Oxime Sulfonate Chemistry for Advanced Microlithography

Journal of Photopolymer Science and Technology Volume 20, Number 5 (2007) 637-642 @TAPJ

Hitoshi Yamato, Toshikage Asakura, Yuichi Nishimae, Akira Matsumoto, Junichi Tanabe, Jean-Luc Birbaum, Peter Murer, Tobias Hintermann and Masaki Ohwa

Technology Center Electronic Materials, Coating Effects Segment, Ciba Specialty Chemicals K.K., 7-1-13, Doi-cho, Amagasaki, Japan 660-0083

Oxime sulfonate compounds are one of the important chemistry as photoacid generator for advanced lithography application and practically used in mass production of semiconductor chips. This chemistry is adjustable for various applications like g-/h-/i-line, KrF and ArF lithography. This paper describes an overview of oxime sulfonate chemistry for semiconductor resist application, including commercially available products. Keywords: oxime sulfonate, photoacid generator, g-line, i-line, KrF, ArF, chemically amplified resist

1. Introduction The development of semiconductor chips is desired resist performance such as resolution, making progress with an astonishing speed, depth-of-focus, line edge roughness and etching enabling electronic apparatus smaller, higher resistance, the acid-labile polymers have been speed, and higher performance. This dynamic intensively studied first and developed notably. For advancement is significantly attributable from the further improvement of the CA resist, PAG is the development of photolithography technology. At key ingredient. Several chemistries have been an early era of integrated circuits (IC) extensively investigated as the photoactive manufacturing lithography technique was component for the CA resists, e.g., iodonium introduced with light source of g-line wavelength sulfonate, sulfonium sulfonate, (436 nm). For further miniaturization of IC the diazomethanedisulfone, N-sulfonyloxyimido wavelength of light source is getting shorter and compounds, nitrobenzyl sulfonate, and so on [3]. shorter, i.e., i-line (365 nm), KrF (248 nm) and Among them, we have particularly paid attention ArF (193 nm). Currently ArF immersion is actively to oxime sulfonate chemistry due to its potential investigated as the most advanced technology, and ability as latent acid and its wide structure EUV (13.5 nm) is discussed as the next generation variation. lithography. When the g-line and i-line light We have developed several oxime sulfonate sources were used, the resist comprised compounds, aiming to g-/h-/i-line, KrF and ArF diazonaphthoquinone (DNQ) as photo-sensitive lithography. In addition, a sensitization of oxime component [1]. However, after introduction of KrF sulfonate has been investigated. These studies are laser, the DNQ resist can’t be employed for the described in this paper. advanced lithography because the absorption of DNQ resist at 248 nm and 193 nm is too high to 2. PAG for g-/h-/i-line application transmit the light throughout the resist to the Recently there are demands for broadband and i-line bottom. As an alternative technology, chemically resist with high sensitivity, high resolution and thick amplified (CA) resist was developed [2]. The CA thickness. DNQ resist has been widely used for resist is composed of polymer bearing acid-labile broadband and i-line applications so far but its groups and photoacid generator (PAG). Photolytic decomposition of PAG during light exposure performance does not satisfy such new demands generates acids in the CA resist. This acid acts as and the CA resist is attracted for these applications. catalyst to facilitate de-protection reaction of ester Chloromethyl triazines with extended conjugation group or acetal group of polymer, rendering are known as suitable PAG for g-/h-/i-line exposure polymer matrix alkaline-soluble. For achieving

637 Received April 6, 2007 Accepted May 21, 2007 J・P肋叩OJy〝7・Scf・乃C加oJ・，VbJ・20，No・5，2007

［41．However hydrochloric acid photochemically retainsagoodsolubilityabove15％inPGMEAas generated from chloromethyl triazineis highly SurrlmarizedinTable2．TbegoodsolubilityofPAG volatile and corrosive and can be a concem minimizestherisk of particle generation dunng regarding potentialdamage ofthe manufactunng resiststorageandimprovesformulationflexibility． equlPment．Since sulfonic acids areless volatile， less mobileandless corrosive，they aretherefore Preferred over hydrochloric acidin the resist ab le 2 S olu b ility in P G M E A applications．Thoughonly afew sulfonic acid iC U P A G lX X Solubility （％） generators sensitive up to g－line arekn0wn・We 10 3 20 havebeeninvestigatingoximesulfonatetypePAG． 108 ＞30 This chemistry can be a4iusted to the target 12 1 17 applicationsand exposure wavelengthrange by Selectionfromawiderangeofchromophoresand acidmoieties． 2．4 Bemeretalreportedoximesulfonateaslatent 1．9 acidcatalystforcoatingapplicationl5］butsuch

qJ COmPOunds do not have absorpt10ninalonger 宣1．4 月 WaVelength．Aiming for gr瓜－／i－1ine 叩Plication， L O t′l IRGACURE㊨pAGlXXseriesisnewlydeveloped 毒0・9

l6］・Figurel shows UV absorption．spectrum， 0．4 indicatlngSu伍cientlyred－ShiftedabsorptlOnPrOfile －0．1 OVerg－line（436nm）withtheLmaxat405nm．Ths 200 300 400 500 600 red－Shiftedprofileisattributablefromtheextended WaYek口車hくnm） COqugatedsystembycombinationofphenylnng Figure2tTVabsorptioTLChangeolICtlPAGlXX 肌dqulnOidestruCtureOfthiophenerlng．Withour upOneXpOSure negative tone modelformulationIRGACURE㊨ PAGlXXshowsagoodsensitivitynotonlywithi－ 1ineexposurebutalsowithg－1ineexposure． Figure2displaysachangeofUVal）SOrPtlOnin acetonitrile solution upon exposure to436mm monochromaticlight．A distinctive absorption at TabIclIRGACURE⑧pAGlⅡ 255nmemergedandtheabsorptlOnabove420mm ICUPAG lXX Acidgene叫ed COmpletely disappeared during exposure・The 103 n－Propanesulfomicacid qu血m yield ofphotolysi岳，Od，WaS determined 108 nJCktanesulfomicacid fromtheabsorptlOndecreaseat436nm，indicatlng

121 p－Toluenesulbnicacid thatofIRGACURE⑧pAG103wasO．13．Similarly theamountofacidgenerated upon exposurewas determinedbytheindicatordyemethod．InFigure 3，thedec托aSeOfthenormalizedal）SOrPt10nat

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190 240 290 340 390 440 490

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FigurelUVabsorptionofICtJPAGlO3 0 100 200 300 400

Exposuretime（min） As7t－COIt）ugation ofanOrganic moleculeis extended，the solubilityofthe molecule usually Figure3AcidgenerationandtJVchangeofICtl becomeslower．HoweverIRGACURE⑧pAGIXX PAGlXXuponexposure

638 J・P加opo抄肌Scf・乃C九oJ・，VbJ・20，No・5，2007

436 mm and the normalized molar acid qompnslng POlyhydroxystyrene（PHS）based concentration（relative to initial molar PAG polymer and PAG was developed for KrF concentration）ofthe photochemically generated lithography・There are mainly two polymer ● acid were plotted agalnst eXPOSure time・It was PlatformSWithdi飽rentacid－hbilegroups・Oneof foundthatthe decrease ofabsorptlOn at436mm themis so－Called acetaltype polymer，i・e・，PHS （photobleaching）was equaltothegeneratedacid Partiallyprotectedwithacetalgroup・Tもeotheris concentration when both were normalized tothe so－CalledESCAPtypepolymer，i・e・，CO－POlymerOf initialmolarPAGconcentration．Thissuggeststhat PHS andtert－butylmethacrylate．The acetaltype

phot0－decompositionofIRGACURE㊨PAGIXX POlymerCanbede－PrOteCtedbelow1100Catpost－ quantitatively generates acid・Tberefore，the exposure baking（PEB），Whilethe ESCAP type quantum yield of photolysis，4＞d，COrreSPOnds POlymerneedstobeheatedintherangeof120－ directlytothatforacidformation，¢a，thus 1300C． IRGACURE⑧pAGIXXisthermallystableup la／¢d＝l to1550Cinthe neatformbut the stal）ilitylS loweredto1400CinapolymermatriX．ThisPAGis The reportedla／．d ratiosfor oxime sulfonates StableenoughfortheapplicationofacetaltypeKrF werefoundintherangeofO．6toO．8［7］．Hence，it resist．On the other hand，thereis ariskinits was concluded thatIRGACURE㊨ pAGIXX applicationforESCAPtypeformulationintermsof PrOvides good or superior photoacid generation thermaldecompositionofPAGatPEB・ e鍋ciency，basedongoodacidconversionyield・ Wehavestudiedthethermalstabilityofoxime TもestorageStabilityofPAGisoneofcritical SulfonateanddevelopedthermallystableKrFPAG， requlrementSfor CA resist application・Because IRGACURE㊨ pAG 203［8］．Ths 00mpOund ev飢Smal1amOuntOfacidcanCauSedegradationof possessestrifluoromethylgroupa句acenttooxime

CAresist．ThestabilityofIRGACURE㊥pAGIXX group， Which stabilizes this molecule・ areevaluatedbymonitorlngaCidconcentrationin IRGACURE㊥pAG203isstableupto1880Ceven thesamplestoredatvarioustemperatureatfrequent inapolymermatriXandover2000Cinaneatform intervals．No acidformation was observed after asshowninFigure5．Tberefore，thisPAGcanbe morethanlyearstorageevenat400C．Whenthe employedin both acetal and ESCAP type sampleisstoredat40C，IRGACURE⑧pAGIXX formulations． hasfoundtobestablemorethan5years，弧dthe evaluationisstillcontinued．

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0 50 100 150 200 250 300

Th℃（W由り J ‾

l ■●

■◆● ■′ ’．■ ■．t ■ Figure4Storage stability ofICtJPAG103in t ●● neatmrm き〇一－霊石工

l l

3．PAGfbrKrFapplication When KrF excimer－laser（248 nm）yas introducesasthelightsourceforresistapplicatlOn，「■● ● －■ ● theconventionalDNQresistcouldnotbeemployed Temp（C） duetoahighabsorptlOnOfnovolakpolymermatriX and DNQ molecules．Tberefore，the CA resist Figure5DSCcurvesofICtJPAG203

639 J・P加opoJym・Scf・mc〝OJ・，VoJ・20，Nb・5，2007

As can be seen 丘om the UV absorptlOn methyladamantylmethacrylate）is a key reaction

spectruminFigure6，IRGACURE⑧pAG203has dunngthelithographyprocess・Tもeoximesulfonate anabsorptlOnValleyaround248mmandshowsa COmPOunds with a stropg acid such as relativelylowabsorptionatthewavelengthofKrF Perfluoroalkylsulfonate have been investlgated・ lithography・SuchalowabsorptlOnCOmbinedwith Usuallysuchcompoundswerefoundtobenotso highsensitivityisahighlydesiredproperty，because stablebecausetheperfluoroalkylsulfonateisagood alowoverallabsorbanCeaSSureSuniformexposure leavlng grOuP・Forinstance，lt WaS attemPtedto

throughout the whole thickness ofthe resist・ synthesize theIRGACURE⑧ pAGlXX with Compared to other PAG typically usedfor KrF Perfluoroalkylsulfonate but the target compound lithographysuchastriphenylsulfoniumsalt（TPS） WaS degraded durlng the purification and not

aJlddiazodisulfone（DAS），IRGACURE⑧pAG203 isolated as a pure material．h the case of

Showsverywell－balanCedbehaviorwithrespecttoa IRGACURE㊥ pAG 203 analogue with number ofapplication－relevant properties as KrF trifluoromethanesulfonate（CGI 261），the pure PAGassummarizedinTable3． COmPOundwasobtainedbutitwasnotsostablein thepresenceofamineinsolution・AfinetunlngOf struCture hasimprovedthe stability of oxime sulfonatewithperfluoroalkylsulfonate，reSultingin

l 父Y 6 4 つ一〇 CGI19XXcompoundsl9］．TもekeystruCtureWaSa l l longperfluoroalkylgroupnexttooximesulfonate，〇〇〇〇 l ● lC U P A 0 2 0 3 父岩言qhO的qく王 0 ．0 1が whichstabilizesthemolecule． ● ● 一一・一・・・IC U P A G 2 0 3 ：● 0 ・5 嘲

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暮 0、．．」．． N Rf 190 240 290 340 390 440 490 －C3F7 CGI1906 RI （4F8H CGI1907 Wavelength／nm （6FlZH CGI1905

Figure6tJVabsorptionofICtJPAG203

AsshowninFigure7，CGI19ⅩⅩwasasstable as TPS inthe presence of triethan01aminein ニ憲些葦…… PGMEAstoredat400C，Whi始CGI261degraded （Wれ％）（W的％）（C）（m此ml） toca．40％after28days．Tbisresultsuggeststhat PAG2（13 0．091 25 18g 1．73 CGI19XXisapplicableforresistformulationas C£ PAG． TPS O．329 1．4 ＞200 0．27

DAS O．019 ND 142 5．06

l L2 0 00 ′0 4 2 0 O O O O O Oくhp肖弓EOZ 1）0．01がIn庵CN d0葛と68dOu ■CGI1905 2）inPGMEA 3）DdqnjnedbyD8Cwh ATPSIげ e叩dammmtdPト恰 ■CGI261

0 10血／吋20 30

4．PAGfbrArFapplication Figure7Storage stability of CGI1905in the On the development of polymer for ArF PreSenCeOfamineinPGMEAat400C formulation，methacrylate unit beanng aliphatic CyClicgroupsuchasadamanty1isincorporatedas acid－hbilegrouptoimproveetching－reSistanceand TheUVabsorptlOnSPeCtraOfCGI19ⅩⅩand transparencyat193nm．Asaresult，PAGreleaslng TPS at equivalent weight％inacetonitrile are astrongacidisrequlred，becausethecleavageof PreSentedin Figure8．The absofbanCe Of CGI ester bonding of the polymer matriⅩ（e・g・，2－ 19XXat193mmisaboutonethirdofthatofTPS．

640 JPわれpoまわ花成伽抱え2仇却b・員2007

ThelowabsorptionofCGI19XXfacilitatesbetter detectionlimit：＜2．6Ⅹ10－12mol／cm2）duetonon－ resistpromeascompa柁dtoTPS・Theupperlimit ionicproperty． Of PAG concentrationin a glVen reSistis a Waterdropletsremainedonthesurhceofresist function bothofPAG solubilityand absorption． after exposun∋and stage sczmnlnglS One Ofthe Thus，thelowal）SOrPtionand good solubilityof CauSeS for theimmersion specific defects． CGI19XXmeansincreasedformulationflexibility 呵drophobicityof the resist surface has been forArFresist． found to playanimportant role to reducethe irrmersion specinc defects．Inaddition，thehigh hydrophobicpropertyofthesurfaceenableshigh StageSCanSPeed，leadingtohighthroughpdl10】・ 1．4 Figure9displaysthe contactangle ofwateron 1．2 AfF modelformulationincludingvarious PAGs． 1 4）くJ The addition of CGI19XX increases the S o．8 J⊃ l｛ hydrophobicityofresistsurhce，Whiletheaddition 眉0・6 く OfTPS decrease the hydrophobicity．CGI19XX 0＿4 canCOntribde to reducethe defects andincrease 0．2

0 the scan speed・These results suggestthat CGI 190 240 290 340 390 19XXareSuitableforAfFimmersionlithography． Wavel印辞h／nm

Figure8 VabsorptionofCGI19XX

卯 85 抑 75 間朗甜

監汐白＼〇一切口468dOU BymonitoringtheremalnlngamOuntOfPAG へ守整容憲・：L‾浮草繹隼瑠 byHPLCanalysisduringexposureat193nm，the

吉、￥ quantum yield of CGI1905was estimated as 三、－・1すくも‥藩一木7‾、’ノチ■‾嘉㌫拉二一調揖・駄・惹群璃需・く・1．．，だ

■、tiゝ‾、、∴J ‾：ミまき・．二、．、肇鄭 … トぎーで・‥ ′1、こ㌧‾r・■・ヾ二・■ 戦ぎ左、：・キン、、‡‾Jウ COmPared with TPS and BPI（dilerf－ ■．．tキ ▼，、‾ヽ・■J し■．，ヾ： ‥、歌登彗煎・ ∴・≧1・－∴瀧・：ふ三ぷ

ゝ・．R、。三三さ勺こ■さ■‾いく′曹〉・、測さ butylphenyliodonium salt）and the resultlS ク・、・トして，1・漣、登蹄＿雄張薫窯～二三二、こ・－しし‾∴∴1‾ず、1．，ヽ‘・－1∴ ．托、こ、■ヾモ■、、＼′ち■隼、ゝ、ゝ二・・堀責■彗＝淡一七 SummarizedinTable4．CGI1905gavethehighest し小、U 、ずこ、1年、べ．し、、ボ∴・緑ノ滋・駕薫呼買芸・鋤適魚礁．．緑藻∵ ．l＿こく、．‡＿豆，、．碓悪・筑・■鶴ニ∫1■㌍浩．鳥誓．・詔賑諭潤一や簸潜 quantumyield，0・27，WhichwassuperiortoTPSby ⅦbPAG TPS CGIl冥汚 CGI19u CGIl咲）7 46％．Ontheotherhand，thequantumyieldofBPI WaSquitelow，0．06．Theiodoniumchromophore does not suitablefor AfFlithographyfromthe Figure9ContactangleofwateronArFresist Viewpointofphotospeed．

5．Sensiti2：ationofoximesulfonate

Tla Db14qleqVuantu mm ●eldofPAGinacetonitri1eylelqOIrAblnaCetOnltrlle As described above， the use of PAG Quantumyieldinsoldion Photolithographywith1ightsourceofg－nl－／i－lineis CGI1905 0．27 extensivelystudiedbesidesthefront－endprocess TPSnf 0．18 Ofsemiconductormanuhcturing．Theyareaimed BPInf 0．06 for new fieldslike MEMS（Micro Electro MechanicalSystems），dielectriclayer，buf艶rlayer AfFimmersionlithographylS becomlngthe Ofsemiconductorchip，displayapplicationsandso mqortechnologyofthenextgenerationfor45nm on．IKACURE㊨pAGIXXcanbeemployedfor node，and wateris employed astheimmersion these 叩Plications，Which has red－Shifted mediumduetoitshighrefractiveindex（n＝1・44） absorptionprolile，leadingtothedirectexcitation andhightranSParenCyat193nm．Thedemanded at such alonger wavelength．Asthe altemative PrOPertiesforPAGinimmerSionapplicationare approach，We haveinvestigatedthe sensitization non－leachingtowaterandcontributiontoreduce abilityofoximesulfonatecompounds・ ● immersion specific defects．The evaluation of IRGACURE㊨ pAG 203 has no slgnificant PAGleachingfrom AfF modelfomulation to absorption at365nm，andit did not glVe any WaterreVealedthatTPShad signilicantleaching SenSitivitywiththenegativetonefomulationupon behavior，2－9Ⅹ10－11molhm2．ontheotherhand， i－line exposure・To this formulation，Various noleaching ofCGI19XXwas observed（below SenSitizeswith50Ⅵ丑％againstPAGwereadded

641 J・P加opoJy〝7・Scf・mc加oJ・，VoJ・20，Nb・5，2007

and their sensitivity ati－line was measured， 4．CONCLUSION respectively．Tもe result ofthe sensitivitywas Tもe oxime sulfonate compounds have high PreFentedin FigurelO・Amhocoumarin（AC）， POtential as PAGandthey are a4iustablefor amlnObenzophenone（ABP），肌danthracene（DBA） variousdemandssuchashighthermalandstorage COmpOunds had e飴ct on the sensitization of Stability，red－ShiRedabsorptionprofileetc・Wehave

IRGACURE㊨ pAG 203，and tnggered the developedseveraloximesulfonatetypePAGforg－ decompositionofPAG，givingphotosensitivityof nl－／i－line，KrF and ArFlithography applications， the formulation ati－line．Among them，9，10－肌d they are currently employedin the mass dibutoxyanthracene most e飴ctively sensitized PrOductionofsemiconductorchips・ IRGACURE㊨ pAG 203．The sensitization

mechanismisassumedanelectron■tranSferfromthe sensitizers to the oxime sulfonate molecule but ACKNOWLEDGMENTS further studies are necessaryforthe mechanism Wewouldliketoexpress oursincerethanksto elucidation．An0ther oxime sulfonate compound， Ms－sMidoriMasaki，YukaKotake，MikaKunoand CGI1907，WaS also studied with respect to RumiYamashitafortheirexperimentalsupport． sensitizationbyDBAasshowninFigurell・Ths PAG showed a good sensitivity ati－linein combination with DBA too．Itis worthwhile to REFERENCE mentionthatanthracene compounds workwellas l．For example， R・ DalTmel， thesensitizerforoximesulfonatecompounds．肋肌棚画伽甲血糊－あがedRe∫f∫ね，pp・9－96， SPIE Optical Engineering Press，Washington， D．C．，1993． 00 釦 60 40 200 0 0 0 0 2．H．ho，J P0少肌滋i．A P叫加C鮎肌，41 ハ…一6、r∈）倉名唱忘S （2003）3863－3870． 3．a）J．V．Crivello，Adv．Polym．Sci．，62（1984）1－ 48．b）M．Shirai，M．Tsunooka，Prog．Polym． Sci．，21（1996）1－45． 4．G．Buhr，R．Dammel，C．R．Lindley，Jbかm．

DBA ABP AC 肋Jer．滋才．助g．61（1989）269－77． Sen51血r 5．G．BemerandW．R血SCh，USpatent4540598． 0／＼＼／へ＼ 6．T．Asakura，H．Yamato，M．Ohwa，J 二二＿朗og呼0少肌滋f．乃C〃仰J・13（2000）223－30・＼、／へ〉0 7．M．Shirai，M．Tsunooka，Bull．C77em．Sbc．tkm． DBA ABP AC 71（1998）2483－2507． 8．a）H．YamatO，T．Asaknra，A．Matsumoto，M． FigurelO Sensitivity ofICtl PAG 203in Ohwa，Proc．肌だ4690（2002）799－808．b）T． combinationwithsensitiZerSati－line Asakura，H．Yamato，A．Matsumoto，P．Murer andM．Ohwa，J Photqpoかm．Sbi．7tchnol・16 （2003）335－346． 9．a）H．YamatO，T．Asakura，T．Hintermarmand

0 00 ′0 4 2 0 0 0 0 0 0 DBAcontent M．Ohwa，Proc．SfW5376（2004）103－114．b）（N∈U＼、∈）きち雲岩拐 againstPAG T．Asaknra，H．Yamato，T．HintermammandM． Ohwa，Proc．SfW5753（2005）140－148．C）H． Yamato，T．Asaknra，andM．Ohwa，Proc．SPIE 6153（2006）61530F／1－61530F／9． 10．S．Owa，H．Nagasaka，Y．Ishii，K．Shiraishiand S．Hirukawa，Proc．SPLE5754（2005）655－668．

CGI1907

PAG

Figurell Sensitivity of PAGin combination withDBAati－line

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