Plasma processing apparatus and plasma processing method

Abstract

To improve the process performance.SOLUTION: A plasma processing apparatus comprises: a first electrode provided on a substrate support part; a second electrode or an antenna opposed to the first electrode; a first high-frequency power supply part connected with the first electrode, and the second electrode or the antenna, and supplying a first high-frequency power pulse; a second high-frequency power supply part connected with the first electrode, and supplying a second high-frequency power pulse; and a controller that controls the first and second high-frequency power supply parts. The controller provides the first high-frequency power pulse with first and second interval times and provides the second high-frequency power pulse with third and fourth interval times, the first high-frequency power pulse being repeatedly turned on and off during the third interval time, the second high-frequency power pulse being repeatedly turned on and off during the first interval time, the second and fourth interval times being overlapped with each other, and controls substrate processing by a plasma of a process gas depending on the outputs of the first and second high-frequency power pulses.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present disclosure relates to a plasma processing apparatus and a plasma processing method. [Background technology]

[0002] Patent Document 1 proposes a plasma processing method in which a pulse wave of high-frequency power for plasma generation and a pulse wave of high-frequency power for biasing, which has a frequency lower than that of the high-frequency power for plasma generation, are applied to a mounting table. In this plasma processing method, the pulse wave of high-frequency power for plasma generation and the pulse wave of high-frequency power for biasing have a phase difference, and the duty ratio of the high-frequency power for plasma generation is controlled to be equal to or greater than the duty ratio of the high-frequency power for biasing. This creates an offset between the pulse wave of high-frequency power for plasma generation and the pulse wave of high-frequency power for biasing. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2016-157735 Summary of the Invention [Problem to be solved by the invention]

[0004] The present disclosure provides techniques that can improve the performance of processes performed in plasma processing apparatuses. [Means for solving the problem]

[0005] According to one aspect of the present disclosure, there is provided a plasma processing chamber that can be evacuated to a vacuum; a first electrode provided on a substrate support member disposed in the plasma processing chamber; a second electrode or an antenna provided opposite the first electrode; a first high frequency power supply unit connected to the first electrode, the second electrode, or the antenna and supplying a first high frequency power pulse for plasma generation to the first electrode, the second electrode, or the antenna; a second high frequency power supply unit connected to the first electrode and supplying a second high frequency power pulse for biasing the first electrode; and a controller that controls the first high frequency power supply unit and the second high frequency power supply unit, wherein the controller is configured to apply the first high frequency power pulse to the first high frequency power pulse. a first interval time and a second interval time during which a pulse is turned off; a second interval time and a third interval time during which the second high frequency power pulse is turned off; the first high frequency power pulse is repeatedly turned on and off during the third interval time; the second high frequency power pulse is repeatedly turned on and off during the first interval time; the second interval time and the fourth interval time overlap; and a plasma processing apparatus is provided in which, in accordance with the outputs of the first high frequency power pulse and the second high frequency power pulse, a substrate is plasma processed by plasma generated from a processing gas supplied into the plasma processing vessel. [Effects of the Invention]

[0006] According to one aspect, the performance of a process performed in a plasma processing apparatus can be improved. [Brief explanation of the drawings]

[0007] [Figure 1] 1 is a schematic cross-sectional view showing an example of a plasma processing system according to an embodiment; [Figure 2] 10A to 10C are diagrams showing an example of a plasma processing method according to a reference example. [Figure 3] 1A to 1C are views showing an example of a plasma processing method according to a first embodiment. [Figure 4] 10A to 10C are diagrams for explaining a plasma processing method according to a reference example. [Figure 5] 1A to 1C are diagrams for explaining a plasma processing method according to a first embodiment. [Figure 6] FIG. 10 is a diagram showing an example of the attenuation characteristics of radicals and the like. [Figure 7] 10A to 10C are diagrams showing an example of a plasma processing method according to a second embodiment. [Figure 8] 10A to 10C are diagrams showing an example of a plasma processing method according to a third embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0008] Hereinafter, embodiments of the present disclosure will be described with reference to the drawings. In the drawings, the same components are denoted by the same reference numerals, and redundant explanations may be omitted.

[0009] [Plasma processing system] An example configuration of a plasma processing system is described below. The plasma processing system includes a capacitively coupled plasma processing apparatus 1 and a control unit 2. The plasma processing apparatus 1 includes a plasma processing chamber 10 that can be evacuated, a gas supply unit 20, a power supply 30, and an exhaust system 40. The plasma processing apparatus 1 also includes a substrate support 11 and a gas inlet unit. The gas inlet unit is configured to introduce at least one processing gas into the plasma processing chamber 10. The gas inlet unit includes a showerhead 13. The substrate support 11 is disposed within the plasma processing chamber 10. The showerhead 13 is disposed above the substrate support 11. In an embodiment, the showerhead 13 forms at least a part of the ceiling of the plasma processing chamber 10. The interior of the plasma processing chamber 10 includes a plasma processing space 10s defined by the showerhead 13, a sidewall 10a of the plasma processing chamber 10, and the substrate support 11. The plasma processing chamber 10 has at least one gas inlet 13a for supplying at least one processing gas to the plasma processing space 10s and at least one gas outlet 10e for exhausting gas from the plasma processing space. The sidewall 10a is grounded. The showerhead 13 and the substrate support 11 are electrically insulated from the housing of the plasma processing chamber 10.

[0010] The substrate support 11 includes a main body 111 and a ring assembly 112. The main body 111 has a central region (substrate support surface) 111a for supporting a substrate W, such as a wafer, and an annular region (ring support surface) 111b for supporting the ring assembly 112. The annular region 111b of the main body 111 surrounds the central region 111a of the main body 111 in a plan view. The substrate W is disposed on the central region 111a of the main body 111, and the ring assembly 112 is disposed on the annular region 111b of the main body 111 so as to surround the substrate W on the central region 111a of the main body 111. In this embodiment, the main body 111 includes a base and an electrostatic chuck. The base includes a conductive member. The conductive member of the base functions as a lower electrode. The electrostatic chuck is disposed on the base. The upper surface of the electrostatic chuck has the substrate support surface 111a. The ring assembly 112 includes one or more annular members. At least one of the one or more annular members is an edge ring. Although not shown, the substrate support 11 may also include a temperature adjustment module configured to adjust at least one of the electrostatic chuck, the ring assembly 112, and the substrate W to a target temperature. The temperature adjustment module may include a heater, a heat transfer medium, a flow path, or a combination thereof. A heat transfer fluid such as brine or gas flows through the flow path. The substrate support 11 may also include a heat transfer gas supply unit configured to supply a heat transfer gas between the back surface of the substrate W and the substrate support surface 111a.

[0011] The showerhead 13 is configured to introduce at least one processing gas from the gas supply unit 20 into the plasma processing space 10s. The showerhead 13 has at least one gas supply port 13a, at least one gas diffusion chamber 13b, and multiple gas inlets 13c. The processing gas supplied to the gas supply port 13a passes through the gas diffusion chamber 13b and is introduced into the plasma processing space 10s from the multiple gas inlets 13c. The showerhead 13 also includes a conductive member. The conductive member of the showerhead 13 functions as an upper electrode. In addition to the showerhead 13, the gas introduction unit may also include one or more side gas injectors (SGIs) attached to one or more openings formed in the sidewall 10a.

[0012] The gas supply unit 20 may include at least one gas source 21 and at least one flow controller 22. In an embodiment, the gas supply unit 20 is configured to supply at least one process gas from a corresponding gas source 21 to the showerhead 13 via a corresponding flow controller 22. Each flow controller 22 may include, for example, a mass flow controller or a pressure-controlled flow controller. Furthermore, the gas supply unit 20 may include one or more flow modulation devices that modulate or pulse the flow rate of the at least one process gas.

[0013] The power supply 30 includes an RF power supply 31 coupled to the plasma processing chamber 10 via at least one impedance matching circuit. The RF power supply 31 is configured to supply at least one RF signal (RF power), such as a source RF signal and a bias RF signal, to the conductive members of the substrate support 11 and / or the conductive members of the showerhead 13. This causes plasma to be formed from at least one process gas supplied to the plasma processing space 10s. Therefore, the RF power supply 31 can function as at least a part of a plasma generating unit configured to generate plasma from one or more process gases in the plasma processing chamber 10. Furthermore, supplying a bias RF signal to the conductive members of the substrate support 11 generates a bias potential on the substrate W, thereby attracting ion components in the formed plasma to the substrate W.

[0014] In the embodiment, the RF power supply 31 includes a first RF generating unit 31a and a second RF generating unit 31b. The first RF generating unit 31a is coupled to a conductive member of the substrate support 11 or a conductive member of the showerhead 13 via at least one impedance matching circuit and is configured to generate a source RF signal (source RF power) for plasma generation. In the embodiment, the source RF signal has a frequency in the range of 13 MHz to 150 MHz. In the embodiment, the first RF generating unit 31a may be configured to generate multiple source RF signals having different frequencies. The generated one or more source RF signals are supplied to the conductive member of the substrate support 11 or the conductive member of the showerhead 13. The second RF generating unit 31b is coupled to the conductive member of the substrate support 11 via at least one impedance matching circuit and is configured to generate a bias RF signal (bias RF power). In the embodiment, the bias RF signal has a frequency lower than that of the source RF signal. In the embodiment, the bias RF signal has a frequency in the range of 400 kHz to 13.56 MHz. In various embodiments, the second RF generator 31b may be configured to generate multiple bias RF signals having different frequencies. The generated bias RF signals are supplied to the conductive members of the substrate support 11. In various embodiments, at least one of the source RF signal and the bias RF signal may be pulsed.

[0015] The conductive member of the base of the substrate support 11 provided in the plasma processing chamber 10 is an example of a first electrode disposed in the processing vessel and supporting the substrate to be processed. The conductive member of the shower head 13 is an example of a second electrode provided opposite the first electrode. An antenna may be provided opposite the first electrode instead of the shower head 13, which is an example of a second electrode. The plasma processing system may include an inductively coupled plasma processing apparatus instead of the capacitively coupled plasma processing apparatus 1. In the inductively coupled plasma processing apparatus, an antenna may be provided above the plasma processing chamber 10 opposite the first electrode supporting the substrate to be processed, and the first RF generator 31a may be connected to the antenna.

[0016] The first RF generating unit 31a may be connected to the first electrode, the second electrode, or the antenna. The first RF generating unit 31a is an example of a first high frequency power supply unit that supplies a first high frequency power pulse (hereinafter also referred to as an "HF pulse"), which is a pulse wave of first high frequency power for generating plasma, to the first electrode, the second electrode, or the antenna. The second RF generating unit 31b is an example of a second high frequency power supply unit that is connected to the first electrode and supplies a second high frequency power pulse (hereinafter also referred to as an "LF pulse"), which is a pulse wave of second high frequency power for biasing, to the first electrode.

[0017] The power supply 30 may also include a DC power supply 32 coupled to the plasma processing chamber 10. The DC power supply 32 includes a first DC generator 32a and a second DC generator 32b. In an embodiment, the first DC generator 32a is connected to a conductive member of the substrate support 11 and configured to generate a first DC signal. The generated first bias DC signal is applied to the conductive member of the substrate support 11. In an embodiment, the first DC signal may be applied to another electrode, such as an electrode in an electrostatic chuck. In an embodiment, the second DC generator 32b is connected to a conductive member of the showerhead 13 and configured to generate a second DC signal. The generated second DC signal is applied to the conductive member of the showerhead 13. In various embodiments, at least one of the first and second DC signals may be pulsed. The first DC generator 32a and the second DC generator 32b are provided in addition to the RF power supply 31.

[0018] The exhaust system 40 may be connected to, for example, a gas exhaust port 10e provided at the bottom of the plasma processing chamber 10. The exhaust system 40 may include a pressure regulating valve and a vacuum pump. The pressure regulating valve regulates the pressure in the plasma processing space 10s. The vacuum pump may include a turbomolecular pump, a dry pump, or a combination thereof.

[0019] The controller 2 processes computer-executable instructions that cause the plasma processing apparatus 1 to perform various processes described in this disclosure. The controller 2 may be configured to control each element of the plasma processing apparatus 1 to perform various processes described herein. For example, the controller 2 controls the first RF generator 31a and the second RF generator 31b. In an embodiment, part or all of the controller 2 may be included in the plasma processing apparatus 1. The controller 2 may include, for example, a computer 2a. The computer 2a may include, for example, a processor (CPU: Central Processing Unit) 2a1, a memory 2a2, and a communication interface 2a3. The processor 2a1 may be configured to perform various control operations based on programs stored in the memory 2a2. The memory 2a2 may include a random access memory (RAM), a read-only memory (ROM), a hard disk drive (HDD), a solid state drive (SSD), or a combination thereof. The communication interface 2a3 may communicate with the plasma processing apparatus 1 via a communication line such as a local area network (LAN).

[0020] Next, an example of a plasma processing method according to a reference example will be described with reference to FIG. 2, and then a plasma processing method according to an embodiment will be described with reference to FIGS. 3 and 4. The plasma processing method according to the embodiment is controlled by a control unit 2. The source RF signal supplied from the first RF generating unit 31a will also be referred to as first high frequency power or HF. The pulse wave of the first high frequency power will also be referred to as HF pulse. The bias RF signal supplied from the second RF generating unit 31b will also be referred to as second high frequency power or LF. The pulse wave of the second high frequency power will also be referred to as LF pulse.

[0021] [Plasma Processing Method According to Reference Example] FIG. 2 is a diagram illustrating an example of a plasma processing method according to a reference example. In the plasma processing method according to the reference example, the HF and LF are pulse waves. The duty ratio of the HF pulse is 50%. The duty ratio of the LF pulse is 20%. In the example of FIG. 2, the phases of the HF and LF are shifted by 50% based on the time when the HF is turned on, and the on times (supply times, application times) of the HF and LF do not overlap. The LF is turned on when the HF is turned off (supply is stopped). In one cycle, the HF is on for 50%, the LF is on for 20%, and both the HF and LF are off for 30%, totaling 100%, or one cycle. For example, the frequency of one cycle is 1 kHz, and the duration of one cycle is 1000 μs.

[0022] While the HF is on, plasma and radicals are generated. While the LF is on, ions in the plasma are attracted to the substrate, promoting etching. While the HF and LF are off, reaction products (reaction products) generated during etching are exhausted from recesses in the film to be etched that are formed on the object to be etched.

[0023] High-power LF power is required to achieve highly anisotropic etching, i.e., vertical etching profiles, while maintaining a high etching rate. However, in the example shown in Figure 2, applying high-power LF power while the LF is on results in high-energy ions etching the target film on the substrate, while also etching the mask with the high-energy ions. Furthermore, the high-energy ions accelerate the etching, generating a large amount of reaction products that adhere to the mask. This can lead to mask clogging above the target film. Mask clogging occurs when reaction products adhere to the mask's sidewalls, narrowing the mask opening or completely blocking the opening. One way to avoid mask clogging is to turn off both the HF and LF and allow a period of time (off time) to accelerate evacuation. However, if the LF off time is too short, reaction products are not efficiently removed from the recesses in the target film.

[0024] Therefore, in the plasma processing method according to the embodiment described below, while controlling the on and off times of the HF pulse and the LF pulse, two more off times are controlled in addition to the off time previously used, for a total of three off times, thereby controlling the RF. This makes it possible to avoid mask clogging while achieving a high mask selectivity. The plasma processing method according to the embodiment will be described below.

[0025] [Plasma Processing Method According to the Embodiment] (First embodiment) The plasma processing method according to the first embodiment will be described with reference to Fig. 3. Fig. 3 is a diagram showing an example of the plasma processing method according to the first embodiment. In the plasma processing method according to the embodiment, as shown in Fig. 3, the pulse period of the HF pulse is represented by frequency F1, the pulse period of the LF pulse is represented by frequency F2, and the HF pulse and the LF pulse are controlled to repeatedly turn on and off in their respective pulse periods.

[0026] 3, the pulse period of the HF pulse indicated by frequency F1 and the pulse period of the LF pulse indicated by frequency F2 are each 10 kHz. However, the pulse period of the HF pulse and the pulse period of the LF pulse are not limited to this and may be in the range of 10 kHz to 20 kHz, and may be the same as in the present disclosure, or may be different.

[0027] Duty 1 (first duty ratio) of the HF pulse indicates the HF on time relative to the total time of the HF on time and off time. In the example of FIG. 3, Duty 1 is 75%, and the HF pulse periodically repeats on and off, with the HF pulse on for 3 / 4 of one cycle and off for 1 / 4. The time during which the HF pulse is repeatedly turned on and off in this manner is also called the "output time of the HF pulse." In the example of FIG. 3, the first to fifth cycles are the output time of the HF pulse.

[0028] The HF pulse has a first interval time and a second interval time during which the HF is turned off. The sixth to seventh cycles are the first interval time ((1) in Figure 3), and the eighth to tenth cycles are the second interval time (2). The first interval time (1) and the second interval time (2) may be continuous or discontinuous.

[0029] Duty 2 (second duty ratio) of the LF pulse indicates the on time of the LF relative to the total time of the on time and off time of the LF. In the example of Figure 3, Duty 2 is 50%, and the LF pulse periodically repeats on and off of the LF so that it is on for 1 / 2 of one cycle and off for 1 / 2 of the cycle. This time during which the LF is repeatedly turned on and off is also called the "output time of the LF pulse." In the example of Figure 3, the 6th to 7th cycles are the output time of the LF pulse.

[0030] The LF pulse has a third interval time and a fourth interval time during which the LF is turned off. The first to fifth cycles are the third interval time ((3)), and the eighth to tenth cycles are the fourth interval time (4). The third interval time (3) and the fourth interval time (4) may be continuous or discontinuous.

[0031] The output time of the HF pulse does not overlap with the output time of the LF pulse. The output time of the HF pulse overlaps with the third interval time (3), and the output time of the LF pulse overlaps with the first interval time (1). In the present disclosure, the output time of the HF pulse is followed by the output time of the LF pulse, which is then followed by an interval time during which both the HF pulse and the LF pulse are turned off, but this is not limited to this. For example, the output time of the LF pulse may be followed by the output time of the HF pulse, which is then followed by an interval time during which both the HF pulse and the LF pulse are turned off. For example, the output time of the LF pulse may be followed by an interval time during which both the HF pulse and the LF pulse are turned off, which is then followed by the output time of the HF pulse.

[0032] In the present disclosure, the output time of the HF pulse and the output time of the LF pulse are completely offset, and the timing of the HF pulse on and the LF pulse on do not overlap. However, the output time of the HF pulse and the output time of the LF pulse may partially overlap. In the present disclosure, the third interval time (3) and the output time of the HF pulse completely overlap, but may partially overlap. In the present disclosure, the first interval time (1) and the output time of the LF pulse completely overlap, but may partially overlap. The first interval time (1) and the third interval time (3) do not overlap. The second interval time (2) and the fourth interval time (4) overlap.

[0033] The interval period in which the second interval time (2) and the fourth interval time (4) overlap is indicated by frequency F3. Frequency F3 is a period in which the interval period in which the second interval time (2) and the fourth interval time (4) overlap repeatedly appears, and is 1 kHz in the example of FIG. 3, but is not limited to this and may be 1 kHz to 2 kHz. The interval period indicated by frequency F3 is longer than the HF and LF pulse periods indicated by frequencies F1 and F2. In the example of FIG. 3, frequencies F1 and F2 are 10 times frequency F3. Frequencies F1 and F2 may be 10 times frequency F3 or more.

[0034] Duty3 indicates the total output time of the HF pulse and the LF pulse relative to the total time (1000 μs in the example of FIG. 3) of the time when the HF pulse is repeatedly turned on and off (HF pulse output time) indicated by Duty1, the time when the LF pulse is repeatedly turned on and off (LF pulse output time) indicated by Duty2, and the interval time when both the HF pulse and the LF pulse are off. In the example of FIG. 3, Duty3 is 70% (HF pulse output time is 50%, LF pulse output time is 20%), but is not limited to this and Duty3 may be 10% to 90%.

[0035] Each of the off times of the HF pulse during the output time of the HF pulse is shorter than the first interval time (1) and the second interval time (2). Each of the off times of the LF pulse during the output time of the LF pulse is shorter than the third interval time (3) and the fourth interval time (4).

[0036] During cycles 1 to 5, the HF pulse is turned on and off five times, during which the LF is controlled to be off, which corresponds to the third interval time (3). During cycles 6 to 7, the LF pulse is turned on and off twice, during which the HF is controlled to be off, which corresponds to the first interval time (1). During cycles 8 to 10, the HF pulse and the LF pulse are both controlled to be off, which corresponds to the second interval time (2) and the fourth interval time (4). In the example of FIG. 3, the interval time during which both the HF and LF are in the off state is set to 30%, but the interval times indicated by the second interval time (2) and the fourth interval time (4) may be 10% or more and 90% or less.

[0037] The control unit 2 controls the first RF generator 31a and the second RF generator 31b in accordance with the outputs of the HF pulse and the LF pulse so as to process the substrate W with plasma generated from the processing gas supplied into the plasma processing chamber 10. This makes it possible to both avoid mask clogging and improve the mask selectivity. The reason for this will be explained with reference to the reference example in FIG. 4 and the embodiments in FIGS. 5 and 6.

[0038] FIG. 4 is a diagram for explaining a plasma processing method according to a reference example. FIG. 5 is a diagram for explaining a plasma processing method according to the first embodiment. FIG. 6 is a diagram showing an example of the attenuation characteristics of radicals and the like. In the reference example and this embodiment, for example, a SiO2 film is formed on a substrate as an etching target film 101, and a mask 102 such as an organic film is formed thereon. The etching target film 101 is etched in accordance with the pattern of the mask 102, thereby forming recesses (holes, etc.) in accordance with the pattern in the etching target film 101. However, the film structure on the substrate W is not limited to this.

[0039] In the plasma processing method according to the reference example shown in Fig. 4, there is an interval time during which the HF pulse and the LF pulse are turned off between cycles 8 and 10. The pulse period of the HF pulse and the LF pulse between cycles 1 and 7 is 1 kHz in the example of Fig. 4. The duty ratio of the HF pulse and the duty ratio of the LF pulse are both 50%. There is a phase difference between the HF and LF, and the LF is turned on at the timing when the HF is turned off.

[0040] The interval period is 0.1 kHz, which is longer than the pulse period of the HF pulse and the LF pulse, and the pulse period of the HF pulse and the LF pulse is 10 times the interval period.

[0041] The interval period is set to 30% of the total time during which the HF pulse and LF pulse are repeatedly turned on and off (total cycle time of 1 to 7 cycles) and the interval time during which the HF and LF pulses are continuously in the off state.

[0042] In period A of the first cycle shown in Fig. 4, the HF pulse is controlled to be on and the LF pulse is controlled to be off. Therefore, in period A, as shown in Fig. 4(a), HF contributes to the generation of plasma and radicals, and ions, electrons, and radicals are generated, resulting in the generation of high-density plasma.

[0043] In period B of the first cycle shown in Figure 4, the LF pulse is controlled to be on and the HF pulse is controlled to be off. Therefore, in period B, high-energy ions are attracted into recesses in the film 101 to be etched by the LF. As a result, etching is promoted by the high-energy ions in period B. Furthermore, since high-density plasma is generated in period A, the number of ions in the high-density plasma is large in period B, and the ion energy is high, which promotes etching and results in a relatively large amount of reaction products.

[0044] If reaction products generated during etching adhere to the side and top surfaces of the mask 102 and form a protective film, the selectivity of the mask 102 can be improved. However, because high-density plasma is generated during Period A, a large number of ions are present in the high-density plasma during the following Period B, resulting in the generation of ions at various angles of incidence, resulting in a wide distribution of ion incidence angles. As shown in FIG. 4(b), ions are incident at various angles on the recesses in the film 101 to be etched, which makes them prone to colliding with the reaction products in the recesses. This collision hinders the exhaust of the reaction products, making it difficult for the reaction products to be exhausted from the recesses in the film 101 to be etched. As a result, the reaction products adhere to the side and top surfaces of the mask 102, preventing the formation of a protective film, and preventing the mask selectivity from being improved.

[0045] The above phenomenon is repeated in periods A and B in the second to seventh cycles shown in Fig. 4. During the intervals between the eighth to tenth cycles, both the HF pulse and the LF pulse are controlled to be off, which promotes the exhaust of reaction products from the recesses in the etching target film 101, as shown in Fig. 4(c).

[0046] 4, in the case of the plasma processing method according to the reference example, the action of the ions in the high-density plasma generated in Period A inhibits the exhaust of reaction products in Period B, making it difficult for the reaction products to adhere to the side or top surface of the mask, making it difficult to improve the mask selectivity.

[0047] In contrast, in the plasma processing method according to this embodiment, the times when both the HF pulse and the LF pulse are turned off are set as "Off time 1," "Off time 2," and "Off time 3," as shown in Fig. 5. The interval between Off time 1 and Off time 2 is shorter than the interval between Off time 3.

[0048] In period C of the first cycle shown in Fig. 5, the HF pulse is controlled to be on and the LF pulse is controlled to be off. Therefore, in period C, as shown in Fig. 5(a), HF contributes to the generation of plasma and radicals, and ions, electrons, and radicals are generated, resulting in the generation of high-density plasma.

[0049] During period D of the first cycle, both the HF pulse and the LF pulse are controlled to be off for a short period of time, for example, 10 to 100 μs. Figure 6 shows the decay characteristics of electrons, ions, and radicals. The horizontal axis of Figure 6 represents time, and the vertical axis represents normalized decay. When the RF power (HF) is switched from on to off, the electron temperature (plasma potential) decays rapidly first. Next, the ions (plasma density) decay. In contrast, the decay of radicals is gradual.

[0050] As a result, in this embodiment, even if the HF is turned off during period D, the radicals necessary for etching are not deactivated and the plasma density can be maintained at a moderate level. In cycles 1 to 5, the HF pulse is turned on and off periodically in this manner, and the HF is turned on intermittently, thereby controlling the plasma density to a moderate level without increasing it. Note that in cycles 1 to 5, the LF pulse is controlled to be off during the third interval time (3).

[0051] In the case of high-density plasma, the number of ions in the plasma is large, so ions are generated at various angles of incidence, resulting in a large distribution of the ion incidence angles. In contrast, by providing Off time 1 during the HF pulse output time and controlling the plasma density to a moderate level, as in this embodiment, the number of ions in the plasma can be reduced compared to high-density plasma. As a result, the distribution of the ion incidence angles can be reduced. In other words, ions with a relatively uniform incidence angle can be generated. As a result, as shown in FIG. 5(b), the angles of the ions incident on the film 101 to be etched are aligned vertically to a certain extent, providing ion directionality.

[0052] In this way, the directional ion incidence with little variation in the ion incidence angle reduces collisions between the reaction products generated during etching and the ions used in the next etching, as shown in Figure 5(c). In cycles 6 and 7, the LF pulse is turned on during period E to attract ions and accelerate etching with the aid of undeactivated radicals. This accelerated etching also increases the amount of reaction products generated during time E. Therefore, during the following period F, a short Off time 2, for example, 10 to 100 μs, is added to the output time of the LF pulse to accelerate the exhaust of reaction products. Accelerating the exhaust of reaction products during etching increases the amount of reaction products adhering to the side and top surfaces of the mask 102. This improves the mask selectivity. During this period, the HF pulse is controlled to be off during the first interval (1).

[0053] Without Off time 2, the LF pulse remains on for the sixth and seventh cycles, and etching progresses due to ion attraction. This increases the amount of reaction products produced, but does not promote exhaust. With Off time 2, etching progresses due to ion attraction and radical action while the LF pulse is on, and the exhaust of reaction products is promoted and the mask selectivity is improved while the LF pulse is off. In this way, by alternating the E period during which the LF pulse is on and the F period during which the LF pulse is off, as shown in Figure 5(c), etching can be promoted, the exhaust of reaction products can be promoted, and the mask selectivity can be improved.

[0054] Off time 3 is the second interval time (2) of the HF pulse and the fourth interval time (4) of the LF pulse, and both the HF pulse and the LF pulse are controlled to be off. During the 8th to 10th cycles, the exhaust of reaction products is sufficiently promoted as shown in FIG. 5(d). As a result, the reaction products adhere to the mask 102 while being exhausted from the recesses formed in the etching target film 101, thereby improving the mask selectivity.

[0055] As described above, the plasma processing method according to this embodiment provides Off time 1. This allows the plasma density to be controlled to a medium level during period D when the HF pulse is turned off.

[0056] In addition, by providing Off time 2, collisions between reaction products generated during etching and ions used in the next etching are reduced during period E when the LF pulse is on, thereby accelerating etching, and collisions with ions are reduced during period F when the LF pulse is off, thereby accelerating evacuation of reaction products and improving mask selectivity. By alternately repeating this, evacuation and mask selectivity can be improved during etching. In addition, by providing Off time 3, evacuation of reaction products can be sufficiently accelerated. As a result, the plasma processing method according to this embodiment can achieve both avoidance of mask clogging and high mask selectivity. This improves the performance of the process performed in the plasma processing apparatus.

[0057] The above is just one example, and in the plasma processing method according to the first embodiment, the HF pulse is periodically turned on and off in the first to fifth cycles, and the LF pulse is periodically turned on and off in the sixth to seventh cycles, but the cycles in which the HF pulse and the LF pulse are repeated are not limited to this.

[0058] (Second embodiment) A plasma processing method according to the second embodiment will be described with reference to FIG. 7. FIG. 7 is a diagram showing an example of the plasma processing method according to the second embodiment. The plasma processing method according to the second embodiment differs from the plasma processing method according to the first embodiment in that the HF pulse has two pulse periods, 20 kHz and 10 kHz, and the duty ratios are different. Also, the LF pulse has the same pulse period but a different duty ratio. The other conditions are the same.

[0059] During the HF pulse output times for the first to fifth cycles, the pulse period is 10 kHz and the duty ratio is 75% for the first, third, and fifth cycles. The pulse period is 20 kHz and the duty ratio is 80% for the second and fourth cycles. As a result, Off time 1 occurs once for the first, third, and fifth cycles, and Off time 1 occurs twice for the second and fourth cycles.

[0060] During the output of the LF pulse from cycle 6 to cycle 7, the pulse period is 10 kHz, the duty ratio is 75% in cycle 6, and the duty ratio is 50% in cycle 7. As a result, Off time 2 occurs once per cycle from cycle 6 to cycle 7.

[0061] The above is just one example, and in the plasma processing method according to the second embodiment, either the frequency or the duty ratio of the pulse period of the HF pulse may be the same. Alternatively, the pulse period of the LF pulse may be different. Furthermore, the frequency and duty ratio of at least one of the HF pulse and the LF pulse may be configured to have three or more types.

[0062] (Third embodiment) A plasma processing method according to the third embodiment will be described with reference to FIG. 8. FIG. 8 is a diagram showing an example of the plasma processing method according to the third embodiment. The plasma processing method according to the third embodiment differs from the plasma processing method according to the first embodiment in that there are two types of HF pulse amplitudes and two types of LF pulse amplitudes. The other conditions are the same.

[0063] During the output time of the HF pulse from cycles 1 to 5, the amplitude of the 1st, 3rd, and 5th cycles is A1, and the amplitude of the 2nd and 4th cycles is A2. During the output time of the LF pulse from cycles 6 to 7, the amplitude of the 6th cycle is B1, and the amplitude of the 7th cycle is B2.

[0064] The above is just one example, and the output time of each HF pulse and LF pulse may be controlled by changing at least one of the pulse period, duty, and amplitude for each cycle. Also, the amplitude of at least one of the HF pulse and LF pulse may be configured with three or more types.

[0065] (others) Duty 1 is set to 90% or less. If Duty 1 is set to 90% or more, the possibility of mask clogging increases and the promotion of exhaust of reaction products from recesses in the etching target film 101 is hindered. Furthermore, Duty 1 is preferably set to 10% or more and 90% or less. If Duty 1 is less than 10%, the time during which HF is turned on is short, and there is a possibility that plasma will not be ignited.

[0066] Duty 2 is preferably 10% or more and 90% or less. If Duty 2 is set to less than 10%, the time that LF is turned on is shortened, which improves the exhaust of reaction products from the recesses of the etching target film 101, but reduces the etching rate. On the other hand, if Duty 2 is set to more than 90%, the etching rate increases, but the exhaust of reaction products from the recesses of the etching target film 101 becomes poor, which may cause mask clogging (mask blockage) and result in an etch stop.

[0067] As described above, the plasma processing apparatus and plasma processing method of this embodiment can avoid mask clogging while achieving a high mask selectivity, thereby improving the performance of the process performed in the plasma processing apparatus.

[0068] The plasma processing apparatus and plasma processing method according to the presently disclosed embodiments should be considered to be illustrative in all respects and not restrictive. The embodiments can be modified and improved in various ways without departing from the spirit and scope of the appended claims. The features described in the above embodiments can be configured in other ways as long as they are not inconsistent, and can be combined as long as they are not inconsistent.

[0069] The plasma processing apparatus of the present disclosure can be applied to any type of apparatus, including atomic layer deposition (ALD) apparatus, capacitively coupled plasma (CCP) apparatus, and inductively coupled plasma (ICP) apparatus. [Explanation of symbols]

[0070] 1. Plasma processing equipment 2. Control Unit 2a Computer 2a1 Processing section 2a2 Storage section 2a3 communication interface 10 Plasma Processing Chamber 11 Substrate support 13. Shower head 21 Gas Source 20 Gas supply unit 30 power supply 31 RF power supply 31a First RF generation unit 31b Second RF generation unit 32a First DC generation unit 32b Second DC generation unit 40 Exhaust system 100 silicon substrate 101 Etching target film 102 Mask 111 Main body 112 Ring Assembly

Claims

1. a plasma processing vessel that can be evacuated; a first electrode provided on a substrate support disposed in the plasma processing chamber; a second electrode or antenna provided opposite the first electrode; a first high frequency power supply unit connected to the first electrode, the second electrode, or the antenna and configured to supply a first high frequency power pulse for plasma generation to the first electrode, the second electrode, or the antenna; a second high frequency power supply connected to the first electrode and configured to supply a second high frequency power pulse for biasing the first electrode; a control unit that controls the first high frequency power supply unit and the second high frequency power supply unit, The control unit providing a first interval time and a second interval time during which the first high frequency power pulse is turned off in the first high frequency power pulse; providing a third interval time and a fourth interval time during which the second high frequency power pulse is turned off in the second high frequency power pulse; the first high frequency power pulse is repeatedly turned on and off during the third interval; the second high frequency power pulse is repeatedly turned on and off during the first interval; the second interval time and the fourth interval time overlap, controlling the plasma processing of a substrate by plasma generated from a processing gas supplied into the plasma processing vessel in accordance with outputs of the first high frequency power pulse and the second high frequency power pulse; the amplitude of at least one of the first high frequency power pulse or the second high frequency power pulse has a plurality of power levels or voltage levels; Plasma processing equipment.

2. a first duty ratio of the first high frequency power pulse and a second duty ratio of the second high frequency power pulse are each 10% or more and 90% or less; The plasma processing apparatus according to claim 1 .

3. a third duty ratio of the second interval time and the fourth interval time is equal to or greater than 10% and equal to or less than 90%; 3. The plasma processing apparatus according to claim 1 or 2.

4. the period of the first high frequency power pulse and the period of the second high frequency power pulse are 10 times or more the period of the second interval time and the fourth interval time, respectively; The plasma processing apparatus according to any one of claims 1 to 3.

5. the periods of the second interval time and the fourth interval time are equal to or greater than 1 kHz and equal to or less than 2 kHz; The plasma processing apparatus according to any one of claims 1 to 4.

6. the period of the first high frequency power pulse and the period of the second high frequency power pulse are each 10 kHz or more and 20 kHz or less; The plasma processing apparatus according to any one of claims 1 to 5.

7. the period of the first high frequency power pulse and the period of the second high frequency power pulse are the same; The plasma processing apparatus according to any one of claims 1 to 6.

8. the duty ratio of the first high frequency power pulse and the duty ratio of the second high frequency power pulse are the same; The plasma processing apparatus according to any one of claims 1 to 7.

9. The first interval time and the third interval time do not overlap. The plasma processing apparatus according to any one of claims 1 to 8.

10. a plasma processing vessel that can be evacuated; a first electrode provided on a substrate support disposed in the plasma processing chamber; a second electrode or antenna provided opposite the first electrode; a first high frequency power supply unit connected to the first electrode, the second electrode, or the antenna and configured to supply a first high frequency power pulse for plasma generation to the first electrode, the second electrode, or the antenna; a second high frequency power supply connected to the first electrode and configured to supply a second high frequency power pulse for biasing the first electrode; A plasma processing method performed in a plasma processing apparatus comprising: providing a first interval time and a second interval time during which the first high frequency power pulse is turned off in the first high frequency power pulse; providing a third interval time and a fourth interval time during which the second high frequency power pulse is turned off in the second high frequency power pulse; the first high frequency power pulse is repeatedly turned on and off during the third interval; the second high frequency power pulse is repeatedly turned on and off during the first interval; the second interval time and the fourth interval time overlap, plasma processing a substrate with plasma generated from a processing gas supplied into the plasma processing vessel in response to outputs of the first high frequency power pulse and the second high frequency power pulse; the amplitude of at least one of the first high frequency power pulse or the second high frequency power pulse has a plurality of power levels or voltage levels; Plasma treatment method.

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