Etching method and plasma treatment device

Abstract

Provided is technology for suppressing bowing in organic film etching. An etching method includes: (a) a step for providing a substrate that includes an organic film and a mask on the organic film, the mask having a side wall that defines at least one opening; (b) a step for forming a recess in the organic film by etching the organic film by using plasma generated from first treatment gas; (c) a step for forming a metal-containing protective film on a side wall of the recess by using plasma generated from a second treatment gas containing a metal-containing gas, the metal-containing gas including at least one gas selected from the group consisting of a tungsten-containing gas, a molybdenum-containing gas and a titanium-containing gas; and (d) a step for etching the bottom of the recess while protecting the side wall of the recess by means of the metal-containing protective film.

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] Patent Document 1 discloses a technique for etching an organic film.

[0003] Publication No. 2013-222852

[0004] The present disclosure provides a technique for suppressing bowing during etching of organic films.

[0005] In one exemplary embodiment of the present disclosure, an etching method includes the steps of: (a) providing a substrate including an organic film and a mask on the organic film, the mask having a sidewall defining at least one opening; (b) etching the organic film using plasma generated from a first process gas to form a recess in the organic film; (c) forming a metal-containing protective film on the sidewall of the recess using plasma generated from a second process gas including a metal-containing gas, the metal-containing gas including at least one gas selected from the group consisting of a tungsten-containing gas, a molybdenum-containing gas, and a titanium-containing gas; and (d) etching a bottom of the recess while protecting the sidewall of the recess with the metal-containing protective film.

[0006] According to one exemplary embodiment of the present disclosure, a technique for suppressing bowing during etching of an organic film 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 showing an example of an etching method. FIG. 4 is a diagram showing an example of the cross-sectional structure of a substrate W provided in process ST1. FIG. 5 is a diagram showing an example of the cross-sectional structure of a substrate W after processing in process ST2. FIG. 6 is a diagram showing an example of the cross-sectional structure of a substrate W after processing in process ST3. FIG. 7 is a flowchart showing another example of an etching method.

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

[0009] In one exemplary embodiment, an etching method is provided, comprising: (a) providing a substrate including an organic film and a mask on the organic film, the mask having a sidewall defining at least one opening; (b) etching the organic film using plasma generated from a first process gas to form a recess in the organic film; (c) forming a metal-containing protective film on the sidewall of the recess using plasma generated from a second process gas including a metal-containing gas, the metal-containing gas including at least one gas selected from the group consisting of a tungsten-containing gas, a molybdenum-containing gas, and a titanium-containing gas; and (d) etching a bottom of the recess while protecting the sidewall of the recess with the metal-containing protective film.

[0010] In one exemplary embodiment, in steps (b), (c), and (d), a metal-containing gas is continuously supplied into the chamber.

[0011] In one exemplary embodiment, in step (d), a metal-containing gas is supplied into the chamber.

[0012] In one exemplary embodiment, steps (b) and (c) are performed simultaneously.

[0013] In one exemplary embodiment, the flow rate of the metal-containing gas is the smallest among the gas species contained in the second process gas.

[0014] In one exemplary embodiment, the method further comprises the step of (e) removing a portion of the metal-containing protective film between steps (c) and (d).

[0015] In one exemplary embodiment, in step (e), the portion of the metal-containing protective film is removed using a plasma generated from a fourth process gas, where the fourth process gas includes a fluorine-containing gas.

[0016] In one exemplary embodiment, the second process gas includes an additive gas to enhance the protection effect of the metal-containing protective film on the sidewalls of the recess.

[0017] In one exemplary embodiment, the additive gas is COS, N ２and CO.

[0018] In one exemplary embodiment, at least one of the first process gas and the second process gas comprises a hydrogen-containing gas or an oxygen-containing gas.

[0019] In one exemplary embodiment, in at least one of steps (b) and (c), a bias RF signal is supplied to the lower electrode in the chamber, and the bias RF signal has a frequency of 200 kHz to 600 kHz and a power of 10 W to 100 W.

[0020] In one exemplary embodiment, in at least one of the steps (b) and (c), the pressure in the chamber is adjusted to 10 mTorr or more and 100 mTorr or less.

[0021] In one exemplary embodiment, in at least one of steps (b) and (c), a source RF signal is supplied to the upper electrode or the lower electrode in the chamber, and the source RF signal has a frequency of 40 MHz or higher.

[0022] In one exemplary embodiment, the first process gas comprises a metal-containing gas.

[0023] In one exemplary embodiment, an etching method is provided, comprising: (a) providing a substrate including an organic film and a mask on the organic film, the mask having sidewalls defining at least one opening; (b) etching the organic film to form a recess in the organic film; (c) forming a metal-containing protective film on the sidewall of the recess, the metal-containing protective film comprising at least one metal selected from the group consisting of tungsten, molybdenum, and titanium; and (d) etching a bottom of the recess while protecting the sidewall of the recess with the metal-containing protective film.

[0024] In one exemplary embodiment, there is provided a plasma processing apparatus including a chamber and a controller, the controller being configured to: (a) provide, into the chamber, a substrate including an organic film and a mask on the organic film, the mask having a sidewall defining at least one opening; (b) etch, in the chamber, the organic film using plasma generated from a first process gas to form a recess in the organic film; (c) form, in the chamber, a metal-containing protective film on the sidewall of the recess using plasma generated from a second process gas including a metal-containing gas, the metal-containing gas including at least one gas selected from the group consisting of a tungsten-containing gas, a molybdenum-containing gas, and a titanium-containing gas; and (d) etch, in the chamber, a bottom of the recess while protecting the sidewall of the recess with the metal-containing protective film.

[0025] 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.

[0026] <An example of a plasma processing system>

[0027] 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.

[0028] 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.

[0029] 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).

[0030] 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.

[0031] 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.

[0032] 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.

[0033] 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.

[0034] 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.

[0035] 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.

[0036] 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.

[0037] 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.

[0038] 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.

[0039] 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.

[0040] 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.

[0041] 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.

[0042] 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.

[0043] 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.

[0044] <Example of Etching Method> Figure 3 is a flowchart showing an example of an etching method (hereinafter also referred to as "the method") according to an illustrative embodiment. As shown in Figure 3, in one embodiment, the method includes step ST1 of providing a substrate, step ST2 of etching an organic film to form a recess in the organic film, step ST3 of forming a metal-containing protective film on the sidewall of the recess, and step ST4 of etching the bottom of the recess. In one embodiment, the treatment in each step may be performed in a plasma processing apparatus 1 (see Figure 2). In the following example, a control unit 2 controls each part of the plasma processing apparatus 1 to perform the method.

[0045] (Step ST1: Providing a Substrate) In one embodiment, in step ST1, the substrate W is provided in the plasma processing space 10s of the plasma processing apparatus 1. The substrate W is provided in the central region 111a of the substrate support 11 and can be held on the substrate support 11 by the electrostatic chuck 1111.

[0046] 4 is a diagram illustrating an example of the cross-sectional structure of the substrate W provided in step ST1. The substrate W may include an organic film CF and a mask MK disposed on the organic film CF. The organic film CF and the mask MK may be formed on 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.

[0047] The organic film CF may be a film to be etched in this method. The organic film CF is a film containing carbon. The organic film CF may be an amorphous carbon (ACL) film, a spin-on carbon (SOC) film, or a photoresist film.

[0048] The mask MK may be a film that functions as a mask in etching the organic film CF. The mask MK may be a silicon-containing film. The mask MK may be a silicon oxynitride film, a silicon nitride film, or a silicon oxide film. The mask MK may be a single-layer mask made of one film, or may be a multi-layer mask made of two or more stacked films. The mask MK may be made of a material that has a lower etching rate with respect to the plasma formed in steps ST2, ST3, and ST4 than the organic film CF.

[0049] The mask MK may have a sidewall S1 that defines at least one opening OP on the organic film CF. That is, the mask MK may have an opening OP. The opening OP may be a space on the organic film CF and may be surrounded by the sidewall S1 of the mask MK. That is, the upper surface of the organic film CF may have a region covered by the mask MK and a region exposed at the bottom of the opening OP.

[0050] The openings OP may have any shape when viewed from above the substrate W, i.e., when the substrate W is viewed from top to bottom in FIG. 4 . 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 walls S1, and the multiple side walls S1 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. Alternatively, the multiple openings OP may each have a hole shape and form an array pattern.

[0051] The base film UF may be a silicon wafer, or an organic film, a dielectric film, a metal film, a semiconductor film, or the like formed on a silicon wafer. The base film UF may be a silicon oxide film. The base film UF may be configured by stacking multiple films. The base film UF may include an etching stop film. 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 arranged so as to be in contact with the organic film CF.

[0052] Each film constituting the substrate W may be formed by any method. The base film UF, the organic film CF, and the mask MK may be formed by a CVD method, an ALD method, a PVD method, a spin coating method, or the like. The opening OP in the mask MK may be formed by etching. The opening OP in the mask MK may be formed by a lithography method. Each film may be a flat film or may have an uneven surface. The substrate W may further have another film below the base film UF.

[0053] At least a part of the process of forming the base film UF, the organic film CF, and the mask MK on the substrate W may be performed in the plasma processing space 10s as part of step ST1. For example, when the opening OP in the mask MK is formed by etching, the etching of the mask MK in step ST1 and the etching in steps ST2, ST3, and ST4 described below may be performed consecutively in the plasma processing space 10s. In one embodiment, the substrate W may be provided in the plasma processing space 10s after all or part of the substrate W is formed in an apparatus or chamber external to the plasma processing apparatus 1.

[0054] When the openings OP in the mask MK are formed by etching, an etching gas may be supplied into the plasma processing space 10s, and the mask MK may be etched by plasma generated from the etching gas. The etching gas may include at least one gas selected from the group consisting of CF gas (fluorocarbon gas), hydrogen fluoride gas, and CHF gas (hydrofluorocarbon gas). The etching gas may further include nitrogen gas.

[0055] In one embodiment, after the substrate W is provided in the central region 111a of the substrate support 11, the temperature of the substrate support 11 or the substrate W is controlled to a given temperature by a temperature control module. Controlling the temperature of the substrate support 11 or the substrate W to a given temperature may include setting the temperature of the heat transfer fluid flowing through the flow path 1110a or the heater temperature to a given temperature, or setting them to a temperature different from the given temperature. The given temperature may be 0°C or higher. The given temperature may be in the range of 10°C or higher and 120°C or lower, or 10°C or higher and 50°C or lower. The timing at which the temperature of the substrate support 11 or the substrate W starts to be controlled to a given temperature may be before or after the substrate W is placed on the substrate support 11, or may be simultaneous with the placement of the substrate W. The temperature of the substrate support 11 or the substrate W may be changed in each of the processes ST1 to ST4.

[0056] (Process ST2: Formation of Recesses) Figure 5 is a diagram illustrating an example of the cross-sectional structure of the substrate W in which the organic film CF has been etched in process ST2. In one embodiment, in process ST2, the organic film CF is etched to form recesses R1 in the organic film CF. Portions of the organic film CF that are not covered by the mask MK (portions exposed in the openings OP) are etched to form the recesses R1. The recesses R1 may have sidewalls S2 and a bottom B1.

[0057] In step ST2, a first processing gas may be supplied from the gas supply unit 20 shown in FIG. 2 into the plasma processing space 10s.

[0058] The first process gas may include a hydrogen-containing gas or an oxygen-containing gas as an etching gas. ２ gas, CO gas, COS gas, H2 gas and NH３ The first process gas may include at least one gas selected from the group consisting of: a noble gas such as Ar gas, He gas, or Kr gas, or N ２ The first process gas may further contain a metal-containing gas, similar to the second process gas in step ST3 described below. The metal-containing gas may contain at least one gas selected from the group consisting of a tungsten-containing gas, a molybdenum-containing gas, and a titanium-containing gas. The tungsten-containing gas may be WF ６ The metal-containing gas may be a gas. The metal-containing gas may have the smallest flow rate among the gas species contained in the first process gas. The metal-containing gas may be 1 sccm or less. The first process gas may not contain a metal-containing gas.

[0059] Plasma is generated from the first process gas supplied into the plasma processing space 10s, and the organic film CF can be etched using this plasma. At this time, a source RF signal can be supplied to the lower electrode of the substrate support 11 and / or the upper electrode of the shower head 13. The source RF signal may have a frequency of 40 MHz or more. The source RF signal may have a frequency of 40 MHz to 200 MHz. The source RF signal may have a power of 100 W to 1000 W. This generates a high-frequency electric field between the shower head 13 and the substrate support 11, and plasma can be generated from the first process gas in the plasma processing space 10s. A bias signal can also be supplied to the lower electrode of the substrate support 11. In this case, a bias potential can be generated between the plasma and the substrate W. Active species such as ions and radicals in the plasma are attracted to the substrate W, and the organic film CF can be etched by the active species. The bias signal can be a bias RF signal supplied from the RF power supply 31 or a bias DC signal supplied from the DC power supply 32. The bias RF signal may have a frequency of 200 kHz to 600 kHz, and a power of 10 W to 100 W. The pressure inside the chamber 10 may be 10 mTorr to 100 mTorr.

[0060] 6 is a diagram illustrating an example of a cross-sectional structure of a substrate W on which a metal-containing protective film is formed in step ST3. In one embodiment, in step ST3, a metal-containing protective film PF is formed on a side wall S2 of the recess R1 of the organic film CF.

[0061] In step ST3, a second process gas may be supplied into the plasma processing space 10s from the gas supply unit 20 shown in FIG. 2. The second process gas may include a metal-containing gas. The metal-containing gas may include at least one gas selected from the group consisting of a tungsten-containing gas, a molybdenum-containing gas, and a titanium-containing gas. The tungsten-containing gas may be WF ６ The metal-containing gas may have the smallest flow rate among the gas species contained in the second process gas, and the flow rate of the metal-containing gas may be 1 sccm or less.

[0062] The second process gas may further include a hydrogen-containing gas or an oxygen-containing gas as an etching gas. ２ gas, CO gas, COS gas, H2 gas and NH ３ The second process gas may include at least one gas selected from the group consisting of: a noble gas such as Ar gas, He gas, or Kr gas, or N ２ It may be a gas.

[0063] The second process gas may further contain an additive gas for enhancing the protective effect of the metal-containing protective film PF on the sidewall S2 of the recess R1. ２ and CO. The metal-containing protective film PF may be modified or thickened by the additive gas. The additive gas may be deposited on the sidewall S2 together with the metal-containing protective film PF.

[0064] Plasma is generated from the second process gas supplied into the plasma processing space 10s, and the metal-containing protective film PF can be formed on the sidewall S2 of the recess R1 of the organic film CF using the plasma. At this time, a source RF signal can be supplied to the lower electrode of the substrate support 11 and / or the upper electrode of the shower head 13. The source RF signal can have a frequency of 40 MHz or more. The source RF signal can have a frequency of 40 MHz to 200 MHz. The source RF signal can have a power of 100 W to 1000 W. This generates a high-frequency electric field between the shower head 13 and the substrate support 11, and plasma can be generated from the second process gas in the plasma processing space 10s. A bias signal can also be supplied to the lower electrode of the substrate support 11. In this case, a bias potential can be generated between the plasma and the substrate W. Active species such as ions and radicals in the plasma are attracted to the substrate W, and the metal-containing protective film PF can be deposited on the sidewall S2 of the recess R1 of the organic film CF by the active species. The bias signal may be a bias RF signal supplied from an RF power supply 31 or a bias DC signal supplied from a DC power supply 32. The bias RF signal may have a frequency of 200 kHz to 600 kHz and a power of 10 W to 100 W. The pressure inside the chamber 10 may be 10 mTorr to 100 mTorr.

[0065] Steps ST2 and ST3 may be performed as separate steps, and in one example, may be performed consecutively. Alternatively, they may be performed simultaneously. Performing steps ST2 and ST3 as separate steps improves controllability regarding the formation of the protective film. On the other hand, performing steps ST2 and ST3 simultaneously improves the overall etching throughput.

[0066] 7 is a diagram illustrating an example of a cross-sectional structure of a substrate W in which the bottom B1 of the recess R1 in the organic film CF is etched in step ST4. In one embodiment, in step ST4, the bottom B1 of the recess R1 is etched while the sidewall S2 of the recess R1 is protected by the metal-containing protective film PF. This forms an opening OP2 in the organic film CF, and the base film UF can be exposed in the opening OP2.

[0067] In step ST3, a third processing gas may be supplied from the gas supply unit 20 shown in FIG. 2 into the plasma processing space 10s.

[0068] The third process gas may include a hydrogen-containing gas or an oxygen-containing gas as an etching gas. ２ gas, CO gas, COS gas, H2 gas and NH ３ The third process gas may include at least one gas selected from the group consisting of: a noble gas such as Ar gas, He gas, or Kr gas, or N ２ It may be a gas.

[0069] The third process gas may not contain a metal-containing gas. Alternatively, the third process gas may contain a metal-containing gas, similar to the second process gas. The metal-containing gas may contain at least one gas selected from the group consisting of a tungsten-containing gas, a molybdenum-containing gas, and a titanium-containing gas. The tungsten-containing gas may be WF ６ The process gas may be a gas. In steps ST2, ST3, and ST4, a process gas containing a metal-containing gas may be continuously supplied into the chamber 10. The flow rate of the metal-containing gas may vary in steps ST2, ST3, and ST4. The flow rate of the metal-containing gas may be the largest in step ST3 among steps ST2, ST3, and ST4.

[0070] Plasma may be generated from the third process gas, and the organic film CF may be etched using the plasma. At this time, a source RF signal may be supplied to the lower electrode of the substrate support 11 and / or the upper electrode of the shower head 13. The source RF signal may have a frequency of 40 MHz or more. The source RF signal may have a frequency of 40 MHz to 200 MHz. The source RF signal may have a power of 100 W to 1000 W. This generates a high-frequency electric field between the shower head 13 and the substrate support 11, and plasma may be generated from the third process gas in the plasma processing space 10s. A bias signal may also be supplied to the lower electrode of the substrate support 11. In this case, a bias potential may be generated between the plasma and the substrate W. Active species such as ions and radicals in the plasma are attracted to the substrate W, and the bottom B1 of the recess R1 in the organic film CF may be etched by the active species. The bias signal may be a bias RF signal supplied from the RF power supply 31 or a bias DC signal supplied from the DC power supply 32. The bias RF signal may have a frequency of 200 kHz to 600 kHz, and a power of 300 W to 1500 W. The pressure inside the chamber 10 may be 10 mTorr to 100 mTorr.

[0071] According to this exemplary embodiment, the etching method includes the steps of: (a) providing a substrate W including an organic film CF and a mask MK on the organic film CF; (b) etching the organic film CF using plasma generated from a first process gas to form a recess R1 in the organic film CF; (c) forming a metal-containing protective film PF on a sidewall S2 of the recess R1 using plasma generated from a second process gas including a metal-containing gas; and (d) etching the bottom B1 of the recess R1 while protecting the sidewall S2 of the recess R1 with the metal-containing protective film PF. This suppresses bowing during etching of the organic film CF. Bowing is a phenomenon in which the opening dimensions of a portion of the sidewall of a recess formed by etching are larger than the opening dimensions of the top of the recess. The bowing portion has, for example, a barrel-like shape in cross section.

[0072] In the above embodiment, as shown in FIG. 8, a step ST3-1 of removing a part of the metal-containing protective film PF may be further included between steps ST3 and ST4.

[0073] In step ST3-1, a fourth process gas may be supplied into the plasma processing space 10s from the gas supply unit 20 shown in FIG. 2. The fourth process gas may include a fluorine-containing gas. The fluorine-containing gas may be at least one gas selected from the group consisting of a nitrogen fluoride gas, a fluorocarbon gas, and a hydrofluorocarbon gas. The nitrogen fluoride gas may be NF ３ The fluorocarbon gas may be CF ４ Plasma may be generated from the fourth process gas, and a portion of the metal-containing protective film PF may be etched using the plasma. This allows the excess metal-containing protective film PF to be removed.

[0074] In the above embodiment, the formation of the metal-containing protective film PF in step ST3 may be performed by various methods such as plasma CVD, thermal CVD, ALD, etc. In steps ST2 and ST4, the organic film may be etched by other methods.

[0075] In the above embodiments, the present method is not limited to an inductively coupled plasma processing apparatus, and may be performed in other types of plasma processing apparatuses, such as a plasma processing apparatus that generates capacitively coupled plasma, a plasma processing apparatus that generates ECR plasma, a plasma processing apparatus that generates helicon wave excited plasma, or a plasma processing apparatus that generates surface wave plasma.

[0076] Embodiments of the present disclosure further include the following aspects.

[0077] (Supplementary Note 1) An etching method comprising: (a) providing a substrate including an organic film and a mask on the organic film, the mask having a sidewall defining at least one opening; (b) etching the organic film using plasma generated from a first process gas to form a recess in the organic film; (c) forming a metal-containing protective film on a sidewall of the recess using plasma generated from a second process gas containing a metal-containing gas, the metal-containing gas containing at least one gas selected from the group consisting of a tungsten-containing gas, a molybdenum-containing gas, and a titanium-containing gas; and (d) etching a bottom of the recess while protecting the sidewall of the recess with the metal-containing protective film.

[0078] (Supplementary Note 2) The etching method according to Supplementary Note 1, wherein the metal-containing gas is continuously supplied into the chamber in the steps (b), (c), and (d).

[0079] (Supplementary Note 3) The etching method according to Supplementary Note 1, wherein in the step (d), the metal-containing gas is supplied into a chamber.

[0080] (Supplementary Note 4) The etching method according to any one of Supplementary Notes 1 to 3, wherein the steps (b) and (c) are carried out simultaneously.

[0081] (Supplementary Note 5) The etching method according to any one of Supplementary Notes 1 to 4, wherein the flow rate of the metal-containing gas is the smallest among the gas species contained in the second process gas.

[0082] (Supplementary Note 6) The etching method according to any one of Supplementary Notes 1 to 5, further comprising the step of removing a portion of the metal-containing protective film between the steps (c) and (d).

[0083] (Supplementary Note 7) The etching method according to Supplementary Note 6, wherein in the step (e), a portion of the metal-containing protective film is removed using plasma generated from a fourth process gas, and the fourth process gas contains a fluorine-containing gas.

[0084] (Supplementary Note 8) The etching method according to any one of Supplementary Notes 1 to 7, wherein the second process gas contains an additive gas for enhancing the protective effect of the metal-containing protective film on the sidewall of the recess.

[0085] (Supplementary Note 9) The additive gas is COS, N ２ and CO.

[0086] (Supplementary Note 10) The etching method according to any one of Supplementary Notes 1 to 9, wherein at least one of the first process gas and the second process gas contains a hydrogen-containing gas or an oxygen-containing gas.

[0087] (Supplementary Note 11) The etching method according to any one of Supplementary Notes 1 to 10, wherein in at least one of the steps (b) and (c), a bias RF signal is supplied to a lower electrode in the chamber, and the bias RF signal has a frequency of 200 kHz or more and 600 kHz or less and a power of 10 W or more and 100 W or less.

[0088] (Supplementary Note 12) The etching method according to any one of Supplementary Notes 1 to 11, wherein in at least one of the steps (b) and (c), the pressure in the chamber is adjusted to 10 mTorr or more and 100 mTorr or less.

[0089] (Supplementary Note 13) The etching method according to any one of Supplementary Notes 1 to 12, wherein in at least one of the steps (b) and (c), a source RF signal is supplied to an upper electrode or a lower electrode in the chamber, and the source RF signal has a frequency of 40 MHz or more.

[0090] (Supplementary Note 14) The etching method according to any one of Supplementary Notes 1 to 13, wherein the first process gas contains the metal-containing gas.

[0091] (Supplementary Note 15) An etching method comprising: (a) providing a substrate including an organic film and a mask on the organic film, the mask having a sidewall defining at least one opening; (b) etching the organic film to form a recess in the organic film; (c) forming a metal-containing protective film on a sidewall of the recess, the metal-containing protective film containing at least one metal selected from the group consisting of tungsten, molybdenum, and titanium; and (d) etching a bottom of the recess while protecting the sidewall of the recess with the metal-containing protective film.

[0092] (Supplementary Note 16) A plasma processing apparatus including a chamber and a control unit, wherein the control unit is configured to perform the following controls: (a) providing, into the chamber, a substrate including an organic film and a mask on the organic film, the mask having a sidewall that defines at least one opening; (b) etching, in the chamber, the organic film using plasma generated from a first process gas to form a recess in the organic film; (c) forming, in the chamber, a metal-containing protective film on a sidewall of the recess using plasma generated from a second process gas including a metal-containing gas, the metal-containing gas including at least one gas selected from the group consisting of a tungsten-containing gas, a molybdenum-containing gas, and a titanium-containing gas; and (d) etching, in the chamber, a bottom of the recess while protecting the sidewall of the recess with the metal-containing protective film.

[0093] The above embodiments are described for the purpose of explanation and are not intended to limit the scope of the present disclosure. Various modifications can be made to the above embodiments without departing from the scope and spirit of the present disclosure. For example, some components in one embodiment can be added to other embodiments. Also, some components in one embodiment can be replaced with corresponding components in other embodiments.

[0094] REFERENCE SIGNS LIST 1: plasma processing apparatus, 2: control unit, 10: plasma processing chamber, 11: substrate support unit, 12: plasma generation unit, MK: mask, OP: opening, S1: side wall, CF: organic film, R1: recess, S2: side wall, B1: bottom, PF: metal-containing protective film, UF: base film, W: substrate

Claims

1. An etching method comprising: (a) providing a substrate comprising an organic film and a mask on the organic film, the mask having a sidewall defining at least one opening; (b) etching the organic film using plasma generated from a first process gas to form a recess in the organic film; (c) forming a metal-containing protective film on a sidewall of the recess using plasma generated from a second process gas comprising a metal-containing gas, the metal-containing gas comprising at least one gas selected from the group consisting of a tungsten-containing gas, a molybdenum-containing gas, and a titanium-containing gas; and (d) etching a bottom of the recess while protecting the sidewall of the recess with the metal-containing protective film.

2. The etching method according to claim 1, wherein the metal-containing gas is continuously supplied into the chamber in steps (b), (c) and (d).

3. The etching method according to claim 1, wherein in step (d), the metal-containing gas is supplied into a chamber.

4. The etching method according to claim 1, wherein steps (b) and (c) are carried out simultaneously.

5. The etching method according to claim 1, wherein the flow rate of the metal-containing gas is the smallest among the gas species contained in the second process gas.

6. The etching method of claim 1, further comprising: (e) between steps (c) and (d), a step of removing a portion of the metal-containing protective film.

7. The etching method according to claim 6, wherein in step (e), a portion of the metal-containing protective film is removed using plasma generated from a fourth process gas, the fourth process gas including a fluorine-containing gas.

8. The etching method according to claim 1, wherein the second process gas contains an additive gas for enhancing the protective effect of the metal-containing protective film on the sidewall of the recess.

9. The additive gas is COS, N ２ and CO.

10. The etching method of claim 1, wherein at least one of the first process gas and the second process gas comprises a hydrogen-containing gas or an oxygen-containing gas.

11. The etching method according to claim 1, wherein in at least one of steps (b) and (c), a bias RF signal is supplied to a lower electrode in the chamber, and the bias RF signal has a frequency of 200 kHz or more and 600 kHz or less and a power of 10 W or more and 100 W or less.

12. The etching method according to claim 1, wherein in at least one of the steps (b) and (c), the pressure inside the chamber is adjusted to 10 mTorr or more and 100 mTorr or less.

13. The etching method according to claim 1, wherein in at least one of steps (b) and (c), a source RF signal is supplied to an upper electrode or a lower electrode in the chamber, and the source RF signal has a frequency of 40 MHz or more.

14. The etching method of claim 1, wherein the first process gas comprises the metal-containing gas.

15. An etching method comprising: (a) providing a substrate comprising an organic film and a mask on the organic film, the mask having a sidewall defining at least one opening; (b) etching the organic film to form a recess in the organic film; (c) forming a metal-containing protective film on a sidewall of the recess, the metal-containing protective film comprising at least one metal selected from the group consisting of tungsten, molybdenum, and titanium; and (d) etching a bottom of the recess while protecting the sidewall of the recess with the metal-containing protective film.

16. A plasma processing apparatus comprising a chamber and a control unit, the control unit configured to execute the following controls: (a) providing, into the chamber, a substrate including an organic film and a mask on the organic film, the mask having a sidewall defining at least one opening; (b) etching, in the chamber, the organic film using plasma generated from a first process gas to form a recess in the organic film; (c) forming, in the chamber, a metal-containing protective film on a sidewall of the recess using plasma generated from a second process gas including a metal-containing gas, the metal-containing gas including at least one gas selected from the group consisting of a tungsten-containing gas, a molybdenum-containing gas, and a titanium-containing gas; and (d) etching, in the chamber, a bottom of the recess while protecting the sidewall of the recess with the metal-containing protective film.

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