阅读说明：本技术 高功率射频螺旋线圈滤波器 (High-power radio frequency spiral coil filter ) 是由 肖恩·凯利·奥布莱恩 赫马·斯沃普·莫皮迪维 赛义德·贾法·雅法良-特哈妮 尼尔·马丁·保罗· 于 2018-12-14 设计创作，主要内容包括：各种实施方式包含一种用于过滤基于等离子体的处理设备中的射频的装置。在各种实施方式中,RF滤波器装置包含以间隔开的布置彼此电耦合并基本平行的多个基本平面的螺旋滤波器。在一个实施方式中,基于接连螺旋的布置,平面螺旋滤波器中的每一个作为内部到内部的电连接或外部到外部的电连接被耦合到平面螺旋滤波器中的一个相邻螺旋滤波器,以便增加总电感值。公开了其他方法、装置、设备和系统。(Various embodiments include an apparatus for filtering radio frequencies in a plasma-based processing device. In various embodiments, an RF filter device includes a plurality of substantially planar spiral filters electrically coupled to one another in a spaced apart arrangement and substantially parallel. In one embodiment, each of the planar spiral filters is coupled to an adjacent one of the planar spiral filters as an internal-to-internal electrical connection or an external-to-external electrical connection based on an arrangement of successive spirals to increase a total inductance value. Other methods, apparatuses, devices and systems are disclosed.)

1. A Radio Frequency (RF) filter device, comprising:

a plurality of substantially planar spiral filters electrically coupled to one another in a spaced-apart arrangement, each of the plurality of substantially planar spiral filters being coupled to an adjacent one of the substantially planar spiral filters as an internal-to-internal electrical connection or an external-to-external electrical connection, the plurality of substantially planar spiral filters being arranged in a successive configuration.

2. The radio frequency filter device according to claim 1, wherein the substantially planar spiral filters are stacked substantially parallel to each other.

3. The radio frequency filter device according to claim 2, wherein the substantially planar spiral filter further comprises an air core.

4. The radio frequency filter device according to claim 2, wherein the substantially planar spiral filter further comprises a ferromagnetic core material.

5. The radio frequency filter device of claim 1, wherein each of the substantially planar spiral filters comprises a twisted wire configuration capable of handling about 500 watts to about 50 kilowatts.

6. The radio frequency filter device of claim 1, wherein the plurality of substantially planar spiral filters provide impedance values from about 500 ohms to about 10 kiloohms.

7. The radio frequency filter device of claim 1, wherein the plurality of substantially planar spiral filters reduce low frequency RF power in a range of about 100kHz to about 3 MHz.

8. The radio frequency filter device according to claim 1, wherein distances between adjacent ones of the plurality of substantially planar spiral filters are substantially equal.

9. The radio frequency filter device of claim 1, wherein a distance between adjacent ones of the plurality of substantially planar spiral filters varies.

10. The radio frequency filter device of claim 9, wherein the distance between adjacent ones of the plurality of substantially planar spiral filters varies to increase convective cooling from each of the substantially planar spiral filters.

11. The radio frequency filter device of claim 9, wherein a distance between adjacent ones of the plurality of substantially planar spiral filters varies to change a total inductance value of the RF filter device.

12. The radio frequency filter device according to claim 1, wherein a pitch of at least one of the plurality of substantially planar spiral filters is radially uniform in all portions of the spiral filter.

13. The radio frequency filter device of claim 1, wherein a pitch of at least one of the plurality of substantially planar spiral filters is different from a pitch of an adjacent one of the plurality of substantially planar spiral filters.

14. The radio frequency filter device of claim 1, wherein a pitch of at least one of the plurality of substantially planar spiral filters varies radially from one section of the spiral filter to another section.

15. A system, comprising:

a low frequency Radio Frequency (RF) filter coupled to an electrostatic chuck in a plasma processing system, the RF filter substantially blocking RF frequencies in a frequency range of about 100kHz to about 3MHz, the RF filter having a plurality of substantially planar spiral filters electrically coupled to one another in a spaced apart arrangement; and

a high frequency RF filter arranged in a solenoid to substantially block RF frequencies above about 3 MHz.

16. The system of claim 15, wherein each of the substantially planar spiral filters is coupled to an adjacent one of the substantially planar spiral filters as an internal-to-internal electrical connection or an external-to-external electrical connection.

17. The system of claim 15, wherein each of the substantially planar spiral filters comprises a first portion and a second portion; and wherein each of said substantially planar spiral filters has a substantially constant pitch with substantially parallel curves from said first portion to said second portion.

18. The system of claim 15, wherein each of the substantially planar spiral filters comprises a first portion and a second portion; and wherein each of the planar spiral filters has a pitch that varies from the first portion to the second portion.

19. The system of claim 15, wherein the pitch of each of the substantially planar spiral filters approximates an archimedean spiral.

20. The system of claim 15, wherein the low frequency RF filter and the high frequency RF filter are physically sized for placement within an RF filter housing in a plasma-based processing system.

21. A Radio Frequency (RF) filter device, comprising:

a plurality of substantially planar spiral filters electrically coupled to each other in a spaced apart arrangement and parallel to each other, each of the plurality of substantially planar spiral filters having a twisted wire configuration capable of handling about 500 watts to about 50 kilowatts.

22. The radio frequency filter device of claim 21, wherein each of the plurality of substantially planar spiral filters is coupled to an adjacent one of the substantially planar spiral filters as an internal-to-internal electrical connection or an external-to-external electrical connection based on an arrangement of successive ones of the plurality of substantially planar spiral filters.

23. The radio frequency filter device according to claim 21, wherein each of the substantially planar spiral filters is arranged to increase constructive interference of magnetic circuits between adjacent ones of the substantially planar spiral filters.

24. The radio frequency filter device according to claim 21, wherein each of the plurality of substantially planar spiral filters is based on an air-core design.

25. A Radio Frequency (RF) filter device, comprising:

a plurality of substantially planar spiral filters electrically coupled to one another in a spaced-apart arrangement, each of the plurality of substantially planar spiral filters being coupled to an adjacent one of the substantially planar spiral filters as either an internal-to-external electrical connection or an external-to-internal electrical connection, adjacent ones of the plurality of substantially planar spiral filters being wound in opposite directions from one another, the plurality of substantially planar spiral filters being arranged in a successive configuration.

26. An apparatus comprising a low frequency Radio Frequency (RF) filter to substantially block RF frequencies in a frequency range of about 100kHz to about 3MHz and at power levels of about 500 watts to about 50 kilowatts, the RF filter having a plurality of substantially planar spiral filters arranged as a hollow device.

Technical Field

The subject matter disclosed herein relates to coils for blocking high power Radio Frequency (RF) signals in plasma processing systems.

Background

Traditionally, coils for low RF frequencies have employed ferromagnetic cores to reduce the length and volume of the inductor coil. However, one of ordinary skill in the art recognizes that ferromagnetic materials have frequency-dependent electrical, magnetic, and thermal properties. Furthermore, coils using these ferromagnetic core designs have shown poor performance repeatability unless strict engineering guidelines are incorporated. These strict guidelines increase the cost of coil production. In addition, custom machined ferromagnetic structures further increase production costs, if desired. As an alternative to coils with ferromagnetic cores, coils with larger air cores may be used. However, air-core coils are typically much larger than equivalent coils based on ferromagnetic cores. Therefore, air-core coils have traditionally been used only where space limitations are not an issue.

The requirements of next generation etch tools, as well as other processing tools, require additional performance characteristics within nearly the same form factor (form factor) as the current generation etch tools. Thus, conventional air core coils generally cannot be justified due to their increased physical size. Therefore, a compact solution for RF frequency coils would be needed, which is also suitable for high power applications. The information described in this section is provided to provide the skilled person with a context for the following disclosed subject matter and should not be taken as admitted to be prior art.

Drawings

FIG. 1 shows a simplified example of a plasma-based processing chamber, which can include a substrate support assembly having an electrostatic chuck (ESC);

fig. 2 illustrates an example of a three-dimensional (3D) representation showing several components of the plasma-based processing system of fig. 1. 1;

fig. 3 illustrates an example of a 3D representation of four stacked spiral RF filters according to various embodiments of the disclosed subject matter;

FIG. 4 illustrates an example cut-away 3D representation of a filter model showing the use of a stacked spiral RF filter according to the example of FIG. 3 and a conventional solenoid RF filter; and

fig. 5 shows an example of a normalized amplitude impedance response plot as a function of normalized frequency for a dual-frequency RF filter according to the filter model of fig. 4.

Detailed Description

The disclosed subject matter will now be described in detail with reference to a few general and specific embodiments as illustrated in the various drawings. In the following description, numerous specific details are set forth in order to provide a thorough understanding of the disclosed subject matter. It will be apparent, however, to one skilled in the art, that the disclosed subject matter may be practiced without some or all of these specific details. In other instances, well known process steps or structures have not been described in detail in order to not obscure the disclosed subject matter.

The disclosed subject matter contained herein describes a high power (e.g., about 500W to about 50kW) induction coil that is used as an RF blocking filter (alternatively referred to herein as an RF filter). The RF filter presents a high impedance to the source side at the target frequency. Therefore, the RF filter is a good attenuator from the viewpoint of the load side. Generally, to achieve these goals at the target frequency, larger diameter inductors or more turns of inductors may be used. To maintain a relatively compact size, the RF filter described herein includes one or more stacked, substantially planar coils. In an embodiment, the RF filter is used primarily to block RF from entering an AC circuit that powers heaters of an electrostatic chuck (ESC) that is handling various substrate types during processing. As understood by those skilled in the art, ESC heaters provide important control to maintain the temperature profile of the process, which ultimately results in better uniformity and etch rate on the substrate.

Traditionally, coils used at low RF frequencies rely on a ferromagnetic core [ including one or more ferrites, such as nickel zinc ferrite (NiZn), manganese zinc ferrite (MnZn), magnesium zinc ferrite (MgZn), nickel magnesium ferrite (NiMg); reinforcing steel bars; iron powder, etc. ]. The ferromagnetic core reduces the length and physical size of the inductor coil. Ferromagnetic materials are known to have frequency-dependent electrical, magnetic and thermal properties, and have been shown to provide poor repeatable performance unless strict engineering guidelines are incorporated. These criteria generally increase material costs. Moreover, custom-machined ferromagnetic structures tend to increase production costs.

Alternatively, a larger air core coil may be designed, but the size of the air core coil may be significantly larger than a comparable coil having a ferromagnetic core and the same inductance value as the air core coil. Therefore, air core coils cannot generally be used when there are space limitations (e.g., the coils must fit into an existing enclosure located near the processing system).

The RF filters disclosed herein may be constructed with or without any type of ferromagnetic core and thus may be formed with only a hollow core. However, the RF filter can also be formed to conform to any space constraints of an RF filter enclosure in an existing plasma processing system. The demand for next generation etch tools is driving other performance features within nearly the same form fitting function as current generation plasma processing tools. Thus, increasing the size of a conventional hollow core is generally not justified. Therefore, a solution would be needed in which certain inductance levels are specified in RF filters having a compact form factor, while also the RF filters must be suitable for high power applications (e.g., about 500W to about 50 kW).

Accordingly, various embodiments are described in detail below, including methods and techniques for designing RF filters having compact form factors that can be used in high power applications. Furthermore, the disclosed subject matter describes apparatus for practicing embodiments of the disclosed subject matter. One or more embodiments of the disclosed subject matter relate to a filter for filtering Radio Frequency (RF) power generated within a plasma-based processing system. RF power can be delivered from at least an electrostatic chuck (ESC), for example, in a plasma-based processing system. The plasma-based processing system can include a first heating element disposed at a first portion of the ESC and a second heating element disposed at a second portion of the ESC. The plasma-based processing system may further include a power source, such as an Alternating Current (AC) power source, for powering the heating element. The RF filter may filter or block RF power from being transmitted in one direction (thereby minimizing electromagnetic compatibility (EMC) faults, interference problems, and/or power loss problems), and may allow AC power (50Hz or 60Hz) to be transmitted to the heating element in the other direction. Thus, the RF filter may eliminate or reduce EMC faults, interference problems, and power dissipation problems that may result from RF power being unjustifiably directed or transferred to certain components of the plasma-based processing system.

Referring now to fig. 1, a simplified example of a plasma-based processing chamber is shown. Fig. 1 is shown to include a plasma-based processing chamber 101A in which a showerhead electrode 103 and a substrate support assembly 107A are disposed in the plasma processing chamber 101A. Typically, the substrate support assembly 107A provides a substantially isothermal surface and may serve as a heating element and heat sink for the substrate 105. The substrate support assembly 107A may comprise an ESC that includes a heating element therein to assist in processing the substrate 105 as described above. As understood by one of ordinary skill in the art, the substrate 105 may be a wafer comprising an elemental semiconductor (e.g., silicon or germanium), a wafer comprising a compound element [ e.g., gallium arsenide (GaAs) or gallium nitride (GaN) ], or various other substrate types known in the art, including conductive, semiconductive, and nonconductive substrates.

In operation, a substrate 105 is loaded onto the substrate support assembly 107A through the load port 109. A gas line 113 supplies one or more process gases to the showerhead electrode 103. The showerhead electrode 103, in turn, delivers one or more process gases into the plasma-based processing chamber 101A. A gas source 111 supplying one or more process gases is coupled to gas line 113. An RF power source 115 is coupled to the showerhead electrode 103.

In operation, the plasma-based processing chamber 101A is evacuated by the vacuum pump 117. RF power is capacitively coupled between the showerhead electrode 103 and a lower electrode (not explicitly shown) contained within or on the substrate support assembly 107A. Two or more RF frequencies are typically supplied to the substrate support assembly 107A. For example, in various embodiments, the RF frequency may be selected from at least one of approximately 1MHz, 2MHz, 13.56MHz, 27MHz, 60MHz, and other frequencies as desired. However, upon reading and understanding the disclosure provided herein, one of ordinary skill in the art will recognize that the coils required to block or partially block a particular RF frequency may be designed as desired. Thus, the specific frequencies discussed herein are provided for ease of understanding only. The RF power is used to energize one or more process gases into a plasma in the space between the substrate 105 and the showerhead electrode 103. As is known in the relevant art, the plasma may assist in depositing various layers (not shown) on the substrate 105. In other applications, the plasma may be used to etch device features into various layers on the substrate 105. As described above, the substrate support assembly 107A may incorporate a heater (not shown) therein. One of ordinary skill in the art will recognize that RF power is coupled through at least the substrate support assembly 107A, although the detailed design of the plasma-based processing chamber 101A may vary.

Referring now to fig. 2, a three-dimensional (3D) representation of several components of the plasma-based processing system of fig. 1 is shown. Chamber portion 101B of the plasma-based processing chamber 101A of fig. 1 is shown to include an RF filter housing 201, an Alternating Current (AC) connector 203, a power cable 205, and an RF power feed cable 207. An uppermost portion 107B of the substrate support assembly 107A of fig. 1 is also shown. As described above, the substrate support assembly 107A may comprise an ESC.

In various embodiments, the ESC may be a tunable ESC (tesc) capable of tunable temperature control in two regions on the uppermost portion 107B of the substrate support assembly 107A. The temperature tuning capability of the ESC may be achieved by using two electrical heating elements (shown in phantom in the substrate support assembly 107A of fig. 1) embedded below the uppermost portion of the ESC and proximate to the substrate 105. For the case of a two-zone TESC, one electrical heating element is used for each of the two zones.

The electrical heating elements may be powered by Alternating Current (AC) supplied by an AC power source (not shown in the figures) through an AC power connector 203 through the RF filter housing 201 and a power cable 205. The RF filter housing 201 also contains an RF filter (not shown in fig. 2, but described in detail below with reference to fig. 3 and 4) to prevent or reduce RF power from being delivered to the electrical heating element. The temperature of each electrical heating element may be controlled by techniques known in the art.

Referring concurrently to fig. 1 and 2, during operation of the plasma-based processing chamber 101A, RF power is supplied to the substrate support assembly 107a (esc) through an RF power feed cable 207 (not shown in fig. 1) and from the RF power supply 115 to the showerhead electrode 103. Thus, the ESC serves as a lower electrode. Equipotential field lines are provided above the substrate 105 between the substrate 105 and the showerhead electrode 103. During plasma processing, positive ions are accelerated across the equipotential field lines to impinge on the surface of substrate 105 to provide a desired etch effect, such as improving etch directionality (one of ordinary skill in the art will recognize any suitable modification needed for film deposition as opposed to etching).

Referring now to fig. 3, a 3D representation of four stacked spiral RF filters 300 is shown. The z-axis is enlarged to show the connections between successive spirals. Fig. 3 is shown as including a first spiral RF filter 301A, a second spiral RF filter 301B, a third spiral RF filter 301C and a fourth spiral RF filter 301D. Each of the helical RF filters is substantially planar and substantially parallel to a subsequent one of the RF filters. For example, in one embodiment, "substantially planar" and "substantially parallel" may be interpreted to mean that elements within the helical RF filter and between the filters are in the range of about 0 ° to about 5 °, respectively, relative to each other. In various embodiments, "substantially planar" and "substantially parallel" may be interpreted to mean that the elements inside the helical RF filter and between the filters are in the range of about 0 ° to about 10 °, respectively, relative to each other. In various embodiments, "substantially planar" and "substantially parallel" may be interpreted to mean that the elements inside the helical RF filter and between the filters are in the range of about 0 ° to about 30 °, respectively, relative to each other. Based on the disclosure provided herein, the skilled artisan will recognize the appropriate meaning of the terms "substantially planar" and "substantially parallel. Further, upon reading and understanding the disclosure provided herein, the skilled artisan will recognize that more helical RF filters or fewer helical RF filters may be utilized, depending on the total impedance value suitable for a given situation and design parameter.

As described in more detail below, each of the spiral RF filters 301A-301D is alternately coupled to successive spiral RF filters on either the inside edge of the spiral or the outside edge of the spiral. For example, first spiral RF filter 301A is connected to second spiral RF filter 301B on medial edge 303A, second spiral RF filter 301B is connected to third spiral RF filter 301C on lateral edge 303B, and third spiral RF filter 301C is connected to fourth spiral RF filter 301D on medial edge 303C. Thus, four stacked spiral RF filters 300 are stacked on top of each other. As explained in more detail below, this arrangement provides a compact solution that also provides sufficient inductance to block low frequency RF power.

With continued reference to fig. 3, alternating inside-to-inside and outside-to-outside connections 303A-303C are used to provide a constructively interfering magnetic circuit, thereby increasing the overall inductance of the coil. As used herein, a coil may be considered to be the same as a helical RF filter. If an arrangement such as that shown in connections 303A-303C of fig. 3 is not employed, the resulting configuration may cancel out at least a portion of the magnetic field, thereby increasing eddy current losses and reducing the overall inductance of the coil. However, in various embodiments, although not explicitly shown, it is readily understood by one of ordinary skill in the art that constructive interference between the coils may be achieved by winding alternating layers of the spiral only in the same direction (e.g., clockwise or counterclockwise). Thus, adjacent layers of the spiral are wound in opposite directions to each other. The spiral is then connected, for example, from the inner terminal of a first coil to the outer terminal of the next coil, and so on. In general, the number of helical RF filters may be designed based on the operating frequency.

In various embodiments, each of the various helical RF filters may take different forms. For example, the helix may be wound such that the pitch (pitch) from one portion of the helix to an adjacent portion of the helix may be substantially constant (e.g., have substantially parallel curves). In other embodiments, the helix may be wound such that the pitch may be variable (e.g., increased or decreased or some combination thereof) from one portion of the helix to an adjacent portion of the helix. In other embodiments, other geometric variations in the pitch of successive helices (e.g., approximations of archimedean helices) may be considered.

Also, in various embodiments, the z-spacing between adjacent ones of the individual spiral RF filters may be adjusted (e.g., with reference to fig. 3) to change the total inductance value of the stacked spiral RF filters. In addition to varying the spacing to design an RF filter with desired electrical characteristics, the spacing may be adjusted to accommodate physical parameters, such as cooling requirements. Larger spacing between adjacent helical RF filters, or larger pitch from one coil portion to another coil portion in a helical RF filter, may allow for increased cooling (e.g., by moving passive or forced air through the coil to increase convective cooling).

Upon reading and comprehending the disclosure provided herein, one of ordinary skill in the art will recognize that for a given set of electrical parameters, such as voltage, current, and thus total power carried within a helical RF filter, a wire (wire), and a gauge (gauge) of the material forming the wire, may be selected. For example, 14 gauge copper wire overall may be sufficient to handle 15 amps of current, but 10 gauge wire (overall) may be required for 30 amps of current, and 6 gauge wire (overall) may be required for 50 amps of current. Additionally, the number of wires per spiral (e.g., strand forming techniques) may vary for a given filter design. Such strand forming techniques are known in the art.

In various embodiments, each individual wire may be coated with an insulating material, such as a coating formed on the wire. Such coatings are known in the art.

Upon reading and understanding the disclosure provided herein, one of ordinary skill in the art will recognize that for a given form factor (overall physical dimension or aspect ratio), the power level within the plasma-based processing system, the frequency or frequencies employed by the system, various ones of the above variables (e.g., dimensions, pitch, materials, etc.) may be varied for a desired design.

Accordingly, various embodiments of the RF filter may transmit AC power to power the electrical heating element. The RF filter may also minimize or block the transfer of RF power from the ESC to other components outside of the plasma-based processing chamber 101A (see fig. 1) to reduce or minimize the EMC fault, interference, and power loss problems described above.

The disclosed subject matter is a significant improvement over various techniques known in the art, such as non-helical (i.e., conventional) solenoids. However, these techniques have not previously been applied as compact form factors for high power plasma processing systems in the high power domain. Furthermore, the various forms of coils employed in the art fail to recognize the alternating inside-to-inside and outside-to-outside connections 303A-303C to provide a constructively interfering magnetic circuit as disclosed herein. Thus, the inner portion (e.g., connection point) of one planar coil is connected to the inner portion of an adjacent coil, the outer portion of a subsequent coil is connected to the outer portion of a subsequent planar coil, and so on. Thus, from the perspective of a given end of the coil, each planar coil is wound in the same direction [ e.g., all wound in a clockwise direction or all wound in a counterclockwise direction (counterclockwise) ]. Overall, a significantly higher inductance can be achieved in a relatively small volume.

Referring now to fig. 4, an example of a cross-sectional 3D representation of a filter model 400 is shown, the filter model 400 employing a stacked helical RF filter according to the example of fig. 3. The filter model 400 shown in fig. 4 with the help of such a coil is capable of filtering both high frequency RF signals (e.g., from about 4MHz to about 100MHz) and low frequency RF signals (e.g., from about 100kHz to about 3MHz) RF power. The illustrated filter model 400 includes a first filter housing volume 410, a second filter housing volume 420, and a partition wall 401 between the first and second (i.e., low and high frequency, respectively) housing volumes 410, 420. The first filter housing volume 410 has a stacked spiral RF filter 403 housed therein. According to fig. 3 and the accompanying description above, the stacked spiral RF filter 403 has "n" layers of stacked spiral coils (where n is an integer greater than or equal to "1"). The second filter housing volume 420 has a conventional RF filter (e.g., solenoid) 405 housed therein.

Fig. 5 shows an example of a normalized amplitude impedance response plot 500 for a dual-frequency RF filter in accordance with the filter model of fig. 4. The normalized impedance magnitude on the ordinate axis is shown as a function of the normalized frequency on the abscissa. Normalized amplitude impedance response plot 500 shows the impedance of low frequency component response curve portion 501 and the impedance of high frequency component response curve portion 503, both as a function of normalized frequency. The normalized amplitude impedance response plot 500 represents a highly favorable RF rejection performance at both frequencies while maintaining the shape fit functional requirements for a particular housing, as shown in the example of fig. 4.

As discussed above, the ordinate and abscissa axes of the normalized magnitude impedance response plot 500 are normalized with respect to impedance and frequency, respectively. In certain exemplary embodiments, the magnitude of the impedance may be in the range of about 500 ohms and about 10 kiloohms, depending on the actual implementation of the RF filter.

As discussed above, another factor for designing an RF filter for multi-channel operation also depends on the particular implementation of the twisted wire technology. The implementation of the stranded wire technique may be taken into account when balancing the inter-channel inductance magnitudes. With respect to the stacked spiral RF filter shown and described above with reference to FIG. 3, obtaining good mutual inductance between the channels allows the coil inductance to be treated as one winding rather than several separate channels electrically coupled in parallel. Good mutual inductance may also reduce or minimize unwanted parasitic resonances. Parasitic resonances can cause RF filters to be less efficient or problematic in systems that generate plasma or harmonic/intermodulation distortion (IMD).

In general, the disclosed subject matter has a number of advantages over contemporary RF filter designs. Advantages include, for example: (1) the need to rely on a ferromagnetic material core is eliminated or reduced, eliminating or reducing the core saturation problem and allowing better repeatability from one manufacturing unit to the next; (2) combinations of one or more ferromagnetic materials may be implemented in certain designs; (3) compact design (e.g., small form factor to fit existing RF filter housings) even when used in conjunction with high power solutions (even if implemented in an air-core design); and (4) the air-core design achieves efficient convective heat transfer through air cooling to reduce or eliminate the heat caused by resistive heating of the wires in the spiral.

Thus, a spiral stacked on top of each other (e.g., a substantially planar spiral) is a compact solution that also provides sufficient inductance to block low frequency RF power. The spirals are alternately connected from inside to outside (see fig. 3) to provide a constructive disturbing magnetic circuit that increases the overall inductance of the spirals as described above. The number of spiral layers may be designed based on the operating frequency. The aspect ratio of the helical RF filter structure may be designed to suit particular physical and electrical considerations. As described herein, the design of an RF filter depends on many factors including, for example, power handling capability, line current handling capability, operating frequency, tolerable RF parasitics, high voltage guidelines, and heat dissipation requirements. The design of the RF filter may use the well-known standard formulas for solenoid coil design as a starting point, but since the RF filter is custom designed, these standard formulas do not have to be followed. As such, the RF filters described herein may be used in the development of RF subsystems for semiconductor capital equipment, and may follow a complex set of radio frequency, mechanical, form fitting functions and high voltage guidelines as discussed herein. Furthermore, the RF filters described herein may also be used in combination with ferromagnetic materials including ferrites of NiZn, MnZn, MgZn, NiMg; reinforcing steel bars; iron powder; and other materials known in the art; or a combination thereof, for a particular design.

Accordingly, the foregoing description includes illustrative examples, devices, systems, and methods that embody the disclosed subject matter. In the description, for purposes of explanation, numerous specific details are set forth in order to provide an understanding of various embodiments of the disclosed subject matter. It will be apparent, however, to one skilled in the art that various embodiments of the subject matter may be practiced without these specific details. In other instances, well-known structures, materials, and techniques have not been shown in detail in order not to obscure the various illustrated embodiments.

As used herein, the term "or" may be interpreted in an inclusive or exclusive sense. Moreover, other embodiments will be understood by those of ordinary skill in the art upon reading and understanding the provided disclosure. Further, upon reading and understanding the disclosure provided herein, one of ordinary skill in the art will readily appreciate that various combinations of the techniques and examples provided herein may all be applied in various combinations.

While various embodiments are discussed separately, these separate embodiments are not intended to be considered independent techniques or designs. As noted above, each of the various portions may be interrelated, and each may be used alone or in combination with the other particulate matter sensor calibration system embodiments discussed herein.

Thus, many modifications and variations will be apparent to practitioners skilled in the art upon reading and understanding the disclosure provided herein. Functionally equivalent methods and devices within the scope of the disclosure, in addition to those enumerated herein, will be apparent to those skilled in the art from the foregoing description. Portions and features of some embodiments may be included in, or substituted for, those of others. Such modifications and variations are intended to fall within the scope of the appended claims. Accordingly, the disclosure is to be limited only by the terms of the appended claims, along with the full scope of equivalents to which such claims are entitled. It is also to be understood that the terminology used herein is for the purpose of describing particular embodiments only, and is not intended to be limiting.

The Abstract of the disclosure is provided to enable the reader to quickly ascertain the nature of the technical disclosure. It is submitted with the understanding that it will not be used to interpret or limit the claims. In addition, in the foregoing detailed description, it can be seen that various features may be grouped together in a single embodiment for the purpose of streamlining the disclosure. The methods of the present disclosure should not be construed as limiting the claims. Thus, the following claims are hereby incorporated into the detailed description, with each claim standing on its own as a separate embodiment.