Plasma processing method and plasma processing apparatus

Abstract

The present invention provides a plasma processing method and a plasma processing apparatus capable of applying a DC voltage to an edge ring while suppressing a shift in the characteristics of plasma applied to the entire substrate. The plasma processing method includes: a step (a) of generating plasma inside a chamber; a step (b) of applying a DC voltage to an edge ring surrounding the periphery of a substrate while the plasma is being generated; a step (c) of acquiring a first voltage of the edge ring while the DC voltage is being applied; a step (d) of stopping the application of the DC voltage; a step (e) of acquiring a second voltage of the edge ring while the application of the DC voltage is being stopped; and a step (f) of calculating a parameter for controlling the DC voltage based on the first voltage and the second voltage.

Description

Technical Field

[0001] This invention relates to plasma processing methods and plasma processing apparatus. Background Technology

[0002] For example, Patent Documents 1 and 2 disclose a plasma processing apparatus in which an edge ring is provided around a substrate placed on a stage and a DC voltage is applied to the edge ring.

[0003] Existing technical documents

[0004] Patent documents

[0005] Patent Document 1: Japanese Patent Application Publication No. 2007-258417

[0006] Patent Document 2: Japanese Patent Application Publication No. 2019-145729 Summary of the Invention

[0007] The technical problem that the invention aims to solve

[0008] The present invention provides a technique that can apply a DC voltage to the edge ring while suppressing the shift of the characteristics of the plasma applied to the entire substrate.

[0009] Technical solutions for solving technical problems

[0010] According to one aspect of the present invention, a plasma processing method is provided, comprising: step (a) generating plasma inside a chamber; step (b) applying a DC voltage to an edge ring surrounding a substrate while generating the plasma; step (c) acquiring a first voltage of the edge ring while applying the DC voltage; step (d) stopping the application of the DC voltage; step (e) acquiring a second voltage of the edge ring while stopping the application of the DC voltage; and step (f) calculating parameters for controlling the DC voltage based on the first voltage and the second voltage.

[0011] Invention Effects

[0012] In one aspect, a DC voltage can be applied to the edge ring while suppressing the deviation of the characteristics of the plasma applied to the entire substrate. Attached Figure Description

[0013] Figure 1 This is a cross-sectional schematic diagram showing a plasma processing apparatus according to one embodiment.

[0014] Figure 2 It is a diagram used to illustrate the tilt state of the tilt angle.

[0015] Figure 3This is a diagram illustrating a control example of the DC voltage applied to the edge ring and the tilt angle, as in the reference example.

[0016] Figure 4 This is a graph that compares the variation in sheath thickness in one embodiment with that in a reference example.

[0017] Figure 5 This is a diagram illustrating an example of controlling the DC voltage applied to the edge ring and the tilt angle in one embodiment.

[0018] Figure 6 This is a graph showing an example of DC voltage X (DC%) and etching rate corresponding to the variation in sheath thickness in one embodiment.

[0019] Figure 7 This is a diagram illustrating an example of a measurement circuit according to one embodiment.

[0020] Figure 8 This is a diagram illustrating a measurement method according to one embodiment.

[0021] Figure 9 This is a flowchart illustrating one embodiment of a plasma processing method (voltage measurement of the edge ring).

[0022] Figure 10 This is a flowchart illustrating a plasma processing method (parameter calculation) according to one embodiment.

[0023] Figure 11 This is a diagram illustrating an example of the initial values ​​of parameters and the amount of change in the tilt angle in one embodiment.

[0024] Explanation of reference numerals in the attached figures

[0025] 1 chamber

[0026] 3 Upper electrode

[0027] 4 First board

[0028] 5. Electrostatic chucks

[0029] 6 Second board

[0030] 10A First High Frequency Power Supply

[0031] 10b Second High Frequency Power Supply

[0032] 15 Gas Supply Department

[0033] 16 Heat transfer gas supply path

[0034] 55 DC power supply

[0035] 90 Control Department

[0036] 100 Plasma Processing Unit

[0037] W substrate

[0038] ST mounting stage. Detailed Implementation

[0039] Hereinafter, the embodiments for carrying out the present invention will be described with reference to the accompanying drawings. In the drawings, the same reference numerals are used to label the same structural parts, and sometimes repeated descriptions are omitted.

[0040] [Plasma Processing Device]

[0041] Reference Figure 1 The plasma processing apparatus 100 of one embodiment will be described. Figure 1 This is a schematic cross-sectional view showing one embodiment of a plasma processing apparatus 100. The plasma processing apparatus 100 has a chamber 1 that is electrically set to ground potential. The chamber 1 is cylindrical and, for example, made of aluminum. A mounting stage ST for mounting a substrate W is disposed within the chamber 1. The mounting stage ST has a first plate 4, a second plate 6, and an electrostatic chuck 5. The first plate 4 and the second plate 6 are formed, for example, of aluminum. The electrostatic chuck 5 is formed, for example, of a dielectric. The first plate 4 is disposed on the second plate 6, and the electrostatic chuck 5 is disposed on the first plate 4.

[0042] An edge ring 7, for example made of silicon, is disposed around the substrate W. The edge ring 7 is also called a focusing ring. A cylindrical inner wall component 9a is disposed around the edge ring 7, the first plate 4, and the second plate 6. The stage ST is disposed at the bottom of the chamber 1 by means of a support component 9 connected to the lower end of the inner wall component 9a and the inner wall component 9a. The support component 9 and the inner wall component 9a are, for example, made of quartz.

[0043] Electrode 5c inside electrostatic chuck 5 is sandwiched between dielectrics 5b and connected to DC power supply 12. When a DC voltage is applied to electrode 5c from DC power supply 12, a Coulomb force is generated, and substrate W is electrostatically attracted to electrostatic chuck 5.

[0044] The first plate 4 has an internal flow path 2d. A heat exchange medium, such as water, supplied from the refrigeration unit circulates through the inlet pipe 2b, flow path 2d, and outlet pipe 2c. A heat transfer gas supply passage 16 is formed inside the mounting stage ST. A heat transfer gas supply source 19 supplies heat transfer gas to the heat transfer gas supply passage 16, introducing the heat transfer gas into the space between the lower surface of the substrate W and the electrostatic chuck 5. The introduced heat transfer gas can be an inert gas such as helium (He) or argon (Ar). Regarding the mounting stage ST, a pin insertion path is provided on the mounting stage ST. A lifting pin capable of passing through the pin insertion path moves up and down via a lifting mechanism to raise and lower the substrate W during transport.

[0045] The second plate 6 is connected to the first high-frequency power supply 10a via a first matching device 11a, and to the second high-frequency power supply 10b via a second matching device 11b. The first high-frequency power supply 10a applies high-frequency electrical power of a first frequency for plasma generation to the second plate 6. The second high-frequency power supply 10b applies high-frequency electrical power of a bias voltage, which is a second frequency lower than the first frequency, to the second plate 6 and is used to attract ions. However, sometimes the high-frequency electrical power supplied from the second high-frequency power supply 10b is used for plasma generation.

[0046] The plasma processing apparatus 100 also includes a DC power supply 55. The DC power supply 55 is connected to a second plate 6 and electrically connected from the second plate 6 via a first plate 4 to an edge ring 7. The DC power supply 55 supplies a DC voltage to the edge ring 7, controlling the thickness of the sheath layer on the edge ring 7. The DC voltage applied to the edge ring 7 is controlled according to the consumption of the edge ring 7.

[0047] An upper electrode 3 is disposed above the stage ST and opposite to the stage ST. The upper electrode 3 has an electrode plate 3b and a top plate 3a. An annular member 95 is disposed around the upper electrode 3 to provide insulation, and the upper opening of the chamber 1 is closed by the upper electrode 3 and the annular member 95. The top plate 3a is made of a conductive material, such as aluminum with an anodized surface, and the electrode plate 3b is detachably supported on its lower part.

[0048] A gas diffusion chamber 3c and a gas inlet 3g for introducing processing gas into the gas diffusion chamber 3c are formed on the top plate 3a. A gas supply pipe 15a is connected to the gas inlet 3g. A gas supply unit 15, a mass flow controller (MFC) 15b, and an on / off valve V2 are sequentially connected to the gas supply pipe 15a, and processing gas is supplied from the gas supply unit 15 to the upper electrode 3 via the gas supply pipe 15a. The on / off valve V2 and the mass flow controller (MFC) 15b control the on / off state and flow rate of the gas.

[0049] Multiple gas flow holes 3d are formed in the lower part of the gas diffusion chamber 3c facing the chamber 1, and are connected to the gas inlet hole 3e formed on the electrode plate 3b. The processing gas is supplied into the chamber 1 in a spray manner through the gas diffusion chamber 3c, the gas flow holes 3d and the gas inlet hole 3e.

[0050] The upper electrode 3 is connected to the DC power supply 72 via a low-pass filter (LPF) 71, and the DC voltage output from the DC power supply 72 is switched on and off using a switch 73. When the process gas is plasmaified by applying high-frequency electrical power to the stage ST from the first high-frequency power supply 10a and the second high-frequency power supply 10b, the switch 73 is turned on as needed to apply the desired DC voltage to the upper electrode 3.

[0051] A cylindrical grounding conductor 1a is provided, extending from the side wall of chamber 1 to a position above the height of the upper electrode 3. The cylindrical grounding conductor 1a has a top wall at its upper part.

[0052] An exhaust port 81 is formed at the bottom of chamber 1, and an exhaust device 83 is connected to the exhaust port 81 via an exhaust pipe 82. The exhaust device 83 has a vacuum pump, which is used to reduce the pressure inside chamber 1 to a specified vacuum level. An inlet and outlet port 84 for substrate W is provided on the side wall inside chamber 1, and the inlet and outlet port 84 can be opened and closed by a gate valve 85.

[0053] A deposit baffle 86 is detachably provided along the inner side wall of chamber 1. Additionally, a deposit baffle 87 is detachably provided along the inner wall component 9a. The deposit baffles 86 and 87 prevent etching byproducts (deposits) from adhering to the inner side wall of chamber 1 and the inner wall component 9a. A conductive component (GND module) 89 is provided at approximately the same height as the substrate W on the deposit baffle 86. This conductive component (GND module) 89 is connected to control the potential relative to ground, thereby preventing abnormal discharge.

[0054] The plasma processing apparatus 100 is controlled by a control unit 90. The control unit 90 is equipped with a processing controller 91, a user interface 92, and a storage unit 93 for controlling the various parts of the plasma processing apparatus 100.

[0055] The user interface 92 includes a keyboard for process managers to input commands for managing the plasma processing device 100, and a display that visually shows the operating status of the plasma processing device 100.

[0056] The storage unit 93 stores plans, including control programs (software) and processing condition data that enable the processing controller 91 to perform various processes implemented in the plasma processing apparatus 100. Furthermore, as needed, any plan can be retrieved from the storage unit 93 and executed by the processing controller 91 according to instructions from the user interface 92. Thus, based on the control of the control unit 90, the plasma processing apparatus 100 processes the substrate W. In addition, the plans, including the control programs and processing condition data, can also be used online by utilizing the state content stored in a computer-readable computer storage medium, or by real-time transmission from other devices via, for example, a dedicated line. Examples of storage media include hard disks, CDs, floppy disks, and semiconductor memories.

[0057] [Measures to Address Edge-of-Life Consumption]

[0058] Edge ring 7 is consumed when exposed to plasma during substrate W processing. For example, when etching substrate W, if edge ring 7 is new, ... Figure 2 As shown by the solid line, the edge ring 7 is configured such that the plasma sheath layer (hereinafter referred to as the "sheath layer") on the edge ring 7 is at the same height as the sheath layer on the substrate W. In this state, ions in the plasma are incident perpendicularly onto the substrate W, forming vertically shaped etch recesses on the etch target film on the substrate W.

[0059] When edge ring 7 is consumed, such as Figure 2 As shown by the dashed line, the height of the sheath on the edge ring 7 becomes lower than the height of the sheath on the substrate W. As a result, in the region at the outer periphery of the substrate W, ions in the plasma are incident at an angle, forming an angled etching recess on the etchable film on the substrate W. This angle of inclination is denoted by θ. The amount of variation in the angle of inclination θ depends on the incident angle of the ions. In other words, the amount of variation in the angle of inclination θ depends on the thickness of the sheath on the edge ring 7, i.e., the amount of edge ring 7 consumed.

[0060] To ensure the ion incident angle is perpendicular and the etched recess is vertically shaped, the DC power supply 55 supplies a DC voltage to the edge ring 7 according to the consumption of the edge ring 7, thereby controlling the sheath thickness on the edge ring 7. This allows the sheath on the edge ring 7 to be adjusted to the same height as the sheath on the substrate W. Consequently, the tilt angle θ can be controlled to approximately 90°, forming a vertically shaped etched recess.

[0061] However, the magnitude of the high-frequency current flowing from the first high-frequency power supply 10a and the second high-frequency power supply 10b to the second plate 6 and then through the first plate 4 to the plasma generation space changes depending on whether a DC voltage is applied to the edge ring 7 or not. For example, when no DC voltage is applied to the edge ring 7, the high-frequency current flowing to the center side of the substrate W and the high-frequency current flowing to the edge side are approximately the same magnitude. In contrast, when a DC voltage is applied to the edge ring 7, the high-frequency current flowing to the center side of the substrate W becomes larger. As a result, the plasma density above the center and middle side of the substrate W becomes higher. Consequently, the following technical problems arise.

[0062] Firstly, although it is desirable to control the plasma characteristics of the outer periphery of the substrate W by applying a DC voltage to the edge ring 7, the plasma characteristics of the substrate as a whole—in the central, outer periphery, and outer periphery regions—also change, affecting the overall processing of the substrate. For example, when the etching rate and other parameters shift across the entire substrate, the quality of the processed substrate as a product deteriorates. Therefore, minimizing the shift in the characteristics of the plasma applied to the entire substrate becomes a technical challenge.

[0063] The second is to construct an application method for applying a DC voltage to the edge ring 7 that minimizes the deviation of the characteristics of the plasma applied to the entire substrate and achieves high-precision control in the region at the outer periphery of the substrate W. For example, the technical problem is that the control of the DC voltage applied to the edge ring 7 does not become complicated by the variety of processes (steps) involved in the processing of a substrate.

[0064] To address the aforementioned technical problems, a plasma processing method is provided, in which the plasma processing apparatus 100 of this embodiment can minimize the deviation of the characteristics of the plasma applied to the entire substrate while controlling the DC voltage applied to the edge ring 7 to be the same.

[0065] [Reference Example: DC Voltage Control Method]

[0066] Before describing this implementation method, refer to Figure 3 The control method for applying DC voltage to edge ring 7 in the reference example will be described. Figure 3 This is a diagram showing a control example of the DC voltage applied to the edge ring 7 and the tilt angle, as in the reference example. Figure 3 The horizontal axis represents the DC voltage V applied to the edge ring 7, and the vertical axis represents the tilt angle θ (°). The value of the DC voltage V is denoted as V(DC). [The following is a separate section:] Figure 3 The simulation conditions for each process are shown.

[0067] Process 1 (New) indicates that the edge ring 7 is a new product when the substrate is subjected to Process 1 under specified conditions. In this case, as shown by solid line P11, by controlling the DC voltage V (DC) applied to the edge ring 7 to a level of 0 to 75 [-V], the tilt angle θ can be adjusted to a level of 89° to 91°.

[0068] Process 1 (old) refers to the case where, under the specified conditions of Process 1 applied to the substrate, the edge ring 7 is consumed within a specified time. In this case, as shown by the dashed line P12, by controlling the DC voltage V (DC) applied to the edge ring 7 to a level of 50 to 110 [-V], the tilt angle θ can be adjusted to a level of 89° to 91°.

[0069] Process 2 (New) indicates that in the case of Process 2, which applies different specified conditions to the substrate than Process 1, the edge ring 7 is a new product. In this case, as shown by solid line P21, by controlling the DC voltage V (DC) applied to the edge ring 7 to a level of 0 to 280 [-V], the tilt angle θ can be adjusted to a level of 89° to 91°.

[0070] Process 2 (old) refers to the case where, under the specified conditions different from those of Process 1, the edge ring 7 is consumed within a specified time. In this case, as shown by the dashed line P22, by controlling the DC voltage V (DC) applied to the edge ring 7 to a level of 150 to 320 [-V], the tilt angle θ can be adjusted to a level of 89° to 91°.

[0071] Accordingly, in the DC voltage control method of the reference example, in order to control the tilt angle θ to 90° according to the processing conditions, it is necessary to control the DC voltage applied to the edge ring 7 to different values. This is because the initial voltage at which the tilt angle θ becomes 90° varies depending on the processing conditions, and the slope of the tilt angle θ relative to the applied DC voltage (i.e., the sensitivity of the tilt angle θ) varies depending on the processing.

[0072] For example, in Process 1 (new), the initial DC voltage for the tilt angle θ to become 90° is approximately 50 [-V], while in Process 2 (new), the initial DC voltage for the tilt angle θ to become 90° is approximately 175 [-V]. Furthermore, the slope of the tilt angle θ differs in Process 1 and Process 2; therefore, even if the same DC voltage is increased from the initial DC voltage, the resulting change in the tilt angle θ is different in Process 1 and Process 2. Consequently, the applied voltage required to adjust the tilt angle θ to 90° when the edge ring 7 is consumed is also different in Process 1 and Process 2.

[0073] Based on the above description, in the control method of the reference example, for the various processes that have been carried out in recent years, it is necessary to apply an appropriate DC voltage to the edge ring 7 according to the processing conditions and the consumption of the edge ring 7, which makes the control of the DC voltage applied to the edge ring 7 complicated.

[0074] [The DC voltage control method of this embodiment]

[0075] In contrast, the DC voltage control method of this embodiment allows for a variety of processing methods to be handled with a single index. Specifically, this embodiment proposes a plasma processing method that uses new parameters for DC voltage control to control the DC voltage applied to the edge ring 7. When the sheath thickness on the edge ring 7 is set to t, in this embodiment, the new parameter used to control the DC voltage applied to the edge ring 7 is represented by the variation in the sheath thickness t.

[0076] Equation (1) for calculating the sheath thickness t is as follows.

[0077]

[0078] Here, V dc Self-biased. N i The ion density is N.i With the electron density N of the plasma e It has the same density as the plasma. T e Let N be the electron temperature of the plasma. ε0 is the vacuum permittivity, e is the elementary charge, and k is the Boltzmann constant. ε0, e, and k are constant values. Among the variables included in equation (1), the ion density N... i and self-biased V dc The electron temperature T of the plasma e The value changes depending on the processing conditions.

[0079] therefore, Figure 4 The sheath thickness t, represented by the vertical axis of the coordinate graph in (a), becomes the self-biased V, represented by the horizontal axis of the coordinate graph. dc The ion density N of each curve on the coordinate graph i That is, the thickness varies depending on the values ​​of N1, N2, and N3. Furthermore, the self-biasing V... dc This indicates the potential of edge ring 7, which is equal to the potential of the substrate.

[0080] Variation in sheath thickness {(t) x -t) / t}, based on equation (1) is transformed as in equation (2).

[0081]

[0082] {(t x -t) / t}×100 represents the variation (%) of the sheath thickness. a in equation (2) is a proportionality constant. Among the variables in equation (2), V dc For self-biasing, X indicates whether the sheath thickness becomes the same as the initial thickness if the DC voltage applied to the edge ring 7 is applied in increments of a certain percentage when the sheath thickness changes by a certain percentage. X is a parameter used for DC voltage control (hereinafter referred to as "parameter X").

[0083] That is, the variation in sheath thickness {(t)} x -t) / t}×100 indicates whether the sheath thickness changes by a certain percentage when the DC voltage applied to the edge ring 7 is applied in increments of X%. The (1+X / 100) on the right side of equation (2) is the value obtained by adding "1", which is the amount of self-biasing, to 1 / 100 of the amount of DC voltage applied to the edge ring 7, i.e., "X / 100". This value is then multiplied by the self-biasing V. dc Equation (2) is used to calculate the potential of edge ring 7. Equation (2) represents the value of the control edge ring 7, i.e., V. dc When (1+X / 100), the variation in sheath thickness (t) can be represented. x -t) / t controls are the same.

[0084] Therefore, in the plasma processing method of this embodiment, the variation in sheath thickness {(t} is calculated using equation (2). x -t) / t}. Refer again. Figure 4 In (a), in the DC voltage control method of the reference example, for example when the self-biased V dc As the ion density N increases, the sheath thickness increases. Furthermore, when the ion density N... i At different times, the sheath thickness changes. For example, the self-biasing V of the transverse axis dc At 300 [V], and the ion density N i The thickness of the sheath changes when the values ​​are N1, N2, and N3.

[0085] In contrast, Figure 4 (b) shows the variation in the sheath thickness of one embodiment compared with the reference example. Figure 4 The vertical axis of (b) represents the self-biasing V of the horizontal axis. dc The variation in sheath thickness when the sheath thickness at 300 [V] is set to 100%. Arrow (A) in the figure indicates that when 10 (%) is substituted into X in equation (2), that is, the self-biased V dc When the initial value of 300 [V] is increased by 10 (%) and controlled to 330 [V], the change in sheath thickness increases by 11% from the initial value to 111%. Arrow (B) in the figure indicates that when 20 (%) is substituted into X in equation (2), the self-biased V dc When the initial value of 300 [V] is controlled to 360 [V], the change in sheath thickness increases by 18% from the initial value to 118%.

[0086] That is, in the plasma processing method of this embodiment, the variation in sheath thickness {(t} is controlled using equation (2). x -t) / t}. At this time, by controlling X%, which is the amount of DC voltage applied to the edge ring 7 in the potential of the edge ring 7, even if the plasma density (ion density) is changed, it is not affected by it, and the amount of variation of the sheath thickness relative to the DC voltage applied to the edge ring 7 can be controlled.

[0087] Figure 5 This is a diagram illustrating a control example using equation (2) to control the DC voltage applied to the edge ring and the tilt angle in this embodiment. Figure 5 In the horizontal axis, the DC voltage applied to the edge ring 7 as shown in equation (2) is denoted as X(DC%). X(DC%) is equal to the parameter X.

[0088] Figure 5 In, also with Figure 3Similar to the reference example, the vertical axis represents the tilt angle θ (°). The simulation conditions for each of the following processes are the same as those for Process 1 (New), Process 1 (Old), Process 2 (New), and Process 2 (Old). Figure 3 same.

[0089] When processing 1 and edge ring 7 is a new product, as shown by solid line P31, by controlling the DC voltage X (DC%) to the level of 0 to 40 [%], the tilt angle θ can be adjusted to the level of 89° to 91°.

[0090] When processing 2 and edge ring 7 is a new product, as shown by solid line P41, by controlling the DC voltage X (DC%) to 0 to 40%, the tilt angle θ can be adjusted to 89° to 91°.

[0091] When processing 1 and edge ring 7 is consumed within a specified time, as shown by dashed line P32, by controlling the DC voltage X (DC%) to a level of 25 to 55 [%], the tilt angle θ can be adjusted to a level of 89° to 91°.

[0092] In process 2, when the edge ring 7 is consumed within a specified time, as shown by the dashed line P42, by controlling the DC voltage X (DC%) to a level of 25 to 55%, the tilt angle θ can be adjusted to a level of 89° to 91°. Thus, in the processing method of this embodiment, by controlling the DC voltage applied to the edge ring 7 using the parameter X (DC voltage X (DC%)), the tilt angle θ can be controlled to be the same regardless of the amount of edge ring consumed, even if the processing conditions are different.

[0093] Figure 6 This is a graph showing an example of DC voltage X (DC%) and etching rate corresponding to the variation in sheath thickness in one embodiment. Figure 6 The horizontal axis represents the DC voltage X (DC%) shown in Equation (2), and the vertical axis represents the etching rate at the center of the resist film on the substrate. Figure 6 Is Figure 5 This is an example of the simulation results under different processing conditions (Processes 1 and 2). By normalizing the etching rate (%), the same results were observed under different processing conditions (Processes 1 and 2). In Processes 1 and 2, with the edge ring 7 being new, the DC voltage X (DC%) was set to 0. In Processes 1 and 2, the etching rate varied within the range of 0% to 25% of the DC voltage X (DC%).

[0094] Therefore, even in Figure 5In processes 1 and 2, which are different processes, by controlling the DC voltage X (DC%) to 25% or higher, it is possible to prevent variations in the etching rate (%) and suppress or minimize deviations in the processing characteristics. Furthermore, by controlling the DC voltage X (DC%), even processes 1 and 2, which have different etching rates at the center of the resist film, can be controlled to be the same.

[0095] As described above, by controlling the DC voltage X (DC%) corresponding to the variation in sheath thickness, the DC voltage applied to the edge ring 7 can be controlled to be the same for a variety of processes with different plasma densities due to different processing conditions.

[0096] [Parameters for DC voltage control]

[0097] Next, refer to Figure 7 The calculation of parameter X (DC voltage X (DC%)) for controlling the DC voltage applied to the edge ring 7 in the plasma processing method of this embodiment is explained. Figure 7 This is a diagram illustrating an example of a measurement circuit used to obtain parameter X in one embodiment.

[0098] Plasma has self-biased V dc The resistance of the sheath and the resistance of the sheath, these resistors are used Figure 7 R1 represents the resistance of the power supply line from the plasma to the FRDC generator 50 and the stage ST. R2 (a fixed value) represents the resistance of the power supply line to the FRDC generator 50 and the stage ST.

[0099] The FRDC generator 50 controls the DC power supply 55 that applies a DC voltage to the edge ring 7 and the voltmeter 56 that monitors the voltage applied to the edge ring 7. According to V=IR, the resistance R1 of the plasma is proportional to the potential of the edge ring 7. The potential of the edge ring 7 is equal to the self-biased V when no DC voltage is applied to the edge ring 7. dc The potential of edge ring 7, when a DC voltage is applied to edge ring 7, is equal to the self-biased V. dc The value is obtained by adding the two voltages, the DC voltage applied to the edge ring 7.

[0100] Furthermore, the resistance of the plasma is determined by the sheath thickness. A portion of the sheath thickness is related to the self-biasing V induced by the plasma. dc Correspondingly, when a DC voltage is further applied to the edge ring 7, a portion of the sheath thickness corresponds to the DC voltage applied to the edge ring 7. R2 is a fixed value. Therefore, using self-biased V dcThe potential of edge ring 7 is proportional to the resistance of the plasma, depending on whether a DC voltage is applied or not. Since the plasma resistance is determined by the sheath thickness, the voltage drop across edge ring 7 when a DC voltage is applied and when no DC voltage is applied represents the variation in sheath thickness.

[0101] Therefore, the potential of the edge ring 7 is measured by voltmeter 56 under various conditions, including when a DC voltage is applied to the edge ring 7 and when no DC voltage is applied, to obtain the data used to calculate the parameter X (DC%) for DC voltage control. Figure 8 This is a diagram illustrating a measurement method according to one embodiment.

[0102] RF is from Figure 1 The second high-frequency power is supplied by the second high-frequency power supply 10b. DC is the DC voltage applied from the DC power supply 55.

[0103] This measurement is performed during the generation of plasma during substrate processing. Specifically, during the measurement, a first high-frequency electrical power supplied from the first high-frequency power supply 10a is continuously applied to maintain the plasma while substrate processing is performed. During this substrate processing, a DC voltage is applied to the edge ring 7 in a pulsed manner. That is, the DC voltage applied to the edge ring 7 is repeatedly switched on and off.

[0104] Voltmeter 56 measures the potential of edge ring 7 during the periods when a DC voltage is applied (on period) and during the periods when no DC voltage is applied (off period). Figure 8 As shown, the voltage measured by voltmeter 56 during the period when a DC voltage is applied to the edge ring 7 is designated as Y, and the voltage measured by voltmeter 56 during the period when no DC voltage is applied to the edge ring 7 is designated as X.

[0105] The voltmeter 56 can also measure the voltage once or multiple times when a DC voltage is applied to the edge ring 7 in a pulsed manner. Alternatively, the voltmeter 56 can also measure the voltage once or multiple times when no DC voltage is applied to the edge ring 7.

[0106] When a DC voltage is applied to edge ring 7, voltmeter 56 measures the voltage generated by the self-biased V. dc The potential formed by the DC voltage applied to edge ring 7 and the voltage itself is taken as the potential of edge ring 7. When no DC voltage is applied to edge ring 7, voltmeter 56 measures the self-biased V. dc The potential is used as the potential of edge ring 7.

[0107] [Plasma Treatment Methods]

[0108] Reference Figure 9 and Figure 10This describes the plasma processing method of this embodiment, which includes the above-described measurement process. Figure 9 This is a flowchart illustrating one embodiment of a plasma processing method (voltage measurement of the edge ring). Figure 10 This is a flowchart illustrating a plasma processing method (parameter calculation) according to one embodiment. The plasma processing method of this embodiment is controlled by a control unit 90 and executed using a plasma processing apparatus 100.

[0109] When it begins Figure 9 During processing, the control unit 90 prepares the substrate W by placing it on the mounting stage ST (step S1). Next, the control unit 90 supplies processing gas for processing the substrate W from the gas supply unit 15, and applies a first high-frequency power and a second high-frequency power to the mounting stage ST from the first high-frequency power supply 10a and the second high-frequency power supply 10b (step S2). This generates plasma 2, which the control unit 90 uses to process the substrate (step S3).

[0110] Next, the control unit 90 applies a DC voltage to the edge ring 7 when generating plasma (step S4). Then, the control unit 90 uses a voltmeter 56 to measure the potential of the edge ring 7 as a first voltage y when the DC voltage is applied (step S5).

[0111] Next, the control unit 90 stops applying DC voltage to the edge ring 7 (step S6). Then, when the DC voltage is stopped, the control unit 90 uses the voltmeter 56 to measure the potential of the edge ring 7 as the second voltage x (step S7).

[0112] Next, the control unit 90 determines whether steps S4 to S7 have been performed a predetermined number of times (step S8). The predetermined number of times is a pre-set number of times, which can be once or multiple times. If the control unit 90 determines that the predetermined number of times has not been performed, it returns to step S4 and performs the processing after step S4 again. If the control unit 90 determines that the predetermined number of times has been performed, it ends the current process.

[0113] Next, explain the process. Figure 10 One embodiment of the plasma processing method is a method for calculating the parameter X used for DC voltage control. Figure 10 The processing was carried out Figure 9 It is executed after processing.

[0114] When it begins Figure 10 During processing, the control unit 90 sets an initial value for parameter X corresponding to the consumption amount of edge ring 7 (step S11). The initial value of parameter X corresponding to the consumption amount of edge ring 7 can also be pre-stored in the storage unit 93. Next, the control unit 90 acquires a first voltage y (step S12) and acquires a second voltage x (step S13).

[0115] Next, the control unit 90 calculates parameter X based on the first voltage y and the second voltage x (step S14). The control unit 90 multiplies the value obtained by dividing the difference between the first voltage y and the second voltage x by the second voltage x by 100, and uses this value as parameter X (%). Next, the control unit 90 determines and controls the DC voltage applied to the edge ring 7 so that parameter X becomes the initial value of parameter X set in step S11 or close to the initial value (step S15).

[0116] Next, the control unit 90 determines whether steps S12 to S15 have been performed a predetermined number of times (step S16). The predetermined number of times is a pre-set number of times, which can be once or multiple times. If the control unit 90 determines that the predetermined number of times has not been performed, it returns to step S12 and performs the processing after step S12 again. If the control unit 90 determines that the predetermined number of times has been performed, it ends the current process.

[0117] exist Figure 9 When the specified number of steps S8 is multiple, it is preferable to... Figure 10 The prescribed number of times for step S16 is multiple. In this case, the steps of applying DC voltage to the edge ring and stopping applying DC voltage are performed alternately and repeatedly. Then, after measuring the first voltage y, the voltage of the edge ring 7 is repeatedly measured with voltmeter 56, and after measuring the second voltage x, the voltage of the edge ring 7 is repeatedly measured with voltmeter 56.

[0118] exist Figure 10 When the specified number of times is multiple, based on Figure 9 The parameters X used for DC voltage control are repeatedly calculated using multiple first voltages y and second voltages x obtained through repeated processes. Then, the DC voltage applied to the edge ring 7 is determined so that the parameter X calculated during the calculation of parameter X is at or close to the initial value of parameter X.

[0119] The control unit 90 controls the DC voltage applied to the edge ring 7 in real time to the voltage determined in step S15. Therefore, the processing conditions and fluctuating plasma density during processing are unaffected, and the DC voltage applied to the edge ring 7 can be controlled with high precision using the parameter X for DC voltage control. Since the potential of the edge ring 7 varies for each wafer and during processing, by applying the DC voltage to the edge ring 7 in real time, the region at the outer periphery of the substrate can be controlled with high precision (e.g., the tilt angle θ). This suppresses the deviation of the plasma characteristics applied to the entire substrate, suppresses unevenness in etching rate, etched recess CD, etc., and thus obtains excellent processing characteristics. Furthermore, it suppresses the case of ion tilting in the region at the outer periphery of the substrate, minimizing the deviation of etched recesses and holes in the substrate layer.

[0120] Alternatively, the application time of the high-frequency electrical power and the consumption of the edge ring 7 can be measured in advance, and the relevant information can be stored in the storage unit 93. Referring to the storage unit 93, the consumption of the edge ring 7 can be obtained based on the application time of the high-frequency electrical power, and the initial value of parameter X can be set based on the consumption. However, it is not limited to this; the consumption of the edge ring 7 can also be obtained by optically measuring the surface of the edge ring 7.

[0121] [Setting the initial values ​​of the parameters]

[0122] Finally, refer to Figure 11 The setting of the initial value of parameter X used for DC voltage control is explained. Figure 11 This is a diagram showing an example of the initial value of parameter X for DC voltage control in one embodiment.

[0123] exist Figure 10 In step 11, the initial value of parameter X corresponding to the consumption of edge ring 7 is pre-stored in storage unit 93, and the initial value of parameter X is obtained according to the consumption of edge ring 7 by referring to storage unit 93.

[0124] However, instead of consuming the edge ring 7, the initial value of parameter X corresponding to the application time of high-frequency electrical power can be pre-stored in the storage unit 93, and the initial value of parameter X can be obtained according to the application time of high-frequency electrical power by referring to the storage unit 93.

[0125] Based on the above information, the control unit 90 can... Figure 10 In step S11, the initial value of parameter X is set not only based on the consumption of edge ring 7, but also based on an indicator representing the consumption of edge ring 7 (e.g., the application time of high-frequency electrical power).

[0126] The control unit 90 determines the value of the DC voltage so that... Figure 10 The parameters calculated in steps S12 to S14 become or are close to the initial value of parameter X in step S15. Therefore, the accuracy of controlling the DC voltage applied to the edge ring 7 can be improved accordingly to the processing conditions. Furthermore, the lifespan of the edge ring 7 can be extended.

[0127] For example, the following example is given: Regarding Figure 11 The initial value of parameter X, shown on the vertical axis of (b), is stored in the storage unit 93 in such a way that the consumption of edge ring 7 is set to 25% between 0 and 0.1, and increases by 5% for every 0.1. When the consumption of edge ring 7 is 0, edge ring 7 is a new product.

[0128] Control the DC voltage applied to edge ring 7 so that Figure 11The change in the tilt angle θ shown on the vertical axis of (a) is between 0 and 0.1 in the consumption of edge ring 7, and becomes or approaches the initial value of parameter X "25%" in step S15.

[0129] During this period, the consumption of edge ring 7 increases between 0 and 0.1, so the change in tilt angle θ gradually increases from 0. When the change in tilt angle θ exceeds the preset upper limit value S, the deviation of tilt angle θ from 90° becomes larger, and the control accuracy of the area at the outer periphery of substrate W decreases.

[0130] Therefore, when the consumption of edge ring 7 becomes 0.1 or more, the initial value of parameter X is changed to 30%. Then, the DC voltage applied to edge ring 7 is controlled so that the parameter calculated in steps S12 to S14 becomes or is close to the initial value of parameter X "30%" in step S15.

[0131] Therefore, by changing the initial value of parameter X from 25% to 30%, Figure 11 The change in tilt angle θ shown on the vertical axis of (a) is discontinuous at 0.1 and becomes 0. The initial value of parameter X is reset every 0.1 according to the consumption of edge ring 7, so that the change in tilt angle θ will not exceed the preset upper limit value S, which can reduce the deviation of tilt angle θ from 90° and suppress the reduction of control accuracy in the area of ​​the outer peripheral end of substrate W.

[0132] Furthermore, the initial value of parameter X is not limited to... Figure 11 Example (b). For example, not limited to the initial value of parameter X increasing by 5% every 5%. Furthermore, the initial value of parameter X is calculated based on equation (2), according to the change in sheath thickness {(t x The relationship between X(%) and the increase in the DC voltage applied to edge ring 7 is calculated as 100 / t and X(%).

[0133] The plasma processing method and plasma processing apparatus have been described above through the above embodiments. However, the mounting stage, plasma processing apparatus, and cleaning method of the present invention are not limited to the above embodiments, and various modifications and improvements can be made within the scope of the present invention. The contents described in the above embodiments and modifications can be combined without contradiction.

[0134] For example, the mounting stage in the above embodiments and modifications has an electrostatic chuck, but it is not limited to this; for example, it may also be a mounting stage without an electrostatic chuck. In this case, the mounting portion of the mounting stage does not have the function of an electrostatic chuck, and the substrate is mounted on the upper surface of the mounting portion.

[0135] The plasma processing apparatus of the present invention is also applicable to any type of plasma including Capacitively Coupled Plasma (CCP), Inductively Coupled Plasma (ICP), Radial LineSlot Antenna, Electron Cyclotron Resonance Plasma (ECR), and Helicon Wave Plasma (HWP). The cleaning process of the present invention can be performed by the aforementioned plasma processing apparatus, which includes: a chamber having a plasma space; a stage disposed within the plasma space; and a plasma generation unit configured to generate plasma from gas supplied to the plasma space.

Claims

1. A plasma processing method, characterized in that, include: Step (a): Generate plasma inside the chamber; Step (b): When generating the plasma, a DC voltage is applied to the edge ring surrounding the substrate; Step (c): Obtain the first voltage of the edge ring when the DC voltage is applied; Step (d): Stop applying the DC voltage; Step (e): Obtain the second voltage of the edge ring when the applied DC voltage is stopped; Step (f): Calculate the difference between the first voltage and the second voltage, divide it by the second voltage, and use the result as a parameter for controlling the DC voltage; and Step (g) determines the value of the DC voltage such that the calculated parameter becomes or is close to the initial value of the parameter.

2. The plasma treatment method as described in claim 1, characterized in that: The method includes step (h), which involves setting initial values ​​for parameters based on the consumption of the edge ring or an indicator representing the consumption.

3. The plasma treatment method as described in claim 2, characterized in that: This includes alternating and repeating steps (b) and (d). Step (c) is repeated after step (b), and step (e) is repeated after step (d). The parameters for controlling the DC voltage are calculated multiple times based on each of the first and second voltages obtained.

4. A plasma processing device, characterized in that: Includes a chamber, an edge ring surrounding the substrate, and a control section. The control unit performs processing, which includes: Step (a): Generate plasma inside the chamber; In step (b), a DC voltage is applied to the edge ring surrounding the substrate during the generation of the plasma; Step (c): Obtain the first voltage of the edge ring when the DC voltage is applied; Step (d): Stop applying the DC voltage; Step (e): Obtain the second voltage of the edge ring when the applied DC voltage is stopped; Step (f) calculates the difference between the first voltage and the second voltage, divided by the second voltage, and uses this value as a parameter for controlling the DC voltage; and Step (g) determines the value of the DC voltage such that the calculated parameter becomes or is close to the initial value of the parameter.

Images