Etching method and plasma processing apparatus

Abstract

To provide an etching method which enables formation of a concave portion having good geometry, and a plasma processing device.SOLUTION: An etching method comprises the steps of: (a) preparing a substrate, provided that the substrate has a silicon-containing film and a mask arranged over the silicon-containing film, the silicon-containing film includes first and second regions, and a boundary line between the first and second regions has an inclined portion extending in a direction inclined with respect to a plane direction in a cross section extending in a direction orthogonal to the plane direction of the substrate; (b) etching the first region by first plasma generated from a first process gas to form a concave portion after the step (a); (c) supplying the substrate with second plasma generated from a second process gas containing tungsten after the step (b); and (d)etching the concave portion by third plasma generated from a third process gas. In the etching method, the concave portion crosses the inclined portion in the cross section after the step (d).SELECTED DRAWING: Figure 3

Description

[Technical field]

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

[0002] In the manufacture of electronic devices, etching of silicon-containing films using plasma is performed. Silicon-containing films are made of silicon-containing materials such as silicon oxide and silicon nitride. For example, in the manufacture of a NAND-type flash memory having a three-dimensional structure, etching of a multilayer film containing a plurality of silicon oxide films and a plurality of silicon nitride films alternately stacked is performed as the silicon-containing film. In the etching of the silicon-containing film, a mask containing carbon such as amorphous carbon is used as a mask. An opening is formed in the mask.

[0003] Etching of a multilayer film is described in Patent Document 1. In the etching described in Patent Document 1, a plasma of a hydrofluorocarbon gas is generated, and the multilayer film is etched by active species of fluorine from the plasma. During etching of the multilayer film, a deposit containing carbon is formed on the mask, and the mask is protected by the deposit. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] US Patent Application Publication No. 2013 / 0059450 Summary of the Invention [Problem to be solved by the invention]

[0005] The present disclosure provides an etching method and a plasma processing apparatus capable of forming a recess having a good shape. [Means for solving the problem]

[0006] In one exemplary embodiment, the etching method includes: (a) preparing a substrate, the substrate having a silicon-containing film and a mask on the silicon-containing film, the silicon-containing film including a first region including a first material including silicon and a second region including a second material different from the first material, the boundary between the first region and the second region having an inclined portion extending in a direction inclined with respect to a surface direction of the substrate in a cross section extending in a direction perpendicular to a surface direction of the substrate; (b) after (a), etching the first region with a first plasma generated from a first process gas to form a recess; (c) after (b), supplying to the substrate a second plasma generated from a second process gas including tungsten; and (d) after (c), etching the recess with a third plasma generated from a third process gas, the recess crossing the inclined portion in the cross section ... Effect of the Invention

[0007] According to one exemplary embodiment, an etching method and a plasma processing apparatus are provided that are capable of forming a recess having a good shape. [Brief description of the drawings]

[0008] [Figure 1] FIG. 1 is a schematic diagram of a plasma processing apparatus according to an exemplary embodiment. [Diagram 2] FIG. 2 is a schematic diagram of a plasma processing apparatus according to an exemplary embodiment. [Diagram 3] FIG. 3 is a flow chart of an etching method according to one exemplary embodiment. [Figure 4] FIG. 4 is a cross-sectional view of an example substrate to which the method of FIG. 3 may be applied. [Diagram 5] FIG. 5 is a cross-sectional view illustrating a step of an etching method according to an example embodiment. [Figure 6] FIG. 6 is a cross-sectional view illustrating a step of an etching method according to an example embodiment. [Figure 7] FIG. 7 is a cross-sectional view illustrating a step of an etching method according to one exemplary embodiment. [Figure 8] FIG. 8 is a cross-sectional view illustrating a step of an etching method according to an example embodiment. [Figure 9] FIG. 9 is a cross-sectional view showing an example of the mechanism by which the sidewall of a recess formed by etching is curved. [Figure 10] FIG. 10 is a cross-sectional view showing an example of a mechanism by which the sidewall of a recess formed by etching becomes less likely to bend. [Figure 11] FIG. 11 is a cross-sectional view showing a schematic example of recesses formed by etching in the first to fifth experiments. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] Various exemplary embodiments are described below.

[0010] In one exemplary embodiment, the etching method includes: (a) preparing a substrate, the substrate having a silicon-containing film and a mask on the silicon-containing film, the silicon-containing film including a first region including a first material including silicon and a second region including a second material different from the first material, the boundary between the first region and the second region having an inclined portion extending in a direction inclined with respect to a surface direction of the substrate in a cross section extending in a direction perpendicular to a surface direction of the substrate; (b) after (a), etching the first region with a first plasma generated from a first process gas to form a recess; (c) after (b), supplying to the substrate a second plasma generated from a second process gas including tungsten; and (d) after (c), etching the recess with a third plasma generated from a third process gas, the recess crossing the inclined portion in the cross section ...

[0011] According to the above etching method, the sidewall of the recess is less likely to bend near the inclined portion of the boundary between the first region and the second region. Therefore, a recess having a good shape can be formed. The mechanism is assumed as follows, but is not limited to this. When forming a recess by etching, near the inclined portion of the boundary between the first region and the second region, the first region is exposed on one sidewall of the recess, and the second region is exposed on the other sidewall of the recess. If (c) is not performed, positive charges are unevenly distributed on one of the two sidewalls of the recess (for example, the sidewall where the first region is exposed) due to positive ions in the plasma for etching. As a result, a positively charged region is formed on the sidewall. As a result, the positive ions are repelled by the charged region and etch the opposite sidewall. This causes the sidewall of the recess to bend. On the other hand, if (c) is performed, a conductive tungsten-containing layer is formed on both sidewalls, so that the positive charges on the charged sidewalls can be removed. Therefore, the straightness of the positive ions is improved, so that the sidewall of the recess is less likely to bend.

[0012] In the step (c), a tungsten-containing layer may be formed on the sidewall of the recess. In this case, the tungsten-containing layer can remove electric charges on the sidewall of the recess.

[0013] In the step (b), the first plasma may be generated at a first pressure, and in the step (c), the second plasma may be generated at a second pressure higher than the first pressure, in which case a tungsten-containing layer is more likely to be formed on the sidewall of the recess in the step (c).

[0014] In the step (b), a first high frequency power may be supplied to generate the first plasma, and in the step (c), a second high frequency power smaller than the first high frequency power may be supplied to generate the second plasma, in which case a tungsten-containing layer is more likely to be formed on the sidewall of the recess in the step (c).

[0015] The etching method may further include a step (e) between the steps (b) and (c), of removing the deposits deposited in the openings of the mask by the step (b). In this case, reduction in the size of the openings of the mask can be suppressed.

[0016] The etching method may further include a step (f) between the steps (b) and (c) of supplying a fourth plasma generated from a fourth process gas containing an oxygen-containing gas to the substrate. In this case, organic matter adhering to the substrate can be removed.

[0017] After step (d), steps (c) and (d) may be repeated, in which case the side walls of the recessed portion become less likely to bend.

[0018] The first material may include silicon oxide.

[0019] The second material may include silicon nitride.

[0020] The second region may include a first layer including the first material and a second layer including the second material, and the first layer and the second layer may be stacked alternately.

[0021] The second process gas may include a tungsten-containing gas.

[0022] The second process gas may include tungsten hexafluoride gas.

[0023] The first process gas is x H y F z (x and z are integers of 1 or more, and y is an integer of 0 or more) may contain gas.

[0024] The third process gas is x H y F z (x and z are integers of 1 or more, and y is an integer of 0 or more) may contain gas.

[0025] In one exemplary embodiment, the etching method includes the steps of: (a) preparing a substrate, the substrate having a silicon-containing film and a mask on the silicon-containing film, the silicon-containing film including a first region including a silicon oxide film and a second region including a silicon oxide film and a silicon nitride film alternately stacked, and in a cross section extending in a direction perpendicular to a surface direction of the substrate, a boundary between the first region and the second region has an inclined portion extending in a direction inclined with respect to the surface direction; and (b) after the step (a), x H y F z (c) after (b), forming a tungsten-containing layer on a side wall of the recess by supplying to the substrate a second plasma generated from a second process gas containing tungsten hexafluoride gas (wherein x and z are integers equal to or greater than 1, and y is an integer equal to or greater than 0). x H y F z (x and z are integers equal to or greater than 1, and y is an integer equal to or greater than 0) and a third process gas comprising an oxygen-containing gas, and after (d), the recess intersects the inclined portion in the cross-section.

[0026] In one exemplary embodiment, a plasma processing apparatus includes a chamber and a substrate support for supporting a substrate in the chamber, the substrate having a silicon-containing film and a mask on the silicon-containing film, the silicon-containing film including a first region including a first material including silicon and a second region including a second material different from the first material, and a boundary between the first region and the second region has an inclined portion extending in a direction inclined with respect to a surface direction of the substrate in a cross section extending in a direction perpendicular to a surface direction of the substrate; and a gas supply unit configured to supply a first process gas, a second process gas, and a third process gas into the chamber, the second process gas being tungsten. a gas supply unit including a gas separator; a plasma generation unit configured to generate a first plasma, a second plasma, and a third plasma from the first process gas, the second process gas, and the third process gas in the chamber, respectively; and a control unit, wherein the control unit is configured to control the gas supply unit and the plasma generation unit to etch the first region with the first plasma to form a recess, supply the second plasma to the substrate after forming the recess, and etch the recess with the third plasma after supplying the second plasma to the substrate, and after etching the recess with the third plasma, the recess crosses the inclined portion in the cross section.

[0027] Various exemplary embodiments will now be described in detail with reference to the drawings, in which the same or corresponding parts are designated by the same reference numerals.

[0028] FIG. 1 is a diagram for explaining a configuration example of a plasma processing system. In one embodiment, the plasma processing system includes a plasma processing device 1 and a control unit 2. The plasma processing system is an example of a substrate processing system, and the plasma processing device 1 is an example of a substrate processing device. The plasma processing device 1 includes a plasma processing chamber 10, a substrate support unit 11, and a plasma generation unit 12. The plasma processing chamber 10 has a plasma processing space. The plasma processing chamber 10 also has at least one gas supply port for supplying at least one processing gas to the plasma processing space, and at least one gas exhaust port for exhausting gas from the plasma processing space. The gas supply port is connected to a gas supply unit 20 described later, and the gas exhaust port is connected to an exhaust system 40 described later. The substrate support unit 11 is disposed in the plasma processing space, and has a substrate support surface for supporting a substrate.

[0029] The plasma generating unit 12 is configured to generate plasma from at least one processing gas supplied into the plasma processing space. The plasma formed in the plasma processing space may be a capacitively coupled plasma (CCP), an inductively coupled plasma (ICP), an electron-cyclotron-resonance plasma (ECR plasma), a helicon wave plasma (HWP), or a surface wave plasma (SWP), etc. Also, various types of plasma generating units may be used, including an alternating current (AC) plasma generating unit and a direct current (DC) plasma generating unit. In one embodiment, the AC signal (AC power) used in the AC plasma generating unit has a frequency in the range of 100 kHz to 10 GHz. Thus, the AC signal includes a radio frequency (RF) signal and a microwave signal. In one embodiment, the RF signal has a frequency in the range of 100 kHz to 150 MHz.

[0030] The control unit 2 processes computer-executable instructions that cause the plasma processing apparatus 1 to execute various steps described in the present disclosure. The control unit 2 may be configured to control each element of the plasma processing apparatus 1 to execute various steps described herein. In one embodiment, a part or all of the control unit 2 may be included in the plasma processing apparatus 1. The control unit 2 may include a processing unit 2a1, a storage unit 2a2, and a communication interface 2a3. The control unit 2 is realized, for example, by a computer 2a. The processing unit 2a1 may be configured to perform various control operations by reading a program from the storage unit 2a2 and executing the read program. This program may be stored in the storage unit 2a2 in advance, or may be acquired via a medium when necessary. The acquired program is stored in the storage unit 2a2 and is read from the storage unit 2a2 by the processing unit 2a1 and executed. The medium may be various storage media readable by the computer 2a, or may be a communication line connected to the communication interface 2a3. The processing unit 2a1 may be a CPU (Central Processing Unit). The storage unit 2a2 may include a random access memory (RAM), a read only memory (ROM), a hard disk drive (HDD), a solid state drive (SSD), or a combination thereof. The communication interface 2a3 may communicate with the plasma processing apparatus 1 via a communication line such as a local area network (LAN).

[0031] The following describes a configuration example of a capacitively coupled plasma processing apparatus as an example of the plasma processing apparatus 1. Fig. 2 is a diagram for explaining the configuration example of a capacitively coupled plasma processing apparatus.

[0032] The capacitively coupled plasma processing apparatus 1 includes a plasma processing chamber 10, a gas supply 20, a power supply 30, and an exhaust system 40. The plasma processing apparatus 1 also includes a substrate support 11 and a gas inlet. The gas inlet is configured to introduce at least one processing gas into the plasma processing chamber 10. The gas inlet includes a showerhead 13. The substrate support 11 is disposed in the plasma processing chamber 10. The showerhead 13 is disposed above the substrate support 11. In one embodiment, the showerhead 13 forms at least a part of a ceiling of the plasma processing chamber 10. The plasma processing chamber 10 has a plasma processing space 10s defined by the showerhead 13, a sidewall 10a of the plasma processing chamber 10, and the substrate support 11. The plasma processing chamber 10 is grounded. The showerhead 13 and the substrate support 11 are electrically insulated from a housing of the plasma processing chamber 10.

[0033] The substrate support 11 includes a main body 111 and a ring assembly 112. The main body 111 has a central region 111a for supporting the substrate W and an annular region 111b for supporting the ring assembly 112. A wafer is an example of the substrate W. The annular region 111b of the main body 111 surrounds the central region 111a of the main body 111 in a plan view. The substrate W is disposed on the central region 111a of the main body 111, and the ring assembly 112 is disposed on the annular region 111b of the main body 111 so as to surround the substrate W on the central region 111a of the main body 111. Therefore, the central region 111a is also called a substrate support surface for supporting the substrate W, and the annular region 111b is also called a ring support surface for supporting the ring assembly 112.

[0034] In one embodiment, the main body 111 includes a base 1110 and an electrostatic chuck 1111. The base 1110 includes a conductive member. The conductive member of the base 1110 may function as a lower electrode. The electrostatic chuck 1111 is disposed on the base 1110. The electrostatic chuck 1111 includes a ceramic member 1111a and an electrostatic electrode 1111b disposed within the ceramic member 1111a. The ceramic member 1111a has a central region 111a. In one embodiment, the ceramic member 1111a also has an annular region 111b. Note that other members surrounding the electrostatic chuck 1111, such as an annular electrostatic chuck or an annular insulating member, may have the annular region 111b. In this case, the ring assembly 112 may be disposed on the annular electrostatic chuck or the annular insulating member, or may be disposed on both the electrostatic chuck 1111 and the annular insulating member. Also, at least one RF / DC electrode coupled to an RF power source 31 and / or a DC power source 32 described later may be disposed in the ceramic member 1111a. In this case, the at least one RF / DC electrode functions as a lower electrode. When a bias RF signal and / or a DC signal described later is supplied to the at least one RF / DC electrode, the RF / DC electrode is also called a bias electrode. Note that the conductive member of the base 1110 and the at least one RF / DC electrode may function as multiple lower electrodes. Also, the electrostatic electrode 1111b may function as a lower electrode. Thus, the substrate support 11 includes at least one lower electrode.

[0035] 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.

[0036] The substrate support 11 may also include a temperature adjustment module configured to adjust at least one of the electrostatic chuck 1111, the ring assembly 112, and the substrate to a target temperature. The temperature adjustment module may include a heater, a heat transfer medium, a flow passage 1110a, or a combination thereof. A heat transfer fluid such as a brine or a gas flows through the flow passage 1110a. In one embodiment, the flow passage 1110a is formed in the base 1110, and one or more heaters are disposed in the ceramic member 1111a of the electrostatic chuck 1111. The substrate support 11 may also include a heat transfer gas supply configured to supply a heat transfer gas to a gap between the back surface of the substrate W and the central region 111a.

[0037] The shower head 13 is configured to introduce at least one processing gas from the gas supply unit 20 into the plasma processing space 10s. The shower head 13 has at least one gas supply port 13a, at least one gas diffusion chamber 13b, and multiple gas inlets 13c. The processing gas supplied to the gas supply port 13a passes through the gas diffusion chamber 13b and is introduced into the plasma processing space 10s from the multiple gas inlets 13c. The shower head 13 also includes at least one upper electrode. Note that the gas introduction unit may include, in addition to the shower head 13, one or more side gas injectors (SGIs) attached to one or more openings formed in the sidewall 10a.

[0038] The gas supply 20 may include at least one gas source 21 and at least one flow controller 22. In one embodiment, the gas supply 20 is configured to supply at least one process gas from a respective gas source 21 through a respective flow controller 22 to the showerhead 13. Each flow controller 22 may include, for example, a mass flow controller or a pressure-controlled flow controller. Additionally, the gas supply 20 may include at least one flow modulation device to modulate or pulse a flow rate of the at least one process gas.

[0039] The power source 30 includes an RF power source 31 coupled to the plasma processing chamber 10 via at least one impedance matching circuit. The RF power source 31 is configured to supply at least one RF signal (RF power) to at least one lower electrode and / or at least one upper electrode. This causes a plasma to be formed from at least one processing gas supplied to the plasma processing space 10s. Thus, the RF power source 31 can function as at least a part of the plasma generating unit 12. In addition, by supplying a bias RF signal to the at least one lower electrode, a bias potential is generated on the substrate W, and ion components in the formed plasma can be attracted to the substrate W.

[0040] In one embodiment, the RF power supply 31 includes a first RF generating unit 31a and a second RF generating unit 31b. The first RF generating unit 31a is coupled to at least one lower electrode and / or at least one upper electrode via at least one impedance matching circuit, and is configured to generate a source RF signal (source RF power) for plasma generation. In one embodiment, the source RF signal has a frequency in the range of 10 MHz to 150 MHz. In one embodiment, the first RF generating unit 31a may be configured to generate a plurality of source RF signals having different frequencies. The generated one or more source RF signals are supplied to at least one lower electrode and / or at least one upper electrode.

[0041] The second RF generating unit 31b is coupled to at least one lower electrode via at least one impedance matching circuit and configured to generate a bias RF signal (bias RF power). The frequency of the bias RF signal may be the same as or different from the frequency of the source RF signal. In one embodiment, the bias RF signal has a frequency lower than the frequency of the source RF signal. In one embodiment, the bias RF signal has a frequency in the range of 100 kHz to 60 MHz. In one embodiment, the second RF generating unit 31b may be configured to generate a plurality of bias RF signals having different frequencies. The generated one or more bias RF signals are supplied to at least one lower electrode. Also, in various embodiments, at least one of the source RF signal and the bias RF signal may be pulsed.

[0042] The power supply 30 may also include a DC power supply 32 coupled to the plasma processing chamber 10. The DC power supply 32 includes a first DC generator 32a and a second DC generator 32b. In one embodiment, the first DC generator 32a is connected to at least one lower electrode and configured to generate a first DC signal. The generated first DC signal is applied to the at least one lower electrode. In one embodiment, the second DC generator 32b is connected to at least one upper electrode and configured to generate a second DC signal. The generated second DC signal is applied to the at least one upper electrode.

[0043] In various embodiments, the first and second DC signals may be pulsed. In this case, a sequence of voltage pulses is applied to at least one lower electrode and / or at least one upper electrode. The voltage pulses may have a rectangular, trapezoidal, triangular or combination of these pulse waveforms. In one embodiment, a waveform generator for generating a sequence of voltage pulses from the DC signal is connected between the first DC generator 32a and at least one lower electrode. Thus, the first DC generator 32a and the waveform generator constitute a voltage pulse generator. When the second DC generator 32b and the waveform generator constitute a voltage pulse generator, the voltage pulse generator is connected to at least one upper electrode. The voltage pulses may have a positive polarity or a negative polarity. Also, the sequence of voltage pulses may include one or more positive polarity voltage pulses and one or more negative polarity voltage pulses in one period. The first and second DC generating units 32a, 32b may be provided in addition to the RF power supply 31, or the first DC generating unit 32a may be provided in place of the second RF generating unit 31b.

[0044] The exhaust system 40 may be connected to, for example, a gas exhaust port 10e provided at the bottom of the plasma processing chamber 10. The exhaust system 40 may include a pressure regulating valve and a vacuum pump. The pressure in the plasma processing space 10s is adjusted by the pressure regulating valve. The vacuum pump may include a turbomolecular pump, a dry pump, or a combination thereof.

[0045] 3 is a flowchart of an etching method according to an example embodiment. The etching method MT shown in FIG. 3 (hereinafter, referred to as "method MT") can be performed by the plasma processing apparatus 1 of the above embodiment. The method MT can be applied to a substrate W.

[0046] 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 has a silicon-containing film SF and a mask MK on the silicon-containing film SF. The substrate W may have an underlayer region UR. The silicon-containing film SF may be provided on the underlayer region UR.

[0047] The mask MK may include carbon. The mask MK may include amorphous carbon. The mask MK may have at least one opening OP on the silicon-containing film SF. The mask MK may have a plurality of openings OP. The opening OP may be a hole pattern or a line pattern. The dimension (width) of the opening OP may be 500 nm or less.

[0048] The silicon-containing film SF includes a first region R1 and a second region R2. The first region R1 and the second region R2 may be provided on an underlying region UR. The second region R2 may be located below the first region R1. The underlying region UR may be located below the second region R2. The opening OP of the mask MK may be provided on the first region R1. Each of the first region R1 and the second region R2 may be a film provided on the underlying region UR. The first region R1 may be disposed in a trench formed in the second region R2.

[0049] In a cross section (cross section in FIG. 4) extending in a direction perpendicular to the surface direction of the substrate W, the boundary line BD between the first region R1 and the second region R2 has an inclined portion BD1 extending in a direction inclined with respect to the surface direction of the substrate W. The surface direction of the substrate W may be a direction perpendicular to the thickness direction of the substrate W or the silicon-containing film SF, or may be the extending direction of the silicon-containing film SF, or may be the extending direction of the surface SFa of the silicon-containing film SF. The inclined portion BD1 may be inclined with respect to a direction perpendicular to the surface direction of the substrate W (thickness direction of the substrate W). The inclined portion BD1 may be a side wall of a trench formed in the second region R2. The opening OP of the mask MK may be provided on the inclined portion BD1.

[0050] The first region R1 includes a first material including silicon. The first material is silicon oxide (SiO x The second region R2 includes a second material. The second material is different from the first material. The second material may include silicon. The second material may include silicon nitride (SiN x), polysilicon, or an organic material. The second region R2 may include a first layer L1 and a second layer L2. The second region R2 may include a plurality of first layers L1 and a plurality of second layers L2. The first layers L1 and the second layers L2 may be alternately stacked. The first layer L1 may include a first material. The second layer L2 may include a second material. The second region R2 may include a third layer L3 extending along an inclined portion BD1 of a boundary line BD between the first region R1 and the second region R2. The third layer L3 may include a third material. The third material may be the same as the second material or may be different from the first material and the second material. The third material may include silicon. The third material may be silicon nitride (SiN x ), polysilicon, or an organic material. The second region R2 does not necessarily have to include the third layer L3.

[0051] The underlying region UR may include at least one of silicon and metal. The underlying region UR may include polysilicon or tungsten.

[0052] Method MT will be described below with reference to Figs. 3 to 8, taking as an example a case where method MT is applied to a substrate W using the plasma processing apparatus 1 of the above embodiment. Each of Figs. 5 to 8 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 MT can be performed in the plasma processing apparatus 1 by controlling each part of the plasma processing apparatus 1 by a control unit 2. In method MT, as shown in Fig. 2, a substrate W on a substrate support 11 (substrate support) arranged in a plasma processing chamber 10 is processed.

[0053] 3, the method MT may include steps ST1 to ST11. Steps ST1 to ST11 may be performed in order. The method MT may not include at least one of steps ST3 to ST5 and steps ST8 to ST11.

[0054] 4 is prepared. The substrate W may be supported by a substrate support 11 in a plasma processing chamber 10. The underlying region UR may be disposed between the silicon-containing film SF and the substrate support 11.

[0055] In step ST2, as shown in Fig. 5, the first region R1 is etched by a first plasma PL1 generated from a first processing gas to form a recess RS. The recess RS may have a sidewall RSa and a bottom RSb. The recess RS corresponds to an opening OP of the mask MK. The recess RS may be a contact hole. In step ST2, the second region R2 may or may not be etched.

[0056] The first process gas may include a gas containing carbon and fluorine. x H y F z (x and z are integers of 1 or more, and y is an integer of 0 or more) gas. The first process gas may include an oxygen-containing gas. The oxygen-containing gas may include oxygen gas and carbonyl sulfide (COS) gas.

[0057] The first plasma PL1 may be generated at a first pressure. The first pressure may be the pressure in the plasma processing chamber 10. In step ST2, a first high frequency power may be supplied to generate the first plasma PL1. The first high frequency power may be RF power HF applied to an upper electrode of the plasma processing apparatus 1. In step ST2, a bias power LF may be applied to an electrode in the main body 111 of the substrate support 11.

[0058] Step ST2 may be performed as follows. First, the gas supply unit 20 supplies a first processing gas into the plasma processing chamber 10. Next, the plasma generation unit 12 generates a first plasma PL1 from the first processing gas in the plasma processing chamber 10. The control unit 2 controls the gas supply unit 20 and the plasma generation unit 12 so that the first region R1 is etched with the first plasma PL1 to form a recess RS.

[0059] In step ST3, a deposit (necking) deposited in the opening OP of the mask MK by step ST2 is removed. The deposit may reduce the size of the opening OP. The deposit may contain carbon. In step ST3, the recess RS may be etched. In step ST3, plasma generated from a processing gas may be supplied to the substrate W. The processing gas in step ST3 may contain a gas containing carbon and fluorine and an oxygen-containing gas. The flow rate of the gas containing carbon and fluorine in step ST3 may be smaller than the flow rate of the gas containing carbon and fluorine in step ST2. The flow rate of the oxygen-containing gas in step ST3 may be larger than the flow rate of the oxygen-containing gas in step ST2.

[0060] In step ST4, it is determined whether the number of times N that step ST2 has been performed is greater than a threshold value N0. If the number of times N that step ST2 has been performed is equal to or less than the threshold value N0, the process returns to step ST2. In this case, steps ST2 to ST3 are repeated. If the number of times N that step ST2 has been performed is greater than the threshold value N0, the process proceeds to the next step ST5. For example, if the threshold value N0 is set to 3, step ST2 is performed four times.

[0061] In step ST5, a fourth plasma generated from a fourth process gas containing an oxygen-containing gas is supplied to the substrate W. This performs ashing. The oxygen-containing gas may contain oxygen gas. The fourth process gas may contain an inert gas. The inert gas may contain a noble gas. The noble gas may contain at least one of helium gas, neon gas, argon gas, krypton gas, and xenon gas.

[0062] In step ST6, as shown in FIG. 6, a second plasma PL2 generated from a second process gas containing tungsten is supplied to the substrate W. The second plasma PL2 may be supplied to the recess RS. A tungsten-containing layer WL may be formed on a sidewall RSa of the recess RS. The tungsten-containing layer WL may be formed on a bottom RSb of the recess RS. In step ST6, the recess RS may be etched. In step ST6, the first region R1 and the second region R2 may be etched. After step ST6, the recess RS may cross an inclined portion BD1 of the boundary line BD in a cross section (cross section in FIG. 6) extending in a direction perpendicular to the surface direction of the substrate W. The tungsten-containing layer WL may contact the inclined portion BD1.

[0063] The second process gas may include a tungsten-containing gas. The tungsten-containing gas may include a tungsten halide gas. The tungsten halide gas may include at least one of tungsten hexafluoride (WF6) gas, tungsten hexabromide (WBr6) gas, tungsten hexachloride (WCl6) gas, and WF5Cl gas. The tungsten-containing gas may include tungsten hexacarbonyl (W(CO)6) gas. The flow rate of the tungsten-containing gas may be 10 sccm or less.

[0064] The second process gas may include at least one of an oxygen-containing gas and an inert gas. The oxygen-containing gas may include oxygen gas. The inert gas may include a noble gas. The noble gas may include at least one of helium gas, neon gas, argon gas, krypton gas, and xenon gas. The second process gas may be carbon-free.

[0065] The second plasma PL2 may be generated at a second pressure. The second pressure may be the pressure in the plasma processing chamber 10. The second pressure is higher than the first pressure in step ST2. In this case, the tungsten-containing layer WL is more likely to be formed on the side wall RSa of the recess RS in step ST6. The second pressure may be 10 mTorr (1.333 Pa) or more. The second pressure may be 100 mTorr (13.33 Pa) or less.

[0066] In step ST6, a second high frequency power may be supplied to generate a second plasma PL2. The second high frequency power may be RF power HF applied to the upper electrode of the plasma processing apparatus 1. The second high frequency power is smaller than the first high frequency power in step ST2. In this case, the tungsten-containing layer WL is more likely to be formed on the side wall RSa of the recess RS in step ST6. The second high frequency power may be 100 W or more. The second high frequency power may be 1000 W or less. In step ST6, a bias power LF may not be applied to the electrode in the main body 111 of the substrate support 11. That is, the bias power LF may be 0 W.

[0067] In step ST6, the temperature of the substrate support 11 may be −20° C. or higher, or the temperature of the substrate support 11 may be 100° C. or lower.

[0068] The processing time of step ST6 may be shorter than the processing time of step ST2. The processing time of step ST6 may be adjusted according to the depth of the recess RS. For example, the processing time of step ST6 may be longer as the recess RS becomes deeper.

[0069] Step ST6 may be performed as follows. First, the gas supply unit 20 supplies a second process gas containing tungsten into the plasma processing chamber 10. Next, the plasma generation unit 12 generates a second plasma PL2 from the second process gas in the plasma processing chamber 10. The control unit 2 controls the gas supply unit 20 and the plasma generation unit 12 to supply the second plasma PL2 to the substrate W.

[0070] In step ST7, as shown in Fig. 7, the recess RS is etched by a third plasma PL3 generated from a third process gas. The second region R2 may be etched by the third plasma PL3. The first region R1 may be etched by the third plasma PL3. The etching conditions for step ST7 may be the same as the etching conditions for step ST2. After step ST7, the recess RS crosses the inclined portion BD1 of the boundary line BD in a cross section (cross section in Fig. 7) extending in a direction perpendicular to the surface direction of the substrate W.

[0071] The third process gas may include a gas containing carbon and fluorine. x H y F z (x and z are integers equal to or greater than 1, and y is an integer equal to or greater than 0) gas. The third process gas may include an oxygen-containing gas. The oxygen-containing gas may include oxygen gas and carbonyl sulfide (COS) gas.

[0072] Step ST7 may be performed as follows. First, the gas supply unit 20 supplies a third process gas into the plasma processing chamber 10. Next, the plasma generation unit 12 generates a third plasma PL3 from the third process gas in the plasma processing chamber 10. The control unit 2 controls the gas supply unit 20 and the plasma generation unit 12 so as to etch the recess RS with the third plasma PL3.

[0073] In step ST8, the deposit deposited in the opening OP of the mask MK in step ST7 is removed. Step ST8 may be performed under the same conditions as step ST3.

[0074] In step ST9, it is determined whether the number of times N that step ST7 has been performed is greater than a threshold value N0. If the number of times N that step ST7 has been performed is equal to or less than the threshold value N0, the process returns to step ST7. In this case, steps ST7 to ST8 are repeated. If the number of times N that step ST7 has been performed is greater than the threshold value N0, the process proceeds to the next step ST10.

[0075] In step ST10, it is determined whether the number of times M that step ST6 is performed is greater than a threshold value M0. If the number of times M that step ST6 is performed is equal to or less than the threshold value M0, the process returns to step ST5. In this case, steps ST5 to ST9 are repeated. If the number of times M that step ST6 is performed is greater than the threshold value M0, the process proceeds to the next step ST11. For example, if the threshold value M0 is set to 3, step ST6 is performed four times. The number of times M that step ST6 is performed may be adjusted according to the depth of the recess RS. For example, the number of times M that step ST6 is performed may be increased as the recess RS becomes deeper.

[0076] In step ST11, the recess RS is etched by plasma generated from a processing gas. As a result, the recess RS is over-etched as shown in FIG. 8. After step ST11, the bottom RSb of the recess RS may reach the underlying region UR. After step ST11, an electronic device can be manufactured from the substrate W. The electronic device may be a NAND flash memory having a three-dimensional structure.

[0077] According to the method MT, the side wall RSa of the recess RS is less likely to bend near the inclined portion BD1 of the boundary line BD between the first region R1 and the second region R2. That is, in a cross section (cross section in FIG. 7) extending in a direction perpendicular to the surface direction of the substrate W, the side wall RSa of the recess RS approaches a straight line. Therefore, a recess RS having a good shape can be formed. As a result, defects in electronic devices due to misalignment of the recess RS caused by bending of the side wall RSa can be suppressed. The mechanism by which the side wall RSa of the recess RS is less likely to bend is presumed to be as follows, but is not limited thereto.

[0078] FIG. 9 is a cross-sectional view showing an example of a mechanism by which the sidewall of a recess formed by etching is curved. When forming the recess RS by etching, in the vicinity of the inclined portion BD1 of the boundary line BD between the first region R1 and the second region R2, the first region R1 is exposed on one sidewall RSa of the recess RS, and the second region R2 is exposed on the other sidewall RSa of the recess RS. If step ST6 is not performed, positive charges are unevenly distributed on the sidewall RSa on which the first region R1 is exposed, among the two sidewalls RSa of the recess RS, due to positive ions ET in the plasma for etching. As a result, a positively charged region EC is formed on the sidewall RSa on which the first region R1 is exposed. On the other hand, no charged region is formed on the sidewall RSa on which the second region R2 is exposed. If the first region R1 contains silicon oxide, the first region R1 has high electronegativity, so that positive charges are likely to accumulate on the sidewall RSa on which the first region R1 is exposed. As a result, the positive ions ET are repelled by the charged region EC and etch the opposite side wall RSa, which causes the side wall RSa of the recess RS to bend in a cross section extending in a direction perpendicular to the surface direction of the substrate W.

[0079] 10 is a cross-sectional view showing an example of the mechanism by which the sidewalls of the recess formed by etching are less likely to bend. By performing step ST6, a conductive tungsten-containing layer WL is formed on both sidewalls RSa, so that the positive charge on the charged sidewalls RSa can be removed. This improves the linearity of the positive ions ET, making the sidewalls RSa of the recess RS less likely to bend.

[0080] Furthermore, according to the method MT, the bottom RSb of the recess RS can be made closer to a desired shape (for example, a circle) than when step ST6 is not performed. This is presumably because the straightness of the positive ions ET is improved.

[0081] When the method MT includes at least one of steps ST3 and ST8, it is possible to suppress a reduction in the size of the opening OP of the mask MK, which in turn suppresses a reduction in the size of the recess RS.

[0082] When the method MT includes the step ST5, it is possible to remove organic matter adhering to the substrate W. This is presumably what makes it easier for the tungsten-containing layer WL to be formed on the side wall RSa of the recess RS.

[0083] In the method MT, when steps ST6 and ST7 are repeated, the sidewall RSa of the recess RS becomes less likely to bend. This is presumably because the tungsten-containing layer WL is also formed on the sidewall RSa exposed by the etching of the recess RS in step ST7.

[0084] 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. In addition, elements in different embodiments can be combined to form other embodiments.

[0085] Various experiments performed to evaluate Method MT will be described below, but the experiments described below are not intended to limit the present disclosure.

[0086] (First experiment) A substrate W having a silicon-containing film SF and a mask MK was prepared. The silicon-containing film SF includes a first region R1 including a silicon oxide film and a second region R2 including alternately stacked silicon oxide films and silicon nitride films. An inclined portion BD1 of a boundary line BD between the first region R1 and the second region R2 extends in a direction inclined with respect to the surface direction of the substrate W in a cross section extending in a direction perpendicular to the surface direction of the substrate W. The mask MK has an opening OP on the first region R1. The first region R1 is provided on the second region R2.

[0087] The method MT was performed on the substrate W. The step ST5 was not performed. The number of times M that the step ST6 was performed was 1.

[0088] (Second experiment) The same method as in the first experiment was carried out, except that the number of times M in which step ST6 was carried out was set to four.

[0089] (Third experiment) The same method as in the first experiment was carried out, except that the number of times M in which step ST6 was carried out was set to 18.

[0090] (4th experiment) The number of times M at which step ST6 was performed was set to 4, and the same method as the method of the first experiment was performed except for performing step ST5. In other words, the same method as the method of the second experiment was performed except for performing step ST5.

[0091] (Fifth experiment) The same method as in the first experiment was carried out, except that step ST6 was not carried out.

[0092] (Cross-sectional shape evaluation of recesses) The cross-sectional shapes of the recesses RS formed by etching in the first to fifth experiments were observed. Fig. 11 is a cross-sectional view showing a schematic example of the recesses formed by etching in the first to fifth experiments. (a) to (e) of Fig. 11 show the results of the first to fifth experiments, respectively.

[0093] In (a) of Fig. 11, in the region near the inclined portion BD1 of the boundary line BD, the bending of the side wall RSa of the recess RS is suppressed compared to (e) of Fig. 11. Therefore, it can be seen that by performing step ST6, the bending of the side wall RSa of the recess RS is suppressed.

[0094] In Fig. 11(b), bending of the side wall RSa of the recess RS is suppressed in the region near the inclined portion BD1 of the boundary line BD compared to Fig. 11(a). In Fig. 11(c), bending of the side wall RSa of the recess RS is suppressed in the region below the inclined portion BD1 of the boundary line BD compared to Fig. 11(b). It can be seen that by increasing the number of times M that step ST6 is performed, bending of the side wall RSa of the recess RS is further suppressed.

[0095] In Fig. 11(d), in the region near the inclined portion BD1 of the boundary line BD, the bending of the side wall RSa of the recess RS is suppressed compared to Fig. 11(b). Therefore, it can be seen that by performing step ST5, the bending of the side wall RSa of the recess RS is further suppressed.

[0096] The present disclosure further includes the following aspects.

[0097] (Appendix 1) (a) providing a substrate, the substrate having a silicon-containing film and a mask on the silicon-containing film, the silicon-containing film including a first region including a first material that includes silicon and a second region including a second material different from the first material, the second region being located below the first region; (b) after (a), a first etching step of etching the first region with a first plasma generated from a first process gas to form a recess; (c) after (b), supplying a second plasma generated from a second process gas containing tungsten to the substrate; (d) after (c), a second etching step of etching the second region located under the recess by a third plasma generated from a third process gas; An etching method comprising:

[0098] (Appendix 2) (a) a step of preparing a substrate, the substrate having a silicon-containing film and a mask on the silicon-containing film, the silicon-containing film including a first region including a silicon oxide film and a second region including a silicon oxide film and a silicon nitride film alternately stacked, the second region being located below the first region, and in a cross section extending in a direction perpendicular to a surface direction of the substrate, a boundary line between the first region and the second region has an inclined portion extending in a direction inclined with respect to the surface direction; (b) After (a) above, C x H y F za first etching step of etching the first region with a first plasma generated from a first process gas containing a gas having a nitrogen atom (wherein x and z are integers equal to or greater than 1, and y is an integer equal to or greater than 0) and an oxygen-containing gas to form a recess; (c) after (b), supplying a second plasma generated from a second process gas containing tungsten hexafluoride gas to the substrate; (d) after (c), a second etching step of etching the second region located under the recess by a third plasma generated from a third process gas; An etching method comprising:

[0099] (Appendix 3) The etching method according to (Supplementary Note 1) or (Supplementary Note 2), wherein at least one of the number of times the step of supplying the second plasma to the substrate is performed and a processing time is adjusted according to the depth of the recess.

[0100] From the foregoing, it will be understood that various embodiments of the present disclosure have been described herein for purposes of illustration, and that various modifications may be made without departing from the scope and spirit of the present disclosure. Accordingly, the various embodiments disclosed herein are not intended to be limiting, with the true scope and spirit being indicated by the appended claims. [Explanation of symbols]

[0101] 1...plasma processing apparatus, 2...control unit, 10...plasma processing chamber, 11...substrate support unit, 12...plasma generation unit, 20...gas supply unit, BD...boundary line, BD1...inclined portion, MK...mask, PL1...first plasma, PL2...second plasma, PL3...third plasma, R1...first region, R2...second region, RS...recess, SF...silicon-containing film, W...substrate.

Claims

1. (a) a step of preparing a substrate, the substrate having a silicon-containing film and a mask on the silicon-containing film, the silicon-containing film including a first region including a first material including silicon and a second region including a second material different from the first material, and in a cross section extending in a direction perpendicular to a surface direction of the substrate, a boundary line between the first region and the second region has an inclined portion extending in a direction inclined with respect to the surface direction; (b) after (a), etching the first region with a first plasma generated from a first process gas to form a recess; (c) after (b), supplying a second plasma generated from a second process gas containing tungsten to the substrate; (d) after (c), etching the recess with a third plasma generated from a third process gas; Including, The etching method, wherein after (d), the recess crosses the inclined portion in the cross section.

2. The etching method according to claim 1 , wherein in (c), a tungsten-containing layer is formed on a side wall of the recess.

3. In (b), the first plasma is generated at a first pressure; 3. The etching method according to claim 1, wherein in (c), the second plasma is generated at a second pressure higher than the first pressure.

4. In the step (b), a first high frequency power is supplied to generate the first plasma; 4. The etching method according to claim 1, wherein in (c), a second high frequency power smaller than the first high frequency power is supplied to generate the second plasma.

5. The etching method according to any one of claims 1 to 4, further comprising the step of: (e) removing deposits deposited in the openings of the mask by (b) between (b) and (c).

6. The etching method according to any one of claims 1 to 5, further comprising: (f) between (b) and (c), a step of supplying to the substrate a fourth plasma generated from a fourth process gas containing an oxygen-containing gas.

7. The etching method according to any one of claims 1 to 6, wherein after (d), (c) and (d) are repeated.

8. The etching method according to any one of claims 1 to 7, wherein the first material comprises silicon oxide.

9. The etching method according to any one of claims 1 to 8, wherein the second material comprises silicon nitride.

10. The etching method according to any one of claims 1 to 9, wherein the second region includes a first layer including the first material and a second layer including the second material, and the first layer and the second layer are alternately stacked.

11. The etching method of any one of claims 1 to 10, wherein the second process gas comprises a tungsten-containing gas.

12. The etching method of any one of claims 1 to 11, wherein the second process gas comprises tungsten hexafluoride gas.

13. The first process gas is ｘ H ｙ F ｚ The etching method according to any one of claims 1 to 12, comprising a gas (x and z are integers of 1 or more, and y is an integer of 0 or more).

14. The third process gas is ｘ H ｙ F ｚ The etching method according to any one of claims 1 to 13, comprising a gas (x and z are integers of 1 or more, and y is an integer of 0 or more).

15. (a) a step of preparing a substrate, the substrate having a silicon-containing film and a mask on the silicon-containing film, the silicon-containing film including a first region including a silicon oxide film and a second region including a silicon oxide film and a silicon nitride film alternately stacked thereon, the boundary between the first region and the second region having an inclined portion extending in a direction inclined with respect to the surface direction in a cross section extending in a direction perpendicular to the surface direction of the substrate; (b) After (a), ｘ H ｙ F ｚ (x and z are integers of 1 or more, and y is an integer of 0 or more) etching the first region with a first plasma generated from a first process gas including a gas containing oxygen and an oxygen-containing gas to form a recess; (c) after (b), forming a tungsten-containing layer on a sidewall of the recess by supplying a second plasma generated from a second process gas containing tungsten hexafluoride gas to the substrate; (d) After (c), ｘ H ｙ F ｚ (x and z are integers of 1 or more, and y is an integer of 0 or more) etching the recess with a third plasma generated from a third process gas including a gas containing oxygen and an oxygen-containing gas; Including, The etching method, wherein after (d), the recess crosses the inclined portion in the cross section.

16. A chamber; a substrate support for supporting a substrate in the chamber, the substrate having a silicon-containing film and a mask on the silicon-containing film, the silicon-containing film including a first region including a first material including silicon and a second region including a second material different from the first material, and a boundary between the first region and the second region has an inclined portion extending in a direction inclined with respect to the surface direction in a cross section extending in a direction perpendicular to a surface direction of the substrate; a gas supply configured to supply a first process gas, a second process gas, and a third process gas into the chamber, the second process gas comprising tungsten; a plasma generating unit configured to generate a first plasma, a second plasma, and a third plasma from the first process gas, the second process gas, and the third process gas in the chamber, respectively; A control unit; Equipped with The control unit is Etching the first region with the first plasma to form a recess; After forming the recess, the second plasma is supplied to the substrate; The gas supply unit and the plasma generation unit are controlled so as to etch the recess by the third plasma after the second plasma is supplied to the substrate, After etching the recess with the third plasma, the recess crosses the inclined portion in the cross section.

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