Adaptive charge neutralization device

Abstract

An exemplary charge neutralization apparatus includes a first emitter nozzle, a power supply configured to supply a high frequency alternating current (AC) signal to the first emitter nozzle, and a control circuitry configured to provide a polarity signal to the power supply to generate a DC offset signal, where a combination of the high frequency AC signal and the DC offset signal causes the power supply to output a positive ion generating pulse or a negative ion generating pulse; control the polarity signal to cause the power supply to provide a positive ion generation period and a negative ion generation period; determine a balance voltage at an output of the first emitter nozzle; and control the polarity signal to adjust the relative duration of the positive ion generation period and the negative ion generation period based on the balance voltage.

Description

[Technical field]

[0001] This disclosure relates generally to ionization, and more particularly to methods and apparatus for adaptive charge neutralization. [Background technology]

[0002] The ion emitter of the charge neutralization device generates and supplies both positive and negative ions into the surrounding air or gas medium. To generate gas ions, the amplitude of the applied voltage must be high enough to create a corona discharge between at least two electrodes arranged as an ionization cell. In the ionization cell, at least one electrode is an ion emitter and the other can be a reference electrode. Summary of the Invention

[0003] A method and apparatus for adaptive charge neutralization, as more fully set forth in the claims, is disclosed substantially as shown by and described in connection with at least one of the drawings.

[0004] These and other features, aspects, and advantages of the present disclosure will be better understood when the following detailed description is read in conjunction with the accompanying drawings, in which like reference characters represent like parts throughout. [Brief description of the drawings]

[0005] [Figure 1] FIG. 1 illustrates an example AC charge neutralization system configured to control ionization output based on balance voltage feedback, according to an embodiment of the disclosure. [Diagram 2] FIG. 2 is a block diagram of an exemplary embodiment of the AC charge neutralization system of FIG. 1. [Diagram 3] 3A-3C show example input signals to the power supply to the emitter of FIG. 2, controlling the output of positive and negative ions via a DC offset signal. [Figure 4]FIG. 3 shows an example output signal from the power supply of FIG. 2 to the emitter outputting positive and negative ions and controlling the balance voltage with the pulse output turned off. [Diagram 5] FIG. 3 shows an example output signal from the power supply of FIG. 2 to the emitter, outputting positive and negative ions and controlling the balance voltage, with the pulse output turned on. [Figure 6] 2 is a flow chart illustrating an example method of controlling ionization output of the AC charge neutralization system of FIG. 1 based on balance voltage feedback. [Figure 7] 3 is a flow chart illustrating an example method of controlling ions output by an ionizer power supply, such as the power supply of FIG. 2. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0006] The drawings are not necessarily to scale and, where appropriate, like or identical reference numbers are used to refer to like or identical components.

[0007] Ionizers, or charge neutralization devices, emit positive and / or negative ions to discharge static electricity that may be present on surfaces or substrates in manufacturing facilities, etc. The disclosed exemplary charge neutralization methods and devices can be used in Class 1 clean room production environments and are particularly useful in semiconductor chip manufacturing.

[0008] Conventional charge neutralization devices release a predetermined balance of positive and negative ions, which may be adjusted by an operator via software and / or an input device. However, conventional charge neutralization devices lack a feedback mechanism to accurately determine whether the predetermined balance is appropriate for the charge present on the target during operation.

[0009] The disclosed exemplary charge neutralization methods and devices adapt the output ion balance based on the balance voltage feedback. The disclosed exemplary charge neutralization methods and devices modulate the high voltage high frequency AC signal using a DC offset signal to control the production of positive and negative ions. To adapt the output ion balance and thereby increase the accuracy of the resulting balance voltage at the target, the disclosed exemplary charge neutralization methods and devices increase or decrease the duty cycle of the DC offset signal to adapt the modulation of the high voltage high frequency AC signal. The disclosed exemplary charge neutralization methods and devices can make the balance voltage more accurate and substantially reduce the swing voltage compared to conventional charge neutralization devices. Some disclosed charge neutralization methods and devices can achieve a swing voltage of + / - 5V, which has significant advantages for voltage and charge sensitive applications such as semiconductor manufacturing.

[0010] As used herein, "exceeding" a threshold voltage can occur in a positive direction (eg, more positive than the threshold) or in a negative direction (eg, more negative than the threshold).

[0011] As used herein, "balance voltage" refers to the net voltage resulting from ionization by the emitter.

[0012] The terms "ionization" and "charge neutralization" are used interchangeably herein.

[0013] An exemplary charge neutralization apparatus is disclosed that includes a first emitter nozzle, a power supply configured to supply a high frequency alternating current (AC) signal to the first emitter nozzle, and a control circuitry configured to: provide a polarity signal to the power supply to generate a DC offset signal, where a combination of the high frequency AC signal and the DC offset signal causes the power supply to output a positive ion generating pulse or a negative ion generating pulse; control the polarity signal to cause the power supply to provide a positive ion generation period and a negative ion generation period; determine a balance voltage at an output of the first emitter nozzle; and control the polarity signal to adjust the relative duration of the positive ion generation period and the negative ion generation period based on the balance voltage.

[0014] In some example devices, the combination of the high frequency AC signal and the DC offset signal has a peak voltage that is greater than a corona generation threshold voltage of the first emitter nozzle. In some example devices, the combination of the high frequency AC signal and the DC offset signal causes the voltage of the first emitter nozzle to exceed only one of the anodic corona generation threshold voltage or the cathodic corona generation threshold voltage per high frequency AC cycle.

[0015] In some exemplary apparatus, the control circuitry is configured to determine the balance voltage based on a feedback signal from the antenna. In some exemplary apparatus, the antenna is positioned adjacent to the ionization target. In some exemplary apparatus, the control circuitry is configured to determine the balance voltage based on a feedback signal from a closed loop controller.

[0016] In some example devices, the power supply applies a signal to the first emitter nozzle that is based on a combination of the high frequency AC signal and a DC offset signal, and the resulting signal causes the voltage at the first emitter nozzle to exceed either the positive corona generation threshold voltage or the negative corona generation threshold voltage. In some example devices, when the control circuitry controls the polarity signal to not generate a DC offset in the power supply, the high frequency AC signal does not exceed either the positive corona generation threshold voltage or the negative corona generation threshold voltage.

[0017] In some exemplary devices, the emitter tip is silicon-based or titanium-based. Some exemplary devices include a plurality of emitter nozzles, including a first emitter nozzle. In some exemplary devices, the control circuitry is configured to modulate a polarity signal based on a balance voltage to control a duty cycle of the positive ion generating pulses or the negative ion generating pulses. In some exemplary devices, the control circuitry is configured to determine the balance voltage based on a feedback signal from the antenna. In some exemplary devices, the first emitter nozzle includes an emitter tip held within a stainless steel sleeve, and the power supply is configured to apply a combination of a high frequency AC signal and a DC offset signal to the emitter tip relative to the sleeve.

[0018] 1 illustrates an example AC charge neutralization system 100 configured to control ionization output based on balance voltage feedback. The example AC charge neutralization system 100 outputs positive and negative ions 102 to neutralize charge on a target device or substrate 104.

[0019] To generate the ions 102, the example system 100 includes one or more ion emitter nozzles 106 coupled to one or more power sources that provide a high voltage high frequency AC signal for generation of the ions 102. The system 100 may include any number of emitter nozzles 106 to disperse the ions 102 over a desired area or size of the target device or substrate 104. By alternating between positive and negative ions, the example system 100 effectively neutralizes static charge present on the target device or substrate 104 while reducing or avoiding charging of the target device or substrate 104 by the ions 102.

[0020] The system 100 of FIG. 1 produces alternating positive and negative ions by controlling the output voltage of the nozzle 106 to output positive and negative ion periods. The relative duration of the positive and negative ion periods can be controlled based on a desired balance. In contrast to conventional charge neutralization systems, the exemplary system 100 achieves a balance voltage within + / - 5V by measuring the balance voltage via the antenna 108 and adjusting the ion balance based on the measurement. For example, the system 100 can adjust the relative duration of the positive and negative ion periods to adjust the output balance. The antenna 108 can be positioned near the target 104 such that the antenna 108 measures a balance voltage indicative of the output of the system 100. Using feedback from the antenna 108, the system 100 repeatedly (e.g., continuously) adjusts the relative balance between the positive and negative ion generation periods.

[0021] Figure 2 is a block diagram of one exemplary embodiment of the AC charge neutralization system 100 of Figure 1. The example of Figure 2 includes an in-line ionizer 200 having a high voltage high frequency (HVHF) power supply 202 that outputs an HVHF signal to an emitter assembly 204 having a plurality of emitters 206. In some examples, the emitters 206 are silicon-based or titanium-based. Based on the HVHF signal from the power supply 202, the emitters 206 generate and output positive and negative ions.

[0022] The HVHF power supply 202 includes a DC-DC converter 208, an AC HV inverter 210, a DC offset generator 212, and an AC HV amplifier 214. The DC-DC converter 208 outputs a DC signal to the inverter 210, which generates an AC signal. The DC offset generator 212 selectively generates a DC offset signal based on the polarity control signals 216, 218. When the positive polarity control signal 216 is active, the DC offset generator 212 generates a positive DC offset. Conversely, when the negative polarity control signal 218 is active, the DC offset generator 212 generates a negative DC offset. When neither of the polarity control signals 216, 218 is active, the DC offset generator 212 does not generate a DC offset. The DC offset voltage, whether positive or negative, is combined with the AC signal output by the AC HV inverter 210 to generate a combined signal.

[0023] The AC HV amplifier 214 amplifies the voltage of the composite signal output by the DC offset generator 212 .

[0024] The example ionizer 200 includes control circuitry 220 that controls the HVHF power supply 202. The example control circuitry 220 may include a general purpose microprocessor, a microcontroller, a system on a chip (SoC), an application specific integrated circuit (ASIC), and / or any other type of digital and / or analog circuitry.

[0025] The control circuitry 220 comprises at least one controller or processor that controls the operation of the ionizer 200. The control circuitry 220 receives and processes a number of inputs related to the performance and demands of the system. The control circuitry 220 may comprise one or more microprocessors, e.g., one or more "general purpose" microprocessors, one or more special purpose microprocessors and / or ASICs, and / or any other type of processing device. For example, the control circuitry 220 may comprise one or more digital signal processors (DSPs).

[0026] The example control circuitry 220 may include one or more storage devices and one or more memory devices. The storage device(s) (e.g., non-volatile storage) may include ROM, flash memory, hard drives, and / or any other suitable optical, magnetic, and / or solid-state storage media, and / or combinations thereof. The storage devices store data (e.g., ionization configuration data), instructions, and / or any other suitable data. The memory device(s) may include volatile memory, such as random access memory (RAM), and / or non-volatile memory, such as read-only memory (ROM). The memory device(s) and / or storage device(s) may store a variety of information and may be used for a variety of purposes. For example, the memory device(s) and / or storage device(s) may store processor-executable instructions (e.g., firmware or software) that are executed by the control circuitry 220.

[0027] The example control circuitry 220 outputs a target voltage level signal to the DC-DC converter 208 to control the DC output voltage to the AC HV inverter 210, and controls the polarity signals 216, 218 to the DC offset generator 212 to control the output. By controlling the polarity signals 216, 218, the example control circuitry 220 can control the balance of positive and negative ions output by the emitter 204.

[0028] The example control circuitry 220 further receives a balance voltage input 222 from a remote ion balance sensor, such as the antenna 108 of FIG. 1. The example control circuitry 220 can further include or receive an input from a balance detector connected to an antenna located near the ionization target. The balance detector can be implemented using a Simco-Ion™ Novx based control system, such as the Novx 3352 Closed-loop Ionizer Controller or the Novx 3362 Closed-loop Ionizer Controller. In other examples, the control circuitry 220 or the ionizer 200 can include a balance detector that receives a feedback signal directly from the antenna 108.

[0029] The example control circuitry 220 can implement a PID controller and / or other types of filters to filter the balance voltage measurements received via the antenna 108. In some examples, the balance voltage input 222 is determined using an analog-to-digital converter (ADC) circuit configured to receive an input signal from the antenna 108, and the control circuitry 220 applies one or more filters and / or control loops to the balance voltage input 222 to adjust a balance value that controls the polarity signals 216, 218. The control circuitry 220 receives the balance voltage input 222 periodically, as frequently as an ADC or other circuit may sample and deliver the balance voltage input 222, in response to one or more event types, and / or at any other time.

[0030] A source of pressurized air, nitrogen, or argon can be connected to the in-line ionizer 200 via an inlet to generate an air or gas flow. In another example, the emitter assembly 204 allows an ambient air flow to carry ions toward the output of the emitter assembly 204. The air or gas flow, if present, entrains positive and negative ions and carries the ions through the ionizer outlet toward a target (e.g., target 104 in FIG. 1).

[0031] 3 shows an example input signal to the power supply 202 of FIG. 2, which controls the output of positive and negative ions via a DC offset signal. The example control circuitry 220 compares the count signal 302 to a balance value 304 that is set by the control circuitry 220 based on a balance set point and a balance voltage input 222. The example control circuitry 220 can control the count signal to increase and decrease based on a clock signal of the control circuitry 220 to maintain consistent timing. When the count signal 302 is less than the balance value 304, the control circuitry 220 controls the negative polarity signal 218 to be active and the positive polarity signal 216 to be inactive. Conversely, when the count signal is greater than the balance value 304, the control circuitry 220 controls the negative polarity signal 218 to be inactive and the positive polarity signal 216 to be active. Thus, the positive polarity signal 216 is active longer as the balance value decreases (e.g., the more positive or negative balance values ​​measured), and the negative polarity signal 218 is active longer as the balance value increases (e.g., the more positive or negative balance values ​​measured). In some examples, the control circuitry 220 can further implement a pulse signal 306 that controls the power supply 202. For example, the pulse signal 306 can be used to control the output of the AC HV inverter 210 to turn the AC high frequency signal on and off. While the polarity signals 216, 218 can be active at a given time, a low value (e.g., off) of the pulse signal 306 turns off the output of the power supply 202 until the pulse signal 306 is changed to a high value (e.g., on). The pulse signal 306 can be used to reduce the ionization swing voltage without significantly affecting the decay time in some types of applications where both the decay time and swing voltage requirements are difficult to achieve. Additionally or alternatively, the pulse signal 306 can be used to inhibit ion recombination.

[0032] 3, the pulse signal 306 has a particular period and duty cycle that can be controlled based on a clock signal of the control circuitry 220. However, in other examples, the period and / or duty cycle of the pulse signal 306 can be adjusted as desired, such as to achieve a particular ionization rate.

[0033] In some examples, the control circuitry 220 can output a warning or alert if the balance value 304 reaches and / or remains at an upper or lower limit value. In such cases, the balance voltage measurement may be in error and / or the ionizer 200 may not provide sufficient ionization for the application.

[0034] 4A illustrates an example output signal 400 from the power supply 202 of FIG. 2 to the emitter 206 outputting positive and negative ions to control the balance voltage with the pulse output (e.g., pulse signal 306 of FIG. 3) turned off. FIG. 4B illustrates a more detailed view of a portion of the output signal 400 exhibiting high frequency. In the example of FIG. 4A, the output signal 400 has a defined emitter period 402 that includes a negative portion 404, a positive portion 406, and one or more off portions 408. The off portion 408 may include one or more predetermined periods occurring between the sequential negative and positive portions, at the beginning of the emitter period 402, and / or at the end of the emitter period 402 to provide sufficient time for the power supply 202 to switch.

[0035] During the negative portion 404, the negative polarity signal 218 is active and the emitter 206 generates and launches negative ions toward the target 104. During the positive portion 406, the positive polarity signal 216 is active and the emitter 206 generates and launches positive ions toward the target 104. During the off portion 408, neither polarity signal 216, 218 is active and the emitter 206 does not generate negative ions because the output signal 400 generated from the power supply 202 is not sufficient to exceed either the positive threshold voltage 410 or the negative threshold voltage 412. The positive portion 406 and / or the negative portion 404 can have respective duty cycles relative to the emitter period 402.

[0036] In response to the balance voltage input 222, the example control circuitry 220 can adjust the duty cycle of the negative portion 404 and / or the positive portion 406 by adjusting the balance signal 304 of FIG. 3, thereby adjusting the polarity signals 216, 218.

[0037] The control circuitry 220 can respond to changes in the balance value 304 by determining the corresponding duration of the negative portion 404 and / or the positive portion 406 .

[0038] FIGURE 5A shows an example output signal 500 from power supply 202 of FIGURE 2 to emitter 206 outputting positive and negative ions to control the balance voltage with a pulsed output (e.g., pulsed signal 306 of FIGURE 3) turned on. FIGURE 5B shows a more detailed view of a portion of output signal 500 showing high frequency. Example output signal 500 is similar to output signal 400 of FIGURE 4A, except that the HV output signal to emitter 204 is turned off based on pulsed signal 306.

[0039] FIG. 6 is a flow chart illustrating an example method 600 for controlling the ionization output of the AC charge neutralization system of FIGS. 1 and 2 based on balance voltage feedback.

[0040] In block 602, the example HVHF power supply 202 generates a high voltage high frequency AC signal. For example, the DC-DC converter 208 and the AC high voltage inverter 210 generate the high voltage high frequency AC signal. In block 604, the control circuitry 220 sets a balance value based on the desired ion output balance. For example, the control circuitry 220 can set the initial balance value 304 based on a balance input that controls the negative portion 404 and / or the positive portion 406.

[0041] At block 606, the control circuitry 220 determines a positive ion duty cycle (e.g., the positive portion 406 of the emitter period 402) and a negative ion duty cycle (e.g., the negative portion 404 of the emitter period 402) based on the balance value 304. For example, the control circuitry 220 may calculate the positive ion duty cycle and the negative ion duty cycle based on the balance value 304 (within a predetermined range) and the predetermined off-time 408. In some other examples, the control circuitry 220 does not calculate the positive ion duty cycle and the negative ion duty cycle, but instead controls the polarity signal (e.g., in real time) based on a comparison of the balance value 304 to the count signal 302.

[0042] In block 608, the control circuitry 220 controls the ions output by the power supply 202 based on the positive ion duty cycle and the negative ion duty cycle. One exemplary method for implementing block 608 is disclosed below with reference to FIG.

[0043] At block 610, the control circuitry 220 measures the balance voltage. For example, the control circuitry 220 may receive a balance voltage input 222 indicative of the balance voltage. At block 612, the control circuitry 220 updates the balance value 304 based on the measured balance voltage and a balance set point. For example, the control circuitry 220 may apply the measured balance voltage and the balance set point to a PID controller to adjust the balance value 304. The PID controller, or other control loop, adjusts the command balance value 304 based on the difference between the measured balance voltage and the balance set point.

[0044] After updating the balance value (block 612 ), control returns to block 606 to continue updating the positive ion duty cycle and the negative ion duty cycle and outputting the HVHF signal to the emitter 206 .

[0045] Figure 7 is a flow chart illustrating an example method 700 of controlling ion output by an ionizer power supply, such as power supply 202 of Figure 2. The example method 700 may be performed by the control circuitry 220 of Figure 2 to implement block 608 of Figure 6. Prior to performing the method 700, the example control circuitry 220 has determined a positive ion duty cycle and a negative ion duty cycle based on the balance signal 304.

[0046] In block 702, the control circuitry 220 generates the positive control signal 216 based on the positive ion duty cycle to control a DC offset (e.g., of the DC offset generator 212). For example, the control circuitry 220 can hold the positive control signal 216 active (e.g., on) and the negative control signal 218 inactive (e.g., off) for the duration of the positive ion duty cycle.

[0047] At block 704, the DC offset generator 212 combines the high voltage high frequency AC signal (e.g., from the AC HV inverter 210) with a DC offset to control the ion output balance. For example, the DC offset generator 212 combines the high voltage high frequency AC signal with a DC offset generated based on the positive polarity control signal 216. For example, the AC HV amplifier 214 amplifies the combined DC offset and AC HVHF signal output to the emitter 206.

[0048] In block 706, the power supply 202 outputs the composite signal to generate positive ions for the duration of the positive ion duty cycle. For example, the emitter 206 generates positive ions while the DC offset generator 212 generates a positive DC offset based on the positive polarity signal 216.

[0049] Following the positive ion duty cycle (e.g., blocks 702-706), in block 708, control circuitry 220 generates the negative polarity control signal 216 based on the negative ion duty cycle to control a DC offset (e.g., of DC offset generator 212). For example, control circuitry 220 can hold the negative polarity control signal 218 active (e.g., on) and the positive polarity control signal 216 inactive (e.g., off) for the duration of the negative ion duty cycle.

[0050] At block 710, the DC offset generator 212 combines the high voltage high frequency AC signal (e.g., from the AC HV inverter 210) with a DC offset to control the ion output balance. For example, the DC offset generator 212 combines the high voltage high frequency AC signal with a DC offset generated based on the negative polarity control signal 218. For example, the AC HV amplifier 214 amplifies the combined DC offset and AC HVHF signal output to the emitter 206.

[0051] In block 712, the power supply 202 outputs a composite signal to generate negative ions for the duration of the negative ion duty cycle, for example, the emitter 206 generates negative ions while the DC offset generator 212 generates a negative DC offset based on the negative polarity signal 218.

[0052] The positive ion duty cycles and the negative ion duty cycles may be separated by off periods (eg, off periods 408) and / or may be interrupted by periodic pulses based on pulse signal 306 of FIG.

[0053] The method and system can be implemented in hardware, software, and / or a combination of hardware and software. The method and / or system can be implemented in a centralized manner in at least one computing system, or in a distributed manner where different elements are distributed across several interconnected computing systems. Any kind of computing system or other device adapted to perform the methods described herein is suitable. A typical combination of hardware and software can include a general-purpose computing system, with programs or other code that, when loaded and executed, controls the computing system to perform the methods described herein. Another typical embodiment can include application specific integrated circuits or chips. Some embodiments can include a non-transitory machine-readable (e.g., computer-readable) medium (e.g., flash drive, optical disk, magnetic storage disk, etc.), which stores one or more lines of code executable by a machine, thereby causing the machine to perform a process as described herein. As used herein, the term "non-transitory machine-readable medium" is defined to include all types of machine-readable storage media and to exclude propagating signals.

[0054] As used herein, the terms "circuitry" and "circuitry" refer to physical electronic components (i.e., hardware) and any software and / or firmware ("code") that may comprise, be executed by, and / or otherwise be associated with hardware. As used herein, for example, a particular processor and memory may include a first "circuitry" when executing a first one or more lines of code, and may include a second "circuitry" when executing a second one or more lines of code. As used herein, "and / or" refers to any one or more of the items in a list linked by "and / or". As an example, "x and / or y" refers to any element of the triplet {(x),(y),(x,y)}. In other words, "x and / or y" means "one or both of x and y". As another example, "x, y, and / or z" means any element of the seven-element set {(x),(y),(z),(x,y),(x,z),(y,z),(x,y,z)}. In other words, "x, y, and / or z" means "one or more of x, y, and z." As used herein, the term "exemplary" means serving as a non-limiting example, instance, or illustration. As used herein, the term "for example" begins a list of one or more non-limiting examples, instances, or illustrations. As used herein, whenever circuitry includes the necessary hardware and code (if either is necessary) to perform a function, the circuitry is "operable" to perform that function, regardless of whether implementation of that function is disabled or enabled (e.g., by a user-configurable setting, factory trim, etc.).

[0055] Although the method and / or system have been described with reference to certain specific embodiments, those skilled in the art will recognize that various modifications and equivalents may be substituted without departing from the scope of the method and / or system. For example, blocks and / or components of the disclosed examples may be combined, divided, rearranged, and / or otherwise modified. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the disclosure without departing from the scope of the disclosure. Thus, the method and / or system is not limited to the particular embodiments disclosed. Instead, the method and / or system includes all embodiments falling within the scope of the appended claims, both literally and under the doctrine of equivalents.

Claims

【Claim 1】 An apparatus for charge neutralization, comprising: a first emitter nozzle; a power supply configured to supply a high-frequency alternating current (AC) signal to the first emitter nozzle; a control circuit unit; and the control circuit unit is configured to: provide a polarity signal to the power supply to generate a DC offset signal, and the power supply outputs a cation generation pulse or an anion generation pulse by a combination of the high-frequency AC signal and the DC offset signal; control the polarity signal to cause the power supply to provide a cation generation period and an anion generation period; determine a balance voltage at the output of the first emitter nozzle; and control the polarity signal to adjust a relative duration between the cation generation period and the anion generation period based on the balance voltage.

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