Etching method and plasma processing device

Abstract

This etching method includes: (a) a step for carrying a substrate into a chamber of a plasma processing device, the substrate having a silicon-containing film and a mask provided on the silicon-containing film, and the silicon-containing film including at least one element selected from the group consisting of nitrogen, phosphorus, and boron; and (b) a step for exposing the substrate to plasma generated from a processing gas containing hydrogen fluoride gas. (b) includes a step for forming a recess in the silicon-containing film, and a step for forming a protective film containing at least one element on a side wall of the recess.

Description

Etching method and plasma processing apparatus

[0001] SUMMARY OF THE INVENTION Exemplary embodiments of the present disclosure relate to an etching method and a plasma processing apparatus.

[0002] In the manufacture of electronic devices, plasma etching of silicon-containing films on substrates is performed. In plasma etching, the silicon-containing film is etched using plasma generated from a process gas. U.S. Patent Application Publication No. 2016 / 0343580 discloses a process gas containing a fluorocarbon gas as a process gas used in plasma etching of silicon-containing films. JP 2016-39310 A discloses a process gas containing a hydrocarbon gas and a hydrofluorocarbon gas as a process gas used in plasma etching of silicon-containing films.

[0003] US Patent Application Publication No. 2016 / 0343580 JP 2016-39310 A

[0004] The present disclosure provides a technique for suppressing shape abnormalities in the sidewalls of recesses formed by etching.

[0005] In one exemplary embodiment, an etching method is provided, comprising: (a) loading a substrate into a chamber of a plasma processing apparatus, the substrate having a silicon-containing film and a mask disposed on the silicon-containing film, the silicon-containing film containing at least one element selected from the group consisting of nitrogen, phosphorus, and boron; and (b) exposing the substrate to plasma generated from a process gas containing hydrogen fluoride gas, wherein (b) comprises forming a recess in the silicon-containing film and forming a protective film containing the at least one element on a sidewall of the recess.

[0006] According to one exemplary embodiment, it is possible to suppress shape abnormalities on the sidewalls of recesses formed by etching.

[0007] FIG. 1 is a diagram schematically illustrating a plasma processing apparatus according to an exemplary embodiment. FIG. 2 is a diagram schematically illustrating a plasma processing apparatus according to an exemplary embodiment. FIG. 3 is a flowchart of an etching method according to an exemplary embodiment. FIG. 4 is a cross-sectional view of an example substrate to which the method of FIG. 3 can be applied. FIG. 5 is a cross-sectional view of another example substrate to which the method of FIG. 3 can be applied. FIG. 6 is a cross-sectional view of yet another example substrate to which the method of FIG. 3 can be applied. FIG. 7 is a cross-sectional view showing one step of an etching method according to an exemplary embodiment. FIG. 8 is a diagram showing an example of experimental results regarding differences in etching rate depending on the ratio of nitrogen contained in a silicon-containing film.

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

[0009] FIG. 1 is a schematic diagram illustrating a plasma processing apparatus according to an exemplary embodiment. In this embodiment, the plasma processing system includes a plasma processing apparatus 1 and a controller 2. The plasma processing system is an example of a substrate processing system, and the plasma processing apparatus 1 is an example of a substrate processing apparatus. The plasma processing apparatus 1 includes a plasma processing chamber 10, a substrate support 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 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 generated in the plasma processing space may be capacitively coupled plasma (CCP), inductively coupled plasma (ICP), electron-cyclotron-resonance plasma (ECR plasma), helicon wave plasma (HWP), or surface wave plasma (SWP). Various types of plasma generators may be used, including alternating current (AC) plasma generators and direct current (DC) plasma generators. In one embodiment, the AC signal (AC power) used in the AC plasma generator has a frequency in the range of 100 kHz to 10 GHz. Thus, AC signals include radio frequency (RF) signals and microwave signals. 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 perform various processes described in this disclosure. The control unit 2 may be configured to control each element of the plasma processing apparatus 1 to perform various processes described herein. In one embodiment, part or all of the control unit 2 may be included in the plasma processing apparatus 1. The control unit 2 may include a processing unit 2a1, a storage unit 2a2, and a communication interface 2a3. The control unit 2 may be implemented by, for example, a computer 2a. The processing unit 2a1 may be configured to read a program from the storage unit 2a2 and execute the read program to perform various control operations. This program may be stored in the storage unit 2a2 in advance or may be acquired via a medium when needed. The acquired program is stored in the storage unit 2a2 and read from the storage unit 2a2 by the processing unit 2a1 for execution. The medium may be various storage media readable by the computer 2a or 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 schematically showing a plasma processing apparatus according to an exemplary embodiment.

[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 process gas into the plasma processing chamber 10. The gas inlet includes a showerhead 13. The substrate support 11 is disposed within 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 portion of the 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 the 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 a substrate W and an annular region 111b for supporting the ring assembly 112. A wafer is an example of a substrate W. The annular region 111b of the 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 can 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 the annular region 111b may also be provided by another member surrounding the electrostatic chuck 1111, such as an annular electrostatic chuck or an annular insulating member. 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. Furthermore, at least one RF / DC electrode coupled to an RF power supply 31 and / or a DC power supply 32, which will be described later, may be disposed within 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, which will be 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. Furthermore, the electrostatic electrode 1111b may function as a lower electrode. Therefore, 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 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 backside of the substrate W and the central region 111a.

[0018] The showerhead 13 is configured to introduce at least one process gas from the gas supply unit 20 into the plasma processing space 10s. The showerhead 13 has at least one gas supply port 13a, at least one gas diffusion chamber 13b, and multiple gas inlets 13c. The process 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 showerhead 13 also includes at least one upper electrode. In addition to the showerhead 13, the gas inlet may also include one or more side gas injectors (SGIs) attached to one or more openings formed in the sidewall 10a.

[0019] The gas supply unit 20 may include at least one gas source 21 and at least one flow controller 22. In one embodiment, the gas supply unit 20 is configured to supply at least one process gas from a corresponding gas source 21 to the showerhead 13 via a corresponding flow controller 22. Each flow controller 22 may include, for example, a mass flow controller or a pressure-controlled flow controller. Additionally, the gas supply unit 20 may include at least one flow modulation device that modulates or pulses the flow rate of the at least one process gas.

[0020] The power supply 30 includes an RF power supply 31 coupled to the plasma processing chamber 10 via at least one impedance matching circuit. The RF power supply 31 is configured to supply at least one RF signal (RF power) to at least one lower electrode and / or at least one upper electrode. This generates a plasma from at least one processing gas supplied to the plasma processing space 10s. Therefore, the RF power supply 31 can function as at least a part of the plasma generation unit 12. Furthermore, by supplying a bias RF signal to the at least one lower electrode, a bias potential is generated on the substrate W, thereby attracting ion components in the formed plasma 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 multiple 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 generator 31b is coupled to at least one lower electrode via at least one impedance matching circuit and is configured to generate a bias RF signal (bias RF power). The frequency of the bias RF signal may be the same as or different from the frequency of the source RF signal. In one embodiment, the bias RF signal has a frequency lower than the frequency of the source RF signal. In one embodiment, the bias RF signal has a frequency in the range of 100 kHz to 60 MHz. In one embodiment, the second RF generator 31b may be configured to generate multiple bias RF signals having different frequencies. The generated one or more bias RF signals are supplied to at least one lower electrode. In various embodiments, at least one of the source RF signal and the bias RF signal may be pulsed.

[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 the 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 the 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 thereof pulse waveform. In one embodiment, a waveform generator for generating the 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 either positive or negative polarity. Furthermore, the sequence of voltage pulses may include one or more positive voltage pulses and one or more negative voltage pulses within one period. The first and second DC generating units 32a and 32b may be provided in addition to the RF power supply 31, or the first DC generating unit 32a may be provided instead 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 regulated by the pressure regulating valve. The vacuum pump may include a turbomolecular pump, a dry pump, or a combination thereof.

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

[0027] 4 is a cross-sectional view of an example substrate W to which the method MT can be applied. The substrate W shown in FIG. 4 is used in the manufacture of devices such as DRAMs and 3D-NANDs. The substrate W has a silicon-containing film SF. The substrate W may further have an underlayer region UR. The silicon-containing film SF may be provided on the underlayer region UR. The underlayer region UR may contain a material different from the material contained in the silicon-containing film SF. The underlayer region UR may contain silicon.

[0028] The silicon-containing film SF contains at least one element (hereinafter also referred to as an additive element) selected from the group consisting of nitrogen (N), phosphorus (P), and boron (B). The silicon-containing film SF may contain nitrogen and at least one element selected from the group consisting of phosphorus and boron. The silicon-containing film SF may include at least one selected from the group consisting of a silicon nitride film and a silicon oxynitride film. The silicon-containing film SF may include a silicon oxide film containing the additive element. The silicon-containing film SF may include a multilayer film including alternately stacked silicon oxide films and silicon nitride films. In this case, the silicon oxide film may contain the additive element, and the silicon nitride film may contain at least one element selected from the group consisting of phosphorus and boron.

[0029] The additive element may be doped into the silicon-containing film SF during its formation. For example, when the silicon-containing film SF is formed by CVD, a gas containing the additive element may be included in the source gas. Alternatively, the additive element may be doped into the silicon-containing film SF after its formation. For example, the additive element may be doped into the silicon-containing film SF by ion implantation.

[0030] The ratio of the additive element contained in the silicon-containing film SF may be 10 atomic % or less. The ratio of the additive element may be 8 atomic % or less. The ratio of the additive element may be 6 atomic % or less. The ratio of the additive element may be 1 atomic % or more. The ratio of the additive element may be 2 atomic % or more. The ratio of the additive element may be 0.5 atomic % or more. When multiple elements of nitrogen, phosphorus, and boron are contained in the silicon-containing film SF, the ratio of the additive element may be the total atomic % of each element.

[0031] The atomic percentage may be a value obtained by dividing the mass ratio of the additive element to the total mass of the silicon-containing film SF by the atomic weight of the additive element. For example, if a silicon nitride film contains 95 mass% silicon and 5 mass% nitrogen, the value obtained by dividing 95 mass% by 28, the atomic weight of silicon, is 3.39. The value obtained by dividing 5 mass% by 14.1, the atomic weight of nitrogen, is 0.35. Expressing these values ​​as percentages, the atomic percentage of silicon is 90.6 atomic%, and the atomic percentage of nitrogen is 9.4 atomic%. The atomic percentage can be measured by, for example, secondary ion mass spectrometry (SIMS) or X-ray photoelectron spectroscopy (XPS).

[0032] The substrate W further includes a mask MK. The mask MK may have an opening OP. The opening OP may have a hole pattern or a line pattern. The mask MK may be provided on the silicon-containing film SF. The mask MK may include at least one selected from the group consisting of silicon, carbon, and a metal. The mask MK may include at least one selected from the group consisting of a silicon-containing film different from the silicon-containing film SF, a carbon-containing film, and a metal-containing film. The silicon-containing film different from the silicon-containing film SF may include a polysilicon film. The carbon-containing film may include an amorphous carbon film. The metal-containing film may include at least one metal selected from the group consisting of tungsten (W), titanium (Ti), and ruthenium (Ru).

[0033] 5 is a cross-sectional view of another example of a substrate W1 to which the method MT can be applied. The silicon-containing film SF may include a first region SF1 and a second region SF2. The first region SF1 may contain the additive element at a first ratio, and the second region SF2 may contain the additive element at a second ratio different from the first ratio. The second ratio may be smaller than the first ratio or larger than the first ratio. The first ratio and the second ratio may be expressed in the atomic percentages described above. In the example of FIG. 5, the second region SF2 is provided on the first region SF1 in the thickness direction of the substrate W1.

[0034] 6 is a cross-sectional view of yet another example of a substrate W2 to which the method MT can be applied. In the substrate W2, the second region SF2 may be aligned with the first region SF1 in the in-plane direction of the substrate W2. The in-plane direction of the substrate W2 is a direction perpendicular to the thickness direction of the substrate W2. The openings OP of the mask MK may include a first opening OP1 and a second opening OP2. The mask MK may have the first opening OP1 in the first region SF1 and the second opening OP2 in the second region SF2. The shapes of the first opening OP1 and the second opening OP2 are different from each other. The first opening OP1 may be a hole-shaped opening. The second opening OP2 may be a slit-shaped opening. In this case, the second ratio in the second region SF2 in which the slit-shaped opening is formed may be different from the first ratio in the first region SF1 in which the hole-shaped opening is formed.

[0035] Method MT will be described below with reference to FIGS. 4 and 7 , taking as an example a case where method MT is applied to a substrate W using the plasma processing apparatus 1 of the above embodiment. In the following description, method MT will be described as being applied to a substrate W, but method MT may also be applied to a substrate W1 or W2 instead of substrate W. Each of FIGS. 4 and 7 is a cross-sectional view showing a step of an etching method according to an exemplary embodiment. When the plasma processing apparatus 1 is used, method MT can be performed in the plasma processing apparatus 1 by controlling each part of the plasma processing apparatus 1 with the control unit 2. In method MT, a substrate W on a substrate support 11 arranged in a plasma processing chamber 10 is processed, as shown in FIG. 2 .

[0036] 3, the method MT may include steps ST1 and ST2. The steps ST1 and ST2 may be performed in sequence.

[0037] 4 is loaded into the plasma processing chamber 10 by, for example, a transfer device. The substrate W may be supported by a substrate support 11 in the plasma processing chamber 10. In the process ST1, the substrate W having the silicon-containing film SF doped with the additive element is loaded into the plasma processing chamber 10.

[0038] 7, in step ST2, plasma PL is generated from a processing gas and the substrate W is exposed to the plasma PL. Step ST2 includes a step (step ST21) of forming a recess RE in the silicon-containing film SF by etching, and a step (step ST22) of forming a protective film DP containing an additive element on a sidewall REa of the recess RE. Step ST21 and step ST22 may be performed simultaneously, or step ST22 may be performed after step ST21.

[0039] As shown in FIG. 7 , a recess RE is formed in the silicon-containing film SF by etching. The recess RE corresponds to the opening OP. The process gas contains fluorine (F) and hydrogen (H). The process gas contains, for example, hydrogen fluoride. The plasma PL contains a hydrogen fluoride (HF) etchant, and the recess RE is formed by etching the silicon-containing film SF with the hydrogen fluoride etchant. The hydrogen fluoride etchant may contain hydrogen fluoride active species and neutral hydrogen fluoride molecules. The hydrogen fluoride active species may contain hydrogen fluoride ions and hydrogen fluoride radicals. Since H—F bonds are difficult to dissociate in the plasma PL, a hydrogen fluoride etchant having an H—F bond is generated. The hydrogen fluoride etchant may be detected, for example, by a quadrupole mass spectrometer (QMS). Alternatively, the hydrogen fluoride etchant may be detected by, for example, an optical emission spectrometer (OES). In this case, for example, a window (not shown) may be provided in the sidewall 10a of the plasma processing chamber 10, and the emission spectrum of the plasma PL obtained through the window may be analyzed qualitatively and quantitatively. The window may be a glass plate, for example, fitted into a through-hole connecting the inside and outside of the plasma processing chamber 10.

[0040] In step ST2, the processing gas may contain a gas of a compound containing hydrogen and fluorine, or may be a mixed gas containing a hydrogen-containing gas and a fluorine-containing gas. The gas of the compound containing hydrogen and fluorine may be a mixture of hydrogen fluoride gas and a hydrofluorocarbon gas (C ｘ H ｙ F ｚ The plasma PL may include at least one selected from the group consisting of hydrogen fluoride gas and hydrofluorocarbon gas. Each of x, y, and z is a positive integer. The hydrogen fluoride gas and hydrofluorocarbon gas may generate a hydrogen fluoride etchant in the plasma PL. The hydrofluorocarbon gas may be CHF ３ , C.H. ２ F ２ , C.H. ３ F, C ２ HF ５ , C２ H ２ F ４ , C ２ H ３ F ３ , C ２ H ４ F ２ , C ３ HF ７ , C ３ H ２ F ２ , C ３ H ２ F ６ , C ３ H ２ F ４ , C ３ H ３ F ５ , C ４ H ５ F ５ , C ４ H ２ F ６ , C ５ H ２ F １０ , c-C ５ H ３ F ７、 and C ３ H ２ F ４ It may be at least one selected from the group consisting of:

[0041] The hydrogen-containing gas contained in the mixed gas is H ２ Gas, NH ３ Gas, H ２ O gas, H ２ O ２ The mixed gas may contain at least one selected from the group consisting of NF 3 , NF 4 , NF 5 , NF 6 , NF 7 , NF 8 , NF 9 , NF 10 , NF 11 , NF 12 , NF 13 , NF 14 , NF 15 , NF 16 , NF 17 , NF 18 , NF 19 , ３ Gas, SF ６ Gas, WF ６ Gas, XeF ２ The mixed gas may contain at least one selected from a hydrogen fluoride gas, a fluorocarbon gas, and a hydrofluorocarbon gas. The mixed gas may generate a hydrogen fluoride etchant in the plasma PL.

[0042] In step ST2, the processing gas may contain at least one gas selected from the group consisting of a nitrogen-containing gas, a phosphorus-containing gas, a carbon-containing gas, a gas containing halogen other than fluorine, a boron-containing gas, and an oxygen-containing gas. The nitrogen-containing gas may be nitrogen gas (N ２ gas), oxynitride gas (NO gas), nitrogen trifluoride gas (NF ３ gas), ammonia gas (NH ３ The phosphorus-containing gas may include at least one selected from the group consisting of phosphorus trifluoride gas (PF 6 ), a mixed gas of nitrogen gas and hydrogen gas, and an amine gas. ３ gas), and phosphorus pentafluoride gas (PF ５ The gas may include at least one selected from the group consisting of:

[0043] The carbon-containing gas is a fluorocarbon gas (C ｘ F ｙ The fluorocarbon gas may include at least one selected from the group consisting of CF4, CF5, CF6, CF7, CF8, CF9, CF10, CF11, CF12, CF13, CF14, CF15, CF16, CF17, CF18, CF19, CF20, CF21, CF22, CF23, CF24, CF25, CF26, CF ４ , C ２ F ２ , C ２ F ４ , C ３ F ８ , C ４ F ６ , C ４ F ８ , and C ５ F ８ The hydrofluorocarbon gas may be at least one selected from the group consisting of CHF ３ , C.H. ２ F ２ , C.H. ３ F, C ２ HF ５ , C ２ H ２ F ４ , C ２ H ３ F ３ , C ２ H ４ F ２ , C ３ HF ７ , C ３ H ２ F ２ , C３ H ２ F ６ , C ３ H ２ F ４ , C ３ H ３ F ５ , C ４ H ５ F ５ , C ４ H ２ F ６ , C ５ H ２ F １０ , c-C ５ H ３ F ７、 and C ３ H ２ F ４ The halogen-containing gas other than fluorine may include at least one selected from the group consisting of a chlorine-containing gas and a bromine-containing gas. The chlorine-containing gas may be Cl ２ The bromine-containing gas may include HBr gas. The boron-containing gas may include boron trichloride gas (BCl ３ The oxygen-containing gas may include oxygen gas (O ２ ), carbon monoxide gas (CO), and carbon dioxide gas (CO ２ ) may contain at least one selected from the group consisting of

[0044] In step ST2, the temperature of the substrate support part 11 that supports the substrate W may be set to 0° C. or lower, −40° C. or lower, −60° C. or lower, or −80° C. or higher. In step ST2, an electric bias may be supplied to the substrate support part 11.

[0045] In step ST22, a protective film DP may be formed on the bottom surface REb, or the protective film DP may not be formed on the bottom surface REb. The mechanism by which recess formation progresses on the bottom surface REb is, for example, as follows, but is not limited to this. In step ST21, hydrogen fluoride ions are incident on the substrate W along the thickness direction of the substrate W. As a result, the protective film DP formed on the bottom surface REb is removed, and etching progresses on the exposed bottom surface REb. On the other hand, the protective film DP remains on the side wall REa, which is less likely to be hit by hydrogen fluoride ions. The protective film DP prevents hydrogen fluoride radicals from entering the side wall REa, so recess formation preferentially progresses on the bottom surface REb, and anisotropic etching is achieved.

[0046] The protective film DP formed on the sidewall REa in step ST22 can be produced by a reaction between chemical species in the plasma PL and the silicon-containing film SF containing an additive element. When the silicon-containing film SF contains nitrogen, an ammonium salt can be produced by the reaction of the silicon-containing film SF with a hydrogen fluoride etchant contained in the processing gas. Therefore, the protective film DP may contain an ammonium salt. The ammonium salt may contain ammonium silicofluoride. The ammonium salt is (NH ４ ) ２ SiF ６ , N.H. ４ SiF ５ , and (NH ４ ) ３ SiF ７ When the silicon-containing film SF contains phosphorus, a phosphate may be generated by the reaction of the silicon-containing film SF with chemical species in the plasma PL. Therefore, the protective film DP may contain a phosphate. The phosphate may be ammonium hexafluorophosphate (NH ４ PF ６ ) may be included. When the silicon-containing film SF contains boron, a borate may be generated by the reaction of the silicon-containing film SF with chemical species in the plasma PL. Therefore, the protective film DP may contain a borate. The borate may be ammonium tetrafluoroborate (NH ４ BF ４ ) may also be included.

[0047] According to the method MT, the additive element contained in the silicon-containing film SF promotes the adsorption of hydrogen fluoride species to the silicon-containing film SF. A reaction between the silicon-containing film SF containing the additive element and the hydrogen fluoride species forms a protective film DP on the sidewall REa of the recess RE. The protective film DP prevents hydrogen fluoride radicals from the hydrogen fluoride species from penetrating the sidewall REa, thereby suppressing etching of the sidewall REa of the recess RE. This makes it possible to suppress shape abnormalities (bowing) on ​​the sidewall REa of the recess RE. Meanwhile, the protective film DP is less likely to be formed on the bottom surface REb of the recess RE due to collisions of hydrogen fluoride ions from the hydrogen fluoride species, thereby promoting etching. The additive element contained in the silicon-containing film SF promotes the adsorption of hydrogen fluoride species to the bottom surface REb of the recess RE, thereby increasing the etching rate of the silicon-containing film SF.

[0048] When the method MT is applied to the substrate W1 shown in FIG. 5 , a recess RE can be formed from the second region SF2 to the first region SF1. In the substrate W1, the second region SF2 is provided on the first region SF1 in the thickness direction of the substrate W1. The second ratio may be greater than the first ratio. The higher the ratio of the additive element, the more the adsorption of the hydrogen fluoride etchant is promoted, and the thickness of the protective film DP adhering to the sidewall REa of the recess RE tends to increase. By making the second ratio greater than the first ratio, the protective film DP formed on the sidewall REa in the second region SF2 can be made thicker. Therefore, bowing can be more easily suppressed on the sidewall REa in the second region SF2. On the other hand, etching progresses more easily on the sidewall REa in the first region SF1 than on the sidewall REa in the second region SF2. This makes it possible to prevent the shape of the recess RE from becoming thinner as it moves away from the mask MK.

[0049] The second ratio may be smaller than the first ratio. In this case, adsorption of hydrogen fluoride species to the bottom surface REb of the recess RE formed in the first region SF1 is promoted. Therefore, the etching rate of the first region SF1 can be increased. Therefore, it is possible to prevent the etching rate of the silicon-containing film SF from decreasing with increasing distance from the mask MK.

[0050] When the method MT is applied to the substrate W2 shown in FIG. 6 , recesses RE may be formed in each of the first region SF1 and the second region SF2. In the substrate W2, the second region SF2 is aligned with the first region SF1 in the in-plane direction of the substrate W2. The mask MK may have a hole-shaped opening (first opening OP1) in the first region SF1 and a slit-shaped opening (second opening OP2) in the second region SF2. The second ratio in the second region SF2 in which the slit-shaped opening is formed may be different from the first ratio in the first region SF1 in which the hole-shaped opening is formed. When the second ratio is larger than the first ratio, the etching rate in the second region SF2 can be increased. When the second ratio is smaller than the first ratio, the etching rate in the first region SF1 can be increased. Therefore, by making the first ratio different from the second ratio, the difference between the etching rate of the first region SF1 and the etching rate of the second region SF2 can be adjusted. For example, the second ratio may be greater than the first ratio. The second region SF2 in which the slit-shaped opening is formed often includes a silicon oxide film. The first region SF1 in which the hole-shaped opening is formed often includes a silicon nitride film or a silicon oxynitride film. The etching rate for a silicon oxide film tends to be smaller than the etching rate for a silicon nitride film or a silicon oxynitride film. Therefore, by making the second ratio greater than the first ratio, the etching rate of the second region SF2 can be increased. As a result, the difference between the etching rate of the first region SF1 and the etching rate of the second region SF2 can be reduced.

[0051] Although various exemplary embodiments have been described above, they are not limited to the above-described exemplary embodiments and various additions, omissions, substitutions, and modifications may be made. Furthermore, elements of different embodiments may be combined to form other embodiments. For example, at least one of the silicon-containing film SF and the mask MK may contain an additive element. When the mask MK contains an additive element, etching the mask MK may cause the additive element contained in the mask MK to adhere to the sidewall REa of the recess RE formed in the silicon-containing film SF. As a result, adsorption of hydrogen fluoride species to the sidewall REa is promoted. A protective film DP is formed on the sidewall REa of the recess RE of the silicon-containing film SF by a reaction between the sidewall REa to which the additive element has adhered and the hydrogen fluoride species.

[0052] The following describes experiments performed to evaluate Method MT, but the experiments described below are not intended to limit the scope of the present disclosure.

[0053] FIG. 8 shows an example of experimental results for the difference in etching rate depending on the nitrogen ratio contained in the silicon-containing film SF. In the experiment, a substrate including a silicon-containing film to be etched was prepared. The substrate samples prepared were a first sample with no nitrogen doping, a second sample with nitrogen doping at a ratio of 6 atomic % to the silicon oxide film, and a third sample with nitrogen doping at a ratio of 28 atomic %. The silicon-containing film of each sample was deposited by plasma-enhanced chemical vapor deposition (PECVD). After the substrate was loaded into a plasma processing chamber, the film to be etched was etched using plasma generated from a processing gas. Hydrogen fluoride gas was used as the processing gas.

[0054] (Results) As shown in Figure 8, the etching rates of the nitrogen-doped second and third samples were approximately 1.5 times that of the undoped first sample. This result indicates that nitrogen doping promotes the adsorption of hydrogen fluoride species onto the silicon-containing film, improving the etching rate. On the other hand, it was found that there was no significant difference between the etching rate of the second sample, which was doped with nitrogen at a ratio of 6 atomic %, and the etching rate of the third sample, which was doped with nitrogen at a ratio of 28 atomic %. This means that the effect of the nitrogen ratio on the etching rate is small, and that the inclusion of nitrogen in the silicon-containing film, even at a small ratio, has the effect of improving the etching rate.

[0055] Various exemplary embodiments included in the present disclosure are now described in [E1] to [E20] below.

[0056] [E1] An etching method comprising: (a) a step of carrying a substrate into a chamber of a plasma processing apparatus, the substrate having a silicon-containing film and a mask provided on the silicon-containing film, the silicon-containing film containing at least one element selected from the group consisting of nitrogen, phosphorus, and boron; and (b) a step of exposing the substrate to plasma generated from a processing gas containing hydrogen fluoride gas, wherein (b) comprises a step of forming a recess in the silicon-containing film and a step of forming a protective film containing the at least one element on a sidewall of the recess.

[0057] [E2] The etching method according to [E1], wherein the silicon-containing film contains nitrogen, and the silicon-containing film contains at least one element selected from the group consisting of phosphorus and boron.

[0058] [E3] The etching method according to [E2], wherein the silicon-containing film includes at least one selected from the group consisting of a silicon nitride film and a silicon oxynitride film.

[0059] [E4] The etching method according to [E1], wherein the silicon-containing film includes a silicon oxide film containing the at least one element.

[0060] [E5] The etching method according to any one of [E1] to [E4], wherein the ratio of the at least one element contained in the silicon-containing film is 10 atomic % or less.

[0061] [E6] The etching method according to any one of [E1] to [E5], wherein the silicon-containing film contains nitrogen, and the protective film contains ammonium silicofluoride.

[0062] [E7] The etching method according to any one of [E1] to [E6], wherein the silicon-containing film has a first region containing the at least one element in a first ratio and a second region containing the at least one element in a second ratio different from the first ratio.

[0063] [E8] The etching method according to [E7], wherein the second region is provided on the first region in the thickness direction of the substrate, and the second ratio is greater than the first ratio.

[0064] [E9] The etching method according to [E7], wherein the second region is provided on the first region in the thickness direction of the substrate, and the second ratio is smaller than the first ratio.

[0065] [E10] The etching method according to [E7], wherein the second region is aligned with the first region in an in-plane direction of the substrate, and the mask has a hole-shaped opening on the first region and a slit-shaped opening on the second region.

[0066] [E11] The etching method according to any one of [E1] to [E10], wherein the processing gas contains at least one selected from the group consisting of a nitrogen-containing gas, a phosphorus-containing gas, a carbon-containing gas, a gas containing a halogen other than fluorine, a boron-containing gas, and an oxygen-containing gas.

[0067] [E12] The etching method according to any one of [E1] to [E11], wherein in (b), the temperature of a substrate support part that supports the substrate is set to 0° C. or less.

[0068] [E13] The etching method according to any one of [E1] to [E12], wherein the mask contains at least one selected from the group consisting of silicon, carbon, and metal.

[0069] [E14] An etching method comprising: (a) a step of carrying a substrate into a chamber of a plasma processing apparatus, the substrate having a silicon-containing film and a mask provided on the silicon-containing film, at least one of the silicon-containing film and the mask containing at least one element selected from the group consisting of nitrogen, phosphorus, and boron; and (b) a step of exposing the substrate to plasma generated from a processing gas containing fluorine and hydrogen, wherein (b) includes a step of forming a recess in the silicon-containing film and a step of forming a protective film containing the at least one element on a sidewall of the recess, and the plasma contains a hydrogen fluoride etchant.

[0070] [E15] The etching method according to [E14], wherein in (b), the recess is formed by etching the silicon-containing film with the hydrogen fluoride etchant.

[0071] [E16] The etching method according to [E14] or [E15], wherein the processing gas contains a gas of a compound containing hydrogen and fluorine, or is a mixed gas containing a hydrogen-containing gas and a fluorine-containing gas.

[0072] [E17] The etching method according to [E16], wherein the compound gas includes at least one selected from the group consisting of hydrogen fluoride gas and hydrofluorocarbon gas.

[0073] [E18] The hydrogen-containing gas contained in the mixed gas is H ２ Gas, NH ３ Gas, H ２ O gas, H ２ O ２ The etching method according to [E16], further comprising at least one selected from the group consisting of a nitrogen gas, a nitrogen-containing gas, and a hydrocarbon gas.

[0074] [E19] The fluorine-containing gas contained in the mixed gas is NF ３ Gas, SF６ Gas, WF ６ Gas, XeF ２ The etching method according to [E16], wherein the gas contains at least one selected from a gas, a fluorocarbon gas, and a hydrofluorocarbon gas.

[0075] [E20] A plasma processing apparatus comprising: a chamber; and a substrate support unit for supporting a substrate in the chamber, the substrate having a silicon-containing film and a mask provided on the silicon-containing film, the silicon-containing film containing at least one element selected from the group consisting of nitrogen, phosphorus, and boron; a gas supply unit configured to supply a process gas containing hydrogen fluoride gas into the chamber; and a plasma generation unit configured to generate plasma from the process gas; and a control unit, wherein the control unit is configured to control the plasma processing apparatus to perform an etching method including: (a) a step of loading the substrate into the chamber; and (b) a step of exposing the substrate to the plasma, the step including a step of forming a recess in the silicon-containing film and a step of forming a protective film containing the at least one element on a sidewall of the recess.

[0076] 1...plasma processing apparatus, 10...plasma processing chamber, 11...substrate support part, 12...plasma generation part, 2...control part, 20...gas supply part, DP...protective film, MK...mask, PL...plasma, RE...recess, REa...sidewall, SF...silicon-containing film, W...substrate

Claims

1. (a) loading a substrate into a chamber of a plasma processing apparatus, the substrate having a silicon-containing film containing nitrogen and a mask disposed on the silicon-containing film, the silicon-containing film containing at least one element selected from the group consisting of phosphorus and boron; (b) exposing the substrate to a plasma generated from a process gas containing hydrogen fluoride gas; Including, The step (b) includes forming a recess in the silicon-containing film and forming a protective film containing the at least one element on a sidewall of the recess. Etching method.

2. 2. The etching method according to claim 1, wherein the silicon-containing film includes at least one selected from the group consisting of a silicon nitride film and a silicon oxynitride film.

3. (a) a step of transporting a substrate into a chamber of a plasma processing apparatus, the substrate having a silicon-containing film and a mask provided on the silicon-containing film, the silicon-containing film including a silicon oxide film containing at least one element selected from the group consisting of nitrogen, phosphorus, and boron; (b) exposing the substrate to a plasma generated from a process gas containing hydrogen fluoride gas; Including, The etching method (b) includes the steps of forming a recess in the silicon-containing film and forming a protective film containing the at least one element on a sidewall of the recess.

4. 4. The etching method according to claim 1, wherein the ratio of the at least one element contained in the silicon-containing film is 10 atomic % or less.

5. the silicon-containing film contains nitrogen; 4. The etching method according to claim 1, wherein the protective film contains ammonium silicofluoride.

6. 4. The etching method according to claim 1, wherein the silicon-containing film has a first region containing the at least one element at a first ratio and a second region containing the at least one element at a second ratio different from the first ratio.

7. the second region is provided on the first region in a thickness direction of the substrate, The etching method of claim 6 , wherein the second ratio is greater than the first ratio.

8. the second region is provided on the first region in a thickness direction of the substrate, The etching method of claim 6 , wherein the second ratio is smaller than the first ratio.

9. the second region is aligned with the first region in an in-plane direction of the substrate, 7. The etching method according to claim 6, wherein the mask has a hole-shaped opening above the first region and a slit-shaped opening above the second region.

10. 4. The etching method according to claim 1, wherein the processing gas contains at least one gas selected from the group consisting of a nitrogen-containing gas, a phosphorus-containing gas, a carbon-containing gas, a gas containing a halogen other than fluorine, a boron-containing gas, and an oxygen-containing gas.

11. 4. The etching method according to claim 1, wherein in (b), a temperature of a substrate support part that supports the substrate is set to 0° C. or lower.

12. 4. The etching method according to claim 1, wherein the mask contains at least one selected from the group consisting of silicon, carbon, and metal.

13. (a) carrying a substrate into a chamber of a plasma processing apparatus, the substrate having a silicon-containing film containing nitrogen and a mask provided on the silicon-containing film, wherein at least one of the silicon-containing film and the mask contains at least one element selected from the group consisting of phosphorus and boron; (b) exposing the substrate to a plasma generated from a process gas comprising fluorine and hydrogen; Including, the step (b) includes forming a recess in the silicon-containing film and forming a protective film containing the at least one element on a sidewall of the recess; the plasma includes a hydrogen fluoride etchant; Etching method.

14. (a) a step of transporting a substrate into a chamber of a plasma processing apparatus, the substrate having a silicon-containing film and a mask disposed on the silicon-containing film, at least one of the silicon-containing film and the mask containing at least one element selected from the group consisting of nitrogen, phosphorus, and boron; (b) exposing the substrate to a plasma generated from a process gas comprising fluorine and hydrogen; Including, the step (b) includes forming a recess in the silicon-containing film and forming a protective film containing the at least one element on a sidewall of the recess; the plasma includes a hydrogen fluoride etchant; the silicon-containing film includes a silicon oxide film containing the at least one element; Etching method.

15. 15. The etching method according to claim 13, wherein in the step (b), the recess is formed by etching the silicon-containing film with the hydrogen fluoride etchant.

16. 15. The etching method according to claim 13, wherein the processing gas contains a gas of a compound containing hydrogen and fluorine, or is a mixed gas containing a hydrogen-containing gas and a fluorine-containing gas.

17. 17. The etching method according to claim 16, wherein the compound gas includes at least one selected from the group consisting of a hydrogen fluoride gas and a hydrofluorocarbon gas.

18. The hydrogen-containing gas contained in the mixed gas is H ２ Gas, NH ３ Gas, H ２ O gas, H ２ O ２ 17. The etching method according to claim 16, wherein the gas contains at least one selected from the group consisting of a nitrogen gas, a nitrogen gas, and a hydrocarbon gas.

19. The fluorine-containing gas contained in the mixed gas is NF ３ Gas, SF ６ Gas, WF ６ Gas, XeF ２ 17. The etching method according to claim 16, wherein the gas comprises at least one selected from the group consisting of a gas, a fluorocarbon gas, and a hydrofluorocarbon gas.

20. A plasma processing apparatus, a chamber; a substrate support for supporting a substrate in the chamber, the substrate having a silicon-containing film containing nitrogen and a mask provided on the silicon-containing film, the silicon-containing film containing at least one element selected from the group consisting of phosphorus and boron; a gas supply configured to supply a process gas containing hydrogen fluoride gas into the chamber; a plasma generating unit configured to generate plasma from the processing gas; A control unit; Equipped with The control unit (a) loading the substrate into the chamber; (b) exposing the substrate to the plasma, the step including the steps of forming a recess in the silicon-containing film and forming a protective film containing the at least one element on a sidewall of the recess; 11. A plasma processing apparatus configured to control the plasma processing apparatus to perform an etching method including:

21. A plasma processing apparatus comprising: a chamber; a substrate support for supporting a substrate in the chamber, the substrate having a silicon-containing film and a mask provided on the silicon-containing film, the silicon-containing film including a silicon oxide film containing at least one element selected from the group consisting of nitrogen, phosphorus, and boron; a gas supply configured to supply a process gas containing hydrogen fluoride gas into the chamber; a plasma generating unit configured to generate plasma from the processing gas; A control unit; Equipped with The control unit (a) loading the substrate into the chamber; (b) exposing the substrate to the plasma, the step including the steps of forming a recess in the silicon-containing film and forming a protective film containing the at least one element on a sidewall of the recess; 11. A plasma processing apparatus configured to control the plasma processing apparatus to perform an etching method including: