WO2024180921A1 - Etching method and plasma processing apparatus - Google Patents

Abstract

The present invention provides a technology for etching regions that have different opening sizes. The present invention provides an etching method which is carried out in a plasma processing apparatus that has a chamber. This method comprises: (a) a step for providing a substrate which comprises an etching object film that contains silicon and oxygen and a mask that is disposed on the etching object film, wherein the mask has at least one of a silicon-containing film and an organic film, while having a first opening and a second opening that has a larger opening size than the first opening; and (b) a step for etching the etching object film through the first opening and the second opening with use of a plasma that is generated from a processing gas which contains a first gas that is composed of at least one gas selected from the group consisting of a C3F6 gas, a C3F7 gas, a C2F6 gas and a C3H2F4 gas.

Description

Etching method and plasma processing apparatus

An exemplary embodiment of the present disclosure relates to an etching method and a plasma processing apparatus.

Patent document 1 discloses the formation of trenches of different depths in a semiconductor substrate using a mask with different opening dimensions.

JP 2000-150632 A

This disclosure provides techniques for etching areas with different opening dimensions.

In one exemplary embodiment of the present disclosure, there is provided an etching method performed in a plasma processing apparatus having a chamber, the etching method including the steps of: (a) providing a substrate having a film to be etched containing silicon and oxygen and a mask on the film to be etched, the mask having a first opening and a second opening having an opening dimension larger than that of the first opening, and including at least one of a silicon-containing film and an organic film; and (b) etching the film to be etched through the first opening and _the second opening using plasma generated from a process gas containing _a first gas, the _first gas being at least one gas selected from the group consisting of _C3F6 gas, _C3F7 gas, _C2F6 gas _, or _C3H2F4 gas _.

In accordance with one exemplary embodiment of the present disclosure, a technique can be provided for etching areas having different opening dimensions.

FIG. 1 is a diagram for explaining a configuration example of a plasma processing apparatus. FIG. 1 is a diagram for explaining a configuration example of a capacitively coupled plasma processing apparatus. 1 is a flow chart illustrating an example of the method. 2 is a diagram showing an example of a cross-sectional structure of a substrate W provided in a process ST1. FIG. 1 is a diagram showing an example of a cross-sectional structure in the vicinity of a mask MK being processed in step ST2; 13 is a diagram showing an example of a cross-sectional structure of the substrate W after being processed in step ST2. FIG. FIG. 1 is a diagram showing the results of Example 1 and Reference Example 1. FIG. 1 shows the results of Example 2 and Reference Example 2. FIG. 1 is a graph showing the results of Examples 3 to 5 and Reference Examples 3 to 4.

Each embodiment of the present disclosure is described below.

In one exemplary embodiment, an etching method is provided that is performed in a plasma processing apparatus having a chamber, the etching method including the steps of: (a) providing a substrate having a film to be etched that contains silicon and oxygen and a mask on the film to be etched, the mask having a first opening and a second opening that is larger in opening dimension than the first opening, and including at least one of a silicon-containing film and an organic film; and (b) etching the film to be etched through the first opening and the second opening using plasma generated from a process gas that includes _{a first} gas, the _{first gas being at least one gas selected from the group consisting of C3F6 gas, C3F7 gas, C2F6 gas , or C3H2F4 gas .}

In one exemplary embodiment, in (b), a first film containing carbon and fluorine is formed on a first sidewall of the mask that defines the first opening, and a second film containing carbon and fluorine is formed on a second sidewall of the mask that defines the second opening, and the film to be etched is etched through the first opening in which the first film is formed and the second opening in which the second film is formed.

In one exemplary embodiment, in (b), the thickness of the second film formed on the second sidewall of the mask is greater than the thickness of the first film formed on the first sidewall of the mask.

In one exemplary embodiment, in (b), a first recess corresponding to the first opening and a second recess corresponding to the second opening are formed in the film to be etched.

In one exemplary embodiment, in (b), a first film is formed continuously from a first sidewall of the mask on a first sidewall of the film to be etched that defines a first recess, and a second film is formed continuously from a second sidewall of the mask on a second sidewall of the film to be etched that defines a second recess.

In one exemplary embodiment, in (b), the thickness of the second film formed on the second sidewall of the film to be etched is greater than the thickness of the first film formed on the first sidewall of the film to be etched.

In one exemplary embodiment, in (b), the first sidewall and the second sidewall of the film to be etched are etched horizontally by the fluorine components in the first film and the second film.

In one exemplary embodiment, in (b), the horizontal etching amount of the second sidewall of the film to be etched is greater than the horizontal etching amount of the first sidewall of the film to be etched.

In one exemplary embodiment, the process gas further comprises an oxygen-containing gas.

In one exemplary embodiment, the process gas further comprises an inert gas.

In one exemplary embodiment, the ratio of the flow rate of the first gas to the total flow rate of the processing gas excluding the inert gas is 33% by volume or more and 50% by volume or less.

In one exemplary embodiment, the process gas further includes a second gas different from the first gas, the second gas being a CF-based gas or a CHF-based gas.

In one exemplary embodiment, the number of double bonds between carbon atoms constituting the second gas is greater than the number of double bonds between carbon atoms constituting the first gas.

In one exemplary embodiment, the second gas is at least one gas selected from the group consisting of C ₄ F ₆ gas, C ₄ F ₈ gas, and C ₅ F ₈ gas.

In one exemplary embodiment, the ratio of the flow rate of the first gas to the combined flow rate of the first gas and the second gas is 33 volume % or more and 67 volume % or less.

In one exemplary embodiment, the process gas further comprises an oxygen-containing gas.

In one exemplary embodiment, the process gas further comprises an inert gas.

In one exemplary embodiment, the ratio of the opening dimension of the second opening to the opening dimension of the first opening is greater than or equal to 1.1 and less than or equal to 20.

In one exemplary embodiment, the mask is a silicon nitride film.

In one exemplary embodiment, there is provided a plasma processing apparatus having a chamber and a controller, the controller performing the following steps: (a) providing a substrate having a film to be etched containing silicon and oxygen and a mask on the film to be etched, the mask having a first opening and a second opening having an opening dimension larger than the first opening, and including at least one of a silicon-containing film and an organic film; and (b) etching the film to be etched through the first opening and the second opening using plasma generated from a process gas containing a first gas, the first gas being at _{least one} gas selected from the group consisting of _C3F6 gas, _C3F7 gas, _C2F6 gas _, or _{C3H2F4 gas .}

Hereinafter, each embodiment of the present disclosure will be described in detail with reference to the drawings. In addition, the same or similar elements in each drawing are given the same reference numerals, and duplicated explanations will be omitted. Unless otherwise specified, the positional relationship such as up, down, left, right, etc. will be described based on the positional relationship shown in the drawings. The dimensional ratios in the drawings do not indicate the actual ratios, and the actual ratios are not limited to the ratios shown in the drawings.
<Configuration Example of Plasma Processing Apparatus>
FIG. 1 is a diagram for explaining a configuration example of a plasma processing apparatus. In one embodiment, the plasma processing apparatus 1 is an example of a substrate processing apparatus. The plasma processing apparatus 1 includes a control unit 2, a plasma processing chamber 10, a substrate support unit 11, and a plasma generation unit 12. The plasma processing chamber 10 has a plasma processing space. The plasma processing chamber 10 also has at least one gas supply port for supplying at least one processing gas to the plasma processing space, and at least one gas 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 unit 11 is disposed in the plasma processing space, and has a substrate support surface for supporting a substrate.

The plasma generating unit 12 is configured to generate plasma from at least one processing gas supplied into the plasma processing space. The plasma formed in the plasma processing space may be capacitively coupled plasma (CCP), inductively coupled plasma (ICP), ECR plasma (Electron-Cyclotron-resonance plasma), Helicon wave excited plasma (HWP), or surface wave plasma (SWP), etc. Additionally, various types of plasma generating units may be used, including AC (Alternating Current) plasma generating units and DC (Direct Current) plasma generating units. In one embodiment, the AC signal (AC power) used in the AC plasma generating unit has a frequency in the range of 100 kHz to 10 GHz. Thus, AC signals include RF (Radio Frequency) signals and microwave signals. In one embodiment, the RF signal has a frequency in the range of 100 kHz to 150 MHz.

The control unit 2 processes computer-executable instructions that cause the plasma processing apparatus 1 to perform the various steps described in this disclosure. The control unit 2 may be configured to control each element of the plasma processing apparatus 1 to perform the various steps described herein. In one embodiment, a part or all of the control unit 2 may be configured as a system external to 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 is realized, for example, by a computer 2a. The processing unit 2a1 may be configured to perform various control operations by reading a program from the storage unit 2a2 and executing the read program. This program may be stored in the storage unit 2a2 in advance, or may be acquired via a medium when necessary. The acquired program is stored in the storage unit 2a2 and is read from the storage unit 2a2 by the processing unit 2a1 and executed. The medium may be various storage media readable by the computer 2a, or may be a communication line connected to the communication interface 2a3. The processing unit 2a1 may be a CPU (Central Processing Unit). The memory unit 2a2 may include a RAM (Random Access Memory), a ROM (Read Only Memory), a HDD (Hard Disk Drive), a SSD (Solid State Drive), or a combination of these. The communication interface 2a3 may communicate with each element of the plasma processing apparatus 1 via a communication line such as a LAN (Local Area Network).

Below, we will explain a configuration example of a capacitively coupled plasma processing device as an example of the plasma processing device 1. Figure 2 is a diagram for explaining a configuration example of a capacitively coupled plasma processing device.

The capacitively coupled plasma processing apparatus 1 includes a control unit 2, a plasma processing chamber 10, a gas supply unit 20, a power supply 30, and an exhaust system 40. The plasma processing apparatus 1 also includes a substrate support unit 11 and a gas inlet unit. The gas inlet unit is configured to introduce at least one processing gas into the plasma processing chamber 10. The gas inlet unit includes a shower head 13. The substrate support unit 11 is disposed in the plasma processing chamber 10. The shower head 13 is disposed above the substrate support unit 11. In one embodiment, the shower head 13 constitutes at least a part of the ceiling of the plasma processing chamber 10. The plasma processing chamber 10 has a plasma processing space 10s defined by the shower head 13, the sidewall 10a of the plasma processing chamber 10, and the substrate support unit 11. The plasma processing chamber 10 is grounded. The shower head 13 and the substrate support unit 11 are electrically insulated from the housing of the plasma processing chamber 10.

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 the substrate W and an annular region 111b for supporting the ring assembly 112. A wafer is an example of a substrate W. The annular region 111b of the main body 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.

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 may 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 other members surrounding the electrostatic chuck 1111, such as an annular electrostatic chuck or an annular insulating member, may have the annular region 111b. 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. At least one RF/DC electrode coupled to an RF power source 31 and/or a DC power source 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. Also, the electrostatic electrode 1111b may function as a lower electrode. Thus, the substrate support 11 includes at least one lower electrode.

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.

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 back surface of the substrate W and the central region 111a.

The shower head 13 is configured to introduce at least one processing gas from the gas supply unit 20 into the plasma processing space 10s. The shower head 13 has at least one gas supply port 13a, at least one gas diffusion chamber 13b, and multiple gas inlets 13c. The processing gas supplied to the gas supply port 13a passes through the gas diffusion chamber 13b and is introduced into the plasma processing space 10s from the multiple gas inlets 13c. The shower head 13 also includes at least one upper electrode. Note that the gas introduction unit may include, in addition to the shower head 13, one or more side gas injectors (SGI) attached to one or more openings formed in the side wall 10a.

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 respective gas source 21 through a respective flow controller 22 to the showerhead 13. 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.

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 causes a plasma to be formed from at least one processing gas supplied to the plasma processing space 10s. Thus, the RF power supply 31 can function as at least a part of the plasma generating unit 12. In addition, by supplying a bias RF signal to at least one lower electrode, a bias potential is generated on the substrate W, and ion components in the formed plasma can be attracted to the substrate W.

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 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.

The second RF generator 31b is coupled to at least one lower electrode via at least one impedance matching circuit and 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 provided to at least one lower electrode. Also, in various embodiments, at least one of the source RF signal and the bias RF signal may be pulsed.

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 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 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.

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 a 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 a positive polarity or a negative polarity. Also, the sequence of voltage pulses may include one or more positive polarity voltage pulses and one or more negative polarity voltage pulses within one period. The first and second DC generating units 32a and 32b may be provided in addition to the RF power source 31, or the first DC generating unit 32a may be provided in place of the second RF generating unit 31b.

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 adjusted by the pressure regulating valve. The vacuum pump may include a turbomolecular pump, a dry pump, or a combination thereof.

<Example of Etching Method>
Fig. 3 is a flow chart showing an example of an etching method (hereinafter also referred to as "the method") according to an exemplary embodiment. As shown in Fig. 3, the method includes a step ST1 of providing a substrate and a step ST2 of etching the substrate. The processes in each step may be performed by the above-mentioned plasma processing apparatus 1. In the following, an example will be described in which the control unit 2 controls each part of the capacitively coupled plasma processing apparatus 1 (see Fig. 2) to perform the method.

(Step ST1: Providing a substrate)
In step ST1, a substrate W is provided in a plasma processing space 10s of the plasma processing apparatus 1. The substrate W is carried into the plasma processing chamber 10 by a transport arm, and placed on a central region 111a of a substrate support 11. The substrate W is attracted to 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 a substrate W provided in process ST1. In one embodiment, the substrate W has a silicon oxide film Ox and a mask MK. The substrate W may further include an undercoat film UF. The substrate W may be used in the manufacture of semiconductor devices. The semiconductor devices include, for example, semiconductor memory devices such as DRAMs and 3D-NAND flash memories.

The substrate W has a first region RE1 and a second region RE2. The first region RE1 and the second region RE2 are regions each having a given range on the substrate W in a plan view of the substrate W (when viewed from above in FIG. 4). The first region RE1 and the second region RE2 may be two regions adjacent to each other, or may be two regions separated from each other. In one embodiment, the first region RE1 is a region in which the density of patterns such as grooves and holes formed in the mask MK is high (hereinafter also referred to as a "high-density region"). In one embodiment, the second region RE2 is a region in which the density of patterns such as grooves and holes formed in the mask MK is low (hereinafter also referred to as a "low-density region").

In one embodiment, the base film UF is provided from the first region RE1 to the second region RE2. The base film UF may be, for example, a silicon wafer, an organic film formed on a silicon wafer, a dielectric film, a metal film, a semiconductor film, or a laminated film of these. In one embodiment, the base film UF may include a silicon-containing film. The silicon-containing film may be, for example, a silicon oxide film, a silicon nitride film, a silicon carbonitride film, a polysilicon film, or a laminated film containing two or more of these films. The silicon-containing film may be, for example, a silicon oxide film and a silicon nitride film alternately laminated. The silicon-containing film may be, for example, a silicon oxide film and a polysilicon film alternately laminated. The silicon-containing film may be, for example, a laminated film containing a silicon nitride film, a silicon oxide film, and a polysilicon film.

In one embodiment, the silicon oxide film Ox is provided on the base film UF from the first region RE1 to the second region RE2. The silicon oxide film Ox is an example of a film to be etched in this method. The film to be etched in this method may be a film containing silicon and oxygen. Examples of films containing silicon and oxygen include a silicon oxide film, a SiON film, a SiCOH film, etc.

In one embodiment, the mask MK is provided on the silicon oxide film Ox from the first region RE1 to the second region RE2. The mask MK has one or more first openings OP1 in the first region RE1. The first openings OP1 are openings defined by a first sidewall s1 of the mask MK. The mask MK has one or more second openings OP2 in the second region RE2. The second openings OP2 are openings defined by a second sidewall s2 of the mask MK.

In one embodiment, the first opening OP1 and the second opening OP2 are openings for forming holes, contact holes, lines and spaces, slits, trenches, etc. in the silicon oxide film Ox. In one example, the first opening OP1 and the second opening OP2 have a shape such as a circle, an ellipse, a line, a rectangle, etc. in a plan view. The first opening OP1 and the second opening OP2 may have similar shapes in a plan view, or may have different shapes. As shown in FIG. 4, the opening dimension CD22 of the second opening OP2 (e.g., the diameter of a circular opening, the minor axis of an elliptical opening, the line width of a linear opening, and the length of the short side or long side of a rectangular opening) is larger than the opening dimension CD12 of the first opening OP1. That is, the ratio of the opening dimension CD22 to the opening dimension CD12 is larger than 1. In one example, the ratio of the opening dimension CD22 to the opening dimension CD12 is 1.1 or more. In one example, the ratio is 20 or less.

In one embodiment, the mask MK has a given pattern. For example, the mask MK may have a line and space pattern (trench) in the first region RE1 and/or the second region RE2. The line and space pattern may be configured by arranging a plurality of openings (first opening OP1/second opening OP2) having a planar line-of-sight shape at regular intervals. For example, the mask MK may have an array pattern in the first region RE1 and/or the second region RE2. The array pattern may be configured by arranging a plurality of openings (first opening OP1 and/or second opening OP2) having a planar circular or elliptical shape at regular intervals. As shown in FIG. 4, the dimension P2 between the patterns of the mask MK in the second region RE2 (e.g., the pitch of the line and space pattern) is larger than the dimension P1 between the patterns of the mask MK in the first region RE1.

In one embodiment, the pattern dimension CD21 (e.g., the line width in a line and space pattern) in the second region RE2 of the mask MK is different from the pattern dimension CD11 in the first region RE1. In one example, the pattern dimension CD21 is larger than the pattern dimension CD11. In one example, the pattern dimension CD21 is smaller than the pattern dimension CD11. In one embodiment, the pattern dimension CD21 and the pattern dimension CD11 are the same.

In one embodiment, the mask MK is formed from a material having an etching rate lower than that of the silicon oxide film Ox with respect to the plasma generated in step ST2. In one embodiment, the mask MK includes a silicon-containing film or an organic film. The silicon-containing film may be, for example, a silicon nitride film, a silicon carbonitride film, a polycrystalline silicon film, or a laminated film including two or more of these films. The organic film may be, for example, an amorphous carbon film, a spin-on carbon (SOC) film, or a photoresist film. The amorphous carbon (ACL) film may be doped with an element such as boron, and may be, for example, a boron-containing amorphous carbon film (B-doped ACL), an arsenic-containing amorphous carbon film (As-doped ACL), a tungsten-containing amorphous carbon film (W-doped ACL), or a xenon-containing amorphous carbon film (Xe-doped ACL).

In one embodiment, each film constituting the substrate W (undercoat film UF, silicon oxide film Ox, and mask MK) may be formed by CVD, ALD, PVD, spin coating, or the like. In one embodiment, the first opening OP1 and the second opening OP2 of the mask MK may be formed by etching the mask MK, or may be formed by lithography. In one embodiment, each film may be a flat film or may have irregularities. In one embodiment, the substrate W may further have another film below the undercoat film UF. In this case, recesses having shapes corresponding to the first opening OP1 and the second opening OP2 may be formed in the silicon oxide film Ox and the undercoat film UF, and used as a mask for etching the other film.

In one embodiment, at least a part of the process for forming each film on the substrate W may be performed within the space of the plasma processing chamber 10. For example, when the first opening OP1 and the second opening OP2 are formed by etching, the etching and the etching of the silicon oxide film Ox in step ST2 may be performed consecutively within the same chamber. In one embodiment, after all of the films on the substrate W are formed in an apparatus or chamber external to the plasma processing apparatus 1, the substrate W may be provided by being loaded into the plasma processing space 10s of the plasma processing apparatus 1.

In one embodiment, after the substrate W is provided to the central region 111a of the substrate support 11, the substrate support 11 is controlled to a given temperature by a temperature control module. In one example, controlling the temperature of the substrate support 11 to a given temperature includes setting the temperature of the heat transfer fluid flowing through the flow path 1110a or the heater temperature to a given temperature, or to a temperature different from the given temperature. The timing at which the heat transfer fluid starts to flow through the flow path 1110a may be before or after the substrate W is placed on the substrate support 11, or may be simultaneous. The temperature of the substrate support 11 may be controlled to a given temperature before step ST1. That is, the substrate W may be provided to the substrate support 11 after the temperature of the substrate support 11 is controlled to a given temperature. In one embodiment, the given temperature is equal to or greater than 0°C and equal to or less than 170°C.

In one embodiment, instead of controlling the substrate support 11 to a given temperature, the substrate W may be controlled to a given temperature. Controlling the temperature of the substrate W to a given temperature includes setting the temperature of the substrate support 11, the temperature of the heat transfer fluid flowing through the flow path 1110a, and/or the heater temperature to a given temperature or to a temperature different from the given temperature.

(Step ST2: Etching)
In step ST2, the silicon oxide film Ox is etched, whereby the portions of the silicon oxide film Ox that are not covered by the mask MK (the portions exposed in the first opening OP1 and the second opening OP2) are etched to form recesses.

First, _a processing gas containing _a first gas is supplied into the plasma processing space 10s from _the gas supply unit _20. The first gas is at least one gas selected from the group consisting of _C3F6 gas, _C3F7 gas, _C2F6 gas _, and _C3H2F4 gas.

In one embodiment, the process gas further comprises an oxygen-containing gas, which in one example is at least one gas selected from the group consisting of _O2 gas, CO gas, and _CO2 gas.

In one embodiment, the process gas further comprises an inert gas, which in one example is a noble gas such as Ar gas, He gas, and Kr gas, or _N2 gas.

In one embodiment, the ratio of the flow rate of the first gas to the total flow rate of the processing gas excluding the inert gas is 33% by volume or more and 50% by volume or less.

In one embodiment, the process gas further includes a second gas, which is a CF-based gas or a CHF-based gas different from the first gas. In one embodiment, the number of double bonds between carbon _atoms constituting the second gas is greater than _the number of double bonds between carbon atoms constituting the first gas. For example, the second gas may be at least one gas selected from the group consisting of _C4F6 gas, _C4F8 gas _{, and C5F8 gas} .

In one embodiment, the ratio (Q1/(Q1+Q2)) of the flow rate of the first gas to the combined flow rate (Q1+Q2) of the flow rate of the first gas (Q1) and the flow rate of the second gas (Q2) is 33 volume % or more and 67 volume % or less.

Next, a source RF signal is supplied to the lower electrode of the substrate support 11 and/or the upper electrode of the shower head 13. This generates a high-frequency electric field between the shower head 13 and the substrate support 11, and plasma is generated from the processing gas in the plasma processing space 10s. A bias signal may be supplied to the lower electrode of the substrate support 11. In this case, a bias potential is generated between the plasma and the substrate W. The bias potential attracts active species such as ions and radicals in the plasma to the substrate W. The bias signal may be a bias RF signal supplied from the second RF generator 31b. The bias signal may also be a bias DC signal supplied from the DC generator 32a.

In one embodiment, the source RF signal and the bias signal may both be continuous waves or pulse waves, or one may be a continuous wave and the other a pulse wave. When the source RF signal and the bias signal are both pulse waves, the periods of the two pulse waves may or may not be synchronized. The duty ratio of the source RF signal and/or bias signal pulse wave may be set appropriately, for example, 1 to 80%, or 5 to 50%. When a bias DC signal is used as the bias signal, the pulse wave may have a rectangular, trapezoidal, triangular, or combination thereof. The polarity of the bias DC signal may be negative or positive, as long as the potential of the substrate W is set to provide a potential difference between the plasma and the substrate to attract ions.

In one embodiment, the supply and halt of at least one of the source RF signal and the bias signal may be alternately repeated. For example, the supply and halt of the bias signal may be alternately repeated while the source RF signal is continuously supplied. For example, the bias signal may be continuously supplied while the supply and halt of the source RF signal are alternately repeated. For example, the supply and halt of both the source RF signal and the bias signal may be alternately repeated.

In one embodiment, during processing in step ST2, the temperature of the substrate support 11 may be controlled to a given temperature set in step ST1. In one embodiment, instead of the temperature of the substrate support 11, the temperature of the substrate W may be controlled to a given temperature.

FIG. 5 is a diagram showing an example of a cross-sectional structure near the mask MK during processing in step ST2. As shown in FIG. 5, in the first region RE1, the portion of the silicon oxide film Ox exposed in the first opening OP1 is etched in the depth direction (from top to bottom in FIG. 5) by active species in the plasma. This forms a recess RC1 corresponding to the first opening OP1. Also, in the first region RE1, a first film FM1 is formed on the mask MK and the silicon oxide film Ox. In one embodiment, the first film FM1 is formed by deposition on the first top tp1 and first sidewall s1 of the mask MK. Also, the first film FM1 is formed by deposition on the first sidewall ss1 and first bottom bt1 of the silicon oxide film Ox that define the first recess RC1.

Similarly, in the second region RE2, the portion of the silicon oxide film Ox exposed at the second opening OP2 is etched in the depth direction by active species in the plasma. This forms a second recess RC2 corresponding to the second opening OP2. In one embodiment in which the second film FM2 is formed on the mask MK and the silicon oxide film Ox in the second region RE2, the second film FM2 is deposited on the second top tp2 and second sidewall s2 of the mask MK. The second film FM2 is also deposited and formed on the second sidewall ss2 and second bottom bt2 of the silicon oxide film Ox that define the second recess RC2.

The first film FM1 and the second film FM2 contain carbon (C) and fluorocarbon ( _CF2 ) dissociated from the first gas into the plasma. The first film FM1 and the second film FM2 on the mask MK can function as a protective film that suppresses etching of the mask MK due to the carbon component. The first film FM1 and the second film FM2 on the silicon oxide film Ox can function as a film that promotes etching of the silicon oxide film Ox due to the fluorine component.

As shown in FIG. 5, the thickness (t2) of the second film FM2 formed on the second sidewall s2 of the mask MK and the second sidewall ss2 of the silicon oxide film Ox is greater than the thickness (t1) of the first film FM1 formed on the first sidewall s1 of the mask MK and the first sidewall ss1 of the silicon oxide film Ox. This is believed to be due to the fact that the second opening OP2 has a larger opening dimension than the first opening OP1, allowing more active species in the plasma to flow in.

The first film FM1 and the second film FM2 can function as films that promote etching of the silicon oxide film Ox due to their fluorine components. As a result, the first sidewall ss1 and the second sidewall ss2 of the silicon oxide film Ox can be etched in the horizontal direction as process ST2 progresses. Here, the thickness (t2) of the second film FM2 formed on the second sidewall ss2 of the silicon oxide film Ox is greater than the thickness (t1) of the first film FM1 formed on the first sidewall ss1 of the silicon oxide film Ox. Therefore, in process ST2, the amount of etching in the horizontal direction of the second sidewall ss2 of the silicon oxide film Ox can be greater than the amount of etching in the horizontal direction of the first sidewall ss1.

In one embodiment, the first film FM1 formed on the first sidewall s1 of the mask MK and the first sidewall ss1 of the silicon oxide film Ox is thicker than the first film FM1 formed on the first top tp1 of the mask MK. In one embodiment, the first film FM1 formed on the first top tp1 of the mask MK is thicker than the first film FM1 formed on the first bottom bt1 of the silicon oxide film Ox.

In one embodiment, the second film FM2 formed on the second sidewall s2 of the mask MK and the second sidewall ss2 of the silicon oxide film Ox is thicker than the second film FM2 formed on the second top tp2 of the mask MK. In one embodiment, the second film FM2 formed on the second top tp2 of the mask MK is thicker than the second film FM2 formed on the second bottom bt2 of the silicon oxide film Ox.

FIG. 6 is a diagram showing an example of the cross-sectional structure of the substrate W after processing in step ST2. In the example shown in FIG. 6, the first recess RC1 and the second recess RC2 are etched in the depth direction by the etching in step ST2, and the bottoms bt1 and bt2 of both recesses reach the base film UF. As shown in FIG. 6, at the end of step ST2, the first film FM1 and the second film FM2 may be removed.

As described above, in process ST2, the amount of etching of the second sidewall ss2 of the silicon oxide film Ox in the horizontal direction can be greater than the amount of etching of the first sidewall ss1 in the horizontal direction. This can reduce the difference in pattern dimensions (CD loading) between the first region RE1 and the second region RE2. For example, the CD loading before process ST2 shown in FIG. 4 is ΔCD1 (CD21-CD11). The CD loading after process ST2 shown in FIG. 6 is ΔCD2 (CD21x-CD11x). In this case, the relationship ΔCD2<ΔCD1 holds. According to this method, the CD loading can be improved before and after etching.

In step ST2, the first gas is at least one _gas selected from the group consisting of _C3F6 gas, _C3F7 gas, _C2F6 gas _{, and C3H2F4 gas} . By using plasma generated from _a process gas containing the first gas, etching of _the silicon _oxide film Ox can be promoted. This is considered to be because the first gas is easily dissociated by single bonds between carbons constituting the first gas, and provides more fluorine, which is an etchant for the silicon oxide film Ox, in the plasma. According to this method, the etching process time can be shortened.

The first film FM1 and the second film FM2 on the mask MK formed in step ST2 can function as a protective film that suppresses etching of the mask MK due to their carbon components. Therefore, etching of the mask MK in the depth direction can be suppressed in step ST2. According to this method, the etching selectivity of the silicon oxide film Ox to the mask MK can be improved.

<Example>
Next, examples of the present processing method will be described, but the present disclosure is not limited to the following examples.
Example 1
In Example 1, a substrate having a structure similar to that of the substrate W shown in FIG. 4 was etched using the plasma processing apparatus 1 shown in FIG. 2 along the flow described with reference to FIG. 3. A silicon nitride film was used as the mask MK. A line and space pattern was formed in each of the first region RE1 and the second region RE2 of the mask MK. The line width of the line formed in the first region RE1 was 26.9 nm, and the pitch was 40 nm. The line width of the line formed in the second region RE2 of the mask MK was 50.8 nm, and the pitch was 200 nm. The processing gas used in step ST2 contained C ₃ F ₆ gas and Ar gas. The etching by step ST2 was performed for 20 seconds. During step ST2, the emission of plasma was analyzed using an OES (Optical Emission Spectrometry) device, and the component ratios of CF ₂ , C, and F in the plasma were measured. Further, from a TEM image of the substrate after etching, the film thicknesses of the first film FM1 and the second film FM2 formed on the top, corners and sidewalls of the mask MK and on the bottom of the silicon oxide film Ox were measured.

(Reference Example 1)
In Reference Example 1, _a substrate having the same configuration as that of Example 1 was etched under the same conditions as those of Example 1, except that the processing gas contained _C4F6 gas and Ar gas. As in Example 1, the component ratios of F, CF, and _CF2 in the plasma in step ST2 were measured. In addition, the film thicknesses of the film DP1 in the first region RE1 and the film DP2 in the second region RE2 formed on the top, corners, and sidewalls of the mask MK and the bottom of the silicon oxide film Ox were measured from the TEM image of the substrate after etching.

FIG. 7 shows the results of Example 1 and Reference Example 1. As shown in the cross-sectional view of FIG. 7, in both Example 1 and Reference Example 1, films (FM1, FM2, DP1, DP2) were formed on the mask MK and the silicon oxide film Ox. In Example 1, the film thickness (5.6 nm/6.3 nm) formed on the sidewall of the mask MK in both regions R1 and R2 was sufficiently larger than the film thickness (2.0 nm/3.9 nm) in Reference Example 1. In particular, the film thickness (6.3 nm) of the second film FM2 on the sidewall of the mask MK in Example 1 was large. On the other hand, in Example 1, the film thickness formed on other parts (the top, corners, and bottom of the recess of the mask MK) was smaller than that of Reference Example 1 in both regions RE1 and RE2. That is, in Example 1, a film was more likely to be formed on the sidewall of the mask MK than in Reference Example 1, and a film was less likely to be formed on other parts. From the above, it is presumed that if etching is continued under the same conditions, etching of the side walls of the mask MK and silicon oxide film Ox in the second region RE2 will proceed more easily in Example 1, resulting in improved CD loading compared to Reference Example 1.

Moreover, in Example 1, the ratios of _CF2 and F in the plasma were higher than those in Reference Example 1. Since the fluorine component in the plasma is greater in Example 1 than in Reference Example 1, it is presumed that when etching is continued under the same conditions, the etching of the silicon oxide film Ox in Example 1 proceeds more easily than in Reference Example 1, and the etching processing time is shortened.

Example 2
In Example 2, a substrate having the same structure as Example 1 was etched using the plasma processing apparatus 1 shown in FIG. 2 along the flow described with reference to FIG. 3. The processing gas used in step ST2 contained C ₃ F ₆ gas, O ₂ gas, and Ar gas. The etching in step ST2 was performed until the bottom of the recess formed in the silicon oxide film Ox reached the undercoat film UF, and the processing time was measured. The etching selectivity of the silicon oxide film Ox to the mask MK was also measured. After etching, the line widths (CD11x and CD21x) of the lines in the first region RE1 and the second region RE2 were measured to obtain the CD loading (ΔCD2). This allowed the CD loading improvement rate (ΔCD improvement rate) before and after etching to be calculated.

(Reference Example 2)
In Reference Example 2, _a substrate having the same configuration as that of Example 2 (Example 1) was etched under the same conditions as those of Example 2, except that the processing gas contained _C4F6 gas, _O2 gas, and Ar gas. As in Example 2, etching was performed until the bottom of the recess formed in the silicon oxide film Ox reached the undercoat film UF, and the processing time was measured. In addition, the etching selectivity of the silicon oxide film Ox to the mask MK was measured. After etching, the line widths (CD11x and CD21x) of the lines in the first region RE1 and the second region RE2 were measured to obtain the CD loading (ΔCD2). This allowed the CD loading improvement rate (ΔCD improvement rate) before and after etching to be calculated.

Figure 8 shows the results of Example 2 and Reference Example 2. As shown in Figure 8, Example 2 had a higher improvement rate in CD loading than Reference Example 2. Furthermore, the etching processing time was 63.7 (seconds) in Example 2, which was significantly shorter than the 90.5 (seconds) in Reference Example 2. The selectivity of the mask MK was the same in Example 2 and Reference Example 2.

(Examples 3 to 5)
In Examples 3 to 5, a substrate having the same structure as in Example 1 was etched using the plasma processing apparatus 1 shown in FIG. 2 along the flow described with reference to FIG. 3. The process gas in step ST2 contained C ₃ F ₆ gas, C ₄ F ₆ gas, O ₂ gas, and Ar gas. In Examples 3 to 5, the flow rate ratio of C ₃ F ₆ gas to the combined flow rate of C ₃ F ₆ gas and C ₄ F ₆ gas was 67 vol%, 67 vol%, and 33 vol%, respectively. In Examples 3 to 5, the flow rate ratio of O ₂ gas to the total flow rate of the process gas excluding Ar gas was 40 vol%, 45 vol%, and 57 vol%, respectively. The etching in step ST2 was performed until the bottom of the recess formed in the silicon oxide film Ox reached the undercoat film UF, and the process time and the selectivity of the mask MK at the end of the etching were measured.

(Reference Examples 3 and 4)
In Reference Examples 3 and 4, substrates having the same configuration as in Examples 3 to 5 (Example 1) were etched under the same conditions as in Examples 3 to 5, except that the processing gas contained C ₄ F ₆ gas, O ₂ gas, and Ar gas. In Reference Examples 3 and 4, the flow rate ratio of O ₂ gas to the total flow rate of the processing gas excluding Ar gas was 60 volume % and 80 volume %, respectively.

Figure 9 shows the results of Examples 3 to 5 and Reference Examples 3 to 4. As shown in Figure 9, Examples 3 to 5 improved the selectivity of the mask MK compared to Reference Examples 3 and 4, and the etching processing time was also significantly reduced.

Embodiments of the present disclosure further include the following aspects:

(Appendix 1)
1. An etching method performed in a plasma processing apparatus having a chamber, comprising:
(a) providing a substrate having a film to be etched containing silicon and oxygen and a mask on the film to be etched, the mask having a first opening and a second opening having a larger opening dimension than the first opening, and including at least one of a silicon-containing film and an organic film;
(b) etching the film to be etched through the first opening and _the second opening using plasma generated from _a process gas containing _a first gas, the _first gas being at least one gas selected from the group consisting of _C3F6 gas, _C3F7 gas, _C2F6 gas _, and _C3H2F4 gas;
An etching method comprising:

(Appendix 2)
In the above (b),
a first film containing carbon and fluorine is formed on a first sidewall of the mask that defines the first opening, and a second film containing carbon and fluorine is formed on a second sidewall of the mask that defines the second opening;
2. The etching method according to claim 1, wherein the etching target film is etched through the first opening in which the first film is formed and the second opening in which the second film is formed.

(Appendix 3)
3. The etching method according to claim 2, wherein in (b), a thickness of the second film formed on the second sidewall of the mask is greater than a thickness of the first film formed on the first sidewall of the mask.

(Appendix 4)
4. The etching method according to claim 2, wherein in (b), a first recess corresponding to the first opening and a second recess corresponding to the second opening are formed in the etching target film.

(Appendix 5)
The etching method of claim 4, wherein in (b), the first film is formed continuously from the first sidewall of the mask on a first sidewall of the etching target film that defines the first recess, and the second film is formed continuously from the second sidewall of the mask on a second sidewall of the etching target film that defines the second recess.

(Appendix 6)
6. The etching method according to claim 5, wherein in (b), a thickness of the second film formed on the second side wall of the etching target film is greater than a thickness of the first film formed on the first side wall of the etching target film.

(Appendix 7)
7. The etching method according to claim 5, wherein in (b), the first sidewall and the second sidewall of the etching target film are etched in a horizontal direction by fluorine components in the first film and the second film.

(Appendix 8)
8. The etching method according to claim 1, wherein in (b), a horizontal etching amount of the second sidewall of the etching target film is greater than a horizontal etching amount of the first sidewall of the etching target film.

(Appendix 9)
9. The etching method of claim 1, wherein the process gas further comprises an oxygen-containing gas.

(Appendix 10)
10. The etching method of any one of claims 1 to 9, wherein the process gas further comprises an inert gas.

(Appendix 11)
11. The etching method according to claim 1, wherein a ratio of a flow rate of the first gas to a total flow rate of the process gas excluding an inert gas is 33 vol.% or more and 50 vol.% or less.

(Appendix 12)
12. The etching method according to claim 1, wherein the process gas further includes a second gas different from the first gas, and the second gas is a CF-based gas or a CHF-based gas.

(Appendix 13)
13. The etching method according to claim 12, wherein a number of double bonds between carbon atoms constituting the second gas is greater than a number of double bonds between carbon atoms constituting the first gas.

(Appendix 14)
_14. The etching method according to claim 12 _, wherein the second gas is at least one gas selected from the group consisting of _C4F6 gas, _C4F8 gas, and _C5F8 gas _.

(Appendix 15)
15. The etching method according to claim 12, wherein a ratio of a flow rate of the first gas to a combined flow rate of the first gas and the second gas is 33 vol.% or more and 67 vol.% or less.

(Appendix 16)
16. The etching method of claim 12, wherein the process gas further comprises an oxygen-containing gas.

(Appendix 17)
17. The etching method of any one of claims 12 to 16, wherein the process gas further comprises an inert gas.

(Appendix 18)
18. The etching method of claim 1, wherein a ratio of an opening dimension of the second opening to an opening dimension of the first opening is 1.1 or more and 20 or less.

(Appendix 19)
19. The etching method according to claim 1, wherein the mask is a silicon nitride film.

(Appendix 20)
A plasma processing apparatus having a chamber and a control unit,
The control unit is
(a) providing a substrate having a film to be etched containing silicon and oxygen and a mask on the film to be etched, the mask having a first opening and a second opening having a larger opening dimension than the first opening, and including at least one of a silicon-containing film and an organic film;
(b) controlling the etching target film through the first opening and the second opening _by using plasma generated from _a process gas containing a first gas, the first gas being at least one gas selected from the group consisting of _{C3F6 gas} , _C3F7 gas, _C2F6 gas _, and _{C3H2F4 gas} ;
The plasma processing apparatus performs the above steps.

(Appendix 21)
1. A device manufacturing method carried out in a plasma processing apparatus having a chamber, comprising:
(a) providing a substrate having a film to be etched containing silicon and oxygen and a mask on the film to be etched, the mask having a first opening and a second opening having a larger opening dimension than the first opening, and including at least one of a silicon-containing film and an organic film;
(b) etching the film to be etched through the first opening and _the second opening using plasma generated from _a process gas containing _a first gas, the _first gas being at least one gas selected from the group consisting of _C3F6 gas, _C3F7 gas, _C2F6 gas _, and _C3H2F4 gas;
A device manufacturing method comprising:

(Appendix 22)
A computer of a plasma processing apparatus having a chamber and a control unit,
(a) providing a substrate having a film to be etched containing silicon and oxygen and a mask on the film to be etched, the mask having a first opening and a second opening having a larger opening dimension than the first opening, and including at least one of a silicon-containing film and an organic film;
(b) controlling the etching target film through the first opening and the second opening _by using plasma generated from _a process gas containing a first gas, the first gas being at least one gas selected from the group consisting of _{C3F6 gas} , _C3F7 gas, _C2F6 gas _, and _{C3H2F4 gas} ;
A program that executes the following.

(Appendix 23)
A storage medium storing the program according to claim 22.

The above embodiments are described for the purpose of explanation and are not intended to limit the scope of the present disclosure. Various modifications of the above embodiments may be made without departing from the scope and spirit of the present disclosure. For example, some components in one embodiment may be added to another embodiment. Also, some components in one embodiment may be replaced with corresponding components in another embodiment.

1: Plasma processing apparatus, 2: Control unit, 10: Plasma processing chamber, 10s: Plasma processing space, 11: Substrate support unit, 13: Shower head, 20: Gas supply unit, 31a: First RF generating unit, 31b: Second RF generating unit, 32a: First DC generating unit, FM1: First film, FM2: Second film, MK: Mask, OP1: First opening, OP2: Second opening, Ox: Silicon oxide film, RC1: First recess, RC2: Second recess, RE1: First region, RE2: Second region, UF: Undercoat film, W: Substrate

Claims (20)

1. 1. An etching method performed in a plasma processing apparatus having a chamber, comprising:
   (a) providing a substrate having a film to be etched containing silicon and oxygen and a mask on the film to be etched, the mask having a first opening and a second opening having a larger opening dimension than the first opening, and including at least one of a silicon-containing film and an organic film;
   (b) etching the film to be etched through the first opening and _the second opening using plasma generated from _a process gas containing _a first gas, the _first gas being at least one gas selected from the group consisting of _C3F6 gas, _C3F7 gas, _C2F6 gas _, and _C3H2F4 gas;
   An etching method comprising:
2. In the above (b),
   a first film containing carbon and fluorine is formed on a first sidewall of the mask that defines the first opening, and a second film containing carbon and fluorine is formed on a second sidewall of the mask that defines the second opening;
   2. The etching method according to claim 1, wherein the etching target film is etched through the first opening in which the first film is formed and the second opening in which the second film is formed.
3. The etching method according to claim 2, wherein in (b), the thickness of the second film formed on the second sidewall of the mask is greater than the thickness of the first film formed on the first sidewall of the mask.
4. The etching method according to claim 2 or 3, wherein in (b), a first recess corresponding to the first opening and a second recess corresponding to the second opening are formed in the film to be etched.
5. The etching method according to claim 4, wherein in (b), the first film is formed continuously from the first sidewall of the mask on a first sidewall of the film to be etched that defines the first recess, and the second film is formed continuously from the second sidewall of the mask on a second sidewall of the film to be etched that defines the second recess.
6. The etching method according to claim 5, wherein in (b), the thickness of the second film formed on the second sidewall of the film to be etched is greater than the thickness of the first film formed on the first sidewall of the film to be etched.
7. The etching method according to claim 5, wherein in (b), the first sidewall and the second sidewall of the film to be etched are etched horizontally by fluorine components in the first film and the second film.
8. The etching method of claim 5, wherein in (b), the amount of etching of the second sidewall of the film to be etched in the horizontal direction is greater than the amount of etching of the first sidewall of the film to be etched in the horizontal direction.
9. The etching method of claim 1, wherein the process gas further includes an oxygen-containing gas.
10. The etching method of claim 9, wherein the process gas further includes an inert gas.
11. The etching method according to claim 9 or 10, wherein the ratio of the flow rate of the first gas to the total flow rate of the processing gas excluding the inert gas is 33% by volume or more and 50% by volume or less.
12. The etching method according to claim 1, wherein the process gas further includes a second gas different from the first gas, and the second gas is a CF-based gas or a CHF-based gas.
13. The etching method according to claim 12, wherein the number of double bonds between carbon atoms constituting the second gas is greater than the number of double bonds between carbon atoms constituting the first gas.
14. _14. The etching method according to claim 12, wherein _the second gas is at least one gas selected from the group consisting of _C4F6 gas, _C4F8 gas, and _C5F8 gas _.
15. The etching method according to claim 12 or 13, wherein the ratio of the flow rate of the first gas to the combined flow rate of the first gas and the second gas is 33 volume % or more and 67 volume % or less.
16. The etching method according to claim 12 or 13, wherein the processing gas further includes an oxygen-containing gas.
17. The etching method according to claim 12 or 13, wherein the process gas further includes an inert gas.
18. The etching method according to claim 1, wherein the ratio of the opening dimension of the second opening to the opening dimension of the first opening is 1.1 or more and 20 or less.
19. The etching method according to claim 1, wherein the mask is a silicon nitride film.
20. A plasma processing apparatus having a chamber and a control unit,
    The control unit is
    (a) providing a substrate having a film to be etched containing silicon and oxygen and a mask on the film to be etched, the mask having a first opening and a second opening having a larger opening dimension than the first opening, and including at least one of a silicon-containing film and an organic film;
    (b) controlling the etching target film through the first opening and the second opening _by using plasma generated from _a process gas containing _a first gas, the first gas being at least one gas selected from the group consisting of _{C3F6 gas} , _C3F7 gas, _C2F6 gas _{, and C3H2F4 gas} ;
    The plasma processing apparatus performs the above steps.

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