Plasma processing device and etching method

Abstract

Provided is a plasma processing device in one illustrative embodiment. A control unit is configured to perform steps (a), (b), (c), and (d). A substrate includes a plurality of silicon oxide films and a plurality of silicon nitride films that are alternately stacked. In the step (b), a first plasma is generated from a first processing gas. A first pulsed voltage signal is applied from a voltage pulse generator to a lower electrode, and has a first voltage level. In the step (c), a second plasma is generated from a second processing gas. A second pulsed voltage signal is applied from the voltage pulse generator to the lower electrode, and has a second voltage level. In the step (d), the steps (b) and (c) are alternately repeated.

Description

Plasma processing apparatus and etching method

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

[0002] In the manufacturing of electronic devices, etching is performed on the substrate. In etching, plasma is generated from a processing gas supplied into a plasma processing chamber. Patent Document 1 discloses a plasma processing apparatus having a gas supply channel for supplying a main gas to the plasma processing chamber and an additive gas channel for mixing an additive gas with the main gas.

[0003] Japanese Patent Publication No. 2023-105636

[0004] This disclosure provides a technique for improving the etching selectivity of one silicon oxide film and one silicon nitride film to the etching of the other film in alternating stacked silicon oxide and silicon nitride films.

[0005] In one exemplary embodiment, a plasma processing apparatus is provided. The plasma processing apparatus comprises a plasma processing chamber, a substrate support, a lower electrode, at least one processing gas supply line, at least one main gas supply line, at least one additive gas supply line, an RF generator, a voltage pulse generator, and a control unit. The substrate support is located within the plasma processing chamber. The lower electrode is located within the substrate support. At least one processing gas supply line is connected to the plasma processing chamber. At least one main gas supply line is connected to at least one processing gas supply line. At least one additive gas supply line is connected to at least one processing gas supply line. The RF generator is configured to supply a source RF signal for generating plasma within the plasma processing chamber. The voltage pulse generator is electrically connected to the lower electrode. The control unit is configured to control the RF generator and the voltage pulse generator to perform steps (a), (b), (c), and (d). In step (a), a substrate is placed on the substrate support. The substrate includes a plurality of alternately stacked silicon oxide films and a plurality of silicon nitride films. In step (b), one silicon oxide film among a plurality of silicon oxide films is etched by a first plasma and a first pulsed voltage signal. In step (b), the first plasma is generated from a first processing gas. The first pulsed voltage signal is applied to the lower electrode from a voltage pulse generator. The first pulsed voltage signal includes a sequence of first voltage pulses having a first voltage level. The first processing gas is supplied into the processing chamber from at least one processing gas supply line. The first processing gas includes a first main gas and a first additive gas. The first main gas is supplied via at least one main gas supply line. The first additive gas is supplied via at least one additive gas supply line. In step (c), one silicon nitride film among a plurality of silicon nitride films is etched by a second plasma and a second pulsed voltage signal. In step (c), the second plasma is generated from a second processing gas. The second pulsed voltage signal is applied to the lower electrode from a voltage pulse generator.The second pulsed voltage signal includes a sequence of second voltage pulses having a second voltage level. The second processing gas is supplied into the processing chamber from at least one processing gas supply line. The second processing gas includes a second main gas and a second additive gas. The second main gas is supplied via at least one main gas supply line. The second additive gas is supplied via at least one additive gas supply line. The second voltage level is lower than the first voltage level. Step (d) alternately repeats steps (b) and (c).

[0006] One exemplary embodiment improves the etching selectivity of one film to the other in the etching of alternately stacked silicon oxide and silicon nitride films.

[0007] Figure 1 is a diagram illustrating an example configuration of a plasma processing system. Figure 2 is a diagram illustrating an example configuration of a capacitively coupled plasma processing apparatus. Figure 3 is a diagram showing the configuration of a gas supply line in a plasma processing apparatus according to one exemplary embodiment. Figure 4 is a timing chart of a source RF signal and a pulsed voltage signal according to one exemplary embodiment. Figure 5 is a flowchart of an etching method according to one exemplary embodiment.

[0008] Various exemplary embodiments will be described in detail below with reference to the drawings. In each drawing, the same or corresponding parts will be denoted by the same reference numerals.

[0009] Figure 1 is a diagram illustrating an example configuration of a plasma processing system. In one embodiment, the plasma processing system includes a plasma processing apparatus 1 and a control unit 2. The plasma processing system is an example of a substrate processing system, and the plasma processing apparatus 1 is an example of a substrate processing apparatus. The plasma processing apparatus 1 includes a plasma processing chamber 10, a substrate support unit 11, and a plasma generation unit 12. The plasma processing chamber 10 has a plasma processing space. The plasma processing chamber 10 also has at least one gas supply port for supplying at least one processing gas to the plasma processing space, and at least one gas outlet for discharging gas from the plasma processing space. The gas supply port is connected to a gas supply unit 20, which will be described later, and the gas outlet is connected to an exhaust system 40, which will be described later. The substrate support unit 11 is located in the plasma processing space and has a substrate support surface for supporting a substrate.

[0010] The plasma generation unit 12 is configured to generate plasma from at least one processing gas supplied into the plasma processing space. The plasma formed in the plasma processing space may be capacitively coupled plasma (CCP), inductively coupled plasma (ICP), ECR (Electron Cyclotron Resonance) plasma, helicon wave excited plasma (HWP), or surface wave plasma (SWP), etc. Various types of plasma generation units, including AC (Alternating Current) plasma generation units and DC (Direct Current) plasma generation units, may also be used. In one embodiment, the AC signal (AC power) used in the AC plasma generation unit has a frequency in the range of 100 kHz to 10 GHz. Therefore, the AC signal includes an RF (Radio Frequency) signal and a microwave signal. In one embodiment, the RF signal has a frequency in the range of 100 kHz to 150 MHz.

[0011] The control unit 2 processes computer-executable instructions that cause the plasma processing apparatus 1 to perform the various processes described herein. The control unit 2 may be configured to control the elements of the plasma processing apparatus 1 to perform the various processes described herein. In one embodiment, part or all of the control unit 2 may be included in the plasma processing apparatus 1. The control unit 2 is implemented, for example, by a computer 2a. The control unit 2 may include a processing unit 2a1, a storage unit 2a2, and a communication interface 2a3. The functions realized by the processing unit 2a1 described herein may be implemented in a circuit or processing circuit, including a general-purpose processor, an application-specific processor, integrated circuits, ASICs (Application Specific Integrated Circuits), a CPU (Central Processing Unit), a conventional circuit, and / or a combination thereof, programmed to realize the described functions. The processor is considered to be a circuit or processing circuit, including transistors and other circuits. The processor may be a programmed processor that executes a program stored in the storage unit 2a2. This program may be pre-stored in the storage unit 2a2 or retrieved via a medium when needed. The acquired program is stored in the storage unit 2a2 and read from the storage unit 2a2 and executed by the processing unit 2a1. The medium may be various storage media readable by the computer 2a, or it may be a communication line connected to the communication interface 2a3. The storage unit 2a2 may include RAM (Random Access Memory), ROM (Read Only Memory), HDD (Hard Disk Drive), SSD (Solid State Drive), or a combination thereof. The communication interface 2a3 may communicate with the plasma processing device 1 via a communication line such as a LAN (Local Area Network).In this disclosure, circuits, units, and means are hardware programmed to perform or configured to perform the functions described. Such hardware may be any hardware described in this disclosure, or any hardware known to be programmed to perform or execute the functions described. If such hardware is a processor that is considered to be a type of circuit, such circuit, means, or unit is a combination of hardware and software used to constitute such hardware and / or processor.

[0012] The following describes an example configuration of a capacitively coupled plasma processing apparatus as an example of a plasma processing apparatus 1. Figure 2 is a diagram illustrating an example configuration of a capacitively coupled plasma processing apparatus.

[0013] The capacitively coupled plasma processing apparatus 1 includes a plasma processing chamber 10, a gas supply unit 20, a power supply system 30, and an exhaust system 40. The plasma processing apparatus 1 also includes a substrate support unit 11 and a gas introduction unit. The gas introduction unit is configured to introduce at least one processing gas into the plasma processing chamber 10. The gas introduction unit includes a shower head 13. The substrate support unit 11 is located inside the plasma processing chamber 10. The shower head 13 is located above the substrate support unit 11. In one embodiment, the shower head 13 constitutes at least a portion of the ceiling of the plasma processing chamber 10. The plasma processing chamber 10 has a plasma processing space 10s defined by the shower head 13, the side walls 10a of the plasma processing chamber 10, and the substrate support unit 11. The plasma processing chamber 10 is grounded. The shower head 13 and the substrate support unit 11 are electrically insulated from the housing of the plasma processing chamber 10.

[0014] The substrate support portion 11 includes a main body portion 111 and a ring assembly 112. The main body portion 111 has a central region 111a for supporting the substrate W and an annular region 111b for supporting the ring assembly 112. A wafer is an example of a substrate W. The annular region 111b of the main body portion 111 surrounds the central region 111a of the main body portion 111 in a plan view. The substrate W is placed on the central region 111a of the main body portion 111, and the ring assembly 112 is placed on the annular region 111b of the main body portion 111 so as to surround the substrate W on the central region 111a of the main body portion 111. Therefore, the central region 111a is also called the substrate support surface for supporting the substrate W, and the annular region 111b is also called the ring support surface for supporting the ring assembly 112.

[0015] In one embodiment, the main body 111 includes a base 1110 and an electrostatic chuck 1111. The base 1110 includes a conductive member. The conductive member of the base 1110 can function as a lower electrode. The electrostatic chuck 1111 is placed on the base 1110. The electrostatic chuck 1111 includes a ceramic member 1111a and an electrostatic chuck electrode 1111b placed within the ceramic member 1111a. The electrostatic chuck electrode 1111b is also called a clamping electrode. In one embodiment, the electrostatic chuck electrode 1111b is electrically connected or coupled to a chuck power supply. The chuck power supply may be a DC power supply or an AC power supply. The ceramic member 1111a has a central region 111a. In one embodiment, the ceramic member 1111a also has an annular region 111b. Furthermore, other members surrounding the electrostatic chuck 1111, such as an annular electrostatic chuck or an annular insulating member, may have an annular region 111b. In this case, the ring assembly 112 may be placed on the annular electrostatic chuck or the annular insulating member, or it may be placed on both the electrostatic chuck 1111 and the annular insulating member. In addition, at least one bias electrode, which is electrically connected or coupled to the power supply 31 and / or power supply 32 described later, may be placed inside the ceramic member 1111a. In this case, at least one bias electrode functions as a lower electrode. Also, the conductive member of the base 1110 and the bias electrode inside the ceramic member 1111a may function as multiple lower electrodes. In one embodiment, the first voltage generation unit 32a, which functions as a voltage pulse generation unit described later, is electrically connected or coupled to the bias electrode inside the ceramic member 1111a, and the first RF generation unit 31a, described later, is electrically connected or coupled to the conductive member of the base 1110. Furthermore, the electrostatic chuck electrode 1111b may function as a lower electrode. Therefore, the substrate support portion 11 includes at least one lower electrode.

[0016] The ring assembly 112 includes one or more annular members. In one embodiment, the one or more annular members include one or more edge rings and at least one covering ring. The edge rings are formed of a conductive or insulating material, and the covering rings are formed of an insulating material.

[0017] The substrate support section 11 may also include a temperature control module configured to adjust at least one of the electrostatic chuck 1111, the ring assembly 112, and the substrate to a target temperature. The temperature control module may include a heater, a heat transfer medium, a flow path 1110a, or a combination thereof. A heat transfer fluid such as brine or gas flows through the flow path 1110a. In one embodiment, the flow path 1110a is formed within the base 1110, and one or more heaters are arranged within the ceramic member 1111a of the electrostatic chuck 1111. The substrate support section 11 may also include a heat transfer gas supply section configured to supply heat transfer gas to the gap between the back surface of the substrate W and the central region 111a.

[0018] 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 a plurality of gas inlet ports 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 through the plurality of gas inlet ports 13c. The showerhead 13 also includes at least one 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 side wall 10a.

[0019] The gas supply unit 20 may include at least one gas source 21 and at least one flow controller 22. In one embodiment, the gas supply unit 20 is configured to supply at least one processing gas to the shower head 13 from a corresponding gas source 21 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 at least one flow modulation device that modulates or pulses the flow rate of at least one processing gas.

[0020] The power supply system 30 includes a power supply 31 that is electrically connected to or coupled to the plasma processing chamber 10. In one embodiment, the power supply 31 is electrically connected to or coupled to the plasma processing chamber 10 via at least one impedance matcher. The impedance matcher may be a mechanically controlled matcher or an electronically controlled matcher. The power supply 31 is configured to supply at least one RF signal (RF power) to at least one lower electrode and / or at least one upper electrode. This generates plasma from at least one processing gas supplied to the plasma processing space 10s. Therefore, the power supply 31 can function as at least part of the plasma generation unit 12. In addition, by supplying a bias RF signal to at least one lower electrode, a bias potential is generated on the substrate W, and ionic components in the formed plasma can be drawn into the substrate W.

[0021] The power supply 31 includes a first RF generation unit 31a and a second RF generation unit 31b. The first RF generation unit 31a is electrically connected or coupled to at least one lower electrode and / or at least one upper electrode and is configured to generate a source RF signal (source RF power) to generate plasma in the plasma processing space 10s. In one embodiment, the first RF generation unit 31a is electrically connected or coupled to at least one lower electrode and / or at least one upper electrode via at least one impedance matcher. In one embodiment, the source RF signal has a frequency in the range of 10 MHz to 150 MHz. In one embodiment, the first RF generation unit 31a may be configured to generate a plurality of source RF signals having different frequencies. One or more generated source RF signals are supplied to at least one lower electrode and / or at least one upper electrode.

[0022] The second RF generation unit 31b is electrically connected to or coupled to at least one lower electrode and is configured to generate a bias RF signal (bias RF power). In one embodiment, the second RF generation unit 31b is electrically connected to or coupled to at least one lower electrode via at least one impedance matcher. When the first RF generation unit 31a is electrically connected to or coupled to a lower electrode, the second RF generation unit 31b may be electrically connected to or coupled to the same lower electrode, or it may be electrically connected to or coupled to a different lower electrode. The frequency of the bias RF signal may be the same as or different from the frequency of the source RF signal. In one embodiment, the bias RF signal has a frequency lower than the frequency of the source RF signal. In one embodiment, the bias RF signal has a frequency in the range of 100 kHz to 60 MHz. In one embodiment, the second RF generation unit 31b may be configured to generate a plurality of bias RF signals having different frequencies. The generated one or more bias RF signals are supplied to at least one lower electrode. In various embodiments, at least one of the source RF signal and the bias RF signal may be pulsed.

[0023] The power supply system 30 may also include a power supply 32 that is electrically connected to or coupled to the plasma processing chamber 10. The power supply 32 includes a first voltage generation unit 32a and a second voltage generation unit 32b. In one embodiment, the first voltage generation unit 32a is electrically connected to or coupled to at least one lower electrode and is configured to generate a first voltage signal. The generated first voltage signal is applied to at least one lower electrode. In one embodiment, the second voltage generation unit 32b is electrically connected to or coupled to at least one upper electrode and is configured to generate a second voltage signal. The generated second voltage signal is applied to at least one upper electrode.

[0024] In various embodiments, the first and / or second voltage signals may be pulsed. In this case, the first voltage generation unit 32a and / or the second voltage generation unit 32b function as voltage pulse generation units configured to generate a sequence of voltage pulses. Thus, the sequence of voltage pulses is applied to at least one lower electrode and / or at least one upper electrode. In one embodiment, the sequence of voltage pulses has a plurality of cycles, each cycle including a burst of voltage pulses in a first period and a constant reference voltage in a second period. That is, in the sequence of voltage pulses, the burst of voltage pulses is repeated. The absolute value of the voltage level of the voltage pulse is greater than the absolute value of the voltage level of the reference voltage. The voltage pulse may have an arbitrary waveform having a rectangle, trapezoid, triangle, or a combination thereof, and the arbitrary waveform may change over time. The voltage pulse may have positive polarity or negative polarity. The sequence of voltage pulses may also include one or more positive voltage pulses and one or more negative voltage pulses within one cycle. The first and second voltage generation units 32a and 32b may be provided in addition to the power supply 31, and the first voltage generation unit 32a may be provided in place of the second RF generation unit 31b.

[0025] The exhaust system 40 may be connected to, for example, a gas outlet 10e located 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.

[0026] As described above, the plasma processing apparatus 1 comprises a plasma processing chamber 10, a substrate support section 11, at least one lower electrode, a first RF generation section 31a, a first voltage generation section 32a, and a control section 2. For example, at least one of the base 1110, at least one bias electrode, and electrostatic chuck electrode 1111b is an example of a lower electrode disposed within the substrate support section 11. The first RF generation section 31a is an example of an RF generator. The first voltage generation section 32a is an example of a voltage pulse generator.

[0027] Figure 3 shows the configuration of a gas supply line in a plasma processing apparatus according to one exemplary embodiment. The plasma processing apparatus 1 further comprises at least one processing gas supply line 50, at least one main gas supply line 60, and at least one additive gas supply line 70. The at least one processing gas supply line 50, at least one main gas supply line 60, and at least one additive gas supply line 70 may be part of the gas supply unit 20.

[0028] At least one processing gas supply line 50 is connected to the plasma processing chamber 10. A flow regulator may be attached to at least one processing gas supply line 50. In one embodiment, at least one processing gas supply line 50 may include a plurality of processing gas supply lines 50, including processing gas supply line 51 (first processing gas supply line), processing gas supply line 52 (third processing gas supply line), and processing gas supply line 53 (second processing gas supply line). In one example, a flow regulator is attached to each of the plurality of processing gas supply lines 50.

[0029] The processing gas supply line 51 is connected to a plurality of gas inlets 13d (a plurality of first gas inlets). The plurality of gas inlets 13d are located in the central region of the top of the plasma processing chamber 10. The processing gas supply line 53 is connected to a plurality of gas inlets 13f (a plurality of second gas inlets). The plurality of gas inlets 13f are located in the outer edge region of the top of the plasma processing chamber 10. The processing gas supply line 52 is connected to a plurality of gas inlets 13e (a plurality of third gas inlets). The plurality of gas inlets 13e are located in the intermediate region between the central region and the outer edge region of the top of the plasma processing chamber 10. The plurality of gas inlets 13d, the plurality of gas inlets 13f, and the plurality of gas inlets 13e are included in the plurality of gas inlets 13c.

[0030] In one example, the processing gas supply line 51 and the multiple gas inlets 13d may be connected via a gas diffusion chamber 13g. The gas diffusion chamber 13g may be formed in the central region of the top. The processing gas supply line 53 and the multiple gas inlets 13f may be connected via a gas diffusion chamber 13k. The gas diffusion chamber 13k is formed in the outer edge region of the top. The processing gas supply line 52 and the multiple gas inlets 13e may be connected via a gas diffusion chamber 13h. The gas diffusion chamber 13h is formed in the intermediate region of the top. The gas diffusion chambers 13g, 13k, and 13h are contained within at least one gas diffusion chamber 13b.

[0031] A processing gas is supplied to the plasma processing space 10s via at least one processing gas supply line 50. The processing gas includes a main gas and an additive gas. In one example, the amount of processing gas supplied from the plurality of gas inlets 13f may be greater than the amount of processing gas supplied from the plurality of gas inlets 13e. In another example, the amount of processing gas supplied from the plurality of gas inlets 13e may be greater than the amount of processing gas supplied from the plurality of gas inlets 13d. In yet another example, the amount of processing gas supplied from the plurality of gas inlets 13e may be greater than either the amount of processing gas supplied from the plurality of gas inlets 13f or the amount of processing gas supplied from the plurality of gas inlets 13d.

[0032] At least one main gas supply line 60 is connected to at least one processing gas supply line 50. In one embodiment, the plasma processing apparatus 1 may further include a flow splitter 80. The flow splitter 80 connects at least one main gas supply line 60 to a plurality of processing gas supply lines 50. The flow splitter 80 is configured to distribute the main gas supplied from at least one main gas supply line 60 to each of the plurality of processing gas supply lines 50. A flow regulator may be attached to at least one main gas supply line 60.

[0033] At least one type of main gas is supplied to at least one processing gas supply line 50 via at least one main gas supply line 60. For example, a noble gas and / or a fluorocarbon gas is supplied via at least one main gas supply line 60. In one example, the noble gas includes at least one of He gas, Ne gas, and Ar gas. In one example, the fluorocarbon gas is CF ４ This includes gas. At least one main gas supply line 60 may be fitted with at least one flow regulator. For example, at least one main gas supply line 60 may include multiple main gas supply lines 60 connected to multiple main gas sources. Each of the multiple main gas supply lines 60 may be fitted with a flow regulator.

[0034] At least one additive gas supply line 70 is connected to at least one processing gas supply line 50. A flow regulator may be installed on at least one additive gas supply line 70. At least one type of additive gas is supplied to at least one processing gas supply line 50 via at least one additive gas supply line 70. For example, fluorocarbon gas, hydrofluorocarbon gas, and / or oxygen gas are supplied via at least one additive gas supply line 70. The fluorocarbon gas supplied via at least one additive gas supply line 70 may be a different fluorocarbon gas from the fluorocarbon gas supplied via at least one main gas supply line. In one example, the fluorocarbon gas is C ４ F ６ Gas, and C ４ F ８ It contains at least one of the following gases. Hydrofluorocarbon gases include CHF. ３ Gas, and CH ３ It contains at least one of the F gases.

[0035] In one embodiment, at least one additive gas supply line 70 includes an additive gas supply line 71 (first additive gas supply line), an additive gas supply line 72 (third additive gas supply line), and an additive gas supply line 73 (second additive gas supply line). Additive gas supply line 71 is connected to the processing gas supply line 51. Additive gas supply line 72 is connected to the processing gas supply line 52. Additive gas supply line 73 is connected to the processing gas supply line 53. At least one additive gas supply line 70 is directly connected to at least one processing gas supply line 50. Additive gas supply lines 71, 72, and 73 are connected to the processing gas supply lines 51, 52, and 53, respectively, without going through the flow splitter 80.

[0036] The first RF generation unit 31a (an example of an RF generator) is configured to supply a source RF signal for generating plasma in the plasma processing chamber 10. The first voltage generation unit 32a (an example of a voltage pulse generator) is electrically connected to the base 1110, at least one bias electrode, and at least one of the electrostatic chuck electrodes 1111b (an example of a lower electrode). The first voltage generation unit 32a is configured to generate a pulsed voltage signal. The bias RF signal described above is an example of a pulsed voltage signal. The pulsed voltage signal includes a sequence of voltage pulses. The waveform of the voltage pulses can be a square wave, a triangular wave, or any waveform. The polarity of the voltage pulses is set so that a potential difference is created between the substrate W and the plasma, thereby attracting ions from the plasma to the substrate W. In one example, the polarity of the voltage pulses may be set to a negative voltage with respect to a reference voltage (e.g., 0V). Hereinafter, the maximum potential difference in the voltage pulses will be described as the voltage level of the pulsed voltage signal.

[0037] Hereinafter, referring to FIGS. 4 and 5, each step executed by the control unit 2 and an etching method (hereinafter referred to as "Method MT") according to one exemplary embodiment will be described. FIG. 4 is a timing chart of a source RF signal and a pulsed voltage signal according to one exemplary embodiment. FIG. 5 is a flowchart of an etching method according to one exemplary embodiment. The control unit 2 controls the first RF generation unit 31a and the first voltage generation unit 32a in a state where the substrate W including a plurality of alternately stacked silicon oxide films and a plurality of silicon nitride films is placed on the substrate support unit 11, and is configured to execute step (a), step (b), step (c), and step (d). Note that the plasma processing apparatus 1 may include a control unit different from the control unit 2 for executing step (a), step (b), step (c), and step (d).

[0038] Method MT includes step S0, step S1, step S2, and step S3. In step S0, the substrate W is provided. In step (a), the substrate W is placed on the substrate support unit 11. The substrate W includes a plurality of alternately stacked silicon oxide films and a plurality of silicon nitride films. Step S0 corresponds to step (a).

[0039] The period Pa shown in FIG. 4 is the period during which step (b) is executed, and the period Pb is the period during which step (c) is executed. HF shown in FIG. 4 shows the timing chart of the source RF signal supplied from the first RF generation unit 31a in each of step (b) and step (c). EB shown in FIG. 4 shows the timing chart of the pulsed voltage signal supplied from the first voltage generation unit 32a in each of step (b) and step (c).

[0040] In step (b), one of the plurality of silicon oxide films is etched by the first plasma and the first pulsed voltage signal. In step (b), the first plasma is generated from the first processing gas. The first pulsed voltage signal is applied from the first voltage generator 32a to the lower electrode and includes a sequence of first voltage pulses having a first voltage level EB1. The first processing gas is supplied into the plasma processing chamber 10 from at least one processing gas supply line 50. The first processing gas includes a first main gas and a first additive gas. The first main gas is supplied via at least one main gas supply line 60. The first additive gas is supplied via at least one additive gas supply line 70.

[0041] Step S1 corresponds to step (b). Step S1 is a step of etching one of the plurality of silicon oxide films by the first plasma and the first pulsed voltage signal. In step S1, the first plasma is generated from the first processing gas. The first pulsed voltage signal includes a sequence of first voltage pulses having a first voltage level EB1. The first processing gas includes a first main gas and a first additive gas.

[0042] Step (c) is a step of etching one of the plurality of silicon nitride films by the second plasma and the second pulsed voltage signal. In step (c), the second plasma is generated from the second processing gas. The second pulsed voltage signal is applied from the first voltage generator 32a to the lower electrode and includes a sequence of second voltage pulses having a second voltage level EB2. The second processing gas is supplied into the plasma processing chamber 10 from at least one processing gas supply line 50. The second main gas is supplied via at least one main gas supply line 60. The second additive gas is supplied via at least one additive gas supply line 70. The second voltage level EB2 is smaller than the first voltage level EB1. In one embodiment, the second voltage level EB2 is at most half of the first voltage level EB1.

[0043] Step S2 corresponds to step (c). Step S2 is a step of etching one silicon nitride film out of a plurality of silicon nitride films using a second plasma and a second pulsed voltage signal. In step S2, the second plasma is generated from a second processing gas. The second pulsed voltage signal includes a sequence of second voltage pulses having a second voltage level EB2. The second processing gas includes a second main gas and a second additive gas. The second voltage level EB2 is less than the first voltage level EB1.

[0044] In process (d), processes (b) and (c) are repeated alternately. For example, as shown in the example in Figure 4, it may be determined whether or not the repetition continues. If the repetition continues (Yes), processes (b) and (c) are repeated. If the repetition does not continue (No), the process terminates. Process S3 corresponds to process (d). In process S3, processes S1 and S2 are repeated alternately. In process S3, it may be determined whether or not the repetition continues.

[0045] The first voltage level EB1 is the maximum voltage difference of the voltage pulses of the first pulsed voltage signal. The second voltage level EB2 is the maximum voltage difference of the voltage pulses of the second pulsed voltage signal. According to the plasma processing apparatus 1, the maximum voltage difference of the voltage pulses in etching the silicon oxide film is greater than the maximum voltage difference of the voltage pulses in etching the silicon nitride film. As a result, the plasma processing apparatus 1 improves the selectivity ratio of etching one film to the other in etching alternatingly stacked silicon oxide and silicon nitride films. In other words, the plasma processing apparatus 1 improves the selectivity ratio of etching the silicon nitride film to the silicon oxide film, and the selectivity ratio of etching the silicon oxide film to the silicon nitride film.

[0046] In one embodiment, step (b) may include a plurality of first cycles in which a first period P1 and a second period P2 are alternately repeated. In each first period P1 of the plurality of first cycles, the source RF signal has a first power level H1. In each second period P2 of the plurality of first cycles, the source RF signal has a second power level H2. The second power level H2 is less than the first power level H1. In each first period P1 of the plurality of first cycles, the first pulsed voltage signal has a first sequence of voltage pulses. In each second period P2 of the plurality of first cycles, the first pulsed voltage signal has a reference voltage level.

[0047] In one embodiment, step (c) may include a plurality of second cycles in which a third period P3 and a fourth period P4 are alternately repeated. In each of the plurality of second cycles, during the third period P3, the source RF signal has a third power level H3. In each of the plurality of second cycles, during the fourth period P4, the source RF signal has a fourth power level H4, which is less than the third power level H3. In each of the plurality of second cycles, during the third period P3, the second pulsed voltage signal has a second sequence of voltage pulses. In each of the plurality of second cycles, during the fourth period P4, the second pulsed voltage signal has a reference voltage level.

[0048] In one embodiment, the control unit 2 may be configured to execute steps (b1), (b2), (c1), and (c2). Hereinafter, we will refer to the period Pa of step (b) shown in Figure 4. In step (b1), the control unit 2 is configured to control the first RF generation unit 31a to alternately repeat a first period P1 in which the power level of the source RF signal is set to a first power level H1 and the source RF signal is supplied, and a second period P2 in which the power level of the source RF signal is set to a second power level H2. The second power level H2 is smaller than the first power level H1.

[0049] In one embodiment, the control unit 2 controls the first RF generation unit 31a to supply a first source RF signal having a first power level H1 during a first period P1. In another embodiment, the control unit 2 controls the first RF generation unit 31a to supply a second source RF signal having a second power level H2 during a second period P2. The second power level H2 may be a power level that can maintain the first plasma. For example, the second power level H2 may be 1 / 10 or less of the first power level H1. The second power level H2 may be zero. In other words, the control unit 2 may control the first RF generation unit 31a to stop supplying the source RF signal during the second period. In the example shown in Figure 4, the first period P1 and the second period P2 are shown by the repetition of H and L in HF, or by the repetition of ON and OFF of the source RF signal.

[0050] In (b2), the control unit 2 is configured to control the first voltage generation unit 32a so as to apply a first pulsed voltage signal to the lower electrode during the first period P1 and to stop applying the first pulsed voltage signal to the lower electrode during the second period P2. In Figure 4, the application of the first pulsed voltage signal and the stopping of the application of the first pulsed voltage signal are shown by the repetition of ON and OFF, or H and L, in the voltage pulse sequence. During the first period P1, when the voltage pulse sequence is ON, an H voltage is applied from among the voltage pulses having a first voltage level EB1. During the second period P2, when the voltage pulse sequence is OFF, the application of the H voltage from among the voltage pulses having a first voltage level EB1 is stopped. During the second period P2, an L voltage may be applied from among the voltage pulses having a first voltage level EB1. The L voltage may have a reference voltage level.

[0051] Hereinafter, we will refer to the period Pb of step (c) shown in Figure 4. In (c1), in step (c), the control unit 2 is configured to control the first RF generation unit 31a to alternately repeat a third period P3 in which the power level of the source RF signal is set to a third power level H3 and the source RF signal is supplied, and a fourth period P4 in which the power level of the source RF signal is set to a fourth power level H4. The fourth power level H4 is smaller than the third power level H3.

[0052] In one embodiment, the control unit 2 controls the first RF generation unit 31a to supply a third source RF signal having a third power level H3 during a third period P3. In another embodiment, the control unit 2 controls the first RF generation unit 31a to supply a fourth source RF signal having a fourth power level H4 during a fourth period P4. The fourth power level H4 may be a power level that can maintain the second plasma. For example, the fourth power level H4 may be 1 / 8 or less of the third power level H3. The fourth power level H4 may be zero. In other words, the control unit 2 may control the first RF generation unit 31a to stop supplying the source RF signal during the fourth period. In the example shown in Figure 4, the third period P3 and the fourth period P4 are shown by the repetition of H and L in HF, and the repetition of ON and OFF of the source RF signal.

[0053] In (c2), the control unit 2 is configured to control the first voltage generation unit 32a so as to apply a second pulsed voltage signal to the lower electrode during the third period P3 and to stop applying the second pulsed voltage signal to the lower electrode during the fourth period P4. In Figure 4, the application of the second pulsed voltage signal and the stopping of the application of the second pulsed voltage signal are shown by the repetition of ON and OFF, or H and L, in the voltage pulse sequence. During the third period P3, when the voltage pulse sequence is ON, an H voltage is applied from among the voltage pulses having the second voltage level EB2. During the fourth period P4, when the voltage pulse sequence is OFF, the application of the H voltage from among the voltage pulses having the second voltage level EB2 is stopped. During the fourth period P4, an L voltage may be applied from among the voltage pulses having the second voltage level EB2. The L voltage may have a reference voltage level. According to steps (b1), (b2), (c1), and (c2), the plasma processing apparatus 1 can further improve the etching selectivity ratio for the silicon oxide film and the silicon nitride film, respectively.

[0054] In one embodiment, the duty cycle D1 of the first period P1 with respect to a period in which the first period P1 and the second period P2 alternately repeat may be smaller than the duty cycle D3 of the third period with respect to a period in which the third period P3 and the fourth period P4 alternately repeat. The duty cycle D1 is given by the following (Equation 1). The duty cycle D3 is given by the following (Equation 2). Duty cycle D1 = first period P1 / (first period P1 + second period P2) (Equation 1) Duty cycle D3 = third period P3 / (third period P3 + fourth period P4) (Equation 2) For example, the duty cycle D1 may be 4 / 5 or less of the duty cycle D3.

[0055] In one embodiment, the first power level may be greater than the third power level. In one example, the first power level may be 1.2 times or more the third power level. In one embodiment, the second power level and the fourth power level may be equal.

[0056] In one embodiment, the period Pa of step (b) may be 25 seconds or less. In one example, the period Pa of step (b) is 5 seconds or more and 25 seconds or less. The period Pb of step (c) may be 25 seconds or less. In one example, the period of step (c) is 7 seconds or more and 25 seconds or less. In one embodiment, the period Pa of step (b) may be shorter than the period Pb of step (c). In one example, the period Pa of step (b) may be 0.75 times or less of the period Pb of step (c).

[0057] In one embodiment, the first main gas and the second main gas may be the same gas. For example, each of the first main gas and the second main gas contains a fluorocarbon. In one example, the first main gas and the second main gas are CF ４ gas. The first main gas and the second main gas may further contain the same gas. For example, the first main gas and the second main gas may further contain a noble gas. In one example, each of the first main gas and the second main gas may further contain Ar gas.

[0058] In one embodiment, the first additive gas and the second additive gas may contain different gases from each other. For example, the first additive gas contains a fluorocarbon. In one example, the first additive gas is C ４ F ６ gas and / or C ４ F ８ gas. For example, the second additive gas contains a hydrofluorocarbon. In one example, the second additive gas is CHF ３ gas and / or CH ３ F gas.

[0059] In one embodiment, the first additive gas and the second additive gas may further contain gases of the same component. For example, each of the first and second additive gases may further contain oxygen gas. In step (b), a first plasma may be generated from a first processing gas containing a first main gas, a first additive gas, and a third additive gas. In step (c), a second plasma may be generated from a second processing gas containing a second main gas, a second additive gas, and a third additive gas. For example, the third additive gas is oxygen gas.

[0060] In one embodiment, the first RF generation unit 31a may adjust the frequency of the source RF signal to match the load-side impedance of the first RF generation unit 31a. For example, the first RF generation unit 31a may adjust the frequency of the source RF signal (fundamental oscillation frequency) to increase the degree of matching of the load-side impedance with respect to the output impedance or characteristic impedance (50 Ω in one example) of the first RF generation unit 31a. The frequency of the source RF signal may be changed at time intervals shorter than the waveform period (shortest period) of the pulsed voltage signal. In this case, the impedance is matched more quickly than the matching by at least one impedance matcher described above.

[0061] Although various exemplary embodiments have been described above, the invention is not limited to the exemplary embodiments described above, and various additions, omissions, substitutions, and modifications may be made. Furthermore, it is possible to combine elements from different embodiments to form other embodiments.

[0062] The plasma processing apparatus 1 may perform step (b) first after step (a). The plasma processing apparatus 1 may perform step (c) first after step (a). In method MT, step S2 may be performed after step S0. In method MT, step S1 may be performed after step S0. Method MT may be performed by the plasma processing apparatus 1.

[0063] Herein, various exemplary embodiments included in this disclosure are described in [E1] to [E18] below.

[0064] [E1] A plasma processing chamber; a substrate support portion disposed within the plasma processing chamber; a lower electrode disposed within the substrate support portion; at least one processing gas supply line connected to the plasma processing chamber; at least one main gas supply line connected to the at least one processing gas supply line; at least one additive gas supply line connected to the at least one processing gas supply line; an RF generator configured to supply a source RF signal for generating plasma in the plasma processing chamber; a voltage pulse generator electrically connected to the lower electrode; and a control unit, wherein the control unit controls the RF generator and the voltage pulse generator to perform the steps of (a) placing a substrate including a plurality of alternately stacked silicon oxide films and a plurality of silicon nitride films on the substrate support portion, (b) A step of etching one of the plurality of silicon oxide films with a first plasma and a first pulsed voltage signal, wherein the first plasma is generated from a first processing gas supplied into the plasma processing chamber from the at least one processing gas supply line, the first processing gas includes a first main gas supplied via the at least one main gas supply line and a first additive gas supplied via the at least one additive gas supply line, and the first pulsed voltage signal includes a sequence of first voltage pulses applied from the voltage pulse generator to the lower electrode and having a first voltage level,(c) Etc. E2 E2 E3 E3 E4 E5 [E4] The plasma processing apparatus according to any one of E1 to 3, wherein the first additive gas and the second additive gas contain different gases. [E5] The plasma processing apparatus according to any one of E1 to 4, wherein the first additive gas contains a fluorocarbon. [E6] The plasma processing apparatus according to any one of E1 to 5, wherein the second additive gas contains a hydrofluorocarbon. [E7] The plasma processing apparatus according to any one of E1 to 6, wherein the first additive gas and the second additive gas further contain a gas of the same component. [E8] The plasma processing apparatus according to E7, wherein the gas of the same component contains oxygen. [E9] The plasma processing apparatus according to any one of E1 to 8, wherein the at least one processing gas supply line includes a plurality of processing gas supply lines, and the plasma processing apparatus further comprises a flow splitter connected between the at least one main gas supply line and the plurality of processing gas supply lines. [E10] The plurality of processing gas supply lines include a first processing gas supply line, a second processing gas supply line, and a third processing gas supply line,The plasma processing apparatus according to E9, wherein the first processing gas supply line is connected to a plurality of first gas inlets located in the central region of the top of the plasma processing chamber, the second processing gas supply line is connected to a plurality of second gas inlets located in the outer edge region of the top, and the third processing gas supply line is connected to a plurality of third gas inlets located in an intermediate region between the central region and the outer edge region of the top. [E11] The plasma processing apparatus according to E10, wherein the at least one additive gas supply line includes a first additive gas supply line connected to the first processing gas supply line, a second additive gas supply line connected to the second processing gas supply line, and a third additive gas supply line connected to the third processing gas supply line. [E12] The plasma processing apparatus according to any one of E1 to E11, wherein the source RF signal has a first power level in the first period of each of a plurality of first cycles and a second power level smaller than the first power level in the second period of each of the plurality of first cycles, and the first pulsed voltage signal has a sequence of the first voltage pulses in the first period and a reference voltage level in the second period, and the plasma processing apparatus according to any one of E1 to E11, wherein the source RF signal has a third power level in the third period of each of a plurality of second cycles and a fourth power level smaller than the third power level in the fourth period of each of the plurality of second cycles, and the second pulsed voltage signal has a sequence of the second voltage pulses in the third period and the reference voltage level in the fourth period. [E13] The plasma apparatus according to E12, wherein the duty cycle of the first period with respect to a period in which the first period and the second period alternate is smaller than the duty cycle of the third period with respect to a period in which the third period and the fourth period alternate. [E14] The plasma apparatus according to E12 or 13, wherein the first power level is greater than the third power level. [E15] The plasma apparatus according to any one of E12 to 14, wherein the second power level and the fourth power level are equal. [E16] The period of (b) is 25 seconds or less.The plasma processing apparatus according to any one of E1 to E15, wherein the period in (c) is 25 seconds or less. [E17] The plasma processing apparatus according to any one of E1 to E16, wherein the period in (b) is shorter than the period in (c). [E18] An etching method comprising: (a) providing a substrate including a plurality of alternately stacked silicon oxide films and a plurality of silicon nitride films; (b) etching one of the plurality of silicon oxide films with a first plasma and a first pulsed voltage signal, wherein the first plasma is generated from a first processing gas including a first main gas and a first additive gas, and the first pulsed voltage signal includes a sequence of first voltage pulses having a first voltage level; (c) etching one of the plurality of silicon nitride films with a second plasma and a second pulsed voltage signal, wherein the second plasma is generated from a second processing gas including a second main gas and a second additive gas, and the second pulsed voltage signal includes a sequence of second voltage pulses having a second voltage level smaller than the first voltage level; and (d) alternatingly repeating (b) and (c).

[0065] The etching method for E18 may be carried out by the plasma processing apparatus described in any one of the items E1 to E17.

[0066] From the above description, it will be understood that the various embodiments of this disclosure are described herein for illustrative purposes and can be modified in various ways without departing from the scope and spirit of this disclosure. Accordingly, the various embodiments disclosed herein are not intended to limit the scope and spirit, and the true scope and spirit are shown by the appended claims.

[0067] 1...Plasma processing apparatus, 2...Control unit, 10...Plasma processing chamber, 11...Substrate support unit, 13c...Gas inlet, 13d...Gas inlet (multiple first gas inlets), 13e...Gas inlet (multiple third gas inlets), 13f...Gas inlet (multiple second gas inlets), 50...Processing gas supply line, 51...Processing gas supply line (first processing gas supply line), 52...Processing gas supply line (third processing gas supply line), 53...Processing gas supply line (second processing gas supply line), 60...Main gas supply line, 70...Additive gas supply Supply line, 71... Additive gas supply line (first additive gas supply line), 72... Additive gas supply line (third additive gas supply line), 73... Additive gas supply line (second additive gas supply line), 80... Flow splitter, D1, D3... Duty cycle, EB1... First voltage level, EB2... Second voltage level, H1... First power level, H2... Second power level, H3... Third power level, H4... Fourth power level, P1... First period, P2... Second period, P3... Third period, P4... Fourth period, Pa, Pb... Period, W... Substrate.

Claims

1. A plasma processing chamber; a substrate support portion disposed within the plasma processing chamber; a lower electrode disposed within the substrate support portion; at least one processing gas supply line connected to the plasma processing chamber; at least one main gas supply line connected to the at least one processing gas supply line; at least one additive gas supply line connected to the at least one processing gas supply line; an RF generator configured to supply a source RF signal for generating plasma within the plasma processing chamber; a voltage pulse generator electrically connected to the lower electrode; and a control unit, wherein the control unit controls the RF generator and the voltage pulse generator to perform the steps of (a) placing a substrate including a plurality of alternately stacked silicon oxide films and a plurality of silicon nitride films on the substrate support portion, (b) A step of etching one of the plurality of silicon oxide films with a first plasma and a first pulsed voltage signal, wherein the first plasma is generated from a first processing gas supplied into the plasma processing chamber from the at least one processing gas supply line, the first processing gas includes a first main gas supplied via the at least one main gas supply line and a first additive gas supplied via the at least one additive gas supply line, and the first pulsed voltage signal includes a sequence of first voltage pulses applied from the voltage pulse generator to the lower electrode and having a first voltage level, (c) A step of etching one of the plurality of silicon nitride films with a second plasma and a second pulsed voltage signal, wherein the second plasma is generated from a second processing gas supplied into the plasma processing chamber from the at least one processing gas supply line, the second processing gas includes a second main gas supplied via the at least one main gas supply line and a second additive gas supplied via the at least one additive gas supply line, and the second pulsed voltage signal includes a sequence of second voltage pulses applied from the voltage pulse generator to the lower electrode and having a second voltage level smaller than the first voltage level,(d) A plasma processing apparatus configured to perform the steps of (b) and (c) being repeated alternately.

2. The plasma processing apparatus according to claim 1, wherein the first main gas and the second main gas are the same gas.

3. The plasma processing apparatus according to claim 2, wherein each of the first main gas and the second main gas contains fluorocarbon.

4. The plasma processing apparatus according to claim 1, wherein the first additive gas and the second additive gas contain different gases.

5. The plasma processing apparatus according to claim 4, wherein the first additive gas contains a fluorocarbon.

6. The plasma processing apparatus according to claim 4, wherein the second additive gas contains hydrofluorocarbon.

7. The plasma processing apparatus according to any one of claims 4 to 6, wherein the first additive gas and the second additive gas further comprise gases having the same components.

8. The plasma processing apparatus according to claim 7, wherein the gas having the same components contains oxygen.

9. The plasma apparatus according to claim 1, wherein the at least one processing gas supply line comprises a plurality of processing gas supply lines, and the plasma apparatus further comprises a flow splitter connected between the at least one main gas supply line and the plurality of processing gas supply lines.

10. The plasma processing apparatus according to claim 9, wherein the plurality of processing gas supply lines include a first processing gas supply line, a second processing gas supply line, and a third processing gas supply line, the first processing gas supply line being connected to a plurality of first gas inlets located in the central region of the top of the plasma processing chamber, the second processing gas supply line being connected to a plurality of second gas inlets located in the outer edge region of the top, and the third processing gas supply line being connected to a plurality of third gas inlets located in an intermediate region between the central region and the outer edge region of the top.

11. The plasma processing apparatus according to claim 10, wherein the at least one additive gas supply line includes a first additive gas supply line connected to the first processing gas supply line, a second additive gas supply line connected to the second processing gas supply line, and a third additive gas supply line connected to the third processing gas supply line.

12. The plasma processing apparatus according to any one of claims 1 to 6, 9 to 11, wherein the source RF signal has a first power level in the first period of each of a plurality of first cycles and a second power level smaller than the first power level in the second period of each of the plurality of first cycles, and the first pulsed voltage signal has a sequence of the first voltage pulses in the first period and a reference voltage level in the second period, and the plasma processing apparatus according to any one of claims 1 to 6, 9 to 11, wherein the source RF signal has a third power level in the third period of each of a plurality of second cycles and a fourth power level smaller than the third power level in the fourth period of each of the plurality of second cycles, and the second pulsed voltage signal has a sequence of the second voltage pulses in the third period and the reference voltage level in the fourth period.

13. The plasma processing apparatus according to claim 12, wherein the duty cycle of the first period with respect to a period in which the first period and the second period alternately repeat is smaller than the duty cycle of the third period with respect to a period in which the third period and the fourth period alternately repeat.

14. The plasma processing apparatus according to claim 12, wherein the first power level is greater than the third power level.

15. The plasma apparatus according to claim 12, wherein the second power level and the fourth power level are equal.

16. The plasma processing apparatus according to any one of claims 1 to 6, 9 to 11, wherein the period in (b) is 25 seconds or less, and the period in (c) is 25 seconds or less.

17. The plasma processing apparatus according to any one of claims 1 to 6, 9 to 11, wherein the period in (b) is shorter than the period in (c).

18. An etching method comprising: (a) providing a substrate comprising a plurality of silicon oxide films and a plurality of silicon nitride films stacked alternately; (b) etching one of the plurality of silicon oxide films with a first plasma and a first pulsed voltage signal, wherein the first plasma is generated from a first processing gas comprising a first main gas and a first additive gas, and the first pulsed voltage signal comprises a sequence of first voltage pulses having a first voltage level; (c) etching one of the plurality of silicon nitride films with a second plasma and a second pulsed voltage signal, wherein the second plasma is generated from a second processing gas comprising a second main gas and a second additive gas, and the second pulsed voltage signal comprises a sequence of second voltage pulses having a second voltage level smaller than the first voltage level; and (d) alternatingly repeating (b) and (c).

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