Raws li qhov thib peb - tiam semiconductor, silicon carbide (SiC) muaj hluav taws xob thiab thermal zog zoo dua li cov silicon, ua rau nws yog ib qho ntawm cov khoom siv zoo tshaj plaws rau fabricating siab - kub, siab - zaus, siab - zog, thiab siab - cov khoom siv hluav taws xob. SiC yog qhov sib xyaw ua ke ntawm silicon thiab carbon. Silicon atoms thiab carbon atoms tsim cov qauv tetrahedral. SiC crystals muaj ntau tshaj 200 paub polytypes, uas yog tsim los ntawm alternating silicon atomic txheej thiab carbon atomic txheej nyob rau hauv ntau txoj kev. Feem ntau yog 3C-SiC (cov qauv cubic, lossis -SiC), 4H-SiC, thiab 6H-SiC (ob qho tib si hexagonal qauv, lossis -SiC).
3C-SiC
3C-SiC yog qhov yooj yim SiC polytype thiab muaj lub cubic kaw- cov qauv ntim. Nyob rau hauv cov qauv no, silicon thiab carbon atoms yog teem nyob rau hauv ib txoj kev tshwj xeeb nyob rau hauv peb - qhov chaw seem, tsim ib tug heev symmetric siv lead ua qauv. Vim nws qhov sib luag, 3C-SiC muaj cov khoom siv hluav taws xob thiab kho qhov muag tsis zoo thiab tam sim no siv me me hauv kev siv tswv yim.
4H-SiC thiab 6H-SiC
Tsis zoo li 3C-SiC, 4H-SiC thiab 6H-SiC muaj hexagonal ze- cov qauv ntim. Ob hom polytypes no zoo dua rau 3C-SiC hauv electron kev txav mus los, thermal conductivity, thiab bandgap. 4H-SiC muaj cov khoom siv hluav taws xob ntau dua, ua rau nws zoo dua rau siab - zaus thiab siab - cov khoom siv hluav taws xob hluav taws xob. Nws yog feem ntau siv nyob rau hauv cov teb xws li tsheb tshiab zog thiab 5G kev sib txuas lus, thiab tam sim no SiC manufacturers feem ntau tsim 4H-SiC. 6H-SiC muaj ib tug bandgap loj dua thiab yog li ntawd ua tau zoo nyob rau hauv siab - kub thiab siab - hluav taws xob ib puag ncig.
Kev Loj Hlob Technologies rau SiC Ib Leeg Crystals
Tam sim no, cov thev naus laus zis tseem ceeb siv rau SiC siv lead ua kev loj hlob muaj xws li lub cev vapor thauj (PVT), siab -kub tshuaj vapor deposition (HTCVD), thiab sab saum toj- seed solution growth (TSSG). Ntawm lawv, PVT tam sim no yog cov paub tab thiab feem ntau siv SiC ib leeg -crystal txoj kev loj hlob hauv Suav teb thiab txawv teb chaws.
Lub cev Vapor Transport (PVT) Method
Lub cev vapor thauj (PVT) yog ib txoj kev siv dav rau kev lag luam loj hlob ntawm SiC ib leeg muaju. Nws tau tsim los ntawm Lely txoj kev, uas tau tsim los ntawm Lely hauv xyoo 1955 los ntawm cov txheej txheem sublimation. Txawm li cas los xij, txoj kev Lely tsis tuaj yeem tswj tau ib leeg - crystal kev loj hlob. Xyoo 1977, Tairov thiab Tsvetkov yog thawj tus siv cov noob sublimation kom loj hlob SiC ib leeg muaju; txoj kev no tseem hu ua "modified Lely method" lossis PVT method.
Hauv PVT, cov noob siv lead ua tau muab tso rau saum lub graphite crucible, thiab siab -purity SiC hmoov yog muab tso rau hauv qab. Sab nraum lub crucible yog ib txheej thermal rwb thaiv tsev; ib qho induction cua sov kauj yog sab nraum lub rwb thaiv tsev txheej, thiab cov dej txias yog nyob rau hauv lub kauj. Nyob rau hauv lub crucible, los ntawm kev tswj qhov kub thiab txias gradient, SiC hmoov yog hloov mus rau hauv lub gaseous lub xeev thiab thauj mus rau cov noob siv lead ua, qhov twg crystal kev loj hlob ces tshwm sim. Cov khoom siv raw rau PVT yog siab -purity SiC hmoov, thiab kev loj hlob kub yog 2100℃-2500 degree. Tam sim no, qee lub tuam txhab SiC hauv tsev siv cov qauv no los ua lawv txoj kev tsim khoom loj. Nws qhov tsis zoo yog qhov kev loj hlob kub, kev siv hluav taws xob siab, thiab tus nqi siab; cov pob zeb loj hlob muaj ntau yam tsis xws luag, uas cuam tshuam rau kev ua haujlwm ntawm cov cuab yeej thiab kev pabcuam lub neej.
Txawm hais tias PVT SiC kev loj hlob thev naus laus zis twb paub tab lawm, cov teeb meem hauv qab no tseem nyob hauv qhov tseeb: Hauv PVT kev loj hlob ntawm SiC ib leeg muaju, cov kev hloov pauv tau yooj yim tshwm sim, ua rau polycrystalline inclusions. Tswj ib leeg polytype thaum SiC siv lead ua kev loj hlob yog qhov teeb meem nyuaj. Siv lub ntsiab 4H-SiC ib leeg crystals ua piv txwv, kev loj hlob ruaj khov ntawm ib hom polytype raug cuam tshuam los ntawm ntau yam, suav nrog cov noob siv lead ua polarity, kev loj hlob kub, kev loj hlob siab, vapor-theem Si / C piv, thiab hom doping, uas txhais tau hais tias kev cai nruj ntawm SiC polytype yuav nyuaj dua. Kev tswj qhov kub thiab txias hauv qhov cub thaum PVT kev loj hlob ntawm SiC ib leeg muaju kuj tseem yog qhov nyuaj heev. Tsis tas li ntawd, PVT cia siab rau kev thauj roj thiab cov txheej txheem tshuaj tiv thaiv ntawm qhov kub thiab txias, uas ua rau muaj kev xav tau siab ntawm cov roj ntws, cov tshuaj tiv thaiv kinetics, thiab lwm yam.
Kev kub siab -Tsub Chemical Vapor Deposition (HTCVD) Txoj Kev
Nyob rau hauv high -kub tshuaj vapor deposition (HTCVD) txoj kev, SiC noob siv lead ua yog muab tso rau hauv ib lub crucible ua los ntawm graphite. Silane thiab cov pa roj carbon - muaj cov pa roj ua ntej raws li cov ntaub ntawv raw tsis tu ncua nkag mus rau hauv crucible los ntawm lub reactor hauv qab. Cov silane tom qab ntawd ncaj qha pyrolyzes rau hauv Si pawg, uas hnov mob nrog hydrocarbons (CxHy) hauv cov pa roj carbon - muaj cov pa roj ua ntej los tsim SiC ib qho siv lead ua hauv qab cov noob siv lead ua.
Piv nrog PVT, HTCVD siv ntau dua -cov ntaub ntawv purity thiab muaj peev xwm tswj tau cov khoom raw khoom noj, C/Si piv, thiab kev loj hlob kub thaum loj hlob, yog li ua tau zoo dua -SiC crystals. Tsis tas li ntawd, ncaj qha pyrolysis ntawm cov cab kuj muab HTCVD lub zog ua haujlwm ntau dua li lwm txoj hauv kev, thiab lub siab - cov pa roj carbon monoxide pab cov pawg tau los ntawm pyrolysis ncav cuag SiC noob siv lead ua, yog li HTCVD loj hlob SiC crystals sai dua lwm txoj kev.
HTCVD muaj qhov zoo xws li cov khoom siv lead ua zoo, kev loj hlob sai, thiab kev pub noj tsis tu ncua. Txawm li cas los xij, vim tias cov cuab yeej loj hlob thiab siab - cov pa roj purity yog kim, txoj kev no muaj cov nqi tsim khoom siab thiab nws cov txheej txheem kev lag luam qeeb. Nyob rau tib lub sijhawm, hauv HTCVD kev loj hlob ntawm SiC ib leeg muaju, vim SiH4 thiab C3H8 yuav tsum decompose ntawm qhov kub thiab txias thiab muaj ntau yam kev cuam tshuam ua ntej thaum kawg loj hlob muaju ntawm SiC noob, yog tias cov roj av decomposes sai heev, cov roj nkag yuav raug thaiv; Yog hais tias cov pa roj decomposes qeeb dhau, cov pa uas tsis muaj kev cuam tshuam yuav nyob twj ywm ntawm qhov hluav taws xob roj thiab ua rau muaj kev thaiv. Qhov no ua rau HTCVD SiC ib leeg -cov cuab yeej siv lead ua kev loj hlob kuj tsis ruaj khov. Tsis tas li ntawd, kev tshawb fawb tam sim no ntawm HTCVD tsis txaus, cov txheej txheem tseem tsis tau paub tab, thiab nws tseem nyob rau theem R & D, yog li HTCVD kev loj hlob ntawm SiC ib leeg crystals tsis tau siv dav hauv kev lag luam.
Sab saum toj - Seeded Solution Growth (TSSG) Method
Nyob rau sab saum toj - seed solution growth (TSSG) method, silicon source is a silicon melt, and the carbon source is a high-purity graphite crucible. Hauv qab 2000 degree, solubility ntawm carbon hauv silicon yaj yog tsawg dua 1%, ua rau nws nyuaj rau ncav cuag Si: C=1: 1 molar ratio yuav tsum tau rau SiC siv lead ua loj hlob. Txawm nyob rau ntawm 2800 degree, solubility ntawm carbon nyob rau hauv silicon tsuas yog 19%. Yog li ntawd, nyob rau hauv cov kua tiag tiag -theem SiC siv lead ua kev loj hlob thwmsim, ib co fluxes yuav tsum tau ntxiv kom cov solubility ntawm carbon nyob rau hauv siab -kub tov. Feem ntau cov fluxes muaj xws li Cr, Fe, Ti, thiab lwm yam. Thaum lub sij hawm siv lead ua kev loj hlob, cov pa roj carbon nyob rau hauv graphite crucible maj dissolves rau hauv cov yaj thiab yog thauj los ntawm cov yaj mus rau cov noob siv lead ua, ua kom muaj cov pa roj carbon ntau ntxiv. Los ntawm kev tswj tsis tau xws li cov noob / crucible rotation ceev, kub teb, thiab tam sim no zaus thiab qhov loj, qhov tsim nyog kub gradients, siab gradients, thiab ntws teb yog tsim nyob rau hauv lub yaj, thiaj li hais tias carbon yuav raug thauj los ntawm lub crucible phab ntsa mus rau lub noob siv lead ua. Txawm li cas los xij, hauv kev loj hlob tiag tiag, cov noob siv lead ua feem ntau yaj, thiab cov khoom siv polycrystalline precipitates ntawm phab ntsa crucible thiab ntawm cov noob siv lead ua. Yog li ntawd, thoob plaws hauv cov txheej txheem kev loj hlob siv lead ua, kev loj hlob tsis zoo yuav tsum tau hloov kho kom tag nrho cov txheej txheem nyob rau hauv qhov tsim nyog dynamic equilibrium, yog li ntawd kev loj hlob siv lead ua txuas ntxiv tuaj yeem ua tiav.
TSSG tuaj yeem npaj SiC crystals nyob rau hauv kev loj hlob me me. Nws kuj muaj cov yam ntxwv tshwj xeeb xws li kev ua kom muaj zog thiab cov kev cai ntawm cov txheej txheem tsis tu ncua, txoj kab uas hla txuas ntxiv kev loj hlob, thiab zoo li siab p- hom doping. Nws tau dhau los ua ib qho kev sib tw tshiab thev naus laus zis rau qis - nqi, siab -SiC substrates. Txawm hais tias TSSG muaj cov txiaj ntsig tseem ceeb hauv kev npaj SiC siv lead ua, nws kuj tseem muaj kev cuam tshuam kev ua haujlwm siab, feem ntau cuam tshuam txog ntau yam txheej txheem uas yuav tsum tau tswj hwm; ib qho kev xaiv tsis tsim nyog tuaj yeem cuam tshuam qhov sib npaug ntawm qhov sib npaug thaum lub sij hawm siv lead ua loj hlob thiab ua rau muaj qhov tsis zoo macroscopic loj.