Variable Output Impedance RF Generator

Abstract

Various RF plasma systems are disclosed that do not require a matching network. In some embodiments, the RF plasma system includes: an energy storage capacitor; a switching circuit coupled to the energy storage capacitor, the switching circuit generating a plurality of pulses having a pulse amplitude and a pulse frequency, the pulse amplitude being greater than 100 volts; a resonant circuit coupled to the switching circuit. In some embodiments, the resonant circuit includes: a transformer having a primary side and a secondary side; and at least one of a capacitor, an inductor, and a resistor. In some embodiments, the resonant circuit has a resonant frequency substantially equal to the pulse frequency, and the resonant circuit increases the pulse amplitude to a voltage greater than 2 kV.

Description

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims priority to U.S. Provisional Patent Application No. 62 / 774,078, filed on November 30, 2018, entitled “VARIABLE OUTPUT IMPEDANCE RFGENERATOR,” which is incorporated by reference in its entirety. Background Art

[0003] The use of RF excited gas discharges in thin film manufacturing technology has become standard. The simplest geometry most often used is that of two planar electrodes with a voltage applied between them. Figure 1 A schematic representation of such a planar RF plasma reactor is shown in The plasma is separated from each electrode by a plasma sheath.

[0004] The positive ions generated in the plasma volume are accelerated across the plasma sheath and arrive at the electrode with an ion energy distribution function (IEDF) determined by the amplitude and waveform of the time-dependent potential difference across the sheath, gas pressure, the physical geometry of the reactor and / or other factors. This ion bombardment energy distribution can determine the degree of anisotropy in the amount of thin film etching, such as damage to the surface caused by ion impact. Summary of the invention

[0005] Some embodiments include an RF system comprising: an energy storage capacitor; a switching circuit coupled to the energy storage capacitor, the switching circuit generating a plurality of pulses having a pulse amplitude and a pulse frequency, the pulse amplitude being greater than 100 volts; a resonant circuit coupled to the switching circuit, the resonant circuit comprising: a transformer having a primary side and a secondary side; and a circuit element selected from the group consisting of a capacitor, an inductor, and a resistor, the resonant circuit having a resonant frequency substantially equal to the pulse frequency, and the resonant circuit increasing the pulse amplitude to a voltage greater than 2 kV; and an energy recovery circuit coupled to the energy storage capacitor and the secondary side of the transformer, the energy recovery circuit comprising a diode and an inductor arranged in series, wherein the energy recovery circuit is configured to allow current to flow from the secondary side of the transformer to charge the energy storage capacitor.

[0006] Some embodiments include an RF plasma system comprising: an energy storage capacitor; a high voltage switching power supply that generates a plurality of pulses having a pulse amplitude and a pulse frequency, the pulse amplitude being greater than 100 volts; and a resonant circuit coupled to the switching power supply, the resonant circuit having a resonant frequency substantially equal to the pulse frequency, and the resonant circuit increasing the amplitude of the plurality of pulses to a voltage greater than 2 kV; a transformer having a primary side and a secondary side; a plasma chamber coupled to the resonant circuit; and an energy recovery circuit coupled to the energy storage capacitor and the secondary side of the transformer, the energy recovery circuit comprising a diode and an inductor arranged in series, the energy recovery circuit coupled to the plasma chamber, the energy recovery circuit releasing charge from the plasma chamber.

[0007] Some embodiments include an RF plasma system comprising: an energy storage capacitor; a high voltage switching power supply electrically coupled to the energy storage capacitor, the high voltage switching power supply generating a plurality of pulses having a pulse amplitude and a pulse frequency, the pulse amplitude being greater than 100 volts and the pulse frequency being greater than 100 kHz; an inductively coupled plasma source comprising a coil electrically coupled to the high voltage switching power supply; and a capacitor, wherein an inductance of the capacitor and the inductively coupled plasma source resonates at a resonant frequency substantially equal to the pulse frequency; and an energy recovery circuit coupled to the inductively coupled plasma source and the energy storage capacitor, the energy recovery circuit comprising a diode and an inductor arranged in series, wherein the energy recovery circuit is configured to allow current to flow from the inductively coupled plasma source to the energy storage capacitor.

[0008] Some embodiments include an RF plasma system comprising: an energy storage capacitor; a high voltage switching power supply that generates a plurality of pulses having a pulse amplitude and a pulse frequency, the pulse amplitude being greater than 100 volts and the pulse frequency being greater than 100 kHz; a capacitively coupled plasma; an inductor, wherein the inductor and a capacitance of the capacitively coupled plasma form a resonant circuit having a resonant frequency substantially equal to the pulse frequency; and an energy recovery circuit coupled to the capacitively coupled plasma and the energy storage capacitor, the energy recovery circuit comprising a diode and an inductor disposed in series, wherein the energy recovery circuit is configured to allow current to flow from the capacitively coupled plasma to the energy storage capacitor.

[0009] Some embodiments include an RF system comprising an energy storage capacitor, a switching circuit, a resonant circuit, and an energy recovery circuit. In some embodiments, the switching circuit may be coupled to the energy storage capacitor. In some embodiments, the switching circuit generates a plurality of pulses having a pulse amplitude and a pulse frequency, wherein the pulse amplitude may be greater than 100 volts. In some embodiments, the resonant circuit may be coupled to the switching circuit and may include: a transformer having a primary side and a secondary side; and at least one of a capacitor, an inductor, and a resistor. In some embodiments, the resonant circuit has a resonant frequency substantially equal to the pulse frequency, and the resonant circuit increases the pulse amplitude to a voltage greater than 2 kV. In some embodiments, the energy recovery circuit may be coupled to the energy storage capacitor and the secondary side of the transformer, and the energy recovery circuit includes a diode and an inductor.

[0010] In some embodiments, the RF system includes a plasma chamber coupled to the resonant circuit. In some embodiments, the switching circuit includes a full-bridge driver or a half-bridge driver.

[0011] In some embodiments, the resonant circuit includes an inductor, and the resonant frequency includes The inductance L includes any stray inductance of the transformer and the inductance of the inductor, and the capacitance C includes any stray capacitance of the transformer.

[0012] In some embodiments, the resonant circuit includes a capacitor, and the resonant frequency includes Therein, the inductance L includes any stray inductance of the transformer, and the capacitance C includes any stray capacitance of the transformer and the capacitance of the capacitor.

[0013] Some embodiments include an RF system comprising an energy storage capacitor, a switching circuit, a resonant circuit, and a plasma chamber. In some embodiments, the switching circuit may be coupled to the energy storage capacitor. In some embodiments, the switching circuit generates a plurality of pulses having a pulse amplitude and a pulse frequency, wherein the pulse amplitude may be greater than 100 volts. In some embodiments, the resonant circuit may be coupled to the switching circuit and may include: a transformer having a primary side and a secondary side; and at least one of a capacitor, an inductor, and a resistor. In some embodiments, the resonant circuit has a resonant frequency substantially equal to the pulse frequency, and the resonant circuit increases the pulse amplitude to a voltage greater than 2 kV. In some embodiments, the plasma chamber is coupled to the resonant circuit.

[0014] In some embodiments, the RF plasma system may include a transformer coupled to the resonant circuit. In some embodiments, the RF plasma system may include a resistive output stage. In some embodiments, the RF plasma system may include an energy recovery stage. In some embodiments, the RF plasma system may include a bias compensation circuit.

[0015] In some embodiments, one or both of the inductance (L) and / or capacitance (C) of the transformer determines the resonant frequency according to the following formula:

[0016] In some embodiments, the resonant frequency includes The inductance L includes any stray inductance of the transformer, and the capacitance C includes any stray capacitance of the transformer.

[0017] In some embodiments, the high voltage switching power supply includes a full-bridge driver or a half-bridge driver.

[0018] In some embodiments, the switching power supply is driven at a frequency selected from the group consisting of 400 kHz, 0.5 MHz, 2.0 MHz, 4.0 MHz, 13.56 MHz, 27.12 MHz, 40.68 MHz, and 50 MHz.

[0019] Some embodiments include an RF system comprising a high voltage switching power supply, an inductively coupled plasma source, and a capacitor. In some embodiments, the high voltage switching power supply generates a plurality of pulses having a pulse amplitude and a pulse frequency, the pulse amplitude being greater than 100 volts. In some embodiments, the inductively coupled plasma source comprises a coil electrically coupled to the high voltage switching power supply. In some embodiments, the capacitor and the inductance of the inductively coupled plasma source resonate at a resonant frequency substantially equal to the pulse frequency.

[0020] In some embodiments, the resonant frequency includes Wherein, the inductance L comprises the inductance of the inductively coupled plasma source, and the capacitance C comprises the capacitance of the capacitor. In some embodiments, the high voltage switching power supply comprises a full-bridge driver or a half-bridge driver.

[0021] Some embodiments include an RF system including a high voltage switching power supply, a capacitively coupled plasma, and an inductor. In some embodiments, the high voltage switching power supply generates a plurality of pulses having a pulse amplitude and a pulse frequency, the pulse amplitude being greater than 100 volts. In some embodiments, the inductor and the capacitance of the capacitively coupled plasma form a resonant circuit having a resonant frequency substantially equal to the pulse frequency.

[0022] In some embodiments, the resonant frequency includes Wherein, the inductance L comprises the inductance of the inductor, and the capacitance C comprises the capacitance of the capacitively coupled plasma. In some embodiments, the high voltage switching power supply comprises a full-bridge driver or a half-bridge driver.

[0023] These illustrative embodiments are not mentioned to limit or define the present disclosure, but to provide examples to aid understanding of the present disclosure. Additional embodiments are discussed in the detailed description, and further description is provided herein. The advantages provided by one or more of the various embodiments may be further understood by examining this specification or by practicing one or more of the embodiments proposed. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] These and other features, aspects and advantages of the present disclosure will be better understood when the following detailed description is read with reference to the accompanying drawings.

[0025] Figure 1 is a schematic representation of a planar RF plasma reactor according to some embodiments.

[0026] Figure 2 is a schematic diagram of an equivalent electronic circuit model of an RF plasma reactor according to some embodiments.

[0027] Figure 3 shows the voltage V across the plasma reactor r and the plasma potential V for equal areas of the target and substrate electrodes P Calculated waveform.

[0028] Figure 4 The potential V across the plasma sheath adjacent to the target electrode is shown. ST and the potential V across the substrate electrode SS Calculated waveform.

[0029] Figure 5 is a block diagram of an RF driver according to some embodiments.

[0030] Figure 6 is a circuit diagram of an RF driver according to some embodiments.

[0031] Figure 7 are waveforms of the voltage across transformer T1 (red), at the pole (green), and at the wafer (blue) for a time frame up to 600 μs.

[0032] Figure 8 is a zoomed in view of the waveform over a 10 μs time frame.

[0033] Fig. 9is a circuit diagram of an RF driver according to some embodiments.

[0034] Fig.10 is a circuit diagram of an RF driver according to some embodiments.

[0035] Fig.11 is a circuit diagram of an RF driver according to some embodiments.

[0036] Fig.12 is a circuit diagram of an RF driver according to some embodiments.

[0037] Fig.13 is a circuit diagram of an RF driver according to some embodiments.

[0038] Fig.14A , Fig. 14B , Fig.15A and Fig. 15B is a circuit diagram of an example resonant circuit.

[0039] Fig.16 is a continuous waveform of the voltage across transformer T1 (red), at the pole (green), and at the wafer (blue).

[0040] Fig.17 Figure 1 is a short burst waveform of the voltage across transformer T1 (red), at the pole (green), and at the wafer (blue).

[0041] Fig.18 is a waveform showing a series of short bursts across transformer T1 (red), at the stem (green), and at the wafer (blue). DETAILED DESCRIPTION

[0042] In some embodiments, systems and methods are disclosed for providing switching power to a plasma chamber without using a matching network. Figure 1 As shown, a typical RF driver 105 requires a matching network 110, for example, to ensure that the impedance of the RF driver 105 matches the impedance of the plasma chamber 115. To accomplish this, the matching network 110 may include any combination of transformers, resistors, inductors, capacitors, and / or transmission lines. Generally, it may be necessary to tune the matching network 110 to ensure that the impedance of the RF driver 105 matches the impedance of the plasma chamber 115. Such tuning may be required during plasma processing. However, the matching network may be relatively slow in tuning (e.g., requiring tens or hundreds of milliseconds at most to tune), which may not allow real-time tuning.

[0043] Embodiments described in the present disclosure include circuits and processes for driving switching power to a plasma chamber without a matching network. In some embodiments, a full (or half) bridge circuit can be used to drive a resonant circuit at its resonant frequency. Because the resonant circuit is driven at its resonant frequency, the output voltage of the resonant circuit may be higher than the input voltage. In some embodiments, this resonant condition can allow a drive voltage of several hundred volts to generate an output voltage of about 4 kV or more at the transformer.

[0044] As used throughout this disclosure, the term "high voltage" may include voltages greater than 500V, 1kV, 10kV, 20kV, 50kV, 100kV, etc.; the term "high frequency" may include frequencies greater than 100Hz, 250Hz, 500Hz, 750Hz, 1kHz, 10kHz, 100kHz, 200kHz, 500kHz, 1MHz, 10MHz, 50MHz, 100MHz, etc., and the term "fast rise time" may include frequencies less than 100Hz, 250Hz, 500Hz, 750Hz, 1kHz, 10kHz, 100kHz, 200kHz, 500kHz, 1MHz, 10MHz, 50MHz, 100MHz, etc. Rise times of approximately 1 ns, 10 ns, 50 ns, 100 ns, 250 ns, 500 ns, 1,000 ns, etc.; the term "fast fall time" may include fall times of less than approximately 1 ns, 10 ns, 50 ns, 100 ns, 250 ns, 500 ns, 1,000 ns, etc.; and the term short pulse width may include pulse widths of less than approximately 1 ns, 10 ns, 50 ns, 100 ns, 250 ns, 500 ns, 1,000 ns, etc.

[0045] Figure 2 2 is a schematic diagram of an equivalent electronic circuit model 200 for an RF driver 105 that can be used as an RF power source and an equivalent circuit of a plasma chamber 115. In this example, V RF is the voltage of the applied RF signal from the RF driver 105 with the matching network 110. V T and V P are the target electrode and plasma potentials, respectively. In addition, V SS =V P and V ST =V T -V P The plasma sheath (V SS ) and the voltage of the target plasma sheath (V ST ) voltage. The DC blocking capacitor is represented by C2; C3 and I T represent the capacitance and conduction current through the sheath adjacent to the target electrode, respectively, while C9 and I S The corresponding values ​​of capacitance and current for the sheath adjacent to the substrate electrode are shown.

[0046] In some embodiments, for the plasma electron densities and voltage frequencies described in the present disclosure, the resistance of the plasma can be small relative to the sheath resistance. However, including the plasma resistance does not introduce any complexity with respect to the circuit model.

[0047] Figure 3 Shown across a plasma reactor (e.g., such as Figure 1 and Figure 2 The voltage V of the plasma reactor shown T and the plasma potential V for equal areas of the target and substrate electrodes P waveform. Figure 4 About A T / A S = 0.2 shows the span and Figure 1 The potential V of the plasma sheath adjacent to the target electrode is shown ST The calculated waveforms of the potential V across the substrate electrode sheath SS The calculation waveform of T and A S are the areas of the target electrode and substrate electrode respectively. Figure 4 A half sine wave of the sheath potential from 0 to -450 V is shown.

[0048] Figure 5 5 is a block diagram of a driver and chamber circuit 500 without a matching network according to some embodiments. The driver and chamber circuit 500 may include an RF driver 505, which may include a voltage source and a full-bridge driver or a half-bridge driver or an equivalent driver. The driver and chamber circuit 500 may include a resonant circuit 510 having a transformer and a resonant element. The driver and chamber circuit 500 may include a half-wave rectifier 515 that may also be electrically coupled to the resonant circuit 510. A resistive output stage 520 (or energy recovery circuit) may be coupled to the half-wave rectifier. A bias compensation circuit 525 may be coupled to the resistive output stage 520. The plasma and chamber 530 and the plasma may be coupled to the bias compensation circuit 525.

[0049] Figure 6 600 is a circuit diagram of a driver and chamber circuit 600 according to some embodiments. In this example, the driver and chamber circuit 600 may include an RF driver 605. The RF driver 605 may be, for example, a half-bridge driver or a full-bridge driver, such as Figure 6As shown. The RF driver 605 may include an input voltage source V1, which may be a DC voltage source (e.g., a capacitor source, an AC-DC converter, etc.). In some embodiments, the RF driver 605 may include four switches S1, S2, S3, and S4. In some embodiments, the RF driver 605 may include a plurality of switches S1, S2, S3, and S4 connected in series or in parallel. For example, these switches S1, S2, S3, and S4 may include any type of solid-state switch (e.g., such as IGBT, MOSFET, SiC MOSFET, SiC junction transistor, FET, SiC switch, GaN switch, photoconductive switch, etc.). These switches S1, S2, S3, and S4 may be switched at high frequencies and / or may generate high voltage pulses. For example, these frequencies may include frequencies of approximately 400kHz, 0.5MHz, 2.0MHz, 4.0MHz, 13.56MHz, 27.12MHz, 40.68MHz, 50MHz, etc.

[0050] Each of the switches S1, S2, S3, and S4 may be coupled in parallel with a corresponding diode D1, D2, D3, and D4, and may include a stray inductance represented by an inductor L1, L2, L3, and L4. In some embodiments, the inductance of the inductors L1, L2, L3, and L4 may be equal. In some embodiments, the inductance of the inductors L1, L2, L3, and L4 may be less than about 50nH, 100nH, 150nH, 500nH, 1,000nH, etc. A combination of a switch (S1, S2, S3, or S4) and a corresponding diode (D1, D2, D3, or D4) may be coupled in series with a corresponding inductor (L1, L2, L3, or L4). Inductors L3 and L4 are connected to ground. Inductor L1 is connected to switch S4 and resonant circuit 610. And inductor L2 is connected to the opposite side of switch S3 and resonant circuit 610.

[0051] In some embodiments, the RF driver 605 can be coupled to a resonant circuit 610. The resonant circuit 610 can include a resonant inductor L5 and / or a resonant capacitor C2 coupled to a transformer T1. The resonant circuit 610 can include a resonant resistor R5, which can include, for example, the stray resistance of any leads between the RF driver 605 and the resonant circuit 610 and / or any component within the resonant circuit 610 (e.g., such as transformer T1, capacitor C2, and / or inductor L5). In some embodiments, the resonant resistor R5 includes only the stray resistance of the wire, trace, or circuit element. Although the inductance and / or capacitance of other circuit elements can affect the drive frequency, the drive frequency can be set primarily by selecting the resonant inductor L5 and / or the resonant capacitor C2. Further refinement and / or tuning may be required to create an appropriate drive frequency based on the stray inductance or stray capacitance. In addition, the rise time of the transformer T1 can be adjusted by changing L5 and / or C2, provided that:

[0052]

[0053] In some embodiments, large inductance values ​​for L5 may result in slower or shorter rise times. These values ​​may also affect the burst envelope. Fig.17 As shown, each burst may include transient and steady state pulses. The transient pulses within each burst may be set by L5 and / or Q of the system until full voltage is reached during the steady state pulse.

[0054] If the switches in the RF driver 605 are at the resonant frequency f resonant Switching is performed, and the output voltage at the transformer T1 will be amplified. In some embodiments, the resonant frequency can be about 400kHz, 0.5MHz, 2.0MHz, 4.0MHz, 13.56MHz, 27.12MHz, 40.68MHz, 50MHz, etc.

[0055] In some embodiments, the resonant capacitor C2 may include the stray capacitance of the transformer T1 and / or the physical capacitor. In some embodiments, the resonant capacitor C2 may have a capacitance of approximately 10 μF, 1 μF, 100 nF, 10 nF, etc. In some embodiments, the resonant inductor L5 may include the stray inductance of the transformer T1 and / or the physical inductor. In some embodiments, the resonant inductor L5 may have an inductance of approximately 50 nH, 100 nH, 150 nH, 500 nH, 1,000 nH, etc. In some embodiments, the resonant resistor R5 may have a resistance of approximately 10 ohms, 50 ohms, 100 ohms, 200 ohms, 500 ohms, etc.

[0056] In some embodiments, the resonant resistor R5 may represent the stray resistance of wires, traces, and / or transformer windings within a physical circuit. In some embodiments, the resonant resistor R5 may have a resistance of approximately 10mohm, 50mohm, 100mohm, 200mohm, 500mohm, etc.

[0057] In some embodiments, transformer T1 may include a transformer as disclosed in U.S. Patent Application No. 15 / 365,094, entitled “High Voltage Transformer”, which is incorporated herein for all purposes. In some embodiments, the output voltage of resonant circuit 610 may be varied by changing the duty cycle (e.g., the switch “on” time or the time the switch is conducting) of switches S1, S2, S3, and / or S4. For example, the longer the duty cycle, the higher the output voltage; and the shorter the duty cycle, the lower the output voltage. In some embodiments, the output voltage of resonant circuit 610 may be varied or tuned by adjusting the duty cycle of the switches in RF driver 605.

[0058] For example, the duty cycle of the switch can be adjusted by the following operations: changing the duty cycle of the signal Sig1 that opens and closes the switch S1; changing the duty cycle of the signal Sig2 that opens and closes the switch S2; changing the duty cycle of the signal Sig3 that opens and closes the switch S3; and changing the duty cycle of the signal Sig4 that opens and closes the switch S4. For example, by adjusting the duty cycle of the switch S1, S2, S3, or S4, the output voltage of the resonant circuit 610 can be controlled.

[0059] In some embodiments, each switch S1, S2, S3, or S4 in the resonant circuit 605 can be switched independently or in combination with one or more of the other switches. For example, the signal Sig1 can be the same signal as the signal Sig3. As another example, the signal Sig2 can be the same signal as the signal Sig4. As another example, each signal can be independent and each switch S1, S2, S3, or S4 can be controlled independently or separately.

[0060] In some embodiments, the resonant circuit 610 may be coupled to a half-wave rectifier 615 which may include a blocking diode D7.

[0061] In some embodiments, the half-wave rectifier 615 can be coupled to a resistive output stage 620. The resistive output stage 620 can include any resistive output stage known in the art. For example, the resistive output stage 620 can include any resistive output stage described in U.S. Patent Application No. 16 / 178,538, entitled “HIGH VOLTAGE RESISTIVE OUTPUT STAGE CIRCUIT,” which is incorporated in its entirety into the present disclosure for all purposes.

[0062] For example, the resistive output stage 620 may include an inductor L11, a resistor R3, a resistor R1, and a capacitor C11. In some embodiments, the inductor L11 may include an inductance of about 5 μH to about 25 μH. In some embodiments, the resistor R1 may include a resistance of about 50 ohms to about 250 ohms. In some embodiments, the resistor R3 may include a stray resistance in the resistive output stage 620.

[0063] In some embodiments, resistor R1 may include multiple resistors arranged in series and / or parallel. Capacitor C11 may represent the stray capacitance of resistor R1 including the capacitance of the arrangement of the series and / or parallel resistors. For example, the capacitance of stray capacitance C11 may be less than 500pF, 250pF, 100pF, 50pF, 10pF, 1pF, etc. For example, the capacitance of stray capacitance C11 may be less than the load capacitance (e.g., such as, less than the capacitance of C2, C3, and / or C9).

[0064] In some embodiments, resistor R1 can discharge a load (e.g., plasma sheath capacitance). In some embodiments, resistive output stage 620 can be configured to discharge an average power exceeding about 1 kilowatt during each pulse period and / or an energy of 1 joule or less in each pulse period. In some embodiments, the resistance of resistor R1 in resistive output stage 620 can be less than 200 ohms. In some embodiments, resistor R1 can include multiple resistors arranged in series or in parallel having a combined capacitance (e.g., C11) of less than about 200 pF.

[0065] In some embodiments, the resistive output stage 620 may include a collection of circuit elements that can be used to control the shape of the voltage waveform on the load. In some embodiments, the resistive output stage 620 may include only passive elements (e.g., resistors, capacitors, inductors, etc.). In some embodiments, the resistive output stage 620 may include active circuit elements (e.g., switches) as well as passive circuit elements. In some embodiments, for example, the resistive output stage 620 may be used to control the voltage rise time of the waveform and / or the voltage fall time of the waveform.

[0066] In some embodiments, the resistive output stage 620 can discharge capacitive loads (e.g., wafers and / or plasma). For example, these capacitive loads can have small capacitances (e.g., approximately 10 pF, 100 pF, 500 pF, 1 nF, 10 nF, 100 nF, etc.).

[0067] In some embodiments, the resistive output stage can be used in circuits with high pulse voltages (e.g., voltages greater than 1 kV, 10 kV, 20 kV, 50 kV, 100 kV, etc.) and / or high frequencies (e.g., frequencies greater than 1 kHz, 10 kHz, 100 kHz, 200 kHz, 500 kHz, 1 MHz, etc.) and / or pulses with frequencies of approximately 400 kHz, 0.5 MHz, 2.0 MHz, 4.0 MHz, 13.56 MHz, 27.12 MHz, 40.68 MHz, 50 MHz, etc.

[0068] In some embodiments, the resistive output stage can be selected to handle high average power, high peak power, fast rise time, and / or fast fall time. For example, the average power rating can be greater than about 0.5 kW, 1.0 kW, 10 kW, 25 kW, etc., and / or the peak power rating can be greater than about 1 kW, 10 kW, 100 kW, 1 MW, etc.

[0069] In some embodiments, the resistive output stage 620 may include a series or parallel network of passive components. For example, the resistive output stage 620 may include a series connection of a resistor, a capacitor, and an inductor. As another example, the resistive output stage 620 may include a capacitor in parallel with an inductor and a capacitor-inductor combination in series with a resistor. For example, L11 may be selected to be large enough so that there is no significant energy injected into the resistive output stage when there is a voltage outside the rectifier. The values ​​of R3 and R1 may be selected so that the L / R time can exhaust the appropriate capacitor in the load faster than the RF frequency.

[0070] In some embodiments, the resistive output stage 620 can be coupled to a bias compensation circuit 625. The bias compensation circuit 625 can include any bias and / or bias compensation circuit known in the art. For example, the bias compensation circuit 625 can include any bias and / or bias compensation circuit described in U.S. Patent Application No. 16 / 523,840, entitled “NANOSECOND PULSER BIAS COMPENSATION,” which is incorporated in its entirety into the present disclosure for all purposes.

[0071] In some embodiments, the bias compensation circuit 625 may include a bias capacitor C7, a blocking capacitor C12, a blocking diode D8, a switch S8 (e.g., a high voltage switch), an offset supply voltage V1, a resistor R2, and / or a resistor R4. In some embodiments, the switch S8 includes a high voltage switch described in U.S. Patent Application No. 62 / 717,637 entitled “HIGH VOLTAGE SWITCH FOR NANOSECOND PULSING” and / or U.S. Patent Application No. 16 / 178,565 entitled “HIGH VOLTAGE”, which are incorporated in their entirety into the present disclosure for all purposes.

[0072] In some embodiments, the offset supply voltage V5 may include a DC voltage source that may bias the output voltage positively or negatively. In some embodiments, capacitor C12 may isolate / separate the offset supply voltage V5 from the resistive output stage 620 and / or other circuit elements. In some embodiments, the bias compensation circuit 625 may allow for potential transfer of power from one portion of the circuit to another. In some embodiments, as high voltage pulses are effective in the chamber, the bias compensation circuit 625 may be used to hold the wafer in place. Resistor R2 may protect / isolate the DC bias supply from the driver.

[0073] In some embodiments, switch S8 can be open while the RF driver 605 is pulsing, and closed when the RF driver 605 is not pulsing. While closed, for example, switch S8 can short-circuit the current across the blocking diode D8. Short-circuiting this current can allow the bias between the wafer and the chuck to be less than 2 kV, which can be within acceptable tolerances.

[0074] In some embodiments, the plasma and chamber 630 can be coupled to the bias compensation circuit 625. For example, the plasma and chamber 630 can be provided by Figure 6 The various circuit components shown are represented.

[0075] Figure 6 A conventional matching network (e.g., such as a 50 ohm matching network or an external matching network or a separate matching network) is not included. In fact, the embodiments described in this document do not require a 50 ohm matching network to tune the switching power applied to the wafer chamber. In addition, the embodiments described in this document provide a variable output impedance RF generator without a conventional matching network. This can allow for rapid changes in the power drawn by the plasma chamber. Typically, such tuning of the matching network takes at least 100 μs-200 μs. In some embodiments, the power change can occur within one or two RF cycles (e.g., 2.5 μs-5.0 μs at 400 kHz).

[0076] Figure 7 are waveforms of the voltage across transformer T1 (red), at the pole (green), and at the wafer (blue) for a time frame up to 600 μs. Figure 8 is a zoomed in view of the waveform over a 10 μs time frame.

[0077] Fig. 9 is a circuit diagram of an RF driver 900 according to some embodiments. For example, the RF driver 900 may include the RF driver 605, the resonant circuit 610, the bias compensation circuit 625, and the plasma and chamber 630. The RF driver 900 is similar to the driver and chamber circuit 600, but without the resistive output stage 620, and includes the energy recovery circuit 905.

[0078] In this example, the energy recovery circuit 905 can be located on or electrically coupled to the secondary side of the transformer T1. For example, the energy recovery circuit 905 can include a diode D9 (e.g., a crowbar diode) across the secondary side of the transformer T1. For example, the energy recovery circuit 905 can include a diode D10 and an inductor L12 (arranged in series) that can allow current to flow from the secondary side of the transformer T1 to charge the power supply C15 and allow current to flow to the plasma and chamber 630. The diode D12 and the inductor L12 can be electrically connected to the secondary side of the transformer T1 and coupled to the power supply C15. In some embodiments, the energy recovery circuit 905 can include a diode D13 and / or an inductor L13 electrically coupled to the secondary of the transformer T1. The inductor L12 can represent a stray inductance and / or can include the stray inductance of the transformer T1.

[0079] When the nanosecond pulse generator is on, current can charge the plasma and chamber 630 (e.g., charging capacitor C3, capacitor C2, or capacitor C9). For example, when the voltage on the secondary side of transformer T1 rises above the charging voltage on power supply C15, some current can flow through inductor L12. When the nanosecond pulse generator is off, current can flow from capacitors within the plasma and chamber 630 through inductor L12 to charge power supply C15 until the voltage across inductor L12 is zero. Diode D9 can prevent capacitors within the plasma and chamber 630 from looping with inductors in the plasma and chamber 630 or bias compensation circuit 625.

[0080] For example, diode D12 can prevent charge from power supply C15 from flowing to the plasma and capacitors within chamber 630 .

[0081] The value of the inductor L12 can be selected to control the current fall time. In some embodiments, the inductor L12 can have an inductance value between 1 μH and 500 μH.

[0082] In some embodiments, the energy recovery circuit 905 can include a switch that can be used to control the flow of current through the inductor L12. For example, the switch can be placed in series with the inductor L12. In some embodiments, when the switch S1 is open and / or no longer pulsing, the switch can be closed to allow current to flow from the plasma and chamber 630 back to the power supply C15.

[0083] For example, the switch in the energy recovery circuit 905 may include a high voltage switch (e.g., such as the high voltage switch disclosed in U.S. Provisional Patent Application No. 62 / 717,637, filed on November 1, 2018, entitled “HIGH VOLTAGE SWITCH WITH ISOLATED POWER”, which claims priority to U.S. Provisional Patent Application No. 62 / 717,637, filed on August 10, 2018, both of which are incorporated by reference in their entirety). In some embodiments, the RF driver 605 may also include a high voltage switch instead of or in addition to the various components shown in the RF driver 605. In some embodiments, the use of a high voltage switch may allow at least the transformer T1 and the switch S1 to be removed.

[0084] Fig.10 is a circuit diagram of a driver and chamber circuit 1000 according to some embodiments. For example, the driver and chamber circuit 1000 may include an RF driver 605, a resonant circuit 610, a resistive output stage 620, and a plasma and chamber 630. Thus, the driver and chamber circuit 1000 is similar to the driver and chamber circuit 600 without the bias compensation circuit 625.

[0085] Fig.11 is a circuit diagram of a driver and chamber circuit 1100 according to some embodiments. For example, the driver and chamber circuit 1100 may include the RF driver 605, the resonant circuit 610, the energy recovery circuit 905, and the plasma and chamber 630. Thus, the driver and chamber circuit 1100 is similar to the driver and chamber circuit 900 without the bias compensation circuit 625.

[0086] Fig.12 6 is a circuit diagram of a driver and inductive discharge plasma 1200 according to some embodiments. For example, the driver and inductive discharge plasma 1200 may include an RF driver 605, a resonant circuit 610, and an inductive discharge plasma 1205. In this example, the inductor L5 may include an antenna coupled to the inductive discharge plasma 1205. The transformer T1 may represent how the inductive discharge plasma 1205 is coupled to the antenna at least partially represented by the inductor L5. The capacitor C2 may resonate with the inductor L5 to determine the resonant frequency. The RF driver 605 may generate pulses driven at the resonant frequency.

[0087] Fig.13 605, a resonant circuit 1310 (which may include a transformer), and a chamber 630. Capacitor C1 may represent the capacitance of the discharge geometry, any stray capacitance in the circuit, or the capacitance of any capacitor in the circuit. L5 may represent the inductance of any stray inductance in the circuit or the inductance of any inductance in the circuit. The RF driver 605 may drive the resonant circuit 1310 with a pulse frequency substantially equal to the resonant frequency of the resonant circuit.

[0088] In some embodiments, each switch S1, S2, S3, or S4 in the resonant circuit 605 can be switched independently or in combination with one or more of the other switches. For example, the signal Sig1 can be the same signal as the signal Sig3. As another example, the signal Sig2 can be the same signal as the signal Sig4. As another example, each signal can be independent and each switch S1, S2, S3, or S4 can be controlled independently or separately.

[0089] In some embodiments, transformer T1 may or may not be included in the driver and capacitive discharge plasma 1300 .

[0090] Fig.14A , Fig. 14B , Fig.15A and Fig. 15B Can be replaced Figure 6 6. Circuit diagram of an example resonant circuit used in the resonant circuit 610 of FIG. These circuits may or may not include the transformer shown in each figure.

[0091] Fig.16 is a continuous waveform of the voltage across transformer T1 (red), at the pole (green), and at the wafer (blue).

[0092] Fig.17 is a short burst waveform of the voltage across transformer T1 (red), at the pole (green) and at the wafer (blue). The waveform shows a 22.5 μs long burst.

[0093] Fig.18 is a waveform showing a series of short bursts across transformer T1 (red), at the pole (green) and at the wafer (blue). The waveform shows repeated 22.5μs long bursts. The embodiments described in this document provide a system in which the timing can be adjusted. For example, the number of pulses in the burst, the frequency, the number of bursts and / or the duty cycle of the burst can all be adjusted by changing the drive signal (Sig1, Sig2, Sig3 or Sig4) to switches S1, S2, S3 or S4.

[0094] In some embodiments, the diode D8 and capacitor C7 in the bias compensation circuit 625 shown in any circuit can be arranged in a stripline so that the current flows in a U-shaped path. For example, the stripline can be a transmission line trace surrounded by a dielectric material between two ground planes suspended on the inner layer of the PCB. In some embodiments, the separation between the diode D8 and the capacitor C7 can be maximized. In some embodiments, the diode D8 and capacitor C7 striplines are as wide as possible (e.g., such as 10, 8, 6, 4, 3, 2, 1, 1 / 2 inches).

[0095] In some embodiments, lead inductance L22 can be minimized or eliminated by connecting point 124 to the input of diode D8 (e.g., at stray inductance L22). In some embodiments, lead inductance L24 can be minimized or eliminated by connecting the low side of capacitor C7 directly to ground (e.g., at stray inductance L24).

[0096] In this example, the bias compensation circuit 625 includes a stray inductance L22 between the diode D8 and the position marked 124, a stray inductance L23 between the diode D8 and the capacitor C7, or a stray inductance L24 between the capacitor C7 and ground. p and the switch side inductor L s For example, the plasma side stray inductance L p All inductances, whether stray, parasitic, or from any element between the bias compensation circuit 625 and the chamber 630 (e.g., such as L9 and any other stray inductances on that side of the circuit) may be included. For example, the switch side inductance L s All inductance, whether stray, parasitic, or from any element between the bias compensation circuit 625 and the switch S1 may be included (eg, such as L11 , L5 , L1 , L2 , L3 , and / or L4 and any other stray inductance on that side of the circuit).

[0097] In some embodiments, the switch side inductor L s Should be greater than the plasma side stray inductance L p In some embodiments, the plasma side stray inductance L p is the switch side inductance L s In some embodiments, the plasma side stray inductance L p Less than approximately 1nH, 10nH, 100nH, 1μH, etc.

[0098] In some embodiments, stray inductance L22 has an inductance less than about 1 nH, 10 nH, 100 nH, 1 μH, etc. In some embodiments, stray inductance L23 has an inductance less than about 1 nH, 10 nH, 100 nH, 1 μH, etc. In some embodiments, stray inductance L24 has an inductance less than about 1 nH, 10 nH, 100 nH, 1 μH, etc. In some embodiments, the sum of stray inductances L22, L23, and L24 is less than about 1 nH, 10 nH, 100 nH, 1 μH, etc.

[0099] In some embodiments, stray inductance L22, L23, or L24 can be minimized in various ways. For example, the conductor along the stray inductance L22, L23, or L24 can be wider than the industry standard (e.g., such as greater than 1 / 8, 1 / 4, 3 / 8, 1 / 2, 1, 2.5, 5 inches, etc.). As another example, various circuit elements (e.g., such as diode D8 or capacitor C7) can include multiple diodes or capacitors in parallel or series.

[0100] In some embodiments, the distance between components can be minimized to reduce stray inductance. For example, the top conductors and bottom conductors of the various bias assembly circuit elements can be separated by less than about 1, 2, 5, 15, 20, 25, 30, 35, 40 centimeters. As another example, the discrete component including diode D8 can be disposed within less than 10, 8, 6, 4, 3, 2, 1, 1 / 2 inches from the location marked 124 or ground. As another example, the discrete component including capacitor C7 can be disposed within less than 10, 8, 6, 4, 3, 2, 1, 1 / 2 inches from the location marked 124 or ground.

[0101] In some embodiments, the volume of discrete components including one or both of diode D8 and / or capacitor C7 may be less than 1200, 1000, 750, 500 cubic centimeters.

[0102] In some embodiments, a resistor R4 may be included across the diode D8. In some embodiments, the resistor R4 may have a resistance value of less than about 1 kΩ to 1 MΩ, such as, for example, less than about 100 kΩ.

[0103] In some embodiments, capacitor C7 may have a capacitance of less than about 1 μF or less than about 1 mF. Capacitor C7 may have a stray inductance of less than about 1 nH, 10 nH, 100 nH, 1 μH, etc.

[0104] The term "or" is inclusive.

[0105] Unless otherwise stated, the term "substantially" means within 5% or 10% of the indicated value or within manufacturing tolerances. Unless otherwise stated, the term "approximately" means within 5% or 10% of the indicated value or within manufacturing tolerances.

[0106] Numerous specific details are set forth herein to provide a thorough understanding of the claimed subject matter. However, it will be appreciated by those skilled in the art that the claimed subject matter may be practiced without these specific details. In other instances, methods, devices, or systems known to those of ordinary skill in the art have not been described in detail so as not to obscure the claimed subject matter.

[0107] Some parts are presented in view of algorithms or symbolic representations of operations on data bits or binary digital signals stored in a computing system memory (e.g., computer memory). These algorithmic descriptions or representations are examples of techniques used by those of ordinary skill in the field of data processing to convey the essence of their work to other technicians in the field. An algorithm is a self-consistent sequence of operations or similar processes that lead to a desired result. In this case, the operation or process involves the physical manipulation of physical quantities. Typically, but not necessarily, these quantities can take the form of electrical or magnetic signals that can be stored, transmitted, combined, compared or otherwise manipulated. It has sometimes proven convenient to refer to these signals as bits, data, values, elements, symbols, characters, terms, numbers, numerical values, etc., primarily for reasons of ordinary use. However, it should be understood that all of these and similar terms are to be associated with appropriate physical quantities and are merely convenient labels. Unless otherwise specifically noted, it should be understood that throughout this specification discussion, terms such as "process," "compute," "calculate," "determine," and "identify" are used to refer to the actions or processes of a computing device (e.g., one or more computers or similar electronic computing devices) that manipulate or transform data represented as physical electronic or magnetic quantities within a memory, register, or other information storage device, transmission device, or display device of a computing platform.

[0108] The one or more systems discussed herein are not limited to any particular hardware architecture or configuration. A computing device may include any suitable arrangement of components that provide a result conditioned on one or more inputs. Suitable computing devices include a multi-purpose microprocessor-based computer system that accesses stored software that programs or configures a computing system from a general-purpose computing device to a dedicated computing device that implements one or more embodiments of the present subject matter. Any suitable programming, scripting, or other type of language or combination of languages ​​may be used to implement the teachings contained herein in software to be used in programming or configuring a computing device.

[0109] Embodiments of the methods disclosed herein may be performed in the operation of these computing devices. The order of the blocks presented in the above examples may be changed—for example, the blocks may be reordered, combined, and / or decomposed into sub-blocks. Certain blocks or processes may be performed in parallel.

[0110] The use of "suitable for" or "configured to" herein is intended to be open and inclusive language that does not exclude devices that are suitable for or configured to perform additional tasks or steps. Furthermore, the use of "based on" is intended to be open and inclusive, as a process, step, calculation, or other action that is "based on" one or more stated conditions or values ​​may actually be based on additional conditions or values ​​beyond those stated. The headings, lists, and numbering included herein are for ease of explanation only and are not intended to be limiting.

[0111] Although the subject matter has been described in detail with respect to specific embodiments thereof, it will be appreciated that changes to these embodiments, variations thereof, and equivalents thereof may be readily made by those skilled in the art upon gaining an understanding of the foregoing. It should therefore be appreciated that the present disclosure is presented for purposes of illustration and not limitation, and does not exclude the inclusion of such modifications, variations, and / or additions to the subject matter, which will be apparent to those of ordinary skill in the art.

Claims

1. An RF system, comprising: Energy storage capacitors; a switching circuit coupled to the energy storage capacitor, the switching circuit generating a plurality of pulses having a pulse amplitude and a pulse frequency, the pulse amplitude being greater than 100 volts; A resonant circuit coupled to the switch circuit, the resonant circuit comprising: a transformer having a primary side and a secondary side; and a circuit element selected from the group consisting of a capacitor, an inductor and a resistor, The resonant circuit has a resonant frequency substantially equal to the pulse frequency, and the resonant circuit increases the pulse amplitude to a voltage greater than 2 kV; and An energy recovery circuit is coupled to the energy storage capacitor and the secondary side of the transformer, the energy recovery circuit comprising a diode and an inductor arranged in series, wherein the energy recovery circuit is configured to allow current to flow from the secondary side of the transformer to charge the energy storage capacitor.

2. The RF system of claim 1, further comprising a plasma chamber coupled to the resonant circuit.

3. The RF system of claim 1, wherein: The switching circuit includes a full-bridge driver or a half-bridge driver.

4. The RF system of claim 1, wherein: The resonant circuit includes an inductor, and the resonant frequency includes The inductance L includes any stray inductance of the transformer and the inductance of the inductor, and the capacitance C includes any stray capacitance of the transformer.

5. The RF system of claim 1, wherein: The resonant circuit includes a capacitor, and the resonant frequency includes Therein, the inductance L includes any stray inductance of the transformer, and the capacitance C includes any stray capacitance of the transformer and the capacitance of the capacitor.

6. An RF plasma system comprising: Energy storage capacitors; a high voltage switching power supply that generates a plurality of pulses having a pulse amplitude and a pulse frequency, the pulse amplitude being greater than 100 volts; and a resonant circuit coupled to the switching power supply, the resonant circuit having a resonant frequency substantially equal to the pulse frequency, and the resonant circuit increasing the amplitude of the plurality of pulses to a voltage greater than 2 kV; a transformer having a primary side and a secondary side; a plasma chamber coupled to the resonant circuit; and, An energy recovery circuit is coupled to the energy storage capacitor and the secondary side of the transformer, the energy recovery circuit comprising a diode and an inductor arranged in series, the energy recovery circuit is coupled to the plasma chamber, and the energy recovery circuit releases the charge of the plasma chamber.

7. The RF plasma system of claim 6, wherein: The transformer is coupled to the resonant circuit.

8. The RF plasma system of claim 7, wherein: The energy recovery circuit allows current to flow from the secondary side of the transformer to charge the energy storage capacitor.

9. The RF plasma system of claim 6, further comprising a bias compensation circuit.

10. The RF plasma system of claim 7, wherein: The resonant frequency is determined by one or both of the inductance (L) and / or capacitance (C) of the transformer according to the following formula:

11. The RF plasma system of claim 10, wherein: The resonant frequency includes The inductance L includes any stray inductance of the transformer, and the capacitance C includes any stray capacitance of the transformer.

12. The RF plasma system of claim 6, wherein: The high voltage switching power supply includes a full-bridge driver or a half-bridge driver.

13. The RF plasma system of claim 6, wherein: The switching power supply is driven at a frequency selected from the group consisting of 400 kHz, 0.5 MHz, 2.0 MHz, 4.0 MHz, 13.56 MHz, 27.12 MHz, 40.68 MHz, and 50 MHz.

14. An RF plasma system comprising: Energy storage capacitors; a high voltage switching power supply electrically coupled to the energy storage capacitor, the high voltage switching power supply generating a plurality of pulses having a pulse amplitude and a pulse frequency, the pulse amplitude being greater than 100 volts and the pulse frequency being greater than 100 kHz; an inductively coupled plasma source comprising a coil electrically coupled to the high voltage switching power supply; and a capacitor, wherein the capacitor and the inductance of the inductively coupled plasma source resonate at a resonant frequency substantially equal to the pulse frequency; and, An energy recovery circuit is coupled to the inductively coupled plasma source and the energy storage capacitor, the energy recovery circuit comprising a diode and an inductor arranged in series, wherein the energy recovery circuit is configured to allow current to flow from the inductively coupled plasma source to the energy storage capacitor.

15. The RF plasma system of claim 14, wherein: The resonant frequency includes The inductance L includes the inductance of the inductively coupled plasma source, and the capacitance C includes the capacitance of the capacitor.

16. The RF plasma system of claim 14, wherein: The high voltage switching power supply includes a full-bridge driver or a half-bridge driver.

17. An RF plasma system comprising: Energy storage capacitors; a high voltage switching power supply that generates a plurality of pulses having a pulse amplitude and a pulse frequency, the pulse amplitude being greater than 100 volts and the pulse frequency being greater than 100 kHz; Capacitively coupled plasma; an inductor, wherein the inductor and the capacitance of the capacitively coupled plasma form a resonant circuit having a resonant frequency substantially equal to the pulse frequency; and, An energy recovery circuit is coupled to the capacitively coupled plasma and the energy storage capacitor, the energy recovery circuit comprising a diode and an inductor arranged in series, wherein the energy recovery circuit is configured to allow current to flow from the capacitively coupled plasma to the energy storage capacitor.

18. The RF plasma system of claim 17, wherein: The resonant frequency includes The inductance L includes the inductance of the inductor, and the capacitance C includes the capacitance of the capacitively coupled plasma.

19. The RF plasma system of claim 17, wherein: The high voltage switching power supply includes a full-bridge driver or a half-bridge driver.

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