Epitaxial growth apparatus and method for manufacturing epitaxial wafer

Abstract

To ensure a desired quality even when a waiting time from the end of a final process in a cassette to the start of a film formation process for wafers in the next cassette varies.SOLUTION: An epitaxial growth apparatus includes a reactor 11 for processing a plurality of wafers W stored in a cassette 21 one by one, a control unit 19 for controlling the reactor, and a load port 20 for setting the cassette, and performs a cleaning process for removing by-products by vapor-phase etching the inside of the reactor at a predetermined frequency before starting a film formation process for the next wafer. When the film formation process for the next cassette is not scheduled before the final process of the cassette is completed, the reactor is controlled by a temperature maintenance process recipe for maintaining the reactor at a predetermined temperature after the final process is completed and before starting a film formation process for the next wafer.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to an epitaxial growth apparatus and a method for producing an epitaxial wafer. [Background technology]

[0002] Epitaxial silicon wafers are manufactured by carrying silicon wafers into a reactor of a CVD apparatus, introducing silicon source gas such as trichlorosilane, and vapor-growth a single crystal silicon film on the main surface of the silicon wafer. During this process, silicon adheres not only to the surface of the silicon wafer but also to the inside of the reactor, and silicon products gradually accumulate as the film formation process is repeated, so a cleaning process is periodically performed to remove the products (see Patent Document 1). This conventional technology corrects the etching time of the cleaning process according to the number of wafers stored in a cassette and the number of multi-depots, optimizing the cleaning process performed after the last wafer in the cassette. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent Publication No. 2021-103756 Summary of the Invention [Problem to be solved by the invention]

[0004] However, in the above-mentioned conventional technology, although the cleaning process performed after the last wafer in the cassette can be optimized, the process between the cassette that has completed the film formation process and the next cassette that will undergo the film formation process is not taken into consideration. Therefore, unless the film formation process of the next cassette is scheduled to be scheduled, the waiting time of the device becomes long. Since the waiting time becomes long, various conditions such as the furnace temperature change, and there is a problem that epitaxial wafers with the desired quality cannot be obtained when the epitaxial growth process is performed according to a specified recipe.

[0005] The problem that the present invention aims to solve is to provide an epitaxial growth apparatus and a method for manufacturing an epitaxial wafer that are capable of manufacturing epitaxial wafers having desired quality even if the waiting time from the end of the final process of a cassette to the start of the next film formation process varies. [Means for solving the problem]

[0006] The present invention relates to a reactor for processing a plurality of wafers stored in a cassette one by one; A control means for controlling process conditions for film formation in the epitaxial growth apparatus including the reactor; a load port for setting the cassette; forming an epitaxial film on a main surface of the wafer in the reactor; At a predetermined frequency, before starting a next film formation process, the inside of the reaction chamber is subjected to a vapor phase etching process to remove a by-product of the vapor phase etching process, and the reaction chamber is cleaned; In an epitaxial growth apparatus which processes cassettes set on the load port in a predetermined order, When the final process of the cassette is completed, it is determined whether or not a film formation process of the next cassette is scheduled; When it is determined that the film formation process of the next cassette is not reserved, the epitaxial growth apparatus controls the reaction furnace according to a temperature maintenance process recipe for maintaining the reaction furnace at a predetermined temperature after the final process is completed and before the film formation process of the next cassette is started. (However, this does not include the case where a dummy wafer is placed in the reactor and the reactor is maintained at a predetermined temperature by processing the dummy wafer based on a dummy process recipe.) The above problem is solved by:

[0007] In the above invention, when replacing the cassette with a next cassette, it is determined whether or not a film formation process for the next cassette is scheduled when a final process for the cassette is completed; When it is determined that no reservation has been made for the film formation process of the next cassette, it is more preferable to control the reactor using the temperature maintenance process recipe after completing the final process and before starting the film formation process of the next cassette.

[0008] In the above invention, the temperature maintenance process recipe may be a recipe including the cleaning process.

[0009] The present invention also provides a method for manufacturing a semiconductor device, comprising the steps of: processing a plurality of wafers stored in a cassette one by one in a reactor; and forming an epitaxial film on a main surface of the wafer; a cleaning process step of removing by-products by vapor-phase etching the inside of the reaction furnace before starting a next film formation process at a predetermined frequency; In a method for manufacturing epitaxial wafers, cassettes set on a load port are processed in a predetermined order, When the final process of the cassette is completed, it is determined whether or not a film formation process of the next cassette is scheduled; When it is determined that the film formation process of the next cassette is not reserved, a temperature maintenance process is carried out to control the temperature of the reaction furnace so as to maintain the temperature at a predetermined temperature after the final process is completed and before the film formation process of the next cassette is started. (However, this does not include the case where a dummy wafer is placed in the reactor and the reactor is maintained at a predetermined temperature by processing the dummy wafer based on a dummy process recipe.) The above problem is solved by:

[0010] In the above invention, when replacing the cassette with a next cassette, it is determined whether or not a film formation process for the next cassette is scheduled when a final process for the cassette is completed; When it is determined that the film formation process for the next cassette is not scheduled, it is more preferable to carry out the temperature maintenance process after the final process is completed and before the film formation process for the next cassette is started. Effect of the Invention

[0011] According to the present invention, even if the waiting time between the end of the final process of the cassette and the start of the next film formation process varies, a temperature maintenance process is carried out to maintain the reactor at a predetermined temperature before the film formation process, so that epitaxial wafers having the desired quality can be manufactured. [Brief description of the drawings]

[0012] [Figure 1] 1 is a schematic configuration diagram showing an embodiment of an epitaxial wafer manufacturing system according to the present invention. [Diagram 2] FIG. 2 is a schematic diagram showing the epitaxial growth apparatus of FIG. 1. [Diagram 3] 2 is a flowchart showing the operation of the epitaxial wafer manufacturing system of FIG. 1. [Figure 4A] 2 is a graph showing temperature transitions in processing steps according to a film forming process recipe and a cleaning process recipe output from the host computer of FIG. 1; [Figure 4B] 2 is a graph showing temperature transitions in processing steps according to a film forming process recipe, a cleaning process recipe, and a temperature maintenance process recipe outputted from the host computer of FIG. 1; DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a schematic diagram showing an embodiment of an epitaxial wafer manufacturing system according to the present invention. As shown in the figure, the epitaxial wafer manufacturing system 1 of this embodiment includes an epitaxial growth apparatus 10 for vapor-phase growing an epitaxial film on a main surface of a bulk silicon wafer (polished wafer), and a host computer 40 for outputting processing conditions for the epitaxial growth apparatus 10. The epitaxial growth apparatus 10 is connected to the host computer 40 via a data communication line, and operates according to a film formation process recipe for a product process (film formation process), a cleaning recipe for a cleaning process, and a temperature maintenance process recipe for a temperature maintenance process, which are output from the host computer 40.

[0014] The database 50 records the specifications of wafer products to be manufactured, manufacturing method information (recipe name) relating to film formation conditions for each wafer product specification, the number of wafers to be continuously processed, etc., the host computer 40 records the details of the reaction recipe, processing parameter settings, etc., and a control unit 19 described below records information from the host computer 40. In this specification, manufacturing method information relating to film formation conditions for each wafer product specification is also referred to as a film formation processing recipe, method information relating to a cleaning processing recipe, and method information relating to a temperature maintenance processing for maintaining the reactor 11 at a predetermined temperature, also referred to as a temperature maintenance processing recipe.

[0015] The epitaxial growth apparatus 10 includes a first reactor 11A and a second reactor 11B for processing wafers one by one, a load port 20 in which a first cassette 21A and a second cassette 21B in which a plurality of wafers are accommodated are installed, and a wafer transfer mechanism 30 provided between the first reactor 11A, the second reactor 11B, and the load port 20. The epitaxial growth apparatus 10 of this embodiment includes the first reactor 11A and the second reactor 11B, and has a redundant configuration capable of processing two wafers in parallel. The load port 20 of this embodiment has a first port 20A and a second port 20B in which the first cassette 21A and the second cassette 21B can be installed, respectively, and can take out wafers from the first cassette 21A and the second cassette 21B, respectively, and send them to the first reactor 11A and the second reactor 11B. The load port 20 may function as a load lock chamber for replacing the atmosphere, or may simply be a cassette installation space without replacing the atmosphere. In the latter case, the wafers in the load port 20 are sent to the first reactor 11A and the second reactor 11B via a load lock chamber prepared separately from the load port 20.

[0016] 2 is a schematic configuration diagram showing the first reactor 11A and the second reactor 11B of the epitaxial growth apparatus 10. Since the first reactor 11A and the second reactor 11B in this embodiment have the same configuration, only the first reactor 11A will be described.

[0017] 2, the epitaxial growth apparatus 10 of this embodiment is a single-wafer type vapor phase growth apparatus that processes wafers W one by one by epitaxial CVD, and includes a first reactor 11A made of quartz and having a gas inlet 111 and a gas outlet 112. The epitaxial growth apparatus 10 of this embodiment also includes a plurality of heaters 12 that heat the inside of the first reactor 11A from the upper and lower outer sides, a susceptor 13 that is provided inside the first reactor 11A and is made of graphite coated with a SiC film and supports the wafer W, a rotation drive mechanism 14 that rotates the susceptor 13, and a control unit 19 that controls each of these components. The control unit 19 also controls the processing order including the transportation and growth of the wafer W.

[0018] The gas inlet 111 of the first reactor 11A is connected to a plurality of raw material tanks 17 via a pipe 15 and a valve 16. The plurality of raw material tanks 17 contain dichlorosilane (SiH 2 Cl 2 ), trichlorosilane (SiHCl 3 a silicon source tank 17a for storing epitaxial source gas such as HCl; a dopant gas tank 17b for storing dopant gas; 3 The first reactor 11A includes a cleaning raw material tank 17c for storing a liquefied raw material of an etchant gas such as argon (Ar) and hydrogen (H2), and a carrier raw material tank 17d for storing a liquefied raw material of a carrier gas such as argon (Ar) and hydrogen (H2). The supply of these raw material gases can be turned on and off and the supply amount can be controlled by controlling the corresponding valves 16 and mass flow controllers. The gas exhaust port 112 of the first reactor 11A is provided on the opposite side of the susceptor 13 to the gas inlet 111, and the gas supplied from the gas inlet 111 to the inside of the first reactor 11A passes above the susceptor 13 and is exhausted from the gas exhaust port 112.

[0019] Returning to FIG. 1, the load port 20 of this embodiment has a presence sensor 22 that detects whether or not a wafer W is accommodated in each slot of the first cassette 21A and the second cassette 21B, and the control unit 19 counts the number of wafers W accommodated in the first cassette 21A and the second cassette 21B based on the output of the presence sensor 22. The number of slots (maximum number of wafers that can be accommodated) of the first cassette 21A and the second cassette 21B is, for example, 25, but 25 wafers W are not always accommodated, and there are cases where the maximum number is not reached, so it is necessary to detect whether or not a wafer W is accommodated in each slot. In this way, the control unit 19 and the presence sensor 22 have the function of counting the number of wafers W accommodated in the first cassette 21A and the second cassette 21B. The load port 20 also has a function of reading the part numbers of the wafer products from the labels attached to the first cassette 21A and the second cassette 21B, and the read part number data is sent to the host computer 40 together with data on the number of wafers W.

[0020] The wafer transport mechanism 30 of this embodiment has a robot arm, and the robot arm mounts or holds the wafer W, and transports the wafer W between the load port 20 and the first reactor 11A and the second reactor 11B. That is, the wafer W before film formation taken out from the first cassette 21A or the second cassette 21B is transported to the first reactor 11A or the second reactor 11B by the wafer transport mechanism 30, while the wafer W after film formation in the first reactor 11A or the second reactor 11B is taken out from the first reactor 11A or the second reactor 11B by the wafer transport mechanism 30 and returned to the original slot of the first cassette 21A or the second cassette 21B. The wafer transport mechanism 30 takes out the wafer W from each slot and returns it to the original slot based on the output of the presence sensor 22.

[0021] The control unit 19 of this embodiment controls the film formation process of the wafer W in the first reactor 11A and the second reactor 11B, the cleaning process in the reactor, and the temperature maintenance process in the reactor. Therefore, during the film formation process, silicon raw material gas and dopant gas are supplied together with the carrier gas, and as necessary, during the cleaning process. Furthermore, during the cleaning process, etching gas is supplied together with the carrier gas to remove silicon products. Furthermore, when a predetermined condition is met, the first reactor 11A and the second reactor 11B are maintained at a predetermined temperature by controlling the heater 12. The control unit 19 controls the valve 16 and the mass flow controller, etc. to control the amount of epitaxial film formation (film thickness), the amount of dopant (resistivity), the amount of etching, the cleaning time, etc. The control unit 19 controls the first reactor 11A and the second reactor 11B based on the film formation process recipe, the cleaning process recipe, and the temperature maintenance process recipe sent from the host computer 40. The maintained temperature according to the temperature maintaining process recipe is, for example, 1050 to 1275°C, preferably 1100 to 1190°C, when a silicon epitaxial film is formed.

[0022] The host computer 40 of this embodiment is configured to be able to communicate with the database 50, and acquires information on the product specifications of the wafers W based on the product number data sent from the load port 20. The product specification information acquired from the database 50 includes the epitaxial film thickness, resistivity, film formation process recipe number, cleaning process recipe number, temperature maintenance process recipe number, number of wafers to be continuously processed, etc. The host computer 40 sets in the control unit 19 reservation information such as the process conditions of the wafers W accommodated in the cassette 21 carried into the load port 20 at the timing of acquisition.

[0023] As shown in FIG. 1, the epitaxial wafer manufacturing system 1 of this embodiment includes two reactors, a first reactor 11A and a second reactor 11B, and a load port 20 also includes two ports, a first port 20A and a second port 20B, and has a function of processing wafers W in parallel. When the epitaxial growth apparatus 10 has a function of processing wafers W in parallel, two operation modes can be set and selected. One of the operation modes is a mode in which a plurality of wafers W stored in a first cassette 21A set in the first port 20A is sequentially processed in the first reactor 11A, and a plurality of wafers W stored in a second cassette 21B set in the second port 20B is sequentially processed in the second reactor 11B, which is also called a parallel operation mode. Another operation mode is a mode in which the wafers W are first taken out one by one in sequence from the first cassette 21A and processed in parallel in both the first reactor 11A and the second reactor 11B, and after the processing of all the wafers W stored in the first cassette 21A is completed, the processing of the wafers W stored in the second cassette 21B is started, which is also called a serial operation mode. In this manner, the wafers W stored in one cassette 21 may be processed using a single reactor, or may be processed in parallel using multiple reactors.

[0024] Here, when the above-mentioned parallel operation mode is selected, the following problem often occurs. That is, the waiting time from the end of the cleaning process, which is the final process of the cassette, until the film formation process of the next wafer may be longer than usual. This may be caused by a short cleaning process time or a delayed cassette exchange timing, which may cause the reservation setting of the film formation process of the next cassette to be made after the end of the final process of the cassette. In addition, although it is not frequent, even when the serial operation mode is selected, a similar problem may occur if the reservation setting of the next cassette is not made.

[0025] If the waiting time from the end of the final process of the cassette until the film formation process of the next wafer becomes long, various conditions such as the internal temperature of the reactor 11 will fluctuate. However, since only one film formation process recipe is set, there is a problem that if epitaxial growth process is performed using this film formation process recipe, epitaxial wafers that satisfy the desired quality such as film thickness and resistivity cannot be obtained.

[0026] FIG. 4A is a graph showing the temperature transition of the process steps according to the film forming process recipe and the cleaning process recipe output from the host computer 40. In the illustrated example, the cleaning process 1 is performed as the final process of the cassette A. That is, the film forming process 1 (heating up → film formation → temperature decreasing) is performed on the last wafer stored in the cassette A, and then the wafer W is removed and the cleaning process 1 (heating up → etching → temperature decreasing) is performed. The time when the cleaning process 1 is completed is the end of the final process of the cassette A. At this time, if the next cassette B is carried into the load port 20 by the time the final process of the cassette A is completed, and the conditions of the film forming process of the wafer W stored in the next cassette B are reserved and set from the host computer 40 to the control unit 19, the wafer W of the next cassette B is loaded into the reaction furnace 11 during the predetermined time T, and the film forming process 2 (heating up → film formation → temperature decreasing) is performed. Here, the predetermined time T is the time required to carry the wafer W into the furnace, and the inside of the furnace is heated with a predetermined lamp power. That is, if the film formation process 2 for the wafers W in the next cassette B is started a predetermined time T after the end of the final process of the cassette A, the fluctuation in the quality of the epitaxial film on the wafers W due to the film formation process 2 is suppressed.

[0027] 4B, if the conditions for the film formation process for the wafers W contained in the next cassette B are not reserved and set in the control unit 19 from the host computer 40 before the cleaning process 1 as the final process of the cassette A is completed, the temperature inside the reactor 11 will drop as shown by the dotted line in the figure. Since only one film formation process recipe is set in the control unit 19, if epitaxial growth is performed using the only film formation process recipe when the temperature inside the reactor 11 is low, the quality of the film thickness, resistivity, etc. will vary.

[0028] For this reason, in the epitaxial wafer manufacturing system 1 of this embodiment, a temperature maintenance process recipe is recorded in the control unit 19 in addition to the film formation process recipe and the cleaning process recipe. This temperature maintenance process recipe is a recipe for controlling the heater 12 and the like to maintain the first reactor 11A and the second reactor 11B at a predetermined temperature, and is a recipe including conditions such as the output, output ratio, and time of the heater 12 so that the temperatures of the first reactor 11A and the second reactor 11B become approximately the same as those in the case where the cleaning process is performed. The temperature maintenance process recipe has various condition values ​​obtained in advance by confirmation experiments using an actual device or computer simulation, and these are recorded in the host computer 40.

[0029] Then, when the next cassette B is set, the host computer 40 sets the conditions of the film formation process for the wafers W accommodated in the control unit 19 and reserves the film formation process. When the final process of the cassette A is completed, the control unit 19 determines whether or not a reservation has been set for the film formation process for the wafers W accommodated in the next cassette B, and if no reservation has been set, the control unit 19 executes the temperature maintenance recipe set in the control unit 19 before the film formation process for the wafers in the cassette B.

[0030] Fig. 4B is a graph showing temperature transitions in processing steps according to a film formation process recipe, a cleaning process recipe, and a temperature maintenance process recipe output from the host computer 40. In the illustrated example, cleaning process 1 is performed as the final process of cassette A, similar to the example shown in Fig. 4A. Then, film formation process 1 (heat up ⇒ film formation ⇒ temperature down) is performed on the last wafer stored in cassette A, and then cleaning process 1 (heat up ⇒ etching ⇒ temperature down) is performed with the wafer W removed. After this cleaning process 1 is completed, the first wafer W in the next cassette B is loaded into the reaction furnace 11 within a predetermined time T, and film formation process 2 (heating up ⇒ film formation ⇒ temperature decrease) is performed. However, if film formation process 2 for the first wafer W in cassette B cannot be started after the predetermined time T has elapsed since the completion of cleaning process 1, which is the final process of cassette A, due to a delay in setting the processing reservation for cassette B, etc., a temperature maintenance process is performed before film formation process 2 for the first wafer W in cassette B, and the temperature inside the reaction furnace 11 is maintained at a predetermined temperature, and then film formation process 2 (heating up ⇒ film formation ⇒ temperature decrease) is performed for the first wafer W in cassette B.

[0031] Next, the operation will be described. Fig. 3 is a flowchart showing the operation of the epitaxial wafer manufacturing system 1 of this embodiment. In this example, the epitaxial wafer manufacturing system 1 shown in Fig. 1 is used in a parallel operation mode, and the operation will be described when the wafers W stored in the first cassette 21A of the first port 20A are subjected to a film formation process in the first reactor 11A.

[0032] First, in step S1, a first cassette 21A is loaded into the first port 20A. The cassette is replaced when the film formation process of all the wafers W stored in the current cassette is completed, in which the cassette storing the wafers W after the film formation process is unloaded from the load port 20, and a new cassette 21 storing the wafers W before the film formation is loaded into the load port 20. Such cassette unloading and loading operations are performed automatically or semi-automatically by a cassette transport device (not shown).

[0033] In step S1, a new first cassette 21A containing uncoated wafers W is loaded into the first port 20A. In the following step S2, the inventory sensor 22 counts the number of wafers W contained in the first cassette 21A, and the count is input to the control unit 19 and also output to the host computer 40.

[0034] In step S3, the host computer 40 acquires information on the product specifications of the wafers W (epitaxial film thickness, resistivity, film formation process recipe number, cleaning process recipe number, temperature maintenance process recipe number, number of wafers to be continuously processed, etc.) from the database 50 based on the product number data sent from the load port 20. The host computer 40 outputs processing conditions and the like for the wafers W accommodated in the cassette 21 carried into the load port 20 to the control unit 19, and reserves the film formation process.

[0035] In step S4, it is determined whether the reservation setting for the cassette that will undergo the film formation process has been completed before the final process of the previous cassette is completed. If the reservation setting has been completed before the final process of the previous cassette is completed, the process proceeds to step S6, and if the reservation setting has not been completed before the final process of the previous cassette is completed, the process proceeds to step S5.

[0036] In step S5, a temperature maintenance process is performed before a film formation process is performed on the first wafer W among the wafers W stored in the first cassette 21A. This is because the furnace body temperature of the reaction furnace 11 may have dropped immediately after a new cassette is loaded.

[0037] In step S6, the control unit 19 controls the wafer transfer mechanism 30 to load the wafers W stored in the first cassette 21A into the first reactor 11A, and controls the first reactor 11A, the valve 16, the mass flow controller, etc. in accordance with the film formation process recipe to form a predetermined epitaxial film on the wafers W. After the formation of the epitaxial film is completed, the control unit 19 controls the wafer transfer mechanism 30 to remove the wafers W on which the film has been formed from the first reactor 11A and store them in the original slot of the first cassette 21A.

[0038] In the following step S7, the control unit 19 controls the first reactor 11A, the valve 16, the mass flow controller, etc. in accordance with the cleaning process recipe to introduce an etching gas into the reactor and remove the by-products, and the host computer 40 controls the removal of the cassette 21A after the film formation process on the wafers W has been completed.

[0039] In the next step S8, the host computer 40 determines whether or not there is a next cassette on the load port 20 via the control unit 19, and if there is, the process proceeds to step S1, and steps S1 to S7 are repeated until there is no more cassette. If there is no more cassette, the production ends.

[0040] The control unit 19 and the host computer 40 in the above embodiment correspond to the control means according to the present invention, and the epitaxial wafer manufacturing system 1 corresponds to the epitaxial growth apparatus according to the present invention. [Explanation of symbols]

[0041] 1...Epitaxial wafer manufacturing system 10…Epitaxial growth equipment 11…Reactor 11A…First reactor 11B…Second reactor 111…Gas inlet 112…Gas exhaust port 12…Heater 13…Susceptor 14...Rotation drive mechanism 15…Plumbing 16…Valve 17…Raw material tank 17a…Silicon raw material tank 17b…Dopant gas tank 17c…Cleaning material tank 17d…Carrier raw material tank 19...Control section 20…Loading port 20A…1st port 20B…Second port 21...Cassette 21A…1st cassette 21B…Second cassette 22...Presence sensor 30...Wafer transport mechanism 40...Host computer 50…Database W: Wafer

Claims

1. a reactor for processing a plurality of wafers stored in a cassette one by one; A control means for controlling process conditions for film formation in the epitaxial growth apparatus including the reactor; a load port for setting the cassette; forming an epitaxial film on a main surface of the wafer in the reactor; At a predetermined frequency, before starting a next film formation process, the inside of the reaction chamber is subjected to a vapor phase etching process to remove a by-product of the vapor phase etching process, and the reaction chamber is cleaned; In an epitaxial growth apparatus which processes cassettes set on the load port in a predetermined order, When the final process of the cassette is completed, it is determined whether or not a film formation process of the next cassette is scheduled; When it is determined that the film formation process for the next cassette is not scheduled, after the final process is completed and before the next film formation process is started, the epitaxial growth apparatus controls the reactor according to a temperature maintenance process recipe for maintaining the reactor at a predetermined temperature (excluding those that maintain the reactor at a predetermined temperature by loading a dummy wafer into the reactor and processing the dummy wafer based on a dummy process recipe).

2. When replacing the cassette with a next cassette, it is determined whether or not a film formation process for the next cassette is scheduled when a final process for the cassette is completed; The epitaxial growth apparatus of claim 1, wherein when it is determined that no reservation has been made for the film formation process of the next cassette, the reaction furnace is controlled according to the temperature maintenance process recipe after the final process is completed and before the film formation process of the next cassette is started.

3. 3. The epitaxial growth apparatus according to claim 1, wherein the temperature maintenance process recipe includes the cleaning process.

4. a film forming step of processing a plurality of wafers stored in a cassette one by one in a reactor and forming an epitaxial film on a main surface of the wafer; a cleaning process step of removing by-products by vapor-phase etching the inside of the reaction furnace before starting a next film formation process at a predetermined frequency; In a method for manufacturing epitaxial wafers, cassettes set on a load port are processed in a predetermined order, When the final process of the cassette is completed, it is determined whether or not a film formation process of the next cassette is scheduled; When it is determined that the film formation process of the next cassette is not scheduled, a temperature maintenance process is carried out to control the temperature of the reactor so as to maintain the temperature at a predetermined temperature after the final process is completed and before the next film formation process is started (however, this does not include a process in which a dummy wafer is placed in the reactor and the reactor is maintained at the predetermined temperature by processing the dummy wafer based on a recipe for a dummy process).

5. When replacing the cassette with a next cassette, it is determined whether or not a film formation process for the next cassette is scheduled when a final process for the cassette is completed; 5. A method for manufacturing an epitaxial wafer as described in claim 4, wherein when it is determined that the film formation process of the next cassette is not scheduled, the temperature maintenance process is carried out after the final process is completed and before the film formation process of the next cassette is started.

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