1. Cov txheej txheem tseem ceeb ntawm cov tshuaj lom neeg ua kom cov pa dej hauv cov ntshav nce siab
Plasma enhanced chemical vapor deposition (PECVD) yog ib txoj kev siv tshuab tshiab rau kev loj hlob ntawm cov zaj duab xis nyias los ntawm kev tshuaj lom neeg ntawm cov khoom siv roj nrog kev pab los ntawm cov plasma tso pa tawm. Vim tias PECVD thev naus laus zis tau npaj los ntawm kev tso pa tawm roj, cov yam ntxwv ntawm cov tshuaj tiv thaiv ntawm cov plasma tsis sib npaug tau siv tau zoo, thiab hom kev muab hluav taws xob ntawm cov tshuaj tiv thaiv tau hloov pauv tseem ceeb. Feem ntau, thaum PECVD thev naus laus zis siv los npaj cov zaj duab xis nyias, kev loj hlob ntawm cov zaj duab xis nyias feem ntau suav nrog peb txoj hauv kev tseem ceeb hauv qab no.
Ua ntej, hauv cov plasma uas tsis sib npaug, cov electrons ua rau cov roj ua haujlwm hauv theem pib kom rhuav tshem cov roj ua haujlwm thiab tsim cov ions thiab cov pab pawg nquag;
Qhov thib ob, txhua yam pawg neeg nquag sib kis thiab thauj mus rau saum npoo thiab phab ntsa ntawm zaj duab xis, thiab cov tshuaj tiv thaiv theem ob ntawm cov tshuaj reactants tshwm sim tib lub sijhawm;
Thaum kawg, txhua yam khoom siv tshuaj tiv thaiv thawj zaug thiab theem ob uas ncav cuag qhov chaw loj hlob raug adsorbed thiab cuam tshuam nrog qhov chaw, nrog rau kev tso tawm cov roj molecules.
Tshwj xeeb, PECVD thev naus laus zis raws li txoj kev tso tawm lub teeb tuaj yeem ua rau cov roj ua haujlwm ionize los ua plasma nyob rau hauv qhov kev txhawb nqa ntawm lub zog hluav taws xob sab nraud. Hauv lub zog tso tawm lub teeb plasma, lub zog kinetic ntawm cov electrons uas tau nrawm los ntawm lub zog hluav taws xob sab nraud feem ntau yog li 10ev, lossis siab dua, uas txaus los rhuav tshem cov tshuaj sib txuas ntawm cov roj molecules reactive. Yog li ntawd, los ntawm kev sib tsoo tsis sib xws ntawm cov electrons muaj zog siab thiab cov roj molecules reactive, cov roj molecules yuav raug ionized lossis decomposed los tsim cov atoms nruab nrab thiab cov khoom molecular. Cov ions zoo raug nrawm los ntawm cov ion txheej accelerating hluav taws xob teb thiab sib tsoo nrog lub electrode sab saud. Kuj tseem muaj ib lub zog hluav taws xob me me ion txheej ze ntawm lub electrode qis dua, yog li lub substrate kuj raug bombarded los ntawm ions rau qee qhov. Yog li ntawd, cov khoom nruab nrab tsim los ntawm kev decomposition diffuses mus rau lub raj phab ntsa thiab substrate. Hauv cov txheej txheem ntawm drift thiab diffusion, cov khoom me me thiab pawg (cov tshuaj lom neeg ua haujlwm nruab nrab atoms thiab molecules hu ua pawg) yuav dhau los ntawm ion molecule reaction thiab pawg molecule reaction vim yog txoj kev luv luv nruab nrab dawb. Cov khoom siv tshuaj lom neeg ntawm cov tshuaj lom neeg nquag (feem ntau yog cov pab pawg) uas ncav cuag lub substrate thiab raug adsorbed yog cov nquag heev, thiab zaj duab xis yog tsim los ntawm kev sib cuam tshuam ntawm lawv.
2. Cov tshuaj lom neeg hauv cov ntshav
Vim tias qhov kev txhawb nqa ntawm cov roj tshuaj tiv thaiv hauv cov txheej txheem tso tawm lub teeb ci feem ntau yog kev sib tsoo hluav taws xob, cov tshuaj tiv thaiv yooj yim hauv cov plasma yog ntau yam, thiab kev sib cuam tshuam ntawm cov plasma thiab cov khoom khov kuj nyuaj heev, uas ua rau nws nyuaj rau kawm txog cov txheej txheem ntawm PECVD txheej txheem. Txog tam sim no, ntau lub tshuab tshuaj tiv thaiv tseem ceeb tau raug kho kom zoo los ntawm kev sim kom tau txais cov yeeb yaj kiab nrog cov khoom zoo tagnrho. Rau kev tso cov yeeb yaj kiab nyias nyias raws li silicon raws li PECVD thev naus laus zis, yog tias lub tshuab tso tawm tuaj yeem pom tob tob, qhov nqi tso tawm ntawm cov yeeb yaj kiab nyias nyias raws li silicon tuaj yeem nce ntxiv ntau ntawm qhov kev ntseeg siab ntawm kev ua kom muaj cov khoom zoo ntawm cov ntaub ntawv.
Tam sim no, hauv kev tshawb fawb ntawm cov yeeb yaj kiab nyias nyias uas siv silicon, hydrogen diluted silane (SiH4) yog siv dav ua cov roj ua rau muaj kev cuam tshuam vim tias muaj qee qhov hydrogen hauv cov yeeb yaj kiab nyias nyias uas siv silicon. H ua lub luag haujlwm tseem ceeb heev hauv cov yeeb yaj kiab nyias nyias uas siv silicon. Nws tuaj yeem sau cov ntawv cog lus dai rau hauv cov qauv khoom siv, txo qhov tsis zoo ntawm lub zog, thiab yooj yim paub txog kev tswj hwm electron ntawm cov khoom siv. Txij li thaum spear et al. thawj zaug paub txog qhov cuam tshuam ntawm cov yeeb yaj kiab nyias nyias uas siv silicon thiab npaj thawj PN kev sib tshuam hauv, kev tshawb fawb txog kev npaj thiab kev siv cov yeeb yaj kiab nyias nyias uas siv silicon raws li PECVD thev naus laus zis tau tsim los ntawm kev dhia thiab ciam teb. Yog li ntawd, cov tshuaj lom neeg hauv cov yeeb yaj kiab nyias nyias uas siv silicon los ntawm PECVD thev naus laus zis yuav piav qhia thiab tham txog hauv qab no.
Nyob rau hauv qhov xwm txheej ntawm lub teeb ci, vim tias cov electrons hauv silane plasma muaj ntau dua li ntau lub zog EV, H2 thiab SiH4 yuav lwj thaum lawv raug sib tsoo los ntawm cov electrons, uas yog cov tshuaj tiv thaiv thawj zaug. Yog tias peb tsis xav txog cov xeev zoo siab nruab nrab, peb tuaj yeem tau txais cov tshuaj tiv thaiv dissociation hauv qab no ntawm sihm (M = 0,1,2,3) nrog H
e+SiH4→SiH2+H2+e (2.1)
e+SiH4→SiH3+ H+e (2.2)
e+SiH4→Si+2H2+e (2.3)
e+SiH4→SiH+H2+H+e (2.4)
e+H2→2H+e (2.5)
Raws li tus qauv cua sov ntawm kev tsim cov molecules hauv av, lub zog xav tau rau cov txheej txheem dissociation saum toj no (2.1) ~ (2.5) yog 2.1, 4.1, 4.4, 5.9 EV thiab 4.5 EV feem. Cov electrons muaj zog siab hauv plasma kuj tuaj yeem dhau los ntawm cov tshuaj tiv thaiv ionization hauv qab no
e+SiH4→SiH2++H2+2e (2.6)
e+SiH4→SiH3++ H+2e (2.7)
e+SiH4→Si++2H2+2e (2.8)
e+SiH4→SiH++H2+H+2e (2.9)
Lub zog xav tau rau (2.6) ~ (2.9) yog 11.9, 12.3, 13.6 thiab 15.3 EV feem. Vim yog qhov sib txawv ntawm lub zog tshuaj tiv thaiv, qhov tshwm sim ntawm (2.1) ~ (2.9) cov tshuaj tiv thaiv tsis sib xws heev. Tsis tas li ntawd, sihm tsim nrog cov txheej txheem tshuaj tiv thaiv (2.1) ~ (2.5) yuav dhau los ntawm cov tshuaj tiv thaiv theem ob hauv qab no kom ionize, xws li
SiH+e→SiH++2e (2.10)
SiH2+e→SiH2++2e (2.11)
SiH3+e→SiH3++2e (2.12)
Yog tias qhov kev tshuaj tiv thaiv saum toj no tau ua tiav los ntawm ib txoj kev ua haujlwm electron, lub zog xav tau yog li 12 eV lossis ntau dua. Vim tias tus lej ntawm cov electrons muaj zog siab tshaj 10ev hauv cov plasma ionized tsis muaj zog nrog electron density ntawm 1010cm-3 yog qhov me me nyob rau hauv lub siab atmospheric (10-100pa) rau kev npaj cov yeeb yaj kiab silicon, Qhov feem pua ntawm ionization feem ntau me dua li qhov feem pua ntawm kev txhawb siab. Yog li ntawd, qhov feem pua ntawm cov tshuaj ionized saum toj no hauv silane plasma yog me heev, thiab pawg nruab nrab ntawm sihm yog qhov tseem ceeb. Cov txiaj ntsig ntawm kev tshuaj xyuas spectrum kuj ua pov thawj qhov xaus no [8]. Bourquard et al. Ntxiv mus, qhov concentration ntawm sihm txo qis hauv qhov kev txiav txim ntawm sih3, sih2, Si thiab SIH, tab sis qhov concentration ntawm SiH3 yog qhov siab tshaj plaws peb zaug ntawm SIH. Robertson et al. Tau tshaj tawm tias hauv cov khoom nruab nrab ntawm sihm, silane ntshiab feem ntau yog siv rau kev tso tawm hluav taws xob siab, thaum sih3 feem ntau yog siv rau kev tso tawm hluav taws xob qis. Qhov kev txiav txim ntawm qhov concentration ntawm siab mus rau qis yog SiH3, SiH, Si, SiH2. Yog li ntawd, cov txheej txheem plasma txheej txheem cuam tshuam rau qhov sib xyaw ntawm cov khoom sihm tsis muaj zog.
Ntxiv rau qhov kev sib cais thiab kev sib xyaw ua ke saum toj no, cov kev sib xyaw ua ke ntawm cov ionic molecules kuj tseem ceeb heev.
SiH2 + SiH4 → SiH3 + SiH3 (2.13)
Yog li ntawd, hais txog qhov concentration ntawm ion, sih3 + ntau dua li sih2 +. Nws tuaj yeem piav qhia vim li cas muaj ntau dua sih3 + ions dua li sih2 + ions hauv SiH4 plasma.
Tsis tas li ntawd xwb, yuav muaj kev sib tsoo ntawm cov atom molecular uas cov hydrogen atoms hauv plasma ntes cov hydrogen hauv SiH4.
H+ SiH4→SiH3+H2 (2.14)
Nws yog ib qho kev ua kom sov thiab ua ntej rau kev tsim ntawm si2h6. Tau kawg, cov pab pawg no tsis yog tsuas yog nyob rau hauv lub xeev hauv av xwb, tab sis kuj zoo siab rau lub xeev zoo siab hauv cov plasma. Cov spectra emission ntawm silane plasma qhia tau hais tias muaj cov kev hloov pauv zoo siab ntawm Si, SIH, h, thiab vibrational zoo siab ntawm SiH2, SiH3.
Lub sijhawm tshaj tawm: Plaub Hlis-07-2021