Plasma processing apparatus and control method thereof

Abstract

The invention provides a plasma processing apparatus and a control method thereof, which can enlarge the formation area of plasma generated on the upper electrode side and improve the processing speed. A plasma processing apparatus according to one embodiment of the present invention has a vacuum chamber, a stage for supporting a substrate, a counter electrode, and a resonance circuit. The stage is disposed inside the vacuum chamber and is connected to a first high-frequency power supply circuit that supplies high-frequency power of a first frequency. The counter electrode is disposed facing the stage and is connected to a second high-frequency power supply circuit that supplies high-frequency power of a second frequency. The resonance circuit passes the high-frequency current of the second frequency from the counter electrode.

Description

Technical Field

[0001] The present invention relates to a plasma processing apparatus such as a dry etching apparatus and a control method thereof. Background Art

[0002] Among vacuum processing devices such as etching devices, there are known capacitively coupled plasma vacuum processing devices. For example, Patent Document 1 discloses a device that generates capacitively coupled plasma by applying a first high-frequency voltage to a lower electrode supporting a processing substrate and a second high-frequency voltage to an upper electrode having a gas introduction mechanism to perform plasma processing.

[0003] Prior art literature

[0004] Patent Literature

[0005] Patent Document 1: Japanese Patent Application Publication No. 2013-225672.

[0006] Problem that the invention aims to solve

[0007] In such a dual-frequency CCP plasma processing apparatus, there is a problem that the plasma formation region generated by the second high frequency voltage on the upper electrode side is difficult to expand to the vicinity of the surface of the processing substrate, and the contribution rate to the processing speed is low. Summary of the invention

[0008] In view of the above circumstances, an object of the present invention is to provide a plasma processing apparatus and a control method thereof that can expand a formation region of plasma generated on an upper electrode side and increase a processing speed.

[0009] Solutions for solving problems

[0010] A plasma processing apparatus according to one embodiment of the present invention includes a vacuum chamber, a stage for supporting a substrate, a counter electrode, and a resonance circuit.

[0011] The stage is disposed inside the vacuum chamber and is connected to a first high-frequency power supply circuit that supplies high-frequency power of a first frequency.

[0012] The counter electrode is arranged to face the worktable, and is connected to a second high-frequency power supply circuit that supplies high-frequency power of a second frequency.

[0013] The resonance circuit allows the high-frequency current of the second frequency to pass from the counter electrode.

[0014] In the plasma processing apparatus, since a resonant circuit is provided between the electrode supply line and the ground potential to allow a high-frequency current of the second frequency from the counter electrode to pass, the impedance of the plasma current flowing from the counter electrode to the workbench is reduced. As a result, the formation area of ​​the plasma generated on the counter electrode side is expanded, and the processing speed can be increased.

[0015] The resonant circuit may also be adjusted so that a resonant frequency between the substrate surface on the workbench and the ground potential is the second frequency.

[0016] The resonant circuit is, for example, an LC series resonant circuit including a coil and a capacitor.

[0017] The first high-frequency power supply circuit may also include: an impedance matching circuit connected to the first high-frequency power supply; a filter circuit that blocks the input of the high-frequency power of the second frequency applied to the power supply line; and a voltage measuring unit that is connected between the impedance matching circuit and the filter circuit and measures the high-frequency voltage output from the impedance matching circuit to the workbench. In this case, the resonant circuit is connected to the power supply line between the workbench and the filter circuit.

[0018] The capacitor may be a variable capacitor whose capacitance value can be adjusted. In this case, the plasma processing apparatus further includes a control unit that controls the capacitance value of the capacitor so that the voltage value measured by the voltage measuring unit is minimized.

[0019] The plasma processing apparatus may further include a ground shield provided between a peripheral surface of the counter electrode and an inner wall surface of the vacuum chamber.

[0020] The second frequency may also be a frequency higher than the first frequency.

[0021] The plasma processing apparatus may further include a gas supply line that supplies an etching gas or a film forming gas to the vacuum chamber.

[0022] In the control method of the plasma processing apparatus according to one embodiment of the present invention, the resonant circuit is an LC series resonant circuit including a coil and a variable capacitor,

[0023] The high-frequency voltage of the first frequency input to the stage is measured, and the capacitance value of the variable capacitor is controlled so that the high-frequency voltage is minimized.

[0024] Effects of the Invention

[0025] According to the present invention, the formation region of the plasma generated on the upper electrode side can be expanded to increase the processing speed. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 It is a schematic side cross-sectional view showing the structure of a plasma processing apparatus according to one embodiment of the present invention.

[0027] Figure 2 This is a conceptual diagram for explaining the subject of the present invention.

[0028] Figure 3 This is a block diagram showing the relationship between the first high-frequency power supply circuit and the resonance circuit in the plasma processing apparatus.

[0029] Figure 4 1 is a diagram for explaining the operation of the plasma processing apparatus, and is an experimental result showing the relationship between the capacitance value of the resonance circuit, the etching rate, and the voltage value of the first frequency.

[0030] Figure 5 1 is a diagram for explaining the operation of the plasma processing apparatus, and is an experimental result showing the relationship between the etching rate and the electric power of the second high-frequency power supply. DETAILED DESCRIPTION

[0031] Hereinafter, embodiments of the present invention will be described with reference to the drawings.

[0032] Figure 1 1 is a schematic side cross-sectional view showing the structure of a plasma processing apparatus 100 according to an embodiment of the present invention. The plasma processing apparatus 100 according to this embodiment is configured as a dual-frequency CCP dry etching apparatus having a vacuum chamber 10, a stage 20 as a lower electrode, and an opposing electrode 30 as an upper electrode.

[0033] The vacuum chamber 10 is connected to a vacuum pump 42 via an exhaust valve 41 and is a sealed container capable of maintaining a reduced pressure environment inside. The vacuum chamber 10 is made of metal and is connected to a ground potential. An opening 12 for carrying in and out a substrate, which is opened and closed by a gate valve 11, is provided on one side of the vacuum chamber 10.

[0034] The workbench 20 is made of metal and is disposed inside the vacuum chamber 10. In the present embodiment, it is provided at the bottom of the vacuum chamber 10 via a support member 21 made of an insulating material. The upper surface of the workbench 20 is formed as a support surface for supporting a substrate W. The substrate W is a processing substrate such as a semiconductor wafer or a glass substrate. Although not shown in the figure, an electrostatic chuck mechanism for holding the substrate W and a temperature adjustment mechanism for heating or cooling the substrate W to a predetermined temperature may also be provided on the workbench 20.

[0035] The workbench 20 is connected to a first high frequency power supply circuit 51 provided outside the vacuum chamber 10. As described later, the first high frequency power supply circuit 51 includes an impedance matching circuit 511 (see Figure 3 ). The first high frequency power supply circuit 51 supplies high frequency power of a first frequency as bias power to the workbench 20. The first frequency is not particularly limited, and is, for example, 2 MHz. In addition, the magnitude of the power is, for example, 500W to 3000W.

[0036] The counter electrode 30 is made of metal, is arranged opposite to the workbench 20, and is provided on the ceiling of the vacuum chamber 10 via a support member 31 made of an insulating material. The counter electrode 30 is connected to a gas supply line 43, and functions as a shower plate for uniformly spraying a processing gas onto the entire surface of the substrate W on the workbench 20.

[0037] The gas supply line 43 is connected to a gas supply source 45 via a flow control valve 44. In the present embodiment, the plasma processing apparatus 100 is configured as a dry etching apparatus, and therefore a reaction gas for etching (e.g., a fluorine-based or hydrocarbon-based gas) is used as the processing gas. In addition, the gas supply line 43 is not limited to being connected to the counter electrode 30, and the processing gas may be supplied into the vacuum chamber 10 from a portion of the side wall of the vacuum chamber 10 or the like.

[0038] The counter electrode 30 is connected to a second high frequency power circuit 52 provided outside the vacuum chamber 10. The second high frequency power circuit 52 includes an impedance matching circuit connected to a second high frequency power source RF2 generating high frequency power of a second frequency. The second high frequency power circuit 52 supplies high frequency power of a second frequency as discharge power for generating plasma of the processing gas to the counter electrode 30. The second frequency is not particularly limited, and is, for example, 27 MHz. In addition, the magnitude of the power is, for example, 500 W to 4 kW.

[0039] In the present embodiment, the plasma processing apparatus 100 introduces a processing gas (etching gas) into the vacuum chamber 10 through the gas supply line 43 while maintaining the interior of the vacuum chamber 10 at a predetermined reduced pressure environment, and applies a high-frequency voltage of the second high-frequency power supply RF2 to the counter electrode 30, thereby generating plasma of the processing gas (etching gas) between the workbench 20 and the counter electrode 30. On the other hand, by applying a high-frequency voltage of the first high-frequency power supply RF1 to the workbench 20, ions in the plasma are accelerated toward the substrate W on the workbench 20. Thus, etching processing is performed on the surface of the substrate W. The processing pressure is, for example, 5Pa to 30Pa.

[0040] Here, in such a dual-frequency CCP plasma processing apparatus, there is a problem that the formation area of ​​the plasma generated by the second high-frequency voltage on the upper electrode side is difficult to expand to the vicinity of the surface of the processing substrate, making it difficult to achieve an increase in the processing speed (etching rate).

[0041] like Figure 2 Conceptually, the cause of the above problem is considered to be as follows: due to the impedance Z between the upper electrode 130 and the lower electrode 120 A Much larger than the impedance Z between the upper electrode 130 and the surrounding vacuum chamber 110 G Therefore, part of the high frequency voltage applied to the upper electrode 130 is consumed by the discharge between the upper electrode 130 and the inner wall of the vacuum chamber 110 surrounding it. As a result, the plasma formed between the upper electrode 130 and the lower electrode 120 does not fully expand to the vicinity of the surface of the substrate on the lower electrode 120, and the etching rate is not improved.

[0042] Therefore, in this embodiment, if Figure 1 As shown, a resonant circuit 53 is connected between the power supply line 510 between the workbench 20 and the first high-frequency power supply circuit 51 and the ground potential, and allows the high-frequency current of the second frequency from the counter electrode 30 to pass. By connecting the resonant circuit 53 between the workbench 20 and the first high-frequency power supply circuit 51, the impedance between the counter electrode 30 and the workbench 20 (equivalent to Figure 2 Z A ) is reduced, making it easier for the plasma current to flow from the opposing electrode 30 to the worktable 20. As a result, the formation area of ​​the plasma generated on the opposing electrode 30 side is expanded, so the processing speed (etching rate) can be improved.

[0043] The resonant circuit 53 is an LC series resonant circuit including a coil L and a capacitor VC1 as described later (see Figure 3 ) so that the resonant frequency between the surface of the substrate W on the workbench 20 and the ground potential is the second frequency (27 MHz) as described above, the inductance value of the coil L and the capacitance value of the capacitor VC1 are adjusted. That is, the resonant circuit 53 is configured to resonate at the second frequency (27 MHz).

[0044] Furthermore, if Figure 1 As shown in FIG. 1 , the plasma processing apparatus 100 of the present embodiment further includes a ground shield 61 provided between the peripheral surface of the counter electrode 30 and the side inner wall surface of the vacuum chamber 10. The ground shield 61 is composed of a metal cylindrical member provided in a manner covering the peripheral surface of the insulating support member 31, wherein the support member 31 covers the peripheral surface of the counter electrode 30. The ground shield 61 is installed in the vacuum chamber 10 and is connected to the ground potential via the vacuum chamber 10.

[0045] Thus, by providing the ground shield 61 around the counter electrode 30, the potential difference between the ground shield 61 and the inner wall surface of the side of the vacuum chamber 10 can be eliminated, and the discharge between the peripheral surface of the counter electrode 30 and the vacuum chamber 10 can be suppressed. That is, due to the impedance (Z G ) does not exist on the surface, so the high-frequency voltage of the second frequency (27 MHz) applied to the counter electrode 30 is not consumed by the discharge between the counter electrode 30 and the surrounding vacuum chamber 10. Therefore, the high-frequency voltage applied to the counter electrode 30 is all used to form plasma between the counter electrode 30 and the worktable 20, so it can make a greater contribution to the expansion of the plasma formation area to the vicinity of the surface of the substrate W.

[0046] In addition, as required, a similar ground shield may be provided around the work table 20. In this case, discharge between the work table 20 and the surrounding vacuum chamber 10 caused by the high frequency voltage of the first frequency (2 MHz) applied to the work table 20 is suppressed. Such a structure can also contribute to the expansion of the plasma formation region to the vicinity of the surface of the substrate W.

[0047] Next, the first high-frequency power supply circuit 51 and the resonance circuit 53 will be described in detail.

[0048] Figure 3 1 is a block diagram showing the relationship between the first high-frequency power supply circuit 51 and the resonance circuit 53. As shown in the figure, the first high-frequency power supply circuit 51 includes an impedance matching circuit (matching circuit) 511, a voltage measuring unit 512, and a filter circuit unit 513.

[0049] The impedance matching circuit 511 is connected to the first high frequency power source RF1. The impedance matching circuit 511 is a circuit that matches the impedance of the first high frequency power source RF1, the impedance of the power supply line (transmission line), and the impedance of the stage 20 (load).

[0050] The voltage measuring unit 512 measures the high frequency voltage output from the impedance matching circuit 511 to the stage 20. The voltage measuring unit 512 is connected between the impedance matching circuit 511 and the filter circuit unit 513, and measures the peak-to-peak value (Vpp) of the high frequency voltage of the first frequency (2 MHz).

[0051] The filter circuit unit 513 is a circuit that blocks the input of the high-frequency power of the second frequency (27 MHz) applied to the power supply line 510 from the counter electrode 30 via the workbench 20. Thus, the first high-frequency power source RF1, the impedance matching circuit 511, and the voltage measuring unit 512 can be protected from the high-frequency power of the second frequency (27 MHz). The structure of the filter circuit unit 513 is not particularly limited, and for example, it is composed of a low-pass filter or a band-pass filter that can only pass the high-frequency power of the first frequency (2 MHz).

[0052] The resonance circuit 53 has the same resonance frequency as the frequency (second frequency) of the second high frequency power source RF2 applied to the counter electrode 30. In the present embodiment, the resonance circuit 53 is an LC series resonance circuit including a coil L and a capacitor VC1, and the capacitor VC1 is a variable capacitor whose capacitance value can be adjusted.

[0053] As described above, the resonance circuit 53 is connected between the power supply line 510 between the workbench 20 and the first high-frequency power supply circuit 51 and the ground potential. As a result, the high-frequency power (plasma current) of the second frequency (27 MHz) flowing in the power supply line 510 can be prevented from being input to the first high-frequency power supply circuit 51 and flowing toward the ground potential, thereby protecting the first high-frequency power supply circuit 51 and reducing the impedance (Z) between the counter electrode 30 and the workbench 20. A ) so that the plasma formation area is expanded to near the surface of the substrate W.

[0054] Here, the coil L constituting the resonance circuit 53 may include inductive reactance components of the components constituting the feed line 510. In this case, the resonance circuit 53 may be constituted by an LC parallel resonance circuit in which the coil L is connected in parallel to the capacitor VC1, based on the reactance components.

[0055] In addition, in the present embodiment, the capacitance value of the capacitor VC1 is adjusted in such a way that the high frequency voltage (bias voltage) of the first frequency (2 MHz) applied to the workbench 20 is minimized. In the present embodiment, there is also a control unit 55 that controls the capacitance value of the capacitor VC1 in such a way that the voltage value measured by the voltage measuring unit 512 is minimized.

[0056] Figure 4 1 is an experimental result showing the relationship between the capacitance value of the capacitor VC1 constituting the resonance circuit 53 and the etching rate and the voltage value Vpp of the first frequency (2MHz). As shown in the figure, the capacitance value of the capacitor VC1 is adjusted so that the voltage value Vpp is minimized, thereby obtaining the maximum etching rate. Therefore, by monitoring the voltage value measured by the voltage measuring unit 512 through the control unit 55, the capacitance value of the capacitor VC1 is controlled so that the voltage value is always minimized, thereby maintaining the etching rate at the maximum while processing the substrate W.

[0057] As an example, when the minimum value of Vpp is about 1550V, the capacitance value of VC1 is about 35.3pF and the etching rate is 280nm / min.

[0058] In addition, when the voltage value Vpp measured by the voltage measuring unit 512 is the minimum value, it is confirmed that the capacitance value of the matching element constituting the impedance matching circuit 511 and the capacitance value of the matching element constituting the impedance matching circuit in the second high-frequency power supply circuit 52 are both extreme values. That is, the voltage value Vpp being the minimum value and the capacitance value of the matching element of the high-frequency power supply circuits 51 and 52 being the extreme value are equivalent to each other. Therefore, instead of adjusting the capacitance value of the capacitor VC1 so that the voltage value Vpp is the minimum, the capacitance value of the capacitor VC1 may be adjusted so that the capacitance value of the matching element is the extreme value.

[0059] According to the plasma processing device of this embodiment constructed as described above, a resonant circuit 53 having a resonant frequency of the second frequency (27 MHz) is connected between the power supply line 510 connecting the workbench 20 and the first high-frequency power supply circuit 51 and the ground potential. Therefore, the impedance between the opposing electrode 30 and the workbench 20 is reduced, making it easy for the plasma current to flow from the opposing electrode 30 to the workbench 20. As a result, the formation area of ​​the plasma generated on the opposing electrode 30 side is expanded, which can increase the processing speed (etching rate).

[0060] Figure 5 1 is an experimental result showing the relationship between the etching rate and the power of the second high-frequency power source RF2 (27MHz), and compares and shows the case with the resonant circuit 53 and the case without the resonant circuit 53. Here, in any of the above cases, the experiment was conducted using a device provided with a grounded shield 61, the power range was 500W to 4kW, and the processing pressure was 10Pa. As shown in the figure, according to the present embodiment with the resonant circuit 53, the increase rate of the etching rate relative to the increased input power can be improved compared to the case without the resonant circuit 53. That is, it is shown that by providing the resonant circuit 53, the plasma formation area is expanded to the vicinity of the surface of the substrate W, and the contribution rate to the processing speed is improved.

[0061] Furthermore, according to this embodiment, the high-frequency voltage of the first frequency (2MHz) input to the workbench 20 is measured, and the capacitance value of the capacitor VC1 of the resonant circuit 53 is controlled in a manner to minimize the high-frequency voltage, thereby enabling the etching process of the substrate W to be continuously performed while maintaining the maximum etching rate.

[0062] As mentioned above, although embodiment of this invention was described, this invention is not limited to the said embodiment, and various changes can be added.

[0063] For example, in the above embodiment, the frequency (first frequency) of the high-frequency voltage input to the workbench 20 is 2 MHz, and the frequency (second frequency) of the high-frequency voltage input to the counter electrode 30 is 27 MHz, but it is not limited thereto. For example, the first frequency may be lower than 13.56 MHz, and the second frequency may be 13.56 MHz or higher. In this case, the reactance value of the coil L and / or the capacitance value of the capacitor VC1 are set so that the resonant frequency of the resonant circuit 53 is the above-mentioned second frequency.

[0064] Furthermore, in the above embodiment, the high-frequency voltage Vpp of the first frequency input to the workbench 20 is monitored, and the capacitance value of the capacitor VC1 in the resonance circuit 53 is adjusted so that the value of the high-frequency voltage Vpp is minimized. In addition, a variable coil capable of adjusting the inductance value may be used as the coil L, and the inductance value of the coil L may be adjusted in such a way that the bias voltage Vpp is minimized. According to such a structure, the same effect as described above can also be obtained.

[0065] Furthermore, in the above embodiment, an etching device is used as an example of a plasma processing device, but in addition, the present invention can also be applied to film forming devices such as CVD devices and sputtering devices. In this case, a process gas for film formation (reaction gas, or argon gas for sputtering) is supplied from the gas supply line 43 to the vacuum chamber 10, and the capacitance value of the resonance circuit 53 is adjusted to minimize the bias voltage, so that the amount of incident ions on the substrate of the film formation object can be maximized, thereby obtaining an effect of improving the coverage of the hole filling film formation, etc.

[0066] Description of Reference Numerals

[0067] 10: Vacuum chamber;

[0068] 20: workbench;

[0069] 30: counter electrode;

[0070] 43: Gas supply pipeline;

[0071] 51: first high frequency power supply circuit;

[0072] 52: second high frequency power supply circuit;

[0073] 55: control unit;

[0074] 61: ground shield;

[0075] 100: plasma treatment device;

[0076] 510: power supply line;

[0077] 511: Impedance matching circuit;

[0078] 512: voltage measuring unit;

[0079] 513: Filter circuit unit.

Claims

1. A plasma processing device, comprising: Vacuum chamber; a workbench for supporting the substrate, which is arranged inside the vacuum chamber and connected to a first high-frequency power supply circuit that supplies high-frequency power of a first frequency; a counter electrode disposed opposite to the workbench and connected to a second high-frequency power supply circuit that supplies high-frequency power of a second frequency; and A resonant circuit is connected between a power supply line and a ground potential, and passes a high-frequency current of the second frequency from the counter electrode. The power supply line connects the workbench and the first high-frequency power supply circuit.

2. The plasma processing apparatus according to claim 1, wherein: The resonant circuit is adjusted so that a resonant frequency between the substrate surface on the stage and the ground potential becomes the second frequency.

3. The plasma processing apparatus according to claim 1 or 2, wherein: The resonant circuit is an LC series resonant circuit including a coil and a capacitor.

4. The plasma processing apparatus according to claim 3, wherein: The first high frequency power supply circuit comprises: an impedance matching circuit connected to the first high frequency power source; a filter circuit that blocks input of the high-frequency power of the second frequency applied to the power supply line; and a voltage measuring unit connected between the impedance matching circuit and the filter circuit, and measuring a high-frequency voltage output from the impedance matching circuit to the workbench, The resonant circuit is connected to the power supply line between the workbench and the filter circuit.

5. The plasma processing apparatus according to claim 4, wherein: The capacitor is a variable capacitor capable of adjusting the capacitance value. The plasma processing apparatus further includes a control unit configured to control a capacitance value of the capacitor so that the voltage value measured by the voltage measuring unit is minimized.

6. The plasma processing apparatus according to claim 1, wherein: The invention further comprises a ground shield provided between the peripheral surface of the counter electrode and the inner wall surface of the vacuum chamber.

7. The plasma processing apparatus according to claim 1, wherein: The second frequency is a frequency higher than the first frequency.

8. The plasma processing apparatus according to claim 1, wherein: The invention further comprises a gas supply line for supplying an etching gas or a film forming gas to the vacuum chamber.

9. A method for controlling a plasma processing device, the method for controlling a plasma processing device according to claim 1, The resonant circuit is an LC series resonant circuit including a coil and a variable capacitor, The high-frequency voltage of the first frequency input to the stage is measured, and the capacitance value of the variable capacitor is controlled so that the high-frequency voltage is minimized.

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