium nitride. [Background technology]

[0002] Generally, when growing a crystalline film of a compound semiconductor on a substrate, a vapor phase growth method such as metal organic chemical vapor deposition or molecular beam epitaxy is used.

[0003] As shown in FIG. 4, when a first conventional vapor phase growth apparatus 600 (see, for example, Patent Document 1) is used to grow a nitride semiconductor crystal film such as aluminum nitride and aluminum gallium nitride on a substrate 610 made of sapphire or the like by metal organic chemical vapor deposition, the substrate 610 is heated to a predetermined temperature while being held on a substrate holder 615, and a source gas 620 is brought into contact with the substrate 610, thereby depositing and forming a nitride semiconductor crystal film on the substrate 610.

[0004] The vapor phase growth apparatus 600 includes a substrate holder 615 for holding a substrate 610, a flow channel 625 for efficiently directing a source gas 620 onto the substrate 610, a susceptor 630 as a heat source, and an RF coil 635 for heating the susceptor 630.

[0005] In vapor phase growth apparatus 600 configured as described above, source gas 620 flows parallel to substrate 610 from a gas supply port toward a gas exhaust port within flow channel 625. Then, with substrate 610 made of sapphire or the like heated to a predetermined temperature, the upper surface of substrate 610 comes into contact with source gas 620 flowing within flow channel 625. As a result, a nitride semiconductor crystal film such as aluminum nitride or aluminum gallium nitride is formed on the upper surface of substrate 620.

[0006] The source gas 620 is supplied from a gas supply port, flows through a flow channel 625, and contributes to the growth of a crystal film on the upper surface of the substrate 610, while the source gas 620 that does not contribute to the growth of the nitride semiconductor crystal film is discharged from a gas exhaust port.

[0007] It is generally known that defects in nitride semiconductor crystals such as aluminum nitride and aluminum gallium nitride are inversely proportional to the crystal growth temperature. That is, to obtain a high-quality crystal film with few crystal defects, the temperature of the upper surface of the substrate 620 must be at least 1200°C or higher. It has also been pointed out that a temperature as high as 1800°C is necessary (see, for example, Patent Document 2).

[0008] However, when conventional vapor phase growth apparatus 600 is heated to such a high temperature, source gas 620 supplied from the horizontal direction of flow channel 625 reacts with itself before reaching substrate 620 unless the gas flow rate is increased, and the amount of source gas 620 reaching the upper surface of substrate 610 decreases. Therefore, there is a problem in that the use efficiency of source gas 620 is low.

[0009] Furthermore, when the substrate 610 is heated to a high temperature of 1200°C or higher, strong thermal convection occurs on the upper surface of the substrate 610 on which the crystalline film is grown. This thermal convection caused by the heated substrate 620 causes the source gas 620 to rise and diffuse into the flow channel 625. Components produced by the reaction of the diffused source gas 620 adhere to the wall surface of the flow channel 625 as well as to the observation window (not shown), etc. This has caused problems such as the generation of dust and the incorporation of impurities into the crystalline film formed on the substrate 620. Furthermore, because the interior of the vapor phase growth apparatus 600 is exposed to high temperatures, there is also the problem that each component of the apparatus deteriorates rapidly, significantly reducing the durability of the apparatus.

[0010] In order to suppress the occurrence of this thermal convection, a second conventional vapor phase growth apparatus 700 (see, for example, Patent Document 3) has been proposed as shown in Figure 5. This vapor phase growth apparatus 700 includes a reaction vessel 710, a susceptor 715, a heater 720, a source gas injection pipe 725, and a sub-injection pipe 730.

[0011] In the vapor phase growth apparatus 700 configured as described above, the substrate 705 is placed on the susceptor 715 and heated to a temperature required for crystal growth by a heater 720. To ensure uniform crystal growth, the susceptor 715 is rotated by a shaft 735 attached to the bottom of the susceptor 715. The reactant gases, which are raw materials, are fed to the vapor phase growth apparatus 700 in the lateral direction. raw material The pressure gas, which is an inert gas, is introduced from the gas injection pipe 725. 705 The air is introduced from the auxiliary injection pipe 730 above the

[0012] That is, the reaction gas is applied to the surface of the heated substrate 705 in a direction parallel to the substrate 705. vinegar At the same time as supplying the reactive gas, a pressure gas for pressing the reactive gas is blown downward from above vertically toward the substrate 705 . [Prior art documents] [Patent documents]

[0013] [Patent Document 1] JP 2010-080614 A [Patent Document 2] Japanese Patent Application Laid-Open No. 2006-70325 [Patent Document 3] Patent No. 2628404 Summary of the Invention [Problem to be solved by the invention]

[0014] Using such a conventional vapor phase growth apparatus 700, a substrate made of sapphire or the like can be grown. 705 When growing nitride semiconductor crystal films such as aluminum nitride and aluminum gallium nitride on the top surface of a substrate at high temperatures exceeding 1200°C, if the reaction gas and the pressure gas are flowed from different directions and collide, turbulence and vortex flows will occur, resulting in the substrate 705 In other words, unevenness in the film thickness occurs, and the substrate705 However, there is a problem in that crystals with different compositions are formed on the upper surface of the crystal film, making it difficult to ensure stable quality of the crystal film.

[0015] Furthermore, according to this configuration, although the pressure gas blown down from vertically above the substrate can suppress the rise of the reaction gas due to convection, the pressure gas slows down the flow of the reaction gas, and the reaction gas falls on the substrate. 705 Before reaching the top surface of the substrate, the reactant gases have already reacted with each other, 705 This leads to a problem that the amount of reactant gas reaching the crystal growth stage is drastically reduced, resulting in a decrease in the proportion of reactant gas contributing to crystal growth and a decrease in the efficiency of raw material use. [Means for solving the problem]

[0016] An aspect of the present invention is a horizontal vapor phase growth apparatus capable of heating to 1200°C or higher, in which a source gas injection unit that injects a source gas and a susceptor surface that heats a substrate are arranged in parallel, and at least one first gas injection member having a plurality of holes for injecting an inert gas toward the source gas is arranged between the source gas injection unit and the susceptor.

[0017] In an embodiment of the present invention, in addition to the first gas injection member, at least one second gas injection member having a substantially cylindrical shape and a plurality of holes for injecting the inert gas toward the susceptor may be disposed above the susceptor.

[0018] In an aspect of the present invention, the first gas injection member and the second gas injection member may be disposed in series.

[0019] In an aspect of the present invention, the first gas injection member and the second gas injection member may be disposed in series.

[0020] In an embodiment of the present invention, the holes of the first gas injection member may be inclined toward the source gas injection portion with respect to the vertical direction so that the angle between the flow line of the source gas and the flow line of the inert gas is an acute angle.

[0021] In an aspect of the present invention, the holes of the first gas injection member may be in a nozzle shape in which the cross-sectional area of ​​the holes on the gas outlet side is smaller than the cross-sectional area of ​​the holes on the gas inlet side.

[0022] In an embodiment of the present invention, in the one or more second gas injection members, the sum of the cross-sectional areas of the multiple holes of the second gas injection member provided on the gas outflow side may be smaller than the sum of the cross-sectional areas of the multiple holes of the second gas injection member provided on the gas inflow side. [Effects of the Invention]

[0023] In view of the above problems, the present invention provides a vapor phase growth apparatus that makes it possible to obtain a uniform crystal film of a nitride semiconductor such as aluminum nitride or aluminum gallium nitride even when crystal is grown at a high temperature exceeding 1200°C, improves the efficiency of use of the source gas 50, and suppresses the temperature rise of each component of the apparatus even at high temperatures. [Brief explanation of the drawings]

[0024] [Figure 1] 1 is a schematic cross-sectional view showing the structure of a vapor phase growth apparatus according to a first embodiment of the present invention. [Figure 2] 3 is a partial cross-sectional view of a first gas injection part in the first embodiment of the present invention. FIG. [Figure 3] FIG. 6 is a partial cross-sectional view of a first gas injection part in a second embodiment of the present invention. [Figure 4] FIG. 1 is a schematic cross-sectional view of a first conventional vapor phase growth apparatus. [Figure 5] FIG. 10 is a schematic cross-sectional view of a second conventional vapor phase growth apparatus. DETAILED DESCRIPTION OF THE INVENTION

[0025] Next, a first embodiment of the present invention will be described with reference to the drawings.

[0026] 1 shows a schematic configuration of a vapor phase growth apparatus 1000 according to this embodiment. This vapor phase growth apparatus 1000 is used to grow a group III nitride semiconductor layer containing aluminum or boron on the upper surface of a substrate 111 made of sapphire or the like.

[0027] The vapor phase growth apparatus 1000 includes a susceptor 112 made of TaC-coated carbon for holding and heating the substrate 111, a resistance heating heater 115 for heating the susceptor 112, and a current introducing bar 142 for applying current to the heater 115. Note that although the heater 115 is a resistance heating type in this embodiment, it may also be a high-frequency electromagnetic induction type heater or a lamp-based heater.

[0028] The source gas 50 reacts and crystallizes, depositing and adhering not only on the upper surface of the substrate 111 but also on the upper surface of the susceptor 112 that holds the substrate 111. When the heating process is repeated in manufacturing a nitride semiconductor, stress is repeatedly applied to the susceptor 112 due to the difference in thermal expansion coefficient between the crystallized deposits and the susceptor, which may result in damage to the susceptor 112. To prevent this, a TaC-coated carbon peripheral ring 116 is provided on the outer periphery of the susceptor 112 to prevent the crystallized deposits from adhering to the susceptor 112.

[0029] This vapor phase growth apparatus 1000 has a plurality of roughly cylindrical holes 120 for injecting a cooling inert gas 55, and is equipped with a first gas injection member 121 arranged to face the substrate 111, a base plate 113 arranged on the susceptor 112 side, and a flow path lid 114 to prevent the atmosphere and surrounding area from being contaminated by reaction deposits.

[0030] As shown in the partial cross-sectional view of the first gas injection unit in the first embodiment of the present invention in FIG. 2, the plurality of substantially cylindrical holes 120 in the first gas injection member 121 are inclined toward the source gas injection unit 150 with respect to the vertical direction so that the angle θ between the flow line of the source gas 50 and the flow line of the inert gas 55 is an acute angle.

[0031] Furthermore, a rotation shaft 145 provided at the bottom of the susceptor 112 and the susceptor 112 are configured to rotate together by a rotation means (not shown).

[0032] Furthermore, the vapor phase growth apparatus 1000 of this embodiment is equipped with a reflector 141 for reducing the downward transmission of heat from the heater 115 and heat from the susceptor 112 heated by the heater 115 through the rotation shaft 145. The heater 115 is made of, for example, TaC-coated carbon or pBN-coated carbon to prevent corrosion of the heater 115 due to ammonia, which is one of the source gases 50 heated to a high temperature. Alternatively, a SiC or high-melting-point metal heater may be used.

[0033] Even if the heater 115 is resistant to highly corrosive ammonia, it is necessary to prevent ammonia from coming into contact with the heater 115 in order to prevent deterioration of the heater 115. Therefore, a heater cover 143 is provided to create a positive pressure around the heater 115, and nitrogen or hydrogen gas is supplied from below inside the rotating shaft 145. In addition, a thermocouple 144 is provided below the susceptor 112, in the center of the heater 115, to measure the temperature of the back surface of the susceptor 112.

[0034] In the vapor phase growth apparatus 1000 of this embodiment, the source gas injection unit 150 comprises an upper gas inlet 153, a middle gas inlet 152, and a lower gas inlet 151. The source gas 50 supplied from the source gas injection unit 150 flows through the upstream flow channel 131 and reacts on the upper surface of the substrate 111 to grow a crystalline film. The source gas 50 that does not contribute to the growth of the crystalline film passes through the downstream flow channel 132 and is exhausted from the exhaust port 155.

[0035] An inert gas inlet 125 for supplying an inert gas 55 for air cooling is provided vertically above the susceptor 112, and a plurality of second gas injection members 122a, 122b are provided between the inert gas inlet 125 and the first gas injection member 121. In this embodiment, two second gas injection members are provided.

[0036] In these second gas injection members 122a, 122b, in order to uniformly distribute the inert gas 55 and increase the flow rate of the inert gas 55, the sum of the cross-sectional areas of the multiple, approximately cylindrical holes in the second gas injection member 122a provided on the outlet side of the inert gas 55 is configured to be smaller than the sum of the cross-sectional areas of the multiple, approximately cylindrical holes in the second gas injection member 122b provided on the inlet side of the inert gas 55.

[0037] Ammonia gas, which is a nitrogen source, and hydrogen or ammonia and nitrogen are introduced from lower gas inlet 151, and hydrogen containing an organometallic source or nitrogen containing an organometallic source and hydrogen or nitrogen are supplied from middle gas inlet 152. Hydrogen or nitrogen is supplied from upper gas inlet 153, but the functions and effects of the present invention are not impaired even if nothing is supplied from upper gas inlet 153.

[0038] As the organic metal raw material, trimethylaluminum, trimethylgallium, triethylgallium, tetraethylboron, etc. are used.

[0039] The inert gas 55 for air cooling supplied from the inert gas inlet 125 may be any of nitrogen, hydrogen, argon, fluorine, and helium.

[0040] A crystal growth method in this example will be described. To grow a nitride semiconductor crystal film such as aluminum nitride or aluminum gallium nitride using the vapor phase growth apparatus 1000 of this embodiment, a source gas 50 is introduced from a source gas injection unit 150. A substrate 111 such as sapphire is heated to a predetermined temperature via a susceptor 112 by a heater 115, and the rotation shaft 145 and the susceptor 112 are rotated integrally at a predetermined speed by a rotation means (not shown), thereby growing a nitride semiconductor crystal film uniformly on the upper surface of the substrate 111.

[0041] Inert gas 55 for air cooling is supplied from inert gas inlet 125, passes through second gas injection members 122b and 122a, and first gas injection member 121, before flowing into upstream flow channel 131. Since the sum of the cross-sectional areas of the multiple holes in second gas injection member 122a is smaller than the sum of the cross-sectional areas of the multiple holes in second gas injection member 122b, according to the law of continuity of fluids, the flow rate of inert gas 55 increases after passing second gas injection member 122b and further increases after passing second gas injection member 122a.

[0042] As shown in the partial cross-sectional view of the first gas injection part in the first embodiment of the present invention in FIG. 2, when the inert gas 55 passes through a plurality of substantially cylindrical holes 120 provided in the first gas injection member 121, the flow lines of the source gas 50 and the inert gas flow lines are aligned. sex The gas 55 is inclined toward the source gas injection part 150 with respect to the vertical direction so that the angle θ formed by the streamline of the gas 55 is an acute angle.

[0043] Therefore, the velocity vector v2 of the inert gas 55 has a horizontal component v2x in addition to a vertical component v2y. The vertical component v2y of the velocity of the inert gas 55 acts to suppress the source gas 50 from convecting vertically upward, thereby allowing the source gas 50 to react efficiently on the upper surface of the substrate 111. On the other hand, the horizontal component v2x of the velocity of the inert gas 55 is added to the horizontal velocity vector v1 of the source gas 50, and the flow velocity of the source gas 50 is accelerated.

[0044] As a result, even in an atmosphere where the temperature for vapor phase growth exceeds 1200°C, it is possible to suppress reaction between the gaseous material 50 before it reaches the substrate 111, and the gaseous material 50 can be efficiently delivered to the substrate 111 heated to a predetermined temperature by the susceptor 112, and can be reacted on the upper surface of the substrate 111. Therefore, the efficiency of use of the gaseous material 50 is significantly improved, and an inexpensive crystal film can be provided.

[0045] To promote crystal growth on the top surface of substrate 111, substrate 111 is maintained at a high temperature of 1200°C or higher, but it is not necessary for areas other than the top surface of substrate 111 to be at a high temperature. In order to prevent thermal degradation of the components of vapor phase growth apparatus 1000 and to prevent reactions in areas other than the top surface of substrate 111 that do not contribute to crystal growth of source gas 50, it is desirable to maintain vapor phase growth apparatus 1000 at as low a temperature as possible.

[0046] In order to cool the vapor phase growth apparatus 1000, it is necessary to maximize the heat transfer coefficient between the inert gas 55 and each component of the vapor phase growth apparatus 1000. The heat transfer coefficient is inversely proportional to the thickness of the thermal boundary layer that occurs between the inert gas 55 and each component of the vapor phase growth apparatus 1000, so the cooling effect can be increased by making the thermal boundary layer thinner. sex The velocity boundary layers generated between the gas 55 and each component of the vapor phase growth apparatus 1000 are in a similar relationship according to Newton's law of cooling, and when the Prandtl number is 1, the two are approximately equal. sex Increasing the flow rate of the gas 55 prevents the temperature of each component of the vapor phase growth apparatus 1000 from rising.

[0047] As described above, the inert gas 55 flowing in through the inert gas inlet 125 is accelerated after passing through the second gas injection members 122b and 122a, and is further accelerated when it passes through the first gas injection member 121 and flows into the upstream flow channel 131. Therefore, the velocity boundary layer generated between the inert gas 55 and each component of the vapor phase growth apparatus 1000 becomes thinner as the flow velocity of the inert gas 55 increases; in other words, the temperature boundary layer becomes thinner. As a result, the heat transfer coefficient increases, and each component of the vapor phase growth apparatus 1000 that has been heated to a high temperature can be cooled, preventing deterioration of each component.

[0048] A partial cross-sectional view of a first gas injection part in the second embodiment of the present invention is shown in Fig. 3. The second embodiment differs from the first embodiment in the shape of the multiple holes 220 provided in the first gas injection part 221 of the second embodiment. The other configurations are exactly the same as those of the first embodiment.

[0049] That is, the holes 220 have a nozzle shape in which the cross-sectional area on the outflow side of the inert gas 55 is smaller than the cross-sectional area on the inlet side of the inert gas 55. When the inert gas 55 flows into the holes 220 at a flow velocity v3, the holes 220 have a nozzle shape in which the cross-section narrows in the gas outflow direction, and therefore, according to the law of continuity of fluids, the flow velocity of the inert gas 55 increases as the cross-sectional area of ​​the holes 220 decreases, and the inert gas 55 flows out at a flow velocity v4. Therefore, the flow velocity of the source gas 50 is increased, and a cooling effect is obtained for each component of the vapor phase growth apparatus 1000. [Explanation of symbols]

[0050] 1000 Metalorganic Chemical Vapor Deposition Equipment 50 Raw material gas 55 Inert Gas 111 Substrate 112 Susceptor 113 Base Plate 114 Channel cover 115 Heater 116 Outer Ring 120 vacancies 121 first gas injection member 122a, 122b Second gas injection members 124 Gas diffusion plate cap 125 Inert gas inlet 131 Upstream Flow Channel 132 Downstream Flow Channel 141 Reflector 142 Current introduction bar 143 Heater Cover 144 Thermocouple 145 Rotational Axis 150 Raw material gas injection section 151 Lower gas inlet 152 Interrupt gas inlet 153 Upper gas inlet 155 exhaust port 220 vacancies 221 Gas injection unit 600 Vapor Phase Growth Equipment 610 PCB 615 PCB holder 620 Raw material gas 620 board 625 Flow Channel 630 Susceptor 635 Coil 700 Vapor Phase Growth Apparatus 705 PCB 710 Reaction vessel 715 Susceptor 720 Heater 725 Raw material gas injection pipe 725 Reaction gas injection tube 730 Sub-injection pipe 735 shaft

Claims

1. A horizontal vapor phase growth apparatus in which a source gas injection unit that injects a source gas in a horizontal direction and a susceptor surface that heats a substrate are arranged in parallel, and the apparatus can heat an upper surface of the substrate to a temperature of 1200°C or higher, at least one first gas injection member having a plurality of holes for injecting an inert gas toward the source gas is disposed between the source gas injection part and the susceptor in a horizontal plane so as to overlap with the first gas injection member, a base plate is disposed between the susceptor, which supports the substrate on its upper surface, and the source gas injection unit; a region where the inert gas is injected onto the base plate from the first gas injection member is provided before the source gas reaches the susceptor; a horizontal vapor phase growth apparatus, wherein the holes of the first gas injection member are inclined with respect to a vertical direction in a direction of travel of the source gas so that a flow line of the source gas and a flow line of the inert gas form an acute angle.

2. 2. The horizontal vapor phase growth apparatus according to claim 1, further comprising, in addition to the first gas injection member, at least one second gas injection member having a substantially cylindrical shape and a plurality of holes for injecting the inert gas toward the susceptor, provided above the susceptor.

3. 3. The horizontal vapor phase growth apparatus according to claim 2, wherein the first gas injection member and the second gas injection member are arranged in series.

4. 2. The horizontal vapor phase growth apparatus according to claim 1, wherein the holes of the first gas injection member are nozzle-shaped, with a cross-sectional area of ​​the holes on the gas outlet side being smaller than a cross-sectional area of ​​the holes on the gas inlet side.

5. 3. The horizontal vapor phase growth apparatus according to claim 2, wherein the sum of the cross-sectional areas of the plurality of holes in the second gas injection member provided on the gas outlet side of the one or more second gas injection members is smaller than the sum of the cross-sectional areas of the plurality of holes in the second gas injection member provided on the gas inlet side.

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