Etching method and plasma treatment device

Abstract

In one exemplary embodiment of the present invention, an etching method comprises the steps of: (a) providing a substrate on a substrate support present in a chamber, the substrate comprising a film and a mask on the film, the mask having an opening, and the film having a recess in communication with the opening; (b) preferentially forming a phosphorus-containing film on the sidewall defining the recess relative to the sidewall defining the opening; and (c) etching the recess after step (b).

Description

Etching method and plasma processing apparatus

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

[0002] Japanese Patent Application Laid-Open No. 2004-124493 discloses a plasma etching method in which a silicon-free organic film is etched with O using a resist film and a mask film as a mask. ２ (oxygen), COS (carbonyl sulfide), and Cl ２ Etching is performed using plasma of a mixed gas containing chlorine.

[0003] JP 2015-12178 A

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

[0005] In one exemplary embodiment, an etching method includes: (a) providing a substrate on a substrate support in a chamber, the substrate comprising a film and a mask on the film, the mask having an opening, the film having a recess communicating with the opening; (b) forming a phosphorus-containing film preferentially on sidewalls defining the recess relative to sidewalls defining the opening; and (c) after (b), etching the recess.

[0006] According to one exemplary embodiment, a technique is provided that can suppress shape abnormalities on the sidewalls of recesses formed by etching.

[0007] 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 an inductively coupled plasma processing apparatus. FIG. 3 is a flowchart of an etching method according to an exemplary embodiment. FIG. 4 is a partially enlarged view of an example substrate to which the method of FIG. 3 can be applied. FIG. 5 is a cross-sectional view illustrating a process of an etching method according to an exemplary embodiment. FIG. 6 is a cross-sectional view illustrating a process of an etching method according to an exemplary embodiment. FIG. 7 is a graph illustrating an example of the relationship between CD and depth of an opening and a recess. FIG. 8 is a graph illustrating an example of the relationship between CD and depth of an opening and a recess after etching. FIG. 9 is a graph illustrating an example of the relationship between CD and depth of an opening and a recess after etching. FIG. 10 is a graph illustrating an example of the relationship between recess depth and bowing CD.

[0008] 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.

[0009] 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.

[0010] The plasma generating unit 12 is configured to generate plasma from at least one processing gas supplied into the plasma processing space. The plasma generated in the plasma processing space may be capacitively coupled plasma (CCP), inductively coupled plasma (ICP), electron-cyclotron-resonance plasma (ECR plasma), helicon wave plasma (HWP), 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.

[0011] The control unit 2 processes computer-executable instructions that cause the plasma processing apparatus 1 to perform various processes described in this disclosure. The control unit 2 may be configured to control each element of the plasma processing apparatus 1 to perform various processes described herein. In one embodiment, part or all of the control unit 2 may be included in the plasma processing apparatus 1. The control unit 2 may include a processing unit 2a1, a storage unit 2a2, and a communication interface 2a3. The control unit 2 may be implemented by, for example, a computer 2a. The processing unit 2a1 may be configured to read a program from the storage unit 2a2 and execute the read program to perform various control operations. This program may be stored in the storage unit 2a2 in advance or may be acquired via a medium when needed. The acquired program is stored in the storage unit 2a2 and read from the storage unit 2a2 by the processing unit 2a1 for execution. The medium may be various storage media readable by the computer 2a or a communication line connected to the communication interface 2a3. The processing unit 2a1 may be a CPU (Central Processing Unit). The storage unit 2a2 may include a random access memory (RAM), a read-only memory (ROM), a hard disk drive (HDD), a solid state drive (SSD), or a combination thereof. The communication interface 2a3 may communicate with the plasma processing apparatus 1 via a communication line such as a local area network (LAN).

[0012] The following describes an example of the configuration of an inductively coupled plasma processing apparatus as an example of the plasma processing apparatus 1. Fig. 2 is a diagram for explaining an example of the configuration of an inductively coupled plasma processing apparatus.

[0013] The 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. The plasma processing apparatus 1 also 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, a sidewall 102 of the plasma processing chamber 10, and the substrate support 11. The plasma processing chamber 10 is grounded.

[0014] The substrate support 11 includes a main body 111 and a ring assembly 112. The main body 111 has a central region 111a for supporting a substrate W and an annular region 111b for supporting the ring assembly 112. A wafer is an example of a substrate W. The annular region 111b of the main body 111 surrounds the central region 111a of the main body 111 in a plan view. The substrate W is disposed on the central region 111a of the main body 111, and the ring assembly 112 is disposed on the annular region 111b of the main body 111 so as to surround the substrate W on the central region 111a of the main body 111. Therefore, the central region 111a is also called a substrate support surface for supporting the substrate W, and the annular region 111b is also called a ring support surface for supporting the ring assembly 112.

[0015] In one embodiment, the main body 111 includes a base 1110 and an electrostatic chuck 1111. The base 1110 includes a conductive member. The conductive member of the base 1110 can function as a bias 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 bias electrode. Note that the conductive member of the base 1110 and the at least one RF / DC electrode may function as multiple bias electrodes. Alternatively, the electrostatic electrode 1111b may function as a bias electrode. Therefore, the substrate support 11 includes at least one bias electrode.

[0016] The ring assembly 112 includes one or more annular members. In one embodiment, the one or more annular members include one or more edge rings and at least one cover ring. The edge rings are formed of a conductive or insulating material, and the cover rings are formed of an insulating material.

[0017] The substrate support 11 may also include a temperature adjustment module configured to adjust at least one of the electrostatic chuck 1111, the ring assembly 112, and the substrate to a target temperature. The temperature adjustment module may include a heater, a heat transfer medium, a flow passage 1110a, or a combination thereof. A heat transfer fluid such as brine or a gas flows through the flow passage 1110a. In one embodiment, the flow passage 1110a is formed in the base 1110, and one or more heaters are disposed in the ceramic member 1111a of the electrostatic chuck 1111. The substrate support 11 may also include a heat transfer gas supply configured to supply a heat transfer gas to a gap between the backside of the substrate W and the central region 111a.

[0018] The gas inlet is configured to introduce at least one process gas from the gas supply unit 20 into the plasma processing space 10s. In one embodiment, the gas inlet includes a center gas injector (CGI) 13. The center gas injector 13 is disposed above the substrate support 11 and attached to a central opening formed in the dielectric window 101. The center gas injector 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 process gas supplied to the gas supply port 13a passes through the gas flow path 13b and is introduced into the plasma processing space 10s from the gas inlet port 13c. Note that the gas inlet may include one or more side gas injectors (SGIs) attached to one or more openings formed in the sidewall 102 in addition to or instead of the center gas injector 13.

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

[0020] The power supply 30 includes an RF power supply 31 coupled to the plasma processing chamber 10 via at least one impedance matching circuit. The RF power supply 31 is configured to supply at least one RF signal (RF power) to at least one bias electrode and the antenna 14. This causes a plasma to be formed 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 generating unit 12. Furthermore, by supplying a bias RF signal to the at least one bias electrode, a bias potential is generated on the substrate W, thereby attracting ions in the formed plasma to the substrate W.

[0021] In one embodiment, the RF power supply 31 includes a first RF generating unit 31a and a second RF generating unit 31b. The first RF generating unit 31a is coupled to the antenna 14 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 the antenna 14.

[0022] The second RF generator 31b is coupled to at least one bias 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 bias electrode. In various embodiments, at least one of the source RF signal and the bias RF signal may be pulsed.

[0023] The power supply 30 may also include a DC power supply 32 coupled to the plasma processing chamber 10. The DC power supply 32 includes a bias DC generator 32a. In one embodiment, the bias DC generator 32a is connected to at least one bias electrode and configured to generate a bias DC signal. The generated bias DC signal is applied to the at least one bias electrode.

[0024] In various embodiments, the bias DC signal may be pulsed. In this case, a sequence of voltage pulses is applied to at least one bias electrode. The voltage pulses may have a rectangular, trapezoidal, triangular, or combination thereof. In one embodiment, a waveform generator for generating the sequence of voltage pulses from the 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 may have 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 cycle. Note that the bias DC generator 32a may be provided in addition to the RF power supply 31 or may be provided instead of the second RF generator 31b.

[0025] The antenna 14 includes one or more coils. In one embodiment, the antenna 14 may include an outer coil and an inner coil arranged coaxially. In this case, the RF power supply 31 may be connected to both the outer coil and the inner coil, or to either the outer coil or the inner coil. 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 the outer coil and the inner coil separately.

[0026] 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.

[0027] 3 is a flowchart of an etching method according to one exemplary embodiment. The etching method MT1 shown in FIG. 3 (hereinafter referred to as "method MT1") can be performed by the plasma processing apparatus 1 of the above embodiment. The method MT1 can be applied to the substrate W of FIG. 4.

[0028] FIG. 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 film FL and a mask MK on the film FL. The mask MK has an opening OP. The opening OP may be defined by a sidewall OPa. The mask MK may have a plurality of openings OP. The opening OP may have a hole pattern or a line pattern. The dimension (CD: Critical Dimension) of the opening OP may be 5 nm or more, 10 nm or more, or 20 nm or more. The dimension of the opening OP may be 200 nm or less, 180 nm or less, 150 nm or less, 100 nm or less, or 50 nm or less. The film FL has a recess RS communicating with the opening OP. The recess RS may be defined by a sidewall RSa. The recess RS may be in communication with the opening OP. The substrate W may include a base region UR below the film FL. The base region UR may be a silicon substrate.

[0029] The mask MK may include at least one of silicon and metal. The mask MK may include at least one of a silicon-containing film and a metal-containing film. An example of a silicon-containing film is silicon oxide (SiO ｘ ) film, silicon nitride (SiN ｘ Examples of metal-containing films include tungsten-containing films, such as tungsten carbide (WC) films, WSiN films, tungsten silicide (WSi) films, and tungsten films.

[0030] The film FL may contain a material different from the material contained in the mask MK. The film FL may contain at least one of carbon or silicon. When the mask MK contains silicon, the film FL may contain carbon. When the mask MK contains metal, the film FL may contain silicon. The film FL may contain at least one of a carbon-containing film or a silicon-containing film. Examples of carbon-containing films include a spin-on carbon (SOC) film and an amorphous carbon film. Examples of silicon-containing films include a silicon oxide film, a silicon nitride film, and a silicon oxynitride film.

[0031] Method MT1 will be described below with reference to FIGS. 3 to 6, taking as an example a case where method MT1 is applied to a substrate W using the plasma processing apparatus 1 of the above embodiment. Each of FIGS. 5 to 6 is a cross-sectional view showing one step of an etching method according to one exemplary embodiment. When the plasma processing apparatus 1 is used, method MT1 can be performed in the plasma processing apparatus 1 by controlling each part of the plasma processing apparatus 1 with a control unit 2. In method MT1, a substrate W on a substrate support 11 arranged in a plasma processing chamber 10 is processed, as shown in FIG. 2.

[0032] 3, the method MT1 includes steps ST1 to ST3. Steps ST1 to ST3 may be performed in order. The method MT1 may further include, after step ST3, repeating a cycle CY including steps ST2 and ST3. The cycle CY may include step ST4 before step ST2. The method MT1 may be performed in-situ. That is, the method MT1 may be performed within the same plasma processing chamber 10.

[0033] (Process ST1) In process ST1, the substrate W of FIG. 4 is provided on the substrate support 11 arranged in the plasma processing chamber 10. The substrate W may be placed on the substrate support 11 as shown in FIG. 2. A substrate W having a recess RS formed therein may be placed on the substrate support 11. Alternatively, a substrate W having no recess RS formed therein may be placed on the substrate support 11, and then the film FL may be etched through the opening OP to form the recess RS. The etching may be performed in the same manner as in process ST3.

[0034] (Process ST2) In process ST2, as shown in FIG. 5 , the phosphorus-containing film PR2 is preferentially formed on the sidewall RSa that defines the recess RS relative to the sidewall OPa that defines the opening OP. The thickness of the phosphorus-containing film PR2 formed on the sidewall RSa may be greater than the thickness of the phosphorus-containing film PR1 formed on the sidewall OPa. The phosphorus-containing film PR2 may be formed on the bottom surface of the recess RS. The phosphorus-containing film PR1 may be formed on the upper surface of the mask MK. Process ST2 may be performed in process ST1. In this case, in process ST1, the substrate W of FIG. 5 is provided on the substrate support 11. The substrate W of FIG. 5 includes a film FL, a mask MK, a phosphorus-containing film PR1, and a phosphorus-containing film PR2.

[0035] At the end of step ST2, the minimum dimension D2 of the recess RS may be smaller than the minimum dimension D1 of the opening OP. The difference in dimension is due to the difference in thickness between the phosphorus-containing film PR2 and the phosphorus-containing film PR1.

[0036] The phosphorus-containing films PR1 and PR2 may be formed by plasma generated from a process gas containing a phosphorus-containing gas. The phosphorus-containing films PR1 and PR2 may be formed by plasma CVD. The phosphorus-containing gas may contain a halogen. The process gas may further contain a noble gas. An example of the noble gas is argon.

[0037] A phosphorus-containing gas is a gas containing phosphorus-containing molecules. ４ O １０ ), tetraphosphorus octoxide (P ４ O ８ ), tetraphosphorus hexaoxide (P ４ O ６ ) and other oxides. ２ O ５ Phosphorus-containing molecules are sometimes called phosphorus trifluoride (PF ３ ), phosphorus pentafluoride (PF ５ ), phosphorus trichloride (PCl ３ ), phosphorus pentachloride (PCl ５ ), phosphorus tribromide (PBr ３ ), phosphorus pentabromide (PBr ５ ), phosphorus iodide (PI ３The phosphorus-containing molecule may be a halide (phosphorus halide) such as phosphorus fluoride (POF). That is, the phosphorus-containing molecule may contain fluorine as a halogen element, such as phosphorus fluoride. Alternatively, the phosphorus-containing molecule may contain a halogen element other than fluorine as a halogen element. The phosphorus-containing molecule may be phosphoryl fluoride (POF ３ ), phosphoryl chloride (POCl ３ ), phosphoryl bromide (POBr ３ The phosphorus-containing molecule may be a phosphoryl halide such as a phosphine (PH ３ ), calcium phosphide (Ca ３ P ２ etc.), phosphoric acid (H ３ P.O. ４ ), sodium phosphate (Na ３ P.O. ４ ), hexafluorophosphate (HPF ６ ) and the like. Phosphorus-containing molecules include fluorophosphines (H ｇ PF ｈ ) where the sum of g and h is 3 or 5. Fluorophosphines include HPF ２ , H ２ PF ３ is exemplified.

[0038] The process gas may contain one or more of the above-mentioned phosphorus-containing molecules as the at least one phosphorus-containing molecule. For example, the process gas may contain PF5 as the at least one phosphorus-containing molecule. ３ , PCl ３ , P.F. ５ , PCl ５ , POCl ３ , P.H. ３ , PBr ３ and PBr ５ When the phosphorus-containing molecules contained in the processing gas are in a liquid or solid form, the phosphorus-containing molecules may be vaporized by heating or the like and supplied into the plasma processing chamber 10.

[0039] The pressure in step ST2 may be five times or less the pressure in step ST3. The pressure in step ST2 may be less than 26.7 Pa (200 mTorr) or may be 20 Pa (150 mTorr) or less. The pressure in step ST2 may be 6.7 Pa (50 mTorr) or more.

[0040] In step ST2, the temperature of the substrate support part 11 may be 50° C. or less.

[0041] In step ST2, no electric bias may be supplied to the substrate support part 11, or an electric bias smaller than the electric bias supplied to the substrate support part 11 in step ST3 may be supplied to the substrate support part 11.

[0042] (Step ST3) In step ST3, as shown in FIG. 6, the recess RS is etched. The recess RS can be etched by plasma generated from a processing gas. If the film FL contains carbon, the processing gas may contain an oxygen-containing gas. If the film FL contains silicon, the processing gas may contain a halogen-containing gas.

[0043] The pressure in step ST3 may be lower than the pressure in step ST2, i.e., less than 6.7 Pa (50 mTorr).

[0044] In step ST3, the temperature of the substrate support part 11 may be equal to or lower than 50° C. The temperature of the substrate support part 11 in step ST3 may be the same as the temperature of the substrate support part 11 in step ST2.

[0045] In step ST3, an electric bias may be supplied to the substrate support 11. Ions in the plasma are attracted to the substrate support 11 by the electric bias.

[0046] In step ST3, a deposit DP may be deposited on the sidewall OPa of the opening OP. The deposit DP may include a by-product generated by etching the film FL. The deposit DP may include silicon.

[0047] After step ST3, cycle CY may be repeated. This allows the recess RS to be deepened. Cycle CY may include step ST4, step ST2, and step ST3. Cycle CY may be repeated until an etching stop condition is met. The etching stop condition may be met when the number of times cycle CY is repeated reaches a threshold value. The aspect ratio of the recess RS after etching is stopped (the ratio of the depth of the recess RS to the dimension of the recess RS) may be 10 or more, 30 or more, 50 or more, or 100 or more.

[0048] (Step ST4) In step ST4, the deposit DP is removed. This allows the recess RS to be etched in a subsequent step while preventing the recess RS from being blocked. The deposit DP may be removed by a process gas without generating plasma. The process gas may include hydrogen fluoride (HF) gas.

[0049] According to the method MT1, the phosphorus-containing film PR2 is preferentially formed on the sidewall RSa of the recess RS, thereby effectively suppressing etching of the sidewall RSa of the recess RS. This makes it possible to suppress shape abnormalities (bowing) of the sidewall RSa of the recess RS formed by etching. The reason why the phosphorus-containing film PR2 is preferentially formed on the sidewall RSa of the recess RS is thought to be, but is not limited to, the promotion of dissociation of phosphorus-containing molecules in the plasma in step ST2. Dissociation of phosphorus-containing molecules can be promoted by reducing the pressure in step ST2, increasing the source RF power for generating plasma in step ST2, reducing the flow rate of phosphorus-containing molecules, or the like.

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

[0051] (First Experiment) First, a substrate including a carbon-containing film and a mask on the carbon-containing film was placed on a substrate support in a plasma processing chamber. The mask was a silicon oxynitride film with multiple openings. Each opening had a hole pattern. Then, the carbon-containing film was etched through the openings in the mask to form recesses. The carbon-containing film was etched by plasma generated from a process gas including an oxygen-containing gas.

[0052] Next, a phosphorus-containing film was formed on the sidewall of the recess using plasma generated from a process gas containing a phosphorus-containing gas and a noble gas. The pressure in the plasma processing chamber was 13.3 Pa (100 mTorr). The temperature of the substrate support was 0°C.

[0053] The recesses were then etched to deepen them, using plasma generated from a process gas containing an oxygen-containing gas.

[0054] (Second Experiment) An experiment was carried out in the same manner as the first experiment, except that the pressure in the plasma processing chamber when forming the phosphorus-containing film was 26.7 Pa (200 mTorr).

[0055] (Third Experiment) An experiment was carried out in the same manner as the first experiment, except that the phosphorus-containing film was not formed.

[0056] (First Evaluation) In the first and second experiments, after forming the phosphorus-containing film and before etching the recesses, the cross section of the substrate was observed to measure the CD and depth of the openings and recesses. The CD and depth were measured in the same manner for the third experiment. The results are shown in FIG. 7. FIG. 7 is a graph showing an example of the relationship between CD and depth. The vertical axis represents depth (μm). The position where the depth is 0 corresponds to the boundary between the mask and the carbon-containing film (the upper end of the recess). The region where the depth is positive corresponds to the opening in the mask. The region where the depth is negative corresponds to the recess in the carbon-containing film. The horizontal axis represents the CD (nm) of the opening or recess. In FIG. 7, line E11 represents the results of the first experiment. line E12 represents the results of the second experiment. line E13 represents the results of the third experiment.

[0057] In the first experiment, the minimum dimension of the recess was smaller than the minimum dimension of the opening, indicating that the phosphorus-containing film was preferentially formed on the sidewalls of the recess relative to the sidewalls of the opening. In the second experiment, the minimum dimension of the recess was larger than the minimum dimension of the opening, indicating that the phosphorus-containing film was preferentially formed on the sidewalls of the opening relative to the sidewalls of the recess.

[0058] (Second Evaluation) In the first and second experiments, after forming the phosphorus-containing film and before etching the recesses, the cross section of the substrate was observed to obtain phosphorus element mapping images. The images were obtained using EDX (Energy Dispersive X-ray spectroscopy) of a TEM (Transmission Electron Microscopy) device. As a result, in the first experiment, the concentration of phosphorus element in the recesses was higher than that in the openings. This indicates that the phosphorus-containing film is preferentially formed on the sidewalls of the recesses relative to the sidewalls of the openings. On the other hand, in the second experiment, the concentration of phosphorus element in the openings was higher than that in the recesses. This indicates that the phosphorus-containing film is preferentially formed on the sidewalls of the openings relative to the sidewalls of the recesses.

[0059] (Third Evaluation) In the first to third experiments, the cross section of the substrate obtained after etching the recesses was observed, and the CD and depth of the openings and recesses were measured in the same manner as in the first evaluation. The results are shown in FIG. 8. FIG. 8 is a graph showing an example of the relationship between the CD and depth of the openings and recesses after etching. The vertical and horizontal axes are the same as those in FIG. 7, respectively. In FIG. 8, line E1 shows the results of the first experiment. line E2 shows the results of the second experiment. line E3 shows the results of the third experiment.

[0060] In the first experiment, the bowing CD (maximum CD of the recess) was 75.4 nm. In the second experiment, the bowing CD was 85.3 nm. Therefore, it can be seen that bowing is suppressed more in the first experiment than in the second experiment.

[0061] (Fourth Experiment) After etching the recessed portion of the substrate obtained in the first experiment, a cycle including the following steps 1 to 3 was repeated three times. Steps 1 to 3 were performed in order.

[0062] In step 1, deposits deposited on the sidewalls of the openings were removed using a process gas containing hydrogen fluoride (HF) gas.

[0063] In step 2, a phosphorus-containing film was formed on the sidewall of the recess, as in the first experiment.

[0064] In step 3, the recess was etched in the same manner as in the first experiment.

[0065] (Fifth Experiment) An experiment similar to the fourth experiment was carried out, except that the pressure in the plasma processing chamber when forming the phosphorus-containing film was 26.7 Pa (200 mTorr).

[0066] (Fourth Evaluation) The cross sections of the substrates obtained in the fourth and fifth experiments were observed, and the CDs and depths of the openings and recesses were measured in the same manner as in the first evaluation. The results are shown in Figure 9. Figure 9 is a graph showing an example of the relationship between the CDs and depths of the openings and recesses after etching. The vertical and horizontal axes are the same as those in Figure 7, respectively. In Figure 9, line E4 shows the results of the fourth experiment. Line E5 shows the results of the fifth experiment.

[0067] In the fourth experiment, the bowing CD was 94.6 nm. In the fifth experiment, the bowing CD was 111.8 nm. Therefore, it can be seen that bowing is more suppressed in the fourth experiment than in the fifth experiment.

[0068] (Relationship between Depth and Bowing CD) FIG. 10 is a graph showing an example of the relationship between recess depth and bowing CD. The vertical axis represents bowing CD (nm). The horizontal axis represents recess depth (nm). The position where the depth is 0 corresponds to the boundary between the mask and the film (the upper end of the recess). The deeper the recess, the larger the depth value. In FIG. 10, line E6 shows the results of an experiment (phosphorus-containing film formation) conducted in the same manner as Experiments 1 and 4. Line E7 shows the results of an experiment (phosphorus-containing film formation) conducted in the same manner as Experiments 2 and 5. Line E8 shows the results of an experiment conducted in the same manner as Experiment 1, except that a silicon-containing film was formed instead of a phosphorus-containing film. Line E9 shows the results of an experiment (no protective film formation) conducted in the same manner as Experiment 3.

[0069] 10, it can be seen that the bowing CD is smaller for line E6 than for lines E7 to E9. Furthermore, it can be seen that the bowing CD does not increase for line E6 even if the recess is deeper.

[0070] 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.

[0071] Various exemplary embodiments included in the present disclosure will now be described below.

[0072] [E1] A method of etching, comprising: (a) providing a substrate on a substrate support in a chamber, the substrate comprising a film and a mask on the film, the mask having an opening, the film having a recess communicating with the opening; (b) forming a phosphorus-containing film preferentially on sidewalls defining the recess relative to sidewalls defining the opening; and (c) after (b), etching the recess.

[0073] [E2] The etching method according to [E1], wherein at the end of (b), the minimum dimension of the recess is smaller than the minimum dimension of the opening.

[0074] [E3] The etching method according to [E1] or [E2], wherein the pressure in (c) is lower than the pressure in (b).

[0075] [E4] The etching method according to any one of [E1] to [E3], wherein the pressure in (b) is 5 times or less the pressure in (c).

[0076] [E5] The etching method according to any one of [E1] to [E4], wherein the pressure in (b) is less than 26.7 Pa.

[0077] [E6] The etching method according to any one of [E1] to [E5], wherein in (b), the phosphorus-containing film is formed by plasma generated from a process gas containing a phosphorus-containing gas.

[0078] [E7] The etching method according to [E6], wherein the phosphorus-containing gas contains a halogen.

[0079] [E8] The etching method according to any one of [E1] to [E7], wherein (b) and (c) are carried out in the same chamber.

[0080] [E9] The etching method according to any one of [E1] to [E8], wherein the film contains at least one of carbon and silicon.

[0081] [E10] The etching method according to any one of [E1] to [E9], wherein the mask includes at least one of silicon and metal.

[0082] [E11] The etching method according to any one of [E1] to [E10], wherein in (b), the temperature of the substrate support part is 50° C. or less.

[0083] [E12] The etching method according to any one of [E1] to [E11], wherein in (b), no electric bias is supplied to the substrate support part, or an electric bias smaller than the electric bias supplied to the substrate support part in (c) is supplied to the substrate support part.

[0084] [E13] The etching method according to any one of [E1] to [E12], further comprising the step of: (d) repeating a cycle including (b) and (c) after (c).

[0085] [E14] The etching method according to [E13], wherein the cycle further includes, before (b), a step of removing deposits on the sidewalls of the opening.

[0086] [E15] An etching method comprising: (a) providing a substrate on a substrate support in a chamber, the substrate comprising a film and a mask on the film, the mask having an opening, the film having a recess communicating with the opening, the substrate further comprising a phosphorus-containing film preferentially formed on a sidewall defining the recess relative to a sidewall defining the opening; and (b) etching the recess.

[0087] [E16] A plasma processing apparatus comprising: a chamber; a substrate support for supporting a substrate in the chamber, the substrate comprising a film and a mask on the film, the mask having an opening, and the film having a recess communicating with the opening; a gas supply unit configured to supply a process gas into the chamber; a plasma generation unit configured to generate plasma from the process gas in the chamber; and a control unit, wherein the control unit is configured to control the gas supply unit and the plasma generation unit to form a phosphorus-containing film preferentially on a sidewall defining the recess relative to a sidewall defining the opening, and then etch the recess.

[0088] [E17] A plasma processing apparatus comprising: a chamber; a substrate support for supporting a substrate in the chamber, the substrate comprising a film and a mask on the film, the mask having an opening, the film having a recess communicating with the opening, the substrate further comprising a phosphorus-containing film preferentially formed on a sidewall defining the recess relative to a sidewall defining the opening; a gas supply unit configured to supply a process gas into the chamber; a plasma generation unit configured to generate plasma from the process gas in the chamber; and a controller configured to control the gas supply unit and the plasma generation unit to etch the recess.

[0089] 1...plasma processing apparatus, 2...controller, 10...plasma processing chamber, 11...substrate support, 12...plasma generating unit, 20...gas supply unit, FL...film, MK...mask, OP...opening, OPa...sidewall, PR2...phosphorus-containing film, RS...recess, RSa...sidewall, W...substrate.

Claims

1. A method of etching, comprising: (a) providing a substrate on a substrate support in a chamber, the substrate comprising a film and a mask on the film, the mask having an opening, the film having a recess communicating with the opening; (b) forming a phosphorus-containing film preferentially on sidewalls defining the recess relative to sidewalls defining the opening; and (c) after (b), etching the recess.

2. The etching method according to claim 1, wherein at the end of step (b), the minimum dimension of the recess is smaller than the minimum dimension of the opening.

3. The etching method according to claim 1 or 2, wherein the pressure in (c) is lower than the pressure in (b).

4. The etching method according to claim 1 or 2, wherein the pressure in (b) is five times or less the pressure in (c).

5. The etching method according to claim 1 or 2, wherein the pressure in (b) is less than 26.7 Pa.

6. The etching method according to claim 1 or 2, wherein in step (b), the phosphorus-containing film is formed by plasma generated from a processing gas containing a phosphorus-containing gas.

7. The etching method of claim 6, wherein said phosphorus-containing gas comprises a halogen.

8. The etching method according to claim 1 or 2, wherein steps (b) and (c) are carried out in the same chamber.

9. The etching method according to claim 1 or 2, wherein the film contains at least one of carbon and silicon.

10. The etching method according to claim 1 or 2, wherein the mask comprises at least one of silicon or metal.

11. The etching method according to claim 1 or 2, wherein in step (b), the temperature of the substrate support is 50° C. or less.

12. An etching method according to claim 1 or 2, wherein in (b), no electrical bias is supplied to the substrate support, or an electrical bias smaller than the electrical bias supplied to the substrate support in (c) is supplied to the substrate support.

13. The etching method according to claim 1 or 2, further comprising the step of: (d) after (c), repeating a cycle including (b) and (c).

14. The etching method of claim 13, wherein the cycle further comprises, before (b), removing deposits on the sidewalls of the opening.

15. A method of etching, comprising: (a) providing a substrate on a substrate support in a chamber, the substrate comprising a film and a mask on the film, the mask having an opening, the film having a recess communicating with the opening, the substrate further comprising a phosphorus-containing film preferentially formed on sidewalls defining the recess relative to sidewalls defining the opening; and (b) etching the recess.

16. A plasma processing apparatus comprising: a chamber; a substrate support for supporting a substrate in the chamber, the substrate comprising a film and a mask on the film, the mask having an opening, and the film having a recess communicating with the opening; a gas supply configured to supply a process gas into the chamber; a plasma generation unit configured to generate plasma from the process gas in the chamber; and a control unit, wherein the control unit is configured to control the gas supply unit and the plasma generation unit to form a phosphorus-containing film preferentially on a sidewall defining the recess relative to a sidewall defining the opening, and then etch the recess.

17. A plasma processing apparatus comprising: a chamber; a substrate support for supporting a substrate in the chamber, the substrate comprising a film and a mask on the film, the mask having an opening, the film having a recess communicating with the opening, the substrate further comprising a phosphorus-containing film preferentially formed on a sidewall defining the recess relative to a sidewall defining the opening; a gas supply unit configured to supply a process gas into the chamber; a plasma generation unit configured to generate plasma from the process gas in the chamber; and a controller, wherein the controller is configured to control the gas supply unit and the plasma generation unit to etch the recess.

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