High Voltage Plasma Control

Abstract

A high-voltage pulsing power supply system is disclosed that includes a DC power source, a switch circuit electrically coupled to the DC power source, a droop control circuit coupled to the switch circuit, and / or an output. The switch circuit includes a plurality of switch modules and generates a plurality of pulses. The droop control circuit includes a droop diode, a droop inductor, and a droop element. The droop diode may be electrically coupled in series between the switch circuit and a primary winding of a transformer and allows negative pulse portions of the plurality of pulses to pass from the switch circuit to the primary winding of the transformer. The droop inductor and droop element are disposed in series across the droop diode to allow negative pulse portions of the plurality of pulses to pass from the switch circuit to the primary winding of the transformer and / or store energy from the negative pulse portions of the plurality of pulses.

Description

[Technical Field]

[0001] The present invention relates to high voltage plasma control. [Background technology]

[0002] The application of RF-excited gas discharges has become standard in thin film and semiconductor manufacturing technologies. Positive ions generated within the plasma volume are accelerated across the plasma sheath to reach the electrode according to an ion energy distribution function, which is determined by the magnitude 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 thin film etching, the magnitude of surface damage caused by ion bombardment, the aspect ratio and / or diameter and / or depth of holes and other etched features, the rate at which features are etched, and more. Control of the ion energy distribution function is critical for processes involving plasma etching.

[0003] A high voltage power supply system is required to generate the potential necessary to accelerate ions within the plasma. The high voltage power supply system is capable of providing well-shaped (e.g., nearly flat pulse-to-pulse) power waveforms to produce a variety of desired ion energy distribution functions. A different waveform may be used for each pulse, with each waveform potentially producing a different ion energy distribution function, which over time produces entirely separate collectively effective ion energy distribution functions. Controlling the ion energy distribution function allows individual features of the etch process to be controlled.

[0004] In some applications, the portion of the waveform that produces the ion energy distribution function can vary across the plasma chamber. For example, in a semiconductor processing system, the ion current in the plasma at the wafer can droop between successive pulses in the waveform. Such waveform variations can directly affect and / or change the desired ion energy distribution function, thereby reducing the effectiveness of any process within the chamber. For example, pulse-to-pulse droop tends to broaden the ion energy distribution function, resulting in a predominance of lower energy ions. Summary of the Invention [Means for solving the problem]

[0005] A high-voltage pulsing power supply system is disclosed. The high-voltage pulsing power supply system includes a DC power supply, a switch circuit electrically coupled to the DC power supply, a droop control circuit coupled to the switch circuit, and / or an output. The output may be coupled to, for example, a plasma chamber. The high-voltage pulsing power supply system may also include an energy recovery circuit. The switch circuit may include multiple switch modules arranged in a full-bridge configuration, a half-bridge configuration, or other bridge configuration and may generate multiple pulses having positive and negative pulse portions. The transformer may include a transformer core, a primary winding, and a secondary winding. The droop control circuit may include a droop diode, a droop inductor, and / or a droop element, which may be a resistive element or an energy recovery circuit. The energy recovery circuit may be, for example, any collection of electrical components typically found in a DC-DC converter that transfers energy from one potential to another.

[0006] The droop element may be, for example, any component or combination of components used to adjust how much current is passed through the droop inductor. The droop element may operate by limiting the energy injected into the droop inductor so that a balanced current or a specified current can be maintained. A passive droop element, such as a fixed resistor, allows a constant balanced current to be maintained, while an active droop element allows the current through the droop inductor to vary over time. The droop diode may be electrically coupled in series between the switch circuit and the primary winding of the transformer and / or may allow the positive pulse portion of the multiple pulses to pass from the switch circuit to the primary winding of the transformer. The inductance in series with the droop diode may be individually selected to achieve a positive pulse with a specific shape. This inductance in series with the droop diode may be set so that the rising pulse has a clean, rounded sinusoidal shape without notches, dips, or multiple peaks / ringing. The droop inductor and droop element may be placed in series across the droop diode to allow the negative pulse portions of the pulses to pass from the switch circuit to the primary winding of the transformer. The combination of the droop inductor and droop element can control how much energy is stored in the droop inductor and / or how much current is passed through the droop inductor. The current through the droop inductor can be closely related to the voltage applied across the plasma and / or the ion energy distribution function generated. The disclosed high-voltage pulsing power supply system can generate multiple different and time-varying composite ion energy distribution functions by varying its output over time, for example, on a pulse-by-pulse and / or burst-by-burst and / or train-by-train basis.

[0007] This summary and the various embodiments presented herein do not limit or define the scope of the disclosure or claims. [Brief explanation of the drawings]

[0008] [Figure 1] FIG. 1 is a circuit diagram of a high voltage pulsing power supply and plasma system. [Figure 2A] ~ [Figure 2B] 2 shows the output waveform from the high voltage pulsing power supply and plasma system shown in FIG. 1. [Figure 3A] ~ [Figure 3B] 2 shows the output waveform from the high voltage pulsing power supply and plasma system shown in FIG. 1. [Figure 4] FIG. 1 is a circuit diagram of a high voltage pulsing power supply and plasma system. [Figure 5A] ~ [Figure 5B] 5 shows the output waveform from the high voltage pulsing power supply and plasma system shown in FIG. [Figure 6A] ~ [Figure 6B] 5 shows the output waveform from the high voltage pulsing power supply and plasma system shown in FIG. [Figure 7] FIG. 1 is a circuit diagram of a high voltage pulsing power supply and plasma system with an energy recovery circuit. [Figure 8A] ~ [Figure 8B] 8 shows the output waveform from the high voltage pulsing power supply and plasma system shown in FIG. 7. [Figure 9] 8 shows the output waveform from the high voltage pulsing power supply and plasma system shown in FIG. 7. [Figure 10A] ~ [Figure 10B] 8 shows the output waveform from the high voltage pulsing power supply and plasma system shown in FIG. 7. [Figure 11] 8 shows the output waveform from the high voltage pulsing power supply and plasma system shown in FIG. 7. [Figure 12] FIG. 1 is a circuit diagram of a high voltage pulsing power supply and plasma system with an active droop control circuit. [Figure 13] 13 shows the output waveform from the high voltage pulsing power supply and plasma system shown in FIG. 12. [Figure 14A] 13 shows the output waveform from the high voltage pulsing power supply and plasma system shown in FIG. 12. [Figure 14B] 14B illustrates the switching logic used to generate the waveforms shown in FIG. 14A. [Figure 15A] 13 shows the output waveform from the high voltage pulsing power supply and plasma system shown in FIG. 12. [Figure 15B] 13 shows the output waveform from the high voltage pulsing power supply and plasma system shown in FIG. 12. [Figure 16A] 13 shows the output waveform from the high voltage pulsing power supply and plasma system shown in FIG. 12. [Figure 16B] 16B illustrates the switching logic used to generate the waveforms shown in FIG. 16A. [Figure 17A] 16B shows an expanded view of the waveform shown in FIG. 16A. [Figure 17B] 16B shows an expanded view of the waveform shown in FIG. 16A. [Figure 17C] 16B shows an expanded view of the waveform shown in FIG. 16A. [Figure 17D] 16B shows an expanded view of the waveform shown in FIG. 16A. [Figure 18] 13 shows the ion energy distribution of ions in an exemplary chamber of the high voltage pulsing power supply and plasma system shown in FIG. 12. [Figure 19] 13 shows the ion energy distribution of ions in an exemplary chamber of the high voltage pulsing power supply and plasma system shown in FIG. 12. [Figure 20A] This shows the lower limit of the energy distribution function. [Figure 20B] The upper limit of the energy distribution function is shown. [Figure 21] FIG. 1 is a circuit diagram of a high voltage pulsing power supply and plasma system having a droop control circuit and an energy control circuit. [Figure 22] 22 shows the ion energy distribution of ions in the high voltage pulsing power supply and plasma system shown in FIG. 21. [Figure 23A] This shows the lower limit of the ion energy distribution. [Figure 23B] The upper limit of the ion energy distribution is shown. [Figure 24] 1 shows a circuit diagram of a high voltage pulsing power supply and plasma system with an active droop control circuit. [Figure 25] 1 is a flowchart of an exemplary process for controlling voltage droop on a wafer between pulses. [Figure 25] 1 is a flowchart of an exemplary process for controlling ion energy distribution on a wafer. [Figure 26] 1 shows an exemplary waveform illustrating two pulse bursts. [Figure 27] FIG. 1 is a block diagram of a computer system that can be used in conjunction with or to implement some embodiments described herein. DETAILED DESCRIPTION OF THE INVENTION

[0009] A high-voltage pulsing power supply is disclosed that generates high-voltage pulses. The high-voltage pulsing power supply may be coupled to, for example, one or more plasma chambers. The high-voltage pulsing power supply may, for example, compensate for voltage droop on a wafer in a plasma processing chamber. The high-voltage pulsing power supply may, for example, perform energy recovery within a pulsing circuit. The high-voltage pulsing power supply may, for example, enable a narrow or specific ion energy distribution ("ion energy distribution function") to be generated in a plasma. The high-voltage pulsing power supply may, for example, enable a wide range of ion energy distribution functions to be generated in a plasma. The high-voltage pulsing power supply may, for example, enable a time-varying ion energy distribution function to be generated in a plasma. The high-voltage pulsing power supply may, for example, enable operation at various wafer voltage levels that may vary over time ("multi-level control") and / or, in particular, the duration of either or both of the positive and negative portions of the pulse may vary over time.

[0010] A pulse is a high-voltage waveform that typically starts at a first voltage, abruptly peaks at a second voltage for a short period of time, and then returns to approximately the first voltage. A pulse may be positive, negative, or bipolar (both positive and negative). A pulse may have a pulse width (e.g., full width, half width), an amplitude (e.g., second voltage), a rise time (e.g., the time it takes the waveform to change from the first voltage to the second voltage), and / or a fall time (e.g., the time it takes the waveform to change from the second voltage back to the first voltage).

[0011] A burst (or burst of pulses) is a sequence of pulses. A train (or pulse train) is a plurality of bursts. Figure 26 is an example of a pulse train with two bursts. Each burst has at least a pulse repetition frequency, a burst duration, and / or a burst period.

[0012] The high-voltage pulsing power supply can compensate for voltage droop (e.g., the gradient of voltage between pulses) on a wafer in a plasma processing chamber. The voltage droop may be, for example, partially eliminated, completely eliminated, partially reversed, and / or completely reversed. For example, a wafer with a negative peak voltage of −6 kV may experience a voltage droop of −2 kV by the end of the negative portion of the pulse. The high-voltage pulsing power supply may hold the wafer voltage constant around −6 kV, for example, throughout the entire negative pulse, most of the negative pulse, or a portion of the negative pulse until the wafer voltage droops. The high-voltage pulsing power supply may also allow the wafer voltage to ramp more negative over time, for example, so that the wafer voltage varies from −6 kV to −10 kV during the negative portion of the pulse. The high-voltage pulsing power supply may operate, for example, in a range of ±100 V to ±100 kV. This voltage range may encompass both the absolute voltage range applied to the wafer as well as the range over which the power supply can vary the voltage from that which would result from wafer droop. A high voltage pulsing power supply may control a negative wafer voltage, for example, when the voltage exceeds 100V.

[0013] The average power delivered by the high-voltage pulsing power supply (e.g., averaged over multiple bursts and / or trains) may be greater than 10 W, 100 W, 1000 W, or 100 kW. A typical average power delivered by the high-voltage pulsing power supply may be, for example, greater than 1 kW. The power delivered by the high-voltage pulsing power supply (e.g., averaged over a single burst) may be, for example, 1, 5, or 30 times the average power delivered.

[0014] The droop control of the negative portion of the pulse (eg, wafer waveform control) may operate over durations of, for example, 100 ns, 1 μs, 10 μs, 100 μs, and / or 1 ms.

[0015] The positive portion of the pulse may be used, for example, to collapse the sheath / electron potential and sweep electrons onto a wafer in the plasma processing chamber to neutralize charge accumulated as ion current flows to the wafer during the negative portion of the pulse. The positive portion of the pulse may operate for durations of, for example, about 100 ns, 1 μs, 10 μs, 100 μs, and / or 1 ms. The width and / or rise time of the positive portion of the pulse may be used, for example, to control the plasma potential relaxation time and degree of ionization, among other properties of the plasma.

[0016] The high-voltage pulsing power supply can control the ratio of the positive portion of the pulse to the negative portion of the pulse. This ratio can range, for example, from 1% to 100%. This ratio can be set, for example, to control the magnetic flux in the transformer core and to control various plasma characteristics, such as how the positive and negative plasma sheaths form and collapse, how much negative charge is transferred to the wafer during the positive portion of the pulse, and / or how much etching of the chamber walls occurs during the positive portion of the pulse. This ratio can be set to optimize the etch process and individual or multiple aspects of the feature. For example, if a small feature size and a high aspect ratio are desired, this ratio can be set at the low end of the range, in which case the positive portion of the pulse is much shorter than the negative portion of the pulse. This ratio can be adjusted to keep the magnetic flux in the transformer core below 1 T.

[0017] The high-voltage pulsing power supply is capable of generating high-voltage pulses when the plasma ion current is between about 10 mA and about 300 A. The high-voltage pulsing power supply is capable of generating high-voltage pulses when the chuck capacitance (e.g., represented by capacitor 12) is between about 0.3 nF and about 1000 nF. The high-voltage pulsing power supply is capable of generating high-voltage pulses in plasmas with neutral densities between about 0.1 mT and about 1000 mT and / or consisting of a single gas species or a variety of gas species. The high-voltage pulsing power supply is capable of generating high-voltage pulses in plasmas with neutral densities between about 10 mT and about 1000 mT per cubic meter. 15 ~10 19 It is possible to generate high voltage pulses in plasmas where particles are ionized. The high voltage pulsing power supply is capable of generating high voltage pulses under a wide range of plasma conditions and / or chamber types.

[0018] For example, inductor 184 in series with droop diode 183 can help generate a positive pulse with a particular shape. Inductor 184 in series with droop diode 183 can be configured to ensure that the rising pulse has a clean, rounded sinusoidal shape (e.g., sinusoidal without notches, dips, or multiple peaks / ringing, as shown in the pulse of waveform 210 of FIG. 2). Inductor 184 can have an inductance, for example, in the range of about 0.1 nH to about 10 μH, as measured on the primary side of a transformer. Inductor 184 can include only parasitic stray inductance (i.e., no physical components). Inductor 184 can have an inductance of less than about 100 nH, for example.

[0019] The high-voltage pulsing power supply may include an energy recovery circuit (e.g., as shown in FIGS. 7 and 12). The energy recovery circuit may include, for example, a DC-DC converter (e.g., a rectifier bridge 730) that transitions energy from one voltage level to another. The energy recovery circuit may operate, for example, at a voltage between about 1 V and about 5000 V. The energy recovery circuit may operate, for example, at a power level between about 10 W and about 100 kW. The energy recovery circuit may operate, for example, as a simple DC-DC converter operating between two fixed voltages that remain constant over time or that vary over time. The time required for the DC-DC converter to adjust to the voltage range in which it operates ranges from about 1 μs to about 1 ms. The DC-DC converter may be based, for example, on various bridge topologies (e.g., half-bridge or full-bridge), among many other possible topologies. The energy recovery circuit may, for example, recover energy from a circuit (e.g., a droop inductor) that would otherwise be lost. While recovering this energy, the energy recovery circuit may, for example, adjust the current flowing through the droop inductor and / or adjust the voltage waveform and / or amplitude applied to the wafer and / or plasma.

[0020] A high-voltage pulsing power supply can produce a narrow ion energy distribution function in the plasma, for example, by reducing and / or eliminating wafer voltage droop. For example, a uniform voltage maintained across the plasma can produce a narrow ion energy distribution function. When a high-voltage pulsing power supply varies the voltage waveform applied to the plasma, a wide range of ion energy distribution functions can be produced in the plasma, for example, ion energy distribution functions that can range from very peaked (e.g., see FIG. 22 ) to flat ion energy distribution functions, to ion energy distribution functions that closely resemble those produced by standard sinusoidal power supplies used in plasma etching.

[0021] As another example, a high-voltage pulsing power supply can generate a time-varying ion energy distribution function. For example, the high-voltage pulsing power supply can adjust the wafer voltage and / or wafer waveform (e.g., pulse width, pulse repetition frequency, pulse period, etc.) on a pulse-by-pulse basis, and / or on a burst-by-burst basis, and / or on a pulse train-by-pulse basis. For example, a series of pulses, each with an ion energy distribution function peak at a different location, can be combined to generate a nearly flat composite ion energy distribution function. Such a composite ion energy distribution function can be generated from any arbitrary number of pulses, including, for example, any arbitrary distribution of waveforms, voltages, and / or ion energy distribution functions.

[0022] The high-voltage pulsing power supply is capable of generating any complex ion energy distribution function. The ion energy distribution function may be programmed and / or adjusted in real time to optimize various wafer etching or ion energy distribution function parameters (e.g., etch rate, mask erosion rate, feature aspect ratio, feature bow growth rate, feature profile, feature size, bottom hole diameter, etc.). The ion energy distribution function may be generated, for example, when (for example) 90% of the ions fall into a band representing 10% of the full width of the energy distribution and / or when the distribution is approximately flat across that entire range. The ion energy distribution function may be varied, for example, over time scales up to 100 ns, or from about 10 μs to about 100 μs. The possible rate of change of the ion energy distribution function may be set, for example, by the rate at which the energy recovery circuitry can adjust the DC voltage level at which the high-voltage pulsing power supply operates.

[0023] A high voltage pulsing power supply may allow operation at multiple wafer voltage levels (or voltage states) that vary over time in discrete bursts or trains as shown in Figure 16A. Such operation is sometimes referred to as multi-level or bi-level control.

[0024] Droop in a plasma chamber can occur, for example, when current flows during the negative portion of an applied waveform (e.g., droop 221 shown in FIG. 2B). This droop can, for example, charge the plasma interface and / or discharge series capacitance, which can cause the voltage seen by the plasma to drop over time. This often occurs, for example, during semiconductor plasma etching processes, because the etching current flows to the wafer surface, lowering the voltage across the chuck capacitance. As the voltage across the chuck capacitance drops, the etching voltage (i.e., the voltage applied across the plasma) also drops.

[0025] Voltage droop can be determined by the equation I=C·dV / dt, where I is the plasma current flowing into the plasma, C is the series capacitance (e.g., wafer chuck capacitance (e.g., capacitor 12)), and dV / dt is the rate at which the voltage across the series capacitance changes due to the flow of plasma current during the etching process. As plasma current flows into the series capacitance, the series capacitance discharges the voltage established at the beginning of the pulse to which the series capacitance was charged, according to the equation I=C·dV / dt. The high-voltage pulsing power supply can operate to cancel the voltage droop seen across the series capacitance and the plasma, for example, by preventing the series capacitance from discharging. To do this, the high-voltage pulsing power supply can apply a ramped voltage across the series capacitance, which effectively cancels the dV / dt droop in voltage caused by the flow of ion current, thereby maintaining a constant voltage across both the series capacitance and the plasma.

[0026] To cancel current droop caused by ion current and / or etching current, the high voltage pulsing power supply can generate another voltage droop and / or voltage change on the other side of the series capacitance to cancel the voltage droop that would otherwise occur. A droop inductor (e.g., droop inductor 187) can, for example, establish a ramp voltage necessary to keep the plasma voltage constant between pulses.

[0027] If the droop inductor is sized to keep the current relatively constant during the pulse (e.g., if it balances the plasma ion current and / or etching current), the natural action of the droop inductor is to impose the dV / dt required to keep the voltage constant across both the plasma and the series capacitance directly across the capacitance. The current flowing through the droop inductor diverges from the ion current flowing in the plasma during the negative portion of the pulse, resulting in a corresponding change in the voltage drop across the plasma and the ion energy distribution function. The current flowing through the droop inductor can determine both the voltage and / or voltage waveform seen across the plasma.

[0028] The high voltage pulsing power supply can control the current flowing through the droop inductor. The droop inductor can include, for example, a physical element such as an inductor and / or stray inductance in other circuit elements. The droop inductor and / or energy recovery circuit can control the current flowing through the droop inductor.

[0029] The size of the droop inductor may be set to any size ranging from about 1 μH to about 10 mH, and the size of the droop inductor may be used to define particular features of the desired waveform, among other things, to adjust the rate at which the waveform is applied to the plasma.

[0030] Ion energy distribution can be an important factor in semiconductor plasma processing. For example, a relatively flat and low ion energy distribution with spikes at specific energy levels can improve an etching process or other process. This can allow, for example, to focus most of the energy from the power supply into a plasma at a specific energy level. The high-voltage pulsing power supplies disclosed herein can be capable of controlling the ion energy distribution in the plasma.

[0031] Real-time feedback and control may be used to control the voltage waveform applied to the wafer. The voltage waveform may be measured directly at or near the chamber or wafer (e.g., at point 134 and / or point 135) and / or calculated based on current and voltage measurements from other circuit elements. The amount of energy recovered and / or dissipated in the energy recovery circuit may be adjusted, for example, to generate a specific wafer voltage waveform. The magnitude of the current flowing through the droop inductor (e.g., droop inductor 187) may be adjusted, for example, by real-time feedback to optimize plasma and wafer etching parameters (e.g., ion energy distribution function). The time scale of the real-time feedback and control may be faster than 1 Hz, 1 kHz, or 100 kHz. An active energy recovery circuit may enable this real-time feedback and control. Even a passive energy recovery circuit may enable real-time feedback and control by using a variable passive element, such as a time-variable resistor. Adjustments for real-time feedback and control can include, for example, the width of the positive portion of the pulse (e.g., rise time), the width of the negative portion of the pulse (e.g., fall time), the time between the positive and negative portions of the pulse, the pulse repetition frequency, switch timing signals, etc. A number of timing elements may be used to achieve real-time feedback and control. Real-time feedback and control can be achieved by varying the voltage applied to the pulsing power supply.

[0032] 1 is a circuit diagram of a high-voltage pulsing power supply and plasma system 100. The high-voltage pulsing power supply and plasma system 100 may include, for example, a high-voltage pulsing power supply 105 and a plasma chamber 106. The plasma chamber 106 represents the effective circuit of the plasma within the plasma chamber.

[0033] Although the high-voltage pulsing power supply 105 is illustrated as a full-bridge configuration, it can also operate in a half-bridge configuration or any other bridge configuration. The high-voltage pulsing power supply 105 may include multiple switch modules in a full-bridge configuration, coupled to a DC power supply 150 and an energy storage capacitor 155, and to a DC power supply 151 and an energy storage capacitor 156. The energy storage capacitor 156 and the DC power supply 151 are switched by switch modules 162 and 164 to generate positive pulses. The energy storage capacitor 155 and the DC power supply 150 are switched by switch modules 161 and 163 to generate the negative portion of each pulse. The DC power supply 150 and the DC power supply 151 may be the same power supply, and the energy storage capacitors 155 and 156 may be the same capacitor charged to the same voltage. The charging voltage range of the DC power supply 150 and the DC power supply 151 may be, for example, from about 0 to about 1000 V, or from about 0 to about 3000 V.

[0034] The high voltage pulsing power supply 105 may be coupled to a droop control circuit 110. The droop control circuit 110 may be coupled, for example, to a transformer 145. The droop control circuit 110 may, for example, mitigate or reduce voltage droop in the plasma chamber (e.g., on a wafer in the plasma chamber).

[0035] The high voltage pulsing power supply and plasma system 100 may generate, for example, a bipolar pulse. The bipolar pulse may be waveformed, for example, to include a positive pulse followed by a negative pulse. The bipolar pulse may be represented as a single pulse having both a positive pulse portion and a negative pulse portion, as shown in FIG. 2A and FIG. 2B as the output waveform 205 and the wafer waveform 210. The peak-to-peak voltage between the positive and negative pulses may be greater than approximately 500V, 1 kV, 2 kV, 5 kV, 10 kV, 15 kV, 20 kV, 100 kV, etc.

[0036] The high voltage pulsing power supply and plasma system 100 may generate pulses including positive pulses that may have peak voltages greater than about 250V, 500V, 1 kV, 2 kV, 5 kV, 10 kV, 15 kV, 100 kV, etc. The high voltage pulsing power supply 105 may generate pulses including negative pulses that may have negative peak voltages less than about −250V, −500V, −1 kV, −2 kV, −5 kV, −10 kV, −15 kV, −100 kV, etc.

[0037] The high voltage pulsing power supply and plasma system 100 can generate pulses with, for example, a high pulse repetition frequency (e.g., greater than 1 kHz, 10 kHz, 100 kHz, 200 kHz, 500 kHz, 1 MHz, etc.), a fast rise time (e.g., a rise time less than about 1 ns, 10 ns, 50 ns, 100 ns, 250 ns, 500 ns, 1000 ns, 10 μs, etc.), a fast fall time (e.g., a fall time less than about 1 ns, 10 ns, 50 ns, 100 ns, 250 ns, 500 ns, 1000 ns, 10 μs, etc.), and / or a short pulse width (e.g., a pulse width less than about 10 μs, 1000 ns, 500 ns, 250 ns, 100 ns, 20 ns, etc.).

[0038] The high voltage pulsing power supply and plasma system 100 may generate pulses including combinations of pulses that may include, for example, any combination of positive pulses, negative pulses, and / or bipolar pulses.

[0039] The high-voltage pulsing power supply and plasma system 100 may include, for example, a high-voltage pulsing power supply 105. The high-voltage pulsing power supply 105 may be, for example, a half-bridge circuit or a full-bridge circuit. The high-voltage pulsing power supply 105 may include a DC power supply 150 with an energy storage capacitor 155.

[0040] The high-voltage pulsing power supply 105 may include, for example, four switch modules 161, 162, 163, and 164. Each of the switch modules 161, 162, 163, and 164 may include, for example, any number of solid-state switches arranged in series or parallel. The switch modules 161, 162, 163, and 164 may include, for example, any type of solid-state switch, such as an IGBT, a MOSFET, a SiC MOSFET, a SiC junction transistor, a FET, a SiC switch, a GaN switch, a photoconductive switch, etc. The switch modules 161, 162, 163, and 164 may be switched at high frequencies and / or generate high-voltage pulses. These frequencies may include, for example, frequencies of approximately 10 kHz, 400 kHz, 0.5 MHz, 2.0 MHz, 4.0 MHz, 13.56 MHz, 27.12 MHz, 40.68 MHz, 50 MHz, etc. These frequencies may be, for example, greater than 10 kHz. Each switch module 161, 162, 163, and 164 may or may not include the same number or type of solid-state switches as the other switch modules.

[0041] Each switch of switch modules 161, 162, 163, and 164 may include one or more solid-state switches S1 (e.g., solid-state switches (e.g., IGBTs, MOSFETs, SiC MOSFETs, SiC junction transistors, FETs, SiC switches, GaN switches, photoconductive switches, etc.)).

[0042] Each switch in the switch modules 161, 162, 163, and 164 may be coupled in parallel with a respective bridge diode 171, 172, 173, and 174, and may include stray inductance and / or stray resistance. Multiple diodes may be used per switch, while some switches may have no associated diode and some switches may share one or more common diodes. The stray inductance of each switch module may be, for example, equal. The stray inductance of the switch modules may be, for example, less than approximately 10 nH, 50 nH, 100 nH, 150 nH, 500 nH, 1000 nH, etc. The stray inductance of each switch module may be, for example, less than approximately 200 nH. The stray inductance of each switch module may be, for example, between approximately 100 nH and approximately 500 nH. The combination of a switch module and its respective bridge diode may be coupled in series with its respective bridge inductor.

[0043] Transformer 145 (or transformer T1) may include, for example, a transformer such as that disclosed in U.S. patent application Ser. No. 15 / 365,094, entitled "High Voltage Transformer," which is incorporated herein by reference for all purposes.

[0044] For example, the duty cycles of the switch modules can be adjusted by changing the duty cycle of the signal Sig1 that opens and closes switch module 161, by changing the duty cycle of the signal Sig2 that opens and closes switch module 162, by changing the duty cycle of the signal Sig3 that opens and closes switch module 163, and by changing the duty cycle of the signal Sig4 that opens and closes switch module 164.

[0045] Each switch module 161, 162, 163, or 164 in the high-voltage pulsing power supply 105 may be switched individually or in conjunction with one or more of the other switch modules, for example. For example, signal Sig1 may be the same signal as signal Sig3. As another example, signal Sig2 may be the same signal as signal Sig4. As another example, each signal may be independent of the others and may control each switch module 161, 162, 163, or 164 independently or separately from the others.

[0046] The high-voltage pulsing power supply and plasma system 100 may not include a conventional matching network, such as a 50 Ω matching network, an external matching network, or a standalone matching network. In fact, the embodiments described herein do not require a 50 Ω matching network to tune the switching power applied to the wafer chamber. Furthermore, the embodiments described herein include a variable output impedance RF generator without a conventional matching network. This may allow for rapid changes in the power drawn by the plasma chamber. Typically, this tuning of the matching network may take at least about 100 μs to about 200 μs. Power changes can occur within one to two RF cycles, e.g., within about 2.5 μs to about 5.0 μs at 400 kHz.

[0047] The high-voltage pulsing power supply 105 may be replaced with, for example, a half-bridge circuit having two switch modules. The high-voltage pulsing power supply 105 may, for example, supply power in multiple configurations. For example, as shown in Figures 1 and 24, multiple power supply and energy storage capacitor combinations may be used to supply power to a full bridge (or half bridge). As another example, as shown in Figures 7, 12, and 21, a single power supply and energy storage capacitor combination may be used to supply power to a full bridge (or half bridge).

[0048] In the droop control circuit 110, a droop resistor 186 may be coupled in series with a droop inductor 187. The series combination of the droop inductor 187 and the droop resistor 186 may be placed in parallel with or across the droop diode 183 and / or inductor 184.

[0049] Droop diode 183 may include, for example, one or more diodes arranged in series or parallel. Droop diode 183 may be rated to pass a current greater than about 100 amperes, for example. Droop diode 183 may be rated to pass a current greater than about 10, 100, 1000, 10,000, etc.

[0050] The inductor 184 may include, for example, a physical inductor and / or may represent parasitic and / or stray inductance. The parasitic and / or stray inductance may include, for example, the inductance of components between the high-voltage pulsing power supply 105 and the plasma chamber 106 and / or the inductance of the transformer 145. The inductor 184 may have, for example, an inductance of approximately 0.1 nH, 1 nH, 10 nH, 100 nH, 1 μH, or 10 μH. The inductor 184 may have, for example, an inductance of less than approximately 500 nH.

[0051] The inductance value of inductor 184 may be set, for example, so that the rising pulse has a good sine wave crest. If the inductance value of inductor 184 is too small, the ring-up on the positive pulse may be too short, for example, and the step in the positive pulse may appear late. For example, if the inductance value of inductor 184 is too small, oscillations across the crest of the positive pulse may be observed. For example, if the inductance value of inductor 184 is too large, the smooth sine wave crest may not have time to complete, and the top of the sine wave may be truncated. For example, if the inductance value of inductor 184 is too large, the positive pulse may become large when its top is truncated by the transition to a falling pulse.

[0052] Droop control circuit 110 controls the voltage ramp on transformer 145 so that the peak voltage occurs during the second half of the pulse. Droop inductor 187 is energized during the negative voltage portion of the bipolar pulse, while droop resistor 186 extracts energy from droop inductor 187. The shape of the applied negative pulse, in combination with droop resistor 186, balances the current in droop inductor 187. This balancing current may have, for example, a pulse-to-pulse ripple of less than 1%, 5%, 20%, or 100% of its average value. The droop inductor may have an inductance such that it reaches equilibrium within, for example, the first 2, 5, 70, or 100 pulses during a burst of pulses. The droop inductor 187 may have an inductance that allows the current through droop inductor 187 to reach equilibrium within, for example, less than 20 pulses. Current flows through droop diode 183 and inductor 184 into transformer 145 during the positive portion of the bipolar pulse.

[0053] Inductor 184 may have, for example, an inductance of approximately 0.1 nH, 3 nH, 100 nH, or 10 μH, which is typically set to less than 200 nH. Droop inductor 187 may have, for example, an inductance of approximately 1 μH, 10 μH, 100 μH, or 3000 μH.

[0054] Droop resistor 186 may have a resistance of, for example, approximately 0.01 Ω, 0.3 Ω, 30 Ω, or 100 Ω, and is typically set to less than 4 Ω.

[0055] Plasma chamber 106 may represent, for example, an ideal or effective circuit of a semiconductor processing chamber (e.g., a plasma deposition system, a semiconductor fabrication system, a plasma sputtering system, a plasma etching system, etc.). The capacitance of capacitor 12 may represent, for example, the capacitance of an electrostatic chuck on which a semiconductor process wafer may be placed. The chuck may include, for example, a dielectric material (e.g., aluminum oxide or other ceramic material and a conductor encased within the dielectric material). For example, capacitor 23 may have a small capacitance (e.g., approximately 10 pF, 100 pF, 500 pF, 1 nF, 10 nF, 100 nF, etc.).

[0056] Capacitor 13 may represent, for example, the sheath capacitance between the plasma and the wafer. Resistor 56 may represent, for example, the sheath resistance between the plasma and the wafer. Inductor 40 may represent, for example, the sheath inductance between the plasma and the wafer. Current source I2 may represent, for example, the ion current through the sheath. For example, capacitor 23 or capacitor 13 may have a small capacitance (e.g., approximately 10 pF, 100 pF, 500 pF, 1 nF, 10 nF, 100 nF, etc.).

[0057] Capacitor 18 may represent, for example, the plasma sheath capacitance to the chamber wall. Resistor 57 may represent, for example, the resistance between the plasma and the chamber wall. Current source I1 may represent, for example, the ion current in the plasma. For example, capacitor 23 or capacitor 18 may have a small capacitance (e.g., about 10 pF, 100 pF, 500 pF, 1 nF, 10 nF, 100 nF, etc.).

[0058] The plasma chamber may include one or more electrodes that may be used to ignite and / or drive the plasma. The one or more electrodes may be electrically coupled to a high-voltage pulsing power supply.

[0059] 2A and 2B show an output waveform 205 at point 134 and a wafer waveform 210 at point 135 of an example circuit of the high voltage pulsing power supply and plasma system 100. The wafer waveform 210 may represent, for example, the voltage on a wafer in a plasma chamber (e.g., a dielectric etch plasma chamber, etc.). Waveform 215 represents the switching logic of the SIG±2 switch module 162 and switch module 164. Waveform 220 represents the switching logic of the SIG±1 switch module 161 and switch module 163. As shown, the inter-pulse portions of the output waveform 205 have a negative slope, which causes the inter-pulse portions of the wafer waveform 210 to be substantially flat.

[0060] Output waveform 205 is generated, for example, with a charging voltage of 600V from DC power supply 151, a positive pulse width of 450 ns, and a negative pulse width of 1950 ns. In this example, droop inductor 187 has a value of approximately 6 μH, droop resistor 186 has a resistance of 0.5 Ω, and inductor 184 has an inductance of approximately 16 nH. This may mitigate or reduce voltage droop within the plasma chamber (e.g., on a wafer within the plasma chamber), as shown, for example, by the flat portion between the two positive pulses of wafer waveform 210.

[0061] 2B also shows an example of two high-voltage pulses. Each pulse of wafer waveform 210 has a positive pulse portion 211 and a negative pulse portion 212. Positive pulse portion 211 is the portion of the pulse where the voltage is greater than zero, and negative pulse portion 212 is the portion of the pulse where the voltage is less than zero. The pulse may have a fast rise time (i.e., a steep positive slope) between negative pulse portion 212 and positive pulse portion 211. And the pulse may have a fast fall time (i.e., a steep negative slope) between positive pulse portion 211 and negative pulse portion 212. The fall time may be slower than the rise time, for example.

[0062] Positive pulse portion 211 may, for example, have a relatively flat upper portion (or at least a portion with a gradual rise and / or fall slope). Positive pulse portion 211 may be of any length. Negative pulse portion 212 may, for example, have a relatively flat lower portion (or at least a portion with a gradual rise and / or fall slope). Negative pulse portion 212 may, for example, be of any length. Negative pulse portion 212 may be longer than positive pulse portion 211.

[0063] The relative height of the positive pulse portion 211 relative to the negative pulse portion 212 is the pulse amplitude. The time between successive positive pulse portions 211 is the pulse period, and the inverse of the pulse period is the pulse repetition frequency. A pulse waveform is neither a sinusoidal nor an RF waveform. In fact, an ideal pulse waveform for a wafer (e.g., wafer waveform 210) resembles a square wave more than a sinusoidal waveform. Furthermore, a sinusoidal waveform cannot have fast rise and / or fall times due to a relatively long flat top portion and / or flat bottom portion, but this is not necessarily true for a pulse waveform. Furthermore, while a sinusoidal waveform has approximately the same length of the positive pulse portion 211 and the negative pulse portion 212, this is not necessarily true for a pulse waveform.

[0064] 2B shows an example of inter-pulse droop 221. As shown, the inter-pulse droop is the negative slope of the negative pulse portion 212.

[0065] Reducing the output voltage can be achieved, for example, by adjusting the time constant so that the charging voltage remains approximately constant. This is sometimes called multi-state operation and involves a series of pulses with different voltages. Multi-state operation can be achieved, for example, by adjusting the positive and negative pulse widths, as shown in Figures 3A and 3B, which show an output waveform 305 at point 134 and a wafer waveform 310 at point 135. In Figure 3A, a positive pulse width of 50 ns and a negative pulse width of 350 ns are used. In Figure 3B, the positive pulse width is 90 ns and the negative pulse width is 2310 ns.

[0066] Multi-state operation can be achieved, for example, by increasing the value of droop resistor 186, since a higher resistance value can reduce the output voltage. For the waveform shown in Figure 3B, droop resistor 186 is set to 6 Ω, whereas 0.5 Ω was used to generate the waveform of Figure 2B.

[0067] 4 is a circuit diagram of an exemplary high-voltage pulsing power supply and plasma system 400. The droop resistor 186 of the plasma system 100 is replaced with a droop capacitor 486 in series with the droop inductor 187. The droop capacitor 486 may have, for example, a capacitance of approximately 10 mF, 25 mF, 50 mF, 100 mF, 250 mF, 500 mF, 1000 mF, 38 F, 200 F, etc. The droop capacitor 486 may, for example, extract energy from the droop inductor. While the droop resistor 186 dissipates energy as resistive losses, the droop capacitor 486 can convert the energy into stored capacitive energy. This stored energy can, for example, increase the voltage difference across the droop capacitor 486. This stored energy can be recovered by an energy recovery circuit (e.g., energy recovery circuit 701 or active droop control circuit 1201 or energy compensation circuit 2101), for example, so that the voltage across droop capacitor 486 remains approximately constant during the burst. The energy recovery circuit may include, for example, a DC-DC converter that maintains the voltage on droop capacitor 486 while delivering excess energy to high-voltage pulsing power supply 105. When an energy recovery circuit is used, the value of droop capacitor 486 may be less than approximately 100 mF, 10 mF, 100 μF, 10 μF, or 1 μF. This value is typically set to less than approximately 30 μF for a full-bridge topology and less than approximately 100 μF for a half-bridge topology.

[0068] 5A and 5B, output waveform 505 is measured at point 134 of high-voltage pulsing power supply and plasma system 400, and wafer waveform 510 is measured at point 135 of an example circuit of high-voltage pulsing power supply and plasma system 400. Wafer waveform 510 may represent, for example, the voltage on a wafer in a plasma chamber. Waveform 515 represents the switching logic of SIG±2 switch module 162 and switch 164. Waveform 520 represents the switching logic of SIG±1 switch module 161 and switch 163. As shown, the inter-pulse portions of output waveform 505 have a negative slope, which causes the inter-pulse portions of wafer waveform 510 to be substantially flat.

[0069] Output waveform 505 and wafer waveform 510 may be generated, for example, with a charge voltage of 600 V from DC power supply 151, a positive pulse width of 450 ns, and a negative pulse width of 1950 ns. An initial charge of −270 V may be applied across droop capacitor 486. In the example shown in FIGS. 5A and 5B, droop capacitor 486 may have a capacitance of approximately 200 mF.

[0070] Figures 6A and 6B show an output waveform 605 at point 134 and a wafer waveform 610 at point 135. The waveform shown in Figure 6A has a positive pulse width of 50 ns and a negative pulse width of 350 ns. The waveform shown in Figure 6B has a positive pulse width of 90 ns, a negative pulse width of 2310 ns, and an initial charging voltage of -575V on the droop capacitor.

[0071] 7 is a circuit diagram of a high-voltage pulsing power supply and plasma system 700, which may include a power supply 705 coupled to the plasma chamber 106. The high-voltage pulsing power supply and plasma system 700 may include a droop control circuit 110 and / or an energy recovery circuit 701. The power supply 705 may be similar to the high-voltage pulsing power supply 105, including a DC power supply 150 and an energy storage capacitor 155.

[0072] The energy recovery circuit 701 is coupled to the droop inductor 187 of the droop control circuit 110. The energy recovery circuit 701 may also be coupled to the DC power supply 150 and the energy storage capacitor 155. The energy recovery circuit 701 may include, for example, a DC-DC converter coupled between the droop control circuit 110 and the energy storage capacitor 155.

[0073] The energy recovery circuit 701 may include a switch module 731 and a switch module 732 arranged in a half-bridge configuration (a full-bridge configuration or other bridge configurations may also be used). Each switch module 731, 732 may include a respective switch diode 741, 742. The energy recovery circuit 701 may also include a transformer 715 coupled to the switch module 731 and / or the switch module 732. The transformer 715 may be inductively coupled to the rectifier bridge 730, which may be coupled to the energy storage capacitor 155 via the energy recovery inductor 706 and / or the energy recovery diode 710. The energy recovery diode 710 may allow charge from the droop capacitor 720 and / or the droop capacitor 725 to flow to charge the energy storage capacitor 155, for example. The values ​​of each element of the energy recovery circuit may be set to allow the voltage on droop capacitor 720 and droop capacitor 725 to change in less than (for example) 2 pulses, 20 pulses, or 200 pulses.

[0074] Energy recovery inductor 706 may have, for example, a low inductance. Energy recovery inductor 706 may have, for example, an inductance of less than about 1 nH, 10 nH, 50 nH, 100 nH, 150 nH, 500 nH, 1000 nH, etc. Energy recovery inductor 706 may include, for example, the inductance of rectifier bridge 730, transformer 715, switch module 731, and / or switch module 732.

[0075] Switch module 731 and / or switch module 732 can be switched on and off, for example, to control the amount of energy extracted from droop inductor 187. This can be done, for example, by adjusting the duty cycle of switch module 731 and / or switch module 732. This can be done, for example, based on feedback from one or more sensors monitoring the voltage across capacitance 12.

[0076] Energy recovery circuit 701 may, for example, transfer energy from droop inductor 187 to charge energy storage capacitor 155. Energy recovery circuit 701 may be coupled across droop capacitor 720 and / or droop capacitor 725.

[0077] 8A and 8B show an output waveform 805 at point 134 and a wafer waveform 810 at point 135 of an example circuit of the high voltage pulsing power supply and plasma system 700. As shown, the inter-pulse portions of the output waveform 805 have a negative slope, which causes the inter-pulse portions of the wafer waveform 810 to be substantially flat.

[0078] In this example, the output may be generated with a charging voltage from the DC power supply of 600V, a positive pulse width of 450ns, and a negative pulse width of 1950ns. In this example, the switching frequency of switch module 731 and switch module 732 is set to 250kHz. Typical operating frequencies may be greater than 1kHz, 10kHz, 100kHz, or 3MHz. In this example, each switch is closed for approximately 1.65μs, resulting in a duty cycle of approximately 2.5%. In this example, an initial charging voltage of approximately −135V is applied across droop capacitor 720 and / or droop capacitor 725, with the sum of the initial charging voltages across these two capacitors being −270V. In this example, the capacitance of each of droop capacitor 720 and / or droop capacitor 725 is approximately 25μF, although other values ​​may be used, such as approximately 1μF, 33μF, 500μF, or less than 3mF. This particular capacitance value may be selected to set both the plasma current ripple and the rate at which the wafer voltage can be adjusted through operation of the energy recovery circuit. Typical adjustment times may be, for example, about 0.1 μs, 1 ms, or longer than about 10 minutes. This initial electromotive force allows the output voltage to quickly reach equilibrium, while the energy recovery circuit duty cycle maintains equilibrium.

[0079] 9 shows an output waveform 905 at point 134 and a wafer waveform 910 at point 135 in an example circuit of high voltage pulsing power supply and plasma system 700. In this example, no initial electromotive force is applied to droop capacitor 720 and / or droop capacitor 725. In this example, the output voltage also reaches equilibrium.

[0080] 10A and 10B show the output waveform 1005 at point 134 and the wafer waveform 1010 at point 135 of an example circuit of the high voltage pulsing power supply and plasma system 700. In this example, the circuit values ​​are the same as those used to generate the waveforms shown in FIGS. 8A and 8B, but the timing for FIG. 10A is 50 ns for the positive pulse and 350 ns for the negative pulse, and for FIG. 10B is 90 ns for the positive portion of the pulse and 2310 ns for the negative portion of the pulse. In this example, the energy recovery circuit duty cycle is reduced to 15%. The duty cycle of the energy recovery circuit can be anywhere from 0% to 100%, which is typical for DC-DC converters.

[0081] 11 shows an output waveform 1105 at point 134 and a wafer waveform 1110 at point 135 in an example circuit of a high-voltage pulsing power supply and plasma system 700. In this example, the output voltage is switched between an approximately 27.5 μs high-voltage burst 1120, an approximately 32.5 μs multi-state burst 1125, and an approximately 27.5 μs high-voltage burst 1130. This transition is made simply by using an energy recovery circuit to set / program the voltage across droop capacitor 720 and / or droop capacitor 725. Increasing the voltage across these capacitors can lead to lower voltage and / or multi-level operation, while decreasing the voltage across these capacitors can lead to higher voltage operation. By adjusting the voltage across these capacitors, the energy recovery circuit (i.e., DC-DC converter) can be used to generate roughly any combination of output voltages that form any desired time-dependent pattern. During the transition from the high voltage burst 1120 to the multi-state burst 1125, the transformer flux may swing negative for a few transition bursts 1125 A. For example, the multi-state positive pulse width may be adjusted and / or the multi-state negative pulse width may be reduced to prevent the transformer from saturating during this transition, thereby reducing the amount of negative flux injected into the transformer core.

[0082] 12 is a circuit diagram of a high voltage pulsing power supply and plasma system 1200 having an active droop control circuit 1201. The active droop control circuit 1201 may also include an energy recovery element (e.g., energy recovery inductor 1225 and diode 1226) that recovers energy from, for example, droop inductor 187 to energy storage capacitor 156.

[0083] The high voltage pulsing power supply and plasma system 1200 includes a high voltage pulsing power supply 705 coupled to an active droop control circuit 1201 and a plasma chamber 106 .

[0084] Active droop control circuit 1201 may include, for example, droop inductor 187 coupled in series with droop capacitor 486 and second droop inductor 1205. The total droop inductance may be divided evenly between droop inductor 187 and droop inductor 1205, or may be divided unevenly between droop inductor 187 and droop inductor 1205. If an even division is selected, the design and construction of each individual inductor may be simplified. A switch circuit (e.g., a half-bridge switch circuit or a full-bridge switch circuit) may be coupled across droop capacitor 486. The switch circuit may also be coupled to transformer 1210.

[0085] Active droop control circuit 1201 may include, for example, switch module 1215, switch module 1216, switch module 1217, switch module 1218, transformer 1210, diode rectifier bridge 1220, energy recovery inductor 1225, and / or energy recovery diode 1226. Diode rectifier bridge 1220 may be coupled to energy recovery inductor 1225 and transformer 1210, or may be coupled between energy recovery inductor 1225 and transformer 1210, for example. Energy recovery inductor 1225 may be coupled to energy storage capacitor 156, which is part of power supply 705.

[0086] By controlling the timing of each switch in active droop control circuit 1201, charge can be removed from droop capacitor 486 and / or added to droop capacitor 486. Active droop control circuit 1201 may be or include any converter that transfers energy from droop capacitor 486 to energy storage capacitor 156 or from energy storage capacitor 156 to droop capacitor 486.

[0087] The active droop control circuit 1201 may include, for example, any of various forms of DC-DC converter. The active droop control circuit 1201 may include, for example, a set of switches arranged in a bridge configuration, a transformer, a rectifier stage, and a filter inductor. One exemplary function of the active droop control circuit 1201 may be to adjust the voltage on the droop capacitor 486. This may be done, for example, on a time scale as needed to generate a desired wafer and / or plasma voltage waveform.

[0088] The value of droop capacitor 486 may be less than approximately 10 mF, 1 mF, 20 μF, or 1 μF. For example, the value of droop capacitor 486 may be less than approximately 100 μF. The specific value of droop capacitor 486 may be selected, for example, to enable and / or facilitate the function of active droop control circuit 1201 to adjust the voltage across droop capacitor 486 on a required time scale. The adjustment time scale may be greater than approximately 1 μs, 1 ms, or 1 hour. A smaller inductance value of droop capacitor 486 may, for example, allow adjustment of the output voltage over a shorter period of time, thereby enabling more rapid adjustment of the ion energy distribution in the plasma and more finely tuning the composite ion energy distribution in the plasma, including the sum of the individual ion energy distributions in the plasma.

[0089] The time scale over which active droop control circuit 1201 adjusts the voltage on droop capacitor 486 may be shorter than 2 pulses, 20 pulses, or 200 pulses, each pulse having a positive portion and a negative portion, which may last a total of 100 ns, 1 μs, 2.5 μs, 100 μs, or 1 ms. The time scale over which active droop control circuit 1201 adjusts the voltage on droop capacitor 486 may be considered short relative to the typical time scale of 100 ms to 1 s over which DC-DC converters typically operate / regulate voltages.

[0090] By adjusting the voltage on the droop capacitor 486, the active droop control circuit 1201 can, for example, control the ion energy distribution in the plasma and / or control the pulse-to-pulse voltage droop on the wafer. Either or both of these can be done in real time, for example, within about 100 μs, 10 μs, 5 μs, 1 μs, 500 ns, 250 ns, 100 ns, etc. It can be advantageous to vary the voltage on the droop capacitor 486 rapidly and / or slowly. A slow variation can achieve a relatively uniform ion energy distribution function from pulse to pulse, while a rapid variation can achieve very different ion energy distribution functions from pulse to pulse. The resulting cumulative ion energy distribution function can be the same whether the voltage across the chuck capacitance (e.g., capacitor 12) is varied slowly or rapidly. In contrast, rapidly varying the voltage across droop capacitor 486 may achieve a cumulative ion energy distribution function that is entirely separate and / or entirely different from that which may be achieved by the ion energy distribution function of any individual pulse.

[0091] Figure 13 shows a waveform comprising a series of pulses generated by high voltage pulsing power supply and plasma system 1200. Figure 14A shows a close-up of two pulses, and Figure 14B shows the various control waveforms used at each switch to generate the waveforms shown in Figures 13 and 14A.

[0092] For example, output waveform 1305 is the waveform measured at point 134, and wafer waveform 1310 is the corresponding waveform measured at point 135. Output waveform 1305 represents the voltage at capacitor 12. Wafer waveform 1310 represents the voltage on the wafer in the plasma chamber. Control waveform 1420 represents the switching logic for SIG±2, which opens and closes switch module 162 and switch module 164, which, when closed, generates positive pulse portion 1305. Control waveform 1415 represents the switching logic for SIG±1, which opens and closes switch module 161 and switch module 163, which generates negative pulse portion 1315. Energy recovery waveform 1425 shows the switching logic of SIG±3, which opens and closes ER switch 1215 and ER switch 1217, and energy recovery waveform 1430 shows the switching logic of SIG±4, which opens and closes ER switch 1216 and ER switch 1218.

[0093] The positive pulse portions of waveforms 1305 and 1310 correspond to the closure of switches 161 and 163 by control waveform 1415 and the opening of switches 162 and 164 by control waveform 1420. The peak and minimum voltages of the positive and negative pulse portions of waveforms 1305 and 1310 may be proportional to the duration of one or both of the on-time of waveform 1425 and / or the on-time of waveform 1430. The duration of the on-time of waveforms 1425 and 1430 may be used to set the voltage on droop capacitor 486. By varying the duration of the on-time of waveforms 1425 and 1430, the voltage on droop capacitor 486 can be varied.

[0094] Additionally, the negative pulse portion of output waveform 1305 has a negative slope or droop, while the negative pulse portion of wafer waveform 1310 is substantially flat. In this example, output waveform 1305 and wafer waveform 1310 may be generated by plasma system 1200 using, for example, a charging voltage of 600V from DC power supply 151, a positive pulse width of 450ns, and a negative pulse width of 1950ns.

[0095] The waveforms shown in Figures 13, 14A, and 14B were generated using a droop capacitor with a capacitance of less than approximately 10 μF. For example, transformer 1201 may have a low turns ratio, such as 3:1 or 2:1, or a high turns ratio, such as 10:1 or 40:1. The particular turns ratio selected will, in part, set both the ripple in the current flowing through the energy recovery circuit and the speed at which active droop control circuit 1201 can regulate the voltage on droop capacitor 486. The higher the turns ratio, the greater the current ripple and the faster active droop control circuit 1201 can regulate the voltage on droop capacitor 486. The switching frequency of switch modules 1215, 1216, 1217, and 1218 may be approximately 200 kHz. An operating frequency between approximately 1 kHz and approximately 10 MHz may be selected. As another example, each switch of switch modules 1215, 1216, 1217, 1218 may be closed for approximately 1.98 μs and / or may have a duty cycle of approximately 79.2%. The selected duty cycle may range from 0% to 100%, allowing active droop control circuit 1201 to recover anywhere from its minimum to maximum amount of energy. Active droop control circuit 1201 may be any form of DC-DC converter.

[0096] FIG. 12 shows a full-bridge topology. Various other DC-DC converter topologies are possible. The DC-DC converter topology may be designed to allow adjustments to the voltage on the droop capacitor 486 to occur rapidly (e.g., in less than 100 μs, 10 μs, or 1 μs). The DC-DC converter topology may also allow adjustments to the voltage on the droop capacitor 486 to occur very slowly (e.g., over 1 s, 1000 s, or even more than a day). Typical operation of the active droop control circuit 1201 may allow the voltage across the droop capacitor 486 to establish any required waveform on any time scale between very fast and very slow. Some plasma processes require rapid voltage adjustments, while other plasma processes require adjustments to the plasma conditions to occur slowly over hours or even days.

[0097] The active droop control circuit 1201 may, for example, allow operation over a range of wafer voltages without changing the input charging voltage. For example, by changing the positive and negative pulse widths of the switch modules 1215, 1216, 1217, and 1218 and / or the duty cycle of the switch modules 1215, 1216, 1217, and 1218, the duration of time the wafer voltage is negative can be increased and / or the output voltage can be increased. Figure 15A shows a wafer waveform 1510 with a wafer voltage of 1 kV generated by the plasma system 1200, with a positive pulse width of 85 ns, a negative pulse width of 2315 ns, and an energy recovery pulse width of 300 ns from the switch modules 1215, 1216, 1217, and 1218. FIG. 15B shows a wafer waveform 1510 with a wafer voltage of 4 kV generated by the plasma system 1200, with a positive pulse width of 200 ns, a negative pulse width of 2200 ns, and an energy recovery pulse width of 730 ns from the switch modules 1215, 1216, 1217, and 1218.

[0098] Also disclosed is a process for generating the waveform shown in Figure 14A using the logic represented by the waveform of Figure 14B. For example, at a first time, the process may include closing a first switch module (e.g., switch module 162 and / or switch module 164) of high-voltage pulsing power supply 705 and opening a second switch module (e.g., switch module 161 and / or switch module 163) to generate positive pulse portion 211 of first high-voltage pulse 1305. The positive pulse portion may have an amplitude greater than about 1 kV, for example.

[0099] At approximately the first time point or shortly thereafter, the process may include closing a third switch module (e.g., switch module 1216 and / or switch module 1218) of the energy recovery circuit 2101 and opening a fourth switch module (e.g., switch module 1215 and / or switch module 1217).

[0100] At a second time point after the first time point, the process may include, for example, opening a first switch module (e.g., switch module 162 and / or switch module 164) and closing a second switch module (e.g., switch module 161 and / or switch module 163) to generate a negative pulse portion 212 of the first high voltage pulse.

[0101] At a third time point after the second time point, the process may include, for example, opening a third switch module.

[0102] At a fourth time point after the third time point, the process may include, for example, closing the first switch module and opening the second switch module to generate another positive pulse portion (having an amplitude greater than about 1 kV) of the second high voltage pulse.

[0103] At or shortly after about the fourth time point, the process may include, for example, closing a fourth switch module at about the fourth time point.

[0104] At a fifth time point after the fourth time point, the process may include, for example, opening the first switch module and closing the second switch module to generate a negative pulse portion of the second high voltage pulse.

[0105] 16A shows an output waveform 1600 at point 134 and a wafer waveform 1610 at point 135 in an example circuit of high voltage pulsing power supply and plasma system 1200. In this example, output waveform 1600 and wafer waveform 1610 have four different voltage states (e.g., a first state 1605, a second state 1610, a third state 1615, and a fourth state 1620) that are controlled by varying the pulse width and / or duty cycle of the switches in active droop control circuit 1201, and / or the pulse width of the pulses generated by power supply 705, and / or the pulse width driving the switches in the energy recovery circuit. Energy recovery control waveform 1625 controls the switching logic of SIG±3, which opens and closes ER switches 1215 and 1217, and energy recovery waveform 1630 shows the switching logic of SIG±4, which opens and closes ER switches 1216 and 1218 (ER stands for energy recovery).

[0106] First state 1605 may have, for example, a duration of about 22.5 μs and a negative voltage of about −10 kV. First state 1605 may be generated, for example, by a 450 ns positive pulse width (+PW) and a 1950 ns negative pulse width (−PW) from power supply 705 and a symmetrical 1980 ns pulse width at about 200 kHz from active droop control circuit 1201.

[0107] The second state 1610 may have, for example, a duration of about 22.5 μs and a negative voltage of about −7.5 kV. The second state 1610 may be generated by a 320 ns positive pulse width (+PW) and a 2080 ns negative pulse width (−PW) from the power supply 705 and a symmetrical 1200 ns pulse width at about 200 kHz from the active droop control circuit 1201.

[0108] The third state 1615 may have, for example, a duration of about 22.5 μs and a negative voltage of about −5 kV. The third state 1615 may be generated by a positive pulse width (+PW) of 215 ns and a negative pulse width (−PW) of 2185 ns from the power supply 705, and a symmetrical 1020 ns pulse width at about 200 kHz from the active droop control circuit 1201.

[0109] The fourth state 1620 may have, for example, a duration of about 22.5 μs and a negative voltage of about −2.5 kV. The fourth state 1620 may be generated by a positive pulse width (+PW) of 115 ns and a negative pulse width (−PW) of 2285 ns from the power supply 705, and a symmetrical 900 ns pulse width at about 200 kHz from the active droop control circuit 1201.

[0110] Various other voltage states having different durations and voltages can also be generated by varying the pulse width and / or duty cycle of each switch in active droop control circuit 1201 and / or the pulse width of the pulses generated by power supply 705. Various voltage states can also be generated by adjusting DC power supply 151.

[0111] FIG. 17A shows a close-up view of the waveform shown in FIG. 16A around 20 μs, showing two pulses in the first state 1605, along with control waveform 1415, control waveform 1420, energy recovery waveform 1425, and energy recovery waveform 1430.

[0112] FIG. 17B shows a close-up of the waveform shown in FIG. 16A around 40 μs, showing two pulses in the second state 1610, along with control waveform 1415, control waveform 1420, energy recovery waveform 1425, and energy recovery waveform 1430.

[0113] FIG. 17C shows a close-up of the waveform shown in FIG. 16A around 60 μs, showing two pulses in the third state 1615, along with control waveform 1415, control waveform 1420, energy recovery waveform 1425, and energy recovery waveform 1430.

[0114] FIG. 17D shows a close-up of the waveform shown in FIG. 16A around 80 μs, showing two pulses in the fourth state 1620, along with control waveform 1415, control waveform 1420, energy recovery waveform 1425, and energy recovery waveform 1430.

[0115] The timing of all control waveforms may be continuously adjusted over all relevant or required time ranges to generate the desired output waveform. The timing precision of the waveform adjustments may be finer than 1 s, 1 ms, 1 μs, 1 ns, or less, as needed to generate the desired waveform. Typically, a particular waveform or waveform pattern will be selected to optimize a particular plasma process (e.g., to increase the plasma etch rate, control the width of an etched feature, control the aspect ratio of an etched feature, control a mask etch rate, etc.). By adjusting the waveform, various plasma processes and features can be controlled. By adjusting the output waveform, the resulting ion energy distribution function can be adjusted. By adjusting the voltage across droop capacitor 486 and all switch timing, the output waveform, output current, resulting ion energy distribution function, and any number of specific plasma and / or etch features can be adjusted. The present invention, in particular, allows for the adjustment of plasma and etch parameters (e.g., ion energy distribution function) over a wide, often continuous, operating space. This can be done in a steady state manner where all pulses are the same for a particular ion energy distribution function, or by modulating the output pulses so that an aggregate waveform with a particular aggregate ion energy distribution function is produced. During any particular etch process, it can be advantageous to continuously optimize the ion energy distribution function throughout the etch process.

[0116] FIG. 18 shows the ion energy distribution function (Ion Energy Distribution Function) of ions in the plasma chamber 106 of the plasma system 1200 for the pulses and configuration described with respect to FIG. 17B.

[0117] FIG. 19 shows the ion energy distribution of ions in the plasma chamber 106 of the plasma system 1200 for the pulses and configuration described with respect to FIG. 17A.

[0118] Figure 20A shows the lower limit of the energy distribution function shown in Figure 19, and Figure 20B shows the upper limit of the energy distribution function shown in Figure 19. The plasma system 1200 is capable of producing an ion energy distribution that is nearly flat for a variety of ion energies, which can lead to a wafer voltage that is nearly constant over long periods of time.

[0119] FIG. 21 is a circuit diagram of a high-voltage pulsing power supply and plasma system 2100 including a droop control circuit 2150 and an energy control circuit 2101. In the droop control circuit 2150, an inductor 2145 is coupled in series with a diode 2140. A rising pulse from the secondary side of the transformer 145 passes through the diode 2140 and the inductor 2145 to the plasma chamber 106. FIG. 21 illustrates the droop control and energy recovery elements located on the secondary side of the transformer. In general, the droop control elements and the active droop control circuit 1201 may be located on either the primary side of the transformer or the secondary side of the transformer. While the overall functionality of the elements remains the same, the specific values ​​used are scaled according to the turns ratio of the transformer, with the inductors being larger by the square of the turns ratio and the capacitors being smaller by one-squared of the turns ratio.

[0120] The series combination of droop inductor 2120 and droop capacitor 2130 may be placed in parallel with or across diode 2140 and / or inductor 2145. Droop control circuit 2101 controls the voltage ramp on transformer 145 so that the peak voltage occurs during the second half of the pulse. Droop inductor 2120 is energized during the negative voltage portion of the bipolar pulse, reaching equilibrium once a full charge voltage is present on inductor 2145 or plasma chamber 106, and energy is extracted from droop inductor 2120 during the positive pulse at approximately the same rate as energy is acquired. During the positive pulse of the bipolar pulse, current flows from the secondary side of transformer 145 through diode 2140 and inductor 2145 to plasma chamber 106.

[0121] Capacitor 2130 may be a resistor or an inductor. If capacitor 2130 is a capacitor, it may be coupled with an active energy recovery circuit that adjusts the voltage across capacitor 2130 to select a desired output voltage waveform.

[0122] The energy compensation circuit 2101 is coupled to the secondary side of the transformer 145 and the energy storage capacitor 156. The energy compensation circuit 2101 includes, for example, an energy recovery diode 2105 and an energy recovery inductor 2110. The energy recovery diode 2105 and the energy recovery inductor 2110 may be coupled to the secondary side of the transformer 145 via a diode 2115 and a droop control circuit. The value of the inductor 2105 may be greater than 1 μH, 10 μH, 100 μH, or 10 mH.

[0123] FIG. 22 shows the ion energy distribution of ions in the plasma chamber 106 of the plasma system 2100 (or any of the plasma systems disclosed herein).

[0124] FIG. 23A shows the lower limit of the ion energy distribution shown in FIG. 22, and FIG. 23B shows the upper limit of the ion energy distribution shown in FIG. 22. Plasma system 2100 (or any plasma system disclosed herein) can produce an ion energy distribution that is nearly flat over a range of ion energies (e.g., nearly flat over a significant portion of ion energies) and peaks in a narrow band of ion energies, which can lead to a nearly constant wafer voltage over long periods of time. By adjusting the various droop control and energy recovery elements, any number of potential ion energy distribution functions can be generated. Specific plasma parameters can be maintained or various plasma parameter ranges can be swept across or controlled by adjusting certain elements in real time.

[0125] Figure 24 is a circuit diagram of a high voltage pulsing power supply and plasma system 2400 with an active droop control circuit 2401. The high voltage pulsing power supply and plasma system 2400 includes a high voltage pulsing power supply 105 coupled to an active droop control circuit 2401 and a plasma chamber 106. The active droop control circuit is operable to generate a variety of output waveforms and a variety of ion energy distribution functions, comparable to the operation of the droop control circuit and active energy recovery circuit described above. Figure 24 is yet another example of this generation.

[0126] Active droop control circuit 2401 may be coupled to droop inductor 187, for example, on the primary side of transformer 145. Active droop control circuit 2401 may add charge to and / or remove charge from droop capacitor 486. When switch 2408 is closed and switch 2410 is open, the charge stored in droop capacitor 486 may dissipate into resistor 2406. Resistor 2406 may have a resistance of approximately 0.1 Ω, 3 Ω, or 367 Ω, for example.

[0127] When switch 2408 is open and switch 2410 is closed, droop capacitor 486 can be charged through inductor 2404 from voltage source 2412. Voltage source 2412 can be, for example, at a voltage of approximately 0 V, 100 V, 500 V, or 5000 V. Voltage source 2412 can provide a voltage that is, for example, always within approximately 10 V, 300 V, or 5000 V of DC power source 150 and / or DC power source 151.

[0128] 25 is a flowchart of an example process 2500 for controlling ion energy distribution on a wafer. At block 2505, multiple high-voltage pulses (e.g., a burst of pulses) are introduced into a plasma by a high-voltage pulser. Process 2500 may be operable for plasma system 2400, plasma system 2100, and / or plasma system 1200.

[0129] The ion energy distribution on the wafer may be measured, estimated, or calculated in block 2510. Estimating the ion energy distribution on the wafer may be done by measuring the output voltage from the pulsing power supply, the voltage on capacitor 12, the output current of the pulsing power supply, and / or the plasma density in the chamber.

[0130] In block 2515, it may be determined whether the ion energy distribution on the wafer, if any, is within an acceptable range. If so, the process 2500 may return to block 2505. If not, the process 2505 may proceed to block 2520.

[0131] At block 2520, an adjustment to the ion energy distribution may be determined based on the measured ion energy distribution and / or a prescribed or desired ion energy distribution.

[0132] The duty cycle and / or pulse width (duration of opening and closing) of the energy recovery switch may be adjusted at block 2525. Process 2500 may then return to block 2505.

[0133] Various other control processes for this system are also contemplated. Parameters that can be measured and / or adjusted using some / any form of real-time feedback and control include the waveforms of all aspects of the output voltage and current, any and / or all switch timings, various component values, ion energy distribution functions, and any number of plasma and / or etch parameters. For example, by controlling the voltage across droop capacitor 720 and / or droop capacitor 725, a particular etch rate, aspect ratio, mask erosion rate, and / or feature size can be maintained. For example, by monitoring and setting the output voltage waveform in real time, a particular ion energy distribution function can be maintained or a particular set of ion energy distribution functions can be developed / swept. The selected ion energy distribution function can be selected to optimize one or many particular etch parameters (e.g., etch rate, aspect ratio, and / or feature size, etc.). For example, by varying the droop rate, the mask erosion rate can be controlled.

[0134] Figure 26 shows an example waveform with two ideal pulse bursts: a first burst 2605 and a second burst 2606. A burst may contain multiple pulses 2610. The burst duration is the time that the burst is on (T on ), and the time the burst is off (T off ) Pulse width (P Width ) is the time that the pulse is on. The pulse period (P Period ) is the time that the pulse is on or off. The duty cycle is the on time (T on ) divided by the burst duration: DC=T on / (T on +T off The burst repetition frequency is the reciprocal of the burst period: f burst =1 / (T on +T off) The pulse repetition frequency is the reciprocal of the pulse period: f pulse =1 / P period It may be expressed as:

[0135] A positive waveform has a burst of pulses with a minimum voltage of V0 and a pulse amplitude of V1, both above zero. A negative waveform has a burst of pulses with a minimum voltage of V0 and a pulse amplitude of V1, both below zero. A bipolar waveform has a burst of pulses with a minimum voltage of V0 below zero and a pulse amplitude of V1 above zero.

[0136] 27 can be used to implement any embodiment of the present invention. For example, computer system 2700 can be used to perform any or all of process 2500 and / or all of the feedback and control processes described above. As another example, computer system 2700 can perform all of the calculations, identifications, and / or determinations described herein. In computer system 2700, hardware elements can be electrically coupled (or otherwise in communication as needed) via bus 2705. The hardware elements may include one or more processors 2710, one or more input devices 2715, and one or more output devices 2720, where the one or more processors 2710 may include, but are not limited to, one or more general-purpose processors and / or one or more special-purpose processors (e.g., digital signal processing chips, graphics accelerator chips, and / or the like), the one or more input devices 2715 may include, but are not limited to, a mouse, a keyboard, and / or the like, and the one or more output devices 2720 may include, but are not limited to, a display device, a printer, and / or the like.

[0137] Computer system 2700 may further include (and / or communicate with) one or more storage devices 2725, which may include, but are not limited to, local storage and / or network-accessible storage, and / or may include, but are not limited to, disk drives, drive arrays, optical storage devices, solid-state storage devices (e.g., random access memory (“RAM”) and / or read-only memory (“ROM”), which may be programmable, flash-updateable, and / or the like). Computer system 2700 may also include a communications subsystem 2730, which may include, but are not limited to, a modem, a network card (wireless or wired), an infrared communications device, a wireless communications device and / or chipset (e.g., a Bluetooth device, an 802.6 device, a Wi-Fi device, a WiMax device, a cellular communications facility, etc.), and / or the like. The communications subsystem 2730 may enable data exchange with a network (e.g., a network described below, to name just a few) and / or any other devices described herein. In many embodiments, the computer system 2700 further includes working memory 2735, which may include a RAM device or a ROM device, as described above.

[0138] Computer system 2700 may also include software elements, currently shown as located in working memory 2735, including an operating system 2740 and / or other code, such as one or more application programs 2745, which may include computer programs of the present invention and / or may be designed to implement methods of the present invention and / or to configure systems of the present invention, as described herein. For example, one or more procedures described with respect to the methods described above may be implemented as code and / or instructions executable by a computer (and / or a processor within a computer). Sets of these instructions and / or code may be stored on a computer-readable storage medium (e.g., storage device 2725, described above).

[0139] In some cases, the storage medium may be incorporated into or in communication with computer system 2700. In other embodiments, the storage medium may be separate from computer system 2700 (e.g., may be a removable medium such as a compact disc) and / or may be provided in the form of an installation package whereby the storage medium can be used to program a general-purpose computer with instructions / code stored thereon. These instructions may be in the form of executable code that can be run on computer system 2700 and / or may be in the form of source code and / or installable code that becomes executable code when compiled and / or installed on computer system 2700 (e.g., using any of a variety of commercially available compilers, installation programs, compression / decompression utilities, etc.).

[0140] The general description above and associated optimization / operational space description may generally apply to all circuits disclosed herein, or all diagrams in one form or another. For example, all circuits may operate similarly if a short positive pulse can reset the system and cancel any charge buildup on the wafer due to previously flowing ion current, if the current in a droop inductor (e.g., droop inductor 187) can set a voltage on the wafer and / or reduce, eliminate, or reverse any voltage droop, if the current can be set by balancing the energy flowing into and out of the droop inductor (e.g., by balancing positive and negative volt-seconds across the inductor), and / or if a net energy balance between the energy flowing into and out of the droop inductor can be set by the energy recovery circuit, whether active or passive in nature.

[0141] Unless otherwise specified, the term "substantially" means within 5-10% of the stated value, or within a manufacturing tolerance. Unless otherwise specified, the term "about" means within 5-10% of the stated value, or within a manufacturing tolerance.

[0142] The conjunction "or" is inclusive.

[0143] The terms "first," "second," "third," etc. are used to distinguish between elements and are not used to imply a particular order of those elements unless otherwise stated or an order is explicitly indicated or required.

[0144] Numerous specific details are set forth to provide a thorough understanding of the claimed subject matter. However, those skilled in the art will understand that the claimed subject matter may be practiced without these specific details. Also, in some instances, methods, apparatuses, or systems that would be well known to those skilled in the art have not been described in detail so as to avoid obscuring the claimed subject matter.

[0145] Some portions are presented as 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 how those skilled in the data processing arts convey the substance of their work to others skilled in the art. An algorithm is a self-consistent sequence of operations or similar processes leading to a desired result. In this context, operations or processes involve physical manipulation of physical quantities. Typically, though not necessarily, such quantities take the form of electrical or magnetic signals capable of being stored, transferred, combined, compared, or otherwise manipulated. It has proven convenient at times, primarily for reasons of common usage, to refer to such signals as bits, data, values, elements, symbols, characters, terms, values, numerals, or the like. It should be understood, however, that all of these and similar terms are to be associated with the appropriate physical quantities and are merely convenient labels. Unless otherwise indicated, throughout the discussion herein, use of terms such as "processing," "computing," "calculating," "determining," "identifying," and the like, will be understood 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 actual electronic or magnetic quantities within the memory, registers, or other information storage, transmission, or display devices of the computing platform.

[0146] The described system or systems are not limited to any particular hardware architecture or configuration. A computing device may include any suitable configuration of components that outputs a result conditioned on one or more inputs. Suitable computing devices include general-purpose microprocessor-based computer systems that access stored software that programs or configures computing systems ranging from general-purpose computing devices to special-purpose computing devices that implement one or more embodiments of the present subject matter. Any suitable programming language, scripting language, or other type of language, or combination of languages, may be used to implement the teachings included in the form of software used to program or configure a computing device.

[0147] Embodiments of the disclosed methods may be implemented in operation of such a computing device. The order of the blocks shown in the above examples may be changed, for example, by reordering the blocks, combining blocks, and / or dividing blocks into sub-blocks. Some blocks or processes may be performed in parallel.

[0148] The use of "adapted to" or "configured to" is intended to be open and inclusive language that does not exclude apparatus adapted or configured to perform additional tasks or steps. Furthermore, the use of "based on" is intended to be open and inclusive in that a process, step, calculation, or other action that is "based on" one or more recited conditions or values ​​may in fact be based on additional conditions or values ​​beyond those recited conditions or values. The included headings, lists, and numbering are for ease of description only and are not intended to be limiting.

[0149] While the present subject matter has been described in detail with reference to specific embodiments thereof, it will be understood that those skilled in the art, upon understanding the foregoing, will be able to readily produce alterations, variations, and equivalents to such embodiments. It will therefore be understood that the present disclosure has been presented for purposes of illustration and not limitation, and is not intended to exclude the inclusion of such modifications, variations, and / or additions to the present subject matter as would be readily apparent to those skilled in the art.

Claims

1. 1. A high voltage pulsing power supply system, comprising: a DC power supply; a switch circuit electrically coupled to the DC power source, the switch circuit including a plurality of switch modules arranged in a full bridge configuration, the switch circuit generating a plurality of pulses having a positive pulse portion and a negative pulse portion and an amplitude greater than about 10 kV; A transformer, a transformer core; a primary winding wound around the transformer core; a secondary winding wound around the transformer core; the transformer including a droop control circuit electrically coupled to the switch circuit and the primary winding, the droop control circuit comprising: a droop diode electrically coupled in series between the switch circuit and the primary winding, the droop diode allowing the negative pulse portions of the plurality of pulses to pass from the switch circuit to the primary winding of the transformer; a droop inductor and a droop element disposed in series across the droop diode, the droop inductor and the droop element allowing the negative pulse portions of the plurality of pulses to pass from the switch circuit to the primary winding of the transformer and storing energy from the negative pulse portions of the plurality of pulses; the droop control circuit including: an output electrically coupled to the secondary winding, the output outputting the plurality of pulses having a substantially flat negative pulse portion; High voltage pulsing power supply system including:

2. 2. The high voltage pulsing power supply of claim 1, wherein the droop element comprises a capacitor or a resistor.

3. 2. The high voltage pulsing power supply of claim 1, wherein the inductance of said droop inductor is between about 1 μH and about 10 mH.

4. 10. The high voltage pulsing power supply of claim 1, further comprising an energy recovery circuit electrically coupled to the droop element and the high voltage power supply, the energy recovery circuit including one or more switch modules that open and close to add charge to or remove charge from the droop element.

5. 10. The high voltage pulsing power supply of claim 1, wherein the high voltage pulsing power supply is coupled to a plasma chamber having a plasma therein, and wherein the output produces an ion energy distribution that is substantially flat over a significant portion of the ion energy and peaks in a narrow band of ion energies.

6. 5. The high voltage pulsing power supply of claim 4, wherein the one or more switch modules of the energy recovery circuit are arranged in a full-bridge or half-bridge configuration.

7. 5. The high voltage pulsing power supply of claim 4, wherein the energy recovery circuit includes a diode and an inductor arranged in series between the droop element and the high voltage power supply.

8. 5. The high voltage pulsing power supply of claim 4, wherein the energy recovery circuit includes a DC-DC converter.

9. 10. The high voltage pulsing power supply of claim 1, further comprising a plasma chamber having one or more electrodes electrically coupled to the output, wherein the plurality of pulses produce an ion energy distribution in the plasma that is substantially flat over a significant portion of the ion energy and peaks in a narrow band of ion energies.

10. 1. A plasma system comprising: a DC power supply; a switch circuit electrically coupled to the DC power source, the switch circuit including a plurality of switch modules arranged in a full bridge configuration, the switch circuit generating a plurality of pulses having a positive pulse portion and a negative pulse portion and an amplitude greater than about 10 kV; A transformer, a transformer core; a primary winding wound around the transformer core; a secondary winding wound around the transformer core; the transformer including a droop control circuit electrically coupled to the switch circuit and the primary winding, the droop control circuit comprising: a droop diode electrically coupled in series between the switch circuit and the primary winding, the droop diode allowing the negative pulse portions of the plurality of pulses to pass from the switch circuit to the primary winding of the transformer; a droop inductor and a droop capacitor disposed in series across the droop diode, the droop inductor and the droop capacitor allowing the negative pulse portions of the plurality of pulses to pass from the switch circuit to the primary winding of the transformer and storing energy from the negative pulse portions of the plurality of pulses; the droop control circuit including: an energy recovery circuit electrically coupled to the droop capacitor and the high voltage power supply, the energy recovery circuit including one or more switch modules that open or close to add or remove charge from the droop capacitor; a plasma chamber having one or more electrodes electrically coupled to the secondary winding, wherein the plurality of pulses produce an ion energy distribution in the plasma that is substantially flat over a substantial portion of the ion energy and peaks in a narrow band of ion energies; A plasma system including:

11. 11. The high voltage pulsing power supply of claim 10, wherein the plurality of pulses includes a substantially flat negative pulse portion.

12. 11. The high voltage pulsing power supply of claim 10, wherein the inductance of the droop inductor is between about 1 μH and about 10 mH.

13. 11. The high voltage pulsing power supply of claim 10, wherein the energy recovery circuit includes a DC-DC converter.

14. 11. The high voltage pulsing power supply of claim 10, wherein the energy recovery circuit includes a transformer between the plurality of switch modules and the DC-DC converter.

15. 11. The high-voltage pulsing power supply of claim 10, wherein the energy recovery circuit includes an energy recovery inductor and a diode disposed in series between the high-voltage power supply and the one or more switch modules.

16. 11. The high voltage pulsing power supply of claim 10, wherein the one or more switch modules of the energy recovery circuit are arranged in a full-bridge or half-bridge configuration.

17. 1. A high voltage pulsing power supply system, comprising: a DC power supply; a switch circuit electrically coupled to the DC power source, the switch circuit including a plurality of switch modules arranged in a full bridge configuration, the switch circuit generating a plurality of pulses having a positive pulse portion and a negative pulse portion and an amplitude greater than about 10 kV; A transformer, a transformer core; a primary winding wound around the transformer core; a secondary winding wound around the transformer core; the transformer including a droop control circuit electrically coupled to the switch circuit and the primary winding, the droop control circuit comprising: a droop diode electrically coupled in series between the switch circuit and the primary winding, the droop diode allowing the negative pulse portions of the plurality of pulses to pass from the switch circuit to the primary winding of the transformer; a droop inductor and a droop capacitor disposed in series across the droop diode, the droop inductor and the droop capacitor allowing the negative pulse portions of the plurality of pulses to pass from the switch circuit to the primary winding of the transformer and storing energy from the negative pulse portions of the plurality of pulses; the droop control circuit including: an energy recovery circuit electrically coupled to the droop capacitor, the energy recovery circuit including a plurality of switch modules arranged in a half-bridge or full-bridge configuration and a DC-DC converter, the plurality of switch modules opening and closing to add charge to or remove charge from the droop capacitor; an output electrically coupled to the secondary winding, the output outputting the plurality of pulses having a substantially flat negative pulse portion; High voltage pulsing power supply system including:

18. 20. The high voltage pulsing power supply of claim 17, further comprising a plasma chamber having one or more electrodes electrically coupled to the output, wherein the plurality of pulses produce an ion energy distribution in the plasma that is substantially flat over a significant portion of the ion energy and peaks in a narrow band of ion energies.

19. 18. The high voltage pulsing power supply of claim 17, wherein the inductance of the droop inductor is between about 1 μH and about 10 mH.

20. 18. The high voltage pulsing power supply of claim 17, wherein the energy recovery circuit includes an energy recovery inductor and a diode disposed in series between the high voltage power supply and the DC-DC converter.

21. generating a first burst of high voltage pulses into a plasma chamber having a plasma therein, the first burst of high voltage pulses comprising a plurality of high voltage pulses having a first duty cycle, each high voltage pulse of the plurality of high voltage pulses having a pulse amplitude greater than 1 kV and a first pulse width; estimating an ion energy distribution function within the plasma; comparing the estimated ion energy distribution function with a required ion energy distribution function; if the difference between the estimated ion energy distribution function and the required ion energy distribution function is greater than a threshold; determining one or both of a second duty cycle and a second pulse width based on the difference between the estimated ion energy distribution function and the required ion energy distribution function; generating a second burst of high voltage pulses into the plasma chamber having a plasma therein, the second burst of high voltage pulses comprising a plurality of high voltage pulses having a second duty cycle, each high voltage pulse of the plurality of high voltage pulses having a pulse amplitude greater than 1 kV and a second pulse width; and, A method comprising:

22. At a first time, closing a first switch module and opening a second switch module of the high voltage pulsing power supply to generate a positive pulse portion of a first high voltage pulse having an amplitude greater than about 1 kV; At approximately a first time, closing a third switch module and opening a fourth switch module of the energy recovery circuit; At a second time after the first time, opening the first switch module and closing the second switch module to generate a negative pulse portion of the first high voltage pulse; at a third time after the second time, opening the third switch module; at a fourth time point after the third time point, closing the first switch module and opening the second switch module to generate a positive pulse portion of a second high voltage pulse having an amplitude greater than about 1 kV; at about the fourth time, closing the fourth switch module; At a fifth time point after the fourth time point, opening the first switch module and closing the second switch module to generate a negative pulse portion of the second high voltage pulse; A method comprising:

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