United States Patent
`
`[19]
`
`US005 l92849A
`[11] Patent Number:
`
`5,192,849
`
` .
`
`Moslehi
`
`[45] Date of Patent:
`
`Mar. 9, 1993
`
`[54] MULTIPURPOSE LOW-THERMAL-MASS
`CHUCK FOR SEMICONDUCTOR
`PROCESSING EQUIPMENT
`Dallas, TEX.
`Il1VCfltOl'Z
`M.
`[73] Assign”; Tens [nu-“mum Inca;-pm-‘ted,
`'
`Dguas, T¢x_
`.
`
`[21] APP!‘ N°" 5551765
`[22] Filed;
`Aug, 19, 1990
`
`Int. 0.5 ................................................ W
`US. Cl. .........3................
`219/121-43 219/1533 155/345
`[58] Field of Search ........ 219/121.43, 121.4, 159-161,
`219/121395 155/345: 543» 5463 427/343
`313/111-21» 111-31» 111~51
`we-I
`-
`us‘ PATENT DOCUMENTS
`4,36l,749 11/1982 Lord ............................... 219/121.43
`4,430,547 2/1984
`..
`4,565,601
`1/1986
`
`1561
`
`
`
`‘:971:653 “/1990
`Primary Examiner-—Mark H. Paschal!
`
`Attorney, Agent, or Finn—Stanton C. Braden; Richard
`L. Donaldson; William E. Hiller
`[57]
`ABSTRACI.
`A
`l°w_mermfl_m‘ss ndiwfrequency
`chuck for semiconductor device processing equipment
`(18) and applicable to plasma processing over a wide
`range of substrate temperatures. The stacked multilayer
`chuck structure comprises process vacuum base plate
`(16), heating module (48), cooling module (44) and
`radio-frequency power plate (50). Vacuum base plate
`pr°vid§
`support .nd 'n fecd-
`throughs (RF power connection,
`inlet/outlet’
`heater wires and thermocouple) for main chuck (20).
`w,,,,_coo1,d vwuum we pm, (15) ,5 therxnany gm.
`lated from main chuck module (20). Heating element
`(48) comprises top layer (so) of electrical insulation and
`:r:::::::,7":‘.;:;:;:§,‘*:::;“.*:.;°:‘::::,‘:::;:::.*::*;;.:;z,:*;::
`ofboron nitride or quartz or SiC-coated graphite. Cool-
`ant module (44) comprises a plurality of coolant tunnels
`and is made of a high thermal conductivity material
`(nickel-plated copper, aluminum or a suitable refractory
`metal). Radio-frequency plate (50) comprises a refrac-
`tory metal or aluminum material.
`25 Claims, 11 Drawing Sheets
`
`1o
`
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`32
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`Intel Corp. et al. Exhibit 1009
`
`Intel Corp. et al. Exhibit 1009
`
`

`
`U.S. Patent
`
`Mar. 9, 1993
`
`' Sheet 1 of 11
`
`5,192,849
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`Intel Corp. et al. Exhibit 1009
`
`Intel Corp. et al. Exhibit 1009
`
`

`
`U.S. Patent
`
`Mar. 9, 1993
`
`Shget 2 of 11
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`5,192,849
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`CXJTLET 2
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`INLET 2
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`78
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`Intel Corp. ‘et al. Exhibit 1009
`
`Intel Corp. et al. Exhibit 1009
`
`

`
`U.S. Patent
`
`Mar.9, 1993
`
`Sheet 3 of 11
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`5,192,849
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`Intel Corp. et al.
`
`.Exhibit 1009
`
`Intel Corp. et al. Exhibit 1009
`
`
`
`
`
`
`

`
`U.S. Patent
`
`Mar. 9, 1993
`
`Sheet 4 of 11
`
`5,192,849
`
`Intel Corp. et a1‘. Exhibit 1009
`
`Intel Corp. et al. Exhibit 1009
`
`

`
`U.S. Patent
`
`Mar. 9, 1993
`
`Sheet 5 of 11
`
`5,192,849
`
`FIG. 7
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`Intel Corp. et al. Exhibit 1009
`
`Intel Corp. et al. Exhibit 1009
`
`

`
`U.S. Patent
`
`Mar. 9, 1993
`
`Sheet 6 of 11
`
`5,192,849
`
`136
`
`134
`
`FIG. 10
`
`'
`
`Intel Corp. et al. Exhibit 1009
`
`Intel Corp. et al. Exhibit 1009
`
`

`
`U.S. Patent
`
`Mar. 9, 1993
`
`.
`
`Sheet 7 of 11
`
`5,192,849
`
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`
`Intel Corp. et al. Exhibit 1009
`
`Intel Corp. et al. Exhibit 1009
`
`

`
`U.S. Patent
`
`Mar. 9, 1993
`
`Sheet 8 of 11
`
`5,192,849
`
`
`
`124
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`Intel Corp. et al. Exhibit 1009
`
`Intel Corp. et al. Exhibit 1009
`
`

`
`U.S. Patent
`
`Mar. 9, 1993
`
`Sheet 9 of 11
`
`5,192,849
`
`‘
`
`Intel Corp. et al. Exhibit 1009
`
`Intel Corp. et al. Exhibit 1009
`
`

`
`U.S. Patent
`
`Mar. 9, 1993
`
`Sheet 10 of 11
`
`5,192,849
`
`"
`
`Intel Corp. et al. Exhibit 1009
`
`Intel Corp. et al. Exhibit 1009
`
`

`
`U.S. Patent
`
`Mar. 9, 1993
`
`Sheet 11 of 11
`
`5,192,849
`
`FIG. 15
`
`'
`
`Intel Corp. et al. Exhibit 1009
`
`Intel Corp. et al. Exhibit 1009
`
`

`
`1
`
`5,192,849
`
`MULTIPURPOSE I1)W-THERMAL-MASS CHUCK
`FOR SEMICONDUCTOR PROCESSING
`EQUIPMENT
`
`TECHNICAL FIELD OF THE INVENTION
`
`The present invention relates in general to a multipur-
`pose low-therrnal-mass chuck for semiconductor pro-
`cessing equipment, and more particularly to a method
`and apparatus for producing radio-frequency plasma,
`wafer heating, and wafer cooling in plasma processing
`applications (etch, deposition, annealing, and surface
`cleaning).
`BACKGROUND OF THE INVENTION
`
`Manufacturers of electronic components use a vari-
`_ ety of techniques to fabricate semiconductor devices.
`One technique that has many applications is known as
`“plasma-assisted” processing. In plasma-assisted pro-
`cessing, a substantially ionized gas, usually produced by
`a radio-frequency electromagnetic gas discharge, pro-
`vides activated neutral and ionic species that chemically
`react to deposit or to etch material layers on semicon-
`ductor wafers in a fabrication reactor. Reactive-ion
`etching (RIE), an example of plasma-assisted processes,
`uses the directional and energetic ions in a plasma to
`anisotropically etch a material layer. RIE can take place
`in a conventional parallel-electrode plasma processing
`equipment or similar semiconductor device fabrication
`reactor.
`
`30
`
`2
`via its interactions with the process chamber walls and
`the plasma electrodes.
`The combined effects of plasma-induced surface dam-
`. age and contamination produce semiconductor devices
`with less than optimal performance characteristics and
`limit fabrication process yield. Thus, with conventional
`plasma-assisted processing techniques, increasing RF
`power to increase plasma density with the intent to raise
`the process rate can have serious detrimental effects. If
`a method existed, however, to increase the plasma den-
`sity and ion flux without also significantly increasing
`ion energies, then a manufacturer may increase plasma-
`assistcd processing rates.
`Therefore, a need exists for a method and apparatus
`to increase plasma density near a semiconductor wafer
`during plasma-assisted processing without at the same
`time increasing ion energy levels.
`As indicated before, another limitation of conven-
`tional plasma-assisted processes derives from the fact
`that, during these processes,_ plasma disperses through-
`out the fabrication process chamber. In so doing, it
`interacts with the process chamber walls. These walls
`contain various metals that the activated plasma species
`can remove, transport to a semiconductor substrate
`surface, and embed into the semiconductor devices. As
`a result, further semiconductor device performance and
`reliability degradation occurs.
`Consequently, there is a need for a method and apps-
`ratus to prevent plasma interaction with fabrication
`reactor process chamber walls during plasma-assisted
`processing.
`To remedy the above problems, manufacturers often
`use a special type of plasma-assisted processing known
`as “magnetron-plasma-enhanced” (MPE) processing.
`MPE processing basically entails crossing a magnetic
`field with an electric field in the proximity of a semicon-
`ductor substrate during plasma processing. The crossed
`magnetic and electric fields cause the plasma to appear
`as a gaseous ball enveloping the semiconductor wafer
`and centered therewith. As a result, the plasma ion
`density is greatest around the semiconductor wafer.
`The plasma that
`the semiconductor substrate sees,
`therefore, does not interact significantly with the pro-
`cess chamber walls. MPE processing also provides
`improved gas excitation and higher plasma density than
`with the conventional plasma-assisted processes. MPE
`processing raises the device processing rate and reduces
`semiconductor device degradation from plasma-
`induced contaminants by making the plasma medium
`concentrate near the semiconductor substrate. Thus,
`MPE processing can produce higher semiconductor
`device processing rates without having to increase the
`local plasma ion energies.
`The electric field for the magnetron-plasma-enhance
`ment can be the result of either an externally applied
`DC bias or, alternatively, a self-induced plasma DC bias
`produced on a radio frequency (RF) power source
`coupled to the wafer stage and the plasma medium.
`Coupling an RF power source to the wafer stage results
`in the formation of an electric field perpendicular to the
`wafer surface across the plasma sheath and produces
`the Exfi magnetron effect (in the presence of a trans-
`verse magnetic field). Conventional chucks for RF
`plasma processing, however, suffer from numerous
`limitations.
`
`Applications of plasma-assisted processing for semi-
`conductor device manufacturing include RIE process-
`. ing of polysilicon, aluminum, oxides, and polyimides;
`plasma-enhanced chemical-vapor deposition (PECVD)
`of dielectrics, aluminum, and other materials; low-tem-
`perature metal—organic
`chemical-vapor
`deposition
`(MOCVD) of metals including aluminum and copper;
`low-temperature dielectric chemical-vapor deposition
`for planarized interlevel dielectric formation; and low-
`temperature growth of epitaxial semiconductor layers.
`In RIE, a high-energy radio-frequency (RF) power
`source is applied across two parallel electrodes to pro-
`duce a plasma via electrical gas discharge. Conven-
`tional plasma processes such as RIE, impose a trade-off
`between processing rate and semiconductor device 45
`quality. To increase the R113 processing rate requires
`greater plasma density and/or ion flux. The plasma
`density and ion flux can be increased by raising the
`electrical RF power absorbed within the plasma me-
`dium. Increasing the RF power to the plasma medium,
`however, raises the plasma ion energy levels. Ions with
`excessive energies may damage semiconductor devices.
`This is because the ions can be so energetic (hundreds of
`electron volts) that upon impact they penetrate and
`cause irradiation damage to the semiconductor device 55
`surface. When this type of ion radiation damage occurs,
`a post-etch surface cleaning and/or annealing process is
`necessary to
`the adverse effects to the semi-
`conductor device performance. Some RIE processes
`may also leave undesirable chemical deposits such as 60
`tluorohydrocarbons on the semiconductor device sur-
`face. Ultimately, the manufacturer must remove these
`deposits from the semiconductor device in order to
`prevent degradation of device fabrication yield. Due to
`lack of plasma confinement, the conventional plasma
`processing techniques may introduce various contami-
`nants (e.g., metals into the semiconductor substrate. The
`contaminants can be transferred by the plasma medium
`
`50
`
`65
`
`Conventional RF chucks used for plasma processing
`in a semiconductor device fabrication chamber use an
`
`Intel Corp. et al. Exhibit 1009
`
`Intel Corp. et al. Exhibit 1009
`
`

`
`5,192,849
`
`3
`RF electrode to generate the plasma. These devices
`usually have a large thermal mass and do not possess
`capability to operate over a wide range of temperatures.
`As a result, they have associated long thermal heat-up
`and cool-down transient times and cause substrate tem-
`perature nonuniformities during heating and cooling.
`During MPE processing, temperatures within a fabrica-
`tion reactor can range from - l50' C. to +750’ C. (The
`conventional RF plasma chucks can usually operate
`either in the lower temperature range (e.g., 0' C. to 200'
`C. for plasma etch processes) or in the medium tempera-
`ture range (for temperatures up to 450' C. for plasma
`deposition processes). The conventional RF plasma
`chuck devices are not multipurpose and are usually
`incompatible with external magnetron sources. Ad-
`vanced anisotropic etch processes can greatly benefit
`from very low or cryogenic substrate temperatures (as
`low as -150’ C.) due to elimination of lateral etch (no
`etch undercut) and enhanced etch selectivity. More-
`over, magnetron-plasma enhancement (with or without
`cryogenic substrate temperature) provides additional
`process
`improvements. Magnetron-plasma-enhanced
`(MPE) cryogenic processing may also have important
`applications for deposition of thin films. MPE process-
`ing at higher temperatures (l00° C. up to 750‘ C.) has
`important applications for thin-film (e.g. metal) deposi-
`tion and plasma annealing. Capabilities for rapid wafer
`temperature cycling and uniform wafer heating and
`cooling over a wide range of temperatures (— 150° C. to
`750' C.) are essential for device fabrication throughput
`and yield. Conventional chucks do not provide all these
`capabilities together. As a result, there is a need for
`multipurpose RF chuck having a low thermal mass for
`rapid semiconductor wafer heating and cooling times.
`There is also a need for an MPE processing RF chuck
`that provides uniform wafer heating and cooling during
`both transient and steady-state conditions, and strong
`magnetic field at the substrate surface using an external
`magnetron source.
`.
`Other limitations associated with the conventional
`RF chucks for MPE processing include limited operat-
`ing temperature ranges and limited magnetic field trans-
`mittance values. As temperatures exceed 500° C.,
`known RF chucks overheat and suffer from component
`and performance degradation. Conventional RF chucks
`also fail at very low or cryogenic temperatures. Thus,
`there is a need for an MPE processing RF source that
`possesses extended temperature ranges of — 150° C. up
`to 750' C. with negligible component or performance
`degradation.
`Known RF chucks also suffer from a large compo-
`nent thickness (e.g., over two inches) that necessarily
`places the semiconductor substrate a distance from an
`external magnetron module. A thinner RF chuck would
`permit placing a semiconductor wafer closer to the
`magnetron, thus allowing either a smaller and less ex-
`pensive magnetron or a greater magnetic field strength
`and process uniformity for an optimal MPE effect. A
`need exists for an RF chuck having a smaller thickness
`than that of conventional devices in order to
`
`the distance between a semiconductor substrate and an
`MPE module and, as a result, enhance the MPE process
`uniformity and throughput.
`‘
`SUMMARY OF THE INVENTION
`
`According to one aspect of the present invention,
`there is provided a multipurpose low-thermal-mass ra-
`dio-frequency chuck for semiconductor processing
`
`4
`equipment for applications such as chemical-vapor de-
`position (CVD) and RF plasma processing of a semi-
`conductor wafer. The stacked chuck structure com-
`prises a coolant module for extracting heat from the
`semiconductor device, a heating element adjoining the
`coolant module for heating the semiconductor device.
`A radio-frequency plate for associating an electromag-
`netic radio-frequency power source with the semicon-
`ductor wafer, and a vacuum base plate for mechanical
`support and providing vacuum seal to a process cham-
`ber.
`Another aspect of the present invention includes a
`plasma processing radio-frequency chuck for magne-
`tron-plasma-enhanced processing of a semiconductor
`wafer. The radio-frequency chuck comprises a coolant
`module (stacked or sandwiched between two electri-
`cally insulating and thermally conducting boron nitride
`disks) for extracting heat from the semiconductor wa-
`fer, a heating element adjacent to the coolant module
`for heating the clamped semiconductor substrate, a
`radio-frequency plate for associating an electromag-
`netic radio-frequency power source with the semicon-
`ductor wafer, and a vacuum base plate for mechanical
`support and providing vacuum seal to an MPE process-
`ing chamber. The coolant module includes a plurality of
`coolant tunnels for permitting a liquid or gas coolant to
`flow and cool the semiconductor wafer. The heating
`element has a top layer of electrical insulation and pas-
`sivation. Beneath the top layer a power resistor made of
`a thin refractory metal film generates thermal energy to
`heat the semiconductor substrate. A bottom layer of
`electrical insulation and adhesion film adjoins the top
`layer and power resistor and seals the power heating
`resistor
`therebetween. Additionally, a metallic or
`graphite wafer adjoins the coolant module (with a
`boron nitride buffer wafer placed in between) and struc-
`turally supports the stacked chuck elements. The radio-
`frequency plate can be made of a silicon-carbide-coated
`graphite wafer or various metals for coupling a radio-
`frequency electromagnetic power to the semiconductor
`wafer surface. The radio-frequency chuck of the pres-
`ent invention has a thickness of less than 1.25" (total
`thickness including the vacuum base plate).
`The RF chuck of the present invention is low thermal
`mass and multipurpose because it not only allows RF
`biasing of the substrate, but it also beats and cools the
`semiconductor wafer with rapid thermal transients over
`a wide range of temperatures. Because it can perform
`these three functions, the RF chuck of the present in-
`vention greatly enhances the performance and applica-
`tion domain of the semiconductor device processing
`chamber. This can also increase MPE processing uni-
`formity and throughput and semiconductor device fab-
`rication yield.
`A technical advantage of the RF chuck of the present
`invention is that it has a low thermal mass for rapid
`semiconductor wafer heating and cooling. The low
`thermal mass of the RF chuck and the configuration of
`the coolant block and power resistor plate ensures that
`the chuck uniformly heats and cools the semiconductor
`device both during transient and steady-state conditions
`within the fabrication reactor.
`Another technical advantage of the RF chuck of the
`present invention is that it possesses an extended tem-
`perature range of operation relative to known RF
`chucks. The RF chuck can operate at temperatures in
`the range of -150‘ C. to 750' C. with negligible com-
`ponent or performance degradation.
`
`10
`
`15
`
`25
`
`30
`
`35
`
`45
`
`55
`
`65
`
`Intel Corp. et al. Exhibit 1009
`
`Intel Corp. et al. Exhibit 1009
`
`

`
`5,192,849
`
`6
`
`present invention with a different boundary arrange-
`ment and termination of the magnets at the periphery of
`the circular magnetic assembly;
`FIG. 10 shows a cross-sectional View of the preferred
`embodiment of the magnetron module shown in
`FIG. 8 (along the A—A and B—B axes);
`FIG. 11 shows a cross-sectional view of the preferred
`embodiment of the magnetron module shown in FIG. 9
`(along the A—A and B—B axes);
`FIG. 12 shows an alternative embodiment of the
`magnetron module of the present invention using a
`distributed grid magnetic array;
`FIG. 13 is an alternative embodiment of the magne-
`tron module of the present invention using a distributed
`square magnetic array;
`FIG. 14 shows an alternative embodiment of the
`magnetron module of the present invention using a
`cylindrical concentric-ring magnetic array; and
`FIG. 15 is an alternative embodiment of the magne-
`tron module of the present invention using distributed
`cylindrical magnetic array with a combination of ring-
`shaped and cylindrical magnets.
`DETAILED DESCRIPTION OF THE
`INVENTION
`
`5
`Yet mother technical advantage of the present inven-
`tion is that it is based on a stacked multilayer design and
`is a thinner device than known RF chuck for plasma
`and MPE processing. This results in a minimal spacing
`betweena semiconductor substrate within the plasma
`process chamber and an external magnetron module.
`This feature results in an increase in overall MPE pro-
`cessing rate and improved process uniformity.
`Another technical advantage of the present invention
`is that it is easily scalable for semiconductor wafer sizes
`larger than the conventional I50 mm wafers (e.g. 200
`mm and larger). Also, the RF chuck of the present
`invention is compatible with single-wafer plasma pro-
`cessing reactors and various magnetron plasma modules
`thereby making it more useful and functional than many
`known RF chucks that can only be used with a limited
`number of processing equipment configurations. A
`manufacturer can expect the RF chuck of the present
`invention to have a long lifetime, be reliable, and be
`applicable to a wide range of plasma processing equip-
`ment configurations.
`Still another technical advantage is that the present
`invention has a wide variety of applications. Plasma-
`assisted processes that the present invention can im-
`prove include high-rate reactive-ion etching (RIE) of 25
`polysilicon, aluminum, oxides, and polyimides; plasma-
`enhanced chemical-vapor deposition (PECVD) of di-
`electrics, aluminum, and other materials; low-tempera-
`ture
`metal-organic
`chemical-vapor
`deposition
`(MOCVD) of metals including aluminum and copper;
`low-temperature dielectric chemical-vapor deposition
`for planarized interlevel dielectric formation and low-
`temperature epitaxial growth of semiconductors. Addi-
`tional applications include magnetron-plasma process-
`ing (e.g., dry development of photoresist layers) and
`cryogenic magnetron plasma processing (for etch and
`deposition processes). Other applications will become
`apparent as manufacturers use the present invention.
`BRIEF DESCRIPTION OF THE DRAWINGS
`
`40
`
`45
`
`The invention, as well as modes of use and further
`advantages, is best understood by reference to the fol-
`lowing description of illustrative embodiments when
`read in conjunction with the accompanying drawings.
`FIG. 1 shows a partially broken-away diagrammatic
`view of the plasma processing system and the multipur-
`pose chuck integrated with the magnetron plasma mod-
`ule that can be used with the present invention;
`FIG. 2 is a cross-sectional view of a preferred em-
`bodiment of the multipurpose chuck coolant module;
`FIG. 3 provides a planar view of a preferred embodi-
`ment of the groove pattern in the multipurpose chuck
`coolant module;
`FIG. 4 is a cross-sectional view of a preferred em-
`bodiment of the multipurpose chuck heating plate;
`FIG. 5 shows a planar view of a preferred embodi-
`ment of the multipurpose chuck power heating element;
`_ FIG. 6 shows a planar view of a preferred embodi-
`ment of the stainless steel vacuum support plate;
`FIG. 7 is a partially broken-away schematic view of 60
`a single-wafer plasma processing system showing use
`and placement of the magnetron module of the present
`invention (face-down wafer processing);
`FIG. 8 shows a planar view of a preferred embodi-
`ment of the hexagonal-array magnetron module of the
`present invention;
`FIG. 9 provides a planar view of a preferred embodi-
`ment of the hexagonal-array magnetron module of the
`
`65
`
`The preferred embodiment of the present invention is
`best understood by referring to FIGS. 1-15, like numer-
`als being used for like and corresponding parts of the
`various drawings.
`FIG. 1 shows a partially brokenaway diagrammatic
`view of low-thermal-mass multipurpose chuck 20 and
`more particularly illustrates its connections and imple-
`mentation within a single-wafer plasma processing sys-
`tem 10. According to FIG. 1, external magnetron mod-
`ule 12 mounts outside vacuum above stainless steel
`vacuum base plate 16 and main section of the multipur-
`pose chuck 20. Stainless steel support vacuum base plate
`16 provides vacuum seal for process chamber and en-
`gages quartz chuck jacket 22. Beginning at the upper
`left portion of FIG. 1 beneath magnetron module 12,
`inert gas (helium or argon) purge line 24 comprises a
`bore 25 through vacuum plate 16. The inert gas purge
`line provides a low gas flow purge between the bottom
`face of the vacuum base plate and the top face of the
`quartz jacket. The small gap between the vacuum base
`plate and the quartz jacket reduces any direct heat
`transfer between the main body of the multipurpose
`chuck and the water-cooled vacuum base plate. The
`main portion of the multipurpose chuck enclosed in the
`quartz jacket can experience temperatures in the desired
`operating range (—l50' C. to 750’ C.); however, the
`vacuum base plate maintains a fairly constant tempera-
`ture due to water cooling, relative thermal insulation
`from the main chuck, and its larger thermal mass com-
`pared to that of the main chuck. Besides the small vac-
`uum gap, the quartz jacket provides an additional ther-
`mal insulation between the vacuum base plate and the
`main portion of the multipurpose chuck. Due to the
`high reflectivity of the electro-polished stainless steel
`vacuum base plate, the radiative component of heat
`transfer between the main chuck and the vacuum base
`plate is rather small. The gap purge flows radially over
`the quartz jacket and prevents formation of any plasma-
`induced deposits in the cylindrical spacing between the
`main chuck and process chamber 14. RF contact 26
`penetrates through vacuum plate 16 via an RF feed-
`through and connects to RF plate of multipurpose
`chuck 20. Although shown on the edge, the RF feed-
`
`Intel Corp. et al. Exhibit 1009
`
`Intel Corp. et al. Exhibit 1009
`
`

`
`5,192,849
`
`7
`through may be placed at the center of the vacuum base
`plate. Coolant inlet 28 connects through vacuum plate
`16 to the coolant block in the interior of chuck 20.
`Heater wire 30 electrically connects (via an electrical
`feed through) through vacuum plate 16 to chuck 20.
`Spring-loaded thermocouple 32 takes a temperature
`signal from chuck 20 Heater wire 34 taps from chuck 20
`and exits through vacuum plate 16 (via another electri-
`cal feed-through). From the interior of chuck 20, cool-
`ant outlet 36 begins and continues through vacuum
`plate 16. Auxiliary chamber walls 38 seal to vacuum
`base plate 16 and surround process chamber 14 with a
`vacuum shield. Within auxiliary chamber walls 38,
`chuck vacuum base plate 16 seals to process chamber
`wall 40 at chamber vacuum seal 42. If necessary, all the
`chuck feed-throughs (RF, coolant, heater) can be made
`at the center with proper thermal and electrical insula-
`tions. Only the RF and heater feed-throughs need to be
`electrically insulated from the vacuum base plate. The
`coolant inlet/outlet can make direct physical and elec-
`trical contact to the vacuum base plate (system electri-
`cal ground). The coolant, heater, thermocouple, inert
`gas and RF power connections may all run from the
`center of the chuck via the center of the magnetron
`module towards the peripheral facilities. Moreover, as
`explained later, the chuck coolant block may employ
`multiple (two) inlets and multiple (two) outlets. The
`chuck coolant lines can be connected to grooves made
`in the vacuum base plate 16 in order to use the vacuum
`base plate 16 as a heat exchanger. Both the vacuum base
`plate and the coolant are connected to the system elec-
`trical ground and properly insulated from the RF
`power connection.
`Basic elements of multipurpose chuck 20 include
`cooling module 44 which incorporates liquid or com-
`press gas coolant tunnels 46. Heating element 48 is sepa-
`rated from the cooling module 44 by a thin (e.g. 0.060”)
`thermally conducting electrically insulating boron ni-
`tride wafer (not shown) and makes electrical contact
`with heater wires 30 and 34. Heating element 48 is
`placed adjacent to the quartz jacket and is thermally
`insulated from vacuum base plate 16. RF plate 50 inte-
`grally connects to a thermally conducting electrically
`insulating boron nitride wafer (not shown) at the bot-
`tom side of cooling module 44 opposite that of heating
`element 48 and connects to RF power contact 26. Semi-
`conductor wafer 52 is clamped against the RF plate 50
`and quartz wafer holding pins 54 hold wafer 52 in place
`inside the plasma processing module. The RF plate 50
`provides radial and circular grooves on its bottom sur-
`face in order to allow flow of a purge gas such as helium
`or argon resulting in improved thermal contact between
`wafer and chuck. The inert gas grooves on the bottom
`face of the RF plate 50 are connected to a center hole
`which is used both for a thermocouple and the wafer
`backside purge. The thermocouple junction is electri-
`cally insulated from the RF plate by a small boron ni-
`tride pin. The two boron nitride wafers (0.040’’ to
`0.100” thick) in the multilayer stacked chuck structure
`provide proper electrical insulation between the RF
`plate and the coolant module as well as between the
`coolant module and the heater plate. There will be some
`capacitive RF coupling between the RF plate and the
`ground coolant block; however, this efiect can be con-
`trolled by proper choice of the boron nitride bufier
`plate thickness and the external RF tuning circuitry.
`Anodized aluminum or stainless steel ground counter-
`electrode 56 consisting of a flat plate and a cylindrical
`
`10
`
`15
`
`25
`
`35
`
`40
`
`45
`
`55
`
`65
`
`8
`extension component surrounds wafer pins 54 and con-
`tains quartz or metallic gas shower head 58. Gas shower
`head 58 provides one path for process gas injection.
`Sapphire or quartz tube 60 provides a second gas injec-
`tion path for remote microwave (or RF induction)
`plasma stream 62 to enter process chamber via ground
`electrode 56. Microwave cavity 64 surrounds sapphire
`or quartz discharge tube 60 which receives gas from gas
`inlet 66 to generate plasma stream 62. Auxiliary cham-
`ber wall 38 seals to vacuum base plate 16 and surrounds
`process chamber wall 40. This arrangement provides an
`improved vacuum integrity for process chamber due to
`the fact that the space between process chamber collar
`40 and auxiliary chamber 38 is pumped down. The
`vacuum shield between process chamber collar 40 and
`auxiliary chamber 38 is also connected to the load-lock
`chamber vacuum (not shown).
`FIGS. 2 and 3 more particularly show the construc-
`tion of cooling module 44 within chuck 20. FIG. 2 is a
`cross-sectional schematic view of coolant module 44
`showing it to comprise a top metal (such as aluminum or
`copper or nickel or molybdenum) plate 68 and a bottom
`metal plate 70 made of a similar material as the top
`plate. Bottom metal plate 70 mechanically seals to top
`metal plate 68 at welded joint 72 and contains coolant
`tunnels 46.
`FIG. 3 provides a planar view of a suggested groove
`pattern in the bottom plate 70 that demonstrates the
`metal groove pattern 74 for coolant flow through cool-
`ant tunnels 46. In bottom plate 70 there are two separate
`sets of coolant tunnels 46. One set uses coolant inlet 28
`and coolant outlet 36 (also shown in FIG. 1), another
`uses coolant inlet 76 and coolant outlet 78 (not shown in
`FIG. 1). The superimposed combination of these two
`coolant tunnels is expected to result in uniform transient
`and steady-state wafer cooling using a gas cooling me-
`dium such as air or helium or a liquid coolant. Various
`other coolant groove patterns may be used. The coolant
`module may be made of anodized aluminum (for a low-
`temperature chuck) or nickel-plated copper (for a high-
`temperature chuck). Other choices of coolant module
`materials include refractory metals such as nickel or
`molybdenum. If anodized aluminum is used in the cool-
`ing module 44, the chuck can be used over a tempera-
`ture range of -150‘ C. to +500’ C. On the other hand,
`nickel, molybdenum, or copper extend the upper tem-
`perature limit to beyond 750‘ C.
`FIGS. 4 and 5 show the construction of heating ele-
`ment 48. FIG. 4 is a cross-sectional view of heating
`element 48 exhibiting top layer 80 of electrical insula-
`tion and passivation through which heater wires 30 and
`34 contact resistor line 82. Bottom layer 84 of electrical
`insulation integrally joins top layer 80 and heater sub-
`strate wafer 86. Heater substrate wafer 86 comprises
`graphite wafer 88 which SiC-coating 90 surrounds.
`FIG. 5 shows a planar view of top layer 80 and displays
`the pattern that thin-film power resistor line 82 makes to
`form a one-zone power heating resistor 92. Alternative
`patterns may be used for multizone wafer heating.
`Contacts 94 provide electrical connection between
`heater wires 30 and 34 and resistor line 82. Electrical
`contact can be made via spring loading the wire. The
`heater substrate 86 may be also made of boron nitride or
`even quartz. Boron nitride is a good choice of heater
`substrate material because of its high thermal conduc-
`tivity and electrical insulation.