Etching method and plasma treatment device

Abstract

The present invention provides an etching technique that enables improvement of a selection ratio. An etching method according to the present disclosure is executed in a plasma treatment device provided with a chamber, and comprises: (a) a step for preparing a substrate on a substrate support part disposed in a chamber, the substrate including a first film containing silicon and nitrogen and including a second film containing silicon and oxygen; (b) a step for supplying the chamber with a treatment gas including a metal-containing gas; and (c) a step for selectively etching the second film with respect to the first film while (b) is being executed, said step including (c1) setting the power for a source RF signal having a first frequency to a first power and generating plasma, and supplying the substrate support part with a first bias signal having a frequency, which does not substantially contribute to the generation of plasma, by using a second power, and (c2) supplying, after (c1), the substrate support part with the first bias signal by using a third power higher than the second power.

Description

Etching method and plasma processing apparatus

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

[0002] As a technique for selectively etching a first region made of silicon oxide relative to a second region made of silicon nitride, there is an etching method described in Japanese Patent Laid-Open No. 2003-222299.

[0003] Japanese Patent Application Laid-Open No. 2016-157793

[0004] The present disclosure provides an etching technique that can improve the selectivity.

[0005] In one exemplary embodiment of the present disclosure, there is provided an etching method performed in a plasma processing apparatus including a chamber, the etching method including: (a) preparing a substrate disposed in the chamber on a substrate support, the substrate including a first film containing silicon and nitrogen and a second film containing silicon and oxygen; (b) supplying a process gas including a metal-containing gas into the chamber; and (c) while (b) is being performed, selectively etching the second film relative to the first film, the etching method including: (c1) setting the power of a source RF signal having a first frequency to a first power to generate plasma, and supplying a first bias signal having a frequency that does not substantially contribute to plasma generation to the substrate support at a second power; and (c2) after (c1), supplying the first bias signal to the substrate support at a third power higher than the second power.

[0006] According to one exemplary embodiment of the present disclosure, an etching technique capable of improving the selectivity can be provided.

[0007] FIG. 1 is a diagram for explaining an example of the configuration of a plasma processing system. FIG. 2 is a diagram for explaining an example of the configuration of a capacitively coupled plasma processing apparatus. FIG. 3 is a flowchart of an etching method according to an exemplary embodiment. FIG. 4 is a diagram showing an example of a cross-sectional structure of a substrate W prepared in process ST1. FIG. 5 is a diagram showing an example of a cross-sectional structure of a substrate W after a portion of a silicon oxide film is etched in process ST2. FIG. 6 is a timing chart showing an example of a source RF signal HF, a bias RF signal MF, and a bias RF signal LF in process ST32. FIG. 7 is a timing chart showing an example of a source RF signal HF, a bias RF signal MF, and a bias RF signal LF in process ST32. FIG. 8 is a timing chart showing an example of a source RF signal HF, a bias RF signal MF, and a bias RF signal LF in process ST32. FIG. 9 is a timing chart showing an example of a source RF signal HF, a bias RF signal MF, and a bias RF signal LF in process ST32. 1 is a timing chart showing an example of a source RF signal HF, a bias RF signal MF, and a bias RF signal LF in process ST32. FIG. 2 is a timing chart showing an example of a source RF signal HF, a bias RF signal MF, and a bias RF signal LF in process ST32. FIG. 3 is a diagram showing an example of a cross-sectional structure of a substrate W processed in process ST3. FIG. 4 is a diagram showing an example of a cross-sectional structure of a substrate W. FIG. 5 is a diagram showing an example of a cross-sectional structure of a substrate W processed in process ST3. FIG. 6 is a diagram showing an example of a cross-sectional structure of a substrate W processed in process ST3.

[0008] Hereinafter, each embodiment of the present disclosure will be described.

[0009] In one exemplary embodiment, an etching method is provided that is performed in a plasma processing apparatus including a chamber, the etching method including the steps of: (a) providing a substrate on a substrate support disposed in the chamber, the substrate including a first film containing silicon and nitrogen and a second film containing silicon and oxygen; (b) supplying a process gas including a metal-containing gas into the chamber; and (c) while (b) is being performed, selectively etching the second film relative to the first film, the steps including: (c1) setting a power of a source RF signal having a first frequency to a first power to generate a plasma and supplying a first bias signal having a frequency that does not substantially contribute to plasma generation to the substrate support at a second power; and (c2) after (c1), supplying the first bias signal to the substrate support at a third power higher than the second power.

[0010] In one exemplary embodiment, in (a), the substrate includes, in a planar view of the substrate, a plurality of first regions and at least one second region between the first regions, the first film is disposed in the plurality of first regions and includes a recess in the at least one second region, and the second film is disposed in the recess, and in (c), the second film is selectively etched relative to the first film to expose at least a portion of a side surface of the first film in the second region.

[0011] In one exemplary embodiment, in (a), a second film is further disposed on the first film, and the substrate includes a mask on the second film that includes a first opening, and the mask is disposed on the second film such that the first opening overlaps the recess in a planar view of the substrate; and in (c), the second film is selectively etched relative to the first film to expose a portion of the top surface of the first film in a plurality of first regions and to expose at least a portion of the side surface of the first film in the second region.

[0012] In one exemplary embodiment, in (a), the mask includes second openings having a larger opening area than the first openings, and the mask is placed on the second film so that the second openings further overlap the recesses in a planar view of the substrate, and the number of recesses that overlap with the first openings is smaller than the number of recesses that overlap with the second openings.

[0013] In one exemplary embodiment, a first film is disposed on a second film, the first film including an opening exposing a portion of the second film, and in (c), a portion of the second film is selectively etched relative to the first film in the opening to form a recess in the second film.

[0014] In one exemplary embodiment, (c) further includes: (c3) between (c1) and (c2), setting the power of the source RF signal to a fifth power equal to or less than the fourth power to generate a plasma; and supplying a first bias signal to the substrate support at a second power.

[0015] In one exemplary embodiment, (c) further includes: (c4) between (c1) and (c3), setting the power of the source RF signal to a sixth power that is lower than the first power and higher than the fourth power to generate a plasma, and supplying a first bias signal to the substrate support at a second power.

[0016] In one exemplary embodiment, the fourth power is zero power.

[0017] In one exemplary embodiment, the fourth power and the fifth power are zero power.

[0018] In one exemplary embodiment, the fifth power is lower than the fourth power and the fifth power is zero power.

[0019] In one exemplary embodiment, the second power is zero power.

[0020] In one exemplary embodiment, the first frequency is between 60 MHz and 200 MHz.

[0021] In one exemplary embodiment, the frequency of the first bias signal is between 100 kHz and 400 kHz.

[0022] In one exemplary embodiment, in (c1), a second bias RF signal having a second frequency lower than the first frequency is supplied to the substrate support at a seventh power, and in (c2), the second bias RF signal is supplied to the substrate support at an eighth power lower than the seventh power.

[0023] In one exemplary embodiment, the second frequency is between 3 MHz and 40 MHz.

[0024] In one exemplary embodiment, the metal-containing gas is a gas that includes a tungsten-containing gas or a molybdenum-containing gas.

[0025] In one exemplary embodiment, the tungsten-containing gas comprises tungsten fluoride.

[0026] In one exemplary embodiment, the process gas comprises a carbon-containing gas.

[0027] In one exemplary embodiment, the carbon-containing gas is a fluorocarbon gas.

[0028] In one exemplary embodiment, an etching method is provided that is performed in a plasma processing apparatus including a chamber, the etching method including: (a) providing a substrate on a substrate support disposed in the chamber, the substrate including a first film including at least one selected from the group consisting of SiN, SiON, SiC, SiOC, and boron nitride, and a second film including silicon and oxygen; (b) supplying a process gas including a metal-containing gas into the chamber; and (c) while (b) is being performed, selectively etching the second film relative to the first film, the etching method including: (c1) setting a power of a source RF signal having a first frequency to a first power to generate plasma and supplying a first bias signal having a frequency that does not substantially contribute to plasma generation to the substrate support at a second power; and (c2) after (c1), supplying the first bias signal to the substrate support at a third power higher than the second power.

[0029] In one exemplary embodiment, a plasma processing apparatus is provided, including a chamber and a controller, wherein the controller performs the following operations: (a) controlling a substrate disposed in the chamber and on a substrate support, the substrate including a first film including silicon and nitrogen and a second film including silicon and oxygen; (b) controlling a process gas including a metal-containing gas into the chamber; and (c) controlling, while (b) is being performed, selectively etching the second film relative to the first film, the control including: (c1) setting a power of a source RF signal having a first frequency to a first power to generate plasma and supplying a first bias signal having a frequency that does not substantially contribute to plasma generation to the substrate support at a second power; and (c2) after (c1), supplying the first bias signal to the substrate support at a third power higher than the second power.

[0030] Hereinafter, each embodiment of the present disclosure will be described in detail with reference to the drawings. In each drawing, the same or similar elements are designated by the same reference numerals, and redundant explanations will be omitted. Unless otherwise specified, the positional relationships, such as up, down, left, and right, will be described based on the positional relationships shown in the drawings. The dimensional ratios in the drawings do not represent actual ratios, and the actual ratios are not limited to the ratios shown in the drawings.

[0031] FIG. 1 is a diagram illustrating an exemplary 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 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 exhaust port for exhausting gas from the plasma processing space. The gas supply port is connected to a gas supply unit 20 (described later), and the gas exhaust port is connected to an exhaust system 40 (described later). The substrate support 11 is disposed in the plasma processing space and has a substrate support surface for supporting a substrate.

[0032] The plasma generating unit 12 is configured to generate plasma from at least one processing gas supplied into the plasma processing space. The plasma generated in the plasma processing space may be capacitively coupled plasma (CCP), inductively coupled plasma (ICP), electron-cyclotron-resonance plasma (ECR plasma), helicon wave plasma (HWP), surface wave plasma (SWP), or the like. Various types of plasma generators may be used, including alternating current (AC) plasma generators and direct current (DC) plasma generators. In one embodiment, the AC signal (AC power) used in the AC plasma generator has a frequency in the range of 100 kHz to 10 GHz. Thus, AC signals include radio frequency (RF) signals and microwave signals. In one embodiment, the RF signal has a frequency in the range of 100 kHz to 150 MHz.

[0033] The control unit 2 processes computer-executable instructions that cause the plasma processing apparatus 1 to perform various processes described in this disclosure. The control unit 2 may be configured to control each element of the plasma processing apparatus 1 to perform 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 may include a processing unit 2a1, a storage unit 2a2, and a communication interface 2a3. The control unit 2 may be implemented by, for example, a computer 2a. The processing unit 2a1 may be configured to read a program from the storage unit 2a2 and execute the read program to perform various control operations. This program may be stored in the storage unit 2a2 in advance or may be acquired via a medium when needed. The acquired program is stored in the storage unit 2a2 and read from the storage unit 2a2 by the processing unit 2a1 for execution. The medium may be various storage media readable by the computer 2a or a communication line connected to the communication interface 2a3. The processing unit 2a1 may be a CPU (Central Processing Unit). The storage unit 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).

[0034] The following describes a configuration example of a capacitively coupled plasma processing apparatus as an example of the plasma processing apparatus 1. Fig. 2 is a diagram for explaining a configuration example of a capacitively coupled plasma processing apparatus.

[0035] The capacitively coupled plasma processing apparatus 1 includes a plasma processing chamber 10, a gas supply 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. The gas inlet is configured to introduce at least one process gas into the plasma processing chamber 10. The gas inlet 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 one embodiment, the showerhead 13 forms 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 showerhead 13, a sidewall 10a of the plasma processing chamber 10, and the substrate support 11. The plasma processing chamber 10 is grounded. The showerhead 13 and the substrate support 11 are electrically insulated from the housing of the plasma processing chamber 10.

[0036] The substrate support 11 includes a main body 111 and a ring assembly 112. The main body 111 has a central region 111a for supporting a 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 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. Therefore, the central region 111a is also called a substrate support surface for supporting the substrate W, and the annular region 111b is also called a ring support surface for supporting the ring assembly 112.

[0037] 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 disposed on the base 1110. The electrostatic chuck 1111 includes a ceramic member 1111a and an electrostatic electrode 1111b disposed within the ceramic member 1111a. The ceramic member 1111a has a central region 111a. In one embodiment, the ceramic member 1111a also has an annular region 111b. Note that the annular region 111b may also be provided by another member surrounding the electrostatic chuck 1111, such as an annular electrostatic chuck or an annular insulating member. In this case, the ring assembly 112 may be disposed on the annular electrostatic chuck or the annular insulating member, or may be disposed on both the electrostatic chuck 1111 and the annular insulating member. Furthermore, at least one RF / DC electrode coupled to an RF power supply 31 and / or a DC power supply 32, which will be described later, may be disposed within the ceramic member 1111a. In this case, the at least one RF / DC electrode functions as a lower electrode. When a bias RF signal and / or a DC signal, which will be described later, is supplied to the at least one RF / DC electrode, the RF / DC electrode is also called a bias electrode. Note that the conductive member of the base 1110 and the at least one RF / DC electrode may function as multiple lower electrodes. Furthermore, the electrostatic electrode 1111b may function as a lower electrode. Therefore, the substrate support 11 includes at least one lower electrode.

[0038] 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 cover ring. The edge rings are formed of a conductive or insulating material, and the cover rings are formed of an insulating material.

[0039] The substrate support 11 may also include a temperature adjustment 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 adjustment module may include a heater, a heat transfer medium, a flow passage 1110a, or a combination thereof. A heat transfer fluid such as brine or a gas flows through the flow passage 1110a. In one embodiment, the flow passage 1110a is formed in the base 1110, and one or more heaters are disposed in the ceramic member 1111a of the electrostatic chuck 1111. The substrate support 11 may also include a heat transfer gas supply configured to supply a heat transfer gas to a gap between the backside of the substrate W and the central region 111a.

[0040] The showerhead 13 is configured to introduce at least one process 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 process 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 at least one upper electrode. In addition to the showerhead 13, the gas inlet may also include one or more side gas injectors (SGIs) attached to one or more openings formed in the sidewall 10a.

[0041] 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 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. Additionally, the gas supply unit 20 may include at least one flow modulation device that modulates or pulses the flow rate of the at least one process gas.

[0042] 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) to at least one lower electrode and / or at least one upper electrode. This generates a plasma from at least one processing gas supplied to the plasma processing space 10s. Therefore, the RF power supply 31 can function as at least a part of the plasma generation unit 12. Furthermore, by supplying a bias RF signal to the at least one lower electrode, a bias potential is generated on the substrate W, thereby attracting ion components in the formed plasma to the substrate W.

[0043] In one 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 at least one lower electrode and / or at least one upper electrode via at least one impedance matching circuit and is configured to generate a source RF signal (source RF power) for plasma generation. 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 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 at least one lower electrode and / or at least one upper electrode.

[0044] The second RF generator 31b is coupled to at least one lower electrode via at least one impedance matching circuit and is configured to generate a bias RF signal (bias RF power). 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 generator 31b may be configured to generate multiple 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.

[0045] 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 one embodiment, the first DC generator 32a is connected to the at least one lower electrode and configured to generate a first DC signal. The generated first DC signal is applied to the at least one lower electrode. In one embodiment, the second DC generator 32b is connected to the at least one upper electrode and configured to generate a second DC signal. The generated second DC signal is applied to the at least one upper electrode.

[0046] In various embodiments, the first and second DC signals may be pulsed. In this case, a sequence of voltage pulses is applied to at least one lower electrode and / or at least one upper electrode. The voltage pulses may have a rectangular, trapezoidal, triangular, or combination thereof pulse waveform. In one embodiment, a waveform generator for generating the sequence of voltage pulses from the DC signal is connected between the first DC generator 32a and at least one lower electrode. Thus, the first DC generator 32a and the waveform generator constitute a voltage pulse generator. When the second DC generator 32b and the waveform generator constitute a voltage pulse generator, the voltage pulse generator is connected to at least one upper electrode. The voltage pulses may have either positive or negative polarity. Furthermore, the sequence of voltage pulses may include one or more positive voltage pulses and one or more negative voltage pulses within one period. The first and second DC generating units 32a and 32b may be provided in addition to the RF power supply 31, or the first DC generating unit 32a may be provided instead of the second RF generating unit 31b.

[0047] 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 in the plasma processing space 10s is regulated by the pressure regulating valve. The vacuum pump may include a turbomolecular pump, a dry pump, or a combination thereof.

[0048] <Example of the Present Method> Figure 3 is a flowchart showing an etching method (hereinafter also referred to as "the present method") according to one exemplary embodiment. The present method includes a step (ST1) of preparing a substrate, a step (ST2) of etching a part of a silicon oxide film, and a step (ST3) of etching the remainder of the silicon oxide film. In one embodiment, the processes in each step may be performed in a plasma processing apparatus 1 (see Figures 1 and 2). In the following example, the present method is performed by a control unit 2 controlling each part of the capacitively coupled plasma processing apparatus 1 (see Figure 2).

[0049] (Process ST1: Preparation of Substrate) A substrate is prepared in process ST1. In process ST1, the substrate W is placed in the central region 111a of the substrate support 11 and held on the substrate support 11 by an electrostatic chuck 1111. FIG. 4 is a diagram showing an example of a cross-sectional structure of the substrate W prepared in process ST1. As shown in FIG. 4, the substrate W may be configured to include an undercoat film UF, a silicon nitride film SNF, a silicon oxide film SOF, and a mask MK. The silicon nitride film SNF is an example of a film containing silicon and nitrogen. Note that, in addition to a silicon nitride film, a SiON film may also be used as the film containing silicon and nitrogen. Furthermore, the substrate W may be formed using at least one film selected from the group consisting of a SiC film, a SiOC film, and a boron nitride film, instead of or in addition to the film containing silicon and nitrogen. The silicon oxide film SOF is an example of a film containing silicon and oxygen. The substrate W may be used in the manufacture of semiconductor devices.

[0050] In one embodiment, the substrate W has a plurality of regions R1 and a plurality of regions R2 in a plan view of the substrate W. The region R1 is an example of a first region. The region R2 is an example of a second region. The regions R1 and R2 may be regions adjacent to each other. The plurality of regions R1 shown as separate regions in the cross section shown in FIG. 4 may be continuous regions in another cross section of the substrate W.

[0051] In one embodiment, the underlayer UF is a silicon wafer or an organic film, a dielectric film, a metal film, a semiconductor film, or the like formed on the silicon wafer. In one embodiment, the underlayer UF may include an etch stop film. As an example, the etch stop film may be a silicon nitride film.

[0052] In one embodiment, the base film UF may be configured by stacking multiple films. When the base film UF is configured by multiple films, the etching stop film may be formed on the uppermost layer of the base film UF. That is, the etching stop film may be disposed so as to be in contact with the silicon oxide film SOF.

[0053] The silicon nitride film SNF may be disposed on the undercoat film UF. In one embodiment, the silicon nitride film SNF may be disposed in a plurality of regions R1 so as to include recesses RC in a plurality of regions R2 in a plan view of the substrate W. The recesses RC may be openings that penetrate the silicon nitride film SNF. The recesses RC may be spaces defined by the side surfaces SS of the silicon nitride film SNF.

[0054] The silicon oxide film SOF is a film to be etched in this method. In this method, the silicon oxide film SOF is a film that is selectively etched with respect to the silicon nitride film SNF. In one embodiment, the silicon oxide film SOF can be disposed at least in the recess RC in a plan view of the substrate W. That is, the silicon oxide film SOF can be disposed in the region R2 or the recess RC so as to be in contact with the side surface SS of the silicon nitride film SNF and the base film UF.

[0055] The silicon oxide film SOF can be disposed in both the region R1 and the second region. That is, as shown in FIG. 4, the silicon oxide film SOF can be disposed on the silicon nitride film SNF in the region R1. Moreover, the silicon oxide film SOF can be disposed in the recess RC in the region R2 and also above the recess RC. That is, the silicon oxide film SOF can be disposed so as to cover the silicon nitride film SNF.

[0056] The mask MK includes an opening pattern for etching the silicon oxide film SOF. The opening pattern may include multiple openings with different opening areas. In the example shown in FIG. 4 , the mask MK has openings OP1 and OP2 (hereinafter, openings OP1 and OP2 are also collectively referred to as "openings OP"). The opening OP1 is an example of a first opening. The opening OP2 is an example of a second opening. The openings OP may have any shape in a plan view of the substrate W. The shape may be, for example, a circle, an ellipse, a rectangle, a line, or a combination of one or more of these. The mask MK may have multiple side surfaces, and the multiple side surfaces may define multiple openings OP. The multiple openings OP may each have a linear shape and be arranged at regular intervals to form a line-and-space pattern.

[0057] In one embodiment, the regions R1 and R2 may have a line shape in the portions overlapping the openings OP. That is, the silicon nitride film SNF and the recesses RC may be configured to have a line-and-space pattern in a plan view of the substrate W. In one embodiment, the number of recesses RC overlapping the opening OP1 may be different from the number of recesses RC overlapping the opening OP2. As an example, as shown in FIG. 4 , the number of recesses RC overlapping the opening OP1 may be one, and the number of recesses RC overlapping the opening OP2 may be multiple. Furthermore, the openings OP1 and OP2 may have different opening areas. That is, the aspect ratios for etching the silicon oxide film SOF may be different between the openings OP1 and OP2.

[0058] The material contained in the mask MK may be appropriately selected depending on the type of film to be etched. In one embodiment, the mask MK is made of a material whose etching rate with respect to the plasma generated in step ST3 is lower than the etching rate of the film to be etched.

[0059] In one embodiment, the mask MK is a carbon-containing mask, a silicon-containing mask, or a metal-containing mask. The carbon-containing mask is, for example, an amorphous carbon (ACL) film, a spin-on carbon (SOC) film, or a photoresist film. The ACL film may be doped with elements such as boron, arsenic, or tungsten. The metal-containing mask may be a metal-containing film containing at least one metal selected from the group consisting of tungsten (W), molybdenum (Mo), and titanium (Ti) or a carbide thereof.

[0060] (Step ST2: Etching Part of Silicon Oxide Film) Next, in step ST2, part of the silicon oxide film SOF is etched. FIG. 5 is a diagram showing an example of the cross-sectional structure of the substrate W after part of the silicon oxide film is etched in ST2. As shown in FIG. 5, part of the silicon oxide film SOF is etched at the opening OP. In one embodiment, the silicon oxide film SOF may be etched to such an extent that the silicon nitride film SNF is not exposed in the opening OP. As an example, the thickness of the silicon oxide film SOF present on the silicon nitride film SNF in the opening OP may be 10 nm or less or 5 nm or less. Also, as an example, the thickness of the silicon oxide film SOF present on the silicon nitride film SNF in the opening OP may be 10% or less of the thickness of the silicon oxide film SOF present on the silicon nitride film SNF in regions other than the opening OP. Note that in one embodiment, the silicon oxide film SOF may be etched until the silicon nitride film SNF is exposed in the region R1.

[0061] In step ST2, the silicon oxide film SOF may be etched by plasma generated from a process gas. In one embodiment, the process gas may include a fluorine-containing gas. The fluorine-containing gas may be a fluorocarbon gas and / or a hydrofluorocarbon gas. The fluorocarbon gas may be, for example, CF ４ Gas, C ２ F ２ Gas, C ２ F ４ Gas, C ３ F ６ Gas, C ３ F ８ Gas, C ４ F ６ Gas, C ４ F ８ Gas and C ５ F ８ The gas may be at least one selected from the group consisting of gases.

[0062] In step ST2, the plasma can be generated by supplying a source RF signal to the upper electrode or the lower electrode. The source RF signal supplied in step ST2 may be a continuous wave. When a source RF signal is supplied to the upper electrode or the lower electrode while a processing gas is being supplied into the plasma processing chamber 10, plasma is generated from the processing gas. Then, activated species in the plasma are attracted to the substrate W, and the activated species etch a portion of the silicon oxide film SOF at the opening OP. In step ST2, a bias signal can be supplied to the lower electrode.

[0063] (Step ST3: Etching Remaining Silicon Oxide Film) Next, in step ST3, the remaining silicon oxide film SOF is etched. Step ST3 includes a step (ST31) of supplying a process gas and a step (ST32) of supplying a source RF signal and a bias signal.

[0064] (Step ST31: Supply of Processing Gas) Next, in step ST31, a processing gas is supplied into the plasma processing chamber 10. Steps ST31 and ST32 may be performed simultaneously, or one may be performed before the other.

[0065] In step ST31, the process gas may contain a gas different from the gas contained in the process gas for etching a portion of the silicon oxide film SOF in step ST2. In one embodiment, the process gas in step ST31 contains a metal-containing gas. The metal-containing gas may be a tungsten-containing gas. The tungsten-containing gas may be a gas containing tungsten and a halogen, and in one example, is WF ｘ Cl ｙ (x and y are each an integer of 0 to 6, and the sum of x and y is 2 to 6.) Specifically, the tungsten-containing gas is tungsten difluoride (WF ２ ) gas, tungsten tetrafluoride (WF ４ ) gas, tungsten pentafluoride (WF ５ ) gas, tungsten hexafluoride (WF ６ tungsten and fluorine-containing gases such as tungsten dichloride (WCl ２) gas, tungsten tetrachloride (WCl ４ ) gas, tungsten pentachloride (WCl ５ ) gas, tungsten hexachloride (WCl ６ ) gas containing tungsten and chlorine. ６ Gas and WCl ６ The flow rate of the tungsten-containing gas may be 5% by volume or less of the total flow rate of the processing gas. Note that the processing gas may contain at least one of a titanium-containing gas, a ruthenium-containing gas, and / or a molybdenum-containing gas instead of or in addition to the tungsten-containing gas.

[0066] In step ST31, the processing gas may further include a carbon-containing gas. The carbon-containing gas may be a fluorocarbon gas. The fluorocarbon gas may be, for example, CF ４ Gas, C ２ F ２ Gas, C ２ F ４ Gas, C ３ F ６ Gas, C ３ F ８ Gas, C ４ F ６ Gas, C ４ F ８ Gas and C ５ F ８ In one embodiment, the carbon-containing gas is a linear gas having unsaturated bonds. Examples of such gases include C ３ F ６ (Hexafluoropropene) gas, C ４ F ８ (Octafluoro-1-butene, octafluoro-2-butene) gas, C ３ H ２ F ４ (1,3,3,3-tetrafluoropropene) gas, C ４ H ２ F ６ (trans-1,1,1,4,4,4-hexafluoro-2-butene) gas, C ４ F ８O (pentafluoroethyl trifluorovinyl ether) gas, CF ３ COF gas (1,2,2,2-tetrafluoroethane-1-one), CHF ２ COF (difluoroacetic acid fluoride) gas and COF ２ In one embodiment, the carbon-containing gas may contain a halogen element other than fluorine, or may contain fluorine and a halogen element other than fluorine. Such a gas may be C ｉ H ｊ F ｋ X ｌ Here, X is a halogen other than fluorine. Furthermore, i and l may be integers of 1 or more, and j and k may be integers of 0 or more. The carbon-containing gas may be, for example, CH ｊ Cl ｌ , C.F. ｋ Br ｌ , C.F. ｋ I ｌ , C ｉ F ｋ Cl ｌ The carbon-containing gas may contain one or more of the following gases: ３ , C.H. ２ Cl ２ and CF ２ Br ２ It may be at least one selected from the group consisting of:

[0067] In step ST31, the process gas may further include an inert gas, which may be a noble gas such as Ar gas, He gas, or Kr gas, and / or nitrogen gas.

[0068] In step ST31, the processing gas may further contain a gas that captures (scavenges) active species containing fluorine. The gas that captures active species containing fluorine may be an oxidizing gas or a reducing gas. Carbon monoxide (CO) may be used as the oxidizing gas. Hydrogen (H ２ ) or other hydrogen-containing gases may be used.

[0069] (Step ST32: Supply of Source RF Signal and Bias Signal) Next, in step ST32, a source RF signal and a bias signal are supplied. While step ST31 is being performed, step ST32 is performed, and plasma is generated from the processing gas in the plasma processing chamber 10.

[0070] 6 to 13 are timing charts showing examples of a source RF signal HF, a bias RF signal MF, and a bias RF signal LF. The source RF signal HF is an example of a source RF signal. The bias RF signal MF is an example of a second bias RF signal. The bias RF signal LF is an example of a first bias signal. Note that the bias RF signal MF may have the functions of both a source RF signal and a bias RF signal.

[0071] In Figures 6 to 13, the vertical axis indicates the relative value of the power of each signal. This power may be the effective value of power (hereinafter simply referred to as "power"). In each figure, powers H1 to H4, powers M1 to M2, and powers L1 to L2 indicate the magnitude relationship of the power of each signal. The absolute and / or relative powers of powers H1 to H4, powers M1 to M2, and powers L1 to L2 may be set arbitrarily. Furthermore, in each figure, the vertical axis does not indicate the relative power relationship between each signal.

[0072] The power H1, the power M1, and the power L1 may be powers that do not substantially contribute to etching the silicon oxide film SOF and / or generating the protective film PF (see FIG. 14). As an example, the power H1, the power M1, and the power L1 may be zero power (0 W, substantially 0 W (including standby power as an example), or a wattage that does not substantially contribute to etching the film to be etched).

[0073] 6 to 13, the horizontal axis represents time. The total period shown in each of these figures represents one cycle of step ST32. In each of these figures, periods P11 to P12, periods P21 to P23, and periods P31 to P34 are shown as dividing the cycle equally, but the absolute or relative time of each period can be set arbitrarily.

[0074] In the examples shown in FIGS. 6 to 13, the frequency of the source RF signal HF may be 60 MHz to 200 MHz. As an example, the frequency of the source RF signal HF is 100 MHz. Also, the frequency of the bias RF signal MF may be 3 MHz to 40 MHz. As an example, the frequency of the bias RF signal MF is 13 MHz. Also, the frequency of the bias RF signal LF may be a frequency that does not substantially contribute to plasma generation. As an example, the frequency may be 100 kHz to 800 kHz. Also, the frequency of the bias RF signal LF may be 400 kHz.

[0075] 6 to 13 are repeatedly performed, and plasma is generated from the processing gas in step ST32, thereby etching the silicon oxide film SOF selectively with respect to the silicon nitride film SNF.

[0076] 14 and 15 are diagrams showing an example of the cross-sectional structure of a substrate W processed in step ST32. When the cycle shown in FIGS. 6 to 13 is repeatedly performed in step ST3, the portions of the silicon oxide film SOF exposed in the openings OP1 and OP2 are etched, as shown in FIG. 14. As a result, the upper surface TS of the silicon nitride film SNF is exposed, as shown in FIG. 14. As etching of the silicon oxide film SOF further progresses in step ST32, a protective film PF is formed on the upper surface TS of the silicon nitride film SNF, and the silicon oxide film SOF is etched in the recess RC. As etching of the silicon oxide film SOF further progresses in step ST32, the base film UF is exposed in the recess RC, and the etching of the silicon oxide film SOF is completed. Details of step ST32 in each of the examples shown in FIGS. 6 to 13 are described below.

[0077] In the example shown in FIG. 6 , one cycle of process ST32 includes periods P11 and P12. First, in period P11, a source RF signal HF is supplied to the upper electrode at power H4. The upper electrode is an example of a counter electrode. In one embodiment, the power H4 may be 50 W to 2,000 W. As an example, the power H4 may be 200 W. Also, in period P11, a bias RF signal MF is supplied to the lower electrode at power M1. In one embodiment, the power M1 may be 0 W to 20 W. As an example, the power M1 may be zero power. Also, in period P11, a bias RF signal LF is supplied to the lower electrode at power L1. As an example, the power L1 may be zero power.

[0078] Next, in period P12, a source RF signal HF is supplied to the upper electrode at power H3. In one embodiment, power H3 may be 20 W to 500 W. As an example, power H3 may be 150 W. Also in period P12, a bias RF signal MF is supplied to the lower electrode at power M1. Also in period P12, a bias RF signal LF is supplied to the lower electrode at power L2. In one embodiment, power L2 may be 10 W to 150 W. As an example, power L2 may be 75 W.

[0079] 6, periods P11 and P12 are repeatedly executed, and plasma is generated from the processing gas in step ST32. In this example, during period P11, activated species that contribute to etching of the silicon oxide film SOF can be generated by the source RF signal HF. Then, during period P12, the activated species generated during period P11 are attracted to the substrate W by the bias RF signal LF, and the silicon oxide film SOF is etched.

[0080] Furthermore, in the period P11, activated species for forming a protective film (described later) are generated by the source RF signal HF, and a protective film PF can be formed on the silicon nitride film SNF.

[0081] In the example shown in FIG. 6 , as the etching of the silicon oxide film SOF progresses through repeated execution of the periods P11 and P12, the upper surface TS of the silicon nitride film SNF is exposed (see FIG. 14 ). When the surface of the silicon nitride film SNF is exposed, a protective film PF may be generated on the surface of the silicon nitride film SNF. The protective film PF may be formed by activated species generated in the period P11. The activated species may be activated species generated from a carbon-containing gas. In one embodiment, the protective film PF may be formed by forming active sites on the surface of the silicon nitride film SNF and adsorbing other activated species to the active sites. The active sites and the activated species may be activated species generated in the period P11.

[0082] 6, as the etching of the silicon oxide film SOF progresses further, the silicon oxide film SOF is further etched in the recess RC while the surface of the silicon nitride film SNF is protected by the protective film PF (see FIG. 15). As a result, the silicon oxide film SOF is selectively etched with respect to the silicon nitride film SNF.

[0083] Next, an example shown in FIG. 7 will be described. In the example shown in FIG. 7, one cycle of process ST32 includes periods P11 and P12. First, in period P11, a source RF signal HF is supplied to the upper electrode at power H4. In one embodiment, the power H4 may be 50 W to 2,000 W. As an example, the power H4 may be 200 W. Also, in period P11, a bias RF signal MF is supplied to the lower electrode at power M2. In one embodiment, the power M2 may be 10 W to 100 W. As an example, the power M1 may be zero power. Also, in period P11, a bias RF signal LF is supplied to the lower electrode at power L1. As an example, the power L1 may be zero power.

[0084] Next, in period P12, a source RF signal HF is supplied to the upper electrode at power H1. As an example, power H1 may be 0 W. Also, in period P12, a bias RF signal MF is supplied to the lower electrode at power M1. As an example, power M1 may be zero power. Also, in period P12, a bias RF signal LF is supplied to the lower electrode at power L2. In one embodiment, power L2 may be 10 W to 150 W. As an example, power L2 may be 75 W.

[0085] 7, periods P11 and P12 are repeatedly executed, and plasma is generated from the processing gas in step ST32. In this example, during period P11, activated species that contribute to etching of the silicon oxide film SOF can be generated by the source RF signal HF. Then, during period P12, the activated species generated during period P11 are attracted to the substrate W by the bias RF signal LF, and the silicon oxide film SOF is etched.

[0086] Furthermore, during period P11, the source RF signal HF generates active species for forming a protective film (described later), and a protective film PF can be formed on the silicon nitride film SNF. Furthermore, the bias RF signal MF can control the amount of active species for forming the protective film PF and / or the composition of the protective film PF. As an example, at least the surface of the protective film PF can be modified by the active species generated by the bias RF signal MF. The modification can include changing the ratio of elements contained in the protective film PF. In one embodiment, the modification can include changing the ratio of the number of fluorine atoms to the number of carbon atoms in the protective film PF. As an example, the modification can be a reduction in the ratio of the number of fluorine atoms to the number of carbon atoms in the protective film PF.

[0087] In the example shown in FIG. 7 , as the etching of the silicon oxide film SOF progresses through repeated execution of the periods P11 and P12, the upper surface TS of the silicon nitride film SNF is exposed (see FIG. 14 ). When the surface of the silicon nitride film SNF is exposed, a protective film PF may be generated on the surface of the silicon nitride film SNF. The protective film PF may be formed by activated species generated by the source RF signal HF during the period P11. The activated species may be activated species generated from a carbon-containing gas. In one embodiment, the protective film PF may be formed by forming active sites on the surface of the silicon nitride film SNF and adsorbing other activated species to the active sites. The active sites and the activated species may be activated species generated during the period P11.

[0088] 7, as the etching of the silicon oxide film SOF progresses further, the silicon oxide film SOF is further etched in the recess RC while the surface of the silicon nitride film SNF is protected by the protective film PF (see FIG. 15). As a result, the silicon oxide film SOF is selectively etched with respect to the silicon nitride film SNF.

[0089] Next, an example shown in FIG. 8 will be described. In the example shown in FIG. 8, one cycle of process ST32 includes periods P21 to P23. First, in period P21, a source RF signal HF is supplied to the upper electrode at power H4. In one embodiment, the power H4 may be 50 W to 2,000 W. As an example, the power H4 may be 200 W. Also, in period P21, a bias RF signal MF is supplied to the lower electrode at power M1. As an example, the power M1 may be zero power. Also, in period P21, a bias RF signal LF is supplied to the lower electrode at power L1. As an example, the power L1 may be zero power.

[0090] Next, in period P22, a source RF signal HF is supplied to the upper electrode at power H1. As an example, power H1 may be 0 W. Also in period P22, a bias RF signal MF is supplied to the lower electrode at power M1. Also in period P22, a bias RF signal LF is supplied to the lower electrode at power L1.

[0091] Next, in period P23, a source RF signal HF is supplied to the upper electrode at power H2. In one embodiment, the power H2 may be between 20 W and 200 W. As an example, the power H2 may be 100 W. Also in period P23, a bias RF signal MF is supplied to the lower electrode at power M1. Also in period P23, a bias RF signal LF is supplied to the lower electrode at power L2. In one embodiment, the power L2 may be between 10 W and 150 W. As an example, the power L2 may be 75 W.

[0092] 8, periods P21 to P23 are repeatedly executed, and plasma is generated from the processing gas in step ST32. In this example, during period P21, activated species that contribute to etching the silicon oxide film SOF can be generated by the source RF signal HF. Then, during period P22, the power of the source RF signals HF and MF is reduced. Then, during period P23, the activated species generated during period P21 are attracted to the substrate W by the bias RF signal LF, and the silicon oxide film SOF is etched. Note that during period P23, the source RF signal HF is supplied to the upper electrode at power H2, thereby maintaining the plasma generated during period P21.

[0093] Furthermore, in the period P21, activated species for forming a protective film (described later) are generated by the source RF signal HF, and a protective film PF can be formed on the silicon nitride film SNF.

[0094] In the example shown in FIG. 8 , as the etching of the silicon oxide film SOF progresses through repeated execution of periods P21 to P23, the upper surface TS of the silicon nitride film SNF is exposed (see FIG. 14 ). When the surface of the silicon nitride film SNF is exposed, a protective film PF may be generated on the surface of the silicon nitride film SNF. The protective film PF may be formed by activated species generated in period P11. The activated species may be activated species generated from a carbon-containing gas. In one embodiment, the protective film PF may be formed by forming active sites on the surface of the silicon nitride film SNF and adsorbing other activated species to the active sites. The active sites and the activated species may be activated species generated in period P21.

[0095] 8, as the etching of the silicon oxide film SOF progresses further, the silicon oxide film SOF is further etched in the recess RC while the surface of the silicon nitride film SNF is protected by the protective film PF (see FIG. 15). As a result, the silicon oxide film SOF is selectively etched with respect to the silicon nitride film SNF.

[0096] Next, an example shown in FIG. 9 will be described. In the example shown in FIG. 9, one cycle of process ST32 includes periods P21 to P23. First, in period P21, a source RF signal HF is supplied to the upper electrode at power H4. In one embodiment, the power H4 may be 50 W to 2,000 W. As an example, the power H4 may be 200 W. Also, in period P21, a bias RF signal MF is supplied to the lower electrode at power M2. In one embodiment, the power M2 may be 10 W to 100 W. As an example, the power M2 may be 50 W. Also, in period P21, a bias RF signal LF is supplied to the lower electrode at power L1. As an example, the power L1 may be zero.

[0097] Next, in period P22, a source RF signal HF is supplied to the upper electrode at power H1. As an example, power H1 may be 0 W. Also in period P22, a bias RF signal MF is supplied to the lower electrode at power M1. Also in period P22, a bias RF signal LF is supplied to the lower electrode at power L1.

[0098] Next, in period P23, a source RF signal HF is supplied to the upper electrode at power H2. In one embodiment, the power H2 may be between 20 W and 200 W. As an example, the power H2 may be 100 W. Also in period P23, a bias RF signal MF is supplied to the lower electrode at power M1. Also in period P23, a bias RF signal LF is supplied to the lower electrode at power L2. In one embodiment, the power L2 may be between 10 W and 150 W. As an example, the power L2 may be 75 W.

[0099] 9 , periods P21 to P23 are repeatedly executed, and plasma is generated from the processing gas in step ST32. In this example, during period P21, activated species that contribute to etching the silicon oxide film SOF can be generated by the source RF signal HF. Then, during period P22, the power of the source RF signals HF and MF is reduced. Then, during period P23, the activated species generated during period P21 are attracted to the substrate W by the bias RF signal LF, and the silicon oxide film SOF is etched. Note that during period P23, the source RF signal HF is supplied to the upper electrode at power H2, thereby maintaining the plasma generated during period P21.

[0100] Furthermore, in period P21, the source RF signal HF generates active species for forming a protective film (described later), and a protective film PF can be formed on the silicon nitride film SNF. Furthermore, the bias RF signal MF can control the amount of active species for forming the protective film PF and / or the composition of the protective film PF. As an example, at least the surface of the protective film PF may be modified by the active species generated by the bias RF signal MF.

[0101] In the example shown in FIG. 9 , as the etching of the silicon oxide film SOF progresses through repeated execution of periods P21 to P23, the upper surface TS of the silicon nitride film SNF is exposed (see FIG. 14 ). When the surface of the silicon nitride film SNF is exposed, a protective film PF may be generated on the surface of the silicon nitride film SNF. The protective film PF may be formed by activated species generated in period P11. The activated species may be activated species generated from a carbon-containing gas. In one embodiment, the protective film PF may be formed by forming active sites on the surface of the silicon nitride film SNF and adsorbing other activated species to the active sites. The active sites and the activated species may be activated species generated in period P21.

[0102] 9, as the etching of the silicon oxide film SOF progresses further, the silicon oxide film SOF is further etched in the recess RC while the surface of the silicon nitride film SNF is protected by the protective film PF (see FIG. 15). As a result, the silicon oxide film SOF is selectively etched with respect to the silicon nitride film SNF.

[0103] Next, an example shown in FIG. 10 will be described. In the example shown in FIG. 10, one cycle of process ST32 includes periods P21 to P23. First, in period P21, a source RF signal HF is supplied to the upper electrode at power H4. In one embodiment, the power H4 may be 50 W to 2,000 W. As an example, the power H4 may be 200 W. Also, in period P21, a bias RF signal MF is supplied to the lower electrode at power M2. In one embodiment, the power M2 may be 10 W to 100 W. As an example, the power M2 may be 50 W. Also, in period P21, a bias RF signal LF is supplied to the lower electrode at power L1. As an example, the power L1 may be zero.

[0104] Next, in period P22, a source RF signal HF is supplied to the upper electrode at power H1. As an example, power H1 may be 0 W. Also in period P22, a bias RF signal MF is supplied to the lower electrode at power M2. Also in period P22, a bias RF signal LF is supplied to the lower electrode at power L1.

[0105] Next, in period P23, a source RF signal HF is supplied to the upper electrode at power H1. As an example, power H1 may be zero power. Also, in period P23, a bias RF signal MF is supplied to the lower electrode at power M1. As an example, power M1 may be zero power. Also, in period P23, a bias RF signal LF is supplied to the lower electrode at power L2. In one embodiment, power L2 may be 10 W to 150 W. As an example, power L2 may be 75 W.

[0106] 10 , periods P21 to P23 are repeatedly executed, and plasma is generated from the processing gas in step ST32. In this example, during period P21, activated species that contribute to etching the silicon oxide film SOF can be generated by the source RF signal HF. Then, during period P22, the power of the source RF signals HF and MF is reduced. Then, during period P23, the activated species generated during periods P21 and P22 are attracted to the substrate W by the bias RF signal LF, and the silicon oxide film SOF is etched. Note that during period P22, the bias RF signal MF is supplied to the upper electrode at power M2, thereby maintaining the plasma generated during period P21.

[0107] Furthermore, in period P21, the source RF signal HF generates active species for forming a protective film (described later), and a protective film PF can be formed on the silicon nitride film SNF. Furthermore, the bias RF signal MF can control the amount of active species for forming the protective film PF and / or the composition of the protective film PF. As an example, at least the surface of the protective film PF may be modified by the active species generated by the bias RF signal MF.

[0108] In the example shown in FIG. 10 , as periods P21 to P23 are repeatedly executed and etching of the silicon oxide film SOF progresses, the upper surface TS of the silicon nitride film SNF is exposed (see FIG. 14 ). When the surface of the silicon nitride film SNF is exposed, a protective film PF may be generated on the surface of the silicon nitride film SNF. The protective film PF may be formed by activated species generated in period P11. The activated species may be activated species generated from a carbon-containing gas. In one embodiment, the protective film PF may be formed by forming active sites on the surface of the silicon nitride film SNF and adsorbing other activated species to the active sites. The active sites and the activated species may be activated species generated in periods P21 and P32.

[0109] 10, as the etching of the silicon oxide film SOF progresses further, the silicon oxide film SOF is further etched in the recess RC while the surface of the silicon nitride film SNF is protected by the protective film PF (see FIG. 15). As a result, the silicon oxide film SOF is selectively etched with respect to the silicon nitride film SNF.

[0110] Next, an example shown in FIG. 11 will be described. In the example shown in FIG. 11, one cycle of process ST32 includes periods P31 to P34. First, in period P31, a source RF signal HF is supplied to the upper electrode at power H4. In one embodiment, the power H4 may be 50 W to 500 W. As an example, the power H4 may be 200 W. Also, in period P31, a bias RF signal MF is supplied to the lower electrode at power M2. In one embodiment, the power M2 may be 10 W to 100 W. As an example, the power M2 may be 50 W. Also, in period P31, a bias RF signal LF is supplied to the lower electrode at power L1. As an example, the power L1 may be zero.

[0111] Next, in period P32, a source RF signal HF is supplied to the upper electrode at power H3. In one embodiment, the power H3 may be 20 W to 500 W. As an example, the power H3 may be 150 W. Also, in period P32, a bias RF signal MF is supplied to the lower electrode at power M1. As an example, the power M1 may be zero power. Also, in period P32, a bias RF signal LF is supplied to the lower electrode at power L1.

[0112] Next, in period P33, a source RF signal HF is supplied to the upper electrode at power H1. As an example, power H1 may be zero. Also in period P33, a bias RF signal MF is supplied to the lower electrode at power M1. Also in period P33, a bias RF signal LF is supplied to the lower electrode at power L1.

[0113] Next, in period P34, a source RF signal HF is supplied to the upper electrode at power H2. In one embodiment, the power H2 may be 20 W to 200 W. As an example, the power H2 may be 100 W. Also, in period P34, a bias RF signal MF is supplied to the lower electrode at power M1. As an example, the power M1 may be zero power. Also, in period P34, a bias RF signal LF is supplied to the lower electrode at power L2. In one embodiment, the power L2 may be 10 W to 150 W. As an example, the power L2 may be 75 W.

[0114] 11 , periods P31 to P34 are repeatedly executed, and plasma is generated from the processing gas in step ST32. In this example, during periods P31 and P32, activated species that contribute to etching the silicon oxide film SOF can be generated by the source RF signal HF. Then, during period P22, the power of the source RF signals HF and MF is reduced. Then, during period P34, the activated species generated during periods P31 and P32 are attracted to the substrate W by the bias RF signal LF, and the silicon oxide film SOF is etched. Note that during period P34, the source RF signal HF is supplied to the upper electrode at power H2, thereby maintaining the plasma generated during periods P31 and P32.

[0115] Furthermore, in periods P31 and P32, the source RF signal HF generates active species for forming a protective film (described later), and a protective film PF can be formed on the silicon nitride film SNF. The bias RF signal MF can control the amount of active species for forming the protective film PF and / or the composition of the protective film PF. As an example, at least the surface of the protective film PF may be modified by the active species generated by the bias RF signal MF.

[0116] In the example shown in FIG. 11 , as periods P31 to P34 are repeatedly executed and etching of the silicon oxide film SOF progresses, the upper surface TS of the silicon nitride film SNF is exposed (see FIG. 14 ). When the surface of the silicon nitride film SNF is exposed, a protective film PF may be generated on the surface of the silicon nitride film SNF. The protective film PF may be formed by activated species generated in period P11. The activated species may be activated species generated from a carbon-containing gas. In one embodiment, the protective film PF may be formed by forming active sites on the surface of the silicon nitride film SNF and adsorbing other activated species to the active sites. The active sites and the activated species may be activated species generated in periods P31 and P32.

[0117] 11, as the etching of the silicon oxide film SOF progresses further, the silicon oxide film SOF is further etched in the recess RC while the surface of the silicon nitride film SNF is protected by the protective film PF (see FIG. 15). As a result, the silicon oxide film SOF is selectively etched with respect to the silicon nitride film SNF.

[0118] Next, an example shown in FIG. 12 will be described. In the example shown in FIG. 12, one cycle of process ST32 includes periods P31 to P34. First, in period P31, a source RF signal HF is supplied to the upper electrode at power H4. In one embodiment, the power H4 may be 50 W to 2,000 W. As an example, the power H4 may be 200 W. Also, in period P31, a bias RF signal MF is supplied to the lower electrode at power M1. As an example, the power M1 may be zero power. Also, in period P31, a bias RF signal LF is supplied to the lower electrode at power L1. As an example, the power L1 may be zero power.

[0119] Next, in period P32, a source RF signal HF is supplied to the upper electrode at power H3. In one embodiment, the power H3 may be between 20 W and 500 W. As an example, the power H3 may be 150 W. Also in period P32, a bias RF signal MF is supplied to the lower electrode at power M2. In one embodiment, the power M2 may be between 10 W and 100 W. As an example, the power M2 may be 50 W. Also in period P32, a bias RF signal LF is supplied to the lower electrode at power L1.

[0120] Next, in period P33, a source RF signal HF is supplied to the upper electrode at power H1. As an example, power H1 may be zero. Also in period P33, a bias RF signal MF is supplied to the lower electrode at power M1. Also in period P33, a bias RF signal LF is supplied to the lower electrode at power L1.

[0121] Next, in period P34, a source RF signal HF is supplied to the upper electrode at power H2. In one embodiment, the power H2 may be 20 W to 200 W. As an example, the power H2 may be 100 W. Also, in period P34, a bias RF signal MF is supplied to the lower electrode at power M1. As an example, the power M1 may be zero power. Also, in period P34, a bias RF signal LF is supplied to the lower electrode at power L2. In one embodiment, the power L2 may be 10 W to 150 W. As an example, the power L2 may be 75 W.

[0122] 12, periods P31 to P34 are repeatedly executed, and plasma is generated from the processing gas in step ST32. In this example, during periods P31 and P32, activated species that contribute to etching the silicon oxide film SOF can be generated by the source RF signal HF. Then, during period P22, the power of the source RF signals HF and MF is reduced. Then, during period P34, the activated species generated during periods P31 and P32 are attracted to the substrate W by the bias RF signal LF, and the silicon oxide film SOF is etched. Note that during period P34, the source RF signal HF is supplied to the upper electrode at power H2, thereby maintaining the plasma generated during periods P31 and P32.

[0123] Furthermore, in periods P31 and P32, the source RF signal HF generates active species for forming a protective film (described later), and a protective film PF can be formed on the silicon nitride film SNF. The bias RF signal MF can control the amount of active species for forming the protective film PF and / or the composition of the protective film PF. As an example, at least the surface of the protective film PF may be modified by the active species generated by the bias RF signal MF.

[0124] In the example shown in FIG. 12 , as periods P31 to P34 are repeatedly executed and etching of the silicon oxide film SOF progresses, the upper surface TS of the silicon nitride film SNF is exposed (see FIG. 14 ). When the surface of the silicon nitride film SNF is exposed, a protective film PF may be generated on the surface of the silicon nitride film SNF. The protective film PF may be formed by activated species generated in period P11. The activated species may be activated species generated from a carbon-containing gas. In one embodiment, the protective film PF may be formed by forming active sites on the surface of the silicon nitride film SNF and adsorbing other activated species to the active sites. The active sites and the activated species may be activated species generated in periods P31 and P32.

[0125] 12, as the etching of the silicon oxide film SOF progresses further, the silicon oxide film SOF is further etched in the recess RC while the surface of the silicon nitride film SNF is protected by the protective film PF (see FIG. 15). As a result, the silicon oxide film SOF is selectively etched with respect to the silicon nitride film SNF.

[0126] Next, an example shown in FIG. 13 will be described. In the example shown in FIG. 13, one cycle of process ST32 includes periods P31 to P34. First, in period P31, a source RF signal HF is supplied to the upper electrode at power H4. In one embodiment, the power H4 may be 50 W to 2,000 W. As an example, the power H4 may be 200 W. Also, in period P31, a bias RF signal MF is supplied to the lower electrode at power M1. As an example, the power M1 may be zero power. Also, in period P31, a bias RF signal LF is supplied to the lower electrode at power L1. As an example, the power L1 may be zero power.

[0127] Next, in period P32, a source RF signal HF is supplied to the upper electrode at power H3. In one embodiment, the power H3 may be 20 W to 500 W. As an example, the power H3 may be 150 W. Also in period P32, a bias RF signal MF is supplied to the lower electrode at power M1. Also in period P32, a bias RF signal LF is supplied to the lower electrode at power L1.

[0128] Next, in period P33, a source RF signal HF is supplied to the upper electrode at power H1. As an example, power H1 may be zero power. Also, in period P33, a bias RF signal MF is supplied to the lower electrode at power M2. In one embodiment, power M2 may be 10 W to 100 W. As an example, power M2 may be 50 W. Also, in period P33, a bias RF signal LF is supplied to the lower electrode at power L1.

[0129] Next, in period P34, a source RF signal HF is supplied to the upper electrode at power H2. In one embodiment, the power H2 may be 20 W to 200 W. As an example, the power H2 may be 100 W. Also, in period P34, a bias RF signal MF is supplied to the lower electrode at power M1. As an example, the power M1 may be zero power. Also, in period P34, a bias RF signal LF is supplied to the lower electrode at power L2. In one embodiment, the power L2 may be 10 W to 150 W. As an example, the power L2 may be 75 W.

[0130] 13 , periods P31 to P34 are repeatedly executed, and plasma is generated from the processing gas in step ST32. In this example, during periods P31 and P32, activated species that contribute to etching the silicon oxide film SOF can be generated by the source RF signal HF. Then, during period P22, the power of the source RF signals HF and MF is reduced. Then, during period P34, the activated species generated during periods P31 and P32 are attracted to the substrate W by the bias RF signal LF, and the silicon oxide film SOF is etched. Note that during period P34, the source RF signal HF is supplied to the upper electrode at power H2, thereby maintaining the plasma generated during periods P31, P32, and / or P33.

[0131] Furthermore, during periods P31, P32, and / or P33, the source RF signal HF generates active species for forming a protective film (described later), and a protective film PF can be formed on the silicon nitride film SNF. The bias RF signal MF can control the amount of active species for forming the protective film PF and / or the composition of the protective film PF. As an example, at least the surface of the protective film PF may be modified by the active species generated by the bias RF signal MF.

[0132] In the example shown in FIG. 13 , as periods P31 to P34 are repeatedly executed and etching of the silicon oxide film SOF progresses, an upper surface TS of the silicon nitride film SNF is exposed (see FIG. 14 ). When the surface of the silicon nitride film SNF is exposed, a protective film PF may be generated on the surface of the silicon nitride film SNF. The protective film PF may be formed by activated species generated in period P11. The activated species may be activated species generated from a carbon-containing gas. In one embodiment, the protective film PF may be formed by forming active sites on the surface of the silicon nitride film SNF and adsorbing other activated species to the active sites. The active sites and the activated species may be activated species generated in periods P31 to P33.

[0133] 13, as the etching of the silicon oxide film SOF progresses further, the silicon oxide film SOF is further etched in the recess RC while the surface of the silicon nitride film SNF is protected by the protective film PF (see FIG. 15). As a result, the silicon oxide film SOF is selectively etched with respect to the silicon nitride film SNF.

[0134] 16 to 18 are diagrams showing an example of the cross-sectional structure of a substrate W. In FIGS. 16 to 18, components denoted with the same reference numerals as those in FIGS. 14 and 15 have the same functions and / or features as those in FIGS. 14 and 15. In the example shown in FIG. 16, a silicon nitride film SNF is disposed on a silicon oxide film SOF in the substrate W. The silicon nitride film SNF includes an opening pattern for etching the silicon oxide film SOF. The opening pattern can include a plurality of openings OP.

[0135] 16 to 18, the silicon oxide film SOF is etched using the silicon nitride film SNF as a mask. That is, the silicon oxide film SOF is selectively etched with respect to the silicon nitride film SNF. The silicon oxide film SOF can be etched by the same method as the present method described with reference to FIG. 3. That is, in the example shown in FIG. 16, when the etching process according to the present method is performed, as shown in FIG. 17, the silicon oxide film SOF is etched while a protective film PF is formed on the upper surface TS of the nitride film SNF, and a recess RC is formed in the silicon oxide film SOF. The silicon oxide film SOF may be etched until the base film UF is exposed, as shown in FIG. 18.

[0136] In one exemplary embodiment of the present disclosure, a source RF signal HF is supplied to the upper electrode at a relatively high power (for example, power H4) and then switched to a relatively low power (for example, power H1 or H2), while a bias RF signal LF is supplied to the lower electrode at a relatively low power (for example, power L1) and then switched to a relatively high power (for example, power L2). This allows activated species in the plasma to be attracted to the substrate W while the electron density in the plasma is relatively low. Therefore, the spread of the CD (critical dimension) of the recess RC can be suppressed. Furthermore, the loading effect can be suppressed between multiple openings OP with different opening areas (for example, openings OP1 and OP2). This can suppress differences in the thickness of the protective film PF between multiple openings OP with different opening areas.

[0137] In one exemplary embodiment of the present disclosure, after the source RF signal HF is supplied to the upper electrode at a relatively high power (for example, power H4), the power of the source RF signal HF may be switched to a relatively low power (for example, power H2) while the source RF signal HF is then switched to a relatively lower power (for example, power H1) than the low power, thereby stabilizing the electron density in the plasma when the bias RF signal LF is switched to and maintained at a relatively high power (for example, power L2).

[0138] In one exemplary embodiment of the present disclosure, the power of the source RF signal HF is gradually reduced (for example, at powers H4 and H3) before the bias RF signal LF is switched to a relatively high power (for example, at power L2), thereby stabilizing the electron density in the plasma when the bias RF signal LF is switched to and maintained at the relatively high power (for example, at power L2) (for example, during period P34).

[0139] In one exemplary embodiment of the present disclosure, before switching the bias RF signal LF to a relatively high power (for example, power L2), the bias RF signal MF is supplied to the lower electrode at an appropriate timing (for example, periods P21, P22, P31, P32, or P33), at a relatively high power (for example, power M2), thereby stably maintaining the plasma generated by the source RF signal HF and / or controlling the electron density in the plasma.

[0140] The present disclosure may include, for example, the following configurations.

[0141] (Supplementary Note 1) An etching method performed in a plasma processing apparatus equipped with a chamber, comprising: (a) preparing a substrate on a substrate support disposed in the chamber, the substrate including a first film containing silicon and nitrogen and a second film containing silicon and oxygen; (b) supplying a process gas containing a metal-containing gas into the chamber; and (c) while (b) is being performed, selectively etching the second film relative to the first film, the etching method comprising: (c1) setting the power of a source RF signal having a first frequency to a first power to generate plasma, and supplying a first bias signal having a frequency that does not substantially contribute to plasma generation at a second power; and (c2) after (c1), supplying the first bias signal to the substrate support at a third power higher than the second power. An example of each power is as follows: First power: power H4 Second power: power L1 Third power: power L2

[0142] (Supplementary Note 2) The etching method according to Supplementary Note 1, wherein (c2) further comprises setting the power of the source RF signal to a fourth power lower than the first power. An example of the fourth power is power H1, H2, and / or H3.

[0143] (Supplementary Note 3) The etching method according to Supplementary Note 1, wherein in (a), the substrate includes, in a planar view of the substrate, a plurality of first regions and at least one second region between the first regions, the first film is disposed in the plurality of first regions and includes a recess in the at least one second region, and the second film is disposed in the recess, and in (c), the second film is selectively etched relative to the first film, and at least a portion of a side surface of the first film is exposed in the second region.

[0144] (Appendix 4) The etching method according to Appendix 2, wherein in (a), the second film is further disposed on the first film, the substrate includes a mask on the second film that includes a first opening, and the mask is disposed on the second film such that the first opening overlaps the recess in a planar view of the substrate, and in (c), the second film is selectively etched relative to the first film, exposing a portion of an upper surface of the first film in the plurality of first regions and exposing at least a portion of a side surface of the first film in the second region.

[0145] (Supplementary Note 5) The etching method according to Supplementary Note 4, wherein in (a), the mask includes second openings having an opening area larger than that of the first openings, the mask is disposed on the second film such that the second openings further overlap the recesses in a plan view of the substrate, and the number of the recesses overlapping with the first openings is smaller than the number of the recesses overlapping with the second openings.

[0146] (Appendix 6) The etching method according to Appendix 1, wherein the first film is disposed on the second film, and the first film includes an opening exposing a portion of the second film, and in (c), the portion of the second film is selectively etched in the opening relative to the first film, thereby forming a recess in the second film.

[0147] (Supplementary Note 7) The etching method according to Supplementary Note 2, wherein (c) further comprises, between (c1) and (c2), the step of: (c3) generating plasma by setting a power of the source RF signal to a fifth power that is equal to or lower than the fourth power, and supplying the first bias signal to the substrate support at the second power. An example of the fifth power is power H1, H2, and / or H3.

[0148] (Supplementary Note 8) The etching method according to Supplementary Note 7, wherein (c) further comprises, between (c1) and (c3), the step of: (c4) generating plasma by setting the power of the source RF signal to a sixth power that is lower than the first power and higher than the fourth power, and supplying the first bias signal to the substrate support at the second power. An example of the sixth power is power H2 and / or H3.

[0149] (Supplementary Note 9) The etching method according to Supplementary Note 2, wherein the fourth power is zero power.

[0150] (Supplementary Note 10) The etching method according to Supplementary Note 7, wherein the fourth power and the fifth power are zero power.

[0151] (Supplementary Note 11) The etching method according to Supplementary Note 7, wherein the fifth power is lower than the fourth power and is zero power.

[0152] (Supplementary Note 12) The etching method according to any one of Supplementary Notes 1 to 11, wherein the second power is zero power.

[0153] (Supplementary Note 13) The etching method according to any one of Supplementary Notes 1 to 12, wherein the first frequency is 60 MHz to 200 MHz.

[0154] (Supplementary Note 14) The etching method according to any one of Supplementary Notes 1 to 13, wherein the frequency of the first bias signal is 100 kHz to 800 kHz.

[0155] (Supplementary Note 15) The etching method according to any one of Supplementary Notes 1 to 14, wherein in (c1), a second bias RF signal having a second frequency lower than the first frequency is supplied to the substrate support at a seventh power, and in (c2), the second bias RF signal is supplied to the substrate support at an eighth power lower than the seventh power. Note that examples of each power are as follows: Seventh power: Power M2 Eighth power: Power M1

[0156] (Supplementary Note 16) The etching method according to Supplementary Note 15, wherein the second frequency is 3 MHz to 40 MHz.

[0157] (Supplementary Note 17) The etching method according to any one of Supplementary Notes 1 to 16, wherein the metal-containing gas is a gas containing a tungsten-containing gas or a molybdenum-containing gas.

[0158] (Supplementary Note 18) The etching method according to Supplementary Note 17, wherein the tungsten-containing gas includes tungsten fluoride.

[0159] (Supplementary Note 19) The etching method according to any one of Supplementary Notes 1 to 16, wherein the processing gas includes a carbon-containing gas.

[0160] (Supplementary Note 20) The etching method according to Supplementary Note 19, wherein the carbon-containing gas is a fluorocarbon gas.

[0161] (Supplementary Note 21) An etching method performed in a plasma processing apparatus including a chamber, the etching method comprising: (a) preparing a substrate on a substrate support disposed in the chamber, the substrate including a first film including at least one selected from the group consisting of SiN, SiON, SiC, SiOC, and boron nitride, and a second film including silicon and oxygen; (b) supplying a process gas including a metal-containing gas into the chamber; and (c) while (b) is being performed, selectively etching the second film relative to the first film, the etching method comprising: (c1) setting a power of a source RF signal having a first frequency to a first power to generate plasma, and supplying a first bias signal having a frequency that does not substantially contribute to plasma generation to the substrate support at a second power; and (c2) after (c1), supplying the first bias signal to the substrate support at a third power higher than the second power.

[0162] (Supplementary Note 22) A plasma processing apparatus including a chamber and a control unit, wherein the control unit executes the following controls: (a) controlling a substrate disposed in the chamber and prepared on a substrate support, the substrate including a first film containing silicon and nitrogen and a second film containing silicon and oxygen; (b) controlling a process gas containing a tungsten-containing gas to be supplied into the chamber; and (c) controlling, while (b) is being performed, a process gas to selectively etch the second film relative to the first film, the process gas including: (c1) setting a power of a source RF signal having a first frequency to a first power to generate plasma, and supplying a first bias signal having a frequency that does not substantially contribute to plasma generation at a second power; and (c2) after (c1), supplying the first bias signal to the substrate support at a third power higher than the second power.

[0163] The exemplary embodiments described above may be modified in various ways without departing from the scope and spirit of the present disclosure. For example, some components in one embodiment may be added to other embodiments within the scope of ordinary creativity of a person skilled in the art. Also, some components in one embodiment may be replaced with corresponding components in other embodiments.

[0164] REFERENCE SIGNS LIST 1: plasma processing apparatus, 2: control section, 11: substrate support section, MK: mask, OP1: opening, OP2: opening, R1: region, R2: region, RC: recess, SS: side surface, TS: upper surface, W: substrate

Claims

1. An etching method performed in a plasma processing apparatus having a chamber, comprising: (a) a step of preparing a substrate on a substrate support disposed in the chamber, the substrate including a first film including silicon and nitrogen and a second film including silicon and oxygen; (b) a step of supplying a process gas including a metal-containing gas into the chamber; and (c) a step of selectively etching the second film relative to the first film while (b) is being performed, the step of: (c1) setting a power of a source RF signal having a first frequency to a first power to generate plasma, and supplying a first bias signal having a frequency that does not substantially contribute to plasma generation to the substrate support at a second power; and (c2) after (c1), supplying the first bias signal to the substrate support at a third power higher than the second power.

2. The etching method of claim 1, wherein (c2) further comprises setting the power of the source RF signal to a fourth power lower than the first power.

3. The etching method of claim 1, wherein in (a), the substrate includes, in a planar view of the substrate, a plurality of first regions and at least one second region between the first regions, the first film is disposed in the plurality of first regions and includes a recess in the at least one second region, and the second film is disposed in the recess, and in (c), the second film is selectively etched relative to the first film, exposing at least a portion of a side surface of the first film in the second region.

4. The etching method of claim 3, wherein in (a), the second film is further disposed on the first film, the substrate includes a mask on the second film including a first opening, the mask being disposed on the second film such that the first opening overlaps the recess in a planar view of the substrate, and in (c), the second film is selectively etched relative to the first film to expose a portion of an upper surface of the first film in the plurality of first regions and to expose at least a portion of a side surface of the first film in the second region.

5. The etching method according to claim 4, wherein in (a), the mask includes second openings having a larger opening area than the first openings, the mask is disposed on the second film such that, in a plan view of the substrate, the second openings further overlap the recesses, and the number of the recesses that overlap the first openings is smaller than the number of the recesses that overlap the second openings.

6. The etching method of claim 1, wherein the first film is disposed on the second film, the first film including an opening exposing a portion of the second film, and in (c), the portion of the second film is selectively etched in the opening relative to the first film to form a recess in the second film.

7. The etching method of claim 2, wherein (c) further comprises the step of: (c3) between (c1) and (c2), setting the power of the source RF signal to a fifth power equal to or lower than the fourth power to generate plasma, and supplying the first bias signal to the substrate support at the second power.

8. The etching method of claim 6, wherein (c) further comprises the step of: (c4) between (c1) and (c3), setting the power of the source RF signal to a sixth power lower than the first power and higher than the fourth power to generate plasma, and supplying the first bias signal to the substrate support at the second power.

9. The etching method of claim 2, wherein said fourth power is zero power.

10. The etching method of claim 7, wherein the fourth power and the fifth power are zero power.

11. The etching method of claim 7, wherein said fifth power is lower than said fourth power and said fifth power is zero power.

12. The etching method of claim 1, wherein said second power is zero power.

13. The etching method of claim 1, wherein the first frequency is between 60 MHz and 200 MHz.

14. The etching method of claim 1, wherein the frequency of the first bias signal is between 100 kHz and 800 kHz.

15. The etching method of claim 1, wherein in (c1), a second bias RF signal having a second frequency lower than the first frequency is supplied to the substrate support at a seventh power, and in (c2), the second bias RF signal is supplied to the substrate support at an eighth power lower than the seventh power.

16. The etching method of claim 15, wherein the second frequency is between 3 MHz and 40 MHz.

17. The etching method according to any one of claims 1 to 15, wherein the metal-containing gas is a gas containing tungsten-containing gas or molybdenum-containing gas.

18. The etching method of claim 17, wherein the tungsten-containing gas comprises tungsten fluoride.

19. The etching method of any one of claims 1 to 16, wherein the process gas comprises a carbon-containing gas.

20. The etching method of claim 18, wherein the carbon-containing gas is a fluorocarbon gas.

21. An etching method performed in a plasma processing apparatus equipped with a chamber, comprising: (a) a step of preparing a substrate on a substrate support disposed in the chamber, the substrate including a first film including at least one selected from the group consisting of SiN, SiON, SiC, SiOC, and boron nitride, and a second film including silicon and oxygen; (b) a step of supplying a process gas including a metal-containing gas into the chamber; and (c) a step of selectively etching the second film relative to the first film while (b) is being performed, the step of: (c1) setting a power of a source RF signal having a first frequency to a first power to generate plasma, and supplying a first bias signal having a frequency that does not substantially contribute to plasma generation to the substrate support at a second power; and (c2) after (c1), supplying the first bias signal to the substrate support at a third power higher than the second power.

22. A plasma processing apparatus comprising a chamber and a control unit, wherein the control unit executes the following controls: (a) controlling a substrate disposed in the chamber and prepared on a substrate support, the substrate including a first film including silicon and nitrogen and a second film including silicon and oxygen; (b) controlling a process gas including a metal-containing gas to be supplied into the chamber; and (c) controlling, while (b) is being performed, selectively etching the second film relative to the first film, the control including: (c1) controlling a power of a source RF signal having a first frequency to a first power to generate plasma, and supplying a first bias signal having a frequency that does not substantially contribute to plasma generation to the substrate support at a second power; and (c2) controlling, after (c1), supplying the first bias signal to the substrate support at a third power higher than the second power.

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