Etching method and plasma processing apparatus

Abstract

To provide an etching method and a plasma processing apparatus that are capable of increasing the etching selection ratio.SOLUTION: An etching method includes the steps of: preparing a substrate, which includes a first region containing silicon and nitrogen and a second region containing silicon and oxygen; and etching the second region while forming a tungsten-containing protective layer on the first region, by exposing the first and second regions to plasma generated from a processing gas containing carbon, fluorine, and tungsten.SELECTED DRAWING: Figure 3

Description

[Technical field]

[0001] Exemplary embodiments of the present disclosure relate to an etching method and a plasma processing apparatus. [Background technology]

[0002] Patent Document 1 discloses a method for selectively etching a first region made of silicon oxide relative to a second region made of silicon nitride by plasma processing of a substrate. The second region has a recess. The first region is provided so as to fill the recess and cover the second region. The first region is etched by plasma generated from a processing gas containing fluorocarbon. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2016-157793 A Summary of the Invention [Problem to be solved by the invention]

[0004] The present disclosure provides an etching method and a plasma processing apparatus capable of improving an etching selectivity ratio. [Means for solving the problem]

[0005] In one exemplary embodiment, an etching method includes providing a substrate, the substrate including a first region including silicon and nitrogen and a second region including silicon and oxygen, and etching the second region while forming a tungsten-containing protective layer on the first region by exposing the first region and the second region to a plasma generated from a process gas including carbon, fluorine, and tungsten. Effect of the Invention

[0006] According to one exemplary embodiment, an etching method and a plasma processing apparatus capable of improving an etching selectivity are provided. [Brief description of the drawings]

[0007] [Figure 1] FIG. 1 is a schematic diagram of a plasma processing apparatus according to an exemplary embodiment. [Diagram 2] FIG. 2 is a schematic diagram of a plasma processing apparatus according to an exemplary embodiment. [Diagram 3] FIG. 3 is a flow chart of an etching method according to one exemplary embodiment. [Figure 4] FIG. 4 is an enlarged cross-sectional view of a portion of an example substrate to which the method of FIG. 3 can be applied. [Diagram 5] FIG. 5 is a cross-sectional view illustrating a step of an etching method according to an example embodiment. [Figure 6] FIG. 6 is a partial enlarged cross-sectional view of an example substrate obtained by performing an etching method according to an example embodiment. [Figure 7] FIG. 7 is an example of a timing chart showing the change over time of the RF power applied to the electrode in the main body and the RF power applied to the counter electrode. [Figure 8] FIG. 8 is an enlarged cross-sectional view of a portion of an example substrate to which the method of FIG. 3 can be applied. [Figure 9] FIG. 9 is a partial enlarged cross-sectional view of an example substrate obtained by performing an etching method according to an example embodiment. [Figure 10] FIG. 10 is a diagram showing an example of an etching step. [Figure 11] FIG. 11 shows TEM images of cross sections of the substrate obtained by carrying out the etching methods in the first and second experiments. [Figure 12] FIG. 12 is a diagram showing an example of a cross section of a substrate obtained by carrying out the etching methods in the third and fourth experiments. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0008] Various exemplary embodiments are described below.

[0009] In one exemplary embodiment, an etching method includes providing a substrate, the substrate including a first region including silicon and nitrogen and a second region including silicon and oxygen, and etching the second region while forming a tungsten-containing protective layer on the first region by exposing the first region and the second region to a plasma generated from a process gas including carbon, fluorine, and tungsten.

[0010] According to the above etching method, the etching selectivity of the second region to the first region can be improved. Also, according to the above etching method, a tungsten-containing protective layer is formed on the first region, so that the shoulder portion of the first region in particular can be protected. As a result, the shoulder portion is less likely to be inclined, so that the area of ​​the flat portion on the upper surface of the first region can be secured to be large.

[0011] In the etching step, the tungsten-containing protective layer may remain on the first region after the second region is removed.

[0012] The process gas may include a carbon and fluorine containing gas and a tungsten containing gas.

[0013] The tungsten-containing gas may include tungsten hexafluoride gas.

[0014] The carbon and fluorine containing gas may include a fluorocarbon gas.

[0015] The process gas may contain oxygen, which makes it difficult for a carbon-containing film to be formed on the first region.

[0016] The first region may have a recess, and the second region may be embedded in the recess. In this case, the recess can be formed by etching the second region.

[0017] The etching step may be performed in a self-aligned contact process.

[0018] In the etching step, a high frequency power and a bias power are supplied to a plasma processing apparatus to generate the plasma, and the etching step may include the steps of: (a) setting the high frequency power to a first power and the bias power to a second power to preferentially deposit a tungsten-containing deposit on the first region; (b) setting the high frequency power to a third power lower than the first power and the bias power to the second power, a transition step; and (c) setting the high frequency power to the third power and the bias power to a fourth power higher than the second power to etch the second region.

[0019] The cycle including the steps (a) to (c) may be repeated two or more times.

[0020] In one exemplary embodiment, an etching method includes providing a substrate including a silicon nitride having an exposed top surface and a silicon oxide having an exposed top surface; forming a tungsten nitride-containing protective layer on the silicon nitride by exposing the silicon oxide and the silicon nitride to a plasma generated from a process gas including tungsten hexafluoride gas; and preferentially etching the silicon oxide relative to the silicon nitride by exposing the silicon oxide and the silicon nitride to a plasma generated from a process gas including tungsten hexafluoride gas.

[0021] The process gas may include a fluorocarbon gas.

[0022] In one exemplary embodiment, a plasma processing apparatus includes a chamber, a substrate support for supporting a substrate in the chamber, the substrate including a first region including silicon and nitrogen and a second region including silicon and oxygen, a gas supply configured to supply a process gas including carbon, fluorine and tungsten into the chamber, a plasma generation unit configured to generate a plasma from the process gas in the chamber, and a controller, the controller configured to control the gas supply and the plasma generation unit such that the second region is etched while forming a tungsten-containing protective layer on the first region by exposing the first region and the second region to the plasma.

[0023] Various exemplary embodiments will now be described in detail with reference to the drawings, in which the same or corresponding parts are designated by the same reference numerals.

[0024] 1 and 2 are diagrams that illustrate a plasma processing apparatus according to an exemplary embodiment.

[0025] In one embodiment, the plasma processing system includes a plasma processing device 1 and a control unit 2. The plasma processing device 1 includes a plasma processing chamber 10, a substrate support unit 11, and a plasma generation unit 12. The plasma processing chamber 10 has a plasma processing space. The plasma processing chamber 10 also has at least one gas supply port for supplying at least one processing gas to the plasma processing space, and at least one gas exhaust port for exhausting gas from the plasma processing space. The gas supply port is connected to a gas supply unit 20, which will be described later, and the gas exhaust port is connected to an exhaust system 40, which will be described later. The substrate support unit 11 is disposed in the plasma processing space, and has a substrate support surface for supporting a substrate.

[0026] The plasma generating unit 12 is configured to generate plasma from at least one processing gas supplied into the plasma processing space. The plasma formed in the plasma processing space may be a capacitively coupled plasma (CCP), an inductively coupled plasma (ICP), an electron-cyclotron-resonance plasma (ECR plasma), a helicon wave plasma (HWP), a surface wave plasma (SWP), or the like. Also, various types of plasma generating units may be used, including an alternating current (AC) plasma generating unit and a direct current (DC) plasma generating unit. In one embodiment, the AC signal (AC power) used in the AC plasma generating unit has a frequency in the range of 100 kHz to 10 GHz. Thus, the AC signal includes a radio frequency (RF) signal and a microwave signal. In one embodiment, the RF signal has a frequency in the range of 200 kHz to 150 MHz.

[0027] The control unit 2 processes computer-executable instructions that cause the plasma processing apparatus 1 to perform various steps described in the present disclosure. The control unit 2 may be configured to control each element of the plasma processing apparatus 1 to perform various steps described herein. In one embodiment, a part or all of the control unit 2 may be included in the plasma processing apparatus 1. The control unit 2 may include, for example, a computer 2a. The computer 2a may include, for example, a processing unit (CPU: Central Processing Unit) 2a1, a storage unit 2a2, and a communication interface 2a3. The processing unit 2a1 may be configured to perform various control operations based on a program stored in the storage unit 2a2. 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).

[0028] An example of the configuration of a plasma processing system will be described below. 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 processing gas into the plasma processing chamber 10. The gas inlet includes a showerhead 13. The substrate support 11 is disposed in 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 part of a 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. The sidewall 10a is grounded. The showerhead 13 and the substrate support 11 are electrically isolated from the plasma processing chamber 10 housing.

[0029] The substrate support 11 includes a main body 111 and a ring assembly 112. The main body 111 has a central region (substrate support surface) 111a for supporting a substrate (wafer) W, and an annular region (ring support surface) 111b for supporting the ring assembly 112. 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. In one embodiment, the main body 111 includes a base and an electrostatic chuck. The main body 111 includes a conductive member. The conductive member of the main body 111 functions as an electrode. The electrostatic chuck is disposed on the base. The upper surface of the electrostatic chuck has a substrate support surface 111a. The ring assembly 112 includes one or more annular members. At least one of the one or more annular members is an edge ring. Although not shown, the substrate support 11 may include a temperature adjustment module configured to adjust at least one of the electrostatic chuck, 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 path, or a combination thereof. A heat transfer fluid such as brine or gas flows through the flow path. The substrate support 11 may also include a heat transfer gas supply unit configured to supply a heat transfer gas between the back surface of the substrate W and the substrate support surface 111a.

[0030] The shower head 13 is configured to introduce at least one processing gas from the gas supply unit 20 into the plasma processing space 10s. The shower head 13 has at least one gas supply port 13a, at least one gas diffusion chamber 13b, and multiple gas inlets 13c. The processing gas supplied to the gas supply port 13a passes through the gas diffusion chamber 13b and is introduced into the plasma processing space 10s from the multiple gas inlets 13c. The shower head 13 also includes a conductive member. The conductive member of the shower head 13 faces the substrate support 11 and functions as an electrode (hereinafter, may be referred to as a counter electrode). In addition to the shower head 13, the gas introduction unit may include one or more side gas injectors (SGI) attached to one or more openings formed in the side wall 10a.

[0031] The gas supply 20 may include at least one gas source 21 and at least one flow controller 22. In one embodiment, the gas supply 20 is configured to supply at least one process gas from a respective gas source 21 through a respective flow controller 22 to the showerhead 13. Each flow controller 22 may include, for example, a mass flow controller or a pressure-controlled flow controller. Additionally, the gas supply 20 may include one or more flow modulation devices to modulate or pulse a flow rate of the at least one process gas.

[0032] The power source 30 includes an RF power source 31 coupled to the plasma processing chamber 10 via at least one impedance matching circuit. The RF power source 31 is configured to supply at least one RF signal (RF power), such as a source RF signal and a bias RF signal, to a conductive member of the substrate support 11 and / or a conductive member of the showerhead 13. This causes a plasma to be formed from at least one processing gas supplied to the plasma processing space 10s. Thus, the RF power source 31 can function as at least a part of a plasma generating unit configured to generate a plasma from one or more processing gases in the plasma processing chamber 10. In addition, by supplying a bias RF signal to the conductive member of the substrate support 11, a bias potential is generated on the substrate W, and ion components in the formed plasma can be attracted to the substrate W.

[0033] 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 the conductive member of the substrate support 11 and / or the conductive member of the shower head 13 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 13 MHz to 150 MHz. In one embodiment, the first RF generating unit 31a may be configured to generate a plurality of source RF signals having different frequencies. The generated one or more source RF signals are supplied to the conductive member of the substrate support 11 and / or the conductive member of the shower head 13. The second RF generating unit 31b is coupled to the conductive member of the substrate support 11 via at least one impedance matching circuit, and is configured to generate a bias RF signal (bias RF power). In one embodiment, the bias RF signal has a lower frequency than the source RF signal. In one embodiment, the bias RF signal has a frequency in the range of 400 kHz to 13.56 MHz. In one embodiment, the second RF generator 31b may be configured to generate multiple bias RF signals having different frequencies. The generated bias RF signal or signals are provided to the conductive members of the substrate support 11. Also, in various embodiments, at least one of the source RF signal and the bias RF signal may be pulsed.

[0034] 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 a conductive member of the substrate support 11 and configured to generate a first DC signal. The generated first bias DC signal is applied to the conductive member of the substrate support 11. In one embodiment, the first DC signal may be applied to another electrode, such as an electrode in an electrostatic chuck. In one embodiment, the second DC generator 32b is connected to a conductive member of the showerhead 13 and configured to generate a second DC signal. The generated second DC signal is applied to the conductive member of the showerhead 13. In various embodiments, at least one of the first and second DC signals may be pulsed. The first and second DC generating units 32a, 32b may be provided in addition to the RF power supply 31, or the first DC generating unit 32a may be provided in place of the second RF generating unit 31b.

[0035] The exhaust system 40 may be connected to, for example, a gas exhaust port 10e provided at the bottom of the plasma processing chamber 10. The exhaust system 40 may include a pressure regulating valve and a vacuum pump. The pressure in the plasma processing space 10s is adjusted by the pressure regulating valve. The vacuum pump may include a turbomolecular pump, a dry pump, or a combination thereof.

[0036] 3 is a flowchart of an etching method according to an example embodiment. The etching method MT shown in FIG. 3 (hereinafter, referred to as "method MT") can be performed by the plasma processing apparatus 1 of the above embodiment. The method MT can be applied to a substrate W.

[0037] 4 is a partially enlarged cross-sectional view of an example substrate to which the method of FIG. 3 can be applied. As shown in FIG. 4, in one embodiment, the substrate W includes a first region R1 and a second region R2. The first region R1 may have at least one recess R1a. The first region R1 may have a plurality of recesses R1a. Each recess R1a may be a recess for forming a contact hole. The second region R2 may be embedded in the recess R1a. The second region R2 may be provided to cover the first region R1.

[0038] The first region R1 includes silicon. The first region R1 may include at least one of nitrogen and carbon. The first region R1 may include silicon nitride (SiN x The first region R1 may include silicon carbide (SiC). The first region R1 may include silicon carbonitride (SiCN). The first region R1 may include silicon. The first region R1 may be a region formed by, for example, CVD or the like, or may be a region obtained by nitriding or carbonizing silicon. The first region R1 may include silicon nitride (SiN x The first portion may include a first portion including silicon carbide (SiC), and a second portion including silicon carbide (SiC). In this case, the first portion has a recess R1a.

[0039] The second region R2 includes silicon and oxygen. The second region R2 includes silicon oxide (SiO x ). The second region R2 may be a region formed by, for example, CVD or the like, or may be a region obtained by oxidizing silicon. The second region R2 may have a recess R2a. The recess R2a has a width larger than the width of the recess R1a.

[0040] The substrate W may include an underlying region UR and at least one raised region RA provided on the underlying region UR. The underlying region UR and the at least one raised region RA are covered by a first region R1. The underlying region UR may include silicon. A plurality of raised regions RA are located on the underlying region UR. Recesses R1a of the first region R1 are located between the plurality of raised regions RA. Each raised region RA may form a gate region of a transistor.

[0041] The substrate W may include a mask MK. The mask MK is provided on the second region R2. The mask MK may include metal or silicon. The mask MK may have an opening OP. The opening OP corresponds to the recess R2a of the second region R2.

[0042] Method MT will be described below with reference to FIGS. 3 to 6, taking as an example a case where method MT is applied to a substrate W using the plasma processing apparatus 1 of the above embodiment. FIG. 5 is a cross-sectional view showing a step of an etching method according to an exemplary embodiment. FIG. 6 is a partially enlarged cross-sectional view of an example substrate obtained by performing the etching method according to an exemplary embodiment. When the plasma processing apparatus 1 is used, method MT can be performed in the plasma processing apparatus 1 by controlling each part of the plasma processing apparatus 1 by a control unit 2. In method MT, as shown in FIG. 2, a substrate W on a substrate support 11 (substrate support) arranged in a plasma processing chamber 10 is processed.

[0043] 3, the method MT includes steps ST1 and ST2. Steps ST1 and ST2 may be performed in sequence.

[0044] In step ST1, a substrate W shown in Fig. 4 is prepared. The substrate W may be supported by a substrate support 11 in a plasma processing chamber 10. The substrate W may have the shape shown in Fig. 4 as a result of plasma etching, or may have the shape shown in Fig. 4 from the beginning when it is provided to the plasma processing chamber 10. In step ST1, the upper surface of the first region R1 and the upper surface of the second region R2 may be exposed. That is, in step ST1, the upper surface of the silicon nitride and the upper surface of the silicon oxide may be exposed.

[0045] In step ST2, as shown in FIG. 5, the first region R1 and the second region R2 are exposed to plasma generated from a processing gas containing carbon, fluorine, and tungsten, thereby etching the second region R2. A mask MK is used in the etching. The etching may be performed as follows. First, the gas supply unit 20 supplies a processing gas containing carbon, fluorine, and tungsten into the plasma processing chamber 10. Next, the plasma generation unit 12 generates plasma from the processing gas in the plasma processing chamber 10. The control unit 2 controls the gas supply unit 20 and the plasma generation unit 12 so that the second region R2 is etched while a tungsten-containing protective layer is formed on the first region R1 by exposing the first region R1 and the second region R2 to the plasma.

[0046] The process gas may include a carbon- and fluorine-containing gas and a tungsten-containing gas. The carbon- and fluorine-containing gas may include at least one of a fluorocarbon gas and a hydrofluorocarbon gas. x F y The gas may include at least one of CF4 gas, C3F8 gas, C4F8 gas, and C4F6 gas. Instead of an oxygen-containing gas (e.g., O2 gas) as a gas for controlling carbon deposition, a C x F y A gas such as C4F8 gas may be used. Instead of the mixture of C4F6 gas and an oxygen-containing gas, a mixture of C4F6 gas and C4F8 gas may be used.x H y F z ) The gas may include at least one of CH2F2 gas, CHF3 gas, and CH3F gas.

[0047] The tungsten-containing gas may include a tungsten halide gas. The tungsten halide gas may include at least one of tungsten hexafluoride (WF6) gas, tungsten hexabromide (WBr6) gas, tungsten hexachloride (WCl6) gas, and WF5Cl gas. The tungsten-containing gas may include tungsten hexacarbonyl (W(CO)6) gas.

[0048] The process gas may or may not include oxygen. The process gas may include an oxygen-containing gas. The oxygen-containing gas may include at least one of O2 gas, CO gas, and CO2 gas. The process gas may include a noble gas, such as argon.

[0049] In step ST2, the temperature of the substrate support 11 may be 100° C. or more, 120° C. or more, 130° C. or more, more than 130° C., 140° C. or more, or 150° C. or more. The temperature of the substrate support 11 may be 250° C. or less, or 200° C. or less.

[0050] In step ST2, the pressure in the plasma processing chamber 10 may be 1 mTorr (0.13 Pa) or more, or may be 10 mTorr (1.3 Pa) or more. The pressure in the plasma processing chamber 10 may be 50 mTorr (6.7 Pa) or less, or may be 30 mTorr (4.0 Pa) or less.

[0051] In step ST2, as shown in FIG. 5, a tungsten-containing film DP (tungsten-containing protective layer) may be formed on the first region R1. The tungsten-containing film DP can particularly protect the shoulder portion SH of the recess R1a of the first region R1. As a result, the shoulder portion SH is less likely to be inclined, and a large area of ​​the flat portion on the upper surface of the first region R1 can be ensured. The tungsten-containing film DP may contain nitrogen. The tungsten-containing film DP may be formed of tungsten nitride (WN x ). A carbon-containing film may be formed on the tungsten-containing film DP. The carbon-containing film may contain fluorine. The tungsten-containing film DP and the carbon-containing film suppress etching of the first region R1. The second region R2 is not covered by the tungsten-containing film DP, so it is etched. By etching the second region R2, a contact hole HL is formed as shown in FIG. 6. The contact hole HL corresponds to the recess R1a of the first region R1. In this manner, step ST2 may be performed in a self-aligned contact (SAC) step. After the second region R2 in the recess R1a is removed, the tungsten-containing film DP remains on the first region R1. The tungsten-containing film DP may be removed by cleaning after step ST2.

[0052] According to the method MT, the etching selectivity of the second region R2 to the first region R1 can be improved. For example, silicon nitride (SiN x Silicon oxide (SiO x The selectivity of the second region R2 containing silicon oxide can be set to 5 or more. Without being bound by theory, the reason is believed to be as follows. The second region R2 containing silicon oxide is etched by active species containing fluorine in the plasma. For example, when WF x SiO x When reacting with WO x Or WO x F y This produces SiO xOn the other hand, the active species containing tungsten in the plasma react with the silicon nitride in the first region R1, and tungsten nitride is deposited on the upper surface of the first region R1. Alternatively, the active species containing tungsten in the plasma reacts with the silicon nitride in the first region R1, and at least a part of the upper surface of the first region R1 is modified, and the modified part contains tungsten nitride. For example, WF x SiN x When reacted with WN x and SiF x is generated. x may be included in a deposition layer on the upper surface of the first region R1, or may be included in a layer obtained by modifying the upper surface of the first region R1. As a result, a tungsten-containing film DP containing tungsten nitride is formed on the first region R1. The tungsten-containing film DP is deposited or the silicon nitride on the upper surface of the first region R1 is modified preferentially in a portion where the active species containing tungsten in the plasma is incident with relatively high energy, that is, on the upper surface of the first region R1. The tungsten-containing film DP suppresses etching of the first region R1. As a result, the etching selectivity of the second region R2 to the first region R1 is improved.

[0053] Furthermore, according to the method MT, since the tungsten-containing film DP functions as an etching mask, there is no need to form a thick carbon-containing film on the tungsten-containing film DP. A thick carbon-containing film may cause clogging of the contact hole. Therefore, the method MT suppresses clogging of the contact hole HL by the carbon-containing film.

[0054] When the processing gas contains oxygen, the carbon-containing film is less likely to be formed on the first region R1. Therefore, blocking of the contact hole HL by the carbon-containing film is suppressed. On the other hand, when the processing gas contains oxygen, the surface of the first region R1 is oxidized to form silicon oxide on the surface of the first region R1. As a result, the surface of the first region R1 is etched. When the processing gas does not contain oxygen, such etching of the first region R1 is suppressed. As a result, the etching selectivity of the second region R2 to the first region R1 is further improved.

[0055] FIG. 7 is an example of a timing chart showing the time change of the bias power applied to the electrode in the main body 111 of the substrate support 11 and the RF power applied to the counter electrode. This timing chart is related to step ST2 in the method MT. In step ST2, bias power may be applied to the electrode in the main body 111. The bias power may be, for example, RF power LF. The following description is an example of power used for a substrate with a diameter of 300 mm. The RF power LF may be 10 W or more and 300 W or less, 30 W or more and 200 W or less, or 50 W or more and 100 W or less. The frequency of the RF power LF may be 100 kHz or more and 40.68 MHz or less. When the RF power LF is small, etching of the first region R1 by ions in the plasma is suppressed. In step ST2, RF power HF may be applied to the counter electrode. The RF power HF may be 50 W or more and 1000 W or less, 80 W or more and 800 W or less, or 100 W or more and 500 W or less. The frequency of the RF power HF may be 27 MHz or more and 100 MHz or less. The RF powers LF and HF may be applied periodically with a period CY. The bias power may be supplied to a conductive member of the substrate support 11. The RF power HF may be supplied to an antenna including one or more coils.

[0056] The ion energy of the plasma may be 50 eV or more and 700 eV or less, 100 eV or more and 600 eV or less, or 120 eV or more and 500 eV or less. When the ion energy is large, the thickness of the tungsten-containing film DP can be increased. Note that the ion energy of the present disclosure may be the average ion energy incident on the upper surface of the substrate, or may be expressed as the distribution of the ion energy incident on the upper surface of the substrate.

[0057] The cycle CY may include a first period PA, a second period PB, and a third period PC. In the first period PA, the RF power LF is maintained at a low power L1 (second power, for example, less than 100 W), and the RF power HF is maintained at a high power H2 (first power, for example, more than 100 W). In the first period PA, the deposition of the tungsten-containing film DP and the carbon-containing film is promoted. In the second period PB, the RF power LF is maintained at a low power L1, and the RF power HF is maintained at a low power L2 (third power, for example, less than 200 W). The low power L2 is smaller than the high power H2 and larger than the low power L1. In the third period PC, the RF power LF is maintained at a high power H1 (fourth power, for example, more than 50 W), and the RF power HF is maintained at a low power L2. The high power H1 is larger than the low power L1 and smaller than the high power H2. In the third period PC, the etching of the second region R2 is promoted. The second period PB is a transition period from the first period PA to the third period PC. In the step ST2, one cycle corresponding to a period CY including the first period PA, the second period PB, and the third period PC may be repeated two or more times.

[0058] The ratio of the first period PA to the cycle CY is smaller than the ratio of the third period PC to the cycle CY. The ratio of the first period PA to the cycle CY may be 10% or more, or may be less than 50%. When the ratio of the first period PA is large, the etching selectivity of the second region R2 to the first region R1 is large. When the ratio of the first period PA is small, the blocking of the contact hole HL is suppressed. The ratio of the third period PC to the cycle CY may be 50% or more. When the ratio of the third period PC is large, the etching selectivity of the second region R2 to the first region R1 is large. The frequency that defines the cycle CY may be 1 kHz or more and 1 MHz or less. The time length of the cycle CY is the reciprocal of the frequency that defines the cycle CY.

[0059] FIG. 8 is a partially enlarged cross-sectional view of an example substrate to which the method of FIG. 3 can be applied. As shown in FIG. 8, in one embodiment, the substrate W includes a first region R1 and a second region R2. The substrate W may include an underlayer region UR. The first region R1 may be provided on the second region R2. The second region R2 may be provided on the underlayer region UR. Each of the first region R1, the second region R2, and the underlayer region UR may be a film. The first region R1 may function as a mask. The first region R1 may have at least one opening OP1. The first region R1 may have a plurality of openings OP1. Each opening OP1 may be an opening for forming a contact hole. The dimension of the opening OP1 may be 200 nm or less. The dimension of the opening OP1 may be 15 nm or more. The first region R1 includes silicon and nitrogen. The first region R1 may not include nitrogen. The second region R2 includes silicon and oxygen. The underlayer region UR may include silicon and nitrogen. The underlayer region UR is made of silicon nitride (SiN x ).

[0060] 9 is a partially enlarged cross-sectional view of an example substrate obtained by performing an etching method according to an exemplary embodiment. When the method MT is applied to the substrate W of FIG. 8, a recess RS corresponding to the opening OP1 is formed in the second region R2 as shown in FIG. 9. The recess RS may be a contact hole. The bottom of the recess RS may reach the underlying region UR. In step ST2, a tungsten-containing film DP may be formed on the first region R1 as shown in FIG. 9.

[0061] According to the method MT, the etching selectivity of the second region R2 to the first region R1 can be improved. In addition, since the flow rate of the gas containing carbon and fluorine can be reduced in step ST2, the deposition of a carbon-containing film on the sidewall of the recess RS can be suppressed. Therefore, the sidewall of the recess RS can be made closer to vertical. Furthermore, since the etching rate in step ST2 can be increased, the etching time can be reduced, for example, by about half.

[0062] 10 is a diagram showing an example of an etching step. In the method MT, the etching step ST2 may include a first step ST21 and a second step ST22. The first step ST21 and the second step ST22 may be performed in sequence. The etching step ST2 may further include a third step ST23 between the first step ST21 and the second step ST22.

[0063] In one exemplary embodiment, in the first step ST21, a tungsten-containing film DP (first tungsten-containing deposit) may be formed on the first region R1 by supplying a bias power (fifth power) to the plasma processing apparatus 1 (see FIG. 5). The thickness of the tungsten-containing film DP may be 2 nm or more and 5 nm or less. The bias power may be RF power LF applied to an electrode in the main body 111 of the substrate support 11. The following description is an example of power used for a substrate with a diameter of 300 mm. The RF power LF may be 50 W or more or 300 W or more. Increasing the RF power LF increases the ion energy of the plasma, so that the thickness of the tungsten-containing film DP can be increased. The RF power LF may be 500 W or less, or may be 800 W or less. Reducing the RF power LF can reduce the reduction amount (etching amount) of the first region R1. In the first step ST21, the plasma processing apparatus 1 may not be supplied with RF power HF applied to the counter electrode. Other process conditions (type of process gas, flow rate ratio of each gas, process time, temperature, pressure, etc.) in the first step ST21 may be the same as the process conditions in the above-mentioned step ST2. The process gas in the first step ST21 may contain oxygen, carbon, fluorine, and tungsten. The second region R2 may be etched in the first step ST21.

[0064] In the third step ST23, the tungsten-containing film DP may be exposed to plasma generated from a process gas containing a hydrogen-containing gas (hydrogen plasma process). The process gas containing a hydrogen-containing gas may be different from the process gas of the first step ST21. The hydrogen-containing gas may contain at least one of H2 gas, SiH4 gas, and CH4 gas. The process gas of the third step ST23 may further contain a noble gas such as argon. The time of the third step ST23 may be 5 seconds or more and 15 seconds or less. If the time of the third step ST23 is long, the reduction amount of the first region R1 due to hydrogen radicals becomes large.

[0065] In the second step ST22, the second region R2 may be etched while forming a further tungsten-containing film DP (second tungsten-containing deposit) on the tungsten-containing film DP by supplying high frequency power and bias power to the plasma processing apparatus 1. The high frequency power may be RF power HF applied to the counter electrode. The bias power (sixth power) in the second step ST22 may be lower than the bias power (fifth power) in the first step ST21. When the bias power changes in each step, the bias power in each step may be an average value of the bias power. The process conditions in the second step ST22 may be the same as the process conditions in the above-mentioned step ST2. The process gas in the second step ST22 may contain oxygen, carbon, fluorine, and tungsten.

[0066] In another exemplary embodiment, in the first step ST21, the process gas may contain a hydrogen-containing gas to form a tungsten-containing film DP (first tungsten-containing deposit) on the first region R1. An example of the hydrogen-containing gas may be the same as the example of the hydrogen-containing gas in the third step ST23. An example of the gas contained in the process gas may be the same as the example of the gas contained in the process gas in the above-mentioned step ST2. Other process conditions in the first step ST21 (such as the flow rate ratio of each gas, process time, temperature, pressure, and applied power) may be the same as the process conditions in the above-mentioned step ST2. The process gas in the first step ST21 may contain hydrogen, carbon, fluorine, and tungsten. The second region R2 may be etched in the first step ST21.

[0067] In the second step ST22, the process gas may contain an oxygen-containing gas, thereby forming a further tungsten-containing film DP (second tungsten-containing deposit) while etching the second region R2. The process conditions in the second step ST22 (type of process gas, flow rate ratio of each gas, process time, temperature, pressure, applied power, etc.) may be the same as the process conditions in the above-mentioned step ST2. The process gas in the second step ST22 may contain oxygen, carbon, fluorine, and tungsten.

[0068] Usually, in an opening having a relatively small dimension, the active species containing tungsten is difficult to transport into the opening, so the thickness of the tungsten-containing film may be small. In contrast, according to the method MT including the first step ST21, a tungsten-containing film DP having high film thickness uniformity can be formed regardless of the dimension of the opening OP of the mask MK (the width of the recess R2a). Therefore, in both the opening OP having a relatively large dimension and the opening OP having a relatively small dimension, the etching selectivity of the second region R2 to the first region R1 can be improved. Furthermore, according to the method MT including the first step ST21, the thickness of the tungsten-containing film DP can be increased. When the processing gas in the first step ST21 contains a hydrogen-containing gas, the thickness of the tungsten-containing film DP can be increased without increasing the RF power LF in the first step ST21. This is presumably because tungsten reduced by the hydrogen-containing gas is deposited by CVD.

[0069] When the third step ST23 is performed or when the process gas in the first step ST21 contains a hydrogen-containing gas, the composition ratio of tungsten in the tungsten-containing film DP can be increased. This is presumably because tungsten oxide is reduced by hydrogen to produce metallic tungsten.

[0070] After the first step ST21, the second region R2 may be etched using a process gas that does not include a tungsten-containing gas without performing the second step ST22.

[0071] Although various exemplary embodiments have been described above, the present invention is not limited to the above-described exemplary embodiments, and various additions, omissions, substitutions, and modifications may be made. In addition, elements in different embodiments can be combined to form other embodiments.

[0072] For example, the application of step ST2 of method MT is not limited to the self-aligned contact (SAC) process, and step ST2 may be applied to other processes in which a high etching selectivity is desired.

[0073] Also, for example, a molybdenum-containing gas may be used instead of or in addition to the tungsten-containing gas. The molybdenum-containing gas may include a molybdenum halide gas. The molybdenum halide gas may include at least one of molybdenum hexafluoride (MoF6) gas and molybdenum hexachloride (MoCl6) gas.

[0074] Various experiments performed to evaluate Method MT will be described below, but the experiments described below are not intended to limit the present disclosure.

[0075] (First experiment) In the first experiment, silicon nitride (SiN x A first region R1 including a silicon oxide (SiO x A substrate W including a first region R2 including a first region R3 and a second region R4 including a second region R5 was prepared. Then, a process ST2 was performed on the substrate W using a plasma processing apparatus 1. In the process ST2, the processing gas is a mixed gas of a fluorocarbon gas, an oxygen gas, and a tungsten hexafluoride gas (WF6). The flow rate ratio of the tungsten hexafluoride gas (WF6) is higher than the flow rate ratio of the fluorocarbon gas and higher than the flow rate ratio of the oxygen gas.

[0076] (Second experiment) In the second experiment, the same method as in the first experiment was carried out, except that tungsten hexafluoride gas (WF6) was removed from the treatment gas in step ST2.

[0077] (Experimental Results) TEM images of the cross section of the substrate W on which the method was performed in the first and second experiments were observed. FIG. 11(a) is a diagram showing a TEM image of the cross section of the substrate obtained by performing the etching method in the first experiment. FIG. 11(b) is a diagram showing a TEM image of the cross section of the substrate obtained by performing the etching method in the second experiment. In FIG. 11(a), a film DP (black part in the figure) formed on the first region R1 was confirmed. From the result of TEM-EDX, it was confirmed that the part corresponding to the film DP in FIG. 11(a) contains tungsten. On the other hand, in FIG. 11(b), no tungsten-containing film was confirmed on the first region R1. Furthermore, in FIG. 11(a), the bottom of the recess formed by etching (the upper surface of the second region R2) is flat. On the other hand, in FIG. 11(b), the bottom of the recess formed by etching (the upper surface of the second region R2) is inclined. Therefore, in the first experiment, it can be seen that the bottom of the recess can be processed into a desired shape by etching.

[0078] (Third experiment) In the third experiment, silicon oxide (SiO x ) and a second region R2 including silicon nitride (SiN x ) and a first region R1 including silicon nitride (SiN x 8 was prepared, which included a base region UR including a first region R2 and a second region R3. Then, a process ST2 was performed on the substrate W using a plasma processing apparatus 1. As a result, a recess RS was formed in the second region R2. In the process ST2, the processing gas was a mixed gas of a fluorocarbon gas, an oxygen gas, a tungsten hexafluoride gas (WF6), and an argon gas. The flow rate ratio of the tungsten hexafluoride gas (WF6) was higher than that of the fluorocarbon gas and higher than that of the oxygen gas. In the process ST2, the RF power HF and the RF power LF shown in FIG. 7 were applied.

[0079] (4th experiment) In the fourth experiment, the same method as in the third experiment was carried out except that in step ST2, tungsten hexafluoride gas (WF6) was removed from the processing gas and the RF power HF and the RF power LF in step ST2 were kept constant. That is, in step ST2, the processing gas was a mixed gas of fluorocarbon gas, oxygen gas, and argon gas.

[0080] (cross section) The TEM images of the cross section of the substrate W on which the method was performed in the third and fourth experiments were observed. (a) and (b) of FIG. 12 are diagrams showing examples of the cross section of the substrate obtained by performing the etching method in the third experiment. (a) of FIG. 12 shows a cross section in an area where a dense pattern was formed. (b) of FIG. 12 shows a cross section in an area where an isolated pattern was formed. (a) and (b) of FIG. 12 confirm the tungsten-containing film DP and the carbon-containing film CDP formed on the first region R1. The carbon-containing film CDP is formed so as to cover the tungsten-containing film DP. Only a very thin carbon-containing film CDP could be confirmed on the side wall of the recess RS formed in the second region R2.

[0081] (c) and (d) of Figure 12 are diagrams showing examples of a cross section of a substrate obtained by carrying out the etching method in the fourth experiment. (c) of Figure 12 shows a cross section in a region where a dense pattern is formed. (d) of Figure 12 shows a cross section in a region where an isolated pattern is formed. In (c) and (d) of Figure 12, no tungsten-containing film DP was confirmed on the first region R1, but a carbon-containing film CDP was confirmed. In addition, a carbon-containing film CDP was confirmed on the side wall of a recess RS formed in the second region R2.

[0082] In FIG. 12(a), the value obtained by subtracting the dimension at the top surface of the second region R2 from the dimension at the bottom surface of the second region R2 was 4.0 nm. In FIG. 12(c), the value obtained by subtracting the dimension at the top surface of the second region R2 from the dimension at the bottom surface of the second region R2 was 5.1 nm. In FIG. 12(b), the value obtained by subtracting the dimension at the top surface of the second region R2 from the dimension at the bottom surface of the second region R2 was 8.5 nm. In FIG. 12(d), the value obtained by subtracting the dimension at the top surface of the second region R2 from the dimension at the bottom surface of the second region R2 was 12.4 nm. Therefore, in the third experiment, the sidewall of the recess RS was closer to vertical than in the fourth experiment. This is considered to be because, in the fourth experiment, etching is less likely to proceed linearly due to the carbon-containing film CDP formed on the sidewall of the recess RS.

[0083] (etching selectivity) The etching selectivity of the second region R2 to the first region R1 was calculated by measuring the etching amount of the first region R1 and the etching amount of the second region R2. In the third experiment, the etching selectivity in the region of (a) in FIG. 12 was 3.7. In the fourth experiment, the etching selectivity in the region of (c) in FIG. 12 was 2.7. In the third experiment, the etching selectivity in the region of (b) in FIG. 12 was 4.5. In the fourth experiment, the etching selectivity in the region of (d) in FIG. 12 was 4.2. Therefore, it was found that the etching selectivity in the third experiment could be improved compared to the fourth experiment. This is considered to be because the first region R1 is less likely to be etched by the tungsten-containing film DP in the third experiment.

[0084] (Fifth experiment) In the fifth experiment, a substrate W having the structure shown in FIG. 4 was prepared. The substrate W was made of silicon nitride (SiN x A first region R1 including a silicon oxide (SiO x) and a second region R2 including an opening OP having a relatively large dimension (hereinafter, a long pattern) and an opening OP having a relatively small dimension (hereinafter, a short pattern). Thereafter, a first process ST21 and a second process ST22 were performed on the substrate W using the plasma processing apparatus 1 (see FIG. 10).

[0085] In the first process ST21, while forming a tungsten-containing film DP on the first region R1, the second region R2 is etched to form a slit having a depth of about 20 nm in the recess R1a (see FIG. 5). In the first process ST21, the process gas is a mixed gas of fluorocarbon gas, oxygen (O2) gas, argon gas, and tungsten hexafluoride gas (WF6). The flow rate ratio of the tungsten hexafluoride gas (WF6) is higher than that of the fluorocarbon gas and higher than that of the oxygen gas. The RF power HF supplied to the plasma processing apparatus 1 is 0 W. The RF power LF supplied to the plasma processing apparatus 1 is 400 W. Therefore, the ion energy of the plasma is relatively large.

[0086] In the second process ST22, the second region R2 is etched while forming the tungsten-containing film DP on the first region R1, to form a slit having a depth of about 70 nm in the recess R1a. In the second process ST22, the processing gas is a mixed gas of fluorocarbon gas, oxygen gas, argon gas, and tungsten hexafluoride gas (WF6). The flow rate ratio of the tungsten hexafluoride gas (WF6) is higher than that of the fluorocarbon gas and higher than that of the oxygen gas. The RF power HF and the RF power LF are supplied to the plasma processing apparatus 1 according to the timing chart of FIG. 7. In the first period PA, the high power H2 is 800 W, and the low power L1 is 50 W. In the third period PC, the low power L2 is 0 W, and the high power H1 is 100 W. Therefore, the average value of the RF power LF in the second process ST22 is lower than that of the RF power LF in the first process ST21.

[0087] (Experiment 6) In the sixth experiment, the same substrate W as in the fifth experiment was prepared. Then, the process ST2 was performed on the substrate W using the plasma processing apparatus 1. The process ST2 includes an etching process and a deposition process. The etching process and the deposition process are performed in this order.

[0088] In the etching step, the second region R2 was etched while the tungsten-containing film DP was formed on the first region R1, to form a slit having a depth of about 20 nm in the recess R1a (see FIG. 5). The process conditions of the etching step were the same as the process conditions (BSL conditions) of the second step ST22 of the fifth experiment.

[0089] In the deposition process, a deposition film was formed on the tungsten-containing film DP while the second region R2 was etched to form a slit having a depth of about 70 nm in the recess R1a. The deposition process includes the etching process and the carbon-containing film deposition process of the sixth experiment. In the carbon-containing film deposition process, the process gas is a mixed gas of carbon monoxide (CO) gas and argon gas. The RF power HF supplied to the plasma processing apparatus 1 is 800 W. The RF power LF supplied to the plasma processing apparatus 1 is 0 W.

[0090] (Experimental Results) TEM images of the cross sections of the substrate W on which etching was performed in the fifth and sixth experiments were observed. In the fifth experiment, in the long pattern, the reduction amount (etching amount) of the first region R1 after the first process ST21 was 4.9 nm, and the reduction amount of the first region R1 after the second process ST22 was 7.3 nm. Therefore, the reduction amount of the first region R1 increased by 2.4 nm due to the second process ST22.

[0091] On the other hand, in the sixth experiment, in the long pattern, the reduction amount of the first region R1 after the etching process was 2.8 nm, and the reduction amount of the first region R1 after the deposition process was 3.8 nm. Therefore, the reduction amount of the first region R1 increased by 1.0 nm due to the deposition process.

[0092] In the fifth experiment, in the short pattern, the reduction amount of the first region R1 after the first process ST21 was 6.7 nm, and the reduction amount of the first region R1 after the second process ST22 was 10.2 nm. Therefore, the reduction amount of the first region R1 increased by 3.5 nm by the second process ST22.

[0093] On the other hand, in the sixth experiment, in the short pattern, the reduction in the first region R1 after the etching process was 4.3 nm, and the reduction in the first region R1 after the deposition process was 10.4 nm. Thus, the reduction in the first region R1 increased by 6.1 nm due to the deposition process. Therefore, in the fifth experiment, the increase in the reduction in the first region R1 due to the second process ST22 can be made smaller in the short pattern compared to the sixth experiment. This is presumably because, in the fifth experiment, the ion energy of the plasma in the first process ST21 is high, and therefore a thick tungsten-containing film DP can be formed in the short pattern.

[0094] In the fifth experiment, after the second process ST22, the width of the slit in the short pattern (the width of the recess R1a) was 12.8 nm, and the width of the slit in the long pattern was 9.4 nm. Therefore, the difference LtS between the width of the slit in the short pattern and the width of the slit in the long pattern was 3.4 nm.

[0095] On the other hand, in the sixth experiment, after the second process ST22, the slit width in the short pattern was 13.8 nm, and the slit width in the long pattern was 8.7 nm. Therefore, the difference LtS between the slit width in the short pattern and the slit width in the long pattern was 5.1 nm. Therefore, in the fifth experiment, the difference LtS can be made smaller than that in the sixth experiment.

[0096] (Experiment 7) In the seventh experiment, the same substrate W as in the fifth experiment was prepared. Then, a first process ST21 was performed on the substrate W using a plasma processing apparatus 1 (see FIG. 10). In the fifth experiment, the process gas in the first process ST21 contained oxygen gas, whereas in the seventh experiment, the process gas in the first process ST21 contained hydrogen (H2) gas.

[0097] In the first process ST21, while forming a tungsten-containing film DP on the first region R1, the second region R2 is etched to form a slit having a depth of about 20 nm in the recess R1a (see FIG. 5). In the first process ST21, the process gas is a mixed gas of fluorocarbon gas, hydrogen gas, argon gas, and tungsten hexafluoride gas (WF6). The flow rate ratio of the tungsten hexafluoride gas (WF6) is higher than that of the fluorocarbon gas and lower than that of the hydrogen gas. The RF power HF supplied to the plasma processing apparatus 1 is 200 W. The RF power LF supplied to the plasma processing apparatus 1 is 100 W.

[0098] (Experimental Results) A TEM image of a cross section of the substrate W on which etching was performed in the seventh experiment was observed. In the seventh experiment, the reduction in the first region R1 in the long pattern after the first process ST21 was 2.7 nm, which was smaller than the reduction in the first region R1 after the first process ST21 in the fifth experiment (4.9 nm).

[0099] In the fifth experiment, the thickness of the tungsten-containing film DP formed on the first region R1 after the first step ST21 was 4.3 nm. In the seventh experiment, the thickness of the tungsten-containing film DP formed on the first region R1 after the first step ST21 was 4.9 nm. Therefore, in the seventh experiment, the thickness of the tungsten-containing film DP is greater than that in the fifth experiment.

[0100] For the substrate W on which the first step ST21 was performed in the fifth and seventh experiments, the tungsten-containing film DP formed on the first region R1 was analyzed by X-ray photoelectron spectroscopy (XPS). In the fifth experiment, the composition ratio of tungsten was 2.4 atom%. In the seventh experiment, the composition ratio of tungsten was 5.0 atom%. Therefore, in the seventh experiment, the composition ratio of tungsten in the tungsten-containing film DP is larger than that in the fifth experiment. This is presumably because WO3 is reduced by hydrogen to produce metallic tungsten.

[0101] (Experiment 8) In the eighth experiment, the same substrate W as in the fifth experiment was prepared. Then, a first step ST21 and a second step ST22 were performed on the substrate W using the plasma processing apparatus 1 (see FIG. 10). The process conditions for the first step ST21 in the eighth experiment were the same as the process conditions for the first step ST21 in the seventh experiment. The process conditions for the second step ST22 in the eighth experiment were the same as the process conditions (BSL conditions) for the second step ST22 in the fifth experiment.

[0102] (Experimental Results) A TEM image of a cross section of the substrate W on which etching was performed in the eighth experiment was observed. In the long pattern, the reduction in the first region R1 after the second process ST22 in the eighth experiment was 3.9 nm, which was equivalent to the reduction in the first region R1 after the deposition process in the sixth experiment (3.8 nm). In the short pattern, the reduction in the first region R1 after the second process ST22 in the eighth experiment was 9.5 nm, which was equivalent to the reduction in the first region R1 after the deposition process in the sixth experiment (10.4 nm).

[0103] In the eighth experiment, after the second process ST22, the width of the slit in the short pattern (the width of the recess R1a) was 12.6 nm, and the width of the slit in the long pattern was 8.3 nm. Therefore, the difference LtS between the width of the slit in the short pattern and the width of the slit in the long pattern was 4.3 nm. Therefore, in the eighth experiment, the difference LtS can be made smaller than in the sixth experiment.

[0104] In the eighth experiment, the deposition step is not performed as in the sixth experiment, so the process time in the eighth experiment is shorter than the process time in the sixth experiment.

[0105] (Experiment No. 9) In the ninth experiment, the same substrate W as in the fifth experiment was prepared. Then, the first step ST21, the third step ST23, and the second step ST22 were performed on the substrate W using the plasma processing apparatus 1 in the same manner as in the fifth experiment except that the third step ST23 was performed (see FIG. 10).

[0106] In the third process ST23, the tungsten-containing film DP was exposed to plasma generated from hydrogen gas (hydrogen plasma process). The RF power HF supplied to the plasma processing apparatus 1 was 300 W. The RF power LF supplied to the plasma processing apparatus 1 was 0 W. The process time of the third process ST23 was 5 seconds.

[0107] (Experimental Results) A TEM image of a cross section of the substrate W on which etching was performed in the ninth experiment was observed. In the ninth experiment, in the long pattern, the reduction in the first region R1 after the first process ST21 was 4.9 nm, and the reduction in the first region R1 after the second process ST22 was 6.3 nm. Thus, the reduction in the first region R1 increased by 1.4 nm due to the second process ST22.

[0108] In the ninth experiment, in the short pattern, the reduction amount of the first region R1 after the first process ST21 was 6.7 nm, and the reduction amount of the first region R1 after the second process ST22 was 9.4 nm. Therefore, the reduction amount of the first region R1 increased by 2.7 nm due to the second process ST22. In the ninth experiment, compared to the fifth experiment, the increase in the reduction amount of the first region R1 due to the second process ST22 can be made smaller in the short pattern.

[0109] In the ninth experiment, after the second process ST22, the width of the slit in the short pattern (the width of the recess R1a) was 12.7 nm, and the width of the slit in the long pattern was 9.8 nm. Therefore, the difference LtS between the width of the slit in the short pattern and the width of the slit in the long pattern was 2.9 nm.

[0110] In the ninth experiment, after the third process ST23, the thickness of the tungsten-containing film DP formed on the first region R1 was about 5.6 nm. Therefore, in the ninth experiment, the thickness of the tungsten-containing film DP was greater than that in the fifth experiment.

[0111] In the ninth experiment, the substrate W on which the first step ST21 and the third step ST23 were performed was analyzed for the tungsten-containing film DP formed on the first region R1 by X-ray photoelectron spectroscopy (XPS). In the ninth experiment, the composition ratio of tungsten was 12.5 atom%. Therefore, in the ninth experiment, the composition ratio of tungsten in the tungsten-containing film DP is higher than in the fifth experiment. This is presumably because WO3 is reduced by hydrogen to produce metallic tungsten.

[0112] (Appendix 1) providing a substrate, the substrate including a first region including silicon and nitrogen and a second region including silicon and oxygen; etching the second region while forming a tungsten-containing protective layer on the first region by exposing the first region and the second region to a plasma generated from a process gas containing carbon, fluorine, and tungsten; An etching method comprising: (Appendix 2) 2. The etching method of claim 1, wherein in the etching step, the tungsten-containing protective layer remains on the first region after the second region is removed. (Appendix 3) 3. The etching method according to claim 1, wherein the process gas comprises a gas containing carbon and fluorine and a tungsten-containing gas. (Appendix 4) 4. The etching method of claim 3, wherein the tungsten-containing gas comprises tungsten hexafluoride gas. (Appendix 5) 5. The etching method according to claim 3, wherein the gas containing carbon and fluorine comprises a fluorocarbon gas. (Appendix 6) 6. The etching method according to claim 1, wherein the process gas contains oxygen. (Appendix 7) 7. The etching method according to claim 1, wherein the first region has a recess, and the second region is embedded in the recess. (Appendix 8) 8. The etching method according to claim 7, wherein the etching step is performed in a self-aligned contact step. (Appendix 9) In the etching step, a high frequency power and a bias power are supplied to a plasma processing apparatus to generate the plasma; The etching step includes: (a) preferentially depositing a tungsten-containing deposit on the first region by setting the radio frequency power at a first power and the bias power at a second power; (b) a transition step of setting the high frequency power to a third power lower than the first power and setting the bias power to the second power; (c) etching the second region by setting the high frequency power to the third power and setting the bias power to a fourth power higher than the second power; The etching method according to any one of claims 1 to 8, comprising: (Appendix 10) 10. The etching method according to claim 9, wherein the cycle including the steps (a) to (c) is repeated two or more times. (Appendix 11) providing a substrate comprising a silicon nitride having an exposed top surface and a silicon oxide having an exposed top surface; forming a tungsten nitride-containing protective layer on the silicon nitride by exposing the silicon oxide and the silicon nitride to a plasma generated from a process gas including tungsten hexafluoride gas; exposing the silicon oxide and the silicon nitride to a plasma generated from a process gas including tungsten hexafluoride gas to preferentially etch the silicon oxide relative to the silicon nitride; An etching method comprising: (Appendix 12) 12. The etching method of claim 11, wherein the process gas comprises a fluorocarbon gas. (Appendix 13) A chamber; a substrate support for supporting a substrate within the chamber, the substrate including a first region including silicon and nitrogen and a second region including silicon and oxygen; a gas supply configured to supply a process gas into the chamber comprising carbon, fluorine and tungsten; a plasma generating unit configured to generate a plasma from the process gas in the chamber; A control unit; Equipped with the control unit is configured to control the gas supply unit and the plasma generation unit so that the second region is etched while a tungsten-containing protective layer is formed on the first region by exposing the first region and the second region to the plasma. (Appendix 14) providing a substrate, the substrate including a first region including silicon and a second region including silicon and oxygen; etching the second region while forming a tungsten-containing protective layer on the first region by exposing the first region and the second region to a plasma generated from a process gas containing carbon, fluorine, and tungsten; Including, The etching step includes a first step and a second step, the first step includes providing a bias power to a plasma processing apparatus to form a first tungsten-containing deposit on the first region, the bias power being a fifth power; the second step etches the second region while forming a second tungsten-containing deposit on the first tungsten-containing deposit by supplying high frequency power and bias power to the plasma processing apparatus, and the bias power in the second step is a sixth power lower than the fifth power. (Appendix 15) the etching step includes a third step between the first step and the second step, 15. The etching method of claim 14, wherein the third step exposes the first tungsten-containing deposit to plasma generated from a process gas including a hydrogen-containing gas. (Appendix 16) providing a substrate, the substrate including a first region including silicon and a second region including silicon and oxygen; etching the second region while forming a tungsten-containing protective layer on the first region by exposing the first region and the second region to a plasma generated from a process gas containing carbon, fluorine, and tungsten; Including, The etching step includes a first step and a second step, In the first step, the process gas includes a hydrogen-containing gas to form a first tungsten-containing deposit on the first region; an etching method in which, in the second step, the process gas contains an oxygen-containing gas, thereby etching the second region while forming a second tungsten-containing deposit on the first tungsten-containing deposit.

[0113] 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. [Explanation of symbols]

[0114] 1...plasma processing apparatus, 2...control unit, 10...plasma processing chamber, 11...substrate support unit, 12...plasma generation unit, 20...gas supply unit, DP...tungsten-containing film (tungsten-containing protective layer), R1...first region, R2...second region, W...substrate.

Claims

1. A process for producing a substrate, the substrate including a mask and a silicon-containing film beneath the mask; generating a plasma from a process gas comprising carbon, fluorine, and tungsten or molybdenum; etching the silicon-containing film by exposing the silicon-containing film to the generated plasma; Including, In the etching step, a tungsten-containing protective layer or a molybdenum-containing protective layer is formed on an upper surface of the mask.

2. The etching method described in claim 1, wherein the mask has an opening for forming a contact hole, and the dimension of the opening is 15 nm or more and 200 nm or less.

3. The mask comprises silicon and nitrogen, and the silicon-containing film comprises silicon and oxygen, The etching method according to claim 1 , wherein the substrate includes an undercoat film below the silicon-containing film, the undercoat film including silicon and nitrogen.

4. The etching method described in claim 1 or 2, wherein in the etching step, a carbon-containing film is not deposited on the side walls of the recess formed in the silicon-containing film.

5. The etching method of claim 1, wherein the processing gas comprises an oxygen-containing gas.

6. A method of manufacturing a semiconductor device comprising the steps of: preparing a substrate, the substrate comprising a mask and a silicon-containing film beneath the mask; generating a first plasma from a first process gas containing tungsten or molybdenum to form a first tungsten-containing film or a first molybdenum-containing film on the mask; generating a second plasma from a second process gas comprising carbon, fluorine, and tungsten or molybdenum; etching the silicon-containing film by exposing the silicon-containing film to the generated second plasma; Including, In the etching step, a second tungsten-containing film or a second molybdenum-containing film is further formed on the first tungsten-containing film or the first molybdenum-containing film on the upper surface of the mask.

7. The etching method described in claim 6, wherein the thickness of the first tungsten-containing film or the first molybdenum-containing film is 2 nm or more and 5 nm or less.

8. The etching method described in claim 6 or 7, comprising, after the step of forming the first tungsten-containing film or the first molybdenum-containing film, a step of exposing the first tungsten-containing film or the first molybdenum-containing film to plasma generated from a process gas including a hydrogen-containing gas.

9. The etching method of claim 6 or 7, wherein the first processing gas includes a hydrogen-containing gas.

10. The etching method of claim 6 or 7, wherein the second process gas comprises an oxygen-containing gas.

11. A chamber, a substrate support for supporting a substrate in the chamber, the substrate including a mask and a silicon-containing film beneath the mask; a gas supply configured to supply a process gas into the chamber, the process gas comprising carbon, fluorine, and tungsten or molybdenum; a plasma generating unit configured to generate a plasma from the process gas in the chamber; A control unit; Equipped with The control unit is configured to control the gas supply unit and the plasma generation unit to perform an etching method, the etching method including: generating the plasma; etching the silicon-containing film by exposing the silicon-containing film to the generated plasma; Including, In the etching step, a tungsten-containing protective layer or a molybdenum-containing protective layer is formed on an upper surface of the mask.

12. A chamber, a substrate support for supporting a substrate in the chamber, the substrate including a mask and a silicon-containing film beneath the mask; a gas supply configured to supply a first process gas comprising tungsten or molybdenum and a second process gas comprising carbon, fluorine, and tungsten or molybdenum into the chamber; a plasma generating unit configured to generate a first plasma from the first process gas in the chamber and to generate a second plasma from the second process gas in the chamber; A control unit; Equipped with The control unit is configured to control the gas supply unit and the plasma generation unit to perform an etching method, the etching method including: generating the first plasma and forming a first tungsten-containing film or a first molybdenum-containing film on the mask; generating the second plasma; etching the silicon-containing film by exposing the silicon-containing film to the generated second plasma; Including, In the etching step, a second tungsten-containing film or a second molybdenum-containing film is further formed on the first tungsten-containing film or the first molybdenum-containing film on the upper surface of the mask.

13. A method of forming a substrate, the substrate comprising: a mask; and a silicon-containing film beneath the mask; generating a plasma from a process gas comprising carbon, fluorine, and tungsten or molybdenum; etching the silicon-containing film by exposing the silicon-containing film to the generated plasma; Including, In the etching step, a tungsten-containing protective layer or a molybdenum-containing protective layer is formed on an upper surface of the mask.

14. A method of forming a substrate, the substrate comprising: a mask; and a silicon-containing film beneath the mask; generating a first plasma from a first process gas containing tungsten or molybdenum to form a first tungsten-containing film or a first molybdenum-containing film on the mask; generating a second plasma from a second process gas comprising carbon, fluorine, and tungsten or molybdenum; etching the silicon-containing film by exposing the silicon-containing film to the generated second plasma; Including, In the etching step, a second tungsten-containing film or a second molybdenum-containing film is further formed on the first tungsten-containing film or the first molybdenum-containing film on the upper surface of the mask.

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