Plasma processing equipment

Abstract

To provide a technique that can form plasma having a desired density distribution while improving the responsiveness of magnetic field generation.SOLUTION: A plasma processing apparatus includes: a processing chamber in which plasma processing of a substrate to be processed is performed; a sample stage disposed inside the processing chamber and holding the substrate to be processed; a solenoid coil arranged to surround the processing chamber and forming a magnetic field within the processing chamber; a yoke having a cylindrical shape, having a structure in which ferromagnetic layers and insulating layers are alternately laminated in a direction around a central axis, and disposed so as to surround the solenoid coil; an excitation power source that supplies excitation power for excitation to the solenoid coil; and a control unit that controls the excitation power source and intermittently supplies the excitation power to the solenoid coil.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a plasma processing apparatus. [Background technology]

[0002] In the technical field of semiconductor integrated circuits, progress is being made in miniaturizing patterning in order to improve performance. To date, progress in two-dimensional miniaturization has led to improved performance through technologies such as shortening wiring lengths, and the increased number of elements that can be manufactured per processed substrate has also led to reduced manufacturing costs per element. On the other hand, as the processing dimensions required for semiconductor elements approach the nanometer order, which is close to the dimensions of atoms, the difficulty of two-dimensional miniaturization has increased significantly, both technically and physically.

[0003] In response to the above technical demands, new technologies such as the application of new materials and three-dimensional device structures are being adopted in semiconductor manufacturing. Plasma processing equipment, which uses plasma for etching and other processes, has traditionally been used in the manufacture of semiconductor devices. However, as semiconductor devices become increasingly miniaturized, a decrease in yield due to plasma processing has become a problem. In particular, variation (non-uniformity) in the shape of the substrate after processing in the radial direction has been one of the causes of the decrease in yield.

[0004] A known plasma processing apparatus is an electron cyclotron resonance (ECR) plasma processing apparatus, which generates plasma by using an electric field of a microwave and a magnetic field formed in a processing chamber. In ECR plasma processing apparatuses, efforts have been made to make the density distribution of the generated plasma uniform in order to improve the uniformity of processing in the radial direction of the substrate.

[0005] For example, Patent Document 1 discloses a technology for providing a plasma processing apparatus or method with improved processing uniformity, which includes a processing chamber arranged inside a vacuum vessel, a sample stage arranged inside the processing chamber on which a wafer to be processed is placed, an electric field forming unit that forms an electric field supplied into the processing chamber, a coil that interacts with the electric field to form a magnetic field for forming plasma in the processing chamber, and a controller that repeatedly increases and decreases the strength of the magnetic field formed by the coil at predetermined intervals to increase and decrease the strength of the plasma in the processing chamber, and which processes the wafer by repeatedly forming and diffusing the plasma. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] International Publication No. 2018 / 061235 Summary of the Invention [Problem to be solved by the invention]

[0007] In conventional plasma processing apparatuses, microwaves are introduced into the processing chamber through a microwave-transparent circular plate located above the processing chamber. Furthermore, the waveguide through which the microwaves propagate is aligned with the central axis of the cylindrical processing chamber to enhance the uniformity of the electric field in the circumferential direction within the processing chamber. Due to this arrangement, the plasma generated within the processing chamber has a locally high density in the central portion of the processing chamber, including the central axis, even from the initial stage of discharge. As a result, in plasma processing apparatuses, the plasma density near the center of the processing chamber is higher than that in the outer peripheral region.

[0008] In Patent Document 1, the magnitude of the magnetic field formed is controlled by intermittently or increasing or decreasing the supply of power to a solenoid coil, thereby diffusing charged particles in the plasma and reducing non-uniformity in the radial density distribution of the processing chamber. According to the inventors' investigations, while the time scale for plasma diffusion in the radial direction of the substrate is milliseconds to tens of milliseconds in typical plasma processing, it was estimated that the excitation speed for forming the magnetic field in the technology disclosed in Patent Document 1 would be 100 milliseconds or more. If the technology disclosed in Patent Document 1 were to be used in plasma processing, it would be necessary to improve the excitation speed by 10 to 100 times. Prior Art Document 1 does not take such a problem into consideration.

[0009] An object of the present invention is to provide a technique capable of forming plasma having a desired density distribution while improving the response of magnetic field generation. [Means for solving the problem]

[0010] The above object is achieved by a plasma processing apparatus comprising: a processing chamber in which plasma processing of a substrate to be processed is performed; a sample stage disposed inside the processing chamber and holding the substrate to be processed; a solenoid coil disposed to surround the processing chamber and forming a magnetic field within the processing chamber; a cylindrical yoke having a structure in which ferromagnetic layers and insulator layers are alternately stacked in a direction around a central axis and disposed to surround the solenoid coil; an excitation power supply that supplies excitation power for exciting the solenoid coil; and a control unit that controls the excitation power supply and causes the excitation power to be intermittently supplied to the solenoid coil. [Effects of the Invention]

[0011] According to the present invention, it is possible to improve the response of the generation of the magnetic field and to form plasma having a desired density distribution. Problems, configurations, and effects other than those described above will become apparent from the following description of the preferred embodiments. [Brief explanation of the drawings]

[0012] [Figure 1] FIG. 1 is a vertical cross-sectional view schematically showing the configuration of a plasma processing apparatus according to an embodiment. [Figure 2] FIG. 2 is a perspective view showing a schematic configuration of the yoke. [Figure 3] FIG. 3 is a timing chart showing the flow of plasma processing in the plasma processing apparatus according to the embodiment. [Figure 4] FIG. 4 is a diagram schematically showing the plasma density distribution in the processing chamber during multiple phases of the etching process according to the embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0013] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. Note that the present invention is not limited to this embodiment. In addition, in the description of the drawings, the same parts are designated by the same reference numerals. In order to facilitate understanding of the invention, the position, size, shape, range, etc. of each component shown in the drawings may not represent the actual position, size, shape, range, etc. Therefore, the present invention is not necessarily limited to the position, size, shape, range, etc. disclosed in the drawings. "Upper" refers to the vertically upper direction when the device is placed horizontally. "Top" refers to the part located at the top of the device. "Plasma density" refers to the density of charged particles such as electrons and ions contained in the plasma.

[0014] (Embodiment) An embodiment of the present invention will be described below with reference to FIGS.

[0015] The configuration of a plasma processing apparatus according to an embodiment will be outlined with reference to Fig. 1. Fig. 1 is a vertical cross-sectional view that schematically shows the configuration of a plasma processing apparatus according to an embodiment.

[0016] (Configuration for generating electric field) 1, a plasma processing apparatus 100 according to an embodiment includes a microwave power supply 101 and a microwave tuner 102, which serve as a heating source for generating plasma. The microwave power supply 101 generates microwaves for generating plasma. The microwave tuner 102 monitors the reflected power of microwaves passing through a waveguide 103 and reduces the reflected wave component. The microwave introduction window 108 is a disk-shaped member made of, for example, quartz, and introduces microwaves transmitted through the waveguide 103 into a processing chamber 107 while maintaining the processing chamber 107 airtight. The microwaves from the microwave power supply 101 pass through the waveguide 103 and the microwave introduction window 108 and are introduced into the processing chamber 107.

[0017] In the processing chamber 107, plasma processing of a substrate 112 to be processed is performed. A sample stage 111 is placed inside the processing chamber 107, and the substrate 112 to be processed is placed therein. The processing chamber 107 has a cylindrical shape and is surrounded by solenoid coils 105 and 106 and a yoke 104. The sample stage 111 is provided in the center of the lower part of the processing chamber 107, and a substrate 112 to be processed (hereinafter also referred to as a "wafer"), such as a semiconductor substrate, is placed and held on the sample stage 111. An electrode is provided inside the sample stage 111, and high-frequency bias power is applied to this electrode. The high-frequency bias power is power for generating an electric field for accelerating ions in the plasma toward the sample stage 111. The high-frequency power transmitted from a high-frequency power source 113 is matched by a high-frequency matching box 114 to impedances resulting from the sample stage 111, the substrate 112 to be processed, and the generated plasma.

[0018] The control unit 115 controls the high frequency power supply 113, the degaussing power supply 116, and the exciting power supply 118 in accordance with the desired plasma processing.

[0019] (Configuration regarding processing gas) Gases required for plasma processing are introduced into the processing chamber 107 through gas inlets 109 and 110. The gas inlets 109 and 110 are controlled by a control unit 115. The gas inlets 109 and 110 are capable of pulse operation and switching operation, and the flow rates are controlled. These are controlled by the control unit 115 in accordance with the desired plasma processing.

[0020] The vacuum pump 120 exhausts gas contained in the processing chamber 107 and adjusts the pressure inside the processing chamber 107 to a predetermined value. The vacuum pump 120 is controlled by the control unit 115.

[0021] (Configuration for generating magnetic field) Next, the configuration for generating a magnetic field will be described. Solenoid coils 105 and 106 are arranged to surround the processing chamber 107 and generate a magnetic field within the processing chamber 107. The solenoid coils 105 and 106 are air-core coils in order to ensure the responsiveness of the generated magnetic field, as described below. The yoke 104 is cylindrical and has a structure in which ferromagnetic layers and insulating layers are alternately stacked around the central axis, and is arranged to surround the solenoid coils 105 and 106. The yoke 104 also functions to guide magnetic flux to the desired location for generating the magnetic field, thereby preventing dissipation of the magnetic flux generated by the solenoid coils 105 and 106 and increasing the density within the processing chamber 107. The structure of the yoke 104 will be described in detail below.

[0022] The demagnetization power supply 116 supplies power to the solenoid coils 105 and 106 to demagnetize the yoke and the processing chamber. Specifically, the demagnetization power supply 116 supplies a pulsed current (hereinafter also referred to as a "degauss pulse current") to the solenoid coils 105 and 106 at a predetermined cycle. For example, the demagnetization power supply 116 supplies a pulsed current having a damped oscillation waveform at a predetermined cycle to the solenoid coils 105 and 106. However, the peak value of this current is set to an upper limit equal to the current value at which the ferromagnetic layer 201 constituting the yoke 104 becomes magnetically saturated. The path of the current supplied from the demagnetization power supply 116 may be shared with the line of the current supplied from the excitation power supply 118 to the solenoid coils 105 and 106, or it may be a line provided on the surface of the yoke that is specialized for demagnetization efficiency and is separate from the line of the current from the excitation power supply 118.

[0023] Furthermore, the excitation power supply 118 supplies power for excitation to the solenoid coils 105 and 106. More specifically, the excitation power supply 118 supplies a pulsed current (hereinafter also referred to as an "excitation pulse current") to the solenoid coils 105 and 106 at a predetermined cycle. For example, the waveform of the current supplied from the excitation power supply 118 is a square wave having a sufficiently flat top with respect to the current rise time. Examples of the configuration of such an excitation power supply 118 include a discharge circuit that combines a so-called pulse forming network with a gate-controllable solid-state switch such as a thyristor or IGBT and a charging power supply, and a discharge circuit that has a sufficient capacitor bank and is controlled by a solid-state switch that is also gate-controllable, but the embodiment is not limited to these.

[0024] By providing separate demagnetization power supply 116 and excitation power supply 118, it is possible to pass current through solenoid coils 105 and 106 according to the purpose of demagnetization or excitation, and demagnetization or excitation can be performed with good reproducibility. Also, because the duration of the output pulse from demagnetization power supply 116 and the duration of the output pulse from the excitation current source differ greatly, insulation is ensured by placing high-frequency filter 117 between the two power supplies.

[0025] As will be described later, the control unit 115 controls the solenoid coils 105 and 106 so that they form a magnetic field intermittently.

[0026] In the plasma processing apparatus 100 having such a configuration, 2.45 GHz microwaves generated by a microwave power supply 101 and tuned by a microwave tuner 102 propagate through a waveguide 103, pass through a microwave introduction window 108, and are supplied to a processing chamber 107. The magnetic field generated by the solenoid coils 105 and 106 is symmetrical about the central axis of the processing chamber 107, as indicated by magnetic field lines 119, and has a so-called divergent orientation (configuration), which diverges from the center of the processing chamber 107 toward the periphery as it moves from the top to the bottom of the processing chamber 107. A processing gas (hereinafter also referred to as "processing gas") is introduced into the processing chamber 107 through gas introduction ports 109 and 110. The processing gas is heated by electron cyclotron resonance (ECR) generated by the interaction of the electric and magnetic fields of the microwaves. Dissociation or ionization occurs in the processing gas, and plasma is generated in the processing chamber 107 by ECR discharge.

[0027] (Details of the yoke configuration) Next, the structure and function of the yoke 104 shown in Fig. 1 will be described in detail with reference to Fig. 2. Fig. 2 is a perspective view schematically showing the structure of the yoke 104.

[0028] In this embodiment, the solenoid coils 105 and 106 are operated by supplying pulsed power from the degaussing power supply 116 and the magnetizing power supply 118. In such a case, it is desirable to design the structures of the yoke 104 and the processing chamber 107 taking into consideration the diffusion transient phenomenon of the magnetic field within the processing chamber 107. As shown in FIG. 2, the yoke 104 has a cylindrical shape and a hollow portion in its center. In the plasma processing apparatus 100, the processing chamber 107 is positioned in the hollow portion. The yoke 104 has a structure in which ferromagnetic layers 201 and dielectric layers 202 are alternately stacked in the circumferential direction (direction around the central axis). Each layer occupies a width corresponding to a predetermined angle around the central axis ca when the yoke 104 is viewed from above. In other words, each layer has a radial shape around the central axis ca when the yoke 104 is viewed from above. In FIG. 2, the yoke 104 is radially divided into 2N pieces, N of which are ferromagnetic layers 201 and N of which are dielectric layers 202 (N is a positive integer). The ferromagnetic layers 201 are made of a ferromagnetic material, and the dielectric layers 202 are made of a low-dielectric material. As can be seen from the cross-sectional view of the yoke 104 shown in FIG. 1, each of the ferromagnetic layers 201 and the dielectric layers 202 has an inverted L shape. As a result of these being alternately connected together to form an integrated unit, the yoke 104 is configured as a cylindrical member that houses the solenoid coils 105 and 106 inside. The value N is the outer circumferential length of the yoke and τ (described later). m and d.

[0029] Assume a plasma processing apparatus with solenoid coils 105 and 106 and yoke 104 arranged as shown in FIG. 1, but with the yoke consisting of a single ferromagnetic material, unlike the embodiment shown in FIG. 2. When pulsed or high-frequency power is applied to the electromagnet, an induced electromotive force is generated inside the yoke due to the displacement magnetic field. In the conductive ferromagnetic material, a diamagnetic current flows in a circular pattern around the central axis ca of the yoke, attempting to generate a magnetic field in the opposite direction to the magnetic field generated by the solenoid coil. This diamagnetic current affects the magnetic field generated by the solenoid coil. This results in a problem: it takes a long time for the solenoid coil to form the desired magnetic field configuration, impairing the responsiveness of the magnetic field formation. Furthermore, a problem occurs in that the magnetic field configuration formed deviates from the design value due to a loss of power for excitation.

[0030] In the plasma processing apparatus 100 according to the embodiment, the yoke 104 includes the dielectric layer 202 in its laminated structure, thereby suppressing the generation of a circular diamagnetic current. This prevents a loss in responsiveness for forming a magnetic field when a current is passed through the solenoid coils 105 and 106, and improves the precision of position control. Furthermore, because the magnetic field penetrates the dielectric layer 202 at the speed of light without loss, the yoke 104 according to the embodiment allows magnetic flux to penetrate three-dimensionally into the ferromagnetic layer 201 sandwiched between the dielectric layers 202, thereby improving the speed and precision of magnetization and demagnetization, as described below.

[0031] (Diffusion phenomenon of magnetic field in processing chamber) Furthermore, in the embodiment, in order to realize high responsiveness in turning on / off the magnetic field formed in the processing chamber 107 or in increasing / decreasing its strength, the diffusion phenomenon of the magnetic field is also taken into consideration in the structure of the processing chamber 107. Generally, the penetration of a magnetic field (diffusion of the magnetic field) into an electric conductor is based on the following magnetic field diffusion equation:

[0032]

number

[0033]

number

[0034]

number

[0035] In the embodiment, when a conductor such as a metal is used as a member of the vacuum vessel forming the processing chamber 107, in order to prevent the response of the magnetic field from being impaired, τ m Materials with physical properties such as magnetic permeability and conductivity are selected so that the value is sufficiently small, and the thickness of the components and other structures are also set. Note that when a dielectric is used as a component of a vacuum vessel, the conductivity is very small and the penetration time is extremely short, so there is no restriction on the thickness of the component and any shape can be selected.

[0036] (Plasma diffusion time) When considering the density distribution of plasma in the processing chamber 107, the time scale of excitation of the magnetic field formed by supplying pulsed power to the electromagnet is set taking into account the radial motion of the plasma in the processing chamber 107.

[0037] Table 1 shows the typical lifetime and density diffusion time of plasma used in plasma processing equipment.

[0038] [Table 1]

[0039] The example shown in Table 1 assumes that the plasma is formed using argon gas (argon plasma), the pressure inside the processing chamber 107 is 0.1 Pa, the degree of ionization of the plasma is 0.01, the ion temperature is 0.1 eV (electron volt), and the electron temperature is 1 eV.

[0040] The "lifetime" phenomenon is estimated to be between 30 ms (milliseconds) and 300 ms. It refers to the time required for neutral particle collisions to relax in the plasma, and is estimated to be 10 to 100 times the collision period. The "free diffusion" phenomenon is estimated to be greater than 0.7 ms. It refers to the time required for ions to traverse the wafer surface due to thermal velocity, and is estimated to be greater than 0.7 ms due to the inclusion of collisions. The "diffusion under a magnetic field (0.085 T)" phenomenon is estimated to be 9,840 ms. It is estimated to be the time required for ions to escape from the magnetic field lines due to a trajectory shift caused by ion collisions in a 0.085 T magnetic field, i.e., the time required for ions to traverse the wafer surface. The "diffusion under a weak magnetic field (0.001 T)" phenomenon is estimated to be 5.14 ms. It is estimated to be the time required for ions to escape from the magnetic field lines due to a trajectory shift caused by ion collisions in a 0.001 T magnetic field, i.e., the time required for ions to traverse the wafer surface.

[0041] From this table, we can see that for a lifetime of 30 ms to 300 ms, the diffusion time of charged particles in plasma is estimated to be on the order of 1 ms under magnetic field-free conditions, but increases to a time scale of nearly 1 s (seconds) under conditions in which a magnetic field of strength 0.0875 T is supplied.

[0042] The reason for this variation in diffusion time is thought to be that the formed magnetic field affects the radial movement of charged particles in the plasma within the processing chamber 107. For this reason, it is thought that by eliminating or reducing the magnetic field before the plasma reaches the end of its life and disappears, the charged particles in the plasma can be sufficiently diffused within the processing chamber 107 in the radial direction, thereby reducing the bias in the plasma density distribution within the processing chamber 107 in the radial direction.

[0043] (Timing chart) The operation of the plasma processing apparatus 100 according to the embodiment will be described with reference to FIG. 3. FIG. 3 is a timing chart showing the flow of plasma processing in the plasma processing apparatus according to the embodiment. FIG. 3 shows the state of processing over time. Here, the chart "Microwave Output" indicates the supply of microwaves from the microwave power supply 101 of the plasma processing apparatus 100 as ON (on, supplied) or OFF (off, not supplied). Furthermore, the chart "High Frequency Bias Current" indicates the high frequency bias power (unit: W) supplied to the sample stage 111. The chart "Excitation Pulse Current (A)" indicates the excitation pulse current (unit: A) supplied from the excitation power supply 118. The chart "Degauss Pulse Current (A)" indicates the degauss pulse current (unit: A) supplied from the degauss power supply 116.

[0044] In the embodiment, when etching the substrate 112 to be processed, the substrate 112 to be processed is transferred from a separate vacuum chamber connected to the processing chamber 107 by a transfer device such as a robot arm and handed over to a sample stage 111 arranged in the processing chamber 107. When the robot arm leaves the processing chamber 107 and the processing chamber 107 inside the vacuum chamber is sealed, the substrate 112 to be processed is electrostatically attracted and held on the sample stage 111. Furthermore, a gas according to the purpose of the processing is introduced into the processing chamber 107, which has been evacuated to a predetermined vacuum level, and the pressure inside the processing chamber 107 is maintained within a range suitable for processing the substrate 112 to be processed. Such processing is performed before the start of the etching processing in the embodiment.

[0045] In FIG. 3, processing gases for etching the substrate to be processed are continuously introduced into the processing chamber 107 through gas inlets 109 and 110 .

[0046] (Pre-phase) First, there is a period during which the substrate 112 to be processed is held on the sample stage 111 and ECR discharge of the plasma is initiated. This period is referred to as the pre-phase. During the pre-phase, the control unit 115 controls the demagnetization power supply 116 to supply demagnetization power before the excitation power supply 118 supplies excitation power. Specifically, as shown at time t1 in the "Degauss Pulse Current (A)" chart, the demagnetization power supply 116 generates a demagnetization pulse current with a pulse width τ1 and supplies it to the solenoid coils 105 and 106. This demagnetizes the solenoid coils 105 and 106, the yoke 104, and the wall materials inside and outside the processing chamber 107. This causes the magnetization states of these components of the plasma processing apparatus 100 to become unmagnetized or to become a common magnetized state. The pulse width τ1 is appropriately selected based on the configuration of the plasma processing apparatus 100, etc., so as to achieve such a magnetization state.

[0047] In addition, in the subsequent phases described below, the control unit 115 also causes the demagnetization power supply 116 to supply demagnetization power before the excitation power supply 118 supplies excitation power. By performing excitation after the plasma processing apparatus 100 is set to a non-magnetic state (non-magnetized state) or a common magnetized state in this way, it is possible to prevent the magnetic field to be formed from being affected by external factors and to form a desired magnetic field.

[0048] Next, the excitation power supply 118 supplies a first power. More specifically, as shown at time t2 in the chart "Excitation Pulse Current (A)," the excitation power supply 118 generates a rectangular excitation pulse current I1 with a pulse width τ2 and supplies it to the solenoid coils 105 and 106. Meanwhile, the degaussing power supply 116 stops supplying the degaussing pulse current at time t2. This forms a magnetic field for generating plasma in the processing chamber 107.

[0049] (Phase A (first period)) Next, a period for generating plasma is set. This period is referred to as Phase A (first period). During Phase A, while the excitation power supply 118 supplies the first power, the microwave power supply 101 outputs microwaves. Specifically, as shown in the "Microwave Output" chart, the microwave power supply 101 supplies microwaves into the processing chamber 107 for a period τ3. This excites the processing gas in the processing chamber 107, causing ionization or dissociation, and generating plasma. Phase A is the same as period τ3. Here, the microwaves are output after a period Δt1 has elapsed since the excitation pulse current (A) was output. Although the excitation pulse current is shown as a square wave, in reality, it has an exponential rise portion. In other words, period Δt1 is determined as the discharge time constant of the circuit consisting of the solenoid coils 105 and 106, which function as electromagnets, and the excitation power supply 118.

[0050] In this embodiment, the end of period τ2 and the end of period τ3 are set to be the same. That is, the supply of the excitation pulse current from excitation power supply 118 or the supply of the magnetic field from solenoid coils 105 and 106 and the supply of microwaves from microwave power supply 101 end at the same time. This stops the ECR discharge of the plasma.

[0051] (Phase B (second period)) Next, a period is provided in which the charged particles in the generated plasma diffuse from the center of the processing chamber toward the periphery. This period is referred to as Phase B (the second period). Phase B follows Phase A, and during Phase B, the excitation power supply 118 stops supplying the first power. Specifically, as shown in the chart "Excitation Pulse Current (A)," the excitation power supply 118 stops supplying the excitation pulse current to the solenoid coils 105 and 106 for a period Δt2 after the supply of the plasma-generating microwaves is stopped. Because no magnetic field is generated within the processing chamber 107, the charged particles in the plasma diffuse radially from the center of the processing chamber 107 toward the periphery. As a result, the density distribution of the charged particles in the plasma changes from a so-called "middle-high" state in Phase A, in which the density is high in the center of the processing chamber 107 and low on the periphery, to a state in which the density distribution decreases in the center and increases on the periphery, reducing the imbalance in the density distribution.

[0052] In Phase B, the current value of the excitation pulse current may be set to a value smaller than the current value in Phase A, as indicated by the dashed line in the chart "Excitation Pulse Current (A)." This results in a weak magnetic field being supplied to the processing chamber 107, which loosens the constraints of the magnetic field, and the charged particles in the plasma diffuse from the center of the processing chamber 107 toward the periphery. This reduces the bias in the plasma density distribution, similar to when the supply of the excitation pulse current is stopped. During the period Δt2, the degaussing power supply 116 supplies a degaussing pulse current to the solenoid coils 105 and 106.

[0053] (Phase C (third period)) Next, a period is provided in which a magnetic field is formed in the diffused plasma. This period is referred to as Phase C (third period). Phase C is the period following Phase B, and during Phase C, the excitation power supply 118 supplies a second power. Specifically, as shown in the chart "Excitation Pulse Current (A)," the excitation power supply 118 starts supplying the excitation pulse current I2 at time t4, after Δt2 has elapsed. Note that, as shown in the charts "Degauss Pulse Current (A)" and , the degauss power supply 116 stops supplying the degauss pulse current at time t4, after Δt2 has elapsed. When the excitation power supply 118 again supplies the excitation pulse current to the solenoid coils 105 and 106, a magnetic field indicated by magnetic field lines 119 formed by the solenoid coils 105 and 106 is provided within the processing chamber 107. This magnetic field acts to suppress diffusion of the plasma generated in Phase B and maintain the plasma density distribution in the radial direction.

[0054] In addition, while plasma is generated in Phase A, the density distribution of the plasma is maintained in Phase C. In other words, the first power supplied in Phase A is a power for forming a magnetic field with an intensity that generates plasma from the processing gas. In addition, the second power supplied in Phase C is a power for forming a magnetic field with an intensity that fixes the density distribution of charged particles in the processing chamber 107 or suppresses diffusion of the charged particles. Specifically, as shown in the chart "Excitation Pulse Current (A)," the current I1 supplied in Phase A and the current I2 supplied in Phase C are set to different values, and in this embodiment, the current value in Phase A is set higher than the current value in Phase C.

[0055] Furthermore, a high frequency bias power is supplied for a period τ4 from the high frequency power supply 113 to an electrode disposed inside the sample stage 111. As a result, ions in the plasma are attracted to the substrate 112 to be processed with the density distribution bias reduced, and the etching process of the target film on the substrate 112 to be processed proceeds.

[0056] (Plasma density distribution) In this embodiment, the steps of the pre-phase, Phase A, Phase B, and Phase C are performed at least once as one cycle to etch the target film on the substrate 112. Fig. 4 is a diagram schematically showing the plasma density distribution in the processing chamber during the multiple phases of the etching process in this embodiment.

[0057] 3 constitutes one cycle of etching processing performed in the embodiment, and this cycle is performed at least once in processing the substrate 112. The control unit 115 monitors the remaining film thickness of the substrate 112, and when it determines that the end condition is met, the plasma processing cycle is stopped.

[0058] As described above, Phase A is a process of generating an ECR discharge to form plasma. As shown in Figure 5(a), an ECR discharge occurs due to the microwave and the magnetic field formed by the solenoid coils 105 and 106, generating plasma. Note that in the graph, "radius" indicates the distance from the center to the periphery of the processing chamber 107, and "plasma density" indicates the density of plasma in the processing chamber 107. Also, the vertical stripes indicate the state in which a magnetic field is formed.

[0059] Phase B is a process for diffusing the generated plasma. As shown in Fig. 5(b), in Phase B, the magnetic field disappears or its strength is reduced, and the charged particles in the plasma diffuse from the center of the processing chamber 107 toward the outer periphery, thereby reducing the imbalance in the density distribution of the plasma, which is larger in the center.

[0060] Phase C is a process for maintaining the plasma density distribution and performing plasma processing on the substrate. As shown in FIG. 5(c), a magnetic field is formed to maintain the plasma density with reduced bias. Furthermore, high-frequency bias power is supplied to the substrate 112 to be processed, and the etching process of the substrate 112 to be processed proceeds.

[0061] In the above embodiment, the charged particles in the plasma generated in Phase A are diffused from the center of the processing chamber 107 toward the outer periphery in Phase B. In Phase C, a magnetic field is formed in the state in which the charged particles in the plasma are diffused. In this way, plasma processing can be performed in a state in which the bias in the plasma density distribution in the processing chamber 107 is reduced, and the variation in the shape of the processing target substrate 112 in the radial direction is reduced, improving the processing yield.

[0062] (Modification of the embodiment) The present disclosure is not limited to the embodiments and can include various modifications.

[0063] For example, in the embodiment, a common excitation pulse current and a common demagnetization pulse current are passed through the solenoid coils 105 and 106. In contrast, as a first modification, the shape of the magnetic field to be formed may be changed by changing the ratio between the current supplied to the solenoid coil 105 and the current supplied to the solenoid coil 106.

[0064] In addition, in the embodiment, the processing gas introduced from the gas inlets 109 and 110 is continuously supplied from the pre-phase to phase C. In contrast, as a second modification, the processing gas may be supplied intermittently from the pre-phase to phase C.

[0065] Furthermore, by combining the first and second modified examples to control the diffusion rates of ions and radicals in the plasma, and further combining this with control of magnetic field generation, it is possible to further improve the uniformity of the processing distribution on the substrate to be processed.

[0066] (Actions and Effects) In the present disclosure, the solenoid coils 105 and 106 are air-core coils. Also, the components of the processing chamber 107 have a magnetic field penetration time τm The structure and materials were selected based on the thickness d of the conductor, and the thickness d of the conductor. This ensures the responsiveness of the magnetic field generated when excitation is performed using the solenoid coils 105 and 106.

[0067] Furthermore, taking into consideration the lifetime of charged particles in the plasma, the plasma diffusion process in Phase B and the maintenance of the plasma density distribution in Phase C are set. Because the magnetic field is controlled taking into consideration the dynamic behavior of the plasma, the density distribution of the plasma used in plasma processing can be optimized.

[0068] The yoke 104 has a laminated structure of ferromagnetic layers and dielectric layers, which reduces the dissipation of the magnetic flux generated by the solenoid coils 105 and 106 and suppresses the generation of magnetic currents. Furthermore, the ferromagnetic layers can be penetrated by magnetic fields from three-dimensional directions, improving the speed and accuracy of magnetization and demagnetization.

[0069] As described above, it is possible to improve the response of the magnetic field generation and to form plasma having a desired density distribution.

[0070] Although the embodiments of the present invention have been described above, the present disclosure is not limited to the above-described embodiments, and various modifications are possible within the scope of the gist of the present disclosure. [Explanation of symbols]

[0071] 101... Microwave power supply, 102···Microwave tuner, 103...waveguide, 104 · · · York, 105... solenoid coil, 106···Solenoid coil, 107···Processing chamber, 108... Microwave introduction window, 109 Gas inlet, 110 Gas inlet, 111... Sample stage, 112....Substrate to be processed, 113...High frequency power supply, 114... High frequency matching box, 115···Control section, 116...power supply for degaussing, 117···High frequency filter, 118...excitation power supply, 119···Magnetic field lines, 120···Vacuum pump 201...Ferromagnetic layer, 202···Dielectric layer.

Claims

1. a processing chamber in which plasma processing of a substrate to be processed is performed; a sample stage disposed inside the processing chamber and holding the substrate to be processed; a solenoid coil disposed to surround the processing chamber and forming a magnetic field within the processing chamber; a cylindrical yoke having a structure in which ferromagnetic layers and insulating layers are alternately stacked in a direction around a central axis, the yoke being disposed so as to surround the solenoid coil; an excitation power supply that supplies excitation power for exciting the solenoid coil; a control unit that controls the excitation power supply to intermittently supply the excitation power to the solenoid coil; A plasma processing apparatus comprising:

2. The excitation power supply is a first period during which a first power is supplied; a second period following the first period, during which the supply of the first power is stopped; 2. The plasma processing apparatus according to claim 1, wherein power is supplied intermittently to the solenoid coil by repeating a cycle of a first period and a second period in which the second power is supplied, after the second period.

3. the first power is power for forming a magnetic field having a strength that generates plasma, 3. The plasma processing apparatus according to claim 2, wherein the second power is a power for forming the magnetic field having an intensity that fixes a density distribution of the charged particles in the plasma or that suppresses diffusion of the charged particles.

4. 3. The plasma processing apparatus according to claim 2, wherein during the third period, a high frequency bias power is supplied to an electrode disposed inside the sample stage.

5. the plasma processing apparatus further includes a demagnetization power supply controlled by the control unit to supply demagnetization power to the solenoid coil; 3. The plasma processing apparatus according to claim 2, wherein the control unit causes the demagnetizing power supply to supply the demagnetizing power before the excitation power supply supplies the excitation power.

6. a period including the first period, the second period, and the third period is defined as one cycle; The plasma processing apparatus according to claim 2 , wherein the control unit controls the processing of the substrate to be processed so that the cycle period is performed at least once.

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