Plasma processing apparatus

Abstract

The present invention provides a plasma processing apparatus comprising: a chamber; comprising a lower electrode; an RF generation section that generates a pulsed RF signal to generate plasma within the chamber, the pulsed RF signal having a first electric power level in a first period within each period and a second electric power level smaller than the first electric power level in a second period within each period; a pulse voltage generation unit electrically connected to the lower electrode and generating a pulse voltage signal having a reference voltage level in a first period and including a sequence of a plurality of voltage pulses having a first voltage level in a second period, the absolute value of the first voltage level being greater than the absolute value of the reference voltage level; a microwave interferometer that monitors the electron density of the plasma within the chamber; and a control section that adjusts the first electrical power level based on the electron density during the first period, and adjusts the first voltage level based on the electron density during the second period.

Description

Technical Field

[0001] This invention relates to plasma processing apparatus. Background Technology

[0002] The etching apparatus disclosed in Patent Document 1 includes: a substrate electrode for applying high-frequency electrical power to a substrate to be etched; and a source electrode for generating plasma supplied to the substrate electrode. Furthermore, it includes: an electron density control unit that controls the high-frequency electrical power applied to the source electrode so that the electron density in the plasma supplied to the substrate electrode is a predetermined set value; and an ion energy control unit that controls the high-frequency electrical power applied to the substrate electrode so that the ion energy in the plasma supplied to the substrate electrode is a predetermined set value.

[0003] Existing technical documents

[0004] Patent documents

[0005] Patent Document 1: Japanese Patent Application Publication No. 2004-128236 Summary of the Invention

[0006] The technical problem that the invention aims to solve

[0007] The present invention provides a plasma processing device capable of suppressing time-varying changes in plasma conditions.

[0008] Technical solutions for solving technical problems

[0009] One aspect of the plasma processing apparatus of the present invention includes: a chamber; a substrate support disposed within the chamber and including a lower electrode; an RF generation unit configured to generate a pulsed RF signal to generate plasma within the chamber, the pulsed RF signal having a first power level in a first period of each cycle and a second power level lower than the first power level in a second period of each cycle; a pulsed voltage generation unit electrically connected to the lower electrode and configured to generate a pulsed voltage signal having a reference voltage level in the first period and including a sequence of multiple voltage pulses having the first voltage level in the second period, the absolute value of the first voltage level being greater than the absolute value of the reference voltage level; a microwave interferometer configured to monitor the electron density of the plasma within the chamber; and a control unit configured to adjust the first power level based on the electron density of the plasma monitored in the first period and to adjust the first voltage level based on the electron density of the plasma monitored in the second period.

[0010] Invention Effects

[0011] According to the present invention, it is possible to suppress time-dependent changes in plasma conditions. Attached Figure Description

[0012] Figure 1 This is a diagram illustrating an example of a plasma processing system according to a first embodiment of the present invention.

[0013] Figure 2 This is a schematic cross-sectional view showing an example of the structure of the plasma processing apparatus in the first embodiment.

[0014] Figure 3 This is a timing diagram illustrating an example of the variation in RF power and DC pulse supply timing and electron density in the first embodiment.

[0015] Figure 4 This is a timing diagram illustrating an example of the timing of the supply of RF power and DC pulses in the first embodiment.

[0016] Figure 5 yes Figure 4 A magnified timing diagram of a portion of the timing diagram shown.

[0017] Figure 6 This is a timing diagram illustrating an example of the variation in RF power and DC pulse supply timing and electron density in the first embodiment.

[0018] Figure 7 This is an example of a graph showing the change in electron density near the offset when the amount of sediment is at an appropriate level.

[0019] Figure 8 It is a schematic diagram showing sediment and etching when the amount of sediment is at an appropriate level.

[0020] Figure 9 This is a diagram illustrating an example of the change in electron density near the point of displacement when the amount of sediment is insufficient.

[0021] Figure 10 This is a schematic diagram illustrating sediment and etching under conditions of insufficient sediment quantity.

[0022] Figure 11 This is an example of a graph showing the change in electron density near the point of displacement when there is an excessive amount of sediment.

[0023] Figure 12 This is a schematic diagram illustrating sediment and etching when there is an excessive amount of sediment.

[0024] Figure 13 This is a diagram illustrating an example of a method for adjusting the electron density at the beginning of period P1.

[0025] Figure 14This is a diagram illustrating an example of a method for adjusting the electron density at the beginning of period P1.

[0026] Figure 15 This is a flowchart illustrating an example of the plasma control process in the first embodiment.

[0027] Figure 16 This is an example of a timing diagram representing one cycle of a synchronization pulse.

[0028] Figure 17 This is an example of a timing diagram representing one cycle of an offset pulse.

[0029] Figure 18 This is an example of a timing diagram representing one cycle of an offset pulse.

[0030] Figure 19 This is an example of a timing diagram representing one cycle of an offset pulse.

[0031] Figure 20 This is a graph illustrating an example of the change in electron density during the repetition period in the second embodiment.

[0032] Figure 21 This is a flowchart illustrating an example of the plasma control process in the second embodiment. Detailed Implementation

[0033] Hereinafter, embodiments of the plasma processing apparatus of the present invention will be described in detail with reference to the accompanying drawings. Furthermore, the technology of the present invention is not limited to the following embodiments.

[0034] In etching processes, the power level of the RF power supply (generating source RF power) is set as one of the parameters for plasma generation in the processing conditions (process conditions). However, when etching is performed over a long period, the impedance of the chamber changes when viewed from the RF power supply side due to the consumption of components within the chamber and the deposition of byproducts (deposits) on the components. With the same power level supplied from the RF power supply, the electron density of the generated plasma changes as the chamber impedance changes over time. That is, the plasma conditions change over time (time-dependent variation). This time-dependent variation of plasma conditions contributes to a decrease in etching rate and changes in etched shape (process shift). Therefore, it is necessary to suppress the time-dependent variation of plasma conditions.

[0035] (First Implementation)

[0036] [Structure of the plasma processing system]

[0037] Figure 1This figure illustrates an example of a plasma processing system according to a first embodiment of the present invention. 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. Furthermore, the plasma processing chamber 10 has at least one gas supply port for supplying at least one processing gas to the plasma processing space and at least one gas outlet for discharging gas from the plasma processing space. The gas supply port is connected to the gas supply unit 20 (described later), and the gas outlet is connected to the exhaust system 40 (described later). The substrate support 11 is disposed within the plasma processing space and has a substrate support surface for supporting a substrate.

[0038] The plasma generation unit 12 is configured to generate plasma from at least one processing gas supplied to the plasma processing space. The plasma generated in the plasma processing space can be capacitively coupled plasma (CCP), inductively coupled plasma (ICP), ECR plasma (ECR), helicon wave plasma (HWP), or surface wave plasma (SWP), etc. Alternatively, various types of plasma generation units, including AC (Alternating Current) plasma generation units and DC (Direct Current) plasma generation units, can be used. In one embodiment, the AC signal (AC power) used in the AC plasma generation unit has a frequency in the range of 100 kHz to 10 GHz. Therefore, the AC signal includes RF (Radio Frequency) signals and microwave signals. In one embodiment, the RF signal has a frequency in the range of 100 kHz to 150 MHz.

[0039] The control unit 2 processes computer-executable commands that cause the plasma processing apparatus 1 to perform the various steps described herein. The control unit 2 can be configured to control various elements of the plasma processing apparatus 1 to perform the various steps 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 is implemented, for example, by a computer 2a. The processing unit 2a1 can be configured to perform various control operations by reading a program from the storage unit 2a2 and executing the read program. The program may be pre-stored in the storage unit 2a2 or retrieved via a medium when needed. The retrieved program is stored in the storage unit 2a2 and read and executed by the processing unit 2a1. 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 central processing unit (CPU). The storage unit 2a2 may include RAM (Random Access Memory), ROM (Read Only Memory), HDD (Hard Disk Drive), SSD (Solid State Drive), or a combination thereof. The communication interface 2a3 may also communicate with the plasma processing device 1 via a communication line such as a LAN (Local Area Network).

[0040] Hereinafter, a structural example of a capacitively coupled plasma processing device, which is one example of plasma processing device 1, will be described. Figure 2 This is a schematic cross-sectional view showing an example of the structure of the plasma processing apparatus in the first embodiment.

[0041] The capacitively coupled plasma processing apparatus 1 includes a plasma processing chamber 10, a gas supply unit 20, a power supply 30, a microwave interferometer 35, and an exhaust system 40. Additionally, the plasma processing apparatus 1 includes a substrate support 11 and a gas inlet. The gas inlet is configured to introduce at least one processing gas into the plasma processing chamber 10. The gas inlet includes a spray head 13. The substrate support 11 is disposed within the plasma processing chamber 10. The spray head 13 is disposed above the substrate support 11. In one embodiment, the spray head 13 constitutes 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 spray head 13, the sidewall 10a of the plasma processing chamber 10, and the substrate support 11. The plasma processing chamber 10 is grounded. The spray head 13 and the substrate support 11 are electrically insulated from the housing of the plasma processing chamber 10.

[0042] The substrate support portion 11 includes a main body portion 111 and a ring assembly 112. The main body portion 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 portion 111 surrounds the central region 111a of the main body portion 111 when viewed from above. The substrate W is disposed on the central region 111a of the main body portion 111, and the ring assembly 112 is disposed on the annular region 111b of the main body portion 111 in such a way that it surrounds the substrate W on the central region 111a of the main body portion 111. Therefore, the central region 111a is also referred to as a substrate support surface for supporting the substrate W, and the annular region 111b is also referred to as an annular support surface for supporting the ring assembly 112.

[0043] In one embodiment, the main body 111 includes a base 1110 and an electrostatic chuck 1111. The base 1110 includes a conductive component. The conductive component of the base 1110 can function as a lower electrode. The electrostatic chuck 1111 is disposed on the base 1110. The electrostatic chuck 1111 includes a ceramic component 1111a and an electrostatic electrode 1111b disposed within the ceramic component 1111a. The ceramic component 1111a has a central region 111a. In one embodiment, the ceramic component 1111a also has an annular region 111b. Furthermore, other components surrounding the electrostatic chuck 1111, such as an annular electrostatic chuck or an annular insulating component, may also have an annular region 111b. In this case, the ring assembly 112 may be disposed on either the annular electrostatic chuck or the annular insulating component, or on both the electrostatic chuck 1111 and the annular insulating component. Additionally, at least one RF / DC electrode coupled to the RF power supply 31 and / or DC power supply 32 (described later) may also be disposed within the ceramic component 1111a. In this case, the at least one RF / DC electrode functions as a lower electrode. When the bias RF signal and / or DC signal (described later) are supplied to the at least one RF / DC electrode, the RF / DC electrode is also referred to as a bias electrode. Furthermore, the conductive components of the base 1110 and the at least one RF / DC electrode may also function as multiple lower electrodes. Additionally, the electrostatic electrode 1111b may also function as a lower electrode. Therefore, the substrate support portion 11 includes at least one lower electrode.

[0044] The ring assembly 112 includes one or more annular components. In one embodiment, the one or more annular components 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 ring is formed of an insulating material.

[0045] Additionally, the substrate support 11 may also include a temperature control 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 control module may include a heater, a heat transfer medium, a flow path 1110a, or a combination thereof. A heat transfer fluid such as brine or gas flows in the flow path 1110a. In one embodiment, the flow path 1110a is formed within the base 1110, and one or more heaters are disposed within the ceramic component 1111a of the electrostatic chuck 1111. Furthermore, the substrate support 11 may also include a heat transfer gas supply section configured to supply heat transfer gas to the gap between the back surface of the substrate W and the central region 111a.

[0046] The spray head 13 is configured to introduce at least one process gas from the gas supply unit 20 into the plasma processing space 10s. The spray head 13 has at least one gas supply port 13a, at least one gas diffusion chamber 13b, and a plurality of gas inlets 13c. The process gas supplied to the gas supply port 13a is introduced into the plasma processing space 10s through the gas diffusion chamber 13b and the plurality of gas inlets 13c. Additionally, the spray head 13 includes at least one upper electrode. Furthermore, in addition to the spray head 13, the gas inlet unit may also include one or more side gas injectors (SGIs) mounted on one or more openings formed in the sidewall 10a.

[0047] The gas supply unit 20 may also 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 type of process gas from a corresponding gas source 21 to the spray head 13 via a corresponding flow controller 22. Each flow controller 22 may, for example, include a mass flow controller or a pressure-controlled flow controller. Furthermore, the gas supply unit 20 may also include at least one flow modulation device for modulating or pulsed the flow of at least one type of process gas.

[0048] 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 allows plasma to be formed from at least one processing gas supplied to the plasma processing space 10s. Therefore, the RF power supply 31 can function as at least a part of the plasma generation unit 12. Furthermore, by supplying a bias RF signal to at least one lower electrode, a bias potential can be generated on the substrate W, introducing ionic components from the formed plasma into the substrate W.

[0049] 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 generation source RF signal (generation source RF power) for plasma generation. In one embodiment, the generation 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 also be configured to generate multiple generation source RF signals with different frequencies. The generated one or more generation source RF signals are supplied to at least one lower electrode and / or at least one upper electrode. The first RF generating unit 31a is an example of an RF generating unit.

[0050] The second RF generation unit 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 that 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 generation unit 31b may also be configured to generate multiple bias RF signals with different frequencies. The generated one or more bias RF signals are supplied to at least one lower electrode. In addition, in various embodiments, at least one of the source RF signal and the bias RF signal may be pulsed.

[0051] Alternatively, 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 generating unit 32a and a second DC generating unit 32b. In one embodiment, the first DC generating unit 32a is connected to at least one lower electrode and is configured to generate a first DC signal. The generated first DC signal is applied to at least one lower electrode. In one embodiment, the second DC generating unit 32b is connected to at least one upper electrode and is configured to generate a second DC signal. The generated second DC signal is applied to at least one upper electrode.

[0052] In various embodiments, the first and second DC signals can also 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 can have rectangular, trapezoidal, triangular, or combinations thereof pulse waveforms. In one embodiment, a waveform generation unit for generating a sequence of voltage pulses based on the DC signals is connected between the first DC generation unit 32a and at least one lower electrode. Therefore, the first DC generation unit 32a and the waveform generation unit constitute a voltage pulse generation unit. Furthermore, the first DC generation unit 32a and the waveform generation unit are an example of a pulsed voltage generation unit. Additionally, in the following description, there may be a case where the first DC generation unit 32a includes a waveform generation unit. When the second DC generation unit 32b and the waveform generation unit constitute a voltage pulse generation unit, the voltage pulse generation unit is connected to at least one upper electrode. The voltage pulses can have positive or negative polarity. Furthermore, the sequence of voltage pulses can also include one or more positive voltage pulses and one or more negative voltage pulses within one cycle. In addition to the RF power supply 31, first and second DC generating units 32a and 32b can also be provided. The first DC generating unit 32a can also be provided instead of the second RF generating unit 31b.

[0053] A microwave interferometer 35 is used to measure (monitor) the electron density Ne of the plasma generated in the plasma processing space 10s. The microwave interferometer 35 has electromagnetic amplitude transformers 36a and 36b, which are mounted opposite each other at two points on the side wall 10a of the plasma processing chamber 10. Microwaves are transmitted from one of the electromagnetic amplitude transformers 36a and 36b, and received by the other. During the plasma processing space 10s, the line connecting the electromagnetic amplitude transformers 36a and 36b traverses the plasma. The microwave interferometer 35 measures the electron density Ne of the plasma based on the phase difference between the transmitted and received microwaves. The microwave interferometer 35 outputs the measured electron density Ne to the control unit 2. Furthermore, the control unit 2 controls the RF power supply 31 (first RF generation unit 31a) based on the input electron density Ne, adjusting the first power level of the generation source RF signal (generation source RF power) for the first period T1 (described later). Furthermore, based on the input electron density Ne, the control unit 2 controls the DC power supply 32 (the first DC generation unit 32a and the waveform generation unit) to adjust the offset period De (described later) for the first DC signal (DC pulse). Also, the control unit 2 can control the DC power supply 32 (the first DC generation unit 32a and the waveform generation unit) to adjust the first voltage level of the second period T1 (described later) for the first DC signal based on the input electron density Ne.

[0054] The exhaust system 40 can be connected, for example, to a gas outlet 10e located at the bottom of the plasma processing chamber 10. The exhaust system 40 may also include a pressure regulating valve and a vacuum pump. The pressure within the plasma processing space 10s can be regulated using the pressure regulating valve. The vacuum pump may include a turbomolecular pump, a dry pump, or a combination thereof.

[0055] [RF power and DC pulse]

[0056] Here, the variations in RF power, the first DC signal (DC pulse), and electron density Ne are explained. The RF power can have two frequencies: the high-frequency generating RF signal is referred to as HF (High Frequency), and the low-frequency bias RF signal is referred to as LF (Low Frequency). In this embodiment, the relationship between HF (hereinafter also referred to as RF (HF),) the DC pulse, and the electron density Ne is explained. Figure 3 This is a timing diagram illustrating an example of the variation in RF power, DC pulse supply timing, and electron density in the first embodiment.

[0057] like Figure 3 As shown, RF power (RF(HF)) and DC pulses are periodically supplied, with the first period T1 and the second period T2 as a cycle. Regarding the RF power, a first power level (High) is supplied in the first period T1, and a second power level (Low) is supplied in the second period T2. Regarding the DC pulses, a DC pulse at a reference voltage level is supplied during the offset period (delay period) De within the first period T1 (described later). Furthermore, after the offset period De, DC pulses are supplied as a sequence of multiple voltage pulses with the first voltage level during the first period T1 excluding the offset period De. Furthermore, regarding the DC pulses, a DC pulse at the reference voltage level is supplied in the second period T2. Additionally, in... Figure 3 For example, the reference voltage level is set to 0V, and the first voltage level is set to a pulse with negative polarity.

[0058] The electron density Ne increases from the beginning of the first period T1, peaks after the offset period De when the DC pulse is supplied, and although it tends to decrease slightly, it maintains the first level. Then, the electron density Ne decreases from the end of the first period T1, i.e., the beginning of the second period T2, to a second level lower than the first level, and maintains the second level. In the first embodiment, for example, the electron density Ne is measured using a microwave interferometer 35 at timing 52 within the first period T1. The measured electron density Ne is used for subsequent adjustment of the first power level of the RF (HF). Alternatively, the electron density Ne can also be measured using a microwave interferometer 35 at timing 53 within the second period T2.

[0059] Next, use Figure 4 and Figure 5 The details of RF power and DC pulse are explained. Figure 4 This is a timing diagram illustrating an example of the timing of the supply of RF power and DC pulses in the first embodiment. Figure 5 It is Figure 4 The timing diagram shown is a magnified portion of the timing diagram. Figure 5 In the middle, magnified Figure 4 The timing diagram for a range of 54. (Example) Figure 4 As shown, in the step of etching the target film on the substrate W, the target film on the substrate W is etched using plasma generated from the process gas by supplying RF power (HF). The RF power supply 31 will... Figure 4 The repetition period C shown is one cycle, during which RF power at "High" and "Low" levels is periodically supplied to the substrate support portion 11 (lower electrode). Additionally, RF power can also be supplied to the spray head 13 (upper electrode). In this invention, the RF power supply 31 (first RF generation portion 31a) is coupled to the lower electrode, supplying... Figure 4 The RF (HF) shown is the RF electrical power.

[0060] exist Figure 4 In this context, "high" (hereinafter also referred to as "high state" or "High") is an example of a first power level indicating RF power. For example, the first power level is greater than 0W. On the other hand, "low" (hereinafter also referred to as "low state" or "Low") is an example of a second power level indicating RF power. The second power level of RF power (RF electricity) is less than the first power level, and is 0W or greater than 0W.

[0061] The first period T1, where the RF power is high, and the second period T2, where it is low, are repeated in this sequence. Alternatively, the RF power can be such that the first period T1 is ON and the second period T2 is OFF, repeating in this sequence. Here, the ON state is the same as the high state with the same first power level, and the OFF state is when the second power level is 0W. The first period T1 has a duty cycle relative to the repetition period C, ranging from 10% to 60%. The duty cycle represents the proportion of the first period T1, which is the proportion of the first period T1 to the total time represented by (first period T1 + second period T2). The repetition period C has a repetition frequency (cycle frequency) ranging from 0.1kHz to 50kHz.

[0062] In supply Figure 5 When a DC pulse is applied, a voltage with a periodic and negative polarity pulse waveform is supplied. The term "periodic" here has two meanings. One meaning is... Figure 4 During the period P1, the connection status and Figure 4 The periodicity of the off state during period P2. That is, the periodicity corresponding to the on and off of the control signal indicating whether to supply DC pulses. The period P1 that is in the on state is except... Figure 5 The first period T1 is excluding the offset period De. The period P2 that becomes the off state is the offset period De and the second period T2. Another meaning is the period within the first period T1 (period P1) excluding the offset period De. Figure 5 The periodicity of the on and off states of the negative polarity pulse waveform is shown.

[0063] The DC power supply 32 designates the period when the RF power is high as the first period T1 and the period when the RF power is low as the second period T2. During the period from the beginning of the first period T1 to the end of the offset period De, the DC pulse is kept off. The offset period De is within the range of 2% to 7% of the repetition period C. The DC power supply 32 supplies DC pulses during the first period T1 (i.e., period P1 = T1 - De) after the offset period De, and turns off the DC pulses during the second period T2. Thus, the DC power supply 32 sequentially repeats the period P1 for supplying negative DC pulses and the period P2 (i.e., when the supply of negative DC pulses stops) (De + T2).

[0064] During period P1, when the DC pulse is in the ON state, the DC pulse is further periodically switched on (ON: negative value) and off (OFF: 0V) as a sequence of voltage pulses (pulse waveform). That is, the absolute value of the first voltage level is greater than the absolute value of the reference voltage level. During period P2, the DC pulse is in the OFF state, meaning the control signal indicating whether to supply DC pulses is off. Furthermore, during period P2, DC pulses with an absolute value smaller than the DC pulses in period P1 can also be supplied.

[0065] In the pulse waveform of the DC pulse during period P1, when the reciprocal of the on-off period (wavelength λ1) of the pulse waveform is set as the pulse frequency f1, the pulse frequency f1 can, for example, be a frequency in the range of 100kHz to 1MHz. Furthermore, the duty cycle in the pulse waveform of the DC pulse during period P1 represents the proportion of the DC pulse's on-time (t1). That is, the duty cycle of the pulse waveform of the DC pulse during period P1 is the proportion of the on-time to the total on-time (t1) and off-time (t2) (t1 / (t1+t2)). Additionally, the DC pulse is not limited to a rectangular wave; it can also be a triangular wave, an impulse pulse waveform, a trapezoidal wave, a sawtooth wave, or a combination thereof.

[0066] Next, use Figures 6 to 14 The improvement of mask selectivity and adjustment of electron density achieved by setting the offset period are explained. Figure 6 This is a timing diagram illustrating an example of the variation in RF power, DC pulse supply timing, and electron density in the first embodiment. Figure 6 and Figure 3 The corresponding timing diagram is a timing diagram represented using RF power and DC pulse control signals. For example... Figure 6 As shown, at the rising edge of the control signal, after the control signal for the RF power (RF(HF)) becomes "ON", and after the offset period De, the control signal for the DC pulse becomes "ON". After the period P1, at the falling edge of the control signal, the control signals for both RF(HF) and the DC pulse simultaneously become "OFF". Specifically, when RF(HF) is "ON", it supplies a first power level of "High", and when it is "OFF", it supplies a second power level of "Low".

[0067] Here, in the time series plot of electron density Ne, the offset period De is the period during which byproducts (hereinafter referred to as deposits) are deposited on substrate W, and period P1 is the etching period. That is, the deposits deposited on substrate W during offset period De protect the mask on substrate W during etching in period P1. That is, it is assumed that the mask selectivity is maximized when an appropriate amount of deposits is deposited. Thus, we focus on the first half of offset period De and period P1 of the time series plot of electron density Ne in relation to the amount of deposits.

[0068] Figure 7 This is a graph illustrating an example of the change in electron density near the point of shift when the amount of sediment is at an appropriate level. Figure 8 This is a schematic diagram illustrating sediment and erosion at an appropriate level of sediment quantity. (Example) Figure 7 As shown in range 55a, when the electron density Ne is at an appropriate level L at the beginning of period P1, such as Figure 8 As shown in state 56a, deposit 59 is deposited on the sidewall of pore 57 and the surface 58 of substrate W, forming a protective film 60 of appropriate thickness. During period P1, as... Figure 8 As shown in state 56b, ions 61 are introduced to etch the bottom of the hole 57, while the sidewalls of the hole 57 and the surface 58 of the substrate W are protected by the protective film 60 and are not etched. That is, because the amount of deposit calculated based on the measured electron density Ne is at an appropriate level, the mask selectivity can be improved.

[0069] Figure 9 This is a diagram illustrating an example of the change in electron density near the point of displacement when the amount of sediment is insufficient. Figure 10 This is a schematic diagram illustrating sediment and etching under conditions of insufficient sediment quantity. (Example) Figure 9 As shown in range 55b, when the electron density Ne is below the appropriate level L at the beginning of period P1, such as Figure 10 As shown in state 62a, the deposit 63 deposited on the sidewalls of the pore 57 and the surface 58 of the substrate W decreases, forming a protective film 64 that is thinner than the protective film 60. During period P1, as... Figure 10 As shown in state 62b, ions 65 are introduced, and the bottom of the hole 57 is etched. However, due to the thinness of the protective film 64, the sidewalls of the hole 57 and the surface 58 of the substrate W are also etched, resulting in a reduced mask selectivity. As shown in range 55b, when the electron density Ne is lower than the appropriate level L at the beginning of period P1, the RF power supply 31 (first RF generation unit 31a) is controlled to increase the first electrical power level of the RF (HF). Here, the appropriate level L is an example of a target value for the electron density Ne.

[0070] Figure 11This is a diagram illustrating an example of the change in electron density near the point of displacement when there is an excess of sediment. Figure 12 This is a schematic diagram illustrating sediment and erosion in cases of excessive sediment accumulation. (Example) Figure 11 As shown in range 55c, when the electron density Ne is higher than the appropriate level L at the beginning of period P1, such as Figure 12 As shown in state 66a, the deposit 67 increases. In this case, not only is the deposit 67 deposited on the sidewalls of the hole 57 and the surface 58 of the substrate W, but the protective film 68 formed is also etched by the deposit 67, becoming thinner than the protective film 60. During period P1, as... Figure 12 As shown in state 66b, ions 69 are introduced, and the bottom of the hole 57 is etched. However, due to the thinness of the protective film 68, the sidewalls of the hole 57 and the surface 58 of the substrate W are also etched, resulting in a reduced mask selectivity. As shown in range 55c, when the electron density Ne is higher than the appropriate level L at the beginning of period P1, the RF power supply 31 (first RF generation unit 31a) is controlled to reduce the first electrical power level of the RF (HF).

[0071] In addition, the electron density Ne can also be adjusted by the length of De during the offset period. Figure 13 This is a diagram illustrating an example of a method for adjusting the electron density at the beginning of period P1. Figure 13 The range shown is 70 and Figure 6 The range 55 corresponds to the electron density Ne at the beginning of period P1. Figure 9 The adjustment example shown in range 55b is for cases where the current level L is insufficient. In the example of range 70, an additional period De1 is added to the offset period De, adjusting it to become the offset period De'. Furthermore, since the first period T1 = offset period De + period P1, when the range 70 is adjusted, period P1' = period P1 - additional period De1, and the first period T1 = offset period De' + period P1'. Thus, even if the electron density Ne at the beginning of period P1 is insufficient compared to the appropriate level L, the DC power supply 32 (first DC generation unit 32a and waveform generation unit) can be controlled to lengthen the offset period De.

[0072] Figure 14 This is a diagram illustrating an example of a method for adjusting the electron density at the beginning of period P1. Figure 14 The range shown is 71 and Figure 6 The range 55 corresponds to the electron density Ne at the beginning of period P1. Figure 11The adjustment example shown in range 55c is when the value is too high compared to the appropriate level L. In the example of range 71, the offset period De is subtracted from the shortening period De2, and the result is adjusted to become the offset period De". Furthermore, since the first period T1 = offset period De + period P1, when range 71 is adjusted, period P1” = period P1 + shortening period De2, and the first period T1 = offset period De” + period P1”. Thus, if the electron density Ne at the beginning of period P1 is too high compared to the appropriate level L, the DC power supply 32 (first DC generation unit 32a and waveform generation unit) can be controlled to shorten the offset period De. Additionally, the adjustment of the first power level of the RF (HF) and the adjustment of the offset period De can also be performed in combination.

[0073] [Plasma Control Methods]

[0074] Next, an example of plasma control processing of the plasma processing apparatus 1 of the first embodiment will be described. Figure 15 This is a flowchart illustrating an example of the plasma control process in the first embodiment. Figure 15 The plasma control process shown is achieved by controlling each part of the plasma processing device 1 by the control unit 2.

[0075] First, the substrate W is placed into the plasma processing chamber 10 and supported on the substrate support 11. Then, the control unit 2 controls the gas supply unit 20 to supply a predetermined flow rate of processing gas into the plasma processing chamber 10. Next, the control unit 2 controls the exhaust system 40 to adjust the pressure inside the plasma processing chamber 10. Then, the control unit 2 controls the RF power supply 31 and the DC power supply 32 to supply RF power and DC pulses to the substrate support 11, which serves as the lower electrode. As a result, plasma containing the processing gas can be generated inside the plasma processing chamber 10. The control unit 2 controls the microwave interferometer 35 to measure the electron density Ne of the plasma (step S1). The microwave interferometer 35 outputs the measured electron density Ne to the control unit 2. Furthermore, the measurement of the electron density Ne of the plasma by the microwave interferometer 35 continues during the plasma processing under adjustment.

[0076] When the electron density Ne, measured by the microwave interferometer 35, is input, the control unit 2 controls the RF power supply 31 and the DC power supply 32 based on the input electron density Ne to adjust at least one of the first power level and the bias period De (step S2). That is, the control unit 2 controls the RF power supply 31 and the DC power supply 32 in a manner that adjusts at least one of the first power level and the bias period De so that the input electron density Ne becomes an appropriate level L.

[0077] When the plasma processing is finished, the processed substrate W is removed from the plasma processing chamber 10 using a robotic arm (not shown).

[0078] As described above, in the first embodiment, since at least one of the first electric power level and the bias period De is adjusted based on the measured electron density Ne, the time-dependent changes in plasma conditions can be suppressed.

[0079] (Second Implementation)

[0080] In the first embodiment described above, the DC pulse is supplied when the RF power is high, but it can also be supplied when the RF power is low. The implementation in this case will be described as the second embodiment. Furthermore, the plasma processing system in the second embodiment is the same as that in the first embodiment except for the timing of the DC pulse supply; therefore, repeated descriptions of the structure and operation are omitted.

[0081] Furthermore, in the first embodiment described above, at least one of the first power level of the first period T1 and the offset period De is adjusted based on the electron density Ne measured in the first period T1. In the second embodiment, for example, the first power level of the RF power is adjusted based on the electron density Ne measured in the first period T1, and the first voltage level of the DC pulse is adjusted based on the electron density Ne measured in the second period T2.

[0082] First, use Figures 16 to 19 The synchronization pulse and the time offset pulse (hereinafter also referred to as the offset pulse) are explained. Figure 16 This is an example of a timing diagram representing one cycle of a synchronization pulse. For example... Figure 16 As shown, the synchronization pulse is the case where the offset is 0° relative to the RF electrical power (RF(HF)) DC pulse. Additionally, in Figure 16 In this example, the duty cycles of the RF (HF) and DC pulses relative to the repetition period C are 30%, respectively. That is, the RF (HF) and DC pulses are simultaneously supplied to the lower electrode (substrate support 11) of the plasma processing chamber 10. Here, the phase is expressed in degrees (angles) with respect to the offset.

[0083] Figures 17 to 19 This is an example of a timing diagram representing one cycle of an offset pulse. Figure 17 The DC pulse shown is the case where it is offset by 54° relative to the RF (HF). That is, Figure 17 The DC pulse shown is a pulse with a 15% phase delay relative to the synchronization pulse. Figure 17In this example, the duty cycles of the RF (HF) and DC pulses are both 30%. That is, after RF (HF) is supplied to the lower electrode (substrate support 11) of the plasma processing chamber 10, and after 15% of the repetition period C, the DC pulse is supplied to the lower electrode (substrate support 11) of the plasma processing chamber 10. That is, the repetition period C sequentially consists of: RF (HF) high state and DC pulse off state, RF (HF) high state and DC pulse on state, RF (HF) low state and DC pulse on state, and RF (HF) low state and DC pulse off state.

[0084] Figure 18 The DC pulse shown is the case where it is offset by 108° relative to the RF (HF). That is, Figure 18 The DC pulse shown is a pulse with a 30% phase delay relative to the synchronization pulse. Figure 18 In this example, the duty cycles of the RF (HF) and DC pulses are both 30%. That is, after RF (HF) is supplied to the lower electrode (substrate support 11) of the plasma processing chamber 10, and after 30% of the repetition period C has elapsed, the DC pulse is supplied to the lower electrode (substrate support 11) of the plasma processing chamber 10. That is, the repetition period C sequentially becomes: RF (HF) is high and DC pulse is off, RF (HF) is low and DC pulse is on, and RF (HF) is low and DC pulse is off.

[0085] Figure 19 The DC pulse shown is for the case where it is offset by -144° relative to the RF (HF). That is, Figure 19 The DC pulse shown is a pulse that is 40% phase ahead (60% phase delayed) relative to the synchronization pulse. Figure 19 In this example, the duty cycles of the RF (HF) and DC pulses are both 30%. That is, after RF (HF) is supplied to the lower electrode (substrate support 11) of the plasma processing chamber 10, and after 60% of the repetition period C has elapsed, the DC pulse is supplied to the lower electrode (substrate support 11) of the plasma processing chamber 10. That is, the repetition period C sequentially consists of: RF (HF) being high and the DC pulse being off, RF (HF) being low and the DC pulse being off, RF (HF) being low and the DC pulse being on, and RF (HF) being low and the DC pulse being off.

[0086] about Figures 16 to 19The synchronization pulse and offset pulse shown are defined as follows: the period during which RF(HF) is high is designated as the first period T1, and the period during which RF(HF) is low is designated as the second period T2. In the second embodiment, the first electrical power level when RF(HF) is high can be adjusted based on the plasma electron density Ne measured during the first period T1. Furthermore, in the second embodiment, the first voltage level when the DC pulse is on can be adjusted based on the plasma electron density Ne measured during the second period T2.

[0087] Next, use Figure 20 An example of adjusting the offset pulse will be explained. Figure 20 This is a graph illustrating an example of the change in electron density during the repetition period in the second embodiment. Figure 20 In, it means Figure 18 The diagram shows the change in electron density Ne when the offset is 108°. That is, in... Figure 20 In the diagram, the repetition period C represents the changes in electron density Ne during period A1 (corresponding to the first period T1), period A2 (corresponding to the DC pulse being on) during period T2, and period A3 (corresponding to the DC pulse being off) during period T2. Specifically, period A1 is when RF (HF) is high and the DC pulse is off, period A2 is when RF (HF) is low and the DC pulse is on, and period A3 is when RF (HF) is low and the DC pulse is off. Figure 20 Graph 72 is, for example, an example of the change in electron density Ne under plasma conditions immediately after maintenance. In graph 72, the electron density Ne during period A1 rises to approximately twice the electron density Ne during period A2.

[0088] At this time, control unit 2 controls RF power supply 31 for a first power level where RF (HF) is high during period A1, so that the electron density Ne is constant at the target value. Additionally, control unit 2 controls DC power supply 32 for a first voltage level where the DC pulse is on during period A2, so that the electron density Ne is constant at the target value. Furthermore, control unit 2 controls RF power supply 31 for a second power level where RF (HF) is low during period A3 to maintain the plasma. Furthermore, the case where the first power level of RF (HF) and the first voltage level of the DC pulse interact during periods A1 and A2 is considered. In this case, the first power level of RF (HF) and the first voltage level of the DC pulse can be adjusted separately during periods A1 and A2. That is, control can be performed based on the balance between the first power level of RF (HF) and the first voltage level of the DC pulse, so that the electron density Ne is constant at the target value in each period A1 and A2. Moreover, this control method can be applied not only to offset pulses but also to synchronization pulses.

[0089] Figure 20 Curve 73 is, for example, an example of the change in electron density Ne under plasma conditions in a case where plasma processing has been carried out for a long time in the plasma processing chamber 10 since maintenance. When curve 73 is compared with curve 72, the electron density Ne during period A1 of curve 73 is lower than that of curve 72, which corresponds to the target value. In this case, control unit 2 controls RF power supply 31 to increase the first power level of RF (HF) during period A1 so that the electron density Ne during period A1 becomes the target value (overlapping with curve 72).

[0090] That is, when the electron density Ne is less than the target value in the first period T1 (period A1), the control unit 2 controls the RF power supply 31 by increasing the first power level of the RF (HF). Conversely, when the electron density Ne exceeds the target value in the first period T1 (period A1), the control unit 2 controls the RF power supply 31 by decreasing the first power level of the RF (HF). Similarly, when the electron density Ne is less than the target value in the second period T2 (e.g., period A2), the control unit 2 controls the DC power supply 32 by increasing the first voltage level of the DC pulse. Conversely, when the electron density Ne exceeds the target value in the second period T2 (e.g., period A2), the control unit 2 controls the DC power supply 32 by decreasing the first voltage level of the DC pulse.

[0091] [Plasma Control Methods]

[0092] Next, an example of plasma control processing of the plasma processing apparatus 1 of the second embodiment will be described. Figure 21This is a flowchart illustrating an example of the plasma control process in the second embodiment. Figure 21 The plasma control process shown is achieved by controlling each part of the plasma processing device 1 by the control unit 2.

[0093] First, the substrate W is placed into the plasma processing chamber 10 and supported on the substrate support 11. Then, the control unit 2 controls the gas supply unit 20 to supply a predetermined flow rate of processing gas into the plasma processing chamber 10. Next, the control unit 2 controls the exhaust system 40 to adjust the pressure inside the plasma processing chamber 10. Then, the control unit 2 controls the RF power supply 31 and the DC power supply 32 to supply RF power and DC pulses to the substrate support 11, which serves as the lower electrode. As a result, plasma containing the processing gas can be generated inside the plasma processing chamber 10. The control unit 2 controls the microwave interferometer 35 to measure the electron density Ne of the plasma (step S11). The microwave interferometer 35 outputs the measured electron density Ne to the control unit 2. Furthermore, the measurement of the electron density Ne of the plasma by the microwave interferometer 35 is continuously performed during plasma processing at the adjustment stage.

[0094] When the electron density Ne, measured from the microwave interferometer 35, is input, the control unit 2 controls the RF power supply 31 to adjust the first power level based on the electron density Ne measured in the first period T1 of the input electron density Ne. Additionally, the control unit 2 controls the DC power supply 32 to adjust the first voltage level based on the electron density Ne measured in the second period T2 of the input electron density Ne (step S12). That is, the control unit 2 controls the RF power supply 31 and the DC power supply 32, adjusting the first power level and the first voltage level so that the input electron density Ne becomes the target value for both the first period T1 and the second period T2.

[0095] When the plasma processing is finished, the processed substrate W is removed from the plasma processing chamber 10 using a robotic arm (not shown).

[0096] As described above, in the second embodiment, since the first electric power level and the first voltage level are adjusted based on the electron density Ne measured in the first period T1 and the second period T2, respectively, the time-dependent changes in plasma conditions can be suppressed.

[0097] According to the second embodiment, the plasma processing apparatus 1 includes a chamber (plasma processing chamber 10); a substrate support 11 including a lower electrode disposed within the chamber; an RF generation unit (RF power supply 31); a pulsed voltage generation unit (DC power supply 32); a microwave interferometer 35; and a control unit 2. The RF generation unit is configured to generate a pulsed RF signal to generate plasma within the chamber. The pulsed RF signal has a first power level in a first period T1 within each cycle (repetition period C), and a second power level smaller than the first power level in a second period T2 within each cycle. The pulsed voltage generation unit is electrically connected to the lower electrode and is configured to generate a pulsed voltage signal. The pulsed voltage signal has a timing sequence of multiple voltage pulses having a reference voltage level in the first period T1 and a first voltage level in the second period T2, wherein the absolute value of the first voltage level is greater than the absolute value of the reference voltage level. The microwave interferometer 35 is configured to monitor the electron density of the plasma within the chamber. The control unit 2 adjusts the first electric power level based on the plasma electron density monitored during the first period T1, and adjusts the first voltage level based on the plasma electron density monitored during the second period T2. As a result, it is possible to suppress time-dependent changes in plasma conditions.

[0098] Furthermore, according to the second embodiment, if the electron density during the first period T1 is less than a target value, the control unit 2 adjusts the power level by increasing the first electrical power level. As a result, the electron density during the first period T1 can be adjusted.

[0099] Furthermore, according to the second embodiment, if the electron density of the first period T1 exceeds a target value, the control unit 2 adjusts the first power level by reducing it. As a result, the electron density of the first period T1 can be adjusted.

[0100] Furthermore, according to the second embodiment, if the electron density during the second period T2 is less than the target value, the control unit 2 adjusts the voltage level by increasing the absolute value of the first voltage level. As a result, the electron density during the second period T2 can be adjusted.

[0101] Furthermore, according to the second embodiment, if the electron density of the second period T2 exceeds a target value, the control unit 2 adjusts the voltage level by reducing the absolute value of the first voltage level. As a result, the electron density of the second period T2 can be adjusted.

[0102] Furthermore, according to the first embodiment, the plasma processing apparatus 1 includes a chamber (plasma processing chamber 10), a substrate support 11 including a lower electrode disposed within the chamber, an RF generation unit (RF power supply 31), a pulsed voltage generation unit (DC power supply 32), a microwave interferometer 35, and a control unit 2. The RF generation unit is configured to generate a pulsed RF signal to generate plasma within the chamber. The pulsed RF signal has a first electrical power level in a first period T1 within each cycle (repetition period C), and a second electrical power level smaller than the first electrical power level in a second period T2 within each cycle. The pulsed voltage generation unit is electrically connected to the lower electrode and is configured to generate a pulsed voltage signal. The pulsed voltage signal has a reference voltage level during a delay period (offset period De) within the first period T1. The first period T1, excluding the delay period, includes a sequence of multiple voltage pulses having the first voltage level. The second period T2 has a reference voltage level. The absolute value of the first voltage level is greater than the absolute value of the reference voltage level. The delay period is within the range of 2% to 7% of the entire period of each cycle. The microwave interferometer 35 is configured to monitor the electron density of the plasma within the chamber. The control unit 2 is configured to adjust at least one of the first electrical power level and the delay period based on the electron density of the plasma monitored during the delay period. As a result, time-varying changes in plasma conditions can be suppressed.

[0103] Furthermore, according to the first embodiment, when the electron density is less than the target value, the control unit 2 adjusts the power level by increasing the first power level or extending the delay period. As a result, the electron density during the first period T1 can be adjusted.

[0104] Furthermore, according to the first embodiment, when the electron density exceeds a target value, the control unit 2 adjusts the power level by reducing the first power level or shortening the delay period. As a result, the electron density during the first period T1 can be adjusted.

[0105] The various embodiments described herein should be considered illustrative in all respects and not restrictive. The various embodiments described above may be omitted, substituted, or modified in various ways without departing from the appended claims and their spirit.

[0106] Explanation of reference numerals in the attached figures

[0107] 1. Plasma processing device

[0108] 2 Control Department

[0109] 10. Plasma processing chamber

[0110] 11. Substrate support

[0111] 20 Gas Supply Department

[0112] 30 power supply

[0113] 31 RF Power Supply

[0114] 31a First RF Generation Unit

[0115] 31b Second RF Generation Unit

[0116] 32 DC power supply

[0117] 32a First DC Generation Unit

[0118] 32b Second DC Generation Unit

[0119] 35 Microwave Interferometer

[0120] 40 Exhaust System

[0121] C. During the repetition period

[0122] De offset period (delay period)

[0123] T1 First Period

[0124] T2 Second Period

[0125] W substrate.

Claims

1. A plasma processing device, characterized in that, include: Chamber; A substrate support portion, disposed within the cavity, includes a lower electrode; An RF generation unit is configured to generate a pulsed RF signal to generate plasma in the chamber, wherein the pulsed RF signal has a first power level in a first period of each cycle and a second power level that is lower than the first power level in a second period of each cycle. A pulsed voltage generating unit, which is electrically connected to the lower electrode, is configured to generate a pulsed voltage signal. The pulsed voltage signal has a reference voltage level during the first period and includes a sequence of multiple voltage pulses having a first voltage level during the second period. The absolute value of the first voltage level is greater than the absolute value of the reference voltage level. A microwave interferometer configured to monitor the electron density of the plasma within the cavity: and The control unit is configured to adjust the first electrical power level based on the electron density of the plasma monitored during the first period, and to adjust the first voltage level based on the electron density of the plasma monitored during the second period.

2. The plasma processing apparatus as described in claim 1, characterized in that: The control unit adjusts the first power level by increasing it when the electron density is less than the target value during the first period.

3. The plasma processing apparatus as described in claim 1, characterized in that: The control unit adjusts the first power level by reducing it if the electron density exceeds a target value during the first period.

4. The plasma processing apparatus according to any one of claims 1 to 3, characterized in that: The control unit adjusts the voltage level by increasing the absolute value of the first voltage level when the electron density is less than the target value during the second period.

5. The plasma processing apparatus according to any one of claims 1 to 3, characterized in that: The control unit adjusts the voltage level by reducing the absolute value of the first voltage level if the electron density exceeds the target value during the second period.

6. A plasma processing apparatus, characterized in that, include: Chamber; A substrate support portion, disposed within the cavity, includes a lower electrode; An RF generation unit is configured to generate a pulsed RF signal to generate plasma in the chamber, wherein the pulsed RF signal has a first power level in a first period of each cycle and a second power level that is lower than the first power level in a second period of each cycle. A pulsed voltage generating unit, electrically connected to the lower electrode, is configured to generate a pulsed voltage signal. The pulsed voltage signal has a reference voltage level during a delay period within the first period, includes a sequence of multiple voltage pulses having a first voltage level during the first period excluding the delay period, has the reference voltage level during the second period, and the absolute value of the first voltage level is greater than the absolute value of the reference voltage level. The delay period is within the range of 2% to 7% of the entire period of each cycle. A microwave interferometer configured to monitor the electron density of the plasma within the cavity: and The control unit is configured to adjust at least one of the first electrical power level and the delay period based on the electron density of the plasma monitored during the delay period.

7. The plasma processing apparatus as described in claim 6, characterized in that: The control unit adjusts the power level by increasing the first power level or extending the delay period when the electron density is less than the target value.

8. The plasma processing apparatus as described in claim 6, characterized in that: The control unit adjusts the power level by reducing the first power level or shortening the delay period when the electron density exceeds the target value.

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