Bai bdo trinh bay cdc ket qua nghien ciru thiet vd che tao cam bien dp sudt va gia toe dp dien trd thu nhd sir dung phiin loai SOI silicon-on-insulator.. Ldp d-xn d giira ciia phien SOI
Trang 1Nshien ciru, Phdt trien va Uhg duns Cong nshe Vdt lieu (KC.02/06-10)- Ha Wgi 27/11/2009
CHE TAO CAM BIEN AP SUAT VA GL\ TOC THU NHO
B A N G C O N G N G H E A N M O N I - O N H O A T H O A
Vu Ngoc Hung1 Le Van Minh l, Nguyen Van Minh \ Trinh Quang Thong1^
1
Vien dao tao Quoc te vk Khoa hoc Vat lieu (TITMS),
: Vien Vat ly Ky thuat flEP), Dai hoc Bach khoa Ha Noi (HUT),
So 1 Dai Co Viet Hai Ba Trung Ha Noi Viet Nam Email: hungvungoc®itims.edu.vn thongtq@nims.edu.vn
Tom tit Bai bdo trinh bay cdc ket qua nghien ciru thiet vd che tao cam bien dp sudt va gia toe dp
dien trd thu nhd sir dung phiin loai SOI (silicon-on-insulator) Ldp d-xn d giira ciia phien SOI duoc diing di dure hien ky thuat dn mdn dimg nhdm dai duoc ad day cdc cdu tnic mdng va beam cd dp chinh xdc cao trong qua trinh an mdn di hudng tir pha hoi Cdc cam bien duoc che tao theo cong nghe
vi co khdi dp dung ky thuat an mdn i-dn hoat hda sau (DRIE) Cdu tnic dien gdm cdc dien trd duoc tao ra bang ky thuat khuich tdn sir dung dung dich pha tap SOD Kich thudc ngoai ciia cd hai loai cam biin chi vao khoang 2x2 mm 2 vd lxl mm 2 Dp day mdng va dam la 10 urn, Cdc cam bien dd the hien cdc dac tnmg dien hinh nhu dp nhay, khd nang dap ung nhu mong muon
I GIOT THIEU
Tren phuong dien lich sir cam bien ap suat va gia toe ap dien tro la cac linh kien dien
hinh duoc che tao bang cong nghe v i co khoi [1] U u diem noi bat ciia cac l i n h kien nay la gia thanh re do duoc che tao hang loat kich thudc nho dd nhay cao va on dinh ve mat co hoc Cac cam bien nay da duoc ung dung rong rai trong nhieu linh vuc nhu cong nghiep 6 to[2], san xuat do dien gia dung, va cac thiet bi y sinh (do huyet ap va ddng chay) [3 4 ] Dac biet la nhu cau ve cac cam bien kich thudc sieu nho cho cac ung dung trong linh vuc y te D d la ly
do ciia viec day manh cac nghien cim mdi cho muc dich nay
Cam bien ap dien ttd sih'c la cac bo chuyen doi cac bien dang co hoc do cac t i c dong ciia
ap suat hoac gia toe thanh tin hieu dien V i the, cau tnic chung ciia linh kien ludn co phan dien bao gom cac ap dien trd tich hop loai p va phan co la cac v i cau tnic nhay co kieu mang hoac thanh dam Phan cau tnic co co the dugc che tao bang k y thuat an mdn udt hoac an mon kho Trong nghien cuu nay phien de silfc kieu SOI, (silicon-on-insulator) co mot ldp oxit silfc kep gitra 2 kdp silfc da dugc sir dung de tao ra mang hoac thanh dam cd do day chinh xac Cac ket qua nghien cuu ve thiet ke va do dac trung l o i ra ciia cam bien se duoc trinh bay trong bai bao nay
H THIET KE VA CHE TAO
Doi vdi cam bien ap dien trd nguoi ta thudng sir dung bdn dien ttd ket noi vdi nhau theo
cau hinh cau dien ttd Wheatston nhu duoc chi ra tren hinh 1 Thdng thudng cac dien ttd nay
se dugc dat tai nhirng khu vuc ma ung suat vat lieu cd gia tri ldn nhat Trong nghien cuu nay cac dien ttd cd kich thudc rdng 30 p m va dai 2 p m Su thay ddi tin hieu l d i ra do thay ddi dien ttd suat dudi tac dons ciia nsoai luc (ap suat hoac eia tdc) duoc xac dinh nhu sau:
-1
D source
K
Trong dd Vsource la dien ap nguon nudi
Do dugc chd tao bang phien SOI gdm mot ldp oxit silfc kep giua hai ldp sih'c, mot dav 10
u m va mot day 450 p m nen mang va dam nhay co ciia cam bien cd dd day tuong img la 10
um V d i muc dich thu nhd kich thudc cac cam bien duoc che tao cd kich thudc ngoai lan luot la l x l mm" va 2x2 mm"
Trang 2Nshien cim Phdt triin yd tine dune Cone nehe Vdt lieu (KC.02/06-10)- Ha Noi 27/11/2009
.xtfag*- scire*
Hinh 1 Cdu hinh cdu dien trd Wheatston
Mechanically sensitive beam Silicon thin diaphragm
Suspension beam Supporter
Rigid frame
Interconnections
I 1
Hinh 2 Cdu true cam bien dp sudt (a)va gia tdc (b) dp dien trd
Cau true cua hai loai cam bien duoc chi ra tren hinh 2 Cam bien ap suat co mot mang
mong nhay ap suat va mot cau dien trd Wheatston Trong k h i do, cam bien gia tdc cd bdn dam nhay co song song v d i cac canh cua khdi gia trong v d i ba cau dien trd Wheatston tich hop trdn dd
Qui trinh che tao hai loai cam bien da duoc xay dung gdm 8 budc, sir dung 4 M A S K quang hoc cho cam bien ap suat va 10 budc, sir dung 5 M A S K quang hoc cho cam bien gia tdc (hinh
3 v a 4 )
Phien duoc sir dung dd che tao cam bidn la phien SOI, dudng kinh 4-inch loai n Phan dien duoc che tao trudc d phia ldp silfc day 10 p m , con cau tnic co duoc thuc hidn che tao sau tir
phia ldp silic day Dau tien, mot ldp oxit silfc {S1O2) mdng duoc tao ra bang phuong phap dxy
hda khd trong mdi trudng thdi k h i dxy va hydro Cac ap dien trd duoc che tao bang phuong phap khudch tan sir dung dung dich khuech tan boron (SOD) D d sau khudch tan xac dinh dd day dien trd duoc dieu chinh bang thdi gian khudch tan vdi tri sd bang 1/10 dd rdng dien trd Trong qua trinh che tao, nhdm (aluminum - A l ) duoc phii ldn be mat phidn hoac de tao dudng dan hoac ddng vai trd vay lieu bao ve cho qui trinh an mdn khd bang cong nghe phun xa
Trang 3Nshien ciru, Phdt trien vd Uhg dung Cons nghe Vdt lieu (KC.02/06-10)- Ha Ndi 27/11/2009
(sputtering technology) Qui trinh quang khac duoc thuc hien tren may quang khac 2 mat (double-side aligner) P E M 800 trong sudt qua trinh che tao
Cau tnic co duoc che tao bang cong nghe an mon kho tren thidt b i RTE-lOiP cua hang
S A M C O (Nhat Ban) Dac diem noi bat cua thidt b i nay la viec su dung cudn day kieu xoay trdn dc (Tornado coil) de tao plasma tang cudng (Inductively couple plasma - ICP)
"' " U ' =
t
8
t
- ' * w ' —1
1 l L i ) " ", f l |
i iSi cz a Si02
mm Buried Si02 r=3 Boron doping layer
Hinh 3 Sa do qui trinh che tao cam bien dp sudt: 7-dxy hda phien, 2-Md cua sd tao dien trd, 3-Phii
dung dich pha tap Bo, 4-Md cira so de tao tiep xiic vdi dien trd, 5- Phu nhdm lam day ddn cho mach,, 6-md cira so de an mdn tao mdng nhay dp sudt, 7-An mdn tao cdu true, 8- tay bd kdp oxit silic S1O2 a
giira cua phien SOI
He an mdn nay su dung hdn hop khi SF6/C4F8 cho qui trinh an mdn kho sau (cd ten goi la
qui trinh Bosch) [ 5 ] Q u i trinh nay dua tren plasma cam ung ket hop de tao ra cac gdc t u do tach ra tir C4F8 Cd hai budc cong nghe tuan hoan lap lai tao thanh mot chu trinh la an m d n (etch) va lang dong (deposition) Trong trudng hop nay, SF6 la k h i dung dd an mdn de Budc lang dong la dd tao ra mot ldp polymer nham hinh thanh ldp bao vd vach cua cau true an mon Day la qua trinh dang hudng, nen ldp polymer be mat se ngay lap tuc duoc tay bd b d i qua trinh ban pha i-dn kieu phun xa va lam Id bd mat si-lic phia dudi cho qua trinh an mdn tiep theo Q day, budc lang dong duoc dat trong 2 giay, con budc an mdn la 4 giay K h i do ldp o x i t
0 giua phien ddng vai trd cho qua trinh an mdn dirng dam bao do day ciia mang nhay ap suat hoac dam nhay co ciia cac cam bien Do vay, do sau an mdn cd the dat hang tram microns v d i vach hoc an mdn hau nhu thang dung va v d i tdc do an mdn cao hon 3-4 lan so v d i ky thuat an mdn udt Phien sau k h i da hoan thien cac cong doan che tao can thiet se duoc cat nhd thanh cac cam bidn rieng le (chip) Cac chip cam bidn sau do se duoc han ndi day (nhdm) ra vd cam bien bang ky thuat han det (wedge bonding) sir dung thiet b i West Bond
Trang 4Nshien cim, Phdt triin yd Ung duns Cong nshe Vdt lieu (KC.02/06-10)- Ha Noi 27/11/2009
10
t
as
9
t
IS
8
t
t
rmSi n Si02 ^ A l
•• Buried Si02 rz=3 Boron doping layer
Hinh 4 So do che tao cam bien gia toe: 7-oxy hoa phien, 2-Md cira so tao dien tro, 3-Phii dung dich
pha tap Bo, 4-Mo cira so de tao tiep xiic voi dien tro, 5-Pphit nhom lam day ddn cho mach, 6-Mo cira
so de dn mdn tao khe dao dong cho khdi gia trong, 7-Dinh dang tao ra thanh dam, 8-Phii nhdm de lam vdt lieu che chan bdo ve cho qua trinh dn mdn khd sau tao cdu true khdi gia trong vd cdc thanh dam nhay co, 9- An mdn khd sau tao cdu tnic, 10-tdy bd kdp oxit silfc SiC>2 d giifa cua phien SOI
III CAC DAC TRUNG THUC NGHIEM
Cac cam bien sau khi dugc che tao da dugc do thu nghiem cac dac trung l o i ra dien hinh Cac he do dac trung l o i ra cua cam bien deu ket noi may tinh de thu nhan, x u ly du lieu va hien thi ket qua do
He do cam bien ap suat su dung bo cung cap ap suat chuan M C I 0 0 va von ke hien so da nang Keithley-2000 de chi thi the l o i ra M o t trong cac ket qua do ciia cam bien dugc chi ra tren hinh 5 cho ca hai loai cam bien kich thuoc 2x2 m m2
va l x l m m2
Do nhay tuong ung cua hai loai cam bien nay la 2.5 mV/V.kPa va 0,186 mV/V.kPa The loi ra the hien dap ung lap lai rat tot va on dinh trong thoi gian dai Dong thoi dap tuyen cam bien bieu hien ro trong dai ap suat tir 0 den 100 kPa The offset la gia tri the tuong ung mot dien ap l o i vao co djnh khi chua
co ap suat tac dong The nay co tri so ~ m V va phu thuoc nhiet do Nhin chung, ket qua khao sat cho thay, the offset giam manh khi nhiet do tang (tir nhiet do phong - 300 K len 330 K , trong khi do, do nhay khong b i anh huong dang ke trong dai nhiet do nay
He do cam bien gia toe sir dung mot bo rung chuan (Mitutoyo MEE-45) va mot thiet bi khuech dai tin hieu (Mitutoyo A M E -100) truoc khi dua vao von ke da nang hien so
Keithley-2000 de chi thi the loi ra Cam bien gia toe dugc nghien cuu che tao 6 day cho phep co the xac dinh gia toe theo 3 phuong (3 bac tu do - 3 DOF) M o t trong nhirng ket qua do dugc trinh bay tren hinh 6
Trang 5Nshien ciru, Phdt trien vd Uhg dung Cons nshe Vdt lieu (KC.02/06-10)- Hd Ndi 27/11/2009
120
-100
„ 80 S£
ca
| 60
>
g 40
a
| 20
• Sensor dimension of lxl mm*
& Sensor dimension of 2x2 mm"
Input voltage of 1.5 V
20 40 60 80 100 Pressure fkPa)
Hinh 5 Ddc trung the loi ra phu thudc dp sudt ciia cam bien dp sudt
m (tin * mm if umm +$n*.*,
+ '- r, fc«Ct J*!*ti#« if t*«*«* y it*
5 10 IS 2 0 25
Acceleration in x-direction (g)
(a)
SO
700
600
> 500
§ 300
B 200
° 100
• 'i u i»i M* fk« v " A** 0*' <•* "I
5 10 15 20 25 Acceleration in z-direction (g) 30
/ / m f t 6 Dac trung the loi ra phu thuoc gia tdc cua cam bien gia toe
Doi voi cau true cam bien lxl mm2, gia toe duoc thay doi tir lg den 25 g Ket qua do cho
thay, do nhay theo phuong Ox, Oy, va Oz dat gia t r i tuong ung la 38.8 p V / g , 43 p V / g va 23.3
p V / g N h u vay, do nhay theo phuong x v a y cao hon theo phuong z V o i cam bien 2x2 m m2, dai gia toe ap dung cung la l g den 25 g Ket qua do cho do nhay theo phuong x la 0,5 m V / g , theo phuong y la 0,52 m V / g va theo phuong z la 0,98 m V / g Dieu nay cho thay, khac v o i trucmg hop tren, do nhay theo phuong x va y nho hon theo phuong z
IV KET LUAN
Cac cam bien ap suat va gia toe MEMS thu nho da dugc thiet ke va che tao thanh cong Mot so tien
bo cong nghe da dugc ap dung Uong qua trinh che tao c£c cam bien nay la ky thuat so M A S K 2 mat va
ky thuat an mon kho sau i-6n hoat hoa (RIE) Cac cam bien da dugc hoan thien bang cong nghe dong
vo linh kien chuan Cac cam bien dugc che tao da the hien cac dac trung va pham chat dung nhu mong muon va chung to kha nang dua vao sir dung cho cac ung dung cu the de do ap suat nhu do huyet ap va
do gia toe thong qua do do rung
L o i c a m o n
Nghien cuu nay duoc thuc hien trong khuon kho de tai nghien cuu khoa hoc va phat tridn
cong nghe vd vat lieu dien tu KC.02.15/06-10
Trang 6Nghien cim Phdt triin \n ting duns Cons nshe Vdt lieu (KC.02/06-10)- Hd Noi 27/11/2009
T a i lieu t h a m khao
1 G Gerlach, R Werthschuetzky, 50 years of piezoresistive sensors history and state of the
art o f piezoresistive sensors, Technisches Messen, 72, 53-76 (2005)
2 Fleming W.J., Overview o f automotive sensors, Sensors Journal, IEEE, V o l 1, 296 -308
(2001)
3 H Joseph, B Swafford, and S Terry, M E M S in the medical world, Sensors, 47-51
(1997)
4 U R L : http://www.meas-spec.com
5 F Larmer and A Schilp, Method of Anisotropically Etching Silicon, U.S Patent
Specification 5501893 (1996), German Patent Specification DE4 241 045 (1994)