Plasma processing device and etching method

Abstract

Provided are a plasma processing device and an etching method for forming a suitable etching shape by promoting radical transport.　The plasma processing device comprises: a plasma processing chamber; a substrate support unit that is provided in the plasma processing chamber and supports a substrate; a gas supply unit that supplies an etching gas to the plasma processing chamber; a lower electrode provided in the substrate support unit; an upper electrode facing the lower electrode; a source power supply that supplies a source RF signal for generating plasma on the upper electrode or the lower electrode; a first bias power supply that supplies a first bias signal to the lower electrode; a second bias power supply that supplies a second bias signal to the lower electrode; and a control unit. The control unit controls: (a) a step for controlling the source power supply to supply the source RF signal of a first power level to the upper electrode or the lower electrode; (b) a step for controlling to repeat (b1) a step for controlling the source power supply to supply the source RF signal of a second power level to the upper electrode or the lower electrode, and (b2) a step for controlling the source power supply to supply the source RF signal of a third power level to the upper electrode or the lower electrode and controlling the first bias power supply to supply the first bias signal to the lower electrode; (c) a step for controlling the second bias power supply to supply the second bias signal to the lower electrode; and a step for controlling to repeat the steps (a), (b), and (c) as one cycle.

Description

Plasma Processing Apparatus and Etching Method

[0001] The present disclosure relates to a plasma processing apparatus and an etching method.

[0002] Patent Document 1 discloses a plasma processing apparatus that repeatedly supplies source power and bias power of a DC pulse.

[0003] Japanese Patent Translation of PCT International Publication No. 2024 - 524842

[0004] In one aspect, the present disclosure provides a plasma processing apparatus and an etching method that promote radical transport to form a suitable etching shape.

[0005] In order to solve the above problems, according to one embodiment, a plasma processing chamber, a substrate support portion provided in the plasma processing chamber for supporting a substrate, a gas supply portion for supplying an etching gas to the plasma processing chamber, a lower electrode provided in the substrate support portion, an upper electrode facing the lower electrode, a source power supply for supplying a source RF signal for generating plasma to the upper electrode or the lower electrode, a first bias power supply for supplying a first bias signal to the lower electrode, a second bias power supply for supplying a second bias signal to the lower electrode, and a control unit, wherein the control unit includes: (a) controlling the source power supply to supply the source RF signal of the first power level to the upper electrode or the lower electrode; (b) (b1) controlling the source power supply to supply the source RF signal of the second power level to the upper electrode or the lower electrode; (b2) controlling the source power supply to supply the source RF signal of the third power level to the upper electrode or the lower electrode and controlling the first bias power supply to supply the first bias signal to the lower electrode; repeating these steps; (c) controlling the second bias power supply to supply the second bias signal to the lower electrode; and controlling to repeat the cycle with the steps (a), (b), and (c) as one cycle, thereby providing a plasma processing apparatus.

[0006] In one aspect, it is possible to provide a plasma processing apparatus and etching method that promote radical transport and form a suitable etching shape.

[0007] An example of a diagram illustrating the configuration of a plasma processing system. An example of a diagram illustrating the configuration of a capacitively coupled plasma processing apparatus. An example of a flowchart showing etching. An example of a diagram showing a pulse pattern. An example of a schematic cross-section of a substrate. An example of a schematic cross-section of a substrate. An example of a schematic cross-section of a substrate. An example of a schematic diagram illustrating the state of the plasma. An example of a schematic diagram illustrating the state of the plasma. An example of a schematic diagram illustrating the state of the plasma. An example of a graph showing the changes in each plasma parameter.

[0008] Various exemplary embodiments will be described in detail below with reference to the drawings. In each drawing, the same or corresponding parts will be denoted by the same reference numerals.

[0009] [Plasma Processing System] Figure 1 is an example of a diagram illustrating an example of the configuration of a plasma processing system. In one embodiment, the plasma processing system includes a plasma processing apparatus 1 and a control unit 2. The plasma processing system is an example of a substrate processing system, and the plasma processing apparatus 1 is an example of a substrate processing apparatus. The plasma processing apparatus 1 includes a plasma processing chamber 10, a substrate support unit 11, and a plasma generation unit 12. The plasma processing chamber 10 has a plasma processing space. The plasma processing chamber 10 also has at least one gas supply port for supplying at least one processing gas to the plasma processing space, and at least one gas outlet for discharging gas from the plasma processing space. The gas supply port is connected to a gas supply unit 20, which will be described later, and the gas outlet is connected to an exhaust system 40, which will be described later. The substrate support unit 11 is located in the plasma processing space and has a substrate support surface for supporting a substrate.

[0010] The plasma generation unit 12 is configured to generate plasma from at least one processing gas supplied into the plasma processing space. The plasma formed in the plasma processing space may be capacitively coupled plasma (CCP), inductively coupled plasma (ICP), ECR (Electron Cyclotron Resonance) plasma, helicon wave excited plasma (HWP), or surface wave plasma (SWP), etc. Various types of plasma generation units, including AC (Alternating Current) plasma generation units and DC (Direct Current) plasma generation units, may also 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 an RF (Radio Frequency) signal and a microwave signal. In one embodiment, the RF signal has a frequency in the range of 100 kHz to 150 MHz.

[0011] The control unit 2 processes computer-executable instructions that cause the plasma processing apparatus 1 to perform the various processes described herein. The control unit 2 may be configured to control the elements of the plasma processing apparatus 1 to perform the various processes described herein. In one embodiment, part or all of the control unit 2 may be included in the plasma processing apparatus 1. The control unit 2 is implemented, for example, by a computer 2a. The control unit 2 may include a processing unit 2a1, a storage unit 2a2, and a communication interface 2a3. The functions realized by the processing unit 2a1 described herein may be implemented in a circuit or processing circuit, including a general-purpose processor, an application-specific processor, integrated circuits, ASICs (Application Specific Integrated Circuits), a CPU (Central Processing Unit), a conventional circuit, and / or a combination thereof, programmed to realize the described functions. The processor is considered to be a circuit or processing circuit, including transistors and other circuits. The processor may be a programmed processor that executes a program stored in the storage unit 2a2. This program may be pre-stored in the storage unit 2a2 or retrieved via a medium when needed. The acquired program is stored in the storage unit 2a2 and read from the storage unit 2a2 and executed by the processing unit 2a1. The medium may be various storage media readable by the computer 2a, or it may be a communication line connected to the communication interface 2a3. 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 communicate with the plasma processing device 1 via a communication line such as a LAN (Local Area Network).In this disclosure, circuits, units, and means are hardware programmed to perform or configured to perform the functions described. Such hardware may be any hardware described in this disclosure, or any hardware known to be programmed to perform or execute the functions described. If such hardware is a processor that is considered to be a type of circuit, such circuit, means, or unit is a combination of hardware and software used to constitute such hardware and / or processor.

[0012] [Plasma Processing Equipment] Below, an example of the configuration of a capacitively coupled plasma processing equipment as an example of plasma processing equipment 1 will be described. Figure 2 is an example of a diagram illustrating the configuration of a capacitively coupled plasma processing equipment (substrate processing equipment) 1.

[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 unit 11 and a gas introduction unit. The gas introduction unit is configured to introduce at least one processing gas into the plasma processing chamber 10. The gas introduction unit includes a shower head 13. The substrate support unit 11 is located inside the plasma processing chamber 10. The shower head 13 is located above the substrate support unit 11. In one embodiment, the shower 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 shower head 13, the side walls 10a of the plasma processing chamber 10, and the substrate support unit 11. The plasma processing chamber 10 is grounded. The shower head 13 and the substrate support unit 11 are electrically insulated from the housing of the plasma processing chamber 10.

[0014] 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 the 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 in a plan view. The substrate W is placed on the central region 111a of the main body portion 111, and the ring assembly 112 is placed on the annular region 111b of the main body portion 111 so as to surround the substrate W on the central region 111a of the main body portion 111. Therefore, the central region 111a is also called the substrate support surface for supporting the substrate W, and the annular region 111b is also called the ring support surface for supporting the ring assembly 112.

[0015] In one embodiment, the main body 111 includes a base 1110 and an electrostatic chuck 1111. The base 1110 includes a conductive member. The conductive member of the base 1110 can function as a lower electrode. The electrostatic chuck 1111 is placed on the base 1110. The electrostatic chuck 1111 includes a ceramic member 1111a and an electrostatic chuck electrode 1111b placed within the ceramic member 1111a. The electrostatic chuck electrode 1111b is also called a clamping electrode. In one embodiment, the electrostatic chuck electrode 1111b is electrically connected or coupled to a chuck power supply. The chuck power supply may be a DC power supply or an AC power supply. The ceramic member 1111a has a central region 111a. In one embodiment, the ceramic member 1111a also has an annular region 111b. Furthermore, other members surrounding the electrostatic chuck 1111, such as an annular electrostatic chuck or an annular insulating member, may have an annular region 111b. In this case, the ring assembly 112 may be placed on the annular electrostatic chuck or the annular insulating member, or it may be placed on both the electrostatic chuck 1111 and the annular insulating member. In addition, at least one bias electrode, which is electrically connected or coupled to the power supply 31 and / or power supply 32 described later, may be placed inside the ceramic member 1111a. In this case, at least one bias electrode functions as a lower electrode. Also, the conductive member of the base 1110 and the bias electrode inside the ceramic member 1111a may function as multiple lower electrodes. In one embodiment, the first voltage generation unit 32a, which functions as a voltage pulse generation unit described later, is electrically connected or coupled to the bias electrode inside the ceramic member 1111a, and the first RF generation unit 31a, described later, is electrically connected or coupled to the conductive member of the base 1110. Furthermore, the electrostatic chuck electrode 1111b may function as a lower electrode. Therefore, the substrate support portion 11 includes at least one lower electrode.

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

[0017] The substrate support section 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 W 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 through the flow path 1110a. In one embodiment, the flow path 1110a is formed within the base 1110, and one or more heaters are arranged within the ceramic member 1111a of the electrostatic chuck 1111. The substrate support section 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.

[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 a plurality of gas inlet ports 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 through the plurality of gas inlet ports 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 side wall 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 processing gas to the shower head 13 from a corresponding gas source 21 via a corresponding flow controller 22. Each flow controller 22 may include, for example, a mass flow controller or a pressure-controlled flow controller. Furthermore, the gas supply unit 20 may include at least one flow modulation device that modulates or pulses the flow rate of at least one processing gas.

[0020] The power supply system 30 includes a power supply 31 that is electrically connected to or coupled to the plasma processing chamber 10. In one embodiment, the power supply 31 is electrically connected to or coupled to the plasma processing chamber 10 via at least one impedance matcher. The impedance matcher may be a mechanically controlled matcher or an electronically controlled matcher. The power supply 31 is configured to supply at least one RF signal (RF power) to at least one lower electrode and / or at least one upper electrode. This generates plasma from at least one processing gas supplied to the plasma processing space 10s. Therefore, the power supply 31 can function as at least part of the plasma generation unit 12. In addition, by supplying a bias RF signal to at least one lower electrode, a bias potential is generated on the substrate W, and ionic components in the formed plasma can be drawn into the substrate W.

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

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

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

[0024] In various embodiments, the first and / or second voltage signals may be pulsed. In this case, the first voltage generation unit 32a and / or the second voltage generation unit 32b function as voltage pulse generation units configured to generate a sequence of voltage pulses. Thus, the sequence of voltage pulses is applied to at least one lower electrode and / or at least one upper electrode. In one embodiment, the sequence of voltage pulses has a plurality of cycles, each cycle including a burst of voltage pulses in a first period and a constant reference voltage in a second period. That is, in the sequence of voltage pulses, the burst of voltage pulses is repeated. The absolute value of the voltage level of the voltage pulse is greater than the absolute value of the voltage level of the reference voltage. The voltage pulse may have an arbitrary waveform having a rectangle, trapezoid, triangle, or a combination thereof, and the arbitrary waveform may change over time. The voltage pulse may have positive polarity or negative polarity. The sequence of voltage pulses may also include one or more positive voltage pulses and one or more negative voltage pulses within one cycle. The first and second voltage generation units 32a and 32b may be provided in addition to the power supply 31, and the first voltage generation unit 32a may be provided in place of the second RF generation unit 31b.

[0025] The exhaust system 40 may be connected to, for example, a gas outlet 10e located 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.

[0026] [Etching Process] Next, an example of the etching process will be explained using Figures 3 and 4. Figure 3 is an example of a flowchart showing the etching process. Figure 4 is an example of a diagram showing a pulse pattern.

[0027] Here, a source RF signal (e.g., 100 MHz) is supplied to the upper electrode from the first RF generation unit 31a (source power supply). Note that the source RF signal is not limited to being supplied to the upper electrode, but may also be supplied to the lower electrode. In addition, a first bias signal (bias RF signal, e.g., 13 MHz) is supplied to the lower electrode from the second RF generation unit 31b (first bias power supply). In addition, a second bias signal (first voltage signal, e.g., a 400 kHz negative DC pulse signal) is supplied to the lower electrode from the first voltage generation unit 32a (second bias power supply). Figure 4 shows the power of the source RF signal, the power of the first bias signal, and the voltage of the second bias signal, respectively. Note that in the following description, the power level may be used to include both AC signals and DC pulse signals.

[0028] Furthermore, as shown in Figure 4, the etching process consists of a first process P1, a second process P2, and a third process P3, with this cycle being repeated a predetermined number of times.

[0029] In step S101, the substrate W is prepared. Here, the control unit 2 controls a transport device (not shown) to transport the substrate W into the plasma processing chamber 10 and to control the substrate W to be supported by the substrate support unit 11.

[0030] As shown in Figure 5A, which will be described later, the substrate W includes a base material 500, a film to be etched 510, and a mask 520 having a pattern of openings 521. In the etching process, the film to be etched 510 is etched through the pattern of openings 521 of the mask 520, forming high aspect ratio recesses 511 (see Figures 5B and 5C, which will be described later) in the film to be etched 510.

[0031] In the following explanation, we will use the case where the film to be etched 510 is a silicon oxide film as an example. The mask 520 only needs to be made of a material that has an etching selectivity ratio with the film to be etched 510, and may be, for example, a metal-containing carbon film (such as a tungsten carbide (WC) film), a photoresist film, a polysilicon film, etc.

[0032] In step S102, the supply of etching gas is started. Here, the control unit 2 controls the exhaust system 40 so that the pressure in the plasma processing space 10s is adjusted to a predetermined pressure (for example, 10 mTorr). The control unit 2 also controls the gas supply unit 20 so that etching gas is supplied from the gas supply unit 20 to the shower head 13. The etching gas is, for example, C ４ F ６ , O ２ A mixed gas of Ar can be used.

[0033] Next, the first process P1 is executed. Specifically, the first process P1 includes step S103.

[0034] In step S103, the control unit 2 controls the first RF generation unit 31a to supply a source RF signal (e.g., 100 MHz) with a first power level L1 from the first RF generation unit 31a to the upper electrode (first process P1). The first bias signal and the second bias signal are not supplied to the lower electrode (OFF). After the process time T1 has elapsed, the control unit 2 proceeds to step S104.

[0035] In the first process P1, a source RF signal at a first power level L1, which is greater than the power levels described later (second to fourth power levels L2 to L4), is supplied to the upper electrode to generate etching gas radicals (e.g., CF radicals) in the plasma.

[0036] Next, the second process P2 is executed. The second process P2 alternately repeats processes P21 and P22. Specifically, the second process P2 includes steps S104 to S106.

[0037] In step S104, the control unit 2 controls the first RF generation unit 31a to supply a source RF signal (e.g., 100 MHz) with a second power level L2 from the first RF generation unit 31a to the upper electrode (process P21). Note that the first bias signal and the second bias signal are not supplied to the lower electrode (OFF). After process time T21 has elapsed, the control unit 2 proceeds to step S105.

[0038] Furthermore, the second power level L2 is smaller than the first power level L1 (L2 < L1). Also, the process time T21 is shorter than the process time T1 and the process time T3 described later. For example, it is preferable that the processing time for one cycle (processes P1 to P3) is in the range of 500 μs to 2000 μs, and the process time T21 is in the range of 5 μs to 50 μs.

[0039] In process P21, etching gas radicals (e.g., CF radicals) are generated in the plasma by supplying a source RF signal at a second power level L2, which is greater than the third power level L3 described later, to the upper electrode.

[0040] In step S105, the control unit 2 controls the first RF generation unit 31a to supply a source RF signal (e.g., 100 MHz) with a third power level L3 from the first RF generation unit 31a to the upper electrode, and controls the second RF generation unit 31b to supply (ON) a first bias signal (e.g., 13 MHz) from the second RF generation unit 31b to the lower electrode (process P22). In other words, the power level of the first bias signal in process P22 is greater than the power level of the first bias signal in process P21. Also, the power level of the first bias signal in process P22 is greater than the power level of the first bias signal in the first and third processes P1 and P3. The second bias signal is not supplied to the lower electrode (OFF). When process time T22 has elapsed, the control unit 2 proceeds to step S106.

[0041] Note that the third power level L3 is smaller than the second power level L2 (L3 < L2). Also, the process time T22 is shorter than the process time T1 and the process time T3 described later. For example, the processing time for one cycle (processes P1 to P3) is within the range of, for example, 500 μs or more and 2000 μs or less, and the process time T22 is preferably within the range of 5 μs or more and 50 μs or less.

[0042] In process P22, by supplying a first bias signal to the lower electrode, ions in the plasma are drawn toward the lower electrode. Then, the ions drawn toward the lower electrode collide with collisions including charge exchange collisions with radicals, thereby imparting kinetic energy to the radicals. The collided radicals are accelerated and travel anisotropically downward (in the direction of the lower electrode). As a result, the amount of radicals reaching the bottom surface of the concave portion 511 is increased.

[0043] In step S106, the control unit 2 determines whether or not a predetermined number of repetitions has elapsed. If the predetermined number of repetitions has not elapsed (S106・NO), the process of the control unit 2 returns to step S104, and steps S104 (process P21) to S105 (process P22) are repeated. If the predetermined number of repetitions has elapsed (S106・YES), the process of the control unit 2 proceeds to step S107. Note that in FIG. 4, the case where the number of repetitions is 5 is shown.

[0044] As described above, in the second process P2, by alternately repeating process P21 and process P22, the radicals generated in process P21 are made to travel with anisotropy in process P22, and the amount of radicals reaching the bottom surface of the concave portion 511 is increased.

[0045] Next, the third process P3 is executed. Specifically, the third process P3 includes step S107.

[0046] In step S107, the control unit 2 controls the first RF generation unit 31a to supply a source RF signal (e.g., 100 MHz) with a fourth power level L4 from the first RF generation unit 31a to the upper electrode, and at the same time, the control unit 2 controls the first voltage generation unit 32a to supply (ON) a second bias signal (e.g., a DC pulse of 400 kHz) from the first voltage generation unit 32a to the lower electrode (third process P3). In other words, the voltage level of the second bias signal in the third process P3 is larger (has a larger absolute value) than the voltage levels of the second bias signals in the first and second processes P1 and P2. Note that the first bias signal is in a state (OFF) where it is not supplied to the lower electrode. Also, the supply of the source RF signal with the fourth power level L4 and the supply of the second bias signal may be started simultaneously. When the process time T3 has elapsed, the process of the control unit 2 proceeds to step S108.

[0047] Note that the fourth power level L4 preferably has a power capable of maintaining plasma in the third process P3, and may be larger than the second power level L2 (L4 > L2), may be equal to the second power level L2 (L4 = L2), or may be smaller than the second power level L2 (L4 < L2). Also, the fourth power level L4 is preferably larger than the third power level L3 (L4 > L3). Thereby, plasma can be suitably maintained in the third process P3.

[0048] Also, the state where the source RF signal is not supplied to the upper electrode (OFF) may be adopted. In other words, the fourth power level L4 may be zero (refer to the dashed-dotted line in FIG. 4).

[0049] In the third process P3, by supplying the second bias signal to the lower electrode, the ion angle (the variation in the incident angle of ions on the substrate surface) is narrowed, and ions are drawn in substantially perpendicular to the substrate W.

[0050] In step S108, the control unit 2 determines whether a predetermined number of repetitions has elapsed. If the predetermined number of repetitions has not elapsed (S108, NO), the control unit 2 returns to step S103, and steps S103 to S107 (processes P1 to P3) are repeated. If the predetermined number of repetitions has elapsed (S108, YES), the etching process is terminated. That is, the supply of the source RF signal, the first bias signal, and the second bias signal is stopped, and the supply of the etching gas is stopped. After that, the substrate W is transported from the plasma processing chamber 10 by a transport device (not shown).

[0051] As described above, by etching the film to be etched 510 with the first process P1, second process P2, and third process P3 as one cycle, high aspect ratio recesses 511 (e.g., vias, trenches, etc.) are formed in the film to be etched 510.

[0052] The shape of the recess 511 formed by the etching process will be explained using Figures 5A to 5C. Figures 5A to 5C are examples of schematic cross-sectional views of the substrate W.

[0053] Figure 5A is an example of a schematic cross-sectional view of a substrate W before etching. As shown in Figure 5A, the substrate W comprises a base material 500, a film to be etched 510, and a mask 520 having a pattern of openings 521.

[0054] Figure 5B is an example of a schematic cross-sectional view of the substrate W during the etching process of the reference example. In the etching process of the reference example, the first process P1 and the third process P3 constitute one cycle, and this cycle is repeated a predetermined number of times. In this case, the radicals 550 move isotropically. The direction of movement is schematically shown by arrows.

[0055] The radicals 550 are consumed on the side walls of the recess 511, forming a bowing shape on the side walls of the recess 511. Furthermore, the amount of radicals reaching the bottom surface of the recess 511 is reduced. Also, the bottom CD (BCD) on the bottom surface of the recess 511 becomes smaller compared to the top CD (Critical Dimension) on the opening side of the recess 511. Additionally, the side walls of the recess 511 become tapered.

[0056] Furthermore, if the first power level L1 of the first process P1 and / or the process time T1 are increased in order to increase the amount of radicals reaching the bottom surface of the recess 511, the bottom CD can be enlarged and the side walls of the recess 511 can be made approximately vertical, but this may further increase the boeing.

[0057] Figure 5C is an example of a schematic cross-sectional view of the substrate W during the etching process shown in Figures 3 and 4. In the etching process shown in Figures 3 and 4, the first process P1, the second process P2, and the third process P3 constitute one cycle, and this cycle is repeated a predetermined number of times. In this case, the radicals 550 move with downward anisotropy. The direction of movement is schematically shown by arrows.

[0058] Radical 550 reduces the amount of radicals consumed at the side walls of the recess 511, suppressing the bowing shape of the side walls of the recess 511. It also increases the amount of radicals that reach the bottom surface of the recess 511. Furthermore, compared to the case in Figure 5B, the bottom CD (BCD) on the bottom surface side of the recess 511 can be made larger. In addition, the side walls of the recess 511 become approximately vertical.

[0059] As described above, the etching process shown in Figures 3 and 4 can suppress bowing and form recesses 511 (etched shapes) where the side walls are substantially vertical. Furthermore, recesses 511 with a high aspect ratio can be formed.

[0060] Next, the plasma state in the second process P2 will be explained using Figures 6A to 6C and Figure 7. Figures 6A to 6C are examples of schematic diagrams illustrating the plasma state. Figure 7 is an example of a graph showing the changes in each plasma parameter. In Figures 6A to 6C, ions are shown as circles with a + sign, and electrons are shown as circles with an e sign. Figure 7 shows the sheath thickness, ion flux Γi, and plasma electron density Ne. Here, we will explain the steady state of process P21 (see Figure 6A and Figure 7(a)), the transient state from process P21 to process P22 (see Figure 6B and Figure 7(b)), and the steady state of process P22 (see Figure 6C and Figure 7(c)).

[0061] Figure 6A shows the steady state of process P21. In process P21, a source RF signal at the second power level L2 is supplied from the first RF generation unit 31a to the upper electrode. This generates a bulk plasma 610 between the upper electrode (not shown in Figure 6A) and the lower electrode 600. A sheath 620 is also formed between the lower electrode 600 and the bulk plasma 610. Another sheath (not shown) is also formed between the upper electrode and the bulk plasma 610. By supplying a source RF signal at the second power level L2, which is higher than the third power level L3, the electron density Ne in the bulk plasma 610 is high.

[0062] Figure 6B shows the transitional state from process P21 to process P22. Regions 631 and 632 are the regions where bulk plasma 610 was generated in the steady state of process P21. In process P22, the first RF generation unit 31a supplies a source RF signal at a third power level L3, which is lower than the second power level L2, to the upper electrode, and the second RF generation unit 31b supplies a first bias signal to the lower electrode. By applying the first bias signal, electrons in region 631 move rapidly, and region 631 also becomes a sheath 620, and the thickness of the sheath 620 increases. Also, as ions from region 631 enter the sheath 620, the ion flux Γi temporarily increases. On the other hand, region 632 is a bulk plasma 610, and inherits the previous state (steady state of process P21), it has a high electron density Ne.

[0063] Subsequently, as shown in Figure 7, the ion flux Γi decreases while maintaining the sheath thickness, and the electron density Ne also decreases.

[0064] Figure 6C shows the steady state of process P22. As shown in Figures 6C and 7, in the steady state of process P22, the sheath thickness is increased, the ion flux Γi decreases, and the electron density Ne decreases compared to the steady state of process P21.

[0065] Thus, in the transient state, the ion flux Γi temporarily increases, causing radicals struck by ions to accelerate and propagate anisotropically downwards (towards the lower electrode). This increases the amount of radicals that reach the bottom surface of the recess 511. Furthermore, by alternately repeating processes P21 and P22, the transient state can be repeatedly generated, thereby increasing the amount of radicals that reach the bottom surface of the recess 511.

[0066] While embodiments of the plasma processing system have been described above, this disclosure is not limited to the embodiments described above, and various modifications and improvements are possible within the scope of the gist of this disclosure as described in the claims.

[0067] The embodiments disclosed above include, for example, the following aspects: (Note 1) A plasma processing chamber, a substrate support section provided within the plasma processing chamber and supporting a substrate, a gas supply section for supplying etching gas to the plasma processing chamber, a lower electrode provided on the substrate support section, an upper electrode facing the lower electrode, a source power supply for supplying a source RF signal to generate plasma to the upper electrode or the lower electrode, a first bias power supply for supplying a first bias signal to the lower electrode, a second bias power supply for supplying a second bias signal to the lower electrode, and a control unit, wherein the control unit controls the following steps to be repeated: (a) the source power supply to supply the source RF signal at a first power level to the upper electrode or the lower electrode, (b) (b1) the source power supply to supply the source RF signal at a second power level to the upper electrode or the lower electrode, and (b2) the source power supply to supply the source RF signal at a third power level to the upper electrode or the lower electrode, and the first bias power supply to supply the first bias signal to the lower electrode, (c) A plasma processing apparatus that controls the second bias power supply to supply the second bias signal to the lower electrode, and controls the process of repeating the cycle, with the steps of (a), (b), and (c) forming one cycle. (Note 2) The plasma processing apparatus according to Note 1, wherein step (c) is controlled to supply the source RF signal of the fourth power level to the upper electrode or the lower electrode and to supply the second bias signal to the lower electrode. (Note 3) The plasma processing apparatus according to Note 1 or Note 2, wherein the first power level is greater than the second power level and the third power level. (Note 4) The plasma processing apparatus according to Note 3, wherein the second power level is greater than the third power level. (Note 5) The plasma processing apparatus according to Note 2, wherein the fourth power level is greater than the third power level.(Note 6) The plasma processing apparatus according to Note 2 or Note 5, wherein step (c) controls the source power supply and the second bias power supply so that the supply of the source RF signal of the fourth power level and the supply of the second bias signal are started simultaneously. (Note 7) The plasma processing apparatus according to any one of Notes 1 to 6, wherein the first bias signal is a bias RF signal. (Note 8) The plasma processing apparatus according to any one of Notes 1 to 7, wherein the second bias signal is a negative DC pulse signal. (Note 9) The plasma processing apparatus according to any one of Notes 1 to 8, wherein the time of step (b1) is in the range of 5 μs to 50 μs, and the time of step (b2) is in the range of 5 μs to 50 μs. (Note 10) An etching method for etching a substrate, comprising: a plasma processing chamber; a substrate support section provided in the plasma processing chamber and supporting a substrate; a gas supply section for supplying etching gas to the plasma processing chamber; a lower electrode provided in the substrate support section; an upper electrode facing the lower electrode; a source power supply for supplying a source RF signal for generating plasma to the upper electrode or the lower electrode; a first bias power supply for supplying a first bias signal to the lower electrode; and a second bias power supply for supplying a second bias signal to the lower electrode, wherein (a) a step of controlling the source power supply to supply the source RF signal of a first power level to the upper electrode or the lower electrode; and (b) An etching method comprising: (b1) controlling the source power supply to supply the source RF signal at a second power level to the upper electrode or the lower electrode; (b2) controlling the source power supply to supply the source RF signal at a third power level to the upper electrode or the lower electrode and the first bias power supply to supply a first bias signal to the lower electrode, and repeating the above steps; (c) controlling the second bias power supply to supply a second bias signal to the lower electrode; and controlling the above steps (a), (b), and (c) to constitute one cycle, and repeating the above cycle.(Note 11) The etching method according to Note 10, wherein step (c) is controlled to supply the source RF signal at the fourth power level to the upper electrode or the lower electrode and to supply the second bias signal to the lower electrode. (Note 12) The etching method according to Note 10 or Note 11, wherein the first power level is greater than the second power level and the third power level. (Note 13) The etching method according to Note 12, wherein the second power level is greater than the third power level. (Note 14) The etching method according to Note 11, wherein the fourth power level is greater than the third power level. (Note 15) The etching method according to Note 11 or Note 14, wherein step (c) is controlled to supply the source RF signal at the fourth power level and the second bias signal simultaneously. (Note 16) The etching method according to any one of Notes 10 to 15, wherein the first bias signal is a bias RF signal. (Note 17) The etching method according to any one of Notes 10 to 16, wherein the second bias signal is a negative DC pulse signal. (Note 18) The etching method according to any one of Notes 10 to 17, wherein the time of step (b1) is in the range of 5 μs or more and 50 μs or less, and the time of step (b2) is in the range of 5 μs or more and 50 μs or less.

[0068] Furthermore, this application claims priority based on Japanese Patent Application No. 2024-193748, filed on November 5, 2024, and the entire contents of these Japanese Patent Applications are incorporated herein by reference.

[0069] W Substrate 1 Plasma processing apparatus 2 Control unit 10 Plasma processing chamber 10s Plasma processing space 11 Substrate support part (lower electrode) 13 Shower head (upper electrode) 20 Gas supply unit 31a First RF generation unit (source power supply) 31b Second RF generation unit (first bias power supply) 32a First voltage generation unit (second bias power supply) 40 Exhaust system 500 Substrate 510 Film to be etched 511 Recess 520 Mask 521 Opening

Claims

Plasma processing chamber and A substrate support section is provided within the plasma processing chamber to support the substrate, A gas supply unit that supplies etching gas to the plasma processing chamber, The lower electrode provided in the substrate support portion, An upper electrode facing the lower electrode, A source power supply that supplies a source RF signal for generating plasma to the upper electrode or the lower electrode, A first bias power supply that supplies a first bias signal to the lower electrode, A second bias power supply that supplies a second bias signal to the lower electrode, It comprises a control unit and, The control unit, (a) A step of controlling the source power supply to supply the source RF signal of the first power level to the upper electrode or the lower electrode, (b) A step of controlling the system to repeat the following steps: (b1) controlling the source power supply to supply the source RF signal at a second power level to the upper electrode or the lower electrode; and (b2) controlling the source power supply to supply the source RF signal at a third power level to the upper electrode or the lower electrode, and the first bias power supply to supply the first bias signal to the lower electrode. (c) A step of controlling the second bias power supply to supply the second bias signal to the lower electrode, A process for controlling the process to repeat the cycle, with the above steps (a), (b), and (c) forming one cycle, and a process for controlling the process, Plasma processing equipment. 　 The aforementioned step (c) is, The source power supply is controlled to supply the source RF signal at the fourth power level to the upper electrode or the lower electrode, and to supply the second bias signal to the lower electrode. The plasma processing apparatus according to claim 1. 　 The first power level is greater than the second power level and the third power level. The plasma processing apparatus according to claim 1. 　 The second power level is greater than the third power level. The plasma processing apparatus according to claim 3. 　 The fourth power level is greater than the third power level. The plasma processing apparatus according to claim 2. 　 The aforementioned step (c) is, The source power supply and the second bias power supply are controlled so that the supply of the source RF signal at the fourth power level and the supply of the second bias signal are started simultaneously. The plasma processing apparatus according to claim 2. 　 The first bias signal is a bias RF signal. The plasma processing apparatus according to claim 1. 　 The second bias signal is a negative DC pulse signal. The plasma processing apparatus according to claim 1. 　 The time for step (b1) is within the range of 5 μs to 50 μs. The time for step (b2) is within the range of 5 μs to 50 μs. The plasma processing apparatus according to claim 1. 　 An etching method comprising: a plasma processing chamber; a substrate support portion provided within the plasma processing chamber for supporting a substrate; a gas supply portion for supplying etching gas to the plasma processing chamber; a lower electrode provided on the substrate support portion; an upper electrode facing the lower electrode; a source power supply for supplying a source RF signal for generating plasma to the upper electrode or the lower electrode; a first bias power supply for supplying a first bias signal to the lower electrode; and a second bias power supply for supplying a second bias signal to the lower electrode, wherein the etching method is performed on the substrate, (a) A step of controlling the source power supply to supply the source RF signal of the first power level to the upper electrode or the lower electrode, (b) A step of controlling the system to repeat the following steps: (b1) controlling the source power supply to supply the source RF signal at a second power level to the upper electrode or the lower electrode; and (b2) controlling the source power supply to supply the source RF signal at a third power level to the upper electrode or the lower electrode, and the first bias power supply to supply the first bias signal to the lower electrode. (c) A step of controlling the second bias power supply to supply the second bias signal to the lower electrode, A step of controlling the process so that the above steps (a), (b), and (c) constitute one cycle and are repeated, Etching method. 　 The aforementioned step (c) is, The source power supply is controlled to supply the source RF signal at the fourth power level to the upper electrode or the lower electrode, and to supply the second bias signal to the lower electrode. The etching method according to claim 10. 　 The first power level is greater than the second power level and the third power level. The etching method according to claim 10. 　 The second power level is greater than the third power level. The etching method according to claim 12. 　 The fourth power level is greater than the third power level. The etching method according to claim 11. 　 The aforementioned step (c) is, The source power supply and the second bias power supply are controlled so that the supply of the source RF signal at the fourth power level and the supply of the second bias signal are started simultaneously. The etching method according to claim 11. 　 The first bias signal is a bias RF signal. The etching method according to claim 10. 　 The second bias signal is a negative DC pulse signal. The etching method according to claim 10. 　 The time for step (b1) is within the range of 5 μs to 50 μs. The time for step (b2) is within the range of 5 μs to 50 μs. The etching method according to claim 10.

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