Substrate processing apparatus, abnormality detection method, and method for manufacturing semiconductor device

Abstract

According to the present disclosure, there is provided a substrate processing apparatus including: a temperature detecting section that detects a temperature of a heat generating section that raises a temperature of a processing chamber by heat generation; a temperature adjusting section that adjusts a proportion of power to be supplied to the heat generating section in a unit time so as to reduce a difference between the temperature detected by the temperature detecting section and a temperature set value; a measuring section that measures a current flowing in a circuit including the heat generating section; and an abnormality detecting section that compares a measured value of the current measured by the measuring section with a theoretical current value calculated based on the proportion of the power outputted from the temperature adjusting section, and determines that an abnormality has occurred when the measured value of the current and the theoretical current value are different.

Description

Technical Field

[0001] This disclosure relates to a substrate processing apparatus, an anomaly detection method, and a method for manufacturing a semiconductor device. Background Technology

[0002] In substrate processing apparatuses used in semiconductor manufacturing, a film-forming process is performed on a substrate while it is heated by the heat from a heater. Semiconductor components such as thyristors are used in the power control of the heater to suppress overheating of the substrate. Patent Document 1 discloses a technique of connecting multiple power sources to stably supply power to a power source. Patent Document 2 discloses a technique of detecting at least one of the current, voltage, and power supplied to the heater used in the substrate processing apparatus, and detecting the heater's state (abnormal heating state, disconnection state) based on the detection result.

[0003] In the market, considering the impact on the substrate processing device and the substrate, it is desirable to reliably detect situations where the components constituting the drive circuit (including heater wires) have malfunctioned.

[0004] Existing technical documents

[0005] Patent documents

[0006] Patent Document 1: International Publication No. 2019 / 053869

[0007] Patent Document 2: Japanese Patent Application Publication No. 11-54244 Summary of the Invention

[0008] The problem that the invention aims to solve

[0009] The purpose of this disclosure is to provide a technique for detecting faults in components that constitute a circuit.

[0010] Methods for solving problems

[0011] According to one aspect of this disclosure, a technology is provided comprising: a temperature detection unit that detects the temperature of a heating element that raises the temperature of a processing chamber by heating; a temperature adjustment unit that adjusts the proportion of power output relative to the power that can be supplied to the heating element per unit time, so as to reduce the difference between the temperature obtained from the temperature detection unit and a temperature setpoint; a measurement unit that measures the current flowing in a circuit including the heating element; and an anomaly detection unit that compares the current measurement value measured by the measurement unit with a theoretical current value calculated based on the proportion of the power output obtained from the temperature adjustment unit, and determines an anomaly if the current measurement value differs from the theoretical current value.

[0012] Invention Effects

[0013] According to this disclosure, it is possible to detect when components constituting a circuit malfunction. Attached Figure Description

[0014] Figure 1 This is a side sectional view showing the substrate processing apparatus of this embodiment.

[0015] Figure 2 This is a diagram showing the functional structure of the control system used in the substrate processing apparatus of this embodiment.

[0016] Figure 3 This is a diagram illustrating the functional structure of the device controller used in the substrate processing apparatus of this embodiment.

[0017] Figure 4 This is a circuit diagram showing the drive circuit of the heater used in the substrate processing apparatus of this embodiment.

[0018] Figure 5 This is a diagram illustrating the functional structure of the anomaly detection controller used in the substrate processing apparatus of this embodiment.

[0019] Figure 6 This is a flowchart of the first anomaly detection method in this embodiment.

[0020] Figure 7 This is a flowchart of the second anomaly detection method in this embodiment.

[0021] Figure 8 It is a graph showing the relationship between the output setpoint of the thyristor and the ammeter monitoring value.

[0022] Figure 9 This is a circuit diagram showing the drive circuit of the heater used in the substrate processing apparatus in other embodiments. Detailed Implementation

[0023] The following is a reference to the appendix. Figure 1 An embodiment of this disclosure will be described below. Furthermore, the drawings used in the following description are schematic, and the dimensional relationships and ratios of the elements shown in the drawings may not necessarily correspond to reality. Additionally, even among multiple drawings, the dimensional relationships and ratios of the elements may not be consistent.

[0024] One embodiment of the present disclosure provides a processing apparatus 10 configured as a substrate processing apparatus 10 used in a substrate processing step, which is a process in the manufacturing process of a semiconductor device.

[0025] like Figure 1As shown, the substrate processing apparatus 10 of this embodiment includes a heating device 20, a reaction tube 54, and a boat 68.

[0026] like Figure 1 As shown, the heating device 20 is a device for heating the substrate W, which is the object to be processed. The heating device 20 includes: a furnace body 22, a side heater 24, which serves as a heating element and is disposed inside the furnace body 22, and a top heater 26.

[0027] The furnace body 22 is formed by stacking multiple insulation materials. However, this disclosure is not limited to this structure, and the furnace body 22 may also be formed from a single insulation material.

[0028] Furthermore, the furnace body 22 is formed as a cylindrical shape with one end closed (e.g., a cylindrical, elliptical, or polygonal cylindrical shape). In this embodiment, the furnace body 22 is configured such that the vertical direction of the heating device 20 is axial, with the upper end in contact with one end of the axial direction closed and the lower end in contact with the other end of the axial direction open. The internal space of the furnace body 22 will be referred to as the furnace interior space 23 below. A side heater 24 and a top heater 26 are disposed in this furnace interior space 23. Additionally, a reaction tube 54 is housed in the furnace interior space 23.

[0029] The furnace body 22 has a cylindrical side wall portion 28 and a top 30 that closes the upper end of the side wall portion 28. Furthermore, in this embodiment, the side wall portion 28 and the top 30 form an internal furnace space 23.

[0030] The side heater 24 is disposed on the inner side (radially inner side) of the side wall portion 28. Furthermore, in this embodiment, the side heater 24 is mounted on the inner surface 28A of the side wall portion 28 such that it covers the inner surface 28A. The side heater 24 generates heat by being supplied with electricity, thereby heating the furnace interior space 23 from the side.

[0031] The side heater 24 is cylindrical and continuous in the circumferential direction along the inner surface 28A of the side wall portion 28. Furthermore, the side heater 24 is divided into multiple sections along the axial direction of the furnace body 22. In this embodiment, the axial direction of the furnace body 22, the axial direction of the side heater 24, and the vertical direction of the heating device 20 are all in the same direction. Moreover, the side heater 24 is configured to allow control of the heating temperature according to the divided heating areas.

[0032] In this embodiment, such as Figure 1 and Figure 2As shown, the side heater 24 is divided into four heating regions in the axial direction. Here, each heating region of the side heater 24 is referred to sequentially from the top of the heating device 20 as heating region 24A, heating region 24B, heating region 24C, and heating region 24D. Furthermore, this disclosure is not limited to the above structure; the side heater 24 may be divided into two or three heating regions in the axial direction, or it may be divided into five or more heating regions in the axial direction. Moreover, the side heater 24 may not be divided into multiple regions; that is, the side heater 24 may be a single unit. In this embodiment, the heating temperature of the side heater 24 is controlled by the temperature control controller 72, which will be described later.

[0033] A top heater 26 is disposed below the top 30. Specifically, the top heater 26 is disposed between the reaction tube 54 and the top 30 in the vertical direction of the heating device 20. The top heater 26 is heated by being supplied with electricity, heating the furnace interior space 23 from above. Furthermore, in this embodiment, the top heater 26 is formed in the form of a plate, for example. In addition, in this embodiment, the heating temperature of the top heater 26 is controlled by a temperature control controller 72.

[0034] As described above, the furnace space 23 is heated from the side and top by the side heater 24 and the top heater 26, thereby heating the processing chamber 55 via the reaction tube 54 housed in the furnace space 23, and raising the temperature inside the processing chamber 55. As a result, the substrate W filled inside the processing chamber 55 is heated.

[0035] like Figure 2 As shown, temperature sensors, serving as temperature detection units, are provided in each heating area of ​​the side heater 24. Specifically, in the heater wires (see reference) provided in each heating area... Figure 4 Temperature sensors are respectively installed near the heating area 24A. In this embodiment, reference numeral 25A indicates the temperature sensor installed in the heating area 24A, reference numeral 25B indicates the temperature sensor installed in the heating area 24B, reference numeral 25C indicates the temperature sensor installed in the heating area 24C, and reference numeral 25D indicates the temperature sensor installed in the heating area 24D. These temperature sensors 25A, 25B, 25C, and 25D detect the temperatures of the heating areas 24A, 24B, 24C, and 24D, respectively. The detected values ​​(detected temperatures) from each temperature sensor are sent to the temperature control controller 72, which serves as a temperature adjustment unit. Furthermore, temperature sensors 25A, 25B, 25C, and 25D can be used as long as they can detect the temperature of the heating area that is their respective measurement target; for example, a thermometer or a thermocouple can be used.

[0036] like Figure 2As shown, a temperature sensor 25E, serving as a temperature detection unit, is provided on the top heater 26. Specifically, the top heater 26 has heater wires (see...) Figure 4 A temperature sensor 25E is installed near the top heater 26. The temperature of the top heater 26 is detected by this temperature sensor 25E. The detected value (detected temperature) is sent to the temperature control controller 72. Furthermore, the temperature sensor 25E only needs to be able to detect the temperature of the top heater 26; for example, a thermometer or a thermocouple can be used.

[0037] Additionally, the heating device 20 includes heater drive units for driving the heaters. In this embodiment, heater drive units are connected to each heating zone of the side heater 24 and the top heater 26, respectively. Drive power is supplied to each heater from these heater drive units. Furthermore, in this embodiment, as... Figure 2 As shown, the heating region 24A of the side heater 24 is connected to the heater drive device 80A, the heating region 24B is connected to the heater drive device 80B, the heating region 24C is connected to the heater drive device 80C, and the heating region 24D is connected to the heater drive device 80D. Additionally, the top heater 26 is connected to the heater drive device 80E. Furthermore, the structures of heater drive devices 80A, 80B, 80C, 80D, and 80E are essentially the same; therefore, the following explanation will use heater drive device 80A as an example.

[0038] like Figure 4 As shown, the heater drive device 80A has a drive circuit 82A. The drive circuit 82A includes: a power supply 84A, a heater wire 86A, a circuit breaker 88A, a contactor 90A, a thyristor 92A as a power supply, and a galvanometer 94A as a measuring unit.

[0039] Power supply 84A supplies power used by heater wire 86A to drive circuit 82A. In this embodiment, AC power is used as power supply 84A. Furthermore, in this embodiment, power supplies are connected according to drive circuits, but this disclosure is not limited to this structure. For example, the same power supply may be used in multiple drive circuits.

[0040] The heater wire 86A is a component that generates heat by being supplied with electricity. The heater wire 86A constitutes the heating area 24A of the side heater 24.

[0041] Circuit breaker 88A is configured in drive circuit 82A between power supply 84A and heater wire 86A. Circuit breaker 88A is a device that blocks emergency current flowing through drive circuit 82A in the event of a fault or abnormality.

[0042] Contactor 90A is configured in drive circuit 82A between circuit breaker 88A and heater wire 86A. Contactor 90A is a device for opening and closing drive circuit 82A. The opening and closing action of contactor 90A is controlled by an anomaly detection controller 74.

[0043] Thyristor 92A is configured in drive circuit 82A between contactor 90A and heater wire 86A. This thyristor 92A is a device that controls the power supplied from power source 84A to heater wire 86A. The switching (on / off) control of thyristor 92A is performed by temperature control controller 72.

[0044] Ammeter 94A is configured in drive circuit 82A between contactor 90A and heater wire 86A. Ammeter 94A is a measuring instrument that measures the current flowing in drive circuit 82A. The current measurement value obtained by ammeter 94A is sent to an anomaly detection controller 74.

[0045] Additionally, a temperature sensor 25A is positioned near the heater wire 86A. The temperature detected by this temperature sensor 25A is sent to the temperature control controller 72.

[0046] The reaction tube 54 is housed within the furnace space 23 of the furnace body 22. The reaction tube 54 is formed as a cylinder with one end closed in the axial direction. In this embodiment, the reaction tube 54 is configured such that the vertical direction of the heating device 20 is axial, with the upper end in contact with one end in the axial direction closed and the lower end in contact with the other end in the axial direction open. Furthermore, the internal space of the reaction tube 54 will be referred to below as the processing chamber 55. A boat-shaped vessel 68 is housed within this processing chamber 55.

[0047] The reaction tube 54 is connected to the gas inlet tube 56. Specifically, the gas inlet tube 56 passes through the lower peripheral wall of the reaction tube 54, bends midway, and extends upwards towards the reaction tube 54. The interior of the gas inlet tube 56 communicates with the processing chamber 55 of the reaction tube 54. The gas inlet tube 56 is connected to a processing gas supply source (not shown) for supplying processing gas to the substrate W. The processing gas is supplied to the processing chamber 55 via the gas inlet tube 56. In addition, in the section between the processing gas supply source and the reaction tube 54 of the gas inlet tube 56, a flow sensor 58 and a flow control valve 60 are sequentially arranged upstream in the flow direction of the processing gas.

[0048] Additionally, the reaction tube 54 is connected to the gas exhaust pipe 62. The interior of the gas exhaust pipe 62 communicates with the processing chamber 55 of the reaction tube 54. In the gas exhaust pipe 62, a pressure sensor 64 and an APC valve 66 serving as a pressure control unit are sequentially arranged upstream in the gas flow direction. Furthermore, the gas exhaust pipe 62 is a piping used to exhaust the gas (processed gas in this embodiment) inside the processing chamber 55.

[0049] Additionally, within the processing chamber 55 of the reaction tube 54, temperature sensors 67A, 67B, 67C, and 67D are sequentially arranged from above the heating device 20. The detected values ​​(detected temperatures) from each temperature sensor are respectively sent to the temperature control controller 72.

[0050] The boat 68 is a substrate holder for holding the substrate W within the reaction tube 54. The boat 68 is configured to support the substrate W in multiple layers at predetermined intervals in a horizontal position. Furthermore, the boat 68 is mounted to a lifting device (not shown) via a cover 69 that closes the lower end of the reaction tube 54. This lifting device allows the boat 68 to move up and down in the vertical direction of the heating device 20. Here, by operating the lifting device, the substrate W supported by the boat 68 is either loaded into or removed from the reaction tube 54.

[0051] In addition, the substrate processing apparatus 10 has a control system. This control system includes: an apparatus controller 70 as a control unit, a temperature control controller 72 as a temperature adjustment unit, an anomaly detection controller 74 as an anomaly detection unit, a flow control controller 76 as a flow control unit, and a pressure control controller 78 as a pressure control unit.

[0052] The device controller 70 functions as a data collection controller. The device controller 70 is configured to collect device data generated by the substrate processing apparatus 10. This device data includes data related to substrate processing (e.g., measured values) such as processing temperature, processing pressure, and processing gas flow rate when the substrate processing apparatus 10 processes the substrate W; data related to the quality of the product substrate (e.g., film thickness and cumulative film thickness); and data related to the structural components of the substrate processing apparatus 10 (e.g., reaction tubes, heaters, valves, MFCs, etc.) (e.g., setpoints, measured values, number of uses, usage time, etc.). This data is generated by activating various structural components when the substrate processing apparatus 10 processes the substrate W. Additionally, the device data includes event data related to various device events generated in the substrate processing apparatus 10. For example, the event data includes alarm information that generates various alarms.

[0053] Additionally, measured data at specific intervals, such as raw waveform data representing specific intervals (e.g., 1 second) from the start to the end of a process, and statistical data generated by processing measured data at specific intervals in each step of the process, are sometimes referred to as process data as data collected during process execution. This process data is included in the device data. Furthermore, statistical data includes maximum, minimum, and average values. Additionally, event data representing various device events generated when the process is not being executed, such as during idle periods when no substrates are being placed in the device, is also included in the device data. For example, event data may include data representing maintenance history.

[0054] The device controller 70 is electrically connected to the temperature control controller 72, the anomaly detection controller 74, the flow control controller 76, and the pressure control controller 78 via a LAN (Local Area Network) such as 100BASE-T, thus enabling it to transmit and receive data from each device, download and upload files, etc.

[0055] The device controller 70 is provided with a port serving as an assembly for plugging and unplugging a recording medium (such as a USB memory) used as an external storage device. An OS (Operation System) corresponding to this port is installed on the device controller 70. Additionally, a host computer or management device (not shown) is connected to the device controller 70 via a communication network, for example.

[0056] The device controller 70 is configured to collect device data, quantify the device's operating status, and display it on a screen. Additionally, the device controller 70 is configured to execute various functions.

[0057] The temperature control controller 72 is configured to regulate the temperature of the furnace space 23 by controlling the heating temperatures of the side heater 24 and the top heater 26 of the heating device 20, respectively. Specifically, the temperature control controller 72 is configured to adjust the proportion of the power output relative to the power supplied to the heater wire 86A per unit time, in order to reduce the difference between the temperature obtained from the temperature sensor 25A and the temperature setpoint. More specifically, in this embodiment, the temperature control controller 72 is configured to adjust (control) the ratio RA of the time the thyristor 92A is turned on relative to the unit time, in order to reduce the difference between the temperature detected by the temperature sensor 25A and the preset temperature setpoint. Furthermore, the unit time referred to here is the time of one cycle of the sine wave of the power supply 84A, which is the AC power supply. In addition, while the current control of the heater drive device 80A (drive circuit 82A) based on the temperature control controller 72 has been described above, the heater drive devices 80B, 80C, 80D, and 80E are also configured to have the current controlled by the temperature control controller 72 in the same manner as the heater drive device 80A.

[0058] The anomaly detection controller 74 is configured to compare the measured value (hereinafter appropriately referred to as "current measurement value") of the current flowing in the drive circuit 82A in the heater drive device 80A with the theoretical current value. As a result, if an anomaly is determined in a component constituting the drive circuit, an alarm is issued to the device controller 70. Specifically, the anomaly detection controller 74 is configured to compare the measured current value MA measured by the ammeter 94A with the theoretical current value TA calculated based on the ratio of the power output to the heater wire 86A obtained from the temperature control controller 72 (see reference 1). Figure 8 The anomaly detection controller 74 compares the measured current value MA with the theoretical current value TA, and determines an anomaly if the measured current value MA differs from the theoretical current value TA. More specifically, in this embodiment, the anomaly detection controller 74 is configured to compare the measured current value MA with the theoretical current value TA calculated based on the ratio RA of the time the thyristor 92A is turned on, obtained from the temperature control controller 72, and determines an anomaly if the measured current value MA differs from the theoretical current value TA. Furthermore, while the anomaly determination based on the anomaly detection controller 74 for the heater drive device 80A (drive circuit 82A) has been described above, the anomaly determination in heater drive devices 80B, 80C, 80D, and 80E is also configured to perform anomaly determination using the anomaly detection controller 74 in the same way as the drive circuit 82A. Hereinafter, the functional structure of the anomaly detection controller 74 will be described using the heater drive device 80A as an example. Furthermore, the measured current value MA and the theoretical current value TA are, of course, the effective values ​​(RMS).

[0059] The anomaly detection controller 74 is configured such that when the measured current value MA is equal to a preset threshold UA (refer to...). Figure 8 In the above cases, the measured current value MA is not compared with the theoretical current value TA and is judged as abnormal.

[0060] Furthermore, the anomaly detection controller 74 is configured such that when the proportion of the output power obtained from the temperature control controller 72 exceeds the limit value SA of the output set value (see reference). Figure 8 In the event that the theoretical current value TA is not calculated and the system is deemed abnormal, the abnormality detection controller 74 is configured such that if the ratio RA that turns on the thyristor 92A, obtained from the temperature control controller 72, exceeds the preset output setting limit value SA, the system will not calculate the theoretical current value TA and will be deemed abnormal.

[0061] Furthermore, the anomaly detection controller 74 is configured to change contactor 90A to the open state if it does not compare the measured current value MA with the theoretical current value TA and determine that an anomaly has occurred. By setting contactor 90A to the open state in this way, the drive circuit 82A is cut off, stopping the power supply to the heater wire 86A.

[0062] Furthermore, the anomaly detection controller 74 is configured to have an alarm setting value LA. It determines the current to be normal when the difference (absolute value of the difference) between the measured current value MA and the theoretical current value TA is less than the alarm setting value LA, and determines the current to be abnormal when the difference (absolute value of the difference) is greater than or equal to the alarm setting value LA. Specifically, in this embodiment, the anomaly detection controller 74 compares the measured current value MA with the theoretical current value TA. If the measured current value MA and the theoretical current value TA are different, it determines the current to be abnormal; however, if the difference (absolute value of the difference) between the measured current value MA and the theoretical current value TA is less than the alarm setting value LA, it re-determines the current to be normal. On the other hand, it is configured to determine the current to be abnormal when the difference (absolute value of the difference) between the measured current value MA and the theoretical current value TA is greater than or equal to the alarm setting value LA, i.e., it continues the anomaly determination process.

[0063] Furthermore, in the film-forming process of this embodiment, the abnormality detection controller 74 may be configured to compare the measured current value MA with the theoretical current value TA. As a result, if an abnormality is determined, that is, if the measured current value MA is different from the theoretical current value TA, the abnormality detection controller 74 sends the abnormality determination result to the device controller 70 and opens the contactor 90A to stop the heater.

[0064] Furthermore, even in the temperature adjustment process (including heating and cooling operations) of this embodiment, the abnormality detection controller 74 may be configured to compare the measured current value MA with the theoretical current value TA, and determine an abnormality if the measured current value MA and the theoretical current value TA are different. However, it is preferable to determine normality if the difference (absolute value of the difference) between the measured current value MA and the theoretical current value TA is less than the alarm setting value LA. On the other hand, it is preferable to determine an abnormality if the difference (absolute value of the difference) between the measured current value MA and the theoretical current value TA is greater than or equal to the alarm setting value LA. That is, it is preferable to determine a warning (alarm) if the measured current value MA and the theoretical current value TA are different, and to determine an abnormality if the difference between the measured current value MA and the theoretical current value TA exceeds a threshold.

[0065] For example, it is preferable that the alarm setting value LA is 0 in the film formation process and a predetermined value that is not 0 in the temperature adjustment process. In this way, the alarm setting value LA can also be changed through the process. Furthermore, the presence or absence of anomaly detection can also be set through the process. Moreover, the anomaly detection controller 74 of this embodiment is configured to change the alarm setting value LA according to the ratio at which the thyristor 92A is turned on. Specifically, in this embodiment, the alarm setting value LA is not constant, such as... Figure 8 As shown in the alarm setting, it varies proportionally according to the ratio at which thyristor 92A is turned on. Furthermore, Figure 8 The alarm setting value shown is obtained by adding the alarm setting value LA to the theoretical current value TA.

[0066] Furthermore, in this embodiment, the alarm setting value can be changed according to the heater drive device. For example, the alarm setting value can be changed separately in the heater drive device 80A for the heating area 24A of the side heater 24 and the heater drive device 80D for the heating area 24D. In addition, this disclosure is not limited to the above structure, and the alarm setting value can be set to the same value in all heater drive devices.

[0067] In addition, the anomaly detection controller 74 includes: a first comparison unit 120, an acquisition unit 122, an arithmetic unit 124, a second comparison unit 126, and a third comparison unit 128.

[0068] The first comparison unit 120 is configured to compare the current measurement value MA with the threshold value UA.

[0069] The acquisition unit 122 is configured to acquire the ratio of the output power from the temperature control controller 72. Specifically, in this embodiment, the acquisition unit 122 is configured to acquire the ratio RA for turning on the thyristor 92A from the temperature control controller 72.

[0070] The calculation unit 124 is configured to calculate the theoretical current value TA based on the proportion of the output power obtained from the temperature control controller 72. Specifically, in this embodiment, the calculation unit 124 is configured to calculate the theoretical current value TA based on the ratio RA at which the thyristor 92A is turned on, obtained from the temperature control controller 72.

[0071] The second comparison unit 126 is configured to compare the ratio of the output power obtained from the temperature control controller 72 with the output setpoint limit value SA. Specifically, in this embodiment, the second comparison unit 126 is configured to compare the ratio of the thyristor 92A to be turned on obtained from the temperature control controller 72 with the output setpoint limit value SA.

[0072] The third comparison unit 128 is configured to compare the measured current value MA with the theoretical current value TA.

[0073] The flow control controller 76 controls the flow control valve 60 and controls the flow rate of the gas introduced into the reaction tube 54 of the processing chamber 55, so that the measured value of the gas flow rate measured by the flow sensor 58 is equal to the set measured value of the gas flow rate. Specifically, the flow control controller 76 in this embodiment is a mass flow controller (hereinafter, appropriately referred to as "MFC").

[0074] The pressure control controller 78 is connected to the pressure sensor 64 and the APC valve 66. The pressure control controller 78 is configured to control the opening degree of the APC valve 66 and the on / off state of the vacuum pump (not shown) based on the pressure value detected by the pressure sensor 64, so that the pressure in the processing chamber 55 becomes the desired pressure at a desired timing.

[0075] Temperature control controller 72, anomaly detection controller 74, flow control controller 76 and pressure control controller 78 are configured such that, in addition to their respective control functions, they can also report the status, alarms indicating faults detected based on sensor information, and the values ​​of each connected sensor as monitoring data to the device controller 70 in real time.

[0076] Furthermore, the device controller 70, temperature control controller 72, anomaly detection controller 74, flow control controller 76, and pressure control controller 78 of this embodiment do not depend on a dedicated system and can be implemented using a conventional computer system. For example, by installing a program stored on a recording medium (floppy disk, CD-ROM, USB memory, etc.) for performing the above-described processes onto a general-purpose computer, each controller that performs the specified processes can be configured.

[0077] Furthermore, the unit used to supply these programs is arbitrary. Besides being supplied via a specified recording medium as described above, it can also be supplied via, for example, a communication line, communication network, or communication system. In this case, for example, the program can be advertised on a bulletin board of the communication network, or provided by overlaying the program onto a carrier wave via the network. Furthermore, when such a provided program is launched, it executes under the control of the OS, just like other applications, thereby enabling the performance of specified processes.

[0078] Next, refer to Figure 3 The structure of the device controller 70 will be described. The device controller 70 is configured to include: a device control unit 100; a device storage unit 102 as a hard disk; an operation display unit 104, which includes a display unit for displaying various information and an input unit for receiving various instructions from the operator; and a communication unit 106, which communicates with the board processing device 10 internally and externally. Here, the operator includes not only the device operator but also device managers, device engineers, maintenance personnel, and operators. The device control unit 100 is configured as a computer, which includes a CPU (Central Processing Unit) 108 as a processing unit, a memory (RAM, ROM, etc.) 110 as temporary storage, and has a clock function (not shown).

[0079] In the device storage unit 102, in addition to process files that define the processing conditions and processing procedures of the substrate, control program files for executing these process files, parameter files that define the parameters for executing the process, error handling program files and error handling parameter files, it also stores various screen files and various icon files (not shown) that contain input screens for inputting process parameters.

[0080] In addition, the device storage unit 102 stores monitoring data containing sensor information output from each controller, as well as alarm history indicating alarms for faults detected by each controller based on the sensor information.

[0081] In addition, operation buttons can also be set as input units in the operation display unit 104, which input operation instructions to the substrate transport system and the substrate processing system.

[0082] The operation display unit 104 displays an operation screen for operating the substrate processing apparatus 10. The operation display unit 104 displays information based on device data generated within the substrate processing apparatus 10 via the operation screen. The operation screen of the operation display unit 104 may be, for example, a touch panel using a liquid crystal display. The operation display unit 104 receives input data (input instructions) from the operator via the operation screen and sends the input data to the device controller 70. Furthermore, the operation display unit 104 is configured to receive instructions (control instructions) for executing a process performed in the memory (RAM) 110 or similar, or for any of the multiple processes stored in the device storage unit 102, of the substrate processing process (also called a process flow), and sends these instructions to the device control unit 100.

[0083] In addition, the operation display unit 104 displays alarm information on the operation screen that indicates the type of alarm for a fault detected by the controller in the event data generated in the board processing device 10.

[0084] Furthermore, in this embodiment, when the device controller 70 is started, various programs are executed to expand the stored screen files and data tables, read the device data, and thereby display each screen indicating the operating status of the device on the operation display unit 104.

[0085] The communication unit 106 is connected to the switch hub, etc. The device controller 70 is configured to send and receive various data with an external computer and other controllers (temperature control controller 72, anomaly detection controller 74, flow control controller 76, and pressure control controller 78) within the board processing device 10 via a network.

[0086] The device controller 70 can also send device data, such as the status of the substrate processing apparatus 10, to an external host computer via a network (not shown). Furthermore, the substrate processing of the substrate processing apparatus 10 is controlled by the control system based on process files, parameter files, etc., stored in the device storage unit 102.

[0087] Furthermore, the device controller 70 is configured to execute a process comprising multiple steps as described above. In the temperature adjustment step (including heating and cooling operations), the device controller 70 uses an anomaly detection controller 74 to compare the measured current value of each drive circuit with the theoretical current value. At this time, the anomaly detection controller 74 determines that the process is normal if the absolute value of the difference between the measured current value and the theoretical current value is less than an alarm setting value, and determines that the process is abnormal if the absolute value of the difference is greater than or equal to the alarm setting value, and sends the determination result to the device controller 70. Additionally, in the film formation process, the device controller 70 uses an anomaly detection controller 74 to compare the measured current value of each drive circuit with the theoretical current value. At this time, if the anomaly detection controller 74 determines that the measured current value MA differs from the theoretical current value TA, it sends the anomaly determination result to the device controller 70 and opens the contactor 90A to stop the heater. Furthermore, the device controller 70 terminates the film formation process due to an anomaly.

[0088] In addition, the device controller 70 is configured, for example, to cause the anomaly detection controller 74 to perform anomaly detection of the drive circuit every one cycle (unit time) of the sine wave of the AC power supply.

[0089] Next, a substrate processing method having a predetermined processing step, implemented using the substrate processing apparatus 10 of this embodiment, will be described. Here, the predetermined processing step is exemplified by a substrate processing step (here, a film deposition process) that is a step in the manufacturing process of a semiconductor device.

[0090] In the substrate processing step, an example of forming a film on an untreated substrate W by supplying a specified processing gas to the untreated substrate W will be described.

[0091] (Substrate handling process)

[0092] First, multiple untreated substrates W are loaded (supported) onto the boat 68. After loading, the boat 68 is moved into the processing chamber 55 by a lifting device (not shown). When the boat 68 is moved into the processing chamber 55, the lower opening of the reaction tube 54 is hermetically closed (sealed) by the cover 69.

[0093] (Pressure adjustment process)

[0094] Vacuum exhaust (pressure reduction exhaust) is performed using a vacuum pump (not shown) to bring the processing chamber 55 to a specified pressure (vacuum level). The pressure inside the processing chamber 55 is measured by a pressure sensor 64, and the APC valve 66 is controlled by feedback based on the measured pressure information.

[0095] (Temperature adjustment process)

[0096] The reaction tube 54 and processing chamber 55 are heated via the furnace space 23 using side heaters 24 and top heaters 26 to bring the untreated substrate W in the processing chamber 55 to a predetermined temperature. This maintains the temperature within the processing chamber 55. At this time, based on temperature information detected by temperature sensors 25A, 25B, 25C, 25D, and 25E, feedback control is performed on the energizing of each heating area of ​​the side heaters 24 and the top heater 26 to ensure that the processing chamber 55 achieves a predetermined temperature distribution.

[0097] Specifically, the conduction ratio of the thyristors supplying power to the heater wires is adjusted to reduce the difference between the heater temperature and the set temperature. Additionally, rotation of the boat 68 and the untreated substrate W is initiated via a rotating mechanism (not shown). Heating within the processing chamber 55, based on the side heaters 24 and the top heater 26, continues at least until the film deposition process is completed. Furthermore, in this embodiment, during the temperature adjustment process, upon receiving a request from the device controller 70, the anomaly detection controller 74 performs anomaly detection at predetermined intervals.

[0098] (Film-forming process)

[0099] When the temperature inside the processing chamber 55 stabilizes at a preset processing temperature, processing gas is supplied to the untreated substrate W inside the processing chamber 55. The processing gas is controlled to a desired flow rate by the flow control controller 76 and supplied to the processing chamber 55 via the gas inlet pipe 56. This performs a predetermined process (e.g., film formation) on the substrate W. Next, the supply of processing gas is stopped, and a vacuum pump (not shown) is used to evacuate the processing chamber 55. At this time, an inactive gas may also be supplied to the processing chamber 55 (inactive gas purging). Furthermore, in this embodiment, during the film formation process, upon receiving a request from the device controller 70, the anomaly detection controller 74 performs anomaly detection at predetermined intervals.

[0100] (Substrate removal process)

[0101] After forming a film of the specified thickness, cooling gas is supplied into the processing chamber 55, displacing the contents of the chamber and restoring the pressure to atmospheric pressure. Then, the cover 69 is lowered using a lifting device, and the boat 68 is removed from the reaction tube 54. Afterward, the processed substrate W is removed from the boat 68.

[0102] Next, the anomaly detection method of this disclosure will be described. First, during the film formation process, the device controller 70 causes the anomaly detection controller 74 to execute the first anomaly detection method, and during the temperature adjustment process, the anomaly detection controller 74 executes the second anomaly detection method. Furthermore, the anomaly detection method will be described below using a heater as an example.

[0103] <First Anomaly Detection Method>

[0104] First, the temperature of the heater is detected using a corresponding temperature sensor (step S200). The detected temperature is then sent to the temperature control controller 72.

[0105] Next, the current flowing in the drive circuit is measured using a galvanometer (step S202). The measured current value is sent to the anomaly detection controller 74.

[0106] Next, the anomaly detection controller 74 obtains the current value (current measurement value) measured by the ammeter (step S204). In addition, the anomaly detection controller 74 obtains the ratio at which the thyristor is turned on from the temperature control controller 72 (step S206).

[0107] Next, the anomaly detection controller 74 compares the ratio at which the thyristor is turned on with the limit value of the output setting (step S208). If the ratio exceeds the limit value, the theoretical current value is not calculated, an anomaly is determined, an alarm is issued (step S210), and the contactor 90A on the drive circuit is turned on (step S212). As a result, the heater stops. On the other hand, if the ratio is below the limit value, the process proceeds to the next step S214.

[0108] Next, the anomaly detection controller 74 compares the measured current value with a threshold (step S214). If the measured current value is above the threshold, it does not compare the measured current value with the theoretical current value and determines it as an anomaly, issuing an alarm (step S210), and opening the contactor 90A on the drive circuit (step S212). Thus, the heater stops. On the other hand, if the ratio is below the limit value, it proceeds to the next step S216.

[0109] Next, the anomaly detection controller 74 calculates the theoretical current value based on the thyristor conduction rate (step S216). Then, the anomaly detection controller 74 compares the measured current value with the theoretical current value (step S218). If the measured current value differs from the theoretical current value, an anomaly is determined, an alarm is issued (step S210), and the contactor 90A on the drive circuit is activated (step S212). Thus, the heater stops. On the other hand, if the measured current value is the same as the theoretical current value, the anomaly detection controller 74 determines that it is normal. If the determination result from the anomaly detection controller 74 is normal, the device controller 70 continues the film deposition process based on the substrate processing apparatus 10.

[0110] <Second Anomaly Detection Method>

[0111] First, the temperature of the heater is detected using a corresponding temperature sensor (step S220). The detected temperature is then sent to the temperature control controller 72.

[0112] Next, the current flowing in the drive circuit is measured using a galvanometer (step S222). The measured current value is sent to the anomaly detection controller 74.

[0113] Next, the anomaly detection controller 74 obtains the current value (current measurement value) measured by the ammeter (step S224). In addition, the anomaly detection controller 74 obtains the ratio at which the thyristor is turned on from the temperature control controller 72 (step S226).

[0114] Next, the anomaly detection controller 74 compares the ratio at which the thyristor is turned on with the limit value of the output setting (step S228). If the ratio exceeds the limit value, the theoretical current value is not calculated, an anomaly is determined, an alarm is issued (step S230), and the contactor 90A on the drive circuit is turned on (step S232). As a result, the heater stops. On the other hand, if the ratio is below the limit value, the process proceeds to the next step S234.

[0115] Next, the anomaly detection controller 74 compares the measured current value with a threshold (step S234). If the measured current value is above the threshold, it does not compare the measured current value with the theoretical current value, determines it as an anomaly, issues an alarm (step S230), and opens the contactor 90A on the drive circuit (step S232). Thus, the heater stops. On the other hand, if the ratio is below the limit value, it proceeds to the next step S236.

[0116] Next, the anomaly detection controller 74 calculates the theoretical current value based on the ratio at which the thyristor is turned on (step S236). Then, the anomaly detection controller 74 compares the measured current value with the theoretical current value (step S238). If the measured current value differs from the theoretical current value, an anomaly is determined, and the process proceeds to step S240. Conversely, if the measured current value is the same as the theoretical current value, the anomaly detection controller 74 determines that the process is normal.

[0117] Next, the anomaly detection controller 74 calculates the difference (absolute value of the difference) between the measured current value and the theoretical current value (step S240). Then, it compares the difference between the measured current value and the theoretical current value with an alarm setting value (step S242). If the difference is greater than or equal to the alarm setting value, an anomaly is determined, and an alarm is issued (step S244). On the other hand, if the difference between the measured current value and the theoretical current value is less than the alarm setting value, it is determined to be normal. If the determination result from the anomaly detection controller 74 is normal, the device controller 70 continues to adjust the temperature based on the substrate processing device 10.

[0118] The procedure in this embodiment is an anomaly determination procedure executed by a substrate processing apparatus 10, which includes: a heater that raises the temperature of a processing chamber 55 by heating; a thyristor that supplies power to heater wires included in the heater; a temperature sensor that detects the temperature of the heater; a temperature control controller 72 that adjusts the ratio at which the thyristor is turned on (relative to the ratio of the time the thyristor is turned on per unit time) to reduce the difference between the temperature detected by the temperature sensor and the temperature setpoint; and an ammeter that measures the current flowing in the drive circuit. The procedure causes the substrate processing apparatus 10 to perform the following process: comparing the current measured by the ammeter with the theoretical current value calculated based on the ratio obtained from the temperature control controller 72, and determining an anomaly if the current measured value differs from the theoretical current value.

[0119] Next, the operation and effects of this embodiment will be explained. In conventional substrate processing apparatuses, a short-circuit mode exists as a failure mode for the thyristor included in the drive circuit of the heater. In the state of thyristor short-circuiting, 100% of the power from the AC power supply is applied to the heater. In this state, the temperature rises indefinitely before the heater reaches thermal equilibrium through the cooling mechanism, etc., and therefore, starting from a defect in the substrate W, a failure may occur in the substrate processing apparatus. Therefore, protection mechanisms are sometimes provided to monitor the temperature inside the processing chamber and cut off the power when it exceeds a threshold. However, in the state of thyristor failure and 100% power being applied to the heater, the temperature rise rate of the processing chamber is faster than in the normal control state, and the temperature distribution inside the processing chamber is also prone to becoming uneven. Therefore, when the power to the heater drive circuit is cut off, a failure may occur in the substrate processing apparatus. In contrast, in the substrate processing apparatus 10 of this embodiment, the measured current value is compared with the theoretical current value, and an anomaly is determined when the measured current value differs from the theoretical current value. Therefore, it is possible to reliably detect any failure in any component constituting the drive circuit. Furthermore, it can detect minute errors between the measured current value and the theoretical current value, thus enabling the detection of early signs of malfunctions in components constituting the drive circuit. Therefore, in this embodiment, by detecting the overcurrent during a short-circuit fault in the thyristor and interrupting the power supply to the heater, accidents caused by abnormal overheating of the heater can be suppressed.

[0120] In addition, in this embodiment, the ratio at which the thyristor is turned on is compared with the limit value of the output setting. If the ratio exceeds the limit value, the theoretical current value is not calculated and it is determined to be abnormal (the component constituting the drive circuit has failed). Therefore, it is possible to reliably detect the breakage of the heater wire.

[0121] Furthermore, in this embodiment, the measured current value is compared with a threshold value. If the measured current value is above the threshold value, the measured current value is not compared with the theoretical current value and is determined to be abnormal. That is, by comparing the measured current value with the threshold value, the occurrence of short-circuit faults (short circuits) of the thyristor can be reliably detected. Moreover, in this embodiment, by detecting a small error between the measured current value and the theoretical current value, a warning (alarm) can be issued before a component constituting the drive circuit malfunctions. In addition, in the substrate processing apparatus 10 of this embodiment, if the apparatus controller 70 receives a warning before a component constituting the drive circuit malfunctions, maintenance can be performed instead of executing the next batch of processing to prevent short-circuit faults from occurring in the film deposition process.

[0122] Furthermore, in this embodiment, if the anomaly detection controller 74 determines an anomaly by not comparing the measured current value with the theoretical current value, it changes the contactor to the open state. Therefore, in the event of an overcurrent or thyristor short-circuit fault, the impact on normally functioning components of the drive circuit can be suppressed. Additionally, the impact on the substrate W and substrate processing apparatus 10 during processing can also be suppressed.

[0123] Furthermore, in the substrate processing apparatus 10 of this embodiment, if the difference between the measured current value and the theoretical current value exceeds a limit value set by the output, an abnormality is determined and an alarm is issued. Therefore, it is possible to detect the details of even minute errors. Thus, for example, it is possible to estimate the extent to which a deviation has caused a precursor to an abnormality.

[0124] In this embodiment, the alarm setting value can be changed according to the ratio at which the thyristor is turned on. It can be assumed that when the ratio at which the thyristor is turned on increases, the load on the heater side increases; therefore, by increasing the alarm setting value as the ratio increases, it is expected that more accurate warnings of abnormalities can be detected. Furthermore, when the ratio at which the thyristor is turned on is low, the alarm setting value can be set to zero.

[0125] Furthermore, in this embodiment, alarm settings are changed according to the heater. In other words, alarm settings are set for each heating area of ​​the side heater 24 and the top heater 26. When the substrate processing apparatus 10 is a vertical assembly, it is assumed that the power supplied to the lower heating area of ​​the side heater 24 is large, resulting in a high load on the drive circuit. Therefore, by setting the alarm settings for the lower heating area of ​​the side heater 24 to be larger than those for the upper heating area, accurate signs of anomalies can be expected to be detected. Additionally, in the lower heating area of ​​the side heater 24, monitoring whether the difference between the measured current value and the theoretical current value exceeds the alarm settings detects signs of anomalies; in the upper heating area, comparing the theoretical current value with the measured current value allows for anomaly detection based on the presence or absence of a difference. This enables detailed anomaly detection.

[0126] Furthermore, in this embodiment, when the substrate processing apparatus 10 is a vertical assembly, the power consumption is considered high during the heating and cooling steps, resulting in a large load on the heater side. Therefore, the difference between the theoretical current calculated based on the thyristor conduction ratio and the measured current value is monitored to detect any signs of an anomaly. Additionally, a constant temperature is maintained throughout the film deposition process, thus the load is considered relatively stable. By comparing the theoretical current value calculated based on the thyristor conduction ratio with the measured current value, and detecting any discrepancies, detailed and accurate anomaly detection is possible.

[0127] In the substrate processing apparatus of this embodiment, an anomaly detection controller 74 performs anomaly determination for multiple heater drive devices, but this disclosure is not limited to this structure. Alternatively, the anomaly detection controller 74 can be set according to the heater drive device, and the anomaly determination for each heater drive device can be performed separately using the corresponding anomaly detection controller 74. Furthermore, after an anomaly determination, the contactor 90A is set to open, but the circuit breaker 88A can also be set to open.

[0128] In the substrate processing apparatus of this embodiment, a dedicated controller is used as the anomaly detection controller 74, but this disclosure is not limited to this structure. For example, as Figure 9 As shown, a general-purpose computer 130 can also be used as the anomaly detection controller 74. In this case, the program is installed from a recording medium (floppy disk, CD-ROM, USB memory, etc.) containing a program for performing anomaly detection processing onto the general-purpose computer 130, thereby enabling the configuration of a controller for performing anomaly detection processing.

[0129] In addition, the substrate processing apparatus heats the furnace space 23 using the side heater 24 and the top heater 26, but it may also have a cooling mechanism for cooling the furnace space 23. As such a cooling mechanism, for example, a mechanism that supplies cooling gas to the furnace space 23 to forcibly cool the furnace space 23 is provided.

[0130] This application asserts a priority interest based on Japanese Application Japan Special Purpose No. 2021-040823, filed on March 12, 2021, the entire disclosure of which is incorporated herein by reference.

[0131] Industrial utilization potential

[0132] This disclosure can be applied to devices equipped with heating units that heat the workpiece. In particular, this disclosure can also be applied to techniques related to the detection of anomalies or early signs of anomalies in heating units.

[0133] Explanation of reference numerals in the attached figures

[0134] 10. Substrate processing apparatus.

Claims

1. A substrate processing apparatus, characterized in that, have: The processing chamber, which processes the substrate; A heating element that raises the temperature of the processing chamber; A thyristor that supplies power to the heating element; A temperature detection unit that detects the temperature of the heating element; The temperature adjustment unit adjusts the conduction ratio of the thyristor to reduce the difference between the temperature detected by the temperature detection unit and the temperature set value. A measuring unit that measures the current flowing in a circuit including the heating element and the thyristor; The anomaly detection unit compares the current measurement value obtained by the measuring unit with the theoretical current value calculated based on the ratio obtained from the temperature adjustment unit, and determines an anomaly if the current measurement value differs from the theoretical current value. The anomaly detection unit also has an alarm setting value. The anomaly detection unit determines that the current is normal if the difference between the measured current value and the theoretical current value is less than the alarm setting value, and determines that the current is abnormal if the difference between the measured current value and the theoretical current value is greater than or equal to the alarm setting value. The anomaly detection unit is configured to change the alarm setting value according to the ratio at which the thyristor is turned on.

2. The substrate processing apparatus according to claim 1, characterized in that, If the measured current value is above the threshold, the anomaly detection unit does not compare the measured current value with the theoretical current value and determines it to be abnormal.

3. The substrate processing apparatus according to claim 1, characterized in that, If the rate at which the thyristor is turned on exceeds the limit of the output setting value, the abnormality detection unit does not calculate the theoretical current value and determines it to be abnormal.

4. The substrate processing apparatus according to claim 2 or 3, characterized in that, The anomaly detection unit is configured to connect to a contactor included in the circuit, and to change the contactor to an open state if the measured current value and the theoretical current value are not compared and an anomaly is determined.

5. The substrate processing apparatus according to claim 1, characterized in that, The anomaly detection unit includes: a first comparison unit that compares the measured current value obtained by the measurement unit with a set value; an acquisition unit that obtains the ratio at which the thyristor is turned on from the temperature adjustment unit; a calculation unit that calculates a theoretical current value based on the ratio; a second comparison unit that compares the ratio at which the thyristor is turned on with a limit value of the output set value; and a third comparison unit that compares the measured current value with the theoretical current value.

6. The substrate processing apparatus according to claim 1, characterized in that, The ratio is the time it takes for the thyristor to conduct relative to one cycle of the sine wave of the AC power supply contained in the circuit.

7. The substrate processing apparatus according to claim 1, characterized in that, The substrate processing apparatus further includes multiple heating regions comprising the heating element. The alarm settings are configured to be changeable based on the heat-generating area.

8. The substrate processing apparatus according to claim 1, characterized in that, The substrate processing apparatus further includes a control unit that executes a process comprising multiple steps. The control unit is configured to, during the heating or cooling step, cause the anomaly detection unit to perform the following anomaly detection: if the difference between the measured current value and the theoretical current value is less than an alarm setting value, it is determined to be normal; if the difference between the measured current value and the theoretical current value is greater than or equal to an alarm setting value, it is determined to be abnormal.

9. The substrate processing apparatus according to claim 1, characterized in that, The substrate processing apparatus further includes a control unit that executes a process comprising multiple steps. The control unit is configured such that, during the film formation step, the anomaly detection unit performs the following anomaly detection: if the measured current value differs from the theoretical current value, it is determined to be an anomaly.

10. The substrate processing apparatus according to claim 9, characterized in that, The control unit is configured to cause an abnormal termination of the film formation step if the measured current value differs from the theoretical current value.

11. The substrate processing apparatus according to claim 8 or 9, characterized in that, The control unit is configured to cause the anomaly detection unit to perform anomaly detection every one cycle of the sine wave of the AC power supply contained in the circuit.

12. An anomaly detection method, characterized in that, have: The process of detecting the temperature of the heating element that raises the temperature of the processing chamber by generating heat; A process of adjusting the conduction ratio of the thyristor supplying power to the heating element in order to reduce the difference between the temperature of the heating element and the temperature set value. A process of measuring the current flowing in a circuit including the heating element and the thyristor; A process is deemed abnormal if the measured current value obtained during the current measurement step is compared with the theoretical current value calculated during the adjustment step, and the measured current value differs from the theoretical current value. A current is considered normal if the difference between the measured current value and the theoretical current value is less than the alarm setting value, and an abnormal current is considered abnormal if the difference between the measured current value and the theoretical current value is greater than or equal to the alarm setting value. The alarm setting value is changed according to the ratio at which the thyristor is turned on.

13. A method for manufacturing a semiconductor device, characterized in that, have: The process of detecting the temperature of the heating element that raises the temperature of the processing chamber by generating heat; A process of adjusting the conduction ratio of the thyristor supplying power to the heating element in order to reduce the difference between the temperature of the heating element and the temperature set value; The process of heating a substrate disposed in the processing chamber while supplying adjusted power to the heating element through the thyristor. The process of heating the substrate includes: A process of measuring the current flowing in a circuit including the heating element and the thyristor; A process is deemed abnormal if the measured current value obtained during the current measurement step is compared with the theoretical current value calculated during the adjustment step, and the measured current value differs from the theoretical current value. A current is considered normal if the difference between the measured current value and the theoretical current value is less than the alarm setting value, and an abnormal current is considered abnormal if the difference between the measured current value and the theoretical current value is greater than or equal to the alarm setting value. The alarm setting value is changed according to the ratio at which the thyristor is turned on.

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