Structural and electrical properties of ultrathin nitrided gate dielectrics by plasma‑assisted methods
著者 郭 若峰
著者別名 Guo, Ruofeng journal or
publication title
博士学位論文要旨 論文内容の要旨および論文審査 結果の要旨/金沢大学大学院自然科学研究科
volume 平成19年3月
page range 280‑286 year 2007‑03‑01
URL http://hdl.handle.net/2297/14625
氏名 学位の種類 学位記番号 学位授与の日付 学位授与の要件 学位授与の題目
郭若峰 博士(学術)
博甲第797号 平成18年3月22日
課程博士(学位規則第4条第1項)
StructuralandElectricalPropertiesofUltrathinNitridedGateDielectrics byPlasma-assistedMethods
(プラズマ援用作製法による極薄窒化ゲート絶縁膜の構造及び電気特性)
猪熊孝夫(自然科学研究科・助教授)
久米田稔(自然科学研究科・教授),高宮三郎(自然科学研究科・教授),
森本章治(自然科学研究科・教授),
佐々木公洋(自然科学研究科・助教授)
論文審査委員(主査)
論文審査委員(副査I
46sかα〃
Accordingtothesemiconductorindustrydevelopment,theprOjectedoxide thicknesswillbelessthanlnminfiltureAtthisthiclmess,theperfbmanceofSiO2 thatismostlyusingasadielectricmaterialisdegradedduetothelealKagecurrent,its permeabilityboronandmetaldiffilsionSi3MandSi-oxynitride(SiOXNy)are consideredasaninterestingcandidatesbecauseofitscharacteristics;suchasahigh density,ahighdielectricconstant,promisingradiationhardness,anditsapplication asaveryefficientdifliJsionbarrierBut,eventhoughanumberofstudieshavebeen donetoinvestigatetheelectronicandmechanicalpropertiesofthedielectricmaterials,
thedetailedcharacteristicofSi3N4andSiOXNyhavenotbeenidentified
lnitially>wediscussthestructuralpropertiesofa-SiQJVylayerswithdiffbrent compositions,preparedusingaplasmanitridationtechniquefbrthermallyoxidized 63-nln-thicka-SiO21ayers,bymeansofcurrent-voltage(1-V),E1ectronSpinRcsonace 巴SR),andFouricrTransfbrmInhFared(FTm)measurements、Inthel-Vmeasurement,
thea-SiOXNylayerswerepreparedonlow-resistivitycrystallineSisubstrates・The bestbreakdownstrengthappearedtobeobtainedatnitridationtemperature,Tn=550 .Candwefbundastrongcorrelationamongthechangesinthel-Vcharacteristicsand
intheESRproperties・Thecorrelationwasdiscussedintemsofthechangeinthe defbctsdensityofthea-SiOXNylayersFromFTmresults,theabsorptionfbrthe
a-SiQNylayerswasobservedataround840cm~’andlO70cm~',wherethepeak fiequencyfbrthe840cm~landlO70Cm~lbandsincreasedanddecreasedwith increasingTn,respectivelyThe840cm~landthelO70cn1bandswereassignedto stretChingmodeofSLNbonds,(Si▲N)strandstretchingmodeofSi-Obonds,(Si-O)str bands,respectiVelyTheseresultswerediscussedinrelationtothechangesinthe structuralpropertiesFurthemOre,incorporationofaproperdensityofnitrogenatoms intoSiO21ayerWassuggestedtoimprovethestructuralproperties,suchasthedefect densitybandimprovetheelectricalproperties,suchasanincreasingthebreakdown strength
6
5
4321-巨己三三)二句巨巴笏{三百己君2m
0
SiO2 400℃450℃500℃550℃600℃
NitridationT℃mperature
FiglValuesofbreakdownstrengthfbra-SiONylayersversustheTnvalues
Secondlybwediscusstheelectricpropertiesofa-SiXNylayerswerepreparedby theexposureofcrystallineSi(C-Si)substratestoNH3plasmautilizingplasma enhancedchemicalvapordeposition(PECVD)apparatus,andtheSisubstrateswere nitridedatdifTerentRFPoweLbetween5Wand25WThesampleswerestudiedby
a-SiXNylayerswasobservedataround900cm~1,andwhichisindependentofRF powers‘The900cm~lbandwereassignedtothestretchingbandsfbrSi-Nbond TheseresultswerediscussedinrelationtothechangesinthestructuralpropertiesFor ESRresults,thespectralpositionschangedatdiflbrentRFpowers・TheNbincreases withincreaseinRFpowerslnthel-Vmeasurement,thea-SixNylayerswereprepared onn-typeC-SisubstrateswithalowresistivitylntheI-Vinversioncharacteristics,
theleakagecurrentdecreasedwiththeincreasesiilRFpowers,indicatingthattheN contentwasefIbctivetoreduceortoeliminateelectronsinjectedfiDmthegate.
4.2x1019 4.0xlO19 3BxlO19
11119999《U(U(U《U■I■Ⅱ靴0剣Ⅱ敏俶取町【。《。旬》Q》②二言のこのpE-Qの
2.8x1019 2.6X1019 2.4xlO19 22xlO19
5W 10W 15w
RFpower(W)
20W 25W
Fig2ESRspindensitybNs,fbra-SiXNylayersversustheRFPowers
IntheI-Vacculnulationcharacteristics,theleakagecurrentdecreasedwithan seinRFpowers,whentheelectronsinthedielectriclayemnjectedfiFomtheノ
lncrease
interface,decreasedTheseresultssuggestthattheincorporationofNatomsinto ultrathingatedielectricswithmonolayerlevelsina-Si,JVy/SilayerreduceSthedirect tunnelingcurrent・Furthermore,incorporationofaproperdensityofNatomsinto Siliconwassuggestedtoimprovetheelectricproperties.
Thirdly)wediscussthepropertiesofa-SiXNylayersnitridedbyNH3plasma withdiffbrentnitridationtime,betweenlOminand90minlnFTmresults,theSi-N
stretchingbandataround900cm~lwasindependentofnitridationtimeForESRの
results,thespectralpositionschangedatdifferentnitridationtime・TheNsdecrease withincreasinginnitridationtimelntheI-Vinversioncharacteristics,theleakage currentdecreasedinnitridedlayerthanthatinSiO21ayerlntheI-Vacculnulation characteristics,theleakagecurrentdecreased,whentheelectronsinthedielectric layeLilljecteMFomtheinterface、Theseresultssuggestthatincolporationofaproper densityofNatomsintoSiliconwassuggestedtoimprovetheelectricalproperties.
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Fig31-VinversioncharacteristicsfbrSiO21ayeranda-SiXNi,layerswith
D
differentnitridationtimeintervalversussuppliedvoltage
Fourthly5wediscusstheefIbctsofpostannealingonthepropertiesofa-SiXNy nitridedbyNH3plasma・ThenitridedlayerswerepostannealedfbrdifIerent between3minand30minatvarioustelnperatures、Inthel-Vinversion )teristics,theleakagecurrentdecreasedwiththeincreasesinpostannealing rature,ta,exceptfbrta=3,in,indicatingthattheNcontentwaseffectivein layersnitrided
time,between characteristics,
temperature,ta,
q〆
reducingoreliminatingelectronsinjectedfiomthegate、Inthel-Vaccumulation characteriStics,theleakagecunPentdecreasedwithanincreaseinta,theNatoms reduceelectronsinjectedfiomtheSisubstrateTheseresultssuggestthatthepost annealingtreatmentofultrathingatedielectlicsreducethetunnelinglnFTmresults,
theintensityofSi-Nstretchingbanddecreasedwithincreasingta・Theseresultswere discussedinrelationtothechangesinthestructuralpropelties、Furthermore,
incorporationofaproperdensityofNatomsintoSilayerwassuggestedtoimprove theelectIicpropelties、
Wealsodiscusstheelectricpropertiesofa-SiXNylayerswerepreparedbythe exposureofC-SisubstratetoNH3plasma・Thenitridedlayerswerepostannealedfbr diffbrentnitridationtemperature,between900.CandllOOoCInthedependenceof FTmresultsonthepostannealingtemperature,thepealKffequencyofSiとNstretchingo’
bandincreasedwithincreasingTa・TheintensityofSi-Nstretchingbanddecreased withincreasingupto950oCInthel-Vinversioncharacteristics,theleakagecurrent decreasedwithincreasinginpostannealingtemperature,Ta,exceptfbrTa=1100oC Inthel-Vaccumulationcharacteristics,theleakagecurrentdecreasedwithanincrease inTaTheseresultssuggestthatinCorporationofaproperdensityofNatomsinto Siliconwassuggestedtoimprovetheelectricalproperties.
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Fig41-Vinversioncharacteristicsunderdifferentpostannealingtimevalues versussuppliedvoltagefbra-SiXNylayers
Lastlybwediscussedthestructureofa-SiJWylayerswerepreparedbythe exposureofcrystallineSi(C-Si)substratestoNH3plasma,thenitridedlayerswere postannealedfbrdiffbrentnitridationtime,betweenlminandl5mininO2gas
ず
ambient、WefbundthatthepostannealinginO2atmospherelowerstheNatoms
content・FromtheFTmresults,weknewtheNatomswereremovedfiFomtheSiN
bond,thestructureandcompositionofSi】JWylayerwerechangedWecanconclude thepostoxidationleadtoastructuralchangeoftheSiXNylayers.
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