Etching method and plasma processing apparatus

Abstract

To provide technique increasing an etching rate in etching which forms in a substrate, a concave portion having a high aspect ratio.SOLUTION: An etching method that is disclosed comprises a step of mounting a substrate on a substrate support portion within a chamber of a plasma processing apparatus. The etching method further comprises a step of etching the substrate to form a concave portion in the substrate by means of plasma generated within the chamber. In the step of etching, an electric bias is supplied to the substrate support portion in order to draw ions into the substrate from the plasma. In the step of etching, at least one of a bias frequency which is an inverse of time length of a waveform period of the electric bias and a pulse duty ratio of a pulsed electric bias is changed to maintain an energy flux of ions for the substrate.SELECTED DRAWING: Figure 4

Description

[Technical Field]

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

[0002] A plasma processing apparatus is used for etching a substrate. The plasma processing apparatus includes a chamber, a substrate support, a radio frequency power supply, and a bias power supply. The substrate support is provided within the chamber. The radio frequency power supply supplies source radio frequency power for generating plasma. The bias power supply supplies bias radio frequency power to the substrate support to attract ions to the substrate. Patent Document 1 listed below discloses plasma etching using such a plasma processing apparatus. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2014-187231 Summary of the Invention [Problem to be solved by the invention]

[0004] The present disclosure provides a technique for increasing the etching rate in etching to form recesses having high aspect ratios in a substrate. [Means for solving the problem]

[0005] In one exemplary embodiment, an etching method is provided. The etching method includes placing a substrate on a substrate support in a chamber of a plasma processing apparatus. The etching method further includes etching the substrate to form a recess in the substrate with plasma generated in the chamber. During the etching step, an electric bias is supplied to the substrate support to attract ions from the plasma to the substrate. During the etching step, at least one of a bias frequency, which is the inverse of the time length of a waveform period of the electric bias, and a pulse duty ratio of the pulsed electric bias is changed to maintain an energy flux of ions to the substrate. [Effects of the Invention]

[0006] According to one exemplary embodiment, it is possible to increase the etching rate in etching to form a recess having a high aspect ratio in a substrate. [Brief explanation of the drawings]

[0007] [Figure 1] FIG. 1 is a diagram illustrating an example of the configuration of a plasma processing system. [Figure 2] FIG. 1 is a diagram illustrating an example of the configuration of a capacitively coupled plasma processing apparatus. [Figure 3] Each of FIGS. 3(a), 3(b), and 3(c) is a timing chart of an electrical bias associated with a plasma processing apparatus according to an example embodiment. [Figure 4] 1 is a flow diagram of an etching method according to an exemplary embodiment. [Figure 5] Each of FIGS. 5(a), 5(b), 5(c), and 5(d) is a timing chart of an electrical bias associated with an etching method according to one example embodiment. [Figure 6] FIG. 2 is a diagram illustrating an example of a bias power supply. DETAILED DESCRIPTION OF THE INVENTION

[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 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 11, and a plasma generation unit 12. The plasma processing chamber 10 has a plasma processing space. The plasma processing chamber 10 also has at least one gas supply port for supplying at least one processing gas to the plasma processing space and at least one gas exhaust port for exhausting gas from the plasma processing space. The gas supply port is connected to a gas supply unit 20 (described later), and the gas exhaust port is connected to an exhaust system 40 (described later). The substrate support 11 is disposed in the plasma processing space and has a substrate support surface for supporting a substrate.

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

[0011] The controller 2 processes computer-executable instructions that cause the plasma processing apparatus 1 to perform various processes described in this disclosure. The controller 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 controller 2 may be included in the plasma processing apparatus 1. The controller 2 may include a processor 2a1, a storage unit 2a2, and a communication interface 2a3. The controller 2 may be implemented by, for example, a computer 2a. The processor 2a1 may be configured to read a program from the storage unit 2a2 and execute the read program to perform various control operations. The 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 processor 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 processor 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 unit 20, a power supply system 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 substrate support 11 is 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 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.

[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 processing 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 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 showerhead 13 also includes at least one upper electrode. In addition to the showerhead 13, the gas introduction unit 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 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 regulating valve regulates the pressure in the plasma processing space 10s. The vacuum pump may include a turbomolecular pump, a dry pump, or a combination thereof.

[0021] The power supply system 30 includes a high frequency power supply 31 and a bias power supply 32. The high frequency power supply 31 constitutes the plasma generating unit 12 of one embodiment. The high frequency power supply 31 is configured to generate a source high frequency power RF. The source high frequency power RF has a source frequency f RF That is, the source radio frequency power RF has a frequency equal to the source frequency fRF It has a sinusoidal waveform with a source frequency f RF The frequency of the RF power source 31 may be in the range of 13 MHz to 100 MHz. The RF power source 31 is electrically connected to the RF electrode via a matching box 33 and is configured to supply source RF power RF to the RF electrode. The RF electrode may be provided within the substrate support 11. The RF electrode may be at least one electrode provided within the conductive member or ceramic member 1111a of the base 1110. Alternatively, the RF electrode may be an upper electrode. When the source RF power RF is supplied to the RF electrode, plasma is generated from the gas in the chamber 10.

[0022] The matching circuit 33 has a variable impedance. The variable impedance of the matching circuit 33 is set so as to reduce reflection of the source high frequency power RF from the load. The matching circuit 33 can be controlled by the control unit 2, for example.

[0023] The bias power supply 32 is electrically coupled to the substrate support 11. The bias power supply 32 is electrically connected to a bias electrode in the substrate support 11 and is configured to supply an electric bias EB to the bias electrode. The bias electrode may be at least one electrode provided in the conductive member or ceramic member 1111a of the base 1110. The bias electrode may be common to the radio frequency electrode. When the electric bias EB is supplied to the bias electrode, ions from the plasma are attracted to the substrate W.

[0024] 3(a), 3(b), and 3(c) will be referred to below in conjunction with FIG. 2. Each of FIG. 3(a), 3(b), and 3(c) is a timing chart of an electric bias associated with a plasma processing apparatus according to an exemplary embodiment. The electric bias EB has a waveform period CY and is periodically supplied to the bias electrode from the bias power supply 32. The waveform period of the electric bias EB is a bias frequency f EB The bias frequency f EBis, for example, a frequency of 100 kHz or more and 50 MHz or less. The time length of the waveform period CY of the electrical bias EB is EB is the reciprocal of

[0025] The electrical bias EB is EB That is, the electric bias EB may be a bias high frequency power LF having a frequency of the bias frequency f EB In this case, the bias power supply 32 is electrically connected to the bias electrode via a matching box 34. The variable impedance of the matching box 34 is set to reduce the reflection of the bias high frequency power LF from the load.

[0026] Alternatively, the electric bias EB may include a voltage pulse PV. The voltage pulse PV is applied to the bias electrode within a waveform period CY. The voltage pulse PV is periodically applied to the bias electrode at time intervals equal to the time length of the waveform period CY. The waveform of the voltage pulse PV may be a square wave, a triangular wave, or any other waveform. The polarity of the voltage pulse PV is set to generate a potential difference between the substrate W and the plasma so as to attract ions from the plasma to the substrate W. The voltage pulse PV may be a negative voltage pulse or a negative DC voltage pulse. When the electric bias EB includes the voltage pulse PV, the plasma processing apparatus 1 does not need to include the matching unit 34.

[0027] 6, the bias power supply 32 may include a DC power supply 32a and a modulator 32b. The modulator 32b is configured to modulate the voltage (e.g., a DC voltage) output from the DC power supply 32a to generate a voltage pulse PV.

[0028] As shown in Fig. 3(b), the bias power supply 32 may supply a pulsed electric bias EB. That is, the bias power supply 32 may alternately repeat the supply of the electric bias EB ("ON" in Fig. 3(b)) and the stop of the supply of the electric bias EB ("OFF" in Fig. 3(b)). The period P during which the electric bias EB is supplied is ON and the period P during which the supply of the electric bias EB is stopped. OFF Pulse period P C Within the period P ON The ratio of the pulses, i.e., the pulse duty ratio PD, can be specified to the bias power supply 32 by the control unit 2. ON is supplied periodically with a waveform period CY.

[0029] Alternatively, as shown in Figure 3(c), the electrical bias EB may be supplied as a continuous wave, i.e., the electrical bias EB may be supplied continuously until its supply is stopped, or may be supplied periodically with a waveform period CY until its supply is stopped.

[0030] An etching method according to one exemplary embodiment will be described below with reference to Figures 4 and 5(a), 5(b), 5(c), and 5(d). Figure 4 is a flow chart of the etching method according to one exemplary embodiment. Figures 5(a), 5(b), 5(c), and 5(d) are timing charts of electrical biases associated with the etching method according to one exemplary embodiment.

[0031] 4 (hereinafter referred to as "method MT") can be performed using a plasma processing apparatus 1. Furthermore, method MT can be performed by controlling each part of the plasma processing apparatus 1 by a control unit 2.

[0032] The method MT starts with step STa, in which the substrate W is placed on the substrate support 11.

[0033] Next, step STb is performed. In step STb, the substrate W is etched by plasma generated in the chamber 10 to form recesses in the substrate W. In step STb, for example, a film on the substrate W is etched.

[0034] In step STb, the gas supply unit 20 is controlled to supply a process gas into the chamber 10. In step STb, the exhaust system 40 is controlled to adjust the pressure in the chamber 10 to a designated pressure. In step STb, the plasma generation unit 12 is controlled to generate plasma from the process gas. In one embodiment, the high frequency power supply 31 is controlled to supply source high frequency power RF to generate the plasma. Also, in step STb, the bias power supply 32 is controlled to supply an electric bias EB to the substrate support 11 to attract ions from the plasma.

[0035] In step STb, the bias power supply 32 is operated at a bias frequency f EB and pulse duty ratio PD.

[0036] The etching rate depends on the product of the ion energy and the amount of ions supplied, i.e., the ion flux. EB Alternatively, the pulse duty ratio PD is changed so as to maintain the product of the ion energy and ion flux, i.e., the ion energy flux, relative to the substrate W. Therefore, the method MT makes it possible to increase the etching rate in etching to form recesses having high aspect ratios in the substrate W.

[0037] In one embodiment, as shown in FIG. 5(a), in step ST2, the bias power supply 32 operates at a bias frequency f EB may be decreased over time. The ion energy is controlled by the bias frequency f EBTherefore, in this case, as the depth of the recess formed in the substrate W increases, the energy of the ions supplied to the substrate W is increased. Also, the ion flux increases as the bias frequency f EB Therefore, the bias frequency f EB By decreasing ρ over time, it is possible to maintain the energy flux of the ions.

[0038] In another embodiment, as shown in FIG. 5(b), in step ST2, the bias power supply 32 operates at a bias frequency f EB The bias frequency f EB When the bias frequency f EB The ion flux increases when the bias frequency f EB By alternately increasing and decreasing the energy flux of the ions, it is possible to maintain the energy flux of the ions.

[0039] In yet another embodiment, as shown in FIG. 5(c), in step ST2, the bias power supply 32 may increase the pulse duty ratio PD over time. The ion energy increases as the pulse duty ratio PD increases. Therefore, in this case, the energy of the ions supplied to the substrate W increases as the depth of the recess formed in the substrate W increases. Furthermore, the ion flux decreases as the pulse duty ratio PD increases. Therefore, by increasing the pulse duty ratio PD over time, it is possible to maintain the ion energy flux.

[0040] In yet another embodiment, as shown in (d) of Figure 5, in step ST2, the bias power supply 32 may alternately increase and decrease the pulse duty ratio PD. When the pulse duty ratio PD is high, the ion energy increases, and when the pulse duty ratio PD is low, the ion flux increases. By alternately increasing and decreasing the pulse duty ratio PD, it is possible to maintain the ion energy flux.

[0041] 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.

[0042] Various exemplary embodiments included in the present disclosure are described below in [E1] to [E13].

[0043] [E1] placing a substrate on a substrate support within a chamber of a plasma processing apparatus; etching the substrate with a plasma generated in the chamber to form a recess in the substrate; Including, an electrical bias is applied to the substrate support to attract ions from the plasma to the substrate during the etching step; In the etching step, at least one of a bias frequency, which is the inverse of a time length of a waveform period of the electric bias, and a pulse duty ratio of the pulsed electric bias is changed so as to maintain an energy flux of ions to the substrate. Etching method. The etching rate depends on the product of ion energy and the amount of ions supplied, i.e., ion flux. In the embodiment of [E1], the bias frequency or pulse duty ratio is changed to maintain the product of ion energy and ion flux, i.e., the ion energy flux, relative to the substrate. Therefore, it is possible to increase the etching rate in etching to form recesses with high aspect ratios in the substrate.

[0044] [E2] The etching method according to [E1], wherein in the etching step, the bias frequency is decreased over time.

[0045] [E3] The etching method according to [E1], wherein the bias frequency is alternately increased and decreased in the etching step.

[0046] [E4] The etching method according to [E1], wherein in the etching step, the pulse duty ratio is increased over time.

[0047] [E5] The etching method according to [E1], wherein in the etching step, the pulse duty ratio is alternately increased and decreased.

[0048] [E6] The etching method according to any one of claims [E1] to [E5], wherein the electrical bias is a bias high frequency power having the bias frequency or a voltage pulse supplied periodically at a time interval equal to the reciprocal of the bias frequency.

[0049] [E7] a chamber; a substrate support disposed within the chamber; a plasma generating unit configured to generate plasma from the gas within the chamber; a bias power supply configured to generate an electrical bias to attract ions to a substrate disposed on the substrate support; Equipped with The bias power supply is configured to change at least one of a bias frequency, which is the inverse of a time length of a waveform period of the electrical bias, and a pulse duty ratio of the pulsed electrical bias, so as to maintain an energy flux of ions to the substrate.

[0050] [E8] The plasma processing apparatus according to [E7], wherein the bias power supply is configured to decrease the bias frequency over time.

[0051] [E9] The plasma processing apparatus according to [E7], wherein the bias power supply is configured to alternately increase and decrease the bias frequency.

[0052] [E10] The plasma processing apparatus according to [E7], wherein the bias power supply is configured to increase the pulse duty ratio over time.

[0053] [E11] The plasma processing apparatus according to [E7], wherein the bias power supply is configured to alternately increase and decrease the pulse duty ratio.

[0054] [E12] The plasma processing apparatus according to any one of [E7] to [E11], wherein the electrical bias is a bias high frequency power having the bias frequency or a voltage pulse supplied periodically at a time interval equal to the reciprocal of the bias frequency.

[0055] [E13] The bias power supply A DC power supply; a modulator configured to modulate a voltage output from the DC power supply to generate the voltage pulses; The plasma processing apparatus according to [E12], comprising:

[0056] 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]

[0057] 1... plasma processing apparatus, 10... chamber, 11... substrate support part, 12... plasma generation part, 31... high frequency power supply, 32... bias power supply

Claims

1. placing a substrate on a substrate support within a chamber of a plasma processing apparatus; etching the substrate with a plasma generated in the chamber to form a recess in the substrate; Including, an electrical bias is applied to the substrate support to attract ions from the plasma to the substrate during the etching step; In the etching step, a bias frequency, which is the reciprocal of the time length of a waveform period of the electrical bias output from a single power supply, is alternately increased and decreased so as to maintain an energy flux of ions to the substrate. Etching method.

2. An etching method as described in claim 1, wherein the electrical bias is a bias high-frequency power having the bias frequency or a voltage pulse supplied periodically at a time interval that is the reciprocal of the bias frequency.

3. A step of placing a substrate on a substrate support within a chamber of a plasma processing apparatus; etching the substrate with a plasma generated in the chamber to form a recess in the substrate; Including, an electrical bias is applied to the substrate support to attract ions from the plasma to the substrate during the etching step; During the etching step, a pulse duty ratio of the pulsed electrical bias is increased over time to maintain an energy flux of ions to the substrate; the pulsed electrical bias comprises voltage pulses periodically applied to the substrate support; Etching method.

4. a chamber; a substrate support disposed within the chamber; a plasma generating unit configured to generate plasma from the gas within the chamber; a bias power supply configured to generate an electrical bias to attract ions to a substrate disposed on the substrate support; Equipped with The bias power supplies are configured to alternately increase and decrease a bias frequency, which is the reciprocal of the time length of a waveform period of the electrical bias output from the single bias power supply, so as to maintain an energy flux of ions to the substrate.

5. A plasma processing apparatus as described in claim 4, wherein the electrical bias is a bias high-frequency power having the bias frequency or a voltage pulse supplied periodically at a time interval that is the reciprocal of the bias frequency.

6. A chamber; a substrate support disposed within the chamber; a plasma generating unit configured to generate plasma from the gas within the chamber; a bias power supply configured to generate an electrical bias to attract ions to a substrate disposed on the substrate support; Equipped with the bias power supply is configured to increase a pulse duty ratio of the pulsed electrical bias over time to maintain an energy flux of ions to the substrate; the pulsed electrical bias comprises voltage pulses periodically applied to the substrate support; Plasma processing equipment.

7. The bias power supply A DC power supply; a modulator configured to modulate a voltage output from the DC power supply to generate the voltage pulses; The plasma processing apparatus according to claim 5 or 6, comprising:

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