Plasma processing method and plasma processing system

Abstract

This invention provides a technique for improving etching rate. The invention provides a plasma processing method performed in a plasma processing apparatus having a chamber. The method includes the following steps: (a) providing a substrate having an etch target film including a silicon oxide film and a silicon nitride film, and a masking film defining an opening on the etch target film onto a substrate support portion within the chamber; (b) generating plasma from a first processing gas containing HF gas, CxFy gas (x and y are integers of 1 or more) or CsHtFu gas (s, t, and u are integers of 1 or more), and oxygen-containing gas to etch the silicon nitride film; and (c) generating plasma from a second processing gas containing HF gas, CvFw gas (v and w are integers of 1 or more), and oxygen-containing gas to etch the silicon oxide film; and in (b) and (c), setting the temperature of the substrate support portion to 0°C or below.

Description

Technical Field

[0001] The exemplary embodiments of the present invention relate to a plasma treatment method and a plasma treatment system. Prior Technology

[0002] Patent document 1 discloses a method for etching a substrate on which a silicon oxide film, a silicon nitride film and a polycrystalline silicon mask are formed. [Previous Technical Documents] [Patent Literature]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2016-21546 Summary of the Invention

[0004] [The problem the invention aims to solve]

[0005] This invention provides a technique for improving etching rate. [Technical means to solve the problem]

[0006] In one exemplary embodiment of the present invention, a plasma processing method is provided, which is a plasma processing method performed in a plasma processing apparatus having a chamber, and includes the following steps: (a) providing a substrate having an etch target film including a silicon oxide film and a silicon nitride film, and a masking film defining an opening on the etch target film onto a substrate support portion in the chamber; (b) generating plasma from a first processing gas containing HF gas, CxFy gas (x and y are integers of 1 or more) or CsHtFu gas (s, t, and u are integers of 1 or more), and oxygen-containing gas to etch the silicon nitride film; and (c) generating plasma from a second processing gas containing HF gas, CvFw gas (v and w are integers of 1 or more), and oxygen-containing gas to etch the silicon oxide film; and in the above (b) and (c), the temperature of the substrate support portion is set to 0°C or below. [Effects of the Invention]

[0007] According to one exemplary embodiment of the present invention, the etching rate can be increased. Simple Explanation of the Diagram

[0008] Figure 1 is a schematic diagram illustrating an exemplary plasma processing system. Figure 2 is a flowchart illustrating one example of this processing method. Figure 3 shows an example of the cross-sectional structure of substrate W. Figure 4 shows an example of the cross-sectional structure of the substrate W after step ST32. Figure 5 shows an example of the cross-sectional structure of the substrate W after step ST34. Figure 6 shows the etching results of Examples 5 to 7. Figure 7 shows the etching results of Example 8. Figure 8 is a diagram showing the etching results of Example 9. Implementation

[0009] The various embodiments of the present invention will be described below.

[0010] In one exemplary embodiment, a plasma processing method is provided, which is performed in a plasma processing apparatus having a chamber, and includes the following steps: (a) providing a substrate having an etch target film including a silicon oxide film and a silicon nitride film, and a masking film defining an opening on the etch target film onto a substrate support portion within the chamber; (b) generating plasma from a first processing gas containing HF gas, CxFy gas (x and y are integers of 1 or more) or CsHtFu gas (s, t, and u are integers of 1 or more), and oxygen-containing gas to etch the silicon nitride film; and (c) generating plasma from a second processing gas containing HF gas, CvFw gas (v and w are integers of 1 or more), and oxygen-containing gas to etch the silicon oxide film; and in (b) and (c), setting the temperature of the substrate support portion to 0°C or below.

[0011] In one exemplary embodiment, the first processing gas contains a gas of a different type than the second processing gas.

[0012] In one exemplary embodiment, the first processing gas comprises CsHtFu gas.

[0013] In one exemplary embodiment, the first processing gas includes CxFy gas, which is a gas different from the CvFw gas included in the second processing gas.

[0014] In one exemplary embodiment, in (b), the temperature of the substrate support portion is set to a first temperature, and in (c), the temperature of the substrate support portion is set to a second temperature that is lower than the first temperature.

[0015] In one exemplary embodiment, in (b), a first output bias signal is supplied to the substrate support portion, and in (c), a second output bias signal smaller than the first output is supplied to the substrate support portion, or no bias signal is supplied to the substrate support portion.

[0016] In one exemplary embodiment, in (b), a pulse wave of a bias signal with a first duty cycle is supplied to the substrate support portion, and in (c), a pulse wave of a bias signal with a second duty cycle smaller than the first duty cycle is supplied to the substrate support portion.

[0017] In one exemplary embodiment, the bias signal is a bias DC (direct current) signal.

[0018] In one exemplary embodiment, in (b), a first frequency bias RF signal is supplied to the substrate support portion, and in (c), a second frequency bias RF signal lower than the first frequency is supplied to the substrate support portion.

[0019] In one exemplary embodiment, in (b), a heat transfer gas at a first pressure is supplied between the substrate and the substrate support, and in (c), a heat transfer gas at a second pressure lower than the first pressure is supplied between the substrate and the substrate support.

[0020] In one exemplary embodiment, in (b), the temperature of the heat transfer fluid supplied to the substrate support is set to a third temperature, and in (c), the temperature of the heat transfer fluid supplied to the substrate support is set to a fourth temperature that is lower than the third temperature.

[0021] In one exemplary embodiment, the masking film is a polycrystalline silicon film, a boron-doped silicon film, a tungsten-containing film, an amorphous carbon film, a tin oxide film, or a titanium-containing film.

[0022] In one exemplary embodiment, the opening width of the masking film is less than 50 nm.

[0023] In one exemplary embodiment, the C xF y gas or C vF w gas includes at least one gas selected from the group consisting of C 2F 2 gas, C 2F 4 gas, C 3F 6 gas, C 3F 8 gas, C 4F 6 gas, C 4F 8 gas and C 5F 8 gas.

[0024] In one exemplary embodiment, the CsHtFu gas comprises at least one gas selected from the group consisting of CHF3 gas, CH2F gas, CH3F gas, C2HF gas, C2HF4 gas, C2HF3 gas, C2HF2 gas, C3HF gas, C3HF2 gas, C3HF4 gas, C3HF6 gas, C3HF5 gas, C4HF6 gas, C4HF5 gas, C4HF5 gas, C4HF8 gas, C5HF6 gas, C5HF10 gas, and C5HF7 gas.

[0025] In one exemplary embodiment, HF gas has the highest flow rate among the first and second processing gases.

[0026] In one exemplary embodiment, at least one of the first processing gas and the second processing gas further comprises a phosphorus-containing gas.

[0027] In one exemplary embodiment, at least one of the first processing gas and the second processing gas further comprises WF 6 gas.

[0028] In one exemplary embodiment, in (b) and (c), the temperature of the substrate support portion is set to below -50°C.

[0029] In one exemplary embodiment, a plasma processing method is provided, which is performed in a plasma processing apparatus having a chamber, and includes the following steps: (a) providing a substrate having an etch target film including a silicon oxide film and a silicon nitride film, and a masking film defining an opening on the etch target film onto a substrate support portion within the chamber; (b) generating a first plasma from a first processing gas, and etching the silicon nitride film by means of HF, CxFy (x and y are integers of 1 or more) or CsHtFu (s, t, and u are integers of 1 or more) and oxygen-active species contained in the first plasma; (c) generating a second plasma from a second processing gas, and etching the silicon oxide film by means of HF, CvFw (v and w are integers of 1 or more) and oxygen-active species contained in the second plasma; and in (b) and (c), setting the temperature of the substrate support portion to 0°C or below.

[0030] In one exemplary embodiment, the HF strain is generated from at least one gas selected from the group consisting of CH₂F₂, C₃H₂F₄, and C₄H₂F₆.

[0031] In one exemplary embodiment, a plasma processing system is provided, comprising a chamber, a substrate support disposed within the chamber, a plasma generation unit, and a control unit. The control unit performs the following control: (a) providing a substrate having an etch target film comprising a silicon oxide film and a silicon nitride film, and a masking film defining an opening on the etch target film onto the substrate support unit; (b) generating plasma from a first processing gas comprising HF gas, CxFy gas (x and y are integers of 1 or more) or CsHtFu gas (s, t, and u are integers of 1 or more), and an oxygen-containing gas using power supplied from the plasma generation unit, and etching the silicon nitride film; (c) generating plasma from a first processing gas comprising HF gas, CvFy gas, and an oxygen-containing gas using power supplied from the plasma generation unit. A plasma is generated by a second processing gas containing oxygen gas (where v and w are integers greater than or equal to 1) to etch the silicon oxide film; in (b) and (c), the temperature of the substrate support portion is set to below 0°C.

[0032] Hereinafter, various embodiments of the present invention will be described in detail with reference to the drawings. Furthermore, the same or identical elements in each drawing will be labeled with the same symbol, and repeated descriptions will be omitted. Unless otherwise specified, positional relationships such as up, down, left, and right will be described based on the positional relationships shown in the drawings. The scale ratios in the drawings do not represent actual ratios, and actual ratios are not limited to the ratios shown in the drawings.

[0033] <Example of Plasma Processing System Configuration> The following describes an example of the configuration of a plasma treatment system. Figure 1 is a diagram illustrating an example of the configuration of a capacitively coupled plasma treatment device.

[0034] 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. Furthermore, the plasma processing apparatus 1 includes a substrate support unit 11 and a gas inlet unit. The gas inlet unit is configured to introduce at least one processing gas into the plasma processing chamber 10. The gas inlet unit includes a cluster nozzle 13. The substrate support unit 11 is disposed within the plasma processing chamber 10. The cluster nozzle 13 is disposed above the substrate support unit 11. In one embodiment, the cluster nozzle 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 cluster nozzle 13, the sidewall 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 cluster head 13 and the substrate support portion 11 are electrically insulated from the housing of the plasma processing chamber 10.

[0035] The substrate support portion 11 includes a body portion 111 and a ring assembly 112. The 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 a substrate W. The annular region 111b of the body portion 111 surrounds the central region 111a of the body portion 111 when viewed from above. The substrate W is disposed on the central region 111a of the body portion 111, and the ring assembly 112 is disposed on the annular region 111b of the body portion 111 in such a way that it surrounds the substrate W on the central region 111a of the body portion 111. Therefore, the central region 111a is also referred to as the substrate support surface for supporting the substrate W, and the annular region 111b is also referred to as the annular support surface for supporting the edge ring assembly 112.

[0036] In one embodiment, the body portion 111 includes a base 1110 and an electrostatic chuck 1111. The base 1110 includes a conductive member. The conductive member of the base 1110 functions as a lower electrode. The electrostatic chuck 1111 is disposed on the base 1110. The electrostatic chuck 1111 includes a ceramic member 1111a and an electrostatic electrode 1111b disposed within the ceramic member 1111a. The ceramic member 1111a has a central region 111a. In one embodiment, the ceramic member 1111a also has an annular region 111b. Furthermore, 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 disposed on the annular electrostatic chuck or the annular insulating member, or on both the electrostatic chuck 1111 and the annular insulating member. Furthermore, RF or DC electrodes can also be disposed within the ceramic component 1111a, in which case the RF or DC electrodes function as lower electrodes. When a bias RF signal or DC signal is connected to the RF or DC electrodes as described below, the RF or DC electrodes are also referred to as bias electrodes. Moreover, the conductive component of the base 1110 and the RF or DC electrodes can also function as two lower electrodes.

[0037] The ring assembly 112 includes one or more annular members. In one embodiment, the one or more annular members include one or more edge rings and at least one cover ring. The edge rings are formed of a conductive or insulating material, and the cover rings are formed of an insulating material.

[0038] Furthermore, the substrate support portion 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 also 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 disposed within the ceramic component 1111a of the electrostatic chuck 1111. Additionally, the substrate support portion 11 may also include a heat transfer gas supply portion configured to supply heat transfer gas between the back surface of the substrate W and the central region 111a.

[0039] The cluster injector 13 is configured to introduce at least one processing gas from the gas supply unit 20 into the plasma processing space 10s. The cluster injector 13 has at least one gas supply port 13a, at least one gas diffusion chamber 13b, and a plurality of gas inlets 13c. The processing gas supplied to the gas supply port 13a is introduced into the plasma processing space 10s through the gas diffusion chamber 13b and the plurality of gas inlets 13c. Furthermore, the cluster injector 13 includes an upper electrode. Moreover, in addition to the cluster injector 13, the gas inlet unit may also include one or more side gas injectors (SGIs) installed in one or more openings formed on the sidewall 10a.

[0040] The gas supply unit 20 may also include at least one gas source 21 and at least one flow controller 22. In one embodiment, the gas supply unit 20 is configured to supply at least one process gas from corresponding gas sources 21 to the nozzle 13 via corresponding flow controllers 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 also include one or more flow modulation elements for modulating or pulsed flow of at least one process gas.

[0041] 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), such as a source RF signal and a bias RF signal, to at least one lower electrode and / or at least one upper electrode. This allows plasma to be formed from at least one processing gas supplied to the plasma processing space 10s. Therefore, 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. Furthermore, by supplying a bias RF signal to at least one lower electrode, a bias potential is generated on the substrate W, allowing the ionic components of the formed plasma to be fed into the substrate W.

[0042] 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 configured to be coupled to at least one lower electrode and / or at least one upper electrode via at least one impedance matching circuit, and generates a source RF signal (source RF power) for plasma generation. In one embodiment, the source RF signal has a frequency in the range of 10 MHz to 150 MHz. In one embodiment, the first RF generating unit 31a may also be configured to generate a plurality of source RF signals with different frequencies. The generated one or more source RF signals are supplied to at least one lower electrode and / or at least one upper electrode.

[0043] The second RF generation unit 31b is configured to be coupled to at least one lower electrode via at least one impedance matching circuit, and generates 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 also be configured to generate a plurality of bias RF signals with different frequencies. One or more bias RF signals generated are supplied to at least one lower electrode. Furthermore, in various embodiments, at least one of the source RF signal and the bias RF signal may be pulsed.

[0044] Furthermore, 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 generating unit 32a and a second DC generating unit 32b. In one embodiment, the first DC generating unit 32a is configured to be connected to at least one lower electrode and generates a first DC signal. The generated first bias DC signal is applied to at least one lower electrode. In one embodiment, the second DC generating unit 32b is configured to be connected to at least one upper electrode and generates a second DC signal. The generated second DC signal is applied to at least one upper electrode.

[0045] In various embodiments, at least one of the first and second DC signals can be pulsed. In this case, a sequence of DC-based voltage pulses is applied to at least one lower electrode and / or at least one upper electrode. The voltage pulses can also have rectangular, trapezoidal, triangular, or combinations thereof pulse waveforms. In one embodiment, a waveform generation unit for generating a sequence of voltage pulses from the DC signal is connected between the first DC generation unit 32a and at least one lower electrode. Therefore, 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 can be positive or negative. Furthermore, the sequence of voltage pulses can also include one or more positive voltage pulses and one or more negative voltage pulses within one cycle. Furthermore, the first and second DC generating units 32a and 32b can be installed separately from the RF power supply 31, or the first DC generating unit 32a can replace the second RF generating unit 31b.

[0046] The exhaust system 40 may be connected, for example, to a gas outlet 10e located at the bottom of the plasma processing chamber 10. The exhaust system 40 may also include a pressure regulating valve and a vacuum pump. The pressure within the plasma processing space 10s is adjusted by the pressure regulating valve. The vacuum pump may also include a turbomolecular pump, a dry vacuum pump, or a combination thereof.

[0047] The control unit 2 processes commands that can be executed by a computer to enable the plasma processing apparatus 1 to perform the various steps described herein. The control unit 2 may be configured to control various elements of the plasma processing apparatus 1 to perform the various steps described herein. In one embodiment, part or all of the control unit 2 may also be included in the plasma processing apparatus 1. The control unit 2 may, for example, include a computer 2a. The computer 2a may also include, for example, a processing unit (CPU: Central Processing Unit) 2a1, a memory unit 2a2, and a communication interface 2a3. The processing unit 2a1 may be configured to perform various control actions by reading a program from the memory unit 2a2 and executing the read program. The program may be pre-stored in the memory unit 2a2 and may also be retrieved via a media when needed. The retrieved program is stored in the memory unit 2a2 and is read from the memory unit 2a2 and executed by the processing unit 2a1. The media can be any memory medium that the computer 2a can read, or it can be a communication line connected to the communication interface 2a3. The memory unit 2a2 can also include RAM (Random Access Memory), ROM (Read Only Memory), HDD (Hard Disk Drive), SSD (Solid State Drive), or combinations thereof. The communication interface 2a3 can also communicate with the plasma processing device 1 via a communication line such as LAN (Local Area Network).

[0048] <An example of a plasma treatment method> Figure 2 is a flowchart illustrating an exemplary embodiment of a plasma processing method (hereinafter also referred to as "this processing method"). As shown in Figure 2, this processing method includes a step ST1 of providing a substrate, a step ST2 of setting the temperature of the substrate support, and a step ST3 of etching the etching target film on the substrate. The processing in each step can be performed in the plasma processing system shown in Figure 1. Hereinafter, the method will be described using the control unit 2 controlling each part of the plasma processing apparatus 1 to perform this processing method on the substrate W as an example.

[0049] (Step ST1: Substrate Provision) In step ST1, the substrate W is provided to the plasma processing space of the plasma processing apparatus 1 for 10 seconds. The substrate W is disposed on the upper surface of the substrate support portion 11 in a manner facing the upper electrode, and is held in the substrate support portion 11 by an electrostatic chuck 1111.

[0050] Figure 3 is a diagram showing an example of the cross-sectional structure of the substrate W provided in step ST1. The substrate W has an etch target film EF and a mask film MF sequentially formed on the base film UF. The substrate W can be, for example, a substrate used to manufacture DRAM (Dynamic Random Access Memory).

[0051] The substrate UF can be, for example, a silicon wafer or an organic film, dielectric film, metal film, semiconductor film, etc., formed on a silicon wafer. The substrate UF can be composed of multiple layers.

[0052] The etched film EF may include, for example, a silicon oxide film (SiO₂ x film) EF₂ and a silicon nitride film EF₁ formed on the silicon oxide film EF₂. The etched film EF is a stacked film comprising the film etched by this process.

[0053] The substrate UF and / or the etched object film EF can be formed by CVD (chemical vapor deposition), spin coating, etc. The substrate UF and / or the etched object film EF can be flat films or films with irregularities.

[0054] A masking film MF is formed on the etched object film EF. The masking film MF defines at least one opening OP on the etched object film EF. The opening OP is a space on the etched object film EF and is surrounded by the sidewalls of the masking film MF. That is, in Figure 3, the upper surface of the etched object film EF has an area covered by the masking film MF and an area exposed at the bottom of the opening OP.

[0055] The openings OP, viewed from above on the substrate W (i.e., from above in Figure 3), can have any shape. These shapes can be, for example, circles, ellipses, rectangles, lines, or combinations of one or more of these. The masking film MF has a plurality of sidewalls, which can also define a plurality of openings OP. Each of the openings OP has a line shape and can be arranged at fixed intervals to form a pattern of lines and gaps. Furthermore, each of the openings OP has a hole shape and can also form an array pattern.

[0056] The opening width of the OP can be less than 50 nm. Alternatively, the opening width can be less than 30 nm. Or, the opening width can be more than 15 nm but less than 25 nm.

[0057] The masking film (MF) can be, for example, a polycrystalline silicon film, a boron-doped silicon film, a tungsten-containing film (e.g., WC film, WSi film, etc.), an amorphous carbon film, a tin oxide film, or a titanium-containing film (e.g., TiN film, etc.). The masking film (MF) can be a single-layer mask comprising one layer, or a multi-layer mask comprising two or more layers. The masking film (MF) can be formed by CVD, spin coating, etc. The masking film (MF) can also be formed by photolithography. The opening (OP) can be formed by etching the masking film (MF).

[0058] At least a portion of the process for forming each component of the substrate W can be performed within the plasma processing chamber 10. In one example, the step of etching the mask film MF to form the opening OP can be performed within the plasma processing chamber 10. That is, the etching of the opening OP and the etching target film EF described below can be performed continuously within the same chamber. Furthermore, after all or part of each component of the substrate W has been formed in a device or chamber outside the plasma processing apparatus 1, the substrate W can also be moved into the plasma processing space 10s of the plasma processing apparatus 1 and placed on the upper surface of the substrate support portion 11.

[0059] (Substrate ST2: Temperature setting of substrate support section) In step ST2, the temperature of the substrate support portion 11 is set to a target temperature below 0°C. The target temperature may also be below -10°C, below -20°C, below -30°C, below -40°C, below -50°C, below -60°C, or below -70°C.

[0060] Setting the temperature of the substrate support portion 11 to a target temperature includes measuring the temperature of the substrate support portion 11 and adjusting the temperature of the substrate support portion 11 by means of the temperature of the substrate support portion 11 becoming the target temperature, but is not limited to this. In one example, setting the temperature of the substrate support portion 11 to a target temperature includes: (a) setting the temperature of the substrate W or the temperature of the heat transfer fluid flowing in the flow path 1110a to the target temperature or a temperature different from the target temperature by means of the temperature of the substrate support portion 11 becoming the target temperature; and (b) setting the temperature of the substrate support portion 11 or the temperature of the heat transfer fluid flowing in the flow path 1110a to the target temperature or a temperature different from the target temperature by means of the temperature of the substrate W becoming the target temperature. Furthermore, "setting" the temperature includes inputting, selecting, or memorizing the temperature in the control unit 2.

[0061] Furthermore, in this processing method, step ST2 can also be performed before step ST1. That is, the substrate W can be provided to the substrate support 11 after the temperature of the substrate support 11 is set to the target temperature.

[0062] (Step ST3: Etching of the target film EF) In step ST3, the film EF to be etched is etched. Step ST3 includes step ST31 of supplying a first processing gas, step ST32 of generating plasma from the first processing gas, step ST33 of supplying a second processing gas, and step ST34 of generating plasma from the second processing gas. During the processing in step ST3, the temperature of the substrate support portion 11 is set to a target temperature below 0°C set in step ST2. In one embodiment, the pressure in the plasma processing space within 10 seconds can be set to below 30 mT (4.0 Pa).

[0063] In step ST31, the first processing gas is supplied to the plasma processing space for 10 seconds. The first processing gas includes HF gas, CxFy gas (x and y are integers of 1 or more) or CsHtFu gas (s, t and u are integers of 1 or more), and oxygen-containing gas.

[0064] In the first processing gas, the flow rate of HF gas can be the highest. In one example, the flow rate of HF gas relative to the total flow rate of the first processing gas can be 70% by volume or more, or it can be 80% by volume or more. Furthermore, in the first processing gas, a gas capable of generating HF in the chamber can be used instead of or in conjunction with HF gas. HF includes at least one of hydrogen fluoride gas, free radicals, and ions. As a gas capable of generating HF, for example, at least one gas selected from the group consisting of CH2F2, C3H2F4, C3H2F6, C3H3F5, C4H2F6, C4H5F5, C4H2F8, C5H2F6, C5H2F10, and C5H3F7 can be used. In one example, as a gas capable of producing HF, at least one gas selected from the group consisting of CH₂F₂, C₃H₂F₄, and C₄H₂F₆ is used.

[0065] The C xF y gas may include at least one gas selected from the group consisting of C 2F 2 gas, C 2F 4 gas, C 3F 6 gas, C 3F 8 gas, C 4F 6 gas, C 4F 8 gas and C 5F 8 gas.

[0066] The CsHtFu gas may include at least one gas selected from the group consisting of CHF3, CH2F2, CH3F, C2HF, C2H2F4, C2H3F3, C2H2F4, C3H2F6, C3H3F5, C4H2F6, C4H5F5, C4H2F8, C5H2F6, C5H2F10, and C5H3F7. Furthermore, the first processing gas may include both CxFy and CsHtFu gases.

[0067] The oxygen-containing gas may be, for example, at least one gas selected from the group consisting of O2, CO, CO2, H2O, and H2O2. In one example, the treatment gas may include an oxygen-containing gas other than H2O, i.e., at least one gas selected from the group consisting of O2, CO, CO2, and H2O2. The flow rate of the oxygen-containing gas may be adjusted according to the flow rate of CxFy gas or CsHtFu gas.

[0068] In step ST32, a source RF signal (RF power) is supplied from the first RF generation unit 31a to the lower electrode and / or the upper electrode. This generates plasma from the first processing gas. Furthermore, as a bias signal (power), a bias RF signal is supplied from the second RF generation unit 31b to the lower electrode, generating a bias potential on the substrate. This draws active species such as ions and free radicals from the generated plasma to the substrate W, etching the silicon nitride film EF1 through the opening OP of the mask film MF. Moreover, as described above, during etching, the temperature of the substrate support 11 is set to a target temperature below 0°C.

[0069] Furthermore, the timing of starting to supply the bias signal can be simultaneous with or different from the timing of starting to supply the source RF signal. Also, a bias DC signal can be used as the bias signal (electricity). That is, a negative bias DC signal can be supplied from the DC generation unit 32a to the lower electrode, causing the substrate W to generate a bias potential. The source RF signal and the bias signal can both be continuous waves, or one can be a continuous wave and the other a pulse wave.

[0070] Figure 4 shows an example of the cross-sectional structure of the substrate W after step ST32. As shown in Figure 4, if the bottom BT of the recess formed in the silicon nitride film EF1 by etching reaches the silicon oxide film EF2, exposing the surface of the silicon oxide film EF2, then step ST32 ends. Alternatively, step ST32 can also end after etching a portion of the silicon oxide film EF2. That is, in step ST32, a portion of the silicon oxide film EF2 can be over-etched in the depth direction.

[0071] In step ST33, the second processing gas is supplied to the plasma processing space for 10 seconds. The second processing gas includes HF gas, CvFw gas (where v and w are integers greater than or equal to 1), and oxygen-containing gas.

[0072] In the second processing gas, the flow rate of HF gas can be the highest. In one example, the total flow rate of HF gas relative to the second processing gas can be 70% or more by volume, or it can be 80% or more by volume. Furthermore, similar to the first processing gas, in the second processing gas, a gas capable of generating HF in the chamber can be used in place of or together with HF gas.

[0073] The gas CvFw may include at least one gas selected from the group consisting of C2F2, C2F4, C3F6, C3F8, C4F6, C4F8 and C5F8.

[0074] The oxygen-containing gas may be, for example, at least one gas selected from the group consisting of O2, CO, CO2, H2O, and H2O2. In one example, the processing gas may include an oxygen-containing gas other than H2O, i.e., at least one gas selected from the group consisting of O2, CO, CO2, and H2O2. The flow rate of the oxygen-containing gas can be adjusted according to the flow rate of the CvFw gas.

[0075] The types of gases contained in the second processing gas may differ from those in the first processing gas. In one example, if the first processing gas contains CxFy gas, the CvFw gas contained in the second processing gas may be a different type of gas than CxFy gas. Furthermore, if the first processing gas contains CsHtFu gas, the second processing gas may not contain CsHtFu gas.

[0076] The types of gases contained in the second processing gas can also be the same as those contained in the first processing gas. In one example, when the first processing gas contains CxFy gas, the CvFw gas contained in the second processing gas can be the same type of gas as CxFy gas.

[0077] The flow rates of the same type of gas commonly contained in the first and second processing gases may be the same or different. For example, the flow rates of HF gas contained in the first and second processing gases may be the same or different.

[0078] In step ST34, a source RF signal (RF power) is supplied from the first RF generation unit 31a to the lower electrode and / or the upper electrode. This generates plasma from the second processing gas. Furthermore, as a bias signal (power), a bias RF signal is supplied from the second RF generation unit 31b to the lower electrode, generating a bias potential on the substrate. This draws active species such as ions and free radicals from the generated plasma to the substrate W, etching the silicon oxide film EF2 in the depth direction through the opening OP of the mask film MF. Moreover, as described above, during etching, the temperature of the substrate support 11 is set to a target temperature below 0°C.

[0079] Furthermore, the timing of starting the bias signal supply can be simultaneous with or different from the timing of starting the source RF signal supply. Also, a bias DC signal can be used as the bias signal (electricity). That is, a negative bias DC signal can be supplied from the DC generation unit 32a to the lower electrode, thereby generating a bias potential in the substrate W. The source RF signal and the bias signal can both be continuous waves, or one can be a continuous wave and the other a pulse wave.

[0080] Figure 5 shows an example of the cross-sectional structure of the substrate W after step ST34. As shown in Figure 5, if the bottom BT of the recess formed in the silicon oxide film EF 2 by etching reaches the substrate film UF, exposing the surface of the substrate film UF, then step ST34 ends. Alternatively, step ST34 can also end after etching a portion of the substrate film UF. That is, in step ST34, a portion of the substrate film UF can be over-etched in the depth direction. Based on the above, this processing method ends.

[0081] In this processing method, with the substrate support portion 11 set to a temperature below 0°C, a plasma generated from a first processing gas containing HF gas is used to etch the silicon nitride film EF1 (step ST32). Furthermore, with the substrate support portion 11 set to a temperature below 0°C, a plasma generated from a second processing gas containing HF gas is used to etch the silicon oxide film EF2 (step ST34). The adsorption coefficient of HF in the plasma relative to both the silicon nitride film EF1 and the silicon oxide film EF2 becomes higher at low temperatures below 0°C. Therefore, in steps ST32 and ST34, the adsorption of HF in the plasma onto the silicon nitride film EF1 and the silicon oxide film EF2 can be promoted. This processing method can thereby increase the etching rate.

[0082] In one embodiment, at least one of the first processing gas and the second processing gas may further include a phosphorus-containing gas. The phosphorus-containing gas can promote the adsorption of HF species in the plasma onto the silicon nitride film EF1 or the silicon oxide film EF2, thereby helping to improve the etching rate.

[0083] Phosphorus-containing gas systems consist of gases containing phosphorus molecules. These phosphorus molecules can also be oxides such as tetraphosphorus decaoxide (P₄O₁₀), tetraphosphorus octaoxide (P₄O₈), and tetraphosphorus hexaoxide (P₄O₆). Tetraphosphorus decaoxide is sometimes referred to as phosphorus pentoxide (P₂O₅). Phosphorus molecules can also be halides (phosphorus halides) 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, phosphorus-containing molecules such as phosphorus fluoride can also contain fluorine as a halogen element. Alternatively, phosphorus-containing molecules can also contain halogen elements other than fluorine as halogen elements. Phosphorus-containing molecules can be phosphatidyl halides such as phosphatidylfluoride (POF3), phosphatidylchloride (POCl3), and phosphatidylbromine (POBr3). Phosphorus-containing molecules can also be phosphine (PH3), calcium phosphide (Ca3P2, etc.), phosphoric acid (H3PO4), sodium phosphate (Na3PO4), hexafluorophosphate (HPF6), etc. Phosphorus-containing molecules can also be fluorophosphine derivatives (HgPFh). Here, the sum of g and h is 3 or 5. Examples of fluorophosphine derivatives include HPF2 and H2PF3. The process gas may contain one or more of the above-mentioned phosphorus-containing molecules as at least one phosphorus-containing molecule. For example, the process gas may contain at least one of PF3, PCl3, PF5, PCl5, POCl3, PH3, PBr3, or PBr5 as at least one phosphorus-containing molecule. Furthermore, when the phosphorus molecules contained in the gas are liquid or solid, each phosphorus molecule can be vaporized by heating and supplied to the plasma processing space within 10 seconds.

[0084] In one embodiment, at least one of the first and second processing gases may further comprise tungsten hexafluoride (WF6) gas. The WF6 gas can help suppress bending during the etching process in step ST32 or step ST34.

[0085] In one embodiment, at least one of the first processing gas and the second processing gas may further include rare gases such as Ar or Kr.

[0086] In one embodiment, the temperature of the substrate support portion 11 during the etching of the silicon nitride film EF 1 (step ST32) can be set to a first temperature. Furthermore, the temperature of the substrate support portion 11 during the etching of the silicon oxide film EF 2 (step ST34) can be set to a second temperature, which is lower than the first temperature. The adsorption coefficient of HF relative to the silicon nitride film is maximized at a higher temperature compared to the adsorption coefficient of HF relative to the silicon oxide film. Therefore, by setting the temperature of the substrate support portion 11 to the first temperature, which is higher than the second temperature, in step ST32, the adsorption of HF relative to the silicon nitride film EF 1 can be promoted. Conversely, the adsorption coefficient of HF relative to the silicon oxide film is maximized at a lower temperature compared to the adsorption coefficient of HF relative to the silicon nitride film. Therefore, by setting the temperature of the substrate support portion to the second temperature, which is lower than the first temperature, in step ST34, the adsorption of HF relative to the silicon oxide film EF 2 can be promoted. Based on the above, the etching rate of the etched object film EF can be further improved.

[0087] In one embodiment, setting the temperature of the substrate support portion 11 to a first temperature and a second temperature involves adjusting the temperature of the substrate support portion 11 by varying the amount of heat input to the substrate W or the substrate support portion 11 using the following controls 1 to 5. In one embodiment, one of controls 1 to 5 is performed. In one embodiment, multiple of controls 1 to 5 are performed.

[0088] (Control 1) In step ST32, a first output bias signal can be supplied to the substrate support 11. Furthermore, in step ST34, a second output bias signal, smaller than the first output, can be supplied to the substrate support 11. The bias signal can be a bias RF signal or a bias DC signal. The output of the bias signal can be adjusted by the second RF generation unit 31b or the bias DC generation unit 32a. The bias signal can be a pulse wave or a continuous wave. Furthermore, when the bias signal is a bias RF signal, the "output" of the bias signal is the actual value of the electrical power of the bias RF signal. When the bias signal is a bias DC signal, the "output" of the bias signal is the absolute value of the voltage of the bias DC signal (or the actual value of the absolute voltage when the bias DC signal is a pulse wave).

[0089] (Control 2) In step ST32, a pulse wave of a bias signal with a first duty cycle can be supplied to the substrate support 11. Furthermore, in step ST34, a pulse wave of a bias signal with a second duty cycle, smaller than the first duty cycle, can be supplied to the substrate support 11. The bias signal can be a bias RF signal or a bias DC signal. The duty cycle of the bias signal can be adjusted by the second RF generation unit 31b or the bias DC generation unit 32a. Moreover, the duty cycle of the bias signal is the ratio of the period with the higher power or voltage level within the period of the pulse wave.

[0090] (Control 3) In step ST32, a bias signal of a first frequency can be supplied to the substrate support portion 11. Furthermore, in step ST34, a bias signal of a second frequency lower than the first frequency can be supplied to the substrate support portion 11. The bias signal can be a bias RF signal or a bias DC signal. The frequency of the bias signal can be adjusted by the second RF generation portion 31b or the bias DC generation portion 32a.

[0091] (Control 4) In step ST32, a heat transfer gas at a first pressure can be supplied from the heat transfer gas supply unit to the space between the substrate W and the substrate support 11 (central region 111a). Furthermore, in step ST34, a heat transfer gas at a second pressure lower than the first pressure can be supplied from the heat transfer gas supply unit to the space between the substrate W and the substrate support 11 (central region 111a). The supply pressure of the heat transfer gas can be adjusted by the heat transfer gas supply unit.

[0092] (Control 5) In step ST32, the temperature of the heat transfer fluid flowing in flow path 1110a can be set to a third temperature. Furthermore, in step ST34, the temperature of the heat transfer fluid can be set to a fourth temperature, which is lower than the third temperature. The third temperature can be the same as the first temperature or a different temperature. The fourth temperature can be the same as the second temperature or a different temperature.

[0093] <Example> Next, embodiments of this processing method will be described. The present invention is not limited to the following embodiments.

[0094] (Example 1) In Example 1, the present processing method was applied using a plasma processing apparatus 1 to etch a substrate having the same structure as the substrate W shown in FIG. 3. A polycrystalline silicon film was used as the masking film MF. The etching conditions for the silicon nitride film EF 1 and the silicon oxide film EF 2 in Example 1 are as described below. Furthermore, the first processing gas contained 80% by volume or more of HF gas, and the second processing gas contained 85% by volume or more of HF gas. Etching conditions for silicon nitride film EF 1 (step ST32): Temperature of substrate support: -70℃ Chamber pressure: 23 mT First gas to be processed: HF, C₄H₂F₆, O₂ Etching conditions for silicon oxide film EF 2 (step ST34): Temperature of substrate support: -70℃ Chamber pressure: 15 mT Second processing gases: HF, C4F8, C4F6, O2

[0095] (Refer to Example 1) In Reference Example 1, a substrate identical to that in Example 1 was etched using a plasma processing apparatus 1. The etching conditions for the silicon nitride film EF 1 and the silicon oxide film EF 2 in Reference Example 1 are described below. Etching conditions for silicon nitride film EF 1: Temperature of substrate support: 50℃ Chamber pressure: 10 mT Gases processed first: C₄F₈ gas, C₄F₆ gas, NF₃ gas, CH₂F₂ gas, O₂ gas Etching conditions for silicon oxide film EF 2: Temperature of substrate support: 70℃ Chamber pressure: 10 mT Second gas to be processed: C4F8 gas, C4F6 gas, NF3 gas, O2 gas

[0096] In Example 1, the etching rate of the target film EF was 546 nm / min, with a selectivity of 6.1 relative to the mask film MF. In contrast, in Reference Example 1, the etching rate of the target film EF was 130 nm / min, with a selectivity of 4.7 relative to the mask film MF. That is, in Example 1, the etching rate was approximately four times that of Reference Example 1, a significant improvement. Furthermore, in Example 1, the selectivity was also approximately 1.3 times that of Reference Example 1, an improvement.

[0097] (Examples 2 to 4) In Examples 2 to 4, the same substrate as in Example 1 was etched using the plasma processing apparatus 1 and the same processing method. The etching conditions for the silicon nitride film EF 1 and the silicon oxide film EF 2 in Example 2 are as described below. The first processing gas and the second processing gas are the same, both containing HF gas at least 80% by volume. Etching conditions for silicon nitride film EF 1 (step ST32): Temperature of substrate support: -70℃ Chamber pressure: 23 mT First gas to be processed: HF, C4F8, C4F6, O2 Etching conditions for silicon oxide film EF 2 (step ST34): Temperature of substrate support: -70℃ Chamber pressure: 23 mT Second processing gases: HF, C4F8, C4F6, O2

[0098] In Example 3, etching was performed under the same conditions as in Example 2, except that 1.6% by volume of phosphorus-containing gas was included as both the first and second processing gases. In Example 4, etching was performed under the same conditions as in Example 2, except that 3.2% by volume of phosphorus-containing gas was included as both the first and second processing gases. In Examples 3 and 4, PF3 gas was used as the phosphorus-containing gas.

[0099] In Example 2, the etching rate of the target film EF was 372 nm / min, with a selectivity of 3.0 relative to the mask film MF. In Example 3, the etching rate of the target film EF was 471 nm / min, with a selectivity of 3.4 relative to the mask film MF. In Example 4, the etching rate of the target film EF was 530 nm / min, with a selectivity of 3.2 relative to the mask film MF. That is, in Examples 3 and 4, which included phosphorus-containing gas as the first and second processing gases, the etching rate and selectivity were further improved compared to Example 2, which did not contain phosphorus-containing gas.

[0100] (Examples 5 to 7) In Examples 5 to 7, the same substrate as in Example 1 was etched using the plasma processing apparatus 1 and the same processing method. The etching conditions for the silicon nitride film EF 1 and the silicon oxide film EF 2 in Example 5 are as described below. Both the first processing gas and the second processing gas contain HF gas at least 85% by volume. Etching conditions for silicon nitride film EF 1 (step ST32): Temperature of substrate support: -70℃ Chamber pressure: 15 mT First-stage gases processed: HF, C4F8, O2 Etching conditions for silicon oxide film EF 2 (step ST34): Temperature of substrate support: -70℃ Chamber pressure: 15 mT Second processing gases: HF, C4F8, O2

[0101] In Example 6, etching was performed under the same conditions as in Example 5, except that 1 sccm of WF 6 gas was included as the second processing gas. In Example 7, etching was performed under the same conditions as in Example 6, except that the flow rate of WF 6 gas was increased by 3 times (3 sccm) compared to Example 6.

[0102] Figure 6 shows the etching results of Examples 5 to 7. In Figure 6, the vertical axis represents the depth D [μm] of the opening OP formed in the mask film MF and the recess of the etched target film EF. The area near 0 μm on the vertical axis is the boundary between the mask film MF and the silicon nitride film EF 1. The area near -0.2 μm on the vertical axis is the boundary between the silicon nitride film EF 1 and the silicon oxide film EF 2. In Figure 6, the horizontal axis represents the opening width CD [nm] of the opening OP formed in the mask film MF and the recess of the etched target film EF. As shown in Figure 6, in Examples 6 and 7, which further include WF 6 gas as the second processing gas, compared with Example 5, which does not include WF 6 gas, the bending CD (maximum opening width) of the mask film MF and the silicon oxide film EF 2 is smaller, and bending is suppressed. Furthermore, the bending CD of the silicon oxide film EF2 was the same in Example 6 (WF6 gas: 1 sccm) and Example 7 (WF6 gas: 3 sccm). That is, the bending suppression effect of the silicon oxide film EF2 can also be obtained by adding a trace amount of WF6 gas of about 1 sccm.

[0103] (Examples 8 and 9) In Examples 8 and 9, the same substrate as in Example 1 was etched using the plasma processing apparatus 1 and the processing method. In Examples 8 and 9, 50% over-etching was performed in step ST34. That is, in step ST34, the silicon oxide film EF2 was etched until the substrate film UF was exposed, and then the substrate film UF was etched in the depth direction in half the time required for etching the silicon oxide film EF2.

[0104] The etching conditions for the silicon nitride film EF1 and the silicon oxide film EF2 in Example 8 are as follows. Both the first and second processing gases contain HF gas at least 85% by volume. Etching conditions for silicon nitride film EF 1 (step ST32): Temperature of substrate support: -70℃ Chamber pressure: 15 mT First-stage gases processed: HF, C4F8, O2 Etching conditions for silicon oxide film EF 2 (step ST34): Temperature of substrate support: -70℃ Chamber pressure: 15 mT Second processing gases: HF, C4F8, C4F6, O2

[0105] In Example 9, except that 2 sccm of WF 6 gas was included as the second processing gas, etching was performed under the same conditions as in Example 8.

[0106] Figure 7 shows the etching results of Example 8. In Figure 7, "Example 8 (OE 0%)" is the result before over-etching in step ST34. "Example 8 (OE 50%)" is the result after over-etching in step ST34. Figure 8 shows the etching results of Example 9. In Figure 8, "Example 9 (OE 0%)" is the result before over-etching in step ST34. "Example 9 (OE 50%)" is the result after over-etching in step ST34. In Figures 7 and 8, the vertical axis represents the depth D [μm] of the opening OP formed in the mask film MF and the recess of the etched target film EF. The area near 0 μm on the vertical axis is the boundary between the mask film MF and the silicon nitride film EF 1. The area near -0.2 μm on the vertical axis is the boundary between the silicon nitride film EF 1 and the silicon oxide film EF 2. In Figures 7 and 8, the horizontal axis represents the opening width CD [nm] of the opening OP formed in the mask film MF and the recess of the etched target film EF.

[0107] As shown in Figure 8, in Example 8, the bending CD of the mask film MF and the silicon oxide film EF 2 is increased due to over-etching in step ST34. In contrast, in Example 9, which includes WF 6 gas as the second processing gas, almost no change was observed in the bending CD of the mask film MF and the silicon oxide film EF 2 before and after the over-etching in step ST34. That is, Example 9, which includes WF 6 gas, can suppress the increase in bending caused by over-etching.

[0108] This processing method can be modified in various ways without departing from the scope and spirit of the present invention. For example, in addition to the capacitively coupled plasma processing apparatus 1, this processing method can also be performed using a plasma processing apparatus that utilizes any plasma source such as inductively coupled plasma or microwave plasma.

[0109] 1: Plasma treatment device 2: Control Department 2a: Computer 2a1: Processing Department 2a2: Memory Department 2a3: Communication Interface 10: Plasma treatment chamber 10a: Sidewall 10e: Gas exhaust outlet 10s: Plasma processing space 11:Substrate support department 13: Cluster Head 13a: Gas supply port 13b: Gas diffusion chamber 13c: Gas inlet 20: Gas Supply Department 21: Gas Source 22: Flow controller 30: Power supply 31: RF power supply 31a: First RF Generation Unit 31b: Second RF Generation Unit 32: DC power supply 32a: First DC Generation Unit 32b: Second DC Generation Unit 40: Exhaust System 111: Ontology Department 111a: Central Region 111b: Annular region 112: Ring Component 1110:Abutment 1110a: Flow path 1111: Electrostatic Chuck 1111a: Ceramic components 1111b: Electrostatic electrode BT: Bottom EF: Etched object film EF 1: Silicon nitride film EF 2: Silicon oxide film MF: Masking film OP: Open ST1: Steps ST2: Steps ST3: Steps ST31: Steps ST32: Steps ST33: Steps ST34: Steps UF: Basement membrane W: substrate

Claims

1. A plasma processing method performed in a plasma processing apparatus having a chamber, comprising the following steps: (a) providing a substrate having an etch target film including a silicon oxide film and a silicon nitride film, and a masking film defining an opening on the etch target film onto a substrate support portion within the chamber; (b) generating plasma from a first processing gas containing HF gas, CxFy gas (x and y are integers of 1 or more) or CsHtFu gas (s, t, and u are integers of 1 or more), and an oxygen-containing gas to etch the silicon nitride film; and (c) generating plasma from a second processing gas containing HF gas, CvFw gas (v and w are integers of 1 or more), and an oxygen-containing gas to etch the silicon oxide film; wherein in (b) and (c), the temperature of the substrate support portion is set to 0°C or below, and the first processing gas contains a gas of a different type than the second processing gas.

2. The plasma processing method of claim 1, wherein the first processing gas comprises the CsHtFu gas.

3. The plasma processing method of claim 1, wherein the first processing gas includes the CxFy gas, and the CxFy gas is a gas different from the CvFw gas included in the second processing gas.

4. A plasma processing method performed in a plasma processing apparatus having a chamber, comprising the following steps: (a) providing a substrate having an etch target film including a silicon oxide film and a silicon nitride film, and a masking film defining an opening on the etch target film onto a substrate support portion within the chamber; (b) generating plasma from a first processing gas containing HF gas, CxFy gas (x and y are integers of 1 or more) or CsHtFu gas (s, t, and u are integers of 1 or more), and oxygen-containing gas to etch the silicon nitride film; and (c) generating plasma from a second processing gas containing HF gas, CvFw gas (v and w are integers of 1 or more), and oxygen-containing gas to etch the silicon oxide film; In (b) and (c) above, the temperature of the substrate support portion is set to 0°C or below, and in (b) above, the temperature of the substrate support portion is set to a first temperature, and in (c) above, the temperature of the substrate support portion is set to a second temperature that is lower than the first temperature.

5. The plasma processing method of claim 4, wherein in (b) above, a first output bias signal is supplied to the substrate support portion, and in (c) above, a second output bias signal smaller than the first output is supplied to the substrate support portion, or no bias signal is supplied to the substrate support portion.

6. The plasma processing method of claim 4 or 5, wherein in (b) above, a pulse wave of a bias signal with a first duty cycle is supplied to the substrate support portion, and in (c) above, a pulse wave of a bias signal with a second duty cycle smaller than the first duty cycle is supplied to the substrate support portion.

7. The plasma processing method as described in claim 5, wherein the bias signal is a bias DC signal.

8. The plasma processing method of claim 4 or 5, wherein in (b) above, a bias RF signal of a first frequency is supplied to the substrate support portion, and in (c) above, a bias RF signal of a second frequency lower than the first frequency is supplied to the substrate support portion.

9. The plasma processing method of claim 4 or 5, wherein in (b) above, a heat transfer gas at a first pressure is supplied between the substrate and the substrate support, and in (c) above, a heat transfer gas at a second pressure lower than the first pressure is supplied between the substrate and the substrate support.

10. The plasma processing method of claim 4 or 5, wherein in (b) above, the temperature of the heat transfer fluid supplied to the substrate support portion is set to a third temperature, and in (c) above, the temperature of the heat transfer fluid supplied to the substrate support portion is set to a fourth temperature that is lower than the third temperature.

11. The plasma treatment method of any one of claims 1 to 5 and 7, wherein the masking film is a polycrystalline silicon film, a boron-doped silicon film, a tungsten-containing film, an amorphous carbon film, a tin oxide film, or a titanium-containing film.

12. The plasma processing method of any one of claims 1 to 5 and 7, wherein the opening width of the masking film is 50 nm or less.

13. The plasma processing method of any one of claims 1 to 5 and 7, wherein the CxFy gas or the CvFw gas comprises at least one gas selected from the group consisting of C2F2 gas, C2F4 gas, C3F6 gas, C3F8 gas, C4F6 gas, C4F8 gas and C5F8 gas.

14. The plasma processing method according to any one of claims 1 to 5 and 7, wherein the aforementioned CsHtFu gas comprises at least one gas selected from the group consisting of 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, C5H2F10 gas and C5H3F7 gas.

15. The plasma processing method of any one of claims 1 to 5 and 7, wherein the flow rate of HF gas is the highest among the first processing gas and the second processing gas.

16. The plasma processing method of any one of claims 1 to 5 and 7, wherein at least one of the first processing gas and the second processing gas further comprises a phosphorus-containing gas.

17. The plasma processing method of any one of claims 1 to 5 and 7, wherein at least one of the first processing gas and the second processing gas further comprises WF6 gas.

18. The plasma processing method of any one of claims 1 to 5 and 7, wherein in (b) and (c) above, the temperature of the substrate support portion is set to -50°C or below.

19. A plasma processing method performed in a plasma processing apparatus having a chamber, comprising the following steps: (a) providing a substrate having an etchable film comprising a silicon oxide film and a silicon nitride film, and a masking film defining an opening on the etchable film onto a substrate support portion within the chamber; (b) generating a first plasma from a first processing gas, and etching the silicon nitride film by means of HF, CxFy (x and y are integers of 1 or more) or CsHtFu (s, t, and u are integers of 1 or more) and oxygen-active species contained in the first plasma; (c) generating a second plasma from a second processing gas, and etching the silicon oxide film by means of HF, CvFw (v and w are integers of 1 or more) and oxygen-active species contained in the second plasma. In (b) and (c) above, the temperature of the substrate support portion is set to below 0°C, and the first processing gas includes a gas of a different type than the second processing gas.

20. The plasma processing method of claim 19, wherein the HF species is generated from at least one gas selected from the group consisting of CH2F2 gas, C3H2F4 gas and C4H2F6 gas.

21. A plasma processing system comprising a chamber, a substrate support disposed within the chamber, a plasma generation unit, and a control unit, wherein the control unit performs the following control: (a) providing a substrate having an etch target film comprising a silicon oxide film and a silicon nitride film, and a masking film defining an opening on the etch target film onto the substrate support unit; (b) using power supplied from the plasma generation unit to generate plasma from a first processing gas comprising HF gas, CxFy gas (x and y are integers of 1 or more), or CsHtFu gas (s, t, and u are integers of 1 or more), and an oxygen-containing gas, and etching the silicon nitride film; (c) Using the power supplied from the plasma generation unit, plasma is generated from a second processing gas containing HF gas, CvFw gas (v and w are integers of 1 or more), and oxygen-containing gas to etch the silicon oxide film; and in (b) and (c) above, the temperature of the substrate support portion is set to 0°C or below.

22. A plasma processing method performed in a plasma processing apparatus having a chamber, comprising the following steps: (a) providing a substrate having an etch target film comprising a silicon oxide film and a silicon nitride film, and a masking film defining an opening on the etch target film onto a substrate support portion within the chamber; (b) generating a first plasma from a first processing gas, and etching the silicon nitride film by means of HF, CxFy (x and y are integers of 1 or more) or CsHtFu (s, t, and u are integers of 1 or more) and oxygen-active species contained in the first plasma; (c) generating a second plasma from a second processing gas, and etching the silicon oxide film by means of HF, CvFw (v and w are integers of 1 or more) and oxygen-active species contained in the second plasma. In (b) and (c) above, the temperature of the substrate support portion is set to 0°C or below, and in (b) above, the temperature of the substrate support portion is set to a first temperature, and in (c) above, the temperature of the substrate support portion is set to a second temperature that is lower than the first temperature.

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