Ignition control method and substrate processing apparatus

Abstract

To enhance the accuracy of a preset value of a variable reactor.SOLUTION: An ignition control method is executed by a substrate processing apparatus comprising: an impedance matching device having an electronic circuit that controls a pair of electrodes in a processing container, a variable reactor, and a current that is passed to the variable reactor; an RF power supply that is connected to the pair of electrodes via the impedance matching device; and a temperature sensor for detecting a temperature of the variable reactor. The ignition control method includes steps of: setting the temperature of the variable reactor to a first temperature; measuring first information indicating an inter-electrode voltage for each of a plurality of adjustment positions of the variable reactor when a high-frequency voltage is applied to the electrode from the RF power supply; determining a preset value of the variable reactor on the basis of the first information measured; controlling the electronic circuit so that the adjustment position of the variable reactor becomes the preset value determined in the case where a second temperature is different from the first temperature by setting the temperature of the variable reactor detected as the second temperature; and correcting the current to be passed to the variable reactor.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present disclosure relates to an ignition control method and a substrate processing apparatus. [Background technology]

[0002] By setting the adjustment position of a variable capacitor or variable reactor of the impedance matching device to an appropriate position (preset value) immediately before application of the high frequency voltage, plasma can be ignited stably.

[0003] For example, Patent Document 1 discloses an electronic matcher that does not include any mechanical elements and is capable of performing impedance matching at high speed. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2017-118434 A Summary of the Invention [Problem to be solved by the invention]

[0005] The present disclosure provides a technique that can improve the accuracy of the preset value of a variable reactor. [Means for solving the problem]

[0006] According to one aspect of the present disclosure, an ignition control method is performed in a substrate processing apparatus including a processing vessel for accommodating a substrate, a pair of electrodes formed in the processing vessel, an impedance matching device having a variable reactor and an electronic circuit for controlling a current flowing through the variable reactor, an RF power source connected to the pair of electrodes via the impedance matching device, and a temperature sensor for detecting a temperature of the variable reactor. The ignition control method includes: (a) measuring first information indicating a voltage between the electrodes for each of a plurality of adjustment positions of the variable reactor when a temperature of the variable reactor is set to a first temperature and a high frequency voltage of a predetermined frequency is applied from the RF power source to the pair of electrodes; (b) determining a preset value of the variable reactor based on the measured first information; (c) acquiring the temperature of the variable reactor detected by the temperature sensor as a second temperature; and (d) correcting the current flowing through the variable reactor by controlling the electronic circuit so that the adjustment position of the variable reactor at the second temperature becomes the determined preset value when the first temperature and the second temperature are different. Effect of the Invention

[0007] According to one aspect, the accuracy of the preset value of the variable reactor can be improved. [Brief description of the drawings]

[0008] [Figure 1] FIG. 1 is a diagram showing an example of the arrangement of a substrate processing apparatus according to an embodiment; [Diagram 2] FIG. 2 is a diagram showing an example of the configuration of an impedance matching device and a plasma box according to an embodiment; [Diagram 3] FIG. 2 is a diagram showing an outline of the operation of a variable reactor. [Figure 4] FIG. 1 is a diagram for explaining temperature changes in a variable reactor and issues that arise when plasma is ignited. [Diagram 5] FIG. 2 is an explanatory diagram of a gas supply source, a control unit, and a controller of the substrate processing apparatus according to the embodiment. [Figure 6] 4 is a flowchart showing an ignition control method according to one embodiment. [Figure 7] 13 is an example of an interelectrode voltage table for each adjustment position of a variable reactor. [Figure 8] 7 is a flowchart showing an example of the correction process in FIG. 6. [Figure 9] 4 is an example of a control current table for a variable reactor according to an embodiment. [Figure 10] 7 is a flowchart showing an example of the film forming process of FIG. 6. [Figure 11] 11 is a time chart showing an example of the film forming process of FIG. 10. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] Hereinafter, an embodiment of the present disclosure will be described with reference to the drawings. In the drawings, the same components are denoted by the same reference numerals, and duplicated descriptions may be omitted.

[0010] [Introduction] In plasma deposition, high quality and deposition speed are required. In addition, various gases are now used to generate plasma, from plasma processing using a single gas to plasma processing using multiple gases.

[0011] The minimum ignition voltage of each gas varies depending on the gas used, as is known from the Paschen's curve. Therefore, the minimum ignition voltage required for plasma ignition varies depending on the gas used. Therefore, stable plasma ignition without reflected waves is required for each different gas. In order to improve the quality of the deposited film, it is also necessary to deal with the effects of temperature changes caused by plasma, reaction products generated by deposition, and regular cleaning of the processing vessel to remove reaction products.

[0012] In order to control these at high speed, a variable reactor is provided in the impedance matching device, and the impedance is matched by the impedance matching device using the variable reactor. During plasma ignition, it is necessary to set the adjustment position of the variable reactor in the impedance matching device to an appropriate position (called a preset value) and match the impedance, but the temperature of the variable reactor changes depending on the environmental temperature and the operation of the device, and the appropriate preset value changes. Therefore, in this embodiment, an ignition control method and a substrate processing apparatus are provided that can improve the accuracy of the preset value of the variable reactor according to the temperature of the variable reactor and perform stable plasma ignition.

[0013] In the following, a substrate processing apparatus that executes an ignition control method according to this embodiment will be described with reference to FIG. 1, and then the ignition control method according to this embodiment will be described.

[0014] [Substrate processing equipment] 1 is a diagram showing a substrate processing apparatus 10 according to an embodiment. The substrate processing apparatus 10 is an ALD (Atomic Layer Deposition) apparatus that accommodates a plurality of wafers 2 in a processing vessel 11 and forms a predetermined film, such as a nitride film, on the plurality of wafers 2, and is a batch-type vertical heat processing apparatus that processes a plurality of wafers. The substrate processing apparatus 10 is an example of an apparatus that executes an ignition control method according to an embodiment described later.

[0015] In the substrate processing apparatus 10 according to this embodiment, for example, a silicon nitride film (SiN) is formed, but the type of film to be formed is not limited to this. The silicon nitride film is formed on the wafer 2 by alternately supplying the plasma of a source gas (e.g., dichlorosilane gas) and a nitriding gas (e.g., ammonia (NH3) gas) to the wafer. In this film forming method, the thickness of the nitride film formed within the surface of the wafer 2 tends to be thicker at the edge of the wafer 2. To suppress this, the plasma of nitrogen (N2) gas is supplied before the step of supplying the plasma of ammonia gas, thereby suppressing the thickness of the film at the edge of the wafer 2.

[0016] The substrate processing apparatus 10 includes a processing vessel 11 that accommodates the wafers 2 and defines an internal space in which the wafers 2 are processed, a lid 20 that airtightly closes an opening at the bottom of the processing vessel 11, and a substrate holder 30 that holds the wafers 2. The wafers 2 are, for example, semiconductor substrates, and more specifically, silicon wafers. The substrate holder 30 is also called a wafer boat.

[0017] The processing vessel 11 has a cylindrical processing vessel body 12 with a ceiling and an open lower end. The processing vessel body 12 is made of, for example, quartz. A flange portion 13 is formed at the lower end of the processing vessel body 12. The processing vessel 11 also has, for example, a cylindrical manifold 14. The manifold 14 is made of, for example, stainless steel. A flange portion 15 is formed at the upper end of the manifold 14, and the flange portion 13 of the processing vessel body 12 is installed on the flange portion 15. A seal member 16, such as an O-ring, is arranged between the flange portion 15 and the flange portion 13.

[0018] The lid 20 is airtightly attached to the opening at the lower end of the manifold 14 via a seal member 21 such as an O-ring. The lid 20 is made of, for example, stainless steel. A through hole is formed in the center of the lid 20, passing through the lid 20 in the vertical direction. A rotating shaft 24 is disposed in the through hole. The gap between the lid 20 and the rotating shaft 24 is sealed by a magnetic fluid seal unit 23. The lower end of the rotating shaft 24 is rotatably supported by an arm 26 of a lift unit 25. A rotating plate 27 is provided at the upper end of the rotating shaft 24. A substrate holder 30 is placed on the rotating plate 27 via a heat retention table 28.

[0019] The substrate holder 30 holds the plurality of wafers 2 at intervals in the vertical direction. The plurality of wafers 2 are held horizontally. The substrate holder 30 is formed of, for example, quartz (SiO2) or silicon carbide (SiC). When the lifting part 25 is raised, the lid body 20 and the substrate holder 30 are raised, and the substrate holder 30 is carried into the inside of the processing vessel 11, and the opening at the lower end of the processing vessel 11 is sealed by the lid body 20. When the lifting part 25 is lowered, the lid body 20 and the substrate holder 30 are lowered, and the substrate holder 30 is carried out to the outside of the processing vessel 11. When the rotating shaft 24 is rotated, the substrate holder 30 rotates together with the rotating plate 27.

[0020] The substrate processing apparatus 10 has three gas supply pipes 40A, 40B, and 40C. The gas supply pipes 40A, 40B, and 40C are made of, for example, quartz (SiO2). The gas supply pipes 40A, 40B, and 40C supply gas into the processing chamber 11. The types of gas will be described later. Note that one gas supply pipe may discharge one type or multiple types of gas in sequence. Also, multiple gas supply pipes may discharge the same type of gas.

[0021] The gas supply pipes 40A, 40B, and 40C include horizontal pipes 43A, 43B, and 43C that horizontally penetrate the manifold 14, and vertical pipes 41A, 41B, and 41C that are vertically disposed inside the processing vessel 11. The vertical pipes 41A, 41B, and 41C include a plurality of gas inlets 42A, 42B, and 42C that are spaced apart in the vertical direction. The gases supplied to the horizontal pipes 43A, 43B, and 43C are sent to the vertical pipes 41A, 41B, and 41C, and are discharged horizontally from the plurality of gas inlets 42A, 42B, and 42C. The vertical pipe 41C is disposed inside the plasma box 19. The vertical pipes 41A and 41B are disposed inside the processing vessel 11.

[0022] The substrate processing apparatus 10 has an exhaust pipe 45. The exhaust pipe 45 is connected to an exhaust device (not shown). The exhaust device includes a vacuum pump and exhausts the inside of the processing vessel 11. An exhaust port 18 is formed in the processing vessel body 12. The exhaust port 18 is disposed so as to face the air supply ports 42A, 42B, and 42C. Gas discharged horizontally from the air supply ports 42A, 42B, and 42C passes through the exhaust port 18 and is exhausted from the exhaust pipe 45. The exhaust device sucks in the gas inside the processing vessel 11 and sends it to the detoxification device. The detoxification device removes harmful components from the exhaust gas and then releases the exhaust gas into the atmosphere.

[0023] The substrate processing apparatus 10 further includes a heating unit 60. The heating unit 60 is disposed outside the processing vessel 11 and heats the inside of the processing vessel 11 from the outside of the processing vessel 11. For example, the heating unit 60 is formed in a cylindrical shape so as to surround the processing vessel body 12. The heating unit 60 is formed of, for example, an electric heater. The heating unit 60 heats the inside of the processing vessel 11, thereby improving the processing capacity of the gas supplied into the processing vessel 11.

[0024] [Plasma Box] 2 is a diagram showing a configuration example of an impedance matching device 53 and a plasma box 19 according to an embodiment. As shown in Fig. 1 and Fig. 2, an opening 17 is formed in a part of the circumferential direction of the processing vessel body 12. A plasma box 19 is formed on a side surface of the processing vessel 11 so as to surround the opening 17. The plasma box 19 is formed so as to protrude radially outward from the processing vessel body 12, and is formed, for example, in a substantially U-shape when viewed in the vertical direction.

[0025] A pair of electrodes (electrode pair) 91, 92 are arranged facing each other across the plasma box 19. The electrodes 91, 92 are a pair of parallel electrodes installed facing each other on the outside of the plasma box 19. The electrodes 91, 92 face each other and are formed to be elongated in the vertical direction, similar to the vertical tube 41C. An RF power supply 55 is connected to the electrodes 91, 92 via an impedance matching device 53, and applies a high-frequency voltage of a predetermined frequency to the electrodes 91, 92.

[0026] The impedance matching device 53 is connected in series between the RF power supply 55 and the electrodes 91 and 92 via the voltage supply lines 51, 52, and 54. The impedance matching device 53 includes a first variable reactor 58, a second variable reactor 59, electronic circuits 75a and 75b, capacitors 56 (C1), 57 (C2), a coil (L1), and a coil (L2). The electronic circuit 75a changes the inductance of the first variable reactor 58 by controlling the current flowing through the first variable reactor 58. The electronic circuit 75b changes the inductance of the second variable reactor 59 by controlling the current flowing through the second variable reactor 59.

[0027] When high frequency power is supplied from the RF power supply 55 to the load side (plasma box 19 side), the impedance matching device 53 matches the impedance between the RF power supply 55 and the load, thereby improving the supply efficiency of the high frequency power.

[0028] The stability of plasma ignition can be improved by responding quickly from when the plasma is excited until it stabilizes and converging in a short time. In addition, the stability of plasma ignition can be achieved by stabilizing the high-frequency power to the plasma and suppressing plasma fluctuations. To achieve this, it is necessary to perform impedance matching at high speed and suppress reflected waves.

[0029] In the ignition control method according to this embodiment, the current flowing through the first variable reactor 58 and the second variable reactor 59 in the impedance matching device 53 is controlled by the electronic circuits 75a and 75b to change the inductance of each variable reactor, thereby performing impedance matching. The rate of change in the inductance of the first variable reactor 58 and the second variable reactor 59 depends on the operating speed of the electronic circuits 75a and 75b, and the time required to match the impedance is on the order of μs (microseconds). Therefore, the impedance matching device 53 having the first variable reactor 58 and the second variable reactor 59 can perform impedance matching quickly in a short time (for example, within one second) immediately before plasma ignition.

[0030] The impedance matching device 53 has a first Vpp sensor 70 that detects the voltage between the electrodes 91, 92, a second Vpp sensor 71 that detects the voltage between the electrode 91 and ground, and a third Vpp sensor 72 that detects the voltage between the electrode 92 and ground. The impedance matching device 53 also has a temperature sensor (TC) 73a that detects the temperature of the first variable reactor 58, and a temperature sensor (TC) 73b that detects the temperature of the second variable reactor 58.

[0031] Furthermore, the impedance matching device 53 has a controller 80. The controller 80 acquires the detection values ​​of the first Vpp sensor 70, the second Vpp sensor 71, and the third Vpp sensor 72 and the detection values ​​of the temperature sensors 73a and 73b. The controller 80 acquires the inter-electrode voltage from the first Vpp sensor 70 and the temperature of the first variable reactor 58 from the temperature sensor 73a, and controls the current flowing to the electronic circuit 75a based on this information. This changes the inductance of the first variable reactor 58. The controller 80 also acquires the inter-electrode voltage from the first Vpp sensor 70 and the temperature of the second variable reactor 59 from the temperature sensor 73b, and controls the current flowing to the electronic circuit 75b based on this information. This changes the inductance of the second variable reactor 59. As described above, the controller 80 can control impedance matching at high speed without the intervention of the control unit 100.

[0032] However, the controller 80 may control the impedance matching in cooperation with a control unit 100 that controls the entire substrate processing apparatus 10. The controller 80 and the control unit 100 are formed of, for example, a computer.

[0033] [Variable reactor operation overview] 3, an overview of the operation of the first variable reactor 58 and the second variable reactor 59 in the impedance matching device 53 will be described. Since the second variable reactor 59 has the same configuration as the first variable reactor 58, the first variable reactor 58 will be described here.

[0034] The first variable reactor 58 has a configuration in which a control winding A between T3 and T4 and an AC winding B between T1 and T2 are wound around an annular magnetic core 74. An electronic circuit 75a (see FIG. 2) is connected between T3 and T4. The electronic circuit 75a variably controls the DC current I flowing through the control winding A. This changes the inductance.

[0035] In the first variable reactor 58, when the temperature of the magnetic core 74 rises due to the surrounding environmental temperature, the magnetic permeability μ rises and the inductance rises. When the temperature of the magnetic core 74 falls, the magnetic permeability μ falls and the inductance falls. Therefore, when a temperature change occurs in the first variable reactor 58, if the same current is passed through the control winding A before and after the temperature change, the preset value shifts, the reflected wave at the time of plasma ignition changes, and depending on the process, this may affect film formation. In particular, it has been found through experiments that while variable capacitors are not easily affected by temperature changes, variable reactors are easily affected by temperature changes and the preset value is easily changed.

[0036] The magnetic permeability μ [H / m] is a numerical representation of the ease of magnetization of the magnetic core 74, and the relationship between the strength H of the magnetic field (magnetic field) and the magnetic flux density B is expressed as B=μH. Also, the inductance L is expressed as the cross-sectional area S [m 2 ], the number of turns N of the control winding A and the AC winding B, and the length l [m] passing through the center of the magnetic core 74. Therefore, as the magnetic permeability μ increases, the inductance L increases. L = μSN 2 / l[H]···(1)

[0037] Immediately before applying a high-frequency voltage from the RF power supply 55 to the electrodes 91, 92, the adjustment positions of the first variable reactor 58 and the second variable reactor 59 of the impedance matching device 53 are set to preset values. This allows the reflected wave to be controlled and the plasma to be ignited stably.

[0038] However, as described above, the inductance changes due to temperature changes in the first variable reactor 58 and the second variable reactor 59, and the accuracy of the preset value may deteriorate. The temperature change of the variable reactor and the problem at the time of plasma ignition will be further described with reference to Fig. 4. Fig. 4 is a diagram for explaining the temperature change of the variable reactor and the problem at the time of plasma ignition.

[0039] The horizontal axis of the graph in Figure 4(a) indicates the temperature of the variable reactor, and the vertical axis indicates the magnetic permeability μ. According to this, as the temperature of the variable reactor rises, the magnetic permeability μ also rises. From equation (1), it can be seen that as the magnetic permeability μ rises, the inductance increases, so as the temperature of the variable reactor rises, the inductance of the variable reactor also increases. However, if the temperature of the variable reactor does not reach the Curie temperature T k When the temperature approaches or exceeds 100° C., the proportional relationship in which the magnetic permeability μ increases with the increase in temperature is lost. Therefore, it is preferable to control the temperatures of the first variable reactor 58 and the second variable reactor 59 to 100° C. or lower.

[0040] In this embodiment, the DC current I flowing through the control winding A (see FIG. 3) is variably controlled in response to temperatures detected by temperature sensors 73a, 73b attached to the first variable reactor 58 and the second variable reactor 59, respectively. This makes the magnetic permeability μ in the magnetic core 74 variable, and changes the inductances of the first variable reactor 58 and the second variable reactor 59. As a result, it is possible to prevent the preset value from fluctuating due to temperature fluctuations of the variable reactors.

[0041] In order to control the temperatures of the first variable reactor 58 and the second variable reactor 59 to 100° C. or less, the impedance matching device 53 has a temperature control unit that controls the temperatures of the first variable reactor 58 and the second variable reactor 59. FIG. 2 shows a thermostatic bath 76 that surrounds the first variable reactor 58 and the second variable reactor 59 as an example of the temperature control unit and can adjust the temperature of each variable reactor. The thermostatic bath 76 controls the temperatures of the first variable reactor 58 and the second variable reactor 59 to at least 100° C. or less. However, the thermostatic bath 76 also causes some fluctuation in the temperatures of the first variable reactor 58 and the second variable reactor 59. The thermostatic bath 76 may surround the entire impedance matching device 53.

[0042] As another example of the temperature adjustment unit, a fan may be attached near the first variable reactor 58 and the second variable reactor 59. As another example of the temperature adjustment unit, a piping structure for flowing a temperature adjustment medium may be formed near the first variable reactor 58 and the second variable reactor 59, and the temperature of the first variable reactor 58 and the second variable reactor 59 may be adjusted by controlling the temperature of the temperature adjustment medium.

[0043] The horizontal axis of the graph in Figure 4(b) indicates the magnetic field strength H, and the vertical axis indicates the magnetic flux density B. As mentioned above, magnetic permeability μ is expressed as B = μH. Figure 4(b) shows the cases where the temperatures of the variable reactor are 25°C, 50°C, and 100°C. As the temperature of the variable reactor increases, the saturation magnetic flux density B s Therefore, the saturation magnetic flux density B s To avoid this, it is preferable to control the temperature of the variable reactor to a temperature lower than 100°C.

[0044] The horizontal axis of the graph in Figure 4(c) indicates the temperature of the variable reactor, and the vertical axis indicates the rate of change of inductance. When the temperature of the variable reactor rises, the rate of change of inductance also increases even if the same current is passed through the variable reactor. Therefore, when the temperature of the variable reactor rises, the deviation of the preset value increases. Therefore, it is better to lower the temperature of the variable reactor and reduce the rate of change of inductance.

[0045] The horizontal axis of the graph in Fig. 4(d) represents the DC current passed through control winding A (see Fig. 3), and the vertical axis represents inductance. Fig. 4(d) shows the cases when the temperatures of the variable reactor are 25°C, 50°C, and 100°C. As the temperature of the variable reactor rises, the range of current values ​​over which the inductance for the DC current passed through control winding A is constant becomes smaller, and the rate at which the inductance changes with respect to the DC current passed through control winding A becomes larger, resulting in a larger deviation from the preset value.

[0046] As described above, the inductance changes due to the temperature fluctuation of the variable reactor caused by the surrounding environment and the operating condition of the apparatus, and the rate of change of the inductance also increases as the temperature rise of the variable reactor increases. This causes the preset value before the input of high frequency power from the RF power source 55 to fluctuate, and the reflected wave at the time of plasma ignition immediately after the input of high frequency power to fluctuate. As a result, the film formation state is adversely affected. Therefore, in the ignition control method according to the present embodiment, the inductance is changed by controlling the current flowing through the control winding A according to the temperature change of the variable reactor, thereby improving the accuracy of the preset value of the variable reactor. From the above, by being able to set a highly accurate preset value, it is possible to stably control the reflected wave and the interelectrode voltage at the time of plasma ignition, and it is possible to provide a substrate processing apparatus 10 capable of stable film formation control.

[0047] Next, the gas supply source, the control unit 100, and the controller 80 will be described with reference to Fig. 5. Fig. 5 is a diagram for explaining the gas supply source, the control unit 100, and the controller 80 of the substrate processing apparatus 10 according to one embodiment.

[0048] In the substrate processing apparatus 10, the gas supply unit includes a source gas supply source 90, a modifying gas supply source 93, and a nitriding gas supply source 96. The source gas supply source 90 supplies a source gas into the processing chamber 11. The source gas contains an element to be nitrided (e.g., silicon).

[0049] As the source gas, for example, dichlorosilane (DCS: SiH2Cl2) gas is used. Note that, although the source gas in this embodiment is DCS gas, the technology of the present disclosure is not limited thereto.

[0050] A raw material gas pipe 91 connects a raw material gas supply source 90 to the gas supply pipes 40A and 40B, and sends raw material gas from the raw material gas supply source 90 to the gas supply pipes 40A and 40B. The raw material gas is discharged horizontally toward the wafers 2 from the gas inlets 42A and 42B of the vertical pipes 41A and 41B. A raw material gas flow rate control valve 92 is provided midway through the raw material gas pipe 91 and controls the flow rate of the raw material gas.

[0051] The modifying gas supply source 93 modifies the Si-containing layer by supplying a modifying gas into the processing vessel 11. The modification of the Si-containing layer includes, for example, removing halogen elements contained in the Si-containing layer. The modifying gas may be nitrogen gas, hydrogen gas, ammonia gas, or a gas containing any of these gases.

[0052] The modified gas pipe 94 connects the modified gas supply source 93 and the gas supply pipe 40C, and sends the modified gas from the modified gas supply source 93 to the gas supply pipe 40C. The modified gas is discharged horizontally from the gas inlet 42C of the vertical pipe 41C toward the wafer 2. The modified gas flow rate control valve 95 is provided midway through the modified gas pipe 94 and controls the flow rate of the modified gas.

[0053] The nitriding gas supply source 96 nitrides the Si-containing layer by supplying a nitriding gas into the processing chamber 11. As the nitriding gas, for example, ammonia (NH3) gas, an organic hydrazine compound gas, an amine-based gas, NO gas, N2O gas, or NO2 gas is used.

[0054] The nitriding gas pipe 97 connects the nitriding gas supply source 96 and the gas supply pipe 40C, and sends the nitriding gas from the nitriding gas supply source 96 to the gas supply pipe 40C. The nitriding gas is discharged horizontally toward the wafer 2 from the gas inlet 42C of the vertical pipe 41C. The nitriding gas flow rate control valve 98 is provided midway through the nitriding gas pipe 97, and controls the flow rate of the nitriding gas.

[0055] Furthermore, a purge gas supply source (not shown) may be provided. By supplying a purge gas into the processing vessel 11, the source gas, the modifying gas, and the nitriding gas remaining inside the processing vessel 11 are removed. For example, an inert gas is used as the purge gas. For example, a rare gas such as Ar gas or N2 gas is used as the inert gas.

[0056] 5, the substrate processing apparatus 10 includes a control unit 100 that controls the substrate processing apparatus 10. The control unit 100 includes a CPU (Central Processing Unit) 101, a memory 102, an input interface 103, and an output interface 104. The memory 102 stores programs that control various processes executed in the substrate processing apparatus 10. The control unit 100 controls the overall operation of the substrate processing apparatus 10 by causing the CPU 101 to execute the programs stored in the memory 102. The control unit 100 receives signals from the outside via the input interface 103 and transmits signals to the outside via the output interface 104.

[0057] Such a program may be stored in a computer-readable medium and installed from the medium into the memory 102 of the control unit 100. Examples of computer-readable media include a hard disk (HD), a flexible disk (FD), a compact disk (CD), a magnet optical disk (MO), and a memory card. The program may be downloaded from a server via the Internet and installed into the memory 102 of the control unit 100.

[0058] The controller 80 has a processor 81 and a memory 82. The memory 82 stores an ignition control program, an interelectrode voltage table 83 (see FIG. 7), and a control current table 84 (see FIG. 9). The controller 80 controls the operation of the impedance matching device 53, including the current control of the electronic circuits 75a and 75b, by causing the processor 81 to execute the ignition control program using various tables stored in the memory 102.

[0059] The ignition control program may be stored in a medium readable by the processor 81 and installed into the memory 82 of the controller 80 from the medium.

[0060] [Ignition control method] The ignition control method according to this embodiment controls the current to each variable reactor based on the temperature change of the first variable reactor 58 and the second variable reactor 59, and sets a highly accurate preset value, thereby performing stable plasma ignition. This improves the controllability of the film thickness and film quality of the wafer 2, making it possible to form a high-quality film.

[0061] An ignition control method according to this embodiment will be described with reference to Figs. 6 and 7. Fig. 6 is a flowchart showing an ignition control method according to one embodiment. Fig. 7 is an example of an interelectrode voltage table at each adjustment position of the variable reactor. The ignition control method according to the embodiment is controlled by the controller 80 or the control unit 100. In this example, when the RF power supply 55 is turned on, a high-frequency voltage of a predetermined frequency (e.g., 13.56 MHz) is applied. Fig. 7 is an example of an interelectrode voltage table at each adjustment position VL1, VL2 of the inductance of each variable reactor when, for example, an RF of 13.56 MHz is applied.

[0062] 6, when the power supply of the substrate processing apparatus 10 is turned on, an idle mode is executed in step S1. In the idle mode, the high frequency voltage from the RF power supply 55 is turned off. In this state, the control unit 100 supplies nitrogen gas from the multiple gas supply ports 42A, 42B, and 42C of the vertical pipes 41A, 41B, and 41C.

[0063] In step S2, the control unit 100 loads the wafer 2 placed on the substrate holder 30 into the processing vessel 11 to prepare for the film formation process. First, outside the processing vessel 11, a transfer device loads multiple wafers 2 onto the substrate holder 30. The substrate holder 30 holds the multiple wafers 2 horizontally and at intervals in the vertical direction. Next, the lifting unit 25 is raised to lift the lid 20 and the substrate holder 30. The wafer 2 is loaded into the processing vessel 11 together with the substrate holder 30, and the opening at the bottom of the processing vessel 11 is sealed with the lid 20.

[0064] In step S3, the control unit 100 sets a process type for the process to be performed on the wafer 2. The process type is identification information that specifies the substrate processing conditions given by the frequency of the high frequency output from the RF power supply 55, the type of gas supplied into the processing vessel 11, and the temperature and pressure in the processing vessel 11.

[0065] In step S4, the control unit 100 sets the temperatures of the first variable reactor 58 and the second variable reactor 59 to a first temperature (for example, 25° C.). The RF power supply 55 supplies low-power high-frequency power (for example, 100 W) having a frequency of, for example, 13.56 MHz such that plasma discharge (ignition) does not occur. The control unit 100 acquires first information indicating interelectrode voltages for each of a plurality of adjustment positions of the first variable reactor 58 and the second variable reactor 59 at this time. The first Vpp sensor 70 measures (detects) the interelectrode voltages for each of a plurality of adjustment positions of the first variable reactor 58 and the second variable reactor 59, and transmits them to the controller 80. This executes a scan mode in which the interelectrode voltages of each adjustment position of a matrix showing the range of 0 to 100% of each adjustment position VL1, VL2 shown in FIG. 7 in 5% increments are measured. That is, the controller 80 scans the range of 0 to 100% of each adjustment position VL1, VL2 in increments of 5%, for example, and creates a table of first information as shown in Fig. 7, that is, interelectrode voltage table 83. After the measurement, the output of low power from the RF power supply 55 is stopped. The interelectrode voltage table 83 is an example of the first information.

[0066] In step S5, the controller 80 determines, as preset values, adjustment positions VL1 and VL2 that provide an interelectrode voltage that is equal to or higher than the discharge voltage according to Paschen's law but is not too high, based on the interelectrode voltage table 83. For example, the controller 80 determines, as the preset value P, the position where VL1 in FIG. 7 is 25% and VL2 is 35%.

[0067] In step S6, the controller 80 acquires the temperatures of the first variable reactor 58 and the second variable reactor 59 detected by the temperature sensors 73a, 73b. The explanation will be continued assuming that the acquired temperatures are the second temperatures. The controller 80 determines whether at least one of the second temperatures of the first variable reactor 58 and the second variable reactor 59 has changed from the first temperature. The first temperatures are the temperatures of the first variable reactor 58 and the second variable reactor 59 when the interelectrode voltage table 83 is created.

[0068] In step S6, when at least one of the second temperature of the first variable reactor 58 and the second temperature of the second variable reactor 59 has changed from the first temperature, the process proceeds to step S7, where the controller 80 performs a correction process.

[0069] For example, the inductance of each variable reactor changes due to the temperature change of the first variable reactor 58 and the second variable reactor 59 with respect to the preset value P in FIG. 7, so that the appropriate preset value deviates from the current preset value by about several percent. For this reason, a state may occur in which the preset value P that has been set is not an appropriate value due to the temperature change of the variable reactor. For example, if the preset value P in FIG. 7 is shifted by one position Q where VL1 is 30% and VL2 is 40% in 5% increments, the interelectrode voltage increases by about two times from 649V to 1111V. In other words, the interelectrode voltage is ignited at 1111V, whereas the plasma should be ignited at 629V. This reduces the film thickness and film quality of the wafer 2.

[0070] Therefore, in the correction process of step S7, the controller 80 controls the electronic circuits 75a and 75b to change the current flowing through the first variable reactor 58 and the second variable reactor 59 in accordance with the second temperature detected by the temperature sensors 73a and 73b. This changes the inductance, making it possible to set a highly accurate preset value. In this way, even if the temperature of the variable reactor changes, the high frequency voltage indicated by the determined preset value is applied to the electrodes 91 and 92. This allows stable control of the reflected wave and the inter-electrode voltage, making it possible to ignite a stable plasma. Details of the correction process will be described later with reference to Figs. 8 and 9.

[0071] In step S8, the control unit 100 determines whether or not high-frequency power capable of igniting plasma has been supplied from the RF power supply 55. When high-frequency power set in a process recipe, for example, has been supplied, the control unit 100 determines that high-frequency power capable of igniting plasma has been supplied from the RF power supply 55, and proceeds to step S9.

[0072] In step S9, the control unit 100 executes a film formation process of the set process type on the wafer 2. The film formation process will be described later with reference to FIGS.

[0073] In step S10, the control unit 100 determines whether or not the RF power supply 55 has been turned off. If the control unit 100 determines that the RF power supply 55 has been turned off, the process proceeds to step S11, where it determines whether or not the process has ended.

[0074] In step S11, if the control unit 100 determines that the process is not completed, the process returns to step S3 and executes subsequent processes. In step S11, if the control unit 100 determines that the process is completed, the process proceeds to step S12 and the substrate is unloaded.

[0075] Then, the process returns to step S1 and waits until the next wafer 2 is loaded (idle mode). When the next wafer 2 is loaded, the same process is performed on the next wafer 2.

[0076] [Correction process] The correction process according to one embodiment will be described with reference to Fig. 8 and Fig. 9. Fig. 8 is a flowchart showing an example of the correction process performed in step S7 in Fig. 6. Fig. 9 is an example of a control current table of a variable reactor according to one embodiment. The correction process in Fig. 8 is controlled by a controller 80.

[0077] In step S21, controller 80 determines whether the second temperature of first variable reactor 58 (the temperature of first variable reactor 58 detected by temperature sensor 93a immediately before RF power supply 55 is turned on) has changed from the first temperature.

[0078] If the controller 80 determines in step S21 that the second temperature is the same as the first temperature, the process proceeds to step S23. If the controller 80 determines in step S21 that the second temperature is different from the first temperature, the process proceeds to step S22, where the controller 80 determines a control current according to the second temperature by referring to the control current table 84, and changes the control current of the first variable reactor 58 by using the electronic circuit 75a.

[0079] In the control current table 84, the control currents of the electronic circuits 75a, 75b corresponding to the temperatures of the first variable reactor 58, VL1 (%) and the second variable reactor 59, VL2 (%) are set.

[0080] For example, in the preset value P in Fig. 7, VL1 is 25%. When the second temperature is 50°C, the first temperature is 25°C, and therefore the controller 80 refers to the control current table 84 shown in Fig. 9(a) and changes the current flowing through the first variable reactor 58 from 5.0 [A] to 3.8 [A].

[0081] In step S23, controller 80 determines whether the second temperature of second variable reactor 59 (the temperature of second variable reactor 59 detected by temperature sensor 93b immediately before RF power supply 55 is turned on) has changed from the first temperature.

[0082] In step S23, if the controller 80 determines that the second temperature is the same as the first temperature, the process ends. In step S23, if the controller 80 determines that the second temperature is different from the first temperature, the process proceeds to step S24, where the controller 80 determines a control current according to the second temperature with reference to the control current table 84 shown in Fig. 9(b), changes the control current of the second variable reactor 59 using the electronic circuit 75b, and ends the process.

[0083] For example, VL2 is 30% at the preset value P in Fig. 7. The controller 80 changes the current flowing through the second variable reactor 59 with reference to a control current table 84 shown in Fig. 9(v).

[0084] [Film formation process] A film formation process according to an embodiment will be described with reference to Fig. 10 and Fig. 11. Fig. 10 is a flow chart showing an example of the film formation process performed in step S9 of Fig. 6. Fig. 11 is a time chart showing an example of the film formation process of Fig. 10. The film formation process of Fig. 10 is mainly controlled by the control unit 100, and the correction process before plasma ignition is controlled by the controller 80. In Fig. 10, a silicon nitride film (SiN) is formed by the ALD method.

[0085] In step S31, the control unit 100 forms a Si-containing layer on the wafer 2 held by the substrate holder 30. Step S31 is performed from time t1 to time t2 shown in FIG. 11. In step S31, a raw material gas is supplied from the raw material gas supply source 90 to the inside of the processing vessel 11 while the inside of the processing vessel 11 is evacuated by an exhaust device connected to the exhaust pipe 45. The raw material gas is, for example, DCS gas. As a result, a Si-containing layer is formed on the wafer 2. The time for step S31 is, for example, 1 second or more and 10 seconds or less.

[0086] In step S32, the control unit 100 performs a purge process. Step S32 is performed from time t2 to time t3 shown in FIG. 11. In step S22, while exhausting the inside of the processing vessel 11 by the exhaust device, the supply of the raw material gas is stopped and a purge gas is supplied into the inside of the processing vessel 11. As a result, the gas remaining inside the processing vessel 11 is replaced with the purge gas. The purge gas may be nitrogen gas, argon gas, other inert gas, or a combination of these. The time of step S32 is, for example, 3 seconds or more and 10 seconds or less. The purge gas may be supplied from a nitriding gas supply source 80 or the like. Note that, as shown in FIG. 11, the purge gas may be continuously supplied in all steps.

[0087] In steps S33 to S35, similarly to steps S5 to S7 in FIG. 6, the controller 80 determines a preset value (step S33: same process as step S5), determines whether or not there has been a temperature change in each variable reactor (step S34: same process as step S6), and performs a correction process if there has been a temperature change (step S35: same process as step S7).

[0088] In step S36, the control unit 100 modifies the Si-containing layer. Step S36 is performed from time t3 to time t4 shown in FIG. 11. In step S36, the inside of the processing vessel 11 is evacuated by the exhaust device, while the modifying gas supply source 93 supplies the modifying gas into the inside of the processing vessel 11. In step S36, high-frequency power is supplied from the RF power supply 55, and plasma is ignited in the plasma box 19 to convert the modifying gas into plasma. The high-frequency frequency of the RF power supply 55 is, for example, 13.56 MHz.

[0089] The modifying gas is, for example, nitrogen gas. The modifying gas may be hydrogen gas or ammonia gas. The modifying gas may be a gas containing nitrogen gas or a gas containing hydrogen gas. The Si-containing layer is modified by the plasmatized modifying gas. The time of step S36 is, for example, 3 seconds or more and 60 seconds or less.

[0090] In step S37, the control unit 100 performs purging. Step S37 is performed from time t4 to time t5 shown in FIG. 11. In step S24, while the inside of the processing vessel 11 is evacuated by the exhaust device, the supply of the modifying gas and the high frequency power is stopped, and a purge gas is supplied into the inside of the processing vessel 11. As a result, the gas remaining inside the processing vessel 11 is replaced with the purge gas. The time for step S37 is, for example, 3 seconds or more and 10 seconds or less. The purge gas may be nitrogen gas or the like, and may be supplied from a nitriding gas supply source 80 or the like.

[0091] In steps S38 to S40, similarly to steps S5 to S7 in FIG. 6, the controller 80 determines a preset value (step S38), determines whether or not there has been a temperature change in each variable reactor (step S39), and performs a correction process (step S40) if there has been a temperature change.

[0092] In step S41, the control unit 100 nitrides the Si-containing layer. Step S41 is performed from time t5 to time t6 shown in Fig. 11. In step S41, the inside of the processing vessel 11 is evacuated by the exhaust device, while the nitriding gas is supplied into the inside of the processing vessel 11 by the nitriding gas supply source 96. Also in step S41, high frequency power is supplied from the RF power supply 55, plasma is ignited in the plasma box 19, and the nitriding gas is turned into plasma.

[0093] The nitriding gas is, for example, ammonia gas. The Si-containing layer is nitrided by the ammonia gas plasma. The time for step S41 is, for example, 5 seconds or more and 120 seconds or less.

[0094] In step S42, the control unit 100 performs purging. Step S42 is performed from time t6 to time t7 shown in FIG. 11. In step S42, while the inside of the processing vessel 11 is evacuated by the exhaust device, the supply of the nitriding gas and the high frequency power is stopped, and a purge gas is supplied into the inside of the processing vessel 11. As a result, the gas remaining inside the processing vessel 11 is replaced with the purge gas. The time for step S42 is, for example, 3 seconds or more and 10 seconds or less. The purge gas may be nitrogen gas or the like, and may be supplied from a nitriding gas supply source 96 or the like.

[0095] In step S43, the control unit 100 determines whether the process has been repeated a set number of times. The set number of times is preset. If the control unit 100 determines that the process has not been repeated the set number of times, the process returns to step S31, and steps S31 to S43 are counted as one cycle and are repeated a predetermined number of times. If the control unit 100 determines in step S43 that the process has been repeated the set number of times, the process ends since a silicon nitride film of the desired film thickness and film quality has been formed. Note that the purging step can be omitted in this film forming method.

[0096] In the ignition control method described above, the correction process of Fig. 8 is executed as shown in steps S5 to S7 of Fig. 6, steps S33 to S35, and steps S38 to S40 of Fig. 10, and the control current of the electronic circuit that controls each variable reactor is changed according to the temperatures of first variable reactor 58 and second variable reactor 59. This makes it possible to change the inductance of each variable reactor, thereby controlling the inductance to a constant value even if the temperature of each variable reactor changes, and improving the accuracy of the preset value.

[0097] In particular, in a film formation process using the ALD method, when the step of plasma ignition is repeated in response to repeated on-off of the gas, the preset value changes each time the gas is turned on and off. For example, in the ignition control method according to this embodiment, the preset value can be corrected in real time immediately before plasma ignition is performed by supplying high-frequency power as shown in steps S33 to S35 and steps S38 to S40 in Fig. 10. This makes it possible to provide a substrate processing apparatus 10 that improves the accuracy of the preset value, stably controls the reflected wave and the inter-electrode voltage, and performs stable film formation.

[0098] As described above, according to the ignition control method and the substrate processing apparatus of the present embodiment, it is possible to set a highly accurate preset value, thereby suppressing reflected waves and performing stable plasma ignition, thereby improving controllability of film thickness and film quality, and forming a high-quality film.

[0099] The ignition control method, the film formation method, and the film formation apparatus according to the embodiments disclosed herein should be considered as illustrative and not restrictive in all respects. The embodiments can be modified and improved in various forms without departing from the scope and spirit of the appended claims. The matters described in the above embodiments can be configured in other ways as long as they are not inconsistent, and can be combined as long as they are not inconsistent.

[0100] For example, in the present embodiment, the description has been given using two variable reactors, but the number of variable reactors included in the impedance matching device 53 is not limited to this and may be one. When the impedance matching device 53 has two variable reactors, one may be a variable reactor and the other a fixed reactor. The ignition control method of the present disclosure can be executed using one variable reactor or one of the variable reactors.

[0101] The ignition control method of the present disclosure can be used in all substrate processing apparatuses that apply a high-frequency voltage between electrodes via an impedance matching device having a variable reactor to generate plasma. For example, the substrate processing apparatus that executes the ignition control method of the present disclosure is not limited to an ALD apparatus. The substrate processing apparatus of the present disclosure may be an ALE (Atomic Layer Etching) apparatus, a CVD (Chemical Vapor Deposition) apparatus, a PVD (Physical Vapor Deposition) apparatus, or the like.

[0102] The substrate processing apparatus of the present disclosure can be applied to any type of apparatus, including Capacitively Coupled Plasma (CCP), Inductively Coupled Plasma (ICP), Radial Line Slot Antenna (RLSA), Electron Cyclotron Resonance Plasma (ECR), and Helicon Wave Plasma (HWP).

[0103] The substrate processing apparatus of the present disclosure is not limited to a batch-type substrate processing apparatus. For example, the substrate processing apparatus may be a single-wafer type apparatus that processes wafers one by one. The substrate processing apparatus may also be a semi-batch type apparatus. The semi-batch type apparatus may be an apparatus that rotates a plurality of wafers arranged around the rotation center line of a turntable together with the turntable and passes the wafers in sequence through a plurality of regions to which different gases are supplied.

[0104] The substrate processing performed by the substrate processing apparatus of the present disclosure includes, for example, a film formation process, an etching process, etc. In particular, the substrate processing apparatus is suitable for film formation by the ALD method and etching by the ALE method.

[0105] The controller 80 may be located inside the impedance matching device 53 or outside the impedance matching device 53. When the controller 80 is located outside the impedance matching device 53, the control unit 100 and the controller 80 in Fig. 5 may be separate as shown in Fig. 5 or may be integrated together. Furthermore, each process of the ignition control method (Fig. 6), the correction process (Fig. 8) and the film forming process (Fig. 10) is not limited to the above description and can be performed by either the control unit 100 or the controller 80. [Explanation of symbols]

[0106] 10 Film deposition equipment 11 Processing vessel 19 Plasma Box 53 Impedance Matching Device 55 RF power supply 58 First variable reactor 59 Second variable reactor 80 Controller 90 Temperature bath 91,92 electrode 100 Control section

Claims

1. a processing vessel for accommodating a substrate; A pair of electrodes formed in the processing vessel; an impedance matching device having a variable reactor and an electronic circuit for controlling a current flowing through the variable reactor; an RF power source connected to the pair of electrodes via the impedance matching device; A temperature sensor for detecting a temperature of the variable reactor; An ignition control method performed in a substrate processing apparatus comprising: (a) setting a temperature of the variable reactor to a first temperature, and measuring first information indicating a voltage between the electrodes for each of a plurality of adjustment positions of the variable reactor when a high frequency voltage of a predetermined frequency is applied from the RF power source to the pair of electrodes; (b) determining a preset value of the variable reactor based on the measured first information; and (c) acquiring a temperature of the variable reactor detected by the temperature sensor as a second temperature; (d) when the first temperature and the second temperature are different, correcting the current flowing through the variable reactor by controlling the electronic circuit so that the adjustment position of the variable reactor at the second temperature becomes the determined preset value; An ignition control method comprising:

2. (d) corrects the determined preset value by referring to a memory that stores a current to be passed through the variable reactor according to a plurality of adjustment positions of the variable reactor for each temperature of the variable reactor and correcting the current to be passed through the variable reactor when the temperature of the variable reactor is the second temperature; The ignition control method according to claim 1 .

3. The (b) measures the first information immediately before plasma ignition. The ignition control method according to claim 1 or 2.

4. (b) supplies the high frequency power from the RF power source with an intensity that does not ignite plasma when measuring the first information. The ignition control method according to claim 1 or 2.

5. The step (d) corrects the current flowing through the variable reactor immediately before plasma ignition. The ignition control method according to claim 1 or 2.

6. a processing vessel for accommodating a substrate; A pair of electrodes formed in the processing vessel; an impedance matching device having a variable reactor and an electronic circuit for controlling a current flowing through the variable reactor; an RF power source connected to the pair of electrodes via the impedance matching device; A temperature sensor for detecting a temperature of the variable reactor; A temperature adjustment unit that adjusts a temperature of at least the variable reactor; A control unit; A substrate processing apparatus comprising: The control unit is (a) setting a temperature of the variable reactor to a first temperature, and measuring first information indicating a voltage between the electrodes for each of a plurality of adjustment positions of the variable reactor when a high frequency voltage of a predetermined frequency is applied from the RF power source to the pair of electrodes; (b) determining a preset value of the variable reactor based on the measured first information; and (c) acquiring a temperature of the variable reactor detected by the temperature sensor as a second temperature; (d) when the first temperature and the second temperature are different, correcting the current flowing through the variable reactor by controlling the electronic circuit so that the adjustment position of the variable reactor at the second temperature becomes the determined preset value; The substrate processing apparatus controls the

7. The temperature adjustment unit is any one of a constant temperature bath surrounding at least the variable reactor, a fan that adjusts the temperature of at least the variable reactor, and a piping structure through which a temperature adjustment medium that adjusts the temperature of at least the variable reactor flows. The substrate processing apparatus according to claim 6 .

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