Semiconductor device manufacturing method and semiconductor manufacturing device

Abstract

When epitaxially growing a drift layer in a thin film (18), the present invention involves simultaneously introducing, in a chamber (11), NH3 having a negative concentration-temperature characteristic and N2 having a positive concentration-temperature characteristic. By doing so, even if the in-plane temperature of a SiC substrate (17) is not uniform during growth, since the use of a dopant gas having a positive concentration-temperature characteristic and a dopant gas having a negative concentration-temperature characteristic enables cancellation of the temperature characteristics of both, it is possible to increase the in-plane concentration uniformity of the drift layer.

Description

Method for manufacturing semiconductor device and semiconductor manufacturing apparatus Cross-reference to related applications

[0001] This application is based on Japanese Patent Application No. 2024-189069 filed on October 28, 2024, and Japanese Patent Application No. 2025-102718 filed on June 18, 2025, the contents of which are incorporated herein by reference.

[0002] The present disclosure relates to a method for manufacturing a semiconductor device and a semiconductor manufacturing apparatus used therefor, which manufacture a semiconductor device by epitaxially growing a thin film by supplying a source gas to a semiconductor substrate. For example, it is suitable to apply the present disclosure when using silicon carbide (hereinafter referred to as SiC) as a semiconductor material.

[0003] Conventionally, in forming an n-type epitaxial film of SiC, in order to achieve impurity concentration uniformity within the wafer surface, NH ２ (ammonia) gas, which has a lower decomposition temperature compared to N ３ (nitrogen) gas, has been used as a dopant gas.

[0004] On the other hand, in Patent Document 1, when forming an n-type epitaxial film with a high impurity concentration of about 1×10 １８ cm －３ or more, in order to avoid device corrosion damage caused by NH ３ gas, it has been proposed to use N ３ gas in combination with NH ２ gas.

[0005] Japanese Unexamined Patent Application Publication No. 2014-103363

[0006] In recent years, due to the increase in wafer diameter and the requirement for reducing device characteristic variations, further uniformity of the concentration within the wafer surface has been required. However, in forming a low-concentration n-type epitaxial film, simply using NH ３ gas with a low decomposition temperature could not satisfy the requirement for concentration uniformity within the wafer surface.

[0007] On the other hand, in Patent Document 1, in forming a high-concentration n-type epitaxial film, in order to reduce device corrosion, NH ３N for gas ２ Although gas is used in combination, it does not take into account the uniformity of the in-wafer concentration when forming low-concentration n-type epitaxial films.

[0008] This disclosure aims to provide a method for manufacturing a semiconductor device and a semiconductor manufacturing apparatus that can improve the uniformity of in-wafer concentration.

[0009] The first aspect of this disclosure is a method for manufacturing a semiconductor device for producing an epitaxial wafer by epitaxially growing a thin film including a drift layer on a semiconductor substrate, comprising: heating the semiconductor substrate while it is placed in a chamber, and further introducing a dopant gas containing the dopant of the drift layer together with a source gas for the semiconductor material into the chamber to epitaxially grow the drift layer, wherein, in the epitaxial growth of the drift layer, when an in-plane temperature distribution occurs in which the temperature is non-uniform within the plane of the semiconductor substrate during epitaxial growth, both a first gas having a positive concentration temperature characteristic in which the concentration of the dopant in the semiconductor increases as the temperature of the semiconductor substrate increases, and a second gas having a negative concentration temperature characteristic in which the concentration of the dopant decreases, are introduced simultaneously as the dopant gas.

[0010] In this way, a first gas with positive concentration-temperature characteristics and a second gas with negative concentration-temperature characteristics are introduced simultaneously. This allows the dopant gas with positive concentration-temperature characteristics and the dopant gas with negative concentration-temperature characteristics to cancel each other out, thereby improving the in-plane concentration uniformity of the drift layer. Therefore, a method for manufacturing a semiconductor device that can improve in-wafer concentration uniformity can be provided.

[0011] Furthermore, the semiconductor manufacturing apparatus in the second aspect of this disclosure includes a chamber constituting a reaction chamber, a mounting stand placed in the reaction chamber on which a semiconductor substrate is installed, and a heating device for heating the semiconductor substrate, and includes a thin film forming unit for epitaxially growing a thin film including a drift layer on the semiconductor substrate by introducing a raw material gas of semiconductor raw materials into the reaction chamber, a supply gas unit for introducing the raw material gas into the chamber, and a dopant gas unit for supplying a dopant gas containing the dopant raw material of the drift layer, wherein the dopant gas unit is a gas cylinder that stores both a first gas having a positive concentration temperature characteristic in which the concentration of the dopant in the semiconductor substrate increases as the temperature increases with respect to the in-plane temperature of the semiconductor substrate during epitaxial growth, and a second gas having a negative concentration temperature characteristic in which the concentration of the dopant decreases. The gas cylinder stores the first gas and the second gas in a mixing ratio set based on the efficiency of dopant uptake in the first gas into the drift layer, the efficiency of dopant uptake in the second gas, and the temperature coefficient that represents the amount of change in the concentration of the dopant in the drift layer in response to a change in the temperature of the semiconductor substrate when the first gas and the second gas are used.

[0012] By using such a semiconductor device, the influence of the in-plane temperature distribution of the semiconductor substrate can be reduced, and the in-plane concentration uniformity of the drift layer can be improved, thus providing a method for manufacturing a semiconductor device that can enhance the in-plane concentration uniformity of the wafer. Furthermore, since only a gas cylinder containing the first gas and the second gas at a set mixing ratio needs to be prepared as the dopant unit, only one type of gas cylinder can be used to store the dopant gas.

[0013] Furthermore, a semiconductor manufacturing apparatus in a third aspect of this disclosure includes a chamber constituting a reaction chamber, a mounting stand placed in the reaction chamber on which a semiconductor substrate is installed, and a heating device for heating the semiconductor substrate, and includes a thin film forming unit for epitaxially growing a thin film including a drift layer on the semiconductor substrate by introducing a raw material gas of semiconductor raw materials into the reaction chamber, a supply gas unit for introducing the raw material gas into the chamber, and a dopant gas unit for supplying a dopant gas containing the dopant raw materials of the thin film, wherein the dopant gas unit has a gas introduction source for introducing a first gas having a positive concentration temperature characteristic in which the concentration of dopants in the semiconductor substrate increases as the temperature increases with respect to the in-plane temperature of the semiconductor substrate during epitaxial growth, and a second gas having a negative concentration temperature characteristic in which the concentration of dopants decreases. The chamber is arranged to divide the reaction chamber into a growth space below and a separation space above the growth space, and includes a shower head with a plurality of through holes connecting the growth space and the separation space, and a cooling unit for cooling the separation space, wherein the gas introduction source is N as the first gas. ２ In addition to introducing NH as the second gas, ３ The supply gas unit introduces silane as the raw material gas.

[0014] By using such a semiconductor device, the influence of the in-plane temperature distribution of the semiconductor substrate can be reduced, and the uniformity of the in-plane concentration of the drift layer can be achieved, thereby providing a semiconductor device manufacturing method that can improve the uniformity of the in-plane concentration of the wafer. Furthermore, by equipping the chamber with a cooling unit, the separation space can be cooled to below 400°C in the cooling unit. This suppresses the decomposition of the source gas and dopant gas, and consequently prevents clogging in the through-holes of the showerhead.

[0015] This figure shows the configuration of a semiconductor manufacturing apparatus according to the first embodiment of this disclosure. This is a cross-sectional view of an epitaxial wafer manufactured by the semiconductor manufacturing apparatus shown in Figure 1. This is a flowchart showing the manufacturing process of an epitaxial wafer. This figure shows the manufacturing profile of an epitaxial wafer. This figure shows the relationship between the distance from the center of the wafer and the n-type impurity concentration. This figure shows the relationship between the temperature and the n-type impurity concentration when a thin film is epitaxially grown. This figure shows the in-plane temperature distribution when a thin film is formed. This figure shows the in-plane concentration distribution of n-type impurities. This figure shows the relationship between the distance from the center of the wafer and the n-type impurity concentration. This figure shows the in-plane temperature distribution when a thin film is formed. This figure shows the relationship between the temperature and the n-type impurity concentration when a thin film is epitaxially grown. This figure shows the configuration of a semiconductor manufacturing apparatus according to the second embodiment of this disclosure. This figure shows the configuration of a semiconductor manufacturing apparatus according to the third embodiment of this disclosure. This figure shows the schematic configuration of a thin film forming section provided in a semiconductor manufacturing apparatus according to the fourth embodiment of this disclosure.

[0016] The embodiments of this disclosure will be described below with reference to the drawings. In each embodiment, including the other embodiments described below, parts that are the same or equivalent to each other will be denoted by the same reference numerals.

[0017] (First Embodiment) A first embodiment of the present disclosure will now be described. The semiconductor manufacturing apparatus shown in this embodiment is used as an apparatus for epitaxially growing a thin film of SiC on a plurality of SiC substrates.

[0018] As shown in Figure 1, the semiconductor manufacturing apparatus of this embodiment has a configuration comprising a thin film forming section 10, a first supply gas unit 20, a second supply gas unit 30, a first dopant gas unit 40, a second dopant gas unit 50, and a carrier gas unit 60. The gases supplied from each unit are introduced into the thin film forming section 10 through various pipes 100 to 150.

[0019] The thin-film forming unit 10 is configured to include a chamber 11, a gas introduction unit 12, a mounting base 13, a heating device 14, an exhaust port 15, a pressure controller (hereinafter referred to as APC (Auto Pressure Control)) 16, and the like. The chamber 11 constitutes a reaction chamber 11a in which a gas is reacted to form a thin film on the surface of the SiC substrate 17. The thin-film forming unit 10 can control the vacuum level inside the chamber 11 by discharging the atmospheric gas inside the chamber 11 through the exhaust port 15, and can also introduce a desired gas into the chamber 11 through the gas introduction unit 12. In this embodiment, the gas introduction unit 12 is located above the mounting base 13 of the chamber 11, and gas is introduced from above the mounting base 13.

[0020] A SiC substrate 17 to be coated is placed on a mounting table 13 in the thin film formation section 10. Then, while heating the SiC substrate 17 from the back side with a heating device 14, the mounting table 13 is rotated at high speed, and a gas containing SiC raw materials is introduced while controlling the atmospheric pressure in the chamber 11 to a constant level with an APC 16. This forms a thin SiC film 18 composed of an epitaxial film. In this way, a so-called epitaxial wafer is manufactured by forming a thin film 18 on the surface of a SiC substrate 17. As shown in Figure 2, the thin film 18 has a structure in which a buffer layer 18a and a drift layer 18b are formed sequentially on the surface of the SiC substrate 17, but it is also possible to have a structure in which only the drift layer 18b is formed without the buffer layer 18a. Also, although only one SiC substrate 17 is shown in Figure 1 for simplification, multiple substrates may be mounted on the mounting table 13.

[0021] The first supply gas unit 20 is a mechanism for introducing a supply gas containing silicon raw material (hereinafter referred to as Si supply gas). The Si supply gas only needs to contain at least silicon source gas, but in this case, H is the carrier gas. ２ This includes hydrogen and HCl (hydrogen chloride), which acts as an etching gas.

[0022] Specifically, the first supply gas unit 20 is equipped with gas introduction sources 21a to 21e, raw material MFCs 22a to 22e and distribution MFCs 23a and 23b, as well as a distribution APC 24 which serves as an APC for distribution. The various parts constituting the first supply gas unit 20 are connected to various pipes 100, 101, and 102, and Si supply gas is supplied to the introduction pipe 150, which will be described later and is connected to the thin film forming section 10.

[0023] The gas introduction sources 21a to 21e are gas cylinders or the like that store multiple gases containing raw materials for growing the thin film 18, and include a carrier gas introduction source 21a, silicon source gas introduction sources 21b and 21c, and etching gas introduction sources 21d and 21e. The carrier gas introduction source 21a is the part that stores the carrier gas, for example, H ２ It stores the silicon source gas. The carrier gas introduction source 21a is connected to the supply pipe 100a. The silicon source gas introduction sources 21b and 21c are parts that store silicon source gas, for example, SiH ４ (Silane) is stored. Silicon source gas introduction sources 21b and 21c are connected to supply pipes 100b and 100c, respectively. Etching gas introduction sources 21d and 21e are parts that store etching gas, and for example, HCl is stored as the etching gas. Etching gas introduction sources 21d and 21e are connected to supply pipes 100d and 100e.

[0024] Note that although the silicon source gas introduction sources 21b and 21c are configured separately here, they may be a single unit. Also, although the etching gas introduction sources 21d and 21e are configured separately here, they may be a single unit.

[0025] Each supply pipe 100a to 100e is equipped with raw material MFCs 22a to 22e, respectively, and the gas flow rate through each supply pipe 100a to 100e, i.e., the amount of each supply gas introduced, can be adjusted. Raw material MFCs 22b and 22c are both connected to silicon source gas introduction sources 21b and 21c where silicon source gas is stored, but raw material MFC 22b is used for controlling high flow rates, and raw material MFC 22c is used for controlling low flow rates. Similarly, raw material MFCs 22d and 22e are both connected to etching gas introduction sources 21d and 21e where etching gas is stored, but raw material MFC 22d is used for controlling high flow rates, and raw material MFC 22e is used for controlling low flow rates. Therefore, it is possible to perform fine flow rate control while flowing silicon source gas and etching gas at a relatively high flow rate.

[0026] Furthermore, each supply pipe 100a to 100e is aggregated into a manifold pipe 101 downstream of the raw material MFCs 22a to 22e, and a mixed gas is formed within the manifold pipe 101.

[0027] The manifold pipe 101 is again connected to a plurality of distribution pipes 102a to 102c on the downstream side. Therefore, the mixed gas is distributed to each of the distribution pipes 102a to 102c and introduced into the introduction pipe 150, which will be described later and is connected to the thin film forming section 10.

[0028] One of the distribution pipes 102a to 102c, in this case distribution pipe 102c, is equipped with a distribution APC 24, while the remaining distribution pipes 102c are equipped with distribution MFCs 23a and 23b. The distribution MFCs 23a and 23b are designed to adjust the gas flow rate through the distribution pipes 102a and 102b, i.e., the amount of mixed gas introduced. The distribution APC 24 adjusts the pressure on the manifold pipe 101 side, i.e., the mixed gas pressure; in other words, it adjusts the pressure difference between the mixed gas pressure and the supply gas pressure in the chamber 11 of the thin film forming section 10. The distribution APC 24 adjusts the mixed gas pressure, which is the pressure in the manifold pipe 101, to a predetermined pressure by discharging the mixed gas to the outside from the manifold pipe 101 side. The location of the discharge of the mixed gas from the distribution APC 24 is arbitrary, but in this embodiment, by connecting the distribution pipe 102c to the introduction pipe 150, the mixed gas discharged by the distribution APC 24 for pressure adjustment is also supplied to the thin film forming section 10.

[0029] The second supply gas unit 30 supplies different raw materials than the first supply gas unit 20, and is a mechanism for introducing a supply gas containing carbon raw materials (hereinafter referred to as C supply gas). The C supply gas only needs to contain at least a carbon source gas, but in this case, the carrier gas is H ２ It also includes that.

[0030] Specifically, the second supply gas unit 30 is equipped with gas introduction sources 31a to 31c, raw material MFCs 32a to 32c and distribution MFCs 33a and 33b, as well as a distribution APC 34. The various parts constituting the second supply gas unit 30 are connected to various pipes 110, 111, and 112, and supply gas C is supplied to the introduction pipe 150, which will be described later and is connected to the thin film forming section 10.

[0031] The gas introduction sources 31a to 31c are gas cylinders or the like that store multiple gases containing raw materials for growing the thin film 18, and include a carrier gas introduction source 31a and carbon source gas introduction sources 31b and 31c. The carrier gas introduction source 31a is the part that stores the carrier gas, and for example, H is used as the carrier gas. ２It stores the carbon source gas. Carrier gas introduction source 31a is connected to supply piping 110a. Carbon source gas introduction sources 31b and 31c are parts that store carbon source gas, for example, C ３ H ８ (Propane) is stored. The carbon source gas introduction sources 31b and 31c are connected to the supply pipes 110b and 110c.

[0032] Each of the supply pipes 110a to 110c is equipped with raw material MFCs 32a to 32c, allowing for adjustment of the gas flow rate through each supply pipe, i.e., the amount of each supply gas introduced. Both raw material MFCs 32b and 32c are connected to carbon source gas introduction sources 31b and 31c, where carbon source gas is stored. Raw material MFC 32b is used for controlling large flow rates, while raw material MFC 32c is used for controlling small flow rates. Therefore, it is possible to perform fine flow rate control while supplying carbon source gas at a relatively large flow rate.

[0033] Furthermore, each supply pipe 110a to 110c is aggregated into a manifold pipe 111 downstream of the raw material MFCs 32a to 32c, and a mixed gas is formed within the manifold pipe 111.

[0034] The manifold pipe 111 is again connected to a plurality of distribution pipes 112a to 112c on the downstream side. Therefore, the mixed gas is distributed to each of the distribution pipes 112a to 112c and introduced into the introduction pipe 150, which will be described later and is connected to the thin film forming section 10.

[0035] One of the distribution pipes 112a to 112c, in this case distribution pipe 112c, is equipped with a distribution APC 34, while the remaining distribution pipes 112a and 112b are equipped with distribution MFCs 33a and 33b. The distribution MFCs 33a and 33b are designed to adjust the gas flow rate through the distribution pipes 112a and 112b, i.e., the amount of mixed gas introduced. The distribution APC 34 adjusts the pressure on the manifold pipe 111 side, i.e., the mixed gas pressure; in other words, it adjusts the pressure difference between the mixed gas pressure and the supply gas pressure in the chamber 11 of the thin film forming section 10. The distribution APC 34 adjusts the mixed gas pressure, which is the pressure in the manifold pipe 111, to a predetermined pressure by discharging the mixed gas from the manifold pipe 111 side to the outside. The location of the discharge of the mixed gas from the distribution APC 34 is arbitrary, but in this embodiment, by connecting the distribution pipe 112c to the introduction pipe 150, the mixed gas discharged from the distribution APC 34 for pressure adjustment is also supplied to the thin film forming section 10.

[0036] The first dopant gas unit 40 is a mechanism for introducing a supply gas (hereinafter referred to as the first dopant gas) containing a first dopant raw material, such as an n-type dopant. The first dopant gas only needs to contain at least the first dopant raw material, but in this case, H is used as the carrier gas. ２ It also includes that.

[0037] Specifically, the first dopant gas unit 40 is equipped with gas introduction sources 41a to 41e, raw material MFCs 42a to 42e and distribution MFCs 43a and 43b, as well as a distribution APC 44. The various parts constituting the first dopant gas unit 40 are connected to various pipes 120, 121, and 122, and the first dopant gas is supplied to an introduction pipe 150, which will be described later and is connected to the thin film forming section 10.

[0038] The gas introduction sources 41a to 41e are composed of gas cylinders for storing various gases and include a carrier gas introduction source 41a and first dopant gas introduction sources 41b to 41e. The carrier gas introduction source 41a is the part that stores the carrier gas, for example, H ２It stores the following. Carrier gas introduction source 41a is connected to supply piping 120a. The first dopant gas introduction sources 41b to 41e are parts that store gas containing the first dopant raw material. The first dopant gas introduction sources 41b and 41c contain N (nitrogen element) which becomes an n-type dopant. ２ It stores. The first dopant gas introduction sources 41d and 41e contain NH containing N which becomes an n-type dopant. ３ It stores N. ２ This corresponds to the first gas, NH ３ This corresponds to the second gas. The first dopant gas introduction sources 41b to 41e are connected to the supply pipes 120b to 120e.

[0039] Each of the supply pipes 120a to 120e is equipped with raw material MFCs 42a to 42e, allowing for adjustment of the gas flow rate through each supply pipe 120a to 120e, i.e., the amount of each supply gas introduced. Raw material MFCs 42b and 42c are connected to first dopant gas introduction sources 41b and 41c of the same gas type, where the gas containing the first dopant raw material is stored. Raw material MFC 42b is used for controlling high flow rates, and raw material MFC 42c is used for controlling low flow rates. Similarly, raw material MFCs 42d and 42e are also connected to first dopant gas introduction sources 41d and 41e of the same gas type, where the gas containing the first dopant raw material is stored. Raw material MFC 42d is used for controlling high flow rates, and raw material MFC 42e is used for controlling low flow rates. Therefore, it is possible to perform fine flow rate control for each gas type while still allowing the first dopant gas to flow at a relatively high flow rate.

[0040] Furthermore, each supply pipe 120a to 120e is aggregated into a manifold pipe 121 downstream of the raw material MFCs 42a to 42e, and a mixed gas is formed within the manifold pipe 121.

[0041] The manifold pipe 121 is again connected to a plurality of distribution pipes 122a to 122c on the downstream side. Therefore, the mixed gas is distributed to each of the distribution pipes 122a to 122c and introduced into the introduction pipe 150, which will be described later and is connected to the thin film forming section 10.

[0042] One of the distribution pipes 122a to 122c, in this case distribution pipe 122c, is equipped with a distribution APC 44, while the remaining distribution pipes 122a and 122b are equipped with distribution MFCs 43a and 43b. The distribution MFCs 43a and 43b are designed to adjust the gas flow rate through the distribution pipes 122a and 122b, i.e., the amount of mixed gas introduced. The distribution APC 44 adjusts the pressure on the manifold pipe 121 side, i.e., the mixed gas pressure; in other words, it adjusts the differential pressure between the mixed gas pressure and the supply gas pressure in the chamber 11 of the thin film forming section 10. The distribution APC 44 adjusts the mixed gas pressure, which is the pressure in the manifold pipe 121, to a predetermined pressure by discharging the mixed gas from the manifold pipe 121 side to the outside. The location of the discharge of the mixed gas from the distribution APC 44 is arbitrary, but in this embodiment, by connecting the distribution pipe 122c to the introduction pipe 150, the mixed gas discharged from the distribution APC 44 for pressure adjustment is also supplied to the thin film forming section 10.

[0043] The second dopant gas unit 50 is a mechanism for introducing a supply gas (hereinafter referred to as the second dopant gas) containing a second dopant raw material, such as a p-type dopant. The second dopant gas only needs to contain at least the second dopant raw material, but in this case, H2 is the carrier gas. ２ It also includes that.

[0044] Specifically, the second dopant gas unit 50 is equipped with gas introduction sources 51a to 51c, raw material MFCs 52a to 52c and distribution MFCs 53a and 53b, as well as a distribution APC 54. The various parts constituting the second dopant gas unit 50 are connected to various pipes 130, 131, and 132, and the second dopant gas is supplied to an introduction pipe 150, which will be described later and is connected to the thin film forming section 10.

[0045] The gas introduction sources 51a to 51c are composed of gas cylinders for storing various gases and include a carrier gas introduction source 51a and second dopant gas introduction sources 51b and 51c. The carrier gas introduction source 51a is the part that stores the carrier gas, and for example, H ２The carrier gas introduction source 51a is connected to the supply pipe 130a. The second dopant gas introduction sources 51b and 51c are parts that store gas containing the second dopant raw material, and store, for example, TMA (trimethylaluminum) containing Al (aluminum) which becomes a p-type dopant. The second dopant gas introduction sources 51b and 51c are connected to the supply pipes 130b and 130c.

[0046] Each of the supply pipes 130a to 130c is equipped with raw material MFCs 52a to 52c, respectively, allowing adjustment of the gas flow rate through each supply pipe 130a to 130c, i.e., the amount of each supply gas introduced. Both raw material MFCs 52b and 52c are connected to the second dopant gas introduction sources 51b and 51c, where the second dopant raw material is stored, but raw material MFC 52b is used for controlling high flow rates, and raw material MFC 52c is used for controlling low flow rates. Therefore, it is possible to perform fine flow rate control while flowing the second dopant raw material at a relatively high flow rate.

[0047] Furthermore, each supply pipe 130a to 130c is aggregated into a manifold pipe 131 downstream of the raw material MFCs 52a to 52c, and a mixed gas is formed within the manifold pipe 131.

[0048] The manifold pipe 131 is again connected to a plurality of distribution pipes 132a to 132c on the downstream side. Therefore, the mixed gas is distributed to each of the distribution pipes 132a to 132c and introduced into the introduction pipe 150, which will be described later and is connected to the thin film forming section 10.

[0049] One of the distribution pipes 132a to 132c, in this case distribution pipe 132c, is equipped with a distribution APC 54, while the remaining distribution pipes 132a and 132b are equipped with distribution MFCs 53a and 53b. The distribution MFCs 53a and 53b are designed to adjust the gas flow rate through the distribution pipes 132a and 132b, i.e., the amount of mixed gas introduced. The distribution APC 54 adjusts the pressure on the manifold pipe 131 side, i.e., the mixed gas pressure; in other words, it adjusts the differential pressure between the mixed gas pressure and the supply gas pressure in the chamber 11 of the thin film forming section 10. The distribution APC 54 adjusts the mixed gas pressure, which is the pressure in the manifold pipe 131, to a predetermined pressure by discharging the mixed gas from the manifold pipe 131 side to the outside. The location of the discharge of the mixed gas from the distribution APC 54 is arbitrary, but in this embodiment, by connecting the distribution pipe 132c to the introduction pipe 150, the mixed gas discharged from the distribution APC 54 for pressure adjustment is also supplied to the thin film forming section 10.

[0050] The carrier gas unit 60 is a mechanism for introducing carrier gas. Among the supply gases introduced into the thin film forming section 10, the carrier gas accounts for the largest amount. For this reason, the carrier gas unit 60 is connected to an introduction pipe 150 that is directly connected to the thin film forming section 10, so that the carrier gas introduced from the carrier gas unit 60 constitutes the main supply gas. This makes it possible to stably form the main supply gas supply gas using carrier gas, so that the main gas can be formed even when other raw material gases are not introduced.

[0051] Specifically, the carrier gas unit 60 is configured to have carrier gas introduction sources 61a to 61c and MFCs for carrier gas (hereinafter referred to as carrier gas MFCs) 62a to 62c, forming the main supply gas via the carrier gas.

[0052] The carrier gas introduction sources 61a to 61c are gas cylinders or the like that store the carrier gas, for example, H ２It stores the following. Carrier gas introduction sources 61a to 61c are each connected to introduction pipes 150a to 150c. Carrier gas MFCs 62a to 62c are provided in each of the introduction pipes 150a to 150c, and the gas flow rate of the carrier gas to each introduction pipe 150a to 150c can be adjusted. The introduction pipes 150a to 150c are connected to the distribution pipes 102a to 102c, 112a to 112c, 122a to 122c, and 132a to 132c of each of the units 20 to 50. As a result, various supply gases from the first supply gas unit 20, the second supply gas unit 30, the first dopant gas unit 40, and the second dopant gas unit 50 are introduced into each of the introduction pipes 150a to 150c and introduced into the chamber 11 together with the carrier gas. More specifically, the introduction pipe 150a is located in the center of the installation base 13, the introduction pipe 150c is located around the outer circumference of the installation base 13, and the introduction pipe 150b is located between them to introduce gas.

[0053] With this configuration, the carrier gas unit 60 can control the carrier gas flow rate in accordance with increases and decreases in the flow rates of various supply gases, thereby broadly changing the distribution ratio of various supply gases without disturbing the gas flow in the chamber 11. Therefore, the thin film 18 to be formed on the SiC substrate 17 can be deposited under a wide range of deposition conditions while controlling in-plane uniformity.

[0054] In the above, the carrier gas introduction sources 21a, 31a, 41a, 51a, and 61a-61c, where the carrier gas is stored, are configured separately, but they may be a single source or a combination of several of them may be used. Also, H may be used as the carrier gas. ２ H is given as an example, ２ Other gases, such as inert gases like Ar, may be used, or these gases may be used in combination. When using multiple gases, it is preferable to install separate introduction sources and MFCs for each type of gas, and to control the flow rate of each individually.

[0055] Next, a thin film formation method in the semiconductor manufacturing apparatus of this embodiment having the above configuration will be described. The thin film formation method described below is applied as part of a method for manufacturing a semiconductor device having a thin film 18 including a drift layer 18b.

[0056] In the semiconductor manufacturing apparatus according to this embodiment, first, as shown in step S1 of Figure 3, a plurality of SiC substrates 17 to be coated are prepared, and then the SiC substrates 17 are placed in the thin-film forming section 10, that is, on the mounting stand 13 inside the chamber 11. Then, as steps S2 and S3 of Figure 3, a thin film 18 is epitaxially grown on the surface of the SiC substrates 17. Here, as step S2, a buffer layer 18a with a relatively high concentration of n-type impurities is formed, and then as step S3, a drift layer 18b with a lower concentration of n-type impurities than the buffer layer 18a is formed. For the buffer layer 18a, the n-type impurity concentration is 5 × 10⁻⁶. １７ ~2 x 10 １８ cm －３ degree, for example, 1 x 10 １８ cm －３ Furthermore, for the drift layer 18b, the n-type impurity concentration is set to 5 × 10⁻⁶. １５ ~3 x 10 １６ cm －３ degree, for example, 1 x 10 １６ cm －３ That is what they say.

[0057] Specifically, the mounting base 13 is rotated at high speed while thin film formation is performed according to the process shown in the profile in Figure 4. That is, a heating process is performed to raise the temperature inside the chamber 11 and the temperature of the SiC substrate 17 by heating with the heating device 14. At the same time, carrier gas is introduced from carrier gas introduction sources 61a to 61c based on the control of the gas flow rate by each carrier gas MFC 62a to 62c in the carrier gas unit 60. Carrier gas is also introduced from the first supply gas unit 20, the second supply gas unit 30, the first dopant gas unit 40, and the second dopant gas unit 50. Furthermore, while maintaining a constant pressure inside the chamber 11, the amount of atmospheric gas discharged from the chamber 11 is adjusted by the APC 16.

[0058] Then, when the chamber 11 and the SiC substrate 17 reach a predetermined temperature, the supply of various gases is started from the first supply gas unit 20, the second supply gas unit 30, the first dopant gas unit 40, and the second dopant gas unit 50. If an n-type impurity layer is to be formed, the first dopant gas is introduced from the first dopant gas unit 40, and if a p-type impurity layer is to be formed, the second dopant gas is introduced from the second dopant gas unit 50. If necessary, dopant gases of different conductivity types can also be introduced simultaneously. As a result, Si supply gas, C supply gas, the first dopant gas, and the second dopant gas are introduced into the chamber 11.

[0059] At this time, when the buffer layer 18a is formed in step S2, N is used as the first dopant gas. ２ Without introducing NH ３ Only is introduced, and when the drift layer 18b is formed in step S3, N is used as the first dopant gas. ２ and NH ３ Both are introduced. First, when the buffer layer 18a is formed, NH gradually ３ After introducing the solution, the flow rate is controlled to a constant level and continued until the buffer layer 18a reaches the desired thickness. Subsequently, when forming the drift layer 18b, N ２ and NH ３ By introducing both together, the inside of chamber 11 becomes N ２ and NH ３ The atmosphere is a mixed gas. Here, gradually N ２ After introducing it, the flow rate is controlled to a constant level, and at the same time, NH is gradually introduced. ３ The amount of introduced material is reduced and then controlled to a constant flow rate. This allows the buffer layer 18a and the drift layer 18b to be formed with the desired n-type impurity concentration. ２ and NH ３ The flow rate, that is, N ２ and NH ３ The mixing ratio will be discussed later.

[0060] Furthermore, at this time, the introduction of carrier gas from the carrier gas unit 60, the first supply gas unit 20, the second supply gas unit 30, the first dopant gas unit 40, and the second dopant gas unit 50 is carried out continuously. As a result, the supply gases from the various units are added to the main carrier gas and introduced into the chamber 11. Therefore, it is possible to transport the various supply gases to the chamber 11 using the stable main carrier gas.

[0061] Then, by adjusting the amount of heating by the heating device 14, a constant temperature is maintained while continuing to introduce various supply gases. This allows for the epitaxial growth of a SiC thin film 18 on the SiC substrate 17. Furthermore, because the mounting stand 13 is rotated at high speed, the gas flow in the chamber 11 is stabilized, improving the in-plane uniformity of the film thickness and concentration of the SiC thin film 18 through gas distribution.

[0062] After this, once the SiC thin film 18 has formed to a predetermined thickness, the introduction of various supply gases is stopped, and heating by the heating device 14 is also stopped to perform a cooling process that lowers the temperature inside the chamber 11 and the SiC substrate 17. At this time, the introduction of carrier gas from the carrier gas unit 60 is continued to reduce the influence of residual supply gas. When the temperature inside the chamber 11 and the SiC substrate 17 drops to, for example, room temperature, the thin film formation process is completed, and an epitaxial wafer with a thin film 18 including a drift layer 18b formed on the SiC substrate 17 is manufactured.

[0063] After manufacturing the epitaxial wafer in this manner, the epitaxial wafer is used to manufacture a semiconductor device, such as an n-channel MOSFET. The structure of the MOSFET is arbitrary, but as an example, the MOSFET is manufactured as follows. First, a saturation current suppression layer is formed on the surface or surface layer of the drift layer 18b by alternately arranging line-shaped n-type JFET portions and p-type field blocking layers to form a stripe-like structure. Then, the MOSFET device structure is formed on this saturation current suppression layer. For example, an n-type current dispersion layer, a p-type base region, and an n-type source region are epitaxially grown in sequence on the saturation current suppression layer, then a trench is formed penetrating the source region and base region, and a gate electrode is formed in the trench via a gate insulating film. Then, a source electrode and gate wiring layer are formed via an interlayer insulating film covering the source region and gate electrode, and a drain electrode is formed on the back surface of the SiC substrate 17. In this way, a semiconductor device having an n-channel trench-gate MOSFET can be manufactured.

[0064] In the thin film formation method described above, when forming the buffer layer 18a, N is used as the first dopant gas. ２ Without introducing NH ３ Only is introduced, and when the drift layer 18b is formed, N is used as the first dopant gas. ２ and NH ３ Both are implemented. For this reason and N ２ and NH ３ This section explains how to set the mixing ratio when introducing both.

[0065] The inventors investigated the factors that cause in-plane concentration distribution to occur when in-plane concentration uniformity cannot be maintained on a wafer.

[0066] First, experiments have shown that N is the n-type dopant gas. ２ When using only NH ３For each case using only one of the materials, a thin film 18 was epitaxially grown on a SiC substrate 17. The relationship between the radial distance of the wafer, i.e., the distance from the center of the wafer, and the n-type impurity concentration was then investigated. Figure 5A shows the results of the investigation, with the radial distance of the wafer on the horizontal axis and the n-type impurity concentration on the vertical axis. As this investigation shows, in all cases, the impurity concentration is almost uniform from the center of the wafer to the edge of the wafer, i.e., near the outer edge of the wafer. However, when it reaches the outer edge of the wafer, the n-type impurity concentration is almost uniform. ２ Then the n-type impurity concentration increases sharply, NH ３ Then N ２ The result showed a gradual decrease compared to the previous change.

[0067] Also, as an n-type dopant gas, N ２ When using only NH ３ For each case where only was used, the temperature of the SiC substrate 17 was varied during the epitaxial growth of the thin film 18 on the SiC substrate 17. Figure 5B shows the results of the investigation with the temperature of the SiC substrate 17 on the horizontal axis and the n-type impurity concentration on the vertical axis. As this investigation shows, in all cases the n-type impurity concentration changed in response to the temperature of the SiC substrate 17, and the way in which it changed was N ２ and NH ３ It was the opposite of N. ２ and NH ３ It is thought to depend on the decomposition temperature of N. ２ Since the decomposition temperature is high due to the covalent bond, and the N after decomposition is activated and incorporated into SiC, it is thought that it is more easily incorporated into SiC in the high-temperature range where decomposition progresses, and the concentration of n-type impurities increases with increasing temperature. Conversely, NH ３ Because it decomposes at low temperatures, it is easily incorporated into SiC even at low temperatures. However, as the temperature increases, the incorporated N in SiC becomes easier to separate, so it is thought that the concentration of n-type impurities gradually decreases with increasing temperature.

[0068] Furthermore, the in-plane temperature distribution when a thin film 18 was formed on the SiC substrate 17 was investigated. Figure 5C shows the investigation results with the wafer radial distance on the horizontal axis and the SiC substrate 17 temperature on the vertical axis. As this investigation result shows, the temperature is almost uniform from the center of the wafer to near the outer edge, but the temperature becomes higher towards the outer edge. This investigation result N ２ This shows the case using NH ３ The same was true when using [the other method].

[0069] From these research findings, the following insights were obtained.

[0070] (1) NH as an n-type dopant gas ３ When using this method, the concentration decreases at the wafer edges, i.e., the outer edges of the wafer, compared to the center of the wafer.

[0071] (2) N as an n-type dopant gas ２ When using this method, the concentration increases at the edges of the wafer compared to the center of the wafer.

[0072] (3) At the n-type impurity concentration, NH ３ Then, the impurity concentration decreases as the temperature increases, which is a negative temperature dependence (hereinafter referred to as negative concentration temperature characteristic). ２ Therefore, there is a positive temperature dependence (hereinafter referred to as positive concentration temperature characteristic) in which the impurity concentration increases as the temperature rises.

[0073] (4) The in-plane concentration distribution is caused by the in-plane temperature non-uniformity of the SiC substrate 17 and the decomposition temperature dependence of the dopant gas, and NH ３ Then the impurity concentration decreases at the wafer edge, N ２ Therefore, the impurity concentration increases at the wafer edge.

[0074] Here, it is thought that if the in-plane temperature distribution of the SiC substrate 17 is eliminated and the in-plane temperature is made uniform, the in-plane concentration distribution can be reduced and in-plane concentration uniformity can be maintained. However, this would require very strict restrictions on the material characteristics and assembly tolerances of the thin-film forming section 10, including the chamber 11, which is practically difficult.

[0075] Therefore, when epitaxially growing the drift layer 18b, NH having a negative concentration gradient ３ and N having a positive concentration gradient ２ are simultaneously introduced into the chamber 11. By doing so, even if the in-plane temperature of the SiC substrate 17 is not uniform during growth, the gradients of the two can be canceled out by the dopant gas with a positive concentration gradient and the dopant gas with a negative concentration gradient. For this reason, it becomes possible to improve the in-plane concentration uniformity of the drift layer 18b.

[0076] In addition, here, based on the negative concentration gradient of NH ３ and the positive concentration gradient of N ２ etc., the mixing ratio when using N ２ and NH ３ is optimized to reduce the influence of the in-plane temperature distribution of the SiC substrate 17. As a result, the in-plane concentration uniformity is achieved as compared with the case of using only NH ３ as the n-type dopant gas.

[0077] For N ２ and NH ３ , the optimization of the mixing ratio is performed based on the setting of each flow rate of NH ３ and N ２ when forming the thin film 18. When forming the thin film 18, the SiC substrate 17 is heated to 1550 to 1700 ° C as a temperature suitable for epitaxial growth. Then, regarding the flow rate of the carrier gas supplied from the carrier gas unit 60 etc. and the total amount of each gas of the Si source gas and the C source gas supplied into the chamber 11, the growth rate of the thin film 18 is set to the target value. Also, based on conditions such as the temperature of the SiC substrate 17 and the flow rates of various gases, the incorporation efficiency of N element into SiC when using N ２ or NH ３ as the first dopant gas is determined. For this reason, based on the incorporation efficiency (cm ２ / sccm) of N ３ or NH －３ and the temperature coefficient (% / °C) of the concentration gradient, the flow rates of NH ３ and N ２ are set so that the n-type impurity concentration of the thin film 18 becomes the target value.

[0078] Specifically, NH ３ Let the flow rate be X, N ２ The flow rate is Y, NH ３ Capture efficiency (cm －３ / sccm) to a, N ２ Capture efficiency (cm －３ / sccm) to b, NH ３ The temperature coefficient (% / °C) of the negative concentration temperature characteristic is c, N ２ Let d (% / °C) be the temperature coefficient of the positive concentration temperature characteristic of . Then, let Nd be the target impurity concentration, and by solving the following system of equations, N ２ and NH ３ The mixing ratio is being determined.

[0079] (Math 1) Nd = aX + byY (Math 2) 0 = acX + bdY Here, N ２ NH ３ The uptake efficiency is the amount of N element uptake per unit flow rate (sccm) of the first dopant gas (cm³). －３ ), that is, the amount of N element that becomes an n-type dopant incorporated into SiC when 1 sccm of the first dopant gas is introduced (cm －３ This shows the temperature coefficient, which is the temperature gradient of the n-type impurity concentration shown in Figure 5B, that is, the amount of change in the n-type impurity concentration with respect to temperature changes.

[0080] According to experiments and simulations, NH ３ The negative concentration temperature characteristic c is in the range of -0.4 to -0.2% / °C, NH ３ The intake efficiency a is 5.5 × 10 １６ ~1.1 x 10 １７ cm －３ It was / sccm. Also, N ２ The temperature coefficient d of the positive concentration temperature characteristic is in the range of +0.3 to +0.9% / °C, N ２ The intake efficiency b is 1.1 × 10⁻⁶ １５ ~2.2 x 10 １５ cm －３ It was / sccm. NH satisfying this range ３ The flow rate X is 0.1 to 0.2 sccm, N ２ The flow rate Y was 5–10 sccm.

[0081] For example, NH３ The negative concentration temperature characteristic c is -0.3% / °C, N ２ The temperature coefficient d of the positive concentration temperature characteristic was calculated to be +0.6% / °C. In this case, NH ３ and N ２ Assuming that is used as the first dopant gas, X = 0.093 sccm and Y = 2.3 sccm.

[0082] In this way, N ２ NH ３ Capture efficiency (cm －３ Based on the temperature coefficient (% / °C) of the concentration temperature characteristics ( / sccm), N ２ and NH ３ The mixing ratio can be optimized when using this. This reduces the influence of the in-plane temperature distribution of the SiC substrate 17, and when using NH as the n-type dopant gas. ３ Compared to using only, it becomes possible to achieve greater uniformity of in-plane concentration. Specifically, as the first dopant gas, N ２ and NH ３ The in-plane concentration distribution of n-type impurities was investigated experimentally using both methods. Figure 5D shows the results of the investigation, with the horizontal axis representing the radial distance of the wafer and the vertical axis representing the n-type impurity concentration in the thin film 18. As this investigation shows, although the n-type impurity concentration decreased slightly at the outer edge of the wafer, it was generally uniform from the center to the outer edge of the wafer. This also indicates that the in-plane concentration uniformity of the drift layer 18b was achieved.

[0083] Currently, NH ３ Although NH is used as an n-type dopant gas, as mentioned above, it is practically difficult to make the temperature uniform in the plane, and it is difficult to maintain uniformity of the concentration in the plane by reducing the temperature distribution in the plane. ３When using this method, as shown in Figure 6A, the relationship between the radial distance of the wafer and the n-type impurity concentration is such that the impurity concentration is almost uniform from the center of the wafer to near the outer edge, but gradually decreases towards the outer edge. In other words, as shown in Figure 6B, during epitaxial growth, the temperature is almost uniform from the center of the wafer to near the outer edge, but the temperature increases towards the outer edge. Also, as shown in Figure 6C, the n-type impurity concentration decreases gradually as the temperature of the SiC substrate 17 increases, resulting in a negative concentration-temperature characteristic. For this reason, currently, in order to increase the n-type impurity concentration at the wafer edges, more n-type dopants are supplied to the outer edges of the wafer compared to the center of the wafer. For example, H ２ Diluted NH ３ When using NH ３ When supplying the same concentration of first dopant gas to the center and outer edge of the wafer, the MFC is controlled so that the supply amount to the outer edge is greater than that to the center. In this way, the n-type impurity concentration can be brought closer to that of the center and outer edge of the wafer, and in-plane concentration uniformity can be achieved. However, adjusting the gas supply amount is difficult. In contrast, in this embodiment, even if an in-plane temperature distribution exists, and even if that temperature distribution changes due to factors such as component assembly, N ２ and NH ３ When used in the optimal ratio, the temperature-dependent properties of the concentration effectively disappear. Therefore, it becomes easier to achieve in-plane concentration uniformity than is currently possible.

[0084] Furthermore, in this embodiment, for example, with respect to the first supply gas unit 20, the mixed gas pressure in the manifold piping 101 is adjusted by the distribution APC 24. That is, when supplying the mixed gas in the manifold piping 101 to each inlet piping 150a to 150c through the distribution piping 102a to 102c, the mixed gas pressure is adjusted not only by the distribution MFCs 23a and 23b, but also by the distribution APC 24. As a result, the mixed gas pressure upstream of the distribution MFCs 23a and 23b is adjusted to the desired pressure. Therefore, the total amount of supply gas, which is the total amount of supply gas supplied from the gas inlet sources 21a to 21e through the raw material MFCs 22a to 22e, can be matched with the total amount of distributed gas, which is the total amount of mixed gas discharged from the manifold piping 101 through the distribution piping 102a to 102c. Therefore, it becomes possible to perform more appropriate flow rate control so that the mixed gas introduced from the distribution pipes 102a to 102c to the introduction pipes 150a to 150c reaches the target flow rate. Consequently, it becomes possible to further improve the in-plane uniformity and depth-direction uniformity of the film quality of the thin film 18 formed on the SiC substrate 17.

[0085] Furthermore, as shown in Figure 1, the supply gas discharged by the distribution APC 24 is supplied to the outer periphery of the chamber 11, that is, to a position corresponding to the outer edge of the mounting base 13, compared to the supply gas from the distribution MFCs 23a and 23b. On the outer periphery of the chamber 11, the gas flow velocity slows down due to the influence of the chamber walls and other factors, resulting in a slower gas supply rate to the SiC substrate 17. Therefore, by introducing the supply gas discharged by the distribution APC 24 to the outer periphery of the chamber 11, and then finely adjusting the amount of supply gas introduced by the distribution MFCs 23a and 23b with precise flow rate control further inside, the in-plane uniformity of the supply gas introduction is improved. This makes it possible to further improve the in-plane uniformity of the thin film 18 formed on the SiC substrate 17.

[0086] Furthermore, the same effect can be obtained not only with the first supply gas unit 20, but also with the second supply gas unit 30, the first dopant gas unit 40, and the second dopant gas unit 50 by using the distribution APCs 34, 44, and 54. Although it is possible to configure all of these as a single unit and generate the mixed gas in a single manifold, separating them allows for independent flow rate control for each source gas and dopant element. This makes it possible to further improve the in-plane uniformity of the thin film 18 formed on the SiC substrate 17.

[0087] Furthermore, the first supply gas unit 20, the second supply gas unit 30, the first dopant gas unit 40, and the second dopant gas unit 50 also include carrier gas as a supply gas. In this way, gas can flow from each unit even when the Si raw material gas, C raw material gas, or dopant gas is not flowing. By adjusting the flow rates of the carrier gas introduced from the carrier gas unit 60 and the carrier gas introduced as supply gas from each unit to predetermined amounts, the flow stabilizes from the moment the Si raw material gas, C raw material gas, or dopant gas is introduced. This makes it possible to further improve the in-plane uniformity and depth-direction uniformity of the film quality of the thin film 18 formed on the SiC substrate 17.

[0088] (Second Embodiment) A second embodiment of the present disclosure will now be described. This embodiment is the same as the first embodiment in that the configuration of the dopant gas introduction source is changed, and in other respects it is the same as the first embodiment, so only the differences will be described.

[0089] In the first embodiment, the first dopant gas introduction sources 41b and 41c are N ２ For supply, the first dopant gas introduction sources 41d and 41e are connected to NH ３ For supply purposes, N ２ and NH ３ Although the supply of N was previously provided from separate gas introduction sources, in this embodiment it is made common. Specifically, as shown in Figure 7, in this embodiment, N is supplied to the first dopant gas introduction sources 41b and 41c. ２ and NH ３Both are stored, and N is introduced from the first dopant gas sources 41b and 41c. ２ and NH ３ It is possible to supply both. For example, the first dopant gas introduction sources 41b and 41c are N ２ NH as a diluent gas ３ A gas cylinder containing a diluted mixed gas can be used. ２ NH inside ３ Regarding the concentration of N into the chamber 11 as described in the first embodiment, ２ and NH ３ The mixing ratio should be adjusted to approximately 1-10%, for example, 1-4%.

[0090] Thus, N is introduced from the first dopant gas sources 41b and 41c. ２ and NH ３ Both may be introduced. In this way, the same effects as in the first embodiment can be obtained. Also, the set mixing ratio N ２ and NH ３ Since it only requires preparing a gas cylinder containing the first dopant gas, only one type of gas cylinder can be used to store the first dopant gas.

[0091] (Third Embodiment) A third embodiment of the present disclosure will now be described. This embodiment is the same as the first embodiment in that the configuration of the dopant gas introduction source is changed, and in other respects it is the same as the first embodiment, so only the differences will be described.

[0092] As shown in Figure 8, in this embodiment, N ２ The first dopant gas introduction sources 41b, 41c and NH are introduced. ３The first dopant gas introduction sources 41d and 41e, which introduce the gas, are introduced into introduction pipes 150a to 150c via separate routes. The manifold pipe 121 is divided into two manifold pipes 121a and 121b, and pipe 122 is also divided into pipes 1221 and 1222. Pipe 1221 is equipped with distribution pipes 122aa, 122ba, and 122ca, and pipe 1222 is equipped with distribution pipes 122ab, 122bb, and 122cb. The first dopant gas introduction sources 41b and 41c are connected to manifold pipe 121a, and the first dopant gas introduction sources 41d and 41e are connected to manifold pipe 121b. The carrier gas introduction source 41aa and MFC 42aa are connected to manifold pipe 121a via supply pipe 120aa. Furthermore, an MFC 43aa is provided in the distribution pipe 122aa between the manifold pipe 121a and the inlet pipe 150a. An MFC 43ba is provided in the distribution pipe 122ba between each manifold pipe 121a and the inlet pipe 150b. An APC 44a is provided in the distribution pipe 122ca between the manifold pipe 121a and the inlet pipe 150c. Similarly, a carrier gas introduction source 41ab and an MFC 42ab are connected to the manifold pipe 121b via the supply pipe 120ab. Furthermore, an MFC 43ab is provided in the distribution pipe 122ab between the manifold pipe 121b and the inlet pipe 150a. An MFC 43bb is provided in the distribution pipe 122bb between each manifold pipe 121b and the inlet pipe 150b. An APC 44b is provided in the distribution pipe 122cb between the manifold pipe 121b and the inlet pipe 150c.

[0093] Thus, N ２ and NH ３ The two are introduced into each inlet pipe 150a to 150c through separate manifold pipes 121a and 121b. With this configuration, the N to each inlet pipe 150a to 150c ２ and NH ３ It becomes possible to set the amount of N introduced independently for each. Therefore, when growing the thin film 18, at various locations on the SiC substrate 17, that is, at various positions from the center of the wafer toward the outer edge of the wafer, ２ and NH ３ The mixing ratio can be changed. This allows the N supplied in the plane of the SiC substrate 17 to be changed. ２ and NH３ The mixing ratio can be set in various ways, making it possible to set a mixing ratio that is suitable for producing a thin film 18 with better film quality.

[0094] (Fourth Embodiment) A fourth embodiment of the present disclosure will now be described. This embodiment provides a more preferred form of the thin film forming section 10 compared to the first to third embodiments, and is otherwise the same as the first to third embodiments, so only the differences will be described.

[0095] The thin film formation section 10 is comprised of an epitaxial growth apparatus having a downflow type gas supply structure that blows the supply gas downward toward the surface 17a of the SiC substrate 17. As shown in Figure 9, the chamber 11 is provided with a gas introduction section 12, which includes first to third inlet ports 12a to 12c to which the respective introduction pipes 150a to 150c are connected. Through these first to third inlet ports 12a to 12c, the supply gas from each introduction pipe 150a to 150c is introduced into the reaction chamber 11a of the chamber 11.

[0096] The reaction chamber 11a is substantially cylindrical, and below each inlet 12a to 12c within the reaction chamber 11a, a showerhead 19 is provided to divide the reaction chamber 11a into an upper separation space 11aa and a lower growth space 11ab. The showerhead 19 is made of, for example, quartz, and has multiple through holes 19a that connect the separation space 11aa and the growth space 11ab.

[0097] The shower head 19 is positioned above the SiC substrate 17 placed on the mounting base 13, and is formed such that the through hole 19a includes a position facing the surface 17a of the SiC substrate 17. Therefore, the various gases supplied to the separation space 11aa are supplied through the through hole 19a toward the surface 17a of the SiC substrate 17 from a direction intersecting the surface 17a of the SiC substrate 17, that is, from a direction substantially perpendicular to the surface 17a.

[0098] A cooling section 11b is provided around the separation space 11aa within the chamber 11 to cool the separation space 11aa. Specifically, the cooling section 11b is provided so as to surround the first to third inlets 12a to 12c. The cooling section 11b is configured such that, for example, cooling water 11bb circulates through a cooling passage 11ba. In practice, the cooling section 11b has a water inlet and a water outlet (not shown), and the separation space 11aa is cooled by introducing cooling water 11bb from the water inlet and discharging the cooling water 11bb from the water outlet. In this embodiment, SiH is used as the silicon source gas. ４ This is supplied to the separation space 11aa. SiH ４ If the decomposition is accelerated, solid silicon may accumulate and cause clogging of the showerhead 19. Therefore, SiH in the separation space 11aa ４ To suppress the decomposition of the dopant, the cooling unit 11b controls the temperature of the separation space 11aa to 400°C or below. Furthermore, when TMA is used as the second dopant raw material, the TMA may decompose and be adsorbed onto the walls of the separation space 11aa or the shower head 19, potentially causing clogging of the shower head 19. For this reason, it is preferable to control the temperature of the separation space 11aa to 400°C or below with the cooling unit 11b in order to suppress the decomposition of the TMA. Here, a configuration in which the cooling unit 11b is provided around the separation space 11aa has been described, but the cooling unit 11b may also be configured in such a way that a predetermined space is formed in the side wall of the chamber 11, and cooling water 11bb circulates through this space as a cooling passage 11ba.

[0099] The first to third inlets 12a to 12c are connected to the inlet pipes 150a to 150c, respectively. Since the chamber 11 is cylindrical, the upper wall 11c of the chamber 11 where the first to third inlets 12a to 12c are formed is circular. The first inlet 12a is provided in a circular shape approximately in the center of the upper wall 11c, the second inlet 12b is annular so as to surround the first passage inlet 12a, and the third inlet 12c is annular so as to surround the first and second inlets 12a and 12b. The first to third inlets 12a to 12c are arranged concentrically with the first inlet 12a as the center. Although the first to third inlets 12a to 12c are configured as circular or annular shapes here, they may also be configured as polygonal shapes or polygonal frame shapes.

[0100] As described above, in this embodiment, an epitaxial growth apparatus with a cooling function is used as the thin film forming section 10. Therefore, the separation space 11aa can be cooled to 400°C or below in the cooling section 11b. This prevents clogging of the through-holes 19a of the shower head 19 due to the formation of solid silicon or the adsorption of decomposed TMA. Thus, in this embodiment, clogging of the through-holes 19a can be prevented without arranging partition walls or the like to divide the separation space 11aa into multiple spaces, and the configuration of the shower head 19 can be simplified.

[0101] (Other Embodiments) While this disclosure has been described in accordance with the embodiments described above, it is not limited to those embodiments and includes various modifications and variations within the scope of equivalents. In addition, various combinations and forms, as well as other combinations and forms that include only one, more, or fewer of those elements, are also within the scope and concept of this disclosure.

[0102] For example, in the above embodiment, N is used as the n-type dopant. ２ and NH ３As explained using the example above, this disclosure can be applied when epitaxially growing a thin film 18 including a drift layer 18b on a SiC substrate 17 using two different dopant gases containing the same conductivity type of dopant. That is, in situations where the SiC substrate 17 is in a non-uniform temperature state during the epitaxial growth of the drift layer 18b, this disclosure can be applied when a first gas with positive concentration temperature characteristics and a second gas with negative concentration temperature characteristics are simultaneously introduced to form the dopant of the drift layer 18b. In that case, by setting the mixing ratio of the first gas and the second gas based on the dopant incorporation efficiency into the drift layer 18b and the temperature coefficient of the concentration temperature characteristics, it becomes possible to achieve in-plane concentration uniformity.

[0103] Furthermore, in each of the above embodiments, when forming the buffer layer 18a, NH ３ When using and forming the drift layer 18b, N ２ and NH ３ Although both were used, N was also used when forming the buffer layer 18a. ２ and NH ３ You may use both.

[0104] Furthermore, in each of the above embodiments, the case in which a thin film 18 including an n-type drift layer 18b is formed on an n-type SiC substrate 17 was described as an example. However, the present disclosure can also be applied to cases in which the conductivity type is reversed from that of the above embodiments. In that case, the dopant gas is N ２ NH ３ A different gas can be used. Then, a first gas with positive concentration-temperature characteristics and a second gas with negative concentration-temperature characteristics can be introduced simultaneously, and their mixing ratio can be set based on the dopant incorporation efficiency into the drift layer 18b and the temperature coefficient of the concentration-temperature characteristics.

[0105] Furthermore, although the above embodiments describe the case in which SiC is used as the semiconductor material, this disclosure can also be applied to cases in which semiconductor materials other than SiC are used. In that case as well, the same effects as in the above embodiments can be obtained by simultaneously introducing both a first gas having positive concentration-temperature characteristics and a second gas having negative concentration-temperature characteristics as two types of dopant gases, along with the source gas of the semiconductor material used.

[0106] Furthermore, this disclosure is not limited to the embodiments described above and can be modified as appropriate. It goes without saying that, in each of the embodiments described above, the elements constituting the embodiment are not necessarily essential unless explicitly stated to be particularly essential or considered fundamentally essential. Also, in each of the embodiments described above, if numerical values ​​such as the number, numerical values, quantities, or ranges of the components of the embodiment are mentioned, the embodiments are not limited to those specific numbers unless explicitly stated to be particularly essential or considered fundamentally limited to those specific numbers. Furthermore, in each of the embodiments described above, if the shape, positional relationship, etc., of the components are mentioned, the embodiments are not limited to those shapes, positional relationships, etc., unless explicitly stated or considered fundamentally limited to those specific shapes, positional relationships, etc.

[0107] (Perspective of this Disclosure) The above disclosure can be understood, for example, from the following perspectives. [First Perspective] A method for manufacturing a semiconductor device that produces an epitaxial wafer by epitaxially growing a thin film (18) including a drift layer (18b) on a semiconductor substrate (17), comprising: heating the semiconductor substrate while the semiconductor substrate is placed in a chamber (11), and further introducing a dopant gas containing the dopant of the drift layer together with a raw material gas for the semiconductor material into the chamber to epitaxially grow the drift layer, wherein, in the epitaxial growth of the drift layer, when an in-plane temperature distribution occurs in which the temperature in the plane of the semiconductor substrate is non-uniform during the epitaxial growth, both a first gas having a positive concentration temperature characteristic in which the concentration of the dopant in the semiconductor substrate increases as the temperature of the semiconductor substrate increases, and a second gas having a negative concentration temperature characteristic in which the concentration of the dopant decreases, are simultaneously introduced as the dopant gas. [Second viewpoint] The method for manufacturing a semiconductor device according to the first viewpoint, wherein when epitaxially growing the drift layer, the mixing ratio of the first gas and the second gas is set based on the efficiency of incorporation of the dopant in the first gas into the drift layer and the efficiency of incorporation of the dopant in the second gas, and the temperature coefficient which is the amount of change in the concentration of the dopant in the drift layer with respect to the temperature change of the semiconductor substrate when the first gas and the second gas are used. [Third viewpoint] When epitaxially growing the drift layer, N is used as the first gas. ２ Using the second gas, NH ３ A method for manufacturing a semiconductor device according to the first or second aspect, wherein the semiconductor substrate is a silicon carbide substrate, and in growing the drift layer epitaxially, a gas cylinder storing a mixed gas adjusted to the mixing ratio of the first gas and the second gas is used as a gas introduction source (41b, 41c), a method for manufacturing a semiconductor device according to any one of the first to third aspects, wherein the semiconductor substrate is a silicon carbide substrate, and in growing the drift layer epitaxially, a gas cylinder storing a mixed gas adjusted to the mixing ratio of the first gas and the second gas is used as a gas introduction source (41b, 41c), a method for manufacturing a semiconductor device according to any one of the first to third aspects, wherein the first gas is N ２Using NH as a diluent gas, the second gas becomes ３A method for manufacturing a semiconductor device according to the third aspect, wherein a gas cylinder containing a diluted mixed gas of the first gas and the second gas, adjusted to the mixing ratio of the first gas and the second gas, is used as a gas introduction source (41b, 41c). [Sixth aspect] A method for manufacturing a semiconductor device according to any one of the first to fifth aspects, wherein, before epitaxially growing the drift layer, a buffer layer (18a) having a higher concentration of the dopant than the drift layer is formed on the semiconductor substrate as the thin film by epitaxial growth, and epitaxial growth of the drift layer means forming the drift layer on the buffer layer. [Seventh aspect] A method for manufacturing a semiconductor device according to the sixth aspect, wherein both the first gas and the second gas are used when forming the buffer layer by epitaxial growth. [Eighth point] A semiconductor manufacturing apparatus comprising: a chamber (11) constituting a reaction chamber (11a); a mounting stand (13) placed inside the reaction chamber on which a semiconductor substrate (17) is installed; a heating device (14) for heating the semiconductor substrate; a thin film forming unit (10) for epitaxially growing a thin film (18) including a drift layer (18b) on the semiconductor substrate by introducing a source gas of semiconductor raw materials into the reaction chamber; a supply gas unit (20, 30) for introducing the source gas into the chamber; and a dopant gas unit (40, 50) for supplying a dopant gas containing the dopant raw materials for the thin film. The dopant gas unit is a gas cylinder that stores both a first gas having a positive concentration-temperature characteristic in which the concentration of the dopant in the semiconductor substrate increases as the temperature increases with respect to the in-plane temperature of the semiconductor substrate during epitaxial growth, and a second gas having a negative concentration-temperature characteristic in which the concentration of the dopant decreases.[Ninth viewpoint] The semiconductor manufacturing apparatus according to the eighth viewpoint, wherein the gas cylinder stores the first gas and the second gas in a mixing ratio set based on the efficiency of incorporation of the dopant in the first gas into the drift layer, the efficiency of incorporation of the dopant in the second gas, and the temperature coefficient which is the amount of change in the concentration of the dopant in the drift layer with respect to the temperature change of the semiconductor substrate when the first gas and the second gas are used. [Tenth viewpoint] The semiconductor substrate is a silicon carbide substrate, and the first gas is N. ２ The second gas is NH ３ A semiconductor manufacturing apparatus according to the eighth or ninth aspect. [Eleventh aspect] The semiconductor substrate is a silicon carbide substrate, and the gas cylinder contains the first gas, N ２ Using NH as a diluent gas, the second gas becomes ３ Dilute the above and use the above mixing ratio as N ２ The aforementioned NH inside ３A semiconductor manufacturing apparatus according to any one of the eighth to tenth aspects, wherein a mixed gas having a concentration of 1 to 10% is stored. [Twelfth aspect] A semiconductor manufacturing apparatus comprising: a chamber (11) constituting a reaction chamber (11a); a mounting stand (13) placed in the reaction chamber on which a semiconductor substrate (17) is installed; a heating device (14) for heating the semiconductor substrate; a thin film forming unit (10) for epitaxially growing a thin film (18) including a drift layer (18b) on the semiconductor substrate by introducing a raw material gas of semiconductor raw materials into the reaction chamber; a supply gas unit (20, 30) for introducing the raw material gas into the chamber; and a dopant gas unit (40, 50) for supplying a dopant gas containing the dopant raw material of the thin film. The dopant gas unit has a gas introduction source (41b to 41e) that introduces a first gas having a positive concentration temperature characteristic in which the concentration of the dopant in the semiconductor substrate increases as the temperature increases with respect to the in-plane temperature of the semiconductor substrate during epitaxial growth, and a second gas having a negative concentration temperature characteristic in which the concentration of the dopant decreases. The chamber is arranged to divide the reaction chamber into a lower growth space (11ab) and a separation space (11aa) above the growth space, and includes a shower head (19) with a plurality of through holes (19a) that connect the growth space and the separation space, and a cooling section (11b) for cooling the separation space. The gas introduction source uses N as the first gas. ２ In addition to introducing NH as the second gas, ３ A semiconductor manufacturing apparatus that introduces a supply gas unit which introduces silane and propane as the raw material gas. [13th aspect] The semiconductor manufacturing apparatus according to the 12th aspect, wherein the gas introduction source is a gas cylinder which contains both the first gas and the second gas. [14th aspect] The semiconductor manufacturing apparatus according to the 12th aspect, wherein the gas introduction source is a gas cylinder which contains the first gas and the second gas separately.

Claims

1. A method for manufacturing a semiconductor device that produces an epitaxial wafer by epitaxially growing a thin film (18) including a drift layer (18b) on a semiconductor substrate (17), comprising: placing the semiconductor substrate in a chamber (11), heating the semiconductor substrate, and further introducing a dopant gas containing the dopant of the drift layer together with a raw material gas for the semiconductor material into the chamber to epitaxially grow the drift layer, wherein, in the epitaxial growth of the drift layer, when an in-plane temperature distribution occurs in which the temperature of the semiconductor substrate is non-uniform during epitaxial growth, both a first gas having a positive concentration-temperature characteristic in which the concentration of the dopant in the semiconductor substrate increases as the temperature of the semiconductor substrate increases, and a second gas having a negative concentration-temperature characteristic in which the concentration of the dopant decreases, are simultaneously introduced as the dopant gas.

2. The method for manufacturing a semiconductor device according to claim 1, wherein when epitaxially growing the drift layer, the mixing ratio of the first gas and the second gas is set based on the efficiency of incorporation of the dopant in the first gas into the drift layer, the efficiency of incorporation of the dopant in the second gas, and the temperature coefficient which is the amount of change in the concentration of the dopant in the drift layer with respect to the temperature change of the semiconductor substrate when the first gas and the second gas are used.

3. When the drift layer is epitaxially grown, N is used as the first gas. ２ Using the second gas, NH ３ A method for manufacturing a semiconductor device according to claim 1 or 2, using the method described above.

4. The method for manufacturing a semiconductor device according to claim 1 or 2, wherein the semiconductor substrate is a silicon carbide substrate, and when epitaxially growing the drift layer, a gas cylinder containing a mixed gas adjusted to the mixing ratio of the first gas and the second gas is used as a gas introduction source (41b, 41c).

5. By epitaxially growing the drift layer, the first gas N ２ Using NH as a diluent gas, the second gas becomes ３ A method for manufacturing a semiconductor device according to claim 3, wherein a gas cylinder containing a diluted mixed gas of the first gas and the second gas, adjusted to the mixing ratio, is used as a gas introduction source (41b, 41c).

6. The method for manufacturing a semiconductor device according to claim 1 or 2, comprising forming a buffer layer (18a) having a higher concentration of the dopant than the drift layer on the semiconductor substrate by epitaxial growth as the thin film before epitaxial growth of the drift layer, wherein epitaxial growth of the drift layer is equivalent to forming the drift layer on the buffer layer.

7. The method for manufacturing a semiconductor device according to claim 6, wherein both the first gas and the second gas are used when forming the buffer layer by epitaxial growth.

8. A semiconductor manufacturing apparatus comprising: a chamber (11) constituting a reaction chamber (11a); a mounting stand (13) placed inside the reaction chamber on which a semiconductor substrate (17) is installed; and a heating device (14) for heating the semiconductor substrate; a thin film forming unit (10) for epitaxially growing a thin film (18) including a drift layer (18b) on the semiconductor substrate by introducing a raw material gas of semiconductor raw materials into the reaction chamber; a supply gas unit (20, 30) for introducing the raw material gas into the chamber; and a dopant gas unit (40, 50) for supplying a dopant gas containing the dopant raw materials of the thin film, wherein the dopant gas unit is a gas cylinder that stores both a first gas having a positive concentration temperature characteristic in which the concentration of dopants in the semiconductor substrate increases as the temperature increases with respect to the in-plane temperature of the semiconductor substrate during epitaxial growth, and a second gas having a negative concentration temperature characteristic in which the concentration of dopants decreases.

9. The semiconductor manufacturing apparatus according to claim 8, wherein the gas cylinder stores the first gas and the second gas in a mixing ratio set based on the efficiency of dopant incorporation from the first gas into the drift layer, the efficiency of dopant incorporation from the second gas, and the temperature coefficient that represents the amount of change in the concentration of the dopant in the drift layer with respect to the temperature change of the semiconductor substrate when the first gas and the second gas are used.

10. The semiconductor substrate is a silicon carbide substrate, and the first gas is N ２ The second gas is NH ３ The semiconductor manufacturing apparatus according to claim 8 or 9.

11. The semiconductor substrate is a silicon carbide substrate, and the gas cylinder stores a mixed gas in which N ２ is used as a dilution gas to dilute NH ３ serving as the second gas, and the concentration of NH ３ in the N ２ is set to 1 to 10% as the mixing ratio. The semiconductor manufacturing apparatus according to claim 9. ２ is used as a dilution gas to dilute NH ３ which serves as the second gas, ３ and the concentration of NH ３ in the N ２ is set to 1 to 10% as the mixing ratio. ２ in the N ２ ３ The semiconductor manufacturing apparatus according to claim 9, in which the mixed gas is stored.

12. A semiconductor manufacturing apparatus comprising: a chamber (11) constituting a reaction chamber (11a); a mounting stand (13) placed inside the reaction chamber on which a semiconductor substrate (17) is installed; a heating device (14) for heating the semiconductor substrate; a thin film forming unit (10) for epitaxially growing a thin film (18) including a drift layer (18b) on the semiconductor substrate by introducing a source gas of semiconductor raw materials into the reaction chamber; a supply gas unit (20, 30) for introducing the source gas into the chamber; and a dopant gas unit (40, 50) for supplying a dopant gas containing the dopant raw materials for the thin film. The dopant gas unit has a gas introduction source (41b to 41e) that introduces a first gas having a positive concentration temperature characteristic in which the concentration of the dopant in the semiconductor substrate increases as the temperature increases with respect to the in-plane temperature of the semiconductor substrate during epitaxial growth, and a second gas having a negative concentration temperature characteristic in which the concentration of the dopant decreases. The chamber is arranged to divide the reaction chamber into a lower growth space (11ab) and a separation space (11aa) above the growth space, and includes a shower head (19) with a plurality of through holes (19a) that connect the growth space and the separation space, and a cooling section (11b) for cooling the separation space. The gas introduction source uses N as the first gas. ２ In addition to introducing NH as the second gas, ３ A semiconductor manufacturing apparatus that introduces a supply gas unit that introduces silane and propane as the raw material gas.

13. The semiconductor manufacturing apparatus according to claim 12, wherein the gas introduction source is a gas cylinder containing both the first gas and the second gas.

14. The semiconductor manufacturing apparatus according to claim 12, wherein the gas introduction source is a gas cylinder separately comprising the first gas and the second gas.

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