Plasma processing system

Abstract

To provide a technology that improves the selection ratio of etching.SOLUTION: Provided is an etching method that is executed in a plasma processing device having a chamber. This method includes the steps of: (a) providing, in a chamber, a substrate that includes an underlying film and a silicon-containing film on the underlying film; (b) etching the silicon-containing film to form a recess using first plasma generated from a first process gas containing a hydrogen fluoride gas, the etching being carried out until before the underlying film is exposed at the recess or until the underlying film is partly exposed at the recess; and (c) further etching the silicon-containing film at the recess under a condition different from the condition of (b).SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] Exemplary embodiments of this disclosure relate to etching methods and plasma processing systems. [Background technology]

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

[0003] [Patent Document 1] Japanese Patent Publication No. 2016-39310 [Overview of the project] [Problems that the invention aims to solve]

[0004] This disclosure provides a technique for improving the selectivity of etching. [Means for solving the problem]

[0005] In one exemplary embodiment of the present disclosure, an etching method is provided which is performed in a plasma processing apparatus having a chamber, the method comprising: (a) providing a substrate having a base film and a silicon-containing film on the base film into the chamber; (b) etching the silicon-containing film to form a recess using a first plasma generated from a first processing gas containing hydrogen fluoride gas, wherein the etching is performed until the base film is not exposed in the recess or until a portion of the base film is exposed in the recess; and (c) further etching the silicon-containing film in the recess under conditions different from those of step (b). [Effects of the Invention]

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

Brief Description of the Drawings

[0007] [Figure 1] It is a diagram schematically showing an exemplary plasma processing system. [Figure 2] It is a flowchart showing an etching method according to the first embodiment. [Figure 3] It is a diagram showing an example of the cross-sectional structure of the substrate W. [Figure 4] It is a diagram showing an example of the cross-sectional structure of the substrate W at the end of the step ST12. [Figure 5] It is a diagram showing an example of the cross-sectional structure of the substrate W at the end of the step ST13. [Figure 6] It is an example of a timing chart when the underlying film UF contains silicon. [Figure 7] It is another example of a timing chart when the underlying film UF contains silicon. [Figure 8] It is an example of a timing chart when the underlying film contains metal. [Figure 9] It is a flowchart showing an etching method according to the second embodiment. [Figure 10] It is a diagram showing the relationship between the ion flux and the ion energy. [Figure 11] It is a timing chart showing an example of the source RF signal and the bias RF signal. [Figure 12] It is a timing chart showing an example of the source RF signal and the bias DC signal.

Modes for Carrying Out the Invention

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

[0009] An etching method performed in a plasma processing apparatus having a chamber in one exemplary embodiment, the method comprising: (a) providing a substrate having an underlying film and a silicon-containing film on the underlying film in the chamber; (b) etching the silicon-containing film using a first plasma generated from a first processing gas containing hydrogen fluoride gas to form a recess, the etching being performed until before the underlying film is exposed in the recess or until a part of the underlying film is exposed in the recess; and (c) further etching the silicon-containing film in the recess under conditions different from those in step (b).

[0010] In one exemplary embodiment, in step (c), a second plasma is generated using a second processing gas different from the first processing gas.

[0011] In one exemplary embodiment, the density of fluorine species in the second plasma is lower than that in the first plasma.

[0012] In one exemplary embodiment, the underlying film contains silicon, and the second processing gas contains a fluorocarbon gas or a hydrofluorocarbon gas and an oxygen-containing gas in an amount of 50% by volume or more based on the total flow rate of the second processing gas excluding the inert gas.

[0013] In one exemplary embodiment, the fluorocarbon gas or the hydrofluorocarbon gas contained in the second processing gas has 2 or more carbon atoms.

[0014] In one exemplary embodiment, the underlying film contains metal, the first processing gas further contains a fluorine-containing gas other than hydrogen fluoride, and the second processing gas does not contain a fluorine-containing gas or contains a fluorine-containing gas at a partial pressure lower than the partial pressure in the first processing gas.

[0015] In one exemplary embodiment, the fluorine-containing gas is at least one of NF3 gas and SF6 gas.

[0016] In one exemplary embodiment, the second treatment gas further comprises at least one of CO gas and a chlorine-containing gas.

[0017] In one exemplary embodiment, in step (c), temperature control is performed so that the temperature of the substrate is higher than the temperature of the substrate in step (b).

[0018] In one exemplary embodiment, temperature control includes one or more of the following: (I) increasing the power of the source RF signal or bias signal supplied to the chamber; (II) decreasing the suction force of the substrate support that supports the substrate; (III) decreasing the pressure of the heat transfer gas supplied between the substrate and the substrate support; and (IV) setting the set temperature of the substrate support higher than the set temperature in step (b).

[0019] In one exemplary embodiment, temperature control includes controlling the substrate temperature to be 30°C or more higher than the substrate temperature in step (b).

[0020] In one exemplary embodiment, in step (c), pressure control is performed such that the pressure inside the chamber is lower than the pressure inside the chamber in step (b).

[0021] In one exemplary embodiment, pressure control includes controlling the pressure in the chamber to be at least 30% lower than the pressure in the chamber during step (b).

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

[0023] In one exemplary embodiment, the first treatment gas comprises at least one of a carbon-containing gas and an oxygen-containing gas.

[0024] In one exemplary embodiment, in step (b), the temperature of the substrate support portion that supports the substrate is controlled to 20°C or less.

[0025] In one exemplary embodiment, the source RF signal supplied to the chamber has a frequency of 40 MHz or higher.

[0026] In one exemplary embodiment, an etching method is provided which is performed in a plasma processing apparatus having a chamber, the method comprising: (a) providing a substrate having a base film and a silicon-containing film on the base film into the chamber; (b) etching the silicon-containing film using a plasma containing HF species to form recesses, wherein the etching is performed until the base film is not exposed in the recesses or until a portion of the base film is exposed in the recesses; and (c) further etching the silicon-containing film in the recesses under conditions different from those of step (b).

[0027] In one exemplary embodiment, the HF species is produced from at least one gas, such as hydrogen fluoride gas or hydrofluorocarbon gas.

[0028] In one exemplary embodiment, the HF species is produced from a hydrofluorocarbon gas having two or more carbon atoms.

[0029] In one exemplary embodiment, the HF species is produced from a mixed gas containing a hydrogen source and a fluorine source.

[0030] In one exemplary embodiment, a plasma processing system is provided comprising a plasma processing apparatus having a chamber and a control unit, wherein the control unit performs the following: (a) control of providing a substrate having a base film and a silicon-containing film on the base film to the chamber; (b) control of etching the silicon-containing film to form recesses using a first plasma generated from a first processing gas containing hydrogen fluoride gas, wherein the etching is performed until the base film is not exposed in the recesses or until a portion of the base film is exposed in the recesses; and (c) control of further etching the silicon-containing film in the recesses under conditions different from those of control (b).

[0031] Hereinafter, each embodiment of this disclosure will be described in detail with reference to the drawings. In each drawing, the same or similar elements are denoted by the same reference numeral, and redundant explanations are omitted. Unless otherwise specified, positional relationships such as top, bottom, 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 actual ratios are not limited to those shown.

[0032] <Example of a plasma processing system configuration> The following describes an example of a plasma processing system configuration. Figure 1 is a diagram illustrating an example of a capacitively coupled plasma processing system configuration.

[0033] The plasma processing system includes a capacitively coupled plasma processing apparatus 1 and a control unit 2. The capacitively coupled plasma processing apparatus 1 includes a plasma processing chamber 10, a gas supply unit 20, a power supply 30, and an exhaust system 40. The plasma processing apparatus 1 also includes a substrate support unit 11 and a gas introduction unit. The gas introduction unit is configured to introduce at least one processing gas into the plasma processing chamber 10. The gas introduction unit includes a shower head 13. The substrate support unit 11 is located inside the plasma processing chamber 10. The shower head 13 is located above the substrate support unit 11. In one embodiment, the shower head 13 constitutes 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 shower head 13, the side walls 10a of the plasma processing chamber 10, and the substrate support unit 11. The plasma processing chamber 10 has at least one gas supply port for supplying at least one processing gas to the plasma processing space 10s and at least one gas outlet for discharging gas from the plasma processing space. The plasma processing chamber 10 is grounded. The shower head 13 and the substrate support part 11 are electrically insulated from the housing of the plasma processing chamber 10.

[0034] The substrate support portion 11 includes a main body portion 111 and a ring assembly 112. The main body portion 111 has a central region 111a for supporting the substrate W and an annular region 111b for supporting the ring assembly 112. A wafer is an example of the substrate W. The annular region 111b of the main body portion 111 surrounds the central region 111a of the main body portion 111 in a plan view. The substrate W is placed on the central region 111a of the main body portion 111, and the ring assembly 112 is placed on the annular region 111b of the main body portion 111 so as to surround the substrate W on the central region 111a of the main body portion 111. Therefore, the central region 111a is also called the substrate support surface for supporting the substrate W, and the annular region 111b is also called the ring support surface for supporting the ring assembly 112.

[0035] 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 placed on the base 1110. The electrostatic chuck 1111 includes a ceramic member 1111a and an electrostatic electrode 1111b placed 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. Other members surrounding the electrostatic chuck 1111, such as an annular electrostatic chuck or an annular insulating member, may also have an annular region 111b. In this case, the ring assembly 112 may be placed on the annular electrostatic chuck or the annular insulating member, or on both the electrostatic chuck 1111 and the annular insulating member. Furthermore, at least one RF / DC electrode, coupled to the RF (Radio Frequency) power supply 31 and / or DC (Direct Current) power supply 32 described later, may be placed within the ceramic member 1111a. In this case, at least one RF / DC electrode functions as a lower electrode. When a bias RF signal and / or DC signal, described later, is supplied to 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 at least one RF / DC electrode may function as multiple lower electrodes. Also, the electrostatic electrode 1111b may function as a lower electrode. Therefore, the substrate support portion 11 includes at least one lower electrode.

[0036] 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 covering ring. The edge rings are formed of a conductive or insulating material, and the covering rings are formed of an insulating material.

[0037] The substrate support section 11 may also include a temperature control 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 control module may include a heater, a heat transfer medium, a flow path 1110a, or a combination thereof. A heat transfer fluid, such as brine or gas, flows through the flow path 1110a. In one embodiment, the flow path 1110a is formed within the base 1110, and one or more heaters are arranged within the ceramic member 1111a of the electrostatic chuck 1111. The substrate support section 11 may also include a heat transfer gas supply section configured to supply heat transfer gas to the gap between the back surface of the substrate W and the central region 111a.

[0038] The showerhead 13 is configured to introduce at least one processing 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 a plurality of gas inlet ports 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 through the plurality of gas inlet ports 13c. The showerhead 13 also includes at least one upper electrode. In addition to the showerhead 13, the gas introduction unit may also include one or more side gas injectors (SGIs) attached to one or more openings formed in the side wall 10a.

[0039] 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 processing gas to the shower head 13 from a corresponding gas source 21 via a corresponding flow controller 22. Each flow controller 22 may include, for example, a mass flow controller or a pressure-controlled flow controller. Furthermore, the gas supply unit 20 may include one or more flow modulation devices that modulate or pulse the flow rate of at least one processing gas.

[0040] The power supply 30 includes an RF power supply 31 coupled to the plasma processing chamber 10 via at least one impedance matching circuit. The RF power supply 31 is configured to supply at least one RF signal (RF power) to at least one lower electrode and / or at least one upper electrode. This causes plasma to be formed from at least one processing gas supplied to the plasma processing space 10s. Thus, the RF power supply 31 can function as at least part of a plasma generation unit configured to generate plasma from one or more processing gases in the plasma processing chamber 10. In addition, by supplying a bias RF signal to at least one lower electrode, a bias potential is generated on the substrate W, and ionic components in the formed plasma can be drawn into the substrate W.

[0041] In one embodiment, the RF power supply 31 includes a first RF generation unit 31a and a second RF generation unit 31b. The first RF generation 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 generation unit 31a may be configured to generate a plurality of source RF signals having different frequencies. One or more generated source RF signals are supplied to at least one lower electrode and / or at least one upper electrode.

[0042] The second RF generation unit 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 generation unit 31b may be configured to generate a plurality of bias RF signals having different frequencies. One or more generated 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.

[0043] 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 generation unit 32a and a second DC generation unit 32b. In one embodiment, the first DC generation unit 32a is connected to at least one lower electrode and configured to generate a first DC signal. The generated first bias DC signal is applied to at least one lower electrode. In one embodiment, the second DC generation unit 32b is connected to at least one upper electrode and configured to generate a second DC signal. The generated second DC signal is applied to at least one upper electrode.

[0044] 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 generation unit for generating a sequence of voltage pulses from a DC signal is connected between the first DC generation unit 32a and at least one lower electrode. Thus, the first DC generation unit 32a and the waveform generation unit constitute a voltage pulse generation unit. When the second DC generation unit 32b and the waveform generation unit constitute a voltage pulse generation unit, the voltage pulse generation unit is connected to at least one upper electrode. The voltage pulses may have positive or negative polarity. The sequence of voltage pulses may also include one or more positive voltage pulses and one or more negative voltage pulses within one cycle. The first and second DC generation units 32a and 32b may be provided in addition to the RF power supply 31, and the first DC generation unit 32a may be provided in place of the second RF generation unit 31b.

[0045] The exhaust system 40 may be connected to, for example, a gas outlet 10e located 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 regulating valve regulates the pressure in the plasma processing space 10s. The vacuum pump may include a turbomolecular pump, a dry pump, or a combination thereof.

[0046] The control unit 2 processes computer-executable instructions that cause the plasma processing apparatus 1 to perform various processes described herein. The control unit 2 may be configured to control each element of the plasma processing apparatus 1 to perform the 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 is implemented, for example, by a computer 2a. The processing unit 2a1 may be configured to perform various control operations by reading a program from the storage unit 2a2 and executing the read program. This program may be stored in the storage unit 2a2 in advance, or it may be obtained via a medium when needed. The obtained program is stored in the storage unit 2a2 and read from the storage unit 2a2 and executed by the processing unit 2a1. The medium may be various storage media readable by the computer 2a, or it may be a communication line connected to the communication interface 2a3. The processing unit 2a1 may be a CPU (Central Processing Unit). The memory unit 2a2 may include RAM (Random Access Memory), ROM (Read Only Memory), HDD (Hard Disk Drive), SSD (Solid State Drive), or a combination thereof. The communication interface 2a3 may communicate with the plasma processing device 1 via a communication line such as a LAN (Local Area Network).

[0047] <First Embodiment> Figure 2 is a flowchart of an etching method according to the first embodiment. As shown in Figure 2, the etching method includes a step ST11 for providing a substrate, a first etching step ST12, and a second etching step ST13. The processing in each step may be performed using the plasma processing system shown in Figure 1. In the following, a case in which the control unit 2 controls each part of the plasma processing apparatus 1 to perform etching on the substrate W will be described as an example.

[0048] (Step ST11: Provision of substrate) In step ST11, the substrate W is placed in the plasma processing space 10s of the plasma processing apparatus 1. The substrate W is placed in the central region 111a of the substrate support portion 11. The substrate W is then held in the substrate support portion 11 by the electrostatic chuck 1111.

[0049] Figure 3 shows an example of the cross-sectional structure of the substrate W provided in step ST11. The substrate W has a silicon-containing film SF formed on a base film UF. The substrate W may further have a mask MF on the silicon-containing film SF. The substrate W may be used in the manufacture of semiconductor devices. Semiconductor devices include, for example, semiconductor memory devices such as DRAM and 3D-NAND flash memory.

[0050] The underlayer film UF is, in some cases, a silicon wafer or an organic film, dielectric film, metal film, or semiconductor film formed on a silicon wafer. The underlayer film UF may be composed of multiple films stacked on top of each other. The underlayer film UF may contain silicon or a metal such as tungsten.

[0051] The silicon-containing film SF is the film to be etched. Examples of silicon-containing films SF include silicon oxide films, silicon nitride films, silicon oxynitride films, polycrystalline silicon films, and carbon-containing silicon films. The silicon-containing film SF may be composed of multiple films stacked on top of each other. For example, the silicon-containing film SF may be composed of alternating layers of silicon oxide films and silicon nitride films. Alternatively, for example, the silicon-containing film SF may be composed of alternating layers of silicon oxide films and polycrystalline silicon films. Furthermore, for example, the silicon-containing film SF may be a multilayer film containing silicon nitride films, silicon oxide films, and polycrystalline silicon films.

[0052] Mask MF is a film that functions as a mask in etching the silicon-containing film SF. Mask MF may be, for example, a hard mask. Mask MF may also be a carbon-containing mask and / or a metal-containing mask. A carbon-containing mask may be, for example, at least one selected from the group consisting of spin-on carbon, tungsten carbide, amorphous carbon, and boron carbide. A metal-containing mask may be, for example, at least one selected from the group consisting of titanium nitride, titanium oxide, and tungsten. A tungsten-containing mask may be, for example, tungsten silicide (WSi) and / or tungsten carbide (WC). Mask MF may also be a boron-containing mask of, for example, silicon boride, boron nitride, or boron carbide.

[0053] As shown in Figure 3, the mask MF defines at least one opening OP on the silicon-containing film SF. The opening OP is a space on the silicon-containing film SF surrounded by the sidewalls of the mask MF. That is, the upper surface of the silicon-containing film SF has a region covered by the mask MF and a region exposed at the bottom of the opening OP.

[0054] The opening OP may have any shape when viewed in plan view of the substrate W, that is, when the substrate W is viewed from top to bottom in Figure 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, and the multiple side walls may define multiple openings OP. Each of the multiple openings OP may have a linear shape and be arranged at regular intervals to form a line and space pattern. Alternatively, each of the multiple openings OP may have a hole shape and form an array pattern.

[0055] Each film constituting the substrate W (underlayment film UF, silicon-containing film SF, mask MF) may be formed by CVD, ALD, spin coating, etc. The opening OP may be formed by etching the mask MF. The mask MF may also be formed by lithography. Each of the above films may be flat or may have irregularities. The substrate W may also have other films beneath the underlayment film UF, and the laminated film of silicon-containing film SF and underlayment film UF may function as a multilayer mask. That is, the laminated film of silicon-containing film SF and underlayment film UF may be used as a multilayer mask to etch the other films.

[0056] At least part of the process for forming each film on the substrate W may be performed within the space of the plasma processing chamber 10. For example, the step of etching the mask MF to form an aperture OP may be performed in the plasma processing chamber 10. That is, the etching of the aperture OP and the silicon-containing film SF, described later, may be performed consecutively within the same chamber. Alternatively, after all or part of each film on the substrate W has been formed in an external apparatus or chamber of the plasma processing apparatus 1, the substrate W may be brought into the plasma processing space 10s of the plasma processing apparatus 1 and placed in the central region 111a of the substrate support section 11 to provide the substrate.

[0057] After the substrate W is placed in the central region 111a of the substrate support section 11, the temperature of the substrate support section 11 is adjusted to a set temperature by the temperature control module. The set temperature may be, for example, 20°C or lower, 0°C or lower, -10°C or lower, -20°C or lower, -30°C or lower, -40°C or lower, -50°C or lower, -60°C or lower, or -70°C or lower. In one example, adjusting or maintaining the temperature of the substrate support section 11 includes setting the temperature of the heat transfer fluid flowing through the channel 1110a or the heater temperature to the set temperature, or to a temperature different from the set temperature. The timing at which the heat transfer fluid begins to flow through the channel 1110a may be before, after, or simultaneously with the placement of the substrate W on the substrate support section 11. Furthermore, the temperature of the substrate support section 11 may be adjusted to the set temperature before process ST11. That is, the substrate W may be placed on the substrate support section 11 after the temperature of the substrate support section 11 has been adjusted to the set temperature.

[0058] (Process ST12: First etching) In step ST12, the silicon-containing film SF is etched using plasma generated from the first processing gas. First, the first processing gas is supplied from the gas supply unit 20 into the plasma processing space 10s. The first processing 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 unit 11 is maintained at the set temperature adjusted in step ST11.

[0059] Next, a source RF signal is supplied to the lower electrode of the substrate support 11 and / or the upper electrode of the shower head 13. This generates a high-frequency electric field between the shower head 13 and the substrate support 11, and a first plasma is generated from the first processing gas in the plasma processing space 10s. A bias signal is also 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. As a result, the silicon-containing film SF is etched, and a recess is formed based on the shape of the opening OP of the mask MF. The first etching is performed until (for example, immediately before) the underlying film UF is exposed, or until a part of the underlying film UF is exposed. That is, step ST12 ends before (for example, immediately before) the underlying film UF of the substrate W is exposed, or at the timing when a part of the underlying film UF is exposed.

[0060] Figure 4 shows an example of the cross-sectional structure of the substrate W at the end of process ST12. As shown in Figure 4, the processing in process ST12 etches the portion of the silicon-containing film SF exposed at the opening OP in the depth direction (from top to bottom in Figure 4), forming a recess RC. Although Figure 4 shows a state where the underlying film UF is not exposed at the end of process ST12, a portion of the underlying film UF may be exposed at the end of process ST12.

[0061] 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. Also in step ST12, the bias signal may be a bias RF signal supplied from the second RF generation unit 31b. Alternatively, the bias signal may be a bias DC signal supplied from the DC generation unit 32a. Both the source RF signal and the bias signal may be continuous waves or pulsed waves, or one may be a continuous wave and the other a pulsed wave. If both the source RF signal and the bias signal are pulsed waves, the periods of both pulsed waves may be synchronized. The duty cycle of the pulsed wave may be set as appropriate, for example, 1 to 80%, or 5 to 50%. The duty cycle is the proportion of the period in the pulsed wave's cycle that is characterized by a high power or voltage level. When a bias DC signal is used, the pulsed wave may have a rectangular, trapezoidal, triangular, or a combination thereof waveform. The polarity of the bias DC signal can be negative or positive, as long as the potential of the substrate W is set to create a potential difference between the plasma and the substrate, thereby attracting ions.

[0062] In step ST12, the HF gas contained in the first process gas may have the highest flow rate (partial pressure) among the process gases (excluding the inert gas if the process gas contains an inert gas). For example, the flow rate of the HF gas may be 50% or more, 60% or more, 70% or more, 80% or more, 90% or more, or 95% or more of the total flow rate of the process gases (or the total flow rate of all gases excluding the inert gas if the process gas contains an inert gas). The flow rate of the HF gas may be less than 100% of the total flow rate of the process gases, 99.5% or less, 98% or less, or 96% or less. For example, the flow rate of the HF gas is adjusted to be 70% or more and 96% or less of the total flow rate of the process gases.

[0063] The first processing gas may further contain at least one selected from the group consisting of carbon-containing gases, oxygen-containing gases, and phosphorus-containing gases.

[0064] The carbon-containing gas may be, for example, either or both of a fluorocarbon gas and a hydrofluorocarbon gas. For example, the fluorocarbon gas may be at least one selected from the group consisting of CF4 gas, C2F2 gas, C2F4 gas, C3F6 gas, C3F8 gas, C4F6 gas, C4F8 gas and C5F8 gas. For example, the hydrofluorocarbon gas may be CHF3 gas, CH2F2 gas, CH3F gas, C2HF5 gas, C2H2F4 gas, C2H3F3 gas, C2H4F2 gas, C3HF7 gas, C3H2F2 gas, C3H2F4 gas, C3H2F6 gas, C3H3F5 gas, C4H2F6 gas, C4H5F5 gas, C4H2F8 gas, C5H2F6 gas, C5H2F 10 The carbon-containing gas may be at least one selected from the group consisting of gas and C5H3F7 gas. Furthermore, the carbon-containing gas may be a linear form having unsaturated bonds. Examples of linear carbon-containing gases having unsaturated bonds include at least one selected from the group consisting of C3F6 (hexafluoropropene) gas, C4F8 (octafluoro-1-butene, octafluoro-2-butene) gas, C3H2F4 (1,3,3,3-tetrafluoropropene) gas, C4H2F6 (trans-1,1,1,4,4,4-hexafluoro-2-butene) gas, C4F8O (pentafluoroethyl trifluorovinyl ether) gas, CF3COF gas (1,2,2,2-tetrafluoroethane-1-one), CHF2COF (difluoroacetic acid fluoride) gas, and COF2 (carbonyl fluoride) gas. Note that the carbon-containing gas may also be a linear form having unsaturated bonds. The linear carbon-containing gas having unsaturated bonds may be at least one selected from the group consisting of, for example, C3F6 (hexafluoropropene) gas, C4F8 (octafluoro-1-butene, octafluoro-2-butene) gas, C3H2F4 (1,3,3,3-tetrafluoropropene) gas, C4H2F6 (trans-1,1,1,4,4,4-hexafluoro-2-butene) gas, C4F8O (pentafluoroethyl trifluorovinyl ether) gas, CF3COF gas (1,2,2,2-tetrafluoroethane-1-one), CHF2COF (difluoroacetic acid fluoride) gas, and COF2 (carbonyl fluoride) gas.

[0065] The oxygen-containing gas may be at least one gas selected from the group consisting of, for example, O2, CO, CO2, H2O, and H2O2. In one example, the oxygen-containing gas may be at least one gas selected from the group consisting of, for example, O2, CO, CO2, and H2O2, other than H2O. The flow rate of the oxygen-containing gas may be adjusted according to the flow rate of the carbon-containing gas.

[0066] A phosphorus-containing gas is a gas that contains phosphorus-containing molecules. Phosphorus-containing molecules include tetraphosphorus decoxide (P4O). 10 ), tetraphosphorus octoxide (P4O8), tetraphosphorus hexoxide (P4O6), and other oxides may be used. Tetraphosphorus decoxide is sometimes called diphosphorus pentoxide (P2O5). The phosphorus-containing molecule may also be a halide (phosphorus halogen) such as phosphorus trifluoride (PF3), phosphorus pentafluoride (PF5), phosphorus trichloride (PCl3), phosphorus pentachloride (PCl5), phosphorus tribromide (PBr3), phosphorus pentabromide (PBr5), and phosphorus iodide (PI3). That is, the phosphorus-containing molecule may contain fluorine as a halogen element, such as phosphorus fluoride. Alternatively, the phosphorus-containing molecule may contain halogen elements other than fluorine as a halogen element. The phosphorus-containing molecule may be a phosphoryl halogen such as phosphoryl fluoride (POF3), phosphoryl chloride (POCl3), and phosphoryl bromide (POBr3). Phosphorus-containing molecules may include phosphine (PH3), calcium phosphide (Ca3P2, etc.), phosphoric acid (H3PO4), sodium phosphate (Na3PO4), hexafluorophosphate (HPF6), etc. Phosphorus-containing molecules may include fluorophosphines (H g PF hIt may be. Here, the sum of g and h is 3 or 5. Examples of fluorophosphines include HPF2 and H2PF3. The processing gas may include, as at least one phosphorus-containing molecule, one or more of the above phosphorus-containing molecules. For example, the processing gas may include, as at least one phosphorus-containing molecule, at least one of PF3, PCl3, PF5, PCl5, POCl3, PH3, PBr3, or PBr5. When each phosphorus-containing molecule contained in the processing gas is liquid or solid, each phosphorus-containing molecule may be vaporized by heating or the like and supplied into the plasma processing space 10s.

[0067] The phosphorus-containing gas is PCl a F b (where 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 (where 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.

[0068] PCl a F b The gas may be, for example, at least one gas selected from the group consisting of PClF2 gas, PCl2F gas, and PCl2F3 gas.

[0069] PC c [[ID=z8]]H d F e The gas may be, for example, at least one gas selected from the group consisting of PF2CH3 gas, PF(CH3)2 gas, PH2CF3 gas, PH(CF3)2 gas, PCH3(CF3)2 gas, PH2F gas, and PF3(CH3)2 gas.

[0070] The phosphorus-containing gas is PCl c F d C e H fThe gas may be one in which c, d, e, and f are integers of 1 or more. The phosphorus-containing gas may also be a gas containing P (phosphorus), F (fluorine), and halogens 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.

[0071] Phosphine-based gases may be used as the phosphorus-containing gas. Examples of phosphine-based gases include phosphine (PH3), compounds in which at least one hydrogen atom of phosphine is substituted with a suitable substituent, and phosphine acid derivatives.

[0072] The substituents that substitute for the hydrogen atoms of phosphine are not particularly limited and include, for example, halogen atoms such as fluorine atoms and chlorine atoms; alkyl groups such as methyl groups, ethyl groups, and propyl groups; and hydroxyalkyl groups such as hydroxymethyl groups, hydroxyethyl groups, and hydroxypropyl groups. Examples include chlorine atoms, methyl groups, and hydroxymethyl groups.

[0073] Examples of phosphinic acid derivatives include phosphinic acid (H3O2P), alkylphosphinic acid (PHO(OH)R), and dialkylphosphinic acid (PO(OH)R2).

[0074] As the phosphine gas, at least one gas selected from the group consisting of PCH3Cl2 (dichloro(methyl)phosphine) gas, P(CH3)2Cl (chloro(dimethyl)phosphine) gas, P(HOCH2)Cl2 (dichloro(hydroxylmethyl)phosphine) gas, P(HOCH2)2Cl (chloro(dihydroxylmethyl)phosphine) gas, P(HOCH2)(CH3)2 (dimethyl(hydroxylmethyl)phosphine) gas, P(HOCH2)2(CH3) (methyl(dihydroxylmethyl)phosphine) gas, P(HOCH2)3 (tris(hydroxylmethyl)phosphine) gas, H3O2P (phosphinic acid) gas, PHO(OH)(CH3)(methylphosphine) gas, and PO(OH)(CH3)2 (dimethylphosphine) gas may be used.

[0075] The flow rate of phosphorus-containing gas included in the first processing gas may be 20% or less by volume, 10% or less by volume, and 5% or less by volume of the total flow rate excluding the inert gas.

[0076] The first processing gas may further contain a tungsten-containing gas. The tungsten-containing gas may be a gas containing tungsten and a halogen, for example, WF x Cl y The gas is a gas (where x and y are integers between 0 and 6, and the sum of x and y is between 2 and 6). Specifically, the tungsten-containing gas may be a gas containing tungsten and fluorine, such as tungsten difluoride (WF2) gas, tungsten tetrafluoride (WF4) gas, tungsten pentafluoride (WF5) gas, tungsten hexafluoride (WF6) gas, or a gas containing tungsten and chlorine, such as tungsten dichloride (WCl2) gas, tungsten tetrachloride (WCl4) gas, tungsten pentachloride (WCl5) gas, or tungsten hexachloride (WCl6) gas. Among these, at least one of WF6 gas and WCl6 gas may be used. The first treatment gas may contain a titanium-containing gas or a molybdenum-containing gas in place of or in addition to the tungsten-containing gas.

[0077] The first processing gas may further contain halogen-containing gases other than fluorine. The halogen-containing gases other than fluorine may be chlorine-containing gases, bromine-containing gases and / or iodine-containing gases. For example, the chlorine-containing gas may be at least one gas selected from the group consisting of Cl2, SiCl2, SiCl4, CCl4, SiH2Cl2, Si2Cl6, CHCl3, SO2Cl2, BCl3, PCl3, PCl5, and POCl3. For example, the bromine-containing gas may be at least one gas selected from the group consisting of Br2, HBr, CBr2F2, C2F5Br, PBr3, PBr5, POBr3, and BBr3. For example, the iodine-containing gas may be at least one gas selected from the group consisting of HI, CF3I, C2F5I, C3F7I, IF5, IF7, I2, and PI3. In one example, the halogen-containing gas other than fluorine may be at least one selected from the group consisting of Cl2 gas, Br2 gas, and HBr gas. In another example, the halogen-containing gas other than fluorine is either Cl2 gas or HBr gas.

[0078] The first processing gas may further contain an inert gas. The inert gas may be, for example, a noble gas such as Ar gas, He gas, or Kr gas, or nitrogen gas.

[0079] Furthermore, the first processing gas may contain a gas capable of generating hydrogen fluoride species (HF species) in the first plasma, instead of some or all of the HF gas. The HF species includes at least one of hydrogen fluoride gas, radicals, and ions.

[0080] Gases capable of producing HF species may be, for example, hydrofluorocarbon gases. Hydrofluorocarbon gases may have 2 or more carbon atoms, 3 or more, or 4 or more. Examples of hydrofluorocarbon gases include CH2F2 gas, C3H2F4 gas, C3H2F6 gas, C3H3F5 gas, C4H2F6 gas, C4H5F5 gas, C4H2F8 gas, C5H2F6 gas, and C5H2F 10It is at least one selected from the group consisting of gases and C5H3F7 gas. Hydrofluorocarbon gases, for example, are at least one selected from the group consisting of CH2F2 gas, C3H2F4 gas, C3H2F6 gas and C4H2F6 gas.

[0081] A gas capable of producing HF species may be, for example, a mixed gas containing a hydrogen source and a fluorine source. The hydrogen source may be at least one selected from the group consisting of, for example, H2 gas, NH3 gas, H2O gas, H2O2 gas, and hydrocarbon gases (CH4 gas, C3H6 gas, etc.). The fluorine source may be a fluorine-containing gas that does not contain carbon, such as NF3 gas, SF6 gas, WF6 gas, or XeF2 gas. Alternatively, the fluorine source may be a fluorine-containing gas that contains carbon, such as fluorocarbon gas and hydrofluorocarbon gas. The fluorocarbon gas may be at least one selected from the group consisting of, for example, CF4 gas, C2F2 gas, C2F4 gas, C3F6 gas, C3F8 gas, C4F6 gas, C4F8 gas, and C5F8 gas. The hydrofluorocarbon gas may be, for example, at least one selected from the group consisting of CHF3 gas, CH2F2 gas, CH3F gas, C2HF5 gas, and hydrofluorocarbon gases containing three or more C atoms (such as C3H2F4 gas, C3H2F6 gas, C4H2F6 gas, etc.).

[0082] (Process ST13: Second etching) The second etching step ST13 is performed following the first etching step ST12. That is, the second etching step ST13 is started before the recessed RC reaches the underlying film UF, or when a portion of the underlying film UF is exposed. The switch from step ST12 to step ST13 may be based on at least one of the depth of the recessed RC, the aspect ratio of the recessed RC, and the etching time.

[0083] First, a second processing gas is supplied from the gas supply unit 20 into the plasma processing space 10s. Similar to step ST12, a source RF signal is supplied to the lower electrode of the substrate support unit 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 unit 11, and a second plasma is generated from the second processing gas in the plasma processing space 10s. In addition, a bias signal is supplied to the lower electrode of the substrate support unit 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 these active species further etch the silicon-containing film SF. Step ST13 is performed until the underlying film UF is exposed, or until a part of the underlying film UF is etched in the depth direction. During the processing in step ST12, the temperature of the substrate support unit 11 may be maintained at the set temperature adjusted in step ST11, or it may be changed as described later.

[0084] Figure 5 shows an example of the cross-sectional structure of the substrate W after the ST13 process. As shown in Figure 5, in the substrate W after the ST13 process, the bottom of the recessed RC reaches the underlying film UF, and the underlying film UF is exposed. At this time, a part of the underlying film UF may be etched in the depth direction. The aspect ratio of the recessed RC in this state may be, for example, 20 or more, and may be 30 or more, 40 or more, 50 or more, or 100 or more.

[0085] In step ST13, the second processing gas may contain the same type of gas as the first processing gas, or it may contain a different type of gas. The second processing gas may, for example, contain HF gas. The second processing gas may further contain, for example, at least one selected from the group consisting of carbon-containing gases, oxygen-containing gases, and phosphorus-containing gases mentioned above. The second processing gas may further contain, for example, tungsten-containing gases, titanium-containing gases, and molybdenum-containing gases mentioned above, inert gases, and halogen-containing gases other than fluorine. The second processing gas may, like the first processing gas, contain a gas capable of generating HF species in the second plasma in place of some or all of the HF gas.

[0086] 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. Also in step ST13, the bias signal may be a bias RF signal supplied from the second RF generation unit 31b. The bias signal may also be a bias DC signal supplied from the DC generation unit 32a. Both the source RF signal and the bias signal may be continuous waves or pulsed waves, or one may be a continuous wave and the other a pulsed wave. If both the source RF signal and the bias signal are pulsed waves, the periods of both pulsed waves may be synchronized. The duty cycle of the pulsed wave may be set as appropriate, for example, 1 to 80%, or 5 to 50%. The duty cycle is the proportion of the period in the pulsed wave's cycle that is characterized by a high power or voltage level. When a bias DC signal is used, the pulsed wave may have a rectangular, trapezoidal, triangular, or a combination thereof waveform. The polarity of the bias DC signal may be negative or positive, as long as the potential of the substrate W is set to create a potential difference between the plasma and the substrate to attract ions. The source RF signal and / or bias RF signal may be supplied continuously from process ST12. Alternatively, the supply of the source RF signal and / or bias RF signal may be stopped at the end of process ST12 and restarted at the beginning of process ST13.

[0087] When starting process ST13, the etching conditions (recipe 2) are changed from the processing conditions (recipe 1) in process ST12. That is, in process ST13, the etching of the silicon-containing film SF is performed using a different recipe than in process ST12. Changing the recipe may include using a second processing gas different from the first processing gas, and / or performing temperature control to increase the temperature of the substrate W compared to process ST12. For example, the processing conditions (recipe 2) in step ST13 may be conditions that improve the selectivity ratio of the silicon-containing film SF to the undercoat film UF compared to the processing conditions (recipe 1) in step ST12. In this case, the processing conditions (recipe 2) in step ST13 may be selected according to the type of film of the undercoat film UF. For example, the processing conditions may differ depending on whether the undercoat film UF contains silicon or metal. Furthermore, changing the recipe may include reducing the process pressure (pressure inside the chamber during processing). That is, in step ST13, the pressure inside the plasma processing space 10s may be reduced compared to step ST12. For example, the pressure inside the plasma processing space 10s in step ST13 may be reduced by 30% or more compared to step ST12.

[0088] Figure 6 is an example of a timing chart when the undercoat UF contains silicon. Figure 6 shows the case where the composition of the processing gas differs between process ST12 and process ST13. In Figure 6, the horizontal axis represents time. The vertical axis represents the flow rates of HF gas, carbon-containing gas, and oxygen-containing gas contained in the processing gas (first processing gas or second processing gas), and the density of fluorine species in the plasma (first plasma or second plasma). "QL1," "QL2," and "QL3" indicate a flow rate that is smaller than or zero than "QH1," "QH2," and "QH3," respectively. Also, "DL" indicates a lower density of fluorine species in the plasma compared to "DH." Note that in Figure 5, "carbon-containing gas" refers to either or both fluorocarbon gas and hydrofluorocarbon gas (if both are present, it is the combined flow rate of both). Furthermore, "fluorine species" are active species of fluorine that have been separated from fluorine-containing gases in the processed gas (e.g., HF gas, fluorocarbon gas, hydrofluorocarbon gas, NF3 gas, or SF6 gas, etc.).

[0089] As shown in Figure 6, when the undercoat UF contains silicon, the flow rate (partial pressure) of HF gas may be reduced and the flow rates (partial pressure) of carbon-containing gas (fluorocarbon gas and / or hydrofluorocarbon gas) and oxygen-containing gas may be increased when switching from process ST12 to process ST13. In one example, when switching from process ST12 to process ST13, the processing gas (second processing gas) may contain carbon-containing gas and oxygen-containing gas at a rate of 50% or more by volume relative to the total flow rate of the second processing gas excluding the inert gas. Furthermore, the number of carbon atoms in the fluorocarbon gas and / or hydrofluorocarbon gas contained in the second processing gas may be 2 or more.

[0090] As etching progresses in step ST13, the underlying film UF is exposed. If the underlying film UF contains silicon, the fluorine species in the plasma also function as etchants for the underlying film UF. In the example timing chart shown in Figure 6, the density of fluorine species in the second plasma generated in step ST13 is lower than the density of fluorine species in the first plasma generated in step ST12. Therefore, etching of the underlying film UF is suppressed. In other words, the selectivity of etching the silicon-containing film SF against the underlying film UF can be improved.

[0091] Figure 7 shows another example of a timing chart when the undercoat UF contains silicon. Figure 7 shows an example of controlling the temperature of the substrate W to be higher in process ST13 compared to process ST12. In Figure 7, the horizontal axis represents time. The vertical axis represents the power of the source RF signal and / or bias signal (signal power), the DC voltage supplied to the electrostatic chuck 1111 (ESC voltage), the heat transfer gas (e.g., He) pressure between the electrostatic chuck 1111 and the back surface of the substrate W, the temperature of the heat transfer fluid flowing through the heater and channel 1110a (temperature control module temperature), and the temperature of the substrate W. In Figure 7, "WL" indicates that the signal power is lower than "WH". "VL" indicates that the ESC voltage is lower than "VH". "PL" indicates that the heat transfer gas pressure is lower than "PH". "TL1" and "TL2" indicate that the temperature is lower than "TH1" and "TH2", respectively.

[0092] As shown in Figure 7, if the undercoat UF contains silicon, the signal power of (I) the source RF signal and / or bias signal (bias RF signal or bias DC signal) may be increased when switching from process ST12 to process ST13. Increasing the signal power may include increasing the effective value of the signal power, increasing the signal supply time, and increasing the duty cycle of the signal. This increases the heat input to the substrate W, causing the temperature of the substrate W to rise.

[0093] As shown in Figure 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 decrease the suction 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 back surface of the substrate W may be reduced. Also, (IV) the temperature of the heater and the heat transfer fluid flowing through the channel 1110a may be increased. In any case, the temperature of the substrate W will rise. Note that one or more of the above temperature control methods (I) to (IV) may be combined. The difference between the temperature of the substrate W in process ST12 (TL2) and the temperature of the substrate W in process ST13 (TH2) may be, for example, 30°C or more. In one example, the temperature of the substrate W in process ST12 (TL2) may be -40°C and the temperature of the substrate W in process ST13 (TH2) may be 0°C.

[0094] As etching progresses in step ST13, the underlying film UF is exposed. In the example timing chart shown in Figure 7, the temperature of the substrate W is higher than in step ST12. Therefore, the amount of etchant (e.g., fluorine species in the plasma) adsorbed onto the underlying film UF decreases. This suppresses etching of the underlying film UF, and the selectivity of etching the silicon-containing film SF onto the underlying film UF may improve.

[0095] Furthermore, when switching from process ST12 to process ST13, both a change in the configuration of the processing gas (for example, Figure 6) and a control to increase the temperature of the substrate W (for example, Figure 7) may be performed.

[0096] Figure 8 is an example of a timing chart when the undercoat UF contains metal. Figure 8 is an example where the composition of the processing gas differs between process ST12 and process ST13. In Figure 8, the horizontal axis represents time. The vertical axis represents the flow rates of HF gas, carbon-containing gas, and NF3 / SF6 gas contained in the processing gas (first or second processing gas), and the density of fluorine species in the plasma (first or second plasma). "QH1" and "QH2" represent flow rates greater than 0, respectively. "QL4" indicates a flow rate less than or equal to "QH4". "DL" indicates a density of fluorine species in the plasma less than that of "DH". In Figure 8, "carbon-containing gas" refers to either or both fluorocarbon gas and hydrofluorocarbon gas (if both are present, the flow rate is the sum of both). "NF3 / SF6 gas" refers to either or both NF3 gas and SF6 gas (if both are present, the flow rate is the sum of both). NF3 gas and SF6 gas are examples of carbon-free fluorine sources that can be used in addition to HF gas, as described above.

[0097] As shown in Figure 8, if the undercoat UF contains metal, the flow rate (partial pressure) of NF3 gas and / or SF6 gas may be reduced when switching from process ST12 to process ST13. In addition, the flow rate (partial pressure) of HF gas may also be reduced.

[0098] As etching progresses in step ST13, the underlying film UF is exposed. If the underlying film UF contains metal, fluorine species in the plasma react with the metal, potentially etching the underlying film UF. In the example timing chart shown in Figure 8, the density of fluorine species in the second plasma generated in step ST13 is lower than the density of fluorine species in the first plasma generated in step ST12. Therefore, etching of the underlying film UF is suppressed. In other words, the selectivity of etching the silicon-containing film SF against the underlying film UF can be improved.

[0099] In step ST13, if the substrate film UF contains metal, further control may be performed to increase the temperature of the substrate W. The control to increase 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 Figure 7. This promotes the volatilization of by-products containing metal in the substrate film UF and suppresses the generation of residue containing the metal. In addition to or instead of this, a gas highly reactive with the metal in the substrate film UF may be added as a second processing gas. For example, if the substrate film UF contains tungsten, CO gas may be added as the second processing gas. The CO gas reacts with W scattered from the substrate film UF during step ST13 to produce volatile W(CO)6. This suppresses the generation of residue containing the metal (W) in the substrate film UF. In addition to or instead of CO gas, the second processing gas may include a chlorine-containing gas such as Cl2 gas, SiCl4 gas, or BCl3 gas.

[0100] According to the etching method of the first embodiment, in step ST13, etching of the silicon-containing film SF is performed under different processing conditions (recipe) than in step ST12. This makes it possible to select the optimal recipe according to the progress of etching, i.e., the depth of the recessed RC. For example, in areas where the depth of the recessed RC is shallow, a recipe that increases the etching rate of the silicon-containing film SF can be selected, and in areas where the recessed RC is deep and the underlying film UF is exposed, a recipe that increases the selectivity ratio for the underlying film UF can be selected.

[0101] <Second Embodiment> Figure 9 is a flowchart showing an etching method according to the second embodiment. As shown in Figure 9, the etching method includes a step ST21 of providing a substrate, a step ST22 of generating plasma, and an etching step ST23. The processing in each step may be performed using the plasma processing system shown in Figure 1. In the following, a case in which the control unit 2 controls each part of the plasma processing apparatus 1 to perform etching on the substrate W will be described as an example.

[0102] (Step ST21: Provision of substrate) In step ST21, the substrate W is provided into the plasma processing space 10s of the plasma processing apparatus 1. The substrate W is provided into the central region 111a of the substrate support portion 11. The substrate W is then held in the substrate support portion 11 by the electrostatic chuck 1111. The substrate W provided in step ST21 may have the same configuration as the substrate W described in the first embodiment (see Figure 3).

[0103] After the substrate W is placed in the central region 111a of the substrate support section 11, the temperature of the substrate support section 11 is adjusted to a set temperature by the temperature control module, similar to the first embodiment. The set temperature may be, for example, 20°C or lower, 0°C or lower, -10°C or lower, -20°C or lower, -30°C or lower, -40°C or lower, -50°C or lower, -60°C or lower, or -70°C or lower. The temperature of the substrate support section 11 may be adjusted to the set temperature before step ST21. Furthermore, during processing in steps ST22 and ST23, the temperature of the substrate support section 11 may be maintained at the set temperature adjusted in step ST21.

[0104] (Process ST22: Plasma generation) In step ST22, plasma is generated from the processing gas. First, the processing gas is supplied from the gas supply unit 20 into the plasma processing space 10s. The processing gas may have the same configuration as the first processing gas and / or second processing gas described in the first embodiment.

[0105] Next, a source RF signal is supplied to the lower electrode of the substrate support 11 and / or the upper electrode of the shower head 13. This generates a high-frequency electric field between the shower head 13 and the substrate support 11, and plasma is generated from the processing gas in the plasma processing space 10s.

[0106] Figure 10 shows the relationship between ion flux and ion energy. As shown in Figure 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 using source RF signals of 40 MHz (RF40), 60 MHz (RF60), and 100 MHz (RF100), the following relationship holds. Ion energy: RF40 > RF60 > RF100 Ion flux: RF40 <RF60<RF100

[0107] In step ST22, the frequency of the source RF signal is selected so that a high-density plasma is generated with low ion energy. Such frequencies may vary depending on the plasma generation method of the plasma processing apparatus. For example, if the plasma processing apparatus 1 supplies a source RF signal to the upper electrode and a bias signal to the lower electrode, the frequency of the source RF signal may be 40 MHz or higher. Alternatively, if the plasma processing apparatus 1 supplies both a source RF signal and a bias signal to the lower electrode, the frequency of the source RF signal supplied to the lower electrode of the substrate support section 11 may be 60 MHz or higher. The frequency of the source RF signal may also be 150 MHz or lower, or 100 MHz or lower.

[0108] Furthermore, a bias signal is supplied to the lower electrode of the substrate support 11. This generates 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. The bias signal may be a bias RF signal supplied from the second RF generation unit 31b. Alternatively, the bias signal may be a bias DC signal supplied from the DC generation unit 32a.

[0109] In step ST22, the source RF signal and the bias signal may both be continuous waves or pulsed waves, or one may be a continuous wave and the other a pulsed wave. If both the source RF signal and the bias signal are pulsed waves, the periods of both pulsed waves may be synchronized. The duty cycle of the pulsed waves may be set as appropriate, for example, 1 to 80% or 5 to 50%. The duty cycle is the proportion of the pulsed wave period in which the power or voltage level is high. When a bias DC signal is used, the pulsed wave may have a rectangular, trapezoidal, triangular, or a combination thereof waveform. The polarity of the bias DC signal may be negative or positive, as long as the potential of the substrate W is set to create a potential difference between the plasma and the substrate to attract ions.

[0110] Figure 11 is a timing chart showing an example of a source RF signal and a bias RF signal. Figure 11 is an example where both the source RF signal and the bias RF signal are pulse waves. The horizontal axis in Figure 11 represents time. In one example, the source RF signal has a frequency between 40 MHz and 100 MHz. The source RF signal is supplied to the lower electrode of the substrate support 11 and / or the upper electrode of the shower head 13 during a first period and a second period alternating with the first period. In Figure 11, the first level is a power level lower than the second level or 0W.

[0111] The bias RF signal is supplied to the lower electrode of the substrate support 11 during the third period and the fourth period, which alternates with the third period. In one example, the bias RF signal has a frequency between 400 kHz and 13.56 MHz. In Figure 11, the third level is a lower power level than the fourth level or is 0W. As shown in Figure 11, the second period and the fourth period may coincide (synchronize). Note that the second period and the fourth period do not have to overlap in part or in whole.

[0112] Figure 12 is a timing chart showing an example of a source RF signal and a bias DC signal. Figure 12 is an example where both the source RF signal and the bias DC signal are pulse waves. The horizontal axis in Figure 12 represents time. The source RF signal is the same as the example shown in Figure 11. The bias DC signal is supplied to the lower electrode of the substrate support 11 during the fifth period and the sixth period which alternates with the fifth period. In Figure 12, the absolute value of the fifth level is less than the absolute value of the sixth level or 0V. As shown in Figure 12, the second period and the sixth period may coincide (synchronize). Note that the second period and the sixth period do not have to overlap in part or in whole.

[0113] 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 generation unit 32b or a bias RF signal supplied from the second RF generation unit 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, causing secondary electrons to be emitted from the upper electrode. The emitted secondary electrons can modify the mask MF and improve its etching resistance. Furthermore, the irradiation of secondary electrons neutralizes the charge state of the substrate W, thereby increasing the straight-line propagation of ions into the recesses of the silicon-containing film SF formed by etching. In addition, if the upper electrode is made of a silicon-containing material, silicon is emitted from the upper electrode along with the secondary electrons due to the collision of positive ions. The emitted silicon can combine with oxygen in the plasma and be deposited on the mask MF as a silicon oxide compound, functioning as a protective film. As described above, supplying a second bias signal to the upper electrode can produce effects such as improved selectivity, suppression of etching shape abnormalities, and improved etching rate.

[0114] (Process ST23: Etching) In step ST23, the silicon-containing film SF is etched by the plasma generated in the plasma processing space 10s, and a recess is formed based on the shape of the opening OP of the mask MF. Etching is terminated when the depth of the recess formed by etching reaches a given depth, or when the etching time reaches a given time.

[0115] In the etching method according to the second embodiment, the frequency of the source RF signal is set to 40 MHz or higher in step ST22. When the frequency of the source RF signal is 40 MHz or higher, even if the power of the source RF signal and / or bias signal is increased to increase the electron density of the plasma, the increase in ion energy is suppressed. That is, by setting the frequency of the source RF signal to 40 MHz or higher, the electron density of the generated plasma can be controlled independently of the ion energy. Therefore, in step ST22, it is possible to generate a higher density plasma compared to the case where the frequency is lower than 40 MHz, while suppressing the increase in the ion energy of the plasma. As a result, in etching in step ST23, the density of the etchant (HF type) increases, and the adsorption of the etchant (HF type) can be promoted by suppressing the heat input to the substrate W. In addition, by suppressing the increase in ion energy, damage to the mask MF can also be reduced. As described above, according to the etching method of the second embodiment, the etching rate of the silicon-containing film SF can be improved, and the selectivity ratio of the silicon-containing film SF to the mask MF can be improved.

[0116] The embodiments described above are for illustrative purposes only and are not intended to limit the scope of this disclosure. The embodiments can be modified in various ways without departing from the scope and spirit of this 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. Furthermore, for example, the etching methods according to each embodiment may be carried out using a plasma processing apparatus with any plasma source other than the capacitively coupled plasma processing apparatus 1, such as an inductively coupled plasma or microwave plasma.

[0117] Embodiments of this disclosure further include the following embodiments:

[0118] (Note 1) An etching method performed in a plasma processing apparatus having a chamber, (a) A step of providing a substrate having a base film and a silicon-containing film on the base film into a chamber, (b) A step of etching the silicon-containing film using a first plasma generated from a first processing gas containing hydrogen fluoride gas to form a recess, wherein the etching is carried out until the underlying film is exposed in the recess or until a part of the underlying film is exposed in the recess, (c) An etching method comprising the step of further etching the silicon-containing film in the recess under conditions different from those of the step in (b).

[0119] (Note 2) The etching method according to Appendix 1, wherein in step (c) above, a second plasma is generated using a second processing gas different from the first processing gas.

[0120] (Note 3) The etching method described in Appendix 2, wherein the second plasma has a lower density of fluorine species than the first plasma.

[0121] (Note 4) The etching method according to Appendix 2 or Appendix 3, wherein the undercoat contains silicon, and the second processing gas contains 50% or more by volume of fluorocarbon gas or hydrofluorocarbon gas and oxygen-containing gas relative to the total flow rate of the second processing gas excluding the inert gas.

[0122] (Note 5) The etching method according to Appendix 4, wherein the fluorocarbon gas or hydrofluorocarbon gas contained in the second processing gas has two or more carbon atoms.

[0123] (Note 6) The etching method according to Appendix 2 or Appendix 3, wherein the undercoat contains a metal, the first processing gas further contains a fluorine-containing gas other than hydrogen fluoride, and the second processing gas either does not contain the fluorine-containing gas or contains the fluorine-containing gas at a partial pressure lower than the partial pressure in the first processing gas.

[0124] (Note 7) The etching method according to Appendix 6, wherein the fluorine-containing gas is at least one of NF3 gas and SF6 gas.

[0125] (Note 8) The etching method according to Appendix 6 or Appendix 7, wherein the second processing gas further comprises at least one of CO gas and a chlorine-containing gas.

[0126] (Note 9) The etching method according to any one of the appendices 1 to 8, wherein in step (c), temperature control is performed so that the temperature of the substrate becomes higher than the temperature of the substrate in step (b).

[0127] (Note 10) The etching method according to Appendix 9, wherein the temperature control includes one or more of the following: (I) increasing the power of the source RF signal or bias signal supplied to the chamber; (II) decreasing the suction force of the substrate support portion that supports the substrate; (III) decreasing the pressure of the heat transfer gas supplied between the substrate and the substrate support portion; and (IV) raising the set temperature of the substrate support portion to a higher temperature than the set temperature in step (b).

[0128] (Note 11) The etching method according to Appendix 9 or Appendix 10, wherein the temperature control includes controlling the temperature of the substrate to be 30°C or higher than the temperature of the substrate in step (b).

[0129] (Note 12) The etching method according to any one of the appendices 1 to 11, wherein in step (c), pressure control is performed so that the pressure in the chamber is lower than the pressure in the chamber in step (b).

[0130] (Note 13) The etching method according to Appendix 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 step (b).

[0131] (Note 14) The etching method according to any one of the appendices 1 to 13, wherein the first processing gas further comprises a phosphorus-containing gas.

[0132] (Note 15) The etching method according to any one of the appendices 1 to 14, wherein the first processing gas comprises at least one of a carbon-containing gas and an oxygen-containing gas.

[0133] (Note 16) The etching method according to any one of Appendix 1 to Appendix 15, wherein in step (b) above, the temperature of the substrate support portion supporting the substrate is controlled to 20°C or less.

[0134] (Note 17) The etching method according to any one of Appendix 1 to Appendix 16, wherein the source RF signal supplied to the chamber has a frequency of 40 MHz or higher.

[0135] (Note 18) An etching method performed in a plasma processing apparatus having a chamber, (a) A step of providing a substrate having a base film and a silicon-containing film on the base film into a chamber, (b) A step of etching the silicon-containing film using a plasma containing HF species to form a recess, wherein the etching is carried out until the underlying film is exposed in the recess or until a part of the underlying film is exposed in the recess, (c) An etching method comprising the step of further etching the silicon-containing film in the recess under conditions different from those of the step in (b).

[0136] (Note 19) The etching method according to Appendix 18, wherein the HF species is generated from at least one gas, such as hydrogen fluoride gas or hydrofluorocarbon gas.

[0137] (Note 20) The etching method described in Appendix 18 or Appendix 19, wherein the HF species is produced from a hydrofluorocarbon gas having two or more carbon atoms.

[0138] (Note 21) The etching method described in Appendix 18, wherein the aforementioned HF species is produced from a mixed gas containing a hydrogen source and a fluorine source.

[0139] (Note 22) A plasma processing apparatus comprising a chamber and a control unit, The control unit, (a) Control to provide a substrate having a base film and a silicon-containing film on the base film to the chamber, (b) A control for etching the silicon-containing film to form a recess using a first plasma generated from a first processing gas containing hydrogen fluoride gas, wherein the etching is performed until the underlying film is exposed in the recess or until a part of the underlying film is exposed in the recess, (c) A plasma processing system that performs control to further etch the silicon-containing film in the recess under conditions different from those of the control in (b).

[0140] (Note 23) A device manufacturing method performed in a plasma processing apparatus having a chamber, (a) A step of providing a substrate having a base film and a silicon-containing film on the base film into a chamber, (b) A step of etching the silicon-containing film using a first plasma generated from a first processing gas containing hydrogen fluoride gas to form a recess, wherein the etching is carried out until the underlying film is exposed in the recess or until a part of the underlying film is exposed in the recess, (c) A device manufacturing method comprising the step of further etching the silicon-containing film in the recess under conditions different from those of the step in (b).

[0141] (Note 24) A computer in a plasma processing system comprising a plasma processing apparatus having a chamber and a control unit, (a) Control to provide a substrate having a base film and a silicon-containing film on the base film to the chamber, (b) A control for etching the silicon-containing film to form a recess using a first plasma generated from a first processing gas containing hydrogen fluoride gas, wherein the etching is performed until the underlying film is exposed in the recess or until a part of the underlying film is exposed in the recess, (c) A program that causes the program to execute a control that further etches the silicon-containing film in the recess under conditions different from the control described in (b).

[0142] (Note 25) A storage medium containing the program described in Appendix 2.

[0143] (Note 26) An etching method performed in a plasma processing apparatus having a chamber, (a) A step of providing a substrate having a silicon-containing film into a chamber, (b) A step of supplying a processing gas containing hydrogen fluoride gas into the chamber and supplying an RF signal having a frequency of 40 MHz or higher to the chamber to generate plasma from the processing gas, (c) An etching method comprising the step of etching the silicon-containing film using the plasma.

[0144] (Note 27) An etching method performed in a plasma processing apparatus having a chamber, (a) A step of providing a substrate having a silicon-containing film into a chamber, (b) A step of supplying a processing gas into the chamber and supplying an RF signal having a frequency of 40 MHz or higher to the chamber to generate a plasma containing HF species from the processing gas, (c) An etching method comprising the step of etching the silicon-containing film using the plasma.

[0145] (Note 28) A plasma processing apparatus having a chamber and a control unit are provided, The control unit, (a) Control for providing a substrate having a silicon-containing film into the chamber, (b) A control system that supplies a processing gas containing hydrogen fluoride gas into the chamber and supplies an RF signal having a frequency of 40 MHz or higher to the chamber to generate plasma from the processing gas, (c) A plasma processing system that performs control for etching the silicon-containing film using the plasma.

[0146] (Note 29) A device manufacturing method performed in a plasma processing apparatus having a chamber, (a) A step of providing a substrate having a silicon-containing film into a chamber, (b) A step of supplying a processing gas containing hydrogen fluoride gas into the chamber and supplying an RF signal having a frequency of 40 MHz or higher to the chamber to generate plasma from the processing gas, (c) A device manufacturing method comprising the step of etching the silicon-containing film using the plasma.

[0147] (Note 30) A computer in a plasma processing system comprising a plasma processing apparatus having a chamber and a control unit, (a) Control for providing a substrate having a silicon-containing film into the chamber, (b) A control system that supplies a processing gas containing hydrogen fluoride gas into the chamber and supplies an RF signal having a frequency of 40 MHz or higher to the chamber to generate plasma from the processing gas, (c) A program that controls the etching of the silicon-containing film using the plasma and performs the following actions.

[0148] (Note 31) A storage medium containing the program described in Appendix 30. [Explanation of Symbols]

[0149] 1...Plasma processing apparatus, 2...Control unit, 10...Plasma processing chamber, 10s...Plasma processing space, 11...Substrate support unit, 13...Shower head, 20...Gas supply unit, 31a...First RF generation unit, 31b...Second RF generation unit, 32a...First DC generation unit, SF...Silicon-containing film, MF...Mask, OP...Opening, RC...Recess, UF...Undercoat, W...Substrate

Claims

1. Chamber and, A substrate support portion arranged within the chamber, A gas supply unit that supplies processing gas into the chamber, A plasma generation unit that generates plasma from the aforementioned processing gas, Control unit and Equipped with, The control unit uses the gas supply unit and the plasma generation unit, (a) To provide a substrate having a base film and a silicon-containing film on the base film in a chamber, (b) A first processing gas containing hydrogen fluoride gas is supplied as the processing gas, and the silicon-containing film is etched by a first plasma generated from the processing gas, (c) Further etching the silicon-containing film under conditions different from those in (b), A plasma processing system configured to perform a process that includes the following.

2. The plasma processing system according to claim 1, wherein in (c) above, a second plasma is generated using a second processing gas different from the first processing gas.

3. The plasma processing system according to claim 2, wherein the second plasma has a lower density of fluorine species than the first plasma.

4. The plasma treatment system according to claim 2, wherein the undercoat contains silicon, and the second treatment gas contains 50% by volume or more of fluorocarbon gas or hydrofluorocarbon gas and oxygen-containing gas relative to the total flow rate of the second treatment gas excluding the inert gas.

5. The plasma processing system according to claim 4, wherein the fluorocarbon gas or hydrofluorocarbon gas contained in the second processing gas has two or more carbon atoms.

6. The plasma treatment system according to claim 2, wherein the undercoat contains a metal, the first treatment gas further contains a fluorine-containing gas other than hydrogen fluoride, and the second treatment gas either does not contain the fluorine-containing gas or contains the fluorine-containing gas at a partial pressure lower than the partial pressure in the first treatment gas.

7. The aforementioned fluorine-containing gas is NF 3 Gas and SF 6 The plasma processing system according to claim 6, wherein the plasma processing system is at least one of the gases.

8. The plasma processing system according to claim 6, wherein the second processing gas further comprises at least one of CO gas and a chlorine-containing gas.

9. The plasma processing system according to claim 1, wherein in (c), the temperature is controlled so that the temperature of the substrate is higher than the temperature of the substrate in (b).

10. The plasma processing system according to claim 9, wherein the temperature control includes one or more of the following: (I) increasing the power of the source RF signal or bias signal supplied to the chamber; (II) decreasing the suction force of the substrate support portion that supports the substrate; (III) decreasing the pressure of the heat transfer gas supplied between the substrate and the substrate support portion; and (IV) raising the set temperature of the substrate support portion to a higher temperature than the set temperature in (b).

11. The plasma processing system according to claim 9, 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 (b).

12. The plasma processing system according to claim 1, wherein in (c), pressure control is performed so that the pressure in the chamber is lower than the pressure in the chamber in (b).

13. The plasma processing system according to claim 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 (b).

14. The plasma processing system according to claim 1, wherein the first processing gas further comprises a phosphorus-containing gas.

15. The plasma processing system according to claim 1, wherein the first processing gas comprises at least one of a carbon-containing gas and an oxygen-containing gas.

16. The plasma treatment system according to claim 1, wherein the first treatment gas further comprises a halogen-containing gas other than fluorine.

17. The plasma processing system according to claim 1, wherein the first processing gas further comprises at least one selected from the group consisting of tungsten-containing gas, titanium-containing gas, and molybdenum-containing gas.

18. The plasma processing system according to claim 1, wherein, in (b) above, the temperature of the substrate support portion supporting the substrate is controlled to 20°C or less.

19. The plasma processing system according to claim 1, wherein the source RF signal supplied to the chamber has a frequency of 40 MHz or higher.

20. Chamber and, A substrate support portion arranged within the chamber, A gas supply unit that supplies processing gas into the chamber, A plasma generation unit that generates plasma from the aforementioned processing gas, Control unit and Equipped with, The control unit, with the gas supply unit and the plasma generation unit, (a) Providing a substrate having a base film and a silicon-containing film on the base film in a chamber, (b) Generating a plasma containing HF species from the processing gas, (c) Etching the silicon-containing film with HF species in the plasma, (d) Further etching the silicon-containing film under conditions different from those in (c), A plasma processing system configured to perform a process that includes the following.

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