Etching method and plasma processing system

Abstract

To provide a technique capable of suppressing abnormalities of the shape of etching.SOLUTION: There is provided an etching method including steps of (a) providing a substrate in a chamber, and (b) etching a silicon nitride film through a mask by using plasma generated from first processing gas. The substrate includes a metal-containing mask and a silicon nitride film arranged below the mask. The first processing gas includes first fluorocarbon gas, second fluorocarbon gas, and hydrofluorocarbon gas. The first fluorocarbon gas is C4F6 gas. The second fluorocarbon gas is fluorocarbon gas different from C4F6 gas. The total flow rate of the first fluorocarbon gas and the second fluorocarbon gas is more than the flow rate of the hydrofluorocarbon gas.SELECTED DRAWING: Figure 3

Description

[Technical field]

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

[0002] Patent Document 1 discloses that a plasma is generated from a process gas containing tungsten hexafluoride gas, a gas containing carbon and fluorine, and an oxygen-containing gas, and a silicon-containing film including a silicon oxide film is etched by the plasma. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent Publication No. 2022-74000 Summary of the Invention [Problem to be solved by the invention]

[0004] The present disclosure provides a technique for suppressing shape abnormalities caused by etching. [Means for solving the problem]

[0005] In one exemplary embodiment of the present disclosure, an etching method is provided that includes: (a) providing a substrate in a chamber, the substrate including a metal-containing mask and a silicon nitride film disposed below the mask; and (b) etching the silicon nitride film through the mask using plasma generated from a first process gas, the first process gas including a first fluorocarbon gas, a second fluorocarbon gas, and a hydrofluorocarbon gas, the first fluorocarbon gas being C4F6 gas, the second fluorocarbon gas being a fluorocarbon gas different from C4F6 gas, and a total flow rate of the first fluorocarbon gas and the second fluorocarbon gas being greater than a flow rate of the hydrofluorocarbon gas. Effect of the Invention

[0006] According to one exemplary embodiment of the present disclosure, a technique for suppressing shape abnormalities due to etching can be provided. [Brief description of the drawings]

[0007] [Figure 1] FIG. 1 is a diagram for explaining a configuration example of a plasma processing system. [Diagram 2] FIG. 1 is a diagram for explaining a configuration example of a capacitively coupled plasma processing apparatus. [Diagram 3] 4 is a flowchart illustrating an example of the present processing method. [Figure 4] 2 is a diagram showing an example of a cross-sectional structure of a substrate W. FIG. [Diagram 5] 1A to 1C are diagrams for explaining an example of a state of a substrate W during etching. [Figure 6] 1 is a diagram showing an example of a cross-sectional structure of the substrate W when etching is completed. [Figure 7] 4 is a flowchart illustrating an example of the present processing method. [Figure 8] 2 is a diagram showing an example of a cross-sectional structure of a substrate W1. FIG. [Figure 9] FIG. 13 is a diagram showing etching results according to an embodiment and a reference example. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0008] Each embodiment of the present disclosure will be described below.

[0009] In one exemplary embodiment, an etching method is provided that includes: (a) providing a substrate in a chamber, the substrate including a metal-containing mask and a silicon nitride film disposed below the mask; and (b) etching the silicon nitride film through the mask using a plasma generated from a first process gas, the first process gas including a first fluorocarbon gas, a second fluorocarbon gas, and a hydrofluorocarbon gas, the first fluorocarbon gas being C4F6 gas, the second fluorocarbon gas being a fluorocarbon gas different from C4F6 gas, and a total flow rate of the first fluorocarbon gas and the second fluorocarbon gas being greater than a flow rate of the hydrofluorocarbon gas.

[0010] In one exemplary embodiment, the flow rate of the first fluorocarbon gas is less than the flow rate of the second fluorocarbon gas.

[0011] In one exemplary embodiment, the hydrofluorocarbon gas includes CH2F2 gas.

[0012] In one exemplary embodiment, the second fluorocarbon gas does not contain a double bond.

[0013] In one exemplary embodiment, the second fluorocarbon gas is C3F8 gas.

[0014] In one exemplary embodiment, the metal comprises tungsten or molybdenum.

[0015] In one exemplary embodiment, the mask comprises tungsten silicide.

[0016] In one exemplary embodiment, the process gas further comprises an oxygen-containing gas.

[0017] In one exemplary embodiment, the process gas further comprises an inert gas.

[0018] In one exemplary embodiment, (b) includes providing a pulsed bias DC signal to the substrate.

[0019] In one exemplary embodiment, a silicon nitride film is disposed directly beneath the mask.

[0020] In one exemplary embodiment, the mask includes a pattern of openings with opening dimensions of 50 nm or less.

[0021] In one exemplary embodiment, the substrate further includes a silicon oxide layer below the silicon nitride layer.

[0022] In one exemplary embodiment, after (b), the method further includes the step of (c) generating a plasma from the second process gas to etch the silicon oxide film.

[0023] In one exemplary embodiment, the second process gas comprises a fluorocarbon gas and does not comprise a hydrofluorocarbon gas.

[0024] In one exemplary embodiment, (b) includes supplying a bias DC signal of a first voltage level to the substrate, and (c) includes supplying a bias DC signal of a second voltage level to the substrate, the absolute value of the second voltage level being greater than the absolute value of the first voltage level.

[0025] In one exemplary embodiment, a plasma processing system is provided that includes a plasma processing apparatus having a chamber and a controller, the controller performing: (a) controlling a substrate to be provided into the chamber, the substrate including a metal-containing mask and a silicon nitride film disposed below the mask; and (b) controlling a plasma generated from a first process gas including a first fluorocarbon gas, a second fluorocarbon gas, and a hydrofluorocarbon gas, the first fluorocarbon gas being C4F6 gas, the second fluorocarbon gas being a fluorocarbon gas different from C4F6 gas, and a total flow rate of the first fluorocarbon gas and the second fluorocarbon gas being greater than a flow rate of the hydrofluorocarbon gas.

[0026] Hereinafter, each embodiment of the present disclosure will be described in detail with reference to the drawings. In each drawing, the same or similar elements are given the same reference numerals, and duplicated explanations will be omitted. Unless otherwise specified, the positional relationship such as up, down, left, right, etc. will be described based on the positional relationship shown in the drawing. The dimensional ratio of the drawings does not indicate the actual ratio, and the actual ratio is not limited to the illustrated ratio.

[0027] <Example of plasma processing system configuration> FIG. 1 is a diagram for explaining a configuration example of a plasma processing system. In one embodiment, the plasma processing system includes a plasma processing device 1 and a control unit 2. The plasma processing system is an example of a substrate processing system, and the plasma processing device 1 is an example of a substrate processing device. The plasma processing device 1 includes a plasma processing chamber 10, a substrate support unit 11, and a plasma generation unit 12. The plasma processing chamber 10 has a plasma processing space. The plasma processing chamber 10 also has at least one gas supply port for supplying at least one processing gas to the plasma processing space, and at least one gas exhaust port for exhausting gas from the plasma processing space. The gas supply port is connected to a gas supply unit 20 described later, and the gas exhaust port is connected to an exhaust system 40 described later. The substrate support unit 11 is disposed in the plasma processing space, and has a substrate support surface for supporting a substrate.

[0028] The plasma generating unit 12 is configured to generate plasma from at least one processing gas supplied into the plasma processing space. The plasma formed in the plasma processing space may be a capacitively coupled plasma (CCP), an inductively coupled plasma (ICP), an electron-cyclotron-resonance plasma (ECR plasma), a helicon wave plasma (HWP), or a surface wave plasma (SWP), etc. Also, various types of plasma generating units may be used, including an alternating current (AC) plasma generating unit and a direct current (DC) plasma generating unit. In one embodiment, the AC signal (AC power) used in the AC plasma generating unit has a frequency in the range of 100 kHz to 10 GHz. Thus, the AC signal includes a radio frequency (RF) signal and a microwave signal. In one embodiment, the RF signal has a frequency in the range of 100 kHz to 150 MHz.

[0029] The control unit 2 processes computer-executable instructions that cause the plasma processing apparatus 1 to execute various steps described in the present disclosure. The control unit 2 may be configured to control each element of the plasma processing apparatus 1 to execute various steps described herein. In one embodiment, a part or all of the control unit 2 may be included in the plasma processing apparatus 1. The control unit 2 may include a processing unit 2a1, a storage unit 2a2, and a communication interface 2a3. The control unit 2 is realized, 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 may be acquired via a medium when necessary. The acquired program is stored in the storage unit 2a2 and is read from the storage unit 2a2 by the processing unit 2a1 and executed. The medium may be various storage media readable by the computer 2a, or may be a communication line connected to the communication interface 2a3. The processing unit 2a1 may be a CPU (Central Processing Unit). The storage unit 2a2 may include a random access memory (RAM), a read only memory (ROM), a hard disk drive (HDD), a solid state drive (SSD), or a combination thereof. The communication interface 2a3 may communicate with the plasma processing apparatus 1 via a communication line such as a local area network (LAN).

[0030] The following describes a configuration example of a capacitively coupled plasma processing apparatus as an example of the plasma processing apparatus 1. Fig. 2 is a diagram for explaining the configuration example of a capacitively coupled plasma processing apparatus.

[0031] The capacitively coupled plasma processing apparatus 1 includes a plasma processing chamber 10, a gas supply 20, a power supply 30, and an exhaust system 40. The plasma processing apparatus 1 also includes a substrate support 11 and a gas inlet. The gas inlet is configured to introduce at least one processing gas into the plasma processing chamber 10. The gas inlet includes a showerhead 13. The substrate support 11 is disposed in the plasma processing chamber 10. The showerhead 13 is disposed above the substrate support 11. In one embodiment, the showerhead 13 forms at least a part of a ceiling of the plasma processing chamber 10. The plasma processing chamber 10 has a plasma processing space 10s defined by the showerhead 13, a sidewall 10a of the plasma processing chamber 10, and the substrate support 11. The plasma processing chamber 10 is grounded. The showerhead 13 and the substrate support 11 are electrically insulated from a housing of the plasma processing chamber 10.

[0032] The substrate support 11 includes a main body 111 and a ring assembly 112. The main body 111 has a central region 111a for supporting 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 111 surrounds the central region 111a of the main body 111 in a plan view. The substrate W is disposed on the central region 111a of the main body 111, and the ring assembly 112 is disposed on the annular region 111b of the main body 111 so as to surround the substrate W on the central region 111a of the main body 111. Therefore, the central region 111a is also called a substrate support surface for supporting the substrate W, and the annular region 111b is also called a ring support surface for supporting the ring assembly 112.

[0033] 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 may function as a lower electrode. The electrostatic chuck 1111 is disposed on the base 1110. The electrostatic chuck 1111 includes a ceramic member 1111a and an electrostatic electrode 1111b disposed within the ceramic member 1111a. The ceramic member 1111a has a central region 111a. In one embodiment, the ceramic member 1111a also has an annular region 111b. Note that other members surrounding the electrostatic chuck 1111, such as an annular electrostatic chuck or an annular insulating member, may have the annular region 111b. In this case, the ring assembly 112 may be disposed on the annular electrostatic chuck or the annular insulating member, or may be disposed on both the electrostatic chuck 1111 and the annular insulating member. Also, at least one RF / DC electrode coupled to an RF power source 31 and / or a DC power source 32 described later may be disposed in the ceramic member 1111a. In this case, the at least one RF / DC electrode functions as a lower electrode. When a bias RF signal and / or a DC signal described later is supplied to the at least one RF / DC electrode, the RF / DC electrode is also called a bias electrode. Note that the conductive member of the base 1110 and the at least one RF / DC electrode may function as multiple lower electrodes. Also, the electrostatic electrode 1111b may function as a lower electrode. Thus, the substrate support 11 includes at least one lower electrode.

[0034] 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.

[0035] The substrate support 11 may also include a temperature adjustment module configured to adjust at least one of the electrostatic chuck 1111, the ring assembly 112, and the substrate to a target temperature. The temperature adjustment module may include a heater, a heat transfer medium, a flow passage 1110a, or a combination thereof. A heat transfer fluid such as a brine or a gas flows through the flow passage 1110a. In one embodiment, the flow passage 1110a is formed in the base 1110, and one or more heaters are disposed in the ceramic member 1111a of the electrostatic chuck 1111. The substrate support 11 may also include a heat transfer gas supply configured to supply a heat transfer gas to a gap between the back surface of the substrate W and the central region 111a.

[0036] The shower head 13 is configured to introduce at least one processing gas from the gas supply unit 20 into the plasma processing space 10s. The shower head 13 has at least one gas supply port 13a, at least one gas diffusion chamber 13b, and multiple gas inlets 13c. The processing gas supplied to the gas supply port 13a passes through the gas diffusion chamber 13b and is introduced into the plasma processing space 10s from the multiple gas inlets 13c. The shower head 13 also includes at least one upper electrode. Note that the gas introduction unit may include, in addition to the shower head 13, one or more side gas injectors (SGIs) attached to one or more openings formed in the sidewall 10a.

[0037] The gas supply 20 may include at least one gas source 21 and at least one flow controller 22. In one embodiment, the gas supply 20 is configured to supply at least one process gas from a respective gas source 21 through a respective flow controller 22 to the showerhead 13. Each flow controller 22 may include, for example, a mass flow controller or a pressure-controlled flow controller. Additionally, the gas supply 20 may include at least one flow modulation device to modulate or pulse a flow rate of the at least one process gas.

[0038] The power source 30 includes an RF power source 31 coupled to the plasma processing chamber 10 via at least one impedance matching circuit. The RF power source 31 is configured to supply at least one RF signal (RF power) to at least one lower electrode and / or at least one upper electrode. This causes a plasma to be formed from at least one processing gas supplied to the plasma processing space 10s. Thus, the RF power source 31 can function as at least a part of the plasma generating unit 12. In addition, by supplying a bias RF signal to the at least one lower electrode, a bias potential is generated on the substrate W, and ion components in the formed plasma can be attracted to the substrate W.

[0039] In one embodiment, the RF power supply 31 includes a first RF generating unit 31a and a second RF generating unit 31b. The first RF generating unit 31a is coupled to at least one lower electrode and / or at least one upper electrode via at least one impedance matching circuit, and is configured to generate a source RF signal (source RF power) for plasma generation. In one embodiment, the source RF signal has a frequency in the range of 10 MHz to 150 MHz. In one embodiment, the first RF generating unit 31a may be configured to generate a plurality of source RF signals having different frequencies. The generated one or more source RF signals are supplied to at least one lower electrode and / or at least one upper electrode.

[0040] The second RF generating unit 31b is coupled to at least one lower electrode via at least one impedance matching circuit and 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 generating unit 31b may be configured to generate a plurality of bias RF signals having different frequencies. The generated one or more bias RF signals are supplied to at least one lower electrode. Also, in various embodiments, at least one of the source RF signal and the bias RF signal may be pulsed.

[0041] The power supply 30 may also include a DC power supply 32 coupled to the plasma processing chamber 10. The DC power supply 32 includes a first DC generator 32a and a second DC generator 32b. In one embodiment, the first DC generator 32a is connected to at least one lower electrode and configured to generate a first DC signal. The generated first DC signal is applied to the at least one lower electrode. In one embodiment, the second DC generator 32b is connected to at least one upper electrode and configured to generate a second DC signal. The generated second DC signal is applied to the at least one upper electrode.

[0042] In various embodiments, the first and second DC signals may be pulsed. In this case, a sequence of voltage pulses is applied to at least one lower electrode and / or at least one upper electrode. The voltage pulses may have a rectangular, trapezoidal, triangular or combination of these pulse waveforms. In one embodiment, a waveform generator for generating a sequence of voltage pulses from the DC signal is connected between the first DC generator 32a and at least one lower electrode. Thus, the first DC generator 32a and the waveform generator constitute a voltage pulse generator. When the second DC generator 32b and the waveform generator constitute a voltage pulse generator, the voltage pulse generator is connected to at least one upper electrode. The voltage pulses may have a positive polarity or a negative polarity. Also, the sequence of voltage pulses may include one or more positive polarity voltage pulses and one or more negative polarity voltage pulses in one period. The first and second DC generating units 32a, 32b may be provided in addition to the RF power supply 31, or the first DC generating unit 32a may be provided in place of the second RF generating unit 31b.

[0043] The exhaust system 40 may be connected to, for example, a gas exhaust port 10e provided at the bottom of the plasma processing chamber 10. The exhaust system 40 may include a pressure regulating valve and a vacuum pump. The pressure in the plasma processing space 10s is adjusted by the pressure regulating valve. The vacuum pump may include a turbomolecular pump, a dry pump, or a combination thereof.

[0044] <An example of a plasma processing method> Fig. 3 is a flow chart showing an example of a plasma processing method (hereinafter also referred to as "this processing method") according to an illustrative embodiment. As shown in Fig. 3, this processing method includes a step ST11 of providing a substrate, and a step ST12 of etching. The processing in each step may be performed in the plasma processing system shown in Fig. 1 or Fig. 2. In the following, an example will be described in which a control unit 2 controls each part of the plasma processing apparatus 1 shown in Fig. 2 to perform this processing method on a substrate W.

[0045] (Step ST11: Providing the substrate) In step ST11, a substrate W is provided in a plasma processing chamber 10 (hereinafter also referred to as "chamber 10"). The substrate W is carried into the chamber 10 by a transfer arm, placed on a substrate support 11 by a lifter, and held by suction on the substrate support 11 as shown in FIG.

[0046] 4 is a diagram showing an example of a cross-sectional structure of a substrate W. The substrate W includes a mask MK and a silicon nitride film SF1 disposed below the mask MK. The silicon nitride film SF1 may be formed on an undercoat film UF. The substrate W may be used for manufacturing semiconductor devices. The semiconductor devices include, for example, memory devices such as DRAMs and 3D-NAND flash memories, and logic devices.

[0047] The undercoat film UF is, for example, a silicon wafer or an organic film, a dielectric film, a metal film, a semiconductor film, etc., formed on a silicon wafer. The undercoat film UF may be configured by laminating a plurality of films.

[0048] The silicon nitride film SF1 is a film to be etched by this processing method. In one embodiment, the silicon nitride film SF1 may be disposed directly below the mask MK, as shown in FIG.

[0049] The mask MK includes at least one metal selected from the group consisting of tungsten, molybdenum, ruthenium, titanium, indium, gallium, and zinc. The mask MK may include, for example, carbides or silicides of tungsten, molybdenum, and titanium. The mask MK may be, for example, a tungsten-containing film. The mask MK may further include tungsten and at least one selected from the group consisting of silicon, carbon, and nitrogen. In one example, the mask MK includes at least one selected from the group consisting of WC (tungsten carbide), WSi (tungsten silicide), WSiN, and WSiC. The mask MK may include, for example, at least one selected from the group consisting of Ru, WSi, TiN, Mo, and InGaZnO. The mask MK may be a single-layer mask consisting of one layer, or may be a multi-layer mask consisting of two or more layers.

[0050] 4, the mask MK defines at least one opening OP on the silicon nitride film SF1. The opening OP is a space on the silicon nitride film SF1 and is surrounded by the sidewall of the mask MK. That is, the upper surface of the silicon nitride film SF1 has a region covered by the mask MK and a region exposed at the bottom of the opening OP.

[0051] The opening OP may have any shape in a plan view of the substrate W, that is, when the substrate W is viewed from the top to the bottom in FIG. 4. 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 MK may have a plurality of side walls that define a plurality of openings OP. This allows the mask MK to have an opening pattern. For example, the mask MK may form a line and space pattern by arranging a plurality of openings OP in a planar line-of-sight shape at regular intervals. Also, for example, the mask MK may form an array pattern by arranging a plurality of circular openings OP in a dot shape.

[0052] The undercoat film UF, the silicon nitride film SF1, and the mask MK may each be formed by any method. For example, the undercoat film UF, the silicon nitride film SF1, and the mask MK may be formed by a CVD method, an ALD method, a PVD method, a spin coating method, or the like. The mask MK may be formed by, for example, lithography. The opening OP of the mask MK may be formed by etching the mask MK. The undercoat film UF, the silicon nitride film SF1, and the mask MK may each be a flat film, or may be a film having irregularities. The substrate W may further include another film under the undercoat film UF. In this case, a recess having a shape corresponding to the opening OP may be formed in the silicon nitride film SF1 and the undercoat film UF, and used as a mask for etching the other film.

[0053] At least a part of the process of forming the undercoat film UF, the silicon nitride film SF1, and the mask MK of the substrate W may be performed in the chamber 10 as part of step ST11. For example, when the opening OP of the mask MK is formed by etching, the etching in step ST11 and the etching process in step ST12 described later may be performed consecutively in the chamber 10. In one embodiment, the substrate W may be provided in the chamber 10 after all or a part of the substrate W is formed in an apparatus or chamber outside the plasma processing apparatus 1.

[0054] In one embodiment, after the substrate W is provided to the central region 111a of the substrate support 11, the substrate support 11 is controlled to a given temperature by a temperature control module. In one example, controlling the temperature of the substrate support 11 to a given temperature includes setting the temperature of the heat transfer fluid flowing through the flow path 1110a or the heater temperature to a given temperature or a temperature different from the given temperature. The timing at which the heat transfer fluid starts to flow through the flow path 1110a may be before or after the substrate W is placed on the substrate support 11, or may be the same as the substrate W. The temperature of the substrate support 11 may be controlled to a given temperature before the step ST11. That is, the substrate W may be provided to the substrate support 11 after the temperature of the substrate support 11 is controlled to a given temperature.

[0055] In one embodiment, instead of controlling the substrate support 11 to a given temperature, the substrate W may be controlled to a given temperature. Controlling the temperature of the substrate W to a given temperature includes setting the temperature of the substrate support 11, the temperature of the heat transfer fluid flowing through the flow path 1110a, and / or the heater temperature to a given temperature or to a temperature different from the given temperature.

[0056] In one embodiment, the temperature of the substrate support 11 or the substrate W may be controlled to a given temperature set in step ST11 during the subsequent processing in step ST12.

[0057] (Step ST12: Etching) In step ST12, the silicon nitride film SF1 is etched, whereby the portions of the silicon nitride film SF1 that are not covered by the mask MK (portions exposed at the openings OP) are etched to form recesses.

[0058] First, a first process gas is supplied into the plasma processing space 10s from the gas supply unit 20. The first process gas contains a first fluorocarbon gas, a second fluorocarbon gas, and a hydrofluorocarbon gas.

[0059] In one embodiment, the first fluorocarbon gas is a fluorocarbon gas containing a double bond between carbon atoms. In one embodiment, the first fluorocarbon gas may be at least one of C4F6 gas and C3F6 gas. In one example, the first fluorocarbon gas is C4F6 gas.

[0060] The second fluorocarbon gas is a fluorocarbon gas different from the first fluorocarbon gas. In one embodiment, the second fluorocarbon gas may be at least one selected from the group consisting of C3F6 gas, C3F8 gas, and C4F8 gas. In one embodiment, the second fluorocarbon gas is a fluorocarbon gas that does not have a double bond. In one embodiment, the second fluorocarbon gas is a fluorocarbon gas having a carbon number of 2 or more. In one example, the second fluorocarbon gas is C3F8 gas. The second fluorocarbon gas may be composed of one or more types of fluorocarbon gas.

[0061] In one embodiment, the hydrofluorocarb gas is 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 At least one selected from the group consisting of CH2F2 gas, CH3F gas, and C5H3F7 gas. In one example, the hydrofluorocarbon gas is CH2F2 gas, CH3F gas, or CHF3 gas.

[0062] In the first process gas, the total flow rate of the first fluorocarbon gas and the second fluorocarbon gas is greater than the flow rate of the hydrofluorocarbon gas. In one embodiment, the flow rate of the first fluorocarbon gas is less than the flow rate of the second fluorocarbon gas.

[0063] In one embodiment, the first process gas further comprises an oxygen-containing gas. 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 oxygen-containing gas is an oxygen-containing gas other than H2O, for example, at least one gas selected from the group consisting of O2, CO, CO2, and H2O2.

[0064] In one embodiment, the first process gas further includes an inert gas, which is, for example, a noble gas such as Ar gas, He gas, or Kr gas, or nitrogen gas.

[0065] 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. As a result, a high-frequency electric field is generated between the shower head 13 and the substrate support 11, active species (ions, radicals) of plasma are generated from the processing gas in the plasma processing space 10s, and the substrate W is etched by the active species. In one embodiment, a bias signal may be supplied to the lower electrode of the substrate support 11. In this case, a bias potential is generated between the plasma and the substrate W, and ions in the plasma are attracted to the substrate W. The bias signal may be a bias DC signal supplied from the DC generator 32a, or a bias RF signal supplied from the second RF generator 31b.

[0066] In one embodiment, both the source RF signal and the bias signal may be continuous waves or pulse waves, or one may be continuous waves and the other may be pulse waves. When both the source RF signal and the bias signal are pulse waves, the periods of both pulse waves may be synchronized or may not be synchronized. The duty ratio of the pulse waves of the source RF signal and / or the bias signal may be appropriately set, for example, 1 to 80%, or 5 to 50%. The duty ratio is the proportion of the period during which the power or voltage level is high in the period of the pulse wave. When a bias DC signal is used as the bias signal, the pulse wave may have a waveform of a rectangle, a trapezoid, a triangle, or a combination of these. The polarity of the bias DC signal may be negative or positive as long as the potential of the substrate W is set so as to apply a potential difference between the plasma and the substrate to attract ions.

[0067] In one embodiment, the supply and stop of at least one of the source RF signal and the bias signal may be alternately repeated. For example, the supply and stop of the bias signal may be alternately repeated while the source RF signal is continuously supplied. For example, the bias signal may be continuously supplied while the supply and stop of the source RF signal are alternately repeated. For example, the supply and stop of both the source RF signal and the bias signal may be alternately repeated.

[0068] In step ST12, the pressure in the chamber 10 may be appropriately set. For example, the pressure in the chamber 10 may be set to 50 mTorr or less, 30 mTorr or less, or 10 mTorr or less.

[0069] 5 is a diagram for explaining an example of the state of the substrate W during etching. As shown in Fig. 5, the portion of the silicon nitride film SF1 exposed at the opening OP is etched in the depth direction (from top to bottom in Fig. 5) by active species in the plasma. As a result, a recess RC having a shape corresponding to the opening OP is formed.

[0070] Here, the hydrofluorocarbon gas in the processing gas is less likely to dissociate into cations than the first fluorocarbon gas and the second fluorocarbon gas. Therefore, when the flow rate of the hydrofluorocarbon gas increases, isotropic etching by radicals derived from the hydrofluorocarbon gas tends to be promoted in the recess RC. In this regard, the first processing gas has a total flow rate of the first fluorocarbon gas and the second fluorocarbon gas that is greater than the flow rate of the hydrofluorocarbon gas. Therefore, excessive promotion of isotropic etching in the recess RC can be suppressed.

[0071] As shown in FIG. 5, in one embodiment, during etching, the first film DP1 and the second film DP2 may adhere to the sidewall of the mask MK or its vicinity (the upper sidewall of the silicon nitride film SF1 that defines the recess RC). The first film DP1 may be a carbon-containing film with a large molecular weight derived from a first fluorocarbon gas (C4F6 gas as an example) in the process gas. The second film DP2 may be a carbon-containing film with a small molecular weight derived from a second fluorocarbon gas (C3F8 gas as an example) in the process gas. If the second film DP2 has a small molecular weight and low adsorptivity, it is likely to reach the bottom of the recess RC. In this regard, in the example shown in FIG. 5, the first film DP1 is polymerized as a whole so as to incorporate the second film DP2, and thus adheres to the sidewall of the mask MK or its vicinity, including the second film DP2. This can prevent the second film DP2 from accumulating at the bottom of the recess RC and obstructing etching.

[0072] The first film DP1 and the second film DP2 can function as a protective film against etching on the sidewall of the mask MK or in the vicinity thereof due to their carbon components. This can prevent the sidewall of the mask MK from being etched in the width direction. This can prevent metal from the mask MK from adhering to the recess RC and impeding etching. In one embodiment, the first film DP1 and the second film DP2 can also be deposited on the upper surface of the mask MK. In this case, the first film DP1 and the second film DP2 can function as a protective film against etching on the upper surface of the mask MK. This can prevent the upper surface of the mask MK from being etched in the depth direction.

[0073] The etching in step ST12 is stopped when a given stop condition is satisfied, which may be appropriately set based on the etching time, the depth of the recess RC, etc.

[0074] Fig. 6 is a diagram showing an example of the cross-sectional structure of the substrate W at the end of etching. Fig. 6 shows an example in which the bottom of the recess RC reaches the undercoat film UF, and the undercoat film UF is exposed. The aspect ratio of the recess RC in this state may be, for example, 20 or more, 30 or more, 40 or more, 50 or more, or 100 or more.

[0075] As described above, in this processing method, excessive promotion of isotropic etching in the recess RC during etching can be suppressed. This can suppress the width dimension (dimension indicated by "W" in FIG. 6) of the silicon nitride film SF1 after etching from becoming smaller (e.g., the bar becomes thinner). Ensuring the width dimension of the silicon nitride film SF1 can contribute to ensuring the performance of a device (e.g., a capacitor) manufactured from the substrate W.

[0076] As described above, this processing method can prevent the second film DP2 from accumulating at the bottom of the recess RC during etching and hindering the etching, thereby accelerating the etching in the depth direction of the recess RC.

[0077] As described above, in this processing method, it is possible to suppress the metal originating from the mask MK from adhering or accumulating on the sidewall of the silicon nitride film SF1 or the bottom of the recess RC during etching, thereby suppressing the occurrence of etching shape abnormalities (e.g., necking, bowing, twisting, etc.) and etch stops.

[0078] As described above, in this processing method, the upper surface of the mask MK can be prevented from being etched in the depth direction during etching, thereby improving the etching selectivity of the silicon nitride film SF1 to the mask MK.

[0079] Fig. 7 is a flow chart showing another example of the present processing method. This example includes a step ST21 of providing a substrate W1, a step ST22 of performing a first etching, and a step ST23 of performing a second etching. Below, differences from the flow chart shown in Fig. 3 will be mainly described, and similar points will not be described.

[0080] In step ST21, a substrate W1 is provided in the chamber 10. FIG. 8 is a diagram showing an example of a cross-sectional structure of the substrate W1. The substrate W1 includes a silicon oxide film SF2 between a silicon nitride film SF1 and an undercoat film UF. As shown in FIG. 8, the silicon oxide film SF2 may be disposed directly below the silicon nitride film SF1. The mask MK, the silicon nitride film SF1, and the undercoat film UF may be configured similarly to the substrate W shown in FIG. 4. In one embodiment, the substrate W1 may be a substrate for a DRAM. In one embodiment, the opening dimension of the opening OP may be 50 nm or less.

[0081] The silicon nitride film SF1 is etched by the first etching in step ST22. The first etching may be performed in the same manner as in step ST12. As a result, a recess having a shape corresponding to the opening OP of the mask MK is formed in the silicon nitride film SF1.

[0082] The silicon oxide film SF2 is etched by the second etching in step ST23. As a result, a recess having a shape corresponding to the opening OP of the mask MK is formed in the silicon oxide film SF2. Step ST23 may be performed consecutively from step ST22. The second etching may be performed under the same conditions as the first etching, or may be performed under partially (or entirely) different conditions as exemplified below.

[0083] For example, in step ST23, a second process gas may be supplied into the plasma processing space 10s. Then, a second etching may be performed using plasma generated from the second process gas. The second process gas may include a gas of a different type and / or flow rate from the first process gas. In one embodiment, the second process gas includes a fluorocarbon gas and does not include a hydrofluorocarbon gas. The second process gas may further include an oxygen-containing gas and / or a noble gas, similar to the first process gas.

[0084] Also, for example, in step ST22, a bias DC signal of a first voltage level may be supplied to the lower electrode of the substrate support 11. Then, in step ST23, a bias signal of a second voltage level may be supplied to the lower electrode. The absolute value of the bias signal of the second voltage level is different from the absolute value of the bias signal of the first voltage level. In one example, the absolute value of the bias signal of the second voltage level is greater than the absolute value of the bias signal of the first voltage level.

[0085] <Example> Next, examples of the present processing method will be described. The present disclosure is not limited to the following examples and reference examples.

[0086] Example 1 In Example 1, a substrate having a structure similar to that of the substrate W1 shown in FIG. 8 was etched using the plasma processing apparatus 1 described in FIG. 2 according to the flow chart described in FIG. 3. A tungsten silicide film having a hole-shaped opening pattern was used as the mask MK. In step ST12, the first processing gas contained C4F6 gas (first fluorocarbon gas), C3F8 gas (second fluorocarbon gas), CH2F2 gas (hydrofluorocarbon gas), and O2 gas (oxygen-containing gas). The flow rate ratio of C4F6 gas to C3F8 gas was 1:6. The total flow rate of C4F6 gas and C3F8 gas was 1.5 times the flow rate of CH2F2 gas. The etching in step ST12 was performed for 2 minutes and 15 seconds.

[0087] Example 2 Example 2 is similar to Example 1, except that the flow rate of C4F6 gas was doubled. The flow rate ratio of C4F6 gas to C3F8 gas was 1:3. The total flow rate of C4F6 gas and C3F8 gas was 1.7 times the flow rate of CH2F2 gas.

[0088] (Reference Examples 1 and 2) Reference Examples 1 and 2 are similar to Example 1, except that a process gas not containing C4F6 gas was used. The process gas used in Reference Example 1 contained C3F8 gas, CH2F2 gas, and O2 gas at the same flow rates as in Example 1. The process gas used in Reference Example 2 contained C3F8 gas and O2 gas at the same flow rates as in Example 1, and contained CH2F2 gas at a flow rate 2.7 times that of Example 1.

[0089] Fig. 9 is a diagram showing the etching results for the embodiment and the reference example. In Fig. 9, "mask remaining thickness" is the dimension in the depth direction of the mask MK after etching. "Recess depth" is the dimension in the depth direction of the recess RC formed in the silicon nitride film SF1 and the silicon oxide film SF2 by etching. "Minimum bar width" is the dimension in the width direction of the silicon nitride film SF1 after etching.

[0090] 1, in both Example 1 and Example 2, the recess depth and the minimum bar width were significantly larger while maintaining the same level of mask residual thickness, compared to Reference Example 1 and Reference Example 2. Furthermore, in Reference Example 1, necking was observed in the recess RC of the silicon nitride film SF1 formed by etching, whereas in both Example 1 and Example 2, no shape abnormality was observed in the recess RC of the silicon nitride film SF1 and the silicon oxide film SF2 formed by etching.

[0091] The embodiments of the present disclosure further include the following aspects.

[0092] (Appendix 1) (a) providing a substrate in a chamber, the substrate including a metal-containing mask and a silicon nitride layer disposed below the mask; (b) etching the silicon nitride film through the mask using plasma generated from a first process gas, the first process gas including a first fluorocarbon gas, a second fluorocarbon gas, and a hydrofluorocarbon gas, the first fluorocarbon gas being C4F6 gas, the second fluorocarbon gas being a fluorocarbon gas other than C4F6 gas, and a total flow rate of the first fluorocarbon gas and the second fluorocarbon gas being greater than a flow rate of the hydrofluorocarbon gas; An etching method comprising:

[0093] (Appendix 2) 2. The etching method of claim 1, wherein a flow rate of the first fluorocarbon gas is less than a flow rate of the second fluorocarbon gas.

[0094] (Appendix 3) 3. The etching method according to claim 1, wherein the hydrofluorocarbon gas includes CH2F2 gas.

[0095] (Appendix 4) 4. The etching method according to claim 1, wherein the second fluorocarbon gas is a fluorocarbon gas that does not contain a double bond.

[0096] (Appendix 5) 5. The etching method according to claim 1, wherein the second fluorocarbon gas is C3F8 gas.

[0097] (Appendix 6) 6. The etching method of claim 1, wherein the metal comprises tungsten or molybdenum.

[0098] (Appendix 7) 7. The etching method of claim 1, wherein the mask comprises tungsten silicide.

[0099] (Appendix 8) 8. The etching method of claim 1, wherein the process gas further comprises an oxygen-containing gas.

[0100] (Appendix 9) 9. The etching method of claim 1, wherein the process gas further comprises an inert gas.

[0101] (Appendix 10) 10. The etching method of any one of claims 1 to 9, wherein (b) comprises providing a pulsed bias DC signal to the substrate.

[0102] (Appendix 11) 11. The etching method according to claim 1, wherein the silicon nitride film is disposed directly under the mask.

[0103] (Appendix 12) 12. The etching method according to claim 1, wherein the mask includes an opening pattern having an opening dimension of 50 nm or less.

[0104] (Appendix 13) 13. The etching method according to claim 1, wherein the substrate further includes a silicon oxide film below the silicon nitride film.

[0105] (Appendix 14) 14. The etching method according to claim 13, further comprising, after the step (b), (c) generating plasma from a second process gas to etch the silicon oxide film.

[0106] (Appendix 15) 15. The etching method of claim 14, wherein the second process gas includes a fluorocarbon gas and does not include a hydrofluorocarbon gas.

[0107] (Appendix 16) (b) includes providing a bias DC signal at a first voltage level to the substrate; 16. The etching method of claim 13, wherein (c) includes supplying a bias DC signal of a second voltage level to the substrate, the absolute value of the second voltage level being greater than the absolute value of the first voltage level.

[0108] (Appendix 17) A plasma processing apparatus including a chamber and a control unit, The control unit is (a) providing a substrate in a chamber, the substrate including a metal-containing mask and a silicon nitride layer disposed below the mask; (b) controlling a process for etching the silicon nitride film through the mask using plasma generated from a first process gas, the first process gas including a first fluorocarbon gas, a second fluorocarbon gas, and a hydrofluorocarbon gas, the first fluorocarbon gas being C4F6 gas, the second fluorocarbon gas being a fluorocarbon gas different from C4F6 gas, and a total flow rate of the first fluorocarbon gas and the second fluorocarbon gas being greater than a flow rate of the hydrofluorocarbon gas; and A plasma processing system.

[0109] (Appendix 18) A computer of a plasma processing system including a plasma processing apparatus having a chamber and a control unit, (a) providing a substrate in a chamber, the substrate including a metal-containing mask and a silicon nitride layer disposed below the mask; (b) controlling a process for etching the silicon nitride film through the mask using plasma generated from a first process gas, the first process gas including a first fluorocarbon gas, a second fluorocarbon gas, and a hydrofluorocarbon gas, the first fluorocarbon gas being C4F6 gas, the second fluorocarbon gas being a fluorocarbon gas different from C4F6 gas, and a total flow rate of the first fluorocarbon gas and the second fluorocarbon gas being greater than a flow rate of the hydrofluorocarbon gas; and A program that executes the following.

[0110] (Appendix 19) A storage medium storing the program according to claim 18.

[0111] The above embodiments are described for the purpose of explanation and are not intended to limit the scope of the present disclosure. Various modifications can be made to the above embodiments without departing from the scope and spirit of the present disclosure. For example, some components in one embodiment can be added to other embodiments. Also, some components in one embodiment can be replaced with corresponding components in other embodiments. [Explanation of symbols]

[0112] REFERENCE SIGNS LIST 1: plasma processing apparatus, 2: control section, 10: plasma processing chamber, 10s: plasma processing space, 11: substrate support section, 13: shower head, 20: gas supply section, 31a: first RF generating section, 31b: second RF generating section, 32a: first DC generating section, SF1: silicon nitride film, MK: mask, OP: opening, RC: recess, UF: base film, W: substrate

Claims

1. (a) providing a substrate in a chamber, the substrate including a metal-containing mask and a silicon nitride layer disposed below the mask; (b) etching the silicon nitride film through the mask using plasma generated from a first process gas, the first process gas including a first fluorocarbon gas, a second fluorocarbon gas, and a hydrofluorocarbon gas, the first fluorocarbon gas being C 4 F 6 gas, and the second fluorocarbon gas is 4 F 6 a flow rate of the first fluorocarbon gas and the second fluorocarbon gas is greater than a flow rate of the hydrofluorocarbon gas; An etching method comprising:

2. 2. The etching method of claim 1, wherein a flow rate of the first fluorocarbon gas is less than a flow rate of the second fluorocarbon gas.

3. The hydrofluorocarbon gas is CH 2 F 2 The etching method of claim 1 comprising a gas.

4. 2. The etching method according to claim 1, wherein the second fluorocarbon gas is a fluorocarbon gas that does not contain a double bond.

5. The second fluorocarbon gas is 3 F 8 The etching method according to claim 4 , wherein the gas is a gas.

6. The etching method of claim 1 , wherein the metal comprises tungsten or molybdenum.

7. 7. The method of claim 6, wherein the mask comprises tungsten silicide.

8. The etching method of claim 1 , wherein the process gas further comprises an oxygen-containing gas.

9. The etching method of claim 1 , wherein the process gas further comprises an inert gas.

10. 2. The etching method of claim 1, wherein (b) comprises providing a pulsed bias DC signal to the substrate.

11. The etching method according to claim 1 , wherein the silicon nitride film is disposed directly below the mask.

12. The etching method according to claim 1 , wherein the mask includes an opening pattern having an opening dimension of 50 nm or less.

13. The etching method according to claim 1 , wherein the substrate further includes a silicon oxide film below the silicon nitride film.

14. 14. The etching method according to claim 13, further comprising, after the step (b), the step of: (c) generating a plasma from a second process gas to etch the silicon oxide film.

15. 15. The etching method of claim 14, wherein the second process gas includes a fluorocarbon gas and does not include a hydrofluorocarbon gas.

16. (b) includes providing a bias DC signal at a first voltage level to the substrate; 15. The etching method of claim 14, wherein (c) comprises providing a bias DC signal of a second voltage level to the substrate, the absolute value of the second voltage level being greater than the absolute value of the first voltage level.

17. A plasma processing apparatus including a chamber and a control unit, The control unit is (a) providing a substrate into a chamber, the substrate including a metal-containing mask and a silicon nitride layer disposed below the mask; (b) controlling etching of the silicon nitride film through the mask using plasma generated from a first process gas, the first process gas including a first fluorocarbon gas, a second fluorocarbon gas, and a hydrofluorocarbon gas, the first fluorocarbon gas being C 4 F 6 gas, and the second fluorocarbon gas is 4 F 6 a flow rate of the first fluorocarbon gas and the second fluorocarbon gas is greater than a flow rate of the hydrofluorocarbon gas; and A plasma processing system.

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