USP_6815359 (1063533), страница 3
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In one embodiment, layer 28 can comprise oneor more layers of materials, such as, a polysilicon stackdescribed With reference to a How diagram shoWn in FIG. 2.comprised of a plurality of alternating layers of titaniumsilicide, tungsten silicide, cobalt silicide, etc. materials. Inanother embodiment, layer 28 is a hard mask layer, such as,An exemplary embodiment of the invention Will be65The How diagram includes a pattern photoresist step 40, adevelop patterned photoresist step 42, a ?uorination step 44,and an etch step 46.US 6,815,359 B265Utilizing lithography system 10, the pattern or imageprovided on mask or reticle 18 is patterned on photoresistmas for etching metals, C4F8/O2-based plasmas for etchinginorganic dielectrics, or NZ/HZ-based plasmas for etchinglayer 30 in the pattern photoresist step 40. Next in step 42,organic dielectrics. As shoWn in FIG.
5, the increased etchWafer 24, including patterned photoresist layer 30, understability of layer 30 permits features thereon, such as, feature50, to maintain pattern integrity (i.e., survive etch step 46)goes development to de?ne features, such as, a feature 50,to be effectively de?ned on layer 28. Accordingly, the bene?tof the full resolving poWer of 193 nm exposures and/or theon photoresist layer 30 (FIG. 3).
Feature 50 can de?ne, butis not limited to, a conducting line, a transistor gate, acontact hole, a via, or a trench. The siZe and shape of feature50 is not shoWn in a limiting fashion.After the patterned photoresist layer 30 has been develenhanced depth of focus provided by ultra-thin photoresistcan be realiZed Without introducing subsequent fabrication10failure or errors due to insuf?cient photoresist thickness ofoped but before such a pattern is transferred onto any of theultra-thin photoresists.underlying layers, such as, layer 28, ?uorination step 44 (orIt is contemplated that before or after ?uorination step 44,Wafer 24 may undergo other fabrication processes, such as,a resist trimming process, before etch step 46.
It is alsocontemplated that shell 52 may be formed by an ion implantation step or by an electron beam exposure step in place of?uorination step 44. In the case of the ion implantation step,alternatively, an electron beam curing step or an ion implantation step) is performed on Wafer 24. It should be understood that Wafer 24 may be removed from chamber 12 andplaced Within a different chamber and/or a different environment Which provides ?uorination tools, such as, the Lam15Research Corp. 4500 Model plasma etch system. Floodions such as argon or ?uorine may be utiliZed.
Such ionselectron beam curing can be done in a tool, such as, theWould cause a certain depth of the exposed surfaces of layer30 to densify, thereby making such areas less porous andmaking it harder for the etchant in etch step 46 to erode layerElectronCure 1200-PR Model manufactured by ElectronVision Corporation. Alternatively, chamber 12 may be con?gured to include additional chambers and/or tools suitableto perform step 44.Referring to FIG. 4, there is shoWn a cross-sectional vieWof a portion of Wafer 24 undergoing ?uorination step 42.Wafer 24 is exposed to a ?uorine-based plasma (not shoWn)2030.
In the case of the electron beam exposure step, a ?oodexposure electron beam of suf?cient energy and dose Willcause decarboxylation, cross-linking, and densi?cation of25to modify the exposed surfaces of photoresist layer 30.It is understood that although the detailed draWings,speci?c examples, and particular values describe the exemplary embodiments of the present invention, they are forpurposes of illustration only.
The exemplary embodimentsAlternatively, Wafer 24 may be exposed to a ?ood electronbeam or ions. The exposed surfaces of photoresist layer 30,for example, a shell 52 comprising the top surface and sideWalls of feature 50, are chemically and structurally changedupon interaction With the ?uorine-based plasma, electronbeam, or implanted ions. The exposed surfaces are densi?ed,becoming harder or structurally more rigid, and thereforeof the present invention are not limited to the precise detailsand descriptions described herein. For example, althoughparticular materials or chemistries are described, other materials or chemistries can be utiliZed.
Various modi?cationsmay be made in the details disclosed Without departing fromthe spirit of the invention as de?ned in the folloWing claims.What is claimed is:1. Amethod of increasing an etch stability of a photoresistmore resistant to high-energy ions and/or reactive radicalspresent in the plasma processes that Will be used to subsequently etch the layers of Wafer 24 not covered by layer 30.In one embodiment, the surface ?uorination occurs utiliZing CF4 plasma at about 1000 sccm ?oW rate, 50 mTorrchamber pressure, 400 W radio frequency (RF) poWer, and50° C. loWer electrode temperature. Alternatively, the?uorine-based plasma may be other ?uorocarbonchemistries, such as, C2F6, CHF3, or C4F8, and includingcombination of gases possibly including additives, such as,inert gases, at operating parameters of 10—2000 sccm ?oWrate, 5—1000 mTorr chamber pressure, 50—2000 W RFpoWer, and 20—80° C.
loWer electrode temperature.Shell 52 has a thickness in the range of 20—500 A relativeto the initial thickness or height of feature 50. The extent of?uorination of the photoresist increases and shell 52 isthicker When ?uorination process time is increased, or atthe material comprising layer 30, again increasing the etchstability of layer 30 in subsequent processes.layer, the method comprising the steps of:40providing the photoresist layer at a thickness less than0.25 pm, for use in vacuum ultraviolet lithography,deep ultraviolet lithography, or extreme ultravioletlithography;45exposing the photoresist layer to a plasma, the photoresistlayer including exposed surfaces; andtransforming the exposed surfaces to form a shell beforeusing the photoresist layer to etch an underlying layer,Wherein the shell increases the etch stability of the50photoresist layer.2.
The method of claim 1, Wherein the plasma has aplasma characteristic of approximately 50 mTorr chamberhigher plasma ?oW rates, moderate poWers, higher chamberpressure.pressures, and/or loWer electrode temperatures.3. The method of claim 2, Wherein the plasma has plasmaFluorination step 44 causes a slight loss or reduction in the 55 characteristics of approximately 100 sccm ?oW rate, 400 Wthickness of layer 30, typically in the range of a feWradio frequency (RF) poWer, and 50° C.
loWer electrodeAngstroms. HoWever, the remaining thickness of layer 30,temperature.including the surface ?uorinated feature 50, Will have amuch enhanced etch stability or etch resistance in compari4. The method of claim 1, Wherein the etch stability isincreased by 20—50% as compared to the etch stability of theson to its un?uorinated counterpart. In one embodiment, the60etch stability is increased by approximately 20—50%.
Etchstability is also referred to as hardness.Upon completion of ?uorination step 44, pattern transferto underlying layers, such as, layer 28, can occur using etchstep 46. In one embodiment, etch step 46 comprises a dryphotoresist layer before exposure to the plasma.5. The method of claim 1, Wherein the transforming stepincludes transforming the exposed surfaces by a depth of upto approximately 50 nm.6. The method of claim 1, Wherein the transforming stepetch using a plasma etchant, such as, Clz/HBr-based plasmasincludes at least one of decarboxylation, cross-linking, anddensi?cation of the exposed surfaces to form the shell, thefor etching silicon-based conductors, Cl2/BCl3-based plasshell being hardened.65US 6,815,359 B287exposing the photoresist layer to a ?uorine-based or7.
An integrated circuit fabrication process, the processcomprising:argons densi?er;transforming the top surface and the side surfaces With thepatterning a feature on a photoresist layer disposed overa substrate, the feature patterned in accordance With adensi?er to form a hardened surface; andetching the substrate in accordance With the transformedfeature, Wherein the exposing step occurs after thedeveloping step and before the etching step, and an etchstability of the feature is a function of the hardenedpattern provided on a mask or reticle and a radiation ata deep ultraviolet or extreme ultraviolet lithographicWavelength;developing the photoresist layer, the patterned photoresistlayer including at least one feature having a top surfaceand side surfaces;exposing the photoresist layer to a ?uorine-based plasma1016. A method of using a feature on a photoresist layerdisposed above a layer or substrate, the feature includingdensi?er;exposed surfaces, the feature being lithographically pattransforming the top surface and the side surfaces With thedensi?er to form a hardened surface; and15etching the substrate in accordance With the transformedfeature, Wherein the exposing step occurs after thedeveloping step and before the etching step, and an etchstability of the feature is a function of the hardenedsurface.8.
The process of claim 7, further comprising providingthe photoresist layer at a thickness of less than approximately 0.25 pm.9. The process of claim 7, Wherein the transforming stepincludes decarboxylation.and an extreme ultraviolet lithographic Wavelength or has amethod comprising:transforming the exposed surfaces to be structurallydenser than the untreated region due to at least one ofa ?uorination, a ?uorine ion implantation and argon ionimplantation; and2517.
The method of claim 16, Wherein a depth of theexposed surfaces is in the range of 2—50 nm.18. The method of claim 16, Wherein the exposed surfacescomprise a top surface and side surfaces of the feature.19. The method of claim 16, Wherein the transformingelectrode temperature.11. The process of claim 7, Wherein the densi?er is a ?oodelectron beam.12. The process of claim 7, Wherein the densi?er is an ionstep includes cross-linking.implantation.35has a depth of 2—50 nm.patterned a feature on a photoresist layer disposed over asubstrate, the feature patterned in accordance With apattern provide on a mask or reticle and a radiation ata deep ultraviolet or extreme ultraviolet lithographicWavelength;developing the photoresist layer, the patterned photoresist20.
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