Method for forming nano-pillar and dry etching device

Abstract

In one exemplary embodiment of the present invention, a method for forming a nano-pillar includes: (a) a step in which a substrate is provided on a substrate support in a chamber, the substrate including a first film, a second film on the first film, and a carbon-containing mask on the second film, the second film including silicon and / or germanium, and the carbon-containing mask having an opening; (b) a step in which a first plasma generated from a first processing gas in the chamber is used to etch the second film through the opening in the carbon-containing mask to form a recess corresponding to the opening in the second film; and (c) a step in which a second plasma generated from a second processing gas in the chamber is used to trim a side wall defining the opening and a side wall defining the recess to form a nano-pillar from the second film.

Description

Nanopillar formation method and dry etching apparatus

[0001] SUMMARY OF THE INVENTION Exemplary embodiments of the present disclosure relate to a method for forming nanopillars and a dry etching apparatus.

[0002] Patent Document 1 discloses a method for forming a pillar-shaped resist pattern with a high aspect ratio. In this method, an initial resist pattern is first formed by electron beam lithography, which has a shape different from that of a pillar and which allows for a higher aspect ratio than that of a pillar structure. The initial resist pattern is then reduced in size by isotropic dry etching.

[0003] Non-Patent Document 1 discloses a method for forming a SiO ２ A method for etching a film with high selectivity is disclosed.

[0004] JP 2008-233480 A

[0005] "Highly selective and verticaletch of silicon dioxide using ruthenium films as an etch mask", WJMitchell, et. al., J. Vac. Sci. Technol. A 39, 043204 (2021)

[0006] The present disclosure provides techniques that allow for the formation of high aspect ratio nanopillars.

[0007] In one exemplary embodiment, a method for forming nanopillars includes: (a) providing a substrate on a substrate support in a chamber, the substrate comprising a first film, a second film on the first film, and a carbon-containing mask on the second film, the second film comprising at least one of silicon or germanium, the carbon-containing mask having an opening; (b) etching the second film through the opening in the carbon-containing mask with a first plasma generated in the chamber from a first process gas to form a recess in the second film corresponding to the opening; and (c) trimming a sidewall defining the opening and a sidewall defining the recess with a second plasma generated in the chamber from a second process gas to form a nanopillar from the second film.

[0008] According to one exemplary embodiment, a technique is provided that allows for the formation of high aspect ratio nanopillars.

[0009] FIG. 1 is a diagram illustrating an example of the configuration of a plasma processing system. FIG. 2 is a diagram illustrating an example of the configuration of a capacitively coupled plasma processing apparatus. FIG. 3 is a flowchart of a method for forming nanopillars according to an exemplary embodiment. FIG. 4 is a partial enlarged view of an exemplary substrate to which the method of FIG. 3 can be applied. FIG. 5 is a cross-sectional view illustrating a step of the method for forming nanopillars according to an exemplary embodiment. FIG. 6 is a cross-sectional view illustrating a step of the method for forming nanopillars according to an exemplary embodiment. FIG. 7 is a cross-sectional view illustrating a step of the method for forming nanopillars according to an exemplary embodiment. FIG. 8 is a cross-sectional view illustrating a step of the method for forming nanopillars according to an exemplary embodiment. FIG. 9 is a graph illustrating an example of the relationship between the state of radicals and potential energy. FIG. 10 is a graph illustrating an example of the relationship between the trimming amount and the CD at the bottom of the nanopillar or the angle of the sidewall of the nanopillar. FIG. 11 is a graph illustrating an example of the relationship between pressure and the CD at the bottom of the nanopillar or the angle of the sidewall of the nanopillar. FIG. 12 is a graph illustrating an example of the relationship between temperature and the trimming amount or the angle of the sidewall of the nanopillar.

[0010] Hereinafter, embodiments of the present disclosure will be described in detail with reference to the accompanying drawings. In the description of the drawings, the same or equivalent elements are designated by the same reference numerals, and redundant description will be omitted.

[0011] FIG. 1 is a diagram illustrating an exemplary configuration of a plasma processing system. In one embodiment, the plasma processing system includes a plasma processing apparatus 1 and a control unit 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.

[0012] 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), surface wave plasma (SWP), or the like. 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.

[0013] 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).

[0014] 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 a configuration example of a capacitively coupled plasma processing apparatus.

[0015] 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.

[0016] 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.

[0017] 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.

[0018] 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.

[0019] 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.

[0020] 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.

[0021] 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.

[0022] 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.

[0023] 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.

[0024] 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.

[0025] 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.

[0026] 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.

[0027] 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.

[0028] 3 is a flowchart of a nanopillar formation method according to one exemplary embodiment. The nanopillar formation method MT1 (hereinafter referred to as "method MT1") shown in FIG. 3 can be performed by the plasma processing apparatus 1 (dry etching apparatus) of the above embodiment. The method MT1 can be applied to the substrate W of FIG. 4.

[0029] 4 is a cross-sectional view of an example substrate to which the method of FIG. 3 can be applied. As shown in FIG. 4, in one embodiment, the substrate W includes a first film F1 and a second film F2 on the first film F1. The substrate W may further include a carbon-containing film FC on the second film F2. The substrate W may further include a third film F3 on the carbon-containing film FC and a resist mask FR on the third film F3. The resist mask FR may have an opening OPR. The resist mask FR may have a dot pattern or a line pattern surrounded by the opening OPR. The substrate W may further include a base region UR below the first film F1. The base region UR may include a silicon substrate.

[0030] The first film F1 is made of silicon, hafnium oxide (HfO), zirconium oxide (ZrO), aluminum oxide (Al ２ O ３ The first film F1 may include at least one material selected from the group consisting of InGaZnO and InGaZnO. The first film F1 may have a thickness of 5 to 10 nm.

[0031] The second film F2 includes a material different from the material of the first film F1. The second film F2 includes at least one of silicon or germanium. The second film F2 may further include at least one of oxygen or nitrogen. The second film F2 may include silicon oxide (SiO ｘ ), silicon nitride (SiN ｘ The second film F2 may include at least one material selected from the group consisting of silicon oxynitride (SiON), where x is a positive real number. The second film F2 may have a thickness greater than that of the first film F1. The thickness of the second film F2 may be 100 to 500 nm.

[0032] The carbon-containing film FC may include at least one material selected from the group consisting of amorphous carbon, spin-on carbon (SOC), and resist (polymer). The carbon-containing film FC may have a thickness of 100 to 500 nm.

[0033] The third film F3 includes a material different from the material of the second film F2. The third film F3 may include silicon. The third film F3 may further include at least one of oxygen or nitrogen. The third film F3 may include at least one material selected from the group consisting of silicon oxide (SiO), silicon nitride (SiN), and silicon oxynitride (SiON). The third film F3 may include spin-on glass (SOG).

[0034] The resist mask FR may include a resist material for ArF.

[0035] Method MT1 will be described below with reference to FIGS. 3 to 8, 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. 4 to 8 are cross-sectional views showing steps of a method for forming nanopillars 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 with a controller 2. In method MT1, a substrate W is processed on a substrate support 11 disposed in a plasma processing chamber 10, as shown in FIG. 2.

[0036] 3, the method MT1 may include steps ST1 to ST4. Steps ST1 to ST4 may be performed in sequence. Step ST1 may include steps ST11 to ST13. Steps ST11 to ST13 may be performed in sequence. The method MT1 may not include step ST4. Steps ST1 to ST4 may be performed in situ.

[0037] (Step ST1) In step ST1, steps ST11 to ST13 may be performed to provide the substrate W shown in Fig. 6 on the substrate support 11 in the plasma processing chamber 10. The substrate W shown in Fig. 6 may be formed as follows.

[0038] <Step ST11> In step ST11, the substrate W shown in Fig. 4 is provided on the substrate support 11 in the plasma processing chamber 10. The substrate W shown in Fig. 4 is provided with a resist mask FR having an opening OPR. The opening OPR can be formed by developing a resist.

[0039] 5, in step ST12, the third film F3 is etched by plasma PL3 through the openings OPR in the resist mask FR. This forms openings OP3 in the third film F3 corresponding to the openings OPR. At the end of step ST12, the resist mask FR may remain on the top surface of the third film F3.

[0040] 6, in step ST13, the carbon-containing film FC is etched by plasma PLC through the opening OP3. This forms a carbon-containing mask MK having an opening OP corresponding to the opening OP3. At the end of step ST13, a third film F3 may remain on the upper surface of the carbon-containing mask MK.

[0041] In step ST1, the substrate W shown in FIG. 6 may be provided without performing steps ST11 to ST13.

[0042] In step ST13 or step ST1, the aspect ratio of the carbon-containing mask MK may be 2 or more, 10 or less, or 4 or less. The aspect ratio of the carbon-containing mask MK is the ratio of the height D2 of the carbon-containing mask MK to the dimension D1 (CD: Critical Dimension) at the bottom of the carbon-containing mask MK. The dimension D1 may be 50 nm or more. The height D2 may be 100 nm or more. The carbon-containing mask MK may have a dot pattern or a line pattern surrounded by openings OP.

[0043] (Process ST2) In process ST2, as shown in FIG. 7, the second film F2 is etched by a first plasma PL1 through the opening OP in the carbon-containing mask MK to form a recess RS in the second film F2 corresponding to the opening OP. The first plasma PL1 is generated from a first processing gas in the plasma processing chamber 10. The bottom of the recess RS may reach the first film F1. In process ST2, the third film F3 may be removed, or a portion of the carbon-containing mask MK may be removed.

[0044] The first process gas in step ST2 may contain a fluorine-containing gas. An example of the fluorine-containing gas is CF. ４ Fluorocarbon gases such as SF ６ Gas and NF ３ The first process gas may further include an inert gas. Examples of the inert gas include nitrogen gas and noble gases.

[0045] The temperature of the substrate support part 11 in step ST2 may be 60° C. or less, or may be 30° C. or less.

[0046] The pressure inside the plasma processing chamber 10 in step ST2 may be higher than 1.6 Pa (12 mTorr) or may be equal to or higher than 1.33 Pa (10 mTorr).

[0047] In step ST2, an electric bias may be applied to the substrate support part 11. The electric bias may be greater than 50 W, or may be 80 W or more.

[0048] The source RF power for generating the first plasma PL1 in step ST2 may be greater than 400 W.

[0049] (Step ST3) In step ST3, as shown in FIG. 8, the sidewall MKa defining the opening OP and the sidewall F2a defining the recess RS are trimmed by a second plasma PL2 to form nanopillars NP from the second film F2. The second plasma PL2 is generated from a second process gas in the plasma processing chamber 10. The trimming may be lateral etching. The trimming reduces the dimensions (CD) of the carbon-containing mask MK and the second film F2. At the end of step ST3, the carbon-containing mask MK may remain on the top surface of the nanopillar NP.

[0050] The aspect ratio of the nanopillar NP may be 4 or more, or 10 or more. The aspect ratio of the nanopillar NP is the ratio of the height D4 of the nanopillar NP to the dimension D3 (CD: Critical Dimension) at the bottom (lower end) F2b of the nanopillar NP. The dimension D3 may be 50 nm or less, or may be 30 nm or less. The height D4 may be 100 nm or more. The nanopillar NP may have a dot pattern or a line pattern surrounded by recesses RS. The dot pattern may include, for example, a plurality of dots arranged in a lattice pattern.

[0051] The angle θ, which is the inclination angle of the sidewall F2a of the nanopillar NP, may be 86° or more, or may be 88° or more. The angle θ is the angle from the bottom F2b of the nanopillar NP through the inside of the nanopillar NP to the sidewall F2a.

[0052] The second process gas in step ST3 may be different from the first process gas. The second process gas may contain fluorine. The second process gas may contain fluorine and carbon. The second process gas may contain a fluorine-containing gas. The second process gas may be CHF ３ The second process gas may contain a gas. The second process gas may further contain an inert gas. Examples of the inert gas include nitrogen gas and noble gas. Examples of the noble gas include helium gas, neon gas, argon gas, krypton gas, and xenon gas. When the second process gas contains an inert gas, the speed at which the sidewalls MKa and F2a are trimmed in step ST3 can be controlled. A high flow rate ratio of the inert gas reduces the trimming speed. The second process gas may contain CHF ３ The gas may further include a fluorine-containing gas different from the gas. An example of a fluorine-containing gas is CF ４ Fluorocarbon gases such as SF ６ Gas and NF ３The second process gas may further include a carbon-containing gas. Examples of the carbon-containing gas include a hydrocarbon gas and a fluorocarbon gas. When the second process gas includes a carbon-containing gas, the carbon-containing mask MK can be protected in step ST3. The second process gas may further include an oxygen-containing gas such as oxygen.

[0053] The second process gas may be a single gas. The single gas may be CHF ３ It may also be a gas.

[0054] The temperature of the substrate support part 11 in step ST3 may be higher than the temperature of the substrate support part 11 in step ST2. In this case, the speed at which the sidewall F2a is trimmed in step ST3 can be improved. The temperature of the substrate support part 11 in step ST3 may be higher than 60°C, may be 70°C or higher, or may be 120°C or lower.

[0055] The pressure in the plasma processing chamber 10 in step ST3 may be lower than the pressure in the plasma processing chamber 10 in step ST2. The pressure in the plasma processing chamber 10 in step ST3 may be 1.6 Pa (12 mTorr) or less, 0.8 Pa (6 mTorr) or less, 0.13 Pa (1 mTorr) or more, or greater than 0 Pa.

[0056] In step ST3, an electric bias may be applied to the substrate support part 11. The electric bias applied to the substrate support part 11 in step ST3 may be smaller than the electric bias applied to the substrate support part 11 in step ST2. The electric bias in step ST3 may be 50 W or less.

[0057] The source RF power for generating the second plasma PL2 in step ST3 may be smaller than the source RF power for generating the first plasma PL1 in step ST2, thereby weakening the dissociation of chemical species in the second plasma PL2. The source RF power for generating the second plasma PL2 may be 400 W or less.

[0058] (Step ST4) In step ST4, the carbon-containing mask MK may be removed by ashing using plasma.

[0059] According to the method MT1, nanopillars NP with a high aspect ratio can be formed using a carbon-containing mask MK with a small aspect ratio. By reducing the aspect ratio of the carbon-containing mask MK, the risk of the carbon-containing mask MK, which has a relatively low film strength, tipping over can be reduced. The mechanism by which trimming of the sidewall F2a progresses in step ST3 is presumed to be as follows, but is not limited to this.

[0060] 9 is a graph showing an example of the relationship between the state of radicals and the potential energy. The horizontal axis represents the state of radicals, and the vertical axis represents the potential energy of the radicals. In step ST3, the second plasma PL2 is CHF ３ When generated from the gas, the second plasma PL2 contains CHF ＋ ion, CHF ＊ Radicals, and F ＊ Radicals exist. Radicals in the gas state S1 move at a certain average speed, so they have kinetic energy E ｖ When a radical is physically adsorbed onto the surface of an object, the radical stops moving, and the kinetic energy E ｖ is converted into thermal energy. Therefore, the radicals in the state S2 physically adsorbed on the surface of the object lose their original potential energy E ０ From kinetic energy E ｖ Therefore, the radical in state S2 loses energy equivalent to (E ０ -E ｖ When the second film F2 is a silicon oxide film, the radicals in the state S2 are physically adsorbed on the surface of the silicon oxide film. In the state S2, the radicals are stabilized at an energy level having an energy of thermal energy or the like E ｃ When the energy E is supplied, a chemical reaction between the surface of the object and the radicals is initiated. ｃ When the energy E is supplied, the kinetic energy of the radicals and the molecules on the surface of the object increases. ｃWhen the wall of the second film F2 is crossed, a chemical reaction starts. The chemical reaction progresses trimming of the second film F2. Since the chemical reaction releases reaction heat, a stable reaction product is obtained in state S3.

[0061] If the temperature of the substrate support part 11 in step ST3 is higher than the temperature of the substrate support part 11 in step ST2, the trimming speed of the sidewall F2a in step ST3 can be improved.

[0062] When the pressure in the plasma processing chamber 10 in step ST3 is lower than the pressure in the plasma processing chamber 10 in step ST2, the verticality of the sidewall F2a can be improved in step ST3. The mechanism by which the verticality is improved is presumed to be as follows, but is not limited to this. When the pressure in step ST3 is low, the radical concentration gradient in the depth direction of the recess RS can be reduced. As a result, a sufficient amount of radicals is supplied near the bottom of the recess RS, thereby improving the verticality of the sidewall F2a.

[0063] If the electric bias applied to the substrate support part 11 in step ST3 is smaller than the electric bias applied to the substrate support part 11 in step ST2, the first film F1 is less likely to be etched in step ST3, and therefore the etching selectivity of the second film F2 to the first film F1 can be improved in step ST3.

[0064] Various experiments performed to evaluate Method MT1 are described below, but the experiments described below are not intended to limit the present disclosure.

[0065] (First Experiment) First, a substrate was provided on a substrate support in a chamber of a dry etching apparatus. The substrate had an InGaZnO film, a silicon oxide film on the InGaZnO film, and a spin-on-carbon (SOC) mask on the silicon oxide film. The silicon oxide film had a thickness of 400 nm. The SOC mask had a thickness of 400 nm. The SOC mask had a dot pattern. The CD of the SOC mask was 100 nm. Therefore, the aspect ratio of the SOC mask was 4.

[0066] Next, the silicon oxide film was etched through the openings in the SOC mask using plasma generated from a process gas containing a fluorine-containing gas, forming recesses in the silicon oxide film corresponding to the openings (etching process). The temperature of the substrate support supporting the substrate was 20°C. The pressure in the chamber was 2.67 Pa (20 mTorr). The bias RF power applied to the substrate support was 100 W. The source RF power for generating the plasma was 500 W. The processing time for the etching process was 900 seconds.

[0067] Next, a single gas, CHF ３ The sidewalls defining the recesses in the silicon oxide film were trimmed using plasma generated from the gas to form nanopillars from the silicon oxide film (trimming step). The temperature of the substrate support supporting the substrate was 120°C. The pressure in the chamber was 0.267 Pa (2 mTorr). The bias RF power applied to the substrate support was 25 W. The source RF power for generating the plasma was 300 W. The treatment time for the trimming step was changed from 0 to 540 seconds to change the amount of trimming of the nanopillar sidewalls.

[0068] (First Experimental Results) For each trimming amount, the CD at the bottom of the nanopillar (dimension D3 in FIG. 8) and the angle θ of the sidewall of the nanopillar (see FIG. 8) were measured. The results are shown in FIG.

[0069] FIG. 10 is a graph showing an example of the relationship between the trimming amount and the CD at the nanopillar bottom or the angle of the nanopillar sidewall. The horizontal axis represents the trimming amount (%). In this experiment, the trimming amount (%) was calculated as the ratio of the processing time of the trimming step to the processing time of the etching step. For example, a trimming amount of 50% indicates that the processing time of the trimming step is half the processing time of the etching step. The vertical axis represents the CD (nm) or the angle θ (°). In FIG. 10, the approximation line L1 shows the CD results, and the approximation line L2 shows the angle θ results. As shown in FIG. 10, as the trimming amount increases, the CD at the nanopillar bottom decreases and the sidewall angle θ approaches vertical. When the trimming amount is 60%, the CD at the nanopillar bottom is approximately 50 nm. In this case, the aspect ratio of the nanopillar is approximately 8.

[0070] (Second Experiment) The treatment time of the trimming step in the first experiment was fixed, and the pressure in the trimming step was changed from 0.267 Pa (2 mTorr) to 2.67 Pa (20 mTorr).

[0071] (Second Experimental Results) At each pressure, the CD at the bottom of the nanopillar and the angle θ of the sidewall of the nanopillar were measured. The results are shown in FIG.

[0072] FIG. 11 is a graph showing an example of the relationship between pressure and the CD at the nanopillar bottom or the angle of the nanopillar sidewall. The horizontal axis represents pressure (mTorr). The vertical axis represents CD (nm) or angle θ (°). In FIG. 11, approximate line L3 shows the CD results, and approximate line L4 shows the angle θ results. As shown in FIG. 11, as the pressure decreases, the CD at the nanopillar bottom decreases and the sidewall angle θ approaches vertical.

[0073] (Third Experiment) The processing time of the trimming step in the first experiment was fixed, and the temperature of the substrate support part in the trimming step was changed from 60°C to 120°C.

[0074] (Third Experimental Results) At each temperature, the trimming amount and the angle θ of the nanopillar sidewall were measured. In this experiment, the trimming amount (%) was calculated as follows: The CD at the bottom of the nanopillar was measured before and after the trimming process, and the trimming amount (%) was determined as the ratio of the CD reduction to the CD before the trimming process. The results are shown in Figure 12.

[0075] FIG. 12 is a graph showing an example of the relationship between temperature and the trimming amount or the angle of the nanopillar sidewall. The horizontal axis represents temperature (°C). The vertical axis represents the trimming amount (%) or the angle θ (°). In FIG. 12, the approximation line L5 shows the results for the trimming amount, and the approximation line L6 shows the results for the angle θ. As shown in FIG. 12, it can be seen that the trimming amount increases as the temperature increases. Furthermore, it can be seen that the angle θ of the sidewall hardly changes even when the temperature changes.

[0076] (Fourth Experiment) A silicon oxide film with a thickness of 150 nm was etched to form a dot pattern with a bottom CD of 50 nm. The dot pattern was then trimmed to form nanopillars with a bottom CD of 30 nm. The aspect ratio of the nanopillars was 5.

[0077] (Fifth Experiment) A silicon oxide film with a thickness of 400 nm was etched to form a dot pattern with a bottom CD of 120 nm. The dot pattern was then trimmed to form nanopillars with a bottom CD of 30 nm. The aspect ratio of the nanopillars was approximately 13.

[0078] Although various exemplary embodiments have been described above, the present invention is not limited to the above-described exemplary embodiments, and various additions, omissions, substitutions, and modifications may be made. Furthermore, elements in different embodiments may be combined to form other embodiments.

[0079] Various exemplary embodiments included in the present disclosure are now described in [E1] to [E16] below.

[0080] [E1] A method of forming nanopillars, comprising: (a) providing a substrate on a substrate support in a chamber, the substrate comprising a first film, a second film on the first film, and a carbon-containing mask on the second film, the second film comprising at least one of silicon or germanium, the carbon-containing mask having an opening; (b) etching the second film through the opening in the carbon-containing mask with a first plasma generated in the chamber from a first process gas to form a recess in the second film corresponding to the opening; and (c) trimming a sidewall defining the opening and a sidewall defining the recess with a second plasma generated in the chamber from a second process gas to form a nanopillar from the second film.

[0081] [E2] The method for forming nanopillars according to [E1], wherein the temperature of the substrate support part in (c) is higher than the temperature of the substrate support part in (b).

[0082] [E3] The method for forming nanopillars according to [E2], wherein the temperature of the substrate support in (c) is higher than 60°C.

[0083] [E4] The method for forming nanopillars according to any one of [E1] to [E3], wherein the pressure in the chamber in (c) is lower than the pressure in the chamber in (b).

[0084] [E5] The method for forming nanopillars according to [E4], wherein the pressure in the chamber in (c) is 1.6 Pa or less.

[0085] [E6] A method for forming nanopillars according to any one of [E1] to [E5], wherein the electrical bias applied to the substrate support in (c) is less than the electrical bias applied to the substrate support in (b).

[0086] [E7] The second process gas is CHF ３ The method for forming nanopillars according to any one of [E1] to [E6], which comprises a gas.

[0087] [E8] The second process gas is a single gas, and the single gas is CHF３ The method for forming nanopillars according to [E7], wherein the gas is a gas.

[0088] [E9] The method for forming nanopillars according to [E7], wherein the second processing gas further contains an inert gas.

[0089] [E10] The method for forming nanopillars according to any one of [E1] to [E9], wherein the aspect ratio of the nanopillars is 4 or more.

[0090] [E11] The method for forming nanopillars according to any one of [E1] to [E10], wherein the dimension of the nanopillars at their bases is 50 nm or less.

[0091] [E12] The method for forming nanopillars according to any one of [E1] to [E11], wherein the second film further contains at least one of oxygen and nitrogen.

[0092] [E13] The method for forming nanopillars according to any one of [E1] to [E12], wherein the first film contains at least one material selected from the group consisting of silicon, hafnium oxide, zirconium oxide, aluminum oxide, and InGaZnO.

[0093] [E14] The method for forming nanopillars according to any one of [E1] to [E13], wherein the carbon-containing mask contains at least one material selected from the group consisting of amorphous carbon, spin-on carbon, and resist.

[0094] [E15] The method for forming nanopillars according to any one of [E1] to [E14], wherein in (a), the aspect ratio of the carbon-containing mask is 4 or less.

[0095] a gas supply unit configured to supply a first process gas and a second process gas into the chamber; a plasma generation 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; and a control unit, wherein the control unit is configured to control the dry etching apparatus to: etch the second film through the opening in the carbon-containing mask with the first plasma to form a recess in the second film corresponding to the opening; and trim a sidewall defining the opening and a sidewall defining the recess with the second plasma to form a nanopillar from the second film.

[0096] 1...plasma processing apparatus (dry etching apparatus), 2...control unit, 10...plasma processing chamber, 11...substrate support unit, 12...plasma generation unit, 20...gas supply unit, F1...first film, F2...second film, F2a...side wall, MK...carbon-containing mask, MKa...side wall, NP...nanopillar, OP...opening, PL1...first plasma, PL2...second plasma, RS...recess, W...substrate.

Claims

1. A method of forming nanopillars, comprising: (a) providing a substrate on a substrate support in a chamber, the substrate comprising a first film, a second film on the first film, and a carbon-containing mask on the second film, the second film comprising at least one of silicon or germanium, the carbon-containing mask having an opening; (b) etching the second film through the opening in the carbon-containing mask with a first plasma generated in the chamber from a first process gas to form a recess in the second film corresponding to the opening; and (c) trimming a sidewall defining the opening and a sidewall defining the recess with a second plasma generated in the chamber from a second process gas to form a nanopillar from the second film.

2. A method for forming nanopillars as described in claim 1, wherein the temperature of the substrate support in (c) is higher than the temperature of the substrate support in (b).

3. The method for forming nanopillars according to claim 2, wherein the temperature of the substrate support in (c) is greater than 60°C.

4. A method for forming nanopillars according to any one of claims 1 to 3, wherein the pressure in the chamber in (c) is lower than the pressure in the chamber in (b).

5. A method for forming nanopillars as described in claim 4, wherein the pressure in the chamber in (c) is 1.6 Pa or less.

6. A method for forming nanopillars according to any one of claims 1 to 3, wherein the electrical bias applied to the substrate support in (c) is less than the electrical bias applied to the substrate support in (b).

7. The second process gas is CHF ３ The method for forming nanopillars according to any one of claims 1 to 3, comprising a gas.

8. The second process gas is a single gas, and the single gas is CHF ３ The method for forming nanopillars according to claim 7, wherein the gas is a gas.

9. The method of forming nanopillars according to claim 7, wherein the second process gas further comprises an inert gas.

10. A method for forming nanopillars according to any one of claims 1 to 3, wherein the aspect ratio of the nanopillars is 4 or more.

11. A method for forming nanopillars according to any one of claims 1 to 3, wherein the dimension of the nanopillars at their bases is 50 nm or less.

12. A method for forming nanopillars according to any one of claims 1 to 3, wherein the second film further contains at least one of oxygen and nitrogen.

13. The method for forming nanopillars according to any one of claims 1 to 3, wherein the first film contains at least one material selected from the group consisting of silicon, hafnium oxide, zirconium oxide, aluminum oxide, and InGaZnO.

14. The method for forming nanopillars according to any one of claims 1 to 3, wherein the carbon-containing mask comprises at least one material selected from the group consisting of amorphous carbon, spin-on carbon, and resist.

15. A method for forming nanopillars according to any one of claims 1 to 3, wherein in (a), the aspect ratio of the carbon-containing mask is 4 or less.

16. A dry etching apparatus comprising: a chamber; and a substrate support for supporting a substrate in the chamber, the substrate comprising a first film, a second film on the first film, and a carbon-containing mask on the second film, the second film comprising at least one of silicon or germanium, the carbon-containing mask having an opening; a gas supply configured to supply a first process gas and a second process gas into the chamber; a plasma generation 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; and a controller, wherein the controller is configured to control the dry etching apparatus to: etch the second film through the opening in the carbon-containing mask with the first plasma to form a recess in the second film corresponding to the opening; and trim a sidewall defining the opening and a sidewall defining the recess with the second plasma to form a nanopillar from the second film.

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