Plasma processing device and system

Abstract

To provide an etching method that can reduce the positive charge amount of a substrate and increase the etching efficiency.SOLUTION: A plasma processing device to be disclosed includes an RF power source and a DC power source. The RF power supplied to a lower electrode or an upper electrode by the RF power source includes, in a first sequence in a repeating period, a first power level in a first state and in a second state, and a second power level in a third state and in a fourth state. The first power level is higher than the second power level. The DC voltage to be applied to the lower electrode by the DC power source includes, in the first sequence in the repeating period, a first voltage level in the first state and in the third state, a second voltage level in the second state, and a third voltage level in the fourth state. The second voltage level has negative polarity and the third voltage level has positive polarity.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] SUMMARY OF THE INVENTION Exemplary embodiments of the present disclosure relate to an etching method and a plasma processing apparatus. [Background technology]

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

[0003] As etching of the substrate by positive ions progresses, the substrate becomes charged. When the substrate is charged, the amount of positive ions supplied to the interior of the opening decreases. As a result, the etching rate may decrease. Alternatively, when the substrate is charged, abnormalities may occur in the shape of the opening formed in the substrate.

[0004] In the technology described in Patent Document 1, to reduce the amount of positive charge on the substrate, a positive DC voltage is applied to the lower electrode from a power supply. Then, the application of the DC voltage to the lower electrode is stopped. Then, a negative DC voltage is applied to the lower electrode from the power supply. As a result, positive ions are attracted to the substrate, causing etching. Thereafter, the application of the DC voltage to the lower electrode is stopped. In the technology described in Patent Document 1, the application of a positive DC voltage to the lower electrode, the stopping of the application of the DC voltage to the lower electrode, the application of a negative DC voltage to the lower electrode, and the stopping of the application of the DC voltage to the lower electrode are repeated. High-frequency power for generating plasma is continuously supplied while the application of a positive DC voltage to the lower electrode, the stopping of the application of the DC voltage to the lower electrode, the application of a negative DC voltage to the lower electrode, and the stopping of the application of the DC voltage to the lower electrode are repeated. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2012-79886 Summary of the Invention [Problem to be solved by the invention]

[0006] Plasma etching requires reducing the amount of positive charge on the substrate and increasing the etching efficiency. [Means for solving the problem]

[0007] A plasma processing apparatus according to one exemplary embodiment includes: a chamber; a substrate support table including a lower electrode and disposed within the chamber; and an upper electrode disposed above the substrate support table; an RF power source configured to supply RF power to the lower electrode or the upper electrode, the RF power having a plurality of power levels during a first sequence in a repetition period, the plurality of power levels including a first power level during a first state and a second state, and a second power level during a third state and a fourth state, the first power level being greater than the second power level; a DC power supply configured to apply a DC voltage to the lower electrode, the DC voltage having a plurality of voltage levels during the first sequence in the repeating period, the plurality of voltage levels including a first voltage level during the first state and during the third state, a second voltage level during the second state, and a third voltage level during the fourth state, the second voltage level having a negative polarity and the third voltage level having a positive polarity; Equipped with. [Effects of the Invention]

[0008] According to one exemplary embodiment, it is possible to reduce the amount of positive charge on the substrate and increase the etching efficiency. [Brief explanation of the drawings]

[0009] [Figure 1] 1 is a flow diagram illustrating an etching method according to an exemplary embodiment. [Figure 2] 1 is a diagram illustrating a schematic diagram of a plasma processing apparatus according to an exemplary embodiment; [Figure 3] 2 is a timing chart of an example related to the etching method shown in FIG. 1. [Figure 4] 4(a) is a diagram showing the state of the plasma and the substrate during 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 period P2 in the timing chart of FIG. [Figure 5] 5(a) is a diagram showing the state of the plasma and the substrate during 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 period P32 in the timing chart of FIG. [Figure 6] FIG. 6(a) is a diagram showing the state of the plasma and the substrate during period P4 in the timing chart of FIG. 3, and FIG. 6(b) is a diagram explaining step ST5 of the etching method shown in FIG. DETAILED DESCRIPTION OF THE INVENTION

[0010] Various exemplary embodiments are described below.

[0011] In one exemplary embodiment, an etching method is provided that is performed using a plasma processing apparatus. The etching method is performed with a substrate placed on a substrate support table provided in a chamber of the plasma processing apparatus. The etching method includes a step of supplying high-frequency power to generate plasma from 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 table while the step of supplying high-frequency power is being performed, 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 to generate negative ions. The etching method further includes a step of applying a positive DC voltage to the lower electrode while the supply of high-frequency power is stopped, in order to supply negative ions to the substrate.

[0012] In the above embodiment, while plasma is being generated by supplying high-frequency power, a negative DC voltage is supplied to the lower electrode. As a result, positive ions collide with the substrate, etching the substrate. Next, the supply of high-frequency power and the application of DC voltage to the lower electrode are stopped. While the amount of negative ions generated is small when high-frequency power is being supplied, when the supply of high-frequency power is stopped, negative ions are efficiently generated by electrons attaching to chemical species in the gas. Next, with the supply of high-frequency power stopped, a positive DC voltage is applied to the lower electrode. As a result, negative ions are supplied to the substrate. According to the above embodiment, the negative ions reduce the amount of positive charge on the substrate. Furthermore, the substrate is etched using both positive and negative ions. Therefore, 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 polarity DC voltage, a step of stopping the supply, and a step of applying a positive polarity DC voltage. During the exhausting step, 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 may be repeated that includes one or more runs of the etching sequence and the draining step.

[0015] In one exemplary embodiment, the draining step may be performed for 10 μs or more during the execution period of the separate sequence. In this embodiment, etching by-products are more reliably drained, thereby further improving the etching efficiency of the substrate.

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

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

[0018] In one exemplary embodiment, in the stopping step, the application of the negative DC voltage to the lower electrode may be stopped before the supply of high-frequency power is 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 pedestal, a radio frequency power supply, a power supply unit, and a controller. The substrate support pedestal has a lower electrode and is disposed within the chamber. The radio frequency power supply is configured to supply radio frequency power to generate plasma from a gas within the chamber. The power supply unit is configured to generate a positive polarity DC voltage and a negative polarity DC voltage. The power supply unit is electrically connected to the lower electrode. The controller is configured to control the radio frequency power supply and the power supply unit. The controller is configured to perform first, second, third, and fourth controls. The first control includes controlling the radio frequency power supply to supply radio frequency power to generate plasma from the gas within the chamber. The second control includes controlling the power supply unit to apply a negative polarity DC voltage to the lower electrode of the substrate support pedestal while supplying radio frequency power to etch the substrate with positive ions from the plasma. The third control includes controlling the power supply unit and the radio frequency power supply to stop applying the negative polarity DC voltage to the lower electrode and stopping the supply of radio frequency power to the lower electrode to generate negative ions. The fourth control includes controlling the power supply unit to apply a positive DC voltage to the lower electrode while the supply of high frequency power is stopped in order 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 configured to further execute a fifth control. The fifth control includes controlling the exhaust device to exhaust gas from the interior 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 the DC voltage to the lower electrode is stopped.

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

[0022] In one exemplary embodiment, during the execution period of the other control sequence, the fifth control may be executed for 10 μsec or more.

[0023] In one exemplary embodiment, the control unit may increase the length of the execution period of the fifth control as the number of times the other control sequence is executed increases.

[0024] In one exemplary embodiment, the plasma processing apparatus may further include a measurement device. The measurement device measures a parameter representing the electron density in the chamber during execution of the third control. The control unit may start execution of the fourth control when it is determined from the parameter that the electron density in the chamber has decreased to satisfy a predetermined criterion.

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

[0026] Various exemplary embodiments will be described in detail below with reference to the drawings, in which the same or equivalent parts are designated by the same reference numerals.

[0027] Fig. 1 is a flow chart showing an etching method according to one example embodiment. The etching method shown in Fig. 1 (hereinafter referred to as "method MT") is performed using a plasma processing apparatus. Fig. 2 is a diagram schematically showing a plasma processing apparatus according to one example embodiment. The plasma processing apparatus 1 shown in Fig. 2 can be used to perform 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 plasma-resistant film is formed on the inner wall surface of the chamber body 12, i.e., the wall surface defining the internal space 10s. This film may be a film formed by anodizing or a ceramic film such as a film formed from yttrium oxide.

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

[0030] A substrate support table, i.e., support table 16, is provided within chamber 10. Support table 16 is configured to support a substrate W placed thereon. The substrate W has a generally disk-like shape. Support table 16 is supported by a support 15. Support 15 extends upward from the bottom of chamber body 12. Support 15 has a generally cylindrical shape. Support 15 is made of an insulating material such as quartz.

[0031] The support table 16 has a lower electrode 18. The support table 16 may further have an electrostatic chuck 20. The support table 16 may further have an electrode plate 19. The electrode plate 19 is made 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 made 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., chlorofluorocarbon) that cools the lower electrode 18 by vaporizing is used. A heat exchange medium circulation device (e.g., a chiller unit) 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 a substrate W is processed in the internal space 10s, it is placed on the electrostatic chuck 20 and held by it. The electrostatic chuck 20 has a body and an electrode. The body of the electrostatic chuck 20 is formed from a dielectric material such as aluminum oxide or aluminum nitride. The body of the electrostatic chuck 20 has a substantially disk shape. The electrostatic chuck 20 includes a substrate mounting region and a focus ring mounting region. The substrate mounting region is a region having a substantially disk shape. The upper surface of the substrate mounting region extends along a horizontal plane. An axis AX that includes the center of the substrate mounting region and extends vertically substantially coincides with the central axis of the chamber 10. When a substrate W is processed in the chamber 10, it is placed on the upper surface of the substrate mounting region.

[0034] The focus ring mounting region extends in the circumferential direction to surround the substrate mounting 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 within the region surrounded by the focus ring FR. That is, the focus ring FR surrounds the edge of the substrate W mounted on the substrate mounting region of the electrostatic chuck 20. The focus ring FR is made of, for example, silicon or silicon carbide.

[0035] The electrode of the electrostatic chuck 20 is provided within the body of the electrostatic chuck 20. The electrode of the electrostatic chuck 20 is a film formed from a conductor. A DC power supply is electrically connected to the electrode of the electrostatic chuck 20. When a DC voltage is applied from the DC power supply to the electrode of the electrostatic chuck 20, an electrostatic attractive force is generated between the electrostatic chuck 20 and the substrate W. The generated electrostatic attractive force attracts the substrate W to the electrostatic chuck 20 and the substrate W is 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, for example, He gas, from a gas supply mechanism to between the upper surface of the electrostatic chuck 20 and the rear 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 body 12. The cylindrical portion 28 extends along the outer periphery of the support 15. The cylindrical portion 28 is made of 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 made of an insulating material. The insulating portion 29 is made of a ceramic such as quartz. 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 table 16. The upper electrode 30 closes the upper opening of the chamber body 12. The upper electrode 30 is supported on the upper part of the chamber 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 thickness direction (vertical direction). The top plate 34 is made of, for example, silicon, but 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 an aluminum member. This film may be a ceramic film, such as a film formed by anodizing or a film formed from yttrium oxide.

[0040] The support 36 detachably supports the top plate 34. The support 36 is made of a conductive material such as aluminum. 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 are respectively connected to the plurality of gas discharge holes 34a. 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 the 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 includes one or more gas sources used in the 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 gases from one or more selected gas sources from 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 may be a plate-shaped member. The baffle member 48 may be formed, for example, by coating an aluminum plate with a ceramic such as yttrium oxide. 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 the 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 turbomolecular pump, and is capable of reducing 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 generating plasma. The frequency of the high-frequency power is, but is not limited to, a frequency 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 box 63 and an electrode plate 19 in order to supply high-frequency power to the lower electrode 18. The matching box 63 has a matching circuit for matching the output impedance of the high-frequency power supply 61 with the impedance on the load side (lower electrode 18 side). Note that the high-frequency power supply 61 does not necessarily have to be electrically connected to the lower electrode 18, and may be connected to the upper electrode 30 via the matching box 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 to be applied to the lower electrode 18. The power supply unit 64 is configured to generate a negative DC voltage and a positive 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 connecting the matching box 63 and the electrode plate 19 to each other via a low-pass filter 66.

[0045] In the plasma processing apparatus 1, a gas is supplied to the internal space 10s. Then, high-frequency power is supplied, and 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 within 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 a weak electromagnetic signal 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 within 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 as a parameter representing the electron density by a control unit MC, which will be described later.

[0047] The measuring device 70 is not limited to a plasma absorption probe. In another example, the measuring device 70 may be an optical emission spectrometer. In this example, the measuring device 70 determines the electron density in the chamber 10 from the emission intensity of the plasma. In yet another example, the measuring device 70 may be a device that determines the electron density in the chamber 10 using laser light.

[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 recipe data stored in the storage device. Under the control of the control unit MC, a process specified by the recipe data is executed in the plasma processing apparatus 1. Etching methods according to various embodiments can be executed in the plasma processing apparatus 1 under the control of each part of the plasma processing apparatus 1 by the control unit MC.

[0049] Method MT will be described below with reference to FIG. 3 in addition to FIG. 1. 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 high-frequency power being ON indicates that high-frequency power is being supplied to generate plasma, and the high-frequency power being OFF indicates that the supply of high-frequency power has been stopped (afterglow state). In the middle part of the timing chart in FIG. 3, the solid line represents the positive ion density, the dashed-dotted line represents the electron density, and the dotted line represents the negative ion density.

[0050] Also, see Figures 4(a), 4(b), 5(a), 5(b), 6(a), and 6(b). Figure 4(a) is a diagram showing the state of the plasma and the substrate in period P1 in the timing chart of Figure 3, and Figure 4(b) is a diagram showing the state of the plasma and the substrate in period P2 in the timing chart of Figure 3. Figure 5(a) is a diagram showing the state of the plasma and the substrate in period P31 in the timing chart of Figure 3, and Figure 5(b) is a diagram showing the state of the plasma and the substrate in period P32 in the timing chart of Figure 3. Figure 6(a) is a diagram showing the state of the plasma and the substrate in period P4 in the timing chart of Figure 3, and Figure 6(b) is a diagram explaining step ST5 of the etching method shown in Figure 1. In these figures, a circle surrounding a "+", a circle surrounding a "-", a circle surrounding an "e", a circle surrounding an "A", a circle surrounding an "A", and * The circles surrounding " represent positive ions, negative ions, electrons, atoms or molecules, and radicals, respectively. Below, the method MT will be described using the case where the plasma processing apparatus 1 is used in its implementation as an example. The following description also explains the control of each part of the plasma processing apparatus 1 by the control unit MC.

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

[0052] In the method MT, step ST1 is performed. 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 the method MT. The high-frequency power is supplied during periods P1 and P2, as shown in FIG. 3 . Periods P1 and P2 are the execution periods of step ST1.

[0053] To perform step ST1, the control unit MC executes a 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 inside 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] 4(a), the plasma PL generated in step ST1 contains positive ions, negative ions, electrons, atoms or molecules, and radicals. The amount of negative ions in the plasma PL generated in step ST1 is relatively small.

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

[0056] To perform the step ST2, the control unit MC performs the second control. In the second control, the control unit MC controls the power supply unit 64 to apply a negative DC voltage to the lower electrode 18.

[0057] When step ST2 is performed, positive ions collide with the substrate W and etch the substrate W. In step ST2, positive ions are supplied to the substrate W, so that the substrate W is positively charged as shown in Fig. 5(a). In Fig. 5(a), the symbol "+" in the substrate W indicates that the substrate W is positively charged.

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

[0059] To perform step ST3, the control unit MC executes a third control. In the third control, the control unit MC controls the power supply unit 64 to stop applying a negative DC voltage to the lower electrode 18. In addition, in the third control, the control unit MC controls the high-frequency power supply 61 to stop supplying high-frequency power. The gas supply unit can continuously supply gas to the chamber 10 from step ST1. The exhaust device 50 can continuously adjust the pressure in the chamber 10 from step ST1.

[0060] In one embodiment, in step ST3, the application of the negative DC voltage to the lower electrode 18 may be stopped before the supply of high frequency power is stopped. In the third control of this embodiment, the control unit MC may control the power supply unit 64 to stop the application of the negative 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 is more reliably prevented.

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

[0062] In one embodiment, step STm is performed 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 measurement device 70. The parameter measured by the measurement device 70 is provided to the control unit MC.

[0063] In the subsequent step STa, the control unit MC determines from the parameters whether the electron density in the chamber 10 has decreased to satisfy a predetermined standard. For example, if the electron density becomes smaller than a threshold value, it is determined that the electron density in the chamber 10 has decreased to satisfy the predetermined standard. Note that the decrease in electron density during the execution of step ST3 reflects an increase in the amount of negative ions in the chamber 10.

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

[0065] During step ST3, electrons bond with chemical species such as atoms, molecules, or radicals to generate negative ions in chamber 10. At the end of step ST3 or in the period immediately before (period P32 in FIG. 3), a sufficient number of negative ions are 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 be terminated after a predetermined time has elapsed from the start of step ST3. The predetermined time is determined in advance as the time required for sufficient negative ions to be generated in the chamber 10 after the start of step ST3.

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

[0068] To perform step ST4, the control unit MC executes a fourth control. In the fourth control, the control unit MC controls the power supply unit 64 to apply a positive DC voltage to the lower electrode 18 while stopping the supply of high-frequency power to the high-frequency power supply 61. The gas supply unit can continuously supply gas to the chamber 10 from step ST1. The exhaust device 50 can continuously adjust the pressure in the chamber 10 from step ST1.

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

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

[0071] In one embodiment, an etching sequence ESQ including steps ST1, ST2, ST3, and ST4 is executed one or more times. In this embodiment, the controller 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 multiple 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 multiple times, the method MT further includes a step STb. In the step STb, it is determined whether 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. When it is determined in the step STb that the stop condition is not satisfied, the etching sequence ESQ (or the etching control sequence) is executed.

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

[0074] To perform step ST5, the control unit MC performs a fifth control. In the fifth control, the control unit MC controls the exhaust device 50 to exhaust 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 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] Etching by-products generated by the etching sequence ESQ may remain in the openings formed in the substrate W. When step ST5 is performed, the etching by-products are exhausted from the chamber 10 as gas, as shown in FIG. 6(b). 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 negatively charged due to the execution of step ST4.

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

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

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

[0079] In one embodiment, during the execution of step ST1, i.e., during periods P1 and P2, high-frequency power may be intermittently supplied from the high-frequency power supply 61 to generate plasma. That is, during the execution of step ST1, multiple pulses of high-frequency power may be intermittently supplied from the high-frequency power supply 61. In one embodiment, during the execution of step ST1, multiple pulses of high-frequency power may be periodically supplied from the high-frequency power supply 61. The period at which the high-frequency power pulses 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 level of the multiple pulses of high-frequency power supplied from the high-frequency power supply 61 during the execution of step ST1 may vary. In one embodiment, the average value of the power level of the multiple pulses of high-frequency power supplied from the high-frequency power supply 61 during the execution of step ST1 may vary with the repetition of the etching sequence ESQ.

[0080] In one embodiment, during the execution of step ST2, i.e., during the period P2, a negative DC voltage may be intermittently applied from the power supply unit 64 to the lower electrode 18. That is, during the execution of step ST2, multiple pulses of the negative DC voltage may be intermittently applied from the power supply unit 64 to the lower electrode 18. In one embodiment, during the execution of step ST2, multiple pulses of the negative DC voltage may be periodically applied from the power supply unit 64 to the lower electrode 18. The period at which the negative DC voltage pulses 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 the negative DC voltage pulses are applied from the power supply unit 64 to the lower electrode 18 may be synchronized with the timing at which the high-frequency power pulses are supplied from the high-frequency power supply 61. In one embodiment, the voltage values ​​of the multiple pulses of the negative DC voltage applied from the power supply unit 64 to the lower electrode 18 during the execution of step ST2 may vary. In one embodiment, the average value of the voltage values ​​of the multiple pulses of the negative DC voltage applied from the power supply unit 64 to the lower electrode 18 during the execution period of the process ST2 may vary as the etching sequence ESQ is repeated.

[0081] In one embodiment, during the execution of step ST4, i.e., during the period P4, a positive DC voltage may be intermittently applied from the power supply unit 64 to the lower electrode 18. That is, during the execution of step ST4, multiple pulses of the positive DC voltage may be intermittently applied from the power supply unit 64 to the lower electrode 18. In one embodiment, during the execution of step ST4, multiple pulses of the positive DC voltage may be periodically applied from the power supply unit 64 to the lower electrode 18. The period during which the positive DC voltage pulses 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 multiple pulses of the positive DC voltage applied from the power supply unit 64 to the lower electrode 18 during the execution of step ST4 may vary. In one embodiment, the average voltage value of the multiple pulses of the positive DC voltage applied from the power supply unit 64 to the lower electrode 18 during the execution of step ST4 may vary with the repetition of the etching sequence ESQ.

[0082] Although various exemplary embodiments have been described above, the present invention is not limited to the above-described exemplary embodiments, and various omissions, substitutions, and modifications may be made. Furthermore, elements in different embodiments may be combined to form other embodiments.

[0083] For example, although the plasma processing apparatus 1 is a capacitively coupled plasma processing apparatus, a 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 performed using any type of plasma processing apparatus other than the plasma processing apparatus 1, such as an inductively coupled plasma processing apparatus.

[0084] From the foregoing, it will be understood that various embodiments of the present disclosure have been described herein for purposes of illustration, and that various modifications may be made without departing from the scope and spirit of the present disclosure. Accordingly, the various embodiments disclosed herein are not intended to be limiting, with the true scope and spirit being indicated by the appended claims. [Explanation of symbols]

[0085] 1...plasma processing apparatus, 10...chamber, 16...support stand, 18...lower electrode, 61...high frequency power supply, 64...power supply unit, MC...control unit.

Claims

1. a chamber; a substrate support table disposed within the chamber and including a lower electrode; an upper electrode disposed above the substrate support; an RF power source configured to supply RF power to the lower electrode or the upper electrode, the RF power having a plurality of power levels during a first sequence in a repeating period, the plurality of power levels including a first power level during a first state and a second state, and a second power level during a third state and a fourth state, the first power level being greater than the second power level; a DC power supply configured to apply a DC voltage to the bottom electrode, the DC voltage having a plurality of voltage levels during the first sequence in the repeating period, the plurality of voltage levels including a first voltage level during the first state and during the third state, a second voltage level during the second state, and a third voltage level during the fourth state, the second voltage level having a negative polarity and the third voltage level having a positive polarity; A plasma processing apparatus comprising:

2. 2. The plasma processing apparatus of claim 1, wherein the first voltage level is equal to a zero voltage level.

3. The plasma processing apparatus of claim 2 , wherein the second power level is equal to a zero power level.

4. The plasma processing apparatus of claim 3 , wherein the first sequence is repeated in the repeating period.

5. The plasma processing apparatus of claim 4 , wherein the repeating cycle includes an exhaust phase after the repeated first sequence.

6. The plasma processing apparatus of claim 5 , wherein the exhaust phase is performed for 10 μsec or more.

7. The plasma processing apparatus of claim 1 , wherein the repeating cycle includes an exhaust phase after the first sequence.

8. The plasma processing apparatus of claim 7 , wherein the exhaust phase is performed for 10 μsec or more.

9. 2. The plasma processing apparatus of claim 1, wherein the DC voltage transitions from the second voltage level to the first voltage level immediately before the RF power transitions from the first power level to the second power level.

10. an RF generator configured to generate RF power, the RF power having a plurality of power levels during a first sequence in a repeating period, the plurality of power levels including a first power level during a first state and a second state, and a second power level during a third state and a fourth state, the first power level being greater than the second power level; a DC generator configured to generate a DC voltage, the DC voltage having a plurality of voltage levels during the first sequence in the repeating period, the plurality of voltage levels including a first voltage level during the first state and during the third state, a second voltage level during the second state, and a third voltage level during the fourth state, the second voltage level having a negative polarity and the third voltage level having a positive polarity; A system comprising:

11. The system of claim 10 , wherein the first sequence is repeated in the repetition period.

12. The system of claim 11 , wherein the repeating period includes an exhaust phase after the repeated first sequence.

13. The system of claim 12 , wherein the exhaust phase is performed for 10 μs or more.

14. The system of claim 10 , wherein the repeating cycle includes an exhaust phase after the first sequence.

15. The system of claim 14 , wherein the exhaust phase is performed for 10 μs or more.

16. 11. The system of claim 10, wherein the DC voltage transitions from the second voltage level to the first voltage level before the RF power transitions from the first power level to the second power level.

17. an RF generator configured to generate RF power, the RF power having a plurality of power levels during a repetition period, the plurality of power levels including a first power level during a first state and a second state, and a second power level during a third state and a fourth state, the first power level being greater than the second power level; a DC generator configured to generate a DC voltage, the DC voltage having a plurality of voltage levels during the repeating period, the plurality of voltage levels including a first voltage level during the first state and during the third state, a second voltage level during the second state, and a third voltage level during the fourth state, the second voltage level having a negative polarity and the third voltage level having a positive polarity; A system comprising:

18. 20. The system of claim 17, wherein the plurality of power levels includes the second power level during a fifth state.

19. 20. The system of claim 18, wherein the fifth state is executed for 10 microseconds or more.

20. 20. The system of claim 17, wherein the DC voltage transitions from the second voltage level to the first voltage level before the RF power transitions from the first power level to the second power level.

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