developing etching process for nanostructures on ingap and ... · icp power(w) 350 2000 2000 2000...

Developing Etching Process for Nanostructures on InGaP and AlInP

Using OX-35 Etcher JieyangJia,LiZhao

Mentors:MaryTang,JamesMcVi7eEE412FinalPresentaion,Spring2014

6/6/2014

Accomplishments

SystemaDcetchingcalibraDonon4materialswith2seriesofrecipes

InGaPandAlInPnanostructuresachieved

Processinsightsthatwillhelpfutureusers

FirstDmeinSNFonOx-35

FirstDmeinSNFwithRIE?

Materials

Recipes

LowERHighER,75W4mT HighER,25W4mT HighER,25W2mT HighER,25W8mT Chamber

CleanChamberpressure(mT) 10 4 4 2 8 20DCpower(W) 120 75 25 25 25 70ICPpower(W) 350 2000 2000 2000 2000 2000Cl2flow(sccm) 0 7 7 7 7 0CH4flow(sccm) 50 8 8 8 8 0H2flow(sccm) 10 5.5 5.5 5.5 5.5 0SF6flow(sccm) 0 0 0 0 0 20O2flow(sccm) 0 0 0 0 0 100

MoDvaDon Methodology Results

MoDvaDon

• Whynanostructures

• WhyInGaP/AlInP

• Whyox-35

Methodology Results

Nanostructures on III-V: PROS

D.Liang,etal.NanoLe(ers2013,13(10)

AnD-reflecDon

Be`erlightmanagement

Be`erlightextracDon

Nanostructures on III-V: CONS

D.Liang,etal.NanoLe(ers2013,13(10)

Be`eropDcalproperDes

LargersurfacerecombinaDonloss

SoluDon:doitonmaterialswithsmallersurfacerecombinaDon!

Why on InGaP and AlInP

InGaP•  SmallersurfacerecombinaDonrate• CommontopjuncDonmaterialformulD-junDonsolarcells

AlInP•  Largebandgap• CommonwindowlayermaterialforPVandLED

Bonus materials: why InP and SiO2

InP• Simplermaterialtoetch,goodstarDngmaterial

SiO2• Maskfornanostructureetching

Why ReacNve-ion Etching (RIE)

• Lowtemperature(allowsphotoresistmask)• Higheretchingrate• Be`erselecDvity• Morecontrollableandrepeatable

ComparingtoInducDveCoupledPlasma(ICP)andElectronCyclotronResonance(ECR)Etching

MoDvaDon Methodology

•  Designofexperiments

•  Processflow

Results

Design of Experiments

4materials:InP,InGaP,AlInP,SiO2nanospheres

2seriesofrecipes:CH4/H2andCl2/CH4/H2processes

Etchingrate,

conformity,mask

condiDon,etc.

Tuning:RFpower,pressure,chemicalcomposiDon(imcomplete)

Process Flow: Nanostructure FormaNon

Wafercut&clean SiO2spheremaskcoaDng

SiO2sphereetch–“ballshrinking”

SampledryetchSamplewetetch

CharacterizaNon

Process Flow: Process CalibraNon

Barematerials PhotoresistcoaDng

Photoresistdeveloping

Etching

CharacterizaNon

Tools

Ox-35Etcher Wetbenches

KarlsussHeadway

MoDvaDon Methodology Results

•  EtchingcalibraDon

•  Nanostructures

Results Overview Material Recipe EtchRate

(verNcal/horizontal)(nm/min)

Undercut(nm/min)

SidewallAngle(dec)

Smoothness

(boUom/sidewall)

PhotoresistCondiNon

Comments

InP LowER 154 81 67.3 Smooth/rough Polymerobserved SignificantpolymerformaDon

HighER,75W4mT 750 NA >86 Smooth/zigzag Degraded,porous

HighER,25W4mT 404 1500 51 Rough/rough Degraded

HighER,25W2mT NA NA NA NA NA Etchingfailed

HighER,25W8mT 269 <0 13.3 Rough/rough Wavy,locallypeeled

InGaP LowER 70 8 84 Smooth/smooth Polymerobserved SignificantpolymerformaDon

HighER,75W4mT >300 <0 >80 Smooth/zigzag Degraded Epietchedthrough

HighER,25W4mT 240 <0 78 Rough/mildzigzag Degraded

HighER,25W2mT 192 NA 75.3 Smooth/smooth NA SiO2mask

HighER,25W8mT 178 300 39 Veryrough/veryrough Wavy

AlInP LowER <5 NA NA NA NA Noetchingobserved

HighER,75W4mT >300 NA NA Smooth/zigzag Porous Epietchedthrough

HighER,25W4mT 428 1140 varying Smooth/rough Porous

HighER,25W2mT 365 NA 82 Smooth/smooth NA SiO2mask

HighER,25W8mT 90 1340 7.1 Veryrough/veryrough Wavy

SiO2 LowER <5 NA NA NA NA Noetchingobserved

HighER,75W4mT 70/2 NA NA NA NA

HighER,25W4mT <50/<50 NA NA NA NA



ChamberClean 400/300 NA NA NA NA

InP ü  CH4/H2recipe:ER=154.4nm/minSWangle=67.3˚SignificantpolymerformaDon

ü  Cl2/CH4/H2recipe:

ER=750nm/minPRmaskwasetchedporous

InGaP ü  CH4/H2recipe:ER=70nm/minSWangle~90˚Verysmoothsidewallsandbo`om“Capping”effect

ü  Cl2/CH4/H225W,8mTrecipe:

ER=178nm/minUndercut=300nm/minSWangle~39˚Goodconformityfornanostructureetching

AlInP ü  CH4/H2recipe:Doesn’tetchatall!

ü  Cl2/CH4/H275W,8mTrecipe:

ER=90nm/minUndercut=1340nm/minSWangle~7.1˚Morechemicalthanphysical

SiO2 Nanospheres ü  CH4/H2andCl2/

CH4/H2recipes:Negligibleetchingrate=goodselecDvity

ü  O2/SF6chambercleanrecipe:

L.ER=400nm/minV.ER=300nm/minIdealforballshrinking!

InGaP Nanostructures Cl2/CH4/H225W4mT,1min

O2/SF670W20mT,1min+Cl2/CH4/H225W8mT,2min

AlInP Nanostructures Cl2/CH4/H225W4mT,1min

O2/SF670W20mT,1min+Cl2/CH4/H225W8mT,2min

Conclusion on Experimental Results

• BothCl2/CH4/H2andCH4/H2recipesetchwell• Cl2recipeisfasterbutrougher

InP

• CH4/H2:slow,smoothandstraight• Cl2/CH4/H2:idealfornanostructureetching

InGaP

Conclusion on Experimental Results

• CH4/H2:doesn’twork!• Cl2/CH4/H2:verysensiDvetoCl2,resulDnginlargeundercut

AlInP

• SurvivesbothCl2/CH4/H2andCH4/H2processes• O2/SF6chambercleanrecipeisidealforshrinking!• ShrinkmoreonInGaPthanAlInP

SiO2nanospheres

Accomplishments

SystemaDcetchingcalibraDonon4materialswith2seriesofrecipes

InGaPandAlInPnanostructuresachieved


AddiNonal Process Insights


•  CH4/H2recipesgeneratesalotofpolymer•  AccumulaDveprocessDmeshouldnot

exceed20minbeforechamberclean•  (orverybadthingwillhappen)

•  InGaP:1min1:6diluteHCLdiprecommendedtoremoveoxide

•  AlInP:AlmostalwayscomeswithGaAscap,1mincitricaciddip+1minHCLdiprecommended

MoDvaDon

• Whynanostructures

• Whyox-35

Methodology

•  Designofexperiments

•  Processflow

Results

•  EtchingcalibraDon

•  Nanostructures

developing etching process for nanostructures on ingap and ... · icp power(w) 350 2000 2000 2000...

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