US20080179008A1 - Reactor for wafer backside polymer removal using an etch plasma feeding a lower process zone and a scavenger plasma feeding an upper process zone - Google Patents
Reactor for wafer backside polymer removal using an etch plasma feeding a lower process zone and a scavenger plasma feeding an upper process zone Download PDFInfo
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- US20080179008A1 US20080179008A1 US11/685,772 US68577207A US2008179008A1 US 20080179008 A1 US20080179008 A1 US 20080179008A1 US 68577207 A US68577207 A US 68577207A US 2008179008 A1 US2008179008 A1 US 2008179008A1
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Images
Classifications
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L21/00—Processes or apparatus adapted for the manufacture or treatment of semiconductor or solid state devices or of parts thereof
- H01L21/67—Apparatus specially adapted for handling semiconductor or electric solid state devices during manufacture or treatment thereof; Apparatus specially adapted for handling wafers during manufacture or treatment of semiconductor or electric solid state devices or components ; Apparatus not specifically provided for elsewhere
- H01L21/683—Apparatus specially adapted for handling semiconductor or electric solid state devices during manufacture or treatment thereof; Apparatus specially adapted for handling wafers during manufacture or treatment of semiconductor or electric solid state devices or components ; Apparatus not specifically provided for elsewhere for supporting or gripping
- H01L21/687—Apparatus specially adapted for handling semiconductor or electric solid state devices during manufacture or treatment thereof; Apparatus specially adapted for handling wafers during manufacture or treatment of semiconductor or electric solid state devices or components ; Apparatus not specifically provided for elsewhere for supporting or gripping using mechanical means, e.g. chucks, clamps or pinches
- H01L21/68714—Apparatus specially adapted for handling semiconductor or electric solid state devices during manufacture or treatment thereof; Apparatus specially adapted for handling wafers during manufacture or treatment of semiconductor or electric solid state devices or components ; Apparatus not specifically provided for elsewhere for supporting or gripping using mechanical means, e.g. chucks, clamps or pinches the wafers being placed on a susceptor, stage or support
- H01L21/68764—Apparatus specially adapted for handling semiconductor or electric solid state devices during manufacture or treatment thereof; Apparatus specially adapted for handling wafers during manufacture or treatment of semiconductor or electric solid state devices or components ; Apparatus not specifically provided for elsewhere for supporting or gripping using mechanical means, e.g. chucks, clamps or pinches the wafers being placed on a susceptor, stage or support characterised by a movable susceptor, stage or support, others than those only rotating on their own vertical axis, e.g. susceptors on a rotating caroussel
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
- H01J37/00—Discharge tubes with provision for introducing objects or material to be exposed to the discharge, e.g. for the purpose of examination or processing thereof
- H01J37/32—Gas-filled discharge tubes
- H01J37/32009—Arrangements for generation of plasma specially adapted for examination or treatment of objects, e.g. plasma sources
- H01J37/32357—Generation remote from the workpiece, e.g. down-stream
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
- H01J37/00—Discharge tubes with provision for introducing objects or material to be exposed to the discharge, e.g. for the purpose of examination or processing thereof
- H01J37/32—Gas-filled discharge tubes
- H01J37/32009—Arrangements for generation of plasma specially adapted for examination or treatment of objects, e.g. plasma sources
- H01J37/32366—Localised processing
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L21/00—Processes or apparatus adapted for the manufacture or treatment of semiconductor or solid state devices or of parts thereof
- H01L21/67—Apparatus specially adapted for handling semiconductor or electric solid state devices during manufacture or treatment thereof; Apparatus specially adapted for handling wafers during manufacture or treatment of semiconductor or electric solid state devices or components ; Apparatus not specifically provided for elsewhere
- H01L21/67005—Apparatus not specifically provided for elsewhere
- H01L21/67011—Apparatus for manufacture or treatment
- H01L21/67017—Apparatus for fluid treatment
- H01L21/67063—Apparatus for fluid treatment for etching
- H01L21/67069—Apparatus for fluid treatment for etching for drying etching
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L21/00—Processes or apparatus adapted for the manufacture or treatment of semiconductor or solid state devices or of parts thereof
- H01L21/67—Apparatus specially adapted for handling semiconductor or electric solid state devices during manufacture or treatment thereof; Apparatus specially adapted for handling wafers during manufacture or treatment of semiconductor or electric solid state devices or components ; Apparatus not specifically provided for elsewhere
- H01L21/67005—Apparatus not specifically provided for elsewhere
- H01L21/67011—Apparatus for manufacture or treatment
- H01L21/67098—Apparatus for thermal treatment
- H01L21/67115—Apparatus for thermal treatment mainly by radiation
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L21/00—Processes or apparatus adapted for the manufacture or treatment of semiconductor or solid state devices or of parts thereof
- H01L21/67—Apparatus specially adapted for handling semiconductor or electric solid state devices during manufacture or treatment thereof; Apparatus specially adapted for handling wafers during manufacture or treatment of semiconductor or electric solid state devices or components ; Apparatus not specifically provided for elsewhere
- H01L21/683—Apparatus specially adapted for handling semiconductor or electric solid state devices during manufacture or treatment thereof; Apparatus specially adapted for handling wafers during manufacture or treatment of semiconductor or electric solid state devices or components ; Apparatus not specifically provided for elsewhere for supporting or gripping
- H01L21/687—Apparatus specially adapted for handling semiconductor or electric solid state devices during manufacture or treatment thereof; Apparatus specially adapted for handling wafers during manufacture or treatment of semiconductor or electric solid state devices or components ; Apparatus not specifically provided for elsewhere for supporting or gripping using mechanical means, e.g. chucks, clamps or pinches
- H01L21/68714—Apparatus specially adapted for handling semiconductor or electric solid state devices during manufacture or treatment thereof; Apparatus specially adapted for handling wafers during manufacture or treatment of semiconductor or electric solid state devices or components ; Apparatus not specifically provided for elsewhere for supporting or gripping using mechanical means, e.g. chucks, clamps or pinches the wafers being placed on a susceptor, stage or support
- H01L21/68728—Apparatus specially adapted for handling semiconductor or electric solid state devices during manufacture or treatment thereof; Apparatus specially adapted for handling wafers during manufacture or treatment of semiconductor or electric solid state devices or components ; Apparatus not specifically provided for elsewhere for supporting or gripping using mechanical means, e.g. chucks, clamps or pinches the wafers being placed on a susceptor, stage or support characterised by a plurality of separate clamping members, e.g. clamping fingers
Definitions
- Plasma processing of a workpiece or semiconductor wafer typically employs carbon-containing process gases (e.g., fluorocarbon or fluoro-hydrocarbon gases) that enhance the etch selectivity of dielectric materials, such as silicon dioxide, relative to other materials such as silicon.
- carbon-containing process gases e.g., fluorocarbon or fluoro-hydrocarbon gases
- These processes are used to treat the front (top) side of the wafer on which the microelectronic thin film structures are formed.
- the opposite (back) side of the wafer is typically unpatterned.
- the carbon-containing process gases tend to form polymer precursors in the plasma, which can leave a polymer residue on the front side of the wafer and on the exposed portion of the backside of the wafer, and even some distance under the unexposed portion of the wafer backside.
- Such residues should be removed to avoid contamination of later processing steps.
- the polymer residues deposited on the wafer front side tend to be easily removed with plasma ion bombardment using appropriate chemistry.
- the wafer edge is beveled, and the curved surface on the backside of the wafer edge is also exposed and therefore susceptible to polymer deposition during plasma processing.
- the backside of the curved surface of the wafer edge is shadowed from ion bombardment during plasma processing so is more difficult to remove, but can be removed in an oxygen plasma at high temperature (e.g., above 300 degrees C.).
- Such difficult-to-remove polymer films require a post-etch polymer removal step using (for example) an oxygen-rich plasma for thorough polymer removal.
- the plasma etch process is used to form openings (e.g., trenches or contact holes) through multiple thin films on the wafer front side.
- Such thin film structures can include (for example) a special carbon-containing dielectric film having an ultra-low dielectric constant (ultra low-K film).
- the ultra low-K film is exposed in cross-section at the side wall of each trench or contact opening formed by the etch process step. Attempting to remove the backside polymer film by heating and exposing the wafer to an oxygen-rich plasma (during a post-etch polymer removal step) will damage the ultra low-K film by removing carbon from it.
- the wafer support pedestal includes an annular collar surrounding the edge of the wafer.
- a collar tends to shield the wafer edge, but cannot be sufficiently close to the wafer edge to prevent polymer deposition on the backside of the wafer edge. This is because some finite gap between the wafer edge and the collar is required to accommodate variations in the robot wafer placement and tolerance stackup.
- the wafer edge-to-collar gap tends to increase as successive wafers are etched in the chamber, since the collar is (typically) formed of a process-compatible material (e.g., quartz, silicon or silicon carbide) that is gradually etched away during plasma etch processing of successive wafers. Therefore, it has seemed inevitable that unwanted polymer is deposited on the wafer, including the backside edge of the wafer.
- a process-compatible material e.g., quartz, silicon or silicon carbide
- a reactor for removing polymer from a backside of a workpiece.
- the reactor includes a vacuum chamber having a ceiling, a floor and a cylindrical side wall.
- a workpiece support apparatus within the chamber is configured to support a workpiece thereon, so that the workpiece has its front side facing the ceiling.
- the support apparatus leaves at least an annular periphery of the backside of the workpiece exposed.
- a confinement member defines a narrow gap with the outer edge of the workpiece, the narrow gap being on the order of about 1% of workpiece diameter, the narrow gap corresponding to a boundary dividing the chamber between an upper process zone and a lower process zone.
- a vacuum pump is coupled to the lower process zone.
- a lower external plasma-generating chamber introduces a plasma by-product into the lower process zone and a supply of a polymer etch precursor gas coupled to the lower external plasma-generating chamber.
- An upper external plasma-generating chamber is coupled to introduce a plasma by-product into the upper process zone and a supply of a scavenger species precursor gas coupled to the upper external plasma-generating chamber.
- the confinement member includes either a the side wall or an annular ring surrounding the workpiece.
- the reactor further includes a lift apparatus capable of lifting the support apparatus to a raised level of the boundary at which the upper process zone is confined to a height on the order of about 1% of the diameter of the chamber.
- the reactor also includes a lower slit passage in the sidewall adjacent the boundary corresponding to the raised level and open exclusively into the lower process zone, with a lower zone vacuum pump coupled to the lower slit passage.
- the reactor includes an apparatus capable of lifting the support apparatus to a raised level of the boundary at which the upper process zone is confined to a height that is sufficiently small to limit gas residency time in the upper process zone to on the order of about 1% of gas residency time in the lower process zone.
- FIG. 1A depicts a backside polymer removal reactor chamber in which polymer etch species are furnished from a first external plasma source toward the backside of the wafer.
- FIGS. 1B and 1C are plan and elevational views, respectively, of an implementation of the workpiece support pedestal in the reactor of FIG. 1A that can be used in each of the reactors described herein.
- FIG. 2 depicts a modification of the backside polymer removal reactor chamber of FIG. 1A in which etchant scavenger species are supplied from a second external plasma source toward the front side of the wafer.
- FIG. 3 depicts another backside polymer removal reactor chamber in which a concentrated stream of hot radicals or ions are directed to the wafer backside edge from a separate plasma source that is near the wafer.
- FIG. 4 is an enlarged view of a portion of the chamber of FIG. 3 depicting the placement of special materials to contain the concentrated stream of hot radicals or ions.
- FIG. 5 depicts a backside polymer removal process carried out with the reactor chamber of FIG. 1A .
- FIG. 6 depicts a backside polymer removal process carried out with the reactor chamber of FIG. 2 .
- FIG. 7 depicts a group of additional steps for the process of FIG. 6 for removing photoresist from the wafer front side.
- FIG. 8 depicts an alternative group of additional steps for the process of FIG. 6 for removing photoresist from the wafer front side.
- FIG. 9 depicts a backside polymer removal process carried out with the reactor of FIG. 3 .
- FIG. 10 depicts an alternative process carried out in the reactor of FIG. 2 for simultaneously removing backside polymer and removing frontside photoresist from the wafer.
- FIG. 11 depicts a modification of the reactor of FIG. 3 in which the external plasma source of the plasma stream is replaced by an internal inductively coupled source.
- FIG. 12 depicts a modification of the reactor of FIG. 11 , in which the internal inductively coupled source is replaced by an internal capacitively coupled source.
- FIG. 13 depicts an alternative approach in which a ring plasma is generated beneath the wafer backside edge by an inductively coupled source.
- FIG. 14 depicts a modification of the reactor of FIG. 13 in which the inductively coupled source is replaced by an internal capacitively coupled source electrode for generating the ring plasma.
- FIG. 15 depicts a modification of the reactor of FIG. 14 in which the internal capacitively coupled source electrode is replaced by an external capacitively coupled source electrode.
- FIG. 16 depicts a feature of the ceiling for shielding the wafer front side during backside polymer removal.
- FIG. 17 is a block diagram of a process for backside polymer removal and front side photoresist strip involving temperature switching.
- FIG. 18 illustrates a first reactor adapted to perform the process of FIG. 17 .
- FIG. 19 illustrates a second reactor adapted to perform the process of FIG. 19 .
- FIGS. 20 and 21 depict a modification of the reactor of FIG. 2 .
- Exemplary embodiments of the invention pertain to removing polymer from the backside edge of a wafer without damaging critical films, such as an ultra low-K dielectric film, by heating the wafer in a chamber while exposing only the backside of the wafer to polymer etch radicals or plasma by-products, such as atomic or free oxygen, from an external plasma source.
- the oxygen radicals may be provided by an external plasma source which is supplied with an oxygen-containing gas or vapor, such as O2, H2O, N2O, CO2, or CO, for example.
- the oxygen-containing gas may be combined or diluted with other gases such as H2, N2 or Ar.
- fluorine-containing gases such as CF4 or NF3
- CF4 or NF3 fluorine-containing gases
- the critical films in the thin film structure on the wafer front side are protected from damage by the polymer etch species by pumping purge gases across the wafer front side.
- the wafer edge and the chamber side wall are separated by a very narrow gap to define a lower process zone with the wafer backside and an upper process zone with the wafer front side. The narrow of the gap is configured to resist or minimize migration of polymer etch species from the lower to the upper process zone where it would attack the ultra low-K film on the wafer front side.
- the external plasma source is coupled to the lower process zone so that the polymer etch species are delivered to the wafer back side. Delivery rate and residence time of polymer etch species are minimized in the upper process zone by restricting the height of the upper process region to a very narrow gap between the wafer and the chamber ceiling.
- the purge gases pumped across the wafer front side may be inert or non-reactive. Such purging reduces the etch rate of the front side critical films relative to the backside polymer removal rate.
- the purge gases may be supplemented with or replaced by reactive scavenger gases that chemically scavenge the backside polymer etch species in the upper process region.
- a further increase in the backside polymer etch rate is attained by employing a second (upper) external plasma source coupled to the upper process zone.
- Gases that are precursors of species that scavenge the polymer etchant are introduced into the upper external plasma source, to produce scavenger radicals for the upper process zone that reduce the amount (partial pressure) of polymer etchant species in the upper process zone.
- pressure is maintained sufficiently low pressure in the upper process zone to enable the upper external plasma source to generate plasma efficiently, while simultaneously achieving a sufficiently high flow rate of scavenger species to protect the wafer front side thin films.
- unused polymer etch species are removed from the lower process zone before they migrate to the upper process zone.
- the upper and lower process zones are separately evacuated near the wafer edge through separate pumping evacuation ports in the sidewall near the wafer edge.
- the scavenger species from the upper external plasma source may be heated before they enter the upper process zone.
- the scavenger species furnished by the upper external plasma source that removes the polymer etch species from the upper process zone may also serve to remove photoresist from the wafer front side.
- photoresist removal may be performed in a separate step in which no polymer etch species are introduced into the lower process zone and the wafer-to-ceiling gap (height of the upper process zone) is increased.
- an agent gas e.g., nitrogen
- that promotes the etching of photoresist from the wafer frontside may be furnished in a small quantity to the upper external plasma source.
- none of the front side thin film layers is susceptible to damage by the polymer etch species, and the steps of backside polymer etch removal and front side photoresist removal are performed simultaneously using the upper and lower external plasma sources.
- the height of the upper process zone is increased by lowering the wafer support pedestal.
- an increase in polymer etch rate relative to etch rate of the critical (ultra low-K) film by the polymer etch species is achieved by locating the lower external plasma source very close to the wafer edge and directing a concentrated stream or jet of plasma products from the lower external plasma source directly at the wafer backside edge while rotating the wafer.
- the concentrated stream may consist of polymer etchant ions, radicals and neutrals, while at a higher pressure the stream consists of etchant radicals and neutrals.
- a plasma reactor for removing polymer residue from the backside of a semiconductor wafer includes a reactor chamber 100 having a side wall 102 , a ceiling 104 that is a gas distribution plate and a floor 106 .
- the ceiling or gas distribution plate 104 has an interior gas manifold 108 and plural gas injection orifices 110 opening from the manifold 108 into the interior of the chamber 100 .
- a wafer support pedestal 112 in the form of a disk-shaped table has a diameter less than the diameter of a workpiece to be supported on the pedestal 112 , so as to expose the backside peripheral annulus of the workpiece.
- the pedestal 112 is supported on a lift member 114 elevated and lowered by a lift actuator 116 .
- a workpiece such as semiconductor wafer 118 can be supported with a center portion of its backside resting on the pedestal 112 .
- the front side of the wafer 118 (the side on which the microelectronic thin film structures are formed) faces the ceiling gas distribution plate 104 .
- the pedestal 112 is sufficiently small to leave an annular periphery of the wafer backside exposed, for backside polymer removal.
- the wafer 118 has a rounded or beveled edge as depicted in FIG. 1A .
- Such a beveled feature may make it difficult to avoid polymer deposition on the wafer backside during plasma (e.g., etch) processing of thin films on the wafer front side.
- radial arms 113 are provided to position the workpiece 118 on the pedestal 112 .
- three symmetrically spaced thin radial arms 113 shown in FIG. 1B are provided and extended outwardly from the periphery of the pedestal 112 .
- the radial arms 113 are below the workpiece support surface of the pedestal 112 so as to leave the entire peripheral annulus of the workpiece backside exposed for backside polymer removal.
- Each radial arm 113 supports a thin axial tab 113 a at its distal end, the tabs 113 a serving to locate the workpiece 118 in coaxial alignment with the pedestal.
- the chamber side wall 102 can include a removable liner or process kit 120 .
- the term sidewall 102 is used to include a liner 120 if one is present.
- a gap 122 between the wafer edge 118 a and the side wall 102 is very small, e.g., about 0.2-2 mm, so as to resist migration of gases through the gap 122 .
- the gap is configured to be sufficiently narrow to present a gas flow resistance that is on the order of about one hundred times greater than gas flow resistance in other portions of the chamber.
- the gap 122 may be on the order of about 1% of the chamber diameter.
- the wafer 118 divides the chamber 100 into an upper process zone 130 bounded in part by the front side or top surface of the wafer 118 and a lower process zone 132 bounded in part by the backside or bottom surface of the wafer 118 .
- a bottom external plasma source 134 receives a polymer etch precursor gas from a gas supply 136 and furnishes polymer etch radicals (e.g., oxygen radicals or atomic oxygen) into the lower process zone 132 through a port 138 in the chamber floor 106 .
- polymer etch precursor gas from a gas supply 136 and furnishes polymer etch radicals (e.g., oxygen radicals or atomic oxygen) into the lower process zone 132 through a port 138 in the chamber floor 106 .
- Some polymer etchant (e.g., oxygen) radicals can migrate from the lower process zone 132 into the upper process zone 130 through the gap 122 and pose a risk of damage to critical layers on the wafer front side, such an ultra low-K thin film.
- a non-reactive purge gas namely a gas that does not react with the thin film materials on the wafer front side, (e.g., nitrogen gas or argon gas) is supplied to the ceiling gas distribution plate 104 from a gas supply 140 in order to flush out the upper process zone 130 and keep it free of etchant species.
- the upper process zone 130 is restricted to a very small height corresponding to a small wafer-to-ceiling gap 144 , e.g., about 0.2-2 mm.
- the gap 144 may be sufficiently small to confine the cross-section of the upper zone 130 to an aspect ratio greater than 100.
- the upper process zone height (gap 144 ) is sufficiently small so that residence time of gas in the upper process zone 130 is less than about one tenth to one hundredth of the gas residence time in the lower process zone 132 .
- the upper process zone height (gap 144 ) is sufficiently small so that gas flow resistance through the gap 144 is on the order of 100 times the gas flow resistance through the lower process zone 132 .
- Such confinement of the upper process zone height may be accomplished by raising the wafer support pedestal 112 with the lift actuator 116 .
- pressure in the chamber 100 is controlled by a vacuum pump 146 that maintains the lower process zone 132 at a sufficiently low pressure to draw plasma by-products out of the lower external plasma source 134 and maintain the external plasma source 134 at a sufficiently low pressure to enable it to efficiently generate plasma.
- the upper and lower process zones 130 , 132 may be evacuated separately through separate slit openings near the wafer edge by separate pumps 210 , 216 . In this case, the vacuum pump 146 may not be necessary.
- the polymer removal process is quickened by heating the wafer 118 to on the order of 300 degrees C., for example, either by an electrical heating element 150 inside the pedestal 112 or by radiant lamps (not shown).
- An electrical heater power supply 152 is coupled to the heating element 150 through wires in the lift member 114 .
- etching of films (e.g., an ultra low-K film) on the wafer front side is minimized or eliminated by maintaining a very high flow rate of a non-reactive purge gas (e.g., nitrogen or argon) through the ceiling gas distribution plate 104 into the upper process zone 130 .
- a non-reactive purge gas e.g., nitrogen or argon
- the purge gas flow rate may be as high as necessary to achieve a desired etch selectivity, raising the pressure of the upper process zone 130 to a very high level.
- the pressure in the lower process zone 132 is maintained at a sufficiently low level (e.g., a few Torr or less) to ensure efficient operation of the external plasma source 134 .
- a sufficiently low level e.g., a few Torr or less
- the chamber interior pressure of the external plasma source 134 typically should not exceed a few Torr, and because the external plasma source 134 is coupled directly to the lower process zone 132 , the pressure in the lower process zone 132 should be maintained at a correspondingly low level.
- This requirement is met by the main chamber vacuum pump 146 (or by the vacuum pump 216 ) regardless of the high flow rate of purge gas into the upper process zone 130 through the gas distribution plate 104 . This permits the purge gas flow rate and upper process zone pressure to be as great as necessary to eliminate or minimize etching of any ultra low-K film on the wafer front side.
- a dissociation agent gas e.g., nitrogen
- the polymer etch precursor gas e.g., oxygen
- a gas supply 158 furnishes an etchant scavenger gas (e.g., hydrogen or carbon monoxide) to the ceiling gas distribution plate 104 .
- an etchant scavenger gas e.g., hydrogen or carbon monoxide
- This may be instead of or in addition to the non-reactive purge gas from the gas supply 140 .
- Some polymer etchant (e.g., oxygen) atoms or molecules that have migrated into the upper process zone 130 are chemically consumed by combining with the scavenger gas (e.g., H2 or CO).
- this scavenger reaction may be accelerated by heating the scavenger gases furnished to the gas distribution plate 104 with an electrical heater 159 .
- the scavenger gas may be carbon monoxide or hydrogen. Carbon monoxide is less reactive with a carbon-containing ultra low-K film than the oxygen gas that it scavenges from the upper process zone 130 .
- Hydrogen gas may be a good choice for the scavenger gas because it may not deplete carbon from the carbon-containing ultra low-K film, and therefore fulfills a requirement of being less reactive with the ULK film than the polymer etch species (oxygen) that it scavenges.
- the scavenger gas is selected so that the product of the chemical reaction between the scavenger and the polymer etchant (e.g., oxygen) does not react at a high rate with the ultra low-K film.
- the product is water and in the case of a carbon monoxide scavenger, the product is carbon dioxide, satisfying the requirement of a scavenging reaction product that is safe for the ultra low-K film.
- the reactor of FIG. 1A is used to remove photoresist from the wafer front side.
- the wafer pedestal 112 may be lowered to the dashed-line position of FIG. 1A , to enlarge the upper process zone 130 with a wafer-to-ceiling gap of about 0.5 to 5 cm. If none of the thin film materials on the wafer front side include a ULK film or other material susceptible to damage from oxygen, then the oxygen radicals from the lower process zone 132 are permitted to migrate into the upper process zone 130 by halting the purge gas flow from the gas supply 140 and/or the scavenger gas flow from the gas supply 158 . Also, such migration may be enhanced if the sidewall-wafer gap 122 is greater at the lowered (dashed-line) wafer position. In this optional mode, the backside polymer and the frontside photoresist are removed simultaneously.
- FIG. 2 depicts a modification of the reactor of FIG. 1A .
- the reactor of FIG. 2 may be particularly advantageous in providing even greater protection for ultra low-K films on the wafer front side during backside polymer removal.
- a second external plasma source 200 is provided in the reactor of FIG. 2 .
- the amount of polymer etchant species (e.g., oxygen) in the upper process zone 130 is reduced more efficiently because the second (upper) external plasma source 200 provides plasma by-products (e.g., radicals) of a scavenger species (e.g., hydrogen or nitrogen) to the ceiling gas distribution plate 104 .
- a scavenger species e.g., hydrogen or nitrogen
- the scavenger species radicals chemically scavenge or combine with some polymer etchant species (e.g., oxygen) that may migrate into the upper process zone 130 .
- etchant species e.g., oxygen
- Such radicals tend to have a faster rate of reaction with the etchant species (than the molecular gas scavenger of the reactor of FIG. 1A ) and therefore provide a higher rate of removal of etchant species (e.g., oxygen) from the upper process zone 130 .
- This provides superior protection from attack upon thin film structures (e.g., an ultra low-K film) on the wafer front side.
- a gas supply 202 furnishes a molecular gas form of a scavenger precursor (e.g., hydrogen or nitrogen gas) to the chamber of the top external plasma source 200 .
- a scavenger precursor e.g., hydrogen or nitrogen gas
- By-products of the plasma generated by the source 200 e.g., either hydrogen radicals or nitrogen radicals
- scavengers of the polymer etch species e.g., oxygen
- the top external plasma source 200 may consist of a dielectric (e.g., quartz) tube chamber 204 encircled by an RF coil antenna 206 that is driven by an RF plasma source power generator 208 through an impedance match element 209 .
- the quartz material is compatible with the hydrogen or nitrogen chemistry of the top external plasma source 200 .
- the top external plasma source 200 produces radicals of the scavenger species that are fed to the ceiling gas distribution plate 104 through a center port 212 .
- a baffle 214 is provided in the center of the gas manifold 108 that blocks direct gas flow from the center port 212 to gas injection orifices 110 near the center of the gas distribution plate 104 .
- a toroidal plasma chamber may be used for either (or both) the top and bottom external plasma sources 200 , 134 .
- Such a toroidal chamber consists of reentrant conduit of a conductive material.
- such a toroidal plasma chamber may include an insulating liner protecting the conductive chamber or conduit.
- the chamber pressure within the top external plasma source 200 should be sufficiently low (e.g., not exceeding several Torr) to ensure efficient plasma generation within the external chamber 204 . Since the top external plasma source 200 is coupled to the upper process zone 130 (through the gas distribution plate 104 ), the upper process zone pressure cannot be too high without extinguishing plasma in the external source 200 . Meeting this limitation may prevent a sufficiently high flow rate of scavenger species into the upper process zone 130 necessary to protect the wafer front side.
- an upper zone vacuum pump 210 is coupled directly to the upper process zone 130 through an upper zone vacuum slit passage 217 that is near (but slightly above, by a few mm or less) the wafer edge and passes through the side wall 102 (and liner 120 if present).
- the upper zone vacuum pump 210 facilitates or ensures a sufficient flow rate through the very thin wafer-sidewall gap 122 .
- the main vacuum pump 146 may be eliminated in the reactor of FIG. 2 , as will be discussed below.
- the pumping rate of the upper zone pump 210 is maintained at a sufficient level to keep the pressure in the upper process zone 130 below a few Torr, for example. This permits a high flow rate of radicals from the top external plasma source 200 and ensures quick removal of scavenger-etchant reaction by-products from the upper process zone 130 .
- the present embodiment provides a low chamber pressure inside the top external plasma source 200 to facilitate efficient plasma generation within the top external plasma source 200 .
- the present embodiment also reduces the migration of scavenger or purge species into the lower process zone 132 that would otherwise dilute the polymer etch species (e.g., oxygen) at the wafer backside.
- a lower zone vacuum pump 216 is coupled to the lower process zone 132 through a lower zone slit passage 218 that is near (but slightly below, by a few mm or less) the wafer edge.
- the upper and lower slit passages 217 , 218 are within a few (or several) mm of each other along the rotational axis of symmetry of the chamber.
- both slit passages 217 , 218 are at heights above and below (respectively) the wafer by about 1 mm, although this distance may be in a range of about 0.5 to 2 mm, for example.
- the slit passage 217 , 218 may be axially displaced from one another by about 1-2 mm. Generally the distance is less than the wafer-to-ceiling gap (the height of the upper process zone 130 ).
- the upper and lower zone vacuum pumps 210 , 216 operate simultaneously to remove through separate slit passages 217 , 218 etchant-scavenger reaction by-products (from the upper zone 130 through the slit passage 217 ) and etchant species and etchant-polymer reaction by-products (from the lower zone 132 through the slit passage 218 ).
- the slit openings 217 , 218 have a narrow (e.g., 0.2-2 mm) axial height and extend around at least nearly the entire circumference of the side wall 102 .
- the slit openings 217 , 218 are each completely enclosed except for their connections to the respective pumps 210 , 216 .
- the main vacuum pump 146 is eliminated in the reactor of FIG. 2 .
- Providing the upper and lower vacuum pumps 210 , 216 increases the flux of etchant species to the wafer backside.
- the upper and lower vacuum pumps 210 , 216 and their slit passages 217 , 218 may also be included in the reactor of FIG. 1A , although they may not be required in the reactor of FIG. 1A because of the lack of an upper external plasma source 200 in FIG. 1A . Because the upper external plasma source 200 is not present in the reactor of FIG. 1A , the purge gases may be pumped through the gas distribution plate 104 at very high pressure to protect the wafer front side. Therefore, the local pumps 210 , 216 and their slit passages 217 , 218 are not necessarily required in the reactor of FIG. 1A .
- Various kinds of plasma sources may be used for the upper and lower external plasma sources 134 , 200 , such as microwave, conventional ICP or toroidal.
- the process chemistries that are to be used in the upper and lower sources 134 , 200 limit the choice of materials.
- Toroidal reactors typically have metallic chambers or conduits, such as anodized aluminum, which is incompatible with the hydrogen chemistry of the upper plasma source 200 .
- toroidal plasma sources are also available with quartz liners or quartz toroidal shaped (round or square) vacuum vessels.
- the choice of external plasma source may be more limited to conventional inductively coupled plasma sources, such as a quartz, alumina, sapphire or Yittria tube wrapped with an RF-driven coil, for example. Sources may also be electrostatically shielded to reduce plasma ion bombardment and subsequent erosion or particle/contamination issues.
- the lower external plasma source 134 may be a toroidal plasma source, consisting of a toroidal chamber 220 fed by the process gas supply 136 , a coiled RF power applicator 222 coupled to the toroidal chamber 220 and a passage 224 from the toroidal chamber 220 to the port 138 .
- the coil 222 may be driven by an RF generator through an impedance match, or may simply driven by a switched power supply (We need to discuss).
- the toroidal chamber 220 is typically formed of metal with a dielectric external film, such as anodized aluminum, which is compatible with the oxygen and nitrogen gases employed in the lower external plasma source 134 . Because the upper external plasma source 200 is supplied with hydrogen gas, anodized aluminum is not a practical material for the upper source 200 , and therefore its chamber 204 , in one example, is formed of another material (such as quartz) that is compatible with hydrogen.
- the reactor of FIG. 2 is used to remove photoresist from the wafer front side.
- oxygen (polymer etchant) flow from the gas supply 136 is halted (or the plasma in the lower source 134 is extinguished).
- this step is carried out with the height of the upper process zone 130 being in the narrow regime (0.2-2 mm) discussed above, to enhance the photoresist removal rate.
- uniformity of the photoresist removal may be enhanced by increasing the upper process zone height, in which case the wafer pedestal 112 is lowered to the dashed-line position of FIG. 2 , to enlarge the upper process zone 130 with a wafer-to-ceiling gap of about 2.5 to 5 cm.
- Hydrogen radicals or related plasma by-products from the upper external plasma source 200 fill the upper process zone 130 and remove photoresist from the wafer front side in a reactive etch process.
- This reaction is promoted by supplementing the hydrogen gas flow to the upper external plasma source 200 with an oxygen-containing gas (H2O or N2O) at a lower flow rate from another gas supply 240 .
- the flow rate of the oxygen-containing gas into the upper plasma source 200 may be less than 5% of the hydrogen flow rate.
- This photoresist removal step may be performed before or after the backside polymer removal step.
- a capacitively coupled plasma is generated from the hydrogen in the upper process zone 130 by an RF power generator 250 coupled through an impedance match 252 across the ceiling gas distribution plate 104 and the wafer support pedestal 112 (in its lowered dashed-line position of FIG. 2 ).
- hydrogen ions are generated in the upper process zone 130 to conduct reactive ion etching of the photoresist on the wafer front side.
- the initial placement of the reactor of FIG. 2 in a plasma etch system may require replacing one of two single wafer load locks normally present in such a system with the reactor of FIG. 2 .
- An etch system typically includes four plasma etch reactors, two single wafer load locks and a factory interface.
- the reactor of FIG. 2 may be configured to perform the functions of the single wafer load lock that it replaces in the plasma etch system.
- wafer ingress/egress slit valves 270 , 272 are provided on opposite sides of the reactor through the side wall 102 (and liner 120 ). The pair of slit valves 270 , 272 enables the reactor of FIG. 2 to function as a single wafer load lock.
- a localized stream or jet of plasma radicals, neutrals, and ions of an etchant species is used to provide an even higher rate of backside polymer removal.
- the stream or jet of plasma species is directed onto a small target area or window of the wafer backside edge while rotating the wafer.
- a local external plasma source 300 may be located near the wafer edge, and a short conduit 302 directs plasma ions from the interior of the local external plasma source 300 as a localized stream of plasma ions, radicals and neutrals to the small target region at the wafer backside edge.
- the conduit 302 is sufficiently short and its output end is sufficiently close to the wafer backside to enable to enable ions from the source 300 to reach the wafer backside.
- the transit distance between the output end of the short conduit and the wafer support plane of the pedestal 112 may be 5% or less of the pedestal or wafer diameter.
- a gas supply 136 furnishes a polymer etch precursor gas to the local external plasma source 300 .
- the wafer pedestal 112 is rotated by a rotation actuator 304 coupled to the support member or leg 114 of the pedestal 112 .
- the local external plasma source 300 By operating the local external plasma source 300 at a low chamber pressure, it becomes a rich source of plasma ions and electrons, and the concentrated stream from the conduit 302 consists of a large proportion of ions in an ion/radical mixture.
- the external plasma source 300 By placing the external plasma source 300 close the wafer 118 and keeping the conduit 302 short, ion loss through recombination is minimized, and the particle stream emanating from the conduit 302 remains rich in ions.
- the backside polymer etch rate is increased by the ion jet stream in the reactor of FIG. 3 ; the ion energy at the wafer backside edge surface may be increased by applying RF bias power between the local external plasma source 300 and the wafer support pedestal.
- an RF bias power generator 310 is coupled through an impedance match element 312 across the wafer support pedestal and the local external plasma source 300 .
- a gas supply 156 can furnish to the local external plasma source 300 a dissociation agent gas (e.g., nitrogen) that promotes the dissociation of the etchant species (e.g., oxygen) in the plasma of the local external plasma source 300 .
- the chamber pressure in the local external plasma source may be increased. Raising the chamber pressure of the local external plasma source 300 reduces the proportion of ions and raises the proportion of radicals in the stream of particles ejected by the conduit 302 . Furthermore, if a purely radical stream is required, then it is not necessary to locate the external plasma source 300 near the wafer. Instead, it may be located (for example) near the bottom of the main chamber 100 (as indicated in dashed line in FIG. 3 ) and the conduit 302 may be relatively long (as shown in dashed line in FIG. 3 ).
- the concentrated jet stream from the plasma source 300 can be very hot (e.g., as much as 600 degrees C.), and this heat can expedite the reaction between the etch species and the backside polymer.
- the entire wafer is initially heated to about 300 degrees C. before exposing the backside to the concentrated radical or ion stream from the local plasma source 300 and conduit 302 .
- metal surfaces can be protected with a dielectric (e.g., quartz) liner 320 that covers the bottom surface of the ceiling gas distribution plate 104 and a dielectric liner 120 that covers the interior surface of the side wall 102 .
- a dielectric liner 320 that covers the bottom surface of the ceiling gas distribution plate 104
- a dielectric liner 120 that covers the interior surface of the side wall 102 .
- the enlarged view of FIG. 4 shows how each slit opening 217 , 218 may open into a larger passage, but is completely enclosed within the chamber wall except for the connection to the respective pump 210 , 216 .
- FIG. 5 depicts an exemplary method that can be carried out in the reactor of FIG. 1A .
- a first step (block 402 ) is to support the wafer (using the pedestal 112 ) so as to expose a peripheral portion of the wafer back side, while beginning to heat the wafer to on the order of 300 degrees C.
- a next step (block 404 ), which may begin before the final wafer temperature (e.g., 300 degrees C.) is reached, is to define an upper process zone 130 above the wafer front side and a lower process zone 132 below the wafer back side with minimal migration of gas between the two zones by maintaining a wafer-to-sidewall gap at less than 2 mm.
- a further step (block 406 ) is to prevent accumulation of etch species at the wafer front side, or (equivalently) facilitate fast evacuation of the upper zone 130 , by maintaining a wafer-to-ceiling gap (the height of the upper process zone 130 ) at a value at which a high gas flow resistance is established, e.g., less than 2 mm.
- This gap should be sufficiently small to confine the upper process zone 130 to a cross-sectional aspect ratio greater than on the order of 100.
- Another step (block 408 ) is to generate a plasma in an external plasma chamber 134 with a polymer etchant precursor gas (e.g., oxygen), and introduce by-products (e.g., radicals, free oxygen) from the plasma into the lower process zone 132 so as to etch polymer from the wafer back side.
- a related step (block 410 ) is to enhance dissociation of the polymer etchant precursor species (oxygen) by introducing a dissociation agent (nitrogen gas) into the external plasma chamber 134 .
- a further step (block 412 ) consists of reducing the amount of polymer etchant precursor species (oxygen) in the upper process zone 130 by injecting a purge gas (e.g., N2 or Ar) into the upper process zone 130 .
- a related step (block 414 ) consists of further reducing etchant species in the upper process zone 130 by introducing into the upper process zone a scavenger gas (e.g., H2 or CO) that scavenges the etch species (e.g., oxygen).
- the scavenger gas may be used in addition to or instead of the non-reactive purge gas.
- FIG. 6 depicts an exemplary method that can be carried out in the reactor of FIG. 2 .
- a first step (block 416 ) is to support the wafer on the pedestal 112 so as to expose a peripheral portion of the wafer back side while heating the wafer to on the order of 300 degrees C.
- a next step (block 418 ) is to define an upper process zone 130 above the wafer front side and a lower process zone 132 below the wafer back side with minimal migration of gas between the two zones by maintaining a wafer-to-sidewall gap at less than 2 mm.
- a further step (block 420 ) is to prevent accumulation of etch species or plasma at the wafer front side by maintaining a wafer-to-ceiling gap (the height of the upper process zone) at less than 2 mm.
- Another (block 422 ) step is to generate a first plasma in a lower external plasma chamber 134 with a polymer etchant precursor gas (e.g., oxygen), and introduce by-products (e.g., radicals, free oxygen) from the plasma into the lower process zone 132 so as to etch polymer from the wafer back side.
- a related step (block 424 ) is to enhance dissociation of the polymer etchant precursor species (oxygen) by introducing a dissociation agent (nitrogen gas) into the lower external plasma chamber, at a flow rate of 1-10% of the oxygen gas flow rate.
- Another step (block 426 ) is to generate a second plasma in an upper external plasma chamber 200 with a scavenger species (H2 or N2) that scavenges the polymer etch species, and introduce by-products of the second plasma (H radicals or N radicals) into the upper process zone 130 .
- a further step (block 428 ) is to evacuate the upper process zone 130 at a pumping port 217 near the wafer edge to remove polymer etchant species (oxygen) from the upper process zone at a sufficiently high rate to avoid damage of critical (carbon-containing or low-k) films on the wafer front side.
- a related step is to evacuate the lower process zone 132 at a pumping port 218 near the edge of the wafer at a sufficiently high rate to minimize migration of polymer etchant species (oxygen) from the lower process zone 132 into the upper process zone 130 and to maximize delivery of polymer etchant species to the backside edge of the wafer.
- polymer etchant species oxygen
- FIG. 7 depicts an exemplary method carried out in an optional mode of the reactor of FIG. 2 , in which the reactor is employed to etch photoresist from the wafer front side.
- a first step (block 432 ) is to stop the flow of polymer etchant species (oxygen) from the lower external plasma source 134 to the lower process zone.
- this height may be increased in preparation for the frontside photoresist removal step, in which case the next (optional) step (block 434 ) is to increase the wafer-to-ceiling gap to a distance (e.g., 0.5-5 cm) at which etchant species can accumulate in the upper process zone 130 .
- the next step (block 436 ) is to introduce at a reduced flow rate an oxygen-containing species (H2O or N2O) along with the H2 gas into the upper external plasma source 200 (at a flow rate of less than 1-10% of the hydrogen gas flow rate) so as to enhance the etch rate of photoresist from wafer front side.
- the process of FIG. 7 may be performed either before or after the process of FIG. 6 .
- the removal rate of photoresist in this step is enhanced if the height of the upper process zone 130 is restricted to the narrow (0.2-2 mm) range.
- uniformity is enhanced by increasing this height, and the step of block 434 may only increase the upper process zone height by a fractional amount.
- FIG. 8 depicts an alternative method for the reactor of FIG. 2 to etch photoresist from the wafer front side, in which a capacitively coupled plasma is generated in the upper process zone 130 .
- a first step (block 438 ) is to stop the flow of polymer etchant species (oxygen) from the lower external plasma chamber 134 to the lower process zone, and then (block 440 ) increase the wafer-to-ceiling gap to about 2 to 5 cm.
- a next step (block 442 ) is to introduce a photoresist removal species gas (H2) into the upper process zone 130 .
- a further step (block 444 ) is to introduce at a reduced flow rate an oxygen-containing species (H2O or N2O) into the upper process region. This reduced flow rate may be about 1-10% of the hydrogen gas flow rate.
- a next step (block 446 ) is to apply RF power into the upper process zone to produce a plasma that removes photoresist from the wafer front side.
- FIG. 9 depicts an exemplary method that can be carried out in the reactor of FIG. 3 , in which backside polymer is removed by a concentrated or localized stream of plasma ions, radicals and neutrals from an external plasma source.
- a first step (block 448 ) is to support the wafer on the pedestal 112 so as to expose a peripheral portion of the wafer back side while heating the wafer to on the order of 300 degrees C.
- a next step (block 450 ) is to define an upper process zone 130 above the wafer front side and a lower process zone 132 below the wafer back side with minimal migration of gas between the two zones by maintaining a wafer-to-sidewall gap at less than 2 mm.
- a further step (block 452 ) is to prevent (or minimize) flow or delivery rate of etch species or plasma at the wafer front side by maintaining a wafer-to-ceiling gap (the height of the upper process zone) at less than 2 mm.
- a further step (block 454 ) is to generate a first plasma in a local external plasma chamber 300 with a polymer etchant precursor gas (e.g., oxygen), and direct a narrow stream of by-products from the first plasma through an injection orifice 302 near the wafer backside directly at the wafer back side, while rotating the wafer.
- a polymer etchant precursor gas e.g., oxygen
- a related step (block 456 ) is to enhance dissociation of the polymer etchant precursor species (oxygen) by introducing a dissociation agent (nitrogen gas) into the local external plasma chamber 300 .
- Another related step (block 457 ) is to enhance the backside polymer etch rate by applying RF bias power across the local external plasma chamber and the wafer.
- Another step (block 458 ) is to generate a second plasma in an upper external plasma source 200 with a scavenger species (H2 or N2) that scavenges the polymer etch species, and introduce by-products of the second plasma (H radicals or N radicals) into the upper process zone 130 .
- Another step (block 460 ) is to evacuate the upper process zone 130 at a pumping port 212 near the wafer edge to remove polymer etchant species (oxygen) from the upper process zone at a sufficiently high rate to avoid damage of critical (carbon-containing or low-k) films on the wafer front side.
- a related step (block 462 ) is to evacuate the lower process zone 132 at a pumping port 218 near the edge of the wafer at a sufficiently high rate to minimize migration of polymer etchant species (oxygen) from the lower process zone 132 the into the upper process zone 130 .
- FIG. 10 depicts an exemplary process carried out in the reactor of FIG. 2 for simultaneously removing polymer from the wafer backside while removing photoresist from the wafer front side.
- the process of FIG. 10 may be carried out, for example, in cases in which there is no film on the wafer front side (such as a ULK film) that is particularly susceptible to damage from polymer etchant species, or in cases in which any critical or ULK films that are present can tolerate the limited flow of polymer etch species escaping from the lower process zone 132 to the upper process zone 130 .
- a first step (block 464 ) is to support the wafer so as to expose a peripheral portion of the wafer back side while heating the wafer to on the order of 300 degrees C.
- a next step (block 466 ) is to define an upper process zone 130 above the wafer front side and a lower process zone 132 below the wafer back side with minimal migration of gas between the two zones by maintaining a wafer-to-sidewall gap at less than 2 mm.
- a further step (block 468 ) is to generate a first plasma in a lower external plasma chamber 134 with a polymer etchant precursor gas (e.g., oxygen), and introduce by-products (e.g., radicals, free oxygen) from the plasma into the lower process zone 132 so as to etch polymer from the wafer back side.
- a polymer etchant precursor gas e.g., oxygen
- by-products e.g., radicals, free oxygen
- a related step (block 470 ) is to enhance dissociation of the polymer etchant precursor species (oxygen) by introducing a dissociation agent (nitrogen gas) into the lower external plasma chamber 134 .
- a step (block 472 ) carried out simultaneously with the step of block 468 is to generate a second plasma in an upper external plasma chamber 200 with a scavenger precursor gas (H2) and a small proportion of an oxygen-containing species (H2O or N2O).
- H2O oxygen-containing species
- By-products of the second plasma e.g., scavenger species (H radicals) and oxygen-containing radicals, are introduced into the upper process zone 130 .
- the scavenger species removes etch species (e.g., oxygen) from the upper process zone 130 , and—with the help of the oxygen-containing species—removes photoresist from the wafer front side.
- etch species e.g., oxygen
- the result of this step is to simultaneously remove backside polymer using the bottom external plasma source 134 and remove front side photoresist with the upper external plasma source 200 .
- the flow rate of the oxygen-containing (H2O or N2O) into the upper external plasma source 200 species may be 1-10% of the hydrogen flow rate into the upper external plasma source 200 , for example.
- FIG. 11 depicts a variation of the reactor of FIG. 3 , in which the plasma by-product stream or jet directed at the wafer backside edge is produced by components within the reactor itself rather than an external plasma source.
- an external plasma source such as the external plasma source 300 shown in FIG. 3 is replaced in the embodiment of FIG. 11 by an internal plasma source 500 consisting of a cylindrical sealed enclosure 502 , which may be formed of an insulating material such as quartz, and a coil 504 wrapped around a portion of the cylindrical enclosure 502 .
- the coil 504 is outside of the chamber.
- the enclosure 502 is closed at its bottom end 502 a and forms a nozzle or conical shaped outlet 502 b at its top end facing and close to the backside edge of the wafer 118 .
- a gas supply 506 storing a polymer etch gas species is coupled to the enclosure 502 through the bottom end 502 a.
- An RF generator 508 is coupled to the coil 504 (through an optional impedance match, not shown) and furnishes sufficient power to produce an inductively coupled plasma inside the enclosure 502 .
- the pressure inside the enclosure 502 is greater than that of the lower process zone 132 . This pressure difference may be controlled by the main vacuum pump 146 and an optional vacuum pump 509 coupled to the enclosure 502 .
- Plasma by-products for example radicals, neutrals and/or ions escape through the nozzle outlet 502 b and form a concentrated or localized stream 510 that impinges upon a target area of the wafer backside edge.
- an optional RF bias power generator 512 may be connected between an interior electrode 514 inside the enclosure 502 and the wafer pedestal 112 .
- the upper external plasma source 200 of FIG. 3 may be employed in the reactor of FIG. 11 , this option is depicted in FIG. 11 only in dashed line. Instead, the solid line image of FIG. 11 shows that (optionally) the purge gas supply 140 may furnish purge gases through the ceiling gas distribution plate 104 with no external plasma source.
- the purge gas may be either non-reactive or may be a reactive scavenger species, as discussed with reference to FIG. 1 .
- the pedestal 112 may be heated as in FIG. 3 , or radiant lamps (not shown) above the ceiling may be employed.
- a liner 520 of a process-compatible material may cover the side and bottom edge surfaces of the pedestal 112
- a liner 522 of a process compatible material may cover the side wall 102 .
- the liners 520 , 522 may be useful in minimizing metal contamination due to etching of chamber surfaces by the plasma stream 510 .
- the process-compatible material may be, for example, quartz.
- the ceiling 104 may be formed of a process-compatible material such as quartz. In this case, the ceiling may be a smooth simple structure without the gas distribution plate features depicted in FIG. 11 .
- the plasma source enclosure 502 of FIG. 11 may be in the shape of a torus, to form a toroidal plasma source.
- the inductive plasma source 500 (the tube enclosure 502 ) is replaced by a capacitively coupled source 530 as illustrated in FIG. 12 .
- the capacitively coupled source 530 includes a conductive electrode 532 having a small discharge portion or area 532 - 1 close to and facing the backside edge of the wafer 118 and at least one axially extending leg 532 - 2 .
- a polymer etch gas species is introduced into the lower process zone 132 through an opening 533 in the chamber floor from a gas supply 506 .
- An RF generator 534 is coupled between the bottom end of the axially extending leg 532 - 2 and the wafer pedestal 112 .
- a second axially extending leg 532 - 3 parallel to the first leg 532 - 2 may be provided.
- RF power from the generator 534 produces a plasma discharge in the small gap between the electrode discharge portion 532 - 1 and a corresponding area on the wafer backside edge.
- the side of the electrode 532 facing the wafer 118 (or the entire electrode 532 ) may be covered by a liner 535 , which may be formed of a process-compatible material such as quartz, which is useful in minimizing or preventing metal contamination.
- the wafer is rotated so that the entire backside edge circumference is exposed to the localized plasma.
- the pedestal 112 may not be necessary, as will be discussed below.
- the need to rotate the wafer to expose its bottom circumference to a plasma stream is eliminated by instead generating a ring of plasma 538 beneath the backside edge extending around the entire circumference.
- This is accomplished by placing the wafer 118 very close the ceiling 104 , as in the foregoing embodiments, and then applying RF power to a coil antenna 540 overlying the edge of the wafer 118 .
- the coil antenna 540 may consist of solenoidal conductive windings, for example.
- FIG. 13 illustrates how the wafer may be elevated by lift pins 542 suspended on the lift spider 544 controlled by the lift actuator 116 . In this case, the wafer is-heated by radiant lamps 548 through the ceiling 104 .
- the above-ceiling coil 540 may be replaced by a coil 540 ′ around the sidewall 102 .
- photoresist is removed from the wafer front side in a separate process.
- the wafer is lowered to the dashed line position of FIG. 13 , and gases are introduced through the ceiling gas distribution plate 104 capable of removing photoresist, as discussed previously in this specification.
- a second inner coil antenna 550 is provided controlling plasma ion density near the center of the wafer. The presence of the second inner coil antenna 550 also improves uniformity of the photoresist removal.
- the two coil antennas 540 , 550 may be driven at independently adjusted RF power levels, to permit tuning of the plasma ion density radial distribution.
- the lamp heaters 548 are placed in open spaces over the ceiling between the inner and outer coil antennas 540 , 550 .
- the heated pedestal 112 of FIG. 11 can be used to hold the wafer 118 in the elevated position of FIG. 13 .
- efficient heat transfer requires the use of an electrostatic chuck on the pedestal 112 .
- An advantage of using the wafer support pedestal is that it enables bias power to be applied to, the wafer in a highly uniform manner while at the same time effecting uniform heating or temperature control of the wafer.
- a liner 520 can also be provided having process-compatible materials to avoid metal contamination and excessive consumption of pedestal materials during plasma processing.
- An advantage of using the radiant lamps 548 to heat the wafer is faster heat transfer (compared to a heated pedestal) in the case of a low chamber pressure where heat conduction or convection is poor.
- FIG. 14 depicts another embodiment of the reactor of FIG. 13 in which the coil antenna 540 for generating a ring plasma is replaced by a ring electrode 560 surrounding the wafer edge, and an RF generator 562 coupled to the ring electrode 560 .
- RF discharge from the ring electrode 560 produces the ring plasma 538 by capacitive coupling.
- FIG. 15 depicts a modification of the reactor of FIG. 14 in which a ring electrode 560 ′ is outside of the chamber 100 .
- FIG. 16 depicts a modification that can be implemented in any of the reactors described herein, in which the ceiling 104 has a shallow cylindrical hollow 570 corresponding to the volume of the wafer 118 .
- the wafer can be lifted into the hollow 570 to effectively shield the wafer front side from polymer etch gases during the backside polymer removal process.
- FIG. 17 illustrates a process in which the reactor chamber is used to perform reactive ion etch of polymer from the wafer backside in a raised wafer position and then photoresist stripping on the wafer front side in a lowered wafer position. Temperature switching is employed to enhance wafer front side protection. Specifically, backside polymer removal is performed at a low wafer temperature and then front side photoresist strip is performed at a high wafer temperature (the order may be reversed). The backside polymer reactive ion etch step may be performed at a sufficiently low wafer temperature to retard the reaction of its by-products (radicals) with thin films (e.g., photoresist) on the wafer front side.
- the front side photoresist strip process uses radicals from a remote source, it is facilitated by raising the wafer temperature to a threshold at which the reaction rate of the radicals with photoresist is significantly increased. If the front side photoresist strip process is a reactive ion etch process, then the wafer temperature does not necessarily have to be increased for this step.
- a first step is to support the wafer on the pedestal so as to expose a peripheral portion of the wafer back side.
- the wafer temperature is set under a threshold temperature (e.g., under 200 degrees C.) below which the reaction rate of polymer etch species radicals with wafer thin film materials is significantly retarded (block 602 ).
- a next step is to define an upper process zone above the wafer front side and a lower process zone below the wafer back side with minimal migration of gas between the two zones by maintaining a wafer-to-sidewall gap at less than 2 mm.
- a further step (block 606 ) is to prevent accumulation of etch species or plasma at the wafer front side by maintaining a wafer-to-ceiling gap (the height of the upper process zone) at less than 2 mm.
- Another step (block 608 ) is to purge the upper process zone to remove any etch species radicals that may leak through the wafer-sidewall gap.
- a further step (block 610 ) is to evacuate the upper process zone at a pumping port near the wafer edge to remove polymer etchant species (oxygen) from the upper process zone at a sufficiently high rate to avoid damage of critical (carbon-containing or low-k) films on the wafer front side.
- a related step is to evacuate the lower process zone at a pumping port near the edge of the wafer.
- Reactive ion etching of the polymer on the wafer backside is performed with a plasma close to the wafer backside edge (block 614 ), until the backside polymer is completely removed.
- Application of plasma to the wafer backside is then stopped, and the wafer is lowered to increase the height of the upper process zone, in order to permit accumulation of plasma or radicals in the upper process zone (block 616 ).
- the wafer temperature is increased above a higher threshold temperature (e.g., above 300 degrees C.) in order to significantly increase the reaction rate of the radicals with photoresist on the wafer front side (block 618 ).
- the reaction rate increase corresponding to the temperature increase from the lower threshold temperature to the higher threshold temperature is about a factor of 5. Radicals from a remote plasma source are employed to strip the front side photoresist (block 620 ). Alternatively, the step (block 618 ) of raising the wafer temperature may be omitted, and a reactive ion etch process is used to strip the photoresist (block 622 ).
- FIG. 18 depicts a modification of the plasma reactor of FIG. 13 that is capable of performing the process of FIG. 17 .
- a front side (e.g., photoresist strip) process gas supply 160 is provided in addition to the purge gas supply 140 through the ceiling 104 .
- the outer coil 540 ′ is moved to an axial location below the wafer plane.
- the heater lamps 548 are moved from the ceiling to the floor at the bottom of the chamber.
- the heater lamps 548 of FIG. 18 may be employed in carrying out the wafer temperature control step of block 602 of FIG. 17 .
- a quartz window 549 is provided in the floor for the heat lamps 548 .
- the purge gas supply 140 of FIG. 18 provides the gas for the purge step of block 608 of FIG. 17 .
- the pumping ports 217 and 218 of FIG. 18 are used in the steps of blocks 610 and 612 of FIG. 17 .
- the reactive ion etch step of block 614 of FIG. 17 is carried out by the splitter 558 of FIG. 18 applying RF power only to the outer coil 540 ′. This creates a ring of plasma beneath the backside wafer edge, as described previously with reference to FIG. 13 , to remove the backside polymer.
- the wafer 118 is lowered to the dashed line position of FIG.
- process gas e.g., a photoresist strip process gas
- process gas e.g., a photoresist strip process gas
- the splitter 558 applies RF power to both the inner and outer coils 540 , 550 , with power being apportioned between the two coils to optimize plasma ion uniformity over the front side of the wafer.
- the RF power and gas flow is maintained until the completion of the reactive ion photoresist etch step of block 622 of FIG. 17 .
- FIG. 19 depicts a modification of the embodiment of FIG. 18 , in which the ceiling 104 is modified to form an upward extending neck 650 having a cylindrical side wall 652 and a neck cap 654 , forming a neck volume 656 .
- the outputs from the purge gas supply 140 and the process gas supply 160 are received in the neck volume.
- the inner coil 550 is wound around the neck sidewall 652 , so that the neck volume 656 functions as the chamber of a remote plasma source.
- the splitter 558 of FIG. 19 applies power only to the outer coil 540 during the backside etch process to form a ring of plasma beneath the wafer backside edge.
- the splitter 558 applies power only to the inner coil 550 during the front side etch process to provide a remote plasma source.
- the reactor of FIG. 11 may be adapted to perform the process of FIG. 17 by adding a remote plasma source 200 and its process gas supply.
- the remote plasma source 200 may be implemented with a coil wrapped around a neck or tube (as shown in FIG. 19 ) or it may be any other type of plasma source, such as a microwave plasma source, for example.
- the wafer pedestal 112 of FIG. 11 may control the wafer temperature in accordance with the process of FIG. 17 , and the pedestal 112 may move between the raised and lowered (dashed-line) positions of FIG. 11 , as an optional feature of the process of FIG. 17 .
- the reactor of FIG. 12 is modified in the same manner to adapt it to perform the process of FIG. 17 , by adding the remote plasma source 200 at the ceiling of the reactor of FIG.
- FIGS. 13 , 14 and 15 show that, while lift pins may be employed to control the wafer position, a movable heated pedestal 112 (partially shown in dashed line in both its elevated and retracted positions) may be employed instead, in which case the heater lamps 548 would not be required.
- the optional use of a wafer pedestal 112 enables bias power to be applied to the wafer. Advantages of this feature include the enhancement of the backside polymer etch process, and the suppression of ions in the upper process zone 130 if the wafer-ceiling gap is less than the plasma sheath thickness.
- Reactive ion etching for removal of backside polymer from the wafer can be accomplished in the process of FIG. 9 using the reactor of FIG. 3 .
- the backside plasma source 300 of FIG. 3 produces a sufficient flow of ions that reach the wafer backside. This condition is realized by holding the chamber pressure of the external plasma source 300 to a low pressure.
- the wafer temperature is held under a low threshold temperature (e.g. below about 200 degrees C. below which the reaction rate of polymer etch radicals with wafer front side thin film materials is very slow (e.g., about 5 times slower than at about 300 degrees C.).
- the reactive ion etch process used to remove the backside polymer is not hampered at low wafer temperatures.
- this low wafer temperature does not prevent the polymer etch ions from reacting with the backside polymer, but it does effectively slow down the reaction rate of polymer etch radicals that may escape from the lower process zone 132 into the upper process zone 130 with the wafer front side materials.
- the small wafer-to-ceiling gap employed during the backside polymer removal step essentially guarantees that most (or all) of the polymer etch species that can survive in the upper process zone 130 are radicals or neutrals, not ions.
- the wafer temperature is raised above a high threshold temperature (e.g., above 300 degrees C.) at which radicals can react at a faster rate with front side thin film materials, such as photoresist (e.g., at a rate about 5 times faster than at the lower threshold temperature of 200 degrees C.).
- a high threshold temperature e.g., above 300 degrees C.
- front side thin film materials such as photoresist
- the wafer temperature is constantly ramping. If the wafer is being heated to ramp its temperature upwardly, then the backside polymer removal step is performed prior to the wafer temperature exceeding the lower threshold temperature, and the front side photoresist strip step is not performed until after the wafer temperature has reached or exceeded the higher threshold temperature.
- the wafer temperature may begin slightly above room temperature, ramps upwardly during the entire process. In the period before the temperature exceeds about 150 degrees C. or 200 degrees C., the backside polymer removal step is performed and halted upon completion. Then, after a pause to allow the wafer temperature to reach or at least get near 300 degrees C., the front side photoresist step is performed.
- the processes of FIGS. 7 and 9 may be performed in any order, an advantage being that they are performed in the same reactor without having to remove the wafer.
- the backside plasma source 300 of FIG. 3 for example
- the backside plasma source is moved so as not to obstruct wafer movement.
- the reactor of FIG. 3 may be modified by replacing the external plasma source 300 with an internal plasma source, such as the internal inductive source 500 , 502 , 508 of FIG. 11 or the internal capacitive source 530 , 532 , 534 of FIG. 12 .
- an internal plasma source such as the internal inductive source 500 , 502 , 508 of FIG. 11 or the internal capacitive source 530 , 532 , 534 of FIG. 12 .
- wafer front side protection is provided by establishing the narrow wafer-ceiling gap and pumping a purge or scavenger gas through that narrow gap. Such protection is improved upon by the feature of holding the wafer temperature below the threshold temperature during backside polymer removal.
- polymer etch radicals react very slowly with photoresist below the low threshold temperature of about 200 degrees C., while a higher reaction rate is obtained above a high threshold temperature of about 300 degrees C.
- the polymer etch rate increases by about a factor of 5 as the wafer temperature increases from the low threshold temperature (e.g., 300 degrees C.) and the high threshold temperature (e.g., 200 degrees C.). Therefore, wafer front side protection is enhanced by holding the wafer temperature below the low threshold temperature of 200 degrees C. (e.g., at 150 degrees C.) during the backside polymer removal process. During the subsequent front side photoresist stripping, the wafer temperature is raised to about 300 degrees C.
- the heated electrostatic chuck or pedestal 112 of FIG. 3 may be employed to control the wafer temperature.
- One advantage of this is that RF plasma bias power may be applied to the wafer to enhance processing.
- a possible disadvantage of using a heated pedestal 112 is that the pedestal 112 may require a protective liner of a compatible material, such as quartz, alumina or yittria.
- radiant lamps At a lower chamber pressure, it may be necessary to use radiant lamps in order to attain a requisite heat transfer rate.
- radiant lamps is that the wafer temperature may be switched between the two temperatures more quickly, particularly if the wafer is lifted above contact with the pedestal 112 during processing.
- FIG. 20 illustrates a modification of the reactor of FIG. 2 in which the plasma by-products (radicals) from the external plasma source 134 are fed into an annular plenum 630 inside the bottom of the pedestal 112 and upwardly through axial cylindrical bores 632 within the pedestal 112 and is shot out through ejection orifices 634 aimed generally at the peripheral edge of the wafer 118 .
- the annular plenum 630 supplies gas or plasma by-products to the bottom of each bore 602 and the ejection orifices or nozzles 634 receive the plasma by-products from the tops of the bores 632 .
- the bores 632 and nozzles 634 are arrayed concentrically.
- the pedestal 112 has a wafer-support surface 636 having a diameter less than that of the wafer 118 so as to leave a peripheral annular region of the wafer backside exposed.
- the pedestal 112 further has a peripheral annular surface 638 that is parallel to but below the wafer support surface, the height difference between the two surfaces 636 , 638 providing a gas flow space 640 between the peripheral annular surface 638 and the wafer backside.
- a boundary between the upper and lower process zones 130 , 132 is established by constricting gas flow at the peripheral edge of the wafer 118 .
- this is accomplished by providing a confinement ring 640 surrounding the pedestal 112 and having an inner edge 640 a adjacent the edge 118 a of the wafer, the two edges 118 a, 640 a being separated by a small gap of about 0.5-5 mm. This gap is sufficiently small to limit gas flow between the upper and lower process zones 130 , 132 and thereby protect the wafer front side during etching of polymer from the wafer backside edge.
- Evacuation of polymer etch species is performed by the main vacuum pump 146 through a horizontal radial space 642 between the annular peripheral surface 638 of the pedestal and a bottom surface 644 of the ring 640 .
- This evacuation extends through a vertical axial space 646 between the side wall 648 of the pedestal 112 and a vertical surface 649 of the ring 640 .
- the chamber 220 of the external plasma source 134 is a toroid and the RF source power applicator 222 consists of a magnetically permeable ring 222 a wrapped around a section the chamber 220 and a coil 222 b wrapped around the ring 222 a and driven through an impedance match 135 by an RF source power generator 137 .
- the chamber 220 is coupled to the plenum 630 via a conduit 224 .
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Abstract
A reactor is provided for removing polymer from a backside of a workpiece. The reactor includes a vacuum chamber having a ceiling, a floor and a cylindrical side wall. A workpiece support apparatus within the chamber is configured to support a workpiece thereon, so that the workpiece has its front side facing the ceiling. The support apparatus leaves at least an annular periphery of the backside of the workpiece exposed. A confinement member defines a narrow gap with the outer edge of the workpiece, the narrow gap being on the order of about 1% of workpiece diameter, the narrow gap corresponding to a boundary dividing the chamber between an upper process zone and a lower process zone. A vacuum pump is coupled to the lower process zone. A lower external plasma-generating chamber introduces a plasma by-product into the lower process zone and a supply of a polymer etch precursor gas coupled to the lower external plasma-generating chamber. An upper external plasma-generating chamber is coupled to introduce a plasma by-product into the upper process zone and a supply of a scavenger species precursor gas coupled to the upper external plasma-generating chamber.
Description
- This application claims the benefit of U.S. Provisional Application Ser. No. 60/898,645, filed Jan. 30, 2007.
- Plasma processing of a workpiece or semiconductor wafer, particularly dielectric etch plasma processing, typically employs carbon-containing process gases (e.g., fluorocarbon or fluoro-hydrocarbon gases) that enhance the etch selectivity of dielectric materials, such as silicon dioxide, relative to other materials such as silicon. These processes are used to treat the front (top) side of the wafer on which the microelectronic thin film structures are formed. The opposite (back) side of the wafer is typically unpatterned. One problem is that the carbon-containing process gases tend to form polymer precursors in the plasma, which can leave a polymer residue on the front side of the wafer and on the exposed portion of the backside of the wafer, and even some distance under the unexposed portion of the wafer backside. Such residues should be removed to avoid contamination of later processing steps. The polymer residues deposited on the wafer front side tend to be easily removed with plasma ion bombardment using appropriate chemistry. However, the wafer edge is beveled, and the curved surface on the backside of the wafer edge is also exposed and therefore susceptible to polymer deposition during plasma processing. The backside of the curved surface of the wafer edge is shadowed from ion bombardment during plasma processing so is more difficult to remove, but can be removed in an oxygen plasma at high temperature (e.g., above 300 degrees C.). Such difficult-to-remove polymer films require a post-etch polymer removal step using (for example) an oxygen-rich plasma for thorough polymer removal.
- In many applications, the plasma etch process is used to form openings (e.g., trenches or contact holes) through multiple thin films on the wafer front side. Such thin film structures can include (for example) a special carbon-containing dielectric film having an ultra-low dielectric constant (ultra low-K film). The ultra low-K film is exposed in cross-section at the side wall of each trench or contact opening formed by the etch process step. Attempting to remove the backside polymer film by heating and exposing the wafer to an oxygen-rich plasma (during a post-etch polymer removal step) will damage the ultra low-K film by removing carbon from it. In semiconductor structures having 60 nm features sizes (or smaller), such damage to the ultra-low K film is permitted only to a depth of about 3 nm beyond the exposed surface (e.g., 3 nm beyond the sidewall of the opening). In contrast, the polymer film deposited on the wafer backside edge is about 700 nm thick. It is generally difficult if not impossible to avoid damaging the ultra low-K (ULK) film beyond the permissible 3 nm depth while exposing the wafer to an oxygen-rich plasma of a sufficient density and for a sufficient time to remove 700 nm of polymer from the backside of the wafer edge or bevel. The required polymer-to-ULK film etch selectivity (over 200:1) for such a polymer removal process in general cannot be maintained reliably in conventional processes.
- In conventional plasma reactor chambers, the wafer support pedestal includes an annular collar surrounding the edge of the wafer. Such a collar tends to shield the wafer edge, but cannot be sufficiently close to the wafer edge to prevent polymer deposition on the backside of the wafer edge. This is because some finite gap between the wafer edge and the collar is required to accommodate variations in the robot wafer placement and tolerance stackup. Moreover, the wafer edge-to-collar gap tends to increase as successive wafers are etched in the chamber, since the collar is (typically) formed of a process-compatible material (e.g., quartz, silicon or silicon carbide) that is gradually etched away during plasma etch processing of successive wafers. Therefore, it has seemed inevitable that unwanted polymer is deposited on the wafer, including the backside edge of the wafer.
- The foregoing problems might be avoided by using a rich mixture of oxygen in the plasma during the initial etch process. However, this approach is not practical if the thin film structure on the wafer includes an ultra-low K film that is exposed on a sidewall of an etched opening. Such a rich oxygen mixture in the etch plasma would cause unacceptable damage to the ultra-low K film.
- There is a need for a way of removing polymer from the backside of the wafer (i.e., the backside of the wafer edge) without harming or damaging any low-K film layers in thin film structure.
- A reactor is provided for removing polymer from a backside of a workpiece. The reactor includes a vacuum chamber having a ceiling, a floor and a cylindrical side wall. A workpiece support apparatus within the chamber is configured to support a workpiece thereon, so that the workpiece has its front side facing the ceiling. The support apparatus leaves at least an annular periphery of the backside of the workpiece exposed. A confinement member defines a narrow gap with the outer edge of the workpiece, the narrow gap being on the order of about 1% of workpiece diameter, the narrow gap corresponding to a boundary dividing the chamber between an upper process zone and a lower process zone. A vacuum pump is coupled to the lower process zone. A lower external plasma-generating chamber introduces a plasma by-product into the lower process zone and a supply of a polymer etch precursor gas coupled to the lower external plasma-generating chamber. An upper external plasma-generating chamber is coupled to introduce a plasma by-product into the upper process zone and a supply of a scavenger species precursor gas coupled to the upper external plasma-generating chamber.
- In one embodiment, the confinement member includes either a the side wall or an annular ring surrounding the workpiece. In one embodiment, the reactor further includes a lift apparatus capable of lifting the support apparatus to a raised level of the boundary at which the upper process zone is confined to a height on the order of about 1% of the diameter of the chamber. In a related embodiment, there is an upper slit passage in the sidewall adjacent the boundary corresponding to the raised level and open exclusively into the upper process zone, and an upper zone vacuum pump coupled to the upper slit passage. In a further embodiment, the reactor also includes a lower slit passage in the sidewall adjacent the boundary corresponding to the raised level and open exclusively into the lower process zone, with a lower zone vacuum pump coupled to the lower slit passage.
- In one embodiment, the reactor includes an apparatus capable of lifting the support apparatus to a raised level of the boundary at which the upper process zone is confined to a height that is sufficiently small to limit gas residency time in the upper process zone to on the order of about 1% of gas residency time in the lower process zone.
- So that the manner in which the above recited embodiments of the invention are attained and can be understood in detail, a more particular description of the invention, briefly summarized above, may be had by reference to the embodiments thereof which are illustrated in the appended drawings. It is to be noted, however, that the appended drawings illustrate only typical embodiments of this invention and are therefore not to be considered limiting of its scope, for the invention may admit to other equally effective embodiments.
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FIG. 1A depicts a backside polymer removal reactor chamber in which polymer etch species are furnished from a first external plasma source toward the backside of the wafer. -
FIGS. 1B and 1C are plan and elevational views, respectively, of an implementation of the workpiece support pedestal in the reactor ofFIG. 1A that can be used in each of the reactors described herein. -
FIG. 2 depicts a modification of the backside polymer removal reactor chamber ofFIG. 1A in which etchant scavenger species are supplied from a second external plasma source toward the front side of the wafer. -
FIG. 3 depicts another backside polymer removal reactor chamber in which a concentrated stream of hot radicals or ions are directed to the wafer backside edge from a separate plasma source that is near the wafer. -
FIG. 4 is an enlarged view of a portion of the chamber ofFIG. 3 depicting the placement of special materials to contain the concentrated stream of hot radicals or ions. -
FIG. 5 depicts a backside polymer removal process carried out with the reactor chamber ofFIG. 1A . -
FIG. 6 depicts a backside polymer removal process carried out with the reactor chamber ofFIG. 2 . -
FIG. 7 depicts a group of additional steps for the process ofFIG. 6 for removing photoresist from the wafer front side. -
FIG. 8 depicts an alternative group of additional steps for the process ofFIG. 6 for removing photoresist from the wafer front side. -
FIG. 9 depicts a backside polymer removal process carried out with the reactor ofFIG. 3 . -
FIG. 10 depicts an alternative process carried out in the reactor ofFIG. 2 for simultaneously removing backside polymer and removing frontside photoresist from the wafer. -
FIG. 11 depicts a modification of the reactor ofFIG. 3 in which the external plasma source of the plasma stream is replaced by an internal inductively coupled source. -
FIG. 12 depicts a modification of the reactor ofFIG. 11 , in which the internal inductively coupled source is replaced by an internal capacitively coupled source. -
FIG. 13 depicts an alternative approach in which a ring plasma is generated beneath the wafer backside edge by an inductively coupled source. -
FIG. 14 depicts a modification of the reactor ofFIG. 13 in which the inductively coupled source is replaced by an internal capacitively coupled source electrode for generating the ring plasma. -
FIG. 15 depicts a modification of the reactor ofFIG. 14 in which the internal capacitively coupled source electrode is replaced by an external capacitively coupled source electrode. -
FIG. 16 depicts a feature of the ceiling for shielding the wafer front side during backside polymer removal. -
FIG. 17 is a block diagram of a process for backside polymer removal and front side photoresist strip involving temperature switching. -
FIG. 18 illustrates a first reactor adapted to perform the process ofFIG. 17 . -
FIG. 19 illustrates a second reactor adapted to perform the process ofFIG. 19 . -
FIGS. 20 and 21 depict a modification of the reactor ofFIG. 2 . - To facilitate understanding, identical reference numerals have been used, where possible, to designate identical elements that are common to the figures. The drawings in the figures are all schematic and not to scale.
- Exemplary embodiments of the invention pertain to removing polymer from the backside edge of a wafer without damaging critical films, such as an ultra low-K dielectric film, by heating the wafer in a chamber while exposing only the backside of the wafer to polymer etch radicals or plasma by-products, such as atomic or free oxygen, from an external plasma source. The oxygen radicals may be provided by an external plasma source which is supplied with an oxygen-containing gas or vapor, such as O2, H2O, N2O, CO2, or CO, for example. The oxygen-containing gas may be combined or diluted with other gases such as H2, N2 or Ar. Other fluorine-containing gases (such as CF4 or NF3) may be added to allow removal of polymer films that contain other materials (such as Si) and are not etched efficiently in O chemistry alone. The critical films in the thin film structure on the wafer front side are protected from damage by the polymer etch species by pumping purge gases across the wafer front side. In addition, the wafer edge and the chamber side wall are separated by a very narrow gap to define a lower process zone with the wafer backside and an upper process zone with the wafer front side. The narrow of the gap is configured to resist or minimize migration of polymer etch species from the lower to the upper process zone where it would attack the ultra low-K film on the wafer front side. The external plasma source is coupled to the lower process zone so that the polymer etch species are delivered to the wafer back side. Delivery rate and residence time of polymer etch species are minimized in the upper process zone by restricting the height of the upper process region to a very narrow gap between the wafer and the chamber ceiling. The purge gases pumped across the wafer front side may be inert or non-reactive. Such purging reduces the etch rate of the front side critical films relative to the backside polymer removal rate.
- In one embodiment, to further reduce the etch rate of the critical films relative to the backside polymer removal rate, the purge gases may be supplemented with or replaced by reactive scavenger gases that chemically scavenge the backside polymer etch species in the upper process region.
- In another embodiment, a further increase in the backside polymer etch rate is attained by employing a second (upper) external plasma source coupled to the upper process zone. Gases that are precursors of species that scavenge the polymer etchant are introduced into the upper external plasma source, to produce scavenger radicals for the upper process zone that reduce the amount (partial pressure) of polymer etchant species in the upper process zone. In one embodiment, pressure is maintained sufficiently low pressure in the upper process zone to enable the upper external plasma source to generate plasma efficiently, while simultaneously achieving a sufficiently high flow rate of scavenger species to protect the wafer front side thin films. In another embodiment, unused polymer etch species are removed from the lower process zone before they migrate to the upper process zone. In one embodiment, the upper and lower process zones are separately evacuated near the wafer edge through separate pumping evacuation ports in the sidewall near the wafer edge. In addition, the scavenger species from the upper external plasma source may be heated before they enter the upper process zone.
- The scavenger species furnished by the upper external plasma source that removes the polymer etch species from the upper process zone (e.g., hydrogen) may also serve to remove photoresist from the wafer front side. In such a case, photoresist removal may be performed in a separate step in which no polymer etch species are introduced into the lower process zone and the wafer-to-ceiling gap (height of the upper process zone) is increased. In addition, an agent gas (e.g., nitrogen) that promotes the etching of photoresist from the wafer frontside may be furnished in a small quantity to the upper external plasma source. In an alternative mode, none of the front side thin film layers is susceptible to damage by the polymer etch species, and the steps of backside polymer etch removal and front side photoresist removal are performed simultaneously using the upper and lower external plasma sources. In this case, the height of the upper process zone is increased by lowering the wafer support pedestal.
- In one embodiment, an increase in polymer etch rate relative to etch rate of the critical (ultra low-K) film by the polymer etch species is achieved by locating the lower external plasma source very close to the wafer edge and directing a concentrated stream or jet of plasma products from the lower external plasma source directly at the wafer backside edge while rotating the wafer. By reducing the lower external plasma source pressure, the concentrated stream may consist of polymer etchant ions, radicals and neutrals, while at a higher pressure the stream consists of etchant radicals and neutrals.
- Referring now to
FIG. 1A , a plasma reactor for removing polymer residue from the backside of a semiconductor wafer includes areactor chamber 100 having aside wall 102, aceiling 104 that is a gas distribution plate and afloor 106. The ceiling orgas distribution plate 104 has aninterior gas manifold 108 and pluralgas injection orifices 110 opening from the manifold 108 into the interior of thechamber 100. Awafer support pedestal 112 in the form of a disk-shaped table has a diameter less than the diameter of a workpiece to be supported on thepedestal 112, so as to expose the backside peripheral annulus of the workpiece. Thepedestal 112 is supported on alift member 114 elevated and lowered by alift actuator 116. A workpiece such assemiconductor wafer 118 can be supported with a center portion of its backside resting on thepedestal 112. The front side of the wafer 118 (the side on which the microelectronic thin film structures are formed) faces the ceilinggas distribution plate 104. Thepedestal 112 is sufficiently small to leave an annular periphery of the wafer backside exposed, for backside polymer removal. Often, thewafer 118 has a rounded or beveled edge as depicted inFIG. 1A . Such a beveled feature may make it difficult to avoid polymer deposition on the wafer backside during plasma (e.g., etch) processing of thin films on the wafer front side. In one embodiment,radial arms 113 are provided to position theworkpiece 118 on thepedestal 112. In one embodiment, three symmetrically spaced thinradial arms 113 shown inFIG. 1B are provided and extended outwardly from the periphery of thepedestal 112. As shown inFIG. 1C , theradial arms 113 are below the workpiece support surface of thepedestal 112 so as to leave the entire peripheral annulus of the workpiece backside exposed for backside polymer removal. Eachradial arm 113 supports a thinaxial tab 113 a at its distal end, thetabs 113 a serving to locate theworkpiece 118 in coaxial alignment with the pedestal. - The
chamber side wall 102 can include a removable liner orprocess kit 120. Hereafter, theterm sidewall 102 is used to include aliner 120 if one is present. Agap 122 between thewafer edge 118 a and theside wall 102 is very small, e.g., about 0.2-2 mm, so as to resist migration of gases through thegap 122. The gap is configured to be sufficiently narrow to present a gas flow resistance that is on the order of about one hundred times greater than gas flow resistance in other portions of the chamber. Thegap 122 may be on the order of about 1% of the chamber diameter. In this way, thewafer 118 divides thechamber 100 into anupper process zone 130 bounded in part by the front side or top surface of thewafer 118 and alower process zone 132 bounded in part by the backside or bottom surface of thewafer 118. A bottomexternal plasma source 134 receives a polymer etch precursor gas from agas supply 136 and furnishes polymer etch radicals (e.g., oxygen radicals or atomic oxygen) into thelower process zone 132 through aport 138 in thechamber floor 106. - Some polymer etchant (e.g., oxygen) radicals can migrate from the
lower process zone 132 into theupper process zone 130 through thegap 122 and pose a risk of damage to critical layers on the wafer front side, such an ultra low-K thin film. In order to prevent this, a non-reactive purge gas, namely a gas that does not react with the thin film materials on the wafer front side, (e.g., nitrogen gas or argon gas) is supplied to the ceilinggas distribution plate 104 from agas supply 140 in order to flush out theupper process zone 130 and keep it free of etchant species. In order to facilitate a thorough and fast purge of theupper process zone 130, theupper process zone 130 is restricted to a very small height corresponding to a small wafer-to-ceiling gap 144, e.g., about 0.2-2 mm. Thegap 144 may be sufficiently small to confine the cross-section of theupper zone 130 to an aspect ratio greater than 100. The upper process zone height (gap 144) is sufficiently small so that residence time of gas in theupper process zone 130 is less than about one tenth to one hundredth of the gas residence time in thelower process zone 132. Also, the upper process zone height (gap 144) is sufficiently small so that gas flow resistance through thegap 144 is on the order of 100 times the gas flow resistance through thelower process zone 132. Such confinement of the upper process zone height may be accomplished by raising thewafer support pedestal 112 with thelift actuator 116. - In one embodiment, pressure in the
chamber 100 is controlled by avacuum pump 146 that maintains thelower process zone 132 at a sufficiently low pressure to draw plasma by-products out of the lowerexternal plasma source 134 and maintain theexternal plasma source 134 at a sufficiently low pressure to enable it to efficiently generate plasma. Alternatively, the upper andlower process zones separate pumps vacuum pump 146 may not be necessary. - In one embodiment, the polymer removal process is quickened by heating the
wafer 118 to on the order of 300 degrees C., for example, either by anelectrical heating element 150 inside thepedestal 112 or by radiant lamps (not shown). An electricalheater power supply 152 is coupled to theheating element 150 through wires in thelift member 114. By raising the wafer temperature to about 300 degrees C., the backside polymer removal rate is significantly increased. - In one embodiment, etching of films (e.g., an ultra low-K film) on the wafer front side is minimized or eliminated by maintaining a very high flow rate of a non-reactive purge gas (e.g., nitrogen or argon) through the ceiling
gas distribution plate 104 into theupper process zone 130. This improves the polymer etch selectivity, i.e., the ratio of the polymer etch rate to the ultra low-K film etch rate. The purge gas flow rate may be as high as necessary to achieve a desired etch selectivity, raising the pressure of theupper process zone 130 to a very high level. The pressure in thelower process zone 132 is maintained at a sufficiently low level (e.g., a few Torr or less) to ensure efficient operation of theexternal plasma source 134. In order for theexternal plasma source 134 to generate a plasma, the chamber interior pressure of theexternal plasma source 134 typically should not exceed a few Torr, and because theexternal plasma source 134 is coupled directly to thelower process zone 132, the pressure in thelower process zone 132 should be maintained at a correspondingly low level. This requirement is met by the main chamber vacuum pump 146 (or by the vacuum pump 216) regardless of the high flow rate of purge gas into theupper process zone 130 through thegas distribution plate 104. This permits the purge gas flow rate and upper process zone pressure to be as great as necessary to eliminate or minimize etching of any ultra low-K film on the wafer front side. - In one embodiment, to further increase the rate of polymer removal from the wafer backside, a dissociation agent gas (e.g., nitrogen) that promotes dissociation of the polymer etch precursor gas (e.g., oxygen) may be supplied at a low flow rate to the
external plasma source 134 from agas supply 156. - In one embodiment, to further reduce the amount of polymer etch species (e.g., oxygen) in the
upper process zone 130, agas supply 158 furnishes an etchant scavenger gas (e.g., hydrogen or carbon monoxide) to the ceilinggas distribution plate 104. This may be instead of or in addition to the non-reactive purge gas from thegas supply 140. Some polymer etchant (e.g., oxygen) atoms or molecules that have migrated into theupper process zone 130 are chemically consumed by combining with the scavenger gas (e.g., H2 or CO). Optionally, this scavenger reaction may be accelerated by heating the scavenger gases furnished to thegas distribution plate 104 with anelectrical heater 159. If the polymer etchant precursor gas is oxygen, then the scavenger gas may be carbon monoxide or hydrogen. Carbon monoxide is less reactive with a carbon-containing ultra low-K film than the oxygen gas that it scavenges from theupper process zone 130. Hydrogen gas may be a good choice for the scavenger gas because it may not deplete carbon from the carbon-containing ultra low-K film, and therefore fulfills a requirement of being less reactive with the ULK film than the polymer etch species (oxygen) that it scavenges. The scavenger gas is selected so that the product of the chemical reaction between the scavenger and the polymer etchant (e.g., oxygen) does not react at a high rate with the ultra low-K film. In the case of a hydrogen scavenger and oxygen as the polymer etchant, the product is water and in the case of a carbon monoxide scavenger, the product is carbon dioxide, satisfying the requirement of a scavenging reaction product that is safe for the ultra low-K film. - In an optional mode, the reactor of
FIG. 1A is used to remove photoresist from the wafer front side. In this mode, thewafer pedestal 112 may be lowered to the dashed-line position ofFIG. 1A , to enlarge theupper process zone 130 with a wafer-to-ceiling gap of about 0.5 to 5 cm. If none of the thin film materials on the wafer front side include a ULK film or other material susceptible to damage from oxygen, then the oxygen radicals from thelower process zone 132 are permitted to migrate into theupper process zone 130 by halting the purge gas flow from thegas supply 140 and/or the scavenger gas flow from thegas supply 158. Also, such migration may be enhanced if the sidewall-wafer gap 122 is greater at the lowered (dashed-line) wafer position. In this optional mode, the backside polymer and the frontside photoresist are removed simultaneously. -
FIG. 2 depicts a modification of the reactor ofFIG. 1A . The reactor ofFIG. 2 may be particularly advantageous in providing even greater protection for ultra low-K films on the wafer front side during backside polymer removal. In the reactor ofFIG. 2 , a secondexternal plasma source 200 is provided. The amount of polymer etchant species (e.g., oxygen) in theupper process zone 130 is reduced more efficiently because the second (upper)external plasma source 200 provides plasma by-products (e.g., radicals) of a scavenger species (e.g., hydrogen or nitrogen) to the ceilinggas distribution plate 104. The scavenger species radicals (hydrogen or nitrogen) chemically scavenge or combine with some polymer etchant species (e.g., oxygen) that may migrate into theupper process zone 130. Such radicals tend to have a faster rate of reaction with the etchant species (than the molecular gas scavenger of the reactor ofFIG. 1A ) and therefore provide a higher rate of removal of etchant species (e.g., oxygen) from theupper process zone 130. This provides superior protection from attack upon thin film structures (e.g., an ultra low-K film) on the wafer front side. Agas supply 202 furnishes a molecular gas form of a scavenger precursor (e.g., hydrogen or nitrogen gas) to the chamber of the topexternal plasma source 200. By-products of the plasma generated by the source 200 (e.g., either hydrogen radicals or nitrogen radicals) are scavengers of the polymer etch species (e.g., oxygen), and are delivered to thegas distribution plate 104 to reduce or eliminate oxygen from theupper process zone 130 and thereby protect the thin film structures on the wafer front side. - As depicted in
FIG. 2 , the topexternal plasma source 200 may consist of a dielectric (e.g., quartz)tube chamber 204 encircled by anRF coil antenna 206 that is driven by an RF plasmasource power generator 208 through animpedance match element 209. The quartz material is compatible with the hydrogen or nitrogen chemistry of the topexternal plasma source 200. The topexternal plasma source 200 produces radicals of the scavenger species that are fed to the ceilinggas distribution plate 104 through acenter port 212. In order to provide uniform distribution of the scavenger species across the gas distribution plate, abaffle 214 is provided in the center of thegas manifold 108 that blocks direct gas flow from thecenter port 212 togas injection orifices 110 near the center of thegas distribution plate 104. A toroidal plasma chamber may be used for either (or both) the top and bottomexternal plasma sources external plasma source 200, such a toroidal plasma chamber may include an insulating liner protecting the conductive chamber or conduit. - The chamber pressure within the top
external plasma source 200 should be sufficiently low (e.g., not exceeding several Torr) to ensure efficient plasma generation within theexternal chamber 204. Since the topexternal plasma source 200 is coupled to the upper process zone 130 (through the gas distribution plate 104), the upper process zone pressure cannot be too high without extinguishing plasma in theexternal source 200. Meeting this limitation may prevent a sufficiently high flow rate of scavenger species into theupper process zone 130 necessary to protect the wafer front side. In one embodiment, an upperzone vacuum pump 210 is coupled directly to theupper process zone 130 through an upper zone vacuum slitpassage 217 that is near (but slightly above, by a few mm or less) the wafer edge and passes through the side wall 102 (andliner 120 if present). The upperzone vacuum pump 210 facilitates or ensures a sufficient flow rate through the very thin wafer-sidewall gap 122. With this feature, themain vacuum pump 146 may be eliminated in the reactor ofFIG. 2 , as will be discussed below. In one embodiment, the pumping rate of theupper zone pump 210 is maintained at a sufficient level to keep the pressure in theupper process zone 130 below a few Torr, for example. This permits a high flow rate of radicals from the topexternal plasma source 200 and ensures quick removal of scavenger-etchant reaction by-products from theupper process zone 130. The present embodiment provides a low chamber pressure inside the topexternal plasma source 200 to facilitate efficient plasma generation within the topexternal plasma source 200. The present embodiment also reduces the migration of scavenger or purge species into thelower process zone 132 that would otherwise dilute the polymer etch species (e.g., oxygen) at the wafer backside. - In one embodiment, to reduce migration of polymer etchant species (e.g., oxygen) from the
lower process zone 132 through the wafer-sidewall gap 122 into theupper process zone 130, a lowerzone vacuum pump 216 is coupled to thelower process zone 132 through a lowerzone slit passage 218 that is near (but slightly below, by a few mm or less) the wafer edge. The upper andlower slit passages FIG. 2 , both slitpassages slit passage zone vacuum pumps separate slit passages upper zone 130 through the slit passage 217) and etchant species and etchant-polymer reaction by-products (from thelower zone 132 through the slit passage 218). - The
slit openings side wall 102. Theslit openings respective pumps - In one embodiment, with the upper and
lower vacuum pumps main vacuum pump 146 is eliminated in the reactor ofFIG. 2 . Providing the upper andlower vacuum pumps - The upper and
lower vacuum pumps slit passages FIG. 1A , although they may not be required in the reactor ofFIG. 1A because of the lack of an upperexternal plasma source 200 inFIG. 1A . Because the upperexternal plasma source 200 is not present in the reactor ofFIG. 1A , the purge gases may be pumped through thegas distribution plate 104 at very high pressure to protect the wafer front side. Therefore, thelocal pumps slit passages FIG. 1A . - Various kinds of plasma sources may be used for the upper and lower
external plasma sources lower sources upper plasma source 200. However, toroidal plasma sources are also available with quartz liners or quartz toroidal shaped (round or square) vacuum vessels. If non-metal, non-coated metal, and non-quartz material is required for comparability with the plasma chemistry, then the choice of external plasma source may be more limited to conventional inductively coupled plasma sources, such as a quartz, alumina, sapphire or Yittria tube wrapped with an RF-driven coil, for example. Sources may also be electrostatically shielded to reduce plasma ion bombardment and subsequent erosion or particle/contamination issues. In one example, the lowerexternal plasma source 134 may be a toroidal plasma source, consisting of atoroidal chamber 220 fed by theprocess gas supply 136, a coiledRF power applicator 222 coupled to thetoroidal chamber 220 and apassage 224 from thetoroidal chamber 220 to theport 138. Thecoil 222 may be driven by an RF generator through an impedance match, or may simply driven by a switched power supply (We need to discuss). Thetoroidal chamber 220 is typically formed of metal with a dielectric external film, such as anodized aluminum, which is compatible with the oxygen and nitrogen gases employed in the lowerexternal plasma source 134. Because the upperexternal plasma source 200 is supplied with hydrogen gas, anodized aluminum is not a practical material for theupper source 200, and therefore itschamber 204, in one example, is formed of another material (such as quartz) that is compatible with hydrogen. - In an optional mode, the reactor of
FIG. 2 is used to remove photoresist from the wafer front side. In this application, oxygen (polymer etchant) flow from thegas supply 136 is halted (or the plasma in thelower source 134 is extinguished). Preferably, this step is carried out with the height of theupper process zone 130 being in the narrow regime (0.2-2 mm) discussed above, to enhance the photoresist removal rate. Alternatively, uniformity of the photoresist removal may be enhanced by increasing the upper process zone height, in which case thewafer pedestal 112 is lowered to the dashed-line position ofFIG. 2 , to enlarge theupper process zone 130 with a wafer-to-ceiling gap of about 2.5 to 5 cm. Hydrogen radicals or related plasma by-products from the upperexternal plasma source 200 fill theupper process zone 130 and remove photoresist from the wafer front side in a reactive etch process. This reaction is promoted by supplementing the hydrogen gas flow to the upperexternal plasma source 200 with an oxygen-containing gas (H2O or N2O) at a lower flow rate from anothergas supply 240. The flow rate of the oxygen-containing gas into theupper plasma source 200 may be less than 5% of the hydrogen flow rate. This photoresist removal step may be performed before or after the backside polymer removal step. - In an alternative embodiment of the optional frontside photoresist removal mode, a capacitively coupled plasma is generated from the hydrogen in the
upper process zone 130 by anRF power generator 250 coupled through animpedance match 252 across the ceilinggas distribution plate 104 and the wafer support pedestal 112 (in its lowered dashed-line position ofFIG. 2 ). In this embodiment, hydrogen ions are generated in theupper process zone 130 to conduct reactive ion etching of the photoresist on the wafer front side. - The initial placement of the reactor of
FIG. 2 in a plasma etch system may require replacing one of two single wafer load locks normally present in such a system with the reactor ofFIG. 2 . An etch system typically includes four plasma etch reactors, two single wafer load locks and a factory interface. For greater versatility, the reactor ofFIG. 2 may be configured to perform the functions of the single wafer load lock that it replaces in the plasma etch system. For this purpose, wafer ingress/egress slitvalves slit valves FIG. 2 to function as a single wafer load lock. - Referring to
FIG. 3 , in one embodiment, a localized stream or jet of plasma radicals, neutrals, and ions of an etchant species is used to provide an even higher rate of backside polymer removal. The stream or jet of plasma species is directed onto a small target area or window of the wafer backside edge while rotating the wafer. For this purpose, a localexternal plasma source 300 may be located near the wafer edge, and ashort conduit 302 directs plasma ions from the interior of the localexternal plasma source 300 as a localized stream of plasma ions, radicals and neutrals to the small target region at the wafer backside edge. In one embodiment, theconduit 302 is sufficiently short and its output end is sufficiently close to the wafer backside to enable to enable ions from thesource 300 to reach the wafer backside. For example, the transit distance between the output end of the short conduit and the wafer support plane of thepedestal 112 may be 5% or less of the pedestal or wafer diameter. Agas supply 136 furnishes a polymer etch precursor gas to the localexternal plasma source 300. In one embodiment, to expose the entire backside periphery or edge of the wafer to the localized plasma stream, thewafer pedestal 112 is rotated by arotation actuator 304 coupled to the support member orleg 114 of thepedestal 112. By operating the localexternal plasma source 300 at a low chamber pressure, it becomes a rich source of plasma ions and electrons, and the concentrated stream from theconduit 302 consists of a large proportion of ions in an ion/radical mixture. By placing theexternal plasma source 300 close thewafer 118 and keeping theconduit 302 short, ion loss through recombination is minimized, and the particle stream emanating from theconduit 302 remains rich in ions. - In one embodiment, the backside polymer etch rate is increased by the ion jet stream in the reactor of
FIG. 3 ; the ion energy at the wafer backside edge surface may be increased by applying RF bias power between the localexternal plasma source 300 and the wafer support pedestal. For this purpose, an RFbias power generator 310 is coupled through animpedance match element 312 across the wafer support pedestal and the localexternal plasma source 300. Agas supply 156 can furnish to the local external plasma source 300 a dissociation agent gas (e.g., nitrogen) that promotes the dissociation of the etchant species (e.g., oxygen) in the plasma of the localexternal plasma source 300. - If a radical stream is desired rather than an ion stream, then the chamber pressure in the local external plasma source may be increased. Raising the chamber pressure of the local
external plasma source 300 reduces the proportion of ions and raises the proportion of radicals in the stream of particles ejected by theconduit 302. Furthermore, if a purely radical stream is required, then it is not necessary to locate theexternal plasma source 300 near the wafer. Instead, it may be located (for example) near the bottom of the main chamber 100 (as indicated in dashed line inFIG. 3 ) and theconduit 302 may be relatively long (as shown in dashed line inFIG. 3 ). The concentrated jet stream from theplasma source 300 can be very hot (e.g., as much as 600 degrees C.), and this heat can expedite the reaction between the etch species and the backside polymer. Preferably, the entire wafer is initially heated to about 300 degrees C. before exposing the backside to the concentrated radical or ion stream from thelocal plasma source 300 andconduit 302. - Referring to
FIG. 4 , special precautions may be taken to minimize metal contamination from the ion stream emanating from theplasma source 300/conduit 302. Specifically, metal surfaces can be protected with a dielectric (e.g., quartz)liner 320 that covers the bottom surface of the ceilinggas distribution plate 104 and adielectric liner 120 that covers the interior surface of theside wall 102. The enlarged view ofFIG. 4 shows how each slitopening respective pump -
FIG. 5 depicts an exemplary method that can be carried out in the reactor ofFIG. 1A . A first step (block 402) is to support the wafer (using the pedestal 112) so as to expose a peripheral portion of the wafer back side, while beginning to heat the wafer to on the order of 300 degrees C. A next step (block 404), which may begin before the final wafer temperature (e.g., 300 degrees C.) is reached, is to define anupper process zone 130 above the wafer front side and alower process zone 132 below the wafer back side with minimal migration of gas between the two zones by maintaining a wafer-to-sidewall gap at less than 2 mm. This gap should be sufficiently small to produce a gas flow resistance that exceeds that of other portions of the chamber by a factor on the order of 100. A further step (block 406) is to prevent accumulation of etch species at the wafer front side, or (equivalently) facilitate fast evacuation of theupper zone 130, by maintaining a wafer-to-ceiling gap (the height of the upper process zone 130) at a value at which a high gas flow resistance is established, e.g., less than 2 mm. This gap should be sufficiently small to confine theupper process zone 130 to a cross-sectional aspect ratio greater than on the order of 100. Another step (block 408) is to generate a plasma in anexternal plasma chamber 134 with a polymer etchant precursor gas (e.g., oxygen), and introduce by-products (e.g., radicals, free oxygen) from the plasma into thelower process zone 132 so as to etch polymer from the wafer back side. A related step (block 410) is to enhance dissociation of the polymer etchant precursor species (oxygen) by introducing a dissociation agent (nitrogen gas) into theexternal plasma chamber 134. In order to avoid or minimize etching thin films on the wafer front side, a further step (block 412) consists of reducing the amount of polymer etchant precursor species (oxygen) in theupper process zone 130 by injecting a purge gas (e.g., N2 or Ar) into theupper process zone 130. A related step (block 414) consists of further reducing etchant species in theupper process zone 130 by introducing into the upper process zone a scavenger gas (e.g., H2 or CO) that scavenges the etch species (e.g., oxygen). The scavenger gas may be used in addition to or instead of the non-reactive purge gas. -
FIG. 6 depicts an exemplary method that can be carried out in the reactor ofFIG. 2 . A first step (block 416) is to support the wafer on thepedestal 112 so as to expose a peripheral portion of the wafer back side while heating the wafer to on the order of 300 degrees C. A next step (block 418) is to define anupper process zone 130 above the wafer front side and alower process zone 132 below the wafer back side with minimal migration of gas between the two zones by maintaining a wafer-to-sidewall gap at less than 2 mm. A further step (block 420) is to prevent accumulation of etch species or plasma at the wafer front side by maintaining a wafer-to-ceiling gap (the height of the upper process zone) at less than 2 mm. Another (block 422) step is to generate a first plasma in a lowerexternal plasma chamber 134 with a polymer etchant precursor gas (e.g., oxygen), and introduce by-products (e.g., radicals, free oxygen) from the plasma into thelower process zone 132 so as to etch polymer from the wafer back side. A related step (block 424) is to enhance dissociation of the polymer etchant precursor species (oxygen) by introducing a dissociation agent (nitrogen gas) into the lower external plasma chamber, at a flow rate of 1-10% of the oxygen gas flow rate. Another step (block 426) is to generate a second plasma in an upperexternal plasma chamber 200 with a scavenger species (H2 or N2) that scavenges the polymer etch species, and introduce by-products of the second plasma (H radicals or N radicals) into theupper process zone 130. In order to reduce or eliminate etching of thin films on the wafer front side, a further step (block 428) is to evacuate theupper process zone 130 at a pumpingport 217 near the wafer edge to remove polymer etchant species (oxygen) from the upper process zone at a sufficiently high rate to avoid damage of critical (carbon-containing or low-k) films on the wafer front side. A related step (block 430) is to evacuate thelower process zone 132 at a pumpingport 218 near the edge of the wafer at a sufficiently high rate to minimize migration of polymer etchant species (oxygen) from thelower process zone 132 into theupper process zone 130 and to maximize delivery of polymer etchant species to the backside edge of the wafer. For maximum delivery of polymer etch species to the wafer backside edge, only the front side and backside pumps 210, 216, are used, themain pump 146 being eliminated or unused. -
FIG. 7 depicts an exemplary method carried out in an optional mode of the reactor ofFIG. 2 , in which the reactor is employed to etch photoresist from the wafer front side. A first step (block 432) is to stop the flow of polymer etchant species (oxygen) from the lowerexternal plasma source 134 to the lower process zone. Although it is preferable to continue to restrict the height of theupper process zone 130, optionally this height may be increased in preparation for the frontside photoresist removal step, in which case the next (optional) step (block 434) is to increase the wafer-to-ceiling gap to a distance (e.g., 0.5-5 cm) at which etchant species can accumulate in theupper process zone 130. However, it is not necessarily required to increase the upper process zone height in order to perform photoresist stripping on the wafer front side. The next step (block 436) is to introduce at a reduced flow rate an oxygen-containing species (H2O or N2O) along with the H2 gas into the upper external plasma source 200 (at a flow rate of less than 1-10% of the hydrogen gas flow rate) so as to enhance the etch rate of photoresist from wafer front side. The process ofFIG. 7 may be performed either before or after the process ofFIG. 6 . The removal rate of photoresist in this step is enhanced if the height of theupper process zone 130 is restricted to the narrow (0.2-2 mm) range. In the other hand, uniformity is enhanced by increasing this height, and the step ofblock 434 may only increase the upper process zone height by a fractional amount. -
FIG. 8 depicts an alternative method for the reactor ofFIG. 2 to etch photoresist from the wafer front side, in which a capacitively coupled plasma is generated in theupper process zone 130. A first step (block 438) is to stop the flow of polymer etchant species (oxygen) from the lowerexternal plasma chamber 134 to the lower process zone, and then (block 440) increase the wafer-to-ceiling gap to about 2 to 5 cm. A next step (block 442) is to introduce a photoresist removal species gas (H2) into theupper process zone 130. A further step (block 444) is to introduce at a reduced flow rate an oxygen-containing species (H2O or N2O) into the upper process region. This reduced flow rate may be about 1-10% of the hydrogen gas flow rate. A next step (block 446) is to apply RF power into the upper process zone to produce a plasma that removes photoresist from the wafer front side. -
FIG. 9 depicts an exemplary method that can be carried out in the reactor ofFIG. 3 , in which backside polymer is removed by a concentrated or localized stream of plasma ions, radicals and neutrals from an external plasma source. A first step (block 448) is to support the wafer on thepedestal 112 so as to expose a peripheral portion of the wafer back side while heating the wafer to on the order of 300 degrees C. A next step (block 450) is to define anupper process zone 130 above the wafer front side and alower process zone 132 below the wafer back side with minimal migration of gas between the two zones by maintaining a wafer-to-sidewall gap at less than 2 mm. A further step (block 452) is to prevent (or minimize) flow or delivery rate of etch species or plasma at the wafer front side by maintaining a wafer-to-ceiling gap (the height of the upper process zone) at less than 2 mm. A further step (block 454) is to generate a first plasma in a localexternal plasma chamber 300 with a polymer etchant precursor gas (e.g., oxygen), and direct a narrow stream of by-products from the first plasma through aninjection orifice 302 near the wafer backside directly at the wafer back side, while rotating the wafer. A related step (block 456) is to enhance dissociation of the polymer etchant precursor species (oxygen) by introducing a dissociation agent (nitrogen gas) into the localexternal plasma chamber 300. Another related step (block 457) is to enhance the backside polymer etch rate by applying RF bias power across the local external plasma chamber and the wafer. Another step (block 458) is to generate a second plasma in an upperexternal plasma source 200 with a scavenger species (H2 or N2) that scavenges the polymer etch species, and introduce by-products of the second plasma (H radicals or N radicals) into theupper process zone 130. Another step (block 460) is to evacuate theupper process zone 130 at a pumpingport 212 near the wafer edge to remove polymer etchant species (oxygen) from the upper process zone at a sufficiently high rate to avoid damage of critical (carbon-containing or low-k) films on the wafer front side. A related step (block 462) is to evacuate thelower process zone 132 at a pumpingport 218 near the edge of the wafer at a sufficiently high rate to minimize migration of polymer etchant species (oxygen) from thelower process zone 132 the into theupper process zone 130. -
FIG. 10 depicts an exemplary process carried out in the reactor ofFIG. 2 for simultaneously removing polymer from the wafer backside while removing photoresist from the wafer front side. The process ofFIG. 10 may be carried out, for example, in cases in which there is no film on the wafer front side (such as a ULK film) that is particularly susceptible to damage from polymer etchant species, or in cases in which any critical or ULK films that are present can tolerate the limited flow of polymer etch species escaping from thelower process zone 132 to theupper process zone 130. A first step (block 464) is to support the wafer so as to expose a peripheral portion of the wafer back side while heating the wafer to on the order of 300 degrees C. A next step (block 466) is to define anupper process zone 130 above the wafer front side and alower process zone 132 below the wafer back side with minimal migration of gas between the two zones by maintaining a wafer-to-sidewall gap at less than 2 mm. A further step (block 468) is to generate a first plasma in a lowerexternal plasma chamber 134 with a polymer etchant precursor gas (e.g., oxygen), and introduce by-products (e.g., radicals, free oxygen) from the plasma into thelower process zone 132 so as to etch polymer from the wafer back side. A related step (block 470) is to enhance dissociation of the polymer etchant precursor species (oxygen) by introducing a dissociation agent (nitrogen gas) into the lowerexternal plasma chamber 134. A step (block 472) carried out simultaneously with the step ofblock 468 is to generate a second plasma in an upperexternal plasma chamber 200 with a scavenger precursor gas (H2) and a small proportion of an oxygen-containing species (H2O or N2O). By-products of the second plasma, e.g., scavenger species (H radicals) and oxygen-containing radicals, are introduced into theupper process zone 130. The scavenger species removes etch species (e.g., oxygen) from theupper process zone 130, and—with the help of the oxygen-containing species—removes photoresist from the wafer front side. During this process, it is preferable to maintain the height of theupper process zone 130 in the narrow range (0.2-2 mm) to enhance the rate of photoresist removal. The result of this step is to simultaneously remove backside polymer using the bottomexternal plasma source 134 and remove front side photoresist with the upperexternal plasma source 200. The flow rate of the oxygen-containing (H2O or N2O) into the upperexternal plasma source 200 species may be 1-10% of the hydrogen flow rate into the upperexternal plasma source 200, for example. -
FIG. 11 depicts a variation of the reactor ofFIG. 3 , in which the plasma by-product stream or jet directed at the wafer backside edge is produced by components within the reactor itself rather than an external plasma source. For this purpose, an external plasma source such as theexternal plasma source 300 shown inFIG. 3 is replaced in the embodiment ofFIG. 11 by aninternal plasma source 500 consisting of a cylindrical sealedenclosure 502, which may be formed of an insulating material such as quartz, and acoil 504 wrapped around a portion of thecylindrical enclosure 502. In the illustrated reactor, thecoil 504 is outside of the chamber. Theenclosure 502 is closed at itsbottom end 502 a and forms a nozzle or conical shapedoutlet 502 b at its top end facing and close to the backside edge of thewafer 118. Agas supply 506 storing a polymer etch gas species is coupled to theenclosure 502 through thebottom end 502 a. AnRF generator 508 is coupled to the coil 504 (through an optional impedance match, not shown) and furnishes sufficient power to produce an inductively coupled plasma inside theenclosure 502. The pressure inside theenclosure 502 is greater than that of thelower process zone 132. This pressure difference may be controlled by themain vacuum pump 146 and anoptional vacuum pump 509 coupled to theenclosure 502. Plasma by-products, for example radicals, neutrals and/or ions, escape through thenozzle outlet 502 b and form a concentrated or localizedstream 510 that impinges upon a target area of the wafer backside edge. In order to control the ion energy of thestream 510, an optional RF biaspower generator 512 may be connected between aninterior electrode 514 inside theenclosure 502 and thewafer pedestal 112. While the upperexternal plasma source 200 ofFIG. 3 may be employed in the reactor ofFIG. 11 , this option is depicted inFIG. 11 only in dashed line. Instead, the solid line image ofFIG. 11 shows that (optionally) thepurge gas supply 140 may furnish purge gases through the ceilinggas distribution plate 104 with no external plasma source. The purge gas may be either non-reactive or may be a reactive scavenger species, as discussed with reference toFIG. 1 . - In one embodiment, to provide a desired (e.g., 300 degree C.) wafer temperature, the
pedestal 112 may be heated as inFIG. 3 , or radiant lamps (not shown) above the ceiling may be employed. In one embodiment, aliner 520 of a process-compatible material may cover the side and bottom edge surfaces of thepedestal 112, and aliner 522 of a process compatible material may cover theside wall 102. Theliners plasma stream 510. The process-compatible material may be, for example, quartz. In one implementation, theceiling 104 may be formed of a process-compatible material such as quartz. In this case, the ceiling may be a smooth simple structure without the gas distribution plate features depicted inFIG. 11 . - In an alternative embodiment, the
plasma source enclosure 502 ofFIG. 11 may be in the shape of a torus, to form a toroidal plasma source. - In another alternative embodiment, the inductive plasma source 500 (the tube enclosure 502) is replaced by a capacitively coupled
source 530 as illustrated inFIG. 12 . The capacitively coupledsource 530 includes aconductive electrode 532 having a small discharge portion or area 532-1 close to and facing the backside edge of thewafer 118 and at least one axially extending leg 532-2. A polymer etch gas species is introduced into thelower process zone 132 through anopening 533 in the chamber floor from agas supply 506. AnRF generator 534 is coupled between the bottom end of the axially extending leg 532-2 and thewafer pedestal 112. A second axially extending leg 532-3 parallel to the first leg 532-2 may be provided. RF power from thegenerator 534 produces a plasma discharge in the small gap between the electrode discharge portion 532-1 and a corresponding area on the wafer backside edge. In one embodiment, the side of theelectrode 532 facing the wafer 118 (or the entire electrode 532) may be covered by aliner 535, which may be formed of a process-compatible material such as quartz, which is useful in minimizing or preventing metal contamination. As in the embodiment ofFIG. 11 , the wafer is rotated so that the entire backside edge circumference is exposed to the localized plasma. - If radiant heating is employed to heat the
wafer 118, then thepedestal 112 may not be necessary, as will be discussed below. - In the reactor of
FIG. 13 , the need to rotate the wafer to expose its bottom circumference to a plasma stream is eliminated by instead generating a ring ofplasma 538 beneath the backside edge extending around the entire circumference. This is accomplished by placing thewafer 118 very close theceiling 104, as in the foregoing embodiments, and then applying RF power to acoil antenna 540 overlying the edge of thewafer 118. Thecoil antenna 540 may consist of solenoidal conductive windings, for example. While the wafer may be held in the elevated position depicted inFIG. 13 with theheated pedestal 112 ofFIG. 11 ,FIG. 13 illustrates how the wafer may be elevated bylift pins 542 suspended on thelift spider 544 controlled by thelift actuator 116. In this case, the wafer is-heated byradiant lamps 548 through theceiling 104. Alternatively, the above-ceiling coil 540 may be replaced by acoil 540′ around thesidewall 102. - In certain embodiments, photoresist is removed from the wafer front side in a separate process. In such embodiments, the wafer is lowered to the dashed line position of
FIG. 13 , and gases are introduced through the ceilinggas distribution plate 104 capable of removing photoresist, as discussed previously in this specification. In other embodiments, a secondinner coil antenna 550 is provided controlling plasma ion density near the center of the wafer. The presence of the secondinner coil antenna 550 also improves uniformity of the photoresist removal. The twocoil antennas separate RF generators separate coil antennas single RF generator 556 whose power is controllably apportioned between the twoantennas power splitter 558. Thelamp heaters 548 are placed in open spaces over the ceiling between the inner andouter coil antennas - The
heated pedestal 112 ofFIG. 11 can be used to hold thewafer 118 in the elevated position ofFIG. 13 . In this case, for a low chamber pressure and in the absence of radiant lamp heaters, efficient heat transfer requires the use of an electrostatic chuck on thepedestal 112. An advantage of using the wafer support pedestal is that it enables bias power to be applied to, the wafer in a highly uniform manner while at the same time effecting uniform heating or temperature control of the wafer. Aliner 520 can also be provided having process-compatible materials to avoid metal contamination and excessive consumption of pedestal materials during plasma processing. - An advantage of using the
radiant lamps 548 to heat the wafer is faster heat transfer (compared to a heated pedestal) in the case of a low chamber pressure where heat conduction or convection is poor. -
FIG. 14 depicts another embodiment of the reactor ofFIG. 13 in which thecoil antenna 540 for generating a ring plasma is replaced by aring electrode 560 surrounding the wafer edge, and anRF generator 562 coupled to thering electrode 560. RF discharge from thering electrode 560 produces thering plasma 538 by capacitive coupling.FIG. 15 depicts a modification of the reactor ofFIG. 14 in which aring electrode 560′ is outside of thechamber 100. -
FIG. 16 depicts a modification that can be implemented in any of the reactors described herein, in which theceiling 104 has a shallow cylindrical hollow 570 corresponding to the volume of thewafer 118. In certain embodiments, the wafer can be lifted into the hollow 570 to effectively shield the wafer front side from polymer etch gases during the backside polymer removal process. -
FIG. 17 illustrates a process in which the reactor chamber is used to perform reactive ion etch of polymer from the wafer backside in a raised wafer position and then photoresist stripping on the wafer front side in a lowered wafer position. Temperature switching is employed to enhance wafer front side protection. Specifically, backside polymer removal is performed at a low wafer temperature and then front side photoresist strip is performed at a high wafer temperature (the order may be reversed). The backside polymer reactive ion etch step may be performed at a sufficiently low wafer temperature to retard the reaction of its by-products (radicals) with thin films (e.g., photoresist) on the wafer front side. If the front side photoresist strip process uses radicals from a remote source, it is facilitated by raising the wafer temperature to a threshold at which the reaction rate of the radicals with photoresist is significantly increased. If the front side photoresist strip process is a reactive ion etch process, then the wafer temperature does not necessarily have to be increased for this step. - Referring now to an exemplary process shown in
FIG. 17 , a first step (block 600) is to support the wafer on the pedestal so as to expose a peripheral portion of the wafer back side. The wafer temperature is set under a threshold temperature (e.g., under 200 degrees C.) below which the reaction rate of polymer etch species radicals with wafer thin film materials is significantly retarded (block 602). A next step (block 604) is to define an upper process zone above the wafer front side and a lower process zone below the wafer back side with minimal migration of gas between the two zones by maintaining a wafer-to-sidewall gap at less than 2 mm. A further step (block 606) is to prevent accumulation of etch species or plasma at the wafer front side by maintaining a wafer-to-ceiling gap (the height of the upper process zone) at less than 2 mm. Another step (block 608) is to purge the upper process zone to remove any etch species radicals that may leak through the wafer-sidewall gap. In order to reduce or avoid etching of thin films on the wafer front side, a further step (block 610) is to evacuate the upper process zone at a pumping port near the wafer edge to remove polymer etchant species (oxygen) from the upper process zone at a sufficiently high rate to avoid damage of critical (carbon-containing or low-k) films on the wafer front side. A related step (block 612) is to evacuate the lower process zone at a pumping port near the edge of the wafer. Reactive ion etching of the polymer on the wafer backside is performed with a plasma close to the wafer backside edge (block 614), until the backside polymer is completely removed. Application of plasma to the wafer backside is then stopped, and the wafer is lowered to increase the height of the upper process zone, in order to permit accumulation of plasma or radicals in the upper process zone (block 616). Then, the wafer temperature is increased above a higher threshold temperature (e.g., above 300 degrees C.) in order to significantly increase the reaction rate of the radicals with photoresist on the wafer front side (block 618). Typically, the reaction rate increase corresponding to the temperature increase from the lower threshold temperature to the higher threshold temperature is about a factor of 5. Radicals from a remote plasma source are employed to strip the front side photoresist (block 620). Alternatively, the step (block 618) of raising the wafer temperature may be omitted, and a reactive ion etch process is used to strip the photoresist (block 622). -
FIG. 18 depicts a modification of the plasma reactor ofFIG. 13 that is capable of performing the process ofFIG. 17 . In this modification, a front side (e.g., photoresist strip)process gas supply 160 is provided in addition to thepurge gas supply 140 through theceiling 104. Theouter coil 540′ is moved to an axial location below the wafer plane. Optionally, theheater lamps 548 are moved from the ceiling to the floor at the bottom of the chamber. Theheater lamps 548 ofFIG. 18 may be employed in carrying out the wafer temperature control step ofblock 602 ofFIG. 17 . Aquartz window 549 is provided in the floor for theheat lamps 548. The small wafer-ceiling gap ofblock 606 ofFIG. 17 is realized at the raised (solid line) position of the wafer in the reactor ofFIG. 18 . Thepurge gas supply 140 ofFIG. 18 provides the gas for the purge step ofblock 608 ofFIG. 17 . The pumpingports FIG. 18 are used in the steps ofblocks FIG. 17 . The reactive ion etch step ofblock 614 ofFIG. 17 is carried out by thesplitter 558 ofFIG. 18 applying RF power only to theouter coil 540′. This creates a ring of plasma beneath the backside wafer edge, as described previously with reference toFIG. 13 , to remove the backside polymer. Upon completion of this step, thewafer 118 is lowered to the dashed line position ofFIG. 18 , and process gas (e.g., a photoresist strip process gas) is introduced through theceiling 104 from thegas supply 160 and into now enlarged upper process zone. Thesplitter 558 applies RF power to both the inner andouter coils block 622 ofFIG. 17 . -
FIG. 19 depicts a modification of the embodiment ofFIG. 18 , in which theceiling 104 is modified to form an upward extendingneck 650 having a cylindrical side wall 652 and aneck cap 654, forming aneck volume 656. The outputs from thepurge gas supply 140 and theprocess gas supply 160 are received in the neck volume. Theinner coil 550 is wound around the neck sidewall 652, so that theneck volume 656 functions as the chamber of a remote plasma source. Thesplitter 558 ofFIG. 19 applies power only to theouter coil 540 during the backside etch process to form a ring of plasma beneath the wafer backside edge. Thesplitter 558 applies power only to theinner coil 550 during the front side etch process to provide a remote plasma source. Because of the distance of theremote source chamber 656 from thewafer 118 in its lowered (dashed line) position ofFIG. 19 , ions from the plasma in the neck recombine before reaching thewafer 118, and therefore the front side etch is a radical-based process, in accordance with the step ofblock 620 ofFIG. 17 . This makes it advantageous to use theheater lamps 548 ofFIG. 19 prior to this step to increase the wafer temperature above the radical reaction threshold temperature, in accordance withblock 618 ofFIG. 17 . - The reactor of
FIG. 11 may be adapted to perform the process ofFIG. 17 by adding aremote plasma source 200 and its process gas supply. Theremote plasma source 200 may be implemented with a coil wrapped around a neck or tube (as shown inFIG. 19 ) or it may be any other type of plasma source, such as a microwave plasma source, for example. Thewafer pedestal 112 ofFIG. 11 may control the wafer temperature in accordance with the process ofFIG. 17 , and thepedestal 112 may move between the raised and lowered (dashed-line) positions ofFIG. 11 , as an optional feature of the process ofFIG. 17 . The reactor ofFIG. 12 is modified in the same manner to adapt it to perform the process ofFIG. 17 , by adding theremote plasma source 200 at the ceiling of the reactor ofFIG. 12 , and moving thepedestal 112 between the solid and dashed-line positions ofFIG. 12 . The same modifications may carried out in each one of the reactors ofFIGS. 13 , 14 and 15. Each one ofFIGS. 13 , 14 and 15 shows that, while lift pins may be employed to control the wafer position, a movable heated pedestal 112 (partially shown in dashed line in both its elevated and retracted positions) may be employed instead, in which case theheater lamps 548 would not be required. In each of the reactors ofFIGS. 11-15 , the optional use of awafer pedestal 112 enables bias power to be applied to the wafer. Advantages of this feature include the enhancement of the backside polymer etch process, and the suppression of ions in theupper process zone 130 if the wafer-ceiling gap is less than the plasma sheath thickness. - Reactive ion etching for removal of backside polymer from the wafer can be accomplished in the process of
FIG. 9 using the reactor ofFIG. 3 . In this aspect, thebackside plasma source 300 ofFIG. 3 produces a sufficient flow of ions that reach the wafer backside. This condition is realized by holding the chamber pressure of theexternal plasma source 300 to a low pressure. In this step, the wafer temperature is held under a low threshold temperature (e.g. below about 200 degrees C. below which the reaction rate of polymer etch radicals with wafer front side thin film materials is very slow (e.g., about 5 times slower than at about 300 degrees C.). The reactive ion etch process used to remove the backside polymer is not hampered at low wafer temperatures. Therefore, this low wafer temperature does not prevent the polymer etch ions from reacting with the backside polymer, but it does effectively slow down the reaction rate of polymer etch radicals that may escape from thelower process zone 132 into theupper process zone 130 with the wafer front side materials. The small wafer-to-ceiling gap employed during the backside polymer removal step essentially guarantees that most (or all) of the polymer etch species that can survive in theupper process zone 130 are radicals or neutrals, not ions. - During the front side photoresist strip step of
FIG. 7 , in which there are no polymer etch species threatening the wafer front side, the wafer temperature is raised above a high threshold temperature (e.g., above 300 degrees C.) at which radicals can react at a faster rate with front side thin film materials, such as photoresist (e.g., at a rate about 5 times faster than at the lower threshold temperature of 200 degrees C.). Typically, the wafer temperature is constantly ramping. If the wafer is being heated to ramp its temperature upwardly, then the backside polymer removal step is performed prior to the wafer temperature exceeding the lower threshold temperature, and the front side photoresist strip step is not performed until after the wafer temperature has reached or exceeded the higher threshold temperature. For example, the wafer temperature may begin slightly above room temperature, ramps upwardly during the entire process. In the period before the temperature exceeds about 150 degrees C. or 200 degrees C., the backside polymer removal step is performed and halted upon completion. Then, after a pause to allow the wafer temperature to reach or at least get near 300 degrees C., the front side photoresist step is performed. The processes ofFIGS. 7 and 9 may be performed in any order, an advantage being that they are performed in the same reactor without having to remove the wafer. When lowering the wafer as required in the process ofFIG. 7 , the backside plasma source (300 ofFIG. 3 for example) is moved so as not to obstruct wafer movement. - The reactor of
FIG. 3 may be modified by replacing theexternal plasma source 300 with an internal plasma source, such as the internalinductive source FIG. 11 or the internalcapacitive source FIG. 12 . In this case, - As previously described in detail in this specification, wafer front side protection is provided by establishing the narrow wafer-ceiling gap and pumping a purge or scavenger gas through that narrow gap. Such protection is improved upon by the feature of holding the wafer temperature below the threshold temperature during backside polymer removal.
- Typically, polymer etch radicals (in the absence of ions) react very slowly with photoresist below the low threshold temperature of about 200 degrees C., while a higher reaction rate is obtained above a high threshold temperature of about 300 degrees C. The polymer etch rate increases by about a factor of 5 as the wafer temperature increases from the low threshold temperature (e.g., 300 degrees C.) and the high threshold temperature (e.g., 200 degrees C.). Therefore, wafer front side protection is enhanced by holding the wafer temperature below the low threshold temperature of 200 degrees C. (e.g., at 150 degrees C.) during the backside polymer removal process. During the subsequent front side photoresist stripping, the wafer temperature is raised to about 300 degrees C.
- At a high chamber pressure on the order of a Torr, the heated electrostatic chuck or
pedestal 112 ofFIG. 3 may be employed to control the wafer temperature. One advantage of this is that RF plasma bias power may be applied to the wafer to enhance processing. A possible disadvantage of using aheated pedestal 112 is that thepedestal 112 may require a protective liner of a compatible material, such as quartz, alumina or yittria. At a lower chamber pressure, it may be necessary to use radiant lamps in order to attain a requisite heat transfer rate. One advantage of radiant lamps is that the wafer temperature may be switched between the two temperatures more quickly, particularly if the wafer is lifted above contact with thepedestal 112 during processing. -
FIG. 20 illustrates a modification of the reactor ofFIG. 2 in which the plasma by-products (radicals) from theexternal plasma source 134 are fed into anannular plenum 630 inside the bottom of thepedestal 112 and upwardly through axialcylindrical bores 632 within thepedestal 112 and is shot out throughejection orifices 634 aimed generally at the peripheral edge of thewafer 118. Theannular plenum 630 supplies gas or plasma by-products to the bottom of each bore 602 and the ejection orifices ornozzles 634 receive the plasma by-products from the tops of thebores 632. As shown inFIG. 21 , thebores 632 andnozzles 634 are arrayed concentrically. In this way, the flow of plasma by-products from theexternal plasma source 134 is collimated withininternal bores 632 of thepedestal 112 and then aimed as a circular array of directed spray patterns from the ejection orifices 634. Thepedestal 112 has a wafer-support surface 636 having a diameter less than that of thewafer 118 so as to leave a peripheral annular region of the wafer backside exposed. Thepedestal 112 further has a peripheralannular surface 638 that is parallel to but below the wafer support surface, the height difference between the twosurfaces 636, 638 providing agas flow space 640 between the peripheralannular surface 638 and the wafer backside. - As in the embodiments of
FIGS. 1-3 , a boundary between the upper andlower process zones wafer 118. In the reactor ofFIG. 20 , this is accomplished by providing aconfinement ring 640 surrounding thepedestal 112 and having aninner edge 640 a adjacent theedge 118 a of the wafer, the twoedges lower process zones main vacuum pump 146 through a horizontalradial space 642 between the annularperipheral surface 638 of the pedestal and abottom surface 644 of thering 640. This evacuation extends through a verticalaxial space 646 between theside wall 648 of thepedestal 112 and avertical surface 649 of thering 640. - In the implementation depicted in the drawing of
FIG. 20 , thechamber 220 of theexternal plasma source 134 is a toroid and the RFsource power applicator 222 consists of a magneticallypermeable ring 222 a wrapped around a section thechamber 220 and acoil 222 b wrapped around thering 222 a and driven through animpedance match 135 by an RFsource power generator 137. Thechamber 220 is coupled to theplenum 630 via aconduit 224. - While the foregoing is directed to embodiments of the invention, other and further embodiments of the invention may be devised without departing from the basic scope thereof, and the scope thereof is determined by the claims that follow.
Claims (20)
1. A reactor for removing polymer from a backside of a workpiece, comprising:
a vacuum chamber having a ceiling, a floor and a cylindrical side wall;
a workpiece support apparatus within said chamber, said workpiece support apparatus configured to support a workpiece thereon, wherein while being placed on said support apparatus, said workpiece has its front side facing said ceiling,, and said support apparatus leaving at least an annular periphery of the backside of said workpiece exposed;
a confinement member defining a narrow gap with the outer edge of said workpiece, said narrow gap being on the order of about 1% of workpiece diameter, said narrow gap corresponding to a boundary dividing said chamber between an upper process zone and a lower process zone, said reactor further comprising a vacuum pump coupled to said lower process zone;
a lower external plasma-generating chamber coupled to introduce a plasma by-product into said lower process zone and a supply of a polymer etch precursor gas coupled to said lower external plasma-generating chamber; and
an upper external plasma-generating chamber coupled to introduce a plasma by-product into said upper process zone and a supply of a scavenger species precursor gas coupled to said upper external plasma-generating chamber.
2. The reactor of claim 1 wherein said confinement member comprises one of: (a) said side wall, and (b) an annular ring surrounding said workpiece.
3. The reactor of claim 1 further comprising:
a lift apparatus capable of lifting said support apparatus to a raised level of said boundary at which said upper process zone is confined to a height on the order of about 1% of the diameter of said chamber;
an upper slit passage in said sidewall adjacent said boundary corresponding to said raised level and open exclusively into said upper process zone and an upper zone vacuum pump coupled to said upper slit passage.
4. The reactor of claim 3 further comprising:
a lower slit passage in said sidewall adjacent said boundary corresponding to said raised level and open exclusively into said lower process zone; and
a lower zone vacuum pump coupled to said lower slit passage.
5. The reactor of claim 1 further comprising:
an apparatus capable of lifting said support apparatus to a raised level of said boundary at which said upper process zone is confined to a height that is sufficiently small to limit gas residency time in said upper process zone to on the order of about 1% of gas residency time in said lower process zone;
an upper slit passage in said sidewall adjacent said boundary corresponding to said raised level and open exclusively into said upper process zone; and
an upper zone vacuum pump coupled to said upper slit passage.
6. The reactor of claim 5 further comprising:
a lower slit passage in said sidewall adjacent said boundary corresponding to said raised level and open exclusively into said lower process zone; and
a lower zone vacuum pump coupled to said lower slit passage.
7. The reactor of claim 1 wherein said support apparatus comprises one of: (a) a heated pedestal, and (b) lift pins.
8. The reactor of claim 1 further comprising one or more radiant lamps for heating the workpiece.
9. The reactor of claim 1 wherein said scavenger precursor gas is a precursor of a species that scavenges a polymer etchant species.
10. The reactor of claim 1 further comprising plural conduits, each of said conduits coupled at one end to said external plasma generating chamber and having an opposite end comprising a gas outlet adjacent to and directed toward the periphery of the backside of said workpiece.
11. A reactor for removing polymer from a backside of a workpiece, comprising:
a vacuum chamber having a ceiling, a floor and a cylindrical side wall;
a workpiece support apparatus within said chamber and having a workpiece support surface defining a boundary between an upper process zone and a lower process zone of said chamber;
a lift apparatus capable of lifting said support apparatus to a raised level of said boundary at which said upper process zone is confined to a height on the order of 1% of the diameter of said chamber;
an upper slit passage in said sidewall adjacent said boundary corresponding to said raised level and open exclusively into said upper process zone;
an upper zone vacuum pump coupled to said upper slit passage;
a lower external plasma-generating chamber coupled to introduce plasma by-products into said lower process zone and a supply of a polymer etch precursor gas coupled to said lower external plasma-generating chamber; and
an upper external plasma-generating chamber coupled to introduce plasma by-products into said upper process zone and a supply of a scavenger species precursor gas coupled to said upper external plasma-generating chamber.
12. The reactor of claim 11 further comprising:
a lower slit passage in said sidewall adjacent said boundary corresponding to said raised level and open exclusively into said lower process zone; and
a lower zone vacuum pump coupled to said lower slit passage.
13. The reactor of claim 11 further comprising an electrical heating element within said workpiece support pedestal.
14. The reactor of claim 11 further comprising radiant lamps for heating the workpiece.
15. The reactor of claim 11 wherein said scavenger precursor gas is a precursor of a species that scavenges a polymer etchant species.
16. The reactor of claim 11 further comprising plural conduits, each of said conduits coupled at one end to said external plasma generating chamber and having an opposite end comprising a gas outlet adjacent to and directed toward the periphery of the backside of said workpiece.
17. A reactor for removing polymer from a backside of a workpiece, comprising:
a vacuum chamber having a ceiling, a floor and a cylindrical side wall;
a workpiece support apparatus within said chamber and having a workpiece support surface defining a boundary between an upper process zone and a lower process zone of said chamber;
a lift apparatus capable of lifting said support apparatus to a raised level of said boundary at which said upper process zone is confined to a height that is sufficiently small to limit gas residency time in said upper process zone to on the order of about 1% of gas residency time in said lower process zone;
an upper slit passage in said sidewall adjacent said boundary corresponding to said raised level and open exclusively into said upper process zone;
an upper zone vacuum pump coupled to said upper slit passage;
a lower external plasma-generating chamber coupled to introduce plasma by-products into said lower process zone and a supply of a polymer etch precursor gas coupled to said lower external plasma-generating chamber; and
an upper external plasma-generating chamber coupled to introduce plasma by-products into said upper process zone and a supply of a scavenger species precursor gas coupled to said upper external plasma-generating chamber.
18. The reactor of claim 17 further comprising:
a lower slit passage in said sidewall adjacent said boundary corresponding to said raised level and open exclusively into said lower process zone; and
a lower zone vacuum pump coupled to said lower slit passage.
19. The reactor of claim 17 wherein said scavenger precursor gas is a precursor of a species that scavenges a polymer etchant species.
20. The reactor of claim 17 further comprising plural conduits, each of said conduits coupled at one end to said external plasma generating chamber and having an opposite end comprising a gas outlet adjacent to and directed toward the periphery of the backside of said workpiece.
Priority Applications (1)
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US11/685,772 US20080179008A1 (en) | 2007-01-30 | 2007-03-14 | Reactor for wafer backside polymer removal using an etch plasma feeding a lower process zone and a scavenger plasma feeding an upper process zone |
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US89864507P | 2007-01-30 | 2007-01-30 | |
US11/685,772 US20080179008A1 (en) | 2007-01-30 | 2007-03-14 | Reactor for wafer backside polymer removal using an etch plasma feeding a lower process zone and a scavenger plasma feeding an upper process zone |
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US20080179008A1 true US20080179008A1 (en) | 2008-07-31 |
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US11/685,902 Abandoned US20080178913A1 (en) | 2007-01-30 | 2007-03-14 | Process for wafer backside polymer removal with a ring of plasma under the wafer |
US11/685,775 Expired - Fee Related US7552736B2 (en) | 2007-01-30 | 2007-03-14 | Process for wafer backside polymer removal with a ring of plasma under the wafer |
US11/685,915 Abandoned US20080179290A1 (en) | 2007-01-30 | 2007-03-14 | Temperature-switched process for wafer backside polymer removal and front side photoresist strip |
US11/685,772 Abandoned US20080179008A1 (en) | 2007-01-30 | 2007-03-14 | Reactor for wafer backside polymer removal using an etch plasma feeding a lower process zone and a scavenger plasma feeding an upper process zone |
US11/685,769 Abandoned US20080179289A1 (en) | 2007-01-30 | 2007-03-14 | Process for wafer backside polymer removal with a plasma stream |
US11/685,770 Abandoned US20080179007A1 (en) | 2007-01-30 | 2007-03-14 | Reactor for wafer backside polymer removal using plasma products in a lower process zone and purge gases in an upper process zone |
Family Applications Before (3)
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US11/685,902 Abandoned US20080178913A1 (en) | 2007-01-30 | 2007-03-14 | Process for wafer backside polymer removal with a ring of plasma under the wafer |
US11/685,775 Expired - Fee Related US7552736B2 (en) | 2007-01-30 | 2007-03-14 | Process for wafer backside polymer removal with a ring of plasma under the wafer |
US11/685,915 Abandoned US20080179290A1 (en) | 2007-01-30 | 2007-03-14 | Temperature-switched process for wafer backside polymer removal and front side photoresist strip |
Family Applications After (2)
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US11/685,769 Abandoned US20080179289A1 (en) | 2007-01-30 | 2007-03-14 | Process for wafer backside polymer removal with a plasma stream |
US11/685,770 Abandoned US20080179007A1 (en) | 2007-01-30 | 2007-03-14 | Reactor for wafer backside polymer removal using plasma products in a lower process zone and purge gases in an upper process zone |
Country Status (2)
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US (6) | US20080178913A1 (en) |
CN (2) | CN101261930B (en) |
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Citations (16)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US4892753A (en) * | 1986-12-19 | 1990-01-09 | Applied Materials, Inc. | Process for PECVD of silicon oxide using TEOS decomposition |
US5306379A (en) * | 1991-09-03 | 1994-04-26 | Sony Corporation | Dry etching apparatus for rectangular substrate comprising plasma bar generation means |
US5858878A (en) * | 1992-12-16 | 1999-01-12 | Tokyo Electron Limited | Semiconductor wafer etching method and post-etching process |
US5914278A (en) * | 1997-01-23 | 1999-06-22 | Gasonics International | Backside etch process chamber and method |
US6074518A (en) * | 1994-04-20 | 2000-06-13 | Tokyo Electron Limited | Plasma processing apparatus |
US6098637A (en) * | 1998-03-03 | 2000-08-08 | Applied Materials, Inc. | In situ cleaning of the surface inside a vacuum processing chamber |
US20030037803A1 (en) * | 2001-08-27 | 2003-02-27 | Applied Materials, Inc. | Method for removing contamination particles from substrates |
US20040137745A1 (en) * | 2003-01-10 | 2004-07-15 | International Business Machines Corporation | Method and apparatus for removing backside edge polymer |
US6936546B2 (en) * | 2002-04-26 | 2005-08-30 | Accretech Usa, Inc. | Apparatus for shaping thin films in the near-edge regions of in-process semiconductor substrates |
US20050284576A1 (en) * | 2004-06-28 | 2005-12-29 | International Business Machines Corporation | Method and apparatus for treating wafer edge region with toroidal plasma |
US20060042651A1 (en) * | 2004-08-30 | 2006-03-02 | Applied Materials, Inc. | Cleaning submicron structures on a semiconductor wafer surface |
US20060045722A1 (en) * | 2004-06-22 | 2006-03-02 | Dainippon Screen Mfg. Co., Ltd. | Substrate reversing device, substrate transporting device, substrate processing device, substrate reversing method, substrate transporting method and substrate processing method |
US20060201623A1 (en) * | 2005-03-09 | 2006-09-14 | Yoo Woo S | Low temperature wafer backside cleaning |
US7170190B1 (en) * | 2003-12-16 | 2007-01-30 | Lam Research Corporation | Apparatus for oscillating a head and methods for implementing the same |
US20070238305A1 (en) * | 2006-04-11 | 2007-10-11 | Applied Materials, Inc. | Plasma dielectric etch process including ex-situ backside polymer removal for low-dielectric constant material |
US20080124919A1 (en) * | 2006-11-06 | 2008-05-29 | Cheng-Lin Huang | Cleaning processes in the formation of integrated circuit interconnect structures |
Family Cites Families (8)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
JPS6074626A (en) * | 1983-09-30 | 1985-04-26 | Fujitsu Ltd | Device for plasma treatment |
JP2888258B2 (en) | 1990-11-30 | 1999-05-10 | 東京エレクトロン株式会社 | Substrate processing apparatus and substrate processing method |
JP3942672B2 (en) * | 1996-04-12 | 2007-07-11 | キヤノンアネルバ株式会社 | Substrate processing method and substrate processing apparatus |
JP3629862B2 (en) | 1996-12-24 | 2005-03-16 | セイコーエプソン株式会社 | Unnecessary object removal method and apparatus for substrate periphery |
US6893907B2 (en) * | 2002-06-05 | 2005-05-17 | Applied Materials, Inc. | Fabrication of silicon-on-insulator structure using plasma immersion ion implantation |
US20050230350A1 (en) * | 2004-02-26 | 2005-10-20 | Applied Materials, Inc. | In-situ dry clean chamber for front end of line fabrication |
US7479207B2 (en) * | 2006-03-15 | 2009-01-20 | Lam Research Corporation | Adjustable height PIF probe |
US20080156772A1 (en) * | 2006-12-29 | 2008-07-03 | Yunsang Kim | Method and apparatus for wafer edge processing |
-
2007
- 2007-03-14 US US11/685,902 patent/US20080178913A1/en not_active Abandoned
- 2007-03-14 US US11/685,775 patent/US7552736B2/en not_active Expired - Fee Related
- 2007-03-14 US US11/685,915 patent/US20080179290A1/en not_active Abandoned
- 2007-03-14 US US11/685,772 patent/US20080179008A1/en not_active Abandoned
- 2007-03-14 US US11/685,769 patent/US20080179289A1/en not_active Abandoned
- 2007-03-14 US US11/685,770 patent/US20080179007A1/en not_active Abandoned
-
2008
- 2008-01-30 CN CN2008100002815A patent/CN101261930B/en not_active Expired - Fee Related
- 2008-01-30 CN CN2008100002783A patent/CN101261929B/en not_active Expired - Fee Related
Patent Citations (16)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US4892753A (en) * | 1986-12-19 | 1990-01-09 | Applied Materials, Inc. | Process for PECVD of silicon oxide using TEOS decomposition |
US5306379A (en) * | 1991-09-03 | 1994-04-26 | Sony Corporation | Dry etching apparatus for rectangular substrate comprising plasma bar generation means |
US5858878A (en) * | 1992-12-16 | 1999-01-12 | Tokyo Electron Limited | Semiconductor wafer etching method and post-etching process |
US6074518A (en) * | 1994-04-20 | 2000-06-13 | Tokyo Electron Limited | Plasma processing apparatus |
US5914278A (en) * | 1997-01-23 | 1999-06-22 | Gasonics International | Backside etch process chamber and method |
US6098637A (en) * | 1998-03-03 | 2000-08-08 | Applied Materials, Inc. | In situ cleaning of the surface inside a vacuum processing chamber |
US20030037803A1 (en) * | 2001-08-27 | 2003-02-27 | Applied Materials, Inc. | Method for removing contamination particles from substrates |
US6936546B2 (en) * | 2002-04-26 | 2005-08-30 | Accretech Usa, Inc. | Apparatus for shaping thin films in the near-edge regions of in-process semiconductor substrates |
US20040137745A1 (en) * | 2003-01-10 | 2004-07-15 | International Business Machines Corporation | Method and apparatus for removing backside edge polymer |
US7170190B1 (en) * | 2003-12-16 | 2007-01-30 | Lam Research Corporation | Apparatus for oscillating a head and methods for implementing the same |
US20060045722A1 (en) * | 2004-06-22 | 2006-03-02 | Dainippon Screen Mfg. Co., Ltd. | Substrate reversing device, substrate transporting device, substrate processing device, substrate reversing method, substrate transporting method and substrate processing method |
US20050284576A1 (en) * | 2004-06-28 | 2005-12-29 | International Business Machines Corporation | Method and apparatus for treating wafer edge region with toroidal plasma |
US20060042651A1 (en) * | 2004-08-30 | 2006-03-02 | Applied Materials, Inc. | Cleaning submicron structures on a semiconductor wafer surface |
US20060201623A1 (en) * | 2005-03-09 | 2006-09-14 | Yoo Woo S | Low temperature wafer backside cleaning |
US20070238305A1 (en) * | 2006-04-11 | 2007-10-11 | Applied Materials, Inc. | Plasma dielectric etch process including ex-situ backside polymer removal for low-dielectric constant material |
US20080124919A1 (en) * | 2006-11-06 | 2008-05-29 | Cheng-Lin Huang | Cleaning processes in the formation of integrated circuit interconnect structures |
Cited By (7)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US20110126762A1 (en) * | 2007-03-29 | 2011-06-02 | Tokyo Electron Limited | Vapor deposition system |
US9157152B2 (en) * | 2007-03-29 | 2015-10-13 | Tokyo Electron Limited | Vapor deposition system |
US20090017635A1 (en) * | 2007-07-12 | 2009-01-15 | Applied Materials, Inc. | Apparatus and method for processing a substrate edge region |
US20090302002A1 (en) * | 2008-02-29 | 2009-12-10 | Applied Materials, Inc. | Method and apparatus for removing polymer from a substrate |
US20090277874A1 (en) * | 2008-05-09 | 2009-11-12 | Applied Materials, Inc. | Method and apparatus for removing polymer from a substrate |
US10903055B2 (en) | 2015-04-17 | 2021-01-26 | Applied Materials, Inc. | Edge ring for bevel polymer reduction |
CN114068273A (en) * | 2020-07-31 | 2022-02-18 | 中微半导体设备(上海)股份有限公司 | Part and preparation method thereof and plasma reaction device |
Also Published As
Publication number | Publication date |
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US20080178913A1 (en) | 2008-07-31 |
US7552736B2 (en) | 2009-06-30 |
CN101261930A (en) | 2008-09-10 |
CN101261929A (en) | 2008-09-10 |
US20080179290A1 (en) | 2008-07-31 |
US20080179007A1 (en) | 2008-07-31 |
US20080179289A1 (en) | 2008-07-31 |
CN101261930B (en) | 2010-12-15 |
US20080179009A1 (en) | 2008-07-31 |
CN101261929B (en) | 2010-10-27 |
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