Substrate processing method and substrate processing system

Abstract

Provided is a technique that makes it possible to reduce variations in etching depth when etching a film to be etched. A substrate processing method includes: (a) a step for providing a substrate, including a film to be etched and a mask having a side wall defining at least one opening on the film to be etched; (b) a step for forming, on the mask, an additional mask containing carbon and hydrogen and having a hydrogen content higher than that of the mask, by using plasma generated from a processing gas containing carbon and hydrogen; and (c) a step for etching the film to be etched by using plasma generated from an etching gas.

Description

Substrate processing method and substrate processing system

[0001] SUMMARY Exemplary embodiments of the present disclosure relate to a substrate processing method and a substrate processing system.

[0002] Patent Document 1 discloses a technique for etching a stack of silicon-containing films.

[0003] Japanese Patent Application Laid-Open No. 2021-118304

[0004] However, in the above-described etching, if the film to be etched is thick, variations in the etching depth in the film to be etched may occur.

[0005] The present disclosure provides a technique capable of reducing variations in etching depth when etching a film to be etched.

[0006] In one exemplary embodiment of the present disclosure, a substrate processing method includes: (a) providing a substrate including a film to be etched and a mask having a sidewall defining at least one opening on the film to be etched; (b) forming an additional mask on the mask, the additional mask containing carbon and hydrogen and having a higher hydrogen content than the mask, using plasma generated from a process gas containing carbon and hydrogen; and (c) etching the film to be etched using plasma generated from an etching gas.

[0007] According to one exemplary embodiment of the present disclosure, it is possible to provide a technique that can reduce variations in etching depth when etching a film to be etched.

[0008] 8A is a diagram for explaining an example of the configuration of a plasma processing system. FIG. 8B is a diagram for explaining an example of the configuration of a capacitively coupled plasma processing apparatus. FIG. 8C is a diagram for explaining an example of the configuration of a substrate processing system. FIG. 8D is a flowchart showing an example of a substrate processing method according to the first embodiment. FIG. 8E is a diagram for explaining an example of the structure of a substrate W in process ST1. FIG. 8F is a diagram for explaining an example of the structure of a substrate W in process ST2. FIG. 8G is a diagram for explaining an example of the structure of a substrate W in process ST3. FIG. 8H is a diagram for explaining an example of the structure of a substrate W in process ST4. FIG. 8H is a diagram for explaining an example of the structure of a substrate W in process ST5. FIG. 8H is a diagram for explaining an example of the structure of a substrate W in process ST6.

[0009] Hereinafter, each embodiment of the present disclosure will be described.

[0010] In one exemplary embodiment, a substrate processing method is provided that includes: (a) providing a substrate that includes a film to be etched and a mask having sidewalls that define at least one opening over the film to be etched; (b) forming an additional mask on the mask that includes carbon and hydrogen, the additional mask having a higher hydrogen content than the mask, using a plasma generated from a process gas that includes carbon and hydrogen; and (c) etching the film to be etched using the plasma generated from the etching gas.

[0011] In one exemplary embodiment, the mask comprises an amorphous carbon film.

[0012] In one exemplary embodiment, the additional mask comprises an amorphous carbon film.

[0013] In one exemplary embodiment, the film to be etched includes a stack of alternating silicon oxide and silicon nitride films.

[0014] In one exemplary embodiment, in (b), the additional mask is formed so that the total thickness of the mask and the additional mask is 4 μm or more.

[0015] In one exemplary embodiment, the openings in the mask are formed by plasma etching.

[0016] In one exemplary embodiment, the etching gas contains carbon and fluorine.

[0017] In one exemplary embodiment, multiple cycles comprising (b) and (c), in that order, are performed.

[0018] In one exemplary embodiment, (a) is followed by (c), followed by one or more cycles comprising (b) and (c), in that order.

[0019] In one exemplary embodiment, there is provided a substrate processing system including a substrate support disposed in a chamber, a plasma generating unit, and a controller, wherein the controller is configured to: (a) control providing, to the substrate support, a substrate including a film to be etched and a mask having a sidewall defining at least one opening on the film to be etched; (b) control the plasma generating unit to generate plasma from a process gas including carbon and hydrogen, and to form an additional mask on the mask, the additional mask including carbon and hydrogen and having a higher hydrogen content than the mask; and (c) control the plasma generating unit to generate plasma from an etching gas, and to etch the film to be etched.

[0020] In one exemplary embodiment, a substrate processing system includes a plurality of chambers and a transfer module capable of transferring a substrate to the plurality of chambers in a vacuum atmosphere, and a control unit performs the controls (a), (b), and (c) using any of the plurality of chambers while maintaining the vacuum atmosphere.

[0021] 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.

[0022] <Example of Plasma Processing System> FIG. 1 is a diagram illustrating an example of the 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.

[0023] 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.

[0024] 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).

[0025] 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.

[0026] The capacitively coupled plasma processing apparatus 1 includes a plasma processing chamber 10 (also simply referred to as the "chamber"), a gas supply unit 20, a power supply 30, and an exhaust system 40. The plasma processing apparatus 1 also includes a substrate support 11 and a gas inlet. 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.

[0027] 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.

[0028] 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.

[0029] 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.

[0030] 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.

[0031] 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.

[0032] 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.

[0033] 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.

[0034] 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.

[0035] 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 100 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.

[0036] 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.

[0037] 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.

[0038] 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.

[0039] 3 is a diagram illustrating an example of the configuration of a substrate processing system. The substrate processing system PS includes substrate processing chambers PM1 to PM6 (hereinafter collectively referred to as "substrate processing modules PM"), a transfer module TM, load lock modules LLM1 and LLM2 (hereinafter collectively referred to as "load lock modules LLM"), a loader module LM, and load ports LP1 to LP3 (hereinafter collectively referred to as "load ports LP"). A controller CT controls each component of the substrate processing system PS to perform a given process on a substrate W.

[0040] The substrate processing modules PM perform processes such as etching, trimming, film formation, annealing, doping, lithography, cleaning, and ashing on substrates W therein. Some of the substrate processing modules PM may be capacitively coupled plasma processing apparatuses as shown in FIG. 2 . That is, at least one of the substrate processing chambers PM1 to PM6 may be coupled to a capacitively coupled plasma generation unit. Some of the substrate processing modules PM may be inductively coupled plasma processing apparatuses. That is, at least one of the substrate processing chambers PM1 to PM6 may be coupled to an inductively coupled plasma generation unit. Some of the substrate processing modules PM may be measurement modules that may measure the thickness of a film formed on a substrate W, the dimensions of a pattern formed on a substrate W, etc., using, for example, an optical technique.

[0041] The transfer module TM has a transfer device for transferring a substrate W between the substrate processing modules PM or between the substrate processing module PM and the load lock module LLM. The substrate processing module PM and the load lock module LLM are arranged adjacent to the transfer module TM. The transfer module TM, the substrate processing module PM, and the load lock module LLM are spatially isolated from or connected to each other by openable and closable gate valves.

[0042] The load lock modules LLM1 and LLM2 are provided between the transfer module TM and the loader module LM. The load lock module LLM can switch its internal pressure between atmospheric pressure and vacuum. "Atmospheric pressure" may be the pressure outside each module included in the substrate processing system PS. "Vacuum" may be a pressure lower than atmospheric pressure, for example, a medium vacuum of 0.1 Pa to 100 Pa. The load lock module LLM transfers a substrate W from the loader module LM, which is at atmospheric pressure, to the transfer module TM, which is at vacuum, and also transfers the substrate W from the transfer module TM, which is at vacuum, to the loader module LM, which is at atmospheric pressure.

[0043] The loader module LM has a transport device for transporting substrates W, and transports substrates W between the load lock module LLM and the load port LP. FOUPs (Front Opening Unified Pods) that can store, for example, 25 substrates W, or empty FOUPs can be placed inside the load port LP. The loader module LM removes substrates W from the FOUPs in the load port LP and transports them to the load lock module LLM. The loader module LM also removes substrates W from the load lock module LLM and transports them to the FOUPs in the load port LP.

[0044] The controller CT controls each component of the substrate processing system PS to perform a given process on the substrate W. The controller CT stores a recipe in which the process procedure, process conditions, transport conditions, etc. are set, and controls each component of the substrate processing system PS to perform the given process on the substrate W in accordance with the recipe. The controller CT may also perform some or all of the functions of the controller 2 shown in FIG. 1 .

[0045] <Example of Substrate Processing Method> (First Embodiment) FIG. 4 is a flowchart showing an example of a substrate processing method according to a first embodiment (hereinafter also referred to as "this processing method"). As shown in FIG. 4, in one embodiment, this processing method includes a process ST1 of providing a substrate, a process ST2 of selectively forming an additional mask on a mask of the substrate, and a process ST3 of etching an etching target film. In one embodiment, the processes ST1, ST2, and ST3 are performed in this order. In one embodiment, the processing in each process may be performed in a substrate processing system (see FIG. 3). In the following example, a controller CT controls each part of the substrate processing system to perform this processing method.

[0046] (Step ST1: Providing a Substrate) In one embodiment, in step ST1, as shown in Fig. 2, a substrate W is provided in the chamber 10 of the plasma processing apparatus 1. The substrate W is provided in the central region 111a of the substrate support 11 and is held on the substrate support 11 by an electrostatic chuck 1111.

[0047] 5 is a diagram illustrating an example of the configuration of a substrate W provided in step ST1. The substrate W includes an underlayer film UF, a stacked film SF on the underlayer film UF, and a mask MK on the stacked film SF. The substrate W may be used in the manufacture of semiconductor devices. Examples of semiconductor devices include memory devices such as DRAMs and 3D-NAND flash memories, and logic devices.

[0048] In one embodiment, the base film UF is 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 configured by stacking a plurality of films.

[0049] In one embodiment, the stacked film SF is a film to be etched in this processing method. In one embodiment, the stacked film SF includes two or more different silicon-containing films. In one embodiment, the stacked film SF includes a stacked structure in which silicon oxide films SF1 and silicon nitride films SF2 are alternately stacked. The stacked film SF may have a thickness of 5 μm or more, or 10 μm or more. The stacked film SF may have 20 or more layers, 50 or more layers, or 100 or more layers. The stacked film SF may include two or more films selected from the group consisting of a single crystal silicon film, a polycrystalline silicon film, a silicon oxide film, and a silicon nitride film.

[0050] In one embodiment, the mask MK is a film that functions as a mask in etching the stacked film SF. The mask MK is, for example, a hard mask. The mask MK includes at least one film selected from the group consisting of a carbon-containing film, a silicon-containing film, and a metal-containing film. The mask MK is, for example, an amorphous carbon film. The amorphous carbon film is doped with hydrogen. The mask MK may be doped with elements such as phosphorus, boron, or nitrogen. The mask MK may be a film including at least one film selected from the group consisting of tungsten carbide (WC), tungsten silicide (WSi), WSiN, and WSiC. The mask MK may be a single-layer mask consisting of one film, or a multi-layer mask consisting of two or more films. The mask MK may have a thickness of 10 μm or less, or 5 μm or less.

[0051] The mask MK has an upper surface U1 and a sidewall S1 that defines at least one opening OP1 on the stacked film SF. The opening OP1 is a space above the stacked film SF and is surrounded by the sidewall S1 of the mask MK. That is, the upper surface of the stacked film SF has an area covered by the mask MK and an area exposed at the bottom of the opening OP1. The mask MK may be formed by depositing a film that will become the mask MK on the stacked film SF and then patterning the film to form the opening OP1. The opening OP1 may be formed by plasma etching.

[0052] The opening OP1 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. 5 . The shape may be, for example, a circle, an ellipse, a rectangle, a line, or a combination of one or more of these. In one embodiment, the mask MK has a plurality of sidewalls S1, and the plurality of sidewalls define a plurality of openings OP1. The plurality of openings OP1 may each have a linear shape and be arranged at regular intervals to form a line-and-space pattern. Alternatively, the plurality of openings OP1 may each have a hole shape and form an array pattern. The width of the opening OP1 may be 120 nm or less, 100 nm or less, 80 nm or less, or 50 nm or less.

[0053] Each film constituting the substrate W (the base film UF, the stacked film SF, and the mask MK) may be formed by chemical vapor deposition (CVD), atomic layer deposition (ALD), molecular layer deposition (MLD), spin coating, or the like. In one embodiment, at least a part of the process of forming each film on the substrate W may be performed as part of process ST1. In one embodiment, all or a part of each film on the substrate W may be performed in the same substrate processing system PS or plasma processing apparatus 1 (chamber 10) as process ST1. Alternatively, all or a part of each film on the substrate W may be formed in an external apparatus or chamber, and then the substrate W may be provided in the chamber of the plasma processing apparatus 1 in which process ST1 is performed.

[0054] (Process ST2: Formation of Additional Mask) FIG. 6 is a diagram for explaining an example of the configuration of a substrate W on which an additional mask MK1 is formed in process ST2. In one embodiment, in process ST2, an additional mask MK1 is selectively formed on the mask MK of the substrate W. The additional mask MK1 is formed using a plasma CVD method. Note that "on the mask MK" includes not only the upper surface of the mask MK but also the upper surface of a film, if any, on the upper surface of the mask MK. Furthermore, "selectively" includes selecting an exposed portion on the mask MK facing upward from the entire exposed portion of the mask MK.

[0055] In one embodiment, in step ST2, a first process gas is supplied into the chamber 10 from the shower head 13 of the plasma processing apparatus 1 shown in FIG. 2. The temperature of the substrate support 11 or the substrate W may be controlled to a first temperature. The first temperature may be 200° C. or higher and 500° C. or lower. The first temperature may be lower than the temperature at which the mask MK is formed by plasma etching.

[0056] The first process gas is a gas containing carbon and hydrogen. The first process gas may include a hydrocarbon gas (CxHy) (x and y are integers of 1 or more). ２ H ２ Gas, C ３ H ６ The first process gas may further include an inert gas, such as a noble gas, Ar gas, He gas, or Kr gas, or N ２ It may be a gas.

[0057] In one embodiment, a plasma is generated from a first process gas supplied into the chamber 10. In this case, a source RF signal is supplied from the power supply 30 to the upper electrode and / or the lower electrode, which generates a high-frequency electric field on the substrate support 11 and generates a plasma from the first process gas in the plasma processing space 10s. The source RF signal has a frequency of 40 MHz or greater. The source RF signal has a first power, which may be in the range of 100 W to 500 W.

[0058] When plasma is generated, a bias signal is supplied to the substrate support 11. 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 DC signal may be a DC pulse voltage. The DC pulse voltage may have an absolute value of 200 V or less. The duty ratio of the DC pulse voltage may be 20% or less, and may be in the range of 5% to 20%, for example, approximately 10%. The frequency of the DC pulse voltage may be in the range of 100 kHz to 1000 kHz. A bias potential is generated between the plasma and the substrate W, and ions and radicals in the plasma are attracted to the substrate W.

[0059] As shown in FIG. 6 , in one embodiment, hydrocarbon ions in the plasma selectively deposit on the upper surface U1 of the mask MK, forming an additional mask MK1. Deposition on the sidewall S1 of the mask MK is prevented by hydrogen radicals in the plasma. The additional mask MK1 is formed substantially only on the upper surface U1 of the mask MK. The additional mask MK1 has a thickness of 0.2 μm or more. The additional mask MK1 has a thickness of 2 μm or less. The combined thickness of the mask MK and the additional mask MK1 may be 4 μm or more, 6 μm or more, or 10 μm or more. For example, the mask MK is an amorphous carbon film containing hydrogen.

[0060] The hydrogen content of the additional mask MK1 is greater than the hydrogen content of the mask MK. The hydrogen content of the additional mask MK1 may be 10% or more, 20% or more, or 30% or more. The hydrogen content of the mask MK may be 30% or less, 20% or less, or 10% or less. The hydrogen content of the mask MK may be substantially 0%. The hydrogen content of the additional mask MK1 may be 5% or more, 10% or more, 15% or more, or 20% or more greater than the hydrogen content of the mask MK.

[0061] (Process ST3: Etching of stacked film SF) FIG. 7 is a diagram for explaining a configuration example of a substrate W in which the stacked film SF has been etched in process ST3. In process ST3, the stacked film SF is etched using plasma generated from an etching gas. Process ST3 may be performed in the same chamber of the plasma processing apparatus 1 as process ST2, or may be performed in a chamber of a different plasma processing apparatus 1. When process ST3 is performed in a different plasma processing apparatus 1, the substrate W may be transferred from the plasma processing apparatus 1 in which process ST2 has been performed to the different plasma processing apparatus 1 within the substrate processing system PS.

[0062] In one embodiment, in step ST3, an etching gas is supplied into the plasma processing space 10s from the shower head 13 shown in FIG. 2 . For example, the etching gas is a gas containing carbon and fluorine. The etching gas may contain at least one carbon-containing gas selected from the group consisting of CF gas (fluorocarbon gas) and CHF gas (hydrofluorocarbon gas), and hydrogen fluoride gas. In one embodiment, the etching gas may contain hydrogen fluoride gas, CF gas, CHF gas, an oxygen-containing gas, and a carbon-free fluorine-containing gas.

[0063] In one embodiment, a plasma is generated from an etching gas supplied into the chamber 10. In this case, a source RF signal is supplied from the power supply 30 to the upper electrode and / or the lower electrode, which generates a high-frequency electric field on the substrate support 11 and generates a plasma from the etching gas in the plasma processing space 10s. The source RF signal may have a frequency of 13 MHz or greater. The source RF signal may have a first power. The first power may be 1 kW or greater.

[0064] When plasma is generated, a bias signal is supplied to the substrate support 11. 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. A bias potential is 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 stacked film SF is etched by these active species. The etching may be anisotropic etching using a plasma of a fluorocarbon gas or a plasma of a hydrofluorocarbon gas.

[0065] 7, in one embodiment, portions of the stacked film SF that are not covered by the mask MK and the additional mask MK1 (portions exposed in the opening OP1) are etched to form an opening OP2 and a recess in the stacked film SF. The stacked film SF may have an opening OP2 with an A / R (Aspect Ratio) of 100 or more. The opening OP2 may have, for example, a CD (Critical Dimension) of 80 nm or less and a depth of 10 μm or more.

[0066] Thereafter, the mask MK is removed by ashing from the substrate W. Ashing of the mask MK may be performed using, for example, plasma of an oxygen-based gas.

[0067] According to this exemplary embodiment, the substrate processing method includes step ST1 of providing a substrate, step ST2 of forming an additional mask MK1 containing carbon and hydrogen on the mask MK using plasma generated from a process gas containing carbon and hydrogen, and step ST3 of etching a film to be etched using plasma generated from an etching gas. In step ST2, the additional mask MK1 is formed so that its hydrogen content is greater than that of the mask MK. This allows the hydrogen contained in the additional mask MK1 to enter the recesses of the stacked film SF during etching in step ST3, thereby removing or reducing residues such as elements and compounds remaining in the recesses. As a result, variation in etching depth when etching a film to be etched can be reduced.

[0068] When the stacked film SF becomes thicker, the mask MK must be thickened. Simply thickening the mask MK makes it difficult to pattern the mask MK, which can result in a defective shape at the opening OP1 of the mask MK. According to this exemplary embodiment, the additional mask MK1 is formed in step ST2, so the thickness of the mask MK can be reduced accordingly. As a result, for example, when forming (patterning) the opening OP1 of the mask MK, it is possible to prevent the opening of the mask MK from being defective in shape.

[0069] Furthermore, if the mask MK becomes thick, warping of the substrate may occur. According to this exemplary embodiment, by forming the additional mask MK1 having a high hydrogen content, it is possible to reduce the thickness of the mask MK while suppressing warping of the substrate.

[0070] <Example> Fig. 8(A) is a diagram depicting a cross-sectional image of a substrate when the stacked film SF is etched in a state where there is no additional mask but where there is a mask MK (Comparative Example). Fig. 8(B) is a diagram depicting a cross-sectional image of a substrate when the stacked film SF is etched in a state where there is an additional mask and a mask MK (Example). Figs. 8(A) and (B) are based on images captured by a scanning electron microscope.

[0071] The comparative example and the example were etched under the same processing conditions. The additional mask and the mask MK were amorphous carbon films. The stacked film SF had a stacked structure in which silicon oxide films SF1 and silicon nitride films SF2 were alternately stacked. The additional mask had a hydrogen content of 30% or more. During etching, multiple holes H were formed in the stacked film SF. The maximum variation in etching depth (difference in depth between the deepest hole H and the shallowest hole H) in the example (with the additional mask) was 10% or less of the maximum variation in the comparative example (without the additional mask). In the example, variation in etching depth was suppressed.

[0072] In this exemplary embodiment, a cycle including steps ST2 and ST3 in this order may be performed multiple times. FIG. 9 is a flowchart showing an example of this processing method. As shown in FIG. 10, in step ST3, the portion of the stacked film SF not covered by the mask MK and the additional mask MK1 (the portion exposed at the opening OP1) is etched, forming a recess R1 in a portion of the stacked film SF. If the cycle including steps ST2 and ST3 has not been performed a predetermined number of times, steps ST2 and ST3 are performed again. As shown in FIG. 11, an additional mask MK1 is formed on the mask MK, and then the bottom of the recess R1 in the stacked film SF is etched even deeper. When the cycle including steps ST2 and ST3 has been performed a predetermined number of times, this processing method ends. At this time, an opening OP2 as shown in FIG. 7 may be formed in the stacked film SF. The predetermined number of cycles may be two or more, five or more, or ten or more. When the thickness of the mask MK becomes smaller than a predetermined value in step ST3, the cycle of steps ST2 and ST3 may be repeated.

[0073] When plasma etching a film to be etched using a mask, as the mask is gradually removed and the remaining film thickness of the mask decreases, the sidewalls of the opening in the film to be etched may be etched laterally, resulting in so-called bowing. According to this exemplary embodiment, a cycle including steps ST2 and ST3 in this order is performed multiple times, so that an additional mask MK1 can be added during etching, thereby maintaining the overall film thickness of the mask. As a result, bowing is suppressed, and the etching profile of the film to be etched can be improved.

[0074] Second Embodiment In the present exemplary embodiment, a process ST3 is performed after a process ST1, and then a cycle including a process ST2 and a process ST3 in this order is performed one or more times. Fig. 12 is a flowchart showing an example of the present processing method.

[0075] 5, in step ST1, a substrate W including an undercoat film UF, a stacked film SF on the undercoat film UF, and a mask MK on the stacked film SF is provided. The substrate W is provided in the chamber 10 of the plasma processing apparatus 1 in which step ST3 is performed.

[0076] Next, in step ST3, the stacked film SF is etched using plasma generated from an etching gas. As shown in FIG. 13 , in one embodiment, the portion of the stacked film SF that is not covered by the mask MK (the portion exposed at the opening OP1) is etched to form a recess R1 in the stacked film SF.

[0077] 14, an additional mask MK1 is selectively formed on the mask MK of the substrate W. The additional mask MK1 has a higher hydrogen content than the mask MK.

[0078] Next, step ST3 is performed, in which the stacked film SF is etched using plasma generated from an etching gas, as shown in Fig. 15. Portions of the stacked film SF that are not covered by the mask MK and the additional mask MK1 (portions exposed at the openings OP1) are etched, and deeper recesses R2 are formed in the stacked film SF.

[0079] Then, if the cycle including steps ST2 and ST3 has not been performed a predetermined number of times, steps ST2 and ST3 are performed again. If the cycle including steps ST2 and ST3 has been performed a predetermined number of times, the processing method ends. At this time, an opening OP2 as shown in FIG. 7 may be formed in the stacked film SF. The cycle including steps ST2 and ST3 may be performed two or more times. Note that the conditions for each step in this embodiment may be the same as those in the first embodiment.

[0080] According to this exemplary embodiment, after steps ST1 and ST3, a cycle including steps ST2 and ST3 in this order is performed one or more times, so that the additional mask MK1 can be added during etching, and the overall film thickness of the mask can be maintained, thereby improving the etching shape of the film to be etched.

[0081] In the above first and second embodiments, when steps ST1 to ST3 are performed, or when steps ST2 and ST3 are repeated, the substrates may be continuously processed in the substrate processing system PS using the transfer module TM and any one of the chambers of the substrate processing chambers PM1 to PM6 while maintaining a vacuum atmosphere.

[0082] The etching target film in the first and second embodiments is not limited to the stacked film SF, and may be at least one single-layer film or multi-layer film selected from the group consisting of a single-crystal silicon film, a polycrystalline silicon film, a silicon oxide film, and a silicon nitride film.

[0083] In the first and second embodiments described above, the present processing 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.

[0084] The present disclosure may include, for example, the following configurations.

[0085] (Supplementary Note 1) A substrate processing method comprising: (a) providing a substrate including a film to be etched and a mask having a sidewall defining at least one opening on the film to be etched; (b) forming an additional mask containing carbon and hydrogen and having a higher hydrogen content than the mask on the mask using plasma generated from a process gas containing carbon and hydrogen; and (c) etching the film to be etched using plasma generated from an etching gas.

[0086] (Supplementary Note 2) The substrate processing method according to Supplementary Note 1, wherein the mask includes an amorphous carbon film.

[0087] (Supplementary Note 3) The substrate processing method according to Supplementary Note 1 or 2, wherein the additional mask includes an amorphous carbon film.

[0088] (Supplementary Note 4) The substrate processing method according to any one of Supplementary Notes 1 to 3, wherein the etching target film includes a stacked film in which silicon oxide films and silicon nitride films are alternately stacked.

[0089] (Supplementary Note 5) The substrate processing method according to any one of Supplementary Notes 1 to 4, wherein in (b), the additional mask is formed so that the combined thickness of the mask and the additional mask is 4 μm or more.

[0090] (Supplementary Note 6) The substrate processing method according to any one of Supplementary Notes 1 to 5, wherein the openings in the mask are formed by plasma etching.

[0091] (Supplementary Note 7) The substrate processing method according to any one of Supplementary Notes 1 to 6, wherein the etching gas contains carbon and fluorine.

[0092] (Supplementary Note 8) The substrate processing method according to any one of Supplementary Notes 1 to 7, wherein a cycle including the steps (b) and (c) in this order is performed a plurality of times.

[0093] (Supplementary Note 9) The substrate processing method according to any one of Supplementary Notes 1 to 8, wherein (c) is performed after (a), and then a cycle including (b) and (c) in this order is performed one or more times.

[0094] (Supplementary Note 10) A substrate processing system comprising: a substrate support unit disposed in a chamber; a plasma generation unit; and a control unit, wherein the control unit is configured to execute the following controls: (a) providing a substrate, including a film to be etched and a mask having a sidewall defining at least one opening on the film to be etched, to the substrate support unit; (b) controlling the plasma generation unit to generate plasma from a process gas containing carbon and hydrogen, and to form an additional mask on the mask, the additional mask containing carbon and hydrogen and having a higher hydrogen content than the mask; and (c) controlling the plasma generation unit to generate plasma from an etching gas, and to etch the film to be etched.

[0095] (Appendix 11) The substrate processing system according to Appendix 10, comprising: a plurality of chambers; and a transfer module capable of transferring a substrate to the plurality of chambers in a vacuum atmosphere; and the control unit performs the controls (a), (b), and (c) using any of the plurality of chambers while maintaining the vacuum atmosphere.

[0096] 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.

[0097] 1: Plasma processing apparatus, 2: Control unit, 10: Plasma processing chamber, 11: Substrate support unit, 12: Plasma generation unit, MK: Mask, OP1: Opening, U1: Upper surface, S1: Side wall, SF: Stacked film, UF: Undercoat film, MK1: Additional mask, W: Substrate

Claims

1. A method of processing a substrate, comprising: (a) providing a substrate including a film to be etched and a mask having sidewalls defining at least one opening over the film to be etched; (b) forming an additional mask on the mask, the additional mask containing carbon and hydrogen and having a higher hydrogen content than the mask, using a plasma generated from a process gas containing carbon and hydrogen; and (c) etching the film to be etched using a plasma generated from an etching gas.

2. The substrate processing method according to claim 1, wherein the mask includes an amorphous carbon film.

3. The substrate processing method according to claim 1, wherein the additional mask includes an amorphous carbon film.

4. The substrate processing method according to claim 1, wherein the film to be etched includes a laminated film in which silicon oxide films and silicon nitride films are alternately laminated.

5. The substrate processing method according to claim 1, wherein in (b), the additional mask is formed so that the combined thickness of the mask and the additional mask is 4 μm or more.

6. The substrate processing method according to claim 1, wherein the openings in the mask are formed by plasma etching.

7. The substrate processing method according to claim 1, wherein the etching gas contains carbon and fluorine.

8. The substrate processing method according to claim 1, wherein a cycle including steps (b) and (c) in this order is performed a plurality of times.

9. The substrate processing method according to claim 1, wherein (c) is performed after (a), and then a cycle including (b) and (c) in this order is performed one or more times.

10. A substrate processing system comprising a substrate support disposed within a chamber, a plasma generating unit, and a control unit, wherein the control unit is configured to: (a) control providing a substrate, including a film to be etched and a mask having a sidewall defining at least one opening on the film to be etched, to the substrate support unit; (b) control the plasma generating unit to generate plasma from a process gas containing carbon and hydrogen, and to form an additional mask on the mask, the additional mask containing carbon and hydrogen and having a higher hydrogen content than the mask; and (c) control the plasma generating unit to generate plasma from an etching gas, and to etch the film to be etched.

11. A substrate processing system as described in claim 10, comprising: a plurality of chambers; and a transfer module capable of transferring substrates to the plurality of chambers in a vacuum atmosphere, wherein the control unit executes the controls (a), (b), and (c) using any of the plurality of chambers while maintaining the vacuum atmosphere.

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