Plasma system

Abstract

Embodiments of the invention include a plasma system. The plasma system includes a plasma chamber; an RF driver configured to drive bursts into the plasma chamber at an RF frequency; a nanosecond pulse generator configured to drive pulses into the plasma chamber at a pulse repetition frequency, the pulse repetition frequency being less than the RF frequency; a high pass filter disposed between the RF driver and the plasma chamber; and a low pass filter disposed between the nanosecond pulse generator and the plasma chamber.

Description

Background Technology

[0001] Semiconductor device manufacturing processes utilize plasma processing at various stages to create semiconductor devices. These semiconductor devices can include processors, memory, integrated circuits, and other types of integrated circuits and devices. Various other processes also utilize plasma processing. Plasma processing involves energizing a gas mixture by introducing RF (radio frequency) energy into the gas molecules. This gas mixture is typically contained within a vacuum chamber called a plasma chamber, and the RF energy is typically introduced into the plasma chamber via electrodes.

[0002] In typical plasma processes, an RF generator generates power in the range of 3 kHz to 300 GHz, as broadly understood, and this power is transmitted to the plasma chamber via RF cables and networks. To provide efficient power transfer from the RF generator to the plasma chamber, intermediate circuitry is used to match the fixed impedance of the RF generator to the variable impedance of the plasma chamber. This intermediate circuitry is commonly referred to as an RF impedance matching network, or more simply as a matching network. Summary of the Invention

[0003] Some embodiments of the present invention include a plasma system. The plasma system includes: a plasma chamber; an RF driver configured to drive bursts into the plasma chamber at an RF frequency; a nanosecond pulse generator configured to drive pulses into the plasma chamber at a pulse repetition frequency less than the RF frequency; a high-pass filter disposed between the RF driver and the plasma chamber; and a low-pass filter disposed between the nanosecond pulse generator and the plasma chamber.

[0004] In some embodiments, the high-pass filter may include a capacitor. In some embodiments, the low-pass filter may include an inductor. In some embodiments, the RF driver may include a nanosecond pulse generator.

[0005] Some embodiments of the present invention include a plasma system. The plasma system includes a plasma chamber, which may include a plurality of walls and a wafer support. When plasma is created within the plasma chamber, a wall-plasma sheath is formed between the plasma and at least one of the plurality of walls, and a wafer-plasma sheath is formed between the plasma and a wafer disposed on the wafer support. The capacitance of the wall-plasma sheath is at least approximately ten times the capacitance of the wafer-plasma sheath. An RF driver drives a burst into the plasma chamber at an RF frequency. A nanosecond pulse generator drives pulses into the plasma chamber at a pulse repetition frequency less than the RF frequency. A first filter is deployed between the RF driver and the plasma chamber. A second filter is deployed between the nanosecond pulse generator and the plasma chamber.

[0006] In some embodiments, the capacitance of the wafer-plasma sheath is less than about 1 nF. In some embodiments, the RF driver drives the burst with a peak voltage greater than about 1 kV and a frequency greater than about 1 MHz. In some embodiments, the nanosecond pulse generator drives the pulse with a peak voltage greater than about 1 kV and a frequency less than the frequency of the burst generated by the RF generator. In some embodiments, the first filter includes a high-pass filter, and the second filter includes a low-pass filter. In some embodiments, the second filter includes a capacitor coupled to ground. In some embodiments, the capacitor has a capacitance of less than about 500 pF.

[0007] Some embodiments of the present invention include a plasma system. The plasma system includes: a plasma chamber; an RF driver electrically coupled to the plasma chamber, the RF driver driving bursts into the plasma chamber at an RF frequency; a nanosecond pulse generator electrically coupled to the plasma chamber, the nanosecond pulse generator driving pulses into the plasma chamber at a pulse repetition frequency less than the RF frequency; a capacitor disposed between the RF driver and the plasma chamber; and an inductor disposed between the nanosecond pulse generator and the plasma chamber.

[0008] In some embodiments, the capacitor has a capacitance of less than approximately 100 pF. In some embodiments, the inductor has an inductance of less than approximately 10 nH. In some embodiments, the inductor has a stray capacitance of less than approximately 5 pF.

[0009] In some embodiments, the plasma chamber includes a plurality of walls and a wafer support such that when plasma is created in the plasma chamber, a wall-plasma sheath is formed between the plasma and at least one of the plurality of walls, and a wafer-plasma sheath is formed between the plasma and a wafer deployed on the wafer support, wherein the capacitance of the wall-plasma sheath is at least about ten times greater than the capacitance of the wafer-plasma sheath.

[0010] In some embodiments, the plasma chamber includes a plurality of walls and a wafer support such that when plasma is created in the plasma chamber, a wall-plasma sheath is formed between the plasma and at least one of the plurality of walls, and a wafer-plasma sheath is formed between the plasma and a wafer deployed on the wafer support, wherein the capacitance of the wall-plasma sheath is at least about fifty times greater than the capacitance of the wafer-plasma sheath.

[0011] Some embodiments of the present invention include a plasma system. The plasma system includes: a plasma chamber; an RF driver configured to drive pulses into the plasma chamber at an RF frequency greater than approximately 200 kHz and a peak voltage greater than 1 kV; an energy trap circuit electrically coupled to the plasma chamber; a rectifier diode electrically coupled between the plasma chamber and the RF driver, such that the rectifier diode rectifies a waveform generated by the RF driver; and a drop control inductor and a drop control resistor arranged in series, such that the series combination of the drop control inductor and the drop control resistor is arranged in parallel with the rectifier diode.

[0012] In some embodiments, the energy trap circuit includes a resistive output stage circuit. In some embodiments, the energy trap circuit includes an energy recovery circuit. In some embodiments, the dropout control inductor has an inductance of less than approximately 10 mH. In some embodiments, the dropout resistance is less than approximately 500 Ω.

[0013] The reference to these illustrative embodiments is not intended to limit or restrict this disclosure, but rather to provide examples to aid understanding. Additional embodiments are discussed in the detailed description and are further described herein. The advantages provided by one or more of the various embodiments can be further understood by examining this specification or by practicing one or more of the embodiments presented. Attached Figure Description

[0014] These and other features, aspects and advantages of this disclosure will be better understood when reading the following detailed description with reference to the accompanying drawings.

[0015] Figure 1An example diagram of a plasma system with an RF driver and a nanosecond pulse generator according to some embodiments is shown.

[0016] Figure 2 An example diagram of a plasma system with an RF driver and a nanosecond pulse generator according to some embodiments is shown.

[0017] Figure 3 An example diagram of a plasma system with an RF driver and a nanosecond pulse generator according to some embodiments is shown.

[0018] Figure 4 An example diagram of a plasma system with an RF driver and a nanosecond pulse generator according to some embodiments is shown.

[0019] Figure 5A The image shows pulses from a nanosecond pulse generator according to some embodiments.

[0020] Figure 5B A burst of pulses from a nanosecond pulse generator is shown according to some embodiments.

[0021] Figure 6A A burst from an RF driver is shown according to some embodiments.

[0022] Figure 6B Multiple bursts from an RF driver are shown according to some embodiments.

[0023] Figure 7 This is a schematic representation of a plasma system according to some embodiments.

[0024] Figure 8 The waveforms generated by a plasma system having an RF driver and a nanosecond pulse generator are shown according to some embodiments.

[0025] Figure 9 The waveforms generated by a plasma system having an RF driver and a nanosecond pulse generator are shown according to some embodiments.

[0026] Figure 10 The waveforms generated by a plasma system having an RF driver and a nanosecond pulse generator are shown according to some embodiments.

[0027] Figure 11 The waveforms generated by a plasma system having an RF driver and a nanosecond pulse generator are shown according to some embodiments. Detailed Implementation

[0028] A plasma system is disclosed. The plasma system includes: a plasma chamber; an RF driver configured to drive an RF burst into the plasma chamber at an RF frequency; a nanosecond pulse generator configured to drive a pulse into the plasma chamber at a pulse repetition frequency less than the RF frequency; a high-pass filter disposed between the RF driver and the plasma chamber; and a low-pass filter disposed between the nanosecond pulse generator and the plasma chamber.

[0029] Figure 5A An example pulse from a nanosecond pulse generator is shown. Figure 5B This illustrates a burst of pulses from a nanosecond pulse generator. A burst can comprise multiple pulses within a short time frame. Pulses from a nanosecond pulse generator can have pulse repetition frequencies of approximately 10 kHz, 50 Hz, 100 kHz, 500 kHz, 1 MHz, etc.

[0030] Figure 6A Example bursts from an RF driver are shown according to some embodiments. Figure 6B Examples of multiple bursts from an RF driver are shown according to some embodiments. Each burst may include a sinusoidal burst having an RF frequency from 200 kHz to 8XX MHz (e.g., 2 MHz, 13.56 MHz, 27 MHz, 60 MHz, and 80 MHz). In some embodiments, the burst repetition frequency (e.g., the burst frequency) may be approximately 10 kHz, 50 Hz, 100 kHz, 500 kHz, 1 MHz, etc. (e.g., 400 kHz). In some embodiments, the RF driver may provide continuous sinusoidal bursts.

[0031] Figure 1 This is a schematic representation of a plasma system 100. In some embodiments, according to certain examples, the plasma system 300 may include a plasma chamber 110 having an RF driver 105 and a nanosecond pulse generator 115. The RF driver 105 may be coupled to an electrode 120 located within the plasma chamber 110. The nanosecond pulse generator 115 may be coupled to the electrode 120 located inside or outside the plasma chamber 110. In some embodiments, the electrode 120 may be part of or coupled to an electrostatic clip.

[0032] In some embodiments, plasma chamber 110 may include a vacuum pump that maintains vacuum conditions within plasma chamber 110. For example, the vacuum pump may be connected to plasma chamber 110 via a dedicated hose or stainless steel tubing. The vacuum pump may be manually controlled or automatically controlled by the machine via a relay or through-hole connector. In some embodiments, plasma chamber 110 may be represented by an idealized or functional circuitry for semiconductor processing chambers (e.g., plasma deposition systems, semiconductor manufacturing systems, plasma sputtering systems, etc.).

[0033] In some embodiments, the plasma chamber 110 may include an input gas source that can introduce gas (or a mixture of input gases) into the chamber before, after, or during the supply of RF power. Ions in the gas create plasma, and the gas is evacuated by a vacuum pump.

[0034] In some embodiments, the plasma system may include a plasma deposition system, a plasma etching system, or a plasma sputtering system. In some embodiments, the capacitance between the electrode (or clip) and the wafer may be less than approximately 1000 nF, 500 nF, 200 nF, 100 nF, 50 nF, 10 nF, 5000 pF, 1000 pF, 100 pF, etc.

[0035] RF driver 105 may include any type of device that generates RF power applied to electrode 120. For example, RF driver 105 may include a nanosecond pulse generator, a resonant system driven by a half-bridge or full-bridge circuit, an RF amplifier, a nonlinear transmission line, an RF plasma generator, etc. In some embodiments, RF driver 105 may include a matching network.

[0036] In some embodiments, RF driver 105 may include one or more RF drivers that can generate RF power signals having multiple different RF frequencies (e.g., 2 MHz, 13.56 MHz, 27 MHz, 60 MHz, and 80 MHz). For example, typical RF frequencies may include frequencies between 200 kHz and 8XX MHz. In some embodiments, RF driver 105 may create and sustain plasma within plasma chamber 110. For example, RF driver 105 provides RF signals to electrodes 120 (and / or antenna 180, see below) to excite various gases and / or ions within the chamber to create plasma.

[0037] In some embodiments, the RF driver 105 may be coupled to an impedance matching circuit, or may include an impedance matching circuit that can match the output impedance of the RF driver 105 to the industry standard characteristic impedance of a 50Ω coaxial cable or any cable.

[0038] The nanosecond pulse generator 115 may include one or more nanosecond pulse generators. In some embodiments, the nanosecond pulse generator 115 may include: all or any part of any device described in U.S. Patent Application Serial No. 14 / 542,487 entitled “High Voltage Nanosecond Pulser,” which is incorporated herein by reference for all purposes; or all or any part of any device described in U.S. Patent Application Serial No. 14 / 635,991 entitled “Galvanically Isolated Output Variable Pulse Generator Disclosure,” which is incorporated herein by reference for all purposes; or all or any part of any device described in U.S. Patent Application Serial No. 14 / 798,154 entitled “High Voltage Nanosecond Pulser With Variable Pulse Width and Pulse Repetition Frequency,” which is incorporated herein by reference for all purposes; or all or any part of any device described in U.S. Patent Application Serial No. 16 / 697,173 entitled “VARIABLE OUTPUT IMPEDANCE RFGENERATOR,” which is incorporated herein by reference for all purposes.

[0039] For example, nanosecond pulse generator 115 may include a nanosecond pulse generator or a nanosecond pulse generator 1000.

[0040] In some embodiments, the nanosecond pulse generator 115 may have a pulse voltage with an amplitude of approximately 1 kV to approximately 40 kV. In some embodiments, the nanosecond pulse generator 115 may be switched with a pulse repetition frequency of up to approximately 2,000 kHz. In some embodiments, the nanosecond pulse generator may be switched with a pulse repetition frequency of approximately 400 kHz. In some embodiments, the nanosecond pulse generator 115 may provide a single pulse with a pulse width varying from approximately 2,000 ns to approximately 1 nanosecond. In some embodiments, the nanosecond pulse generator 115 may be switched with a pulse repetition frequency greater than approximately 10 kHz. In some embodiments, the nanosecond pulse generator 115 may operate on a load with a rise time of less than approximately 400 ns.

[0041] In some embodiments, the nanosecond pulse generator 115 can generate pulses from a power supply having a voltage greater than 2 kV, a rise time of less than about 400 ns on the load, and a pulse repetition frequency greater than about 10 kHz.

[0042] In some embodiments, the nanosecond pulse generator 115 may include one or more solid-state switches (e.g., solid-state switches such as IGBTs, MOSFETs, SiC MOSFETs, SiC junction transistors, FETs, SiC switches, GaN switches, photoconductive switches, etc.), one or more snubber resistors, one or more snubber diodes, one or more snubber capacitors, and / or one or more freewheeling diodes. The one or more switches and / or circuits may be arranged in parallel or in series. In some embodiments, one or more nanosecond pulse generators may be combined in series or in parallel to form the nanosecond pulse generator 115. In some embodiments, multiple high-voltage switches may be combined in series or in parallel to form the nanosecond pulse generator 115.

[0043] In some embodiments, the nanosecond pulse generator 115 may include circuitry (e.g., a resistive output stage, a trap, or an energy recovery circuit) for removing charge from a capacitive load on a fast time scale. In some embodiments, the charge removal circuitry may dissipate charge from the load on a fast time scale (e.g., 1 ns, 10 ns, 50 ns, 100 ns, 250 ns, 500 ns, 1,000 ns, etc.).

[0044] In some embodiments, a DC bias power supply stage may be included to positively or negatively bias the output voltage of counter electrode 120. In some embodiments, a capacitor may be used to isolate / disconnect the DC bias voltage from charge removal circuitry or other circuit elements. It may also allow potential transfer from one part of the circuit to another. In some applications, potential transfer may be used to hold the wafer in place.

[0045] In some embodiments, the RF driver 105 may generate a burst of RF frequency having a pulse repetition frequency greater than that of the pulse generated by the nanosecond pulse generator 115.

[0046] In some embodiments, capacitor 130 may be deployed (e.g., in series) between RF driver 105 and electrode 120. For example, capacitor 130 may be used to filter low-frequency signals from nanosecond pulse generator 115. These low-frequency signals may have frequencies of approximately 100 kHz to 10 MHz (e.g., approximately 10 MHz, for example) (e.g., most of the spectrum content). For example, capacitor 130 may have a value of approximately 1 pF to 1 nF (e.g., less than approximately 100 pF, for example).

[0047] In some embodiments, inductor 135 may be deployed (e.g., in series) between nanosecond pulse generator 115 and electrode 120. For example, inductor 135 may be used to filter high-frequency signals from RF driver 105. These high-frequency signals may have frequencies from approximately 1 MHz to 200 MHz (e.g., greater than approximately 1 MHz or 10 MHz). Inductor 135 may have values ​​from approximately 10 nH to 10 μH (e.g., greater than approximately 1 μH). In some embodiments, inductor 135 may have a low coupling capacitance across it. In some embodiments, the coupling capacitance may be less than 1 nF.

[0048] In some embodiments, one or both of capacitor 130 and inductor 135 may isolate pulses generated by RF driver 105 from pulses generated by nanosecond pulse generator 115. For example, capacitor 130 may isolate pulses generated by nanosecond pulse generator 115 from pulses generated by RF driver 105. Inductor 135 may isolate pulses generated by RF driver 105 from pulses generated by nanosecond pulse generator 115.

[0049] Figure 2 This is a schematic representation of a plasma system 200. According to some embodiments, the plasma system 200 includes a plasma chamber 110 comprising an RF driver 105 and a filtered nanosecond pulse generator 115. The various parts of the plasma system 200 may be similar to... Figure 1 The plasma system 100 is described. In this embodiment, filter 140 may replace capacitor 130, and / or filter 145 may replace inductor 135. The filters alternately protect the RF driver from pulses generated by the NSP bias generator and protect the nanosecond pulse generator from RF generated by the RF driver. A large number of different filters can be used to achieve this purpose.

[0050] In some embodiments, the RF driver 105 may generate a burst with an RF frequency fp that is greater than the pulse repetition frequency in each burst generated by the nanosecond pulse generator 115.

[0051] In some embodiments, filter 140 may be deployed (e.g., in series) between RF driver 105 and electrode 120. Filter 140 may be a high-pass filter that allows high-frequency pulses with frequencies from about 1 MHz to 200 MHz (e.g., about 1 MHz or 10 MHz). For example, filter 140 may include any type of filter that allows these high-frequency signals to pass through.

[0052] In some embodiments, filter 145 may be deployed (e.g., in series) between nanosecond pulse generator 115 and electrode 120. Filter 145 may be a low-pass filter that allows low-frequency pulses with frequencies less than approximately 100 kHz to 10 MHz (e.g., approximately 10 MHz). For example, filter 145 may include any type of filter that allows these low-frequency signals to pass through.

[0053] In some embodiments, one or both of filters 140 and 145 may isolate pulses generated by RF driver 105 from pulses generated by nanosecond pulse generator 115. For example, filter 140 may isolate pulses generated by nanosecond pulse generator 115 from pulses generated by RF driver 105. Filter 145 may isolate pulses generated by RF driver 105 from pulses generated by nanosecond pulse generator 115.

[0054] Figure 3 This is a schematic representation of a plasma system 300. According to some embodiments, the plasma system 300 may include a plasma chamber 110 having an RF driver 105 and a nanosecond pulse generator 115.

[0055] RF driver 105 may include any type of device that generates RF power applied to antenna 180. In some embodiments, RF driver 105 may include one or more RF drivers that can generate RF power signals having multiple different RF frequencies (e.g., 2 MHz, 13.56 MHz, 27 MHz, and 60 MHz).

[0056] In some embodiments, the RF driver 105 may be coupled to an impedance matching circuit, or may include an impedance matching circuit that matches the output impedance of the RF driver 105 (typically 50Ω) to the variable impedance of the plasma load (typically much smaller and may be reactive).

[0057] In some embodiments, the RF driver 105 may include one or more nanosecond pulse generators.

[0058] In some embodiments, the RF driver 105 can generate pulses with an RF frequency that is greater than the pulse repetition frequency of the pulses generated by the nanosecond pulse generator 115.

[0059] In some embodiments, capacitor 150 may be deployed (e.g., in series) between RF driver 105 and antenna 180. For example, capacitor 150 may be used to filter low-frequency signals from nanosecond pulse generator 115. For example, these low-frequency signals may have frequencies less than approximately 100 kHz to 10 MHz (e.g., approximately 10 MHz). For example, capacitor 150 may have a value of approximately 1 pF to 1 nF (e.g., less than approximately 100 pF).

[0060] In some embodiments, inductor 155 may be deployed (e.g., in series) between nanosecond pulse generator 115 and electrode 120. For example, inductor 135 may be used to filter high-frequency signals from RF driver 105. For example, these high-frequency signals may have frequencies greater than about 1 MHz to 200 MHz (e.g., greater than about 1 MHz or 10 MHz). For example, inductor 155 may have values ​​less than about 10 nH to 10 μH (e.g., greater than about 1 μH). In some embodiments, inductor 155 may have a low coupling capacitance across it.

[0061] In some embodiments, one or both of capacitor 150 and inductor 155 may isolate pulses generated by RF driver 105 from pulses generated by nanosecond pulse generator 115. For example, capacitor 150 may isolate pulses generated by nanosecond pulse generator 115 from pulses generated by RF driver 105. Inductor 155 may isolate pulses generated by RF driver 105 from pulses generated by nanosecond pulse generator 115.

[0062] Figure 4 This is a schematic representation of a plasma system 400 having an RF driver 105 and a nanosecond pulse generator 115 according to some embodiments. The RF driver 105 can include any type of RF driver. The portions of the plasma system 400 can be similar to... Figure 3 The plasma system 300 in the middle. Filter 140 can replace Figure 3 The capacitor 150 and / or filter 145 used can replace the inductor 135.

[0063] The plasma system 600 includes a plasma chamber. An RF driver 105 and / or a nanosecond pulse generator 115 generate bursts and / or pulses that drive the plasma within the plasma chamber. The plasma chamber is an idealized and / or effective circuit representation of the plasma and the plasma chamber.

[0064] In some embodiments, the RF driver 105 may generate a burst of RF frequency having a pulse repetition frequency greater than that of the pulse generated by the nanosecond pulse generator 115.

[0065] In some embodiments, filter 140 may be deployed (e.g., in series) between RF driver 105 and electrode 120. Filter 140 may be a high-pass filter that allows high-frequency pulses with frequencies greater than approximately 1 MHz to 200 MHz (e.g., greater than approximately 1 MHz or 10 MHz). For example, filter 140 may include any type of filter that allows such high-frequency signals to pass through.

[0066] In some embodiments, filter 145 may be deployed (e.g., in series) between nanosecond pulse generator 115 and electrode 120. Filter 145 may be a low-pass filter that allows low-frequency pulses with frequencies less than approximately 100 kHz to 10 MHz (e.g., approximately 10 MHz). For example, filter 145 may include any type of filter that allows these low-frequency signals to pass through.

[0067] In some embodiments, one or both of filters 140 and 145 may isolate pulses generated by RF driver 105 from pulses generated by nanosecond pulse generator 115, and / or vice versa. For example, filter 140 may isolate pulses generated by nanosecond pulse generator 115 from pulses generated by RF driver 105. Filter 145 may isolate pulses generated by RF driver 105 from pulses generated by nanosecond pulse generator 115.

[0068] Figure 7 Example circuit diagram 700 illustrates the equivalent impedance of an RF driver 105 and a nanosecond pulse generator 720 for driving plasma within a plasma chamber 730 according to some embodiments. In some embodiments, the RF driver 105 may operate at a frequency of approximately 60 MHz.

[0069] In some embodiments, impedance filter 140 may also function as a high-pass filter, protecting RF driver 105 from the output of a nanosecond pulse generator. For example, capacitors may filter the output of the nanosecond pulse generator. For example, RF driver 105 may operate at frequencies greater than 1 MHz, 10 MHz, 100 MHz, 1,000 MHz, etc. For example, impedance matching networks may include any type of impedance matching network that can function as a high-pass filter. In some embodiments, impedance matching networks (e.g., when they include series capacitors less than 10 nF, 1 nF, 100 pF, 10 pF, 1 pF) may also function as high-pass filters (e.g., filter 140).

[0070] The plasma chamber 110 can be represented by a plurality of equivalent circuit elements shown in an effective (or idealized) plasma chamber.

[0071] In some embodiments, the plasma chamber can be represented by an idealized or functional circuit for a semiconductor processing chamber (e.g., a plasma deposition system, a semiconductor manufacturing system, a plasma sputtering system, etc.). For example, a capacitor can represent the capacitance of a clip on which a wafer can be placed. For example, the clip may include a dielectric material. For example, the capacitor may have a small capacitance (e.g., approximately 10 pF, 100 pF, 500 pF, 1 nF, 10 nF, 100 nF, etc.).

[0072] A plasma sheath can be formed within a plasma chamber, which may include a non-neutral region to balance electron and ion losses. A wafer-sheath capacitor represents the capacitance of a plasma sheath that can be formed between the plasma and the top surface of a wafer. For example, a resistor can represent the sheath resistance between the plasma and the wafer. For example, an inductor can represent the sheath inductance between the plasma and the wafer. For example, a current source can represent the ion current passing through the sheath. For example, a wafer-sheath capacitor can have small capacitances (e.g., approximately 10 pF, 100 pF, 500 pF, 1 nF, 10 nF, 100 nF, etc.).

[0073] A wall-sheath capacitor represents the capacitance that can be formed between one or more walls of a plasma and a plasma chamber. For example, a resistor can represent the resistance between plasmas that handle the chamber walls. For example, a current source can represent the ion current in the plasma. For example, a wall-sheath capacitor C1 (e.g., the capacitance of a wall-sheath capacitor) can have a small capacitance (e.g., approximately 10 pF, 100 pF, 500 pF, 1 nF, 10 nF, 100 nF, etc.).

[0074] Various other plasma sheaths can be formed between the chamber or electrode portion and the plasma.

[0075] The sheath capacitance can be estimated from the Child-Langmuir sheath. The Child-Langmuir sheath can be calculated using the following formula:

[0076]

[0077] in, s is the Debye length, and s is the sheath length. It is the electron temperature. It is the bias voltage at the boundary, and This is the electron density reduction factor at the sheath edge. The sheath capacitance can then be calculated from the following formula:

[0078]

[0079] Where A is the area of ​​the sheath boundary, and It is the dielectric constant of free space.

[0080] In some embodiments, the wall-sheath capacitance C1 (e.g., the capacitance of a capacitor) can be greater than the wafer-sheath capacitance C3 (e.g., the capacitance of a capacitor). For example, the ratio of wall-sheath capacitance C1 to wafer-sheath capacitance C3 can be greater than 10 ( ). As another example, the wall-sheath capacitance C1 should be ten times the wafer-sheath capacitance C3. ).

[0081] As another example, the ratio of wall-sheath capacitance C1 to sheath capacitance C3 can be greater than 50 ( As another example, the wall-sheath capacitance C1 should be fifty times the wafer-sheath capacitance C3. ).

[0082] The RF driver 105 may include any type of device that generates RF power applied to the electrodes in the plasma chamber. For example, the RF driver 105 may include a nanosecond pulse generator, a resonant system driven by a half-bridge or full-bridge circuit, an RF amplifier, a nonlinear transmission line, an RF plasma generator, etc.

[0083] In some embodiments, the RF driver 105 may include one or more RF drivers that can generate RF power signals having multiple different RF frequencies (e.g., 2 MHz, 13.56 MHz, 27 MHz, 60 MHz, 80 MHz, etc.). For example, typical RF frequencies may include frequencies between 200 kHz and 8XX MHz. In some embodiments, the RF driver 105 may create and sustain a plasma within a plasma chamber. For example, the RF driver 105 may provide RF signals to electrodes (and / or antennas, see below) to excite various gases and / or ions within the chamber to create a plasma.

[0084] In some embodiments, the RF driver 105 may be coupled to a matching network, or may include a matching network that matches the output impedance of the RF driver 105 (typically 50Ω) to the variable impedance of the plasma load (typically much smaller and may be reactive).

[0085] The nanosecond pulse generator 720 may include one or more nanosecond pulse generators. In some embodiments, the nanosecond pulse generator 720 may include all or any part of any device described in U.S. Patent Application Serial No. 14 / 542,487 entitled “High Voltage Nanosecond Pulser”, which is incorporated herein by reference for all purposes; all or any part of any device described in U.S. Patent Application Serial No. 14 / 635,991 entitled “Galvanically Isolated Output Variable Pulse Generator Disclosure”, which is incorporated herein by reference for all purposes; or all or any part of any device described in U.S. Patent Application Serial No. 14 / 798,154 entitled “High Voltage Nanosecond Pulser With Variable Pulse Width and Pulse Repetition Frequency”, which is incorporated herein by reference for all purposes.

[0086] In some embodiments, the nanosecond pulse generator may have a pulse voltage with an amplitude of approximately 1 kV to approximately 40 kV. In some embodiments, the nanosecond pulse generator may be switched with a pulse repetition frequency of up to approximately 2,000 kHz. In some embodiments, the nanosecond pulse generator may be switched with a pulse repetition frequency of approximately 400 kHz. In some embodiments, the nanosecond pulse generator 720 may provide a single pulse with a pulse width varying from approximately 2,000 ns to approximately 1 nanosecond. In some embodiments, the nanosecond pulse generator may be switched with a pulse repetition frequency greater than approximately 10 kHz. In some embodiments, the nanosecond pulse generator may operate on a load with a rise time of less than approximately 400 ns.

[0087] In some embodiments, the nanosecond pulse generator can generate pulses from a power supply having a voltage greater than 2 kV, a rise time of less than about 80 ns, and a pulse repetition frequency greater than about 10 kHz.

[0088] In some embodiments, a nanosecond pulse generator may include one or more solid-state switches (e.g., solid-state switches such as IGBTs, MOSFETs, SiC MOSFETs, SiC junction transistors, FETs, SiC switches, GaN switches, photoconductive switches, etc.), one or more snubber resistors, one or more snubber diodes, one or more snubber capacitors, and / or one or more freewheeling diodes. The one or more switches and / or circuits may be arranged in parallel or in series. In some embodiments, one or more nanosecond pulse generators may be combined in series or in parallel to form a nanosecond pulse generator. In some embodiments, multiple high-voltage switches may be combined in series or in parallel to form a nanosecond pulse generator.

[0089] In some embodiments, the nanosecond pulse generator may include circuitry (e.g., a resistive output stage, a trap, or an energy recovery circuit) for removing charge from a capacitive load on a fast time scale. In some embodiments, the charge removal circuitry may dissipate the charge from the load on a fast time scale (e.g., 1 ns, 10 ns, 50 ns, 100 ns, 250 ns, 500 ns, 1,000 ns, etc.).

[0090] In some embodiments, the RF driver may include an RF source, a resonant circuit, a half-wave rectifier, a resistive output stage, and / or a bias compensation circuit. The RF source 805 may be a full-bridge driver (or a half-bridge driver). The RF source may include an input voltage source, which may be a DC voltage source (e.g., a capacitor source, an AC-DC converter, etc.). In some embodiments, the RF source may include four switches. In some embodiments, the RF source may include multiple switches connected in series or in parallel. For example, these switches may include any type of solid-state switch (e.g., IGBT, MOSFET, SiC MOSFET, SiC junction transistor, FET, SiC switch, GaN switch, opto-switch, etc.). These switches may switch at high frequencies and / or may generate high-voltage pulses. For example, these frequencies may include approximately 400 kHz, 0.5 MHz, 2.0 MHz, 4.0 MHz, 13.56 MHz, 27.12 MHz, 40.68 MHz, 50 MHz, etc.

[0091] Each switch in the switch may be coupled in parallel with a corresponding diode and may include stray inductance represented by an inductor. In some embodiments, the inductances of the inductors may be equal. In some embodiments, the inductances of the inductors may be less than approximately 50 nH, 100 nH, 150 nH, 500 nH, 1,000 nH, etc. The combination of the switch and the corresponding diode may be coupled in series with the corresponding inductor. The inductor is connected to ground. The inductor is connected to the switch and the resonant circuit. The inductor is connected to the opposite side of the switch and the resonant circuit.

[0092] In some embodiments, the RF source may be coupled to a resonant circuit. The resonant circuit 810 may include a resonant inductor and / or a resonant capacitor coupled to a transformer. The resonant circuit may include a resonant resistor, which may include stray resistance of any lead between the RF source and the resonant circuit and / or any component within the resonant circuit (e.g., a resonant capacitor, resonant resistor, and / or resonant inductor). In some embodiments, the resonant resistor may include only stray resistance of wires, traces, or circuit elements. While the inductance and / or capacitance of other circuit elements can affect the drive frequency, the drive frequency can be largely set by selecting the resonant inductor and / or resonant capacitor. Further refinement and / or tuning may be required to create the correct drive frequency given stray inductance or stray capacitance. Furthermore, the rise time across the transformer can be adjusted by changing the resonant inductor (L) and / or resonant capacitor (C), provided that:

[0093]

[0094] In some embodiments, a large inductance value for the resonant inductor may result in a slower or shorter rise time. These values ​​may also affect the burst envelope. Each burst may include a transient and a steady-state pulse. The transient pulse within each burst may be set by the Q of the resonant inductor and / or the system until the full voltage is reached during the steady-state pulse.

[0095] If the switch in the RF source operates at the resonant frequency When the switch is turned on, the output voltage at the transformer will be amplified. In some embodiments, the resonant frequency may be approximately 400 kHz, 0.5 MHz, 2.0 MHz, 4.0 MHz, 13.56 MHz, 27.12 MHz, 40.68 MHz, 50 MHz, etc.

[0096] In some embodiments, the resonant capacitor may include the stray capacitance of a transformer and / or a 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 may include the stray inductance of a transformer and / or a physical inductor. In some embodiments, the resonant inductor may have an inductance of approximately 50 nH, 100 nH, 150 nH, 500 nH, 1000 nH, etc. In some embodiments, the resonant resistor may have a resistance of approximately 10 Ω, 25 Ω, 50 Ω, 100 Ω, 150 Ω, 500 Ω, etc.

[0097] In some embodiments, the transformer may be optional. In some embodiments, one or more of a resistor, a resonant inductor, and / or a resonant capacitor may be deployed on the secondary side of the transformer 814.

[0098] In some embodiments, a resonant resistor may represent the stray resistance of wires, traces, and / or transformer windings within a physical circuit. In some embodiments, a resonant resistor may have a resistance of approximately 10 mΩ, 50 mΩ, 100 mΩ, 200 mΩ, 500 mΩ, etc.

[0099] In some embodiments, the transformer may include a transformer as disclosed in U.S. Patent Application No. 15 / 365,094 entitled “High Voltage Transformer,” which is incorporated herein by reference for all purposes. In some embodiments, the output voltage of the resonant circuit can be changed by altering the duty cycle of the switch (e.g., the “on” time of the switch or the time during which the switch is positively conducting). For example, a longer duty cycle results in a higher output voltage, while a shorter duty cycle results in a lower output voltage. In some embodiments, the output voltage of the resonant circuit can be changed or tuned by adjusting the duty cycle of the switch in the RF source.

[0100] For example, the duty cycle of the switch can be adjusted by: changing the duty cycle of the open and closed switch signal Sig1; changing the duty cycle of the open and closed switch signal Sig2; changing the duty cycle of the open and closed switch signal Sig3; and changing the duty cycle of the open and closed switch signal Sig4. For example, by adjusting the duty cycle of the switch, the output voltage of the resonant circuit or the voltage on the load can be controlled in real time.

[0101] In some embodiments, each switch in the RF source can switch independently or in combination with one or more other switches. For example, signal Sig1 can be the same signal as signal Sig3. As another example, signal Sig2 can be the same signal as signal Sig4. As yet another example, each signal can be independent and can control each switch independently or separately.

[0102] In some embodiments, the resonant circuit may be coupled to a half-wave rectifier that may include rectifier diodes.

[0103] In some embodiments, the half-wave rectifier may be coupled to a resistive output stage. The resistive output stage may include any resistive output stage known in the art. For example, the resistive output stage may include any resistive output stage described in U.S. Patent Application No. 16 / 178,538 entitled “HIGH VOLTAGE RESISTIVEOUTPUT STAGE CIRCUIT”, which is fully incorporated herein by reference for all purposes.

[0104] For example, a resistive output stage may include inductors, resistors, and capacitors. In some embodiments, the inductor may include an inductance of approximately 5 μH to approximately 25 μH. In some embodiments, the resistor may include a resistance of approximately 50 Ω to approximately 250 Ω. In some embodiments, the resistor may include stray resistance in the resistive output stage.

[0105] In some embodiments, a resistor may include a plurality of resistors arranged in series and / or parallel. A capacitor may represent the stray capacitance of a resistor, which includes the capacitance of the arrangement of resistors in series and / or parallel. For example, the capacitance of a stray capacitor may be less than 500pF, 250pF, 100pF, 50pF, 10pF, 1pF, etc. For example, the capacitance of stray capacitor 824 may be less than the load capacitance.

[0106] In some embodiments, the resistor can discharge a load (e.g., a plasma sheath capacitor). In some embodiments, the resistor output stage can be configured to discharge an average power of more than about 1 kilowatt during each pulse cycle, and / or discharge one joule or less of energy during each pulse cycle. In some embodiments, the resistance of the resistor in the resistor output stage can be less than 200 Ω. In some embodiments, the resistor can include multiple resistors arranged in series or parallel with a combined capacitance (e.g., a capacitor) of less than about 200 pF.

[0107] In some embodiments, the resistive output stage may include a collection of circuit elements that can be used to control the shape of the voltage waveform across a load. In some embodiments, the resistive output stage may include only passive elements (e.g., resistors, capacitors, inductors, etc.). In some embodiments, the resistive output stage may include active circuit elements (e.g., switches) as well as passive circuit elements. In some embodiments, for example, the resistive output stage may be used to control the voltage rise time and / or voltage fall time of the waveform.

[0108] In some embodiments, the resistive output stage can discharge capacitive loads (e.g., wafers and / or plasma). For example, these capacitive loads may have small capacitances (e.g., approximately 10 pF, 100 pF, 500 pF, 1 nF, 10 nF, 100 nF, etc.).

[0109] In some embodiments, the resistive output stage can be used in circuits having pulses with high pulse voltages (e.g., voltages greater than 1kV, 10kV, 20kV, 50kV, 100kV, etc.) and / or high frequencies (e.g., frequencies greater than 1kHz, 10kHz, 100kHz, 200kHz, 500kHz, 1MHz, etc.) and / or frequencies of approximately 400kHz, 0.5MHz, 2.0MHz, 4.0MHz, 13.56MHz, 27.12MHz, 40.68MHz, 50MHz, etc.

[0110] 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 rated power can be greater than about 0.5kW, 1.0kW, 10kW, 25kW, etc., and / or the peak rated power can be greater than about 1kW, 10kW, 100kW, 1MW, etc.

[0111] In some embodiments, the resistive output stage may include a series or parallel network of passive components. For example, the resistive output stage may include a series connection of a resistor, a capacitor, and an inductor. As another example, the resistive output stage may include a capacitor in parallel with an inductor and a capacitor-inductor combination in series with a resistor. For example, the inductor may be chosen to be large enough that no significant energy is injected into the resistive output stage when a voltage is present leaving the rectifier. The values ​​of the resistors and resistors may be chosen such that the L / R time can deplete the appropriate capacitor in the load faster than the RF frequency.

[0112] In some embodiments, the resistive output stage may be coupled to the bias compensation circuit 825. The bias compensation circuit may include any bias and / or bias compensation circuit known in the art. For example, the bias compensation circuit may 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 fully incorporated herein by reference for all purposes. In some embodiments, the resistive output stage and / or bias compensation circuit may be optional.

[0113] In some embodiments, the nanosecond pulse generator may include a resistor output stage similar to a resistor output stage.

[0114] In some embodiments, the bias compensation circuit may include a bias capacitor 826, a DC blocking capacitor, a choke diode, a switch (e.g., a high-voltage switch), an offset supply voltage, a resistor, and / or a resistor. In some embodiments, the switch includes the high-voltage switch described in U.S. Patent Application No. 82 / 717,637 entitled “HIGH VOLTAGE SWITCH FOR NANOSECOND PULSING” and / or U.S. Patent Application No. 16 / 178,565 entitled “HIGH VOLTAGE SWITCH FOR NANOSECOND PULSING”, which are incorporated herein by reference in their entirety for all purposes.

[0115] In some embodiments, the offset supply voltage may include a DC voltage source that can either positively or negatively bias the output voltage. In some embodiments, a DC blocking capacitor may isolate / disconnect the offset supply voltage from the resistive output stage and / or other circuit elements. In some embodiments, a bias compensation circuit may allow potential transfer of power from one part of the circuit to another. In some embodiments, the bias compensation circuit may be used to hold the wafer in place when a high-voltage pulse is effective indoors. Resistors may protect / isolate the DC bias supply from the driver.

[0116] In some embodiments, the switch can open while the RF source is pulsing and close when the RF source is not pulsing. Simultaneously with closing, for example, the switch can short-circuit the current across the choke diode. Short-circuiting this current allows the bias between the wafer and the clip to be less than 2kV, which can be within acceptable tolerances.

[0117] In this example, the RF driver circuit may include an RF source, a resonant circuit, a half-wave rectifier, an energy recovery circuit 905, and / or a bias compensation circuit. The RF source may be a full-bridge driver (or a half-bridge driver).

[0118] This RF driver is similar to an RF driver in that the resistive output stage is replaced by an energy recovery circuit. The resistive output stage and the energy recovery circuit can be referred to as an energy trap circuit. In some embodiments, the energy recovery circuit and / or bias compensation circuit may be optional.

[0119] In this example, the energy recovery circuit may be located on or electrically coupled to the secondary side of the transformer. For example, the energy recovery circuit may include a diode (e.g., a crowbar diode) spanning the secondary side of the transformer. Alternatively, the energy recovery circuit may include a diode and an inductor (arranged in series) that allow current to flow from the secondary side of the transformer to charge power supply 806 and to allow current to flow to plasma chamber 725. The diode and inductor may be electrically connected to the secondary side of the transformer and coupled to the power supply. In some embodiments, the energy recovery circuit may include a diode and / or an inductor electrically coupled to the secondary side of the transformer. The inductor may represent a stray inductance and / or may include the stray inductance of transformer 814.

[0120] When the pulse generator stage is turned on (generating pulses), current can charge the plasma chamber 725. For example, when the voltage on the secondary side of the transformer rises above the charging voltage on the power supply, some current can flow through the inductor. When the nanosecond pulse generator is turned off, current can flow from the capacitor in the plasma chamber through the inductor to charge the power supply until the voltage across the inductor is zero. Diodes prevent the capacitor in the plasma chamber from ringing with the inductor in the plasma chamber or the bias compensation circuit.

[0121] For example, diodes can prevent charge from flowing from the power source into the capacitors inside the plasma chamber.

[0122] The inductor value can be selected to control the current drop time. In some embodiments, the inductor may have an inductance value between 1 μH and 500 μH.

[0123] In some embodiments, the energy recovery circuit may include a switch that can be used to control the flow of current through the inductor. For example, the switch may be placed in series with the inductor.

[0124] For example, the switch in the energy recovery circuit may include a high-voltage switch (e.g., the high-voltage switch disclosed in U.S. Patent Application No. 16 / 178,565, filed November 1, 2018, entitled “HIGHVOLTAGE SWITCH WITH ISOLATED POWER,” which claims priority to U.S. Provisional Patent Application No. 62 / 717,637, filed August 10, 2018, both of which are incorporated herein by reference in their entirety). In some embodiments, the RF source may include a high-voltage switch that replaces or complements the various components shown in the RF driver.

[0125] In another example, the nanosecond pulse generator may be coupled to RF driver 105 and filter 140. In this example, the nanosecond pulse generator may include a pulse generator stage, a resistive output stage, and / or bias compensation circuitry.

[0126] In some embodiments, the nanosecond pulse generator 1000 (or pulse generator stage) can introduce pulses with the following properties into the load stage: voltages greater than 1kV, 10kV, 20kV, 50kV, 100kV, 1,000kV, etc.; rise times less than approximately 1ns, 10ns, 50ns, 100ns, 250ns, 500ns, 1,000ns, etc.; and fall times less than approximately 1ns, 10ns, 50ns, 100ns, 250ns, 500ns, 1,000ns, etc.; and frequencies greater than approximately 1kHz, 10kHz, 100kHz, 200kHz, 500kHz, 1MHz, etc.

[0127] In some embodiments, for example, the pulse generator stage may include any device capable of generating pulses greater than 500V, peak currents greater than 10 amperes, or pulse widths less than approximately 10,000 ns, 1,000 ns, 100 ns, 10 ns, etc. As another example, the pulse generator stage may generate pulses with amplitudes greater than 1 kV, 5 kV, 10 kV, 50 kV, 200 kV, etc. As yet another example, the pulse generator stage may generate pulses with rise or fall times less than approximately 5 ns, 50 ns, or 300 ns, etc.

[0128] In some embodiments, the pulse generator stage can generate multiple high-voltage bursts. For example, each burst can include multiple high-voltage pulses having fast rise and fast fall times. For example, the multiple high-voltage pulses can have a pulse repetition frequency of approximately 10 Hz to 10 kHz. More specifically, for example, the multiple high-voltage bursts can have burst repetition frequencies of approximately 10 Hz, 100 Hz, 250 Hz, 500 Hz, 1 kHz, 2.5 kHz, 5.0 kHz, 10 kHz, etc.

[0129] Within each of the multiple high-voltage bursts, the high-voltage pulse can have a pulse repetition frequency of approximately 1 kHz, 10 kHz, 100 kHz, 200 kHz, 500 kHz, 1 MHz, etc.

[0130] In some embodiments, the burst repetition frequency time is from one burst until the next burst. This is the frequency at which the bias compensation switch operates.

[0131] In some embodiments, the pulse generator stage may include one or more solid-state switches (e.g., solid-state switches such as IGBTs, MOSFETs, SiC MOSFETs, SiC junction transistors, FETs, SiC switches, GaN switches, photoconductive switches, etc.) coupled to the voltage source 1020. In some embodiments, the pulse generator stage may include one or more source snubber resistors, one or more source snubber diodes, one or more source snubber capacitors, or one or more source freewheeling diodes. One or more switches and / or circuits may be arranged in parallel or in series.

[0132] In some embodiments, the pulse generator stage may generate multiple high-voltage pulses having high frequency, fast rise time, fast fall time, and being at a high frequency. The pulse generator stage 1010 may include one or more nanosecond pulse generators.

[0133] In some embodiments, the pulse generator stage may include a high-voltage pulse generation power supply.

[0134] For example, a pulse generator stage may include any pulse generator described in U.S. Patent Application Serial No. 14 / 542,487 entitled "High Voltage Nanosecond Pulser," which is fully incorporated herein by reference for all purposes. For example, a pulse generator stage may include any pulse generator described in U.S. Patent No. 9,601,283 entitled "Efficient IGBT Switching," which is fully incorporated herein by reference for all purposes. For example, a pulse generator stage may include any pulse generator described in U.S. Patent Application Serial No. 15 / 365,094 entitled "High Voltage Transformer," which is fully incorporated herein by reference for all purposes.

[0135] For example, the pulse generator stage may include a high-voltage switch. As another example, the pulse generator stage may include any switch described in U.S. Patent Application Serial No. 16 / 178,565, filed November 1, 2018, entitled “High Voltage Switch with Isolated Power,” which is fully incorporated herein for all purposes.

[0136] In some embodiments, the pulse generator stage may include a transformer. The transformer may include a transformer core (e.g., a toroidal or non-toroidal core); at least one primary winding wound around the transformer core once or less; and a secondary winding wound around the transformer core multiple times.

[0137] In some embodiments, the transformer may include a single-turn primary winding and a multi-turn secondary winding surrounding a transformer core. For example, a single-turn primary winding may include one or more conductors wound around the transformer core one or fewer times. For example, a single-turn primary winding may include more than 2, 10, 20, 50, 100, 250, etc., individual single-turn primary windings. In some embodiments, the primary winding may include conductive sheets.

[0138] For example, a multi-turn secondary winding may include a single conductor wound multiple times around the transformer core. For example, a multi-turn secondary winding may be wound around the transformer core more than 2 times, 10 times, 25 times, 50 times, 100 times, 250 times, 500 times, etc. In some embodiments, multiple multi-turn secondary windings may be wound around the transformer core. In some embodiments, the secondary winding may include conductive sheets.

[0139] In some embodiments, a high-voltage transformer can be used to output a voltage greater than 1,000 volts with a fast rise time of less than 150 nanoseconds, less than 50 nanoseconds, or less than 5 ns.

[0140] In some embodiments, the high-voltage transformer may have low impedance and / or low capacitance. For example, the high-voltage transformer has stray inductances of less than 100nH, 50nH, 30nH, 20nH, 10nH, 2nH, or 100pH measured on the primary side, and / or the transformer has stray capacitances of less than 100pF, 30pF, 10pF, or 1pF measured on the secondary side.

[0141] Transformers may include those disclosed in U.S. Patent Application No. 15 / 365,094 entitled “High Voltage Transformer,” which is incorporated herein for all purposes.

[0142] In another example, the nanosecond pulse generator may be coupled to RF driver 105 and filter 140. In this example, the nanosecond pulse generator may include a pulse generator stage, energy recovery circuitry, and / or bias compensation circuitry. Various other circuit elements may be included.

[0143] The nanosecond pulse generator is similar to the nanosecond pulse generator 1000, but it lacks a resistive output stage and includes an energy recovery circuit. In some embodiments, the energy recovery circuit 905 and / or the bias compensation circuit may be optional.

[0144] In this example, the energy recovery circuit may be located on or electrically coupled to the secondary side of the transformer. For example, the energy recovery circuit may include a diode (e.g., a crowbar diode) spanning the secondary side of the transformer. Alternatively, the energy recovery circuit may include a diode and an inductor (arranged in series) that allow current to flow from the secondary side of the transformer to charge the power supply and to allow current to flow into the plasma chamber. The diode and inductor may be electrically connected to the secondary side of the transformer and coupled to the power supply. The diodes and inductors may be arranged in any order. In some embodiments, the energy recovery circuit may include a diode and / or an inductor electrically coupled to the secondary side of the transformer. The inductor may represent a stray inductance and / or may include the stray inductance of the transformer.

[0145] When the RF source is on, current can charge the plasma chamber. For example, when the voltage on the secondary side of the transformer rises above the charging voltage on the power supply, some current can flow through the inductor. When the nanosecond pulse generator is off, current can flow from the capacitor in the plasma chamber through the inductor to charge the power supply until the voltage across the inductor is zero. Diodes prevent the capacitor in the plasma chamber from ringing with the inductor in the plasma chamber or the bias compensation circuit.

[0146] For example, diodes can prevent charge from flowing from the power source into the capacitors inside the plasma chamber.

[0147] The inductance value of the inductor can be selected to control the current drop time. In some embodiments, the inductor may have an inductance value between 1 μH and 500 μH.

[0148] In some embodiments, the energy recovery circuit may include a switch that can be used to control the flow of current through the inductor. For example, the switch may be placed in series with the inductor.

[0149] For example, the switch in an energy recovery circuit may include a high-voltage switch (e.g., the high-voltage switch disclosed in U.S. Patent Application No. 16 / 178,565, filed 1 August 2011 entitled “HIGHVOLTAGE SWITCH WITH ISOLATED POWER”, which claims priority to U.S. Provisional Patent Application No. 62 / 717,637, filed 10 August 2018, both of which are incorporated herein by reference in their entirety).

[0150] In another embodiment, the RF driver circuitry is similar to that of an RF driver. The transformer can be removed, or a transformer can be used.

[0151] An RF source can drive a resonant circuit at the resonant frequency of a resonant inductor, resonant capacitor, and / or resonant resistor.

[0152] A rectifier diode (without a dropout control inductor and a dropout control resistor) rectifies the sinusoidal waveform generated by the RF source and resonant circuit. The result on the wafer is shown in the waveform, which shows the voltage measured over time. The voltage generated by the RF source and resonant circuit is shown in the waveform. The flat portion of the waveform has a drop that progresses in the negative direction. The drop is the non-flat portion of the waveform caused by the ion current in the plasma. In this example, the drop is the upward slope of the portion of the waveform shown, which slopes upward from approximately 8 kV to 5 kV. In some embodiments, it may be beneficial to keep this portion of the waveform at a near-constant voltage, as this is directly related to the ion energy falling onto the wafer surface.

[0153] Appropriate selection of the drop control inductor and drop control resistor, based on the RF frequency, RF voltage, and ion current on the wafer, can compensate for drops in the waveform. The drop control inductor and drop control resistor allow a portion of the negative portion of the resonant sine wave to flow to point 1210, replacing the charge loss on capacitor 730 caused by the ion current flowing to point 1215. The drop control inductor or drop control resistor can be replaced by a drop control capacitor, or a drop control capacitor can be added. The drop control resistor may include or contain stray resistance throughout the circuit. The values ​​of the drop control inductor and drop control resistor can be selected based on the resonant frequency of the resonant circuit, the amplitude of the output resonant voltage (e.g., the waveform), and / or the amplitude of the ion current on the wafer surface.

[0154] In some embodiments, the drop control inductor, drop control resistor, and / or drop control capacitor can be predetermined or controlled in real time. For example, the drop control inductor may include a variable inductor, the drop control resistor may include a variable resistor, and / or the drop control capacitor may include a variable capacitor.

[0155] In some embodiments, the impedance of the drop control resistor and / or drop control inductor at a given frequency and voltage may be equal to or less than the required discharge rate of the balancing capacitor.

[0156] Dropouts on the wafer can be removed by including a dropout control inductor and a dropout control resistor. The dropout control inductor and dropout control resistor allow current to flow back through the circuit, causing a negative progress rectification that should be flat, rather than sloping downwards. In some embodiments, it may be beneficial to keep the negative progress rectification portion at a near-constant voltage, as this is directly related to the energy of ions falling onto the wafer surface.

[0157] In some embodiments, the dropout control inductor may have an inductance of less than approximately 100mH, 50mH, 10mH, 5mH, etc. In some embodiments, the dropout control inductor may have an inductance of less than approximately 0.1mH, 0.5mH, 1mH, 5mH, 10mH, etc.

[0158] In some embodiments, the dropout control resistor may include a resistor or stray resistor of less than approximately 10mΩ, 50mΩ, 100mΩ, 250mΩ, 500mΩ, etc.

[0159] An RF driver circuit can be similar to an RF driver circuit, except that the resistive output stage is replaced by an energy recovery circuit. The resistive output stage and energy recovery circuit can be referred to as an energy trap circuit. A drop control inductor and a drop control resistor can correct any drop in the circuit.

[0160] Unless otherwise specified, the term "substantially" means within 5% or 10% of the value referred to or within manufacturing tolerances. Unless otherwise specified, the term "approximately" means within 5% or 10% of the value referred to or within manufacturing tolerances.

[0161] The term "or" is inclusive.

[0162] This document sets forth numerous specific details to provide a thorough understanding of the claimed subject matter. However, those skilled in the art will understand that the claimed subject matter can be practiced without these specific details. In other instances, methods, apparatus, or systems well-known to those skilled in the art have not been described in detail so as not to obscure the claimed subject matter.

[0163] Given that the algorithms or symbolic representations of operations on data bits or binary digital signals stored in the memory of a computing system (e.g., computer memory) present certain parts, these algorithmic descriptions or representations are examples of techniques used by those of ordinary skill in the art of data processing to convey the essence of their work to others of skill in the art. An algorithm is a self-consistent sequence of operations or similar processes that leads to a desired result. In this case, the operations or processes involve the physical manipulation of physical quantities. Typically, but not necessarily, these quantities may take the form of electrical or magnetic signals that can be stored, transmitted, combined, compared, or otherwise manipulated. Primarily for general reasons, it has sometimes proven convenient to refer to these signals as bits, data, values, elements, symbols, characters, items, numbers, numerical values, etc. However, it should be understood that all these and similar terms are intended to be associated with appropriate physical quantities and are merely convenient labels. Unless otherwise stated, it should be understood that throughout the discussion of this specification, terms such as “processing,” “computing,” “operation,” “determining,” and “identifying” are used to refer to the actions or processes of a computing device (e.g., one or more computers or one or more similar electronic computing devices) that manipulate or translate data representing physical electronic or magnetic quantities within a memory, register, or other information storage, transmission, or display device of a computing platform.

[0164] 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 multipurpose microprocessor-based computer systems that access stored software of a dedicated computing device that programs or configures the computing system from a general-purpose computing device to implement one or more embodiments of this 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 the software intended for programming or configuring the computing device.

[0165] Embodiments of the methods disclosed herein can be executed during the operation of these computing devices. The order of the blocks presented in the examples above can be changed; for example, the blocks can be reordered, combined, and / or broken down into sub-blocks. Specific blocks or processes can be executed in parallel.

[0166] The use of “applies to” or “configured to” in this document indicates an open and inclusive language that does not exclude applicability to or configuration for devices performing additional tasks or steps. Furthermore, the use of “based on” is open and inclusive in that a process, step, calculation, or other action “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 in this document are for ease of interpretation only and are not intended to be limiting.

[0167] While this subject matter has been described in detail with respect to specific embodiments thereof, it should be understood that modifications, variations, and equivalents of these embodiments can be readily made by those skilled in the art in implementing the foregoing understanding. Therefore, it should be understood that this disclosure has been presented for illustrative purposes and not for limitation, and that such modifications, variations, and / or additions to this subject matter are not excluded and will be apparent to those skilled in the art.

Claims

1. A plasma system, comprising: Plasma chamber; An RF driver, electrically coupled to the plasma chamber, drives bursts into the plasma chamber using an RF frequency; A nanosecond pulse generator, the nanosecond pulse generator including a power supply and multiple switches; A transformer, comprising a primary side and a secondary side, wherein the primary side is electrically coupled to the plurality of switches and the secondary side is electrically coupled to the plasma chamber, and the nanosecond pulse generator drives pulses having a pulse repetition frequency less than the RF frequency into the plasma chamber via the transformer; An energy recovery circuit is electrically coupled to the secondary side of the transformer, and the nanosecond pulse generator allows current to flow from the secondary side of the transformer to charge the power supply and allows current to flow to the plasma chamber. A drop capacitor, disposed between the RF driver and the plasma chamber, allows the pulse to enter the plasma chamber; and A drop control inductor is deployed between the nanosecond pulse generator and the plasma chamber. The drop control inductor allows pulses with a pulse repetition frequency of less than 100 kHz to enter the plasma chamber. The drop control inductor has a stray capacitance value of less than 5 pF.

2. The plasma system as claimed in claim 1, wherein, The capacitor has a capacitance of less than 100pF.

3. The plasma system as claimed in claim 1, wherein, The inductor has an inductance of less than 10 nH.

4. The plasma system as claimed in claim 1, wherein, The plasma chamber includes multiple walls and a wafer support, such that when plasma is created within the plasma chamber, a wall-plasma sheath is formed between the plasma and at least one of the multiple walls, and a wafer-plasma sheath is formed between the plasma and a wafer deployed on the wafer support, wherein the capacitance of the wall-plasma sheath is at least ten times greater than the capacitance of the wafer-plasma sheath.

5. The plasma system as claimed in claim 1, wherein, The plasma chamber includes a plurality of walls and a wafer support, such that when plasma is created in the plasma chamber, a wall-plasma sheath is formed between the plasma and at least one of the plurality of walls, and a wafer-plasma sheath is formed between the plasma and a wafer deployed on the wafer support, wherein the capacitance of the wall-plasma sheath is at least fifty times greater than the capacitance of the wafer-plasma sheath.

6. A plasma system, comprising: Plasma chamber; power supply; An RF driver configured to drive pulses into the plasma chamber at an RF frequency greater than 200 kHz and a peak voltage greater than 1 kV; A transformer, comprising a primary side and a secondary side, wherein the primary side is electrically coupled to the RF driver and the secondary side is electrically coupled to the plasma chamber; A drop control inductor and a drop resistor are arranged in series, such that the series combination of the drop control inductor and the drop resistor is electrically coupled to the primary side of the RF driver and the transformer. An energy recovery circuit is electrically coupled to the secondary side of the transformer and the power supply.

7. The plasma system of claim 6, wherein, The drop control inductor has an inductance of less than 10mH.

8. The plasma system of claim 6, wherein, The drop resistance is less than 500Ω.

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