JP2023129234A - Plasma processing apparatus - Google Patents

Abstract

To provide a technique for reducing reflection of source high frequency power due to impedance mismatch.SOLUTION: A plasma processing apparatus disclosed herein includes a chamber, a substrate support, a bias power source, a high frequency electrode, a high frequency power source, a matching box, and a capacitor. The substrate support is provided within the chamber. The bias power source is electrically coupled to the substrate support and configured to provide electrical bias energy to the substrate support. The high frequency power supply is electrically connected to the high frequency electrode and is configured to provide source high frequency power to the high frequency electrode for generating plasma from gas within the chamber. The matching box is connected between the high frequency power source and the high frequency electrode. The capacitor is separated from the matching box and connected between the high frequency electrode and the ground.SELECTED DRAWING: Figure 2

Description

BACKGROUND OF THE INVENTION Exemplary embodiments of the present disclosure relate to plasma processing apparatus.

Plasma processing apparatuses are used in plasma processing of substrates. The plasma processing apparatus includes a chamber, a substrate support, a high frequency power source, and a bias power source. The substrate support section is provided within the chamber and supports a substrate placed thereon. A radio frequency power source provides source radio frequency power to generate a plasma within the chamber. A bias power supply provides bias power to the substrate support to draw ions from the plasma to the substrate. Patent Document 1 below discloses a capacitively coupled plasma processing apparatus as such a plasma processing apparatus.

JP 2017-108159 Publication

The present disclosure provides techniques for reducing reflections of source RF power due to impedance mismatch.

In one exemplary embodiment, a plasma processing apparatus is provided. The plasma processing apparatus includes a chamber, a substrate support, a bias power source, a high frequency electrode, a high frequency power source, a matching box, and a capacitor. A substrate support is provided within the chamber. The bias power supply is electrically coupled to the substrate support and configured to provide electrical bias energy to the substrate support for ion attraction. The electrical bias energy has a waveform period and is generated periodically. The radio frequency power supply is electrically connected to the radio frequency electrode and is configured to provide source radio frequency power to the radio frequency electrode for generating plasma from the gas within the chamber. The matching box is connected between the high frequency power source and the high frequency electrode. The capacitor is separated from the matching box and connected between the high frequency electrode and ground.

According to one exemplary embodiment, reflections of source RF power due to impedance mismatch may be reduced.

1 is a diagram for explaining a configuration example of a plasma processing system. FIG. 2 is a diagram for explaining a configuration example of a capacitively coupled plasma processing apparatus. 1 is a diagram illustrating an example configuration of a power supply system in a plasma processing apparatus according to an exemplary embodiment. FIG. 3 is a diagram showing an example of a waveform of electric bias energy. FIG. 2 is a plan view of a plurality of capacitors of a plasma processing apparatus according to one exemplary embodiment. 2 is a timing chart of an example of electric bias energy and source frequency of source high-frequency power. Each of FIGS. 7A and 7B is a timing chart of an example of source high frequency power and electric bias energy. Each of FIGS. 8A and 8B is a timing chart of an example of source high frequency power and electric bias energy. 2 is a timing chart of an example of electric bias energy and source frequency of source high-frequency power. Each of FIGS. 10(a) to 10(d) is a timing chart of another example of electric bias energy. FIGS. 11(a) and 11(b) are graphs showing the results of the experiment.

Various exemplary embodiments will be described in detail below with reference to the drawings. In addition, the same reference numerals are given to the same or corresponding parts in each drawing.

FIG. 1 is a diagram for explaining a configuration example of a plasma processing system. In one embodiment, a plasma processing system includes a plasma processing apparatus 1 and a controller 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 section 11, and a plasma generation section 12. The plasma processing chamber 10 has a plasma processing space. The plasma processing chamber 10 also includes at least one gas supply port for supplying at least one processing gas to the plasma processing space, and at least one gas exhaust port for discharging gas from the plasma processing space. The gas supply port is connected to a gas supply section 20, which will be described later, and the gas discharge port is connected to an exhaust system 40, which will be described later. The substrate support section 11 is disposed within the plasma processing space and has a substrate support surface for supporting a substrate.

The plasma generation unit 12 is configured to generate plasma from at least one processing gas supplied into the plasma processing space. The plasmas formed in the plasma processing space include capacitively coupled plasma (CCP), inductively coupled plasma (ICP), and ECR plasma (Electron-Cyclotron-resonance plasma). ), helicon wave excited plasma (HWP: Helicon wave plasma) or surface wave plasma (SWP).

Control unit 2 processes computer-executable instructions that cause plasma processing apparatus 1 to perform various steps described in this disclosure. The control unit 2 may be configured to control each element of the plasma processing apparatus 1 to perform the various steps described herein. In one embodiment, part or all of the control unit 2 may be included in the plasma processing apparatus 1. The control unit 2 may include a processing unit 2a1, a storage unit 2a2, and a communication interface 2a3. The control unit 2 is realized by, for example, a computer 2a. The processing unit two a1 may be configured to read a program from the storage unit two a2 and perform various control operations by executing the read program. This program may be stored in the storage unit 2a2 in advance, or may be acquired via a medium when necessary. The acquired program is stored in the storage unit 2a2, and is read out 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 may be a communication line connected to the communication interface 2a3. The processing unit 2a1 may be a CPU (Central Processing Unit). The storage unit 2a2 may include a RAM (Random Access Memory), a ROM (Read Only Memory), an HDD (Hard Disk Drive), an SSD (Solid State Drive), or a combination thereof. The communication interface 2a3 may communicate with the plasma processing apparatus 1 via a communication line such as a LAN (Local Area Network).

A configuration example of a capacitively coupled plasma processing apparatus as an example of the plasma processing apparatus 1 will be described below. FIG. 2 is a diagram for explaining a configuration example of a capacitively coupled plasma processing apparatus.

The capacitively coupled plasma processing apparatus 1 includes a plasma processing chamber 10, a gas supply section 20, a power supply system 30, and an exhaust system 40. Further, the plasma processing apparatus 1 includes a substrate support section 11 and a gas introduction section. The gas inlet is configured to introduce at least one processing gas into the plasma processing chamber 10 . The gas introduction section includes a shower head 13. Substrate support 11 is arranged within plasma processing chamber 10 . The shower head 13 is arranged above the substrate support section 11 . In one embodiment, showerhead 13 forms at least a portion of the ceiling of plasma processing chamber 10 . The plasma processing chamber 10 has a plasma processing space 10s defined by a shower head 13, a side wall 10a of the plasma processing chamber 10, and a substrate support 11. Plasma processing chamber 10 is grounded. The substrate support 11 is electrically insulated from the casing of the plasma processing chamber 10 .

The substrate support part 11 includes a main body part 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 111 surrounds the central region 111a of the main body 111 in plan view. The substrate W is placed on the central region 111a of the main body 111, and the ring assembly 112 is placed on the annular region 111b of the main body 111 so as to surround the substrate W on the central region 111a of the main body 111. Therefore, the central region 111a is also called a substrate support surface for supporting the substrate W, and the annular region 111b is also called a ring support surface for supporting the ring assembly 112.

In one embodiment, body portion 111 includes a base 1110 and an electrostatic chuck 1111. Base 1110 includes a conductive member. Electrostatic chuck 1111 is placed on base 1110. Electrostatic chuck 1111 includes a ceramic member 1111a and an electrostatic electrode 1111b disposed within ceramic member 1111a. Ceramic member 1111a has a central region 111a. In one embodiment, ceramic member 1111a also has an annular region 111b. Note that another member surrounding the electrostatic chuck 1111, such as an annular electrostatic chuck or an annular insulating member, may have the annular region 111b. In this case, ring assembly 112 may be placed on the annular electrostatic chuck or the annular insulation member, or may be placed on both the electrostatic chuck 1111 and the annular insulation member.

Ring assembly 112 includes one or more annular members. In one embodiment, the one or more annular members include one or more edge rings and at least one cover ring. The edge ring is made of a conductive or insulating material, and the cover ring is made of an insulating material.

Further, the substrate support unit 11 may include a temperature control module configured to adjust at least one of the electrostatic chuck 1111, the ring assembly 112, and the substrate to a target temperature. The temperature control module may include a heater, a heat transfer medium, a flow path 1110a, or a combination thereof. A heat transfer fluid such as brine or gas flows through the flow path 1110a. In one embodiment, a channel 1110a is formed within the base 1110 and one or more heaters are disposed within the ceramic member 1111a of the electrostatic chuck 1111. Further, the substrate support section 11 may 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.

The shower head 13 is configured to introduce at least one processing gas from the gas supply section 20 into the plasma processing space 10s. The shower head 13 has at least one gas supply port 13a, at least one gas diffusion chamber 13b, and a plurality of gas introduction 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 from the plurality of gas introduction ports 13c. The showerhead 13 also includes at least one upper electrode. In addition to the shower head 13, the gas introduction section may include one or more side gas injectors (SGI) attached to one or more openings formed in the side wall 10a.

The gas supply 20 may include at least one gas source 21 and at least one flow controller 22 . In one embodiment, the gas supply 20 is configured to supply at least one process gas from a respective gas source 21 to the showerhead 13 via a respective flow controller 22 . Each flow controller 22 may include, for example, a mass flow controller or a pressure-controlled flow controller. Additionally, gas supply 20 may include at least one flow modulation device that modulates or pulses the flow rate of at least one process gas.

The exhaust system 40 may be connected to a gas outlet 10e provided at the bottom of the plasma processing chamber 10, for example. Evacuation system 40 may include a pressure regulating valve and a vacuum pump. The pressure within the plasma processing space 10s is adjusted by the pressure regulating valve. The vacuum pump may include a turbomolecular pump, a dry pump, or a combination thereof.

In one embodiment, the plasma processing apparatus 1 may further include a ground member 14. The ground member 14 is made of metal such as aluminum and is electrically grounded. The ground member 14 extends below the substrate support 11 such that a space HS is interposed between the substrate support 11 and the ground member 14 . Moreover, the ground member 14 extends so as to surround the space HS.

In one embodiment, the ground member 14 may include a first ground member 141 and a second ground member 142. The first ground member 141 extends below the substrate support 11 so as to face the lower surface of the substrate support 11 . The space HS is interposed between the first ground member 141 and the substrate support section 11. The second ground member 142 has a substantially cylindrical shape. The second ground member 142 is provided so as to surround the space HS. In one embodiment, the insulating member 113 may be provided on the second ground member 142. The insulating member 113 has a substantially cylindrical shape and extends along the outer periphery of the electrostatic chuck 1111 and the base 1110.

In one embodiment, the ground member 14 (in one example, the first ground member 141) may provide an opening 14h below the center of a high-frequency electrode (in one example, the base 1110), which will be described later, in the substrate support section 11. . The plasma processing apparatus 1 may further include a power supply body 15 extending downward from the center of the high-frequency electrode (base 1110 in one example) of the substrate support part 11 through the opening 14h. The power supply body 15 has a rod-like or cylindrical shape and extends in the vertical direction.

Hereinafter, FIG. 3 will be referred to in conjunction with FIG. 2. FIG. 3 is a diagram illustrating a configuration example of a power supply system in a plasma processing apparatus according to one exemplary embodiment. Power supply system 30 includes a high frequency power supply 31 and a bias power supply 32. The high frequency power supply 31 constitutes the plasma generation section 12 of one embodiment. The high frequency power supply 31 is configured to generate source high frequency power RF. The source radio frequency power RF has a source frequency f _RF . That is, the source high frequency power RF has a sinusoidal waveform whose frequency is the source frequency f _RF . The source frequency f _RF may be a frequency within the range of 10 MHz to 150 MHz. The high frequency power source 31 is electrically connected to the high frequency electrode via the matching box 33, and is configured to supply source high frequency power RF to the high frequency electrode. The high frequency electrode may be provided within the substrate support 11. The high frequency electrode may be at least one electrode provided within the conductive member or ceramic member 1111a of the base 1110. Alternatively, the high frequency electrode may be the upper electrode. In one embodiment, the high frequency power source 31 may be electrically connected to a high frequency electrode (for example, a conductive member of the base 1110) via the power supply body 15. When source radio frequency power RF is supplied to the radio frequency electrodes, a plasma is generated from the gas within the chamber 10.

Matching box 33 has variable impedance. In one embodiment, the matching box 33 is provided below the ground member 14. The variable impedance of the matching box 33 is set to reduce reflection of the source high frequency power RF from the load. The matching device 33 can be controlled by the control unit 2, for example.

In one embodiment, the high frequency power supply 31 may include a signal generator 31g, a D/A converter 31c, and an amplifier 31a. The signal generator 31g generates a high frequency signal having a source frequency _fRF . The signal generator 31g may include a programmable processor or a programmable logic device such as a field-programmable gate array (FPGA). The signal generator 31g may be composed of a single programmable device together with a signal generator 32g described later, or may be composed of a separate programmable device from the signal generator 32g.

The output of the signal generator 31g is connected to the input of the D/A converter 31c. The D/A converter 31c converts the high frequency signal from the signal generator 31g into an analog signal. The output of the D/A converter 31c is connected to the input of the amplifier 31a. The amplifier 31a amplifies the analog signal from the D/A converter 31c to generate source high frequency power RF. The amplification factor of the amplifier 31a is specified by the control unit 2 to the high frequency power source 31. Note that the high frequency power supply 31 does not need to include the D/A converter 31c. In this case, the output of the signal generator 31g is connected to the input of the amplifier 31a, and the amplifier 31a amplifies the high frequency signal from the signal generator 31g to generate source high frequency power RF.

Bias power supply 32 is electrically coupled to substrate support 11 . The bias power supply 32 is electrically connected to the bias electrode within the substrate support 11 and is configured to supply electrical bias energy BE to the bias electrode. The bias electrode may be at least one electrode provided within the conductive member or ceramic member 1111a of the base 1110. The bias electrode may be common to the high frequency electrode. In one embodiment, the bias power supply 32 may be electrically connected to a bias electrode (eg, a conductive member of the base 1110) via the power supply 15. Ions from the plasma are attracted to the substrate W when electrical bias energy BE is supplied to the bias electrode.

Hereinafter, FIG. 4 will be referred to in conjunction with FIGS. 2 and 3. FIG. 4 is a diagram showing an example of a waveform of electric bias energy. The bias power supply 32 is configured to periodically apply electric bias energy BE having a waveform period CY to the bias electrode. That is, the electric bias energy BE is applied to the bias electrode in each of the plurality of waveform periods CY. Each of the plurality of waveform periods CY is defined by a bias frequency. The bias frequency is, for example, a frequency of 50 kHz or more and 27 MHz or less. The time length of each of the plurality of waveform periods CY is the reciprocal of the bias frequency. The plurality of waveform cycles CY appear sequentially in time.

As shown in FIG. 4, the electric bias energy BE may be a bias high frequency power LF having a bias frequency. That is, the electric bias energy BE may have a sinusoidal waveform whose frequency is the bias frequency. In this case, the bias power supply 32 is electrically connected to the bias electrode via the matching box 34. The variable impedance of the matching box 34 is set to reduce reflection of the bias high frequency power LF from the load.

Alternatively, the electrical bias energy BE may include pulses of voltage PV. A voltage pulse PV is applied to the bias electrode within a waveform period CY. The voltage pulse PV is periodically applied to the bias electrode at time intervals having the same length as the waveform period CY. The waveform of the pulse PV can be a rectangular wave, a triangular wave, or any waveform. The polarity of the voltage of the pulse PV is set so as to create a potential difference between the substrate W and the plasma so that ions from the plasma can be drawn into the substrate W. The pulse PV may be a negative voltage pulse or a negative DC voltage pulse. Note that when the electric bias energy BE is a voltage pulse PV, the plasma processing apparatus 1 does not need to include the matching box 34.

In one embodiment, bias power supply 32 may include a signal generator 32g, a D/A converter 32c, and an amplifier 32a, as shown in FIG. The signal generator 32g periodically generates a bias signal having a specified waveform and waveform period CY. Signal generator 32g may be comprised of a programmable processor or a programmable logic device such as an FPGA.

The output of the signal generator 32g is connected to the input of the D/A converter 32c. The D/A converter 32c converts the bias signal from the signal generator 32g into an analog signal. The output of the D/A converter 32c is connected to the input of the amplifier 32a. Amplifier 32a amplifies the analog signal from D/A converter 32c to generate electrical bias energy BE. The amplification factor of the amplifier 32a is specified by the control unit 2 to the bias power supply 32. Note that the bias power supply 32 does not need to include the D/A converter 32c. In this case, the output of signal generator 32g is connected to the input of amplifier 32a, which amplifies the bias signal from signal generator 32g to generate electrical bias energy BE.

As shown in FIG. 2, the plasma processing apparatus 1 further includes at least one capacitor 16. At least one capacitor 16 is separated from matching devices 33 and 34. At least one capacitor 16 is connected between the high frequency electrode and ground. In one embodiment, at least one capacitor 16 is connected between the power supply 15 and the ground member 14 (eg, the first ground member 141). In one embodiment, at least one capacitor 16 may be located within the space HS. At least one capacitor 16 may be a vacuum capacitor. Furthermore, at least one capacitor 16 and the high-frequency electrode may be electrically connected to each other only by a conductive path. Further, at least one capacitor 16 and the ground member 14 may be electrically connected to each other only by a conductive path. That is, at least one capacitor 16 may be connected between the high frequency electrode and the ground only via an electrical path that does not include a resistive element.

Refer to FIG. 5 below. FIG. 5 is a top view of a plurality of capacitors of a plasma processing apparatus according to one exemplary embodiment. The plasma processing apparatus 1 may include a plurality of capacitors 16 as at least one capacitor 16. The plurality of capacitors 16 are connected in parallel between the high frequency electrode and the ground. In one embodiment, the plurality of capacitors 16 are connected in parallel between the power supply body 15 and the ground member 14 (for example, the first ground member 141). A plurality of capacitors 16 may be arranged within the space HS.

The plurality of capacitors 16 may be arranged circumferentially around the power supply body 15 at equal intervals. The plurality of wirings extending from each of the plurality of capacitors 16 to the power supply body 15 may have substantially the same length, and the plurality of wirings extending from each of the plurality of capacitors 16 to the power supply body 15 may have a plurality of contacts arranged at equal intervals in the circumferential direction. May be in contact. Further, the plurality of wirings extending from each of the plurality of capacitors 16 to the ground member 14 may have substantially the same length, and the plurality of wirings extending from each of the plurality of capacitors 16 to the ground member 14 may have a plurality of contacts arranged at equal intervals in the circumferential direction. It may be in contact with 14.

In one embodiment, the radio frequency power supply 31 is configured to adjust the source frequency in each of the plurality of phase periods SP within the waveform period CY of the electrical bias energy BE to reduce the degree of reflection of the source radio frequency power RF. ing. Adjustment of the source frequency is performed by the first feedback and/or the second feedback. Details of the first feedback and the second feedback will be described later.

In the plasma processing apparatus 1, the potential of the substrate W varies within the waveform period CY of the electric bias energy BE, and as a result, the thickness of the sheath (plasma sheath) on the substrate W varies within the waveform period CY. Variations in the thickness of the sheath on the substrate W result in variations in the capacitance of the sheath within the waveform period CY. However, in the plasma processing apparatus 1, the sheath and the capacitor 16 have a parallel connection relationship between the high frequency power source 31 and the ground, so the combined capacitance of the sheath capacitance and the capacitor capacitance is Variations in sheath capacitance are small. Therefore, according to the plasma processing apparatus 1, reflection of the source high frequency power RF due to impedance mismatch caused by variations in the thickness of the sheath is reduced.

In addition, in the plasma processing apparatus 1, since the fluctuation of the sheath capacitance is small with respect to the combined capacitance of the sheath capacitance and the capacitor capacitance, the source The amount of frequency adjustment becomes smaller.

[First feedback]

The first feedback will be explained below with reference to FIG. 6. FIG. 6 is a timing chart of an example of source frequencies of electric bias energy and source high-frequency power. A first feedback is provided for adjustment of the source frequency in a plurality of phase periods SP within each of a plurality of consecutive waveform periods CY. Each of the plurality of waveform periods CY includes N phase periods SP(1) to SP(N). N is an integer of 2 or more. The N phase periods SP(1) to SP(N) divide each of the plurality of waveform periods CY into N phase periods. In the following description, the waveform period CY(m) represents the m-th waveform period among the plurality of waveform periods CY. The phase period SP(n) represents the n-th phase period among the phase periods SP(1) to SP(N). Moreover, the phase period SP (m, n) represents the n-th phase period in the waveform period CY (m).

Adjustment of the source frequency in the first feedback may be performed by the high frequency power supply 31 (or its signal generator 31g). The high frequency power supply 31 adjusts the source frequency of the source high frequency power RF during the phase period SP (m, n) according to the change in the degree of reflection of the source high frequency power RF.

The plasma processing apparatus 1 may further include a sensor 35 and/or a sensor 36 to determine the degree of reflection of the source high frequency power RF. The sensor 35 is configured to measure the power level Pr of the reflected wave of the source high frequency power RF from the load. Sensor 35 includes, for example, a directional coupler. This directional coupler may be provided between the high frequency power supply 31 and the matching box 33. Note that the sensor 35 may be configured to further measure the power level Pf of the traveling wave of the source high-frequency power RF. The power level Pr of the reflected wave measured by the sensor 35 is notified to the high frequency power supply 31. In addition, the power level Pf of the traveling wave may be notified from the sensor 35 to the high frequency power source 31.

Sensor 36 includes a voltage sensor and a current sensor. The sensor 36 is configured to measure the voltage V _RF and the current I _RF in the power supply path connecting the high frequency power source 31 and the high frequency electrode to each other. Source high frequency power RF is supplied to the high frequency electrode via this power supply path. The sensor 36 may be provided between the high frequency power supply 31 and the matching box 33. The voltage V _RF and the current I _RF are notified to the high frequency power supply 31 .

The high frequency power supply 31 generates a representative value from the measured values in each of the plurality of phase periods SP. The measured value may be the power level Pr of the reflected wave acquired by the sensor 35. The measured value may be a value of the ratio of the power level Pr of the reflected wave to the output power level of the source high frequency power RF (ie, reflectance). The measured value may be a phase difference θ between the voltage V _RF and the current I _RF acquired by the sensor 36 in each of the plurality of phase periods SP. The measured value may be the impedance Z on the load side of the high frequency power supply 31 in each of the plurality of phase periods SP. The impedance Z is determined from the voltage V _RF and the current I _RF acquired by the sensor 36. The representative value may be an average value or a maximum value of the measured values in each of the plurality of phase periods SP. The high frequency power supply 31 uses a representative value in each of the plurality of phase periods SP as a value representing the degree of reflection of the source high frequency power RF.

In the first feedback, the high frequency power source 31 increases the degree of reflection by using different source frequencies in corresponding phase periods SP(n) in each of two or more waveform periods CY before the waveform period CY(m). Identify changes in

Identifying the relationship between a change in the source frequency (frequency shift) and a change in the degree of reflection of the source high-frequency power by using different source frequencies in the phase period SP(n) in each of two or more waveform periods CY. is possible. Therefore, according to the plasma processing apparatus 1, it is possible to adjust the source frequency used in the phase period SP (m, n) according to the change in the degree of reflection so as to reduce the degree of reflection. Further, according to the plasma processing apparatus 1, it is possible to rapidly reduce the degree of reflection in each of the plurality of waveform periods CY in which the electric bias energy BE is applied to the bias electrode of the substrate support part 11.

In one embodiment, the two or more waveform periods CY prior to waveform period CY(m) include waveform period CY(m-M ₁ ) and waveform period CY(m-M ₂ ). Here, M ₁ and M ₂ are natural numbers satisfying M ₁ >M ₂ . In one embodiment, the waveform period CY(m-M ₁ ) is the waveform period CY(m-2Q) and the waveform period CY(m-M ₂ ) is the waveform period CY(m-Q). "Q" and " _M2 " may be "1", and "2Q" and " _M1 " may be "2". "Q" may be an integer of 2 or more.

In the first feedback, the high frequency power source 31 gives the source frequency f(m-M ₂ ,n) one frequency shift from the source frequency f(m-M ₁ ,n). Here, f (m, n) represents the source frequency of the source high frequency power RF used in the phase period SP (m, n). f(m,n) is expressed as f(m,n)=f(m−M ₂ ,n)+Δ(m,n). Δ(m,n) represents the amount of frequency shift. One frequency shift is one of a frequency decrease and a frequency increase. If one frequency shift is a decrease in frequency, Δ(m,n) has a negative value. If one frequency shift is an increase in frequency, Δ(m,n) has a positive value.

In the first feedback, when the degree of reflection is reduced by using the source frequency f(m-M ₂ , n) obtained by one frequency shift, the high-frequency power source 31 changes the source frequency f(m, n) is set to a frequency that has one frequency shift with respect to the source frequency f(m−M ₂ ,n). For example, when the power level Pr (m-M ₂ , n) decreases from the power level Pr (m-M ₁ , n) due to one frequency shift, the high-frequency power supply 31 changes the source frequency f (m, n) is set to a frequency that has one frequency shift with respect to the source frequency f(m−M ₂ ,n). Note that Pr (m, n) represents the power level Pr of the reflected wave of the source high frequency power RF during the phase period SP (m, n).

In the first feedback, the degree of reflection may increase by using the source frequency f(m−M ₂ ,n) obtained by one frequency shift. For example, a case may occur in which the power level Pr (m-M ₂ , n) of the reflected wave increases from the power level Pr (m-M ₁ , n) of the reflected wave due to one frequency shift. In this case, the high frequency power supply 31 may set the source frequency f(m, n) to a frequency that has the other frequency shift with respect to the source frequency f(m-M ₂ , n).

In another embodiment, the source frequency of the source radio frequency power RF in the phase period SP(m,n) is the corresponding phase period SP(n) in each of the two or more waveform periods CY preceding the waveform period CY(m). The frequency that minimizes the degree of reflection may be determined from two or more degrees of reflection (for example, power level Pr) obtained by using different source frequencies. The frequency that minimizes the degree of reflection may be determined by a least squares method using each of the different frequencies and the corresponding degree of reflection.

[Second feedback]

A second feedback may be used where bias power supply 32 periodically applies electrical bias energy BE to the bias electrode during each of a plurality of pulse periods PP. Here, FIG. 7(a), FIG. 7(b), FIG. 8(a), and FIG. 8(b) are referred to. Each of FIGS. 7A, 7B, 8A, and 8B is a timing chart of an example of the source high-frequency power RF and the electric bias energy BE. In these figures, "ON" of the source high frequency power RF indicates that the source high frequency power RF is being supplied, and "OFF" of the source high frequency power RF indicates that the supply of the source high frequency power RF is stopped. It shows that there is. Furthermore, in these figures, "ON" of the electrical bias energy BE indicates that the electrical bias energy BE is applied to the bias electrode, and "OFF" of the electrical bias energy BE indicates that the electrical bias energy BE is applied to the bias electrode. This indicates that no bias is applied to the electrode. Furthermore, in these figures, "HIGH" of the electrical bias energy BE indicates that electrical bias energy BE having a higher level than the level of the electrical bias energy BE indicated by "LOW" is applied to the bias electrode. ing.

The plurality of pulse periods PP appear sequentially in time. The plurality of pulse periods PP may appear in order at time intervals (periods) that are the reciprocal of the pulse frequency. In the following description, the pulse period PP(k) represents the k-th pulse period among the plurality of pulse periods PP. The pulse frequency is lower than the bias frequency, for example, a frequency of 1 kHz or more and 100 kHz or less. As described above, electrical bias energy BE is periodically applied to the bias electrode in each of the plurality of pulse periods PP. Electrical bias energy BE may not be applied to the bias electrode during periods other than the plurality of pulse periods PP. Alternatively, electrical bias energy BE having a level lower than the level of electrical bias energy BE in the plurality of pulse periods PP may be applied to the bias electrode in periods other than the plurality of pulse periods PP.

As shown in FIG. 7(a), the source high frequency power RF may be supplied as a continuous wave. In the example shown in FIG. 7A, the plurality of overlapping periods OP in which the source high-frequency power RF is supplied in the plurality of pulse periods PP each coincide with the plurality of pulse periods PP.

Alternatively, as shown in FIG. 7(b), FIG. 8(a), and FIG. 8(b), pulses of source high frequency power RF may be supplied. As shown in FIG. 7B, the pulse of the source high-frequency power RF may be supplied in each of a plurality of periods that respectively coincide with the plurality of pulse periods PP. In the example shown in FIG. 7B, the plurality of overlapping periods OP in which the source high-frequency power RF is supplied in the plurality of pulse periods PP each coincide with the plurality of pulse periods PP. As shown in FIGS. 8A and 8B, the pulse of the source high-frequency power RF may be supplied in each of a plurality of periods that partially overlap with the plurality of pulse periods PP. In the examples shown in each of FIGS. 8(a) and 8(b), each of the multiple overlapping periods OP in which the source high-frequency power RF is supplied in the multiple pulse periods PP is is part of the corresponding pulse period PP. Note that in the following description, overlapping period OP(k) represents the k-th overlapping period among the plurality of overlapping periods OP.

Electrical bias energy BE is applied to the bias electrode in each of a plurality of waveform periods CY within each of a plurality of pulse periods PP. That is, the electrical bias energy BE is applied to the bias electrode periodically within each of the plurality of pulse periods PP. In the following description, the waveform period CY(m) represents the m-th waveform period among the plurality of waveform periods CY(1) to CY(M) in each of the plurality of overlapping periods OP. Moreover, the waveform period CY (k, m) represents the m-th waveform period within the k-th overlapping period. Further, the phase period SP(n) represents the n-th phase period among the plurality of phase periods SP(1) to SP(N) in each of the plurality of waveform periods CY in each of the plurality of overlapping periods OP. ing. Moreover, the phase period SP (m, n) represents the n-th phase period in the waveform period CY (m). Further, the phase period SP(k, m, n) represents the n-th phase period in the waveform period CY(m) within the k-th overlapping period OP(k).

The source frequency of each of the plurality of phase periods SP in each of the plurality of waveform periods CY in each of the overlapping periods OP(1) to OP(T-1) may be determined by the first feedback described above. Note that T is an integer of 3 or more. Alternatively, the source frequency of each of the plurality of phase periods SP in each of the plurality of waveform periods CY in each of the overlapping periods OP(1) to OP(T-1) is registered in a table prepared in advance. It may be set to the frequency.

The second feedback may be used in adjusting the source frequency of the source high frequency power RF in the overlapping period after the overlapping period OP(T). The second feedback will be explained below with reference to FIG. FIG. 9 is a timing chart of an example of source frequencies of electric bias energy and source high-frequency power.

In the second feedback, the high frequency power supply 31 adjusts the source frequency f(k, m, n) according to the change in the degree of reflection of the source high frequency power RF. In the second feedback, the changes in the degree of reflection are different from each other in corresponding phase periods SP(n) in the waveform period CY(m) in two or more overlapping periods OP before the overlapping period OP(k). It is specified by using the source frequency of the source high frequency power RF.

In the second feedback, by using different source frequencies in the same phase period within the same waveform period in each of two or more overlapping periods OP, the source frequency can be changed (frequency shift) and the degree of reflection of the source high-frequency power can be changed. It is possible to identify the relationship between changes in Therefore, according to the second feedback, depending on the change in the degree of reflection, it is possible to adjust the source frequency used in the phase period SP(k, m, n) so as to reduce the degree of reflection. be. Further, according to the second feedback, it is possible to rapidly reduce the degree of reflection in each of the plurality of waveform periods CY in each of the plurality of overlapping periods OP.

In one embodiment, the two or more overlapping periods OP before the overlapping period OP(k) include a (k-K ₁ )th overlapping period OP(k-K 1 ) and a (k-K ₂ )th overlapping period OP(k-K ₁ ). Includes period OP(k-K ₂ ). Here, K ₁ and K ₂ are natural numbers satisfying K ₁ >K ₂ .

In one embodiment, the overlapping period OP(k-K ₁ ) is the overlapping period OP(k-2). The overlapping period OP(k-K ₂ ) is the overlapping period after the overlapping period OP(k-K ₁ ), and in one embodiment is the overlapping period OP(k-1). That is, in one embodiment, K ₂ and K ₁ are 1 and 2, respectively.

The high frequency power source 31 has a source frequency f (k-K ₂ , m, n) in the phase period SP (k-K 2 , m, n) and a source frequency f (k-K ₂ , m, n) in the phase period SP (k-K ₁ , m, n). gives one frequency shift from . Here, f (k, m, n) represents the source frequency of the source high frequency power RF used in the phase period SP (k, m, n). f(k, m, n) is expressed as f(k, m, n)=f(k-K ₂ , m, n)+Δ(k, m, n). Δ(k,m,n) represents the amount of frequency shift. One frequency shift is one of a frequency decrease and a frequency increase. If one frequency shift is a decrease in frequency, Δ(k,m,n) has a negative value. If one frequency shift is an increase in frequency, Δ(k,m,n) has a positive value.

In the second feedback, if the degree of reflection decreases when using the source frequency f (k-K ₂ , m, n) obtained by one frequency shift, the high-frequency power source 31 changes the source frequency f (k, m, n) is set to a frequency that has one frequency shift with respect to the source frequency f (k-K ₂ , m, n). For example, when the power level Pr (k-K ₂ , m, n) decreases from the power level Pr (k-K ₁ , m, n) due to one frequency shift, the high-frequency power supply 31 changes the source frequency f ( k, m, n) are set to frequencies that have one frequency shift with respect to the source frequency f(k-K ₂ , m, n). Note that Pr (k, m, n) represents the power level Pr of the reflected wave of the source high frequency power RF during the phase period SP (k, m, n).

In the second feedback, the degree of reflection may increase by using the source frequency f(k−K ₂ , m, n) obtained by one frequency shift. For example, a case may occur in which the power level Pr (k-1, m, n) of the reflected wave increases from the power level Pr (k-2, m, n) of the reflected wave due to one frequency shift. In this case, the high frequency power supply 31 may set the source frequency f (k, m, n) to a frequency that has a frequency shift of the other with respect to the source frequency f (k-K ₂ , m, n). .

Hereinafter, reference will be made to FIGS. 10(a) to 10(d). Each of FIGS. 10(a) to 10(d) is a timing chart of another example of electric bias energy. In one embodiment, the plurality of overlapping periods OP may include the first to Kath overlapping periods OP(1) to OP(K _{a )} . Here, _Ka is a natural number of 2 or more.

The high-frequency power supply 31 is configured to provide each of the first to Ma _-th waveform cycles CY(1) to CY(M _a ) among the plurality of waveform cycles CY included in each of the overlapping periods OP(1) to OP(K _a ). Initial processing may be performed in . Here, M _a is a natural number. In the initial processing, a frequency set group including a plurality of frequency sets for each of the waveform periods CY(1) to CY(M _a ) may be used, and the plurality of frequency sets included in the frequency set group may be mutually exclusive. May be different. Further, a plurality of frequency set groups may be used for each of the overlapping periods OP(1) to OP(K _a ), and these frequency set groups may be different from each other. The high frequency power source 31 is a source of power during a plurality of phase periods SP in each of the first to Ma _-th waveform cycles CY(1) to CY(M _a ) in each of the overlapping periods OP(1) to OP(K _a ). As the frequency, a plurality of frequencies included in the corresponding frequency set are respectively used. Note that the plurality of frequency sets and the plurality of frequency set groups may be stored in the storage section of the control section 2 or the high frequency power supply 31.

The high-frequency power source 31 may perform the above-described first feedback after the waveform period CY (M _a ) among the plurality of waveform periods CY in each of the overlapping periods OP ( 1 ) to OP (K _a ). That is, the high frequency power supply 31 may perform the above-described first feedback in the waveform periods CY(M _a +1) to CY(M) included in each of the overlapping periods OP(1) to OP(K _a ). .

In one embodiment, the plurality of overlapping periods OP may further include (K _a +1)-th to K _b -th overlapping periods OP(K _a +1) to OP(K _b ). Here, K _b is a natural number greater than or equal to (K _a +1), and may satisfy K _b =K _a +1.

The high-frequency power supply 31 is configured to perform the first to M _b1 waveform cycles CY(1) to CY(M _b1 ) among the plurality of waveform cycles CY included in each of the overlapping periods OP(K _a +1) to OP(K _b ). The above initial processing may be performed in each of the above steps. Here, M _b1 is a natural number. M _b1 and M _a may satisfy M _b1 <M _a .

The high-frequency power supply 31 is configured to generate waveform cycles CY (M b1 +1) from (M _b1 +1)th to M _b2 of the plurality of waveform cycles CY included in each _of the overlapping periods OP (K _a +1) to OP (K _b ). ) to CY(M _b2 ), the above-mentioned second feedback may be performed. Here, M _b2 is a natural number satisfying M _b2 > M _b1 .

The high frequency power supply 31 may perform the above-described first feedback after the waveform period CY (M _b2 ) in each of the overlapping periods OP (K _a +1) to OP (K _b ). That is, the high frequency power supply 31 performs the above-mentioned first feedback in the waveform periods CY(M _b2 +1) to CY(M) included in each of the overlapping periods OP(K _a +1) to OP(K _b ). Good too.

Furthermore, the high frequency power supply 31 generates the first to _Mcth waveform _{cycles CY} (1) to CY( M _c ), the second feedback described above may be performed. Here, M _c is a natural number. Furthermore, the high frequency power source 31 may perform the above-described first feedback after the waveform period CY(M _c ) in each of the overlapping periods OP(K _b +1) to OP(K). That is, even if the high frequency power supply 31 performs the above-described first feedback in the waveform periods CY(M _c +1) to CY(M) included in each of the overlapping periods OP(K _b +1) to OP(K), good.

In another embodiment, in the first feedback, the source frequency of the source radio frequency power RF in the phase period SP(k,m,n) is of the waveform period CY(k,m) within the overlap period OP(k). From two or more degrees of reflection (e.g., power level Pr) obtained by using different source frequencies of the source high-frequency power RF in corresponding phase periods SP(n) in each of the previous two or more waveform periods CY , may be determined as a frequency that minimizes the degree of reflection. The frequency that minimizes the degree of reflection may be determined by a least squares method using each of the different frequencies and the corresponding degree of reflection.

In addition, in the second feedback, the source frequency f(k, m, n) is set to the corresponding phase within the waveform period CY(m) within two or more overlapping periods OP before the overlapping period OP(k). From two or more degrees of reflection (for example, power level Pr) obtained by using different source frequencies of the source high-frequency power RF in the period SP(n), the frequency that minimizes the degree of reflection may be determined. good. The frequency that minimizes the degree of reflection may be determined by a least squares method using each of the different frequencies and the corresponding degree of reflection.

Although various exemplary embodiments have been described above, various additions, omissions, substitutions, and changes may be made without being limited to the exemplary embodiments described above. Also, elements from different embodiments may be combined to form other embodiments.

In another embodiment, the plasma processing apparatus 1 may include one capacitor 16 that has an annular shape and surrounds the power supply body 15 instead of the plurality of capacitors 16.

In another embodiment, the plasma processing apparatus may be an inductively coupled plasma processing apparatus, an ECR plasma processing apparatus, a helicon wave excitation plasma processing apparatus, or a surface wave plasma processing apparatus. In any of the plasma processing apparatuses, the source high-frequency power RF is used for plasma generation, and the source frequency of the source high-frequency power RF used in the plurality of phase periods SP of the plurality of waveform periods CY is the same as that of the plasma processing apparatus 1. Adjusted as described above with respect to.

The first to fourth experiments conducted to evaluate the plasma processing apparatus 1 will be described below. In each of the second and fourth experiments, the plasma processing apparatus 1 had three capacitors 16 each having a capacitance of 350 (pF). In each of the first experiment and the third experiment, all of the plurality of capacitors 16 were removed from the plasma processing apparatus 1. In each of the first and second experiments, source radio frequency power RF was provided with a source frequency of 40.68 MHz and an output power level of 1 kW. In each of the third experiment and the fourth experiment, a source high frequency power RF having a source frequency adjusted by the first feedback described above with a reference frequency of 40.68 MHz and an output power level of 1 kW was used. supplied. In each of the first to fourth experiments, bias high frequency power LF having power levels of 2 kW, 5 kW, and 10 kW was supplied. In the first to fourth experiments, a silicon oxide film was etched.

In each of the first to fourth experiments, the coupling efficiency (%) of source high frequency power RF was determined. The coupling efficiency is the ratio of the load power level to the traveling wave power level of the source high frequency power RF. The load power level is a power level obtained by subtracting the power level of the reflected wave of the source high-frequency power RF from the power level of the traveling wave of the source high-frequency power RF. Furthermore, in each of the first and second experiments, the average value of the etching rate of the silicon oxide film was determined. Further, in the third experiment and the fourth experiment, the amount of adjustment of the source frequency was determined. The amount of adjustment of the source frequency is the difference between the maximum value and the minimum value of the source frequency within the waveform period CY.

The results of the first to fourth experiments are shown in FIGS. 11(a) and 11(b). FIG. 11(a) shows the coupling efficiency of the source high-frequency power RF obtained in each of the first to fourth experiments. As shown in FIG. 11(a), the binding efficiency in the second experiment was considerably higher than the binding efficiency in the first experiment. Therefore, it was confirmed that even if the source frequency is constant, high coupling efficiency of the source high frequency power RF can be obtained by using the plasma processing apparatus 1 having a plurality of capacitors 16. Furthermore, the binding efficiency in the third experiment was higher than that in the first experiment, and the binding efficiency in the fourth experiment was higher than the binding efficiency in the second experiment and the binding efficiency in the third experiment. It was also expensive. Therefore, it was confirmed that high coupling efficiency could be obtained by the first feedback. Furthermore, it has been confirmed that by performing the first feedback using the plasma processing apparatus 1 having a plurality of capacitors 16, a considerably high coupling efficiency can be obtained. Furthermore, when the power level of the bias high-frequency power LF is 2 kW, the average value of the etching rate of the silicon oxide film in the second experiment is higher than the average value of the etching rate of the silicon oxide film in the first experiment. , 21.1% higher. Furthermore, when the power level of the bias high-frequency power LF is 5 kW, the average value of the etching rate of the silicon oxide film in the second experiment is higher than the average value of the etching rate of the silicon oxide film in the first experiment. , 13.7% higher. Furthermore, when the power level of the bias high-frequency power LF is 5 kW, the average value of the etching rate of the silicon oxide film in the second experiment is higher than the average value of the etching rate of the silicon oxide film in the first experiment. , 11.1% higher. Therefore, it was confirmed that a high etching rate could be obtained by using the plasma processing apparatus 1 having a plurality of capacitors 16.

FIG. 11(b) shows the amount of adjustment of the source frequency in each of the third experiment and the fourth experiment. As shown in FIG. 11(b), the amount of adjustment of the source frequency in the fourth experiment was considerably smaller than the amount of adjustment of the source frequency in the third experiment. From this, it was confirmed that by using the plasma processing apparatus 1 having a plurality of capacitors 16, it is possible to considerably reduce the amount of adjustment of the source frequency in the first feedback.

Various exemplary embodiments included in the present disclosure are now described in [E1] to [E9] below.

[E1]
a chamber;
a substrate support provided in the chamber;
a bias power source electrically coupled to the substrate support and configured to provide electrical bias energy to the substrate support for ion attraction, the electrical bias energy having a waveform period; The bias power supply is periodically generated;
high frequency electrode,
a high frequency power source electrically connected to the high frequency electrode and configured to supply source high frequency power to the high frequency electrode for generating plasma from a gas in the chamber;
a matching box connected between the high frequency power source and the high frequency electrode;
a capacitor separated from the matching box and connected between the high frequency electrode and ground;
A plasma processing apparatus comprising:

In the E1 embodiment, the potential of the substrate varies within the waveform period of the electrical bias energy, and as a result, the thickness of the sheath (plasma sheath) on the substrate varies within the waveform period. Variations in the thickness of the sheath on the substrate result in variations in the capacitance of the sheath within the waveform period. However, in the E1 embodiment, the sheath and the capacitor have a parallel connection relationship between the high frequency power source and the ground, so the sheath's combined capacitance of the sheath's capacitance and the capacitor's capacitance is Variations in capacitance are small. Thus, embodiments of E1 reduce reflections of source RF power due to impedance mismatches due to variations in sheath thickness.

[E2]
The plasma processing apparatus according to E1, wherein the high-frequency electrode is provided within the substrate support section.

[E3]
A grounding member that is grounded, and extends below the substrate support so that a space is interposed between the substrate support and the ground member, and extends so as to surround the space. , further comprising the ground member,
The matching box is provided below the ground member,
the capacitor is located within the space;
The plasma processing apparatus described in E2.

[E4]
further comprising a power supply body extending downward from the center of the high frequency electrode through an opening provided by the ground member, the power supply body electrically connecting the high frequency electrode and the matching box to each other;
The plasma processing apparatus includes, as the capacitor, a plurality of capacitors connected in parallel between the high frequency electrode and the ground member,
The plurality of capacitors are arranged at equal intervals along a circumferential direction around the power supply body,
The plasma processing apparatus described in E3.

[E5]
The plasma processing apparatus according to any one of E1 to E4, wherein the capacitor is a vacuum capacitor.

[E6]
The high frequency power source is configured to adjust a source frequency of the source high frequency power in each of a plurality of phase periods within the waveform period of the electrical bias energy to reduce a degree of reflection of the source high frequency power. The plasma processing apparatus according to any one of E1 to E5.

[E7]
The plasma processing apparatus according to any one of E1 to E5, wherein the capacitor and the high-frequency electrode are electrically connected to each other only by a conductive path.

[E8]
The electric bias energy is bias high-frequency power having a bias frequency that is the reciprocal of the time length of the waveform period, or voltage pulses periodically generated at time intervals of the waveform period, E1 to E7. The plasma processing apparatus according to any one of the items.

[E9]
The plasma processing apparatus according to any one of E1 to E8, which is a capacitively coupled plasma processing apparatus.

From the foregoing description, it will be understood that various embodiments of the disclosure are described herein for purposes of illustration and that various changes may be made without departing from the scope and spirit of the disclosure. Will. Therefore, the various embodiments disclosed herein are not intended to be limiting, with the true scope and spirit being indicated by the following claims.

DESCRIPTION OF SYMBOLS 1... Plasma processing apparatus, 10... Chamber, 11... Substrate support part, 31... High frequency power supply, 32... Bias power supply, 33... Matching device, 16... Capacitor.

Claims (9)

a chamber;
a substrate support provided in the chamber;
a bias power source electrically coupled to the substrate support and configured to provide electrical bias energy to the substrate support for ion attraction, the electrical bias energy having a waveform period; The bias power supply is periodically generated;
high frequency electrode,
a high frequency power source electrically connected to the high frequency electrode and configured to supply source high frequency power to the high frequency electrode for generating plasma from a gas within the chamber;
a matching box connected between the high frequency power source and the high frequency electrode;
a capacitor separated from the matching box and connected between the high frequency electrode and ground;
A plasma processing apparatus comprising: The plasma processing apparatus according to claim 1, wherein the high frequency electrode is provided within the substrate support section. A grounding member that is grounded, and extends below the substrate support so that a space is interposed between the substrate support and the ground member, and extends so as to surround the space. , further comprising the ground member,
The matching box is provided below the ground member,
the capacitor is located within the space;
The plasma processing apparatus according to claim 2. further comprising a power supply body extending downward from the center of the high frequency electrode through an opening provided by the ground member, the power supply body electrically connecting the high frequency electrode and the matching box to each other;
The plasma processing apparatus includes, as the capacitor, a plurality of capacitors connected in parallel between the high frequency electrode and the ground member,
The plurality of capacitors are arranged at equal intervals along a circumferential direction around the power supply body,
The plasma processing apparatus according to claim 3. The plasma processing apparatus according to any one of claims 1 to 4, wherein the capacitor is a vacuum capacitor. The high frequency power source is configured to adjust a source frequency of the source high frequency power in each of a plurality of phase periods within the waveform period of the electrical bias energy to reduce a degree of reflection of the source high frequency power. The plasma processing apparatus according to any one of claims 1 to 4. 5. The plasma processing apparatus according to claim 1, wherein the capacitor and the high-frequency electrode are electrically connected to each other only by a conductive path. The electrical bias energy is bias high frequency power having a bias frequency that is the reciprocal of the time length of the waveform period, or is a voltage pulse periodically generated at a time interval of the waveform period. 4. The plasma processing apparatus according to any one of 4. The plasma processing apparatus according to any one of claims 1 to 4, which is a capacitively coupled plasma processing apparatus.

Images