KR102549253B1 - Silicon-based charge neutralization system - Google Patents

Abstract

An embodiment of the present invention includes generating a high frequency alternating current (AC) voltage; The high-frequency AC voltage is applied to at least one non-metallic radiator (300a) - the at least one non-metallic radiator includes at least 70% to 99.99% silicon by weight, and the at least one radiator has at least one oxide layer that is destroyed. comprising a treated surface portion (310a) of the -transferring; and generating ions from the at least one non-metallic emitter in response to the high frequency AC voltage. Another embodiment of the present invention provides a low emission charge neutralization device capable of performing the above operations.

Description

Silicon-based charge neutralization system

Cross reference to related applications

This application is filed on June 18, 2009 entitled "Silicon Emitter of Ionizer with High Frequency Waveform," claiming priority to US Provisional Patent Application Serial No. 61/132,422, filed on June 18, 2008. It is a continuation-in-part of filed US patent application Ser. No. 12/456,526, claiming priority to this US application. Both of the above US patent applications Ser. Nos. 12/456,626 and 61/132,422 are incorporated herein by reference.

Statement Regarding Federally Sponsored Research

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field of invention

The present invention relates primarily to ionizers used for static charge neutralization and control. More specifically, the present invention targets the need for reliable, low particle emission ionizers in the semiconductor, electronics and/or flat panel industries.

With the AC ionizer, each emitter receives a high positive voltage during one time period and a high negative voltage during another time period. Each emitter therefore generates a corona discharge with outputs of positive and negative ions.

Streams (clouds) of positive and negative ions are directed towards the charged target to neutralize the charge and avoid electrostatic charge related technical problems.

The background description provided herein is intended to generally present the subject matter of the present invention. To the extent that work is described in this background section, the work of the presently named inventor, as well as aspects of the description that are not recognized as prior art at the time of filing, are hereby admitted, either explicitly or implicitly, as prior art to the present invention. It doesn't work.

The charge neutralizer's ion emitter generates positive and negative ions and feeds them 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 an ionization cell, at least one electrode may be an ion emitter and the other may be a reference electrode. It is also possible that the ionization cell comprises at least two ionization electrodes.

Along with the useful positive and negative gas ions, the charge neutralizer's emitter can create and expel corona by-products containing unwanted particles. In semiconductor processing and similar clean processes, particle release/contamination is correlated with defects, product reliability issues and lost profits.

Several factors known in the art affect the amount of unwanted particles released. Some basic factors include, for example, the material composition, geometry and design of the ion emitter. A second factor includes the arrangement of the radiator connections to the high voltage power supply. Another important factor relates to the profile of the power applied to the ion emitter (magnitude and time dependence of high voltage and current).

The power waveform can be used to control the voltage profile applied to the emitter by the high voltage power supply. Voltage/current waveforms can be used to control ion generation and particle emission by the emitter.

Corona discharge can be excited by DC (direct current) voltage or AC (alternating current) voltage or a combination thereof. For many applications of the present invention, the preferred power waveform is the high frequency high voltage (HF-HV) output from a high frequency (HF) power supply as described below. This high voltage output can be continuous rather than uninterrupted. That is, the voltage output may change in amplitude over time or be disconnected periodically.

The material composition of the emitter is known to affect the particle emission level of the ionizer. Common emitter materials include stainless steel, tungsten, titanium, silicon oxide, single crystal silicon, silicon carbide, and other nickel or gold plated metals. This list is not exhaustive. In the experience of the inventors, metallic emitters may generate more particles as a result of corona related corrosion and spattering. Moreover, metallic or generally highly conductive particles are sometimes considered "killer particles" in the semiconductor industry (i.e., the particles can short-circuit closely spaced conductive traces of a wafer/chip). So, in the framework of this patent application, the inventors basically consider a non-metallic ion emitter as will be explained later.

In one of these materials, super clean (greater than 99.99% plus purity) single crystal silicon is proposed by Scott Gehlke in U.S. Patent No. 5,447,763 in view of low particle release. This monocrystalline silicon has been adopted by the semiconductor industry as the de facto clean emitter standard. Super clean silicon carbide (at least 99.99% pure) proposed in US Patent Application Publication No. 2006/0071599 by Curtis et al. is another non-metallic material. However, silicon carbide emitters are expensive and tend to emit undesirable particles.

Known ionizers with single crystal silicon emitters are powered by two high voltage DC power supplies. Systems such as the "NiLstat" 5000 (Ion Systems, Inc.), a room ionization system for cleanroom ceiling installations, typically produce less than 60 particles per cubic foot of air that are 10 nanometers (diameter) or larger. Other emitter materials typically produce more than 200 particles per cubic foot of air that are 10 nanometers (diameter) or larger. Some materials produce thousands of particles per cubic foot of air that are 10 nanometers (diameter) or larger.

Although some of (1) the components of the radiator material, (2) the components of the connector construction of the non-metallic radiator, and (3) the application of the special power waveform are known to be independently important, in the prior art it is difficult to achieve high ionization reliability and cleanliness. We did not consider the benefits of strategically combining these factors for

As a result of recent experiments by the inventors, the inventors have found a new combination that leads to stable ion generation and unexpectedly low level particle generation by the emitter. Clean and/or low particle emission ionizers have utility in several high tech industries. In particular, the semiconductor industry has a clearly defined need for super clean ionizers. Ionizers are needed to minimize static charges and electric fields that can destroy semiconductor devices. Particle emission as low as possible is also required because extraneous particles can damage the reliability of semiconductor devices. Advanced semiconductor technology builds 24-16 nanometer features on wafers. In the case of nanometer features, control of particles larger than 10 nanometers is absolutely necessary.

It should be understood that the foregoing general description in this background section is illustrative only and does not limit the invention defined in the claims.

As a result of recent experiments by the inventors, (1) the composition of the silicon-based material and the radiator design, (2) the arrangement and/or configuration of the radiator connectors, and (3) the type of power voltage waveform determine the reliable performance of the radiator and the radiator. It appears to be thought of as a complex new beneficial combination for low particle emission by The combination discovered by the inventors leads to stable ion generation and unexpectedly low level particle generation by the emitter. Clean and/or low particle emission ionizers have utility in several high tech industries. In particular, the semiconductor industry has a well-defined need for super clean ionizers. Ionizers are needed to minimize static charges and electric fields that can destroy semiconductor devices. Particle emission as low as possible is also required because extraneous particles can damage the reliability of semiconductor devices. Advanced semiconductor technology builds 24-16 nanometer features on wafers. In the case of nanometer features, control of particles larger than 10 nanometers is absolutely necessary.

Emitter electrode compositions comprising silicon-based materials, electrode connectors, and matching of power waveforms applied to the emitter have proven to be a novel method of achieving previously unattainable levels of reliability and cleanliness of charge neutralizing ionizers. The key to exemplary embodiments of the present invention is a non-metallic ion emitter having a material/chemical composition in the range of 70% to 99.99% silicon by weight, design and surface treatment (preparation) of the emitter electrode, connection arrangement of the emitter, and high voltage in the high frequency range. There is a combination of operations in the power supply and so on. In this combination, the high frequency high voltage power generates a corona discharge mode characterized by a low onset voltage. In one embodiment of the present invention, the ions generated from the at least one non-metallic emitter include positive and negative ions generated at a minimum starting HF voltage and power.

This combination is valid and applicable to many different types of cleanroom ionizers/charge neutralizers. As an example, the ionizer of one embodiment of the present invention can be thought of as an inline ionizer targeting a class 1 clean room production environment. The ionizer may have an inlet stream of clean dry air (CDA) or nitrogen, argon or other noble gases. The gas or air passes along the silicon-based emitter inside the ionization cell. The ionization cell/chamber is typically sealed except for the air/gas inlet and outlet openings.

The design of the inline charge neutralization ionizer according to the embodiment of the present invention can utilize a small power source such as a high frequency high voltage source. An output connector of the power supply receives at least one silicon-based radiator. The ionization cell produces clean bipolar ionization. The air stream (or nitrogen or argon stream or other gas stream) is sufficient to move the ions from the ionizing emitter (cell or chamber) to the target of charge neutralization.

The high-frequency voltage profile of the power supply has an AC frequency range of approximately 1KHz to 100KHz. The peak voltage exceeds the emitter's corona initiation voltage (negative and positive voltages). At high frequency AC, the emitter's ionic current is substantially limited by the electrical resistance of the silicon-based material.

In this application, high voltage is defined as the potential difference between the at least one ion generating electrode and the reference electrode. In some high frequency AC ionization cells, the reference electrode may be isolated from the ionization electrode by a dielectric wall. Therefore, the possibility of direct electron and ion avalanches (such as spark discharge) between the electrodes is substantially eliminated and particle emission from the emitter is greatly reduced. During the operating mode, ions are generated whenever the voltage amplitude exceeds the corona positive and negative starting voltages applied to the ionizing electrodes.

The other frequency (optional) is appropriate when the high frequency AC voltage profile is periodic rather than continuous. That is, a high frequency AC voltage exceeding the starting voltage contour is generated only within a predefined time interval. In this scenario, a high frequency AC voltage is applied to the emitter during the active time interval (typically less than about 0.01 second to about 1 second or more), but a voltage lower than the starting voltage may be applied during the inactive time interval. This optional high frequency voltage waveform may also include an inherently on/off high voltage mode. The normal undervoltage or on/off frequency range is approximately 0.1Hz to 500Hz, but frequencies can fall outside this range.

Some silicon-containing emitter compositions are provided as examples. These compositions are (a) doped crystalline silicon, (b) doped polysilicon, (c) a combination of doped silicon and silicon oxide, and (d) doped silicon deposited on a substrate. Dopants and additives are primarily aimed at controlling surface and volume electrical resistivity as well as mechanical properties of silicon-based emitters. They are preferably taken from a group of known non-metallic dopants such as boron, arsenic, carbon, phosphorus and other elements.

Accordingly, at least one exemplary embodiment of the present invention provides a method comprising generating a high frequency alternating current (AC) voltage; transmitting a high frequency AC voltage to at least one non-metallic radiator; A low emission charge neutralization method comprising generating ions from at least one non-metallic emitter in response to a high frequency AC voltage, wherein the at least one emitter is at least 70% silicon by weight to 99.99% by weight. less than silicon, and the at least one non-metallic emitter includes at least one treated surface portion having a destroyed oxide layer.

At least one illustrative embodiment of the present invention also provides an apparatus comprising elements allowing the functions described above. For example, one embodiment of the present invention provides a low emission charge neutralization device comprising from at least 70% silicon by weight to less than 99.99% silicon by weight, wherein the at least one non-metallic emitter is destroyed silicon and at least one treated surface portion having an oxide layer, wherein the at least one non-metallic emitter generates ions in response to a high frequency AC voltage.

It should be understood that the foregoing general description and the following detailed description are merely examples and do not limit the invention defined in the claims.

The accompanying drawings, which are incorporated in and constitute a part of this specification, show (several) embodiments of the present invention and, together with the description, serve to explain the principles of the present invention.

Non-limiting and non-exhaustive embodiments of the present invention will be described with reference to the accompanying drawings, in which like reference numerals denote like parts except where otherwise specified.
However, the accompanying drawings show exemplary embodiments of the present invention and are therefore not to be considered limiting of its scope, as the present invention may admit other equally effective embodiments.
1(a) is a view showing a conventional single crystal silicon ion emitter or (typically) a non-metallic ion emitter.
1(b) and 1(c) are views of conventional parts and assemblies of single crystal silicon radiators with metal sleeves and grooves.
2 is a diagram showing a conventional DC room ionizing ceiling system with two single crystal silicon radiators.
3(a) is a diagram showing a silicon-containing radiator according to an embodiment of the present invention, wherein the radiator includes a radiator shaft having a preselected surface roughness (or treated surface portion).
3(b) is a diagram showing a radiator according to another embodiment of the present invention, wherein the radiator includes a radiator shaft portion having a partially conductive surface plating or a partially conductive surface coating (or other type of treated surface portion).
3(c) is a diagram illustrating a device for monitoring surface electrical resistance and/or volume electrical resistance of a radiator and a silicon-containing radiator according to an embodiment of the present invention.
4(a) and 4(b) show a silicon-containing radiator having two variants of a radial compression spring sleeve and a metal pin, in accordance with various embodiments of the invention.
5(a), 5(b) and 5(c) show three silicon-containing radiators having different configurations of tapered portions and tips, according to various embodiments of the invention.
6 is a diagram showing HF waveforms for performing “soft” plasma cleaning of a tip of a silicon-containing emitter during a “start-up” of a corona ionization period, in accordance with an embodiment of the invention.
7(a), 7(b) and 7(c) are diagrams illustrating example high frequency power voltage waveforms applied to a silicon-based radiator during a mode of operation, in accordance with various embodiments of the invention.
8(a) and 8(b) show examples of modulated high frequency voltage waveforms in accordance with various embodiments of the invention.
FIG. 9( a ) shows an ionization cell/chamber of an inline ionizer according to an embodiment of the invention in which a high frequency AC power silicon based emitter generates both polarity ions and an air/gas flow displaces a stream of ions from the emitter; FIG. am.
9(b) is a diagram illustrating a gas channel and an ionization cell according to an embodiment of the present invention.
9(c) is a simplified block diagram of an inline ionizer having a silicon based radiator, in accordance with an embodiment of the invention.
10(a), 10(b), 10(c) and 10(d) show details of a nozzle having a simplified structure of a high frequency AC ionizing bar and a silicon-based ion emitter, in accordance with an embodiment of the invention. am.

In the following detailed description, for purposes of explanation, several specific details are set forth in order to provide a thorough understanding of the various embodiments of the present invention. Those skilled in the art will recognize that these various embodiments of the invention are illustrative only and are not intended to be limiting in any way. Those skilled in the art will readily conceive of other embodiments having the benefit of the present invention.

Also, for clarity, not all of the common features of the embodiments described herein are shown or described. Those skilled in the art will readily appreciate that the development of any such practical implementation will require many implementation-specific decisions to achieve particular design goals. These design goals will vary from implementation to implementation and from developer to developer. Moreover, it will be appreciated that such development efforts, while complex and time consuming, are nonetheless routine techniques taken to obtain the benefit of the present invention by those skilled in the art. The various embodiments disclosed herein are not intended to limit the scope and spirit of the invention.

Exemplary embodiments implementing the principles of the present invention are described herein with reference to the drawings. However, the present invention is not limited to the specifically described and illustrated embodiments. Those skilled in the art will understand that many other embodiments are possible without departing from the basic concept of the invention. The principles of the present invention therefore extend to any work falling within the scope of the appended claims.

As used herein, the terms "a" and "an" do not indicate a limitation of quantity, but indicate that there is at least one item recited.

Experimentally, inline ionizers combining (1) a silicon-containing emitter configured as a pin-type electrode in contact with a conductive socket and a capacitance (2) receiving a high-frequency AC voltage waveform (2) an electrically balanced ion gas with very few particles have been demonstrated. It has been found by the inventors to reliably create streams. The foregoing combination produces ionization with a level of reliability and cleanliness not otherwise achievable by conventionally known non-metallic silicon-containing emitters or high frequency AC voltage waveforms. Accumulated particles greater than 10 nm in diameter were measured during the cleanliness test. Particle counters (eg CNC condensation particle counters) did not separate the particles into size ranges.

For example, a cleanroom ionization system (such as a NiLstat ionization system) connected to a DC or pulsed DC (+/- 20 kV) power supply (disclosed in U.S. Pat. No. 5,447,763) (the system shown in FIG. 2). (similar to 200) produces approximately 60 particles (greater than 10 nanometers in diameter) per cubic foot of air. In contrast, ionizers of embodiments of the present invention typically yield less than 10 nanoparticles of the same diameter per cubic foot of air. Ten particles per cubic foot of air larger than ten nanometers is nominally six times cleaner than the cleanest conventional ionizer at the time of this application.

As a contrasting example, a metallic emitter (tungsten) was tested with a conventional system (eg, the system of US Pat. No. 5,447,763) and exhibited unacceptable cleanroom particle emissions. Our experiments using a tungsten radiator with a high frequency AC high voltage waveform similar to that proposed in US Patent Application Publication No. 2003/0007307 (inventor: Lee et al.) showed a significant improvement in cleanliness compared to the conventional system disclosed in US Patent No. 5,447,763. There was little profit. The particle concentration count results for both cases of testing the tungsten emitter were greater than 600 particles per cubic foot of air (greater than 10 nanometers).

However, high purity (99.99% plus purity) single crystal silicon radiators (such as the radiators shown in Figs. 1(a), 1(b) and 1(c)) have high electrical resistance (megaohm range). When this emitter is connected to a high frequency (HF) AC voltage source, sometimes ion production is not sufficient for effective charge neutralization. The main reason for this is that most of the HF (high frequency) current/voltage goes to the stray capacitor and not to the emitter tip.

One other problem associated with high purity (99.99% plus purity) single crystal silicon emitters is that the emitters tend to develop a surface oxide “skin” (the oxide layer or skin is the surface of the silicon emitter 101c in FIG. 1(c)). It is shown as a dotted line 102c encircling the surface). This skin/layer 102c is composed of highly insulating silicon oxide (SiO ₂ ). Silicon oxide growth on the surface of pristine silicon wafers is described in a publication, for example, by Stanford University, California under the name "Growth of native oxide" at the Stanford University Nanofabrication Facility dated August 28, 2003. explained.

The net result of the silicon oxide layer growth phenomenon is that the non-metallic silicon emitter/pin surrounded by the insulating layer does not have a good reliable connection with the electrical socket and thus is not connected to the high voltage output of the HF power supply.

Another non-metallic ion emitter is described in US Patent Application Publication No. 2006/0071599 to Curtis et al. This emitter is made of high purity 99.99% silicon carbide. This material is a composite containing about 30% carbon. Silicon carbide is known in the art to have high hardness. Silicon carbide is also expensive to process to produce as a finned emitter configuration. Silicon carbide also has high electrical conductivity in its metallic form. Conductive particles from composites with a high carbon content are often undesirable in the semiconductor industry.

The wide acceptance of silicon materials in the semiconductor industry means the relatively low cost of ion emitter materials. Moreover, the mechanical properties of silicon-based materials have simplified processing (cutting, polishing, etc.). Small concentrations of silicon dopants and additives are primarily aimed at improving the mechanical properties of silicon-based emitters as well as controlling surface and volume electrical resistance. These may preferably be taken from a group of known non-metallic dopants such as boron, arsenic, carbon, phosphorus and the like.

A silicone-based composition having a silicone component in a weight ratio of 70% to 99.99% made it possible to achieve an electrical resistance in the kilohm range of the emitter in an embodiment of the present invention. This resistance is low enough to conduct high-frequency currents and support steady corona discharge. Thus, two predetermined factors coherently interact to produce the observed cleanliness improvement: the composition and design of the silicon-based radiator, and the high frequency AC radiator drive power/voltage waveform.

One of the advantages of the combination of silicon-based emitters and HF voltage waveforms is that the onset voltage of the corona discharge is much lower (about 1000V~ 3000V or more).

A possible explanation for this effect is that in the high frequency range (about 1 kHz to over 100 kHz) the voltage applied to the emitter changes polarity in the millisecond range or in the microsecond range. This is why the corona charge carriers (positive and negative ions, electrons) do not have enough time to travel away from the emitter tip. Additionally, the specific surface charge retention (sometimes called "charge memory") property of silicon-based materials may play a role in electrode surface electron emission. This is the reason for the low positive and negative high frequency corona initiation voltages. Due to the lower voltage of the HF corona discharge, particle emission from silicon-based emitters is also low.

The scientific basis for improved particle emission in the corona discharge of equilibrating ionizers due to the interaction between the non-metallic silicon-based emitter and the high-frequency AC voltage waveform is currently being studied. Recognized theories of corona discharge and/or ionization and/or particle emission from non-metallic emitters do not predict or completely explain the observed experimental cleanliness.

However, it is clearly understood how to make and use the present invention. The following description is intended to explain to those skilled in the art of static charge control how to make and use the present invention.

Experimental work has shown that in some cases ionizers with new emitters or emitters that have not been used for a long time show problems in initiating HF corona discharges or reliably producing ion generation in combination with HF voltage waveforms and silicon-based emitter compositions. It relates to embodiments of the present invention that include. The measurement results indicate a high contact resistance between the silicon emitter and the electrical socket. This high resistance is one of the reasons for corona initiation problems in ionizers. The process of forming a relatively thick (10-100 or more angstroms) oxide "skin" on a silicon wafer in open air is described in "Natural Oxide Growth" of the Stanford University Nanofabrication Facility, described above. For example, in 6 days the SiO ₂ surface layer can reach a thickness of 12 Å. Silicon oxide is known to be a good insulator. So this skin growth results in higher surface and contact resistance of silicon-based emitters. Oxide layer growth rates are variable and oxygen and ozone concentrations (see "Oxidation of Silicon by Ozone" at web link http://iopscience.iop.org/0953-8984/21/18/183001/pdf/cm9_18_183001.pdf) , depends on many ambient atmospheric factors such as temperature, humidity, etc. Ozone is one of the by-products of corona discharge and can accelerate the oxidation of silicon emitters. This phenomenon has a sufficient effect for the relatively low power voltage of HF ionizers with silicon-based non-metallic emitters. An exemplary embodiment of the present invention includes surface treatment of a silicon-based radiator to lower contact resistance between the radiator and the metallic socket.

1(a) shows a conventional silicon radiator 100a. The radiator 100a includes four separate parts, namely, a tip portion 101a, a tapered portion 102a, a shaft 103a, and a tail portion 104a. The shape and size of the tip 101a depends on the available high voltage and current from HVPS (high voltage power supply), the material of the emitter, and the production technology and method. The emitter tip 101a is generally the most important part of any ion emitter. The radiator tip 101a is directly exposed to the corona discharge and determines the lifespan of the radiator. The silicon radiator has a generally cylindrical shaft 103a. The shaft 103a mainly defines the length of the radiator and the distance between the taper and the socket or receptacle connected to the high voltage power supply. The tapered portion or cone 102a is a transitional component between the tip portion 101a and the shaft 103a. Silicon is a brittle material in nature and the taper angle compromises the mechanical strength and electrical properties of the emitter. The tail portion 104a may be rounded, beveled, or torso. This part should make it easy to insert the radiator 100a into the socket or receptacle. Standard high purity silicon emitters have a smooth surface as a result of chemical polishing (which is usually achieved by a strong acid treatment).

1(b) shows a silicon radiator having a metallic sleeve. The silicon emitter 100a includes a stainless steel tube 102b (or sleeve 102b) with a non-metallic silicon portion 101b and a dimple 105b. The sleeve 102b must protect the brittle silicon radiator 101a from mechanical (handling) damage. The sleeve 102b should also improve the electrical connection of the non-metallic high purity silicon emitter and the metallic socket or receptacle. Reference numerals 103b and 104b show an assembled state of the silicon radiator 100a and the metallic sleeve 102b. Reference numeral 106b shows a cross-sectional view of the assembled radiator shaft 103a.

Most (or a substantial portion) of the silicon shaft 103b is inserted into the metal sleeve 102b as indicated by reference numeral 103b. In order to secure the sleeve 102b to the silicon shaft 103a and to achieve reliable electrical contact therebetween, it is common to make at least one projection 105b (dimple) in the sleeve 102b. Considering the tolerances of the dimensions of all three components (diameter of the silicon emitter shaft, inner diameter of the sleeve and depth of the dimple), the assembly operation is very demanding (see cross-sectional view of the silicon shaft and dimple, indicated at 106b).

1(c) shows another design of the silicon radiator 100c. Emitter portion 101c is shown as having a surface oxide layer ("skin") indicated by dotted lines. The radiator 100c includes a sleeve 103c having a silicon portion 101c and a dimple 104c. The sleeve 103c may have one or more cross sections/extensions 106c with grooves 107c. The radiator assembly is indicated by reference number 105c. This design makes it possible to retain the emitter within the nozzle and uses extension 106c to insert extension 106c into another socket or receptacle.

2 shows a conventional DC room ionization system 200 similar to that used in U.S. Patent No. 5,447,763. The ionizer has a pair of rods, namely, a positive (+) rod 201 and a negative (-) rod 202 supporting a single crystal silicon radiator. The load is connected to a dedicated positive and negative high voltage power supply (HVDC) device 103 (located within the chassis). A cross-sectional view of the emitter rod is shown at 204 . The end of the rod 202 has a high voltage cable 206 connected to an HV DC power supply 203 and a socket type connector 205. Socket 205 receives a silicon type radiator 207 indicated by reference numeral 204 . Another part of the rod 202 serves as a shield to protect the radiator 207, the connector 205 and the HV cable 206 from destructive force. The rod design makes the silicon radiators 201 and 202 interchangeable.

It is at least some goal of exemplary embodiments of the present invention to propose low particle emission by means of an economical silicon-based charge neutralization system. The composition of the silicon-based emitter with 70% to 99.99% silicon by weight along with high-frequency corona discharge makes it possible to achieve the goal of low particle emission. In the case of the non-metallic silicon electrode of the ionization system, the next major goal is to provide a reliable electrical connection between the silicon based emitter and the HF high voltage power supply.

FIG. 3( a ) shows a polishing or sand casting treatment part 310a (ie, a treated surface part 310a) of a shaft 301a into which a radiator 300a can be inserted into a high voltage socket (not shown). )), showing a silicon-based radiator 300a according to an embodiment of the present invention. This portion 310a of the shaft surface 302a has a roughness H in the range of approximately 0.5 microns to 10 microns (see 303a). During surface treatment, for example by sanding, the oxide "skin" pre-formed on shaft surface 302a will be destroyed and erased or otherwise removed. Sanding creates an emitter shaft surface contour that can make multi-spot contact with a high voltage socket (not shown). Optionally, a similar surface treatment may be applied to the rounded end 304a of the tail 314a of the emitter 300a. The radiator tip 305a, the taper 306a and the 311a portion of the shaft 301a have regular chemically polished surfaces.

Another embodiment of a silicon-based emitter is shown in FIG. 3(b). According to this embodiment of the present invention, the silicon-based radiator 300b is a portion 310b of the radiator shaft 301b having a metallic plating or metallic coating 302b (or a conductive plating or metallic coating 302b) treated surface portion 310b), which makes portion 310b of shaft 301b a good surface conductor and protects contact portion 316 of radiator 300b from long-term oxidation. The contact portion 316 may be at the tail portion 314b of the radiator shaft 301b.

Other known silicon plating methods (for example, plating methods such as vacuum deposition, electrolytic plating, spray, etc.) can be used. The plating material, such as metal, may include, for example, nickel, brass, silver, gold, and other metals as well as alloys acceptable to the semiconductor industry.

3(c) shows a silicon-containing radiator and a device for monitoring surface electrical resistance and/or volume electrical resistance of the silicon-containing radiator according to an embodiment of the present invention. This represents an example of an electrical quality control operation of the silicon-based radiator 300c as shown in FIG. 3(c). Control and/or monitoring includes electrical resistance measurement or monitoring the electrical resistance and/or composition of the emitter 300c or the treated surface portion 302c of the emitter 300c. The conductive electrodes 303c and 304c are attached to or connected to the sanded portion 302c (or the treated surface portion 302c) of the radiator shaft 301c and the tail portion 314c of the radiator 300c, respectively. A standard resistance (R) measuring device 305 may be used to measure the electrical resistance (R) and record the measurement. In this way, complex surface and volume resistivity and emitter composition can be monitored. The required normal quality and composition of a silicon-based emitter (having 70% to 99.99% silicon by weight) should have a composite resistance in the kilo ohm range. After surface treatment and control operations, the emitter 300c may be inserted into a standard metallic socket (not shown) to minimize the formation of a new layer of silicon oxide "skin".

At least some of the exemplary embodiments described herein can address two problems: (1) creating a reliable electrical connection between a non-metallic silicon-based radiator and a socket, and (2) protecting the radiator's contacts from oxidation. there is.

4(a) and 4(b) show a silicon containing emitter and metal fin with two variants of a radial compression spring sleeve, in accordance with various embodiments of the present invention. A silicon-containing emitter and metal fins are inserted into the sleeve as described below. The silicon-based radiator 400a of FIG. 4(a) according to an embodiment of the present invention will be described first. According to this exemplary embodiment, the radiator 400a includes a radiator portion 401a, and the silicon portion of the radiator portion 401a has a reduced length/shaft diameter ratio. A short silicon-based radiator portion 401a is connected to a metal radial compression spring sleeve 402a from one side 430 of the sleeve 402a. The other side 431 of the sleeve 402a is connected to a solid metal extension pin 403a. The metal pins 403a and 403b described herein may be metal electrodes 403a and 403b respectively inserted into the spring type sleeves 402a and 402b. This pin 403a may have at least one (or more) grooves and variable length "L2" required in socket and ionization cell (including reference electrode) designs. For example, pin 403a includes grooves 435 and 436, but in other embodiments pin 403a may have only one groove. Fin 403a may be, for example, a solid metal fin or tube. The pin 403a may be manufactured using a conventional CNC or automated metal cutter or other metal processing method. Reference numeral 405a shows an radiator assembly 410a having a silicon radiator 400a according to this exemplary embodiment. The radial compression spring sleeve 402a has a much larger contact area due to the silicon portion 401a compared to the conventional sleeve 102b having dimples 105b as shown in FIGS. 1(a) and 1(b). have As a result, a more reliable electrical connection is obtained and the mechanical stress applied to the brittle silicon radiator portion 401a is smaller. The design of a silicon emitter with a metal sleeve has some requirements to prevent "secondary" corona discharge from the edge of the sleeve to a nearby reference electrode. The main parameters to be considered are the diameter (D) of the silicon radiator shaft 440, the length (L) of the exposed portion 441 of the silicon radiator shaft 440, and the tapered portion ( 442) is the angle α of the taper and the thickness S of the sleeve 402a. For a high-concentration electric field at the radiator tip 421a of the silicon portion 401a (or the radiator tip 421b of the silicon portion 401b), the first S/D ratio should be within a range of approximately 0.03 to 0.06. . Another necessary condition related to the distance between the radiator tip 421a and the sleeve 402 is the second L/S ratio, which is (2 to 5)/tan {tangent} (0.5α). must be within range. The parameter α is the angle of the taper of the tapered portion of the shaft 440 of the at least one non-metallic radiator portion 401a or 401b. These conditions of the new silicon emitter design according to an embodiment of the present invention will satisfy several criteria/specifications. That is, reliable electrical connections, good mechanical strength, and a minimal probability of "secondary" corona will result in particle emission from the metal parts.

Figure 4(b) shows another embodiment of a silicon-based radiator 400b that includes a metallic radial compression spring sleeve 402b of a different configuration. In this case, the radiator 400 includes a silicon radiator portion 401b having a diameter D1, and one end 461 of the metal sleeve 402b has a diameter D3. The silicon radiator portion 401b has a radiator tip portion 421b. Portion 403b is a solid metal pin 403b with diameter D4 and the other end 462 of metal sleeve 402b has diameter D2. The difference between the diameters of the silicon radiator portion 401b and the metal sleeve 402b (D1 > D3) provides the necessary compressive force to provide reliable and good electrical contact between the silicon portion 401b and the metal sleeve 402b. . Similarly, the difference between the diameters (D2 < D4) provides reliable and good electrical contact between the metal sleeve 402b and the metal pin 403b. Reference numerals 404b and 406b show assembled silicon radiators 400b. Reference numeral 405b is a cross-sectional view showing the silicon radiator 401b and the sleeve portion 402b having a large contact area with minimal contact pressure and local stress, according to this exemplary embodiment. The assembly operation is simplified. Both exemplary embodiments (emitters 400a, 400b) use a minimal amount of expensive silicon-based material, have a large reliable contact area between the non-metallic emitter shaft and the metal sleeve, and good dimensions for a standard socket or receptacle. have consistency

In some cases, silicon based radiators have problems initiating high frequency corona discharges and reliably produce ion generation despite having normal standard/volume electrical resistance and good electrical connections to high voltage sockets. According to our experiments, the crux of this problem is due to the formation of a thick insulating oxide "skin" on the surface of the emitter tip (the "working hose" of the emitter). One or more exemplary embodiments of the present invention address this problem. The shape of the tip of the silicon-containing emitter can have some positive effect on the formation rate and thickness of the isolating oxide “skin”.

5(a), 5(b) and 5(c) show three silicon-containing emitters having different configurations of tapered and pointed ends, in accordance with various embodiments of the present invention. The various tip and taper configurations shown in FIGS. 5(a), 5(b) and 5(c) determine the operating HF corona initiation voltage and ionization current parameters.

5(a) shows a silicon-based emitter 501 having a flat truncated tip. This tip design tends to produce an annular, high-frequency corona discharge (flat tip 510 meets tapered portion 511 of emitter 501). This emitter 501 can reduce ionic current density and particle emission. However, it is characterized by a higher starting HF corona voltage. The tapered portion 511 has an angle of α with respect to the flat tip portion 510 .

The silicon-based emitter 502 (FIG. 5(b)) has a small rounded tip 514 with a radius Z ranging from approximately 60 microns to 400 microns, which is cheaper to manufacture and minimizes corona current fluctuations. . A tapered portion 516 (of the radiator 502) extends from a small rounded tip 514.

A sharp silicon-based emitter 503 (FIG. 5(c)) has a pointed tip 520 having a radius Y ranging from approximately 40 microns to 50 microns or less. This emitter 503 has the lowest corona initiation voltage (V _on ). However, the ionic current density of emitter 503 is the highest, and spatter, corrosion, and oxide "skin" growth have the highest rates. This silicon based emitter 503 is preferably used for ionization in oxygen free gases such as nitrogen or argon. The tapered/conical portion 521 of the emitter 503 preferably has an angle α with respect to the pointed tip 520 ranging from approximately 10 degrees to 20 degrees. All silicon-based emitters 501, 502, 503 have compositions according to exemplary embodiments of the present invention and will provide low particle count when installed in inline ionizers, ionization bars and other charge neutralizers powered by HF AC voltages. can The degree of sharpness and curvature of the tip (i.e., the configuration of the tip) determines or affects ionizer operating parameters including initiation voltage, ion current and ion balance, but does not affect the scope of the present invention.

One or more exemplary embodiments of the present invention address oxide "skin" growth at the tip of a silicon emitter. Embodiments use a specific mode of corona discharge to clean the silicon emitter tip from the oxide skin and assist in starting the ionizer independent of the emitter contour.

6 shows an HF waveform performing a “soft” plasma cleaning of a tip of a silicon-containing emitter during the “start-up” of a corona ionization cycle, in accordance with an embodiment of the present invention.

A high voltage “HF start” type waveform 600 is applied to the emitter. This high voltage drive mode provides groups of short duration dipole voltage bursts (numbered from 1 to hundreds of dipole pulses 605) to the emitter during the start-up period (denoted as the Ts period). Due to the very short duration of the power contour, in the range of milliseconds, microseconds or less, the HF corona associated with the plasma has very limited energy. This method prevents both the temperature rise of the emitter tip and the surface destruction (splashing, corrosion and particle emission) of the emitter tip. The short duration HF plasma burst performs only "soft" cleaning of the emitter tip from the silicon oxide skin. The duration of the “start-up” time period Ts, burst pulse amplitude and number of pulses can vary and depends on the thickness of the silicon oxide skin, gas medium, emitter tip design, and the like. The voltage amplitude of the HF burst pulse is greater than the normal (operating) corona-initiating positive (+)Von and negative ((-)Von) voltages (shown in FIG. 6 by two horizontal dotted lines 610 and 615, respectively). much higher (about 25% to 100% or more). An initial “start-up” mode helps initiate normal/operating high-frequency corona discharges and ion generation. During normal/operating mode (during time Top). The high voltage amplitude can be only 10-20% higher than the corona initiation voltage (+)Von or (-)Von to minimize particle emission. In continuous mode of operation, HF corona discharge can protect the silicon emitter from oxidation in a clean dry gas medium. Therefore, soft plasma cleaning of the at least one non-metallic emitter is performed during the start-up period of the corona ionization period by a voltage/power waveform different from the voltage/power waveform during the operating period.

7(a), 7(b) and 7(c) show examples of high frequency power voltage waveforms applied to a silicon-based radiator during a mode of operation, in accordance with an embodiment of the invention. Different operating HF voltage waveforms effectively create dipole ionization of silicon-based emitters. The function of the high-frequency AC voltage is to generate positive ions (positive and negative ions) with a minimum driving voltage. To generate ions, the peak voltage (positive and negative peak voltage) exceeds the corona onset voltage. As shown in FIG. 7(a), the high frequency AC voltage contour 700 is continuous, but the contour can also be modulated continuous, discrete and periodic.

Figure 7(a) shows a continuous sinusoidal power voltage 700 having a frequency range from approximately 1 kHz up to approximately 100 kHz. The positive and negative voltage amplitudes of the voltage 700 are higher than the positive corona onset voltage (+)Von 705 and lower than the negative corona onset voltage (-)Von 710 . This type of voltage waveform 700 provides maximum power and produces maximum ion current for the silicon-based emitter described herein.

FIG. 7( b ) shows a voltage waveform 750 comprising a group of pulse trains 752 having “on” periods 755 and “off” periods 756 . Waveform 750 includes at least one modulation section, each modulation section including a train of pulses 752 having on periods 755 and off periods 756. During the on-period 755 of the pulse train 752, the waveform 750 has an amplitude 758 that exceeds the positive corona initiation voltage threshold 705 and exceeds the negative corona initiation voltage threshold 710 of the particular emitter. . During the off period 756 of the pulse train 752, the waveform 750 has an amplitude 760 that does not exceed the corona onset voltage thresholds 705 and 710. In the example of FIG. 7( b ), this amplitude 760 is a voltage of approximately zero magnitude. Additional details of the waveforms 700, 750, and 780 shown in FIGS. 7(a), 7(b) and 7(c) are in commonly assigned and commonly owned U.S. Patent No. 8,009,405 to Peter Gefter et al., respectively. Also described in During the "off" period 756 (which may be a small duty factor) corona discharge (ion generation) and particle emission cease. The duty cycle can vary from about 100% down to about 0.1% or less depending on the ion power required. A minimum impact factor helps to control particle emission rates and emitter erosion rates.

7(c) shows that the duty cycle is close to 100%, but the voltage amplitude applied to the silicon emitter is periodic at a voltage lower than the corona initiation voltage (ranging from about 90% to about 50% or less from the corona initiation voltage). Another variant of the voltage waveform 780 falling to . The advantage of this waveform is that it can minimize particle emission and high voltage swings (voltage/field fluctuations).

Waveform 780 includes at least one modulating section, each modulating section including a train of pulses 782 having on periods 785 and inactive periods 786. During the on-period 785 of the pulse train 782, the waveform 780 exceeds the positive corona initiation voltage threshold ((+)Vmax) 705 and the negative corona initiation voltage threshold ((-)Vmax) of the particular emitter. has an amplitude 788 exceeding (710). During the inactive period 786 of pulse train 782, waveform 780 has amplitude 790 that does not exceed corona onset voltage thresholds 705 and 710, but amplitude 790 is greater than zero volts.

8(a) and 8(b) show examples of modulated high frequency voltage waveforms according to an embodiment of the present invention. 8(a) shows a continuous modulated waveform 800 as a result of mixing (combination) of a high frequency voltage and a low frequency voltage. The low frequency component (or offset voltage) is shown in Fig. 8(b). This voltage waveform 850 generates ions predominantly by the high frequency component (similar to waveform 700 shown in Fig. 7(a)) and moves ions away from the emitter by the low frequency component.

In-line ionizers with silicon-based emitters can be used in the semiconductor industry's most critical operations/processes (eg, airborne particulate cleanliness class 1 environments). 9(a), 9(b) and 9(c) show a simplified diagram of an ionization cell and a block diagram of an inline ionizer. With the in-line ionizer design, the application of the HF frequency voltage can be similar to the waveform shown in Fig. 8(a) extending in the range from approximately 20 kHz up to approximately 100 kHz.

9(a) shows an ionization cell/chamber of an inline ionizer according to an embodiment of the present invention. A high frequency AC power silicon based emitter 902a generates ions of both polarities. Air/gas flow 908a displaces the stream of ions from emitter 902a. As shown in Fig. 9(a), an ionization cell 900a is connected to a HF HV generator 901a. A silicon-based radiator 902a is located in the socket 903a and connected through a capacitor C1 connected to the HF generator 901a. The radiator 902a may have a sanded or metal plated portion of the shaft as described above with respect to FIGS. 3(a) and 3(b), respectively, to provide a reliable connection to the socket 903a.

Emitter 902a is typically positioned in the middle of air/gas channel 904a. Preferably, the reference electrode 905a is located outside of the channel 904a and close to the outlet 906a of the channel 904a. The reference electrode 905a is connected to the control system 907a. Positive ions 920 and negative ions 921 are generated by emitter 902a when the peak voltage (positive or negative voltage) of the high frequency AC voltage (applied to emitter 901a) exceeds the corona initiation voltage. An air/gas flow 908a from an external source (not shown) is still needed to move the generated ion cloud toward distant target charge neutralization (not shown). The corona discharge near the tip 909a of the emitter 902a creates a high-concentration HF plasma 910a with ions and electrons near the tip 909a of the silicon emitter 902a. The corona initiation voltage is approximately (+)5~6kV for positive ions and (-)4.5~5.5kV for negative ions.

Generation/emission corona by-products, such as particles in the plasma, are minimized by the methods, apparatus, and instrumentalities described above as a combination of ion emitter composition, ion emitter design, and power voltage waveform.

9(b) shows another view 900b of the ionization cell and gas channel in block 901b, in accordance with an embodiment of the present invention. Channel 902b has an inlet 933b and an outlet 934b. A silicon based emitter 905b with socket 906b may be fabricated as an interchangeable unit positioned within cavity 960 of channel 902b. The emitter socket 906b and the reference electrode 907b are connected to a high voltage HF power supply 908b. The ionizing gas flow (indicated by arrow 961) moves the ion cloud toward a charged target 909b, such as a wafer, and the ion cloud will neutralize these charges on the charged target 909b.

9(c) shows a simplified block diagram of an inline ionizer 900c with a silicon-based radiator 904c in accordance with an embodiment of the present invention. Cations and anions 901c are generated inside ionization cell 902c. A high voltage HV-HF power supply 903c provides the voltage and current required to generate ions 901c. Power supply 903c delivers a high frequency AC voltage through capacitor C1 to silicon-based radiator 904c. The voltage at the silicon-based emitter 904c is related to the reference electrode 905c.

A source of compressed air, nitrogen or argon is connected to the inline ionizer 900c through an inlet to create an air stream or gas stream 906c. Air stream or gas stream 906c entrains positive and negative ions 901c and directs the ions 901c through ionizer outlet 934c to a target (e.g., target 909b in FIG. 9(b)). transport towards

The inline ionizer 900c has a control system 907c that includes a microprocessor 908c, a gas pressure sensor 909c, a corona discharge sensor 910c and an operating status indicator 911c. The inline ionizer 900c often works in semiconductor tools having wafer load/unload operations. The reason is that the inline ionizer 900c can have a relatively long idle ("stand off") period without corona discharge and gas flow. During such a period of time, a silicon oxide layer may grow at the tip of the silicon emitter. As already described with respect to the exemplary embodiment shown in FIGS. 3( a ) and 6 , control system 907c initiates the gas ionization process by starting high voltage power supply 903c in “start-up” mode. Corona discharge sensor 905c and processor 908c continue to monitor the corona discharge status until strong and stable corona and ion production is achieved. After that, the control system 907c and power supply 903c are switched to normal operation mode.

10(a), 10(b), 10(c) and 10(d) show a simplified structure of a high frequency AC ionizing bar 1000a and a nozzle having a silicon-based ion emitter, according to an embodiment of the present invention. it showed details. 10(a) and 10(b) show, as an example, a high frequency AC ionization bar 1000a having a plurality of raw silicon-based radiators 1001a-1008a. Each silicon emitter has a stainless steel sleeve. The stainless steel sleeve is shown as sleeve 1020c in FIG. 10(c) and as sleeve 1020d in FIG. 10(d). Each stainless steel sleeve 1020a is installed in a nozzle. Each nozzle has a socket and optionally one or two air/gas jet orifices. A cross-sectional view of the nozzle is shown as nozzle 1030c in FIG. 10(c) and as nozzle 1030d in FIG. 10(d).

Socket 1009c is connected to a common high voltage bus located inside enclosure 1010a of ionization bar 1000a and an orifice to a manifold (not shown). Cross section 1040 of nozzle 1030d shows the relative position of silicon emitter 1003d (with sleeve and groove as described above with respect to FIGS. 4(a) and 4(b)) and orifice 1004d. . The bus distributes HF power from the high voltage AC power supply to each nozzle and emitter. The HF-HV power supply with the microprocessor based control system is preferably located within the same enclosure 1010a. The silicon-based ion emitter receives an HF AC voltage ranging from approximately 6 kV to 8 kV with a fundamental frequency of approximately 10 kHz to 26 kHz (similar to that shown in Fig. 7(a)). This HF high voltage generates a corona discharge between each of the radiators 1001a to 1008a and the reference electrode 1011a. This high-frequency AC voltage is sufficient to produce clean dipole ionization when emitter compositions in the range of 70% to 99% silicon are used. As mentioned above, high frequencies by themselves cannot move the ion cloud very far. The HF ionizing bar 1000a is often installed in a flat panel or semiconductor tool at a relatively short distance from the target (e.g., approximately 50 mm to 300 mm). In this case, the electric field of a charged target (not shown) attracts ions of opposite polarity. However, for efficient charge neutralization at longer distances (eg, approximately 400 mm to 1500 mm), ion clouds require assistance from air/gas flows or electric fields or combinations thereof. Sometimes an HF ionization bar can be used with a HEPA filter to provide a laminar flow of clean air.

FIG. 8(a) shows a modulated HF waveform 800 that creates an additional low frequency field (with a frequency of about 0.1 Hz to 200 Hz) to aid ion transport to the target. During the T2 period, the amplitude 802 of the positive voltage wave 804 and the amplitude 806 of the negative voltage wave 808 are almost equal, so the offset voltage is close to zero and the ion cloud oscillates near the silicon emitter. In contrast, during a period such as T1, the voltage waveform 800 has a positive offset 810, and the (repelled) bipolar ion cloud moves toward the target (see FIG. 8(b)). Similarly, during a period such as T3, the voltage waveform 800 has a negative offset 815 and the (repelled) cathode ion cloud moves toward the target. The amplitude and frequency of the offset voltage depends on the distance between the ionization bar 1000a and the target.

The high frequency ionization bar 1000a with a silicon based emitter produces low emission, clean air/gas ionization, eg charges of large objects moving at high speed (such as flat panels) over distances of approximately 400mm to 1500mm. can neutralize them.

Another embodiment of the present invention provides a low emission charge neutralization method, wherein at least one of the aforementioned non-metallic emitters has a reduced silicon section length/shaft diameter ratio.

Another embodiment of the present invention provides a low emission charge neutralization method, wherein the aforementioned sleeve comprises a metal radial compression spring sleeve, and the difference between the diameters of at least one radiator, a metal pin, and the sleeve is at least one radiator; It creates a compressive force that provides a reliable electrical connection between the sleeve and the metal electrode.

Another embodiment of the present invention provides a low emission charge neutralization device, wherein at least one of the aforementioned non-metallic emitters has a reduced length/shaft diameter ratio.

Another embodiment of the present invention provides a low emission charge neutralization device, wherein the aforementioned sleeve comprises a metal radial compression spring sleeve, and the difference between the diameters of at least one radiator, a metal pin, and the sleeve is at least one radiator; It creates a compressive force that provides a reliable electrical connection between the sleeve and the metal electrode.

Another embodiment of the present invention is a non-metallic ion emitter having a chemical composition in the range of at least 70% to 99.99% silicon by weight, emitter geometry and surface treatment (preparation), and connection arrangement between a high voltage power supply device operating in the high frequency range and the emitter. The combination provides an apparatus and method for producing a reliable and low particle emission charge neutralizer. With this combination, the emitter reliably generates a high-frequency corona discharge characterized by a low starting voltage and low particle emission. This combination is effective for many different types of cleanroom ionizers/charge neutralizers targeting Class 1 cleanrooms. The combination of a silicon-containing emitter and a high frequency AC voltage creates an ionizer that is cleaner than conventional ionizers based on particle counts greater than 10 nanometers. This improvement in cleanliness was experimentally determined by the inventors.

The foregoing description of exemplary embodiments of the invention, including what is set forth in the Summary section, is not intended to be exhaustive or to limit the invention to the precise forms disclosed. While specific embodiments and examples of the present invention have been described herein for explanatory purposes, various equivalent modifications are possible within the scope of the present invention, as will be appreciated by those skilled in the art.

Such modifications may be made to the present invention in light of the foregoing detailed description. Terms used in the claims below should not be construed as limiting the invention to the specific embodiments disclosed in the specification and claims. Rather, the scope of the present invention is to be determined entirely by the following claims, to be interpreted in accordance with established doctrines of claim interpretation.

Claims (20)

A method for low emission charge neutralization, comprising:
generating a high frequency alternating current (AC) voltage;
sending the high frequency AC voltage to at least one non-metallic emitter;
said at least one non-metallic emitter comprises greater than 70 weight percent and less than 99.99 weight percent silicon;
transmitting the high frequency AC voltage to the at least one non-metallic emitter, wherein the at least one non-metallic emitter comprises at least one treated surface section having a destroyed oxidation layer. step; and
generating ions from the at least one non-metallic emitter in response to the high frequency AC voltage;
including,
A method for low emission charge neutralization wherein an emitter shaft comprising a silicon based section and a metal electrode is inserted into a spring type sleeve. 2. The method of claim 1, wherein the at least one treated surface portion of the at least one non-metallic emitter comprises an area having a preselected roughness due to an abrasive or sanding processing. method. The method of claim 1 , wherein the treated surface portion comprises metallic plating or metallic coating. The method of claim 1 , further comprising providing a measurement device for monitoring the electrical resistance and composition of the at least one non-metallic emitter. delete 2. The method of claim 1, wherein the at least one non-metallic emitter comprises a tip configuration and a tapered configuration, both of which are operating high frequency (HF) determining corona onset voltage and ionization current parameters. 2. The method of claim 1, performing plasma cleaning of the at least one non-metallic emitter during a start up period of a corona ionization period by a voltage/power waveform different from a voltage/power waveform during an operating period. Further comprising a method. The method of claim 1 , wherein generating the ions comprises generating positive ions and negative ions with a minimum onset HF voltage and power during an operating period. According to claim 1,
the at least one non-metallic emitter comprises a first ratio (S/D) in the range of 0.03 to 0.06;
where S is the thickness of a sleeve containing said at least one non-metallic emitter;
D is the diameter of the shaft of the at least one non-metallic emitter. According to claim 1,
the at least one non-metallic emitter comprises a second ratio (L/S) in the range of (2 - 5)/[tan{tangent} (0.5α)];
where L is the length of the exposed portion of the shaft of the at least one non-metallic emitter;
S is the thickness of a sleeve containing said at least one non-metallic emitter;
wherein α is the angle of the taper of a tapered portion of the shaft of the at least one non-metallic emitter. A device for neutralizing low-emission charges,
at least one non-metallic emitter comprising greater than 70 weight percent and less than 99.99 weight percent silicon;
said at least one non-metallic emitter comprising at least one treated surface portion having a destroyed silicon oxide layer;
the at least one non-metallic emitter generates ions in response to a high frequency AC voltage;
wherein said at least one non-metallic emitter and a metal electrode are inserted in a spring-type sleeve. 12. The apparatus of claim 11, wherein the at least one treated surface portion comprises an abrasive processed portion or a sanded processed portion. 12. The apparatus of claim 11, wherein the at least one treated surface portion comprises a metallic plating or metallic coating. 12. The apparatus of claim 11, wherein the electrical resistance and composition of the at least one treated surface portion relative to the at least one non-metallic emitter is monitored. delete 12. The method of claim 11, wherein the at least one non-metallic emitter comprises a tip feature and a tapered feature, both the tip feature and the tapered feature determining operating HF corona onset voltage and ionization current parameters. Device. 12. The apparatus of claim 11, wherein the soft plasma cleaning of the at least one non-metallic emitter is performed during a startup period of a corona ionization period with a voltage/power waveform different from a voltage/power waveform during an operating period. 12. The apparatus of claim 11, wherein the ions include positive ions and negative ions generated with a minimum HF onset voltage and power. 12. The method of claim 11, wherein the at least one non-metallic emitter comprises a first ratio (S/D) in the range of 0.03 to 0.06,
where S is the thickness of a sleeve containing said at least one non-metallic emitter;
wherein D is the diameter of the shaft of the at least one non-metallic emitter. 12. The method of claim 11, wherein the at least one non-metallic emitter comprises a second ratio (L/S) within the range (2 - 5)/[tan{tangent} (0.5α)],
where L is the length of the exposed portion of the shaft of the at least one non-metallic emitter;
S is the thickness of a sleeve containing said at least one non-metallic emitter;
wherein α is the angle of taper of the tapered portion of the shaft of the at least one non-metallic emitter.

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