(12) United States Patent
`Si
`
`USOO6284.11 OB1
`(10) Patent No.:
`US 6,284,110 B1
`(45) Date of Patent:
`Sep. 4, 2001
`
`(54) METHOD AND APPARATUS FOR RADIO
`FREQUENCY ISOLATION OF LIQUID HEAT
`TRANSFER MEDIUM SUPPLY AND
`DISCHARGE LINES
`
`5/1994 (EP) ............................... HO1J/37/32
`O596551A
`0887836 A 12/1998 (EP) ............................... HO1J/37/32
`58045378 A 3/1983 (JP).
`... C23L/15/00
`1O3O3132 A 11/1998 (JP) - - - - - -
`HO1 L/21/205
`
`(75) Inventor: Edward L. Sill, Phoenix, AZ (US)
`(73) Assignee: Tokyo Electron Limited, Tokyo (JP)
`
`9742648 A 11/1997 (WO) - - - - - - - - - - - - - - - - - - - - - - - - - - - - - HO1J/37/32
`
`* cited b
`cited by examiner
`
`(*) Notice:
`
`Subject to any disclaimer, the term of this
`patent is extended or adjusted under 35
`U.S.C. 154(b) by 0 days.
`
`(21) Appl. No.: 09/291,890
`(22) Filed:
`Apr. 14, 1999
`(51) Int. Cl." ................................................. C23C 14/34.
`(52) U.S. Cl. ....................... 204298.09: 118/58, 156/345,
`16577,165fisl. 165184
`(58) Field of Search ......................... 204/298.09: 118/58,
`156/345; 165/181, 184
`
`(56)
`
`Primary Examiner Nam Nguyen
`Assistant Examiner Steven H. Ver Steeg
`(74) Attorney, Agent, or Firm Wood, Herron & Evans,
`LLP
`ABSTRACT
`(57)
`A passive first-order band reject, or notch, filter character
`istic is introduced into a Supply and/or return line (18, 20) of
`a heat transfer System (12) that uses electrically conductive
`liquid heat transfer medium in contact with radio frequency
`electrified components (14) typical in Sputtering or etching
`manufacturing equipment. The heat transfer medium line
`(20) is coiled to create an inherent inductance (L2). A
`References Cited
`capacitive element (C2) is operatively connected across the
`coil (29) in the heat transfer medium line (20), the amount
`U.S. PATENT DOCUMENTS
`of capacitance chosen So that the resonant frequency is at the
`7/1989 Miller ............................. 315/111.51
`4,849,675
`RF frequency of the components (14) being thermally
`5,334,302 * 8/1994 Kubo et al. ...
`... 204/298.18
`i. : s9. t et al.
`2012: conditioned. Thus, a high impedance is created for that
`5,906,683 * 5/1999 Chen et al. .......
`"E, frequency. The coil (29) and capacitor (C2) combination is
`5,935,396 * 8/1999 Buckfeller et al. ............. 204/298.09
`protected from physical and electromagnetic interference by
`an enclosure (44).
`
`2 - - -2
`
`OIlllllO . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
`
`FOREIGN PATENT DOCUMENTS
`0184812 A 6/1986 (EP) ................................ HOSH/1/46
`
`16 Claims, 5 Drawing Sheets
`
`
`
`RF POWER n f/2
`
`Page 1 of 11
`
`APPLIED MATERIALS EXHIBIT 1057
`
`

`

`U.S. Patent
`
`Sep. 4, 2001
`
`Sheet 1 of 5
`
`US 6,284,110 B1
`
`
`
`24
`
`
`
`
`
`High
`impedance
`Conduit
`
`26
`
`Liquid Supply
`
`22
`
`
`
`Electrically Charged
`Components
`
`Electrically
`Charged
`Components
`
`Page 2 of 11
`
`

`

`U.S. Patent
`US. Patent
`
`Sep. 4, 2001
`Sep. 4, 2001
`
`Sheet 2 of 5
`Sheet 2 0f5
`
`US 6,284,110 B1
`US 6,284,110 B1
`
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`Page 3 ofll
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`Page 3 of 11
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`Page 4 of 11
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`

`

`U.S. Patent
`
`Sep. 4, 2001
`
`Sheet 4 of 5
`
`US 6,284,110 B1
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`

`

`U.S. Patent
`US. Patent
`
`Sep. 4, 2001
`Sep. 4, 2001
`
`Sheet 5 of 5
`Sheet 5 0f5
`
`US 6,284.110 B1
`US 6,284,110 B1
`
`
`
`RF POWER
`RF POWER
`IN
`N
`J- 103
`i/103
`
`fe
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`
`
`
`Page 6 ofll
`
`Page 6 of 11
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`

`

`1
`METHOD AND APPARATUS FOR RADIO
`FREQUENCY ISOLATION OF LIQUID HEAT
`TRANSFER MEDIUM SUPPLY AND
`DISCHARGE LINES
`
`FIELD OF THE INVENTION
`The present invention pertains to radio frequency isola
`tion to heat transfer Supply and discharge lines through
`which electrically conductive heat transfer medium flows.
`More particularly, the present invention pertains to high
`impedance heat transfer Supply and discharge lines for use
`in Sputtering and etching equipment used in the Semicon
`ductor industry.
`BACKGROUND OF THE INVENTION
`Sputter coating is a coating process that involves the
`transport of almost any material from a Source, called the
`target, to a Substrate of almost any material. The proceSS
`takes place in a reduced preSSure chamber containing argon
`or other process gas. The reduced preSSure, or vacuum, is
`needed to increase the distance that the Sputtered atoms can
`travel without undergoing collision with each other or with
`other particles. The argon gas is ionized which results in a
`bluish-purple glow of a plasma. Ejection of target Source
`material is accomplished by bombardment of the target
`Surface with gas ions that have been accelerated toward the
`target by a high Voltage. As a result of momentum transfer
`between incident ion and target, particles of atomic dimen
`Sion are ejected from the target. These ejected particles
`traverse the vacuum chamber and are Subsequently depos
`ited on a Substrate as a thin film. A similar process is
`generally used in Sputter etching, however, the target is
`replaced by the object to be etched.
`Radio frequency (RF) power, introduced into a process
`chamber via an inductive coil encircling the chamber, is
`often advantageously used in Sputter coating and etching to
`enhance the development of the plasma. RF Sputter coating
`and etching allows the deposition of insulating as well as
`conductive materials and the etching of Substrates, utilizing
`lower voltages, such as 500 to 2,500 V, to accelerate the
`argon gas ions to the target or Substrate being etched. The
`lower Voltage at the same power provides higher deposition
`and etching rates with reduced Substrate damage. In
`addition, RF power may be used to bias the substrate to
`change the characteristics of film deposition, especially for
`insulating films. Such RF power biasing of the Substrate can
`improve adhesion and the added heat due to the bias power
`can provide higher mobility of Source material on the
`Substrate Surface which can improve Step coverage. Lower
`resistivity and changes in film stress can be obtained with RF
`Voltage bias, as well. Gas incorporation into the film is
`usually increased. Oxide films Such as Silicon dioxide will
`have improved optical qualities and higher density when RF
`bias is used during deposition.
`Electronically isolating certain System components with
`respect to RF energization is desirable when using RF power
`in Sputtering and etching. Otherwise, the plasma may be
`altered, adversely affecting the Sputtering or etching process.
`In the case of RF biasing of the substrate, lack of RF
`isolation can result in undesired RF power dissipation.
`Consequently, it is desirable to RF isolate certain compo
`nents within a Sputtering or etching System. This RF isola
`tion provides an interruption of a potential RF path to ground
`from the RF energized component.
`Another aspect of Sputtering and etching Systems is the
`requirement to thermally condition (heat or cool) certain
`
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`US 6,284,110 B1
`
`2
`System components or the Substrate. This is usually accom
`plished by circulating a liquid heat transfer medium in heat
`transfer relationship to the System component, or Substrate
`Support, as the case may be. AS previously mentioned, the
`substrate may be biased by RF power for improved depo
`Sition or etching characteristics. Under Such conditions, the
`heat transfer components must be electrically isolated from
`the RF applied to the Substrate Support. For example, in
`Sputter coating target cooling is often desirable, whereas in
`Sputter etching wafer cooling may be needed. In Such
`Situation, a liquid coolant is circulated through the Susceptor
`or wafer Support, as the case may be. In wafer processing
`configurations wherein an RF coil is placed around the
`Sputtering or etching chamber to create and/or enhance the
`plasma, the RF coil has resistance that generates heat,
`requiring the RF coil to be cooled by circulating a liquid heat
`transfer coolant medium through the RF coil. The heat
`transfer component must be isolated from the RF applied to
`the RF coil.
`A problem arises when cooling an RF coil and/or heating
`or cooling a Substrate Support or target holder as a result of
`the fact that the heat transfer media, usually water, in the
`lines used for circulating the heat transfer media through the
`coil or Substrate Support or target interferes with RF isolation
`of components Such as the RF coil, Substrate Support, target
`holder, etc. Maintaining the desired RF isolation while
`circulating a liquid heat transfer medium is required to
`prevent degradation of the Sputtering or etching process.
`Water is typically used as the heat transfer liquid medium
`due to the Safety, low cost, and ready availability of water.
`For example, in a simple open cooling System, cool tap
`water is Supplied through a Supply line to the Sputtering or
`etching System component to be cooled at which place the
`water is circulated and thereafter discharged to a drain via a
`discharge line. Tap water typically contains dissolved min
`erals that cause the water to be leSS chemically reactive to
`many materials. However, the dissolved minerals also create
`ions in the water that make the water electrically conductive,
`which can be disadvantageous when heating or cooling
`Sputtering or etching System components energized with RF.
`Consequently, in many applications, the electrically conduc
`tive tap water is first purified to remove the minerals, making
`it resistive. Resistive water is corrosive to many materials
`Such as metals. As a consequence, a balance is Sought in the
`level of water purification to achieve an acceptable level of
`conductivity verSuS corrosiveness. In addition, chemical
`additives are generally added to the water to mitigate the
`corrosive effects, incurring additional expense and inconve
`nience in preparation and disposal of the liquid. These
`additives in Some instances introduce detrimental effects
`Such as reducing the resistivity of the water or decreasing the
`environmental Safety of the liquid. Moreover, Systems uti
`lizing this type of component cooling or heating have to be
`designed to accommodate a certain amount of electrical
`power loss through the liquid heat transfer medium.
`Achieving the requisite balance in water purity involves
`the expense of buying or processing the water to the appro
`priate purity level. Filtering and monitoring of the water is
`then required to maintain the purity within the acceptable
`range. Even with these additional requirements, there is still
`Some degradation of performance and reliability of the
`components heated or cooled by the resistive water.
`Other relatively abundant and environmentally safe heat
`transfer liquids are also available; however, many of these
`are also electrically conductive, but by their nature cannot be
`processed to a more resistive condition and are thus inap
`propriate for use.
`
`Page 7 of 11
`
`

`

`US 6,284,110 B1
`
`3
`Relying on the resistivity of the water to provide the RF
`isolation dictates that the water Supply and discharge lines be
`increased in length, Since the electrical resistance afforded
`by the water is a function of water path length to ground,
`assuming the resistivity of the water and diameter of the
`water lines are fixed. For example, typical resistive water
`cooling Systems employ 12 to 13 feet of polypropylene
`tubing of about a quarter inch in outer diameter in each of
`the water Supply and discharge lines to generate 1 MS2 of
`resistance.
`Consequently, what is needed are high impedance liquid
`heat transfer medium Supply and discharge lines that are not
`dependent principally upon the resistivity of the heat transfer
`liquid in isolating radio frequency energized components.
`
`SUMMARY OF THE INVENTION
`
`These and other needs are Satisfied in accordance with
`certain principles of the present invention by a) coiling at
`least a portion of the liquid heat transfer medium Supply
`and/or discharge lines Such that the lines have a high
`inherent inductance and b) connecting a capacitive element
`in parallel with the coiled lines, with the capacitance being
`chosen Such that the resonant frequency, and thus the highest
`impedance, of the coiled line ?capacitor combination occurs
`at the RF frequency in use.
`The present invention, by virtue of being a passive device,
`requires no power Source, and is leSS Sensitive to variations
`in the electrical conductivity of the liquid, thus eliminating
`expensive liquid processing and filtering. Other advantages
`include reducing the length of liquid heat transfer medium
`Supply and discharge lines normally employed.
`These and other objectives and advantages of the present
`invention will be more readily apparent from the following
`detailed description of the embodiments.
`BRIEF DESCRIPTION OF THE DRAWINGS
`FIG. 1 is a block diagram of liquid cooled or heated
`System component having high impedance liquid heat trans
`fer medium Supply and discharge lines.
`FIG. 2 is an electrical schematic of the liquid cooled or
`heated system component of FIG. 1 wherein the high
`impedance liquid heat transfer medium lines are shown in
`both a fixed capacitance and variable capacitance embodi
`ment.
`FIG. 3 is a diagrammatic perspective View of a fixed
`capacitance embodiment of a high impedance line of FIGS.
`1 and 2.
`FIG. 4 is a plot of impedance as a function of frequency
`for an illustrative embodiment.
`FIG. 5 is an equivalent electrical Schematic of a high
`impedance line wherein the electrical resistance of the
`components is shown.
`FIG. 6 is a plot of the impedance and bandwidth of the
`high impedance line of FIG. 5 shown as a function of the
`resistance of the coil, illustrating that as DC resistance of the
`coil increases and/or resistance of an additional resistor in
`parallel to the coil increases, the peak impedance decreases
`and the bandwidth widens.
`FIG. 7 is a croSS Sectional depiction of a Soft etching
`System utilizing liquid cooling of an RF coil and a wafer
`Support, with the cooling Supply and discharge lines appro
`priate candidates for the high impedance lines of this inven
`tion.
`FIG. 8 is a depiction of the cooling line to the RF coil
`incorporating a high impedance conduit on the Supply Side.
`
`4
`FIG. 9 is a depiction of the cooling line to the wafer
`Support, incorporating a high impedance conduit to both the
`Supply and discharge Sides.
`
`DETAILED DESCRIPTION OF THE
`INVENTION
`FIG. 1 diagrammatically illustrates a thermally condi
`tioned system 10 having a closed heat transfer system 12 for
`heating or cooling one or more electrically charged compo
`nents 14. A heat eXchanger 16 brings a liquid heat eXchange
`medium, Such as water, into thermal and electrical contact
`with the electrically charged components 14. The heat
`exchanger 16, for example, may be metal tubing (not shown)
`placed in physical contact with the components 14 or in
`contact with a thermally conducting material (not shown)
`located between, and in heat transfer contact with, the tubing
`and the components 14. The closed heat transfer system 12
`has a liquid Supply line 18, and a liquid return heat line 20,
`generally referred to as water lines. The liquid is processed
`and pressurized by a liquid Supply 22. Interposed in the lines
`18, 20 are high impedance liquid conduits 24, 26 constructed
`in accordance with the principles of the invention.
`FIG.2 shows an electrical schematic for the system 10 of
`FIG. 1. The electrically charged components 14 are shown
`as being electrified by a sinusoidal power Supply 28 having
`an output V(f), where the frequency f is generally in the radio
`frequency (RF) band. The supply heat transfer medium line
`18 is shown having a known resistivity R1 and the return
`Supply line 20 is shown having a known resistance R2, these
`values being a function of the resistivity of the liquid in the
`lines 18 and 20, the length and diameter of the lines 18, 20,
`and the resistivity of the material from which the lines 18
`and 20 are made.
`The high impedance conduit 24 is shown as having an
`inductor L1 electrically in parallel with the parallel combi
`nation of a fixed capacitor C1 and a trim capacitor C.
`Parallel capacitances are additive. Therefore, a Small trim
`capacitor can adjust the equivalent capacitance for the
`overall capacitive element. Capacitors are electrical circuit
`elements used to Store electrical charge temporarily, typi
`cally comprising conductorS Separated by a dielectric.
`Consequently, capacitorS C1 and C, contribute to electrical
`characteristics but not to fluid flow characteristics of the
`high impedance conduit 26.
`The return high impedance conduit 26 is shown as having
`an inductor L2 in parallel with a fixed capacitor C2. Both
`conduits 24, 26 are referenced to ground. The embodiments
`shown in FIG. 2 are exemplary and other embodiments are
`contemplated. For instance, a Single variable capacitor could
`be used, or a plurality of fixed capacitors in parallel could be
`used, to achieve the desired equivalent capacitance.
`The resistance values of R1 and R2 would dictate the
`electrical power loss through the lines 18, 20 but for the
`introduction of the high impedance conduits 24, 26.
`However, the contribution of the resistance values of R1 and
`R2 can be discounted as negligible as compared to the
`conduits 24, 26, which would have the equivalent imped
`ance of:
`
`Where Z is the impedance of an inductor (i.e., j2Juf) and
`Z is the impedance of the capacitor (i.e., 1/2 f(). This
`equivalent impedance Z is maximized at the reso
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`S
`nant frequency f. the inductor-capacitor combination,
`which can be calculated as:
`
`US 6,284,110 B1
`
`6
`of the high impedance conduit 30. Consequently, the full
`electrical response of the heat transfer System 12 considering
`resistance provides a more accurate prediction. Design
`choice, Such as choice of capacitive element 34 with appro
`priate resistive characteristics, may be made for the desired
`peak impedance and width of band reject characteristics.
`Referring to FIG. 6, a plot of the impedance and band
`width of the high impedance conduit 30 of FIG. 5, illustrat
`ing that as DC resistance R of the coil 32 increases or the
`additional resistance of a Second resistor R, in parallel to
`coil 30, decreases, the peak impedance decreases and the
`bandwidth increases of the high impedance conduit 30.
`Referring to FIG. 7, a cross sectional depiction is shown
`of a soft etching system 50 utilizing water coolant heat
`transfer lines 52, 54 for a housing seal 56, and for a wafer
`support 58, respectively. An RF coil 60a for enhancing the
`plasma, shown encircling the belljar vacuum process cham
`ber 62, is water-cooled copper tubing, the copper providing
`an electrical conductor for the RF power, with the frequency
`of the RF power being 450 kHz. The RF coil 60a is a portion
`of a heat transfer line 60b shown and discussed below for
`FIG. 8.
`A high Vacuum is maintained within the enclosure 61
`formed by a bell jar vacuum proceSS chamber 62 and
`aluminum housing 64, in part by an O-ring Seal 66 between
`an aluminum support 68 and a stainless steel flange 70 of the
`aluminum housing 64. High Vacuum is maintained at the
`contact between the belljar 62 and the aluminum Support 68
`by a high temperature VITON o-ring (not shown). To
`prevent thermal damage to the o-ring Seal 66, cooling water
`is delivered to the Support 68 by heat transfer line 52. Heat
`transfer line 52, however, is not an appropriate candidate for
`high impedance circuits since the line 52 is at ground
`potential.
`Heat transfer line 54 is an appropriate candidate for high
`impedance conduits Since line 54 is near RF energized
`components.
`The wafer support 58 has an internal volume 72 open to
`atmospheric pressure through its downward opening 74. A
`silicon wafer 76 sets upon an RF energized table 78, the RF
`energy biasing the wafer 76, with the RF power supplied
`having a frequency of 13.56 MHz.
`Wafer hold-down components 80 are similarly RF ener
`gized and provide physical Support to the quartz clamp 82
`holding down the silicon wafer 76. The quartz clamp 82 is
`held in position by support 84 beside the wafer receptacle
`58. The upper portion of wafer receptacale 58, the susceptor
`85, is raised to contact the clamp 82 and lowered to allow
`placement of a wafer 76 on the table 78 by actuating the
`bellows like lower portion 86 of the wafer receptacle 58.
`The table 78 has a downwardly extending thin flange 87,
`made thin to minimize heat loss from the top of the heated
`table 78 to the base 88 of the heated table 78, which provides
`physical contact and Support to the wafer hold-down com
`ponents 80. The base 88 in turn is supported by a receptacle
`Support 90, generally made of Stainless Steel, which for ease
`of manufacturing is shown composed of a plurality of
`components. Internal Seals 92 are thus provided to prevent
`atmospheric pressure in the internal Volume 72 from escap
`ing to the enclosure 61. RF isolation between the RF
`energized base 88 and the receptacle support 90 is provided
`by ceramic flange 94. Seals 96 prevent atmospheric pressure
`from escaping past the ceramic flange 94. The bottom of the
`flange 87 of the heated table 78 is positioned near the
`ceramic flange 94 and its seals 96. The flange 87 is suscep
`tible to damage due to heat as are the Seals 96. Consequently,
`the cooling water line 54 is provided at this point.
`
`1
`
`JR - , VIf
`
`In the illustrative embodiment shown in FIG. 3, the
`adjustable high impedance conduit 26 is designed for the
`resonant frequency of 13.56 MHz, one of the standard
`frequency used in the industry exciting the argon gas in
`etching and Sputter deposition Systems. Lower frequencies,
`such as 450 kHz, are often used when exciting inductively
`couple plasmas. The water line 20 may be of an electric
`insulative material tubing of about a quarter inch in outer
`diameter. The water line 20 is coiled into a five-turn coil L2
`of two inch Outer diameter, resulting in an inductance value
`of about 1.0 mH. More turns for the coil 29 could be chosen
`to increase the impedance but this would trade off higher
`impedance for a narrower bandwidth of a high impedance
`region and would also increase the overall length of the coil
`29. An enclosure 44 surrounds the coil 29, providing pro
`tection from physical damage to the coil 29. Preferably, the
`enclosure 44 would be a grounded Faraday RF shield, a
`conductive enclosure that protects internal components from
`external electromagnetic radiation and reduces emission of
`electromagnetic radiation from the coil 29 to the external
`environment. A capacitor C2 of 332 pF is operatively placed
`across the coil 29. Electrical connection between the liquid
`and the capacitor C2 could be achieved in numerous ways.
`For instance, an electrical conductor could be inserted
`through the water line 20. Also, the coil could have metal
`connectors at each end to aid in assembly and capacitor C2
`could contact these connectors. Preferably, the capacitor C2
`and connections to the coil 29 would be insulated. These
`inductance and capacitance values result in an impedance
`for the high-impedance conduit of over 30 MS2, as shown in
`FIG. 4. This value compares to a requirement of 900 feet of
`water line 20 to achieve a comparable impedance if merely
`coiling the water line 20 without the capacitor C2.
`Referring to FIG. 5, an equivalent electrical Schematic is
`shown for a high impedance conduit 30 wherein the elec
`trical resistance of the components is considered. A first
`resistor R, shown in Series with coil 32, models the resis
`tance of the coil 32 and liquid therein. For example, the coil
`32 may be of conductive material resulting in a low value for
`first resistor R. Alternatively, the coil 32 may be of insu
`lative material Such that R results from the characteristics
`of the liquid, and thus R has a higher resistance value. A
`Second resistor R, in parallel to the Series combination of
`the coil 32 and first resistor R, represents an additional
`resistor added to a high impedance conduit 30 to control the
`peak impedance and bandwidth. The trimmable capacitor 34
`is shown in parallel with the series combination of the coil
`32 and first resistor R. A second resistor R is shown in
`parallel to the series combination of the coil 32 and first
`resistor R and also in parallel to the trimmable capacitor 34.
`Second resistor R2 represents an additional resistor added to
`a high impedance conduit 30 to control the peak impedance
`and bandwidth, or accounts for resistance characteristics of
`trimmable capacitor 34.
`Consideration of the resistance of the coil 32 may be
`required, for example, in Selecting an appropriate RF power
`Supply (not shown) to a component in a sputtering or etching
`System, for instance, when the Specific amount of electrical
`power dissipated by the heat transfer System 12 is critical. AS
`another example, the frequency of the RF power Supply may
`not be constant, thus dictating a wider operable bandwidth
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`7
`The importance of isolating RF power in the Soft etching
`system 50 is shown by the addition of RF insulating ring 98,
`a portion of the receptacle Support 90 in close non-touching
`proximity to the wafer hold-down components 80. The space
`between the RF insulating ring 98 and the wafer hold-down
`components 80 is So Small as to form a dark Space Shield, a
`Space too small to allow the formation of a plasma.
`Similarly, isolating heat transfer lines 52, 54, and 62 is
`necessary to prevent RF power from generating plasma, or
`otherwise conducting power to ground, at other locations.
`The soft etching system 50 is exemplary, with other
`Sputter coating and Sputter etching Systems having heat
`transfer lines and RF powered components Similarly being
`candidates for high impedance conduits.
`Referring to FIG. 8, the cooling line 60b to the RF coil
`60a is shown incorporating a high impedance conduit 100
`on the supply side 102. The cooling line 60b is energized by
`RF power as represented by capacitive coupling 103.
`Referring to FIG. 9, the cooling line 54 to the heated table
`78 is shown incorporating high impedance conduits 104,
`106 to both the supply side 108 and discharge side 110,
`respectively. The cooling line 54 is energized by RF power
`as represented by capacitive coupling 112.
`Although the embodiments described utilize passive
`capacitive elements to create a first-order notch filter, it
`would be further consistent with the invention to utilize
`active elements Such as operational amplifiers. In addition,
`it would be further consistent with the invention to create
`higher-order notch filters or other filtering characteristics.
`For example, the Sputtering or etching System may have
`components energized by an RF power Source capable of
`varying the frequency of the RF power. Active components
`within a high impedance conduit can be employed to tune
`the impedance to correspond to the frequency of the RF
`power. In addition, the RF power present in the Sputtering or
`etching System could have more than one frequency, Such as
`the RF coil enhancing the plasma being at one frequency
`whereas RF bias to the Substrate being at another frequency.
`Thus, a high impedance conduit could be provided with a
`broader bandwidth or with several notch filters tuned to
`these frequencies of interest Such as with a higher order
`filter. Alternatively, a plurality of high impedance conduits,
`each blocking an RF frequency, could be placed in Series to
`achieve a multiple notch or broader bandwidth high imped
`CC.
`Moreover, although the capacitive element is shown as
`physically placed down the longitudinal axis of the coil,
`many orientations would be acceptable So long as the
`capacitive element is electrically in parallel with the coil.
`In addition, although the preferred embodiments as shown
`are used in cooling or heating components of Sputtering
`Systems, the invention is useful in chemical vapor deposition
`Systems and ionized physical vapor deposition Systems
`incorporating Sources of RF energy.
`AS described herein, open and closed System heat transfer
`Systems 12 are appropriate for high impedance conduits. An
`open System includes having one liquid path, either the input
`to or the output from the device being cooled or heated,
`electrically isolated between the electrical power Source and
`the device being cooled. AS Such, the high impedance
`conduit is omitted on that isolated liquid path. For example,
`tap water is pumped into a heat eXchanger, requiring the high
`impedance conduit, whereas the output from the heat
`eXchanger has Such a long drain path through an insulating
`conduit that the resistivity of the cooling water is Sufficient
`for electrical isolation. Alternatively, the output is discretely
`discharged in a fashion where no continuous Short to ground
`exists.
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`US 6,284,110 B1
`
`8
`Those skilled in the art will appreciate that the imple
`mentation of the present invention herein can be varied, and
`that the invention is described in preferred embodiments.
`For example, although a cooling System is described in
`detail, a high impedance conduit would be similarly
`employed for heating. Accordingly, additions and modifica
`tions can be made, and details of various embodiments can
`be interchanged, without departing from the principles and
`intentions of the invention.
`What is claimed is:
`1. A high impedance liquid heat transfer medium conduit
`configured for a heat transfer System using heat eXchange
`medium in thermal and electrical contact with a component
`to be thermally conditioned which is energized by radio
`frequency power of a predetermined frequency, the conduit
`comprising:
`a coiled liquid heat transfer medium line; and
`a capacitive element operatively connected in parallel
`with the coiled liquid heat transfer medium line, the
`coiled line and capacitive element collectively consti
`tuting a parallel LC circuit resonant at a frequency
`approximating the predetermined frequency.
`2. The high impedance conduit of claim 1, wherein the
`heat eXchange medium is water.
`3. The high impedance conduit of claim 1, wherein the
`capacitive element further comprises a variable capacitor
`Such that the capacitance can be varied to tune the LC circuit
`to resonate at the predetermined frequency.
`4. The high impedance conduit of claim 3, wherein the
`variable capacitor includes a fixed capacitor in parallel with
`a trim capacitor.
`5. The high impedance conduit of claim 1, wherein the
`resonant frequency is approximately 13.56 MHz.
`6. The high impedance conduit of claim 1, wherein the
`resonant frequency is approximately 450 kHz.
`7. The high impedance conduit of claim 1, further com
`prising a protective enclosure Surrounding the coiled liquid
`heat transfer medium line and the capacitive element.
`8. The high impedance conduit of claim 1, wherein the
`capacitive element and the coiled liquid heat transfer
`medium line have a resonant frequency of approximately the
`predetermined frequency.
`9. The high impedance conduit of claim 1, wherein the
`components are incorporated in a Semiconductor manufac
`turing System.
`10. The high impedance liquid heat transfer medium
`conduit of claim 1, wherein the coiled liquid heat transfer
`medium line comprises an electrically insulating material.
`11. A high impedance liquid heat transfer medium conduit
`configured for a heat transfer System using heat eXchange
`medium in thermal and electrical contact with a component
`to be thermally conditioned which is energized by radio
`frequency power of a predetermined frequency, the conduit
`comprising:
`a