Etching method and plasma processing apparatus

Abstract

In one exemplary embodiment, an etching method includes the steps of: (a) providing a substrate provided with a carbon-containing film and a mask on the carbon-containing film; and (b) etching the carbon-containing film by plasma generated from a processing gas containing an oxygen-containing gas and a sulfur-containing gas, in which in (b), pulses of bias power are supplied to a substrate support section that supports the substrate, the pulses are periodically repeated, and the frequency of the period of the prescribed pulse is 5 kHz or more.

Description

Technical Field

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

[0002] In the manufacture of electronic devices, plasma etching is sometimes performed on a film to form a recessed portion. To form such a recessed portion, a mask is formed on the film to be etched. Patent Document 1 discloses a method for plasma etching a film on a substrate. In this method, a first high-frequency power (e.g., 40 MHz) with a relatively high frequency and a second high-frequency power (e.g., 2 MHz) with a relatively low frequency are applied to a second electrode supporting the substrate. A DC voltage is applied to a first electrode disposed opposite the second electrode in a processing container. Thus, plasma etching is performed.

[0003] Previous technical literature

[0004] Patent Literature

[0005] Patent Document 1: Japanese Patent Application Laid-Open No. 2007-180358 Summary of the Invention

[0006] Technical issues to be solved by the invention

[0007] The present invention provides a technique for etching a film while suppressing shape abnormality of a recessed portion.

[0008] Means for solving technical problems

[0009] In an exemplary embodiment, the etching method includes the following steps: (a) providing a substrate having a carbon-containing film and a mask on the carbon-containing film; and (b) etching the carbon-containing film by plasma generated from a processing gas containing an oxygen-containing gas and a sulfur-containing gas, wherein in (b), pulses of bias power are supplied to a substrate support portion supporting the substrate, the pulses are periodically repeated, and the frequency of the pulse cycle is specified to be greater than 5 kHz.

[0010] Effects of the Invention

[0011] According to an exemplary embodiment, there is provided a technique for etching a film while suppressing shape abnormality of a recessed portion. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Figure 1 This is a diagram schematically showing a plasma processing apparatus according to an exemplary embodiment.

[0013] Figure 2 This is a diagram schematically showing a plasma processing apparatus according to an exemplary embodiment.

[0014] Figure 3 is a flow chart of an etching method according to an exemplary embodiment.

[0015] Figure 4 It can be applied Figure 3 A cross-sectional view of a substrate according to an example of the method.

[0016] Figure 5 It is a cross-sectional view showing one step of an etching method according to an exemplary embodiment.

[0017] Figure 6 This is an example of a timing chart showing temporal changes in bias power.

[0018] Figure 7 This is a cross-sectional view showing one step in an example of an etching method.

[0019] Figure 8 This is an example of a timing chart showing temporal changes in bias power according to a modification.

[0020] Figure 9 Yes means through Figure 5 FIG. 1 is a diagram showing an example of a planar shape of the bottom of a recess formed by the steps.

[0021] Figure 10 Yes means through Figure 7 FIG. 1 is a diagram showing an example of a planar shape of the bottom of a recess formed by the steps.

[0022] Figure 11 This is a graph showing an example of the relationship between the depth of the recess and the deformation of the shape of the recess at each depth.

[0023] Figure 12 This is a graph showing an example of the relationship between the power value of the high power pulse of the bias power and the distortion value. DETAILED DESCRIPTION

[0024] Hereinafter, various exemplary embodiments will be described in detail with reference to the accompanying drawings. In addition, in each of the drawings, the same or equivalent parts are marked with the same reference numerals.

[0025] Figure 1: is a diagram for illustrating a structural example of a plasma processing system. In one embodiment, the plasma processing system includes a plasma processing device 1 and a control unit 2. The plasma processing system is an example of a substrate processing system, and the plasma processing device 1 is an example of a substrate processing device. The plasma processing device 1 includes a plasma processing chamber 10, a substrate support portion 11, and a plasma generating portion 12. The plasma processing chamber 10 has a plasma processing space. In addition, the plasma processing chamber 10 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 the gas supply portion 20 described later, and the gas exhaust port is connected to the exhaust system 40 described later. The substrate support portion 11 is arranged in the plasma processing space and has a substrate supporting surface for supporting a substrate.

[0026] The plasma generating section 12 is configured to generate plasma from at least one processing gas supplied into the plasma processing space. The plasma formed in the plasma processing space may also be a capacitively coupled plasma (CCP: Capacitively Coupled Plasma), an inductively coupled plasma (ICP: Inductively Coupled Plasma), an ECR plasma (Electron-Cyclotron-Resonance Plasma: Electron Cyclotron Resonance Plasma), a helicon wave excited plasma (HWP: Helicon Wave Plasma), or a surface wave plasma (SWP: Surface Wave Plasma), etc. Furthermore, various types of plasma generating sections including an AC (Alternating Current: Alternating Current) plasma generating section and a DC (Direct Current: Direct Current) plasma generating section may be used. In one embodiment, the AC signal (AC power) used in the AC plasma generating section has a frequency in the range of 100kHz to 10GHz. Therefore, the AC signal includes an RF (Radio Frequency: Radio Frequency) signal and a microwave signal. In one embodiment, the RF signal has a frequency in the range of 100kHz to 150MHz.

[0027] The control unit 2 processes computer executable instructions that cause the plasma processing device 1 to perform the various processes described in the present invention. The control unit 2 can be configured to control the various elements of the plasma processing device 1 in a manner that performs the various processes described herein. In one embodiment, a portion or all of the control unit 2 can be included in the plasma processing device 1. The control unit 2 can include a processing unit 2a1, a storage unit 2a2, and a communication interface 2a3. The control unit 2 is implemented, for example, by a computer 2a. The processing unit 2a1 can be configured to read a program from the storage unit 2a2 and execute the read program, thereby performing various control operations. The program can be stored in the storage unit 2a2 in advance, or it can be obtained through a medium when necessary. The obtained program is stored in the storage unit 2a2, and is read from the storage unit 2a2 by the processing unit 2a1 and executed. The medium can be various storage media readable by the computer 2a, or it can be a communication line connected to the communication interface 2a3. The processing unit 2a1 can also be a CPU (Central Processing Unit). The storage unit 2a2 may include RAM (Random Access Memory), ROM (Read Only Memory), HDD (Hard Disk Drive), SSD (Solid State Drive), or a combination thereof. The communication interface 2a3 may also communicate with the plasma processing apparatus 1 via a communication line such as a LAN (Local Area Network).

[0028] Hereinafter, a configuration example of an inductively coupled plasma processing apparatus will be described as an example of the plasma processing apparatus 1 . Figure 2 It is a diagram for explaining a configuration example of an inductively coupled plasma processing apparatus.

[0029] An inductively coupled plasma processing apparatus 1 includes a plasma processing chamber 10, a gas supply unit 20, a power supply 30, and an exhaust system 40. The plasma processing chamber 10 includes a dielectric window 101. Furthermore, the plasma processing apparatus 1 includes a substrate support 11, a gas inlet, and an antenna 14. The substrate support 11 is disposed within the plasma processing chamber 10. The antenna 14 is disposed on or above the plasma processing chamber 10 (i.e., on or above the dielectric window 101). The plasma processing chamber 10 has a plasma processing space 10s defined by the dielectric window 101, the sidewalls 102 of the plasma processing chamber 10, and the substrate support 11. The plasma processing chamber 10 is grounded.

[0030] The substrate support portion 11 includes a main body 111 and a ring assembly 112. The main body 111 has a central area 111a for supporting a substrate W, and an annular area 111b for supporting the ring assembly 112. A wafer is an example of a substrate W. When viewed from above, the annular area 111b of the main body 111 surrounds the central area 111a of the main body 111. The substrate W is arranged on the central area 111a of the main body 111, and the ring assembly 112 is arranged on the annular area 111b of the main body 111 so as to surround the substrate W on the central area 111a of the main body 111. Therefore, the central area 111a is also referred to as a substrate supporting surface for supporting the substrate W, and the annular area 111b is also referred to as a ring supporting surface for supporting the ring assembly 112.

[0031] In one embodiment, the main body 111 includes a base 1110 and an electrostatic chuck 1111. The base 1110 includes a conductive component. The conductive component of the base 1110 can function as a bias electrode. The electrostatic chuck 1111 is arranged on the base 1110. The electrostatic chuck 1111 includes a ceramic component 1111a and an electrostatic electrode 1111b arranged in the ceramic component 1111a. The ceramic component 1111a has a central area 111a. In one embodiment, the ceramic component 1111a also has an annular area 111b. In addition, other components surrounding the electrostatic chuck 1111, such as an annular electrostatic chuck or an annular insulating component, may have the annular area 111b. In this case, the ring assembly 112 may be arranged on the annular electrostatic chuck or the annular insulating component, or on both the electrostatic chuck 1111 and the annular insulating component. Furthermore, at least one RF / DC electrode, coupled to the RF power supply 31 and / or DC power supply 32 (described later), may be disposed within the ceramic component 1111a. In this case, the at least one RF / DC electrode functions as a bias electrode. Alternatively, the conductive component of the base 1110 and the at least one RF / DC electrode may function as multiple bias electrodes. Furthermore, the electrostatic electrode 1111b may function as a bias electrode. Therefore, the substrate support 11 includes at least one bias electrode.

[0032] The ring assembly 112 includes one or more ring-shaped components. In one embodiment, the one or more ring-shaped components include one or more edge rings and at least one cover ring. The edge ring is formed of a conductive material or an insulating material, and the cover ring is formed of an insulating material.

[0033] Furthermore, the substrate support portion 11 may 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 path 1110a, or a combination thereof. A heat transfer fluid such as brine or gas flows through the flow path 1110a. In one embodiment, the flow path 1110a is formed in the base 1110, and one or more heaters are arranged in the ceramic component 1111a of the electrostatic chuck 1111. Furthermore, the substrate support portion 11 may include a heat transfer gas supply portion configured to supply a heat transfer gas to the gap between the back surface of the substrate W and the central area 111a.

[0034] The gas inlet portion is configured to introduce at least one processing gas from the gas supply portion 20 into the plasma processing space 10s. In one embodiment, the gas inlet portion includes a central gas injection portion (CGI: Center Gas Injector) 13. The central gas injection portion 13 is arranged above the substrate support portion 11 and is installed in the central opening portion formed in the dielectric window 101. The central gas injection portion 13 has at least one gas supply port 13a, at least one gas flow path 13b and at least one gas inlet port 13c. The processing gas supplied to the gas supply port 13a is introduced into the plasma processing space 10s from the gas inlet port 13c through the gas flow path 13b. In addition, the gas inlet portion may include one or more side gas injection portions (SGI: Side Gas Injector) installed in one or more openings formed in the side wall 102 on the basis of or in place of the central gas injection portion 13.

[0035] 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 gas inlet via a corresponding flow controller 22. Each flow controller 22 may include, for example, a mass flow controller or a pressure-controlled flow controller. Furthermore, the gas supply unit 20 may include at least one flow modulation device for modulating or pulsing the flow of the at least one process gas.

[0036] 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 bias electrode and antenna 14. This generates a plasma from at least one process gas supplied to the plasma processing space 10s. Therefore, the RF power supply 31 can function as at least a portion of the plasma generating unit 12. Furthermore, by supplying a bias RF signal (bias RF power) to at least one bias electrode, a bias potential is generated on the substrate W, and ions in the generated plasma are introduced into the substrate W.

[0037] In one embodiment, the RF power supply 31 includes a first RF generator 31a and a second RF generator 31b. The first RF generator 31a is coupled to the antenna 14 via at least one impedance matching circuit and generates a source RF signal (source RF power) for plasma generation. In one embodiment, the source RF signal has a frequency in the range of 10 MHz to 150 MHz. In one embodiment, the first RF generator 31a can be configured to generate multiple source RF signals having different frequencies. The generated one or more source RF signals are supplied to the antenna 14.

[0038] The second RF generating unit 31b is configured to generate a bias RF signal by combining at least one impedance matching circuit with at least one bias electrode. The frequency of the bias RF signal may be the same as or different from the frequency of the source RF signal. In one embodiment, the bias RF signal has a frequency lower than the frequency of the source RF signal. In one embodiment, the bias RF signal has a frequency in the range of 100 kHz to 60 MHz. In one embodiment, the second RF generating unit 31b may be configured to generate a plurality of bias RF signals having different frequencies. The generated one or more bias RF signals are supplied to at least one bias electrode. Furthermore, in various embodiments, at least one of the source RF signal and the bias RF signal may be pulsed.

[0039] Furthermore, the power supply 30 may include a DC power supply 32 coupled to the plasma processing chamber 10. The DC power supply 32 includes a bias DC generator 32a. In one embodiment, the bias DC generator 32a is configured to be connected to at least one bias electrode and generate a bias DC signal. The generated bias DC signal is applied to the at least one bias electrode.

[0040] In various embodiments, the bias DC signal can be pulsed. In this case, a sequence of voltage pulses is applied to at least one bias electrode. The voltage pulses can have a rectangular, trapezoidal, triangular, or a combination thereof pulse waveform. In one embodiment, a waveform generator for generating a sequence of voltage pulses from a DC signal is connected between the bias DC generator 32a and at least one bias electrode. Thus, the bias DC generator 32a and the waveform generator constitute a voltage pulse generator. The voltage pulses can have positive or negative polarity. Furthermore, the sequence of voltage pulses can include one or more positive polarity voltage pulses and one or more negative polarity voltage pulses within one cycle. Furthermore, the bias DC generator 32a can be provided in addition to the RF power supply 31, or it can be provided in place of the second RF generator 31b.

[0041] Antenna 14 includes one or more coils. In one embodiment, antenna 14 may include an outer coil and an inner coil arranged on the same axis. In this case, RF power supply 31 may be connected to both the outer coil and the inner coil, or to either one. In the former case, the same RF generator may be connected to both the outer coil and the inner coil, or separate RF generators may be connected to each coil.

[0042] The exhaust system 40 can be connected to a gas outlet 10e provided at the bottom of the plasma processing chamber 10, for example. The exhaust system 40 can 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 can include a turbomolecular pump, a dry pump, or a combination thereof.

[0043] Figure 3 is a flow chart of an etching method according to an exemplary embodiment. Figure 3 The etching method MT shown (hereinafter referred to as "method MT") can be performed by the plasma processing apparatus 1 of the above-described embodiment. The method MT can be applied to a substrate W.

[0044] Figure 4 It can be applied Figure 3 A cross-sectional view of a substrate W according to an example of the method. Figure 4 As shown in FIG. 1 , in one embodiment, the substrate W includes a carbon-containing film FL and a mask MK on the carbon-containing film FL. The substrate W may further include a base region UR below the carbon-containing film FL.

[0045] The carbon-containing film FL may include an amorphous carbon film. The carbon-containing film FL may have a thickness of 2000 nm or more, or 3000 nm or more. The carbon-containing film FL may have a thickness of 5000 nm or less.

[0046] The mask MK may have an opening OP. The mask MK may have a plurality of openings OP. The opening OP may have a hole pattern or a line pattern. The size of the opening OP (CD: Critical Dimension) may be less than 100 nm. The mask MK may include a silicon-containing film. The mask MK may include a silicon nitride oxide film (SiON), a silicon oxide film (SiO2), a silicon nitride film (SiN x ) or tungsten silicide (W x Si y ) membrane.

[0047] The base region UR may include a silicon-containing film. For example, the base region UR may include at least one film used for a memory device such as a DRAM or a 3D-NAND.

[0048] Hereinafter, regarding the method MT, a case where the method MT is applied to a substrate W using the plasma processing apparatus 1 of the above embodiment is taken as an example, and reference is made to Figures 3 to 6 Provide explanation. Figure 5 1 is a cross-sectional view showing one step of an etching method according to an exemplary embodiment. When the plasma processing apparatus 1 is used, the method MT can be executed in the plasma processing apparatus 1 by controlling each part of the plasma processing apparatus 1 by the control unit 2. In the method MT, Figure 2 As shown, a substrate W disposed on a substrate support 11 within a plasma processing chamber 10 is processed.

[0049] like Figure 3 As shown, method MT includes step ST1 and step ST2. Step ST1 and step ST2 can be performed sequentially.

[0050] (Process ST1)

[0051] In step ST1, provide Figure 4 The substrate W is shown. The substrate W can be disposed in a plasma processing chamber 10. The substrate W can be supported by a substrate support 11 in the plasma processing chamber 10. The base region UR can be disposed between the substrate support 11 and the carbon-containing film FL.

[0052] (Process ST2)

[0053] In step ST2, Figure 5As shown, the carbon-containing film FL is etched through the opening OP by the plasma PL generated from the processing gas. A recess RS is formed on the carbon-containing film FL by etching. The recess RS has side walls RSa and a bottom RSb. The bottom RSb can reach the base region UR. The aspect ratio of the recess RS can be greater than 20 or greater than 30. The aspect ratio of the recess RS can be less than 50. The aspect ratio of the recess RS is the ratio of the depth of the recess RS to the dimension (CD) of the recess RS. The processing gas includes an oxygen-containing gas and a sulfur-containing gas. Examples of oxygen-containing gases include oxygen. Examples of sulfur-containing gases include carbonyl sulfide (COS) gas. The processing gas can include an inert gas. Examples of inert gases include argon. The temperature of the substrate support 11 in step ST2 can be less than 0°C or less than -40°C. The temperature of the substrate support 11 in step ST2 can be less than 80°C. If the temperature of the substrate support portion 11 is lowered, the etching rate of the carbon-containing film FL can be increased, and the shape abnormality (bending) of the side wall RSa of the recess RS can be suppressed.

[0054] exist Figure 5 FIG. 1 shows an example of the trajectory of ions IN generated in the plasma PL. The ions IN are, for example, argon ions (Ar) generated by dissociation of argon gas in the plasma. + ). By supplying bias power to at least one bias electrode, a bias potential is generated on the substrate W. As a result, ions IN in the plasma PL are introduced into the substrate W. The ions IN travel toward the bottom RSb of the recess RS. The trajectory of the ions IN from the plasma PL toward the substrate W is represented by a solid line. The ion IN is incident on the bottom RSb, promoting ion-assisted reaction. Ion-assisted reaction refers to the phenomenon that the incident ions IN promote surface reaction. The ions IN sometimes enter the substrate W at a certain angle. In this case, the ions IN collide with the side wall MKa of the mask MK, and the reflected ions IN (represented by the dotted line) can enter the recess RS.

[0055] Figure 6 This is an example of a timing diagram showing the temporal change of bias power. Figure 6 In FIG. 1 , the vertical axis represents the power value of the bias power WB, and the horizontal axis represents the time t. This timing diagram is related to step ST2. Figure 6As shown, in step ST2, pulses PS of bias power WB are supplied to the substrate support portion 11. The pulses PS of bias power WB may be high-frequency power applied to the bias electrode in the main body 111 of the substrate support portion 11. The pulses PS of bias power WB are repeated periodically with a period CY1. The period CY1 may include a high power period HP and a low power period LP. The low power period LP is a period following the high power period HP. During the high power period HP, the pulses PS of bias power WB may be maintained at high power HW. During the low power period LP, the pulses PS of bias power WB may be maintained at low power LW. The low power LW may be a power value lower than the high power HW, or may be a state where the bias power WB is turned off (0 W).

[0056] The frequency FP of the period CY1 of the pulse PS is specified to be 5 kHz or higher. The frequency FP may be 15 kHz or higher. The frequency FP may be 25 kHz or lower, or 15 kHz or lower. The duty cycle of the pulse PS may be 30% or higher, 60% or lower, or 50% or lower. The duty cycle of the pulse PS may be 90% or lower. The duty cycle of the pulse PS is the ratio of the high power period HP to the period CY1. The level of the pulse PS (the power value of the high power HW) may be 2000 W or higher, 6000 W or lower, or 5000 W or lower.

[0057] In step ST2, plasma PL may be generated by supplying source power. The source power may be applied to Figure 2 The high-frequency power of the antenna 14 is supplied. The frequency of the source power is higher than the frequency of the bias power WB. In step ST2, a continuous wave (CW) source power may be supplied, or a pulse of the source power may be supplied. When a power pulse is supplied, the pulse may be generated by switching the power on / off, or the pulse may be generated according to the magnitude of the power value. When a pulse of the source power is supplied in step ST2, the shape abnormality (bending) of the side wall RSa of the recess RS can be suppressed.

[0058] According to the above-mentioned plasma processing apparatus 1 and method MT, a recess RS is formed on the carbon-containing film FL by etching in step ST2. Compared with the case where the frequency FP of the pulse PS of the bias power WB supplied to the substrate support part 11 in step ST2 is lower than 5 kHz, the shape abnormality of the recess RS can be suppressed. For example, the shape abnormality (bending) of the side wall RSa of the recess RS can be suppressed. For example, the distortion of the planar shape of the bottom RSb of the recess RS can be suppressed. One mechanism by which the shape abnormality of the recess RS is suppressed is presumed to be as follows, but is not limited to this. If the frequency FP of the pulse PS of the bias power WB is higher than 5 kHz, the charging of the mask MK caused by the collision of the ions IN in the plasma PL with the mask MK is suppressed. As a result, the trajectory of the ions IN in the plasma PL becomes difficult to bend. Therefore, it is possible to suppress the collision of the ions IN with the side wall RSa of the recess RS and the etching of the side wall RSa. In addition, it is possible to suppress the collision of the ions IN with the mask MK and the etching of the mask MK.

[0059] Another mechanism for suppressing the shape abnormality of the recess RS is speculated as follows, but the present invention is not limited thereto. Figure 7 The presumed mechanism is explained.

[0060] Figure 7 This is a cross-sectional view showing one step in an example of an etching method. Figure 7 Indicates that except for the frequency FP of the pulse PS of the bias power WB being less than 5kHz, the Figure 5 The process is carried out in the same manner as the process ST2. Figure 7 In the process, the carbon-containing film FL1 is etched through the opening OP1 by the plasma PL1 generated from the processing gas. The recess RS1 is formed in the carbon-containing film FL1 by the etching. Figure 7 In, with Figure 5 In contrast, the number of ions IN1 increases when the angle θ formed between the direction perpendicular to the main surface of substrate W1 and the direction of travel of ions IN1 increases. This is presumably because the low frequency FP of pulse PS makes it easier for electrons to remain in opening OP1 of mask MK1. The retained electrons collide with ions IN1, bending the trajectories of ions IN1 and causing many ions IN1 to travel in a lateral direction.

[0061] Since many ions IN1 travel in a lateral direction, the number of ions IN1 that collide with the side wall MKa1 of the mask MK1 increases, making it easier for the side wall MKa1 of the mask MK1 to be scraped off. As a result, the side wall MKa1 is tilted toward the bottom RSb1, with the size of the opening OP1 decreasing from the upper end to the lower end of the opening OP1. As a result, the ions IN1 that collide with the side wall MKa1 and are reflected are more likely to collide with the upper portion of the side wall RSa1 of the recess RS1. Therefore, it is speculated that a bend BN is more likely to form in the upper portion of the side wall RSa1. In addition, since the ions IN1 travel in a lateral direction, the number of ions IN1 that are perpendicularly incident on the bottom RSb1 decreases. Therefore, the deformation of the planar shape of the recess RS1 in the cross section perpendicular to the depth direction of the recess RS1 becomes greater.

[0062] When the duty ratio of the pulse PS is 50% or less, the period during which chemical species in the recess RS formed by etching are exhausted becomes longer, thereby suppressing clogging of the opening of the recess RS by deposits formed by the chemical species in the recess RS.

[0063] In the case where the carbon-containing film FL has a thickness of 2000 nm or more, deformation of the planar shape of the bottom RSb of the recess RS can be further suppressed.

[0064] If the power value of the high power HW of the pulse PS is 2000 W to 5000 W, deformation of the planar shape of the bottom RSb of the recess RS can be suppressed, and reduction in etching selectivity of the carbon-containing film FL to the mask MK can be suppressed.

[0065] Figure 8 FIG. 1 is an example of a timing chart showing the temporal change of the bias power WB according to the modification. Figure 8 As shown, the process ST2 can include a first period PA and a second period PB. The second period PB is a period after the first period PA. The first period PA and the second period PB can be repeated periodically with a period CY2. In the first period PA, the Figure 6 The pulse PS described in the first period PA may be supplied with a high power HW (first level) pulse PS. In the second period PB, the bias power WB may not be supplied to the substrate support portion 11. Alternatively, in the second period PB, a bias power WB of a low power LW (second level) lower than the power value of the high power HW may be supplied to the substrate support portion 11. In the second period PB, the bias power WB may be maintained at the low power LW. The power value of the low power LW is the same as Figure 6 Similarly, it can be a power value lower than the high power HW, or it can be a state where the bias power WB is turned off (0 W).

[0066] When step ST2 includes the first period PA and the second period PB, the chemical species within the recess RS formed by etching during the first period PA are expelled during the second period PB. Therefore, compared to a case without the second period PB, clogging of the opening of the recess RS by deposits formed by the chemical species within the recess RS can be suppressed. Furthermore, suppressing clogging facilitates the entry of ions IN into the recess RS, thereby promoting etching. Consequently, compared to a case without the second period PB, the etching selectivity of the carbon-containing film FL relative to the mask MK can be improved.

[0067] The second frequency (frequency FB) defining the period CY2 between the first period PA and the second period PB can be greater than or equal to 100 Hz and less than or equal to 1 kHz. If the frequency FB is greater than or equal to 100 Hz, the first period PA, during which deposits can form at the opening of the recess RS, can be shortened. On the other hand, if the frequency FB is less than or equal to 1 kHz, the second period PB, during which chemical species within the recess RS can be discharged, can be extended. Therefore, if the second frequency is greater than or equal to 100 Hz and less than or equal to 1 kHz, clogging of the opening of the recess RS by deposits can be further suppressed. The frequency FB can be greater than or equal to 500 Hz. The frequency FB can be less than or equal to 500 Hz.

[0068] Various experiments conducted to evaluate the method MT are described below. The experiments described below do not limit the present invention.

[0069] (Experiment 1)

[0070] In the first experiment, a substrate having an amorphous carbon film and a mask on the amorphous carbon film was prepared. The thickness of the amorphous carbon film was 3500 nm. The mask was a SiON film having a circular opening. With respect to the substrate, a recess was formed by etching the amorphous carbon film with plasma generated from a processing gas. The planar shape of the recess is ideally circular. The processing gas contains oxygen, COS gas, and argon gas. During etching, pulses of bias power were supplied to the substrate support. The pulses were repeated periodically. The frequency of the pulse cycle was specified to be 10 kHz. The high power value of the bias power pulse was 3500 W. The low power value of the bias power pulse was 0 W. The duty cycle of the bias power pulse was 30%.

[0071] (Experiment 2)

[0072] The second experiment was conducted in the same manner as the first experiment except that the frequency of the cycle of the pulses that specify the bias power was set to 1 kHz instead of 10 kHz.

[0073] (Experiment 3)

[0074] The third experiment was conducted in the same manner as the first experiment except that the frequency of the cycle of the pulses that specify the bias power was set to 300 Hz instead of 10 kHz.

[0075] (First Experimental Results)

[0076] In the first to third experiments, the deformation of the planar shape of the recessed portions formed in the amorphous carbon film was measured according to the depth of the recessed portions. Figure 9 Yes means through Figure 5 FIG. 1 is a diagram showing an example of a planar shape of the bottom of a recess formed in step ST2. Figure 9 The experimental results of the first experiment (pulse frequency 10 kHz) are shown. Figure 10 Yes means through Figure 7 FIG. 1 is a diagram showing an example of a planar shape of the bottom of a recess formed by the steps. Figure 10 The experimental results of the third experiment (pulse frequency 300Hz) are shown. Figure 10 Compared to the planar shape of the bottom shown in Figure 9 The plane shape of the bottom shown in has a smaller deformation. In other words, when the ideal plane shape of the bottom is a circle, if the frequency of the pulse is high, the plane shape of the bottom is close to a perfect circle.

[0077] Figure 11 This is a graph showing an example of the relationship between the depth of the concave portion and the deformation of the planar shape of the concave portion at each depth. The vertical axis of the graph represents the depth of the concave portion. The horizontal axis of the graph represents the value of the deformation of the planar shape of the concave portion. The value of the deformation of the planar shape of the concave portion is measured by terminal PC offline length measurement software manufactured by Hitachi, Ltd. The closer the deformation value is to 1, the smaller the deformation is. In the case where the ideal planar shape of the concave portion is a circle, the closer the deformation value is to 1, the closer the planar shape of the concave portion is to a perfect circle. In other words, in the case where the ideal planar shape of the concave portion is a circle, the closer the deformation value is to 1, the higher the roundness of the planar shape of the concave portion. From Figure 11 It can be seen that the difference based on the frequency of the pulse begins to appear significantly from the depth of the concave portion at around 1250nm. When the pulse frequency is 10kHz, the decrease in the deformation value is suppressed from the depth of the concave portion at around 1250nm to 3500nm. As the pulse frequency decreases, the deformation value decreases from the depth of the concave portion at around 1250nm to 3500nm. Therefore, the deformation value at the bottom of the concave portion (near the depth of 3500nm) becomes the maximum when the frequency is 10kHz. Figure 11 As a result, it can be seen that when the pulse frequency is 10 kHz, even when the depth of the concave portion is deepened, the deformation value can be maintained to be large (the deformation is small).

[0078] In addition, in the first to third experiments, the degree of curvature generated in the upper part of the side wall of the recess was confirmed. As a result, it was confirmed that when the pulse frequency was 10kHz, the curvature was suppressed compared with the cases of 300Hz and 1kHz. In addition, in the first to third experiments, the shape of the mask after etching was confirmed. It was confirmed that when the pulse frequency was 10kHz, the deformation of the mask was suppressed compared with the cases of 300Hz and 1kHz (refer to Figure 7 ). It can be seen that the reduction in the etching selectivity of the amorphous carbon film with respect to the mask can be suppressed.

[0079] As seen from the above, when the pulse frequency is 5 kHz or higher, the shape abnormality of the recess (deformation of the planar shape of the bottom of the recess and curvature generated in the upper portion of the side wall of the recess) can be suppressed.

[0080] (Experiment 4)

[0081] The fourth experiment was conducted in the same manner as the first experiment except that the power value of the high power pulse of the bias power was set to 2000 W instead of 3500 W.

[0082] (Experiment 5)

[0083] The fifth experiment was conducted in the same manner as the first experiment except that the power value of the high power pulse of the bias power was set to 5000 W instead of 3500 W.

[0084] (Experiment 6)

[0085] The sixth experiment was conducted in the same manner as the first experiment except that the power value of the high power pulse of the bias power was set to 6000 W instead of 3500 W.

[0086] (Experiment 7)

[0087] The seventh experiment was conducted in the same manner as the first experiment except that the power value of the high power pulse of the bias power was set to 3000 W instead of 3500 W.

[0088] (Results of the second experiment)

[0089] In the first experiment and the fourth to sixth experiments, the values ​​of the deformation of the planar shape of the bottom of the recess were measured respectively. As a result, it can be seen that as the power value of the high power pulse increases, the deformation increases. In addition, by measuring the thickness of the mask, the etching selectivity of the amorphous carbon film relative to the mask was calculated. As a result, it can be seen that as the power value of the high power pulse increases, the etching selectivity decreases. It is speculated that there is the following correlation between the case where the deformation increases and the case where the etching selectivity decreases. The mask deforms as the etching selectivity decreases. Therefore, the number of ions colliding with the side walls of the mask and heading laterally increases, making it difficult for the ions to reach the bottom. As a result, the deformation of the planar shape of the bottom of the recess increases.

[0090] (Results of the third experiment)

[0091] In each of the fourth to seventh experiments, a value quantifying the twisting of the concave portion (hereinafter referred to as a twisting value) was measured. Figure 12 This is a graph showing an example of the relationship between the high power value of the bias power pulse and the distortion value. Twist refers to the twist from the upper end of the side wall of the concave to the bottom. The distortion value is the cross section of the concave (refer to Figure 5 ), when the central axis of the concave portion is set, the value obtained by quantifying the amount by which the center of the bottom of the concave portion deviates from the central axis. The measurement result is as follows: Figure 12 As shown, it can be seen that as the power value of the high power pulse increases, the twist value decreases (the twist is suppressed).

[0092] (Experiment 8)

[0093] The eighth experiment was conducted in the same manner as the first experiment except that the duty ratio of the bias power pulse was set to 40% instead of 30%.

[0094] (Experiment 9)

[0095] The ninth experiment was conducted in the same manner as the first experiment except that the duty ratio of the bias power pulse was set to 60% instead of 30%.

[0096] (Results of the fourth experiment)

[0097] In Experiments 1, 8, and 9, the deformation and distortion of the planar shape of the bottom of the concave portion were measured. The results showed that the deformation did not significantly change even when the pulse duty cycle was changed. On the other hand, the distortion decreased as the pulse duty cycle increased.

[0098] Furthermore, in Experiments 1, 8, and 9, the amount of deposits clogging the opening of the recess was determined. The results show that as the pulse duty cycle increases, the amount of deposits increases, leading to further clogging of the recess opening. As the pulse duty cycle increases, the length of the low-power period decreases. A shorter low-power period shortens the period during which chemical species are discharged, i.e., the exhaust period, and therefore, it is speculated that deposits tend to accumulate more easily. Chemical species include ions and free radicals.

[0099] In the tenth to twelfth experiments described below, a bias power supply pattern different from that of the first to ninth experiments was used.

[0100] (Experiment 10)

[0101] Used Figure 8 The bias power supply pattern in the modified example described in [1] was used. The frequency FB of the period CY2 defining the first period PA and the second period PB was 100 Hz. The duty cycle, which is the ratio of the first period to the period, was 50%. The frequency of the bias power pulses was 10 kHz. The high power value of the pulses was 3500 W. The duty cycle of the bias power pulses was 60%. Experiment 10 was conducted in the same manner as Experiment 9, except for the above conditions.

[0102] (Experiment 11)

[0103] The eleventh experiment was conducted in the same manner as the tenth experiment except that the frequency FB was set to 500 Hz instead of 100 Hz.

[0104] (Experiment 12)

[0105] The twelfth experiment was conducted in the same manner as the tenth experiment, except that the frequency FB was set to 1 kHz instead of 100 Hz.

[0106] (Results of the fifth experiment)

[0107] In the 9th to 12th experiments, the amount of deposits that can block the opening of the recess was confirmed. As a result, it was confirmed that the amount of deposits decreased in the 10th to 12th experiments compared to the 9th experiment. In the 10th to 12th experiments, it is speculated that the length of the exhaust period is longer than that of the 8th experiment by setting the second period, so there is a tendency that deposits are difficult to deposit. In the 10th to 12th experiments, it was confirmed that the reduction in the amount of deposits was the lowest in the 11th experiment. When the frequency FB is 500Hz, the period becomes shorter than when the frequency FB is 100Hz, so the first period in one period is short. It is believed that there is a tendency that deposits are difficult to deposit. When the frequency FB is 500Hz, the period becomes longer than when the frequency FB is 1kHz, so the second period in one period is long. It is believed that it is easy to ensure the exhaust time and there is a tendency that deposits are difficult to deposit.

[0108] Furthermore, in Experiments 9 through 12, the deformation and distortion values ​​of the planar shape of the bottom of the concave portion were measured. There was no significant difference in the deformation and distortion values ​​between Experiments 9 through 12. Therefore, it was found that even when the bias power supply pattern was changed, there was no significant difference in the deformation and distortion values.

[0109] Here, various exemplary embodiments included in the present invention are described in the following [E1] to [E11].

[0110] [E1]

[0111] An etching method comprising the following steps:

[0112] (a) providing a substrate having a carbon-containing film and a mask on the carbon-containing film; and

[0113] (b) etching the carbon-containing film by plasma generated from a process gas containing an oxygen-containing gas and a sulfur-containing gas,

[0114] In the above (b), pulses of bias power are supplied to a substrate support portion supporting the substrate, wherein the pulses are repeated periodically.

[0115] The frequency of the pulse cycle is specified to be 5 kHz or higher.

[0116] [E2]

[0117] The etching method according to [E1], wherein

[0118] The aforementioned (b) includes a first period and a second period following the first period.

[0119] During the first period, the pulse of the first level is supplied.

[0120] During the second period, bias power is not supplied to the substrate support portion, or bias power of a second level lower than the first level is supplied to the substrate support portion.

[0121] [E3]

[0122] The etching method according to [E2], wherein

[0123] The frequency is the first frequency,

[0124] The first period and the second period are repeated alternately and periodically.

[0125] A second frequency defining a cycle between the first period and the second period is greater than or equal to 100 Hz and less than or equal to 1 kHz.

[0126] [E4]

[0127] The etching method according to any one of [E1] to [E3], wherein

[0128] The duty cycle of the pulse is less than 50%.

[0129] [E5]

[0130] The etching method according to any one of [E1] to [E4], wherein

[0131] In the above (b), a continuous wave of high frequency power is supplied to generate the plasma.

[0132] [E6]

[0133] The etching method according to any one of [E1] to [E5], wherein

[0134] The carbon-containing film has a thickness of 2000 nm or more.

[0135] [E7]

[0136] The etching method according to any one of [E1] to [E6], wherein

[0137] The recessed portion formed in the carbon-containing film by the etching in (b) has an aspect ratio of 20 or greater.

[0138] [E8]

[0139] The etching method according to any one of [E1] to [E7], wherein

[0140] The mask includes a silicon-containing film.

[0141] [E9]

[0142] The etching method according to any one of [E1] to [E8], wherein

[0143] The process gas further includes an inert gas.

[0144] [E10]

[0145] The etching method according to any one of [E1] to [E9], wherein

[0146] The level of the pulse is greater than or equal to 2000 W and less than or equal to 5000 W.

[0147] [E11]

[0148] A plasma processing device comprising:

[0149] cavity;

[0150] a substrate support portion for supporting a substrate in the cavity, wherein the substrate comprises a carbon-containing film and a mask on the carbon-containing film;

[0151] a gas supply unit configured to supply a processing gas including an oxygen-containing gas and a sulfur-containing gas into the chamber;

[0152] a plasma generating unit configured to generate plasma from the processing gas in the chamber;

[0153] a power supply for supplying bias power to the substrate support portion; and

[0154] Control Department,

[0155] The control unit is configured to supply the bias power pulse to the substrate support unit and control the gas supply unit, the plasma generation unit, and the power supply to etch the carbon-containing film with the plasma, with the frequency of the pulse cycle being set to 5 kHz or higher.

[0156] As described above, various embodiments of the present invention have been described in this specification for illustrative purposes. It should be understood that various modifications may be made to the various embodiments of the present invention without departing from the scope and spirit of the present invention. Therefore, the various embodiments disclosed in this specification are not intended to be limiting, and the true scope and spirit are indicated by the scope of the attached technical solutions.

[0157] Explanation of symbols

[0158] 1-Plasma processing device, 2-Control unit, 10-Plasma processing chamber, 11-Substrate support unit, 12-Plasma generation unit, 20-Gas supply unit, 30-Power supply, FL-Carbon-containing film, FP-Frequency, MK-Mask, PL-Plasma, PS-Pulse, W-Substrate, WB-Bias power

Claims

1. An etching method, characterized in that: The process includes the following steps: (a) providing a substrate having a carbon-containing film and a mask on the carbon-containing film; and (b) etching the carbon-containing film by plasma generated from a process gas containing an oxygen-containing gas and a sulfur-containing gas, In the above (b), pulses of bias power are supplied to a substrate support portion supporting the substrate, wherein the pulses are repeated periodically. The frequency of the pulse cycle is specified to be 5 kHz or higher.

2. The etching method according to claim 1, wherein The aforementioned (b) includes a first period and a second period following the first period, During the first period, the pulse of the first level is supplied. During the second period, bias power is not supplied to the substrate support portion, or bias power of a second level lower than the first level is supplied to the substrate support portion.

3. The etching method according to claim 2, wherein: The frequency of the pulse is a first frequency, The first period and the second period are repeated alternately and periodically. A second frequency defining a cycle between the first period and the second period is greater than or equal to 100 Hz and less than or equal to 1 kHz.

4. The etching method according to any one of claims 1 to 3, wherein The duty cycle of the pulse is less than 50%.

5. The etching method according to any one of claims 1 to 3, wherein In the above (b), a continuous wave of high frequency power is supplied to generate the plasma.

6. The etching method according to any one of claims 1 to 3, wherein The carbon-containing film has a thickness of 2000 nm or more.

7. The etching method according to any one of claims 1 to 3, wherein The recessed portion formed in the carbon-containing film by the etching in (b) has an aspect ratio of 20 or greater.

8. The etching method according to any one of claims 1 to 3, wherein The mask includes a silicon-containing film.

9. The etching method according to any one of claims 1 to 3, wherein The process gas further includes an inert gas.

10. The etching method according to any one of claims 1 to 3, wherein: The level of the pulse is greater than or equal to 2000 W and less than or equal to 5000 W.

11. A plasma processing device, characterized in that: have: cavity; a substrate support portion for supporting a substrate in the cavity, wherein the substrate comprises a carbon-containing film and a mask on the carbon-containing film; a gas supply unit configured to supply a processing gas including an oxygen-containing gas and a sulfur-containing gas into the chamber; a plasma generating unit configured to generate plasma from the processing gas in the chamber; a power supply for supplying bias power to the substrate support portion; and Control Department, The control unit is configured to supply the bias power pulse to the substrate support unit and control the gas supply unit, the plasma generation unit, and the power supply to etch the carbon-containing film with the plasma, with the frequency of the pulse cycle being set to 5 kHz or higher.

Images