United States Patent [19]
`Mahawili
`
`[11] Patent Number:
`[45] Date of Patent:
`
`5,059,770
`Oct. 22, 1991
`
`[54] MULTI-ZONE PLANAR HEATER
`ASSEMBLY AND METHOD OF OPERATION
`
`4,503,807 3/1985 Nakayama ......................... .. 219/405
`
`4,545,327 10/1935 Campbell 4,859,832 8/1989 Uehara .............................. .. 219/411
`
`[75] Inventor: Imad Mahawili, Sunnyvale, Calif.
`_
`_
`[73] Asslgneei XIIatkIICIIS'gFhHSOB Company, P310
`to, a 1 .
`5
`1 N
`21
`[
`1 App '
`0" 409’12
`[22] Filed:
`Sep. 19, 1989
`[51] Int. c1.5 .............................................. .. F27B 5/14
`[52] Us Cl
`219/391, 219/390
`.
`.
`. .................................. --
`g
`[58] Field of Search
`219/391 395 390 405
`M11 464: 465’ 466’ 46,;
`’
`’
`’
`’
`References Cited
`U_S_ PATENT DOCUMENTS
`-
`_
`21,722,252 13/ 1929 alig?lnd ........................... .. 519/465
`3,836,751
`2151111281; ‘ . I .
`' ' ‘ l l‘
`219/390
`3’842’794 10/1974 Ing _______ __ "
`.... .. 219/464
`4,002,883 1/1977 Hurko
`................ .. 219/405
`4,l01,759 7/1978 Anthony
`4,292,276 9/1981 Enomoto ........................... .. 219/390
`
`""""
`
`[56]
`
`_
`_
`Primary Examiner-Teresa J _ Walberg
`Attorney, Agent, or Firm—John A. Bucher
`
`ABSTRACT
`[57]
`A heater assembly and method of operation for use in
`processing of a substrate such as a semiconductor wafer,
`f°r example in a chemical vapor deposition (CVD)
`reactor chamber, the heater assembly including a di
`electric heater bas'e, radially Spaced apart and Gil-cum
`ferentlally extending heater element segments being
`arranged on the heater base, operation of the plurality
`of heater elements being independently regulated, a
`heater shroud being arranged in spaced apart relation
`over the heater elements while supporting the substrate
`for maintaining a blanket of inert gas between the heater
`elements and the heater Shroud. Inert gas is preferably
`introduced through a central opening in the heater base
`and is selectively regulated for facilitating processing of
`the substrate
`
`25 Claims, 2 Drawing Sheets
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`US. Patent
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`Oct. 22, 1991
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`Sheet 1 of 2
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`5,059,770
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`US. Patent
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`Oct. 22, 1991
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`Sheet 2 of 2
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`5,059,770
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`5,059,770
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`MULTI-ZONE PLANAR HEATER ASSEMBLY
`AND METHOD OF OPERATION
`
`FIELD OF THE INVENTION
`The present invention relates to a heater assembly
`and method of its operation for use in processing a
`substrate such as a semiconductor wafer and more par
`ticularly to such a heater assembly and method of oper
`ation for use in a chemical vapor deposition (CVD)
`reactor.
`
`O
`
`SUMMARY OF THE INVENTION
`Accordingly, there has been found to remain a need
`for an improved heater assembly and method of opera
`tion for use in such techniques. Generally, semiconduc
`tor wafer processing techniques such as those described
`above require temperature uniformity across the entire
`wafer area, typically with a variation of no more than
`i2° C. in order to achieve uniform ?lm processing
`(deposition or etch, for example) on the wafer or sub
`strate. Such temperature uniformity is required in pro
`
`60
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`65
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`25
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`BACKGROUND OF THE INVENTION
`In semiconductor wafer processing, for example,
`CVD, and similar methods, substrates such as silicon
`wafers are typically heated to various temperatures in
`order to carry out different thin ?lm deposition or etch
`operations. Various techniques have been employed in
`the prior art for heating these thin substrates, including:
`(1) infrared heating; (2) visible light source heating; (3)
`radio frequency coupled heaters; and (4) hot plate heat
`ers.
`In the ?rst type of heater, the substrate was physi
`cally rotated past an array of infrared lamps in an effort
`to achieve required uniform temperatures throughout
`the silicon wafer. However, the physical rotation step
`tended to interfere with distribution of gas ?ow over
`and onto the wafer, thus resulting in processing limita
`tions.
`In the second heating method, temperature unifor
`mity was attempted by employing very complex and
`expensive optical reflectors. Stability and uniformity of
`temperatures were determined by complex radiative
`interaction of the various surfaces according to their
`respective emissivities.
`The third method, while also complex and expensive,
`has been commonly employed particularly for process
`ing temperatures in the range of 1,000—1,200 degrees
`centigrade (°C.). However, this method has offered
`sub-optimal temperature uniformity on the substrate
`while being very dif?cult to manipulate in order to
`achieve even a moderate level of temperature unifor
`mity.
`The fourth method has typically been employed for
`low temperature applications, for example below 500°
`C. Such hot plate heaters have commonly consisted of
`an embedded resistance wire in a ceramic or dielectric
`plate or a high thermally conductive metal such as
`aluminum. While satisfactory temperature uniformity
`has been achieved by this method, it has not been found
`suitable for use in high temperature processing due, for
`example, to limits established by metal melting points,
`bonding materials employed and the emission of con
`taminants from the heating element and the metals par
`ticularly at such higher temperatures.
`
`45
`
`2
`cesses which may be carried out in a temperature range
`of typically 250°—l,250° C.
`Semiconductor processing techniques are further
`complicated by the requirement for heating of the wa
`fers or substrates from one side only in order to allow a
`gas delivery system (on the other side of the substrate)
`to be at a different temperature for optimal chemical
`processing. A fundamental problem arises in such heat
`ing techniques in that heat losses in central portions of
`the substrate tend to be very different from heat losses
`in edge portions. Thus, if a substrate is uniformly heated
`across its area, heat loss characteristics of the substrate
`normally cause it to assume a temperature pro?le
`which, when viewed in diametric cross-section, will be
`relatively low at the diametric edges and relatively high
`midway between those diametric extremities. Further
`more, relative heat losses and the temperaturepro?le
`referred to above vary at different temperature levels
`and at different pressures. Thus, as processing tempera
`tures are increased for a substrate, there will be a corre
`sponding increase in the temperature pro?le, that is, a
`greater contrast between maximum and minimum tem
`peratures in different areas of the substrate. In addition,
`the temperature pro?le is also affected by processing
`pressure. This is due in part to the fact that, at pressures
`below about 5 Torr, the heat transfer mechanism is
`mostly by radiation whereas, above about 10 Torr, the
`heat transfer mechanism involves a combination of radi
`ation and convection.
`In any event, the preceding discussion is set forth in
`order to further emphasize the difficulties in maintain
`ing uniform surface temperatures throughout a sub
`strate, particularly where the substrate is being pro
`cessed at a variety of temperatures and/or pressures.
`It is therefore an object of the invention to provide an
`improved heater assembly and method of operation for
`the heater assembly in the processing of substrates or
`wafers in order to overcome one or more problems as
`discussed above.
`More speci?cally, it is an object of the invention to
`provide a heater assembly for use in the processing of
`substrates or wafers in order to develop and maintain a
`uniform elevated temperature throughout the substrate,
`the heater assembly including a dielectric heater base
`having a generally circular surface, a plurality of heater
`elements forming radially spaced and circumferentially
`extending segments which substantially cover the circu
`lar surface of the heater base, a heater shroud arranged
`in spaced apart relation from the heater element seg
`ments and intermediate the heater elements and the
`substrate, separate means for operating the plurality of
`heater elements and means for maintaining a blanket of
`inert gas adjacent the heater element segments.
`Such a combination provides a multi-zone planar
`heater assembly and method of operation therefor per
`mitting modi?cation in heating patterns for the sub
`strate in order to eliminate or minimize temperature
`pro?le effects as discussed above. In particular, the
`heater assembly may be provided with any number of
`heater element segments which are preferably radially
`separated and circumferentially extending in con?gura
`tion. With such a heater con?guration, the different
`heater element segments can be adjusted to achieve
`different heating temperatures in order to either com
`pensate for or substantially eliminate temperature varia
`tions throughout the substrate.
`The heater element segments are preferably formed
`from electrically conductive material or metal capable
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`At the same time, the ability to adjust the ?ow rate
`and/or the type of inert gas even further enhances ver
`satility of the heater assembly. For example, in addition
`to preventing oxidation, increased inert gas flow may be
`provided, for example, between processing operations
`in order to more rapidly cool down both the heater
`assembly and the substrate to facilitate interchange of
`substrates where sequential operations are contem
`plated.
`Additional objects and advantages of the invention
`are made apparent in the following description having
`reference to the accompany drawings.
`
`10
`
`3
`of resistance heating. The dielectric heater base is then
`preferably formed from a dielectric material having a
`similar coefficient of thermal expansion as the heater
`element segments while also being selected to resist
`separation from the heater elements and to remain di
`mensionally stable during rapid and extensive tempera
`ture variations. A particularly preferred combination of
`materials is a heater base formed from boron nitride
`with the heater element segments being formed from
`pyrolytic graphite.
`In a preferred method of construction, the conduc
`tive material for the heater elements is uniformly depos
`ited upon the heater base, circumferential regions of the
`conductive material then being removed, for example
`by machining, to de?ne the radially spaced apart heater
`element segments. Each heater element segment is also
`preferably interrupted by a radially extending line or
`region so that electric contact can be made on opposite
`end portions of each heater segment for causing resis
`tance heating.
`It is yet a further object of the invention to provide a
`heater assembly and method of operation including
`means for maintaining an inert gas blanket over the
`heater element, for example, to prevent oxidation, etc.
`Preferably, a central opening in the heater base forms an
`inlet for the inert gas so that it ?ows radially outwardly
`over the heater elements. The inert gas can then be
`exhausted about the periphery of the heater shroud.
`Preferably, the heater assembly is adapted for use in
`reactor chambers, more particularly in a CVD reactor
`chamber. For example, the heater assembly of the pres
`ent invention is contemplated for use in a CVD deposi
`tion method as disclosed in a copending US. patent
`application Ser. No. 07/370,331 ?led June 22, 1989 by
`the present inventor and entitled METHOD OF DE
`POSITING SILICON DIOXIDE FILM AND
`PRODUCT. In addition, the heater assembly of the
`present invention is also contemplated for use within a
`CVD reactor chamber of the type disclosed in another
`copending US. patent application Ser. No. 07/386,903
`?led July 28, 1989 by the present inventor and entitled
`CHEMICAL VAPOR DEPOSITION REACTOR
`AND METHOD OF OPERATION. Those two co
`pending applications are accordingly incorporated
`herein by reference as though set forth in their entirety
`in order to assure a more complete understanding of the
`present invention.
`It is a further related object of the invention to pro
`vide a method of operation for a heater assembly as
`summarized above. In both the heater assembly design
`and method of operation, it is contemplated that the
`means for regulating operation of the multiple heating
`elements and also the means for regulating flow of inert
`gas can be varied in order to facilitate processing of the
`wafer. In particular, by adjusting the heating effect of
`the different heater elements, temperature variations
`occurring diametrically across a substrate can readily be
`substantially eliminated or reduced to a satisfactory
`level, even for a wide variety of operating temperatures
`and/or pressures. Furthermore, heating capacities of
`the respective heating elements are selected in order to
`permit rapid heating of the substrate to greatly elevated
`temperatures in a very short period of time. For exam
`ple, it is contemplated that the heater assembly of the
`present invention may be employed to heat a substrate
`or semiconductor wafer from ambient to a desired pro
`cessing temperature, typically l,OO0°—l,lOO° C., over a
`time interval of about one minute.
`
`BRIEF DESCRIPTION OF THE DRAWINGS
`FIG. 1 is a plan view of the heater assembly with a
`substrate or silicon wafer in the form of a cylindrical
`disk being mounted thereupon.
`FIG. 2 is a side view, with parts in section, taken
`along section line II—II of FIG. 1 in order better illus
`trate internal construction of the heater assembly.
`FIG. 3 is a plan view of the heater assembly, similar
`to FIG. 1 but with the substrate and heater shroud
`removed to better illustrate a plurality of heating ele
`ment segments.
`FIG. 4 is a schematic representation of the heater
`assembly, generally in side view, arranged within a
`CVD reactor.
`
`DESCRIPTION OF THE PREFERRED
`EMBODIMENT
`Referring now to the drawings and particularly
`FIGS. 1-3, a heater assembly constructed according to
`the present invention is generally indicated at 10. The
`heater assembly 10 is preferably adapted for use within
`a reactor such as that schematically indicated at 12 in
`FIG. 4. The CVD reactor 12 may, for example, be of a
`type contemplated and described in greater detail
`within either of the copending references noted above.
`Accordingly, no further description of the CVD reac
`tor or its general mode of operation is believed neces
`sary within the scope of the present invention.
`Referring particularly to FIG. 2, the heater assembly
`10 includes a water cooled, heater support monolith 14
`capable of being mounted within a reactor chamber as
`illustrated in FIG. 4.
`A tubular riser 16 is centrally secured to the monolith
`with a heater support point 18 being mounted there
`upon. Both the tubular riser 16 and heater support point
`18 are preferably formed from nickel plated stainless
`steel in order to withstand contemplated high tempera
`tures and to avoid introducing contaminants thereinto.
`A disk-shaped heater base 20 formed from a suitable
`dielectric material as described in greater detail below is
`mounted upon the support plate 18 with a plurality of
`heater elements, collectively indicated at 22, being ar
`ranged on a generally circular surface 24 of the heater
`base. Construction of the heater base 20 and heater
`elements 22 is described in greater detail below.
`As for the overall construction of the heater assem
`bly, a cover or shroud 26 is also supported by the mono
`lith 14 in spaced apart relation from the heater elements
`22. Preferably, the shroud 26 is formed from a material
`such as quartz and includes means for supporting a
`substrate or silicon wafer 26 on its upper surface di
`rectly above the heater elements 22.
`The shroud 26 includes a flange or skirt extending
`downwardly in spaced apart relation about both the
`heater base 20 and support plate 18. The skirt 30 is also
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`spaced'apart from a cylindrical ?ange portion 30 of the
`formed centrally in the heater base 20. With the opening
`52 being formed in the heater base 20, the surface 24
`monolith 14. Thus, the shroud 26 serves both to support
`the substrate 28 above the heater elements and also to
`covered by the heater element segments 22A-C is actu
`enclose a space above the heater elements to assure
`ally an annulus as best illustrated in FIG. 3.
`formation of an inert gas blanket over the heater ele
`In any event, when inert gas is introduced through
`ments as described in greater detail below.
`the opening 52 in the heater base 20, it enters the space
`Referring particularly to FIG. 3 in combination with
`32 between the heater element segments and the shroud
`FIG. 2, the heater elements 22 include a plurality of
`26, the inert gas ?owing radially outwardly to blanket
`heater element segments indicated respectively at 22A,
`all of the heater element segments. As the inert gas
`22B and 22C which are slightly spaced apart radially
`?ows radially outwardly past the heater element seg
`from each other while being circumferentially extend
`ments and heater base, it then ?ows around an exhaust
`ing to cover substantially the entire surface 24 of the
`passage formed by the skirt 30 and escapes into the
`heater base 20. Although the heater assembly of the
`reactor chamber 12 to be exhausted along with other
`present invention is thus described with three speci?c
`gases from the reactor in a conventional manner.
`heater element segments, it will be apparent that any
`‘Within the heater assembly 10 as described above, the
`number of such segments could be employed as neces
`heater element segments 22A-C are preferably formed
`sary for assuring uniform temperature control over the
`from pyrolytic graphite which is particularly suited for
`substrate 28.
`withstanding high temperatures contemplated by the
`The heater element segments 22A-C are preferably
`invention. At the same time, it is important that the
`formed from an electrically conductive material, more
`dielectric material forming the heater base 20 be formed
`preferably a metal, deposited directly upon the heater
`from a material having a similar coefficient of thermal
`base 20. The deposited material is then removed, for
`expansion as the heater element segments in order to
`example, by means of machining in order to form cir
`prevent separation therebetween, the dielectric material
`cumferential regions or gaps 34 and 36 providing radial
`of the heater base 20 further being selected to remain
`spacing between the respective heater element seg
`dimensionally stable and to prevent emission of contam
`ments 22A-C.
`inants during rapid and extensive temperature varia
`A radially extending region or gap 38 is also formed
`tions. Most preferably, the heater base 20 is formed
`to intersect all three heater element segments. With the
`from boron nitride which satis?es the requirements
`heater element segments thus being formed upon the
`summarized above. In addition, the boron nitride mate
`heater base, electrode pairs 40A-C extend upwardly
`rial has a white color tending to re?ect heat upwardly
`through the support plate 18 and heater base 20 as illus
`toward the substrate (see FIGS. 2-4). In addition, the
`trated in FIG. 2 for respective connection with the
`pyrolytic graphite can be deposited with good adhesion
`heater element segments 22A-C on opposite sides of the
`onto the boron nitride and readily machined away in
`radial gap 38. The electrode pairs are coupled with a
`order to form the circumferential and radial gaps 34-38
`suitable power source 42, see FIG. 4, the power source
`as described above.
`being capable of individually regulating power supply
`The pyrolytic graphite is preferably deposited to a
`to the respective heater element segments in order to
`thickness of about 0.040 inches in order to provide de
`closely and accurately adjust heating temperatures de
`sired or required ?lm resistance. The heater base 20 may
`veloped by the respective segments.
`be formed with a typical diameter of about 10 inches
`Central portions of the heater element segments
`and a thickness of about 0.25 inches.
`22A-C opposite the electrode pairs 40A-C, are inter
`As noted above, a wide variety of power capabilities
`connected with thermocouple pairs 44A-C respec
`is provided by the power source 42 for the respective
`tively. The thermocouple pairs 44A-C form part of a
`heater element segments 22A-C. In one example, the
`standard proportional/integral/differentially (PID)
`outer heater element segment 22A may be designed
`electronic temperature controller (forming part of the
`with a power delivery capability of up to about 4,000
`power source 42 and not otherwise illustrated) in order
`watts, the intermediate heater element segment 22B
`to provide individual control for the respective heater
`with a power delivery capability of up to about 3,500
`element segments.
`watts and the inner heater element segment 22C with a
`In any event, with the capability of sensing the output
`power delivery capability of up to about 2,500 watts.
`energy or temperature of each heater element segment
`With such a con?guration and with materials as pref
`or zone 22A-C, a temperature pro?le across a diametri
`erably noted above, the heater assembly is capable of
`cal section of the heater can be electronically manipu
`operation under a wide variety of operating parameters
`lated, in a manner well known to those skilled in the art,
`contemplated in various processing techniques.
`in order to achieve close regulation and minimum varia
`The method of operation for the heater assembly is
`tion over the temperature profile. In any event, such
`believed apparent from the preceding description.
`controls permit the maintenance of a desired tempera
`However, the method of operation is described brie?y
`ture pro?le under widely varying conditions of pressure
`below in order to assure a complete understanding of
`and temperature in order to maintain a uniform temper
`the invention.
`ature ?eld within :2" C. across the substrate 28.
`Initially, the heater assembly is constructed and ar
`As noted above, an inert gas blanket is preferably
`ranged as described above, preferably within a reactor
`maintained over the heater element segments 22A-C in
`chamber such as that illustrated in FIG. 4.
`order to prevent oxidation of the segments and also to
`A substrate such as the silicon wafer indicated at 28 is
`facilitate and enhance operation of the heater assembly.
`then mounted upon the heater shroud 26. Operation of
`In that regard, an inert gas such as nitrogen, helium,
`the heater assembly 10 is initiated by actuating the
`argon, etc. is supplied from a source 46 (see FIG. 4)
`power source 42 under a desired set of operating param
`through a ?ow regulating device 48 into a passage 50
`extending axially upwardly through the monolith 14,
`eters according to the particular application and by
`initiating the ?ow of inert gas from the source 46.
`riser 16 and heater support plate 18 to an opening 52
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`diate the heater elements and the semiconductor
`With appropriate power levels being supplied to the
`wafer, and
`heater element segments 22A-C, they are rapidly
`means for maintaining a blanket of inert gas between
`heated to respective temperatures assuring a generally
`the heater elements and the heater shroud.
`uniform temperature pro?le across any selected diamet
`2. The heater assembly of claim 1 wherein the heater
`ric section of the substrate 28.
`elements are formed from pyrolytic graphite.
`The material of the heater element segments 22A-C
`3. The heater assembly of claim 1 wherein the heater
`is protected from oxidation under the severe tempera
`elements are formed by uniformly depositing the con
`tures developed by inert gas flow as described above.
`ductive material over the circular surface of the dielec
`With the substrate uniformly heated as described
`tric heater base and then selectively removing portions
`above, a deposition or etch process may then be carried
`of the conductive material to form the heater elements.
`out within the reactor chamber 12 in a manner contem
`4. The heater assembly of claim 3 wherein the heater
`plated and well known to those skilled in the art.
`element segments are separated from each other by
`The heater assembly of the present invention further
`circumferentially extending regions, each heater ele
`facilitates such operations in that where successive de
`ment segment being interrupted by a radially extending
`position or etching processes are contemplated, power
`region, the separate means for respectively regulating
`from the power source 42 may be interrupted and ?ow
`operation of the plurality of heater elements comprising
`of inert gas from the source 46 increased in order to
`electrical couplings formed on portions of each heater
`rapidly cool various portions of the heater assembly 10
`element segment opposite the respective radially ex
`and the substrate 28. Thus, rapid interchange of sub
`tending region.
`strates is made possible with greater efficiency for both
`5. The heater assembly of claim 1 wherein the heater
`the heater assembly and reactor chamber 12. Even
`base is formed from dielectric material selected to have
`greater cooling may be achieved, for example, by sup
`a similar coef?cient of thermal expansion as the conduc
`plying a different inert gas capable of high thermal
`tive metal in the heater elements, the dielectric material
`conductivity than an inert gas employed during the
`also being selected to resist separation from the conduc
`particular process. When the heater assembly is cooled
`tive metal and to remain dimensionally stable during
`and the substrate 28 cooled and replaced, the operating
`rapid an extensive temperature variations.
`steps described above may then be repeated for simi
`6. The heater assembly of claim 5 wherein the heater
`larly processing the subsequent substrate.
`base is formed from boron nitride and the heater ele
`The heater assembly 10 is contemplated for develop
`ment segments are formed pyrolytic graphite.
`ing temperatures over a wide range as noted above. For
`7. The heater assembly of claim 1 wherein the heater
`example, typical temperatures developed in the sub
`shroud includes means for supporting the wafer there
`strate may range from approximately 200° C. to about
`1,200“ C. and the heater assembly 10 is particularly
`upon.
`8. The heater assembly of claim 1 wherein the means
`effective for assuring uniform temperatures over that
`for maintaining an inert gas blanket comprises a central
`entire temperature range.
`opening in the heater base forming an inert gas inlet so
`Thus, there has been described an effective heater
`that inert gas from the central inlet ?ows radially out
`assembly and method of operation for developing and
`wardly between the heater element segments and the
`maintaining uniform elevated temperatures in a sub
`heater shroud.
`strate. Numerous variations and modi?cations in addi
`9. The heater assembly of claim 8 further comprising
`tion to those speci?cally described above will be appar
`means formed about a peripheral portion of the heater
`ent from the preceding description. Accordingly, the
`shroud for venting the inert gas.
`scope of the present invention is defined only by the
`10. The heater assembly of claim 8 further comprising
`following appended claims which provide further ex
`means for regulating inert gas flow through the central
`amples of the invention.
`opening for facilitating processing of the semiconductor
`What is claimed is:
`wafer.
`1. A heater assembly for use in semiconductor wafer
`11. The heater assembly of claim 1 wherein the means
`processing for developing and maintaining a uniform
`for maintaining an inert gas blanket comprises a central
`elevated temperature in the wafer, comprising
`opening in the heater base forming an inert gas inlet so
`a dielectric heater base having a circular surface,
`that inert gas from the central inlet ?ows radially out~
`a plurality of heater elements arranged on the circular
`wardly between the heater element segments and the
`surface of the heater base and formed from conduc
`heater shroud.
`tive material capable of resistive heating, the plu
`12. The heater assembly of claim 11 further compris
`rality of heater elements forming radially spaced,
`ing means formed about a peripheral portion of the
`circumferentially extending segments which, in
`heater shroud for venting the inert gas.
`combination, substantially cover the circular sur
`13. The heater assembly of claim 11 further compris
`face, the heater element segments being separated
`ing means for regulating inert gas ?ow through the
`from each other by circumferentially extending
`central opening for facilitating processing of the semi
`regions, each heater element segment being inter
`rupted by a radially extending region,
`conductor wafer.
`14. The heater assembly of claim 1 wherein the heater
`separate means for respectively regulating operation
`assembly and wafer are arranged in a chemical vapor
`of the plurality of heater elements, the separate
`deposition (CVD) reactor chamber.
`means for respectively regulating operation of the
`15. A method of heating a substrate during semicon
`plurality of heater elements comprising electrical
`ductor wafer processing and for developing and main
`couplings operatively coupled with each heater
`taining a uniform elevated temperature in the substrate,
`element segment opposite the respective radially
`comprising the steps of
`extending region,
`forming a heater assembly to include a dielectric
`a heater shroud arranged in spaced apart relation
`heater base having a circular surface, a plurality of
`from the plurality of heater elements and interme
`
`40
`
`45
`
`55
`
`65
`
`LAM Exh 1008-pg. 7
`
`

`
`9
`heater elements arranged on the circular surface of
`the heater base, the plurality of heater elements
`forming radially spaced, circumferentially extend
`ing segments which, in combination, substantially
`cover the circular surface, and a heater shroud
`arranged in spaced apart relation from the plurality
`of heater elements and intermediate the heater
`elements and the substrate,
`maintaining a blanket of inert gas between the heater
`elements and the heater shroud during operation of
`the heater assembly, and
`separately regulating operation of the plurality of
`heater elements in order to achieve different heat
`ing temperatures in the respective heater elements
`and thereby substantially eliminate temperature
`variations throughout the substrate for facilitating
`and enhancing processing of the substrate.
`16. The method of claim 15 wherein the heater ele
`ments are formed from a conductive material selected
`for resistive heating.
`17. The method of claim 16 wherein the heater ele
`ments are formed from pyrolytic graphite.
`18. The method of claim 16 wherein the heater ele
`ments are formed by uniformly depositing the conduc
`tive material on the circular surface of the heater base
`and then selectively removing portions of the metal to
`form the heater elements.
`
`5,059,770
`10
`19. The method of claim 15 further comprising the
`step of supporting the substrate in thermally conductive
`relation upon the heater shroud.
`20. The method of claim 15 wherein the inert gas
`blanket is maintained by introducing inert gas through a
`central opening in the heater base and allowing the inert
`gas to flow radially outwardly over the heater elements.
`21. The method of claim 20 further comprising the
`step of venting the radially flowing inert gas about a
`peripheral portion of the heater shroud.
`22. The method of claim 21 further comprising the
`step of regulating inert gas flow through the central
`opening of the heater base for facilitating processing of
`the substrate.
`23. The method of claim 22 further comprising the
`step of mounting the heater assembly and substrate
`within a chemical vapor deposition (CVD) reactor
`chamber and thereafter operating the heater assembly
`as part