Etching method and plasma processing apparatus

Abstract

To provide a technique that can improve an etching selection ratio and an etching rate.SOLUTION: An etching method includes the steps of: (a) providing a substrate that includes a laminated film that includes alternately stacked silicon oxide films and silicon nitride films; (b) etching the silicon oxide film using first plasma generated from a first process gas that contains WF6 gas, CF4 gas or COF2 gas, fluorocarbon gas with two or more carbon atoms, and noble gas; (c) etching the silicon nitride film using second plasma generated from a second process gas that contains CF4 gas or COF2 gas, hydrofluorocarbon gas, and noble gas; and (d) repeating the steps (b) and (c). In the step (b), the flow rate of the noble gas is the highest in all the gases contained in the first processing gas. In the step (c), the flow rate of the noble gas is the highest in all the gases contained in the second processing gas.SELECTED DRAWING: Figure 3

Description

[Technical field]

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

[0002] Patent Document 1 discloses an etching method for etching a substrate on which a first silicon-containing film and a second silicon-containing film are alternately laminated. The method includes a first etching step and a second etching step. In the first etching step, the first silicon-containing film of the substrate is etched by plasma of a first processing gas. In the second etching step, the second silicon-containing film of the substrate is etched by plasma of a second processing gas. The first etching step to the second etching step are repeated a predetermined number of times. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent Publication No. 2021-118304 Summary of the Invention [Problem to be solved by the invention]

[0004] The present disclosure provides a technique that can improve the etching selectivity and etching rate. [Means for solving the problem]

[0005] In one exemplary embodiment, an etching method is provided, which includes the steps of: (a) providing a substrate having a laminated film including a silicon oxide film and a silicon nitride film alternately laminated thereon; (b) etching the silicon oxide film with a first plasma generated from a first process gas including WF6 gas, CF4 gas or COF2 gas, a fluorocarbon gas having a carbon number of 2 or more, and a noble gas; (c) etching the silicon nitride film with a second plasma generated from a second process gas including CF4 gas or COF2 gas, a hydrofluorocarbon gas, and a noble gas; and (d) repeating the steps (b) and (c), in which in the step (b), the noble gas has the largest flow rate among all gases contained in the first process gas, and in the step (c), the noble gas has the largest flow rate among all gases contained in the second process gas. Effect of the Invention

[0006] According to one exemplary embodiment, the etching selectivity and etching rate can be improved. [Brief description of the drawings]

[0007] [Figure 1] FIG. 1 is a diagram for explaining an example of the configuration of a plasma processing system. [Diagram 2] FIG. 2 is a diagram for explaining a configuration example of a capacitively coupled plasma processing apparatus. [Diagram 3] FIG. 3 is a flow chart of an etching method according to one exemplary embodiment. [Figure 4] FIG. 4 is a partial enlarged view of an example substrate to which the method of FIG. 3 may be applied. [Diagram 5] FIG. 5 is a cross-sectional view illustrating a step of an etching method according to an example embodiment. [Figure 6] FIG. 6 is a cross-sectional view illustrating a step of an etching method according to an example embodiment. [Figure 7] FIG. 7 is a partial enlarged view of another example of a substrate to which the method of FIG. 3 can be applied. [Figure 8] FIG. 8 is a cross-sectional view illustrating a step of an etching method according to one exemplary embodiment. [Figure 9] FIG. 9 is a cross-sectional view illustrating a step of an etching method according to one example embodiment. [Figure 10] FIG. 10 is a schematic diagram showing a cross section of an example of a substrate when etching of a silicon oxide film is completed. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0008] Various exemplary embodiments will now be described in detail with reference to the drawings, in which the same or corresponding parts are designated by the same reference numerals.

[0009] 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.

[0010] 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.

[0011] 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).

[0012] 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.

[0013] 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.

[0014] 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.

[0015] 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.

[0016] 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.

[0017] 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.

[0018] 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.

[0019] 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.

[0020] 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.

[0021] 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.

[0022] 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.

[0023] 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.

[0024] 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.

[0025] 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.

[0026] 3 is a flow chart of an etching method according to one exemplary embodiment. The etching method MT1 (hereinafter, referred to as "method MT1") shown in FIG. 3 can be performed by the plasma processing apparatus 1 of the above embodiment.

[0027] Fig. 4 is a partial enlarged view of an example of a substrate to which the method of Fig. 3 can be applied. The substrate W shown in Fig. 4 includes a stacked film ST including a silicon oxide film F1 and a silicon nitride film F2 that are alternately stacked. The stacked film ST includes a plurality of silicon oxide films F1 and a plurality of silicon nitride films F2. An example of the silicon oxide film F1 is SiO xThe laminated film ST may include a silicon oxide film F2. x is a positive real number. An example of the silicon nitride film F2 includes a SiN film. The top layer of the laminated film ST may be a silicon oxide film F1. The bottom layer of the laminated film ST may be a silicon oxide film F1. The substrate W may include a mask MK on the laminated film ST. The mask MK has an opening OP. The opening OP may have a hole shape or a slit shape. The mask MK may be a carbon-containing film. Examples of the carbon-containing film include an amorphous carbon film and a photoresist film. The substrate W may include an underlayer region UR under the laminated film ST. The underlayer region UR may include a material different from the material of the bottom layer of the laminated film ST.

[0028] The laminated film ST may have a recess RS located below the opening OP. The recess RS may have a hole shape or a slit shape. The recess RS may have a width CD2 smaller than a width CD1 of the opening OP. In this case, a shoulder SH of the recess RS is located within the opening OP when viewed from the thickness direction of the substrate W. Each of the widths CD1 and CD2 may be a critical dimension along the surface direction of the substrate W. The depth of the recess RS may be the same as the sum of the thickness of one silicon oxide film F1 and the thickness of one silicon nitride film F2. In this case, a layer the same as the top layer of the laminated film ST is exposed at the bottom surface of the recess RS.

[0029] Method MT1 will be described below with reference to Figs. 2 to 6, taking as an example a case where method MT1 is applied to a substrate W using the plasma processing apparatus 1 of the above embodiment. Figs. 5 to 6 are cross-sectional views showing a step of an etching method according to one exemplary embodiment. When the plasma processing apparatus 1 is used, method MT1 can be performed in the plasma processing apparatus 1 by controlling each part of the plasma processing apparatus 1 by a control unit 2. In method MT1, a substrate W on a substrate support 11 arranged in a plasma processing chamber 10 is processed as shown in Fig. 2.

[0030] 3, the method MT1 may include steps ST1 to ST4. Steps ST1 to ST4 may be performed in sequence.

[0031] (Process ST1) 4, a substrate W is provided. The substrate W may be loaded onto a substrate support 11 in a plasma processing chamber 10.

[0032] (Process ST2) As shown in FIG. 5, the silicon oxide film F1 is etched by a first plasma PL1 generated from a first processing gas. The silicon nitride film F2 can function as an etching stop layer. At the end of step ST2, the supply of the first processing gas may be stopped. The first processing gas includes WF6 gas, CF4 gas or COF2 gas, a fluorocarbon gas having a carbon number of 2 or more, and a noble gas. The first processing gas may further include an oxygen-containing gas. The flow rate of the noble gas is the highest among all gases included in the first processing gas. The flow rate of WF6 gas may be the lowest among all gases included in the first processing gas. The flow rate of the CF4 gas or COF2 gas may be higher than the flow rate of the fluorocarbon gas having a carbon number of 2 or more. An example of a fluorocarbon gas having a carbon number of 2 or more includes C4F6 gas. An example of a noble gas includes argon gas. An example of an oxygen-containing gas includes oxygen gas. In step ST2, the flow rate of the CF4 gas may be higher than the flow rate of the C4F6 gas.

[0033] The first process gas may include a metal-containing gas, a CF4 gas or a COF2 gas, a fluorocarbon gas having two or more carbon atoms, and a noble gas. The metal-containing gas may include a metal halide gas. The metal-containing gas may include at least one gas selected from the group consisting of WF6 gas, WCl6 gas, MoF6 gas, MoCl6 gas, and TiCl4 gas.

[0034] At the start of step ST2, the stacked film ST may have a recess RS located under the opening OP, and the recess RS may have a width CD2 smaller than the width CD1 of the opening OP, as shown in Fig. 4. Even at the end of step ST2, the recess RS may have a width CD2 smaller than the width CD1 of the opening OP, as shown in Fig. 5.

[0035] Step ST2 may be performed as follows. A first process gas is supplied into the plasma processing chamber 10 by the gas supply unit 20. The plasma generating unit 12 generates a first plasma PL1 from the first process gas in the plasma processing chamber 10. The control unit 2 controls the gas supply unit 20 and the plasma generating unit 12 so that the silicon oxide film F1 is etched by the first plasma PL1.

[0036] (Process ST3) As shown in FIG. 6, the silicon nitride film F2 is etched by the second plasma PL2 generated from the second process gas. The silicon oxide film F1 can function as an etching stop layer. At the end of step ST3, the supply of the second process gas may be stopped. The second process gas includes CF4 gas or COF2 gas, a hydrofluorocarbon gas, and a noble gas. The second process gas may further include an oxygen-containing gas. The flow rate of the noble gas is the largest among all the gases included in the second process gas. The flow rate of the CF4 gas or COF2 gas may be smaller than the flow rate of the hydrofluorocarbon gas. Examples of the hydrofluorocarbon gas include CHF3 gas and CH3F gas. Examples of the noble gas include argon gas. Examples of the oxygen-containing gas include oxygen gas. In step ST3, the flow rate of the CF4 gas may be smaller than the total flow rate of the CHF3 gas and CH3F gas.

[0037] Step ST3 may be performed as follows. The gas supply unit 20 supplies a second process gas into the plasma processing chamber 10. The plasma generating unit 12 generates a second plasma PL2 from the second process gas in the plasma processing chamber 10. The control unit 2 controls the gas supply unit 20 and the plasma generating unit 12 so that the silicon nitride film F2 is etched by the second plasma PL2.

[0038] (Process ST4) In step ST4, step ST2 and step ST3 are repeated. The cycle including step ST2 and step ST3 may be repeated multiple times. From step ST2 to step ST4 (between step ST2, step ST3, and step ST4), CF4 gas or COF2 gas and a noble gas may be continuously supplied.

[0039] According to the method MT1, in step ST2, the first processing gas contains WF6 gas. Therefore, the etching selectivity of the silicon oxide film F1 to the silicon nitride film F2 can be improved. It is believed that the etching selectivity is improved because the WF6 gas deposits tungsten-containing deposits on the silicon nitride film F2. Furthermore, the WF6 gas can improve the etching rate of the silicon oxide film F1. The same effect can be obtained with metal-containing gases other than WF6 gas.

[0040] Furthermore, in step ST2, when etching of the silicon oxide film F1 is completed, deposits containing carbon and fluorine may be deposited on the silicon nitride film F2 by the fluorocarbon gas having a carbon number of 2 or more. If the flow rate of the noble gas is high, the amount of such deposits can be reduced, so that in step ST3, the silicon nitride film F2 can be etched after removing the deposits in a short time. As a result, the duration of step ST3 can be shortened.

[0041] At the start of step ST2, if the recess RS of the stacked film ST has a width CD2 smaller than the width CD1 of the opening OP, the silicon nitride film F2 is less likely to be etched at the shoulder SH of the recess RS (the upper end of the side wall of the recess RS) in step ST2 (see FIG. 5). Therefore, the silicon oxide film F1 below the silicon nitride film F2 is less likely to be etched at the shoulder SH of the recess RS. This makes it possible to suppress the expansion of the width CD2 of the recess RS caused by the lateral etching of the silicon oxide film F1. Furthermore, since it is possible to suppress the silicon oxide film F1 from remaining at the edge of the bottom surface of the recess RS in step ST2, it is also possible to suppress the reduction of the width CD2 of the recess RS.

[0042] Fig. 7 is a partial enlarged view of another example of a substrate to which the method of Fig. 3 can be applied. The substrate W1 shown in Fig. 7 includes a stacked film ST including silicon oxide films F1 and silicon nitride films F2 stacked alternately. The stacked film ST includes a plurality of silicon oxide films F1 and a plurality of silicon nitride films F2. The top layer of the stacked film ST may be a silicon oxide film F1. The bottom layer of the stacked film ST may be a silicon oxide film F1. The substrate W1 may include a mask MK on the stacked film ST. The mask MK has at least one opening OP. The substrate W may include an undercoat region UR under the stacked film ST.

[0043] The opening OP may include a first opening OP1 and a second opening OP2. The stacked film ST has a flat upper surface TS below the opening OP. The upper surface TS may be flat throughout the entirety of the opening OP. The upper surface TS may include a flat first upper surface TS1 below the first opening OP1 and a flat second upper surface TS2 below the second opening OP2. The first upper surface TS1 may be flat throughout the entirety of the first opening OP1. The second upper surface TS2 may be flat throughout the entirety of the second opening OP2. The first upper surface TS1 and the second upper surface TS2 may be located at different heights. That is, the first upper surface TS1 and the second upper surface TS2 may be located at different positions in the thickness direction of the substrate W1. The stacked film ST may not have a recess below the first opening OP1, but may have a recess below the second opening OP2. The second upper surface TS2 corresponds to the bottom surface of the recess. In the thickness direction of the substrate W1, the difference in height between the first upper surface TS1 and the second upper surface TS2 may be equal to the sum of the thickness of one silicon oxide film F1 and the thickness of one silicon nitride film F2.

[0044] Hereinafter, the case where method MT1 is applied to substrate W1 using the plasma processing apparatus 1 of the above embodiment will be described with reference to Figures 2 to 3 and 7 to 9. Figures 8 to 9 are cross-sectional views showing a step of an etching method according to one exemplary embodiment. Method MT1 can be applied to substrate W1 in the same way as method MT1 is applied to substrate W in Figure 4.

[0045] (Process ST1) 7, a substrate W1 is provided. The substrate W1 may be loaded onto a substrate support 11 in a plasma processing chamber 10.

[0046] (Process ST2) As shown in FIG. 8, a silicon oxide film F1 is etched by a first plasma PL1 generated from a first process gas.

[0047] At the start of step ST2, as shown in FIG. 7, the stacked film ST has a flat upper surface TS below the opening OP. The opening OP may include a first opening OP1 and a second opening OP2. The upper surface TS may include a flat first upper surface TS1 below the first opening OP1 and a flat second upper surface TS2 below the second opening OP2. The first upper surface TS1 and the second upper surface TS2 may be located at different heights. Even at the end of step ST2, as shown in FIG. 8, the first upper surface TS1 and the second upper surface TS2 may be located at different heights.

[0048] (Process ST3) As shown in FIG. 9, the silicon nitride film F2 is etched by a second plasma PL2 generated from a second process gas.

[0049] (Process ST4) In step ST4, steps ST2 and ST3 are repeated. Steps ST2 and ST3 may be repeated multiple times.

[0050] Various experiments performed to evaluate Method MT1 are described below, but the experiments described below are not intended to limit the present disclosure.

[0051] (First experiment) In the first experiment, first, a substrate was provided on a substrate support in a chamber of a plasma processing apparatus (step ST1). The substrate had a laminated film including silicon oxide films and silicon nitride films that were alternately laminated.

[0052] Next, the silicon oxide film was etched by a first plasma generated from a first process gas (step ST2). The first process gas contained WF6 gas, CF4 gas, C4F6 gas, argon gas, and oxygen gas. Of all the gases contained in the first process gas, the flow rate of argon gas was the highest. Of all the gases contained in the first process gas, the flow rate of WF6 gas was the lowest. The flow rate of CF4 gas was higher than the flow rate of C4F6 gas.

[0053] Next, the silicon nitride film was etched by a second plasma generated from a second process gas (step ST3). The second process gas contained CF4 gas, CHF3 gas, CH3F gas, argon gas, and oxygen gas. Of all the gases contained in the second process gas, the flow rate of argon gas was the highest. The flow rate of CF4 gas was smaller than the total flow rate of CHF3 gas and CH3F gas.

[0054] (Second experiment) The second experiment was carried out in the same manner as the first experiment, except that the WF6 gas was removed from the first process gas.

[0055] (First experiment result) In the step of etching the silicon oxide film (step ST2), the etching rates of the silicon oxide film and the silicon nitride film were calculated. The etching rate of the silicon oxide film in the first experiment was higher than the etching rate of the silicon oxide film in the second experiment. This shows that the etching rate of the silicon oxide film is increased by WF6 gas. Also, the etching rate of the silicon nitride film in the first experiment was lower than the etching rate of the silicon nitride film in the second experiment. This shows that the etching rate of the silicon nitride film is decreased by WF6 gas. This shows that the etching selectivity of the silicon oxide film to the silicon nitride film can be improved by WF6 gas.

[0056] (Third experiment) The second experiment was carried out in the same manner as the first experiment, except that a substrate having the same structure as substrate W in FIG. 4 was used.

[0057] (Experiment 4) The fourth experiment was carried out in the same manner as the third experiment, except that the WF6 gas was removed from the first process gas.

[0058] (Second experiment results) When the step of etching the silicon oxide film (step ST2) was completed, the cross section of the substrate was observed.

[0059] FIG. 10 is a schematic diagram showing a cross section of an example substrate at the end of etching of a silicon oxide film. The solid line E3 shown in FIG. 10 indicates the surface of the recess and the interface between adjacent films in the third experiment. The dashed line E4 indicates the surface of the recess and the interface between adjacent films in the fourth experiment. As shown in FIG. 10, in both the third and fourth experiments, the top film at the shoulder of the recess was a silicon nitride film. The reduction in thickness (etching amount) of the top film in the third experiment was less than the reduction in thickness (etching amount) of the top film in the fourth experiment. It is therefore understood that WF6 gas suppresses etching of the shoulder of the recess.

[0060] Although various exemplary embodiments have been described above, the present invention is not limited to the above-described exemplary embodiments, and various omissions, substitutions, and modifications may be made. In addition, elements in different embodiments can be combined to form other embodiments.

[0061] Various exemplary embodiments included in the present disclosure are now described in [E1] to [E20] below.

[0062] [E1] (a) providing a substrate having a laminate including alternating silicon oxide and silicon nitride films; (b) etching the silicon oxide film by a first plasma generated from a first process gas including WF6 gas, CF4 gas or COF2 gas, a fluorocarbon gas having two or more carbon atoms, and a noble gas; (c) etching the silicon nitride film by a second plasma generated from a second process gas including CF4 gas or COF2 gas, a hydrofluorocarbon gas, and a noble gas; (d) repeating steps (b) and (c); Including, In the (b), the flow rate of the noble gas is the highest among all gases contained in the first process gas; The etching method according to (c), wherein the noble gas has the highest flow rate among all gases contained in the second process gas.

[0063] According to the method [E1], in (b), the first processing gas contains WF6 gas. Therefore, the etching selectivity of the silicon oxide film to the silicon nitride film can be improved, and the etching rate of the silicon oxide film can be improved. It is believed that the etching selectivity is improved because the WF6 gas deposits tungsten-containing deposits on the silicon nitride film.

[0064] [E2] The etching method according to [E1], wherein the flow rate of the WF6 gas is the smallest among all gases contained in the first process gas.

[0065] [E3] The etching method according to [E1] or [E2], wherein the fluorocarbon gas having two or more carbon atoms includes C4F6 gas.

[0066] [E4] The etching method according to [E3], wherein in (b), the flow rate of the CF4 gas is greater than the flow rate of the C4F6 gas.

[0067] [E5] The etching method according to any one of [E1] to [E4], wherein the hydrofluorocarbon gas includes at least one gas selected from the group consisting of CHF3 gas and CH3F gas.

[0068] [E6] The etching method according to [E5], wherein in (c), the flow rate of the CF4 gas is smaller than a total flow rate of the CHF3 gas and the CH3F gas.

[0069] [E7] The etching method according to any one of [E1] to [E6], wherein the second process gas further contains an oxygen-containing gas.

[0070] [E8] the substrate includes a mask on the film stack, the mask having an opening; The etching method according to any one of [E1] to [E7], wherein at the start of (b), the laminated film has a recess located below the opening, and the recess has a width smaller than a width of the opening.

[0071] In this case, in (b), the silicon nitride film is difficult to etch at the shoulder portion (upper end of the side wall) of the recess. Therefore, the silicon oxide film below the silicon nitride film is difficult to etch at the shoulder portion of the recess. Therefore, it is possible to suppress the expansion of the width of the recess caused by the lateral etching of the silicon oxide film.

[0072] [E9] the substrate includes a mask on the film stack, the mask having an opening; The etching method according to any one of [E1] to [E7], wherein at the start of (b), the laminated film has a flat upper surface below the opening.

[0073] [E10] the opening includes a first opening and a second opening; the top surface includes a first planar top surface below the first opening and a second planar top surface below the second opening; The etching method according to [E9], wherein at the start of (b), the first upper surface and the second upper surface are positioned at different heights.

[0074] [E11] The etching method according to any one of [E1] to [E10], wherein the substrate includes a mask on the laminated film, and the mask is a carbon-containing film.

[0075] [E12] The etching method according to [E11], wherein the carbon-containing film includes at least one selected from the group consisting of an amorphous carbon film and a photoresist film.

[0076] [E13] The etching method according to any one of [E1] to [E12], wherein the uppermost layer of the laminated film is a silicon oxide film.

[0077] [E14] The etching method according to any one of [E1] to [E13], wherein the bottom layer of the laminated film is a silicon oxide film.

[0078] [E15] The etching method according to any one of [E1] to [E14], wherein an uppermost layer of the laminated film is a silicon oxide film, and a lowermost layer of the laminated film is a silicon oxide film.

[0079] [E16] The etching method according to any one of [E1] to [E15], wherein the CF4 gas or the COF2 gas and the noble gas are continuously supplied during the steps (b), (c), and (d).

[0080] [E17] (a) providing a substrate having a laminate including alternating silicon oxide and silicon nitride films; (b) etching the silicon oxide film with a first plasma generated from a first process gas including a metal-containing gas, CF4 gas or COF2 gas, a fluorocarbon gas having two or more carbon atoms, and a noble gas; (c) etching the silicon nitride film by a second plasma generated from a second process gas including CF4 gas or COF2 gas, a hydrofluorocarbon gas, and a noble gas; (d) repeating steps (b) and (c); Including, In the (b), the flow rate of the noble gas is the highest among all gases contained in the first process gas; The etching method according to (c), wherein the noble gas has the highest flow rate among all gases contained in the second process gas.

[0081] [E18] The etching method according to [E17], wherein the metal-containing gas contains a metal halide gas.

[0082] [E19] The etching method according to [E17], wherein the metal-containing gas contains at least one gas selected from the group consisting of WF6 gas, WCl6 gas, MoF6 gas, MoCl6 gas, and TiCl4 gas.

[0083] [E20] A plasma processing apparatus comprising: A chamber; a substrate support for supporting a substrate in the chamber, the substrate comprising a stack of films including alternating silicon oxide films and silicon nitride films; a gas supply configured to supply a first process gas and a second process gas into the chamber, the first process gas including WF6 gas, CF4 gas or COF2 gas, a fluorocarbon gas having a carbon number of two or more, and a noble gas, and the second process gas including CF4 gas or COF2 gas, a hydrofluorocarbon gas, and a noble gas; a plasma generating unit configured to generate a first plasma and a second plasma from the first process gas and the second process gas in the chamber, respectively; A control unit; Equipped with The control unit is configured to control the plasma processing apparatus to perform an etching method, the etching method including: (b) etching the silicon oxide film with the first plasma generated from the first process gas; (c) etching the silicon nitride film with the second plasma generated from the second process gas; (d) repeating steps (b) and (c); Including, In the (b), the flow rate of the noble gas is the highest among all gases contained in the first process gas; In the plasma processing apparatus, in the above (c), the noble gas has the largest flow rate among all gases contained in the second processing gas.

[0084] From the foregoing, it will be understood that various embodiments of the present disclosure have been described herein for purposes of illustration, and that various modifications may be made without departing from the scope and spirit of the present disclosure. Accordingly, the various embodiments disclosed herein are not intended to be limiting, with the true scope and spirit being indicated by the appended claims. [Explanation of symbols]

[0085] 1...plasma processing apparatus, 2...control unit, 10...plasma processing chamber, 11...substrate support unit, 12...plasma generation unit, 20...gas supply unit, F1...silicon oxide film, F2...silicon nitride film, PL1...first plasma, PL2...second plasma, ST...laminated film, W, W1...substrate.

Claims

1. (a) providing a substrate having a stack including alternating silicon oxide and silicon nitride films; (b) WF ６ Gas and CF ４ Gas or COF ２ Etching the silicon oxide film with a first plasma generated from a first process gas including a gas, a fluorocarbon gas having two or more carbon atoms, and a noble gas; (c) CF ４ Gas or COF ２ etching the silicon nitride film with a second plasma generated from a second process gas comprising a gas, a hydrofluorocarbon gas, and a noble gas; (d) repeating (b) and (c); Including, In the (b), the flow rate of the noble gas is the highest among all gases contained in the first process gas; The etching method according to (c), wherein the noble gas has a largest flow rate among all gases contained in the second process gas.

2. Among all gases contained in the first process gas, the WF ６ 2. The etching method of claim 1, wherein the gas flow rate is minimal.

3. The fluorocarbon gas having a carbon number of 2 or more is ４ F ６ 3. The etching method of claim 1, further comprising a gas.

4. In the above (b), the CF ４ The flow rate of the gas is ４ F ６ The etching method according to claim 3 , wherein the flow rate of the gas is greater than the flow rate of the gas.

5. The hydrofluorocarbon gas is CHF ３ Gas and CH ３ 3. The etching method according to claim 1, further comprising at least one gas selected from the group consisting of F gas.

6. In the (c) above, the CF ４ The flow rate of the gas is ３ Gas and the CH ３ The etching method according to claim 5 , wherein the total flow rate of the F gas is smaller than that of the F gas.

7. The etching method according to claim 1 , wherein the second process gas further contains an oxygen-containing gas.

8. the substrate includes a mask on the film stack, the mask having an opening; 3. The etching method according to claim 1, wherein at the start of step (b), the laminated film has a recess located below the opening, the recess having a width smaller than a width of the opening.

9. the substrate includes a mask on the film stack, the mask having an opening; 3. The etching method according to claim 1, wherein at the start of step (b), the film stack has a flat upper surface below the opening.

10. the opening includes a first opening and a second opening; the top surface includes a first planar top surface below the first opening and a second planar top surface below the second opening; 10. The etching method according to claim 9, wherein at the start of step (b), the first upper surface and the second upper surface are positioned at different heights from each other.

11. The etching method according to claim 1 , wherein the substrate comprises a mask on the film stack, the mask being a carbon-containing film.

12. The etching method according to claim 11 , wherein the carbon-containing film includes at least one selected from the group consisting of an amorphous carbon film and a photoresist film.

13. 3. The etching method according to claim 1, wherein the uppermost layer of the laminated film is a silicon oxide film.

14. 3. The etching method according to claim 1, wherein the bottom layer of the laminated film is a silicon oxide film.

15. 3. The etching method according to claim 1, wherein an uppermost layer of the laminated film is a silicon oxide film, and a lowermost layer of the laminated film is a silicon oxide film.

16. Between (b), (c) and (d), the CF ４ Gas or the COF ２ 3. The etching method according to claim 1, wherein the gas and the noble gas are supplied continuously.

17. (a) providing a substrate having a stack including alternating silicon oxide and silicon nitride films; (b) a metal-containing gas and CF ４ Gas or COF ２ Etching the silicon oxide film with a first plasma generated from a first process gas including a gas, a fluorocarbon gas having two or more carbon atoms, and a noble gas; (c) CF ４ Gas or COF ２ etching the silicon nitride film with a second plasma generated from a second process gas comprising a gas, a hydrofluorocarbon gas, and a noble gas; (d) repeating (b) and (c); Including, In the (b), the flow rate of the noble gas is the highest among all gases contained in the first process gas; The etching method according to (c), wherein the noble gas has a largest flow rate among all gases contained in the second process gas.

18. 20. The etching method of claim 17, wherein the metal-containing gas comprises a metal halide gas.

19. The metal-containing gas is WF ６ Gas, WCl ６ Gas, MoF ６ Gas, MoCl ６ Gas and TiCl ４ 20. The etching method of claim 17, comprising at least one selected from the group consisting of gases.

20. A plasma processing apparatus comprising: A chamber; a substrate support for supporting a substrate in the chamber, the substrate comprising a stack of films including alternating silicon oxide films and silicon nitride films; a gas supply configured to supply a first process gas and a second process gas into the chamber, the first process gas being WF ６ Gas and CF ４ Gas or COF ２ gas, a fluorocarbon gas having a carbon number of 2 or more, and a noble gas, and the second process gas is CF ４ Gas or COF ２ a gas supply including a gas, a hydrofluorocarbon gas, and a noble gas; a plasma generating unit configured to generate a first plasma and a second plasma from the first process gas and the second process gas in the chamber, respectively; A control unit; Equipped with The control unit is configured to control the plasma processing apparatus to perform an etching method, the etching method including: (b) etching the silicon oxide film with the first plasma generated from the first process gas; (c) etching the silicon nitride film with the second plasma generated from the second process gas; (d) repeating (b) and (c); Including, In the (b), the flow rate of the noble gas is the highest among all gases contained in the first process gas; In the plasma processing apparatus, in the above (c), the noble gas has a largest flow rate among all gases contained in the second process gas.

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