Plasma treatment device having matching box

Abstract

An example of a plasma processing device includes an RF generator, a matching box (the matching box comprises an input terminal connected to the RF generator, a sensor configured to detect high-frequency electricity, an impedance control circuit, and an output terminal), a matching controller connected to the sensor and configured to control the impedance control circuit, a reactor chamber connected to the output terminal, and a harmonic filter circuit connected to a transmission line between the sensor and the reactor chamber.

Description

Technology Field

[0001] An example regarding a plasma processing device is described. Background Technology

[0002] A plasma processing unit generates plasma and provides processes such as deposition, etching, and film modification on a substrate. Harmonics with frequencies that are integer multiples of the fundamental wave are generated from the plasma within the reactor chamber. In some cases, these harmonics affect impedance matching operations through a matching box. When impedance matching operations through a matching box are affected by harmonics, an increase in reflected waves occurs in a stationary state during plasma processing, and in some cases, high reflected wave spikes are generated at the end of plasma processing.

[0003] Some embodiments described herein can solve the aforementioned problems. Some embodiments described herein can provide a plasma processing apparatus in which the influence of harmonics on the matching operation is reduced.

[0004] In some examples, the plasma processing device comprises an RF generator, a matching box (the matching box includes an input terminal connected to the RF generator, a sensor configured to detect high-frequency electricity, an impedance control circuit, and an output terminal), a matching controller connected to the sensor and configured to control the impedance control circuit, a reactor chamber connected to the output terminal, and a harmonic filter circuit connected to a transmission line between the sensor and the reactor chamber. Brief explanation of the drawing

[0005] Figure 1 shows an exemplary configuration of a plasma processing device. Figure 2 shows a circuit diagram of a matching box. Figure 3 shows a harmonic filter circuit according to another example. Figure 4 shows the intensity of high-frequency electricity according to a comparative example. Figure 5 is a timing chart of plasma treatment according to a comparative example. Figure 6 shows the intensity of high-frequency electricity. Figure 7 is a timing chart of plasma treatment. Specific details for implementing the invention

[0006] The plasma processing apparatus will be described below with reference to the attached drawings. Identical or corresponding components are indicated by the same reference numerals, and in some cases, redundant descriptions thereof will be omitted.

[0007] Implementation example

[0008] FIG. 1 is a diagram showing an exemplary configuration of a plasma processing apparatus. The plasma processing apparatus includes, for example, an RF generator (14) provided in a rack (12). For example, the RF generator (14) outputs two types of high-frequency electricity having different frequencies. For example, the RF generator (14) outputs a first high-frequency electricity of 27 MHz or higher and a second high-frequency electricity of 430 KHz or lower. In this example, these types of high-frequency electricity are superimposed and provided to a reactor chamber through a single path. The frequency of the first high-frequency electricity is, for example, 27.12 MHz, and the frequency of the second high-frequency electricity is, for example, 400 KHz or 430 KHz. In another example, the RF generator (14) outputs a first high-frequency electricity of 1 GHz or higher and a second high-frequency electricity of a frequency lower than the frequency of the first high-frequency electricity.

[0009] In another example, the RF generator (14) outputs high-frequency electricity of one frequency. For example, the RF generator outputs high-frequency electricity of 27 MHz or higher or high-frequency electricity of 1 GHz or higher.

[0010] The power of the high-frequency electricity output from the RF generator (14) is, for example, 3 kW or more. In other examples, other high-frequency power may be used.

[0011] The RF generator (14) is connected to the input terminal (18a) of the matching box (18). The matching controller (20) is connected to the matching box (18). The matching controller (20) generates a signal to adjust the impedance of the matching box (18) and transmits the signal to the matching box (18).

[0012] The matching box (18) has an output terminal (18e) connected to the reactor chamber (22). The reactor chamber (22) is a device that stores a substrate to be processed and performs plasma processing on the substrate.

[0013] The RF generator (14) is connected to a computer (24), and the computer (24) is connected to a human-machine interface (MMI) (26). The computer (24) and the MMI (26) provide a monitor signal of the RF generator (14) to a customer host computer. For example, information such as the moving wave power and reflected wave power of the RF generator (14) is provided to the customer host computer through the computer (24) and the MMI (26). For example, the MMI (26) generates a waveform as shown in FIGS. 5 and FIGS. 7, provides the waveform to the customer host computer, and displays instantaneous values ​​such as moving wave power and reflected wave power. In addition to RF power information, various types of information for monitoring the RF generator (14) may be provided to the customer host computer.

[0014] The aforementioned components are provided as a main frame (16).

[0015] FIG. 2 is a circuit diagram showing an exemplary configuration of a matching box (18). For example, the matching box (18) includes an input terminal (18a), a sensor (18b), a harmonic filter circuit (F1 and F2), an impedance control circuit (18A), and an output terminal (18e). The input terminal (18a) is connected to the sensor (18b). The sensor (18b) detects high-frequency electricity. The sensor (18b) detects high-frequency electricity of, for example, 27.12 MHz. In another example, the sensor (18b) detects high-frequency electricity having the frequency of the first high-frequency electricity.

[0016] The sensor (18b) is connected to an impedance control circuit (18A). In this example, the impedance control circuit (18A) includes a variable capacitor (18c, 18d) and an inductor (L3). The impedance control circuit (18A) may have other configurations capable of changing the impedance.

[0017] The harmonic filter circuits (F1 and F2) are connected to a transmission line connecting the sensor (18b) and the impedance control circuit (18A). The harmonic filter circuit (F1) is a series circuit of an inductor (L1) and a capacitor (C1). The harmonic filter circuit (F2) is a series circuit of an inductor (L2) and a capacitor (C2). For example, the harmonic filter circuit (F1) is provided to reduce the second harmonic, and the harmonic filter circuit (F2) is provided to reduce the third harmonic. The harmonic filter circuits (F1 and F2) may have cutoff frequencies for reducing the second and third harmonics, respectively.

[0018] Depending on the operating environment, such as process conditions, impedance, or the frequency of high-frequency electricity, the type and intensity of the generated harmonics vary. Accordingly, the intensity of the second and third harmonics is high in one operating environment, the intensity of the second through fourth harmonics is high in another operating environment, and only the intensity of the second harmonic is high in yet another operating environment. The harmonic filter circuits (F1 and F2) of FIG. 2 are provided to reduce the second and third harmonics, but in other examples, the harmonic filter circuits may be provided with an optional number corresponding to the harmonics to be reduced. Thus, three or more harmonic filter circuits, each comprising an LC series circuit, may be provided to attenuate three or more harmonics. Each harmonic filter circuit includes at least one LC series circuit.

[0019] The impedance control circuit (18A) is connected to the output terminal (18e). The matching box (18) may include a ground terminal (18f) connected to the reactor chamber (22).

[0020] The matching controller (20) is connected to the aforementioned sensor (18b). The matching controller (20) receives the detection result from the sensor (18b) and controls the impedance adjustment circuit (18A). In this example, the matching controller (20) adjusts the capacitance of each variable capacitor (18c, 18d) to achieve impedance matching. For example, when a variable capacitor whose capacitance changes according to the amount of rotation of the rotation axis is used, the motor, upon receiving a signal from the matching controller, rotates the rotation axis to adjust the capacitance of the variable capacitor. The motor may be connected to the matching controller via a signal line and a power line.

[0021] In the example shown in FIG. 2, harmonic filter circuits (F1 and F2) are provided in the matching box (18). In another example, the harmonic filter circuits (F1 and F2) may be provided in a transmission line connecting the matching box (18) and the reactor chamber (22) as shown in FIG. 3. As exemplarily shown in FIG. 2 and FIG. 3, each harmonic filter circuit may be connected to an optional location on the transmission line between the sensor and the reactor chamber.

[0022] To clarify the significance of the plasma processing apparatus according to the present disclosure, a comparative example will be described below. The plasma processing apparatus according to the comparative example has the same configuration as the plasma processing apparatus according to the embodiment, but does not have a harmonic filter circuit. FIGS. 4 and 5 are drawings showing the content of plasma processing according to the comparative example. FIGS. 4 is a drawing showing the intensity of high-frequency electricity detected by a matching box in plasma processing using the plasma processing apparatus according to the comparative example. FIGS. 4 shows the generation of peaks of the fundamental wave of 27.12 MHz, the second harmonic, the third harmonic, and the fourth harmonic. FIGS. 5 is a timing chart of the plasma processing in which the harmonics shown in FIGS. 4 are generated. In this example, two types of high-frequency electricity, labeled "RF forward" and "LRF (low RF) forward," are provided from an RF generator, and "RF reflection" and "LRF reflection" are generated as reflected wave electricity for the corresponding high-frequency electricity, respectively.

[0023] In the comparative example, since the sensor within the matching box receives harmonics, the matching operation by the matching controller is also affected by harmonics. Consequently, in the comparative example, the reflected wave, indicated as "RF reflection," increases during and at the end of the plasma treatment.

[0024] FIGS. 6 and 7 are diagrams showing the content of plasma processing when the plasma processing apparatus of FIGS. 1 and 2 is used. FIG. 6 is a diagram showing the intensity of high-frequency power detected by a matching box. Harmonics traveling from the reactor chamber (22) toward the sensor (18b) are reduced through harmonic filter circuits (F1 and F2), and thus the second and third harmonics are significantly attenuated compared to the example shown in FIG. 4. The reason the fourth harmonic (108.48 MHz) is hardly detected is believed to be that the fourth harmonic is attenuated along with the third harmonic through the harmonic filter circuit (F2) to attenuate the third harmonic. FIG. 7 is a timing chart of plasma processing in which harmonics are attenuated as shown in FIG. 6. FIG. 7 shows that "RF reflection" is reduced compared to the example shown in FIG. 5.

[0025] FIGS. 4 through 7 show that harmonics of high-frequency electricity, referred to as high-RF (HRF) such as 27.12 MHz, are detected by the sensor (18b) and lead to incomplete matching operation. In experiments conducted by the inventors, the influence of harmonics on matching operation is particularly large when the HRF is provided at a power of 3 kW or more.

[0026] LRF that can be superimposed on HRF also causes harmonics. However, these LRF harmonics cause less actual damage than HRF harmonics. Therefore, the reduction of "RF reflection" can be prioritized over the reduction of "LRF reflection" in Figures 5 and 7. Harmonics of high-frequency electricity with VHF (Very High Frequency) at a level higher than HRF (approximately GHz) cause the same problems as HRF harmonics. Therefore, when VHF is used, a harmonic filter circuit to attenuate VHF harmonics can be provided between the sensor and the reactor chamber.

Claims

Claim 1 A plasma processing apparatus comprising: an RF generator; a matching box including an input terminal connected to the RF generator, a sensor configured to detect high-frequency electricity, an impedance control circuit, and an output terminal; a matching controller connected to the sensor and configured to control the impedance control circuit; a reactor chamber connected to the output terminal; a transmission line between the sensor and the reactor chamber; a first harmonic filter circuit connected between the transmission line and a first ground, wherein the first harmonic filter circuit comprises a first inductor and a first capacitor connected in series; and a second harmonic filter circuit connected between the transmission line and a second ground, wherein the second harmonic filter circuit comprises a second inductor and a second capacitor connected in series, wherein the second harmonic filter circuit is configured to reduce the second harmonic frequency of the output of the RF generator. Claim 2 In claim 1, the plasma processing device, wherein the first harmonic filter circuit is provided in the matching box. Claim 3 A plasma processing device according to claim 1, wherein the first harmonic filter circuit is provided in a transmission line connecting the matching box and the reactor chamber. Claim 4 delete Claim 5 A plasma processing device according to claim 1, wherein the first harmonic filter circuit is configured to reduce the first harmonic frequency of the output of an RF generator. Claim 6 A plasma processing device according to claim 1, wherein the RF generator outputs two types of high-frequency electricity having different frequencies. Claim 7 A plasma processing device according to claim 6, wherein the RF generator is configured to output a first high-frequency electric current of 27 MHz or higher and a second high-frequency electric current of 430 KHz or lower. Claim 8 A plasma processing apparatus according to claim 6, wherein the RF generator is configured to output a first high-frequency electricity of 1 GHz or higher and a second high-frequency electricity having a frequency lower than the frequency of the first high-frequency electricity. Claim 9 A plasma processing device according to claim 8, wherein the power of the first high-frequency electric current is 3 kW or more. Claim 10 A plasma processing device according to claim 7, wherein the power of the first high-frequency electric current is 3 kW or more. Claim 11 In claim 7, the plasma processing device is configured such that the sensor detects high-frequency electricity having the frequency of the first high-frequency electricity.

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