Substrate processing method and substrate processing device

Abstract

The present invention provides a substrate processing method and a substrate processing apparatus capable of performing etching at a higher speed and with a higher selectivity than a gas switching method. The substrate processing method comprises: step a) supplying a processing gas containing a fluorocarbon and a rare gas into a processing container equipped with a mounting table, wherein a processing object including a first region composed of silicon oxide is mounted on the mounting table; step b) plasma-treating the processing object using a first plasma of the processing gas generated under first plasma generation conditions; step c) plasma-treating the processing object with a bias potential applied to the processing object using a second plasma of the processing gas generated under second plasma generation conditions different from the first plasma generation conditions; and step d) repeating steps b and c.

Description

Technical Field

[0001] The present invention relates to a substrate processing method and a substrate processing device. Background Art

[0002] With the miniaturization of semiconductors, dry etching processes are required to balance etching selectivity with the suppression of etching defects in narrow spaces (removal performance). To address this, a method called ALE (Atomic Layer Etching) has been proposed, which promotes etching by repeating an etchant deposition step and an ion irradiation step. In ALE, the deposition and ion irradiation steps are separated by switching the process gases used.

[0003] Prior art literature

[0004] Patent Literature

[0005] Patent Document 1: Japanese Patent Application Laid-Open No. 2015-173240.

[0006] Patent Document 2: Japanese Patent Application Laid-Open No. 2016-136616. Summary of the Invention

[0007] Problems to be solved by the invention

[0008] The present invention provides a substrate processing method and a substrate processing device capable of performing etching at a higher speed and with a higher selectivity than a gas switching method.

[0009] Technical means to solve the problem

[0010] A substrate processing method according to one embodiment of the present invention comprises: step a, supplying a processing gas containing a fluorocarbon and a rare gas into a processing container provided with a carrier, wherein a processing object including a first region composed of silicon oxide is placed on the carrier; step b, performing plasma treatment on the processing object using a first plasma of the processing gas generated under a first plasma generation condition; step c, performing plasma treatment on the processing object having a bias potential generated on the processing object using a second plasma of the processing gas generated under a second plasma generation condition different from the first plasma generation condition; and step d, repeating steps b and c.

[0011] Effects of the Invention

[0012] According to the present invention, etching can be performed at a higher speed and with a higher selectivity than the gas switching method. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 FIG. 1 is a diagram showing an example of a plasma processing system in one embodiment of the present invention.

[0014] Figure 2 This is a diagram showing an example of separation of deposition and etching steps by gas switching.

[0015] Figure 3 This is a diagram showing an example of separation of deposition and etching steps based on RF signal pulses.

[0016] Figure 4 This is a diagram showing an example of the structure of a substrate etched by the plasma processing apparatus according to this embodiment.

[0017] Figure 5 This is a diagram schematically showing an example of the state of an etched substrate.

[0018] Figure 6 This is a flowchart showing an example of etching processing in this embodiment.

[0019] Figure 7 This is a diagram showing an example of the RF signal and the state in the processing space in this embodiment.

[0020] Figure 8 This is a diagram showing an example of the relationship between the RF signal and the deposition or etching amount in this embodiment.

[0021] Figure 9 This is a diagram showing an example of one cycle of the RF signal in this embodiment.

[0022] Figure 10 It is a diagram showing an example of experimental results in this embodiment and comparative examples.

[0023] Figure 11 This is a diagram showing an example of analysis results of light emission data at each frequency of an RF signal.

[0024] Figure 12 This is a diagram showing an example of analysis results of light emission data at each frequency of an RF signal.

[0025] Figure 13 This is a diagram showing an example of experimental results when the flow rate of the fluorocarbon relative to the flow rate of Ar was changed.

[0026] Figure 14 This is a diagram showing an example of experimental results when the delay amount of the offset is changed.

[0027] Figure 15 This is a diagram showing an example of experimental results when the pulse frequency and offset time of the RF signal are changed.

[0028] Figure 16 This is a diagram showing an example of a table for determining plasma generation conditions.

[0029] Description of Reference Numerals

[0030] 1 Plasma treatment system

[0031] 1a Plasma treatment device

[0032] 1b Control Unit

[0033] 10 Plasma processing chamber

[0034] 11 Support

[0035] 20 Gas supply unit

[0036] 30 RF power supply unit

[0037] 40 Exhaust System

[0038] 71 silicon substrate

[0039] 72 silicon nitride film

[0040] 73 Silicon oxide film

[0041] 74 Mask

[0042] W substrate DETAILED DESCRIPTION

[0043] Hereinafter, embodiments of the disclosed substrate processing method and substrate processing apparatus will be described in detail based on the accompanying drawings.

[0044] In ALE, the process gas used must be switched between the deposition and ion irradiation steps, requiring time to replace the process gas within the process vessel. This results in longer processing times and reduced production efficiency. Consequently, there is a need for a technology that can achieve higher etching speeds and higher selectivity than gas switching methods.

[0045] [Structure of Plasma Processing System 1]

[0046] Figure 1 FIG. 1 is a diagram showing an example of a plasma processing system in one embodiment of the present invention. Figure 1As shown, in one embodiment, a plasma processing system 1 includes a plasma processing device 1a and a control unit 1b. The plasma processing device 1a is an example of a substrate processing device. The plasma processing device 1a includes a plasma processing chamber 10, a gas supply unit 20, an RF (Radio Frequency) power supply unit 30, and an exhaust system 40. In addition, the plasma processing device 1a includes a support unit 11 and an upper electrode shower head 12. The support unit 11 is arranged in the lower area of ​​the plasma processing space 10s in the plasma processing chamber 10. The upper electrode shower head 12 is arranged above the support unit 11 and can function as a part of the ceiling of the plasma processing chamber 10.

[0047] The support portion 11 is configured to support the substrate W in the plasma processing space 10s. In one embodiment, the support portion 11 includes a lower electrode 111, an electrostatic chuck 112, and an edge ring 113. The electrostatic chuck 112 is disposed on the lower electrode 111 and is capable of supporting the substrate W on the upper surface of the electrostatic chuck 112. The edge ring 113 is configured to surround the substrate W on the upper surface of the peripheral portion of the lower electrode 111. In addition, although not shown in the figure, in one embodiment, the support portion 11 may also include a temperature adjustment module that can adjust at least one of the electrostatic chuck 112 and the substrate W to a target temperature. The temperature adjustment module may also include a heater, a flow path, or a combination thereof. A temperature adjustment fluid such as a refrigerant or a heat transfer gas can flow in the flow path.

[0048] The upper electrode shower head 12 is configured to supply one or more process gases (processing gases) from the gas supply unit 20 to the plasma processing space 10s. In one embodiment, the upper electrode shower head 12 has a gas inlet 12a, a gas diffusion chamber 12b, and a plurality of gas outlets 12c. The gas inlet 12a is fluidically connected to the gas supply unit 20 and the gas diffusion chamber 12b. The plurality of gas outlets 12c are fluidically connected to the gas diffusion chamber 12b and the plasma processing space 10s. In one embodiment, the upper electrode shower head 12 is configured to supply one or more process gases from the gas inlet 12a via the gas diffusion chamber 12b and the plurality of gas outlets 12c to the plasma processing space 10s.

[0049] The gas supply unit 20 may also include one or more gas sources 21 and one or more flow controllers 22. In one embodiment, the gas supply unit 20 is configured to supply one or more process gases from corresponding gas sources 21 via corresponding flow controllers 22 to the gas inlet 12a. Each flow controller 22 may also include, for example, a mass flow controller or a pressure-controlled flow controller. Furthermore, the gas supply unit 20 may also include one or more flow modulation devices for modulating or pulsing the flow of one or more process gases.

[0050] The RF power supply unit 30 is configured to supply RF power, such as one or more RF signals, to one or more electrodes, such as the lower electrode 111, the upper electrode showerhead 12, or both the lower electrode 111 and the upper electrode showerhead 12. This generates plasma from one or more process gases supplied to the plasma processing space 10s. Thus, the RF power supply unit 30 can function as at least a portion of a plasma generation unit capable of generating plasma from one or more process gases in the plasma processing chamber 10. In one embodiment, the RF power supply unit 30 includes a first RF power supply unit 30a and a second RF power supply unit 30b.

[0051] The first RF power supply unit 30a includes a first RF generator 31a and a first matching circuit 32a. In one embodiment, the first RF power supply unit 30a is configured to supply a first RF signal from the first RF generator 31a to the upper electrode shower head 12 via the first matching circuit 32a. For example, the first RF signal may have a frequency within the range of 27 MHz to 100 MHz.

[0052] The second RF power supply unit 30b includes a second RF generator 31b and a second matching circuit 32b. In one embodiment, the second RF power supply unit 30b can supply a second RF signal from the second RF generator 31b to the lower electrode 111 via the second matching circuit 32b. For example, the second RF signal has a frequency in the range of 400 kHz to 13.56 MHz. Alternatively, a DC (direct current) pulse generator can be used in place of the second RF generator 31b.

[0053] Although not shown in the figure, other embodiments are contemplated within the present invention. For example, in alternative embodiments, the RF power supply unit 30 may supply a first RF signal from an RF generator to the lower electrode 111, a second RF signal from another RF generator to the lower electrode 111, and a third RF signal from another RF generator to the upper electrode shower head 12. Furthermore, in other alternative embodiments, a DC voltage may be applied to the upper electrode shower head 12.

[0054] In various embodiments, the amplitude of one or more RF signals (i.e., the first RF signal, the second RF signal, etc.) may be pulsed or modulated. Amplitude modulation may include pulsing the amplitude of the RF signal between an on state and an off state, or between two or more different on states.

[0055] The exhaust system 40 can be connected to the exhaust port 10e provided at the bottom of the plasma processing chamber 10. The exhaust system 40 can include a pressure valve and a vacuum pump. The vacuum pump can include a turbomolecular pump, a roughing pump, or a combination thereof.

[0056] In one embodiment, the control unit 1b processes computer-executable commands that cause the plasma processing apparatus 1a to perform the various steps described herein. The control unit 1b is capable of controlling various components of the plasma processing apparatus 1a to execute the various steps described herein. In one embodiment, part or all of the control unit 1b may be included in the plasma processing apparatus 1a. The control unit 1b may include, for example, a computer 51. The computer 51 may include, for example, a processing unit (CPU: Central Processing Unit) 511, a storage unit 512, and a communication interface 513. The processing unit 511 may perform various control operations based on programs stored in the storage unit 512. The storage unit 512 may include RAM (Random Access Memory), ROM (Read Only Memory), an HDD (Hard Disk Drive), an SSD (Solid State Drive), or a combination thereof. The communication interface 513 may communicate with the plasma processing apparatus 1a via a communication line such as a LAN (Local Area Network).

[0057] [Comparison of ALE methods]

[0058] Here, use Figure 2 and Figure 3, comparing the control diagrams for QuasiALE (hereinafter also referred to as Q-ALE) using a gas switching method and PulseALE using an RF switching method according to this embodiment. In the following description, the deposition step and the ion irradiation step are referred to as the deposition step and the etching step, respectively. Figure 2 This is a diagram showing an example of separation of deposition and etching steps by gas switching. Figure 3 This is a diagram showing an example of separation of deposition and etching steps based on RF signal pulses.

[0059] exist Figure 2 In graph 60, the ratio of the fluorocarbon to the noble gas in the process gas is shown in graph 61. Q-ALE includes a deposition step 62a, in which the fluorocarbon is supplied, and an etching step 62b, in which a noble gas, such as Ar, is supplied instead of the fluorocarbon. Specifically, a single Q-ALE cycle, interval 62, consists of the deposition step 62a and the etching step 62b. Furthermore, a bias voltage 63 is applied during the etching step 62b. If interval 62 is, for example, 4 to 7 seconds, then interval 64, the process gas switching from the deposition step 62a to the etching step 62b, takes approximately 0.5 to 1 second.

[0060] exist Figure 3 In graph 65, the ratio of the fluorocarbon to the noble gas in the process gas is shown in graph 66, which is lower than graph 61a, corresponding to the ratio in deposition step 62a of Q-ALE. PulseALE includes a deposition step 67a, in which only a first RF signal is supplied to the upper electrode showerhead 12, and an etching step 67b, in which only a second RF signal is supplied to the lower electrode 111. Specifically, a period 67 corresponding to one cycle of PulseALE consists of the deposition step 67a and the etching step 67b. In graph 65, the second RF signal is shown as graph 68. In this case, period 67 is, for example, 1 millisecond (1000 microseconds). The switching of the RF signal from deposition step 67a to etching step 67b is much faster than the switching of the process gas. In this embodiment, deposition step 67a, in which radical adsorption is performed, and etching step 67b, in which a desorption reaction is performed using ion assist, are independently controlled. In the following description, milliseconds and microseconds are expressed as "ms" and "μs," respectively.

[0061] [Structure of substrate W]

[0062] Figure 4 FIG. 1 is a diagram showing an example of the structure of a substrate etched by the plasma processing apparatus according to this embodiment.

[0063] The substrate W is, for example, Figure 4As shown, a silicon substrate 71 is provided with a silicon nitride film 72, a silicon oxide film 73, and a mask 74. The silicon nitride film 72 serves as an etching stopper. The silicon oxide film 73 serves as the film to be etched. The mask 74 is a silicon nitride film having openings in a predetermined pattern, such as a comb-shaped opening. In the etching process of this embodiment, the silicon oxide film 73 in the openings of the mask 74 is etched until it reaches the silicon nitride film 72. In this case, the openings of the mask 74 are narrow, and the aspect ratio of the trench formed by etching is high, resulting in a trade-off between removal efficiency and mask selectivity.

[0064] Figure 5 This is a diagram schematically showing an example of the state of an etched substrate. Figure 5 Region 70a is an example of a normal state in which the silicon oxide film 73 is etched until it reaches the silicon nitride film 72. On the other hand, region 70b is an example of a state in which the silicon oxide film 73 is not etched until it reaches the silicon nitride film 72, but the etching is stopped midway, resulting in a state in which poor removal occurs as shown in region 75. In this embodiment, various conditions are set so that the result of the plasma treatment is the normal state shown in region 70a.

[0065] [Etching method]

[0066] Next, the etching method of this embodiment will be described. Figure 6 This is a flowchart showing an example of etching processing in this embodiment.

[0067] In the etching method of this embodiment, the control unit 1b opens an opening (not shown) and introduces a substrate W having a mask 74 formed on a silicon oxide film 73 into the plasma processing chamber 10. The substrate W is then placed on the electrostatic chuck 112 of the support unit 11 (stage). The substrate W is held on the electrostatic chuck 112 by applying a DC voltage to the electrostatic chuck 112. The control unit 1b then closes the opening and controls the exhaust system 40 to exhaust gas from the plasma processing space 10s, thereby achieving a predetermined vacuum level in the plasma processing space 10s. Furthermore, the control unit 1b controls a temperature control module (not shown) to adjust the temperature of the substrate W to a predetermined temperature (step S1).

[0068] Next, the control unit 1b starts the supply of the processing gas (step S2). The control unit 1b supplies a mixed gas of C4F6, O2 and Ar (hereinafter referred to as C4F6 / O2 / Ar gas) as a processing gas containing a fluorocarbon and a rare gas to the gas inlet 12a. In addition, the fluorocarbon may also be other compounds having a carbon-fluorine bond such as CF2 and C3F4. After being supplied to the gas inlet 12a, the processing gas is supplied to the gas diffusion chamber 12b and diffused. After the processing gas diffuses in the gas diffusion chamber 12b, it is supplied to the plasma processing space 10s of the plasma processing chamber 10 in a spray shape through a plurality of gas outlets 12c, and is filled in the plasma processing space 10s.

[0069] The control unit 1b supplies the first RF signal (first RF power) for plasma excitation to the upper electrode shower head 12 by controlling the RF power supply unit 30. In the plasma processing space 10s, plasma is generated by supplying the first RF signal for plasma excitation to the upper electrode shower head 12. That is, in the plasma processing space 10s, radicals and ions are generated by using the first RF signal. The substrate W is subjected to plasma treatment using the generated plasma. That is, the control unit 1b performs plasma treatment on the substrate W using the first plasma of the processing gas generated under the first plasma generation condition (step S3). The first plasma mainly generates radicals and ions of fluorocarbons. The substrate W is exposed to the first plasma, and the deposit containing fluorocarbons adheres to the silicon oxide film 73 and the mask 74. That is, step S3 is equivalent to Figure 3 Deposition step 67a is shown.

[0070] The control unit 1b stops the supply of the first RF signal and stops the generation of plasma for a predetermined time by controlling the RF power supply unit 30 (step S4). At this time, the supply of the second RF signal is also stopped.

[0071] The control unit 1b controls the RF power supply unit 30 to supply a second RF signal (second RF power) for plasma excitation and bias to the lower electrode 111. In the plasma processing space 10s, the second RF signal for plasma excitation and bias is supplied to the lower electrode 111, generating plasma. Specifically, in the plasma processing space 10s, the second RF signal generates radicals and ions, and controls the ion energy. The generated plasma is used to plasma-treat the substrate W. Specifically, the control unit 1b uses the second plasma of the process gas generated under the second plasma generation conditions to plasma-treat the substrate W (step S5). The second plasma primarily generates Ar ions. Exposure of the substrate W to the second plasma etches the silicon oxide film 73. Specifically, the Ar ions are attracted toward the lower electrode 111 by the bias potential, and the interaction between the deposits on the silicon oxide film 73 and the Ar ions causes the substrate W to be etched. In the following description, the deposits on the silicon oxide film 73 and the deposits on the mask 74 may be omitted.

[0072] Specifically, one or more active species derived from atoms and molecules of the fluorocarbon compound, for example, fluorine and radicals from one or more active species of the fluorocarbon compound, are used to deposit a precipitate on the silicon oxide film 73. The precipitate on the silicon oxide film 73 interacts with Ar ions attracted by the bias potential, thereby etching the silicon oxide film 73. Similarly, the mask 74 is etched by the interaction between the precipitate on the mask 74 and the Ar ions attracted by the bias potential, but at a significantly lower etching rate than the silicon oxide film 73.

[0073] The control unit 1b determines whether the predetermined shape has been achieved through steps S3 to S5 (step S6). If the control unit 1b determines that the predetermined shape has not been achieved (step S6: No), the process returns to step S3. On the other hand, if the control unit 1b determines that the predetermined shape has been achieved (step S6: Yes), the process ends. Furthermore, the process may include a step in which the control unit 1b stops supplying the first and second RF signals between steps S5 and S6 to exhaust the transported product.

[0074] Upon completion of the process, the control unit 1b stops the supply of the process gas. Furthermore, the control unit 1b applies a DC voltage of opposite polarity to the electrostatic chuck 112 to remove static electricity, thereby peeling the substrate W from the electrostatic chuck 112. The control unit 1b opens an opening (not shown). The substrate W is then removed from the plasma processing space 10s of the plasma processing chamber 10 through the opening. In this manner, the plasma processing system 1 enables faster etching and higher selectivity than a gas switching method.

[0075] [PulseALE Details]

[0076] Next, use Figure 7 and Figure 8 , details of steps S3 to S5 are explained. Figure 7 FIG is a diagram showing an example of the RF signal and the state in the processing space in this embodiment. Figure 7 As shown, in this embodiment, deposition and etching are repeated by repeating intervals 80 to 82 corresponding to steps S3 to S5. One cycle of intervals 80 to 82 is repeated at, for example, 1 kHz (1000 μs). In the following description and figures, the first RF signal is sometimes represented as HF (High Frequency) and the second RF signal is sometimes represented as LF (Low Frequency).

[0077] First, in a period 80 corresponding to step S3, a first RF signal (HF) is supplied to perform plasma treatment on the substrate W using the first plasma. The second RF signal (LF) is not supplied in the period 80. The period 80 is, for example, 25% of one cycle.

[0078] Next, in interval 81, neither the first RF signal (HF) nor the second RF signal (LF) is supplied. The state of the plasma processing space 10s in interval 81 is shown in FIG83. As shown in FIG83, when the supply of the first RF signal (HF) is stopped, the plasma potential 84 drops sharply and basically becomes zero. In contrast, when the supply of the first RF signal (HF) is stopped, the ions 85 decrease, but some remain when the supply of the second RF signal (LF) is started. In addition, the free radicals 86 slowly decrease even if the supply of the first RF signal (HF) is stopped, and a considerable amount remains when the supply of the second RF signal (LF) is started. That is, in interval 81, a change in the free radical / ion ratio and a decrease in the electron temperature are caused. Interval 81 is, for example, 25% of the time of one cycle. In addition, in Figure 3 In the graph 65 , no interval corresponding to the interval 81 is set.

[0079] Next, in interval 82, a second RF signal (LF) is supplied, and the substrate W is plasma-treated with the second plasma. In interval 82, the first RF signal (HF) is not supplied. In interval 82, ions and radicals remaining in the plasma processing space 10s in interval 81 are attracted to the lower electrode 111 side by the bias potential, thereby primarily etching the silicon oxide film 73. By providing interval 81, variations in the ion incident angle can be suppressed in interval 82, allowing for efficient etching of narrow gaps. Interval 82, for example, lasts for 50% of a single cycle. Thereafter, the control unit 1b repeats steps S3 to S5, thereby repeating intervals 80 to 82, i.e., deposition and etching, and progressing the etching of the silicon oxide film 73.

[0080] Figure 8 FIG. 1 is a diagram showing an example of the relationship between the RF signal and the deposition amount or etching amount in this embodiment. Figure 8 As shown in FIG90 , when only the first RF signal (HF) is supplied, a deposition mode is achieved in which both the silicon oxide film (SiO2) and the silicon nitride film (SiN) are deposited. Furthermore, the deposition amount of the silicon oxide film (SiO2) is approximately 2.5 times that of the silicon nitride film (SiN). On the other hand, when only the second RF signal (LF) is supplied, an etching mode is achieved in which both the silicon oxide film (SiO2) and the silicon nitride film (SiN) are etched. Here, the etching amount of the silicon oxide film (SiO2) is approximately 25 times that of the silicon nitride film (SiN), thereby reducing the mask loss as a mask for the silicon nitride film (SiN), thereby improving the mask selectivity.

[0081] [Experimental Results]

[0082] Next, use Figure 9 and Figure 10 The experimental results are explained. Figure 9 : is a diagram showing an example of one cycle of the RF signal in this embodiment. Figure 9 As shown in the figure, in this experiment, one cycle is set to 1000μs (1kHz). Figure 7 The supply time of the first RF signal (HF) corresponding to interval 80 is 250μs, the stop time of the first RF signal (HF) and the second RF signal (LF) corresponding to interval 81 is 250μs, and the supply time of the second RF signal (LF) corresponding to interval 82 is 500μs.

[0083] <Processing conditions>

[0084] Pressure in plasma processing chamber 10: 30 mTorr (4.00 Pa)

[0085] Temperature: 100°C

[0086] Electric power of the first RF signal (60 MHz): 400 W (pulse)

[0087] Electric power of the second RF signal (13 MHz): 200 W (pulse)

[0088] Pulse frequency: 1kHz

[0089] Pulse duty cycle: HF / LF / LF offset = 25 / 50 / 50%

[0090] Process gas (C4F6 / O2 / Ar) flow ratio: 0.29 / 0.34 / 100

[0091] Figure 10 It is a diagram showing an example of experimental results in this embodiment and comparative examples. Figure 10 These are experimental results using PulseALE in this embodiment and Q-ALE as a comparative example. In Q-ALE, the deposition process used C₄F₆ / O₂ / Ar, while the etching process used Ar. The deposition process took 2.5 seconds, while the etching process took 3.5 seconds. The etched sample used a line and space pattern with a 25nm pitch, a Line CD (Critical Dimension) of 12nm, a Space CD of 13nm, and a silicon oxide film thickness of 50nm.

[0092] First, the etching time was shortened to 384.9s with PulseALE, compared to 780s with Q-ALE. Furthermore, it was found that both Q-ALE and PulseALE could remove the silicon oxide film down to the silicon nitride film that formed the etch stop layer. The remaining amount of silicon nitride film (residual SiN) used as a mask was 32.9nm with PulseALE, compared to 30.6nm with Q-ALE, indicating improved mask selectivity. The CD value of the silicon oxide film directly above the etch stop layer (bottom CD: OxBCD) was 13.0nm with Q-ALE and 13.8nm with PulseALE, indicating that both were essentially the same. As described above, PulseALE in this embodiment can achieve a mask selectivity (SiN selectivity) that is equal to or greater than that of Q-ALE while also improving production efficiency.

[0093] [Analysis Results]

[0094] Next, use Figure 11 and Figure 12, the analysis results based on the OES (Optical Emission Sensor) in PulseALE are explained. Figure 11 and Figure 12 This is a diagram showing an example of analysis results of light emission data at each frequency of an RF signal. Figure 11 Graph 101 shows a plot of the ratio of emission data from a first RF signal (HF, 60 MHz) to emission data from a second RF signal (LF, 13 MHz) (hereinafter referred to as the HF / LF ratio) by wavelength. In graph 101, as shown in region 102, a strong peak is observed in the wavelength region corresponding to molecules containing carbon (C) (CF).

[0095] on the other hand, Figure 12 Graph 103 shows a plot of the ratio of emission data from the second RF signal (LF, 13 MHz) to the emission data from the first RF signal (HF, 60 MHz) (hereinafter referred to as the LF / HF ratio) by wavelength. In graph 103, as shown in region 104, the peak in the wavelength region corresponding to argon (Ar) is strong. This demonstrates that, in PulseALE, using a 60 MHz first RF signal and a 13 MHz second RF signal, separation of the deposition and etching steps is possible, similar to Q-ALE.

[0096] [Based on the effect of Ar dilution]

[0097] Next, use Figure 13 , the dilution effect of C4F6 gas based on Ar gas is explained. Figure 13 This is a diagram showing an example of experimental results when the flow rate of fluorocarbon is changed relative to the flow rate of Ar. Figure 13 In the example, the flow rate ratio of C4F6 gas to Ar gas was set to 1.6%, 0.5%, and 0.29%, respectively, and the case where O2 gas and LF output were optimized was compared. In addition, as the pattern on the substrate W, two patterns were used: 2Line (only 2 lines are arranged side by side) and Dense (4 of them in the figure) (a dense pattern) with multiple lines arranged side by side. Dense is the same as Figure 10 The same pattern as the sample is shown in Figure 2. Other processing conditions are as follows. Furthermore, as an optimization of LF output, increasing the Ar flow rate reduced the thickness of the polymer deposited on the mask, so the LF output was adjusted to prevent the mask from being scraped off.

[0098] <Processing conditions>

[0099] Pressure in plasma processing chamber 10: 30 mTorr (4.00 Pa)

[0100] Temperature: 100°C

[0101] Electric power of the first RF signal (60 MHz): 400 W (pulse)

[0102] Electric power of the second RF signal (13 MHz): 200 W (pulse)

[0103] Pulse frequency: 1kHz

[0104] Pulse duty cycle: HF / LF / LF

[0105] Offset = 25 / 50 / 50%

[0106] With a flow rate ratio of 1.6%, the C4F6 / O2 / Ar gas flow ratios were set at 1.6 / 2.1 / 100, and the LF output was set at 300 W. The results showed that the CD values ​​(OxBCD) of the silicon oxide film directly above the etch stop layer were 16.1 nm for 2Line and 13.0 nm for Dense. Furthermore, the residual amount of the silicon nitride film (residual SiN) was 29.2 nm for 2Line and 27.4 nm for Dense.

[0107] With a flow rate ratio of 0.5%, the C₄F₆ / O₂ / Ar gas flow ratios were set at 0.5 / 0.5 / 100, and the LF output was set at 250 W. The results showed that the CD values ​​(OxBCD) of the silicon oxide film were 14.7 nm for 2Line and 14.4 nm for Dense. Furthermore, the residual amount of the silicon nitride film (residual SiN) was 31.6 nm for 2Line and 28.7 nm for Dense.

[0108] When the flow ratio is 0.29%, the flow ratio of C4F6 / O2 / Ar gas is set to 0.29 / 0.34 / 100, and the LF output is set to 100W. As a result, the CD value (OxBCD) of the silicon oxide film is 15.5nm for 2Line and 13.8nm for Dense. In addition, the residual amount of the silicon nitride film (SiN residual amount) is 33.7nm for 2Line and 32.9nm for Dense. According to the above, it can be seen that the residual amount of the silicon nitride film (SiN residual amount) is the largest when the flow ratio is 0.29%. By greatly diluting the C4F6 gas with Ar gas, the mask selectivity is improved. That is, by suppressing the difference in C4F6 caused by the difference in LF supply, the mask selectivity is improved. x F yThe increase in the amount of free radicals increases the separation effect between deposition and etching, and by improving the control of each of deposition and etching, the mask selectivity can be further improved. In addition, the amount of free radicals reduced by Ar dilution can be adjusted by the output during HF supply.

[0109] [Effect of Bias Offset]

[0110] Next, use Figure 14 The effect of shifting the timing of supplying LF will be described. Figure 14 This is a diagram showing an example of experimental results when the delay amount of the bias is changed. Figure 14 In this example, the timing of LF application, i.e., the time of bias potential application, was set 250 μs after the HF supply ended within 1000 μs, and comparisons were made for delays of 0%, 12%, and 25%. Furthermore, when bias delay is expressed as an offset, a delay of 0% corresponds to an offset of 25%, a delay of 12% corresponds to an offset of 37%, and a delay of 25% corresponds to an offset of 50%. Furthermore, the patterns used on substrate W were 2Line (two lines in a row) and Dense (multiple lines in a row) in the Line and Space mode. Other processing conditions are as follows.

[0111] <Processing conditions>

[0112] Pressure in plasma processing chamber 10: 30 mTorr (4.00 Pa)

[0113] Temperature: 100°C

[0114] Electric power of the first RF signal (60 MHz): 200 W (pulse)

[0115] Electric power of the second RF signal (13 MHz): 500 W (pulse)

[0116] Pulse frequency: 1kHz

[0117] Pulse duty cycle: HF / LF=25 / 50%

[0118] Process gas (C4F6 / O2 / Ar) flow ratio: 0.5 / 0.5 / 100

[0119] When the delay is 0%, the etching time is 204.5s. The remaining amount of silicon nitride film (SiN residue) is 32.1nm for 2Line and 30.5nm for Dense. Furthermore, the CD value (OxBCD) of the silicon oxide film is 17.0nm for 2Line and 17.0nm for Dense, which does not reach the etch stop layer (Unopen).

[0120] With a 12% delay, the etching time was 197.4 seconds. The remaining silicon nitride film (SiN residual) was 28.9 nm for 2Line and 24.4 nm for Dense. Furthermore, the CD value (OxBCD) of the silicon oxide film was 17.3 nm for 2Line and 17.3 nm for Dense, indicating that the etching did not reach the etch stop layer (unopen).

[0121] With a 25% delay, the etching time was 201.1s, and the residual amount of the silicon nitride film (residual SiN) was 31.6nm for 2Line and 28.7nm for Dense. Furthermore, the CD values ​​(OxBCD) of the silicon oxide film were 14.7nm for 2Line and 14.4nm for Dense. As can be seen from the above, delaying the LF supply timing increases the potential during LF supply, improving removal efficiency and mask selectivity. This is due to plasma deactivation, which lowers the electron temperature and improves the perpendicularity of the ions.

[0122] [Pulse frequency and offset time]

[0123] Next, use Figure 15 , the experimental results of the case where the pulse frequency and offset time are changed are described. Figure 15 FIG. 1 is a diagram showing an example of experimental results when the pulse frequency and offset time of the RF signal are changed. Figure 15 In this example, condition A, with a pulse frequency of 1 kHz and an LF offset time of 250 μs, condition B, with a pulse frequency of 0.5 kHz and an LF offset time of 500 μs, and condition C, with a pulse frequency of 0.5 kHz and an LF offset time of 1250 μs, were compared. Furthermore, two patterns, 2Line (two lines arranged side by side) and Dense (multiple lines arranged side by side), were used as patterns on substrate W. Other processing conditions are as follows.

[0124] <Processing conditions>

[0125] Pressure in plasma processing chamber 10: 30 mTorr (4.00 Pa)

[0126] Temperature: 100°C

[0127] Electric power of the first RF signal (60 MHz): 200 W (pulse)

[0128] Electric power of the second RF signal (13 MHz): 500 W (pulse)

[0129] Process gas (C4F6 / O2 / Ar) flow ratio: 0.5 / 0.5 / 100

[0130] Under condition A, the pulse frequency was set to 1 kHz, the HF supply time (HF ON) was set to 250 μs, the LF supply time (LF ON) was set to 500 μs, and the LF offset time was set to 250 μs. As a result, the etching time was 201.1 s, and the residual amount of the silicon nitride film (SiN residual amount) was 31.6 nm for 2Line and 28.7 nm for Dense. Furthermore, the CD value (OxBCD) of the silicon oxide film was 14.7 nm for 2Line and 14.4 nm for Dense.

[0131] Under condition B, the pulse frequency was set to 0.5 kHz, the HF supply time (HF ON) was set to 500 μs, the LF supply time (LF ON) was set to 1000 μs, and the LF offset time was set to 500 μs. As a result, the etching time was 204.5 s, and the residual amount of the silicon nitride film (SiN residual amount) was 30.4 nm for 2Line and 28.3 nm for Dense. Furthermore, the CD value (OxBCD) of the silicon oxide film was 15.7 nm for 2Line and 15.3 nm for Dense.

[0132] Under condition C, the pulse frequency was set to 0.5 kHz, the HF supply time (HF ON) was set to 250 μs, the LF supply time (LF ON) was set to 500 μs, and the LF offset time was set to 1250 μs. As a result, the etching time was 379.7 s, and the residual amount of the silicon nitride film (SiN residual amount) was 30.3 nm for 2Line and 24.3 nm for Dense. Furthermore, the CD value (OxBCD) of the silicon oxide film was 16.4 nm for 2Line and 14.1 nm for Dense. As shown above, while the results were the same when comparing conditions A and B, when comparing conditions A and C, the potential increased excessively when the offset time was too long, deteriorating the mask selectivity. In other words, while the removal of narrow gaps improved with a longer LF offset time, the amount of mask residual tended to decrease. This is because the time from stopping the HF supply increases, which reduces the plasma density during the LF supply, increasing the plasma potential and ion energy during the LF supply. Therefore, under conditions where deposition and etching vary due to differences in the process gas mixing ratio and HF / LF output ratio, the LF shift timing can be used to optimize mask selectivity and removal performance.

[0133] [Determination of plasma generation conditions]

[0134] Next, use Figure 16, the determination of plasma generation conditions is explained. Figure 16 This is a diagram showing an example of a table for determining plasma generation conditions. Figure 16 Table 200 shown is an example of a table showing the results of inputting OES emission data and bias values ​​corresponding to the combination of HF output (first RF power) and LF output (second RF power) while fixing the process gas conditions.

[0135] First, the control unit 1b sets the processing gas conditions constant and supplies the HF output (first RF power) and LF output (second RF power) individually to the plasma processing chamber (processing vessel) 10 at multiple output values. For example, the control unit 1b sets the HF output to 0 W and increases the LF output by 50 W from 0 W. Next, the control unit 1b sets the HF output to 50 W and increases the LF output by 50 W from 0 W. In this manner, the control unit 1b obtains emission data and bias values ​​when varying the HF output (first RF power) and LF output (second RF power) and enters them into the matrix 201 of the table 200. The HF and LF output values ​​in the table 200 are illustrative only; emission data and bias values ​​for even higher outputs can also be obtained.

[0136] Here, the luminescence data is data of active species in the plasma processing space 10s. In addition, active species are CF type, CF / Ar ratio, Ar type, etc., for example, Figure 11 and Figure 12 The data corresponding to the active species of the region 102 and the region 104 are shown in FIG. 1 . The bias value is a value of Vpp, Vdc, etc., that is, data of a bias potential.

[0137] When generating tables 200 that input the acquired emission data and bias values, control unit 1b determines the first plasma generation conditions based on each table 200. From each matrix 201, control unit 1b combines the HF output (first RF power) and LF output (second RF power) corresponding to data where the value of the CF active species is higher than the other data and the bias potential of the bias value is zero, and determines these as the first plasma generation conditions. In other words, control unit 1b determines the first plasma generation conditions during the deposition step.

[0138] Next, the control unit 1b determines, from each matrix 201, the combination of HF output (first RF power) and LF output (second RF power) corresponding to data in which the value of CF active species is lower than the other data and the bias potential of the bias value is higher than a predetermined value, as the second plasma generation condition. In other words, the control unit 1b determines the second plasma generation condition in the etching step (activation step). This allows for the determination of more effective plasma generation conditions.

[0139] As described above, according to this embodiment, the control unit 1b executes step a of supplying a processing gas containing a fluorocarbon and a rare gas into a processing container (plasma processing chamber 10) equipped with a mounting table (support unit 11), wherein a processing object (substrate W) including a first region composed of silicon oxide is mounted on the mounting table. The control unit 1b then executes step b of plasma-treating the processing object using a first plasma of the processing gas generated under first plasma generation conditions. The control unit 1b then executes step c of plasma-treating the processing object with a bias potential applied to the processing object using a second plasma of the processing gas generated under second plasma generation conditions different from the first plasma generation conditions. The control unit 1b then executes step d of repeating steps b and c. As a result, etching can be performed at a higher speed and with a higher selectivity than that achieved by a gas switching method.

[0140] Furthermore, according to this embodiment, the conditions of the process gas introduced in step b are the same as those of the process gas introduced in step c. As a result, since the process gas does not need to be switched, the deposition step and the etching step can be switched at high speed.

[0141] Furthermore, according to this embodiment, the value of the fluorocarbon generated in step b is higher than the value of the fluorocarbon generated in step c. As a result, the amount of radicals and ions generated by the first plasma can be increased.

[0142] Furthermore, according to this embodiment, the numerical value for the fluorocarbon is the amount of active species of the fluorocarbon, which can increase the amount of radicals and ions generated by the first plasma.

[0143] Furthermore, according to this embodiment, the numerical value for the fluorocarbon refers to the amount of active species of the fluorocarbon relative to the active species of the noble gas. This results in a greater separation between deposition and etching, improved controllability of each, and thus improved mask selectivity.

[0144] In addition, according to this embodiment, the control unit 1b executes step e without generating plasma. Step d repeats step b, step e, and step c in this order. As a result, a desired shape can be obtained on the object to be processed (substrate W) by etching.

[0145] Furthermore, according to this embodiment, the process gas conditions introduced in step e are the same as those introduced in steps b and c. As a result, since the process gas does not need to be switched, the deposition step and the etching step can be switched at high speed.

[0146] Furthermore, according to this embodiment, the time for step e is 250 microseconds or longer and less than 1250 microseconds. As a result, a desired shape can be formed on the object to be processed (substrate W) by etching.

[0147] Furthermore, according to this embodiment, the first plasma is generated by supplying first RF power having a first frequency into the processing container, and the first frequency is 40 MHz or higher. As a result, a deposit can be formed on the object to be processed (substrate W).

[0148] Furthermore, according to this embodiment, the second plasma is generated by supplying second RF power having a second frequency into the processing container, and the second frequency is 13.56 MHz or less, thereby enabling etching of the object to be processed (substrate W).

[0149] Furthermore, according to this embodiment, the second RF power is supplied to the mounting table, thereby attracting radicals and ions to the object to be processed (substrate W) to etch the object to be processed.

[0150] Furthermore, according to this embodiment, the first plasma generation condition and the second plasma generation condition are identical except for the condition regarding RF power. As a result, the deposition step and the etching step can be switched at high speed.

[0151] Furthermore, according to this embodiment, the flow rate of the fluorocarbon in the processing gas is set to 0.5% or less relative to the flow rate of the rare gas, thereby further improving the mask selectivity.

[0152] Furthermore, according to this embodiment, the object to be processed further includes a second region made of silicon nitride, and the first region is selectively etched between the first region and the second region. As a result, a desired shape can be obtained on the object to be processed (substrate W).

[0153] Furthermore, according to this embodiment, in step b, a deposit containing a fluorocarbon compound is formed on the object to be processed. In step c, the first region is etched through the interaction between the deposit and rare gas ions generated by the second plasma and incident upon the object to be processed on the stage due to the bias potential. As a result, a desired shape can be obtained on the object to be processed (substrate W).

[0154] Furthermore, according to this embodiment, the first plasma generation condition is determined by fixing the process gas conditions, acquiring data on active species and bias potential when first and second RF powers having a first frequency are supplied separately into the process container at multiple output values, and determining the first plasma generation condition based on the output values ​​of the first and second RF powers corresponding to data where the value of the CF active species in the active species and bias potential data is higher than other data and the bias potential is zero. Furthermore, the second plasma generation condition is determined based on the output values ​​of the first and second RF powers corresponding to data where the value of the CF active species in the active species and bias potential data is lower than other data and the bias potential is higher than a predetermined value. As a result, more effective plasma generation conditions can be determined.

[0155] Furthermore, according to this embodiment, the control unit 1b executes step a of supplying a process gas containing a fluorocarbon and a rare gas into a processing container equipped with a mounting table, wherein a processing object including a first region composed of silicon oxide is mounted on the mounting table. The control unit 1b executes step b of generating a first plasma of the process gas by supplying first RF power having a first frequency into the processing container. The control unit 1b executes step c of generating a second plasma of the process gas by supplying second RF power having a second frequency lower than the first frequency into the processing container, thereby attracting ions contained in the second plasma toward the processing object. The supply and stop of the first and second RF powers are independently controlled at predetermined frequencies in steps b and c, and the first and second RF powers are supplied exclusively. As a result, etching can be performed at a higher speed and with a higher selectivity than a gas switching method.

[0156] Although various exemplary embodiments have been described above, the present invention is not limited to the exemplary embodiments described above, and various additions, omissions, substitutions, and changes may be made. Furthermore, elements in different exemplary embodiments may be combined to form other exemplary embodiments.

[0157] Furthermore, in the above embodiment, a plasma processing apparatus 1a that uses capacitively coupled plasma as a plasma source to perform etching or other processing on a substrate W is described as an example. However, the disclosed technology is not limited thereto. Any apparatus that uses plasma to process a substrate W may be used, and the plasma source is not limited to capacitively coupled plasma. For example, any plasma source such as inductively coupled plasma, microwave plasma, or magnetron plasma may be used.

Claims

1. A substrate processing method in a substrate processing device, characterized in that: have: Step a, supplying a processing gas containing a fluorocarbon compound and a rare gas into a processing container provided with a mounting table, wherein a processing object including a first region composed of silicon oxide is mounted on the mounting table; Step b, performing plasma treatment on the object to be processed using a first plasma of the processing gas generated under a first plasma generating condition; Step e without generating plasma; Step c, performing plasma treatment on the object to be processed with a bias potential generated on the object to be processed using a second plasma of the processing gas generated under a second plasma generating condition different from the first plasma generating condition; and Step d: Repeat step b, step e, and step c in the order of step b, step e, and step c.

2. The substrate processing method according to claim 1, wherein: The conditions of the process gas introduced in the step b and the conditions of the process gas introduced in the step c are the same.

3. The substrate processing method according to claim 1 or 2, wherein: The numerical value of the fluorocarbon generated in step b is higher than the numerical value of the fluorocarbon generated in step c.

4. The substrate processing method according to claim 3, wherein: The numerical values ​​for the fluorocarbons are the amounts of the active species of the fluorocarbons.

5. The substrate processing method according to claim 3, wherein: The numerical value for the fluorocarbon is the amount of the active species of the fluorocarbon relative to the active species of the rare gas.

6. The substrate processing method according to claim 1, wherein: The conditions of the process gas introduced in the step e are the same as the conditions of the process gas introduced in the steps b and c.

7. The substrate processing method according to claim 1, wherein: The time of step e is greater than 250 microseconds and less than 1250 microseconds.

8. The substrate processing method according to claim 1 or 2, wherein: The first plasma is generated by supplying first RF electric power having a first frequency into the processing container, The first frequency is greater than 40 MHz.

9. The substrate processing method according to claim 1 or 2, wherein: The second plasma is generated by supplying a second RF electric power having a second frequency into the processing container, The second frequency is lower than 13.56 MHz.

10. The substrate processing method according to claim 9, wherein: The second RF electric power is supplied to the mounting table.

11. The substrate processing method according to claim 1 or 2, wherein: The first plasma generation condition and the second plasma generation condition are the same conditions except for the condition regarding RF electric power.

12. The substrate processing method according to claim 1 or 2, wherein: The flow rate of the fluorocarbon in the processing gas is 0.5% or less relative to the flow rate of the rare gas.

13. The substrate processing method according to claim 1 or 2, wherein: The object to be processed further includes a second region made of silicon nitride, and the first region is selectively etched in both the first region and the second region.

14. The substrate processing method according to claim 1 or 2, wherein: The step b forms a deposit containing the fluorocarbon on the treated object, The step c is to etch the first region through interaction between the deposit and ions of the rare gas, wherein the ions of the rare gas are generated by the second plasma and incident on the object to be processed on the mounting table due to the bias potential.

15. The substrate processing method according to claim 9, wherein: The first plasma generation condition is determined by fixing the condition of the process gas, obtaining data on active species and the bias potential when first RF power and second RF power having a first frequency are supplied separately into the process container at a plurality of output values, and determining the first plasma generation condition based on output values ​​of the first RF power and the second RF power corresponding to data in which a value of CF active species in the data on the active species and the bias potential is higher than other data and the bias potential is zero. The second plasma generation condition is determined based on the output values ​​of the first RF power and the second RF power corresponding to data in which the value of the CF active species in the data of the active species and the bias potential is lower than other data and the bias potential is higher than a specified value.

16. A substrate processing method in a substrate processing device, characterized in that: include: Step a, supplying a processing gas containing a fluorocarbon compound and a rare gas into a processing container provided with a mounting table, wherein a processing object including a first region composed of silicon oxide is mounted on the mounting table; Step b, generating a first plasma of the process gas by supplying a first RF power having a first frequency into the process container; Step e without generating plasma; Step c, generating a second plasma of the processing gas by supplying a second RF power having a second frequency lower than the first frequency into the processing container, and attracting ions contained in the second plasma to the processing object; and Step d, repeating step b, step e, and step c in the order of step b, step e, and step c, The supply and stop of the first RF power and the second RF power are controlled independently of each other at a prescribed frequency in step b and step c. The first RF electric power and the second RF electric power are exclusively supplied.

17. A substrate processing device, characterized in that: include: Processing containers; a mounting table disposed in the processing container and configured to mount a workpiece including a first region made of silicon oxide; and Control Department, The control unit is configured to control the substrate processing device to perform the following steps: Step a, supplying a processing gas containing a fluorocarbon and a rare gas into the processing container; Step b, performing plasma treatment on the object to be processed using a first plasma of the processing gas generated under a first plasma generating condition; Step e without generating plasma; Step c, performing plasma treatment on the object to be processed with a bias potential generated on the object to be processed using a second plasma of the processing gas generated under a second plasma generating condition different from the first plasma generating condition; and Step d: Repeat step b, step e, and step c in the order of step b, step e, and step c.

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