Plasma processing apparatus

Abstract

To provide an etching method capable of reducing a positive charge amount of a substrate and also capable of improving etching efficiency.SOLUTION: An etching method according to an exemplary embodiment is performed in a state where a substrate is placed on a substrate support base provided in a chamber of a plasma processing apparatus. In the etching method, high-frequency power is supplied to generate plasma from gas in a chamber. Next, in order to etch the substrate with positive ions from the plasma, a negative-polarity DC voltage is applied to a lower electrode of the substrate support base during the supply of the high-frequency power. Then, in order to generate negative ions, the application of a negative-polarity DC voltage and the supply of high-frequency power to the lower electrode are stopped. Next, in order to supply negative ions to the substrate, a positive-polarity DC voltage is applied to the lower electrode in a state where the supply of high-frequency power is stopped.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] Exemplary embodiments of the present disclosure relate to an etching method and a plasma processing apparatus.

Background Art

[0002] A plasma processing apparatus is used in plasma etching of a substrate. The plasma processing apparatus has a chamber and a substrate support table. The substrate support table has a lower electrode and is provided in the chamber. When plasma etching is performed, the substrate is placed on the substrate support table. Then, plasma is generated from a gas in the chamber. The substrate is etched by positive ions from the plasma. As a result, an opening is formed in the substrate.

[0003] As the etching of the substrate by positive ions progresses, the substrate becomes charged. In a state where the substrate is charged, the supply amount of positive ions into the inside of the opening decreases. As a result, the etching rate may decrease. Alternatively, in a state where the substrate is charged, an abnormality may occur in the shape of the opening formed in the substrate.

[0004] In order to reduce the positive charge amount of the substrate, in the technique described in Patent Document 1, a positive-polarity DC voltage is applied from a power source to the lower electrode. Then, the application of the DC voltage to the lower electrode is stopped. Then, a negative-polarity DC voltage is applied from the power source to the lower electrode. As a result, positive ions are drawn into the substrate and etching is performed. Thereafter, the application of the DC voltage to the lower electrode is stopped. In the technique described in Patent Document 1, the application of the positive-polarity DC voltage to the lower electrode, the stop of the application of the DC voltage to the lower electrode, the application of the negative-polarity DC voltage to the lower electrode, and the stop of the application of the DC voltage to the lower electrode are repeated. The high-frequency power for generating plasma is continuously supplied when the repetition of the application of the positive-polarity DC voltage to the lower electrode, the stop of the application of the DC voltage to the lower electrode, the application of the negative-polarity DC voltage to the lower electrode, and the stop of the application of the DC voltage to the lower electrode is being performed.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0006] In plasma etching, it is required to reduce the positive charge amount of the substrate and increase the etching efficiency.

Means for Solving the Problems

[0007] In one exemplary embodiment, an etching method executed using a plasma processing apparatus is provided. The etching method is executed with a substrate placed on a substrate support provided in a chamber of the plasma processing apparatus. The etching method includes a step of supplying high-frequency power to generate plasma from a gas in the chamber. The etching method further includes a step of applying a negative DC voltage to a lower electrode of the substrate support during execution of the step of supplying high-frequency power to etch the substrate with positive ions from the plasma. The etching method further includes a step of stopping the application of the negative DC voltage to the lower electrode and the supply of high-frequency power to generate negative ions. The etching method further includes a step of applying a positive DC voltage to the lower electrode in a state where the supply of high-frequency power is stopped to supply negative ions to the substrate.

Advantages of the Invention

[0008] According to one exemplary embodiment, it becomes possible to reduce the positive charge amount of the substrate and increase the etching efficiency.

Brief Description of the Drawings

[0009]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Mode for Carrying Out the Invention

[0010] Hereinafter, various exemplary embodiments will be described.

[0011] In one exemplary embodiment, an etching method executed using a plasma processing apparatus is provided. The etching method is executed in a state where a substrate is placed on a substrate support provided in a chamber of the plasma processing apparatus. The etching method includes a step of supplying high-frequency power to generate plasma from a gas in the chamber. The etching method further includes a step of applying a negative DC voltage to a lower electrode of the substrate support during execution of the step of supplying high-frequency power in order to etch the substrate with positive ions from the plasma. The etching method further includes a step of stopping the application of the negative DC voltage to the lower electrode and the supply of high-frequency power in order to generate negative ions. The etching method further includes a step of applying a positive DC voltage to the lower electrode in a state where the supply of high-frequency power is stopped in order to supply negative ions to the substrate.

[0012] In the above embodiment, a negative DC voltage is supplied to the lower electrode while plasma is being generated by the supply of high-frequency power. As a result, positive ions collide with the substrate, and the substrate is etched. Next, the supply of high-frequency power and the application of the DC voltage to the lower electrode are stopped. In a state where high-frequency power is being supplied, the amount of negative ions generated is small, but when the supply of high-frequency power is stopped, negative ions are efficiently generated by the attachment of electrons to chemical species in the gas. Next, a positive DC voltage is applied to the lower electrode in a state where the supply of high-frequency power is stopped. As a result, negative ions are supplied to the substrate. According to the above embodiment, negative ions reduce the positive charge amount of the substrate. Also, the substrate is etched using both positive ions and negative ions. Therefore, the etching efficiency is improved.

[0013] In one exemplary embodiment, the etching method may further include a step of exhausting gas from the internal space of the chamber. The exhausting step is performed after one or more executions of an etching sequence including a step of supplying high-frequency power, a step of applying a negative DC voltage, a stopping step, and a step of applying a positive DC voltage. When the exhausting step is performed, the supply of high-frequency power is stopped, and the application of the DC voltage to the lower electrode is stopped.

[0014] In one exemplary embodiment, another sequence including one or more executions of the etching sequence and the exhausting step may be repeated.

[0015] In one exemplary embodiment, during the execution of the above another sequence, the exhausting step may be performed for 10 μs or more. In this embodiment, etching by-products are more reliably exhausted. As a result, the etching efficiency of the substrate is further improved.

[0016] In one exemplary embodiment, as the number of executions of the above-described another sequence increases, the time length of the execution period of the discharging step may be increased. In this embodiment, as the depth of the opening formed in the substrate increases, the time length of the execution period of the discharging step is increased. Therefore, etching by-products are more reliably discharged.

[0017] In one exemplary embodiment, during the execution of the stopping step, a parameter representing the electron density in the chamber may be measured. The step of applying a positive-polarity DC voltage may be started when it is determined from the parameter that the electron density in the chamber is decreasing so as to satisfy a predetermined criterion. The decrease in the electron density during the execution of the stopping step reflects an increase in the amount of negative ions. Therefore, according to this embodiment, the step of applying a positive-polarity DC voltage is started when it is determined that sufficient negative ions have been generated.

[0018] In one exemplary embodiment, in the stopping step, before the supply of the high-frequency power is stopped, the application of a negative-polarity DC voltage to the lower electrode may be stopped. According to this embodiment, abnormal discharge is more reliably prevented.

[0019] In another exemplary embodiment, a plasma processing apparatus is provided. The plasma processing apparatus includes a chamber, a substrate support, a high-frequency power source, a power supply unit, and a control unit. The substrate support has a lower electrode and is provided in the chamber. The high-frequency power source is configured to supply high-frequency power to generate plasma from a gas in the chamber. The power supply unit is configured to generate a positive DC voltage and a negative DC voltage. The power supply unit is electrically connected to the lower electrode. The control unit is configured to control the high-frequency power source and the power supply unit. The control unit is configured to execute first control, second control, third control, and fourth control. The first control includes controlling the high-frequency power source to supply high-frequency power to generate plasma from the gas in the chamber. The second control includes controlling the power supply unit to apply a negative DC voltage to the lower electrode of the substrate support during the supply of high-frequency power to etch the substrate with positive ions from the plasma. The third control includes controlling the power supply unit and the high-frequency power source to stop applying a negative DC voltage to the lower electrode and supply high-frequency power to generate negative ions. The fourth control includes controlling the power supply unit to apply a positive DC voltage to the lower electrode in a state where the supply of high-frequency power is stopped to supply negative ions to the substrate.

[0020] In one exemplary embodiment, the plasma processing apparatus may further include an exhaust device connected to the chamber. The control unit may be further configured to execute fifth control. The fifth control includes controlling the exhaust device to discharge gas from the internal space of the chamber. The fifth control is executed after one or more executions of an etching control sequence including the first control, the second control, the third control, and the fourth control. When the fifth control is executed, the supply of high-frequency power is stopped, and the application of a DC voltage to the lower electrode is stopped.

[0021] In one exemplary embodiment, the control unit may repeatedly execute another control sequence including one or more executions of the etching control sequence and the fifth control.

[0022] In one exemplary embodiment, during the execution period of the above-described another control sequence, the fifth control may be executed for 10 μs or more.

[0023] In one exemplary embodiment, as the number of executions of the above-described another control sequence increases, the control unit may increase the duration of the fifth control.

[0024] In one exemplary embodiment, the plasma processing apparatus may further include a measuring device. The measuring device measures a parameter representing the electron density in the chamber during the execution of the third control. When it is determined from the parameter that the electron density in the chamber is decreasing so as to satisfy a predetermined standard, the control unit may start the execution of the fourth control.

[0025] In one exemplary embodiment, in the third control, the control unit may control the power supply unit so as to stop applying a negative-polarity DC voltage to the lower electrode before stopping the supply of high-frequency power.

[0026] Hereinafter, various exemplary embodiments will be described in detail with reference to the drawings. In each drawing, the same or corresponding parts will be denoted by the same reference numerals.

[0027] FIG. 1 is a flowchart showing an etching method according to one exemplary embodiment. The etching method shown in FIG. 1 (hereinafter referred to as "method MT") is executed using a plasma processing apparatus. FIG. 2 is a diagram schematically showing a plasma processing apparatus according to one exemplary embodiment. The plasma processing apparatus 1 shown in FIG. 2 can be used for the execution of method MT.

[0028] The plasma processing apparatus 1 is a capacitively coupled plasma processing apparatus. The plasma processing apparatus 1 includes a chamber 10. The chamber 10 provides an internal space 10s therein. In one embodiment, the chamber 10 includes a chamber body 12. The chamber body 12 has a substantially cylindrical shape. The internal space 10s is provided within the chamber body 12. The chamber body 12 is made of, for example, aluminum. The chamber body 12 is electrically grounded. A film having plasma resistance is formed on the inner wall surface of the chamber body 12, that is, the wall surface defining the internal space 10s. This film can be a ceramic film such as a film formed by anodization or a film formed from yttrium oxide.

[0029] A passage 12p is formed in the side wall of the chamber body 12. The substrate W passes through the passage 12p when being transported between the internal space 10s and the outside of the chamber 10. A gate valve 12g is provided along the side wall of the chamber body 12 to open and close the passage 12p.

[0030] A substrate support, that is, a support 16, is provided in the chamber 10. The support 16 is configured to support the substrate W placed thereon. The substrate W has a substantially disc shape. The support 16 is supported by a support body 15. The support body 15 extends upward from the bottom of the chamber body 12. The support body 15 has a substantially cylindrical shape. The support body 15 is formed of an insulating material such as quartz.

[0031] The support 16 has a lower electrode 18. The support 16 may further have an electrostatic chuck 20. The support 16 may further have an electrode plate 19. The electrode plate 19 is formed of a conductive material such as aluminum and has a substantially disc shape. The lower electrode 18 is provided on the electrode plate 19. The lower electrode 18 is formed of a conductive material such as aluminum and has a substantially disc shape. The lower electrode 18 is electrically connected to the electrode plate 19.

[0032] A flow path 18f is formed in the lower electrode 18. The flow path 18f is a flow path for a heat exchange medium. As the heat exchange medium, a liquid refrigerant or a refrigerant (e.g., freon) that cools the lower electrode 18 by its vaporization is used. A circulation device (e.g., a chiller unit) for the heat exchange medium is connected to the flow path 18f. This circulation device is provided outside the chamber 10. The heat exchange medium is supplied to the flow path 18f from the circulation device via a pipe 23a. The heat exchange medium supplied to the flow path 18f is returned to the circulation device via a pipe 23b.

[0033] The electrostatic chuck 20 is provided on the lower electrode 18. When the substrate W is processed in the internal space 10s, it is placed on the electrostatic chuck 20 and held by the electrostatic chuck 20. The electrostatic chuck 20 has a main body and an electrode. The main body of the electrostatic chuck 20 is formed of a dielectric such as aluminum oxide or aluminum nitride. The main body of the electrostatic chuck 20 has a substantially disc shape. The electrostatic chuck 20 includes a substrate placement region and a focus ring mounting region. The substrate placement region is a region having a substantially disc shape. The upper surface of the substrate placement region extends along a horizontal plane. An axis AX that includes the center of the substrate placement region and extends in the vertical direction substantially coincides with the central axis of the chamber 10. When the substrate W is processed in the chamber 10, it is placed on the upper surface of the substrate placement region.

[0034] The focus ring mounting region extends in the circumferential direction so as to surround the substrate placement region. A focus ring FR is mounted on the upper surface of the focus ring mounting region. The focus ring FR has an annular shape. The substrate W is disposed in a region surrounded by the focus ring FR. That is, the focus ring FR surrounds the edge of the substrate W placed on the substrate placement region of the electrostatic chuck 20. The focus ring FR is formed of, for example, silicon or silicon carbide.

[0035] The electrodes of the electrostatic chuck 20 are provided inside the main body of the electrostatic chuck 20. The electrodes of the electrostatic chuck 20 are films formed from a conductor. A DC power supply is electrically connected to the electrodes of the electrostatic chuck 20. When a DC voltage is applied from the DC power supply to the electrodes of the electrostatic chuck 20, an electrostatic attraction force is generated between the electrostatic chuck 20 and the substrate W. Due to the generated electrostatic attraction force, the substrate W is attracted to the electrostatic chuck 20 and held by the electrostatic chuck 20.

[0036] The plasma processing apparatus 1 may further include a gas supply line 25. The gas supply line 25 supplies a heat transfer gas, such as He gas, from a gas supply mechanism between the upper surface of the electrostatic chuck 20 and the back surface (lower surface) of the substrate W.

[0037] The plasma processing apparatus 1 may further include a cylindrical portion 28 and an insulating portion 29. The cylindrical portion 28 extends upward from the bottom of the chamber main body 12. The cylindrical portion 28 extends along the outer periphery of the support 15. The cylindrical portion 28 is formed from a conductive material and has a substantially cylindrical shape. The cylindrical portion 28 is electrically grounded. The insulating portion 29 is provided on the cylindrical portion 28. The insulating portion 29 is formed from a material having insulating properties. The insulating portion 29 is formed from a ceramic such as quartz, for example. The insulating portion 29 has a substantially cylindrical shape. The insulating portion 29 extends along the outer periphery of the electrode plate 19, the outer periphery of the lower electrode 18, and the outer periphery of the electrostatic chuck 20.

[0038] The plasma processing apparatus 1 further includes an upper electrode 30. The upper electrode 30 is provided above the support base 16. The upper electrode 30 closes the upper opening of the chamber main body 12. The upper electrode 30 is supported at the upper part of the chamber main body 12.

[0039] The upper electrode 30 includes a top plate 34 and a support 36. The lower surface of the top plate 34 defines an internal space 10s. A plurality of gas discharge holes 34a are formed in the top plate 34. Each of the plurality of gas discharge holes 34a penetrates the top plate 34 in the plate thickness direction (vertical direction). The top plate 34 is formed of, for example, silicon, although it is not limited thereto. Alternatively, the top plate 34 may have a structure in which a plasma-resistant film is provided on the surface of a member made of aluminum. This film may be a ceramic film such as a film formed by anodization or a film formed of yttrium oxide.

[0040] The support 36 detachably supports the top plate 34. The support 36 is formed of a conductive material such as aluminum, for example. A gas diffusion chamber 36a is provided inside the support 36. A plurality of gas holes 36b extend downward from the gas diffusion chamber 36a. The plurality of gas holes 36b communicate with the plurality of gas discharge holes 34a, respectively. A gas introduction port 36c is formed in the support 36. The gas introduction port 36c is connected to the gas diffusion chamber 36a. A gas supply pipe 38 is connected to the gas introduction port 36c.

[0041] A gas source group 40 is connected to a gas supply pipe 38 via a valve group 41, a flow rate controller group 42, and a valve group 43. The gas source group 40, the valve group 41, the flow rate controller group 42, and the valve group 43 constitute a gas supply unit. The gas source group 40 includes a plurality of gas sources. The plurality of gas sources include sources of one or more gases used in etching methods according to various embodiments. Each of the valve group 41 and the valve group 43 includes a plurality of valves (e.g., on-off valves). The flow rate controller group 42 includes a plurality of flow rate controllers. Each of the plurality of flow rate controllers in the flow rate controller group 42 is a mass flow controller or a pressure-controlled flow rate controller. Each of the plurality of gas sources in the gas source group 40 is connected to the gas supply pipe 38 via a corresponding valve in the valve group 41, a corresponding flow rate controller in the flow rate controller group 42, and a corresponding valve in the valve group 43. The plasma processing apparatus 1 can supply gas from one or more selected gas sources in the gas source group 40 to the internal space 10s at individually adjusted flow rates.

[0042] A baffle member 48 is provided between the cylindrical portion 28 and the side wall of the chamber body 12. The baffle member 48 can be a plate-like member. The baffle member 48 can be configured, for example, by coating a ceramic such as yttrium oxide on an aluminum plate material. A plurality of through holes are formed in the baffle member 48. Below the baffle member 48, an exhaust pipe 52 is connected to the bottom of the chamber body 12. An exhaust device 50 is connected to this exhaust pipe 52. The exhaust device 50 has a pressure controller such as an automatic pressure control valve and a vacuum pump such as a turbo molecular pump, and can reduce the pressure in the internal space 10s.

[0043] The plasma processing apparatus 1 further includes a high-frequency power supply 61. The high-frequency power supply 61 is a power supply that generates high-frequency power for plasma generation. The frequency of the high-frequency power is not limited, but is in the range of 27 to 100 MHz, for example, 40 MHz or 60 MHz. The high-frequency power supply 61 is connected to the lower electrode 18 via a matching unit 63 and an electrode plate 19 in order to supply high-frequency power to the lower electrode 18. The matching unit 63 has a matching circuit for matching the output impedance of the high-frequency power supply 61 and the impedance on the load side (lower electrode 18 side). Note that the high-frequency power supply 61 may not be electrically connected to the lower electrode 18, and may be connected to the upper electrode 30 via the matching unit 63.

[0044] The plasma processing apparatus 1 further includes a power supply unit 64. The power supply unit 64 is configured to generate a DC voltage applied to the lower electrode 18. The power supply unit 64 is configured to generate a negative-polarity DC voltage and a positive-polarity DC voltage. The power supply unit 64 is electrically connected to the lower electrode 18. In one embodiment, the power supply unit 64 is connected to an electrical path that connects the matching unit 63 and the electrode plate 19 to each other via a low-pass filter 66.

[0045] In the plasma processing apparatus 1, gas is supplied to the internal space 10s. Then, when high-frequency power is supplied, the gas is excited in the internal space 10s. As a result, plasma is generated in the internal space 10s. The substrate W is processed by chemical species such as ions and / or radicals from the generated plasma.

[0046] In one embodiment, the plasma processing apparatus 1 may further include a measurement device 70. The measurement device 70 is configured to measure a parameter representing the electron density in the chamber 10. In one example, the measurement device 70 is a plasma absorption probe. In this example, the measurement device 70 includes a network analyzer 70a, a high-pass filter 70f, and a probe 70p. The probe 70p extends from the outside of the chamber 10 to the inside of the chamber 10. The network analyzer 70a is connected to the probe 70p via the high-pass filter 70f. The network analyzer 70a supplies an electromagnetic wave signal of weak power to the probe 70p while changing its frequency, and acquires the S11 parameter from the reflected signal returned from the probe 70p. The network analyzer 70a identifies the electron density in the chamber 10 from the frequency corresponding to the minimum peak of the S11 parameter in the frequency characteristics of the S11 parameter. The identified electron density is used by the control unit MC described later as a parameter representing the electron density.

[0047] The measurement device 70 is not limited to a plasma absorption probe. In another example, the measurement device 70 may be an emission spectroscopic analyzer. In this example, the measurement device 70 identifies the electron density in the chamber 10 from the emission intensity of the plasma. In yet another example, the measurement device 70 may be a device that identifies the electron density in the chamber 10 using a laser beam.

[0048] The plasma processing apparatus 1 further includes a control unit MC. The control unit MC is a computer including a processor, a storage device, an input device, a display device, etc., and controls each part of the plasma processing apparatus 1. Specifically, the control unit MC executes a control program stored in the storage device and controls each part of the plasma processing apparatus 1 based on the recipe data stored in the storage device. By the control by the control unit MC, the process specified by the recipe data is executed in the plasma processing apparatus 1. The etching methods according to various embodiments can be executed in the plasma processing apparatus 1 by the control of each part of the plasma processing apparatus 1 by the control unit MC.

[0049] Hereinafter, with reference to FIG. 1 and FIG. 3, the method MT will be described. FIG. 3 is a timing chart of an example related to the etching method shown in FIG. 1. In FIG. 3, the vertical axis represents high-frequency power, positive ion density, negative ion density, electron density, and the output voltage of the power supply unit 64. In FIG. 3, the fact that the high-frequency power is ON indicates that high-frequency power is being supplied for plasma generation, and the fact that the high-frequency power is OFF indicates that the supply of high-frequency power has been stopped (afterglow state). In the middle of the timing chart of FIG. 3, the solid line represents the density of positive ions, the dashed-dotted line represents the electron density, and the dotted line represents the negative ion density.

[0050] Also refer to FIG. 4(a), FIG. 4(b), FIG. 5(a), FIG. 5(b), FIG. 6(a), and FIG. 6(b). FIG. 4(a) is a diagram showing the state of the plasma and the substrate during the period P1 in the timing chart of FIG. 3, and FIG. 4(b) is a diagram showing the state of the plasma and the substrate during the period P2 in the timing chart of FIG. 3. FIG. 5(a) is a diagram showing the state of the plasma and the substrate during the period P31 in the timing chart of FIG. 3, and FIG. 5(b) is a diagram showing the state of the plasma and the substrate during the period P32 in the timing chart of FIG. 3. FIG. 6(a) is a diagram showing the state of the plasma and the substrate during the period P4 in the timing chart of FIG. 3, and FIG. 6(b) is a diagram for explaining the step ST5 of the etching method shown in FIG. 1. In these diagrams, the circles enclosing "+", "-", "e", "A", and "A * " enclosing " respectively represent positive ions, negative ions, electrons, atoms or molecules, and radicals. Hereinafter, the method MT will be described by taking as an example the case where the plasma processing apparatus 1 is used in its execution. Also, in the following description, the control of each part of the plasma processing apparatus 1 by the control unit MC will also be described.

[0051] Method MT is executed with the substrate W placed on the support base 16. On the support base 16, the substrate W is held by the electrostatic chuck 20. The substrate W has, in one example, a base region UR, a film EF, and a mask MK. The film EF is provided on the base region UR. The film EF is the film to be etched in method MT. The mask MK is provided on the film EF. The mask MK provides an opening on the film EF. In method MT, the pattern of the mask MK is transferred to the film EF. That is, in method MT, an opening is formed in the film EF.

[0052] In method MT, step ST1 is executed. In step ST1, high-frequency power is supplied to the lower electrode 18 (or the upper electrode 30) to generate plasma from the gas in the chamber 10. The gas may be continuously supplied into the chamber 10 during the execution of method MT. The high-frequency power is supplied in periods P1 and P2 as shown in FIG. 3. Periods P1 and P2 are the execution periods of step ST1.

[0053] For the execution of step ST1, the control unit MC executes first control. In the first control, the control unit MC controls the gas supply unit to supply gas into the chamber 10. In the first control, the control unit MC controls the exhaust device 50 to set the pressure in the chamber 10 to a specified pressure. Also, in the first control, the control unit MC controls the high-frequency power supply 61 to supply high-frequency power to the lower electrode 18 (or the upper electrode 30).

[0054] As shown in FIG. 4(a), the plasma PL generated in step ST1 includes positive ions, negative ions, electrons, atoms or molecules, and radicals. In the plasma PL generated in step ST1, the amount of negative ions is relatively small.

[0055] Step ST2 is executed during the execution of step ST1. That is, step ST2 is executed while supplying high-frequency power for generating plasma. In step ST2, as shown in FIG. 4(b), a negative DC voltage is applied to the lower electrode 18 in order to etch the substrate W (i.e., its film EF) with positive ions from the plasma PL generated in step ST1.

[0056] For the execution of step ST2, the control unit MC executes second control. In the second control, the control unit MC controls the power supply unit 64 so as to apply a negative DC voltage to the lower electrode 18.

[0057] When step ST2 is executed, positive ions collide with the substrate W to etch the substrate W. In step ST2, since positive ions are supplied to the substrate W, the substrate W is charged with positive charges as shown in FIG. 5(a). In FIG. 5(a), the symbol “+” in the substrate W indicates that the substrate W is charged with positive charges.

[0058] Next, step ST3 is executed. In step ST3, the application of the negative DC voltage to the lower electrode 18 is stopped in order to generate negative ions. Also, in step ST3, the supply of high-frequency power is stopped.

[0059] For the execution of step ST3, the control unit MC executes third control. In the third control, the control unit MC controls the power supply unit 64 so as to stop the application of the negative DC voltage to the lower electrode 18. Also, in the third control, the control unit MC controls the high-frequency power supply 61 so as to stop the supply of high-frequency power. Note that the gas supply unit may continuously supply gas to the chamber 10 from step ST1. The exhaust device 50 may continuously adjust the pressure in the chamber 10 from step ST1.

[0060] In step ST3 of an embodiment, before the supply of high-frequency power is stopped, the application of a negative-polarity DC voltage to the lower electrode 18 may be stopped. In the third control of this embodiment, the control unit MC may control the power supply unit 64 so as to stop the application of a negative-polarity DC voltage to the lower electrode 18 before stopping the supply of high-frequency power to the high-frequency power supply 61. According to this embodiment, abnormal discharge can be more reliably prevented.

[0061] In the period immediately after the start of step ST3 (period P31 in FIG. 3), the plasma PL includes positive ions, negative ions, electrons, atoms or molecules, and radicals as shown in FIG. 5(a). In the plasma PL, the number of negative ions is relatively small.

[0062] In one embodiment, step STm is executed during the execution of step ST3. In step STm, the above-described parameter representing the electron density in the chamber 10 is measured by the measuring device 70. The parameter measured by the measuring device 70 is supplied to the control unit MC.

[0063] In the subsequent step STa, the control unit MC determines whether or not the electron density in the chamber 10 has decreased so as to satisfy a predetermined standard from the parameter. For example, when the electron density becomes smaller than the threshold value, it is determined that the electron density in the chamber 10 has decreased so as to satisfy a predetermined standard. Note that the decrease in the electron density during the execution of step ST3 reflects an increase in the amount of negative ions in the chamber 10.

[0064] In step STa, when it is determined that the electron density in the chamber 10 has not decreased so as to satisfy a predetermined standard, step ST3 continues. That is, the execution of the third control by the control unit MC continues. On the other hand, in step STa, when it is determined that the electron density in the chamber 10 has decreased so as to satisfy a predetermined standard, step ST3 ends and the process proceeds to step ST4. That is, when it is determined from the parameter that the electron density in the chamber 10 has decreased so as to satisfy a predetermined standard, the control unit MC ends the third control and starts the execution of the fourth control.

[0065] During the execution of step ST3, electrons bind to chemical species such as atoms, molecules, or radicals in chamber 10 to generate negative ions. At the end of step ST3 or during a period immediately before that (period P32 in FIG. 3), negative ions are sufficiently generated in chamber 10 as shown in FIG. 5(b).

[0066] In one embodiment, step STm and step STa may be omitted. In this embodiment, step ST3 (and the third control) may end after a lapse of a predetermined time from its start point. The predetermined time is determined in advance as the time required for negative ions to be sufficiently generated in chamber 10 after the start of step ST3.

[0067] Step ST4 is executed during period P4 after the execution of step ST3. In step ST4, in order to supply the negative ions generated in step ST3 to substrate W, a DC voltage of positive polarity is applied to lower electrode 18 with the supply of high-frequency power stopped.

[0068] For the execution of step ST4, control unit MC executes fourth control. In the fourth control, control unit MC controls power supply unit 64 to apply a DC voltage of positive polarity to lower electrode 18 with the supply of high-frequency power to high-frequency power supply 61 stopped. Note that gas supply unit can continuously supply gas to chamber 10 from step ST1. Exhaust device 50 can continuously adjust the pressure inside chamber 10 from step ST1.

[0069] In step ST4, since a DC voltage of positive polarity is applied to lower electrode 18, as shown in FIG. 6(a), negative ions are drawn to substrate W. The negative ions collide with substrate W to etch substrate W (i.e., film EF). Also, the negative ions reduce the amount of positive charge on substrate W.

[0070] As described above, in method MT, while plasma is being generated by the supply of high-frequency power, a negative-polarity DC voltage is supplied to the lower electrode 18. As a result, positive ions collide with the substrate W, and the substrate W is etched. Next, the supply of high-frequency power and the application of a DC voltage to the lower electrode 18 are stopped. In a state where high-frequency power is being supplied, the amount of negative ions generated is small, but when the supply of high-frequency power is stopped, negative ions are efficiently generated by the attachment of electrons to chemical species in the gas. Next, with the supply of high-frequency power stopped, a positive-polarity DC voltage is applied to the lower electrode 18. As a result, negative ions are supplied to the substrate W. In method MT, the negative ions reduce the positive charge amount of the substrate. Also, the substrate W is etched using both positive ions and negative ions. Therefore, the etching efficiency is improved.

[0071] In one embodiment, an etching sequence ESQ including step ST1, step ST2, step ST3, and step ST4 is executed one or more times. In this embodiment, the control unit MC executes an etching control sequence including first control, second control, third control, and fourth control one or more times. When the etching sequence ESQ is executed a plurality of times, the repetition frequency of the etching sequence ESQ may be 10 kHz or more and 500 kHz or less. The repetition frequency of the etching sequence ESQ may be 50 kHz or more and 400 kHz or less. Alternatively, the frequency may be greater than 400 kHz.

[0072] When the etching sequence ESQ is executed a plurality of times, method MT further includes step STb. In step STb, it is determined whether or not a stop condition is satisfied. The stop condition is satisfied when the etching sequence ESQ (or the etching control sequence) has been executed a predetermined number of times. In step STb, when it is determined that the stop condition is not satisfied, the etching sequence ESQ (or the etching control sequence) is executed.

[0073] In one embodiment, when it is determined that the stop condition is satisfied in step STb, step ST5 is executed. In step ST5, the exhaust device 50 discharges gas from the internal space of the chamber 10. In step ST5, the supply of high-frequency power by the high-frequency power supply 61 is stopped, and the application of the DC voltage to the lower electrode 18 by the power supply unit 64 is stopped.

[0074] To execute step ST5, the control unit MC executes fifth control. In the fifth control, the control unit MC controls the exhaust device 50 to discharge gas from the internal space of the chamber 10. In the fifth control, the control unit MC controls the high-frequency power supply 61 to stop the supply of high-frequency power. Also, in the fifth control, the control unit MC controls the power supply unit 64 to stop the application of the DC voltage to the lower electrode 18. Note that the gas supply unit may continuously supply gas to the chamber 10 from step ST1, or may stop the supply of the gas during the execution of step ST5.

[0075] The etching by-products generated by the etching sequence ESQ can remain in the opening formed in the substrate W. When step ST5 is executed, as shown in FIG. 6(b), the etching by-products are discharged from the chamber 10 as gas. In FIG. 6(b), the circle surrounding "B" represents the etching by-products. Note that the symbol "-" in the substrate W in FIG. 6(b) indicates that the substrate W is charged with a negative charge by the execution of step ST4.

[0076] In one embodiment, another sequence ASQ including one or more executions of the etching sequence ESQ and step ST5 may be repeated. The repetition frequency of sequence ASQ can be 100 Hz or more and 10 kHz or less. The ratio that the period of one or more executions of the etching sequence ESQ occupies during one execution period of sequence ASQ can be 30% or more and 70% or less. In this embodiment, the control unit MC repeatedly executes another control sequence. The another control sequence includes one or more executions of the etching control sequence and the fifth control. In this embodiment, as shown in FIG. 1, the method MT includes step STc. In step STc, it is determined whether the stop condition is satisfied. In step STc, it is determined whether the stop condition is satisfied. The stop condition is satisfied when sequence ASQ (or another control sequence) has been executed a predetermined number of times. When it is determined in step STc that the stop condition is not satisfied, sequence ASQ (or another control sequence) is executed again. On the other hand, when it is determined in step STc that the stop condition is satisfied, the method MT ends.

[0077] In one embodiment, during one execution of sequence ASQ, step ST5 may be executed for 10 μs or more. In this embodiment, the fifth control is executed for 10 μs or more during the execution period of the above-mentioned another control sequence. According to this embodiment, the etching by-products are more reliably discharged. As a result, the etching efficiency of the substrate W is further improved.

[0078] In one embodiment, as the number of executions of sequence ASQ increases, the execution period of step ST5 may be increased. In this embodiment, the control unit MC increases the execution period of the fifth control as the number of executions of the above-mentioned another control sequence increases. In this embodiment, as the depth of the opening formed in the substrate W increases, the execution period of step ST5 increases. Therefore, the etching by-products are more reliably discharged.

[0079] In one embodiment, during the execution period of step ST1, that is, during periods P1 and P2, high-frequency power may be intermittently supplied from the high-frequency power supply 61 to generate plasma. That is, a plurality of pulses of high-frequency power may be intermittently supplied from the high-frequency power supply 61 during the execution period of step ST1. In one embodiment, a plurality of pulses of high-frequency power may be periodically supplied from the high-frequency power supply 61 during the execution period of step ST1. The period at which pulses of high-frequency power are supplied from the high-frequency power supply 61 may be a period defined by a frequency of 100 kHz or more and 1 MHz or less. In one embodiment, the power levels of the plurality of pulses of high-frequency power supplied from the high-frequency power supply 61 during the execution period of step ST1 may vary. In one embodiment, the average value of the power levels of the plurality of pulses of high-frequency power supplied from the high-frequency power supply 61 during the execution period of step ST1 may vary in the repetition of the etching sequence ESQ.

[0080] In one embodiment, during the execution period of step ST2, that is, during period P2, a negative-polarity DC voltage may be intermittently applied from the power supply unit 64 to the lower electrode 18. That is, a plurality of pulses of the negative-polarity DC voltage may be intermittently applied from the power supply unit 64 to the lower electrode 18 during the execution period of step ST2. In one embodiment, a plurality of pulses of the negative-polarity DC voltage may be periodically applied from the power supply unit 64 to the lower electrode 18 during the execution period of step ST2. The period at which pulses of the negative-polarity DC voltage are applied from the power supply unit 64 to the lower electrode 18 may be a period defined by a frequency of 100 kHz or more and 1 MHz or less. The timing at which pulses of the negative-polarity DC voltage are applied from the power supply unit 64 to the lower electrode 18 may be synchronized with the timing at which pulses of high-frequency power are supplied from the high-frequency power supply 61. In one embodiment, the voltage values of the plurality of pulses of the negative-polarity DC voltage applied from the power supply unit 64 to the lower electrode 18 during the execution period of step ST2 may vary. In one embodiment, the average value of the voltage values of the plurality of pulses of the negative-polarity DC voltage applied from the power supply unit 64 to the lower electrode 18 during the execution period of step ST2 may vary in the repetition of the etching sequence ESQ.

[0081] In one embodiment, during the execution period of step ST4, that is, during period P4, a DC voltage of positive polarity may be intermittently applied from the power supply unit 64 to the lower electrode 18. That is, during the execution period of step ST4, a plurality of pulses of the DC voltage of positive polarity may be intermittently applied from the power supply unit 64 to the lower electrode 18. In one embodiment, during the execution period of step ST4, a plurality of pulses of the DC voltage of positive polarity may be periodically applied from the power supply unit 64 to the lower electrode 18. The period at which the pulses of the DC voltage of positive polarity are applied from the power supply unit 64 to the lower electrode 18 may be a period defined by a frequency of 100 kHz or more and 1 MHz or less. In one embodiment, the voltage values of the plurality of pulses of the DC voltage of positive polarity applied from the power supply unit 64 to the lower electrode 18 during the execution period of step ST4 may vary. In one embodiment, the average value of the voltage values of the plurality of pulses of the DC voltage of positive polarity applied from the power supply unit 64 to the lower electrode 18 during the execution period of step ST4 may vary in the repetition of the etching sequence ESQ.

[0082] Although various exemplary embodiments have been described above, various omissions, substitutions, and changes may be made without being limited to the exemplary embodiments described above. Also, it is possible to form other embodiments by combining elements in different embodiments.

[0083] For example, although the plasma processing apparatus 1 is a capacitively coupled plasma processing apparatus, the plasma processing apparatus according to another embodiment may be another type of plasma processing apparatus such as an inductively coupled plasma processing apparatus. Also, the method MT may be executed using any type of plasma processing apparatus other than the plasma processing apparatus 1, for example, an inductively coupled plasma processing apparatus.

[0084] From the above description, it will be understood that the various embodiments of the present disclosure are described herein for the purpose of explanation and that various changes can be made without departing from the scope and spirit of the present disclosure. Therefore, the various embodiments disclosed herein are not intended to be limiting, and the true scope and spirit are indicated by the appended claims.

Explanation of Symbols

[0085] 1... Plasma processing apparatus, 10... Chamber, 16... Support table, 18... Lower electrode, 61... High-frequency power supply, 64... Power supply unit, MC... Control unit.

Claims

1. A chamber, a substrate support having a lower electrode and provided in the chamber, an exhaust device connected to the chamber, a high-frequency power supply configured to supply high-frequency power to generate plasma from a gas in the chamber, a power supply unit configured to generate a positive DC voltage and a negative DC voltage and electrically connected to the lower electrode, a control unit configured to control the high-frequency power supply and the power supply unit, comprising: The control unit: a first control for controlling the high-frequency power supply to supply high-frequency power to generate plasma from the gas in the chamber; a second control for controlling the power supply unit to apply a negative DC voltage to the lower electrode of the substrate support during the supply of the high-frequency power to etch the substrate with positive ions from the plasma; a third control for controlling the power supply unit and the high-frequency power supply to stop applying the negative DC voltage to the lower electrode and supplying the high-frequency power to generate negative ions; a fourth control for controlling the power supply unit to apply a positive DC voltage to the lower electrode while the supply of the high-frequency power is stopped to supply the negative ions to the substrate; a fifth control for controlling the power supply unit to stop applying the positive DC voltage to the lower electrode while the supply of the high-frequency power is stopped; configured to execute a plurality of times a first sequence including these; After executing the first sequence a plurality of times, the control unit is further configured to execute a sixth control for controlling the exhaust device to discharge gas from the internal space of the chamber in a state where no gas is supplied to the chamber and the supply of the high-frequency power and the application of the DC voltage to the lower electrode are stopped. A plasma processing apparatus.

2. The plasma processing apparatus according to claim 1, wherein the repetition frequency of the first sequence is 10 kHz or more and 500 kHz or less.

3. The plasma processing apparatus according to claim 1 or 2, wherein the control unit is configured to repeatedly execute a second sequence including the plurality of executions of the first sequence and the sixth control.

4. The plasma processing apparatus according to claim 3, wherein the repetition frequency of the second sequence is 100 Hz or more and 10 kHz or less.

5. The plasma processing apparatus according to claim 3 or 4, wherein a ratio of a period during which the first sequence is executed a plurality of times during an execution period of the second sequence is 30% or more and 70% or less.

6. The plasma processing apparatus according to any one of claims 3 to 5, wherein the sixth control is executed for 10 μs or more during an execution period of the second sequence.

7. The plasma processing apparatus according to any one of claims 1 to 6, wherein during a period in which the second control is performed, the power supply unit applies the negative DC voltage to the lower electrode in a cycle repeated at a frequency of 100 kHz or more and 1 MHz or less.

8. The plasma processing apparatus according to any one of claims 1 to 7, wherein during a period in which the fourth control is performed, the power supply unit applies the positive DC voltage to the lower electrode in a cycle repeated at a frequency of 100 kHz or more and 1 MHz or less.

9. The plasma processing apparatus according to any one of claims 1 to 8, wherein in the third control, the control unit controls the power supply unit to stop applying the negative DC voltage to the lower electrode before stopping the supply of the high-frequency power.

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