Photolithography
Chng 1: GII THIU CHUNGI. POLYMER CM QUANG
1. Gii thiuPolymer cm quang l nhng loi polymer nhy cm vi cc ngun
nh sng. Ngun quang hc ng rn bc x c th l tia cc tm (UV), nh sng,
laser c quan tm nghin cu trong nhng nm 1990. Nhng k thut ny da trn
nhng phn ng ha hc i hi s kch hot ca cc vng nh sng UV, kh kin, IR,
hay proton. Qu trnh ng rn cng xy ra bng cc chui ht electron, tia X,
tia , plasma, sng siu m. Photoresist:
L mt dng c bit ca polymer cm quang, chng c ngdng rng ri trong
lnh vc quang khc, c kh nng to hnh nh ni (relief) trn sn phm v gip
chng li qu trnh khc n mn trn b mt sn phm. Polymer cm quang ni chung
v photoresist ni ring gm c 2 loi: loi to nh DNG v loi to nh M. Loi
to nh DNG l h gm cc polymer c trng lng phn t ln, di tc dng ca cc bc
x s chuyn sang cc polymer hoc cc monomer c trng lng phn t thp hn, c
kh nng ho tan tt hn trong dung mi thch hp. Hay polymer ban u (c cha
cc nhm chc nhy quang) l loi kh ho tan, di tc dng ca bc x s hiu chnh
nhm chc tan d hn. Loi to nh M l cc h m ban u gm l h d ho tan, sau
chuyn sang dng kh ho tan do thc hin cc phn ng quang polyme ho to
mng ngang hay c hiu chnh nhm chc. 2. ng dng Polymer cm quang c s
dng ch yu trong lnh vc sn, mng ph, vecni trn cc nn g, kim loi,
nha,.. Ngoi ra cn c s dng rt nhiu trong ngnh cng nghip hnh nh, cng
ngh in n, in t.
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Photolithography
II.
QUANG KHC: 1. Khi nim: Quang khc hay photolithography l k thut s
dng trong cng ngh bn dn v cng ngh vt liu nhm to ra cc chi tit ca vt
liu v linh kin vi hnh dng v kch thc xc nh bng cch s dng bc x nh sng
lm bin i cc cht cm quang ph trn b mt to ra hnh nh cn to. Phng php
ny c s dng ph bin trong cng nghip bn dn v vi in t, nhng khng cho
php to cc chi tit nh do hn ch ca nhiu x nh sng, nn c gi l quang khc
micro (micro lithography). 2. Nguyn l h quang khc Mt h quang khc
bao gm mt ngun pht tia t ngoi, chm tia t ngoi ny c khuch i ri sau
chiu qua mt mt n (photomask). Mt n l mt tm chn sng c in trn cc chi
tit cn to (che sng) che khng cho nh sng chiu vo vng cm quang, to ra
hnh nh ca chi tit cn to trn cm quang bin i. Sau khi chiu qua mt n,
bng ca chm sng s c hnh dng ca chi tit cn to, sau n c hi t trn b mt
phin ph cm quang nh mt h thu knh hi t. Mt n L mt tm thy tinh c hnh
nh. Hnh nh c to bng cch n mn c chn lc lp crom mng ph (khong 70 nm)
trn tm thy tinh to vng ti v vng sng. Khi chiu nh sng qua ch no khng
c crom th cho nh sng i qua, ch no c crom s cn nh sng.
Cr
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Photolithography
Cc giai on c bn to quang khc: - Chun b b mt - Sy s b - Ph
photoresist ln - Chuyn hnh nh t mt n ln photoresist - Ra, to hnh nh
ln photoresist - n mn lp oxit bn di photoresist v tch lp
photoresist
3. ng dng ca quang khc Quang khc c s dng rng ri nht trong cng
nghip bn dn ch to cc vi mch in t. Ngoi ra, quang khc c s dng trong
ngnh khoa hc v cng ngh vt liu ch to cc chi tit vt liu nh, ch to cc
linh kin vi c in t (MEMS). Hn ch ca quang khc l do nh sng b nhiu x
nn khng th hi t chm sng xung kch c qu nh, v th nn khng th ch to cc
chi tit c kch thc nano ( phn gii ca thit b quang khc tt nht l 50
nm), do khi ch to cc chi tit nh cp nanomet, ngi ta phi thay bng cng
ngh quang khc chm in t (electron beam lithography).
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Photolithography
III.
QUI TRNH 1. Chun b b mt: Tch tp cht trn b mt wafer: Phng php: -
Thi kh nit c p sut cao - V sinh bng ha cht - Dng nc c p sut cao -
Dng c ra Sy tch m Trn b mt cc wafer thng c m do cn phi loi b bng
cch gia nhit khong 150~200oC Ph lp primer: Mc ch: lm tng kh nng kt
dnh gia wafer v photoresist. Primer thng s dng l HMDS
(hexamethyldislazane) 2. Ph photoresist - Coating (Spin Casting)
giai on ny nn c quay trn spinner trong mi trng chn khng. Cc thng s
kim sot trong giai on ny: - Tc 3000-6000 vng/pht - Thi gian quay:
15-30 giy dy lp ph: 0.5-15m Cng thc thc nghim tnh dy lp ph
photoresistt= kp 2 w
vi k: hng s ca thit b quay spinner (80-100) p: hm lng cht rn
trong resist (%) w: tc quay ca spinner (vng/1000)
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PhotolithographyPh lp photoresit
Cc s c thng gp trong qu trnh ph lp photoresist:S c dy khng u
Nguyn nhn Hng khc phc b mt kh khng u C th t 1 vng trn cc ng bin dy
hn (c ng bin. th dy hn 20-30 ln) Dng dung mi phun ln lp bin hon tan
Do trong resist c cc ht rn c ng knh ln hn dy lp ph.
Xut hin cc ng sc
Dy ng bin
ng sc trn b mt
3. Sy s b Pre-Baking (Soft-Baking) Mc ch: lm bay hi dung mi c
trong photoresist. Trong qu trnh sy dy lp ph s gim khong 25%. Phng
php thc hin: a. Dng l i lu nhit iu kin: - nhit : 90-100oC - thi
gian: 20 pht b. Dng tm gia nhit - nhit : 75-85oC - thi gian: 45 giy
c. Dng sng viba v n hng ngoi. 4. Chiu (exposure) Trong giai on ny,
h s c chiu nh sng chuyn hnh nh ln nn, mt n c t gia h thu knh v nn.
C 3 phng php chiu da vo v tr t mt n: - mt n tip xc - mt n t cch
photoresist khong cch nh
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Photolithography
-
mt n t cch xa photoresist, nh sng c chiu qua h thu knh. Hnh nh
thu nh 1:4 n 1:10.
So snh 3 phng php:Phng php Mt n tip xc u im Gi c hp l phn gii
cao: 0.5 m Khuyt im Lm h mt n do lp oxit trn mt n b xt. Cc vt bn
trn mt n s in ln phototresit Do nh hng ca nhiu x nn hn ch chnh xc
ca hnh nh. lp li ca hnh nh km Gi thnh cao B nh hng ca nhiu x
Mt n t cch Gi c hp l photoresist khong phn gii thp: 1-2 m cch nh
Mt n t cch xa phn gii rt cao: < 0.07 m) photoresist Khng gy h
hng mt n
So snh cc h quang khc:
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Photolithography
5. Trng ra (development) Dng ha cht tch cc photoresist cha ng
rn. i vi photoresist m: - cht ra: xylen - cht sc li: n-butylacetate
i vi photoresist dng: - cht ra: (NaOH, KOH), nonionic soln (TMAH) -
cht sc li: nc - T l ha tan ca vng chiu v vng khng c chiu l 4:1. Do
photoresist dng nhy hn photoresist m. Thng s kim sot trong qu trnh
ra: nhit ra, thi gian ra, phng php ra, cht ra.
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Photolithography
Underexposur e Overexposur ePhng php ra: - phng php nhng: a trc
tip dung dch ra - phng php phun
6. Sy kh Post-Baking (Hard-Baking) Mc ch: lm cho photoresist cng
hon ton, ng thi tch ton b dung mi ra khi resist. iu kin sy: - nhit
: 49-54oC - thi gian: 30 pht 7. n mn Etching C hai loi n mn: n mn t
: s dng i vi chi tit c phn gii > 3m n mn kh : s dng i vi chi tit
c phn gii < 3m
n mn t L phng php n gin nht v kinh t nht ha tan cc resist cha ng
rn. Phng php ny c s dng nhiu nht trong vic sn xut mn hnh TFT LCD, v
cng sut to ra ln hn phng php n mn kh. Dng c bao gm: - 1 thng cha ha
cht ha tan resist cha ng rn - 1 mt n. Mt n ny c tc dng gi hnh nh ng
theo yu cu. Mt khng tan trong dung mi hoc tan chm hn rt nhiu so vi
phn resist cha ng rn Nhc im ca phng php: - n mn u khng c nh hng nn
d n mn vo lp oxit bn di lp photoresist. Do to hnh nh khng ng vi yu
cu
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Photolithography
-
Ha cht s dng ch yu l cc acid nn phi quan tm n tc ng n mi
trng.
n mn kh u im: - n mn c nh hng C th chia thnh cc loi sau: Dng ion
hot ha (RIE): c 1 dng kh c a vo bung t pha trn v c ht ra di y bng
bm. Kh s dng ty thuc vo tnh cht ca photoresist. Nhng kh ny c s dng
to ra plasma bng ngun in c tn s radio 13.56 MHz v vi trm wat.
Plasma c to thnh khi kh b ion ha. Khi , vng kp wafer bt u tch in m,
trong khi kh tch in dng. S khc bit v in th lm cho ion kh di chuyn n
vng kp v nguyn liu v xy ra phn ng ha hc. Cc ion dng cng gy n mn.
Phn n mn ha hc to ra s n mn ng hng cn n mn t nhin s c tc dng n mn c
nh hng. Cc thng s cn kim sot trong phng php ny l: p sut sut, lu lng
kh v cng sut RF.
Hnh 4: Cu to bun RIE
-
Dng hi n mn. Tuy nhin phng php ny ch dng n mn silic. Phng php ny
tng t nh phng php dng ion, khc bit duy nht l cc ion khng phn ng vi
nguyn liu c n mn.
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Photolithography
8. Tch lp photoresist Stripping Mn hnh LCD c ra v sy kh. Dng
dung dch kim hoc kh ha tan photoresist v dng mt lp khc chuyn hnh nh
ln mn hnh. a. Dng ha cht tch photoresist: - S dng ha cht nng ha tan
photoresist - Cc ha cht thng s dng: acid sulfuric, acid phosphoric
v hydrogen peroxide u im: tch photoresist nhanh Nhc im: gi thnh ha
cht cao, tc ng n mi trng b. Phng php kh (dng kh) Phng php ny khng c
hi do s dng kh oxy plasma oxy ha hon ton photoresist nn cn c gi l
tro ha photoresist. Lng kh to thnh s c tch bng bm chn khng. CxHy
(resist) + O2 CO + CO2 + H2O Phng php tt nht l s dng hi isopropyl
alcohol c tinh khit >70% c gia nhit t 80-100oC. Khi tch
photoresit c tch ra v to b mt sch.
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Photolithography
CHNG 2: MEMS (Micro-Electro Mechanical System)I. GII THIU: MEMS
l s tch hp ca cc yu t c (mechanical elements), cm bin (sensors), b
kch hot (actuators) v cc yu t in chung (electronics) trn mt nn
Silicon (Substrate) bng cng ngh vi ch to (micro-fabrication tech).
Trong khi nhng thnh phn c thuc tnh in t (electronics) c ch to dng
cng ngh mch tch hp (IC) nh: CMOS, bipolar, BICMOS, th nhng thnh phn
vi c (micro-mechanical components) c ch to dng qu trnh vi c
(micro-machining) ph hp l ct i c chn la nhng phn wafer Si hoc thm
vo nhng lp c cu trc mi to nn cc thit b c v c in. Vi c in t: l mt
cng ngh pht sinh t cng ngh bn dn vi mch. M, Cng ngh vi c in t vit
tt l MEMS vit tt t danh t Micro Electron Mechanical Systems, u chu
v Nht Bn gi l MST (Micro 11
Photolithography
System Technology). Vi c in t (MEMS) da trn phng php gia cng c
hc ca vt liu bn dn (micro-machining) . Vi c in t gia cng linh kin c
ln t mm n micromet, cng ngh k tip pht trin t cng ngh vi c in t l
cng ngh siu vi c in t gi l NEMS. Da trn cc quy trnh v vt liu IC
truyn thng: - Bn in quang, oxit ho nhit, khuch tn cht pha, cy ion,
LPCVD (Low Pressure Chemical Vapor Deposition), PECVD (Plasma
Enhanced Chemical Vapor Deposition), s lm bay hi, khc, khc t, khc
plasma, khc ion phn ng. - Si, SiO2, SiN, Al II. CNG NGH CH TO VI C
Ngoi ra, cc quy trnh v vt liu b sung c s dng trong MEMS:
- Khc t khng ng hng ca Si n tinh th, khc ion phn ng su (DRIE
Deep Reactive Ion Etching), in quang dng tia X, m in, mng mng LPCVD
lc nh, mt n phim dy, khun xoay, khun c cng ngh micro, ni kt micro
khi. - Phim hng s p in (v d PZT), phim t (v d Ni, Fe, Co), vt liu
nhit cao (v d SiC v s), nhm, thp khng g, platinum, vng, ming thy
tinh, plastic (v d PVC v PDMS). Vi nhng vt liu v quy trnh ny, k
thut in quang l quy trnh n quan trng nht cho php to ra ICs v MEMS c
kch thc vi m ng tin cy vi th tch b. Cc cng on chnh ca cng ngh MEMS
1. Khc: cng ngh MEMS thng c thc hin trn bn dn gi l wafer bn dn. 2.
Lm kh wafer. 3. In Vi mch: to mch trn hai mt wafer. 4. Khc theo mt
hng. 5. Dn cc wafer li. Cc phng php gia cng da trn vt liu bn dn v
cht n mn, vt liu bn dn thng dng nht l Silic. Yu cu l silic phi tinh
khit. Phn ng n mn ca ho cht trn Si thay i theo tng mt, v khc nhau
mi loi vt liu. n mn n hng (anisotropic) 12
Photolithography
n mn nhiu hng (isotropic). gia tng hng n mn trong n mn n hng, ta
dng phng php n mn bng ion hot tnh (Reactive Ion Etching). thnh n mn
thng ng c th dng hai loi ion, mt loi n mn b y v mt loi bo v cho
thnh, cch n mn ny c thc hin trong mi trng kh nn gi l Khc kh (dry
etch). Trong khi , KOH hay TMAS cng c th n mn Si theo nhiu hng khc
nhau to ra thnh nghing, thc hin cch n mn ny trong dung mi t nn gi l
Khc t. thc hin khc ti v tr mong mun, wafer cn c che bng cc mt n khc
nhau, gi l vt liu che. Cht cm quang c hai nhim v l to khng gian b
khc v gi li khng gian khng b khc. Cht cm quang ny khng b tc dng bi
vt liu n mn. Vt liu cm quang gi l photoresist. Phng php khc dng vt
liu cm quang vi nh sng gi l quang khc (photolithgraphy). Trong qu
trnh quang khc, Si c trng bng my trng quay (spinner), sau c sy lm
mt dung mi, qua cng on chiu nh sng, in vi mch ln bn dn. V vt liu cm
quang ch cm c di sng t ngoi nn my in vi mch s dng nh sng tm, trong
n chiu nh sng tm c cc loi khc nhau. Phng php khc kh s dng ion hot
tnh c khn nng cho ra nhng mu rt cao, rt nh gi l high aspect ratio
(l t l gia ng knh vi chiu su)
Cng ngh quang khc trong in t
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Photolithography
Cc ng dng Cng ngh sn xut compact disc Cng ngh cp quang Cng ngh
LCDs Cng ngh chip in t Cng ngh sn xut compact disc
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Photolithography
Mt s ch thch cho cng ngh compact disc Cht cm quang l nha c ngun
gc phenolic (novolac/diazanaphthoquinone) H positive photoresist,
khi c qu trnh quang, sinh ra indene carboxylic acids, thc y qu trnh
ha tan phenolic resin trong dung mi kim.
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