Monitoring method and plasma processing apparatus

Abstract

To stably control a plasma processing using a pulse wave of a RF power.SOLUTION: A monitoring method is performed by a plasma processing apparatus including: a mounting stage that is arranged in a processing container, and mounts a substrate; an antenna that is provided to an upper part of the processing container; a RF power supply that is connected to the antenna and supplies the RF power; a matching circuit that is arranged between the antenna and the RF power supply; and a measurement part that measures an output end voltage of the matching circuit. The monitoring method includes: a step (a) of preparing the substrate onto the mounting stage; a step (b) of supplying the pulse wave of the RF power of a predetermined duty ratio from the RF power supply; and a step (c) of monitoring a state of a plasma on the basis of a conversion value of a Vpp voltage obtained by converting the Vpp voltage of the output end voltage on the basis of the duty ratio, the RF power, and relative information of the Vpp voltage and the RF power.SELECTED DRAWING: Figure 9

Description

[Technical Field]

[0001] The present disclosure relates to a monitoring method and a plasma processing apparatus. [Background technology]

[0002] For example, Patent Document 1 proposes a plasma processing apparatus having a vacuum chamber with a rotating table on which multiple substrates are placed and rotated, and an antenna facing the upper surface of the rotating table. In this plasma processing apparatus, while the rotating table is rotating, a plasma processing gas is supplied into the vacuum chamber and a pulsed RF power wave is supplied to the antenna. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent Publication No. 2021-180215 Summary of the Invention [Problem to be solved by the invention]

[0004] The present disclosure provides a monitoring method and a plasma processing apparatus for stably controlling a plasma process using a pulsed RF power wave. [Means for solving the problem]

[0005] According to one aspect of the present disclosure, there is provided a monitoring method performed by a plasma processing apparatus having a processing vessel, a mounting stage disposed within the processing vessel and configured to mount a substrate thereon, an antenna disposed on an upper portion of the processing vessel, an RF power supply connected to the antenna and supplying RF power, a matching box disposed between the antenna and the RF power supply, and a measurement unit configured to measure an output end voltage of the matching box, the monitoring method including: (a) a step of preparing a substrate on the mounting stage; (b) a step of supplying a pulse wave of RF power having a predetermined duty ratio from the RF power supply; and (c) a step of monitoring a state of plasma based on a converted value of Vpp voltage obtained by converting a Vpp voltage of the output end voltage based on the duty ratio, the RF power, and correlation information between the Vpp voltage and the RF power. In the step (c), a converted value of the Vpp voltage is calculated based on the formula (1),

number

[0006] According to one aspect, it is possible to provide a monitoring method and a plasma processing apparatus for stably controlling a plasma process using a pulsed RF power wave. [Brief explanation of the drawings]

[0007] [Figure 1] 1 is a cross-sectional view showing an example of the configuration of a plasma processing apparatus according to an embodiment; [Figure 2] FIG. 2 is a plan view of the plasma processing apparatus of FIG. 1. [Figure 3] 2 is a cross-sectional view taken along a concentric circle of a rotary table of the plasma processing apparatus of FIG. 1. [Figure 4] 2 is a cross-sectional view of a plasma source provided in the plasma processing apparatus of FIG. 1. [Figure 5] FIG. 2 is a circuit diagram of a matching box provided in the plasma processing apparatus of FIG. [Figure 6] FIG. 10 is a diagram showing an example of the correlation between RF power and Vpp voltage when plasma is ignited and when it is not ignited. [Figure 7]FIG. 1 is a diagram showing an example of the average electron density and average electron temperature of continuous wave and pulse wave RF power. [Figure 8] FIG. 4 is a diagram showing an example of an output of a pulse wave of RF power in a monitoring method according to an embodiment. [Figure 9] 1 is a flowchart illustrating an example of a monitoring method according to an embodiment. [Figure 10] 10 is a diagram for explaining determination of the state of plasma by the monitoring method of FIG. 9. DETAILED DESCRIPTION OF THE INVENTION

[0008] Hereinafter, embodiments of the present disclosure will be described with reference to the drawings. In the drawings, the same components are denoted by the same reference numerals, and redundant explanations may be omitted.

[0009] In this specification, deviations in directions such as parallel, right angles, orthogonal, horizontal, vertical, up / down, left / right, etc. are permitted to the extent that they do not impair the effects of the embodiments. The shape of the corners is not limited to right angles and may be rounded like an arch. Parallel, right angles, orthogonal, horizontal, vertical, circular, and coincident may also include approximately parallel, approximately right angles, approximately orthogonal, approximately horizontal, approximately vertical, approximately circular, and approximately coincident.

[0010] [Plasma processing equipment] An example of a plasma processing apparatus according to an embodiment will be described with reference to FIGS. 1 to 4. FIG. 1 is a cross-sectional view showing an example of the configuration of a plasma processing apparatus according to an embodiment. FIG. 2 is a plan view of the plasma processing apparatus of FIG. 1. For ease of explanation, the top plate 11 is not shown in FIG. 2. FIG. 3 is a cross-sectional view taken along a concentric circle of the turntable 2 of the plasma processing apparatus of FIG. 1. FIG. 4 is a cross-sectional view of a plasma source 80 provided in the plasma processing apparatus of FIG. 1.

[0011] As shown in FIG. 1, the plasma processing apparatus includes a vacuum vessel (processing vessel) 1 having a generally circular planar shape, and a rotary table 2 disposed within the vacuum vessel 1, having a center of rotation at the center of the vacuum vessel 1, and for revolving a wafer (substrate) W.

[0012] The vacuum vessel 1 is a processing chamber for accommodating a wafer W and performing a film forming process on the surface of the wafer W to deposit a thin film. The vacuum vessel 1 includes a top plate 11 provided in a position facing the recess 24 of the turntable 2, and a vessel body 12. A ring-shaped seal member 13 is provided on the periphery of the upper surface of the vessel body 12. The top plate 11 is configured to be detachable from the vessel body 12.

[0013] A separation gas supply pipe 51 is connected to the center of the upper surface of the vacuum vessel 1 to supply a separation gas in order to prevent different process gases from mixing with each other in a central region C of the vacuum vessel 1.

[0014] The rotary table 2 is fixed at its center to a roughly cylindrical core portion 21, and is configured to be freely rotatable around a vertical axis, or clockwise in the example shown in Figure 2, by a drive portion 23, relative to a rotation axis 22 that is connected to the underside of the core portion 21 and extends vertically.

[0015] The driving unit 23 is provided with an encoder 25 that detects the rotation angle of the rotary shaft 22. In this embodiment, the rotation angle of the rotary shaft 22 detected by the encoder 25 is transmitted to the control device 120 and is used by the control device 120 to identify the position of the wafer W placed in each recess 24 on the rotary table 2. The rotary table 2 is an example of a mounting table that is disposed in a processing chamber and on which a substrate is placed.

[0016] The rotary shaft 22 and the drive unit 23 are housed in a case body 20. A flange portion on the upper surface of the case body 20 is airtightly attached to the underside of the bottom surface 14 of the vacuum vessel 1. A purge gas supply pipe 72 is connected to the case body 20 to supply Ar gas or the like as a purge gas (separation gas) to the region below the turntable 2. The outer periphery of the core portion 21 on the bottom surface 14 of the vacuum vessel 1 is formed in an annular shape so as to approach the turntable 2 from below, forming a protrusion 12a.

[0017] A circular recess 24 capable of receiving a wafer W having a diameter of, for example, 300 mm is formed on the surface of the turntable 2. The recesses 24 are provided at a plurality of locations, for example, six locations, along the rotation direction of the turntable 2 (the direction indicated by arrow A in FIG. 2). The recesses 24 have an inner diameter that is slightly larger than the diameter of the wafer W, specifically, approximately 1 to 4 mm. The depth of the recess 24 is configured to be approximately equal to or larger than the thickness of the wafer W. The bottom surface of the recess 24 is formed with through-holes (not shown) through which, for example, three lift pins (described later) pass to push up the wafer W from below and lift it up and down.

[0018] 2, a first processing region P1, a second processing region P2, and a third processing region P3 are provided at a distance from one another along the rotation direction of the turntable 2. At a position on the turntable 2 facing the passage region of the recess 24, a plurality of gas nozzles 31, 32, 33, 34, 35, 41, and 42, for example, made of quartz, for example, seven gas nozzles, are arranged radially at intervals from one another in the circumferential direction of the vacuum chamber 1.

[0019] Each of the gas nozzles 31 to 35, 41, and 42 is disposed between the turntable 2 and the top plate 11. Each of the gas nozzles 31 to 34, 41, and 42 is attached, for example, to extend horizontally from the outer peripheral wall of the vacuum vessel 1 toward the central region C, facing the turntable 2. On the other hand, the gas nozzle 35 extends from the outer peripheral wall of the vacuum vessel 1 toward the central region C, then bends and extends linearly counterclockwise (opposite to the rotation direction of the turntable 2) along the central region C.

[0020] 2, the plasma processing gas nozzles 33, 34, 35, separation gas nozzle 41, first processing gas nozzle 31, separation gas nozzle 42, and second processing gas nozzle 32 are arranged in this order from a transfer port 15 (described later) in a clockwise direction (the direction of rotation of the turntable 2). Note that the gas supplied by the second processing gas nozzle 32 is often a gas of the same quality as the gas supplied by the plasma processing gas nozzles 33 to 35, but if the plasma processing gas nozzles 33 to 35 can supply a sufficient amount of the gas, the second processing gas nozzle 32 may not necessarily be provided.

[0021] Alternatively, a single plasma processing gas nozzle may be used instead of the plasma processing gas nozzles 33 to 35. In this case, for example, a plasma processing gas nozzle extending from the outer peripheral wall of the vacuum vessel 1 toward the central region C may be provided, similar to the second processing gas nozzle 32. Each of the gas nozzles 31 to 35, 41, and 42 is connected to a respective gas supply source (not shown) via a flow rate control valve.

[0022] Gas nozzles 31-35, 41, and 42 have gas discharge holes 36 for discharging the above-mentioned gases formed at multiple locations, for example at equal intervals, along the radial direction of turntable 2 on the lower surface side (the side facing turntable 2) of each gas nozzle. The gas nozzles 31-35, 41, and 42 are arranged such that the distance between the lower edge of each nozzle and the upper surface of turntable 2 is, for example, about 1-5 mm.

[0023] The region below the first process gas nozzle 31 is a first process region P1 for adsorbing the source gas onto the wafer W, and the region below the second process gas nozzle 32 is a second process region P2 for supplying an oxidizing gas capable of oxidizing the source gas to generate an oxide onto the wafer W. The region below the plasma process gas nozzles 33 to 35 is a third process region P3 for modifying a film on the wafer W.

[0024] The first process gas nozzle 31 supplies a silicon-containing gas when forming a silicon oxide film or a silicon nitride film, and a metal-containing gas when forming a metal oxide film or a metal nitride film. Thus, the first process gas nozzle 31 is a nozzle that supplies a source gas (precursor) containing raw materials that are the main components of the thin film.

[0025] In this embodiment, a molecular layer of an oxide film is deposited on the wafer W in the second processing region P2. To form an oxide film, the plasma processing gas supplied from the plasma processing gas nozzles 33-35 is, for example, a gas containing oxygen. However, when forming a nitride film, the plasma processing gas supplied from the plasma processing gas nozzles 33-35 is, for example, a gas containing nitrogen.

[0026] The separation gas nozzles 41 and 42 are provided to form a separation region D that separates the first processing region P1 from the second processing region P2 and the third processing region P3 from the first processing region P1. The separation gas supplied from the separation gas nozzles 41 and 42 is an inert gas such as nitrogen or a rare gas such as helium or argon. The separation gas also functions as a purge gas. Note that no separation region D is provided between the second processing region P2 and the third processing region P3. This is because the oxidizing gas supplied to the second processing region P2 and the mixed gas supplied to the third processing region P3 both contain oxygen atoms in the oxygen gas contained in the mixed gas, and both function as oxidizing agents. Therefore, there is no need to separate the second processing region P2 from the third processing region P3 using a separation gas.

[0027] The plasma processing gas nozzles 33 to 35 are configured to supply gas to different regions on the turntable 2, and therefore the flow rate ratio of each component of the mixed gas may be varied for each region so that the modification process is performed uniformly throughout.

[0028] 3 is a cross-sectional view along a concentric circle of the turntable 2 of the plasma processing apparatus of FIG. 1, from separation region D through the first processing region P1 to separation region D. A roughly fan-shaped convex portion 4 is provided on the top plate 11 of the vacuum vessel 1 in separation region D. The convex portion 4 is attached to the back surface of the top plate 11. Within the vacuum vessel 1, a flat, low ceiling surface (hereinafter referred to as the "first ceiling surface 44") that is the underside of the convex portion 4, and ceiling surfaces (hereinafter referred to as the "second ceiling surfaces 45") that are higher than the first ceiling surface 44 and located on both sides of the first ceiling surface 44 in the circumferential direction are formed.

[0029] 2, the convex portion 4 forming the first ceiling surface 44 has a fan-shaped planar shape with its top cut in an arc shape. A groove 43 is formed in the circumferential center of the convex portion 4 so as to extend radially. Separation gas nozzles 41 and 42 are housed in the groove 43. The periphery of the convex portion 4 (the portion on the outer edge side of the vacuum vessel 1) is bent in an L shape so as to face the outer end surface of the turntable 2 and be slightly spaced from the vessel body 12 in order to prevent mixing of the process gases.

[0030] A nozzle cover 230 is provided above the first process gas nozzle 31 to allow the first process gas to flow along the wafer W and to allow the separation gas to flow along the top plate 11 side of the vacuum chamber 1, avoiding the vicinity of the wafer W. As shown in FIG. 3 , the nozzle cover 230 includes a cover body 231 and a flow rectifier plate 232. The cover body 231 has a generally box-like shape with an open bottom to accommodate the first process gas nozzle 31. The flow rectifier plates 232 are plate-like bodies connected to the open bottom end of the cover body 231 on the upstream and downstream sides in the rotation direction of the turntable 2. The side wall surface of the cover body 231 on the rotation center side of the turntable 2 extends toward the turntable 2 so as to face the tip of the first process gas nozzle 31. The side wall surface of the cover body 231 on the outer edge side of the turntable 2 is notched so as not to interfere with the first process gas nozzle 31. The nozzle cover 230 is not essential and may be provided as needed.

[0031] 2, a plasma source 80 is provided above the plasma processing gas nozzles 33 to 35 to convert the plasma processing gas discharged into the vacuum chamber 1 into plasma. The plasma source 80 uses an antenna 83 to generate inductively coupled plasma.

[0032] 4 is a cross-sectional view of a plasma source 80 provided in the plasma processing apparatus of FIG. 1. The plasma source 80 is provided above the vacuum chamber 1. It is configured by winding an antenna 83 made of a metal wire or the like in a coil shape, for example, three times around a vertical axis. The plasma source 80 is also disposed so as to surround a strip region extending in the radial direction of the turntable 2 in a plan view and to straddle the diameter of the wafer W on the turntable 2.

[0033] The antenna 83 is connected to an RF power supply 85 configured to supply RF power having a frequency of, for example, 13.56 MHz via a matching box 84. The antenna 83 is provided so as to be airtightly separated from the internal region of the vacuum vessel 1. In addition, in Fig. 4, a connection electrode 86 is provided to electrically connect the antenna 83 to the matching box 84 and the RF power supply 85.

[0034] The antenna 83 may be provided with a structure that allows it to be bent up and down, a vertical movement mechanism that can automatically bend the antenna 83 up and down, and a mechanism that can move the center of the turntable 2 up and down, as needed. These structures are omitted in Fig. 4.

[0035] As shown in FIG. 4, the top plate 11 has an opening 11a that is generally fan-shaped in plan view, formed above the plasma processing gas nozzles 33-35. The opening 11a includes an annular member 82 that is airtightly attached to the opening 11a along the edge of the opening 11a, as shown in FIG. 4. The housing 90 is airtightly attached to the inner circumferential surface of the annular member 82. That is, the outer circumferential side of the annular member 82 contacts the inner circumferential surface 11b of the opening 11a of the top plate 11, and the inner circumferential side contacts a flange portion 90a of the housing 90 (described later), thereby airtightly attaching the opening 11a. The housing 90, made of a dielectric material such as quartz, is attached to the opening 11a via the annular member 82, in order to position the antenna 83 below the top plate 11. The bottom surface of the housing 90 forms the ceiling surface 46 of the third processing region P3.

[0036] The internal atmosphere of the vacuum vessel 1 is set airtight via the annular member 82 and the housing 90. Specifically, the annular member 82 and the housing 90 are fitted into the opening 11a, and then the housing 90 is pressed downward in the circumferential direction by a pressing member 91 formed in a frame shape on the upper surfaces of the annular member 82 and the housing 90 so as to fit along the contact portion between the annular member 82 and the housing 90. Furthermore, the pressing member 91 is fixed to the top plate 11 by bolts (not shown) or the like. This sets the internal atmosphere of the vacuum vessel 1 airtight.

[0037] 4, protrusions 92 are formed around the periphery of the lower side (plasma processing region P3) of the housing 90. The protrusions 92 prevent the seal member 11c from being directly exposed to the plasma, i.e., the seal member 11c is isolated from the plasma processing region P3. Therefore, even if the plasma attempts to diffuse from the plasma processing region P3 toward the seal member 11c, the plasma will pass through below the protrusions 92 and will be deactivated before reaching the seal member 11c.

[0038] 4, plasma processing gas nozzles 33 to 35 are provided in the third processing region P3 below the housing 90 and are connected to an argon gas supply source 140, a hydrogen gas supply source 141, an oxygen gas supply source 142, and an ammonia gas supply source 143. However, it is sufficient that either the hydrogen gas supply source 141 or the ammonia gas supply source 143 is provided, and it is not necessary that both are provided.

[0039] Additionally, flow rate controllers 130, 131, 132, and 133 are provided between the plasma processing gas nozzles 33-35 and the argon gas supply source 140, hydrogen gas supply source 141, oxygen gas supply source 142, and ammonia gas supply source 143, respectively. The argon gas supply source 140, hydrogen gas supply source 141, oxygen gas supply source 142, and ammonia gas supply source 143 supply Ar gas, H gas, O gas, and NH gas, respectively, to the plasma processing gas nozzles 33-35. The flow rates of Ar gas, H gas, O gas, and NH gas are controlled by the flow rate controllers 130, 131, 132, and 133, respectively, and the Ar gas, H gas, O gas, and NH gas are supplied to the plasma processing gas nozzles 33-35 at a predetermined flow rate ratio (mixing ratio). However, as described above, when only one of the hydrogen gas supply source 141 and the ammonia gas supply source 143 is provided, the flow rate controllers 131 and 133 are also provided corresponding to the other one. The flow rate controllers 130 to 133 may be mass flow controllers, for example.

[0040] 4, a grounded Faraday shield 95 is housed in the upper side of the housing 90. The Faraday shield 95 is made of a conductive metal plate, such as copper, that is formed so as to roughly fit the internal shape of the housing 90. The Faraday shield 95 has a horizontal surface 95a that is fixed horizontally along the bottom surface of the housing 90, and a vertical surface 95b that extends upward in the circumferential direction from the outer end of the horizontal surface 95a, and may be configured so as to have, for example, a roughly hexagonal shape in plan view.

[0041] 1 and 2, a side ring 100, which is a cover body, is disposed on the outer periphery of the turntable 2 at a position below the turntable 2. A first exhaust port 61 and a second exhaust port 62 are formed on the upper surface of the side ring 100 so as to be spaced apart from each other in the circumferential direction.

[0042] The first exhaust port 61 is formed between the first process gas nozzle 31 and the separation region D located downstream of the first process gas nozzle 31 in the rotation direction of the turntable 2, at a position closer to the separation region D. The second exhaust port 62 is formed between the plasma source 80 and the separation region D located downstream of the plasma source 80 in the rotation direction of the turntable 2, at a position closer to the separation region D.

[0043] The first exhaust port 61 is an exhaust port for exhausting a first processing gas and a separation gas, and the second exhaust port 62 is an exhaust port for exhausting a plasma processing gas and a separation gas. As shown in Fig. 1, the first exhaust port 61 and the second exhaust port 62 are each connected to a vacuum pump 64, which is a vacuum exhaust mechanism, by an exhaust pipe 63 in which a pressure adjusting unit 65 such as a butterfly valve is installed.

[0044] As described above, since the housing 90 is disposed from the central region C side to the outer edge side, the gas flowing from the upstream side in the rotation direction of the turntable 2 to the second processing region P2 may be restricted by the housing 90 as it attempts to flow toward the second exhaust port 62. For this reason, groove-shaped gas flow paths 101 for gas flow are formed on the upper surface of the side ring 100 on the outer periphery side of the housing 90.

[0045] 1, a protrusion 5 is provided in the center of the underside of the top plate 11. The protrusion 5 is formed in a generally annular shape in the circumferential direction, continuing from the central region C side portion of the convex portion 4, and has its underside formed at the same height as the underside (first ceiling surface 44) of the convex portion 4. A labyrinth structure 110 is arranged above the core portion 21 on the rotation center side of the turntable 2 closer to the protrusion 5 than the core portion 21, to prevent various gases from mixing with each other in the central region C.

[0046] As described above, the housing 90 is formed up to a position close to the central region C, and therefore the core portion 21 that supports the center of the turntable 2 is formed closer to the rotation center so that the upper portion of the turntable 2 avoids the housing 90. Therefore, various gases tend to mix more easily on the central region C side than on the outer edge side. Therefore, by forming the labyrinth structure portion 110 on the upper side of the core portion 21, a gas flow path is created and mixing of the gases can be prevented.

[0047] As shown in Fig. 1, a heater unit 7, which is a heating mechanism, is provided in the space between the turntable 2 and the bottom surface 14 of the vacuum vessel 1. The heater unit 7 is configured to heat the wafer W on the turntable 2 via the turntable 2 to, for example, a temperature between room temperature and approximately 700°C. In Fig. 1, cover members 71 are provided on the sides of the heater unit 7, and a covering member 7a is provided to cover the upper side of the heater unit 7. In addition, purge gas supply pipes 73 for purging the space in which the heater unit 7 is disposed are provided at multiple locations around the circumference of the bottom surface 14 of the vacuum vessel 1 below the heater unit 7.

[0048] 2, a transfer port 15 is formed in the side wall of the vacuum chamber 1 for transferring the wafer W between the transfer arm 10 and the rotary table 2. The transfer port 15 is configured to be airtightly opened and closed by a gate valve G.

[0049] The recess 24 of the turntable 2 is located opposite the transfer opening 15, and the wafer W is transferred between the turntable 2 and the transfer arm 10. Therefore, a lift pin and a lift mechanism (not shown) are provided at a location corresponding to the transfer position on the lower side of the turntable 2 to penetrate the recess 24 and lift the wafer W from the backside.

[0050] The plasma processing apparatus of the embodiment is also provided with a control device 120 consisting of a computer for controlling the operation of the entire apparatus. A program for performing substrate processing, which will be described later, is stored in the memory of the control device 120. The program is made up of steps for executing various operations of the apparatus, and is installed into the control device 120 from a storage unit 121, which is a storage medium such as a hard disk, compact disk, magneto-optical disk, memory card, or flexible disk. The storage unit 121 stores correlation information 122 between RF power and a Vpp voltage, which will be described later.

[0051] [Matching box] Next, the circuit configuration of the matching box 84 provided in the plasma processing apparatus of Fig. 1 and the states during non-ignition and ignition will be described with reference to Fig. 5. Fig. 5(a) shows the state during non-ignition, i.e., when plasma P is not generated, and Fig. 5(b) shows the state during ignition, i.e., when plasma P is generated.

[0052] The matching box 84 is disposed between the RF power supply 85 and the antenna 83. The antenna 83 is connected to the RF power supply 85 via the matching box 84, and is supplied with RF power from the RF power supply 85.

[0053] The matching box 84 is connected in series between the RF power supply 85 and the antenna 83 via the voltage supply lines 54, 55, and 56. The matching box 84 includes a first variable capacitor C1, a second variable capacitor C2, a coil L1, and a coil L2. However, the circuit configuration of the matching box 84 is an example, and the number and positions of the variable capacitors and coils are not limited to this. A block capacitor C BThe voltage supply line 56 also has a resistance component such as a resistor Rt.

[0054] When RF power is supplied from the RF power source 85 to the plasma load side (plasma P side: see Figure 2(b)) via the antenna 83, the matching device 84 matches the impedance between the RF power source 85 and the plasma load, thereby increasing the efficiency of RF power supply.

[0055] Furthermore, the matching box 84 has a voltmeter 88. The voltmeter 88 is an example of a measurement unit that measures the voltage at the output end of the matching box 84. The peak-to-peak voltage of the voltage at the output end of the matching box 84 measured by the voltmeter 88 is also referred to as "Vpp" or "Vpp voltage."

[0056] The correlation between RF power and Vpp voltage when ignition is performed and when not ignition is performed will be described with reference to Fig. 6. A correlation table, which is an example of correlation information 122 between RF power and Vpp voltage shown in Fig. 6, is stored in, for example, storage unit 121 (see Fig. 1).

[0057] The horizontal axis of Figure 6 is the RF power (RF Power) [W] supplied from the RF power supply 85 to the antenna 83, and the vertical axis is the Vpp voltage [V]. Line A shows the calculated value of the Vpp voltage when no ignition has occurred. Line B shows the actually measured value of the Vpp voltage when no ignition has occurred. The calculated value and the actually measured value of the Vpp voltage when no ignition has occurred are almost the same.

[0058] Line C shows the measured Vpp voltage at the time of ignition. Line D shows the upper limit for detecting abnormal Vpp discharge, which is used to prevent abnormal discharge. The measured Vpp voltage at the time of non-ignition is the peak-to-peak voltage of the output terminal voltage measured by voltmeter 88 at the time of non-ignition in Figure 5(a). The measured Vpp voltage at the time of ignition is the peak-to-peak voltage of the output terminal voltage measured by voltmeter 88 at the time of ignition in Figure 5(b). As shown in Figure 6, at the same RF power, the Vpp voltage at the time of non-ignition is approximately twice the Vpp voltage at the time of ignition. This is because when inductively coupled plasma (ICP) plasma (hereinafter referred to as "ICP plasma") is generated using antenna 83 shown in Figure 5(b), the plasma P contributes to the impedance as a conductor. In contrast, when plasma is not yet generated, as shown in Figure 5(a), the insulating gas in the plasma space does not contribute to the impedance, and as a result, the Vpp voltage before ignition is thought to be approximately twice the Vpp voltage when ignition occurs.

[0059] Hereinafter, the state in which "ICP plasma" is generated, that is, the state of the Vpp voltage at the time of ignition, will be referred to as "ICP mode." The state in which ICP plasma is not generated will be referred to as "unignited." Therefore, the unignited state includes a state in which "CCP plasma" is generated and a state in which plasma is extinguished (plasma is not generated). The state in which "CCP plasma" is generated without ignition will be referred to as "CCP mode." The plasma properties differ between "CCP mode" and "ICP mode." In CCP mode, a capacitively coupled plasma (CCP plasma) is generated by the voltage difference between the antenna 83 and ground caused by the magnetic field. In ICP mode, an inductively coupled plasma (ICP plasma) is generated using the antenna 83.

[0060] ICP mode generates a stronger plasma than CCP mode, so for example, if you want to perform a plasma process in ICP mode but instead perform the plasma process in CCP mode, you may not get the desired process results.

[0061] Therefore, the current mode, either ICP mode or CCP mode, is confirmed by monitoring the Vpp voltage from the output end voltage of the matching circuit 84 measured by the voltmeter 88. As described above, the correlation table in Fig. 6 can be used to determine whether the mode is "ICP mode" or "CCP mode" from the value of the Vpp voltage. Furthermore, if it is determined that the Vpp voltage exceeds the Vpp abnormal discharge detection upper limit shown by line D in Fig. 6, an abnormal discharge will occur, so the Vpp voltage is controlled so as not to exceed the Vpp abnormal discharge detection upper limit.

[0062] In ICP mode, a stronger plasma is generated than in CCP mode, and therefore, in ICP mode, depending on the gas supplied, the plasma may cause significant damage to the dielectric material such as quartz that constitutes the housing 90.

[0063] Therefore, in order to reduce damage to the housing 90 caused by the plasma and to adjust the film quality when forming a film on the wafer W, a pulsed RF power (hereinafter also referred to as "RF pulsed power") is supplied to the antenna 83. FIG. 7 is a diagram showing an example of the average electron density and average electron temperature of continuous and pulsed RF power. Hereinafter, continuous RF power will also be referred to as "CW" and pulsed RF power will also be referred to as "PW." As shown in FIG. 7(a), when CW (continuous RF power) is supplied to the antenna 83, the electron density Ne and electron temperature Te are maintained constant during plasma generation. On the other hand, as shown in FIG. 7(b), when PW (pulsed RF power) is supplied, the electron density Ne and electron temperature Te fluctuate periodically during plasma generation. The average value of electron density Ne (average Ne), shown by the dotted line in Figure 7(b), is almost the same as the electron density Ne in Figure 7(a). However, the average value of electron temperature Te (average Te) is lower than the electron temperature Te in Figure 7(a). This is because electrons are smaller and lighter than ions, and therefore collide with the wall of the vacuum chamber and disappear instantly. In contrast, ions and atomic nuclei are heavier than electrons, and therefore take longer to collide with the wall and disappear. Therefore, electrons with collision energy disappear first during the RF pulse power off time. As a result, there are no electrons colliding with the casing 90 or the surrounding area of ​​the substrate, thereby reducing damage to the quartz casing 90 and the substrate. Furthermore, the electron temperature Te decreases. If the RF pulse power on time arrives before the ions disappear, the ion-induced reaction can continue, and the electron density Ne can be maintained. As a result, as shown in Figure 7(b), with RF pulse power, the average value of electron temperature Te decreases, while the average value of electron density Ne is maintained.

[0064] However, when RF pulse power is supplied, the Vpp voltage decreases as the off time becomes longer. For example, Fig. 8 is a diagram showing an example of the output of RF pulse power in a monitoring method of one embodiment. In Fig. 8, the horizontal axis represents time, and the vertical axis represents the output of RF power (RF pulse power) output by the RF power supply 85. Also in Fig. 8, the solid line represents the forward power Pf sent from the RF power supply 85 to the plasma load including the antenna 83, and the dashed line represents the reflected power Pr from the plasma load toward the RF power supply 85.

[0065] Period T1 begins at time t0 and is a waiting time (e.g., 0.5 seconds) before processing that ends at time t1. Period T2 begins at time t1 and is a period (processing period) during processing that ends at time t2, and a pulse wave of RF power (traveling wave power Pf) is supplied to substrate T2 from RF power supply 85. During period T2 during processing, one cycle consists of one ON time (ON time) and one OFF time (OFF time), and RF pulse power is supplied whose duty ratio is expressed by equation (a). Duty ratio = ON time / (ON time + OFF time) (a)

[0066] It was found that when the duty ratio of the RF pulse power decreases, the time that the RF power output by the RF power supply 85 is on becomes shorter, and the Vpp voltage decreases. The correlation table in Fig. 6 shows the correlation (correlation information 122) between the RF power and the Vpp voltage when the RF power is a continuous wave. For this reason, even if the correlation table in Fig. 6 is used as is to monitor the plasma based on the Vpp voltage at the output end measured when the RF power is a pulse wave, the mode cannot be determined correctly, which poses a problem of making it difficult to monitor the plasma stably.

[0067] Therefore, this embodiment provides a monitoring method for stably controlling a plasma process using a pulsed RF power. In the monitoring method according to this embodiment, the converted value of Vpp voltage is calculated from the actual measured value of Vpp voltage using equation (1).

[0068]

number

[0069] Using the above equation (1), the converted value of Vpp voltage is calculated from the actual measured value of Vpp voltage based on the duty ratio calculated from equation (2). This makes it possible to stably monitor ICP plasma using the correlation table in Figure 6, even when the RF power is changed from continuous wave to pulsed wave or from pulsed wave to continuous wave.

[0070] In the matching box 84 shown in FIG. 5, there is no reflected power Pr during period T2 during plasma processing, and matching is possible. Therefore, mode discrimination cannot be performed by monitoring the state of the reflected power Pr. Furthermore, monitoring the mode by monitoring the plasma light also poses the problem of making it difficult to set a threshold value for mode discrimination because the plasma light fluctuates significantly depending on the film formation status of the substrate W. In contrast, the Vpp voltage at the output end of the matching box 84 is less susceptible to the influence of gas species, pressure, and substrate type. Therefore, stable monitoring of ICP plasma is possible by pre-storing a correlation table between RF power and Vpp voltage for each RF power and applying the actual measured Vpp voltage value and RF power to the correlation table (see FIG. 6). Furthermore, to address the decrease in Vpp voltage that occurs when the process conditions for RF power are changed from continuous wave to pulsed wave, a conversion value for Vpp voltage is calculated using equation (1). By applying the conversion value for Vpp voltage to the correlation table (see FIG. 6), stable monitoring of ICP plasma is possible using the same correlation table as when continuous wave RF power was being supplied. The monitoring method of this embodiment will be described in detail below.

[0071] [Monitoring method] The monitoring method of this embodiment includes at least the following steps (a) to (c). (a) A step of preparing a substrate on a mounting table (rotary table 2) (b) A step of supplying a pulse wave of RF power with a predetermined duty ratio from the RF power source 85. (c) A process of monitoring the state of the plasma based on the converted value of the Vpp voltage obtained by converting the Vpp voltage of the output terminal voltage of the matching circuit 84 measured by the voltmeter 88 based on the duty ratio, the RF power supplied from the RF power supply 85, and correlation information between the Vpp voltage and the RF power.

[0072] The monitoring method of this embodiment may further include the following steps (d) and (e). (d) A step of stopping the supply of pulsed RF power from the RF power source 85 and supplying continuous RF power. (e) after performing (d), monitoring the state of the plasma based on the Vpp voltage of the output terminal voltage, the RF power, and the correlation information.

[0073] An example of the monitoring method of this embodiment will be described in detail with reference to Fig. 9 and Fig. 10. Fig. 9 is a flowchart showing an example of the monitoring method of one embodiment. Fig. 10 is a diagram for explaining determination of the plasma state by the monitoring method of Fig. 9.

[0074] Each process of the monitoring method in Fig. 9 is controlled by the control device 120. When the monitoring method in Fig. 9 is started, in step S1, the control device 120 determines whether the waiting period (period T1 in Fig. 8) has elapsed. Note that the above process (a) is executed before step S1.

[0075] In step S1, the control device 120 waits until a standby period (period T1 in FIG. 8) has elapsed, and after the standby period has elapsed, the control device 120 proceeds to step S2 and determines whether the RF power supplied from the RF power supply 85 is CW (continuous wave) or PW (pulsed wave).

[0076] If the control device 120 determines in step S2 that the RF power is CW (continuous wave), the process proceeds to step S3. On the other hand, if the control device 120 determines in step S2 that the RF power is PW (pulsed wave), the process proceeds to step S7.

[0077] In step S3, the control device 120 acquires the actual measurement value of the Vpp voltage from the output end voltage of the matching device 84 measured by the voltmeter 88. Next, in step S4, the control device 120 determines whether the actual measurement value of the Vpp voltage is within the range from the upper Vpp limit to the lower Vpp limit. The correlation table of FIG. 6 was obtained in advance by experiment and is stored in the storage unit 121. Of these, the upper Vpp limit and the lower Vpp limit are set to ±30% of the actual measurement value of the Vpp voltage at ignition, indicated by line C. In other words, the upper Vpp limit is the value of the actual measurement value at ignition × 1.3, and the lower Vpp limit is the value of the actual measurement value at ignition × 0.7. However, the method of setting the upper Vpp limit and the lower Vpp limit is not limited to this. FIG. 10 shows an example of the upper Vpp limit (line U) and the lower Vpp limit (line L).

[0078] If the controller 120 determines in step S4 that the actual measured value of the Vpp voltage is within the range from the upper limit Vpp to the lower limit Vpp, it determines in step S5 that the mode is ICP and that ICP plasma is being generated. After this determination, the process proceeds to step S12.

[0079] If the controller 120 determines in step S4 that the measured value of the Vpp voltage exceeds the Vpp upper limit or falls below the Vpp lower limit, it determines in step S6 that the mode is CCP and that CCP plasma is being generated. After this determination, the process proceeds to step S12.

[0080] If the RF power is PW (pulse wave), in step S7, the control device 120 acquires the actual measured value of the Vpp voltage from the output end voltage of the matching box 84 measured by the voltmeter 88. Next, in step S8, the control device 120 calculates the converted value of the Vpp voltage using equation (1).

[0081] Next, in step S9, the control device 120 determines whether the converted value of the Vpp voltage is within the range from the upper Vpp limit to the lower Vpp limit. If the control device 120 determines that the converted value of the Vpp voltage is within the range from the upper Vpp limit to the lower Vpp limit, then in step S10, the control device 120 determines that the ICP mode is in effect and that ICP plasma is being generated. After this determination, the process proceeds to step S12.

[0082] If the controller 120 determines in step S9 that the converted value of the Vpp voltage exceeds the Vpp upper limit or falls below the Vpp lower limit, it determines in step S11 that the mode is CCP and that CCP plasma is being generated. After this determination, the process proceeds to step S12.

[0083] In step S12, the control device 120 determines whether the processing period (period T2 in FIG. 8) has elapsed. The control device 120 repeats the processes of steps S2 to S12 until the processing period has elapsed, and when it determines in step S12 that the processing period has elapsed, the control device 120 ends this process.

[0084] In steps S6 and S11, it may be determined that the plasma has disappeared (that the plasma is not being generated) instead of determining that the mode is CCP. After RF power is applied using the preset matching position state of the matching box 84, which was previously matched in an unignited state, as a preset, if the plasma is unignited or in CCP mode, Vpp will be higher than the threshold. If the plasma disappears from a normally matched state in an ICP plasma state, Vpp will be lower than the threshold. If the plasma disappears during the process of going from unignited to ignition and matching, either of these situations will occur, but in this case, a reflected wave will continue to be emitted. Therefore, the RF power source 85 detects this reflected wave, and the control device 120 acquires the detected value of this reflected wave, determining that a matching abnormality has occurred and issuing an alarm.

[0085] 10 shows a correlation table, which is an example of correlation information 122 between RF power and Vpp voltage. Line A shows the calculated value of Vpp voltage when no ignition has occurred. Line E shows the converted value of Vpp voltage calculated from the actual measured value of Vpp voltage when ignition has occurred. Line D shows the upper limit of Vpp abnormal discharge detection for preventing abnormal discharge. Line U is the upper limit of Vpp, and line L is the lower limit of Vpp.

[0086] 9, if it is determined that the converted value of the Vpp voltage is within the area surrounded by lines U and L with respect to the supplied RF power, it is determined to be in ICP mode. If it is determined that the converted value of the Vpp voltage is outside the area surrounded by lines U and L, it is determined to be in CCP mode (or plasma has been extinguished).

[0087] It is determined that an abnormal discharge has occurred when the converted value of the Vpp voltage exceeds the Vpp abnormal discharge detection upper limit indicated by line D. In this case, the control device 120 can suppress the abnormal discharge by managing the supply of RF power not to exceed the Vpp abnormal discharge detection upper limit.

[0088] According to the monitoring method described above, the converted value of Vpp voltage (Vpp converted value) is calculated from the actual measured value of Vpp voltage (Vpp actual measured value) based on the duty ratio using equation (1). This makes it possible to stably monitor ICP plasma using the correlation tables (Figures 6, 10, etc.) used before the change, even when the RF power is changed from a continuous wave to a pulsed wave.

[0089] This allows stable processing by ICP plasma supplied with RF pulse power to be performed on the substrate W. Furthermore, in substrate processing supplied with RF pulse power, if the duty ratio is lowered, the possibility of plasma extinction increases, but the plasma extinction can also be monitored with high accuracy using this monitoring method.

[0090] This allows stable monitoring of the ICP plasma, thereby reducing damage to the housing 90 made of a dielectric material such as quartz, and reducing particles. In addition, damage to the wafer W itself caused by the plasma (charging damage) can be suppressed.

[0091] As described above, the monitoring method and plasma processing apparatus of this embodiment make it possible to stably control a plasma process using a pulsed RF power wave.

[0092] The monitoring method and plasma processing apparatus according to the presently disclosed embodiments should be considered to be illustrative in all respects and not restrictive. The embodiments can be modified and improved in various ways without departing from the spirit and scope of the appended claims. The features described in the above embodiments can be configured in other ways as long as they are not inconsistent, and can be combined as long as they are not inconsistent.

[0093] For example, the method is not limited to using the above formula (1) to find the converted value of Vpp voltage from the actual measured value of Vpp voltage. For example, if the ON time of RF pulse power is fixed and the OFF time is variable, the converted value of Vpp voltage may be found from the actual measured value of Vpp voltage using formula (2). Vpp conversion value = Vpp actual measurement value × (1 + OFF time × Koff1) × Koff2 (2) Koff1 and Koff2 are constants, and are values ​​that are determined in advance with the on-time fixed.

[0094] Furthermore, for example, when the on-time of RF pulse power is variable and the off-time is fixed, the converted value of Vpp voltage may be obtained from the actually measured value of Vpp voltage using equation (3). Vpp conversion value = Vpp actual measurement value × (1 + Kon1 / ON time) × Kon2 (3) Koff1 and Koff2 are constants, and are values ​​that are determined in advance with the OFF time fixed.

[0095] The plasma processing apparatus of the present disclosure is not limited to the plasma processing apparatus of FIG. 1, but can also be applied to an inductively coupled plasma (ICP) type apparatus. [Explanation of symbols]

[0096] 1 Vacuum container 2 Rotating Tables 33-35 Plasma treatment gas nozzle 83 Antenna 84 Matching box 85 RF power supply 120 Control device

Claims

1. A processing vessel; a mounting table disposed in the processing chamber and configured to mount a substrate thereon; an antenna provided on an upper portion of the processing vessel; an RF power source connected to the antenna and supplying RF power; a matching box disposed between the antenna and the RF power source; a measurement unit for measuring an output terminal voltage of the matching circuit; A monitoring method performed by a plasma processing apparatus having (a) preparing a substrate on the stage; (b) supplying a pulse wave of RF power having a predetermined duty ratio from the RF power source; (c) monitoring a plasma state based on a converted value of a Vpp voltage obtained by converting the Vpp voltage of the output terminal voltage based on the duty ratio, the RF power, and correlation information between the Vpp voltage and the RF power; Including, In the step (c), a converted value of the Vpp voltage is calculated based on the formula (1), [Equation 1] the Vpp converted value is a converted value of the Vpp voltage, the Vpp actual measured value is an actual measured value of the Vpp voltage, K is a constant, In the step (c), when it is determined that the converted value of the Vpp voltage is within a range from the upper limit value of the Vpp voltage to the lower limit value of the Vpp voltage, it is determined that ICP plasma is being generated; In the step (c), when it is determined that the converted value of the Vpp voltage exceeds the upper limit value of the Vpp voltage or falls below the lower limit value of the Vpp voltage, it is determined that CCP plasma is being generated or that plasma is not being generated. Monitoring method.

2. In the step (c), a state of plasma is monitored based on a result of determining whether the converted value of the Vpp voltage is within a range from an upper limit value of the Vpp voltage to a lower limit value of the Vpp voltage, based on the correlation information. The monitoring method of claim 1 .

3. (d) stopping the supply of the pulsed RF power from the RF power source and supplying a continuous RF power; (e) after performing (d), monitoring the state of the plasma based on the Vpp voltage of the output terminal voltage, the RF power, and the correlation information, 3. The monitoring method according to claim 1 or 2.

4. A processing vessel; a mounting table disposed in the processing chamber and configured to mount a substrate thereon; an antenna provided on an upper portion of the processing vessel; an RF power source connected to the antenna for supplying RF power; a matching box disposed between the antenna and the RF power source; a measurement unit for measuring an output terminal voltage of the matching circuit; A plasma processing apparatus having a control device, The control device (a) preparing a substrate on the stage; (b) supplying a pulse wave of RF power having a predetermined duty ratio from the RF power source; (c) monitoring a plasma state based on a converted value of a Vpp voltage obtained by converting the Vpp voltage of the output terminal voltage based on the duty ratio, the RF power, and correlation information between the Vpp voltage and the RF power; configured to control In the step (c), a converted value of the Vpp voltage is calculated based on the formula (1), [Equation 1] the Vpp converted value is a converted value of the Vpp voltage, the Vpp actual measured value is an actual measured value of the Vpp voltage, K is a constant, In the step (c), when it is determined that the converted value of the Vpp voltage is within a range from the upper limit value of the Vpp voltage to the lower limit value of the Vpp voltage, it is determined that ICP plasma is being generated; In the step (c), when it is determined that the converted value of the Vpp voltage exceeds the upper limit value of the Vpp voltage or falls below the lower limit value of the Vpp voltage, it is determined that CCP plasma is being generated or that plasma is not being generated. Plasma processing equipment.

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