文章编号: 100025714(2006)032237205
OpticalandMechanicalPropertiesofAlNThinFilmsDepositidby
3
ReactiveMagnetronSputtering
IgorV.Svadkovski1,ZHUChang2,DmitriyA.Golosov1,SergeyM.Zavatskiy1
(1.BelarusianStateUniversityofInformaticsandRadioelectronics,6,P.Brovka,Minsk220013,Belarus;
2.Xi’anTechnologicalUniversity)
Abstract: ThereactivemagnetronsputteringofAlinAr/N2mixtureworkinggaseshasbeeninvestiga2ted.Itisconcludedthat,atlow2pressureoperationofmagnetronsputteringsystemandhighpumpingratethepotentialofdischargedependsdirectlyonthereactivegasconcentration.Therefractiveindex,extinctioncoefficientsandhardnessofthedepositedfilmsdependontheN2concentration.Itispossibletorepeatedlydepositaluminumnitridethinfilmssoastomaketheirrefractiveindexesremainbetween2.25and2.4,extinctioncoefficient10-3andhardnessover20GPabyreactivemagnetronsputteringmethod.ThenecessarynitrogenconcentrationinAr/N2workinggasmixturemustbeabove40%.Thesefilmscanbeusedasopticalcoatingsandprotectivecoatings.
KeyWords: reactivemagnetromsputtering;depositedfilms;nitrogenconcentration;hardnessCLCnumber: O484.4 Documentcode: A
pendonthestoichometryandstructureofthede2positedfilm.
Aluminiumnitridefilms,asarule,havebeendepositedbyusingdifferentmethodsofreactivesputtering.Oneofthemostperspectivemethodsofdielecticalthinfilmsformationisreactivemag2netronsputtering,becauseitallowstoproducecompoundfilmswhichhavethefollowingmagne2
tronsystemadvantages(highdepositionrate,lowsubstratetemperature,simpleequipment,etc).Sobothpropertiesofaluminumnitridethinfilmsanditsformationprocessinvestigationareveryprom2ising.
Introduction
Aluminiumnitrideiscurrentlyconsideredasthecandidateforagreatvarietyofapplicationsinmicroelectronics[122],corrosionprotectivecoat2ings[324]andlarge2areaopticalcoatings[5]becauseofitsuniguepropertiessuchaswidebandgap(6.2eV),highrefractiveindex(1.9～2.1forpolycrystallinefilms),highchemicalandthermalstability,highdensity(3.3g/cm3),highelectricalresistivity(～1014ohm/cm)andsoon.Thesefilmsarealsoem2ployedasopticaldevicesintheultravioletspectralregion,acousto2opticandsurfaceacousticwavedevices,integratedcircuitpackaging,andsoon.
PracticalapplicationofAlNthinfilmsislim2itedbythedifficultyinrepeatingthecharacteris2ticsofthegivenfilm.Itisbecauseoptical,electri2calandtribologicalcharacteristicsstronglyallde2
1 Experimental
Theschemeofexperimentalsetupfordeposi2tionofAlNfilmsbyreactivemagnetronsputte2ringmethodisshowninFig.1.Thevacuum
3Receiveddate:2005212227
Biography:IgorV.Svadkovski(19652),Male,BelarusianStateUniversityofInformaticsandRadioelectronics,AssociateProfessor,En2
gagedinplasma.
238 西 安 工 业 学 院 学 报 第26卷
chamberisequippedwithmagnetronsputteringsystem(MSS)andionsource(IS).Themainfea2tureofMSSisthatitcandecreaseworkingpres2sureto0.03Pa.Thereasonisthatitisbestforthemagneticsystemtoadoptadditionalelec2tromagaticcoilandmagneticfieldconfigurationonthetargetsurface[6].Itgivespossibilityto
workatlowgasflows(downto50sccm).
supplyistotallyantiarcsystem.
OpticalcharacteristicofdepositedAlNfilms(refractiveindexn,extinctioncoefficientk)atwavelength630nmismeasunedbyellipsimetrymethodbyellipsometerLEF23M21atlightangle65°.Dispersionoftherefractiveindexandextinc2tioncoefficientintherangeofwavelength245～1650nmhasbeenstudiedbyspectroscopicEllip2someterM2000UIatlightangle75°.Knoophard2nessoffilmshasbeenmeasuredbymicrohardnessmeterLeikaVMHTMot.Indenterloadis10gandtimeofloadis10s.
2 Resultsanddiscussion
HowMSSdischargevdtagedependsonac2tivegasN2flowatsputteringofAltargethasbeenresearchedinpowerstabilizationmode.ArflowinvacuumchamberwasequaltoqAr=35sccm.
Fig.1 SchemeofexperimentalsetupfordepositionAlNfilmsbyreactivemagnetronsputteringmethod
Pressureinvacuumchamberwasabout0.06Pa.Itwasdeterminedthatatlow2pressureoperationofMSSandhighpumpingrateinpowerstabiliza2tionmodethemagnetrondischargevoltagewasdirectlydependentonthereactivegasconcentra2tioninthevacuumchamber(Fig.2).Thehysteresiseffectissometimesabsentinreactivemagnetronsputteringprocess,whichmakesitpossibletocontrolreactivegasflowbystabilizingdischargevoltagesoastocontrolthereactivemagnetronsputteningprocess.
ThehighpurityAltarget(99.995%)ofdiam2eterof160mmandthicknessof8mmhasbeensuccessfullysputteredinAr/N2gasmixture.Inordertocontrolthegasflows,itisnecessarytousemassflowcontrollerRRG21.Theconcentra2tionofN2inAr/N2gasmixturevariesfrom0to40%.Si(100),opticalglassBK7,pyroceramandpolishingstainlesssteelallcanbeusedassub2strates.Substratesweresituatedatthedistanceof8.5сmfromtheUBMtargetsurface.Beforedep2osition,first,ionclearingofsubstratesisper2formed.SotheionsourceonthebaseHall2currentacceleratoriscleaned.Thevacuumchamberispumpedtothebasepressureof10-3PaandthenArisfedintomaketheworkingpressuregodownto2.0×10-2Pa.Timeofclearing,ionener2gyanddischargecurrentinthewholeexperimentremain3min,700eVand40mА,respectively.
Fig.2 MSSdischargevoltageasafunctionofN2flowatdepositionofAlNfilmsbyreactivemagnetronsputtering
stabilizationofdischargepowermode
FortheMSSworking,theontputpowperofthepowersupplyis1.5kworsoandthecurcuitandpowerneedtooperateinstabilizationmode.Topreventthearconthetargetsurfacethepower
AlNfilmsaredepositeduptothethicknessof0.2
～1.2μmattheaveragedepositionrateof0.8nm/s.Fig.3showsthedependenceofKnoophardnessof
第3期 IgorV.Svadkovski,etal:OpticalAndMechanicalPropertiesofAlN……239
AlNfilmsdepositedbyreactivemagnetronsput2teringonN2concentrationinAr/N2gasmixture.Thefilmsaredepositedatthefollowingcondi2tions:Ut=430V,Pt=1.0kW(powerstabilizationofdischarge),p=0.06Pa,qAr=35sccm,andthedis2tancefromthesubstratetothetargetis10.5cm.HardnessofAlNfilmscanreach20GPa.Ithasbeenfoundthatthemaximalhardnessoffilmsiscorre2spondingtoorneartostoichiometricalcompositions.
Asisshowninthefig.whenthereisalackofnitride,therefractiveindexoffilmscanachieve2.5.However,thesefilmshaveahighextinctioncoef2ficientintherangeof0.121.0(seeFig.5).Atwavelengthlessthan300nmtherefractiveindexsharplydecreases.SuchcurvebehaviorisabsentfortheAINfilmsneartoorequaltostochiomet2ricalcomposition(Fig.4c,d,e).Therefractivein2dexofthesefilmsdecreaseswiththeincreaseofwavelength.Therefractiveindexofthefilm,neartostochiometricalcompositionandinthewave2lengthrangeof60021600nm,iscloseto2.1.Re2fractiveindexdecreasesalittlewiththeinereaseofreactivegasflow.Curvebehaviorforextinctioncoefficientoffilmsisdifferent.Extinctioncoeffi2cientdecreaseswiththeincreaseofnitrogenflow.
Fig.3 KnoophardnessofAlNfilmsdepositedbyreactivemagnetronsputteringasafunctionofN2
concentrationinAr/N2gasmixture
Fig.4showstherefractiveindexdispersionoffilmsAlNdepositedbyreactivemagnetronsputteringatdifferentreactivegasN2flow:a210sccm,b212sccm,c216sccm,d217sccm,e218sccm.Thefilmsaredepositedunderthefollowingstabi2lizationconditions:dischargepowerPt=0.9kW(It=2.2A)andthedistancebetweensubstrateandtarget=11cm,Arflow33sccm,p=0.06Pa,depositiontimet=10min.
a210sccm,b212sccm,c216sccm,d217sccm,e218sccmFig.5 Extinctioncoefficientdispersionofaluminumnitridefilmsdepositedbyreactivemagnetronsputtering
atdifferentreactivegasN2
Fig.6showshowtherefractiveindesandex2tinctioncoefficiontofAINthinfilmsdepositedbyreactivemagnetronsputteringmethoddependonreactivegasflow(N2)at630nmwavelength.WhenthedepositionofAINfilmsisneartostvi2chiometricalcomposition,thenitrogenflowismorethan20sccm(35%).Undersuchcondition,therefractiveindexoffilmscanreach2.4.Theextinctioncoefficientoffilmssharplydecreaseswhennitrogenflowismorethan16.0sccm(30%).
a210sccm,b212sccm,c216sccm,d217sccm,e218sccmFig.4 RefractiveindexdispersionoffilmsAlNdepositedbyreactivemagnetronsputteringat
differentreactivegasN2
Thealuminumnitridefilmswithextinctioncoeffi2cientdownto10-3havebeendeposited.Howev2er,thesefilmshadahighlevelofinternalstresses.Therangeofcriticalfilmthicknessisupto400～
240 西 安 工 业 学 院 学 报 第26卷
500nm.Beyondthelimit,thefilmwillliftoffaf2terinteractionwithair.
tridethinfilmswithrefractiveindexintherangeof2.25～2.4,extinctioncoefficientdownto10-3andhardnessmorethan20GPa.ThenitrogenconcentrationinAr/N2gasmixtureshouldbea2bove40%.Thesefilmscanbeusedasopticalandprotectivecoatings.
3 Conclusion
Sobyreactivemagnetronsputteringmethoditispossibletorepeatedlydepositaluminumni2
Fig.6 Refractiveindex
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磁控溅射法镀制氮化铝薄膜特性研究
斯维德科夫斯基1,朱昌2,格洛索夫1,扎瓦兹基1
(1.白俄罗斯国立无线电信息大学薄膜实验室,明斯克220013;2.西安工业大学)
3
摘 要: 氮化铝薄膜具有高折射率,良好的化学稳定性,耐磨摩、高电阻等特性在微电子器件和光学薄膜中有着广泛地应用.本文研究了反应式磁控溅射方法利用Ar/N2混合气体镀制氮化铝薄膜的工艺过程,实验表明在高真空和高泵浦速率条件下,放电电压直接依赖于反应气体
3收稿日期:2005212227
作者简介:斯维德科夫斯基(19652),男,白俄罗斯国立无线电信息大学副教授,主要研究方向为等离子体技术.
第3期 IgorV.Svadkovski,etal:OpticalAndMechanicalPropertiesofAlN……241
珠浓度.薄膜的折射率,消光系数和薄膜硬度都依赖于氮气浓度的比例.通过工艺研究,找到了氮气在不同浓度下对氮化铝薄膜的折射率,消光系数以及薄膜硬度的影响,找出了镀制氮化镀
制氮化铝薄膜的最佳工艺参数.在Ar/N2工作气体中氮气含量保持在40%条件下,用反应式磁控溅射方法,可以精确镀制出良好的氮化铝薄膜,其中折射率范围在2.25～2.4之间,消光系数为10-3,薄膜显微硬度大于20GPa.该薄膜可以广泛应用于微电子器件和光电器件上.关键词: 反应式磁控溅射;镀膜;氮气浓度;硬度中图号: O484.4 文献标识码: A
(责任编辑、校对 张立新)
(上接第222页)
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SONGYu2gui,WANGTie2ling,MAYing
(SchoolofOptoelectronicEngineering,Xi’anTechnologicalUniversity,Xi’an710032,China)
Abstract: Inordertoincreasetheoutdoorapplicationrobustofsky2screenandmeettherequirementsofnetworkedmeasurementinprovingground,customizingcapabilityofsignalrecognizingpabilitywereim2proved,characteristicsofenvironmentaldisturbanceonskyscreen,signalrecognizingschemeandimple2mentationbasedondigitalfilterwereanalyzed.Onenovelschemeofsky2screensignalrecognitionbasedonsinglechipanditsfeasibilitywerediscussed.Theprinciple,keyparameter,circuitschematicandsoft2waredevelopmentwereintroduced.Primitiveexperimentalresultsincludingrecognizingdelaywithin2μsanddelayconsistencywithin0.1μsindicatethatsuchsolutionisapplicableandfeasible.KeyWords: provingground;singlechip;skyscreen;robustness
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