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Structural and electrical properties of ultrathin nitrided gate dielectrics by plasma-assisted methods

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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

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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

(3)

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

4321-巨己三三)二句巨巴笏{三百己君2m

SiO2 400℃450℃500℃550℃600℃

NitridationT℃mperature

FiglValuesofbreakdownstrengthfbra-SiONylayersversustheTnvalues

Secondlybwediscusstheelectricpropertiesofa-SiXNylayerswerepreparedby theexposureofcrystallineSi(C-Si)substratestoNH3plasmautilizingplasma enhancedchemicalvapordeposition(PECVD)apparatus,andtheSisubstrateswere nitridedatdifTerentRFPoweLbetween5Wand25WThesampleswerestudiedby

(4)

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

lncrease

interface,decreasedTheseresultssuggestthattheincorporationofNatomsinto ultrathingatedielectricswithmonolayerlevelsina-Si,JVy/SilayerreduceSthedirect tunnelingcurrent・Furthermore,incorporationofaproperdensityofNatomsinto Siliconwassuggestedtoimprovetheelectricproperties.

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Thirdly)wediscussthepropertiesofa-SiXNylayersnitridedbyNH3plasma withdiffbrentnitridationtime,betweenlOminand90minlnFTmresults,theSi-N

stretchingbandataround900cm~lwasindependentofnitridationtimeForESR

results,thespectralpositionschangedatdifferentnitridationtime・TheNsdecrease withincreasinginnitridationtimelntheI-Vinversioncharacteristics,theleakage currentdecreasedinnitridedlayerthanthatinSiO21ayerlntheI-Vacculnulation characteristics,theleakagecurrentdecreased,whentheelectronsinthedielectric layeLilljecteMFomtheinterface、Theseresultssuggestthatincolporationofaproper densityofNatomsintoSiliconwassuggestedtoimprovetheelectricalproperties.

㎡ががががげげげげが

◆。●▲▼ ◆q●▲▼ ◆q●▲▼

←E◎豆)「 ◆『●*△q●Ⅱ

◆●▼△ゴ◆●▼▲

q◆●▼▲

。◆●▼▲

|d◆●▼▲

q◆●▼▲

■SiO2

●10min

▲30min

▼45min

◆60min

<gOmin

0.0 0.2 0.4 0.6 0.8 1.0

VM

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

(6)

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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(7)

1hA

10-3

10-4

田▼

昼■▼く。

△■▼ぐ

E’05ージ

つ10-8

▲■▼ぐ く今

▲■▼く d●

▲■▼く

▼く

107 ▼く ■NH3

●3min

▲10min

▼15min

●20min

<30min

1dB

10-9

0.2 0.4 0.6

VⅣ)

0.8 1.0

Fig41-Vinversioncharacteristicsunderdifferentpostannealingtimevalues versussuppliedvoltagefbra-SiXNylayers

Lastlybwediscussedthestructureofa-SiJWylayerswerepreparedbythe exposureofcrystallineSi(C-Si)substratestoNH3plasma,thenitridedlayerswere postannealedfbrdiffbrentnitridationtime,betweenlminandl5mininO2gas

ambient、WefbundthatthepostannealinginO2atmospherelowerstheNatoms

content・FromtheFTmresults,weknewtheNatomswereremovedfiFomtheSiN

bond,thestructureandcompositionofSi】JWylayerwerechangedWecanconclude thepostoxidationleadtoastructuralchangeoftheSiXNylayers.

(8)

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。-,○四判圏鞠丹臥讃虐鱈献載U沐翼童一mJっぺ蓬試圀赫廊献割器で計・蕪一mm三訴叩討貯叺凶‐○訴恥-,

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、苦いe蟄鵲舜淑雰乢山凡剣鵬言信蝿-,片が②]弧議戴彌e罰凋駕蠅汽試ラペ鋤皿井杏加献軌抑小岱e 代雌洲⑩昔/H罫河昇燕汁(椛葦)行崗斗ぴぴe代童冊で計。

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一口]①量ぐ①忌巨、(ずの己○里ロロロの口氏口胴曰三①ぐ②一口①、

Absorbance(arbunits)

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