Plasma treatment device, bias power source, and plasma treatment method

Abstract

A plasma treatment device disclosed herein comprises a chamber, a substrate support part, a gas supply part, a high-frequency power source, and a bias power source. The high-frequency power source is configured to supply a source high-frequency signal in order to generate plasma from a treatment gas. The bias power source is configured to supply a sequence of voltage pulses to the substrate support part by generating the voltage pulses at a time interval that is a reciprocal of a first frequency, in order to attract ions from the plasma to a substrate on the substrate support part. The bias power source is configured to gradually increase or decrease the voltage levels of a plurality of voltage pulses included in the sequence within a period having a time length that is a reciprocal of a second frequency which is lower than the first frequency and included within the range of 20-100 kHz, and to repeat the period.

Description

Plasma processing apparatus, bias power supply, and plasma processing method

[0001] SUMMARY Exemplary embodiments of the present disclosure relate to a plasma processing apparatus, a bias power supply, and a plasma processing method.

[0002] A plasma processing apparatus is used in plasma processing of a substrate. The plasma processing apparatus described in Patent Document 1 includes a source RF generating unit and first and second bias RF generating units. The source RF generating unit generates a source RF signal for plasma generation. The first and second bias RF generating units are coupled to a substrate support. The frequency of the bias signal generated by the first bias RF generating unit is different from the frequency of the bias signal generated by the second bias RF generating unit.

[0003] JP 2022-41874 A

[0004] The present disclosure provides a technique for obtaining different ion energy distributions while suppressing an increase in the number of bias power supplies.

[0005] In one exemplary embodiment, a plasma processing apparatus is provided. The plasma processing apparatus includes a chamber, a substrate support within the chamber, a gas supply, a radio frequency power supply, and a bias power supply. The gas supply is configured to supply a process gas into the chamber. The radio frequency power supply is configured to supply a source radio frequency signal to generate a plasma from the process gas. The bias power supply is configured to supply a sequence of voltage pulses to the substrate support by generating voltage pulses at a time interval that is the reciprocal of a first frequency to attract ions from the plasma to a substrate on the substrate support. The bias power supply is configured to stepwise increase or decrease the voltage level of multiple voltage pulses included in the sequence within a period having a time length that is the reciprocal of a second frequency that is lower than the first frequency and is in the range of 20 kHz to 100 kHz, and to repeat the period.

[0006] According to one exemplary embodiment, a technique is provided for obtaining different ion energy distributions while limiting the number of bias power supplies.

[0007] 5A is a diagram for explaining an example configuration of a plasma processing system; FIG. 5B is a diagram for explaining an example configuration of a plasma processing system; FIG. 5C is a diagram for explaining an example configuration of a bias power supply according to an exemplary embodiment; FIG. 5D is a diagram for explaining an example voltage pulse sequence that can be output by a bias power supply according to an exemplary embodiment; FIG. 5E is a diagram for explaining an example voltage pulse sequence that can be output by a bias power supply according to an exemplary embodiment; FIG. 5F is a diagram for explaining an example voltage pulse sequence that can be output by a bias power supply according to an exemplary embodiment; FIG. 5G is a diagram for explaining an example voltage pulse sequence that can be output by a bias power supply according to an exemplary embodiment; FIG. 5H is a diagram for explaining an example voltage pulse sequence that can be output by a bias power supply according to an exemplary embodiment; FIG. 5H is a diagram for explaining an example voltage pulse sequence that can be output by a bias power supply according to an exemplary embodiment; FIG. 5H is a diagram for explaining an example voltage pulse sequence that can be output by a bias power supply according to an exemplary embodiment; FIG. 5H is a diagram for explaining an example voltage pulse sequence that can be output by a bias power supply according to an exemplary embodiment; FIG. 5H is a diagram for explaining an example voltage pulse sequence that can be output by a bias power supply according to an exemplary embodiment; 1A-1C are cross-sectional views of an example substrate associated with a plasma processing method according to one exemplary embodiment;FIGS.

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

[0009] FIG. 1 is a 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 formed in the plasma processing space may be capacitively coupled plasma (CCP), inductively coupled plasma (ICP), electron-cyclotron-resonance plasma (ECR plasma), helicon wave plasma (HWP), or surface wave plasma (SWP). Various types of plasma generators may be used, including alternating current (AC) plasma generators and direct current (DC) plasma generators. In one embodiment, the AC signal (AC power) used in the AC plasma generator has a frequency in the range of 100 kHz to 10 GHz. Thus, AC signals include radio frequency (RF) signals and microwave signals. In one embodiment, the RF signal has a frequency in the range of 100 kHz to 150 MHz.

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

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

[0013] The capacitively coupled plasma processing apparatus 1 includes a plasma processing chamber 10, a gas supply 20, a power supply 30, and an exhaust system 40. The plasma processing apparatus 1 also includes a substrate support 11 and a gas inlet. The gas inlet is configured to introduce at least one process gas into the plasma processing chamber 10. The gas inlet includes a showerhead 13. The substrate support 11 is disposed within the plasma processing chamber 10. The showerhead 13 is disposed above the substrate support 11. In one embodiment, the showerhead 13 forms at least a portion of the ceiling of the plasma processing chamber 10. The plasma processing chamber 10 has a plasma processing space 10s defined by the showerhead 13, a sidewall 10a of the plasma processing chamber 10, and the substrate support 11. The plasma processing chamber 10 is grounded. The showerhead 13 and the substrate support 11 are electrically insulated from the housing of the plasma processing chamber 10.

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

[0015] In one embodiment, the main body 111 includes a base 1110 and an electrostatic chuck 1111. The base 1110 includes a conductive member. The conductive member of the base 1110 can function as a lower electrode. The electrostatic chuck 1111 is disposed on the base 1110. The electrostatic chuck 1111 includes a ceramic member 1111a and an electrostatic electrode 1111b disposed within the ceramic member 1111a. The ceramic member 1111a has a central region 111a. In one embodiment, the ceramic member 1111a also has an annular region 111b. Note that the annular region 111b may also be provided by another member surrounding the electrostatic chuck 1111, such as an annular electrostatic chuck or an annular insulating member. In this case, the ring assembly 112 may be disposed on the annular electrostatic chuck or the annular insulating member, or may be disposed on both the electrostatic chuck 1111 and the annular insulating member. Furthermore, at least one RF / DC electrode coupled to an RF power supply 31 and / or a DC power supply 32, which will be described later, may be disposed within the ceramic member 1111a. In this case, the at least one RF / DC electrode functions as a lower electrode. When a bias RF signal and / or a DC signal, which will be described later, is supplied to the at least one RF / DC electrode, the RF / DC electrode is also called a bias electrode. Note that the conductive member of the base 1110 and the at least one RF / DC electrode may function as multiple lower electrodes. Furthermore, the electrostatic electrode 1111b may function as a lower electrode. Therefore, the substrate support 11 includes at least one lower electrode.

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

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

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

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

[0020] The power supply 30 includes an RF power supply 31 coupled to the plasma processing chamber 10 via at least one impedance matching circuit. The RF power supply 31 is configured to supply at least one RF signal (RF power) to at least one lower electrode and / or at least one upper electrode. This generates a plasma from at least one processing gas supplied to the plasma processing space 10s. Therefore, the RF power supply 31 can function as at least a part of the plasma generation unit 12. Furthermore, by supplying a bias RF signal to the at least one lower electrode, a bias potential is generated on the substrate W, thereby attracting ion components in the formed plasma to the substrate W.

[0021] In one embodiment, the RF power supply 31 includes a first RF generating unit 31a and a second RF generating unit 31b. The first RF generating unit 31a is coupled to at least one lower electrode and / or at least one upper electrode via at least one impedance matching circuit and is configured to generate a source RF signal (source RF power) for plasma generation. In one embodiment, the source RF signal has a frequency in the range of 10 MHz to 150 MHz. In one embodiment, the first RF generating unit 31a may be configured to generate multiple source RF signals having different frequencies. The generated one or more source RF signals are supplied to at least one lower electrode and / or at least one upper electrode.

[0022] The second RF generator 31b is coupled to at least one lower electrode via at least one impedance matching circuit and is configured to generate a bias RF signal (bias RF power). The frequency of the bias RF signal may be the same as or different from the frequency of the source RF signal. In one embodiment, the bias RF signal has a frequency lower than the frequency of the source RF signal. In one embodiment, the bias RF signal has a frequency in the range of 100 kHz to 60 MHz. In one embodiment, the second RF generator 31b may be configured to generate multiple bias RF signals having different frequencies. The generated one or more bias RF signals are supplied to at least one lower electrode. In various embodiments, at least one of the source RF signal and the bias RF signal may be pulsed.

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

[0024] In various embodiments, the first and second DC signals may be pulsed. In this case, a sequence of voltage pulses is applied to at least one lower electrode and / or at least one upper electrode. The voltage pulses may have a rectangular, trapezoidal, triangular, or combination thereof pulse waveform. In one embodiment, a waveform generator for generating the sequence of voltage pulses from the DC signal is connected between the first DC generator 32a and at least one lower electrode. Thus, the first DC generator 32a and the waveform generator constitute a voltage pulse generator. When the second DC generator 32b and the waveform generator constitute a voltage pulse generator, the voltage pulse generator is connected to at least one upper electrode. The voltage pulses may have either positive or negative polarity. Furthermore, the sequence of voltage pulses may include one or more positive voltage pulses and one or more negative voltage pulses within one period. The first and second DC generating units 32a and 32b may be provided in addition to the RF power supply 31, or the first DC generating unit 32a may be provided instead of the second RF generating unit 31b.

[0025] The exhaust system 40 may be connected to, for example, a gas exhaust port 10e provided at the bottom of the plasma processing chamber 10. The exhaust system 40 may include a pressure regulating valve and a vacuum pump. The pressure in the plasma processing space 10s is regulated by the pressure regulating valve. The vacuum pump may include a turbomolecular pump, a dry pump, or a combination thereof.

[0026] In the plasma processing apparatus 1, the control unit 2 is used as a main control unit. In the plasma processing apparatus 1, the first RF generating unit 31a is used as a high-frequency power supply that generates a source RF signal (source high-frequency signal) for plasma generation.

[0027] Hereinafter, reference will be made to FIGS. 3 and 4 in addition to FIGS. 1 and 2. FIG. 3 is a diagram schematically illustrating a bias power supply according to an exemplary embodiment. FIG. 4 is a diagram illustrating an example sequence of voltage pulses that can be output by a bias power supply according to an exemplary embodiment. As shown in FIG. 3, the plasma processing apparatus 1 includes a bias power supply 50. The bias power supply 50 is used in the plasma processing apparatus 1 as a bias power supply including the above-described first DC generation unit 32a. Note that the plasma processing apparatus 1 including this bias power supply 50 does not necessarily have to include the second RF generation unit 31b.

[0028] As shown in FIG. 4, the bias power supply 50 generates a sequence of voltage pulses VP to attract ions from the plasma in the plasma processing chamber 10 to the substrate W on the substrate support 11. ＶＰ The sequence S is configured to supply the substrate support 11 with the ＶＰ The time interval Ti (minimum time interval) at which the voltage pulse VP is generated is the reciprocal of the first frequency. The first frequency is, for example, 200 kHz or more and 1 MHz or less. The first frequency may be 800 kHz or less. The first frequency may be, for example, 400 kHz.

[0029] As shown in FIG. 4, the bias power supply 50 operates in the sequence S ＶＰ The bias power supply 50 can adjust the voltage levels of the plurality of voltage pulses VP in a sequence S within a period CY having a time length Tc that is the reciprocal of the second frequency. ＶＰ The voltage levels of the plurality of voltage pulses VP included in the period CY may be increased or decreased stepwise, and the period CY may be repeated. The second frequency is lower than the first frequency. The second frequency is in the range of 20 kHz to 100 kHz. In the example shown in FIG. 4, the sequence S ＶＰ The voltage levels of the multiple voltage pulses VP included in the voltage pulse generator 100 increase stepwise.

[0030] Each of the multiple voltage pulses VP has a voltage level in the negative direction relative to a reference potential V. The voltage level of each of the multiple voltage pulses VP is the difference between the reference potential V and the potential of the voltage pulse. The reference potential V may be, for example, ground potential (0 V).

[0031] The bias power supply 50 may be configured to be able to change the duty ratio of the voltage pulse VP. ＯＮ / L Ｔｉ Here, L ＯＮ is the time length during which the voltage pulse VP is in the ON state during the time interval Ti, and L Ｔｉ is the time length of the time interval Ti. The duty ratio may be set to, for example, 0.2.

[0032] In one embodiment, the bias power supply 50 may include a variable DC power supply 51 and a pulse generator 52. The variable DC power supply 51 is configured to be able to adjust the voltage level of the output voltage from its negative terminal. The positive terminal of the variable DC power supply 51 is connected to a ground or a reference potential line. The negative terminal of the variable DC power supply 51 is electrically coupled to the substrate support 11 via the pulse generator 52. The pulse generator 52 pulses the output voltage of the variable DC power supply 51 to generate a sequence S of voltage pulses VP. ＶＰ is configured to generate

[0033] The bias power supply 50 may include a control unit 50c as at least one control unit. The control unit 50c may include a power supply control unit 51c. The power supply control unit 51c controls the variable DC power supply 51 to change the voltage level of the output voltage of the variable DC power supply 51. The control of the voltage level of the output voltage of the variable DC power supply 51 by the power supply control unit 51c causes the sequence S ＶＰ For example, the voltage level of the output voltage of the variable DC power supply 51 is adjusted by the control of the power supply control unit 51c, and the sequence S ＶＰ The voltage levels of the plurality of voltage pulses VP included in the voltage pulse generator 10 are increased or decreased in stages.

[0034] The pulse generator 52 may include a switching circuit 52s. The bias power supply 50 generates a sequence S of voltage pulses VP by alternately opening and closing the switching circuit 52s. ＶＰ At least one control unit of the bias power supply 50 may further include a pulse control unit 52c. In one embodiment, the control unit 50c may include the pulse control unit 52c. The opening and closing of the switching circuit 52s is controlled by the pulse control unit 52c. The pulse control unit 52c also controls the duty ratio of the voltage pulse VP. The pulse control unit 52c may be part of the pulse generator 52. The pulse control unit 52c may be located outside the pulse generator 52. The power supply control unit 51c may also constitute a power supply device 51S together with the variable DC power supply 51. The power supply control unit 51c may also be located outside the power supply device 51S. The power supply control unit 51c and the pulse control unit 52c may also be configured as a single control unit. The single control unit may be part of either the power supply device 51S or the pulse generator 52, or may be separate from them. The single control unit may be the control unit 50c or the control unit 2.

[0035] Reference is now made to Figures 5(a), 5(b), and 5(c). Figure 5(a) shows an example ion energy distribution when multiple voltage pulses in a sequence have the same voltage level. Figure 5(b) shows an example ion energy distribution when a bias RF signal is used. Figure 5(c) shows a schematic diagram of an example ion energy distribution when multiple voltage pulses in a sequence have stepwise increased or decreased voltage levels.

[0036] Sequence S ＶＰ When the voltage levels of the plurality of voltage pulses VP in the sequence S are constant and identical to each other, the energy distribution E1 of the ions supplied to the substrate on the substrate support 11 has a relatively narrow width centered on the peak, as shown in FIG. ＶＰIn the case where the voltage levels of the voltage pulses VP in the sequence S are constant and identical to each other, the ions have a high monochromaticity of energy. ＶＰ On the other hand, when a bias RF signal is used as the electric bias, the energy distribution E2 of the ions supplied to the substrate on the substrate support 11 has a relatively wide width, as shown in (b) of FIG.

[0037] Sequence S within cycle CY ＶＰ When the voltage levels of the plurality of voltage pulses VP in the period CY are increased or decreased stepwise, the energy distribution E3 of the ions supplied to the substrate on the substrate support 11 has a distribution including multiple peaks, as shown in (c) of Figure 5. The multiple peaks in the distribution E3 are generated by the sequence S in the period CY. ＶＰ The peaks correspond to the voltage levels of the multiple voltage pulses VP in the plasma processing apparatus 1. As shown in FIG. 5C, distribution E3 is similar to distribution E2 shown in FIG. 5B. Therefore, the bias power supply 50 can provide the highly monochromatic ion energy distribution shown in FIG. 5A and the relatively wide energy distribution shown in FIG. 5C with a single power supply. In other words, the bias power supply 50 can obtain different ion energy distributions while suppressing an increase in the number of bias power supplies. Therefore, the plasma processing apparatus 1 can reduce the space required for bias power supplies around the chamber 10.

[0038] 6 and 7, which are diagrams illustrating another example of a sequence of voltage pulses that can be output by a bias power supply according to an exemplary embodiment. In the example shown in FIG. 4, a sequence S ＶＰ 6, the bias power supply 50 generates a sequence S within a period CY. ＶＰ 4 and 7, the bias power supply 50 may reduce the voltage level of the plurality of voltage pulses VP in a sequence SＶＰ The duty ratio of each of the plurality of voltage pulses VP may be changeable.

[0039] A plasma processing method according to one exemplary embodiment will be described below with reference to FIGS. 8 to 12. Control of each component in the plasma processing apparatus 1 will also be described with reference to these figures. FIG. 8 is a flow chart illustrating the plasma processing method according to one exemplary embodiment. FIG. 9 is a partially enlarged cross-sectional view of an example substrate to which the plasma processing method shown in FIG. 8 can be applied. FIG. 10 is a timing chart relating to one step of the plasma processing method according to one exemplary embodiment. FIGS. 11 and 12 are each a cross-sectional view of an example substrate related to the plasma processing method according to one exemplary embodiment. In the plasma processing method shown in FIG. 8 (hereinafter referred to as "method MT"), each component of the plasma processing apparatus 1 can be controlled by a controller 2.

[0040] 8, the method MT includes steps ST1, ST2, and ST3. The method MT may further include a step STJ.

[0041] In step ST1, a substrate W is prepared. The substrate W is transferred into the chamber 10 by a transfer device (e.g., a transfer robot). The substrate W is placed on a substrate support 11 in the chamber 10. The substrate W may be held by an electrostatic chuck 1111 during the execution of the method MT.

[0042] 9, the substrate W may include a first region R1 and a second region R2. The first region R1 may have at least one recess R1a. The first region R1 may have a plurality of recesses R1a. Each recess R1a may be a recess for forming a contact hole. The recess R1a may be filled with a second region R2. The second region R2 may be provided so as to cover the first region R1.

[0043] In one embodiment, the first region R1 includes silicon and nitrogen. The first region R1 includes silicon nitride (SiN ｘThe first region R1 may include a silicon nitride (SiN). The first region R1 may be a region formed by, for example, CVD or the like, or may be a region obtained by nitriding silicon. ｘ The first portion may include a first portion including silicon carbide (SiC), and a second portion including silicon carbide (SiC). In this case, the first portion has the recess R1a.

[0044] The aspect ratio of the recess R1a may be, for example, 3 or more, 4 or more, 5 or more, or 10 or more. The aspect ratio of the recess R1a indicates the ratio of the depth of the recess R1a to the maximum width dimension of the recess R1a.

[0045] The second region R2 includes silicon and oxygen. The second region R2 includes silicon oxide (SiO ｘ The second region R2 may be a region formed by, for example, CVD or the like, or may be a region obtained by oxidizing silicon.

[0046] The substrate W may further include a third region R3. The third region R3 is provided on the second region R2. The third region R3 may include a metal, carbon, and nitrogen. Here, the metal includes tungsten. The third region R3 may have an opening OP3. The width of the opening OP3 may correspond to the width of the recess R1a.

[0047] The substrate W may include an underlying region UR and at least one raised region RA provided on the underlying region UR. The underlying region UR and the at least one raised region RA are covered by a first region R1. The underlying region UR may include silicon. A plurality of raised regions RA are located on the underlying region UR. Recesses R1a of the first region R1 are located between the plurality of raised regions RA. Each raised region RA may form a gate region of a transistor.

[0048] The substrate W may include a mask MK. The mask MK is provided on the third region R3. The mask MK may include metal or silicon. The mask MK may have an opening OPM. The opening OPM corresponds to the opening OP3 in the third region R3.

[0049] The substrate W prepared in process ST1 may have the shape shown in FIG. 9 as a result of plasma etching, or may have the shape shown in FIG. 9 from the beginning when it is provided to the plasma processing chamber 10.

[0050] In the method MT, step ST2 is then performed. In step ST2, the controller 2 controls the gas supply unit 20 to supply a processing gas into the chamber 10.

[0051] The processing gas may include a metal constituting the chemical species from the plasma and an etching component for etching the second region R2. In one example, the processing gas may include a metal-containing gas. The processing gas may include an etching component-containing gas. The processing gas may include a carbon-containing gas. The processing gas may include a hydrogen-containing gas. Also, in one example, the processing gas may include, as a metal-containing gas, at least one selected from the group consisting of a tungsten-containing gas, a molybdenum-containing gas, and a titanium-containing gas immediately before the first region R1 is exposed. In one example, the processing gas includes a halide gas as an etching component. The metal-containing gas may be a metal halide-containing gas. The etching component is a component that etches the second region R2.

[0052] The metal-containing gas may include at least one selected from the group consisting of a tungsten-containing gas, a molybdenum-containing gas, and a titanium-containing gas. The tungsten-containing gas may include a tungsten halide gas. The tungsten halide gas may be tungsten hexafluoride (WF ６ ) gas, tungsten hexabromide (WBr ６ ) gas, tungsten hexachloride (WCl ６ ) Gas and WF ５ The tungsten-containing gas may include at least one of tungsten hexacarbonyl (W(CO) ６ The molybdenum-containing gas may include a molybdenum halide gas. The molybdenum halide gas may include molybdenum hexafluoride (MoF ６ ) gas, and molybdenum hexachloride (MoCl ６The titanium-containing gas may include at least one selected from the group consisting of titanium tetrachloride (TiCl ４ ) may also be included.

[0053] The etching component-containing gas includes a halogenated gas. The halogenated gas may include at least one selected from the group consisting of a fluorine-containing gas, a chlorine-containing gas, and a bromine-containing gas. The fluorine-containing gas may include a fluorocarbon gas.

[0054] The carbon-containing gas is CH ４ Gas, C ２ H ２ Gas, C ２ H ４ Gas, CH ３ F gas, CH ２ F ２ Gas, CHF ３ The gas may include at least one selected from the group consisting of a nitrogen gas and a CO gas.

[0055] The hydrogen-containing gas is H ２ Gas, SiH ４ Gas and NH ３ The gas may include at least one selected from the group consisting of:

[0056] The process gas may further include a noble gas, such as argon gas, helium gas, xenon gas, or neon gas. ２ ) gas.

[0057] In the method MT, step ST3 is then performed. In step ST3, the second region R2 is etched using plasma PL generated from the processing gas in the chamber 10. In step ST3, the second region R2 may be etched so as to expose a shoulder portion SH of the recess R1a of the first region R1. Step ST3 is performed while the processing gas supplied in step ST2 is present in the chamber. Step ST3 may also be performed while step ST2 is being performed.

[0058] 10 is a timing chart relating to one step of a plasma processing method according to one exemplary embodiment. In FIG. 10, "HF" indicates the power level of the source high frequency signal HF supplied by the first RF generator 31a for generating plasma. Also, "MF" ON indicates that the first sequence is being supplied to the substrate support 11 from the bias power supply 50, and "MF" OFF indicates that the supply of the first sequence is stopped. The first sequence is a sequence S of a plurality of voltage pulses VP whose voltage levels are increased or decreased stepwise within a period CY as shown in FIG. 4, FIG. 6, or FIG. 7. ＶＰ Furthermore, "LF" ON indicates that the second sequence is being supplied to the substrate support 11 from the bias power supply 50, and "LF" OFF indicates that the supply of the second sequence is stopped. The second sequence is a sequence S of a plurality of voltage pulses VP having the same and constant voltage level. ＶＰ is.

[0059] 10 , the process ST3 includes a first period P1, a second period P2, a third period P3, and a fourth period P4. During the first period P1, the control unit 2 controls the first RF generating unit 31 a (i.e., the high-frequency power supply) to supply a source high-frequency signal HF having a first power level L1 to generate a plasma PL from the processing gas. During the first period P1, the supply of the first sequence and the second sequence may be stopped. During the first period P1, chemical species from the plasma PL are deposited on the surface of the substrate W to form a deposit DP as shown in FIG. 11 . In one embodiment, the deposit DP is formed of tungsten, WF ６ The metal inclusions may include the above-mentioned metal inclusions.

[0060] The second period P2 is a period following or following the first period P1. During the second period P2, the control unit 2 controls the first RF generator 31a to supply a source radio frequency signal HF having a second power level L2 to generate a plasma PL from the processing gas. The second power level L2 may be lower than the first power level L1. Also, during the second period P2, the control unit 2 controls the bias power supply 50 to supply a first sequence to the substrate support 11. The maximum voltage level of the multiple voltage pulses VP in the first sequence during the second period P2 may be lower than the constant voltage levels of the multiple voltage pulses VP in the second sequence during the third period P3 and the fourth period P4. During the second period P2, ions from the plasma PL are attracted to the deposit DP, modifying the deposit DP. During the second period P2, the deposits DP etched by ions from the plasma PL may re-adhere to the shoulder portion SH and the like.

[0061] The third period P3 is a period following or following the second period P2. During the third period P3, the control unit 2 controls the first RF generator 31a to supply a source radio frequency signal HF having a third power level L3 to generate a plasma PL from the processing gas. The third power level L3 may be lower than the first power level L1. The third power level L3 may be the same as or different from the second power level L2. During the third period P3, the control unit 2 controls the bias power supply 50 to supply a second sequence to the substrate support 11. During the third period P3, highly energetic ions from the plasma PL are attracted to the deposit DP, etching the deposit DP on the second region R2 and the second region R2. Note that the angular distribution of ions during the third period P3 may be wider than the angular distribution of ions during the fourth period P4.

[0062] The fourth period P4 is a period following or following the third period P3. During the fourth period P4, the controller 2 controls the first RF generator 31a to set the power level of the source radio frequency signal HF to a fourth power level L4. The fourth power level L4 is lower than the second power level L2 and the third power level L3. The fourth power level L4 may be zero. Also during the fourth period P4, the controller 2 controls the bias power supply 50 to supply a second sequence to the substrate support 11. During the fourth period P4, ions in the plasma PL remaining in the chamber 10 are attracted to the substrate W to further etch the second region R2. During the fourth period P4, the amount of ion flux and the energy of the ions are appropriately adjusted, and the ions are supplied to the second region R2 with relatively high vertical linearity. This results in a highly vertical shape being formed on the substrate W by etching the second region R2 (see, for example, FIG. 12 ). At the end of the fourth period P4, the deposit DP on the substrate W may have disappeared.

[0063] In the subsequent step STJ, it is determined whether a stop condition is satisfied. The stop condition is satisfied, for example, when the number of repetitions of the cycle including step ST2 and step ST3 reaches a predetermined number. If the stop condition is not satisfied, the cycle including step ST2 and step ST3 is repeated. On the other hand, if the stop condition is satisfied, the method MT ends.

[0064] Below, examples of processing circuits that can be used as one or more processing circuits in a plasma processing apparatus, such as the control unit 2, the control unit 50c, the power control unit 51c, and the pulse control unit 52c, are described. FIG. 13 is a block diagram of a processing circuit that implements the operations described herein on a computer. FIG. 13 illustrates a processing circuit 130 that can be used to control a control process on any computer. The descriptions or blocks in the flowcharts represent modules, segments, or portions of code that include one or more executable instructions for implementing specific logical functions or steps of the process. As will be understood by those skilled in the art, other examples having functions that can be executed in an order different from that shown or described, such as substantially simultaneously or in reverse order, depending on the functionality involved, are included within the scope of exemplary embodiments of the present disclosure. The various elements, features, and processes described herein may be used independently of each other or combined in various ways. All conceivable combinations and subcombinations may be included within the scope of the present disclosure.

[0065] In Figure 13, processing circuitry 130 includes a CPU 1200 that performs one or more of the control processes described above and / or below. Process data and instructions may be stored in memory 1202. These process data and instructions may be stored on a storage medium disk 1204, such as a hard disk drive (HDD) or a portable storage medium, or may be stored remotely. Furthermore, the claimed disclosure is not limited by the form of computer-readable medium on which instructions for processes according to the present invention are stored. For example, these instructions may be stored on a CD, DVD, flash memory, RAM, ROM, PROM, EPROM, EEPROM, hard disk, or any other information processing device, such as a server and / or computer, with which processing circuitry 130 communicates.

[0066] Additionally, the claimed disclosure may be provided as a utility application, a background daemon, a component of an operating system, or a combination thereof. The claimed disclosure may be executed in conjunction with a CPU 1200 and an operating system known to those skilled in the art, such as Microsoft Windows, UNIX, Solaris, LINUX, Apple MAC-OS, or the like.

[0067] The hardware elements making up the processing circuit 130 can be realized by various circuit elements. Furthermore, each function of the above-described embodiments can be implemented by a circuit including one or more processing circuits. As shown in FIG. 13, the processing circuit includes a specifically programmed processing unit, such as a processing unit (CPU) 1200. The processing circuit also includes devices such as application specific integrated circuits (ASICs) or conventional circuit components configured to perform the described functions.

[0068] 13, processing circuitry 130 includes a CPU 1200 that performs the above-described processing. Processing circuitry 130 may be a general-purpose computer or a specialized machine. In one embodiment, processing circuitry 130 functions as a specialized machine when processing device 1200 is programmed to control plasma generation unit 12 and gas supply unit 20 and / or to control bias power supply 50.

[0069] Alternatively or additionally, CPU 1200 may be implemented on an FPGA, ASIC, PLD, or using discrete logic circuitry, as will be appreciated by those skilled in the art. Furthermore, CPU 1200 may be implemented as multiple processing units cooperating to perform in parallel the instructions of the processes of the present invention described above.

[0070] The processing circuitry 130 of Figure 13 also includes a network controller 1206, such as an Intel Ethernet PRO network interface card from Intel Corporation of America, for interfacing with a network 1228. As can be appreciated, the network 1228 may be a public network such as the Internet, a private network such as a LAN or WAN, or any combination thereof, and may also include sub-networks such as PSTN or ISDN. The network 1228 may also be wired, such as an Ethernet network, or wireless, such as a cellular network including EDGE, 3G, and 4G wireless cellular systems. The wireless network may also be Wi-Fi, Bluetooth, or any other known form of wireless communication.

[0071] The processing circuitry 130 further includes a display device controller 1208, such as a graphics card or graphics adapter, for interfacing with a display device 1210, such as a monitor. A general-purpose I / O interface 1212 interfaces with a keyboard and / or mouse 1214 and a touch panel 1216, which may be integral with or separate from the display device 1210. The general-purpose I / O interface also connects to various peripheral devices 1218, such as printers and scanners.

[0072] The storage controller 1224 is connected to the storage media disk 1204 via a communication bus 1226, such as ISA, EISA, VESA, PCI, etc., and all components of the processing circuit 130 are connected to each other. The display device 1210, keyboard and / or mouse 1214, and the general features and functions of the display device controller 1208, storage controller 1224, network controller 1206, audio controller 1220, and general purpose I / O interface 1212 are not described herein for the sake of brevity, as they are well known.

[0073] The exemplary circuit elements described in this disclosure may be substituted with other elements and may have different structures than the examples described herein. Furthermore, circuits configured to implement the features described herein may be implemented in multiple circuit units (e.g., chips), or these features may be combined into the circuitry of a single chipset.

[0074] The functions and features described herein may also be performed by various distributed components on a system. For example, one or more processing devices may perform the functions of these systems, where the processing devices are distributed across multiple components communicating within a network. Distributed components may include various human interface and communication devices (e.g., display monitors, smartphones, tablets, personal digital assistants (PDAs)), as well as one or more client and server machines that can share processing. The network may be a private network, such as a LAN or WAN, or a public network, such as the Internet. Input to the system may be received directly by a user or remotely in real time or as a batch process. Furthermore, portions of the embodiments may be implemented on modules or hardware other than those described above. Accordingly, other embodiments are within the scope of the claims.

[0075] 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.

[0076] 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.

[0077] Various exemplary embodiments included in the present disclosure are now described in [E1] to [E19] below.

[0078] a bias power supply configured to supply a sequence of voltage pulses to the substrate support by generating voltage pulses at a time interval that is the reciprocal of a first frequency to attract ions from the plasma to a substrate on the substrate support, wherein the bias power supply is configured to stepwise increase or decrease a voltage level of a plurality of voltage pulses included in the sequence within a period having a time length that is the reciprocal of a second frequency that is lower than the first frequency and is in the range of 20 kHz to 100 kHz, and to repeat the period.

[0079] [E2] The plasma processing apparatus according to E1, wherein each of the plurality of voltage pulses has a voltage level in a negative direction relative to a reference potential, and the voltage level of each of the plurality of voltage pulses is a difference between the reference potential and the potential of the voltage pulse.

[0080] [E3] The plasma processing apparatus according to E1 or E2, wherein the bias power supply includes: a variable DC power supply; a pulse generator configured to generate the sequence of voltage pulses by pulsing an output voltage of the variable DC power supply; and at least one controller configured to control the variable DC power supply and the pulse generator, and the at least one controller configured to control the variable DC power supply to change a voltage level of the output voltage in order to increase or decrease the voltage level of the plurality of voltage pulses in a stepwise manner.

[0081] [E4] The apparatus further comprises a main controller, wherein the main controller is configured to perform the following steps, with the substrate, the first region including silicon and nitrogen and the second region including silicon and oxygen, being placed on the substrate support: (a) supplying a process gas from the gas supply unit into the chamber; and (b) etching the second region using plasma generated from the process gas in the chamber, wherein (b) comprises: (b1) supplying the source radio frequency signal having a first power level from the radio frequency power supply during a first period to generate plasma from the process gas in the chamber and deposit chemical species from the plasma on the substrate; (b2) supplying the source radio frequency signal having a second power level lower than the first power level from the radio frequency power supply during a second period after the first period to generate plasma from the process gas, the second power level being lower than the first power level, the second power level being lower than the first power level, to the substrate support; and (b3) (b3) a step of supplying the source radio frequency signal having a third power level lower than the first power level from the radio frequency power supply to generate plasma from the process gas and etch the second region during a third period after the second period, the step including supplying the sequence of voltage pulses from the bias power supply to the substrate support; and (b4) a step of supplying the sequence of voltage pulses from the bias power supply to the substrate support during a fourth period after the third period to further etch the second region using the plasma generated from the process gas, the step including setting the power level of the source radio frequency signal to a fourth power level lower than the second power level and the third power level, wherein the bias power supply is configured to: in (b3) and (b4), set the voltage levels of the plurality of voltage pulses included in the sequence to a substantially constant level; and in (b2), increase or decrease the voltage levels of the plurality of voltage pulses included in the sequence within the period stepwise, and repeat the period.The plasma processing apparatus according to any one of E1 to E3.

[0082] [E5] The plasma processing apparatus according to E4, wherein the bias power supply is configured to set a maximum voltage level of the plurality of voltage pulses in (b2) to a level lower than the voltage levels of the plurality of voltage pulses in (b3) and (b4).

[0083] [E6] The plasma processing apparatus according to E4 or E5, wherein the fourth power level is zero.

[0084] [E7] The plasma processing apparatus according to any one of E4 to E6, wherein the second power level and the third power level are the same.

[0085] [E8] The plasma processing apparatus according to any one of E4 to E7, wherein the processing gas contains a metal that constitutes the chemical species and an etching component for etching the second region.

[0086] [E9] The plasma processing apparatus according to any one of E4 to E8, wherein the main control unit is configured to repeat (b).

[0087] [E10] The plasma processing apparatus according to any one of E1 to E9, wherein the bias power supply is configured to be able to change the duty ratio of the voltage pulse.

[0088] [E11] A bias power supply for use in a plasma processing apparatus, comprising: a variable DC power supply; a pulse generator configured to generate a sequence of voltage pulses by pulsing an output voltage of the variable DC power supply; and at least one controller configured to control the variable DC power supply and the pulse generator, wherein the at least one controller is configured to: control the pulse generator to generate the voltage pulses at a time interval that is the reciprocal of a first frequency and supply the sequence to the substrate support in order to attract ions from plasma in a chamber of the plasma processing apparatus to a substrate on a substrate support in the chamber; and control the variable DC power supply to change the voltage level of the output voltage so as to increase or decrease stepwise the voltage level of a plurality of voltage pulses included in the sequence within a period having a time length that is the reciprocal of a second frequency that is lower than the first frequency and is in the range of 20 kHz to 100 kHz, and to repeat the period.

[0089] [E12] The bias power supply of E11, wherein each of the plurality of voltage pulses has a voltage level that is negative relative to a reference potential, and the voltage level of each of the plurality of voltage pulses is the difference between the reference potential and the potential of the voltage pulse.

[0090] [E13] A plasma processing method comprising: (a) preparing a substrate in a chamber of a plasma processing apparatus, the substrate including a first region containing silicon and nitrogen and a second region containing silicon and oxygen; (b) supplying a processing gas into the chamber of the plasma processing apparatus; and (c) etching the second region using plasma generated from the processing gas in the chamber, wherein the plasma processing apparatus includes a bias power supply configured to supply a sequence of voltage pulses to the substrate support by generating voltage pulses at a time interval that is the reciprocal of a first frequency to attract ions from the plasma to the substrate on the substrate support in the chamber, and wherein (c) includes stepwise increasing or decreasing a voltage level of a plurality of voltage pulses included in the sequence within a period having a time length that is the reciprocal of a second frequency that is lower than the first frequency and is in the range of 20 kHz to 100 kHz, and repeating the period.

[0091] [E14] The plasma processing apparatus includes a radio frequency power supply configured to supply a source radio frequency signal to generate plasma from the process gas, and (c) comprises: (c1) supplying the source radio frequency signal having a first power level from the radio frequency power supply to generate plasma from the process gas in the chamber during a first time period and depositing chemical species from the plasma on the substrate; (c2) supplying the source radio frequency signal having a second power level lower than the first power level from the radio frequency power supply to generate plasma from the process gas during a second time period after the first time period, the second power level being lower than the first power level, the second power level being lower than the first power level, the bias power supply supplying the sequence of voltage pulses to the substrate support; and (c3) supplying the source radio frequency signal having a third power level lower than the first power level from the radio frequency power supply to generate plasma from the process gas and etch the second region during a third time period after the second time period, the third power level being lower than the first power level, the bias power supply supplying the sequence of voltage pulses to the substrate support; and (c4) and (c2) a step of supplying the sequence of voltage pulses from the bias power supply to the substrate support to further etch the second region using the plasma generated from the process gas during a fourth period after the third period, the step including setting a power level of the source radio frequency signal to a fourth power level lower than the second power level and the third power level; wherein in (c3) and (c4), the voltage levels of the plurality of voltage pulses included in the sequence are set to a substantially constant level; and in (c2), the voltage levels of the plurality of voltage pulses included in the sequence within the period are increased or decreased stepwise, and the period is repeated.

[0092] [E15] The plasma processing method according to E14, wherein a maximum voltage level of the plurality of voltage pulses in (c2) is lower than the voltage levels of the plurality of voltage pulses in (c3) and (c4).

[0093] [E16] The plasma processing method according to E14 or E15, wherein the fourth power level is zero.

[0094] [E17] The plasma processing method according to any one of E14 to E16, wherein the second power level and the third power level are the same.

[0095] [E18] The plasma processing method according to any one of E14 to E17, wherein the processing gas contains a metal that constitutes the chemical species and an etching component for etching the second region.

[0096] [E19] The plasma processing method according to any one of E13 to E18, wherein (c) is repeated.

[0097] 1... plasma processing apparatus, 10... plasma processing chamber, 11... substrate support section, 12... plasma generation section, 20... gas supply section, 50... bias power supply, 50c... control section, 51c... power supply control section, 51... variable DC power supply, 52... pulse generator.

Claims

a bias power supply configured to supply a sequence of voltage pulses to the substrate support by generating voltage pulses at a time interval that is the reciprocal of a first frequency to attract ions from the plasma to a substrate on the substrate support, wherein the bias power supply is configured to stepwise increase or decrease the voltage level of a plurality of voltage pulses included in the sequence within a period having a time length that is the reciprocal of a second frequency that is lower than the first frequency and is in the range of 20 kHz to 100 kHz, inclusive, and to repeat the period.

2. A plasma processing apparatus as claimed in claim 1, wherein each of said plurality of voltage pulses has a voltage level in a negative direction relative to a reference potential, and said voltage level of each of said plurality of voltage pulses is the difference between said reference potential and the potential of said voltage pulse.

3. The plasma processing apparatus according to claim 1 or 2, wherein the bias power supply includes: a variable DC power supply; a pulse generator configured to generate the sequence of voltage pulses by pulsing the output voltage of the variable DC power supply; and at least one controller configured to control the variable DC power supply and the pulse generator, and the at least one controller configured to control the variable DC power supply to change the voltage level of the output voltage in order to increase or decrease the voltage level of the plurality of voltage pulses in a stepwise manner.

4. The apparatus further comprises a main control unit, wherein the main control unit is configured to execute the following steps, with the substrate, which includes a first region containing silicon and nitrogen and a second region containing silicon and oxygen, placed on the substrate support: (a) supplying a process gas from the gas supply unit into the chamber; and (b) etching the second region using plasma generated from the process gas in the chamber, wherein (b) comprises: (b1) supplying the source radio frequency signal having a first power level from the radio frequency power supply during a first period to generate plasma from the process gas in the chamber and deposit chemical species from the plasma on the substrate; (b2) supplying the source radio frequency signal having a second power level lower than the first power level from the radio frequency power supply during a second period after the first period to generate plasma from the process gas, the second power level including supplying the sequence of voltage pulses from the bias power supply to the substrate support; and (b3) (b3) a step of supplying the source radio frequency signal having a third power level lower than the first power level from the radio frequency power supply to generate plasma from the process gas and etch the second region during a third period after the second period, the step including supplying the sequence of voltage pulses from the bias power supply to the substrate support; and (b4) a step of supplying the sequence of voltage pulses from the bias power supply to the substrate support during a fourth period after the third period to further etch the second region using the plasma generated from the process gas, the step including setting the power level of the source radio frequency signal to a fourth power level lower than the second power level and the third power level, wherein the bias power supply is configured to: in (b3) and (b4), set the voltage levels of the plurality of voltage pulses included in the sequence to a substantially constant level; and in (b2), increase or decrease the voltage levels of the plurality of voltage pulses included in the sequence within the period stepwise, and repeat the period.

3. The plasma processing apparatus according to claim 1 or 2.

5. The plasma processing apparatus of claim 4, wherein the bias power supply is configured to set the maximum voltage level of the plurality of voltage pulses in (b2) to a level lower than the voltage levels of the plurality of voltage pulses in (b3) and (b4).

6. The plasma processing apparatus of claim 4, wherein the fourth power level is zero.

7. The plasma processing apparatus of claim 4, wherein the second power level and the third power level are the same as each other.

8. The plasma processing apparatus according to claim 4, wherein the processing gas contains an etching component for etching the metal constituting the chemical species and the second region.

9. The plasma processing apparatus according to claim 4, wherein the main control unit is configured to repeat (b).

10. The plasma processing apparatus according to claim 1 or 2, wherein the bias power supply is configured to be able to change the duty ratio of the voltage pulse.

11. A bias power supply for use in a plasma processing apparatus, comprising: a variable DC power supply; a pulse generator configured to generate a sequence of voltage pulses by pulsing the output voltage of the variable DC power supply; and at least one controller configured to control the variable DC power supply and the pulse generator, wherein the at least one controller is configured to: control the pulse generator to generate the voltage pulses at a time interval that is the reciprocal of a first frequency and supply the sequence to the substrate support in order to attract ions from plasma in a chamber of the plasma processing apparatus to a substrate on a substrate support in the chamber; and control the variable DC power supply to change the voltage level of the output voltage so as to increase or decrease stepwise the voltage level of a plurality of voltage pulses included in the sequence within a period having a time length that is the reciprocal of a second frequency that is lower than the first frequency and is in the range of 20 kHz to 100 kHz, and to repeat the period.

12. A bias power supply as recited in claim 11, wherein each of said plurality of voltage pulses has a negative-going voltage level relative to a reference potential, and the voltage level of each of said plurality of voltage pulses is the difference between said reference potential and the potential of said voltage pulse.

13. A plasma processing method comprising: (a) providing a substrate in a chamber of a plasma processing apparatus, the substrate including a first region containing silicon and nitrogen and a second region containing silicon and oxygen; (b) supplying a processing gas into the chamber of the plasma processing apparatus; and (c) etching the second region using plasma generated from the processing gas in the chamber, wherein the plasma processing apparatus includes a bias power supply configured to supply a sequence of voltage pulses to the substrate support by generating voltage pulses at a time interval that is the reciprocal of a first frequency to attract ions from the plasma to the substrate on a substrate support in the chamber, and (c) comprising stepwise increasing or decreasing the voltage level of a plurality of voltage pulses included in the sequence within a period having a time length that is the reciprocal of a second frequency that is lower than the first frequency and is in the range of 20 kHz to 100 kHz, and repeating the period.

14. The plasma processing apparatus includes a radio frequency power supply configured to supply a source radio frequency signal to generate plasma from the process gas, and (c) includes: (c1) supplying the source radio frequency signal having a first power level from the radio frequency power supply to generate plasma from the process gas in the chamber during a first time period and depositing chemical species from the plasma on the substrate; (c2) supplying the source radio frequency signal having a second power level lower than the first power level from the radio frequency power supply to generate plasma from the process gas during a second time period after the first time period, the second power level including supplying the sequence of voltage pulses from the bias power supply to the substrate support; (c3) supplying the source radio frequency signal having a third power level lower than the first power level from the radio frequency power supply to generate plasma from the process gas and etch the second region during a third time period after the second time period, the third power level including supplying the sequence of voltage pulses from the bias power supply to the substrate support; and (c4).

14. The plasma processing method of claim 13, further comprising: a step of supplying the sequence of voltage pulses from the bias power supply to the substrate support to further etch the second region using the plasma generated from the processing gas during a fourth period after the third period, the step including setting a power level of the source radio frequency signal to a fourth power level lower than the second power level and the third power level; wherein in (c3) and (c4), voltage levels of the plurality of voltage pulses included in the sequence are set to a substantially constant level; and in (c2), voltage levels of the plurality of voltage pulses included in the sequence within the period are increased or decreased stepwise, and the period is repeated.

15. The plasma processing method of claim 14, wherein a maximum voltage level of the plurality of voltage pulses in (c2) is lower than the voltage levels of the plurality of voltage pulses in (c3) and (c4).

16. The plasma processing method according to claim 14 or 15, wherein the fourth power level is zero.

17. The plasma processing method according to claim 14 or 15, wherein the second power level and the third power level are the same as each other.

18. The plasma processing method according to claim 14 or 15, wherein the processing gas contains a metal constituting the chemical species and an etching component for etching the second region.

19. The plasma processing method according to any one of claims 13 to 15, wherein (c) is repeated.

Images