Etching method and etching device

Abstract

The disclosed etching method comprises: (a) a step of providing a substrate having a base film, a silicon-containing film on the base film, and a mask on the silicon-containing film in a chamber; (b) a step of forming a recess by etching the silicon-containing film using a first plasma that is generated from a first processing gas that contains hydrogen fluoride gas and a tungsten-containing gas; and (c) a step of further etching the silicon-containing film using a second plasma that is generated from a second processing gas that contains hydrogen fluoride gas after the step (b), wherein the second processing gas does not contain a tungsten-containing gas or contains a tungsten-containing gas at a flow rate that is less than the flow rate of the tungsten-containing gas in the first processing gas.

Description

Etching method and etching apparatus

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

[0002] Patent Document 1 discloses a technique for etching a film in a substrate containing silicon using a mask containing amorphous carbon or an organic polymer.

[0003] JP 2016-39310 A

[0004] The present disclosure provides techniques for improving etched profiles.

[0005] In one exemplary embodiment of the present disclosure, there is provided an etching method including: (a) providing a substrate having an underlayer film, a silicon-containing film on the underlayer film, and a mask on the silicon-containing film in a chamber; (b) etching the silicon-containing film using a first plasma generated from a first process gas including a hydrogen fluoride gas and a tungsten-containing gas to form a recess; and (c) after the step (b), further etching the silicon-containing film using a second plasma generated from a second process gas including a hydrogen fluoride gas, wherein the second process gas does not include the tungsten-containing gas or includes the tungsten-containing gas at a flow rate that is lower than a flow rate of the tungsten-containing gas in the first process gas.

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

[0007] FIG. 1 is a diagram for explaining an example of the configuration of a capacitively coupled plasma processing apparatus. FIG. 2 is a flowchart showing an etching method according to a first embodiment. FIG. 3 is a diagram showing an example of a cross-sectional structure of a substrate W. FIG. 4 is a diagram showing an example of a cross-sectional structure of a substrate W at the end of process ST12. FIG. 5 is a diagram showing an example of a cross-sectional structure of a substrate W at the end of process ST13. FIG. 6 is an example of a timing chart when the undercoat film UF contains silicon. FIG. 7 is another example of a timing chart when the undercoat film UF contains silicon. FIG. 8 is an example of a timing chart when the undercoat film contains metal. FIG. 9 is a flowchart showing an etching method according to a second embodiment. FIG. 10 is a diagram showing the relationship between ion flux and ion energy. FIG. 11 is a timing chart showing an example of a source RF signal and a bias RF signal. FIG. 12 is a timing chart showing an example of a source RF signal and a bias DC signal. FIG. 13 is a flowchart showing an etching method according to a third embodiment. FIG. 14 is a diagram showing an example of a cross-sectional structure of a substrate W at the end of process ST32. FIG. 15 is a diagram showing an example of a cross-sectional structure of a substrate W at the end of process ST33. FIG. 16 is an example of a timing chart of the third embodiment.

[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 having an underlayer film, a silicon-containing film on the underlayer film, and a mask on the silicon-containing film in a chamber; (b) etching the silicon-containing film to form a recess using a first plasma generated from a first process gas comprising hydrogen fluoride gas and a tungsten-containing gas; and (c) after step (b), further etching the silicon-containing film using a second plasma generated from a second process gas comprising hydrogen fluoride gas, wherein the second process gas does not include a tungsten-containing gas or includes a tungsten-containing gas at a flow rate that is less than a flow rate of the tungsten-containing gas in the first process gas.

[0010] In one exemplary embodiment, the tungsten-containing gas is WF ６ Includes.

[0011] In one exemplary embodiment, the first process gas further comprises a phosphorus-containing gas.

[0012] In one exemplary embodiment, the second process gas does not include a phosphorus-containing gas or includes a phosphorus-containing gas at a flow rate that is less than the flow rate of the phosphorus-containing gas in the first process gas.

[0013] In one exemplary embodiment, the second process gas further comprises xenon gas.

[0014] In one exemplary embodiment, the first process gas does not include xenon gas or includes xenon gas at a flow rate that is less than the flow rate of xenon gas in the second process gas.

[0015] In one exemplary embodiment, step (b) is performed before the underlayer is exposed in the recesses or until at least a portion of the underlayer is exposed in the recesses.

[0016] In one exemplary embodiment, step (b) is performed until a portion of the underlayer is etched.

[0017] In one exemplary embodiment, a cycle comprising steps (b) and (c) is performed multiple times.

[0018] In one exemplary embodiment, step (b) etches the silicon-containing film while forming a first protrusion at a first position on the mask that reduces the width of the opening in the mask, and forming a second protrusion at a second position on the mask that is lower than the first position and reduces the width of the opening in the mask.

[0019] In one exemplary embodiment, in step (b), a reverse tapered recess is formed in the silicon-containing film, and in step (c), the shape of the recess is made rectangular.

[0020] In one exemplary embodiment, an etching method is provided, comprising: (a) providing a substrate having an underlayer film, a silicon-containing film on the underlayer film, and a mask on the silicon-containing film in a chamber; (b) etching the silicon-containing film using a first plasma generated from a first process gas to form a recess; and (c) after step (b), further etching the silicon-containing film using a second plasma generated from a second process gas, wherein the first process gas comprises a gas or a gas mixture containing fluorine and hydrogen and a metal-containing gas, the second process gas comprises a gas or a gas mixture containing fluorine and hydrogen, and the second process gas does not include the metal-containing gas or includes the metal-containing gas at a flow rate that is less than the flow rate of the metal-containing gas in the first process gas.

[0021] In one exemplary embodiment, the metal-containing gas comprises at least one metal selected from the group consisting of tungsten, molybdenum, titanium, and ruthenium.

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

[0023] In one exemplary embodiment, the second process gas does not include a phosphorus-containing gas or includes a phosphorus-containing gas at a flow rate that is less than the flow rate of the phosphorus-containing gas in the first process gas.

[0024] In one exemplary embodiment, the second process gas further comprises a noble gas, which may comprise at least one gas selected from the group consisting of argon gas, krypton gas, xenon gas, and radon gas.

[0025] In one exemplary embodiment, the first process gas does not include a noble gas or includes a noble gas at a flow rate that is less than the flow rate of the noble gas in the second process gas.

[0026] In one exemplary embodiment, an etching apparatus is provided, the apparatus comprising: a chamber; a substrate support within the chamber; a plasma generator; and a controller configured to control the plasma generator. The controller is configured to perform a process including: (a) providing a substrate into the chamber, the substrate having an underlayer film, a silicon-containing film on the underlayer film, and a mask on the silicon-containing film; (b) etching the silicon-containing film using a first plasma generated from a first process gas including a hydrogen fluoride gas and a tungsten-containing gas to form a recess; and (c) after step (b), further etching the silicon-containing film using a second plasma generated from a second process gas including a hydrogen fluoride gas, the second process gas either not including a tungsten-containing gas or including a tungsten-containing gas at a flow rate lower than a flow rate of the tungsten-containing gas in the first process gas.

[0027] 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.

[0028] <Configuration Example of Plasma Processing System> A configuration example of a plasma processing system will be described below. Fig. 1 is a diagram for explaining a configuration example of a capacitively coupled plasma processing apparatus.

[0029] The plasma processing system includes a capacitively coupled plasma processing apparatus 1 and a controller 2. 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 has at least one gas inlet for supplying at least one processing gas to the plasma processing space 10s and at least one gas outlet for exhausting gas from the plasma processing space 10s. 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.

[0030] 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.

[0031] 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 (Radio Frequency) power supply 31 and / or a DC (Direct Current) power supply 32 (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 (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.

[0032] 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.

[0033] 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.

[0034] 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.

[0035] 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 one or more flow modulation devices to modulate or pulse the flow rate of the at least one process gas.

[0036] 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 process gas supplied to the plasma processing space 10s. Therefore, the RF power supply 31 can function as at least a part of a plasma generating unit configured to generate a plasma from one or more process gases in the plasma processing chamber 10. 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.

[0037] 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.

[0038] 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.

[0039] 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 as a first bias DC signal. 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.

[0040] In various embodiments, at least one of 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.

[0041] 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.

[0042] 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).

[0043] First Embodiment Fig. 2 is a flowchart showing an etching method according to a first embodiment. As shown in Fig. 2, the etching method includes a substrate providing step ST11, a first etching step ST12, and a second etching step ST13. The processes in each of steps ST11 to ST13 may be performed in the plasma processing system shown in Fig. 1. That is, the etching method according to the first embodiment may be performed using the plasma processing apparatus 1 as the etching apparatus. Below, the etching method according to the first embodiment will be described using, as an example, a case in which a control unit 2 controls each part of the plasma processing apparatus 1 to etch a substrate W.

[0044] (Process ST11: Providing a Substrate) In process ST11, 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. Then, the substrate W is held on the substrate support 11 by the electrostatic chuck 1111.

[0045] 3 is a diagram showing an example of the cross-sectional structure of a substrate W. In step ST11, the substrate W shown in FIG. 3 may be provided. The substrate W includes, as an etching target film, a silicon-containing film SF formed on an underlayer UF. The substrate W may further include a mask MF on the silicon-containing film SF. 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.

[0046] The underlayer UF may be, for example, a silicon wafer, an organic film formed on a silicon wafer, a dielectric film, a metal film, or a semiconductor film. The underlayer UF may be composed of a plurality of stacked films. The underlayer UF may contain silicon or a metal such as tungsten.

[0047] The silicon-containing film SF is a film to be etched. For example, the silicon-containing film SF includes a silicon oxide film, a silicon nitride film, a silicon oxynitride film, a polycrystalline silicon film, or a carbon-containing silicon film. The silicon-containing film SF may be composed of a plurality of stacked films. For example, the silicon-containing film SF may include silicon oxide films and silicon nitride films that are alternately stacked. Alternatively, for example, the silicon-containing film SF may include silicon oxide films and polycrystalline silicon films that are alternately stacked. Alternatively, for example, the silicon-containing film SF may be a stacked film including a silicon nitride film, a silicon oxide film, and a polycrystalline silicon film.

[0048] The mask MF is a film that functions as a mask in etching the silicon-containing film SF. The mask MF may be, for example, a hard mask. The mask MF may also be a carbon-containing mask and / or a metal-containing mask. The carbon-containing mask may be formed, for example, from at least one selected from the group consisting of spin-on carbon, tungsten carbide, amorphous carbon, and boron carbide. The metal-containing mask may be formed, for example, from at least one selected from the group consisting of titanium nitride, titanium oxide, and tungsten. The tungsten-containing mask may be formed, for example, from tungsten silicide (WSi) and / or tungsten carbide (WC). The mask MF may also be a boron-containing mask formed, for example, from silicon boride, boron nitride, or boron carbide.

[0049] 3, the mask MF defines at least one opening OP on the silicon-containing film SF. The opening OP is a space above the silicon-containing film SF and is surrounded by the sidewall of the mask MF. That is, the upper surface of the silicon-containing film SF has an area covered by the mask MF and an area 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. 3 . 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 MF may have multiple side walls that 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] Each of the films constituting the substrate W (base film UF, silicon-containing film SF, mask MF) may be formed by a CVD method, an ALD method, a spin coating method, or the like. The opening OP may be formed by etching the mask MF. The mask MF may also be formed by lithography. Note that each of the above films may be a flat film or may have an uneven surface. The substrate W may further have another film below the base film UF, and the stacked film of the silicon-containing film SF and base film UF may function as a multilayer mask. In other words, the stacked film of the silicon-containing film SF and base film UF may be used as a multilayer mask to etch the other film.

[0052] At least a part of the process of forming each film on the substrate W may be performed within the space of the plasma processing chamber 10. In one example, the step of etching the mask MF to form the opening OP may be performed in the plasma processing chamber 10. That is, the opening OP and the etching of the silicon-containing film SF, which will be described later, may be performed consecutively within the same chamber. Alternatively, after all or a part of each film on the substrate W is formed in an apparatus or chamber external to the plasma processing apparatus 1, the substrate W may be loaded into the plasma processing space 10s of the plasma processing apparatus 1 and placed in the central region 111a of the substrate support 11, thereby providing the substrate.

[0053] After the substrate W is provided in the central region 111a of the substrate support 11, the temperature of the substrate support 11 is adjusted to a set temperature by the temperature adjustment module. The set temperature may be, for example, 20°C or less, 0°C or less, -10°C or less, -20°C or less, -30°C or less, -40°C or less, -50°C or less, -60°C or less, or -70°C or less. In one example, adjusting or maintaining the temperature of the substrate support 11 includes setting the temperature of the heat transfer fluid flowing through the flow path 1110a and the heater temperature to their respective set temperatures, or to temperatures different from the respective set temperatures. Note that the timing at which the heat transfer fluid starts flowing through the flow path 1110a may be before, after, or simultaneously with the time at which the substrate W is placed on the substrate support 11. Alternatively, the temperature of the substrate support 11 may be adjusted to the set temperature before the process ST11. That is, the substrate W may be provided to the substrate support 11 after the temperature of the substrate support 11 is adjusted to the set temperature.

[0054] (Step ST12: First Etching) In step ST12, the silicon-containing film SF is etched using plasma generated from a first process gas. First, the first process gas is supplied from the gas supply unit 20 into the plasma processing space 10s. The first process gas contains hydrogen fluoride (HF) gas. The HF gas functions as an etchant. During the processing in step ST12, the temperature of the substrate support 11 is maintained at the set temperature adjusted in step ST11.

[0055] Next, a source RF signal is supplied to the lower electrode of the substrate support 11 and / or the upper electrode of the shower head 13. This generates a high-frequency electric field between the shower head 13 and the substrate support 11, generating a first plasma from the first process gas in the plasma processing space 10s. Furthermore, a bias signal is supplied to the lower electrode of the substrate support 11, generating a bias potential difference between the plasma and the substrate W. The bias potential difference attracts active species, such as ions and radicals, in the plasma to the substrate W. This etches the silicon-containing film SF, forming a recess in the silicon-containing film SF based on the shape of the opening OP in the mask MF. The first etching may be performed before (e.g., just before) the base film UF is exposed, or until at least a portion of the base film UF is exposed. That is, step ST12 may be terminated before (e.g., just before) the base film UF of the substrate W is exposed, or at the timing when at least a portion of the base film UF is exposed.

[0056] 4 is a diagram showing an example of the cross-sectional structure of the substrate W at the end of step ST12. As shown in FIG. 4 , the processing in step ST12 etches the portion of the silicon-containing film SF exposed in the opening OP in the depth direction (from top to bottom in FIG. 4 ), forming a recess RC. Note that FIG. 4 shows a state in which the base film UF is not exposed at the end of step ST12. That is, step ST12 may be stopped with the silicon-containing film SF remaining between the base film UF and the bottom of the recess RC, and step ST13 may be started in this state and performed for a period including the time when the base film UF is exposed. Alternatively, at least a portion of the base film UF may be exposed in the recess RC at the end of step ST12. Furthermore, a cycle including steps ST12 and ST13 may be performed multiple times until the base film UF is exposed or until a portion of the base film UF is etched.

[0057] In step ST12, the source RF signal may have a frequency in the range of 10 MHz to 150 MHz. For example, the source RF signal may have a frequency of 40 MHz or higher or 60 MHz or higher. In step ST12, the bias signal may be a bias RF signal supplied from the second RF generator 31b. The bias signal may also be a bias DC signal (e.g., a sequence of voltage pulses) supplied from the DC generator 32a. Both the source RF signal and the bias signal may be continuous waves or pulse waves, or one of the source RF signal and the bias signal may be continuous waves and the other may be pulse waves. When both the source RF signal and the bias signal are pulse waves, the periods of the two pulse waves may be synchronized. The duty ratio of the pulse waves may be set appropriately, for example, between 1 and 80%, or between 5 and 50%. The duty ratio is the proportion of a period during which the power or voltage level is high in the pulse wave period. Also, if a bias DC signal is used, each voltage pulse in the sequence may have a waveform that is rectangular, trapezoidal, triangular, or a combination thereof. The polarity of the bias DC signal may be negative or positive, provided that the potential of the substrate W is set to provide a potential difference between the plasma and the substrate to attract ions.

[0058] In step ST12, the HF gas contained in the first process gas may have the highest flow rate (partial pressure) among all the gases in the first process gas (or all the other gases in the first process gas excluding the inert gas if the first process gas contains an inert gas). For example, the flow rate of the HF gas may be 50 vol.% or more, 60 vol.% or more, 70 vol.% or more, 80 vol.% or more, 90 vol.% or more, or 95 vol.% or more with respect to the total flow rate of the first process gas (or the total flow rate of all the gases in the first process gas excluding the inert gas if the first process gas contains an inert gas). The flow rate of the HF gas may be less than 100 vol.%, 99.5 vol.% or less, 98 vol.% or less, or 96 vol.% or less with respect to the total flow rate of the first process gas. For example, the flow rate of the HF gas is adjusted to 70 vol.% or more and 96 vol.% or less with respect to the total flow rate of the first process gas.

[0059] The first process gas may further include at least one selected from the group consisting of a carbon-containing gas, an oxygen-containing gas, and a phosphorus-containing gas.

[0060] The carbon-containing gas may be, for example, one or both of a fluorocarbon gas and a hydrofluorocarbon gas. In one example, the fluorocarbon gas is CF ４ Gas, C ２ F ２ Gas, C ２ F ４ Gas, C ３ F ６ Gas, C ３ F ８ Gas, C ４ F ６ Gas, C ４ F ８ Gas and C ５ F ８ In one example, the hydrofluorocarbon gas may be at least one selected from the group consisting of CHF ３ Gas, CH ２ F ２ Gas, CH ３ F gas, C ２ HF ５ Gas, C ２ H ２ F ４ Gas, C ２ H ３ F ３ Gas, C ２ H ４ F ２ Gas, C ３ HF ７ Gas, C ３ H ２ F ２ Gas, C ３ H ２ F ４ Gas, C ３ H ２ F ６ Gas, C ３ H ３ F ５ Gas, C ４ H ２ F ６ Gas, C ４ H ５ F ５ Gas, C ４ H ２F ８ Gas, C ５ H ２ F ６ Gas, C ５ H ２ F １０ Gas and C ５ H ３ F ７ The carbon-containing gas may be at least one selected from the group consisting of carbon-containing gases. The carbon-containing gas may be a linear gas having an unsaturated bond. The linear carbon-containing gas having an unsaturated bond may be, for example, C ３ F ６ (Hexafluoropropene) gas, C ４ F ８ (Octafluoro-1-butene, octafluoro-2-butene) gas, C ３ H ２ F ４ (1,3,3,3-tetrafluoropropene) gas, C ４ H ２ F ６ (trans-1,1,1,4,4,4-hexafluoro-2-butene) gas, C ４ F ８ O (pentafluoroethyl trifluorovinyl ether) gas, CF ３ COF gas (1,2,2,2-tetrafluoroethane-1-one), CHF ２ COF (difluoroacetic acid fluoride) gas and COF ２ (carbonyl fluoride) gas.

[0061] The oxygen-containing gas is, for example, O ２ , CO, CO ２ , H ２ O and H ２ O ２ In one example, the oxygen-containing gas may be at least one gas selected from the group consisting of H ２ Oxygen-containing gases other than O, e.g., O ２ , CO, CO ２ and H ２ O ２ The flow rate of the oxygen-containing gas may be adjusted depending on the flow rate of the carbon-containing gas.

[0062] A phosphorus-containing gas is a gas containing phosphorus-containing molecules. ４ O １０ ), tetraphosphorus octoxide (P ４ O ８ ), tetraphosphorus hexaoxide (P ４ O ６ ) and other oxides. ２ O ５ Phosphorus-containing molecules are sometimes called phosphorus trifluoride (PF ３ ), phosphorus pentafluoride (PF ５ ), phosphorus trichloride (PCl ３ ), phosphorus pentachloride (PCl ５ ), phosphorus tribromide (PBr ３ ), phosphorus pentabromide (PBr ５ ), phosphorus iodide (PI ３ The phosphorus-containing molecule may be a halide (phosphorus halide) such as phosphorus fluoride (POF). That is, the phosphorus-containing molecule may contain fluorine as a halogen element, such as phosphorus fluoride. Alternatively, the phosphorus-containing molecule may contain a halogen element other than fluorine as a halogen element. The phosphorus-containing molecule may be phosphoryl fluoride (POF ３ ), phosphoryl chloride (POCl ３ ), phosphoryl bromide (POBr ３ The phosphorus-containing molecule may be a phosphoryl halide such as a phosphine (PH ３ ), calcium phosphide (Ca ３ P ２ etc.), phosphoric acid (H ３ P.O. ４ ), sodium phosphate (Na ３ P.O. ４ ), hexafluorophosphate (HPF ６ ) and the like. Phosphorus-containing molecules include fluorophosphines (H ｇ PF ｈ ) where the sum of g and h is 3 or 5. Fluorophosphines include HPF ２ , H ２ PF ３The processing gas may contain one or more of the above-mentioned phosphorus-containing molecules as the at least one phosphorus-containing molecule. For example, the processing gas may contain PF5 as the at least one phosphorus-containing molecule. ３ , PCl ３ , P.F. ５ , PCl ５ , POCl ３ , P.H. ３ , PBr ３ , or PBr ５ When the phosphorus-containing molecules contained in the processing gas are liquid or solid, the phosphorus-containing molecules may be vaporized by heating or the like and supplied into the plasma processing space 10s.

[0063] The phosphorus-containing gas is PCl ａ F ｂ (a is an integer of 1 or more, b is an integer of 0 or more, and a+b is an integer of 5 or less) Gas or PC ｃ H ｄ F ｅ (d and e are each an integer of 1 or more and 5 or less, and c is an integer of 0 or more and 9 or less) gas.

[0064] PCl ａ F ｂ The gas is, for example, PClF ２ Gas, PCl ２ F gas and PCl ２ F ３ The gas may be at least one gas selected from the group consisting of:

[0065] PC ｃ H ｄ F ｅ The gas is, for example, PF ２ CH ３ Gas, PF(CH ３ ) ２ Gas, pH ２ CF ３ Gas, pH (CF ３ ) ２ Gas, PCH ３ (CF ３ ) ２ Gas, pH ２ F gas and PF ３ (CH ３ ) ２The gas may be at least one gas selected from the group consisting of gases.

[0066] The phosphorus-containing gas is PCl ｃ F ｄ C ｅ H ｆ (c, d, e, and f are each an integer of 1 or more) gas. The phosphorus-containing gas may be a gas containing P (phosphorus), F (fluorine), and a halogen other than F (fluorine) (e.g., Cl, Br, or I) in its molecular structure, a gas containing P (phosphorus), F (fluorine), C (carbon), and H (hydrogen) in its molecular structure, or a gas containing P (phosphorus), F (fluorine), and H (hydrogen) in its molecular structure.

[0067] The phosphorus-containing gas may be a phosphine-based gas. ３ ), compounds in which at least one hydrogen atom of a phosphine has been substituted with an appropriate substituent, and phosphinic acid derivatives.

[0068] The substituent substituting the hydrogen atom of the phosphine is not particularly limited, and examples thereof include halogen atoms such as a fluorine atom and a chlorine atom, alkyl groups such as a methyl group, an ethyl group, and a propyl group, and hydroxyalkyl groups such as a hydroxymethyl group, a hydroxyethyl group, and a hydroxypropyl group; and examples thereof include a chlorine atom, a methyl group, and a hydroxymethyl group.

[0069] The phosphinic acid derivatives include phosphinic acid (H ３ O ２ P), alkylphosphinic acid (PHO(OH)R), and dialkylphosphinic acid (PO(OH)R ２ ) are listed.

[0070] The phosphine-based gas is, for example, PCH ３ Cl ２ (dichloro(methyl)phosphine) gas, P(CH ３ ) ２ Cl (chloro(dimethyl)phosphine) gas, P(HOCH ２ ) Cl ２ (Dichloro(hydroxylmethyl)phosphine) gas, P(HOCH ２ )２ Cl (chloro(dihydroxymethyl)phosphine) gas, P(HOCH ２ ) (CH ３ ) ２ (Dimethyl(hydroxylmethyl)phosphine) gas, P(HOCH ２ ) ２ (CH ３ ) (methyl(dihydroxymethyl)phosphine) gas, P(HOCH ２ ) ３ (tris(hydroxylmethyl)phosphine) gas, H ３ O ２ P (phosphinic acid) gas, PHO(OH)(CH ３ ) (methylphosphinic acid) gas and PO(OH)(CH ３ ) ２ At least one gas selected from the group consisting of (dimethylphosphinic acid) gas may be used.

[0071] The flow rate of the phosphorus-containing gas contained in the first process gas may be 20% by volume or less, 10% by volume or less, or 5% by volume or less of the total flow rate of the first process gas excluding the flow rate of the inert gas.

[0072] The first process gas may further include a tungsten-containing gas (W-containing gas). The tungsten-containing gas may be a gas containing tungsten and a halogen, and in one example, WF ｘ Cl ｙ (x and y are each an integer of 0 to 6, and the sum of x and y is 2 to 6.) Specifically, the tungsten-containing gas is tungsten difluoride (WF ２ ) gas, tungsten tetrafluoride (WF ４ ) gas, tungsten pentafluoride (WF ５ ) gas, tungsten hexafluoride (WF ６ tungsten and fluorine-containing gases such as tungsten dichloride (WCl ２ ) gas, tungsten tetrachloride (WCl ４ ) gas, tungsten pentachloride (WCl ５ ) gas, tungsten hexachloride (WCl ６The tungsten-containing gas may be one or more of tungsten and chlorine-containing gases such as WF ６ Gas and WCl ６ The first process gas may be at least one of the following gases. The first process gas may contain a titanium-containing gas or a molybdenum-containing gas instead of or in addition to the tungsten-containing gas. That is, the first process gas may contain at least one metal-containing gas. The at least one metal-containing gas may contain at least one metal selected from the group consisting of tungsten, molybdenum, titanium, and ruthenium.

[0073] The first process gas may further include a halogen-containing gas. The first process gas may further include a halogen-containing gas other than fluorine, i.e., a fluorine-free halogen-containing gas and / or a fluorine-containing halogen-containing gas. The halogen-containing gas other than fluorine may be a chlorine-containing gas, a bromine-containing gas, and / or an iodine-containing gas. In one example, the chlorine-containing gas is Cl. ２ , SiCl ２ , SiCl ４ , CCl ４ , SiH ２ Cl ２ , Si ２ Cl ６ , CHCl ３ , S.O. ２ Cl ２ , BCl ３ , PCl ３ , PCl ５ and POCl ３ The bromine-containing gas may be at least one gas selected from the group consisting of Br ２ , HBr, CBr ２ F ２ , C ２ F ５ Br, PBr ３ , PBr ５ , POBr ３ and BBr ３ The iodine-containing gas may be at least one gas selected from the group consisting of HI, CF, and the like. ３ I, C ２ F ５ I, C ３F ７ I, IF ５ , IF ７ , I ２ , P.I. ３ In one example, the halogen-containing gas other than fluorine may be at least one gas selected from the group consisting of Cl ２ Gas, Br ２ In one example, the halogen-containing gas other than fluorine may be at least one selected from the group consisting of Cl gas and HBr gas. ２ The fluorine-containing halogen-containing gas is NF ３ Gas (nitrogen trifluoride gas) and / or SF ６ It may contain a gas (sulfur hexafluoride gas).

[0074] The first process gas may further include an inert gas, which may be, for example, a noble gas such as Ar gas, He gas, Ne gas, Kr gas, Xe gas, or Rn gas, and / or nitrogen gas.

[0075] The first processing gas may contain, in place of a part or all of the HF gas, a gas capable of generating hydrogen fluoride species (HF species) in the first plasma. The HF species include at least one of hydrogen fluoride gas, radicals, and ions.

[0076] The gas capable of generating HF species may be a single gas or a mixed gas containing fluorine and hydrogen. The single gas containing fluorine and hydrogen may be, for example, a hydrofluorocarbon gas. The hydrofluorocarbon gas may have two or more carbon atoms, three or more carbon atoms, or four or more carbon atoms. In one example, the hydrofluorocarbon gas is CH ２ F ２ Gas, C ３ H ２ F ４ Gas, C ３ H ２ F ６ Gas, C ３ H ３ F ５ Gas, C ４ H ２ F ６ Gas, C ４ H ５ F ５ Gas, C ４ H２ F ８ Gas, C ５ H ２ F ６ Gas, C ５ H ２ F １０ Gas and C ５ H ３ F ７ The hydrofluorocarbon gas is at least one selected from the group consisting of CH ２ F ２ Gas, C ３ H ２ F ４ Gas, C ３ H ２ F ６ Gas and C ４ H ２ F ６ The gas is at least one selected from the group consisting of:

[0077] The hydrogen source in the mixed gas containing fluorine and hydrogen is, for example, H ２ Gas, NH ３ Gas, H ２ O gas, H ２ O ２ Gas and hydrocarbon gas (CH ４ Gas, C ３ H ６ The fluorine source may be at least one selected from the group consisting of NF ３ Gas, SF ６ Gas, WF ６ gas or XeF ２ The fluorine source may be a fluorine-containing gas that does not contain carbon, such as a fluorocarbon gas or a hydrofluorocarbon gas. The fluorine source may also be a fluorine-containing gas that contains carbon, such as a fluorocarbon gas or a hydrofluorocarbon gas. An example of a fluorocarbon gas is CF ４ Gas, C ２ F ２ Gas, C ２ F ４ Gas, C ３ F ６ Gas, C ３ F ８ Gas, C ４ F ６ Gas, C ４ F ８Gas and C ５ F ８ The hydrofluorocarbon gas may be at least one selected from the group consisting of CHF ３ Gas, CH ２ F ２ Gas, CH ３ F gas, C ２ HF ５ Gas and hydrofluorocarbon gas containing three or more C (C ３ H ２ F ４ Gas, C ３ H ２ F ６ Gas, C ４ H ２ F ６ The gas may be at least one selected from the group consisting of:

[0078] (Step ST13: Second Etching) The second etching step ST13 is performed following the first etching step ST12. The second etching step ST13 may be started before the recess RC reaches the base film UF. That is, step ST13 may be started in a state where the silicon-containing film SF remains between the base film UF and the bottom of the recess RC, and may be performed during a period that includes the time when the base film UF is exposed. Alternatively, the second etching step ST13 may be started when at least a portion of the base film UF is exposed in the recess. Switching from step ST12 to step ST13 may be performed based on at least one of the depth of the recess RC, the aspect ratio of the recess RC, and the etching time.

[0079] In step ST13, first, a second process gas is supplied from the gas supply unit 20 into the plasma processing space 10s. In step ST13, similar to step ST12, a source RF signal is supplied to the lower electrode of the substrate support 11 and / or the upper electrode of the shower head 13. This generates a high-frequency electric field between the shower head 13 and the substrate support 11, generating a second plasma from the second process gas in the plasma processing space 10s. Also in step ST13, a bias signal is supplied to the lower electrode of the substrate support 11, generating a bias potential between the plasma and the substrate W. The bias potential attracts active species, such as ions and radicals, in the plasma to the substrate W, and the silicon-containing film SF is further etched by these active species. Step ST13 is performed until the base film UF is exposed or until at least a portion of the base film UF is etched in the depth direction. During the processing in step ST12, the temperature of the substrate support 11 may be maintained at the set temperature adjusted in step ST11 or may be changed as described below.

[0080] 5 is a diagram showing an example of the cross-sectional structure of the substrate W at the end of step ST13. As shown in FIG. 5, in the substrate W after processing in step ST13, the bottoms of the recesses RC reach the base film UF, exposing the base film UF. At this time, a portion of the base film UF may be etched in the depth direction. The aspect ratio of the recesses RC in this state may be, for example, 20 or more, 30 or more, 40 or more, 50 or more, or 100 or more.

[0081] In step ST13, the second process gas may contain the same type of gas as the first process gas, or may contain a different type of gas. The second process gas may contain, for example, HF gas. The second process gas may further contain, for example, at least one gas selected from the group consisting of the above-mentioned carbon-containing gas, oxygen-containing gas, and phosphorus-containing gas. The second process gas may further contain, for example, the above-mentioned tungsten-containing gas, titanium-containing gas, molybdenum-containing gas, inert gas, and halogen-containing gas. Like the first process gas, the second process gas may contain a gas capable of generating HF species in the second plasma instead of part or all of the HF gas.

[0082] In step ST13, the source RF signal may have a frequency in the range of 10 MHz to 150 MHz. For example, the source RF signal may have a frequency of 40 MHz or higher or 60 MHz or higher. In step ST13, the bias signal may be a bias RF signal supplied from the second RF generator 31b. The bias signal may also be a bias DC signal (e.g., a sequence of voltage pulses) supplied from the DC generator 32a. Both the source RF signal and the bias signal may be continuous waves or pulse waves, or one of the source RF signal and the bias signal may be continuous waves and the other may be pulse waves. When both the source RF signal and the bias signal are pulse waves, the periods of the two pulse waves may be synchronized. The duty ratio of the pulse waves may be set appropriately, for example, between 1 and 80%, or between 5 and 50%. The duty ratio is the proportion of a period during which the power or voltage level is high in the pulse wave period. Furthermore, when a bias DC signal is used, each voltage pulse in the sequence may have a waveform of a rectangle, a trapezoid, a triangle, or a combination thereof. The polarity of each voltage pulse in the bias DC signal may be negative or positive as long as the potential of the substrate W is set so as to apply a potential difference between the plasma and the substrate and attract ions. The supply of the source RF signal and / or the bias signal may be performed continuously from step ST12. Furthermore, the supply of the source RF signal and / or the bias signal may be stopped at the end of step ST12 and restarted at the start of step ST13.

[0083] When starting process ST13, the etching process conditions (recipe 2) are changed from the process conditions (recipe 1) in process ST12. That is, in process ST13, the etching of the silicon-containing film SF is performed using a recipe different from that in process ST12. The change in the recipe may include using a different second process gas from the first process gas and / or performing temperature control to increase the temperature of the substrate W compared to process ST12. In one example, the process conditions (recipe 2) in process ST13 may be conditions that improve the selectivity of the silicon-containing film SF to the underlayer film UF compared to the process conditions (recipe 1) in process ST12. In this case, the process conditions (recipe 2) in process ST13 may be selected depending on the film type of the underlayer film UF. For example, the process conditions may be different depending on whether the underlayer film UF contains silicon or a metal. The change in the recipe may also include lowering the process pressure (the pressure in the chamber during processing). That is, the pressure in the plasma processing space 10s in step ST13 may be reduced compared to that in step ST12. For example, the pressure in the plasma processing space 10s in step ST13 may be reduced by 30% or more compared to that in step ST12.

[0084] FIG. 6 is an example of a timing chart for when the underlayer UF contains silicon. In the example shown in FIG. 6, the composition of the process gas differs between step ST12 and step ST13. In FIG. 6, the horizontal axis represents time. The vertical axis represents the flow rates of the HF gas, carbon-containing gas, and oxygen-containing gas contained in the process gas (first process gas or second process gas), and the density of fluorine species in the plasma (first plasma or second plasma). "QL1," "QL2," and "QL3" represent flow rates that are smaller than the flow rates represented by "QH1," "QH2," and "QH3," or zero. Furthermore, "DL" represents a density of fluorine species in the plasma that is smaller than the density of fluorine species in the plasma represented by "DH." In FIG. 6, the "carbon-containing gas" refers to one or both of a fluorocarbon gas and a hydrofluorocarbon gas. When the carbon-containing gas is both a fluorocarbon gas and a hydrofluorocarbon gas, the flow rate of the carbon-containing gas is the sum of the flow rates of the fluorocarbon gas and the hydrofluorocarbon gas. The term "fluorine species" refers to fluorine-containing gases (e.g., HF gas, fluorocarbon gas, hydrofluorocarbon gas, NF ３ Gas or SF ６ It is an active species of fluorine dissociated from oxygen (e.g., gas).

[0085] 6, when the undercoat film UF contains silicon, the flow rate (partial pressure) of the HF gas may be reduced and the flow rates (partial pressures) of the carbon-containing gas (fluorocarbon gas and / or hydrofluorocarbon gas) and the oxygen-containing gas may be increased when switching from step ST12 to step ST13. In one example, when switching from step ST12 to step ST13, the process gas (second process gas) may contain 50 volume % or more of the carbon-containing gas and the oxygen-containing gas with respect to the total flow rate of the second process gas excluding the flow rate of the inert gas. Furthermore, the carbon number of the fluorocarbon gas and / or the hydrofluorocarbon gas contained in the second process gas may be 2 or more.

[0086] As the etching in step ST13 progresses, the base film UF is exposed. If the base film UF contains silicon, the fluorine species in the plasma also function as an etchant for the base film UF. In the example of the timing chart shown in FIG. 6 , the density of the fluorine species in the second plasma generated in step ST13 is lower than the density of the fluorine species in the first plasma generated in step ST12. Therefore, etching of the base film UF is suppressed. That is, the etching selectivity of the silicon-containing film SF relative to the base film UF can be improved.

[0087] FIG. 7 is another example of a timing chart when the undercoat film UF contains silicon. FIG. 7 illustrates an example of control for increasing the temperature of the substrate W in step ST13 compared to the temperature of the substrate W in step ST12. In FIG. 7 , the horizontal axis represents time. The vertical axis represents the signal level (the power of the source RF signal and / or the level of the bias signal (the absolute value of the power of the bias RF signal or the voltage level of the voltage pulse)), the DC voltage (ESC voltage) supplied to the electrostatic chuck 1111, the pressure of the heat transfer gas (e.g., He) supplied to the gap between the electrostatic chuck 1111 and the backside of the substrate W, the heater temperature and / or the temperature of the heat transfer fluid (temperature control module temperature) flowing through the flow path 1110a, and the temperature of the substrate W. In FIG. 7 , "WL" represents a signal level lower than the signal level indicated by "WH." "VL" represents an ESC voltage lower than the ESC voltage indicated by "VH." "PL" represents a heat transfer gas pressure lower than the heat transfer gas pressure indicated by "PH." "TL1" and "TL2" indicate temperatures lower than the temperatures indicated by "TH1" and "TH2", respectively.

[0088] 7 , when the undercoat film UF contains silicon, (I) the signal level of the source RF signal and / or the signal level of the bias signal may be increased when switching from process ST12 to process ST13. Increasing the signal level may include increasing the effective value of the signal level (e.g., power), lengthening the signal supply time, and increasing the signal duty ratio. This increases the heat input to the substrate W, and the temperature of the substrate W rises.

[0089] As shown in FIG. 7 , when switching from process ST12 to process ST13, (II) the DC voltage (ESC voltage) supplied to the electrostatic chuck 1111 may be reduced to reduce the chucking force of the electrostatic chuck 1111. Also, (III) the pressure of the heat transfer gas (e.g., He) between the electrostatic chuck 1111 and the backside of the substrate W may be reduced. Also, (IV) the temperature of the heater and / or the temperature of the heat transfer fluid flowing through the flow path 1110a may be increased. In either case, the temperature of the substrate W increases. Note that one or more of the temperature controls (I) to (IV) above may be combined. The difference between the temperature (TL2) of the substrate W in process ST12 and the temperature (TH2) of the substrate W in process ST13 may be, for example, 30° C. or more. For example, the temperature (TL2) of the substrate W in process ST12 may be −40° C., and the temperature (TH2) of the substrate W in process ST13 may be 0° C.

[0090] As the etching in step ST13 progresses, the base film UF is exposed. Here, in the example of the timing chart shown in FIG. 7 , the temperature of the substrate W in step ST13 is higher than the temperature of the substrate W in step ST12. Therefore, the amount of etchant (e.g., fluorine species in plasma) adsorbed to the base film UF is reduced. This suppresses etching of the base film UF, and the etching selectivity of the silicon-containing film SF to the base film UF can be improved.

[0091] When switching from process ST12 to process ST13, both a change in the composition of the processing gas (for example, the change in the composition of the processing gas described with reference to FIG. 6) and control to increase the temperature of the substrate W (for example, the control described with reference to FIG. 7) may be performed.

[0092] 8 is an example of a timing chart when the undercoat film UF contains a metal. Fig. 8 shows an example when the composition of the process gas is different between step ST12 and step ST13. In Fig. 8, the horizontal axis represents time. The vertical axis represents the ratio of the HF gas, the carbon-containing gas, and the NF gas contained in the process gas (first process gas or second process gas). ３ / SF ６The flow rates of the respective gases and the density of fluorine species in the plasma (first plasma or second plasma) are shown. "QH1" and "QH2" each indicate a flow rate greater than 0. "QL4" indicates a flow rate that is smaller than the flow rate indicated by "QH4" or is zero. "DL" indicates a density of fluorine species in the plasma that is smaller than the density of fluorine species in the plasma indicated by "DH". In FIG. 8, the "carbon-containing gas" is one or both of a fluorocarbon gas and a hydrofluorocarbon gas. When the carbon-containing gas is both a fluorocarbon gas and a hydrofluorocarbon gas, the flow rate of the carbon-containing gas is the sum of the flow rates of the fluorocarbon gas and the hydrofluorocarbon gas. In FIG. 8, "NF ３ / SF ６ Gas" is NF ３ Gas and SF ６ One or both of the gases. ３ / SF ６ Gas" is NF ３ Gas and SF ６ If both gases are present, NF ３ / SF ６ The gas flow rate is NF ３ Gas and SF ６ The flow rate is the sum of the flow rates of each gas. ３ Gas and SF ６ The gas is an example of a carbon-free fluorine source that can be used in addition to the HF gas described above.

[0093] As shown in FIG. 8, when the undercoat film UF contains a metal, a fluorine-containing gas other than hydrogen fluoride, such as NF ３ gas and / or SF ６ The flow rate (partial pressure) of the gas may be reduced. In addition, the flow rate (partial pressure) of the HF gas may be reduced.

[0094] As the etching in step ST13 progresses, the base film UF is exposed. If the base film UF contains a metal, the fluorine species in the plasma may react with the metal and etch the base film UF. In the example of the timing chart shown in FIG. 8 , the density of the fluorine species in the second plasma generated in step ST13 is lower than the density of the fluorine species in the first plasma generated in step ST12. Therefore, etching of the base film UF is suppressed. That is, the etching selectivity of the silicon-containing film SF relative to the base film UF may be improved.

[0095] If the underlayer UF contains a metal, control for increasing the temperature of the substrate W may be further performed in step ST13. The control for increasing the temperature of the substrate W may be performed by combining one or more of the temperature controls (I) to (IV) described above with reference to FIG. 7 . This promotes volatilization of by-products containing the metal contained in the underlayer UF, thereby suppressing the generation of residues containing the metal. In addition to or instead of this, a gas highly reactive with the metal of the underlayer UF may be added as the second process gas. For example, if the underlayer UF contains tungsten, CO gas may be added as the second process gas. The CO gas reacts with W scattered from the underlayer UF during step ST13 to produce volatile W(CO). ６ This suppresses the generation of residues containing metal (W) from the underlayer UF. The second process gas may contain Cl in addition to or instead of CO gas. ２ Gas, SiCl ４ Gas or BCl ３ The gas may include a chlorine-containing gas such as a gas.

[0096] According to the etching method of the first embodiment, in step ST13, the etching of the silicon-containing film SF is performed under processing conditions (recipe) different from those in step ST12. This allows an optimal recipe to be selected depending on the progress of the etching, i.e., the depth of the recess RC. For example, in a region where the recess RC is shallow, a recipe that increases the etching rate of the silicon-containing film SF can be selected, and in a region where the recess RC is deep and the base film UF is exposed, a recipe that increases the etching selectivity of the silicon-containing film SF relative to the base film UF can be selected.

[0097] Second Embodiment Fig. 9 is a flowchart showing an etching method according to a second embodiment. As shown in Fig. 9, the etching method according to the second embodiment includes a step ST21 of providing a substrate, a step ST22 of generating plasma, and an etching step ST23. The processes in each of steps ST21 to ST23 may be performed in the plasma processing system shown in Fig. 1. That is, the etching method according to the second embodiment may be performed using a plasma processing apparatus 1 as the etching apparatus. The etching method according to the second embodiment will be described below using as an example a case in which a control unit 2 controls each part of the plasma processing apparatus 1 to etch a substrate W.

[0098] (Process ST21: Providing a Substrate) In process ST21, a 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. The substrate W is then held on the substrate support 11 by the electrostatic chuck 1111. The substrate W provided in process ST21 may be the same as the substrate W (see FIG. 3) described in relation to the first embodiment.

[0099] In the second embodiment, after the substrate W is provided to the central region 111a of the substrate support 11, the temperature of the substrate support 11 is adjusted to a set temperature by the temperature adjustment module, as in the first embodiment. The set temperature may be, for example, 20°C or less, 0°C or less, -10°C or less, -20°C or less, -30°C or less, -40°C or less, -50°C or less, -60°C or less, or -70°C or less. The temperature of the substrate support 11 may be adjusted to the set temperature before step ST21. Furthermore, during the processes in steps ST22 and ST23, the temperature of the substrate support 11 may be maintained at the set temperature adjusted in step ST21.

[0100] (Step ST22: Plasma Generation) In step ST22, plasma is generated from the processing gas. First, the processing gas is supplied into the plasma processing space 10s from the gas supply unit 20. The processing gas may be the same gas as the first processing gas and / or the second processing gas described in the first embodiment.

[0101] Next, in step ST22, a source RF signal is supplied to the lower electrode of the substrate support 11 and / or the upper electrode of the shower head 13. This generates a high-frequency electric field between the shower head 13 and the substrate support 11, and generates plasma from the processing gas in the plasma processing space 10s.

[0102] FIG. 10 is a diagram showing the relationship between ion flux and ion energy. As shown in FIG. 10, the higher the frequency of the source RF signal, the lower the ion energy. Also, the higher the frequency of the source RF signal, the greater the ion flux and the higher the electron density. For example, when a source RF signal (RF40) having a frequency of 40 MHz is used, when a source RF signal (RF60) having a frequency of 60 MHz is used, and when a source RF signal (RF100) having a frequency of 100 MHz is used, the following relationships hold for ion energy and ion flux: Ion energy: RF40>RF60>RF100 Ion flux: RF40<RF60<RF100

[0103] In step ST22, the frequency of the source RF signal is selected so that high-density plasma is generated with low ion energy. This frequency may vary depending on the plasma generation method of the plasma processing apparatus. For example, in the plasma processing apparatus 1, when a source RF signal is supplied to the upper electrode and a bias signal is supplied to the lower electrode, the frequency of the source RF signal may be 40 MHz or higher. Furthermore, in the plasma processing apparatus 1, when a source RF signal and a bias signal are supplied to the lower electrode, the frequency of the source RF signal supplied to the lower electrode of the substrate support 11 may be 60 MHz or higher. Furthermore, the frequency of the source RF signal may be 150 MHz or lower, or 100 MHz or lower.

[0104] Furthermore, in step ST22, a bias signal is supplied to the lower electrode of the substrate support 11. This generates a bias potential difference between the plasma and the substrate W. The bias potential difference attracts active species such as ions and radicals in the plasma to the substrate W. The bias signal may be a bias RF signal supplied from the second RF generator 31b. The bias signal may also be a bias DC signal (e.g., a sequence of voltage pulses) supplied from the DC generator 32a.

[0105] In process ST22, each of the source RF signal and the bias signal may be a continuous wave or a pulse wave. Alternatively, in process ST22, one of the source RF signal and the bias signal may be a continuous wave and the other may be a pulse wave. When both the source RF signal and the bias signal are pulse waves, the periods of the two pulse waves may be synchronized. The duty ratio of the pulse wave may be set appropriately, for example, 1 to 80% or 5 to 50%. The duty ratio is the proportion of the period during which the power or voltage level is high in the pulse wave period. When a bias DC signal is used, each voltage pulse in the sequence may have a rectangular, trapezoidal, triangular, or a combination thereof. The polarity of each voltage pulse in the bias DC signal may be negative or positive, as long as the potential of the substrate W is set so as to create a potential difference between the plasma and the substrate and attract ions.

[0106] FIG. 11 is a timing chart showing an example of a source RF signal and a bias RF signal. FIG. 11 shows an example in which both the source RF signal and the bias RF signal are pulse waves. The horizontal axis of FIG. 11 represents time. In one example, the source RF signal has a frequency of 40 MHz or more and 100 MHz or less. The source RF signal is supplied to the lower electrode of the substrate support 11 and / or the upper electrode of the showerhead 13 in a first period and a second period alternating with the first period. The source RF signal has a first level (power level) in the first period and a second level (power level) in the second period. In FIG. 11, the first level is a power level lower than the second level or is 0 W.

[0107] A bias RF signal is supplied to the lower electrode of the substrate support 11 during a third period and a fourth period alternating with the third period. The bias RF signal, for example, has a frequency of 400 kHz or more and 13.56 MHz or less. The bias RF signal has a third level (power level) during the third period and a fourth level (power level) during the fourth period. In FIG. 11 , the third level is a power level lower than the fourth level or is 0 W. As shown in FIG. 11 , the second period and the fourth period may coincide (synchronize) with each other. Note that the second period and the fourth period may not overlap with each other partially or entirely.

[0108] FIG. 12 is a timing chart showing an example of a source RF signal and a bias DC signal. FIG. 12 shows an example in which both the source RF signal and the bias DC signal are pulse waves. The horizontal axis of FIG. 12 represents time. The source RF signal shown in FIG. 12 is the same as the source RF signal in the example shown in FIG. 11. The bias DC signal is supplied to the lower electrode of the substrate support 11 during a fifth period and a sixth period alternating with the fifth period. The bias DC signal has a fifth level (voltage level) during the fifth period and a sixth level (voltage level) during the sixth period. In FIG. 12, the absolute value of the fifth level is smaller than the absolute value of the sixth level or is 0 V. As shown in FIG. 12, the second period and the sixth period may coincide (synchronize). Note that the second period and the sixth period may not overlap in part or in whole with each other.

[0109] In step ST22, a second bias signal may be supplied to the upper electrode. The second bias signal may be a second DC signal supplied from the second DC generator 32b and / or a bias RF signal supplied from the second RF generator 31b. The second bias signal may be a continuous wave or a pulsed wave. In this case, positive ions present in the plasma processing space 10s are attracted to the upper electrode and collide with it, resulting in the emission of secondary electrons from the upper electrode. The emitted secondary electrons may modify the mask MF and improve its etching resistance. Furthermore, the irradiation of the secondary electrons neutralizes the charged state of the substrate W, thereby enhancing the linearity of ions into recesses in the silicon-containing film SF formed by etching. Furthermore, if the upper electrode is made of a silicon-containing material, the collision of the positive ions emits silicon from the upper electrode along with the secondary electrons. The emitted silicon combines with oxygen in the plasma to form a silicon oxide compound. The silicon oxide compound may deposit on the mask MF and function as a protective film. As described above, supplying the second bias signal to the upper electrode can produce effects such as improving the selectivity, suppressing etching shape abnormalities, and improving the etching rate.

[0110] (Step ST23: Etching) In step ST23, the silicon-containing film SF is etched by plasma generated in the plasma processing space 10s, and a recess is formed in the silicon-containing film SF based on the shape of the opening OP in the mask MF. When the depth of the recess formed by etching reaches a predetermined depth or when the etching time reaches a predetermined time, the etching is terminated.

[0111] In the etching method according to the second embodiment, in step ST22, the frequency of the source RF signal is set to 40 MHz or higher. When the frequency of the source RF signal is 40 MHz or higher, even if the power level of the source RF signal and / or the level of the bias signal (the power level of the bias RF signal or the voltage level of the bias DC signal) is increased to increase the electron density of the plasma, an increase in ion energy is suppressed. That is, when the frequency of the source RF signal is set to 40 MHz or higher, it is possible to control the electron density of the generated plasma independently of the ion energy. Therefore, in step ST22, a higher-density plasma can be generated while suppressing an increase in the ion energy of the plasma compared to when the frequency is lower than 40 MHz. As a result, in the etching in step ST23, the density of the etchant (HF species) is increased and heat input to the substrate W is suppressed. As a result, in the etching in step ST23, adsorption of the etchant (HF species) can also be promoted. In addition, in the etching in step ST23, suppressing an increase in ion energy can also reduce damage to the mask MF. Therefore, according to the etching method according to the second embodiment, the etching rate of the silicon-containing film SF can be improved, and the etching selectivity of the silicon-containing film SF with respect to the mask MF can be improved.

[0112] Third Embodiment FIG. 13 is a flowchart showing an etching method according to a third embodiment. Similar to the first embodiment, the etching method according to the third embodiment includes a substrate providing step ST31, a first etching step ST32, and a second etching step ST33. The processes in each of steps ST31 to ST33 may be performed in the plasma processing system shown in FIG. 1 . That is, the etching method according to the third embodiment may be performed using a plasma processing apparatus 1 as the etching apparatus. The etching method according to the third embodiment will be described below using an example in which a controller 2 controls each component of the plasma processing apparatus 1 to etch a substrate W. Note that descriptions of parts of the third embodiment that overlap with those of the first or second embodiment will be omitted or simplified.

[0113] (Process ST31: Providing a Substrate) In process ST31, a 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. The substrate W is then held on the substrate support 11 by the electrostatic chuck 1111. The substrate W provided in process ST31 may be the same as the substrate W (see FIG. 3) described in relation to the first embodiment.

[0114] In the third embodiment, after the substrate W is provided in the central region 111a of the substrate support 11, the temperature of the substrate support 11 is adjusted to a set temperature by the temperature adjustment module. The set temperature may be, for example, 20°C or less, 0°C or less, -10°C or less, -20°C or less, -30°C or less, -40°C or less, -50°C or less, -60°C or less, or -70°C or less. In one example, adjusting or maintaining the temperature of the substrate support 11 includes setting the temperature of the heat transfer fluid flowing through the flow path 1110a and the heater temperature to their respective set temperatures, or to temperatures different from the respective set temperatures. Note that the timing at which the heat transfer fluid starts flowing through the flow path 1110a may be before, after, or simultaneously with the time at which the substrate W is placed on the substrate support 11. Alternatively, the temperature of the substrate support 11 may be adjusted to the set temperature before step ST31. That is, the substrate W may be provided to the substrate support 11 after the temperature of the substrate support 11 is adjusted to the set temperature.

[0115] (Step ST32: First Etching Step) In step ST32, the silicon-containing film SF is etched using plasma generated from a first process gas. First, the first process gas is supplied from the gas supply unit 20 into the plasma processing space 10s. The first process gas contains HF gas and a W-containing gas.

[0116] Next, a source RF signal is supplied to the lower electrode of the substrate support 11 and / or the upper electrode of the shower head 13. This generates a high-frequency electric field between the shower head 13 and the substrate support 11, generating a first plasma from the first process gas in the plasma processing space 10s. Furthermore, a bias signal is supplied to the lower electrode of the substrate support 11, generating a bias potential difference between the plasma and the substrate W. The bias potential difference attracts active species, such as ions and radicals, in the plasma toward the substrate W. This etches the silicon-containing film SF, forming a recess in the silicon-containing film SF based on the shape of the opening OP in the mask MF. The first etching may be performed before (e.g., just before) the base film UF is exposed, or until at least a portion of the base film UF is exposed. That is, step ST32 may be terminated before (e.g., just before) the base film UF of the substrate W is exposed, or at the timing when at least a portion of the base film UF is exposed.

[0117] FIG. 14 is a diagram showing an example of the cross-sectional structure of the substrate W at the end of step ST32. As shown in FIG. 14 , the processing in step ST32 etches the portion of the silicon-containing film SF exposed in the opening OP in the depth direction (from top to bottom in FIG. 14 ), forming a recess RC. Note that FIG. 14 shows a state in which the base film UF is not exposed at the end of step ST32. That is, step ST32 may be stopped with the silicon-containing film SF remaining between the base film UF and the bottom of the recess RC, and step ST33 may be started in this state and performed during a period that includes the time when the base film UF is exposed. Alternatively, at least a portion of the base film UF may be exposed in the recess RC at the end of step ST32.

[0118] When the silicon-containing film SF is etched, a first protrusion CV1 is formed on the sidewall of the mask MF at a first position on the mask MF near the top edge of the opening OP. The first protrusion reduces the width of the opening OP in the mask MF. The first protrusion CV1 is thought to be formed by deposition of a deposit component contained in the first process gas and / or a reaction by-product generated by etching at the first position. The first protrusion CV1 can be formed from a carbon-containing material derived from a carbon-containing gas, which will be described later.

[0119] Furthermore, as described above, since the first process gas contains a W-containing gas in addition to HF gas, a second convex portion CV2 that reduces the width of the opening OP is formed at a second position on the sidewall of the mask MF in addition to the first convex portion CV1. The second position is lower than the first position. The second convex portion CV2 is formed of a W-containing material (or a metal-containing material) derived from the W-containing gas (or a metal-containing gas). The second convex portion CV2 suppresses ion incidence on the sidewall of the recess RC and on the bottom of the recess RC. Therefore, according to this embodiment, the phenomenon of horizontal etching of the silicon-containing film SF (bowing) is suppressed. Meanwhile, the shape of the recess RC (shape in vertical cross section) is tapered toward the bottom (reverse tapered).

[0120] In addition, when the first protrusion CV1 is formed of a carbon-containing material and the second protrusion CV2 is formed of a W-containing material (or a metal-containing material), the amounts of hydrogen species and fluorine species in the first plasma may be adjusted in step ST32 to form the second protrusion CV2 below the first protrusion CV1. To achieve this, the flow rate of a hydrogen source gas, which is a source of hydrogen species in the first process gas, and the flow rate of a fluorine source gas, which is a source of fluorine species in the first process gas, may be adjusted. The fluorine species reduce the amount of W-containing material (or metal-containing material) near the upper end of the opening OP in the mask MF. The hydrogen species reduce the amount of fluorine species. Therefore, as the ratio of the amount of fluorine species to the amount of hydrogen species increases, the second position becomes lower. Therefore, by adjusting the amounts of fluorine species and hydrogen species, it is possible to adjust the second position where the second protrusion CV2 is formed.

[0121] In step ST32, the HF gas contained in the first process gas may have the largest flow rate among the first process gas (if the first process gas contains an inert gas, all gases in the first process gas excluding the inert gas). The flow rate of the HF gas may be adjusted within the same range as the flow rate of the HF gas in the first embodiment.

[0122] In step ST32, the tungsten-containing gas (W-containing gas) contained in the first process gas may be a gas containing tungsten and a halogen, and in one example, WF ｘ Cl ｙ (x and y are each an integer of 0 to 6, and the sum of x and y is 2 to 6.) Specifically, the W-containing gas is tungsten difluoride (WF ２ ) gas, tungsten tetrafluoride (WF ４ ) gas, tungsten pentafluoride (WF ５ ) gas, tungsten hexafluoride (WF ６ tungsten and fluorine-containing gases such as tungsten dichloride (WCl ２ ) gas, tungsten tetrachloride (WCl ４ ) gas, tungsten pentachloride (WCl ５ ) gas, tungsten hexachloride (WCl ６ Among these, the W-containing gas may be one or more of tungsten and chlorine-containing gases such as WF ６ Gas and WCl ６ The first process gas may be at least one of the following gases. Instead of or in addition to the W-containing gas, the first process gas may contain one or more of a molybdenum-containing gas, a titanium-containing gas, and a ruthenium-containing gas. That is, the first process gas may contain at least one metal-containing gas selected from the group consisting of a tungsten-containing gas, a molybdenum-containing gas, a titanium-containing gas, and a ruthenium-containing gas. In other words, the first process gas may contain at least one metal-containing gas. The at least one metal-containing gas may contain at least one metal selected from the group consisting of tungsten, molybdenum, titanium, and ruthenium.

[0123] The first process gas may further include a phosphorus-containing gas. The first process gas may further include a carbon-containing gas. The first process gas may further include an oxygen-containing gas. The first process gas may further include a halogen-containing gas. The first process gas may include a halogen-containing gas other than fluorine, i.e., a fluorine-free halogen-containing gas and / or a fluorine-containing halogen-containing gas. In one example, the first process gas includes a phosphorus-containing gas, a carbon-containing gas, and a halogen-containing gas in addition to HF gas and a W-containing gas. The phosphorus-containing gas, carbon-containing gas, oxygen-containing gas, and halogen-containing gas that the first process gas may include may be the corresponding gases listed in the description of the first embodiment.

[0124] As described above, the first process gas may further contain a halogen-containing gas, similar to the first process gas in the first embodiment. In one example, the halogen-containing gas is NF ３ The first process gas may contain NF 3 ３ Instead of gas, or NF ３ In addition to the gas, the first process gas may also contain one or more other halogen-containing gases. ３ Instead of gas, or NF ３ In addition to gas, Cl ２ The gas may further include HBr gas.

[0125] The first process gas may not contain at least one noble gas, or may contain a noble gas at a flow rate lower than that of the noble gas in the second process gas described below. The first process gas may contain a first noble gas and / or a second noble gas as the noble gas. The first noble gas may include at least one noble gas selected from the group consisting of krypton (Kr) gas, xenon (Xe) gas, and radon (Rn) gas. The second noble gas may include at least one noble gas selected from the group consisting of Ar, Ne, and He.

[0126] The first processing gas may contain a gas capable of generating hydrogen fluoride species (HF species) in the first plasma instead of a part or all of the HF gas. The HF species include at least one of hydrogen fluoride gas, radicals, and ions. The gas capable of generating HF species may be a single gas or a mixed gas containing fluorine and hydrogen. The single gas or mixed gas containing fluorine and hydrogen may be any of the gases listed in the description of the first embodiment.

[0127] (Step ST33: Second Etching Step) Step ST33 is performed following step ST32. In one example, step ST33 may be started before the recess RC reaches the base film UF. That is, step ST33 may be started in a state in which the silicon-containing film SF remains between the base film UF and the bottom of the recess RC. Alternatively, step ST33 may be started when at least a portion of the base film UF is exposed in the recess RC. Switching from step ST32 to step ST33 may be performed based on at least one of the depth of the recess RC, the aspect ratio of the recess RC, and the etching time.

[0128] In step ST33, first, a second process gas is supplied from the gas supply unit 20 into the plasma processing space 10s. In step ST33, similar to step ST12, a source RF signal is supplied to the lower electrode of the substrate support 11 and / or the upper electrode of the shower head 13. This generates a high-frequency electric field between the shower head 13 and the substrate support 11, generating a second plasma from the second process gas in the plasma processing space 10s. Also in step ST33, a bias signal is supplied to the lower electrode of the substrate support 11, generating a bias potential difference between the plasma and the substrate W. The bias potential difference attracts active species, such as ions and radicals, in the plasma to the substrate W, and the silicon-containing film SF is further etched by these active species. Step ST33 is performed until the base film UF is exposed or until a portion of the base film UF is etched in the depth direction. During the processes in steps ST32 and ST33, the temperature of the substrate support 11 may be maintained at the set temperature adjusted in step ST31 or may be changed.

[0129] 15 is a diagram showing an example of the cross-sectional structure of the substrate W during processing in step ST33. As shown in FIG. 15 , in the substrate W after processing in step ST33, the bottoms of the recesses RC reach the base film UF, exposing the base film UF in the recesses RC. At this time, a portion of the base film UF may be etched in the depth direction. In step ST33, plasma generated from the second processing gas can be used to expand the opening width of the bottoms of the recesses RC, thereby making the shape of the recesses RC (shape in vertical cross section) rectangular. The aspect ratio of the recesses RC in this state may be, for example, 20 or more, 30 or more, 40 or more, 50 or more, or 100 or more.

[0130] In step ST33, the HF gas contained in the second process gas may have the largest flow rate (partial pressure) among all the gases in the second process gas (if the second process gas contains an inert gas, all the gases in the second process gas excluding the inert gas). The flow rate of the HF gas may be adjusted within the same range as the flow rate of the HF gas in the first embodiment.

[0131] The second process gas may include at least one noble gas, the first noble gas and / or the second noble gas, and nitrogen gas.

[0132] The second process gas may include a halogen-containing gas, similar to the first process gas, and may include a carbon-containing gas, similar to the first process gas.

[0133] The second process gas may not contain a W-containing gas (or a metal-containing gas), or may contain a W-containing gas at a flow rate lower than the flow rate of the W-containing gas (or a metal-containing gas) in the first process gas. In one example, the second process gas does not contain a W-containing gas (or a metal-containing gas). Note that when the second process gas contains a W-containing gas (or a metal-containing gas), the W-containing gas (or a metal-containing gas) may be any of the W-containing gases (or metal-containing gases) described above.

[0134] The second process gas may contain no phosphorus-containing gas or may contain a phosphorus-containing gas at a flow rate lower than the flow rate of the phosphorus-containing gas in the first process gas. In one example, the second process gas does not contain a phosphorus-containing gas. Note that if the second process gas contains a phosphorus-containing gas, the phosphorus-containing gas may be any of the phosphorus-containing gases described above.

[0135] 16 is an example of a timing chart of the third embodiment. In FIG. 13, the horizontal axis represents time. The vertical axis represents the flow rates of the HF gas, W-containing gas, first noble gas, and phosphorus-containing gas contained in the process gas (first process gas or second process gas). "QH1", "QH2", "QH3", and "QH4" each represent a flow rate greater than 0. "QL1", "QL2", "QL3", and "QL4" represent a flow rate smaller than "QH1", "QH2", "QH3", and "QH4", or zero, respectively.

[0136] As shown in FIG. 16 , when switching from process ST32 to process ST33, the flow rate (partial pressure) of the W-containing gas (or metal-containing gas) and / or the flow rate of the phosphorus-containing gas may be decreased, and the flow rate (partial pressure) of the first noble gas may be increased.

[0137] According to the etching method of the third embodiment, in step ST32, the silicon-containing film SF is etched with a first process gas containing HF gas and a W-containing gas (or a metal-containing gas). In step ST33, the silicon-containing film SF is further etched with a second process gas containing HF gas. In step ST32, a second convex portion CV2 is formed on the sidewall of the mask MF, thereby suppressing bowing of the silicon-containing film SF. Although the shape (shape in vertical cross section) of the recess RC formed in step ST32 is inverted tapered, the recess RC's bottom opening width can be enlarged in step ST33 to form a rectangular shape. The enlargement of the bottom opening width of the recess RC in step ST33 is partly achieved by using a second process gas in which the flow rate of the W-containing gas (or a metal-containing gas) is reduced or set to zero.

[0138] In the above description, the case where step ST32 is switched to step ST33 before the recesses RC reach the base film UF or when at least a portion of the base film UF is exposed has been described. However, in the third embodiment, the timing of switching from step ST32 to step ST33 is not limited to this. For example, step ST32 may be switched to step ST33 after the recesses RC reach the base film UF and a portion of the base film UF is etched. Furthermore, for example, a cycle including step ST32 and step ST33 may be performed multiple times until the base film UF is exposed or a portion of the base film UF is etched.

[0139] As described above, in the third embodiment, the first process gas may further contain a phosphorus-containing gas. The second process gas may contain no phosphorus-containing gas or may contain a phosphorus-containing gas at a flow rate lower than that of the phosphorus-containing gas in the first process gas. The phosphorus-containing gas increases the etching rate of the silicon-containing film SF at the bottom of the recess RC and suppresses lateral etching of the sidewalls defining the recess RC. Therefore, when the first process gas contains a phosphorus-containing gas, the etching rate of the silicon-containing film SF can be increased and bowing can be suppressed. When the second process gas does not contain a phosphorus-containing gas or contains a phosphorus-containing gas at a flow rate lower than that of the phosphorus-containing gas in the first process gas, the width of the bottom of the recess RC, i.e., the width of the bottom of the recess RC near (or directly above) the base film UF, can be increased. As described above, step ST32 may be stopped with the silicon-containing film SF remaining between the base film UF and the bottom of the recess RC, and step ST33 may be started in this state.

[0140] In the third embodiment, the second process gas may further contain the above-mentioned first noble gas (e.g., xenon gas). In this case, the first process gas may not contain the first noble gas, or may contain the first noble gas at a flow rate lower than the flow rate of the first noble gas in the second process gas. In this case, the first process gas and the second process gas may further contain a halogen-containing gas. The halogen-containing gas may be NF３ The halogen-containing gas may include Cl. ２ The second process gas may further include one or more other halogen-containing gases, such as a noble gas and / or a HBr gas. By using the second process gas including the first noble gas, it is possible to increase the width of the bottom of the recess RC, for example, the width of the recess RC near (or immediately above) the underlayer UF.

[0141] In a third embodiment, the first process gas is NF ３ The halogen-containing gas may further comprise a halogen-containing gas, such as NF ３ In addition to gas, Cl ２ The second process gas may further include one or more other halogen-containing gases, such as NF 3 and / or HBr. Similar to the first process gas, the second process gas may also include a halogen-containing gas. The second process gas may include NF 3 and / or HBr. ３ No gas or NF in the first process gas ３ NF at a flow rate lower than the gas flow rate ３ The second process gas may include an oxygen-containing gas (e.g., O ２ The first process gas may further include a noble gas (e.g., a xenon gas) and a noble gas. The first process gas may not include a noble gas, or may include a noble gas at a flow rate lower than the flow rate of the noble gas in the second process gas. In this case, each of the noble gases in the first process gas and the second process gas may be a first noble gas (e.g., a xenon gas) or a second noble gas (e.g., an argon gas), or may include both the first noble gas and the second noble gas. In this case, too, it is possible to increase the width of the bottom of the recess RC, for example, the width of the recess RC near (or immediately above) the underlayer UF.

[0142] The above-described embodiments have been described for illustrative purposes and are not intended to limit the scope of the present disclosure. Various modifications can be made to the above-described embodiments without departing from the scope and spirit of the present disclosure. For example, the etching method according to the first embodiment may be used in combination with the etching method according to the second embodiment and / or the etching method according to the third embodiment. Furthermore, the etching method according to the second embodiment may be used in combination with the etching method according to the third embodiment. Furthermore, for example, the etching methods according to the embodiments may be performed using a plasma processing apparatus using any plasma source, such as an inductively coupled plasma or microwave plasma, in addition to the capacitively coupled plasma processing apparatus 1.

[0143] In the various embodiments described above, a metal-containing gas, such as the W-containing gas, is included in the process gas (e.g., the first process gas) as a metal supply source. However, the metal supply source may be an upper electrode formed from a metal-containing material and / or an edge ring made from a metal-containing material. That is, the metal-containing material released from the upper electrode and / or the edge ring in the first etching step may form the second protrusion CV2.

[0144] In the etching methods according to the various embodiments described above, the first process gas and the second process gas do not necessarily contain a metal-containing gas such as the W-containing gas described above. In the etching methods according to the various embodiments described above, a metal supply source does not necessarily have to be used.

[0145] In the etching methods according to the various embodiments described above, the film to be etched may be a film other than the silicon-containing film SF.

[0146] Embodiments of the present disclosure further include the following aspects.

[0147] (Supplementary Note 1) An etching method performed in a plasma processing apparatus having a chamber, the etching method comprising: (a) providing a substrate having an underlayer film and a silicon-containing film on the underlayer film into the chamber; (b) etching the silicon-containing film using a first plasma generated from a first process gas containing hydrogen fluoride gas to form a recess, the etching being performed before the underlayer film is exposed in the recess or until at least a portion of the underlayer film is exposed in the recess; and (c) further etching the silicon-containing film in the recess under conditions different from those in the step (b).

[0148] (Supplementary Note 2) The etching method according to Supplementary Note 1, wherein in the step (c), a second plasma is generated using a second process gas different from the first process gas.

[0149] (Supplementary Note 3) The etching method according to Supplementary Note 2, wherein the second plasma has a density of fluorine species that is lower than a density of fluorine species in the first plasma.

[0150] (Supplementary Note 4) The etching method according to Supplementary Note 2 or Supplementary Note 3, wherein the base film contains silicon, and the second process gas contains a fluorocarbon gas or a hydrofluorocarbon gas and an oxygen-containing gas in an amount of 50 volume % or more with respect to a total flow rate of the second process gas excluding a flow rate of an inert gas.

[0151] (Supplementary Note 5) The etching method according to Supplementary Note 4, wherein the number of carbon atoms in the fluorocarbon gas or the hydrofluorocarbon gas contained in the second process gas is 2 or more.

[0152] (Supplementary Note 6) The etching method according to Supplementary Note 2 or Supplementary Note 3, wherein the base film contains a metal, the first process gas further contains a fluorine-containing gas other than hydrogen fluoride, and the second process gas does not contain the fluorine-containing gas or contains the fluorine-containing gas at a partial pressure lower than the partial pressure of the fluorine-containing gas in the first process gas.

[0153] (Supplementary Note 7) The fluorine-containing gas is NF ３ Gas and SF６ 7. The etching method according to claim 6, wherein the gas is at least one of:

[0154] (Supplementary Note 8) The etching method according to Supplementary Note 6 or Supplementary Note 7, wherein the second process gas further contains at least one of CO gas and a chlorine-containing gas.

[0155] (Supplementary Note 9) The etching method according to any one of Supplementary Notes 1 to 8, wherein in the step (c), temperature control is performed so that the temperature of the substrate is higher than the temperature of the substrate in the step (b).

[0156] (Supplementary Note 10) The etching method according to Supplementary Note 9, wherein the temperature control includes one or more of: (I) increasing the power of a source RF signal or a bias signal supplied to the chamber; (II) decreasing the suction force of a substrate support that supports the substrate; (III) decreasing the pressure of a heat transfer gas supplied to a gap between the substrate and the substrate support; and (IV) increasing the set temperature of the substrate support to a temperature higher than the set temperature in step (b).

[0157] (Supplementary Note 11) The etching method according to Supplementary Note 9 or Supplementary Note 10, wherein the temperature control includes controlling the temperature of the substrate to be 30° C. or more higher than the temperature of the substrate in the step (b).

[0158] (Supplementary Note 12) The etching method according to any one of Supplementary Note 1 to Supplementary Note 11, wherein in the step (c), pressure control is performed so that the pressure in the chamber is lower than the pressure in the chamber in the step (b).

[0159] (Supplementary Note 13) The etching method according to Supplementary Note 12, wherein the pressure control includes controlling the pressure in the chamber to be 30% or more lower than the pressure in the chamber in the step (b).

[0160] (Supplementary Note 14) The etching method according to any one of Supplementary Note 1 to Supplementary Note 13, wherein the first process gas further contains a phosphorus-containing gas.

[0161] (Supplementary Note 15) The etching method according to any one of Supplementary Note 1 to Supplementary Note 14, wherein the first process gas contains at least one of a carbon-containing gas and an oxygen-containing gas.

[0162] (Supplementary Note 16) The etching method according to any one of Supplementary Notes 1 to 15, wherein in the step (b), the temperature of a substrate support part that supports the substrate is controlled to 20° C. or less.

[0163] (Supplementary Note 17) The etching method according to any one of Supplementary Note 1 to Supplementary Note 16, wherein the source RF signal supplied to the chamber has a frequency of 40 MHz or more.

[0164] (Supplementary Note 18) An etching method performed in a plasma processing apparatus having a chamber, the etching method comprising: (a) providing a substrate having an underlayer film and a silicon-containing film on the underlayer film into the chamber; (b) etching the silicon-containing film using plasma containing an HF species to form a recess, the etching being performed before the underlayer film is exposed in the recess or until at least a portion of the underlayer film is exposed in the recess; and (c) further etching the silicon-containing film in the recess under conditions different from those in the step (b).

[0165] (Supplementary Note 19) The etching method according to Supplementary Note 18, wherein the HF species are generated from at least one gas selected from the group consisting of hydrogen fluoride gas and hydrofluorocarbon gas.

[0166] (Supplementary Note 20) The etching method according to Supplementary Note 18 or Supplementary Note 19, wherein the HF species are generated from a hydrofluorocarbon gas having two or more carbon atoms.

[0167] (Supplementary Note 21) The etching method according to Supplementary Note 18, wherein the HF species are generated from a mixed gas containing a hydrogen source and a fluorine source.

[0168] (Supplementary Note 22) A plasma processing system comprising: a plasma processing apparatus having a chamber; and a controller, wherein the controller is configured to perform the following controls: (a) providing a substrate having an underlayer film and a silicon-containing film on the underlayer film into the chamber; (b) etching the silicon-containing film using a first plasma generated from a first process gas containing hydrogen fluoride gas to form a recess, the etching being performed before the underlayer film is exposed in the recess or until at least a portion of the underlayer film is exposed in the recess; and (c) further etching the silicon-containing film in the recess under conditions different from the conditions in the control of (b).

[0169] (Supplementary Note 23) A device manufacturing method carried out in a plasma processing apparatus having a chamber, the device manufacturing method comprising: (a) providing a substrate having an underlayer film and a silicon-containing film on the underlayer film into the chamber; (b) etching the silicon-containing film using a first plasma generated from a first process gas containing hydrogen fluoride gas to form a recess, the etching being performed before the underlayer film is exposed in the recess or until at least a portion of the underlayer film is exposed in the recess; and (c) further etching the silicon-containing film in the recess under conditions different from those in the step (b).

[0170] (Supplementary Note 24) A program causing a computer of a plasma processing system including a plasma processing apparatus having a chamber and a control unit to execute the following: (a) control of providing a substrate having an underlayer film and a silicon-containing film on the underlayer film to the chamber; (b) control of etching the silicon-containing film using a first plasma generated from a first process gas including hydrogen fluoride gas to form a recess, the etching being performed before the underlayer film is exposed in the recess or until at least a part of the underlayer film is exposed in the recess; and (c) control of further etching the silicon-containing film in the recess under conditions different from those of the control of (b).

[0171] (Supplementary Note 25) A storage medium storing the program according to Supplementary Note 2.

[0172] (Supplementary Note 26) An etching method performed in a plasma processing apparatus having a chamber, comprising: (a) providing a substrate having a silicon-containing film in the chamber; (b) supplying a process gas containing hydrogen fluoride gas into the chamber and supplying an RF signal having a frequency of 40 MHz or more to the chamber to generate plasma from the process gas; and (c) etching the silicon-containing film using the plasma.

[0173] (Supplementary Note 27) An etching method performed in a plasma processing apparatus having a chamber, the etching method comprising: (a) providing a substrate having a silicon-containing film in the chamber; (b) supplying a processing gas into the chamber and supplying an RF signal having a frequency of 40 MHz or more to the chamber to generate plasma containing HF species from the processing gas; and (c) etching the silicon-containing film using the plasma.

[0174] (Supplementary Note 28) A plasma processing system comprising: a plasma processing apparatus having a chamber; and a controller, wherein the controller is configured to perform the following operations: (a) control of providing a substrate having a silicon-containing film into the chamber; (b) control of supplying a process gas including hydrogen fluoride gas into the chamber, and control of generating plasma from the process gas by supplying an RF signal having a frequency of 40 MHz or more to the chamber; and (c) control of etching the silicon-containing film using the plasma.

[0175] (Supplementary Note 29) A device manufacturing method carried out in a plasma processing apparatus having a chamber, the device manufacturing method comprising: (a) providing a substrate having a silicon-containing film in the chamber; (b) supplying a process gas containing hydrogen fluoride gas into the chamber and supplying an RF signal having a frequency of 40 MHz or more to the chamber to generate plasma from the process gas; and (c) etching the silicon-containing film using the plasma.

[0176] (Supplementary Note 30) A program causing a computer of a plasma processing system including a plasma processing apparatus having a chamber and a control unit to execute the following: (a) control of providing a substrate having a silicon-containing film into the chamber; (b) control of supplying a processing gas including hydrogen fluoride gas into the chamber and supplying an RF signal having a frequency of 40 MHz or more to the chamber to generate plasma from the processing gas; and (c) control of etching the silicon-containing film using the plasma.

[0177] (Supplementary Note 31) A storage medium storing the program according to Supplementary Note 30.

[0178] (Appendix A1) An etching method comprising: (a) providing a substrate having an underlayer, a silicon-containing film on the underlayer, and a mask on the silicon-containing film into a chamber; (b) etching the silicon-containing film using a first plasma generated from a first process gas containing hydrogen fluoride gas and a tungsten-containing gas to form a recess; and (c) after the step (b), further etching the silicon-containing film using a second plasma generated from a second process gas containing hydrogen fluoride gas, wherein the second process gas does not contain the tungsten-containing gas or contains the tungsten-containing gas at a flow rate that is lower than a flow rate of the tungsten-containing gas in the first process gas.

[0179] (Appendix A2) The tungsten-containing gas is WF ６ 10. The etching method of claim 1, comprising:

[0180] (Appendix A3) The etching method according to appendix A1 or A2, wherein the first process gas further contains a phosphorus-containing gas.

[0181] (Appendix A4) The etching method according to appendix A4, wherein the second process gas does not contain a phosphorus-containing gas or contains a phosphorus-containing gas at a flow rate lower than a flow rate of the phosphorus-containing gas in the first process gas.

[0182] (Appendix A5) The etching method according to Appendix A4, wherein the etching of the silicon-containing film in the step (b) is stopped in a state where the silicon-containing film is left between the base film and a bottom of the recess, and the etching of the silicon-containing film in the step (c) is started in the above state and is performed for a period including the time when the base film is exposed.

[0183] (Appendix A6) The etching method according to any one of Appendices A1 to A5, wherein the second process gas further contains xenon gas.

[0184] (Appendix A7) The etching method according to appendix A6, wherein the first process gas does not contain xenon gas or contains xenon gas at a flow rate lower than a flow rate of xenon gas in the second process gas.

[0185] (Appendix A8) The etching method according to Appendix A7, wherein each of the first process gas and the second process gas contains nitrogen trifluoride gas.

[0186] (Appendix A9) The etching method according to A4 or A5, wherein the first process gas contains nitrogen trifluoride gas, the second process gas does not contain nitrogen trifluoride gas or contains nitrogen trifluoride gas at a flow rate lower than a flow rate of the nitrogen trifluoride gas in the first process gas, the second process gas further contains an oxygen-containing gas and a noble gas, and the first process gas does not contain a noble gas or contains a noble gas at a flow rate lower than a flow rate of the noble gas in the second process gas.

[0187] (Appendix A10) The etching method according to any one of Appendices A1 to A9, wherein the step (b) is performed before the base film is exposed in the recess or until at least a part of the base film is exposed in the recess.

[0188] (Appendix A11) The etching method according to any one of Appendices A1 to A9, wherein the step (b) is performed until a part of the base film is etched.

[0189] (Appendix A12) The etching method according to any one of Appendices A1 to A9, wherein a cycle including the step (b) and the step (c) is performed a plurality of times.

[0190] (Appendix A13) The etching method according to any one of Appendices A1 to A12, wherein the step (b) etches the silicon-containing film while forming a first convex portion at a first position of the mask, the first convex portion reducing a width of the opening of the mask, and forming a second convex portion at a second position of the mask that is lower than the first position, the second convex portion reducing a width of the opening of the mask.

[0191] (Appendix A14) The etching method according to Appendix A13, wherein the first processing gas further contains a carbon-containing gas that is a source of the first convex portion, the tungsten-containing gas in the first processing gas is a source of the second convex portion, and in the step (b), an amount of hydrogen species and an amount of fluorine species in the first plasma are adjusted so as to form the second convex portion below the first convex portion.

[0192] (Appendix A15) The etching method according to any one of Appendices A1 to A14, wherein in the step (b), an inversely tapered recess is formed in the silicon-containing film, and in the step (c), the shape of the recess is made rectangular.

[0193] (Appendix A16) An etching method comprising: (a) providing a substrate having an underlayer film, a silicon-containing film on the underlayer film, and a mask on the silicon-containing film into a chamber; (b) etching the silicon-containing film using a first plasma generated from a first process gas to form a recess; and (c) after the step (b), further etching the silicon-containing film using a second plasma generated from a second process gas, wherein the first process gas comprises a single gas or a mixed gas containing fluorine and hydrogen, and a metal-containing gas; the second process gas comprises a single gas or a mixed gas containing fluorine and hydrogen; and the second process gas does not contain the metal-containing gas or contains the metal-containing gas at a flow rate lower than a flow rate of the metal-containing gas in the first process gas.

[0194] (Appendix A17) The etching method according to Appendix A16, wherein the metal-containing gas contains at least one metal selected from the group consisting of tungsten, molybdenum, titanium, and ruthenium.

[0195] (Appendix A18) The etching method according to appendix A16 or A17, wherein the first process gas further contains a phosphorus-containing gas.

[0196] (Appendix A19) The etching method according to appendix A18, wherein the second process gas does not contain a phosphorus-containing gas or contains a phosphorus-containing gas at a flow rate lower than a flow rate of the phosphorus-containing gas in the first process gas.

[0197] (Appendix A20) The etching method according to Appendix A19, wherein the etching of the silicon-containing film in the step (b) is stopped in a state where the silicon-containing film is left between the base film and a bottom of the recess, and the etching of the silicon-containing film in the step (c) is started in the above state and is performed for a period including the time when the base film is exposed.

[0198] (Appendix A21) The etching method according to any one of Appendices A16 to A20, wherein the second process gas further contains a noble gas.

[0199] (Additional Note A22) The etching method according to Additional Note A21, wherein the first process gas does not contain the noble gas or contains the noble gas at a flow rate lower than a flow rate of the noble gas in the second process gas.

[0200] (Appendix A23) The etching method according to appendix A21 or A22, wherein the noble gas includes at least one gas selected from the group consisting of argon gas, krypton gas, xenon gas, and radon gas.

[0201] (Appendix A24) The etching method according to appendix A22 or A23, wherein each of the first process gas and the second process gas contains nitrogen trifluoride gas.

[0202] (Appendix A25) The etching method according to Appendix A19 or A20, wherein the first process gas contains nitrogen trifluoride gas, the second process gas does not contain nitrogen trifluoride gas or contains nitrogen trifluoride gas at a flow rate lower than a flow rate of the nitrogen trifluoride gas in the first process gas, the second process gas further contains an oxygen-containing gas and a noble gas, and the first process gas does not contain a noble gas or contains a noble gas at a flow rate lower than a flow rate of the noble gas in the second process gas.

[0203] (Appendix A26) The etching method according to any one of Appendices A16 to A25, wherein the step (b) etches the silicon-containing film while forming a first convex portion at a first position of the mask, the first convex portion reducing a width of the opening of the mask, and forming a second convex portion at a second position of the mask that is lower than the first position, the second convex portion reducing a width of the opening of the mask.

[0204] (Appendix A27) The etching method according to Appendix A26, wherein the first processing gas further contains a carbon-containing gas that is a source of the first convex portion, the metal-containing gas in the first processing gas is a source of the second convex portion, and in (b), an amount of hydrogen species and an amount of fluorine species in the first plasma are adjusted so as to form the second convex portion below the first convex portion.

[0205] (Appendix A28) An etching apparatus comprising: a chamber; a substrate support within the chamber; a plasma generation unit; and a controller configured to control the plasma generation unit, wherein the controller is configured to perform a process comprising: (a) providing, into the chamber, a substrate having an underlayer, a silicon-containing film on the underlayer, and a mask on the silicon-containing film; (b) etching the silicon-containing film using a first plasma generated from a first process gas containing hydrogen fluoride gas and a tungsten-containing gas to form a recess; and (c) after the process (b), further etching the silicon-containing film using a second plasma generated from a second process gas containing hydrogen fluoride gas, wherein the second process gas does not contain the tungsten-containing gas or contains the tungsten-containing gas at a flow rate lower than a flow rate of the tungsten-containing gas in the first process gas.

[0206] (Appendix A29) The tungsten-containing gas is WF ６ 10. The etching apparatus of claim A28, comprising:

[0207] (Appendix A30) The etching apparatus according to appendix A28 or A29, wherein the first process gas further contains a phosphorus-containing gas.

[0208] (Appendix A31) The etching apparatus according to appendix A30, wherein the second process gas does not contain a phosphorus-containing gas or contains a phosphorus-containing gas at a flow rate lower than a flow rate of the phosphorus-containing gas in the first process gas.

[0209] (Appendix A32) The etching apparatus according to claim A31, wherein the control unit is configured to: stop the etching of the silicon-containing film in (b) in a state where the silicon-containing film remains between the base film and the bottom of the recess; and start the etching of the silicon-containing film in (c) in the state, for a period including the time when the base film is exposed.

[0210] (Appendix A33) The etching apparatus according to any one of Appendices A28 to A32, wherein the second process gas further contains xenon gas.

[0211] (Appendix A34) The etching apparatus according to appendix A33, wherein the first process gas does not contain xenon gas or contains xenon gas at a flow rate lower than a flow rate of the xenon gas in the second process gas.

[0212] (Appendix A35) The etching apparatus according to Appendix A34, wherein each of the first process gas and the second process gas contains nitrogen trifluoride gas.

[0213] (Appendix A36) The etching apparatus according to Appendix A31 or A32, wherein the first process gas contains nitrogen trifluoride gas, the second process gas does not contain nitrogen trifluoride gas or contains nitrogen trifluoride gas at a flow rate lower than a flow rate of the nitrogen trifluoride gas in the first process gas, the second process gas further contains an oxygen-containing gas and a noble gas, and the first process gas does not contain a noble gas or contains a noble gas at a flow rate lower than a flow rate of the noble gas in the second process gas.

[0214] (Appendix A37) The etching apparatus according to any one of Appendices A28 to A36, wherein the first process gas further contains a carbon-containing gas that is a source for forming a first convex portion at a first position of the mask, the first convex portion reducing the width of the opening of the mask; the tungsten-containing gas in the first process gas is a source for forming a second convex portion at a second position of the mask that is lower than the first position, the second convex portion reducing the width of the opening of the mask; and the control unit is configured to adjust an amount of hydrogen species and an amount of fluorine species in the first plasma in order to form the second convex portion below the first convex portion in (b).

[0215] (Appendix A38) The etching apparatus according to any one of Appendices A28 to A37, further comprising: a gas supply unit configured to supply the first process gas and the second process gas into the chamber; and the control unit configured to further control the gas supply unit.

[0216] (Appendix A39) An etching apparatus comprising: a chamber; a substrate support unit within the chamber; a plasma generation unit; and a control unit configured to control the plasma generation unit, wherein the control unit is configured to perform a process comprising: (a) providing, into the chamber, a substrate having a film to be etched and a mask on the film to be etched; and (b) etching the film to be etched using plasma generated from a process gas containing hydrogen fluoride gas to form a recess, and to perform (b) in a state where a metal supply source is present within the chamber, thereby etching the film to be etched while forming a first protrusion at a first position of the mask that reduces a width of an opening in the mask, and forming a second protrusion at a second position of the mask that is lower than the first position and reduces a width of the opening in the mask.

[0217] (Appendix A40) The etching apparatus according to Appendix A39, wherein the process gas further contains a metal-containing gas, and the metal supply source is the metal-containing gas.

[0218] (Appendix A41) An etching apparatus according to Appendix A39, wherein the metal supply source is formed from a metal-containing material and is an upper electrode arranged above the substrate support portion so as to face the substrate support portion and / or an edge ring made of a metal-containing material arranged around the substrate supported by the substrate support portion.

[0219] Some experimental examples will be described below.

[0220] (First and second experimental examples)

[0221] In the first and second experimental examples, etching of a silicon-containing film on a sample substrate was performed using the plasma processing apparatus 1. The sample substrate had a multilayer film as a silicon-containing film on an underlayer, and a mask formed of amorphous carbon on the multilayer film. The multilayer film included a plurality of silicon oxide films and a plurality of silicon nitride films alternately stacked. The etching in the first and second experimental examples included a first etching step and a second etching step following the first etching step. In the first experimental example, HF gas, PF 4, and PF 5 were used as the first processing gas in the first etching step. ３ A mixed gas containing NF 3 gas and a halogen-containing gas was used. ３ Gas, Cl ２ In the first experimental example, the second process gas in the second etching step included PF 5 gas and HBr gas. ３ In the second experimental example, the same mixed gas as the first process gas in the first experimental example was used as the first process gas in the first etching step and the second process gas in the second etching step. In the first and second experimental examples, the first etching step was stopped in a state where the silicon-containing film remained between the base film and the bottom of the recess, and the second etching step was started in this state.

[0222] In the first and second experimental examples, the maximum width (i.e., bowing CD) and the width at the bottom of the recess (i.e., bottom CD) of the recess formed in the silicon-containing film were determined. The difference between the bowing CD and the bottom CD, i.e., the CD bias, was then determined. The bowing CD of the first experimental example was substantially equal to the bowing CD of the second experimental example, and the bottom CD of the first experimental example was approximately 11 nm larger than the bottom CD of the second experimental example. Furthermore, the CD bias of the second experimental example was 47.6 nm, while the CD bias of the first experimental example was 35.2 nm. These results confirmed that by reducing the flow rate of the phosphorus-containing gas in the second process gas from the flow rate of the phosphorus-containing gas in the first process gas or setting it to zero, it is possible to increase the bottom CD and reduce the CD bias, i.e., to rectangularize the vertical cross-sectional shape of the recess.

[0223] (Third to fifth experimental examples)

[0224] In the third to fifth experimental examples, etching of a silicon-containing film on the same sample substrate as in the first experimental example was performed using the plasma processing apparatus 1. The etching in the third to fifth experimental examples included a first etching step and a second etching step following the first etching step. In the third and fourth experimental examples, HF gas, WF ６ Gas, PF ３ A mixed gas containing NF 3 gas, a halogen-containing gas, and a carbon-containing gas was used. ３ Gas, Cl ２ In the third experimental example, the second etching step included WF as the second process gas. ６ Gas and PF ３ In the fourth experimental example, the second etching step included a mixed gas containing WF as the second process gas, which was the same as the first process gas in the third experimental example, except that the mixed gas did not contain WF. ６ Gas and PF ３In the fifth experimental example, the same mixed gas as the first process gas in the fourth experimental example was used except that the mixed gas did not contain WF gas and further contained xenon gas. ６ The same mixed gas as the first process gas in the third experimental example was used except that it did not contain any silicon-containing film. In the fifth experimental example, the same mixed gas as the second process gas in the third experimental example was used as the second process gas in the second etching step. In the third to fifth experimental examples, the first etching step was stopped in a state where the silicon-containing film remained between the base film and the bottom of the recess, and the second etching step was started in this state.

[0225] In the third to fifth experimental examples, the maximum width of the recess formed in the silicon-containing film (i.e., bowing CD) and the width at the bottom of the recess (i.e., bottom CD) were determined. Then, the difference between the bowing CD and the bottom CD, i.e., the CD bias, was determined. The bowing CDs of the third and fourth experimental examples were approximately 7 nm smaller than the bowing CD of the fifth experimental example. From these results, it was found that WF ６ It was confirmed that bowing can be suppressed by using a first process gas containing a metal-containing gas such as xenon gas. Furthermore, the bottom CD in the third experimental example was approximately equal to that in the fifth experimental example, but the bottom CD in the fourth experimental example was approximately 5 nm larger than that in the fifth experimental example. This confirmed that a relatively large bottom CD can be obtained by using a second process gas containing a first noble gas such as xenon gas. Furthermore, the CD bias in the fifth experimental example was 37.6 nm, while the bottom CD in the third experimental example was 33.7 nm and the bottom CD in the fourth experimental example was 25.9 nm. These results suggest that WF ６ It has been confirmed that the use of a first process gas containing a metal-containing gas such as xenon gas can suppress the bowing CD and make the cross-sectional shape of the recessed portion rectangular. It has also been confirmed that the use of a second process gas containing a first noble gas such as xenon gas can increase the bottom CD and make the cross-sectional shape of the recessed portion more rectangular.

[0226] (Sixth and Seventh Experimental Examples)

[0227] In the sixth and seventh experimental examples, etching of a silicon-containing film on the same sample substrate as in the first experimental example was performed using the plasma processing apparatus 1. The etching in the sixth and seventh experimental examples included a first etching step and a second etching step following the first etching step. In the sixth and seventh experimental examples, HF gas, PF ３ A mixed gas containing NF 3 gas, a halogen-containing gas, and a carbon-containing gas was used. ３ Gas, Cl ２ The carbon-containing gas included a fluorocarbon gas. In the sixth and seventh experimental examples, a mixed gas containing all the same gases as in the first process gas in each experimental example and a noble gas was used as the second process gas in the second etching step. In the sixth experimental example, the noble gas was xenon gas, and in the seventh experimental example, the noble gas was argon gas. In the sixth and seventh experimental examples, the first etching step was stopped in a state where the silicon-containing film remained between the base film and the bottom of the recess, and the second etching step was started in this state.

[0228] In the sixth and seventh experimental examples, the maximum width of the recess formed in the silicon-containing film (i.e., bowing CD) and the width at the bottom of the recess (i.e., bottom CD) were determined. The difference between the bowing CD and the bottom CD, i.e., the CD bias, was then determined. The bowing CDs in the sixth and seventh experimental examples were approximately equal. The bottom CD in the sixth experimental example was 29 nm larger than the bottom CD in the seventh experimental example. The CD bias in the seventh experimental example was 67 nm, while the CD bias in the sixth experimental example was 30 nm. These results confirmed that the use of a first noble gas such as xenon gas in the second etching step can increase the bottom CD and further rectangularize the cross-sectional shape of the recess.

[0229] (Experimental Examples 8 to 10)

[0230] In the eighth to tenth experimental examples, etching of a silicon-containing film on the same sample substrate as in the first experimental example was performed using the plasma processing apparatus 1. The etching in the eighth to tenth experimental examples included a first etching step and a second etching step following the first etching step. In the eighth to tenth experimental examples, HF gas, WF ６ Gas, PF ３ A mixed gas containing NF 3 gas, a halogen-containing gas, and a carbon-containing gas was used. ３ Gas, Cl ２ In the eighth experimental example, the second etching step included a WF 2 gas as the second process gas, and a HBr gas as the carbon-containing gas. ６ Gas and PF ３ In the ninth experimental example, the same mixed gas as the first process gas in the eighth experimental example was used except that the second process gas in the second etching step did not contain NF 3 gas and further contained xenon gas. ３ Instead of gas ２ In the tenth experimental example, the same mixed gas as the second process gas in the eighth experimental example was used except that the second process gas in the second etching step contained argon gas instead of xenon gas.

[0231] In the eighth to tenth experimental examples, the maximum width of the recess formed in the silicon-containing film (i.e., bowing CD) and the width at the bottom of the recess (i.e., bottom CD) were determined. Then, the difference between the bowing CD and the bottom CD, i.e., the CD bias, was determined. In the ninth experimental example, the bottom CD was 0.7 nm smaller than the bottom CD of the eighth experimental example, but the bowing CD was 2.3 nm smaller than the bowing CD of the eighth experimental example. Therefore, in the ninth experimental example, the CD bias was 1.6 nm smaller than the CD bias of the eighth experimental example. From these results, it can be seen that the NF ３ Instead of gas ２It was confirmed that bowing can be suppressed by using an oxygen-containing gas such as NF gas, and the cross-sectional shape of the recess can be made more rectangular. In addition, in the tenth experimental example, the bottom CD was enlarged compared to the bottom CD of the ninth experimental example, and as a result, the CD bias was 2.3 nm smaller than the CD bias of the ninth experimental example. From these results, it can be seen that the use of an oxygen-containing gas such as NF gas in the second etching step ３ Alternative to gas ２ It has been confirmed that by using a second noble gas, such as argon gas, as a noble gas used in combination with the gas, it is possible to increase the bottom CD and make the profile of the recess more rectangular in vertical cross section.

[0232] From the foregoing, it will be understood that various embodiments of the present disclosure have been described herein for purposes of illustration, and that various modifications may be made without departing from the scope and spirit of the present disclosure. Accordingly, the various embodiments disclosed herein are not intended to be limiting, with the true scope and spirit being indicated by the appended claims.

[0233] 1...plasma processing apparatus, 2...controller, 10...plasma processing chamber, 10s...plasma processing space, 11...substrate support, 13...shower head, 20...gas supply unit, 31a...first RF generator, 31b...second RF generator, 32a...first DC generator, SF...silicon-containing film, MF...mask, OP...opening, RC...recess, UF...undercoat film, W...substrate.

Claims

1. An etching method comprising: (a) providing a substrate having an underlayer, a silicon-containing film on the underlayer, and a mask on the silicon-containing film in a chamber; (b) etching the silicon-containing film with a first plasma generated from a first process gas containing hydrogen fluoride gas and a tungsten-containing gas to form a recess; and (c) after (b), further etching the silicon-containing film with a second plasma generated from a second process gas containing hydrogen fluoride gas, wherein the second process gas does not contain a tungsten-containing gas or contains a tungsten-containing gas at a flow rate less than a flow rate of the tungsten-containing gas in the first process gas.

2. The tungsten-containing gas is WF ６ The etching method of claim 1 , comprising:

3. The etching method according to claim 1 or 2, wherein the first process gas further contains a phosphorus-containing gas.

4. The etching method according to claim 3, wherein the second process gas does not contain a phosphorus-containing gas or contains a phosphorus-containing gas at a flow rate lower than a flow rate of the phosphorus-containing gas in the first process gas.

5. The etching method according to claim 4, wherein the etching of the silicon-containing film in (b) is stopped in a state where the silicon-containing film is left between the base film and a bottom of the recess, and the etching of the silicon-containing film in (c) is started in the state and is performed for a period including the time when the base film is exposed.

6. The etching method according to claim 1 or 2, wherein the second process gas further contains xenon gas.

7. The etching method according to claim 6, wherein the first process gas does not contain xenon gas or contains xenon gas at a flow rate less than a flow rate of the xenon gas in the second process gas.

8. The etching method of claim 7, wherein each of the first process gas and the second process gas comprises nitrogen trifluoride gas.

9. The etching method according to claim 4, wherein the first process gas contains nitrogen trifluoride gas; the second process gas does not contain nitrogen trifluoride gas or contains nitrogen trifluoride gas at a flow rate lower than a flow rate of the nitrogen trifluoride gas in the first process gas; the second process gas further contains an oxygen-containing gas and a noble gas; and the first process gas does not contain a noble gas or contains a noble gas at a flow rate lower than a flow rate of the noble gas in the second process gas.

10. The etching method according to claim 1, wherein (b) is performed before the base film is exposed in the recess or until at least a portion of the base film is exposed in the recess.

11. The etching method according to claim 1, wherein the step (b) is carried out until a portion of the base film is etched.

12. The etching method of claim 1, wherein a cycle including (b) and (c) is performed a plurality of times.

13. The etching method according to claim 1, wherein (b) etches the silicon-containing film while forming a first convex portion at a first position of the mask, the first convex portion reducing a width of the opening of the mask, and forming a second convex portion at a second position of the mask lower than the first position, the second convex portion reducing a width of the opening of the mask.

14. The etching method according to claim 13, wherein the first processing gas further contains a carbon-containing gas which is a source of the first convex portion, the tungsten-containing gas in the first processing gas is a source of the second convex portion, and in (b), an amount of hydrogen species and an amount of fluorine species in the first plasma are adjusted so as to form the second convex portion below the first convex portion.

15. The etching method according to claim 1, further comprising the steps of: forming an inversely tapered recess in the silicon-containing film in (b); and forming the recess into a rectangular shape in (c).

16. An etching method comprising: (a) providing a substrate having an underlayer, a silicon-containing film on the underlayer, and a mask on the silicon-containing film in a chamber; (b) etching the silicon-containing film with a first plasma generated from a first process gas to form a recess; and (c) after (b), further etching the silicon-containing film with a second plasma generated from a second process gas, wherein the first process gas comprises a single gas or a mixed gas containing fluorine and hydrogen, and a metal-containing gas, the second process gas comprises a single gas or a mixed gas containing fluorine and hydrogen, and the second process gas does not contain the metal-containing gas or contains the metal-containing gas at a flow rate less than a flow rate of the metal-containing gas in the first process gas.

17. The etching method of claim 16, wherein the metal-containing gas contains at least one metal selected from the group consisting of tungsten, molybdenum, titanium, and ruthenium.

18. The etching method according to claim 16 or 17, wherein the first process gas further comprises a phosphorus-containing gas.

19. The etching method of claim 18, wherein the second process gas does not contain a phosphorus-containing gas or contains a phosphorus-containing gas at a flow rate less than a flow rate of the phosphorus-containing gas in the first process gas.

20. The etching method according to claim 19, wherein the etching of the silicon-containing film in (b) is stopped in a state where the silicon-containing film is left between the base film and a bottom of the recess, and the etching of the silicon-containing film in (c) is started in the state and is performed for a period including the time when the base film is exposed.

21. The etching method of claim 16, wherein the second process gas further comprises a noble gas.

22. The etching method of claim 21, wherein the first process gas does not include the noble gas or includes the noble gas at a flow rate that is less than a flow rate of the noble gas in the second process gas.

23. The etching method according to claim 21 or 22, wherein the noble gas includes at least one gas selected from the group consisting of argon gas, krypton gas, xenon gas, and radon gas.

24. The etching method of claim 22, wherein the first process gas and the second process gas each comprise nitrogen trifluoride gas.

25. The etching method according to claim 19, wherein the first process gas contains nitrogen trifluoride gas; the second process gas does not contain nitrogen trifluoride gas or contains nitrogen trifluoride gas at a flow rate lower than a flow rate of the nitrogen trifluoride gas in the first process gas; the second process gas further contains an oxygen-containing gas and a noble gas; and the first process gas does not contain a noble gas or contains a noble gas at a flow rate lower than a flow rate of the noble gas in the second process gas.

26. The etching method according to claim 16, wherein (b) etches the silicon-containing film while forming a first convex portion at a first position of the mask, the first convex portion reducing a width of the opening of the mask, and forming a second convex portion at a second position of the mask lower than the first position, the second convex portion reducing a width of the opening of the mask.

27. The etching method according to claim 26, wherein the first process gas further contains a carbon-containing gas which is a source of the first convex portion, the metal-containing gas in the first process gas is a source of the second convex portion, and in (b), an amount of hydrogen species and an amount of fluorine species in the first plasma are adjusted so as to form the second convex portion below the first convex portion.

28. An etching apparatus comprising: a chamber; a substrate support within the chamber; a plasma generating unit; and a controller configured to control the plasma generating unit, wherein the controller is configured to perform a process comprising: (a) providing, into the chamber, a substrate having an undercoat film, a silicon-containing film on the undercoat film, and a mask on the silicon-containing film; (b) etching the silicon-containing film using a first plasma generated from a first process gas containing hydrogen fluoride gas and a tungsten-containing gas to form a recess; and (c) after (b), further etching the silicon-containing film using a second plasma generated from a second process gas containing hydrogen fluoride gas, wherein the second process gas does not contain the tungsten-containing gas or contains the tungsten-containing gas at a flow rate lower than a flow rate of the tungsten-containing gas in the first process gas.

29. The tungsten-containing gas is WF ６ 29. The etching apparatus of claim 28, comprising:

30. The etching apparatus of claim 28 or 29, wherein the first process gas further comprises a phosphorus-containing gas.

31. The etching apparatus of claim 30, wherein the second process gas does not contain a phosphorus-containing gas or contains a phosphorus-containing gas at a flow rate less than a flow rate of the phosphorus-containing gas in the first process gas.

32. The etching apparatus according to claim 31, wherein the control unit is configured to: stop the etching of the silicon-containing film in (b) in a state in which the silicon-containing film is left between the base film and a bottom of the recess; and start the etching of the silicon-containing film in (c) in the state, for a period including the time when the base film is exposed.

33. The etching apparatus of claim 28 or 29, wherein the second process gas further comprises xenon gas.

34. The etching apparatus of claim 33, wherein the first process gas does not contain xenon gas or contains xenon gas at a flow rate less than a flow rate of the xenon gas in the second process gas.

35. The etching apparatus of claim 34, wherein the first process gas and the second process gas each comprise nitrogen trifluoride gas.

36. The etching apparatus of claim 31, wherein the first process gas contains nitrogen trifluoride gas; the second process gas does not contain nitrogen trifluoride gas or contains nitrogen trifluoride gas at a flow rate lower than a flow rate of the nitrogen trifluoride gas in the first process gas; the second process gas further contains an oxygen-containing gas and a noble gas; and the first process gas does not contain a noble gas or contains a noble gas at a flow rate lower than a flow rate of the noble gas in the second process gas.

37. The etching apparatus of claim 28, wherein the first process gas further contains a carbon-containing gas that is a source for forming a first protrusion at a first position of the mask that reduces a width of the opening of the mask, the tungsten-containing gas in the first process gas is a source for forming a second protrusion at a second position of the mask lower than the first position that reduces a width of the opening of the mask, and the control unit is configured to adjust an amount of hydrogen species and an amount of fluorine species in the first plasma in (b) to form the second protrusion below the first protrusion.

38. The etching apparatus of claim 28, further comprising a gas supply configured to supply the first process gas and the second process gas into the chamber, and the controller configured to further control the gas supply.

39. An etching apparatus comprising: a chamber; a substrate support within the chamber; a plasma generating unit; and a control unit configured to control the plasma generating unit, wherein the control unit is configured to perform a process comprising: (a) providing, into the chamber, a substrate having a film to be etched and a mask on the film to be etched; and (b) etching the film to be etched using plasma generated from a process gas containing hydrogen fluoride gas to form a recess, and to perform (b) in a state in which a metal supply source is present within the chamber, so as to etch the film to be etched while forming, at a first position of the mask, a first protrusion that reduces a width of an opening in the mask, and forming, at a second position of the mask lower than the first position, a second protrusion that reduces the width of the opening in the mask.

40. The etching apparatus of claim 39, wherein the process gas further comprises a metal-bearing gas, and the metal source is the metal-bearing gas.

41. The etching apparatus of claim 39, wherein the metal supply source is formed from a metal-containing material and is an upper electrode disposed above the substrate support so as to face the substrate support, and / or an edge ring made of a metal-containing material disposed around the periphery of the substrate supported by the substrate support.