Method for preparing a reactor restart for the production of an epitaxial wafer

Abstract

Method for preparing a restart of an epitaxial reactor (100) in which epitaxial growth for a wafer is performed, the method comprising the steps: - Introducing a nitrogen gas through a gas inlet (103) into a process chamber provided in the epitaxial reactor (100) to purge the inside of the process chamber with the gas for a predetermined time and, while the inside of the process chamber is being purged, introducing a process gas and a carrier gas into a gas line connected to the gas inlet (103) to purge the gas line for a specified period of time; - Heating the inside of the process chamber non-linearly over time from a predetermined first temperature to a second temperature by stepwise adjusting the power of a heat source, with the power being set to a different value for each step; and - Measurement of the lifetime of minority carriers, hereinafter referred to as MCLT value, for the epitaxy wafer after the epitaxy wafer has been grown.

Description

(Technical field)

[0001] The present invention relates to a method for preparing to restart an interior of a chamber, and more particularly, it relates to a method for preparing to restart an epitaxial reactor for the production of a subsequent epitaxial wafer to remove moisture and contaminants remaining in the chamber after completion of the growth of an epitaxial wafer. (State of the art)

[0002] A conventional silicon wafer is manufactured through a single crystal growth process, a cutting process, a grinding process, a lapping process, a polishing process, and a cleaning process to remove abrasive or foreign substances adhering to a wafer after the polishing process.

[0003] A wafer produced by such a process is called a polished wafer, and a wafer on which another monocrystalline film (epitaxial layer) is grown on a surface of a polished wafer is called an epitaxial wafer or epitaxial wafer.

[0004] The epitaxial wafer has fewer defects than the polished wafer and has the ability to control the concentration and type of impurities. Furthermore, the epitaxial layer exhibits high purity and excellent crystallinity, which is beneficial for improving the yield and product properties of a highly integrated semiconductor device. Chemical vapor deposition (CVD) is a process for growing a thin layer of material on a target, such as a semiconductor wafer. A layer of varying conductivity can be deposited on the wafer to create desired electrical properties.

[0005] A chemical vapor deposition apparatus for depositing an epitaxial layer on a wafer surface is configured to include a process chamber in which an epitaxial layer is deposited, a susceptor disposed in the chamber, a heater provided in upper and lower portions of the process chamber, and a gas injection unit for introducing a treatment gas onto a wafer. The gas injected from the gas injection unit forms an epitaxial layer on a wafer disposed on the susceptor.

[0006] The chamber of an epitaxial reactor (epitaxial reactor) used to grow an epitaxial layer on a wafer contains a high level of moisture and metal impurities generated when an epitaxial process is performed at high temperatures. The presence of such impurities within the chamber makes it impossible to produce a high-quality epitaxial wafer. Therefore, after completing the epitaxial wafer manufacturing process, it is necessary to remove any remaining impurities within the chamber and create an atmosphere in which the epitaxial process of the next batch can be performed.

[0007] This means that after various processes have been performed within the chamber, preventive maintenance (PM) is performed. Residual moisture and metal contamination remain within the chamber after the PM. Therefore, a process is performed to prepare a growth device for restarting so that an epitaxial wafer can be produced again.

[0008] When a restart of an epitaxial growth system is performed, a process step is provided to remove moisture and various contamination sources in the epitaxial reactor, which remain in a thermally stabilized state, and steps of heating and stabilizing within the chamber for a sufficient time to ensure the quality of the wafer are provided, and which can be repeated to perform the restart process.

[0009] However, since the productivity of an epitaxial plant decreases with the increase of the time required to perform a restart operation, it is necessary to find a method capable of improving the productivity of an epitaxial plant by reducing the time required for a restart operation of an epitaxial reactor.

[0010] JP 2004-260086 A relates to a method for producing a silicon wafer. This involves cleaning a susceptor using nitrogen, followed by a heat treatment. WO 2014 / 061413 A1 describes a method for determining the degree of contamination of an epitaxial reactor. US 2012 / 0108039 A1 discloses a method for cleaning a substrate surface, in which the substrate surface is treated with chlorine gas. (The technical problem)

[0011] To solve the above-mentioned problems, the present invention was proposed, the present invention provides a method for more effectively discharging sources of moisture and contamination to the exterior of a process chamber in a method for preparing a restart of an epitaxial reactor for producing an epitaxial wafer and shortening the restart time of the reactor. (technical solution)

[0012] As a method for preparing a restart of an epitaxial reactor in which epitaxial growth is performed on a wafer, one embodiment may include the steps of: injecting a nitrogen gas into a process chamber provided in the epitaxial reactor and purging the gas for a predetermined time; heating the inside of the process chamber nonlinearly with time; and measuring MCLT for the epitaxial wafer after fabricating the epitaxial wafer.

[0013] In one embodiment, the step of introducing a nitrogen gas into a process chamber provided in the epitaxial reactor and purging the gas for a predetermined time is performed simultaneously with a step of purging a process gas and a carrier gas into a gas line that simultaneously introduces a gas into the process chamber.

[0014] The process gas, also called source gas or treatment gas, can be a trichlorosilane (TCS) gas and the carrier gas an H2 gas.

[0015] Preferably, the step of introducing a nitrogen gas into a process chamber provided in the epitaxial reactor and purging the gas for a predetermined time, and the step of purging a TCS gas into a gas line injecting a gas into the process chamber is performed for at least two hours or longer.

[0016] An embodiment may further comprise a step of heating the process chamber to a predetermined first temperature and then stabilizing the process chamber after purging the interior of the process chamber with a nitrogen gas. Preferably, the first temperature is adjustable in the range of 800 to 840°C.

[0017] In addition, the step of heating the interior of the process chamber non-linearly in time may include a step of setting power of a heat source corresponding to the first temperature to gradually increase in time after stabilizing the interior of the process chamber to the first temperature.

[0018] The step of non-linearly heating the interior of the process chamber according to time may include steps of heating and stabilizing the interior of the process chamber to a predetermined first temperature and annealing the inside or interior of the process chamber to a predetermined range of a second temperature.

[0019] Preferably, the second temperature is adjustable in the range from 800 to 1200°C, which is a limit temperature at which melting of a reflector contained in an epitaxial reactor does not yet occur.

[0020] In one embodiment, a step of introducing hydrogen gas into the upper and lower sections of a susceptor can be performed while the step of nonlinearly heating the interior of the process chamber is performed. Preferably, the power of the heat source is adjustable in the range of 40 to 95 kW.

[0021] In addition, a process of adjusting the power of the heat source to gradually increase it may be performed once or several times, and a step of equalizing the temperatures of upper and lower portions of a susceptor may be performed after a bake-out process of the process chamber is completed.

[0022] In one embodiment, the step of equalizing the temperatures of the upper and lower portions of the susceptor may be performed by changing the emissivities of an upper or lower sub-dome of the process chamber.

[0023] An embodiment may include repeatedly performing a process of depositing a silicon layer on a surface of a susceptor and then etching and removing the silicon layer.

[0024] In one embodiment, after the step of heating the inside of the process chamber non-linearly in time, a step of checking whether or not a residual dopant is present within the process chamber may be performed.

[0025] The step of checking whether a residual dopant exists or not may further comprise, within the process chamber, producing an intrinsic wafer with no dopant and measuring the conductivity of the intrinsic wafer and measuring the conductivity of the intrinsic wafer in a subsequent step if the conductivity of the intrinsic wafer is greater than a predetermined value.

[0026] In addition, a process for removing the epitaxial wafer from inside the process chamber and cleaning the process chamber after the epitaxial wafer is fabricated can be performed repeatedly.

[0027] In one embodiment, the step of measuring MCLT for the epitaxial wafer is performed at one time for a plurality of runs, when a manufacturing process of an epitaxial wafer is referred to as a batch or a run.

[0028] The epitaxial wafer is manufactured as a dummy wafer, and a wafer corresponding to a run in which the actual MCLT measurement is performed can be manufactured as an actual wafer.

[0029] In one embodiment, when the MCLT reaches a predetermined value, the steps of providing an epitaxial reactor for restart are completed. [beneficial effects]

[0030] According to one embodiment, the method for manufacturing a reactor for producing an epitaxial wafer cleans and dries the interior of a process chamber using a nitrogen gas at room temperature and for a certain period of time after a PM process is performed, and thus the time required to prepare for a restart of a reactor can be shortened compared to the prior art.

[0031] According to one embodiment, the method for providing a reactor for producing an epitaxial wafer gradually increases the power of a heat source for transferring heat to an interior of a process chamber in a step of annealing the interior of the process chamber after a PM process is completed. This allows moisture and contaminants remaining in the process chamber, which may cause unstable flow, to be effectively removed by the flow of hydrogen gas.

[0032] According to one embodiment, since moisture and contaminants remaining in a process chamber are removed at a faster rate than in a prior art epitaxial reactor restart preparation method, the time required to achieve a minimum MCLT value for performing an epitaxial reactor restart can be reduced. Accordingly, the time required to prepare for a reactor restart is also reduced, thus improving the productivity of an epitaxial plant. [Description of the drawing] Fig. 1 is a view illustrating an epitaxial reactor in preparation for restarting an epitaxial reactor of an embodiment. Fig. 2 is a flowchart illustrating a method for preparing to restart an epitaxial reactor according to one embodiment. Fig. 3 shows a state in which a TCS gas is purged according to an embodiment. Fig. 4 is a graph showing a change in an MCLT level within a process chamber according to the prior art, as well as for an embodiment in a method for fabricating an epitaxial reactor. Fig. 5 is a graph illustrating a change in a level of MCLT within a process chamber according to a type of preparation for a restart of an epitaxial reactor. [Embodiments of the invention]

[0033] In the following, embodiments of the present invention will be described in detail with reference to the accompanying drawings. However, the present invention is not limited or restricted to the embodiments. In the description of the present invention, a detailed description of well-known functions or configurations is omitted in order to more clearly explain the spirit of the present invention.

[0034] In one embodiment, preventive maintenance (PM) is performed for an epitaxial reactor, and thereafter, a procedure for a process of a restart operation for removing moisture and remaining contaminants existing in the epitaxial reactor is proposed, thereby reducing the time required for a restart operation compared to a conventional method.

[0035] Fig. 1 is a view illustrating an epitaxial growth system to which an epitaxial reactor restart provisioning process is applied according to an embodiment.

[0036] Referring to Fig. 1, an epitaxial growth system 100 may be configured to include a top liner 105 and a bottom liner 102, a top cap 106, a bottom cap 101, a susceptor 107, a preheat ring 108, a susceptor support 109, a gas inlet 103, a gas outlet 104, and a main shaft 110.

[0037] The gas inlet 103 connected to a gas supply line is formed on one side of the epitaxial growth system 100, the gas outlet 104 connected to a gas supply line may be formed on the other side of the epitaxial growth system 100, and the epitaxial growth system 100 may include the bottom cover 101 and the top cover 106.

[0038] The bottom liner 102 may be arranged to surround the susceptor 107, and the top liner 105, also called the upper section liner, may be provided to face an upper section of the bottom liner 102 or the lower section liner. The preheating ring 108 is arranged annularly along an inner surface of the bottom liner 102 adjacent to the susceptor 107 and rests on the bottom liner 102. The preheating ring 108 is arranged to surround the susceptor 107 so that a temperature of a gas transferred to a wafer is uniform.

[0039] The susceptor 107 is a device on which a wafer is placed while performing an epitaxial process, and the susceptor 107 may be formed with a plate made of a material such as carbon graphite or silicon carbide. The susceptor 107 is supported by the main shaft 110, which is located at a lower portion of the susceptor 107, and the susceptor holder 109, which is formed at various positions in an edge direction of the susceptor 107 in the main shaft 110. An epitaxial process may be performed while the susceptor 107 is fixed at the same height as the preheating ring 108, as shown in FIG. Fig. 1 is shown.

[0040] An epitaxial layer is grown from the vapor phase on a wafer at high temperatures in a process chamber within an epitaxial reactor, as described above, producing an epitaxial wafer. At this point, if metal impurities or residual moisture are present inside the process chamber, the resulting epitaxial wafer will be contaminated by metal impurities, making the quality of the epitaxial wafer unsafe.

[0041] Accordingly, the process chamber performs preventive maintenance (PM) after various processes have been performed, thus generating residual moisture within the process chamber. To solve this problem, residual moisture can be removed by a process such as baking the chamber's interior.

[0042] Fig. 2 is a flowchart illustrating a method for preparing to restart an epitaxial reactor according to one embodiment. Referring to Fig. 2, the method for preparing a restart of an epitaxial reactor according to one embodiment is performed after the fabrication of an epitaxial wafer is completed, then PM is performed within a reactor. The method for preparing a restart of an epitaxial reactor may include purging the inside of the process chamber with a nitrogen gas in step S10, raising a temperature within the chamber in a step S20, annealing the inside of the chamber in a step S30, equalizing temperatures in the upper and lower portions of a susceptor in step S40, stabilizing the susceptor in step S50, checking whether or not a dopant is present in the process chamber in step S60, and removing metallic contamination sources within the process chamber in step S70.

[0043] Each step will now be described in detail: Step S10 of purging the process chamber with nitrogen gas is a step of introducing nitrogen gas through a gas inlet while maintaining the interior of the process chamber at room temperature, then circulating the gas within the process chamber and discharging it through a gas outlet. Step S10 can preferably be performed within the process chamber for about 3 hours, but this can be varied depending on the condition of the chamber's interior.

[0044] Additionally, while purging the interior of the process chamber, a gas line can be purged, which feeds a gas into and out of the process chamber. A process gas and a carrier gas can flow through and be fed into a gas line for a specific period of time, creating an atmosphere capable of removing contaminants and moisture remaining in the gas line. At this point, trichlorosilane (TCS) can be used as the process gas or source gas, and H2 as the carrier gas.

[0045] In one embodiment, unlike the process of raising a temperature of the process chamber in preparation for restarting a reactor when performing a conventional PM, the step S10 of circulating a nitrogen gas may be performed, thereby creating an atmosphere within the process chamber that enables faster removal of residual moisture and contaminants within the process chamber.

[0046] In step S20 of raising the temperature within the process chamber, the temperature within the process chamber is raised to a predetermined first temperature over time and stabilized, while the interior of the process chamber is maintained at the first temperature for approximately 10 minutes. The first temperature can be selected in the range of 800 to 840°C at this point.

[0047] The step S30 of baking the inside of the chamber is a step of nonlinearly heating the inside of the process chamber in time, the step can be carried out by gradually increasing the value of the power applied to the process chamber.

[0048] The interior of the process chamber can be controlled by sequentially increasing the power of a heat source from 40 kW to 95 kW, which is a corresponding power of a heat source, in a state where the predetermined first temperature is maintained at 800°C, and setting the increment for each step to 10 kW. For example, if the process chamber is heated at a power of 40 kW for a certain period of time, then the process chamber is heated at a power of 50 kW for a certain period of time, and then the power value can be sequentially increased up to 95 kW.

[0049] If the power of the heat source is gradually increased, the temperature within the process chamber can rise to a predetermined second temperature; this second temperature can be set in the range from 800 to 1200°C. Since a reflector formed in an epitaxial reactor can be melted when a power value of 95 kW is applied, the temperature of 1200°C, which corresponds to a power of 95 kW, is set as a threshold temperature in the process when carrying out one embodiment. With a constant power of the heat source, a temperature change within the process chamber changes linearly. However, if the power of the heat source is gradually increased, as in one embodiment, a temperature change within the process chamber occurs nonlinearly.

[0050] As described above, the power of the heat source gradually increases and is set to a different value for each step. This causes a thermal state within the process chamber to become unstable, and thereby increases the kinetic energy of particles, including moisture and contaminants, contained in the process chamber. In one embodiment, during preparation for restarting an epitaxial reactor, the process of gradually increasing the power of the heat source to increase a temperature within the process chamber may be repeated several times in the step of annealing the inside of the process chamber. Preferably, the process may be performed two to five times depending on the efficiency of the annealing process. At this point, a process of introducing a hydrogen gas into upper and lower portions of the susceptor may be performed.

[0051] The interior of the process chamber becomes thermally unstable while the process of raising a temperature inside the process chamber is carried out, and when a hydrogen gas is introduced into the process chamber through a main valve and a slit valve, moisture and substances can be more effectively removed from the process chamber by being carried away by the hydrogen.

[0052] That is, the step of raising the inside of the process chamber to a higher temperature than the prior art is performed to make the thermal condition inside the process chamber uneven, and thus the speed of discharging moisture and residue inside the process chamber can be further increased.

[0053] The step S40 of equalizing the temperatures of the upper and lower sections of a susceptor results in the temperatures of the upper and lower covers of the process chamber, corresponding to the upper and lower parts of the susceptor, becoming equal after the state within the process chamber has been thermally unstable, leading to the removal of various contaminants. This step can be a preparatory step for a stabilization process of a replaced susceptor. After measuring the temperatures of the upper and lower covers, if the temperature values ​​are different, the emissivity of the upper and lower covers can be adjusted, and the intensity of the heat supplied by the heater can be changed, thus maintaining the temperature within the process chamber at the same level.

[0054] The susceptor stabilization step S50 may include depositing a silicon layer on a surface of the susceptor used to fabricate an epitaxial wafer or a replaced susceptor, and then etching and removing the silicon film.

[0055] A susceptor used in a previous process contains moisture or contaminants on its wafer contact surface after a high-temperature process, and a replaced susceptor may also have metal substances and various adsorbed residues on a surface. Therefore, it is necessary to stabilize the surface of the susceptor to remove moisture, contaminants, metal substances, and various other residues. In one embodiment, a silicon gas is directed onto a surface of the susceptor for 120 seconds, forming a 4 to 5 µm silicon film thereon. Subsequently, an etching gas is directed onto the silicon film for 90 seconds, removing the silicon film. This process is repeated approximately four times, after which the susceptor is stabilized, i.e., clean.

[0056] Step S60 of checking whether a dopant is present within the process chamber is a process in which the resistivity or conductivity of an epitaxial wafer is measured and whether a dopant remains within the process chamber. This step may include a step of placing a wafer into the process chamber and producing an epitaxial wafer with a thickness of 10 µm, removing the epitaxial wafer after a predetermined time, and measuring the resistivity of the wafer. An intrinsic epitaxial wafer is obtained without doping a dopant within the process chamber. An intrinsic epitaxial wafer will have a constant resistivity, but a change in this value allows the determination that a dopant remains within the process chamber because the resistance value of the wafer has changed.

[0057] Accordingly, in one embodiment, if the resistivity of a wafer does not meet the level of 300 ohm cm, a CP-MCLT recovery process, which is a next step, may be performed while additionally checking the resistivity of a wafer and determining whether a dopant remains.

[0058] Step S70 of removing a source of metallic contamination within the process chamber is a step of growing an epitaxial layer on a wafer and performing a chemical passivation (CP) recovery process. Step S70 is a step of measuring an MCLT level within the process chamber, and repeats the step of placing a wafer into the process chamber and fabricating an epitaxial wafer. When a process of cleaning and etching within the process chamber after fabricating an epitaxial wafer is referred to as one pass, a step of measuring an MCLT level of an epitaxial wafer may be performed at the time of performing a plurality of passes. In one embodiment, epitaxial wafers with 50, 100, 150, 200, and 250 passes are taken as reference wafers, and an MCLT value is measured.

[0059] Wafers used in each run can be reference wafers, test wafers, or dummy wafers, and epitaxial wafers can be used with actual wafers in runs with numbers of, for example, 50, 100, 150, 200, and 250 and as test wafers.

[0060] After removing a test wafer with an epitaxial layer formed thereon from the process chamber, a process is performed to remove a formed oxide film using hydrofluoric acid. Iodine is also thinly deposited on the epitaxial wafer, and then a wafer surface is scanned to measure the MCLT level.

[0061] The minority carrier lifetime (MCLT) can be a measure to determine whether the epitaxial growth system is ready for a restart. The MCLT level refers to the average time required for the recombination of excess minority electrons (holes). The more impurities there are in a process chamber, the lower the MCLT.

[0062] Therefore, the MCLT values ​​of sample wafers corresponding to 50, 100, 150, 200, and 250 passes are measured. If an MCLT value meets a predetermined value, it can be determined that preparation for restarting an epitaxial growth system is complete. If an MCLT value does not meet a predetermined value, steps S10 to S60 are repeated to achieve an MCLT level required to prepare for restarting. In one embodiment, when an MCLT has reached a predetermined value, the restart process of an epitaxial growth system is complete, and the predetermined value is set to 2500 µs, which means that contaminants present within the process chamber, such as metal particles, have been sufficiently removed and will not affect the quality of a subsequently produced epitaxial wafer.

[0063] Fig. 3 shows a case where purging is carried out with a TCS gas according to an embodiment.

[0064] How Fig. 3 shows an MCLT level while the process chamber is purged with a nitrogen gas in step S10 of one embodiment, and simultaneously, the gas line is purged with a TCS gas. The results of the MCLT level measurements for two epitaxial reactors (CENO6A, CENO6B) show that when the gas line is not purged with a TCS gas (Normal), the MCLT levels are 2324 and 3990 µs, respectively. However, when a TCS gas is purged through the gas line for a certain period of time, it can be seen that an MCLT level is rapidly increased when purging with a TCS gas for at least 2 hours or more.

[0065] Fig. Figure 4 is a graph illustrating a change in an MCLT level within a process chamber according to the prior art, as well as an embodiment of a method for re-enabling an epitaxial reactor. In the case of the embodiment, compared to the prior art, purging the inside of the process chamber with a nitrogen gas and purging a gas line with a TCS gas, annealing the inside of the chamber, and removing a metallic contamination source within the process chamber are performed. If the above process is not performed, the time to prepare an epitaxial reactor for re-enabling is 8 days to meet the MCLT level of 2500 µs required for re-enabling.However, when the manufacturing process as described in the embodiment is performed, the time for preparing an epitaxial reactor for restart is 4 days to meet an MCLT level of 2500 µs required for restart, and it can be found that the time required for restarting an epitaxial reactor is shortened to about one half.

[0066] Fig. Figure 5 is a graph illustrating a change in an MCLT level within the process chamber due to a device replacement during preparation for a restart of an epitaxial reactor. Such consumable devices may require replacement during the recovery of an epitaxial wafer after repeated or repeated production of an epitaxial wafer. An upper dome and a susceptor on which a wafer is mounted are primarily replaced, and Fig.Figure 5 shows the time required to prepare a restart of an epitaxial reactor for the MCLT level when replacing an upper dome or a susceptor.

[0067] At time PM, i.e., without replacing any devices within an epitaxial reactor, the MCLT level at which an epitaxial reactor can be restarted is approximately 2500 µs, after approximately 200 passes of an epitaxial wafer. If an upper dome is replaced, the MCLT level reaches approximately 2500 µs after 300 passes, and the epitaxial reactor can be restarted. If an upper dome and a susceptor are replaced simultaneously, the MCLT level reaches approximately 2500 µs after approximately 350 passes, and the epitaxial reactor can then be restarted.

[0068] This means that a relatively large amount of contaminants, such as metal particles, are present on the surface of replaced devices where no epitaxial process is performed. When replacing epitaxial reactor devices, steps S10 to S70 described in one embodiment may be performed repeatedly to achieve an MCLT level required for a restart.

[0069] As described above, according to one embodiment, a method for manufacturing a reactor for producing an epitaxial wafer is performed, wherein purging and drying the inside of the process chamber using a nitrogen gas at room temperature for a certain period of time is performed after completion of a PM process. In the step of annealing the inside of the process chamber, the power of the heat source for heat transfer into the process chamber is gradually increased, thereby effectively removing moisture and impurities present inside the process chamber. In addition, a run is also performed to repeatedly produce an epitaxial wafer, and the presence of metallic impurities remaining in the epitaxial reactor is checked by measuring an MCLT level for an epitaxial wafer in a certain run.

[0070] With the reactor recovery method described above, in one embodiment, the time to prepare for a reactor restart can be reduced compared to a conventional method, and thus the productivity of an epitaxial device can be improved. (Industrial applicability)

[0071] The present invention has industrial applicability because it can improve the removal of moisture and contaminants from a process chamber, thus reducing the time required to prepare for a reactor restart. Thus, the productivity of an epitaxial plant can be improved. Reference symbol 100 epitaxial growth system, reactor, epitaxial reactor 101 Lower part cover 102 lower part liner 103 Gas inlet 104 Gas outlet 105 Top Liner 106 Top cover 107 Susceptor 108 Preheating ring 109 susceptor carriers 110 Main shaft

Claims

[1] A method for preparing a restart of an epitaxial reactor (100) in which epitaxial growth is carried out for a wafer, the method comprising the steps of: - introducing a nitrogen gas through a gas inlet (103) into a process chamber provided in the epitaxial reactor (100) to purge an inside of the process chamber with the gas for a predetermined time and, while the inside of the process chamber is being purged, introducing a process gas and a carrier gas into a gas line connected to the gas inlet (103) to purge the gas line for a predetermined period of time; - heating the inside of the process chamber non-linearly over time from a predetermined first temperature to a second temperature by stepwise adjusting a power of a heat source, wherein the power is set to a different value for each step; and - Measurement of the minority carrier lifetime, hereinafter referred to as MCLT value, for the epitaxial wafer after growth of the epitaxial wafer. [2] A method for preparing a restart of an epitaxial reactor (100) according to claim 1, wherein the treatment gas is a trichlorosilane, hereinafter referred to as TCS, and the carrier gas is an H2 gas. [3] A method for preparing a restart of an epitaxial reactor (100) according to claim 1, wherein the step of introducing a nitrogen gas into a process chamber provided in the epitaxial reactor (100) and purging with this gas for a predetermined time, and the step of purging a TCS gas into a gas line introducing a gas into the process chamber is performed for at least two hours or longer. [4] A method for preparing a restart of an epitaxial reactor (100) according to claim 1, further comprising a step of heating the process chamber to the predetermined first temperature and then stabilizing the process chamber after purging the interior of the process chamber with a nitrogen gas. [5] A method for preparing a restart of an epitaxial reactor (100) according to claim 4, wherein the first temperature is set in the range of 800 to 840°C. [6] A method for preparing a restart of an epitaxial reactor (100) according to claim 4, wherein the step of non-linearly heating the inside of the process chamber is performed to gradually increase in time after the inside of the process chamber stabilizes to the first temperature. [7] A method for preparing for a restart of an epitaxial reactor (100) according to claim 1, wherein the step of heating the interior of the process chamber non-linearly in time comprises steps of heating and stabilizing the interior of the process chamber to a predetermined first temperature and annealing the interior of the process chamber to the second temperature. [8] A method for preparing a restart of an epitaxial reactor (100) according to claim 7, wherein the second temperature is set in the range of 800 to 1200 °C, which is a limit temperature at which a reflector included in an epitaxial reactor (100) does not yet begin to melt. [9] A method for preparing for a restart of an epitaxial reactor (100) according to claim 1, wherein a step of introducing a hydrogen gas into upper and lower portions of a susceptor (107) is performed while performing the step of non-linearly heating the inside of the process chamber in a time-dependent manner in the preparation for a restart of an epitaxial reactor (100) according to claim 8, wherein the second temperature is set in the range of 800 to 1200 °C, which is not a limit temperature at which a reflector included in an epitaxial reactor (100) does not start to melt. [10] A method for preparing a restart of an epitaxial reactor (100) according to claim 6, wherein the power of the heat source is set in the range of 40 to 95 kW. [11] A method for preparing a restart of an epitaxial reactor (100) according to claim 6, wherein a method for gradually increasing the power of the heat source is performed at least once or more times. [12] A method for preparing a restart of an epitaxial reactor (100) according to claim 1, wherein a step of equalizing the temperatures of upper and lower portions of a susceptor is performed after an annealing process of the process chamber is completed. [13] A method for preparing to restart an epitaxial reactor (100) according to claim 12, wherein the step of equalizing the temperatures of upper and lower portions of the susceptor (107) is performed by changing the emissivity of an upper region of the dome and a lower region of the dome of the process chamber. [14] A method for preparing a restart of an epitaxial reactor (100) according to claim 1, comprising repeatedly performing a process of depositing a silicon layer on a surface of a susceptor (107) and then etching and removing the silicon layer. [15] A method for preparing a restart of an epitaxial reactor (100) according to claim 1, wherein after the step of heating the inside of the process chamber non-linearly in time, a step of checking whether or not a residue of dopant is present within the process chamber is carried out. [16] A method for preparing a restart of an epitaxial reactor (100) according to claim 15, wherein for the step of checking whether a residual dopant exists or not within the process chamber, further comprising the step of manufacturing an intrinsic wafer with no dopant within the process and measuring a resistivity of the intrinsic wafer in a subsequent step, preferably when a resistivity of the intrinsic wafer is smaller than a predetermined value. [17] A method for preparing a restart of an epitaxial reactor (100) according to claim 1, wherein a process for removing the epitaxial wafer from the process chamber and cleaning the process chamber are repeatedly performed after the production of the epitaxial wafer. [18] A method for preparing a restart of an epitaxial reactor (100) according to claim 1, wherein the step of measuring an MCLT value for the epitaxial wafer is performed at the time of a plurality of previous runs, wherein a process of manufacturing an epitaxial wafer is referred to as a run. [19] A method for preparing a restart of an epitaxial reactor (100) according to claim 18, wherein the epitaxial wafer is manufactured as a dummy wafer, and a wafer corresponding to a run in which the actual MCLT measurement is performed is manufactured as an actual wafer. [20] A method for preparing for a restart of an epitaxial reactor (100) according to claim 1, wherein a step of preparing for a restart of an epitaxial reactor (100) is terminated when the MCLT value has reached a predetermined value.

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