Plasma processing apparatus and control method for plasma processing apparatus

Abstract

The present invention provides a plasma processing apparatus with impedance matching and a control method for the plasma processing apparatus. [Solution] A plasma processing apparatus comprising: a pair of plasma electrodes; an impedance matching circuit disposed between the pair of plasma electrodes and a high-frequency power supply and including a first variable inductor and a second variable inductor; and a control unit, wherein the control unit has an efficiency map that associates the inductance of the first variable inductor and the inductance of the second variable inductor with the efficiency of the matching circuit, and is capable of performing an impedance matching step of changing these inductances; a step of determining the efficiency of the matching circuit based on the matched inductances of the first variable inductor and the second variable inductor and the efficiency map; and a step of calculating the output power of the high-frequency power supply and controlling the output power of the high-frequency power supply based on the efficiency of the matching circuit and the supplied power.

Description

Technical Field

[0001] The present disclosure relates to a plasma processing apparatus and a method for controlling the plasma processing apparatus.

Background Art

[0002] Patent Document 1 discloses a method for controlling a plasma processing apparatus, which includes a high-frequency power source that applies high-frequency power to a substrate holding unit in a chamber, a matcher provided between the substrate holding unit and the high-frequency power source, and a plasma generation unit that generates plasma from a gas by the high-frequency power.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] On one side, the present disclosure provides a plasma processing apparatus for impedance matching and a method for controlling the plasma processing apparatus.

Means for Solving the Problems

[0005] To solve the above problems, according to one embodiment, a plasma processing apparatus is provided comprising: a high-frequency power supply; a pair of plasma electrodes; an impedance matching circuit disposed between the pair of plasma electrodes and the high-frequency power supply and including a first variable inductor and a second variable inductor; and a control unit, wherein the control unit has an efficiency map that associates the inductance of the first variable inductor and the inductance of the second variable inductor with the efficiency of the impedance matching apparatus, and is configured to perform the following steps: changing the inductance of the first variable inductor and the inductance of the second variable inductor to achieve impedance matching; determining the efficiency of the impedance matching apparatus based on the impedance-matched inductance of the first variable inductor and the inductance of the second variable inductor and the efficiency map; calculating the output power of the high-frequency power supply based on the determined efficiency of the impedance matching apparatus and the power supplied to the plasma electrodes; and controlling the output power of the high-frequency power supply based on the calculated output power. [Effects of the Invention]

[0006] In one aspect, it is possible to provide an impedance-matched plasma processing apparatus and a control method for the plasma processing apparatus. [Brief explanation of the drawing]

[0007] [Figure 1] A schematic diagram showing an example configuration of a substrate processing apparatus. [Figure 2] A circuit diagram showing an example of a circuit that supplies high-frequency power to a plasma electrode. [Figure 3] A schematic diagram showing the configuration of a variable inductor. [Figure 4] An example flowchart illustrating impedance matching. [Figure 5] An example of an efficiency map for a matching circuit. [Modes for carrying out the invention]

[0008] The following describes embodiments for implementing this disclosure with reference to the drawings. In each drawing, the same reference numerals are used for identical components, and redundant explanations may be omitted.

[0009] [Substrate Processing Equipment] An example of the substrate processing apparatus (plasma processing apparatus) 100 according to this embodiment will be described with reference to Figure 1. Figure 1 is a schematic diagram showing an example of the configuration of the substrate processing apparatus 100. In the following description, the substrate processing apparatus 100 will be described as an example of a film deposition apparatus that forms a silicon nitride film on a substrate W using an ALD (Atomic Layer Deposition) process with, for example, a plasma of silicon-containing gas and nitrogen-containing gas.

[0010] The substrate processing apparatus 100 has a cylindrical processing container 1 with a top and an open bottom. The entire processing container 1 is made of, for example, quartz. A top plate 2 made of quartz is provided near the top of the processing container 1, and the area below the top plate 2 is sealed. A cylindrical metal manifold 3 is connected to the opening at the bottom of the processing container 1 via a sealing member 4 such as an O-ring.

[0011] The manifold 3 supports the lower end of the processing container 1, and a wafer boat 5 (substrate holder) on which a large number of semiconductor wafers (for example, 25 to 150 wafers, hereinafter referred to as "substrates W") are placed in multiple layers is inserted into the processing container 1 from below the manifold 3. In this way, a large number of substrates W are housed in the processing container 1 in a substantially horizontal manner with spacing along the vertical direction. The wafer boat 5 is made of, for example, quartz. The wafer boat 5 has three rods 6 (two are shown in Figure 1), and the large number of substrates W are supported by grooves (not shown) formed in the rods 6.

[0012] The wafer boat 5 is placed on the table 8 via a heat-insulating cylinder 7 made of quartz. The table 8 is supported on a rotating shaft 10 that passes through a metal (stainless steel) cover 9 that opens and closes the opening at the lower end of the manifold 3.

[0013] A magnetic fluid seal 11 is provided at the penetration portion of the rotating shaft 10, which hermetically seals the rotating shaft 10 and supports it so that it can rotate. A sealing member 12 is provided between the periphery of the lid 9 and the lower end of the manifold 3 to maintain airtightness inside the processing container 1.

[0014] The rotating shaft 10 is attached to the tip of an arm 13 supported by a lifting mechanism (not shown), such as a boat elevator, and the wafer boat 5 and the lid 9 move up and down together and are inserted into and removed from the processing container 1. Alternatively, a table 8 may be fixed to the lid 9 side, allowing the substrate W to be processed without rotating the wafer boat 5.

[0015] Furthermore, the substrate processing apparatus 100 has a gas supply unit 20 (processing gas supply unit) that supplies predetermined gases such as processing gas and purging gas into the processing container 1.

[0016] The gas supply unit 20 has gas supply pipes 21, 22, and 23. Gas supply pipe 21 is made of, for example, quartz, and extends vertically by penetrating the side wall of the manifold 3 inward and bending upward. Multiple gas holes 21g are formed at predetermined intervals in the vertical portion of gas supply pipe 21 over a length corresponding to the wafer support range of the wafer boat 5. Each gas hole 21g discharges gas horizontally. Gas supply pipe 22 is made of, for example, quartz, and extends vertically by penetrating the side wall of the manifold 3 inward and bending upward. Multiple gas holes 22g are formed at predetermined intervals in the vertical portion of gas supply pipe 22 over a length corresponding to the wafer support range of the wafer boat 5. Each gas hole 22g discharges gas horizontally. Gas supply pipe 23 is made of, for example, quartz, and consists of a short quartz tube provided penetrating the side wall of the manifold 3.

[0017] The gas supply pipe 21 has its vertical portion (the vertical portion where the gas hole 21g is formed) provided inside the processing vessel 1. A processing gas (raw material gas) is supplied to the gas supply pipe 21 from a gas supply source 21a via a gas pipe. The gas pipe is provided with a flow rate controller 21b and an on-off valve 21c. Thus, the processing gas from the gas supply source 21a is supplied into the processing vessel 1 via the gas pipe and the gas supply pipe 21. Note that the processing gas supplied from the gas supply source 21a is, for example, a silicon-containing gas. The silicon-containing gas is, for example, DCS (dichlorosilane, SiH2Cl2).

[0018] The gas supply pipe 22 has its vertical portion (the vertical portion where the gas hole 22g is formed) provided in a plasma generation space described later. A processing gas (reaction gas, nitriding gas) is supplied to the gas supply pipe 22 from a gas supply source 22a via a gas pipe. The gas pipe is provided with a flow rate controller 22b and an on-off valve 22c. Thus, the processing gas from the gas supply source 22a is supplied into the plasma generation space via the gas pipe and the gas supply pipe 21, is plasmaized in the plasma generation space, and is supplied into the processing vessel 1. Note that the processing gas supplied from the gas supply source 22a is, for example, a nitrogen-containing gas. The nitrogen-containing gas is, for example, NH3.

[0019] A purge gas is supplied to the gas supply pipe 23 from a purge gas supply source (not shown) via a gas pipe. The gas pipe (not shown) is provided with a flow rate controller (not shown) and an on-off valve (not shown). Thus, the purge gas from the purge gas supply source is supplied into the processing vessel 1 via the gas pipe and the gas supply pipe 23. Note that the purge gas supplied from the purge gas supply source is, for example, an inert gas such as argon (Ar) or nitrogen (N2). Also, although the case where the purge gas is supplied into the processing vessel 1 via the gas supply pipe 23 has been described, it is not limited thereto, and the purge gas may be supplied into the processing vessel 1 via either of the gas supply pipes 21 and 22.

[0020] A plasma generation mechanism 30 is formed in a part of the side wall of the processing container 1. The plasma generation mechanism 30 converts the processing gas from the gas supply source 22a into plasma.

[0021] The plasma generation mechanism 30 includes a plasma partition wall 32, a pair of plasma electrodes 33 (only one is shown in FIG. 1), a power supply line 34, a matching device 35, a coaxial cable 36, a high-frequency power supply 37, and an insulating protection cover 38.

[0022] The plasma partition wall 32 is airtightly welded to the outer wall of the processing container 1. The plasma partition wall 32 is formed of, for example, quartz. The plasma partition wall 32 has a concave cross-section and covers an opening 31 formed in the side wall of the processing container 1. The opening 31 is formed elongated in the vertical direction so as to cover all the substrates W supported by the wafer boat 5 in the vertical direction. A gas supply pipe 22 for discharging the processing gas is arranged in the inner space defined by the plasma partition wall 32 and communicating with the inside of the processing container 1, that is, the plasma generation space. Note that a gas supply pipe 21 for discharging the processing gas is provided at a position close to the substrate W along the inner wall of the processing container 1 outside the plasma generation space.

[0023] The pair of plasma electrodes 33 (only one is shown in FIG. 1) each have an elongated shape and are arranged opposite to each other along the vertical direction on the outer surfaces of the walls on both sides of the plasma partition wall 32. Each plasma electrode 33 is held by, for example, a holding portion (not shown) provided on the side surface of the plasma partition wall 32. A power supply line 34 is connected to the lower end of each plasma electrode 33.

[0024] The power supply line 34 electrically connects each plasma electrode 33 and the matching device 35. In the illustrated example, one end of the power supply line 34 is connected to the lower end of each plasma electrode 33 and the other end is connected to the matching device 35.

[0025] The matching device 35 has an impedance matching circuit 510 (see FIG. 2 described later) and is a device that performs impedance matching between the high-frequency power supply 37 and the substrate processing apparatus

[0026] The coaxial cable 36 electrically connects the matching unit 35 and the high-frequency power supply 37.

[0027] The high-frequency power supply 37 is connected to the lower end of each plasma electrode 33 via a coaxial cable 36, a matching unit 35, and a power supply line 34, supplying high-frequency power of, for example, 13.56 MHz to the pair of plasma electrodes 33. This supplies high-frequency power to the plasma generation space defined by the plasma partition wall 32. The processing gas (nitrogen-containing gas) discharged from the gas supply pipe 22 is plasma-generated in the plasma generation space to which high-frequency power is supplied, and supplied to the inside of the processing container 1 through the opening 31.

[0028] The insulating protective cover 38 is attached to the outside of the plasma compartment wall 32 so as to cover the plasma compartment wall 32. A refrigerant passage (not shown) is provided in the inner portion of the insulating protective cover 38, and the plasma electrode 33 is cooled by flowing a refrigerant such as cooled nitrogen (N2) gas through the refrigerant passage. A shield (not shown) may also be provided between the plasma electrode 33 and the insulating protective cover 38 so as to cover the plasma electrode 33. The shield is made of a good conductor such as metal and is grounded.

[0029] An exhaust port 40 (exhaust section) for vacuuming the inside of the processing container 1 is provided on the side wall portion of the processing container 1 facing the opening 31. The exhaust port 40 is formed to be long and narrow vertically, corresponding to the wafer boat 5. An exhaust port cover member 41, formed in a U-shape in cross-section, is attached to the portion of the processing container 1 corresponding to the exhaust port 40. The exhaust port cover member 41 extends upward along the side wall of the processing container 1. An exhaust pipe 42 for exhausting the processing container 1 through the exhaust port 40 is connected to the lower part of the exhaust port cover member 41. An exhaust device 44, including a pressure control valve 43 for controlling the pressure inside the processing container 1 and a vacuum pump, is connected to the exhaust pipe 42, and the inside of the processing container 1 is exhausted through the exhaust pipe 42 by the exhaust device 44.

[0030] A cylindrical heating mechanism 50 is provided around the processing container 1. The heating mechanism 50 heats the processing container 1 and the substrate W inside it. The heating mechanism 50 controls the temperature of the processing container 1 to reach a desired temperature. As a result, the substrate W inside the processing container 1 is heated by radiant heat from the walls of the processing container 1, etc.

[0031] The substrate processing apparatus 100 also has a control unit 60. The control unit 60 controls the operation of each part of the substrate processing apparatus 100, for example, the supply and cessation of gases by opening and closing the on / off valves 21c and 22c, the control of gas flow rates by flow controllers 21b and 22b, and the exhaust control by the exhaust device 44. The control unit 60 also controls the on / off of high-frequency power by the high-frequency power supply 37, and the temperature of the processing container 1 and the substrate W inside it by the heating mechanism 50. The control unit 60 also controls the matching unit 35.

[0032] The control unit 60 may be, for example, a computer. Furthermore, the computer program that controls the operation of each part of the substrate processing device 100 is stored in a storage medium. The storage medium may be, for example, a flexible disk, compact disk, hard disk, flash memory, DVD, etc.

[0033] In the substrate processing apparatus 100 shown in Figure 1, a plasma generation mechanism 30 located on the side of the processing container 1 generates plasma from the processing gas, and the activated processing gas is supplied to the substrate W inside the processing container 1. However, the apparatus is not limited to this configuration. The substrate processing apparatus 100 may also be configured to generate plasma from the processing gas within the processing container 1 and supply the activated processing gas to the substrate W inside the processing container 1. In this case, the pair of plasma electrodes 33 are arranged facing each other across the processing container 1. Furthermore, the wall surface of the processing container 1 becomes a plasma partition wall that divides the plasma generation space.

[0034] [Substrate processing process for substrate processing equipment] Next, an example of the operation of the substrate processing apparatus 100 will be described. Here, we will explain as an example a film deposition process in which a silicon nitride film is formed on a substrate W using an ALD process with a silicon-containing gas and a nitrogen-containing gas plasma.

[0035] In one example of a film deposition process, a process of supplying raw material gas, a first purging process, a nitriding process, and a second purging process are repeated for a predetermined number of cycles to form a silicon nitride film on the substrate W. In each process, N2 gas, which is the purging gas, is continuously supplied from the gas supply pipe 23 throughout the film deposition process.

[0036] The process of supplying the raw material gas involves supplying silicon-containing gas into the processing container 1. In the raw material gas supply process, the control unit 60 opens the on-off valve 21c and supplies silicon-containing gas from the gas supply source 21a through the gas supply pipe 21 into the processing container 1. As a result, the silicon-containing gas is adsorbed onto the surface of the substrate W.

[0037] The first purging step is a step of purging excess silicon-containing gas, etc., from the processing container 1. In the first purging step, the control unit 60 closes the on-off valve 21c and stops the supply of silicon-containing gas. As a result, the purge gas that is constantly supplied from the gas supply pipe 23 purges excess silicon-containing gas, etc., from the processing container 1.

[0038] The nitriding process involves generating a plasma of nitrogen-containing gas and supplying nitrogen (N)-containing active species (ions, radicals, etc.) into the processing container 1. In the nitriding process, the control unit 60 opens the on-off valve 22c and supplies nitrogen-containing gas from the gas supply source 22a through the gas supply pipe 22 to the plasma generation space within the plasma compartment wall 32. The control unit 60 also controls the high-frequency power supply 37 to supply high-frequency power to the plasma electrode 33, generating plasma in the plasma generation space within the plasma compartment wall 32. That is, nitrogen (N)-containing active species are generated in the plasma generation space and supplied into the processing container 1 through the opening 31. This nitrides the silicon-containing gas adsorbed on the surface of the substrate W, forming a silicon nitride film on the surface of the substrate W.

[0039] The second purging step is a step to purge excess nitrogen-containing gas, etc., from the processing container 1. In the second purging step, the control unit 60 closes the on-off valve 22c and stops the supply of nitrogen-containing gas. The control unit 60 also controls the high-frequency power supply 37 to stop the supply of high-frequency power and stop plasma generation. As a result, the purge gas that is constantly supplied from the gas supply pipe 23 purges excess nitrogen-containing gas, etc., from the processing container 1.

[0040] The above process of supplying raw material gas, the first purging process, the nitriding process, and the second purging process constitute one cycle, and by repeating a predetermined number of cycles, a silicon nitride film of a desired thickness is formed on the substrate W.

[0041] Furthermore, the film deposition process may include a modification step to improve the uniformity of the in-plane film thickness of the silicon nitride film and to improve the film quality of the silicon nitride film.

[0042] The reforming process involves generating a plasma of a reforming gas (e.g., hydrogen gas) and supplying the active species (ions, radicals, etc.) of the reforming gas into the processing container 1. In the reforming process, the control unit 60 supplies the reforming gas from a reforming gas supply source (not shown) through a gas supply pipe 22 to the plasma generation space within the plasma compartment wall 32. The reforming gas is, for example, hydrogen (H2) gas. The control unit 60 also controls the high-frequency power supply 37 to supply high-frequency power to the plasma electrode 33, generating plasma in the plasma generation space within the plasma compartment wall 32. That is, active species of the reforming gas are generated in the plasma generation space and supplied into the processing container 1 through the opening 31. This reforms the silicon nitride film formed on the surface of the substrate W.

[0043] The reforming process was described using a configuration in which a reformed gas activated using plasma is supplied into the processing container 1 as an example, but it is not limited to this configuration. The reforming process may also consist of a configuration in which a reformed gas is supplied into the processing container 1.

[0044] Thus, the plasma generated in the plasma generation space is used in processes such as nitriding (for example, a process to generate plasma of NH3 gas) and reforming (for example, a process to generate plasma of H2 gas). In the ALD cycle, cycles including the nitriding and reforming processes are repeated at high speed. That is, each time a plasma of a different gas is generated, the matching unit 35 performs impedance matching. For this reason, it is preferable that the time required to match the impedance in the matching unit 35 be short.

[0045] Incidentally, in a matching circuit using a variable capacitor with adjustable capacitance, the loss in the matching circuit is small, and even if the matching position (capacitance of the variable capacitor that matches the impedance) changes, the change in the loss in the matching circuit is small. For this reason, in order to compensate only for the loss in the coaxial cable 36 from the high-frequency power supply 37 to the matching circuit, a dummy load (not shown) is connected in place of the matching circuit, and the control unit 60 sets the high-frequency output power (RF output power), which has been corrected for the loss, to the high-frequency power supply 37 so that the desired high-frequency power (RF supply power) is supplied to the end of the coaxial cable 36. In addition, the capacitance of the variable capacitor is changed by a motor. For this reason, in a matching circuit using a variable capacitor, the time it takes to match the impedance is, for example, on the order of seconds.

[0046] In addition, a matching unit 35 using a variable inductor capable of rapidly adjusting the inductance may be mounted on the substrate processing device 100. With a matching unit 35 using a variable inductor, the time required to match the impedance is, for example, on the order of milliseconds.

[0047] However, in a matching circuit 35 using a variable inductor, the losses in the matching circuit 35 (losses due to the resistance of the variable inductor windings, copper loss) are larger compared to a matching circuit using a variable capacitor, and the changes in losses in the matching circuit 35 due to changes in the matching position (inductance of the variable inductor that matches impedance) are also larger. For this reason, in a substrate processing device 100 equipped with a matching circuit 35 using a variable inductor, it is necessary to consider not only the losses in the coaxial cable 36 from the high-frequency power supply 37 to the matching circuit 35, but also the losses in the matching circuit 35.

[0048] Furthermore, the substrate processing apparatus 100 has machine variations due to physical tolerances and installation errors. For example, there are machine variations in the distance between the pair of plasma electrodes 33, the distance from one plasma electrode 33 (plasma electrode 331, described later in Figure 2) to the grounded heating mechanism 50 (or grounded shield), the distance from the other plasma electrode 33 (plasma electrode 332, described later in Figure 2) to the grounded heating mechanism 50 (or grounded shield), and the thickness of the plasma partition wall 32 placed between the pair of plasma electrodes 33.

[0049] These instrumental differences may affect the state of the plasma 39 (see Figure 2, described later) generated in the plasma generation space within the plasma compartment wall 32. Specifically, these instrumental differences cause changes in the matching position of the matching unit 35, which in turn changes the losses in the matching unit 35, and increases the instrumental differences in the high-frequency power (RF supply power) supplied to the plasma electrodes 33 (plasma electrodes 331 and 332, described later in Figure 2).

[0050] [Matching box] Next, the matching unit 35 will be explained further using Figure 2. Figure 2 is a circuit diagram showing an example of a circuit that supplies high-frequency power to the plasma electrode 33. In Figure 2, the signal flow is illustrated with dashed arrows.

[0051] The plasma electrode 33 has one plasma electrode 331 and the other plasma electrode 332. The pair of plasma electrodes 331 and 332 are arranged facing each other on the outside of the plasma compartment wall 32. Inside the plasma compartment wall 32, a plasma generation space is formed where plasma 39 is generated.

[0052] The high-frequency power supply 37 comprises a power supply 410, a high-frequency sensor 420, and a power supply control unit 430. The high-frequency power supply 37 also includes a high-frequency line 451.

[0053] The high-frequency line 451 receives high-frequency power output from the power supply 410.

[0054] The power supply 410 includes, for example, a high-frequency oscillator and an amplifier. The high-frequency oscillator is an oscillator that generates a sine wave or fundamental wave at a predetermined frequency (e.g., 13.56 MHz). The amplifier is an amplifier that amplifies the power of the sine wave or fundamental wave output from the high-frequency oscillator with a variablely controllable gain or amplification factor. The power supply 410 is controlled by a power supply control unit 430.

[0055] The radio frequency (RF) sensor 420 is mounted on the radio frequency line 451 and detects the radio frequency power output from the radio frequency power supply 37. The radio frequency sensor 420 also has a directional coupler on the radio frequency line 451. The radio frequency sensor 420 detects the power PF1 of the traveling wave propagating in the forward direction on the radio frequency line 451, that is, from the radio frequency power supply 37 to the matching circuit 35. The radio frequency sensor 420 also detects the power RF1 of the reflected wave propagating in the reverse direction on the radio frequency line 451, that is, from the matching circuit 35 to the radio frequency power supply 37. The radio frequency sensor 420 then outputs the detection results to the power supply control unit 430.

[0056] The power control unit 430 controls the power supply 410 according to the control signal from the control unit 60. The power control unit 430 also controls the power supply 410 according to the detection result detected by the high-frequency sensor 420. The power control unit 430 also outputs the detection result detected by the high-frequency sensor 420 to the control unit 60.

[0057] The coaxial cable 36 connects the high-frequency power supply 37 and the matching unit 35. Specifically, the inner conductor (core wire) of the coaxial cable 36 connects the high-frequency line 451 of the high-frequency power supply 37 and the high-frequency power supply line 551 of the matching unit 35. The outer conductor (shield) of the coaxial cable 36 is grounded.

[0058] The matching unit 35 includes an impedance matching circuit 510, a high-frequency sensor 520, a voltage sensor 530, and a matching unit control unit 540. The matching unit 35 also includes a high-frequency power supply line 551, a ground line 552, a first load line 553, and a second load line 554.

[0059] The high-frequency power supply line 551 is connected to the high-frequency line 451 of the high-frequency power supply 37 via a coaxial cable 36. In other words, the high-frequency power supply line 551 is a line to which high-frequency power is supplied from the high-frequency power supply 37.

[0060] Grounding line 552 is the line that is grounded.

[0061] The first load line 553 is connected to one plasma electrode 331 via the power supply line 341. The second load line 554 is connected to the other plasma electrode 332 via the power supply line 342.

[0062] The impedance matching circuit 510 has a plurality of reactance elements 511 to 516. The impedance matching circuit 510 is also connected to a high-frequency power supply line 551, a ground line 552, a first load line 553, and a second load line 554.

[0063] The reactance element 511 and the variable reactance element 512 are arranged in series between the high-frequency power supply line 551 and the ground line 552. The reactance element (first fixed reactance element) 511 is a fixed capacitor (capacitor) having capacitance C1. The variable reactance element (first variable reactance element, first variable inductor) 512 is a variable inductor with adjustable inductance VL1(Load). The inductance VL1(Load) of the variable reactance element 512 is controlled by the matching unit control unit 540.

[0064] The reactance element 513 and the variable reactance element 514 are arranged in series between the first load line 553 and the second load line 554. The reactance element (second fixed reactance element) 513 is a fixed capacitor (capacitor) having capacitance C2. The variable reactance element (second variable reactance element, second variable inductor) 514 is a variable inductor with adjustable inductance VL2(Phase). The inductance VL2(Phase) of the variable reactance element 512 is controlled by the matching unit control unit 540.

[0065] The reactance element (third fixed reactance element) 515 is placed between the high-frequency power supply line 551 and the first load line 553. The reactance element 515 is a fixed inductor (coil) having inductance L1.

[0066] The reactance element (fourth fixed reactance element) 516 is placed between the ground line 552 and the second load line 554. The reactance element 516 is a fixed inductor (coil) having inductance L2.

[0067] Here, an example of the configuration of variable reactance elements (variable inductors) 512 and 514, in which the inductance can be adjusted, will be explained using Figure 3. Figure 3 is a schematic diagram showing the configuration of a variable inductor.

[0068] The variable inductor has a ring-shaped core 600 and coils 601 and 602 wound around the core 600. Coil 601 corresponds to variable reactance elements 512 and 514 and is connected to an impedance matching circuit 510. Coil 602 is connected to a power supply (not shown), and the current flowing through coil 602 is controlled by a matching circuit control unit 540.

[0069] Here, the inductance L at terminals T1-T2 of coil 601 is given by the permeability μ [H / m] of core 600 and the cross-sectional area S [m²] of core 600. 2 Using the number of turns N in the coil 601 and the length l [m] of the core 600, it can be expressed by the following formula.

[0070] L=μSN 2 / l[H]

[0071] Furthermore, the permeability μ of the core 600 can be varied by varying the DC current I flowing through terminals T3-T4 of the coil 602.

[0072] In other words, the matching circuit control unit 540 can change the inductance of coil 601 by controlling the power supply and thereby controlling the DC current I flowing through coil 602. That is, the inductance of coil 601 can be changed according to the response speed of changing the DC current I flowing through coil 602. This allows the inductance of the variable reactance elements 512 and 514 to be adjusted at high speed, and the time required for impedance matching by the matching circuit 35 can be shortened.

[0073] Returning to Figure 2, the radio frequency (RF) sensor 520 is installed on the high-frequency power supply line 551 and detects the high-frequency power supplied from the high-frequency power supply 37. The high-frequency sensor 520 also has a directional coupler on the high-frequency power supply line 551. The high-frequency sensor 520 detects the power PF2 of the traveling wave propagating in the forward direction on the high-frequency power supply line 551, that is, from the high-frequency power supply 37 to the matching unit 35. The high-frequency sensor 520 also detects the power RF2 of the reflected wave propagating in the reverse direction on the high-frequency power supply line 551, that is, from the matching unit 35 to the high-frequency power supply 37. The high-frequency sensor 520 then outputs the detection results to the matching unit control unit 540.

[0074] The voltage sensor 530 includes a first voltage sensor 531, a second voltage sensor 532, and a third voltage sensor 533.

[0075] The first voltage sensor 531 detects the potential difference between the first load line 553 and the ground line 552, and detects the peak value of this potential difference. Hereinafter, the peak value detected by the first voltage sensor 531 will also be referred to as the first peak value Vpp1. The first voltage sensor 531 then outputs the detection result to the matching unit control unit 540.

[0076] The second voltage sensor 532 detects the potential difference between the second load line 554 and the ground line 552, and detects the peak value of this potential difference. Hereinafter, the peak value detected by the second voltage sensor 532 will also be referred to as the second peak value Vpp2. The second voltage sensor 532 then outputs the detection result to the matching unit control unit 540.

[0077] The third voltage sensor 533 detects the potential difference between the first load line 553 and the second load line 554, and detects the peak value of this potential difference. Hereinafter, the peak value detected by the third voltage sensor 533 will also be referred to as the third peak value Vpp3. The third voltage sensor 533 then outputs the detection result to the matching unit control 540.

[0078] Although the voltage sensor 530 shown in Figure 2 has been described as including three components: a first voltage sensor 531, a second voltage sensor 532, and a third voltage sensor 533, it is not limited to this configuration. The third voltage sensor 533 may be omitted. In this case, the matching unit 540 may calculate the potential difference between the first load line 553 and the second load line 554 from the difference between the potential difference detected by the first voltage sensor 531 and the potential difference detected by the second voltage sensor 532, and then calculate the third peak value Vpp3. Similarly, the voltage sensor 530 may be configured to include at least two of the first voltage sensor 531, the second voltage sensor 532, and the third voltage sensor 533.

[0079] The impedance matching control unit 540 controls the variable reactance elements 512 and 514 of the impedance matching circuit 510 according to the control signal from the control unit 60. The impedance matching control unit 540 also controls the variable reactance elements 512 and 514 of the impedance matching circuit 510 according to the detection results detected by the high-frequency sensor 520 and the voltage sensor 530 (first voltage sensor 531, second voltage sensor 532, third voltage sensor 533). The impedance matching control unit 540 also outputs the detection results detected by the high-frequency sensor 520 and the voltage sensor 530 to the control unit 60.

[0080] The power supply line 34 includes power supply line 341 and power supply line 342. Power supply line 341 connects the first load line 553 of the matching unit 35 to one of the plasma electrodes 331. Power supply line 342 connects the second load line 554 of the matching unit 35 to the other plasma electrode 332.

[0081] With this configuration, the matching circuit 35 is configured so that the inductance of the variable reactance elements 512 and 514 can be controlled by the matching circuit control unit 540.

[0082] Therefore, based on the detection result of the high-frequency sensor 520, the matching unit control 540 controls the inductance of the variable reactance elements 512 and 514 so that the power RF2 of the reflected wave is reduced (approaches zero). In other words, the matching unit control 540 controls the inductance of the variable reactance elements 512 and 514 so that the impedance on the load side, including the impedance matching circuit 510, becomes a predetermined impedance.

[0083] In addition, the matching unit 540 controls the inductance of the variable reactance elements 512 and 514 based on the detection result of the voltage sensor 530 so that the first peak value Vpp1 (i.e., the peak value of one of the plasma electrodes 331) becomes a predetermined set value.

[0084] Furthermore, the matching unit 540 controls the inductance of the variable reactance elements 512 and 514 based on the detection result of the voltage sensor 530 so that the second peak value Vpp2 (i.e., the peak value of the other plasma electrode 332) becomes a predetermined set value.

[0085] In other words, the matching unit 35 shown in Figure 2 can adjust the pulse peak value of one plasma electrode 331 (first pulse peak Vpp1) and the pulse peak value of the other plasma electrode 332 (second pulse peak Vpp2). It can also adjust the pulse peak value of the voltage between plasma electrodes 331 and 332 (third pulse peak Vpp3). This suppresses differences in the state of the plasma 39 due to variations in the substrate processing apparatus 100. Furthermore, the matching unit 35 can reduce the influence of variations in the substrate processing apparatus 100 on the process results.

[0086] [Impedance matching process] Next, the impedance matching process will be explained using Figures 4 and 5. Figure 4 is an example of a flowchart illustrating the impedance matching process.

[0087] As mentioned above, the matching circuit 35 using variable inductors (variable reactance elements 512, 514) can perform impedance matching at high speed. On the other hand, changes in the matching position can change the losses in the matching circuit 35, and the power (voltage amplitude) of the high-frequency power supplied to the plasma electrodes 33 (plasma electrodes 331, 332) may also change. For this reason, the high-frequency output power of the high-frequency power supply 37 is controlled so that the power (voltage amplitude) of the high-frequency power supplied to the plasma electrodes 33 (plasma electrodes 331, 332) is at a predetermined value.

[0088] In step S101, an efficiency map is prepared that associates the positions of the variable inductors (variable reactance elements 512, 514) with the efficiency (or loss) of the matching circuit 35. The efficiency map is stored in the control unit 60.

[0089] Figure 5 shows an example of an efficiency map of the matching circuit 35. The efficiency map is an efficiency map that associates the inductance VL1 of the variable reactance element 512 and the inductance VL2 of the variable reactance element 514 with the efficiency of the matching circuit 35. That is, it is an efficiency map that makes it possible to determine the efficiency of the matching circuit 35 based on the inductance VL1 of the variable reactance element 512 and the inductance VL2 of the variable reactance element 514. The efficiency of the matching circuit 35 is the ratio (%) of the high-frequency power output from the matching circuit 35 to the power of the high-frequency power input to the matching circuit 35.

[0090] The vertical Tune indicates the variable range of the inductance VL1 (Load) of the variable reactance element 512, from 0% to 100%. The horizontal Match indicates the variable range of the inductance VL2 (Phase) of the variable reactance element 514, from 0% to 100%.

[0091] Alternatively, the map may be such that Tune indicates the variable range of the signal for varying the inductance VL1(Load) (DC current I in the example of Figure 3) as 0% to 100%, and Match also indicates the variable range of the signal for varying the inductance VL1(Load) (DC current I in the example of Figure 3) as 0% to 100%.

[0092] The efficiency (or loss) of the matching circuit 35 corresponding to each Tune and each Match is then shown.

[0093] For example, if the inductance VL1 (Load) of the variable reactance element 512 is 55% of the variable range (Tune: 55) and the inductance VL2 (Phase) of the variable reactance element 514 is 80% of the variable range (Match: 80), then 85.5% is stored as the efficiency of the matching circuit 35.

[0094] The map also stores the output power (in other words, the RF power supplied to the plasma electrode 33) output from the matching unit 35 when a predetermined output power (RF output power) is supplied from the high-frequency power supply 37. In the example in Figure 5, the output power (RF power supplied) output from the matching unit 35 when 100W of output power (RF output power) is supplied from the high-frequency power supply 37 is shown in the upper row, and the efficiency of the matching unit 35 is shown in the lower row.

[0095] Furthermore, the range of impedance matching positions differs depending on the gas used to generate the plasma. For example, when generating H2 plasma, impedance matching occurs within the range of Tune: 50-80% and Match: 30-50%. When generating N2 plasma, impedance matching occurs within the range of Tune: 60-70% and Match: 40-65%. When generating NH3 plasma, impedance matching occurs within the range of Tune: 70-85% and Match: 50-80%.

[0096] The efficiency map may also be experimentally determined by supplying a predetermined output power (100W in the example of Figure 5) (RF output power) from the high-frequency power supply 37 to the matching unit 35 via the coaxial cable 36, connecting a dummy load (not shown) in place of the plasma electrode 33, and detecting the output power output from the matching unit 35 while changing the positions of the variable reactance elements 512 and 514. Alternatively, the efficiency map may be determined by calculation or simulation from the circuit configuration of the impedance matching circuit 510.

[0097] In step S102, a recipe is prepared. The recipe includes various settings for substrate processing (e.g., processes that generate plasma, such as nitriding and modification processes). For example, the recipe includes information such as the type of processing gas used in substrate processing and the power of the high-frequency power supplied to the plasma electrode 33. The recipe is stored in the control unit 60.

[0098] In step S103, the position of the variable inductor is moved to a preset position. Here, the control unit 60 selects the preset position of the variable inductor according to the type of processing gas used for substrate processing as described in the recipe. That is, as shown in Figure 5, a range is defined for each processing gas, and the preset position is set within that range. The control unit 60 sets the inductance VL1 of the variable reactance element 512 and the inductance VL2 of the variable reactance element 514 to preset values ​​via the matching unit control unit 540.

[0099] By setting the inductance VL1 of variable reactance element 512 and the inductance VL2 of variable reactance element 514 to preset values ​​based on the recipe, the amount of change until impedance matching is achieved can be suppressed. In other words, the impedance matching time can be shortened.

[0100] In step S104, the efficiency of the matching circuit 35 corresponding to the preset position is determined from the efficiency map, and the output of the high-frequency power supply 37 is calculated from the determined efficiency and the RF power supplied to the plasma electrodes 33 (plasma electrodes 331, 332) set in the recipe. The control unit 60 determines the efficiency of the matching circuit 35 from the efficiency map and the preset position of the variable inductor (inductance VL1 set to a preset value and inductance VL2 set to a preset value). The control unit 60 also calculates the output of the high-frequency power supply 37 (RF output power) from the RF power supplied to the plasma electrodes 33 (plasma electrodes 331, 332) set in the recipe (RF supply power).

[0101] In step S105, the output of the high-frequency power supply 37 is controlled. Here, the control unit 60 controls the power supply 410 via the power supply control unit 430 so that the output (RF output power) of the high-frequency power supply 37 becomes the output (RF output power) calculated in step S104.

[0102] In step S106, the position of the variable inductor is matched and controlled. Here, the impedance matching control unit 540 changes the inductance VL1 of the variable reactance element 512 and the inductance VL2 of the variable reactance element 514 to match the impedance. In order to efficiently utilize the energy of the plasma, it is preferable to select the matching position (inductance VL1 and inductance VL2) of the variable inductor that has a higher efficiency for the impedance matching unit 35. Specifically, it is preferable for the impedance matching control unit 540 to actively select the matching position (inductance VL1 and inductance VL2) of the variable inductor that results in an efficiency of 80% or more for the impedance matching unit 35 as shown in the efficiency map in Figure 5.

[0103] In step S107, the efficiency of the matching circuit 35 corresponding to the matching position is determined from the efficiency map, and the output of the high-frequency power supply 37 is calculated from the determined efficiency and the RF power supplied to the plasma electrodes 33 (plasma electrodes 331, 332) set in the recipe. The control unit 60 determines the efficiency of the matching circuit 35 from the efficiency map and the matching position of the variable inductor (inductance VL1 and inductance VL2). The control unit 60 also calculates the output of the high-frequency power supply 37 (RF output power) from the RF power supplied to the plasma electrodes 33 (plasma electrodes 331, 332) set in the recipe (RF supply power).

[0104] In step S108, the output of the high-frequency power supply 37 is controlled. Here, the control unit 60 controls the power supply 410 via the power supply control unit 430 so that the output (RF output power) of the high-frequency power supply 37 becomes the output (RF output power) calculated in step S107.

[0105] In step S109, it is determined whether or not to terminate the matching process. If the matching process is not terminated (S109 - NO), the control unit 60 returns to step S106. Then, the matching process of the matching circuit 35 (S106) to the output control of the high-frequency power supply 37 (S107, S108) is considered one cycle, and this cycle is repeated. If the matching process is terminated (S109 - YES), the control unit 60 terminates its process.

[0106] Furthermore, the processes from step S103 to step S109 are performed for each step that generates the plasma of the recipe (e.g., nitriding step, modification step, etc.). This reduces the time required for impedance matching in the ALD cycle and improves the processing performance of the substrate processing apparatus 100.

[0107] Furthermore, when the process of generating a plasma of the processing gas is repeated by the ALD cycle, the preset position (preset value) in step S103 may be the impedance-matched value from the previous process of generating the plasma of the processing gas.

[0108] As described above, the matching unit 35 can reduce the impedance matching time and control the high-frequency output power (RF output power) of the high-frequency power supply 37 so that the high-frequency power (RF supply power) supplied to the plasma electrode 33 is a predetermined value set in the recipe.

[0109] In the example described above, the control unit 60 that controls the matching circuit 35 and the high-frequency power supply 37 processes the control shown in Figure 4, but this configuration is not the only one. The matching circuit control unit 540 of the matching circuit 35 and the power supply control unit 430 of the high-frequency power supply 37 may exchange information to process the control shown in Figure 4.

[0110] It should be noted that the present invention is not limited to the configurations shown in the above embodiments, including combinations with other elements. These aspects can be modified without departing from the spirit of the present invention and can be appropriately determined according to their application. [Explanation of Symbols]

[0111] 1. Processing container 20 Gas Supply Department 21, 22, 23 Gas supply pipes 30 Plasma generation mechanism 31 Aperture 32 Plasma Compartment Wall 33,331,332 Plasma electrodes 34,341,342 Power supply lines 35,35A matching box 36 Coaxial Cables 37 High frequency power supply 38 Insulating protective cover 39 Plasma 40 Exhaust vents 50 Heating mechanism 60 Control Unit 100 Substrate Processing Equipment (Plasma Processing Equipment) 410 Power supply 420 High-Frequency Sensors 430 Power Control Unit 451 High-Frequency Line 510 Impedance Matching Circuit 511 Reactance element (first fixed reactance element) 513 Reactance element (second fixed reactance element) 515 Reactance element (third fixed reactance element) 516 Reactance element (fourth fixed reactance element) 512 Variable reactance element (first variable reactance element, first variable inductor) 514 Variable reactance element (second variable reactance element, second variable inductor) 520 High-Frequency Sensor 530~533 Voltage Sensor 540 Matching Unit Control Unit 551 High-frequency power supply line 552 Grounding line 553 1st load line 554 Second Load Line

Claims

1. High-frequency power supply and A pair of plasma electrodes, A matching circuit is disposed between a pair of plasma electrodes and the high-frequency power supply and includes an impedance matching circuit comprising a first variable inductor and a second variable inductor. It comprises a control unit and, The control unit, The system has an efficiency map that associates the inductance of the first variable inductor and the inductance of the second variable inductor with the efficiency of the matching circuit. A step of changing the inductance of the first variable inductor and the inductance of the second variable inductor to achieve impedance matching, A step of determining the efficiency of the matching circuit based on the impedance-matched inductances of the first variable inductor and the second variable inductor, and the efficiency map, and calculating the output power of the high-frequency power supply based on the determined efficiency of the matching circuit and the power supplied to the plasma electrode, The system is configured to perform the step of controlling the output power of the high-frequency power supply based on the calculated output power, Plasma processing equipment.

2. The control unit, The system is configured to further perform a cycle in which the steps of impedance matching, calculating the output power of the high-frequency power supply, and controlling the output power of the high-frequency power supply constitute one cycle, and the cycle is repeated. The plasma processing apparatus according to claim 1.

3. The control unit, Before repeating the above cycle, A step of setting the inductance of the first variable inductor and the inductance of the second variable inductor to preset values, A step of determining the efficiency of the matching circuit based on the preset values ​​of the inductance of the first variable inductor and the inductance of the second variable inductor and the efficiency map, and calculating the output power of the high-frequency power supply based on the determined efficiency of the matching circuit and the power supplied to the plasma electrode, A step of controlling the output power of the high-frequency power supply based on the calculated output power, and a further executable configuration The plasma processing apparatus according to claim 2.

4. The matching device is A high-frequency power supply line from which high-frequency power is supplied from the aforementioned high-frequency power supply, The grounding line to be grounded, One of the plasma electrodes is connected to a first load line, A second load line connected to the other plasma electrode, The impedance matching circuit is connected to the high-frequency power supply line, the first load line, the second load line, and the ground line, The impedance matching circuit described above is A first fixed reactance element and a first variable inductor are arranged in series between the high-frequency power supply line and the ground line. A second fixed reactance element and a second variable inductor are arranged in series between the first load line and the second load line. A third fixed reactance element is disposed between the high-frequency power supply line and the first load line, The system includes a fourth fixed reactance element positioned between the second load line and the ground line, The plasma processing apparatus according to claim 1.

5. The aforementioned impedance matching process is: The matching position of the inductance of the first variable inductor and the inductance of the second variable inductor is selected such that the efficiency of the matching circuit in the efficiency map is 80% or more. The plasma processing apparatus according to claim 1.

6. High-frequency power supply and A pair of plasma electrodes, A control method for a plasma processing apparatus comprising a matching circuit having an impedance matching circuit including a first variable inductor and a second variable inductor, which is disposed between a pair of plasma electrodes and the high-frequency power supply, The system has an efficiency map that associates the inductance of the first variable inductor and the inductance of the second variable inductor with the efficiency of the matching circuit. A step of changing the inductance of the first variable inductor and the inductance of the second variable inductor to achieve impedance matching, A step of determining the efficiency of the matching circuit based on the impedance-matched inductances of the first variable inductor and the second variable inductor, and the efficiency map, and calculating the output power of the high-frequency power supply based on the determined efficiency of the matching circuit and the power supplied to the plasma electrode, The system is configured to perform the step of controlling the output power of the high-frequency power supply based on the calculated output power, A method for controlling a plasma processing device.

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