1. Cov txheej txheem tseem ceeb ntawm plasma txhim kho cov tshuaj vapor deposition
Plasma enhanced chemical vapor deposition (PECVD) yog ib lub tshuab tshiab rau kev loj hlob ntawm cov yeeb yaj kiab nyias los ntawm cov tshuaj tiv thaiv ntawm cov tshuaj gaseous nrog kev pab los ntawm glow discharge plasma. Vim tias PECVD thev naus laus zis tau npaj los ntawm kev tso pa tawm, cov tshuaj tiv thaiv cov yam ntxwv ntawm cov ntshav tsis sib npaug yog siv tau zoo, thiab cov khoom siv hluav taws xob ntawm cov tshuaj tiv thaiv yog qhov hloov pauv. Feem ntau hais lus, thaum PECVD thev naus laus zis tau siv los npaj cov yeeb yaj kiab nyias, kev loj hlob ntawm cov yeeb yaj kiab nyias feem ntau suav nrog peb cov txheej txheem hauv qab no.
Ua ntej, nyob rau hauv cov ntshav tsis sib npaug, cov electrons hnov mob nrog cov tshuaj tiv thaiv cov pa hauv thawj theem kom decompose cov tshuaj tiv thaiv roj thiab tsim cov sib xyaw ntawm ions thiab cov pab pawg nquag;
Qhov thib ob, txhua yam ntawm cov pab pawg nquag tau nthuav tawm thiab thauj mus rau saum npoo thiab phab ntsa ntawm cov yeeb yaj kiab, thiab cov kev cuam tshuam thib ob ntawm cov reactants tshwm sim tib lub sijhawm;
Thaum kawg, txhua yam ntawm thawj thiab theem nrab cov tshuaj tiv thaiv cov khoom mus txog qhov kev loj hlob nto yog adsorbed thiab hnov mob rau saum npoo, nrog rau kev tso tawm ntawm cov roj molecules.
Tshwj xeeb tshaj yog, PECVD thev naus laus zis raws li txoj kev tso tawm glow tuaj yeem ua rau cov tshuaj tiv thaiv roj ionize rau hauv cov ntshav hauv qab qhov kev xav ntawm sab nraud electromagnetic teb. Nyob rau hauv glow discharge plasma, lub kinetic zog ntawm electrons ceev los ntawm sab nraud hluav taws xob teb feem ntau yog hais txog 10ev, los yog ntau dua, uas yog txaus los rhuav tshem cov tshuaj bonds ntawm reactive gas molecules. Yog li ntawd, los ntawm inelastic sib tsoo ntawm high-zog electrons thiab reactive gas molecules, cov roj molecules yuav ionized los yog decomposed los tsim nruab nrab atoms thiab molecular khoom. Cov ions zoo yog nrawm los ntawm ion txheej accelerating hluav taws xob teb thiab sib tsoo nrog rau sab sauv electrode. Kuj tseem muaj ib qho me me ion txheej hluav taws xob nyob ze ntawm cov hluav taws xob qis, yog li lub substrate kuj tau tawg los ntawm ions rau qee qhov. Yog li ntawd, cov khoom nruab nrab uas tsim los ntawm decomposition diffuses mus rau lub raj phab ntsa thiab substrate. Nyob rau hauv tus txheej txheem ntawm drift thiab diffusion, cov hais thiab pab pawg (cov tshuaj active nruab nrab atoms thiab molecules hu ua pab pawg) yuav undergo ion molecule cov tshuaj tiv thaiv thiab pab pawg neeg molecule cov tshuaj tiv thaiv vim lub luv luv nruab nrab dawb txoj kev. Cov khoom siv tshuaj lom neeg ntawm cov tshuaj active tshuaj (feem ntau yog pab pawg) uas ncav cuag lub substrate thiab yog adsorbed yog heev nquag, thiab zaj duab xis yog tsim los ntawm kev sib cuam tshuam ntawm lawv.
2. Cov tshuaj tiv thaiv hauv plasma
Vim hais tias qhov excitation ntawm cov tshuaj tiv thaiv roj nyob rau hauv lub glow discharge txheej txheem yog feem ntau electron kev sib tsoo, lub theem pib cov kev tshwm sim nyob rau hauv lub plasma yog ntau yam, thiab kev sib cuam tshuam ntawm cov ntshav thiab cov khoom nto kuj complex, uas ua rau nws nyuaj rau kawm lub mechanism. PECVD process. Txog tam sim no, ntau lub tshuab tshuaj tiv thaiv tseem ceeb tau ua kom zoo dua los ntawm kev sim kom tau txais cov yeeb yaj kiab nrog cov khoom zoo tagnrho. Rau qhov tso tawm ntawm silicon-raws li nyias zaj duab xis raws li PECVD thev naus laus zis, yog tias cov txheej txheem tso tawm tuaj yeem nthuav tawm tob, qhov tso nyiaj ntawm silicon-raws li nyias zaj duab xis tuaj yeem nce siab heev ntawm qhov chaw ntawm kev ua kom lub cev zoo ntawm cov ntaub ntawv.
Tam sim no, nyob rau hauv kev tshawb fawb ntawm silicon-raws li nyias films, hydrogen diluted silane (SiH4) yog dav siv raws li cov tshuaj tiv thaiv roj vim hais tias muaj ib co ntawm cov hydrogen nyob rau hauv cov silicon-raws li nyias films. H plays lub luag haujlwm tseem ceeb hauv cov yeeb yaj kiab silicon-raws li nyias. Nws tuaj yeem sau cov dangling bonds nyob rau hauv cov khoom siv, zoo heev txo qhov tsis xws luag zog theem, thiab yooj yim paub lub valence electron tswj cov ntaub ntawv txij li thaum hmuv li al. Ua ntej paub txog cov nyhuv doping ntawm silicon nyias zaj duab xis thiab npaj thawj PN hlws ris nyob rau hauv, kev tshawb fawb ntawm kev npaj thiab kev siv ntawm silicon-raws li nyias zaj duab xis raws li PECVD technology tau tsim los ntawm leaps thiab ciam teb. Yog li ntawd, cov tshuaj tiv thaiv hauv silicon-raws li nyias zaj duab xis tso los ntawm PECVD thev naus laus zis yuav raug piav qhia thiab sib tham hauv qab no.
Nyob rau hauv lub glow discharge condition, vim hais tias cov electrons nyob rau hauv lub silane plasma muaj ntau tshaj li ob peb EV zog, H2 thiab SiH4 yuav decompose thaum lawv raug collided los ntawm electrons, uas belongs rau cov thawj cov tshuaj tiv thaiv. Yog tias peb tsis xav txog cov xeev siab nruab nrab, peb tuaj yeem tau txais cov kev cuam tshuam 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 kub ntawm kev tsim cov av hauv lub xeev molecules, lub zog xav tau rau cov txheej txheem kev sib cais saum toj no (2.1) ~ (2.5) yog 2.1, 4.1, 4.4, 5.9 EV thiab 4.5 EV raws li. Lub zog hluav taws xob siab hauv plasma kuj tseem tuaj yeem ua raws li cov lus qhia 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 raws li. Vim qhov sib txawv ntawm cov tshuaj tiv thaiv lub zog, qhov tshwm sim ntawm (2.1) ~ (2.9) cov tshuaj tiv thaiv tsis sib xws. Tsis tas li ntawd, lub sihm tsim nrog cov txheej txheem tshuaj tiv thaiv (2.1) ~ (2.5) yuav dhau los ua cov tshuaj tiv thaiv theem nrab rau ionize, xws li
SiH+e → SiH++ 2e (2.10)
SiH2+e → SiH2++ 2e (2.11)
SiH3+e → SiH3++ 2e (2.12)
Yog hais tias cov tshuaj tiv thaiv saum toj no yog ua los ntawm ib qho kev siv hluav taws xob, lub zog xav tau yog li 12 eV lossis ntau dua. Nyob rau hauv kev pom ntawm qhov tseeb hais tias tus naj npawb ntawm high-zog electrons saum toj no 10ev nyob rau hauv lub weakly ionized plasma nrog electron ceev ntawm 1010cm-3 yog kuj me me nyob rau hauv lub atmospheric siab (10-100pa) rau kev npaj ntawm silicon-raws li films, cumulative. ionization probability feem ntau me dua qhov excitation probability. Yog li ntawd, qhov kev faib ua feem ntawm cov saum toj no ionized tebchaw nyob rau hauv silane plasma yog heev me me, thiab lub nruab nrab pab pawg neeg ntawm sihm yog dominant. Cov txiaj ntsig kev soj ntsuam huab hwm coj kuj tseem ua pov thawj qhov xaus no [8]. Bourquard et al. Txuas ntxiv tau taw qhia tias qhov concentration ntawm sihm txo qis hauv qhov kev txiav txim ntawm sih3, sih2, Si thiab SIH, tab sis qhov concentration ntawm SiH3 yog feem ntau peb npaug ntawm SIH. Robertson et al. Tshaj tawm tias nyob rau hauv cov khoom nruab nrab ntawm sihm, ntshiab silane feem ntau yog siv rau kev tawm hluav taws xob siab, thaum sih3 feem ntau yog siv rau kev tawm hluav taws xob tsawg. Qhov kev txiav txim siab ntawm qhov siab mus rau qis yog SiH3, SiH, Si, SiH2. Yog li ntawd, cov txheej txheem plasma tsis cuam tshuam rau cov khoom sib xyaw ntawm sihm nruab nrab.
Ntxiv nrog rau qhov kev sib cais saum toj no thiab cov tshuaj tiv thaiv ionization, cov tshuaj tiv thaiv theem nrab ntawm ionic molecules kuj tseem ceeb heev.
SiH2 + SiH4 → SiH3 + SiH3 (2.13)
Yog li ntawd, nyob rau hauv cov nqe lus ntawm ion concentration, sih3 + yog ntau tshaj sih2 +. Nws tuaj yeem piav qhia vim li cas thiaj muaj sih3 + ions ntau dua sih2 + ions hauv SiH4 plasma.
Tsis tas li ntawd, yuav muaj cov tshuaj tiv thaiv molecular atom sib tsoo uas cov hydrogen atoms hauv plasma ntes cov hydrogen hauv SiH4.
H + SiH4 → SiH3 + H2 (2.14)
Nws yog cov tshuaj tiv thaiv exothermic thiab precursor rau kev tsim ntawm si2h6. Ntawm chav kawm, cov pab pawg no tsis yog nyob rau hauv lub xeev hauv av xwb, tab sis kuj zoo siab rau lub xeev zoo siab hauv cov ntshav. Lub emission spectra ntawm silane plasma qhia tau hais tias muaj optically nkag mus tau zoo siab xeev ntawm Si, SIH, h, thiab vibrational zoo siab xeev ntawm SiH2, SiH3
Post lub sij hawm: Apr-07-2021