KHOA H O C - C O N NGUOl - XA H O I Phirong phap kiem dinh chan khdng oho tao mang mong Mot he thong che tao mang mong du dit tien the nao di chang niTa, vin khong may huTu ich neu Chung ta Jchong the biet chan khong cua he thong Xac djnh chan khong cua phong chufa VI the tror mot yeu to' rat quan trong cong nghe vi mach Bai viet trmh bay ve mot soap ke tieu bieu va nguyen ly hoat dpng cua chung Nhihig thiet bj do chan khong chinh la ap ke thu dien, ap ke nhiet dien va ap ke ion hoa Ben canh la nhOhg thong tin ve cac thiet b[ khong kem phan quan trpng viec che tao mang mong nhiT bp dieu chmh lUU lutfng (MFC), mpt so'thiel bj tieu bieu de khao sat chd ro ri va cac yeu to'trong phong chufa bcrm, nhiTbo phan ti'ch dil* (RGA) va bp cam bien dp ri bing heli N hu dd trinh bay nhdng so trUde, dudi ten ri (virtual leak) Hinh la mdt vi du ve linh kien dien td ddi hdi mdng mdng cdc chd't nha td bdc tUdng phdng chda vdi nhijfng tinh ndng khde nhau, va phong d dp chdn khdng khoang 200 mTorr dp chdn khdng cd tdc dpng manh din tinh quang dien td eua mdng mdng Nlu chi nhin mdt phdng chda (chamber) cua he t h i n g c h l tao mdng mdng, chdng ta khd cd t h i dodn dupe Phikn tu gas o&ci du i«i chinh xdc dp chdn khdng, nhd't la phdng chda d mat dp chdn khdng eao hay cUc eao Chung ta 1-216p hydrogen, carbort mono»de ^r4 nHfog«n can nhijfng dung cu hdu hieu vd chinh xdc de dp chdn khdng T h i l t hi k i l m dinh dp chdn khdng cd hai nhiem vu: (1) Quylt dinh dp chdn khdng can 5-20 l&p tvuxSc thim thau vio tuj^ng hi4u lin j vat ly dung va (2) Xdc dinh cho hi ri Ve nhiem vu (1), dp chdn khdng thay doi vdi cdc he thd'ng bPm chdn khdng dung V l nhiem vu (2), sau ldp ddt be 1- \6p n\j6c Ihiim thiu vio t i n ^ j hi8u ung h6a hoc thing c h l tao mang mdng, dieu trddc tien ehdng ta phai lam Id k i l m sodt xem phdng chda ed bi ri bay Cek \6f> carbon, mangan«M, hydrogenr mirogw, oxyg«% khong? Vi day Id chuyen rd't thddng xay tftki b* mat ctia buctuciig SirrdritfennrtfauP Sd rd ri nhilu nguyen nhdn khdc nhau: Cd t h i td phdng chda, cd h a t bui hay nhdng vdt cP nam tren vdng O rings; nhijCng ong gas bay cdc phdn noi cae ong gas khdng du chat, vdng dem kin bi tray xxidc, sd nha cua cdc nguyen lieu hay mdng mdng cdn sdt lai phdng chda hay sU nha td tddng eua phdng chda phdng chda ddPe bum tdi chdn khdng trung binh khoang 200 mTorr d i n lO^ Torr Hien tUpng dupe biit Hinh 1: Nhiing chdt nhd tU bUc tUdng cua phdng chUa [1] De xdc dinh dp ri, dilu trUde tien la dung phdPng phdp thdng thudng, chang ban nbU dung bPm cP bpc bPm phdng chda d i n dp chdn khong sP bp, roi dung nddc xd phdng xit vdo cdc phan dang nghi ngd vd ehd hi ri la nPi cd bpt xd phdng O nbOrng chd ri nhd hPn, dp chdn khdng dat khoang 10-210* Torr, ehdng ta ed the dung isopropanol xit vdo eho nghi ngd vd dp sud't nPi dp k l chdn khdng noi So thang 10.201 l ^ f j Q ^ f j Q C 87 KHOA H O C - C O N N G L f O l - X A HOI lien vdi phdng chda se tang len Chung ta cung co the dung bp cam bien dp ri bdng hcli de xac dinh cho hi ri Bd cam bien dd ri bang heli (Helium leak detector) Day la thiet bi hdu hieu de va xac dinh dp ri phdng chda Cd hai each de theo ddi dp ri he thdng che tao mang mdng: Dd Id hd bdng each danh hpi vdi heli: Sau bo"m phdng chda den dp chan khdng sP bp, chung ta qud dp phong chda vdi heli, sau dd dung ddu dd d l tim chd ri Gidi ban phat hien cua phUPng phdp vao khoang >x\0 ** mluir.lJsci: Dd Id hd vdi dp ri cam bien chan khdng: Mpt phdng chda da chan khdng kin, chdng ta xit nhdng cho cd t h i ri vdi heli d l tim cho ri Tiep theo dd, ke khdi lUpng se dupe dung d l theo ddi heli (amu = 4) Gidi han phdt hien cua loai thiet hi vao khodng 5x10'- mbar.L I sec Bd phan tich cdn tax (Besidual gas analyzer (BGAl Dung cu biin thai td t h i l t hi dd lo bd dung heli vd thudng dupe sd dung viec dp sud't cue bp cua eac chd't phdng chda Thudng thi bd phdn tich RGA dUpc noi vdi phdng chda bdng mpt gd vanb cd kich thude 2,75 inches (khoang cm) Thilt hi ed ba bp phdn chinh: Nguon ion, bp lpc khdi lupng b i n eUc va bp cam biin ion Phdn td cua chd't td nguon ion hi ion hda vd dupe tdch rdi theo khii lUpng bd lpc khoi lUpng Va lupng ion d nhdng khoi ldpng khdc cd t b i dupe RGA thudng boat ddng d dp chdn khdng cao khoang 10"^ Torr d l trdnh sU xung dot gida ion tao vdi nhdng phdn td chd't Mpt ed'u tao dien binh cua bd RGA ddPe bilu thi d hinh Ion ngudn B9 Ipc kh6i lirgng O^u (Am bi4n Hinh 2: Cdu tgo cda bd RGA (Hdng Inficon) «- Hoat tfong „,, ^, KHOA HOC ^"^ ^ „ OOH Ngudn ion: Day irium bpc vdi chd't thorium oxide hay yttrium oxide dUPe dung ldm spfi filamdng Spi filamdng dUpe nung ndng d l phdng thich electron Nhdng electron ndy dpi phd cdc chat mdi den, tao dien tich Dipn trddng se ddpe dung de dieu khiln nhdng phdn td tich dien hay bi ion hda Ion tren andt bi keo di bdi ldpng dien the noi thau kinh tap trung vd tao mdt chum ion (beam) Thau kinh tap trung ddpe gid d dien the am dd'i vdi andt Chum ion ndy se di vdo bp lpc khdi lupng; nhdng phan cdn lai dap vdo thdu kinh p dau ra, trd thdnh trung tinh vd tao nen dong dien chay Bp lpc khdi lupng bd'n cUc: Bin cdc ndy nam song song vdi tao thdnh mdt hinh vuong Bp lpc khdi lupng ndy loai td't ed ion, trd nhiing ion cd ty so khdi ldpng dien tich (mass-to-ebarge ratio) ddc biet Bp edm bien ion: Cd t h i d dang cup Faraday' (Faraday cup), bp nhdn dien td (EM)" bay dddi sd k i t hpp eua hai dang o a u lay mau gas gan phien ba' dan iwaleti Hani hA !nj liiiih :>: l\(l\ Di^n ngu6n lap dat vol phong chua inguon: Transpector CIS2 i-lcmg ill/icon) 12J Hinh gidi thieu mot phdng chilu kit noi vdi RGA Vdi phdPng phdp dung bp RGA, dd lieu thddng ddPc trinh bdy bang tam bilu vdi ty s l khIi Iddng dien tich (mass-to-eharge ratio) d true X vd cam dp (spectra sensitivity) d true Y RGA dUPe diing d l tim nhdng nguyen t l phdng chda cua he thing c h l tao mdng mong Bang liet kd ty so dong vi (isotope ratios) cua vdi nguyen t l tieu bieu KHOA HOC - C O N NGUOl - XA HOI Ty SO dong vj Thftnh phin c N O Khdi lif(?ng Ty s6 luong d6i 12 98.892 13 108 14 99.63 15 37 16 99.759 17 0,0374 18 0.2039 F 19 100.0 Ne 20 90.92 21 0.257 22 8.82 Na 23 100.0 Al 27 100.0 Si 28 92.27 29 4.68 30 3.05 P 31 100.0 S 32 95.06 33 0.74 34 4.18 36 0.016 35 75.4 Cl Ar 37 24.6 36 0.337 38 0.063 40 99.600 Bdng 1: Ty sd dong vi cua vdi nguyen td tiiu Lam the nao phan biet hai phan tir cd cung khdi lutmg RGAP Vi du nhu N^ va CO cd cdng khdi lUpng 28 Hai phan td co the phan biet dUpe bdng each dung cracking mo hinh (cracking patterns) N^ thUdng dupe thu gom lai dUdi dang '^^ cd khd^i lUpng bdng 28; nhUng khoang 6-7% cua phdn td bien dang ^i va ^ vdi khoi lUpng bang 14 Dong vi N'-'cung CO mpt dinh nhd vdi khoi lUpng 15 Trong dd eo dinh nhd '^^0,0 y^j j^j^g'j i^/gng theo thd tu bang 12, 16 va 14 Tuy theo khoi lUpng cua cdc dinh nay, chung ta co t h i phdn biet dUpe sU khac gida hai phdn td N^ va CO Dudi day la vai dinh nghia ve nhdng td thudng de cap nhieu bp RGA: Cracking mo hinh Hinh bieu hien cracking mo binh cua methane (CH^) bieu Mpt vi du ve ede dong vi eua argon td bilu RGA dUPc bilu thi d hinh KX) Hlnh 5: Cracking md hinh cua methane bg RGA [3] Ty so khoi Idctng - di?n tich ratio: mie) Id gi? Hlnh 4: Ddng vi cua argon [3] (Mass-to-charge Ty so m/e la ty so gida phdn td lUpng va so electrons rdi khdi ed'u true nguyen td Vi du nhU, carbon dioxide (COg) cd phan td lUpng bang 44; mpt electron rdi khdi, phdn td hi ion hda don le ed m/e bang 44/1 hay 44 Trong dd vdi sU rdi khdi eua hai hat electron, phdn td hi ion hai So thang 10.2011 K H O H O C "^ KHOA HOC - C O N N G U O l - XA HOI lan cd m/e = 44/2 = 22 Dam vi khdi Idgfng nguyen unit) Id gi? td (Atomic mass Moi nguyen to hda hpc ed nhdng dong vi khde nhu dUpe t h i hien bang Chdng ban nhu dong vi cua carbon la ',JC.','C,',^C Moi dong vi cd khdi ldpng hpi khdc Gia tri trung binh cua nbdlig khdi ldpng ddpe dinh nghia Id khdi ldpng nguyen td trung binh (average atomic mass) hay thudng gpi tdt la atomic mass unit (amu) Chang han nhu amu cua carbon Id 12,01, hydrogen (1,008) va nitrogen (14,01) amu = 1,66 x 10 '•* ,i,' Ap ke thu dien (Capacitance manometer) Cdu tao cua dp ke thu dien dPpc the hien d hinh Diafam Do chan khong cin Dung cu ndy dung d l dp sud't vdi dO chinh xdc ± 0.1% d i n lO'-^Torr Nguyen tdc boat ddng eua dp k l ndy ed t h i cdt nghia nhd sau: Thay dli dp suat phdng chda se tao sd di dpng eua mdng diafam ddn hIi (flexible diaphragm) so sdnh vdi mpt mdng khde dddc gid d mpt vi tri nhd't dinh Mdng diafam ndy Id mpt tam kim loai, thddng lam bdng chdt Inconel Dp thu didn (capacitance) ddpe bang khodng cdch eua hai mdng diafam Dilm ylu eua loai dp k l ndy Id gid ddt, de thay dli vdi nhiet dp vd loai chd't dung Hinh 6(b) Id mpt dp k l thu dien hipn bdn tren tbi trUdng Ap kd nhidt didn (Thermocouple gauges) Loai dung cu ndy ed t h i dp suat khoang td 760 d i n lO'^ Torr Cd t h i dung d l dp chdn khdng sp bp cua bPm ho trp, chang ban nhd bpm turbo hay dp sud't eua phdng chda luc ede bPm dang hoat ddng Spi ddy den ddpe dun ndng va nhiet dien dung d l nhiet dp eua spi ddy den Nhiet dp thddng tdng len vdi dp giam eua dp sud't Loai dp k l re hpn nhdng khdng chinh xdc Ap ke Chan khdng Pirani (Pirani gauges) Dien cUc co dinh Hinh (a): Cdu tgo cua dp ki' thu diin Cdu tao eua dp k l chdn khdng Pirani ddpe the hien d hinh Cofliptnutor ^t^^ :mhs ^f^''''' —(T]-vwv Hlnh (a): Sa cda dp ki' chdn khdng Pirani (compensator: Bd phdn bd; manometer: Ap ke); (b) Ap ke hiin bdn trin thi trUdng (Model 945, Hdng MKS) [5] Hlnh (b): Ap ke thu diin hien bdn tren thi trudng (Baratron, Model 631 C cua Hdng MKS) [4] on Hoattfong^ ,^, KHOA HOC "^ ,^ „„ Cau tao eua loai dp k l dUa vdo mang Iddi Wheatstone R, hinh (a) dung de dilu chinh sU thdng bang cua dp k l Gia tdng dp suat se gia tang sU hao nhiet sU giam gid tri dien trd (resistance) eua day ndng va clu Wheatstone KHOA H O C - C O N trd md't thang bdng K i t qua la nhilu ndng ldpng phdn tdn day ndng, dan den sU gia tdng dien t h i Dien t h i cang tang thi day dien cdng ndng hPn va mang ludi Wheatstone trd thdng bang trd lai Mdi dp sud't deu ddpe d mot nhiet dp ddy ndng nhd't dinh NGUOI - X A HOI Tdi hO thing chan khAng Ldp v6 thuy tinh xiM ' Odu thu ion Lirti Bd dieu chinh luu lutmg (Mass flow controller -MFC) S^i t