Fire control method, film forming method, and film forming apparatus

Abstract

To raise a film thickness of a film formed on a substrate and controllability of film quality.SOLUTION: There is provided an ignition control method which is executed by a film forming device comprising a processing container that accommodates a substrate, a plasma box which is formed in the processing container, an electrode pair which is placed so as to sandwich the plasma box, and an RF power supply which is connected to the electrode pair via a matching box having a variable capacitor. The ignition control method includes: a step for storing, in a storage unit, first information that indicates a voltage between the electrodes at each of a plurality of adjustment positions of the variable capacitor when a high frequency voltage of a first frequency is applied to the electrode pair and second information that indicates a voltage between the electrodes and the substrate; a step for referring to the storage unit and determining an initial position of the variable capacitor on the basis of the first and second information; and a step for setting the variable capacitor adjustment position to the initial position and selecting a plasma ignited region from the plasma box and the processing container.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present disclosure relates to an ignition control method, a film forming method, and a film forming apparatus.

Background Art

[0002] Patent Document 1 and Patent Document 2 disclose a batch type film forming apparatus that accommodates a plurality of substrates in a processing container and forms a nitride film on the plurality of substrates by an ALD (Atomic Layer Deposition) method.

[0003] Patent Document 1 proposes a film forming method having a step of supplying a raw material gas containing silicon, a step of supplying hydrogen gas activated by plasma, a step of supplying nitriding gas activated by heat to nitride silicon elements, a step of supplying nitriding gas activated by plasma to nitride silicon elements, and a step of supplying a purge gas between each step. Thereby, a silicon nitride film can be formed to have a desired film thickness distribution.

[0004] Patent Document 2 proposes a film forming method having a step of supplying a raw material gas containing silicon, a step of supplying a reformed gas containing hydrogen gas activated by plasma, a step of supplying nitriding gas activated by heat to nitride silicon elements, and a step of supplying a purge gas between each step. Thereby, damage to the underlying film on which the silicon nitride film is formed can be reduced.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0006] The present disclosure provides a technique capable of enhancing the controllability of the film thickness and film quality of a film formed on a substrate.

Means for Solving the Problems

[0007] According to one aspect of the present disclosure, there is provided a method for controlling ignition, which is executed in a film forming apparatus including a processing container for accommodating a substrate, a plasma box formed in the processing container, an electrode pair disposed so as to sandwich the plasma box, and an RF power source connected to the electrode pair via a matcher having a variable capacitor. The method includes a step of storing in advance in a storage unit first information indicating the voltage between the electrodes for each of a plurality of adjustment positions of the variable capacitor when a high-frequency voltage of a first frequency is applied from the RF power source to the electrode pair, and second information indicating the voltage between the electrode and the substrate; a step of determining an initial position of the variable capacitor based on the first information and the second information with reference to the storage unit; and a step of setting the adjustment position of the variable capacitor to the initial position and selecting a region for plasma ignition from the plasma box and the processing container.

Advantages of the Invention

[0008] According to one aspect, it is possible to enhance the controllability of the film thickness and film quality of a film formed on a substrate.

Brief Description of the Drawings

[0009]

Figure 1

Figure 2

Figure 3

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Figure 5

Figure 6

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Figure 8

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Figure 10

Figure 11

Figure 12

Mode for Carrying Out the Invention

[0010] Hereinafter, embodiments for carrying out the present disclosure will be described with reference to the drawings. In each drawing, the same reference numerals are given to the same components, and redundant descriptions may be omitted.

[0011] [Film Forming Apparatus] First, the film forming apparatus 10 according to the present embodiment will be described with reference to FIG. 1. FIG. 1 is a diagram showing the film forming apparatus 10 according to the embodiment. The film forming apparatus 10 accommodates a plurality of wafers in a processing container 11 and forms a nitride film on the plurality of wafers by the ALD (Atomic Layer Deposition) method. The film forming apparatus 10 is an example of an apparatus that executes such a film forming method.

[0012] The film forming apparatus 10 is a batch-type vertical heat treatment apparatus that processes a plurality of wafers. However, the film forming apparatus 10 is not limited to such a heat treatment apparatus. For example, the film forming apparatus 10 may be a single-wafer processing apparatus that processes wafers one by one. Further, the film forming apparatus 10 may 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 rotary table together with the rotary table and passes them through a plurality of regions where different gases are supplied in order.

[0013] The nitride film is, for example, a silicon nitride film (SiN), but is not limited thereto. The silicon nitride film formed by the film formation method executed by the film forming apparatus 10 according to the present embodiment is formed on the wafer by alternately supplying a source gas (for example, dichlorosilane gas) and a plasma of a nitriding gas (for example, ammonia (NH 3 ) gas) to the wafer.

[0014] In such a film formation method, the film thickness of the nitride film formed in the plane of the wafer tends to be thicker at the edge of the wafer. In order to suppress this, there is a method of suppressing the film thickness at the edge of the wafer by supplying a plasma of nitrogen (N 2 ) gas before the step of supplying a plasma of ammonia gas, but further film thickness adjustment is desired. Therefore, the film formation method according to the present embodiment provides a technique capable of further enhancing the controllability of the film thickness and film quality.

[0015] The film forming apparatus 10 includes a processing container 11 that houses the wafer 2 and forms a space inside which the wafer 2 is processed, a lid body 20 that airtightly closes the opening at the lower end of the processing container 11, and a substrate holder 30 that holds the wafer 2. The wafer 2 is, for example, a semiconductor substrate, and more specifically, for example, a silicon wafer. The substrate holder 30 is also called a wafer boat.

[0016] The processing container 11 has a ceilinged cylindrical processing container main body 12 with an open lower end. The processing container main body 12 is formed of, for example, quartz. A flange portion 13 is formed at the lower end of the processing container main body 12. Further, the processing container 11 has, for example, a cylindrical manifold 14. The manifold 14 is formed 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 container main body 12 is installed on the flange portion 15. A seal member 16 such as an O-ring is disposed between the flange portion 15 and the flange portion 13.

[0017] The lid 20 is airtightly attached to the opening at the lower end of the manifold 14 via a sealing member 21 such as an O-ring. The lid 20 is formed of, for example, stainless steel. A through hole penetrating the lid 20 in the vertical direction is formed at the center of the lid 20. 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 portion 23. The lower end portion of the rotating shaft 24 is rotatably supported by an arm 26 of the elevating portion 25. A rotating plate 27 is provided at the upper end portion of the rotating shaft 24. A substrate holder 30 is installed on the rotating plate 27 via a heat-insulating table 28.

[0018] The substrate holder 30 holds a plurality of wafers 2 at intervals in the vertical direction. The plurality of wafers 2 are each held horizontally. The substrate holder 30 is formed of, for example, quartz (SiO 2 ) or silicon carbide (SiC). When the elevating portion 25 is raised, the lid 20 and the substrate holder 30 are raised, the substrate holder 30 is carried into the interior of the processing container 11, and the opening at the lower end of the processing container 11 is sealed by the lid 20. Also, when the elevating portion 25 is lowered, the lid 20 and the substrate holder 30 are lowered, and the substrate holder 30 is carried out of the processing container 11. Further, when the rotating shaft 24 is rotated, the substrate holder 30 rotates together with the rotating plate 27.

[0019] The film forming apparatus 10 has three gas supply pipes 40A, 40B, and 40C. The gas supply pipes 40A, 40B, and 40C are formed of, for example, quartz (SiO 2 ). The gas supply pipes 40A, 40B, and 40C supply gas into the processing container 11. The types of gas will be described later. Note that one gas supply pipe may discharge one type or a plurality of types of gas in order. Also, a plurality of gas supply pipes may discharge the same type of gas.

[0020] The gas supply pipes 40A, 40B, and 40C have horizontal pipes 43A, 43B, and 43C that penetrate the manifold 14 horizontally, and vertical pipes 41A, 41B, and 41C that are vertically arranged inside the processing container 11. The vertical pipes 41A, 41B, and 41C have a plurality of air supply ports 42A, 42B, and 42C spaced apart in the vertical direction. The gas supplied to the horizontal pipes 43A, 43B, and 43C is sent to the vertical pipes 41A, 41B, and 41C and discharged horizontally from the plurality of air supply ports 42A, 42B, and 42C. The vertical pipe 41C is arranged inside the plasma box 19. The vertical pipes 41A and 41B are arranged inside the processing container 11.

[0021] The film forming 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 evacuates the inside of the processing container 11. An exhaust port 18 is formed in the processing container body 12 to evacuate the inside of the processing container 11. The exhaust port 18 is arranged so as to face the air supply ports 42A, 42B, and 42C. The gas discharged horizontally from the air supply ports 42A, 42B, and 42C is exhausted from the exhaust pipe 45 after passing through the exhaust port 18. The exhaust device sucks the gas inside the processing container 11 and sends it to a decontamination device. The decontamination device removes the harmful components of the exhaust gas and then discharges the exhaust gas into the atmosphere.

[0022] The film forming apparatus 10 further has a heating unit 60. The heating unit 60 is arranged outside the processing container 11 and heats the inside of the processing container 11 from the outside of the processing container 11. For example, the heating unit 60 is formed in a cylindrical shape so as to surround the processing container body 12. The heating unit 60 is composed of, for example, an electric heater. The heating unit 60 improves the processing ability of the gas supplied into the processing container 11 by heating the inside of the processing container 11.

[0023] [Plasma Box] FIG. 2 is an explanatory diagram of the voltage between electrodes and the voltage between the electrode and the wafer in the film forming apparatus 10 according to the embodiment. As shown in FIGS. 1 and 2, an opening 17 is formed in a part of the circumferential direction of the processing container body 12. A plasma box 19 is formed on the side surface of the processing container 11 so as to surround the opening 17. The plasma box 19 is formed so as to protrude radially outward from the processing container body 12 and is formed in a U shape, for example, when viewed in the vertical direction.

[0024] A pair of electrodes (electrode pair) 91 and 92 are arranged so as to sandwich the plasma box 19. The electrode pair 91 and 92 are a pair of parallel electrodes installed facing the outside of the plasma box 19. Similar to the vertical tube 41C, the electrode pair 91 and 92 are formed to be slender in the vertical direction facing each other. The electrode pair 91 and 92 are connected to the RF power supply 55 via the matcher 53, and a high-frequency voltage is applied from the RF power supply 55.

[0025] The matching unit 53 is connected in series between the RF power supply 55 and the electrode pair 91, 92 via the voltage supply lines 51, 52, 54. The matching unit 53 includes a first variable capacitor 57 (C1), a second variable capacitor 58 (C2), and coils (fixed inductances) L1, L2. The control unit 100 shown in FIG. 1 obtains the change amounts of the first variable capacitor 57 and the second variable capacitor 58 by the ignition control method described later, and changes the mechanical adjustment positions (also simply referred to as adjustment target values) of the first variable capacitor 57 and the second variable capacitor 58 according to the change amounts. The change of the mechanical adjustment position controls the rotation of the respective motors for the first variable capacitor 57 and the second variable capacitor 58 (not shown). Thereby, the capacitances C1 and C2 of the first variable capacitor 57 and the second variable capacitor 58 are adjusted respectively. Thereby, the matching unit 53 adjusts its own impedance to match the output impedance of the RF power supply 55 and the load impedance. A sensor 56 is provided in the matching unit 53 to measure the voltage applied between the electrode pair 91, 92 (the voltage between the distances D1 in FIG. 2, hereinafter also referred to as the "inter-electrode voltage"). Further, the sensor 59 measures the voltage applied between the electrode pair 91 and the ground. The voltage measured by the sensor 59 can be regarded as the voltage applied between the end of the electrode 91 on the processing container 11 side and the end of the wafer 2 (the voltage between the distances D2 in FIG. 2, hereinafter also referred to as the "electrode-wafer voltage") if the wafer is regarded as the ground potential.

[0026] [Gas Supply] The plasma box 19 houses the vertical pipes 41C for the reforming gas and the nitriding gas. The reforming gas is discharged horizontally from the air supply port 42C of the vertical pipe 41C toward the opening 17 and supplied into the inside of the processing container body 12 through the opening 17. Similarly, the nitriding gas is discharged horizontally from the air supply port 42C of the vertical pipe 41C toward the opening 17 and supplied into the inside of the processing container body 12 through the opening 17.

[0027] The vertical pipes 41A and 41B for the raw material gas are located outside the plasma box 19 and are arranged outside the opening 17 inside the processing container main body 12. Note that the vertical pipe 41B for the nitriding gas may be arranged inside the plasma box 19, and each gas may be supplied separately from the vertical pipe 41C for the reformed gas.

[0028] By applying a high-frequency voltage between the electrode pairs 91 and 92, a high-frequency electric field is applied to the internal space of the plasma box 19. The reformed gas is plasmaized by the high-frequency electric field in the internal space of the plasma box 19. When the reformed gas contains nitrogen gas, the nitrogen gas is plasmaized and nitrogen radicals are generated. When the reformed gas contains hydrogen gas, the hydrogen gas is plasmaized and hydrogen radicals are generated. When the reformed gas contains ammonia gas, the ammonia gas is plasmaized and ammonia radicals are generated. These active species are supplied into the processing container main body 12 through the opening 17 to reform the Si-containing layer.

[0029] The reforming of the Si-containing layer includes, for example, removing the halogen element contained in the Si-containing layer. By removing the halogen element, unbonded hands of Si can be formed. As a result, the Si-containing layer can be activated, and the nitridation of the Si-containing layer can be promoted. In this embodiment, the nitridation of the Si-containing layer is performed after the reforming of the Si-containing layer.

[0030] FIG. 3 is an explanatory diagram of the gas supply unit and the control unit of the film forming apparatus 10 according to the embodiment. In the film forming apparatus 10, the gas supply unit includes a raw material gas supply source 70, a reformed gas supply source 75, and a nitriding gas supply source 80. The raw material gas supply source 70 supplies the raw material gas into the processing container 11. The raw material gas contains an element to be nitrided (for example, silicon).

[0031] As the raw material gas, for example, dichlorosilane (DCS: SiH 2 Cl 2 ) gas is used. Note that the raw material gas in this embodiment is DCS gas, but the technology of the present disclosure is not limited to this. As the raw material gas, in addition to DCS gas, monochlorosilane (MCS: SiH 3Cl) gas, trichlorosilane (TCS: SiHCl 3 ) gas, silicon tetrachloride (STC: SiCl 4 ) gas, hexachlorodisilane (HCDS: Si 2 Cl 6 ) gas, etc. can be used. By supplying these gases to the wafer 2, a layer containing silicon (Si-containing layer) can be formed on the wafer 2. Since the source gas contains a halogen element, the Si-containing layer contains a halogen element in addition to Si.

[0032] The source gas pipe 72 connects the source gas supply source 70 and the gas supply pipes 40A and 40B, and sends the source gas from the source gas supply source 70 to the gas supply pipes 40A and 40B. The source gas is discharged horizontally toward the wafer 2 from the air supply ports 42A and 42B of the vertical pipes 41A and 41B. The source gas flow control valve 73 is provided in the middle of the source gas pipe 72 to control the flow rate of the source gas.

[0033] The reforming gas supply source 75 reforms the Si-containing layer by supplying reforming gas into the processing container 11. The reforming of the Si-containing layer includes, for example, removing the halogen element contained in the Si-containing layer. By removing the halogen element, dangling bonds of Si can be formed. As a result, the Si-containing layer can be activated and the nitridation of the Si-containing layer can be promoted. As the reforming gas, nitrogen gas, hydrogen gas, ammonia gas, or a gas containing any of these gases can be used.

[0034] The reforming gas pipe 77 connects the reforming gas supply source 75 and the gas supply pipe 40C, and sends the reforming gas from the reforming gas supply source 75 to the gas supply pipe 40C. The reforming gas is discharged horizontally toward the wafer 2 from the air supply port 42C of the vertical pipe 41C. The reforming gas flow control valve 78 is provided in the middle of the reforming gas pipe 77 to control the flow rate of the reforming gas.

[0035] The nitriding gas supply source 80 nitrides the Si-containing layer by supplying nitriding gas into the processing container 11. As the nitriding gas, for example, ammonia (NH 3)Gas, organic hydrazine compound gas, amine-based gas, NO gas, N 2 O gas, or NO 2 gas is used. As the organic hydrazine compound gas, for example, hydrazine (N 2 H 4 ) gas, diazene (N 2 H 2 ) gas, or monomethylhydrazine (MMH) gas, etc. are used. As the amine-based gas, for example, monomethylamine gas, etc. are used.

[0036] The nitriding gas pipe 82 connects the nitriding gas supply source 80 and the gas supply pipe 40C, and sends nitriding gas from the nitriding gas supply source 80 to the gas supply pipe 40C. The nitriding gas is discharged horizontally toward the wafer 2 from the air supply port 42C of the vertical pipe 41C. The nitriding gas flow control valve 83 is provided in the middle of the nitriding gas pipe 82 to control the flow rate of the nitriding gas.

[0037] Furthermore, a purge gas supply source (not shown) may be provided. By supplying purge gas into the processing container 11, the raw material gas, reformed gas, and nitriding gas remaining inside the processing container 11 are removed. As the purge gas, for example, an inert gas is used. As the inert gas, a rare gas such as Ar gas, or N 2 gas is used.

[0038] As shown in FIG. 3, the film forming apparatus 10 includes a control unit 100 that controls the film forming apparatus 10. The control unit 100 is configured by, for example, a computer, and includes a CPU (Central Processing Unit) 101 and a memory 102. Programs for controlling various processes executed in the film forming apparatus 10 are stored in the memory 102. The control unit 100 controls the operation of the film forming apparatus 10 by causing the CPU 101 to execute the programs stored in the memory 102. Also, the control unit 100 includes an input interface 103 and an output interface 104. The control unit 100 receives signals from the outside through the input interface 103 and transmits signals to the outside through the output interface 104.

[0039] Such a program may be stored in a computer-readable storage medium and installed from the storage medium into the memory 102 of the control unit 100. Examples of the computer-readable storage medium include a hard disk (HD), a flexible disk (FD), a compact disk (CD), a magneto-optical disk (MO), a memory card, and the like. Note that the program may be downloaded from a server via the Internet and installed into the memory 102 of the control unit 100.

[0040] [Paschen curve] FIG. 4 is a diagram showing a Paschen curve. The horizontal axis represents the multiplication value pd of the pressure p and the electrode distance d in the processing container 11, and the vertical axis represents the discharge voltage V. B As shown in FIG. 2, the distance between the electrodes 91 and 92 is D1, the electrode-wafer distance is D2, and D1 < D2. Therefore, the multiplication value pd on the horizontal axis satisfies the relationship pD1 < pD2.

[0041] Assume a case where nitrogen (N 2 ) gas is supplied into the plasma box 19 and the processing container 11. 2 The discharge voltage V at the intersection point A of the Paschen curve N of the N B gas and the dotted line indicating pD1 is 1000V. That is, in the plasma box 19 in a nitrogen gas atmosphere, by applying a voltage equal to or higher than the discharge start voltage according to the Paschen curve N, that is, a voltage of 1000V or higher, between the electrodes 91 and 92, plasma ignition can occur in the plasma box 19 and plasma can be generated. That is, in the plasma box 19, the minimum ignition voltage between the electrodes 91 and 92 is 1000V, and it can be seen that even if a voltage lower than 1000V is applied between the electrodes 91 and 92, plasma ignition does not occur in the plasma box 19.

[0042] In contrast, the discharge voltage V at the intersection point B of the Paschen curve N of the N 2 gas and the broken line indicating pD2 BIt becomes 500V. That is, in the processing container 11 in a nitrogen gas atmosphere, a voltage equal to or higher than the discharge start voltage according to the Paschen curve N, that is, a voltage of 500V or higher, is applied between the electrode 91 and the wafer, so that plasma can be ignited and plasma can be generated in the processing container 11. That is, in the processing container 11, the minimum ignition voltage between the electrode 91 and the wafer is 500V, and it can be seen that even if a voltage lower than 500V is applied between the electrode 91 and the wafer, plasma is not ignited in the processing container 11.

[0043] Conventionally, in order to remotely supply the active gas (for example, nitrogen gas plasma) generated in the plasma box 19 to the processing container 11, there have been problems such as an increase in the film thickness on the side closer to the edge of the wafer 2 in the processing container 11 and problems with the film quality. On the other hand, the ignition control method according to the present embodiment provides a method capable of selecting to generate plasma on the processing container 11 side or to generate plasma on the plasma box 19 side. Thereby, it becomes possible to control the film thickness and film quality of the wafer 2 at the edge and the center.

[0044] The selection of plasma ignition in the plasma box 19 and plasma ignition in the processing container 11 can be achieved by controlling the "inter-electrode voltage" or the "electrode-wafer voltage" with respect to the discharge voltage obtained from the Paschen curve.

[0045] Therefore, in order to control the "inter-electrode voltage" and the "electrode-wafer voltage" at the time of ignition with respect to the discharge voltage obtained from the Paschen curve, the mechanical adjustment positions (hereinafter referred to as adjustment positions) of the first variable capacitor 57 and the second variable capacitor 58 in the matcher 53 are controlled. Thereby, the capacitances C1 and C2 of the first variable capacitor 57 and the second variable capacitor 58 are adjusted. In addition to adjusting the capacitances C1 and C2, the frequency of the RF power supply 55 may be variably controlled. In this case, the RF power supply 55 uses a frequency-variable RF power supply.

[0046] [Table] "The "inter - electrode voltage" and the "electrode - wafer voltage" measure the voltage for each adjustment position of the first variable capacitor 57 and the second variable capacitor 58 for each frequency of the high - frequency wave supplied by the RF power supply 55 around the alignment position during plasma generation, and create a table storing the measured values. The created table is stored in the memory 102 in advance. Thereby, referring to the table stored in the memory 102, the adjustment positions of the first variable capacitor 57 and the second variable capacitor 58 that suppress the reflected wave at ignition can be determined, and the adjustment positions that can select plasma ignition in the plasma box 19 or the processing container 11 can be determined. By setting the initial positions of the first variable capacitor 57 and the second variable capacitor 58 to the adjustment positions where plasma ignition in the plasma box 19 or the processing container 11 can be selected, the region for plasma ignition can be selected from the plasma box 19 and the processing container 11."

[0047] Figure 5 is an example of a table storing the measured values of the inter - electrode voltage (Figure 5(a)) and the electrode - wafer voltage (Figure 5(b)) at each adjustment position of the first variable capacitor 57 and the second variable capacitor 58 when a high - frequency voltage with a frequency of 13.56 MHz is applied. Figure 6 is an example of a table storing the measured values of the inter - electrode voltage (Figure 6(a)) and the electrode - wafer voltage (Figure 6(b)) at each adjustment position of the first variable capacitor 57 and the second variable capacitor 58 when a high - frequency voltage with a frequency of 14.56 MHz is applied."

[0048] The measured values stored in the table of Figure 5(a) are an example of the first information indicating the inter - electrode voltage for each of a plurality of adjustment positions of the variable capacitor when a high - frequency voltage with a frequency of 13.56 MHz, which is an example of the second frequency, is applied from the RF power supply 55 to the electrode pair 91, 92."

[0049] The measured values stored in the table of Figure 5(b) are an example of the second information indicating the electrode - wafer voltage for each of a plurality of adjustment positions of the variable capacitor when a high - frequency voltage with a frequency of 13.56 MHz is applied between the electrode and the wafer from the RF power supply 55. At this time, the wafer is regarded as being at the ground potential."

[0050] The measured values stored in the table of FIG. 6(a) are an example of third information indicating the voltage between electrodes for each of a plurality of adjustment positions of the variable capacitor when a high-frequency voltage having a frequency of 14.56 MHz, which is an example of a first frequency, is applied from the RF power supply 55 to the electrode pair 91, 92.

[0051] The measured values stored in the table of FIG. 6(b) are an example of fourth information indicating the voltage between the electrode and the wafer for each of a plurality of adjustment positions of the variable capacitor when a high-frequency voltage having a frequency of 14.56 MHz is applied between the RF power supply 55 and the electrode-wafer. The first to fourth information is stored in advance in the memory 102. The memory 102 is an example of a storage unit that stores the first to fourth information. The first to fourth information is shown in a table format in this example, but it may not be stored in a table format.

[0052] In both FIGS. 5 and 6, when measuring the measured values stored in the table, nitrogen gas was supplied from the air supply ports 42A, 42B, 42C of the vertical pipes 41A, 41B, 41C. However, it is sufficient to supply nitrogen gas from at least any one of the air supply ports 42A, 42B, 42C of the vertical pipes 41A, 41B, 41C.

[0053] When a high-frequency voltage with a frequency of 13.56 MHz and a power of 100 W is applied between the electrodes 91 and 92 from the RF power supply 55, the measured values of the voltage between the electrodes are shown in the table of Fig. 5(a), and the measured values of the voltage between the electrode and the wafer are shown in the table of Fig. 5(b). The adjustment positions of the first variable capacitor 57 and the second variable capacitor 58 are shifted in 5% increments from 0% of the minimum position to 100% of the maximum position, thereby changing the capacitances C1 and C2 of the first variable capacitor 57 and the second variable capacitor 58 for each adjustment position. The measured values of the voltage between the electrodes when the capacitances C1 and C2 are changed in 5% increments are stored in the table of Fig. 5(a), and the measured values of the voltage between the electrode and the wafer are stored in the table of Fig. 5(b). The creation conditions of the tables in Figs. 6(a) and (b) are different in that the frequency of the high-frequency output from the RF power supply 55 is changed to 14.56 MHz, and the other points are the same as the creation conditions of the tables in Figs. 5(a) and (b). However, in Figs. 5 and 6, although the capacitances C1 and C2 are changed in 5% increments, this is not the only case, and the increment value may be changed, such as changing the capacitances C1 and C2 in 1% increments.

[0054] When creating any of the tables in Figs. 5(a) and (b), Figs. 6(a) and (b), no plasma ignition occurs in the plasma box 19 and the processing container 11. That is, the voltage between the electrodes and the voltage between the electrode and the wafer are measured in a state where no plasma discharge occurs in the plasma box 19 and the processing container 11. By using a low high-frequency voltage and pressure at which no plasma is generated during the measurement of the voltage between the electrodes and the voltage between the electrode and the wafer in this way, stable voltage measurement becomes possible.

[0055] Also, the information on the matching position MP1 when the plasma is stably matched between the electrodes and the information on the matching position MP2 when the plasma is stably matched between the electrode and the wafer are stored in the memory 102.

[0056] In the tables of FIGS. 5(a) and (b), the position where C1 is 60% and C2 is 25% is the matching position MP1 when plasma ignition (discharge) occurs between the electrodes and the plasma is stably matched. In the tables of FIGS. 5(a) and (b), the position where C1 is 80% and C2 is 30% is the matching position MP2 when plasma ignition (discharge) occurs between the electrode and the wafer and the plasma is stably matched.

[0057] Also in the tables of FIGS. 6(a) and (b), the matching position MP1 between the electrodes and the matching position MP2 between the electrode and the wafer at the same positions as in the tables of FIGS. 5(a) and (b) are shown. From the tables of FIGS. 5 and 6, it can be seen that when the high-frequency frequency is increased, the regions of high voltages of 1000 V or more for both the inter-electrode voltage and the electrode-wafer voltage shift from the center to the left side.

[0058] FIGS. 7(a) and (b) are explanatory diagrams for determining the initial positions of the first variable capacitor 57 and the second variable capacitor 58 with reference to the tables of FIGS. 6(a) and (b) when a high-frequency voltage of 14.56 MHz is applied. FIGS. 8(a) and (b) are explanatory diagrams for determining the initial positions of the first variable capacitor 57 and the second variable capacitor 58 with reference to the tables of FIGS. 5(a) and (b) when the high-frequency frequency is changed from 14.56 MHz to 13.56 MHz.

[0059] For each of the frequencies of 14.56 MHz and 13.56 MHz, a table is created by measuring for each adjustment position of the first variable capacitor 57 and the second variable capacitor 58 (FIGS. 5 and 6). Thereby, for each frequency, the control positions (adjustment positions) that suppress the reflected wave at the time of plasma ignition in each of the plasma box 19 and the processing container 11 centered on the matching positions MP1 and MP2 can be determined as the initial positions of the first variable capacitor 57 and the second variable capacitor 58.

[0060] For example, when applying a high-frequency voltage with a frequency of 14.56 MHz, referring to the tables in FIGS. 6(a) and (b), a region Ar relatively close to the alignment positions MP1 and MP2 is specified as a region with few reflected waves. The specified results are shown in FIGS. 7(a) and (b). Then, a region in the plasma box 19 where stable discharge occurs within the region Ar, that is, a region BA of the adjustment position of the variable capacitor where plasma ignition occurs between the electrodes in a state where almost no reflected waves are present, is specified. In FIG. 7(a), since the voltage between the electrodes is 1000 V or more in the region, plasma ignition is possible between the electrodes. When plasma ignites and stable discharge occurs between the electrodes, the voltage between the electrode and the wafer is not relevant.

[0061] From the above, when applying a high-frequency voltage with a frequency of 14.56 MHz, referring to the table in FIG. 7(a), the initial positions of the first variable capacitor 57 and the second variable capacitor 58 are determined such that the capacitances C1 and C2 are in either of the regions BA. Thereby, when applying a high-frequency wave with a frequency of 14.56 MHz, the initial positions of the adjustment positions of the first variable capacitor 57 and the second variable capacitor 58 are controlled such that the capacitances C1 and C2 are within the region BA in FIG. 7(a). Thereby, plasma can be ignited within the plasma box 19.

[0062] Next, when the frequency of the high frequency is changed from 14.56 MHz to 13.56 MHz, referring to the tables in FIGS. 5(a) and (b), a region Ar relatively close to the alignment positions MP1 and MP2 is specified. The specified results are shown in FIGS. 8(a) and (b). Note that the frequency of the high frequency can be changed from 14.56 MHz to 13.56 MHz instantaneously (about several msec), but at this time, the first variable capacitor 57 and the second variable capacitor 58 cannot follow and hardly move. In this state, in the region Ar, a region where stable discharge occurs in the processing container 11, that is, a region RA of the adjustment position of the variable capacitor where plasma ignition occurs between the electrode and the wafer with almost no reflected wave is specified. In FIG. 8(b), since there is a position where the voltage between the electrode and the wafer is 500 V or more within the region RA, plasma ignition is possible between the electrode and the wafer. When plasma ignition occurs between the electrode and the wafer and stable discharge occurs, the voltage between the electrodes is less than 1000 V, which is the minimum ignition voltage.

[0063] Therefore, referring to the table in FIG. 8(a), the voltage between the electrodes is less than 1000 V within the region RA in FIG. 8(a). Thus, when applying a high frequency with a frequency of 13.56 MHz, the initial positions of the adjustment positions of the first variable capacitor 57 and the second variable capacitor 58 are controlled so that the capacitances C1 and C2 become positions where the voltage between the electrode and the wafer within the region RA in FIG. 8(b) is 500 V or more. Thereby, plasma ignition can be caused in the processing container 11.

[0064] Also, by switching the frequency of the high frequency of the RF power supply 55 between 13.56 MHz and 14.56 MHz and controlling the initial positions of the adjustment positions of the first variable capacitor 57 and the second variable capacitor 58, the region where plasma ignition occurs can be switched at high speed.

[0065] As described above, when the high-frequency of the RF power supply 55 is set to the first frequency (e.g., 14.56 MHz), when determining the initial positions of the first variable capacitor 57 and the second variable capacitor 58, the inter-electrode voltage (first information) and the electrode-wafer voltage (second information) in the table when applying the high-frequency voltage of each frequency are used. However, in addition to the first information and the second information, it is preferable to use the information of the first alignment position MP1 and the second alignment position Mp2.

[0066] Also, when the high-frequency of the RF power supply 55 is set to a second frequency (e.g., 13.56 MHz) different from the first frequency, when determining the initial positions of the first variable capacitor 57 and the second variable capacitor 58, the inter-electrode voltage (third information) and the electrode-wafer voltage (fourth information) in the table when applying the high-frequency voltage of each frequency are used. However, in addition to the third information and the fourth information, it is preferable to use the information of the first alignment position MP1 and the second alignment position Mp2.

[0067] [Ignition control method] Next, an ignition control method using the initial positions of the first variable capacitor 57 and the second variable capacitor 58 determined as described above will be described with reference to FIGS. 9 and 10. FIG. 9 is a flowchart showing the ignition control method according to the embodiment. FIG. 10 is a time chart showing the ignition control method according to the embodiment. The ignition control method according to the embodiment is controlled by the control unit 100.

[0068] In this example, as shown in FIG. 10(b), from time T 0 to time T 1 the RF power supply 55 is turned off, and at time T 1 the RF power supply 55 is turned on, and a high-frequency voltage of 14.56 MHz is applied. Then, at time T 2 the frequency is changed from 14.56 MHz to 13.56 MHz, and a high-frequency voltage of 13.56 MHz is applied from the RF power supply 55.

[0069] The process of FIG. 9 starts when the power supply of the film forming apparatus 10 is turned on. The frequency of the high frequency output from the RF power supply 55 is set in advance to the first frequency (step S1). The first frequency is 14.56 MHz in this example. In the idle mode, the high frequency voltage is off (step S3), and the control unit 100 supplies nitrogen gas from the plurality of air supply ports 42A, 42B, 42C of the vertical pipes 41A, 41B, 41C in this state.

[0070] The control unit 100 determines whether the RF power supply 55 is turned on and a high frequency voltage is applied between the electrodes 91, 92 (step S5). The idle mode continues until a high frequency voltage is applied between the electrodes 91, 92, and at time T 1 when the RF power supply 55 is turned on and a high frequency voltage is applied between the electrodes 91, 92, the ignition mode is entered (step S7). In the ignition mode, the control unit 100 controls the adjustment positions of the first variable capacitor 57 and the second variable capacitor to the determined initial positions. The control unit 100 selects the determined initial position from either a position where ignition is possible in the plasma box 19 or a position where ignition is possible in the processing container 11 and controls the initial positions of the first variable capacitor 57 and the second variable capacitor. By controlling the initial positions of the variable capacitors in this way, it is possible to select the region where plasma ignition occurs from the plasma box 19 and the processing container 11.

[0071] Next, the control unit 100 determines whether the RF power supply 55 is turned off (step S9). If the RF power supply 55 is turned off, the process returns to step S3 and transitions to the idle mode.

[0072] If the RF power supply 55 is not turned off, it is determined whether the ignition time (a predetermined time from the ignition mode) has elapsed (step S11). At time T 1 when the ignition time has elapsed from time T 2 to time T 1 the frequency of the high frequency output from the RF power supply 55 is changed to the second frequency (step S13). In this example, the second frequency is 13.56 MHz. The ignition time from time T 2 to time T is, for example, 1.0 ms to 400 ms. As shown in FIG. 10(a), at time T1 From time T 2 Until the ignition time, the reflected high-frequency waves increase. After that, when the high-frequency is changed to 13.56 MHz, a stable mode is achieved (step S15).

[0073] Next, the control unit 100 determines whether the RF power supply 55 has been turned off (step S17). While the RF power supply 55 is on, the stable mode is maintained (step S15). When the RF power supply 55 is turned off, the process returns to step S3 and transitions to the idle mode.

[0074] According to the ignition control method described above, the region where plasma ignition occurs can be selected from the plasma box 19 and the processing container 11. Thereby, the controllability of the film thickness of the film on the wafer 2 can be improved. For example, the film thickness distribution of a silicon nitride film or the like formed on the wafer 2 can be controlled, such as changing the film thickness of the film on the wafer 2 from a mountain shape with a thick center to a bowl shape with a thin center. For example, by igniting plasma on the plasma box 19 side, the film thickness on the edge side of the film on the wafer 2 can be increased, or by igniting plasma on the processing container 11 side, the film thickness on the center side of the film on the wafer 2 can be increased, or the overall film thickness can be increased. Also, by selecting the region where plasma ignition occurs from the plasma box 19 and the processing container 11, the film quality such as the stress of the film on the wafer 2 can be controlled.

[0075] In the above description, both the frequency of the high-frequency output from the RF power supply 55 and the capacitance of the variable capacitor are changed. However, the region where plasma ignition occurs may be selected from the plasma box 19 and the processing container 11 by changing only the capacitance of the variable capacitor without changing the high-frequency. This can also improve the controllability of the film thickness and film quality of the film formed on the wafer.

[0076] [Film Deposition Method] Next, the film deposition method according to the embodiment will be described with reference to FIGS. 11 and 12. FIG. 11 is a flowchart showing the film deposition method according to the embodiment. FIG. 12 is a time chart showing the film deposition method according to the embodiment. The film deposition method according to the embodiment is controlled by the control unit 100.

[0077] When the film formation method is started, the control unit 100 carries the wafer 2 into the inside of the processing container 11 and prepares it (step S20). In step S20, first, outside the processing container 11, the transfer device places a plurality of wafers 2 on the substrate holder 30. The substrate holder 30 horizontally holds the plurality of wafers 2 at intervals in the vertical direction. Next, the elevating unit 25 is raised to raise the lid 20 and the substrate holder 30. The wafer 2 is carried into the inside of the processing container 11 together with the substrate holder 30, and the opening at the lower end of the processing container 11 is sealed by the lid 20.

[0078]

[0079] Next, the control unit 100 performs a purge process (step S23). This step S23 is performed from time t2 to time t3 shown in FIG. 12. In this step S23, while exhausting the inside of the processing container 11 by the exhaust device, a purge gas is supplied into the inside of the processing container 11. Thereby, the gas remaining inside the processing container 11 is replaced with the purge gas. The purge gas may be nitrogen gas, argon gas, or other inert gas or a combination thereof. The time of this step S23 is, for example, 3 seconds or more and 10 seconds or less. The purge gas may be supplied from a nitride gas supply source 80 or the like.

[0080] ​Next, the control unit 100 performs a modification process on the Si-containing layer (step S25). This step S25 is performed from time t3 to time t4 shown in FIG. 12. In this step S25, while exhausting the inside of the processing container 11 by the exhaust device, the reforming gas is supplied into the processing container 11 by the reforming gas supply source 75. Further, in this step S25, plasma is ignited in either the plasma box 19 or the processing container 11 to plasmaize the reforming gas. In this step S25, the ignition control method according to the embodiment is executed, and the control unit 100 controls the initial positions of the first variable capacitor 57 and the second variable capacitor 58 so that the region where plasma is ignited is selected in either the plasma box 19 or the processing container 11.

[0081] The reforming gas is, for example, nitrogen gas. The reforming gas may be hydrogen gas or ammonia gas. The reforming gas may be a gas containing nitrogen gas or a gas containing hydrogen gas. The Si-containing layer is modified with the plasmaized reforming gas. The modification of the Si-containing layer includes, for example, removing the halogen element contained in the Si-containing layer. By removing the halogen element, unbonded hands of Si can be formed. As a result, the Si-containing layer can be activated and the nitridation of the Si-containing layer can be promoted. The frequency of the high frequency of the RF power supply 55 is, for example, 13.56 MHz or 14.56 MHz. The time of step S25 is, for example, 3 seconds or more and 60 seconds or less.

[0082] Next, the control unit 100 performs a purge process (step S27). This step S27 is performed from time t4 to time t5 shown in FIG. 12. In this step S27, while exhausting the inside of the processing container 11 by the exhaust device, the purge gas is supplied into the processing container 11. Thereby, the gas remaining inside the processing container 11 is replaced with the purge gas. The time of this step S27 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 the nitriding gas supply source 80 or the like.

[0083] Next, the control unit 100 performs a nitriding process on the Si-containing layer (Process S29). This Process S29 is performed from time t5 to time t6 shown in FIG. 12. In this Process S29, while exhausting the inside of the processing container 11 by the exhaust device, a nitriding gas is supplied into the processing container 11 by the nitriding gas supply source 80. Further, in this Process S29, plasma is ignited in either the plasma box 19 or the processing container 11 to turn the nitriding gas into plasma. In this Process S29, the ignition control method according to the embodiment is executed, and the control unit 100 controls the initial positions of the first variable capacitor 57 and the second variable capacitor 58 so that the region where plasma is ignited is selected in either the plasma box 19 or the processing container 11. The nitriding gas is, for example, ammonia gas. The Si-containing layer is nitrided with the plasmaized ammonia gas. The time of Process S29 is, for example, 5 seconds or more and 120 seconds or less.

[0084] Next, the control unit 100 performs a purge process (Process S31). This Process S31 is performed from time t6 to time t7 shown in FIG. 12. In this Process S31, while exhausting the inside of the processing container 11 by the exhaust device, a purge gas is supplied into the processing container 11. Thereby, the gas remaining inside the processing container 11 is replaced with the purge gas. The time of this Process S31 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 the nitriding gas supply source 80 or the like.

[0085] Next, the control unit 100 determines whether the set number of times has been repeated (Process S33). The set number of times is set in advance. When the control unit 100 determines that the set number of times has not been repeated, it returns to Process S21 and repeats the cycle of Processes S21 to S31. While repeating the cycle, the temperature of the wafer 2 is, for example, 400°C or more and 600°C or less, and the atmospheric pressure inside the processing container 11 is, for example, 13 Pa or more and 665 Pa or less.

[0086] When the control unit 100 determines that the set number of times has been repeated, since a silicon nitride film with a desired film thickness and film quality has been formed, this process is terminated.

[0087] In the film formation method described above, the purge step can be omitted. The film formation method according to the embodiment includes the following steps (a), (b), and (c). (a) A step of supplying a raw material gas containing an element to be nitrided to a substrate and forming a layer containing the element on the substrate (b) A step of supplying activated nitrogen gas, hydrogen gas, or ammonia gas by plasma after supplying the raw material gas to the substrate (c) A step of supplying a gas containing nitrogen activated by plasma and nitriding the element And in the step (b), a region where plasma ignition is performed using the above-described ignition control method is selected from the plasma box and the processing vessel.

[0088] [Effect] Conventionally, plasma is generated in a quartz plasma box 19 disposed on the side surface of the processing vessel 11, and the activated gas is supplied into the processing vessel 11. In contrast, in the present embodiment, plasma can be generated in the processing vessel 11 by controlling the voltage between electrodes and the voltage between the electrode and the wafer at the time of plasma ignition. Further, plasma ignition can be alternately performed in the plasma box 19 and the processing vessel 11, or plasma ignition can be performed in at least one of the plasma box 19 and the processing vessel 11. Thereby, the controllability of the film thickness and film quality of the silicon nitride film on the wafer on the substrate can be enhanced.

[0089] Note that the alignment position at the time of plasma generation (ignition) may change due to the influence of the cumulative film thickness of the silicon nitride film on the wall surface of the processing vessel 11, cleaning in the processing vessel 11, maintenance of the film forming apparatus 10, and the like. In this case, the initial position of the variable capacitor at the time of ignition and the frequency of the RF power supply 55 may be corrected according to the amount of change in the alignment position. By using a previously created table and the changed alignment position, plasma ignition in the plasma box 19 or the processing vessel 11 with suppressed reflected waves becomes possible even after the alignment position has changed.

[0090] As described above, according to the ignition control method, film formation method, and film formation apparatus of the present embodiment, the region where plasma ignition is performed can be selected from the plasma box and the processing chamber. Thereby, the controllability of the film thickness and film quality of the film formed on the wafer can be enhanced.

[0091] The ignition control method, film formation method, and film formation apparatus according to the embodiment disclosed this time should be considered to be illustrative and not restrictive in all respects. The embodiment can be modified and improved in various forms without departing from the scope and gist of the appended claims. Matters described in the above plurality of embodiments can also adopt other configurations and can be combined within a non - conflicting range.

Explanation of Reference Numerals

[0092] 10 Film formation apparatus 11 Processing chamber 19 Plasma box 53 Matching unit 57 First variable capacitor 58 Second variable capacitor 100 Control unit

Claims

1. A processing container for accommodating a substrate, A plasma box formed in the processing container, A pair of electrodes arranged so as to sandwich the plasma box, An RF power source connected to the pair of electrodes via a matcher having a variable capacitor, A method for controlling ignition executed by a film forming apparatus having, A step of prestoring in a storage unit first information indicating the voltage between the electrodes for each of a plurality of adjustment positions of the variable capacitor when a high-frequency voltage of a first frequency is applied from the RF power source to the pair of electrodes, and second information indicating the voltage between the electrode and the substrate, A step of determining an initial position of the variable capacitor based on the first information and the second information with reference to the storage unit, A step of setting an adjustment position of the variable capacitor to the initial position and selecting a region for plasma ignition from the plasma box and the processing container, including the ignition control method.

2. The step of determining the initial position determines the initial position of the variable capacitor based on information on a first matching position in the plasma box, information on a second matching position in the processing container, the first information, and the second information. The ignition control method according to claim 1.

3. The step of storing in the storage unit prestores third information indicating the voltage between the electrodes for each of a plurality of adjustment positions of the variable capacitor when a high-frequency voltage of a second frequency different from the first frequency is applied to the pair of electrodes, and fourth information indicating the voltage between the electrode and the substrate, The RF power source is capable of controlling the frequency variably, and has a step of controlling the frequency of the RF power source to the second frequency, The step of determining the initial position updates the initial position of the variable capacitor based on the third information and the fourth information with reference to the storage unit when the frequency of the RF power source is controlled to the second frequency, The step of selecting sets the adjustment position of the variable capacitor to the updated initial position and selects a region for plasma ignition from the plasma box and the processing container. The ignition control method according to claim 1 or 2.

4. The step of determining the initial position updates the initial position of the variable capacitor based on information on a first matching position in the plasma box, information on a second matching position in the processing container, the third information, and the fourth information. The ignition control method according to claim 3.

5. Step (a): Supplying a raw material gas containing an element to be nitrided to a substrate and forming a layer containing the element on the substrate; Step (b): After supplying the raw material gas to the substrate, supplying nitrogen gas, hydrogen gas or ammonia gas activated by plasma to modify the layer containing the element; Step (c): Supplying a gas containing nitrogen activated by plasma to nitride the element. In a film forming method for forming a nitride film on a substrate, the method includes: In the step (b), selecting a region where plasma ignition is performed using the ignition control method according to any one of claims 1 to 4 from a plasma box and a processing container. A film forming method.

6. A processing container for accommodating a substrate; A plasma box formed in the processing container; A pair of electrodes arranged so as to sandwich the plasma box; An RF power source connected to the pair of electrodes via a matcher having a variable capacitor; A film forming apparatus having a control unit, wherein: The control unit: Storing in advance in a storage unit first information indicating the voltage between the electrodes for each of a plurality of adjustment positions of the variable capacitor when a high-frequency voltage of a first frequency is applied from the RF power source to the pair of electrodes, and second information indicating the voltage between the electrodes and the substrate; Determining an initial position of the variable capacitor based on the first information and the second information with reference to the storage unit; A film forming apparatus that controls a step of setting an adjustment position of the variable capacitor to the initial position and selecting a region where plasma ignition is performed from the plasma box and the processing container.

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