K I J q
Vp = In - + ) (3. 21)
^o
4 5
vi ty le JQ/JO la r^t ion (vao co 10 -10 ) nin eo the coi Khi
roi sang
J (tong cong. = J t + J q ~ J q (3.22)
Neu l i p t y so giiia dien t r o t o i v a d i i n t r o sang cua lop
^,
chuyen t i e p t a eo t h e t h ^ y Rt/^q ~ 10 .
Dieu do cho th^y, Khi chieu sang mau, Khong rihiing d i i n dung cua
n a u t h a y doi (C " 1/V ) ma d i i n t r o cua n a u ciiig t h a y doi r a t Ion
t h e o c h i e u hiiong riho d i . Mau d i o t t r o n g mach cau d i i n dung co t h e dlioc xem tiiong diicng v o l mach gan 2 l i r i h Kien nac song song: t u d i e n v a d i e n t r o . Khi c h i e u sang, t u d i i n t a n g l i n (vi t h e Vq := V-V^) con d i i n t r o giam Tharih phan ciia t u d i i n l u c nay co t b e mot p h a i diioc v a r i c a p bu l a i , n o t phan co the chirih t a y b o i t u C (Hirih 3. 9) song tharih p h ^ d i e n t r o Khong dioc bu t r i i . Ket qua l a c^u b i mat e i n bang nghiem t r o n g t h e o tharih p h i n d i e n t r o (tharih i t i a h dong pha v o i t i n h i i u 5, 6 MHz nuoi c i u ) dan den lam bao h o a Khoi KEIỊ. Trang t h a i nay g i y arih hiiong xau den tharih phan d i e n dung ma t a can xut ly, do dac.
•62-
D e Khac phuc tirih trang nay, chung toi d a lap v a o nharih dói xung v o i m a u do tren cau m o t chiét a p Rq. Ghiet ap n a y eho p h e p c a u c a n bang v e tharih p h ^ dien t r o K h i m ^ u bi c h i e u sang trong K h i do (Hinh
3. 2 0 ) . % % ^h H Hinh 3. 20. Cau do d i e n dung sau cac biioc h i e u chirih.
d). Khao s a t do on dinh cua he dọ
Do chirih xac ciia phep do n.TS xii l y bang t i c h p h i n Boxcar phu thuoc vao do on dirih cua may p h a t rihip 555 v i no quyet dirih do on dirih cua xung Kieh mau, cua cac v i t r i cong t^, t ^ v a cuoi cung l a v i t r i TjjQx ^^^^a dirih phọ
Ta b i e t rang, cita so t o e do ê^ diioe b i e u d i e n t h e o cong thute: en = [Ln ( t g / t j ) ] / ( t ^ - t ^ ) (3.23)
v a
ê - AT exp (Bp/KT) (3. 24!
— ' I
Gia sii do on dirih t a n so cua IC555 A t / t " 1 0 , t r o n g d i e u Kien eac t u , t r o mach p h a t c h a t liiong cao, t a eo t h e t i r i h s a i so cua ê t h e o s a l só t 2 v a t^ rihii sau:
- 4
63 -
- 4
Sai so tiiong doi cua t ^ : A t j / t j ~ 2. 10
Theo (3.23) s a i so tUong doi ciia ê : ^^n ^^n " ^^
" , - 4 Theo (3. 24) s a i so tiiong dSi cua T ^ : ATn/Tnj ~ 5. 10
4
Dieu nay cho th^y, neii do on dirih cua may p h a t rihip vao c o 10 t h i t r o n g Khoang rihiet do 100 K - 300 K, s a i so theo rihiit do cua cac
d i n h i*io DLTS c h i vao CO 0, 1 K (ATmgx " 1/10)-
K^t qua do rihieu l i n t r e n mot so mau e h u i n da cho t h a y :
Vol cac g i a t r i t j , t g Khong t h a y d o i , v o l t i n so p h a t xung Khong t h a y doi, cac pho ghi diioc co do t r u n g Khop cao, eac dirih pho cho do
l e c h A Tj|3x "^^ CO 0, 1 K (vi dii dirih DLTS cua mau S i c h i e u xa d i e n t i i
o Khoang Tu^x *" 225 K). Qua day c6 t h e Ket l u i n l a h e co do on dirih dam bao doi v o l phep do ELTS dung cong t i c h phan Boxcar Kep.
e ) Xac d i i ^ v i t r i cac cong Boxcar
Nhii cong thute (3. 23) da c h i r a , eac g i a t r i t^, t 2 l a r a t quan t r o n g d o i v o l v i i c xac dirih do chirih xac cua cua so t o e do ệ Vi viy, v i i c xac dirih chirih xac t j , t g t r o n g cac phep do l a h i t siie e i n t h i e t . Tuy rihiin, mot Kho Khan gap p h a i l a r a t Kho quan s a t dong t h a i h a i
cong naỵ Tren so do Hirih 3. 16, t a c6 t h i quan s a t cac xung no cong
t a i cac c h i n so 5 ciia IC 74123. Unic t e da cho thliy, v i e e c[uan s a t , do dac cac g i a t r i t j , t g mot e a c h r i e n g r e gap p h a i s a i só doc Kha Ion, arih hiiong dang Ke den g i a e ^ v a do vay dan den s a i so Ion cho v i i e t i r i h nang liiong Kicti h o a t B j c u a eac t i m
-64-
xung cong noi t r e n , cho phep do dae, quan s a t ehung t r e n man hirih eiia may dao dong Kỵ Bien phap nay lam giam s a i so doe va r a t thuan t i e n t r o n g sii dung.
f) Khao s a t do nhay cua he do
Dung cac Khoi tut (1) den (9) t r e n Hirih 3. 8. Duta dian B vao t r u e Y ciia tii Kỵ True X q u e t t h e o t h o i gian. Mau do diioc tliay bang t u 500
pF v a song song voi no mac mot t u b i i n doi riho (ea IpF). Da ghi dutoe chirih l e c h b i e n do Y Khi t h a y doi t u ipF. Ty so cherih l e c h diioc darih
-4
g i a l a S/N ~ 20. Qua do co t h e darih g i a AC/C " 2, 5. 10 doi v o i phep do C(V) va do nhay con cao hon neu do t h e o phiiong phap dien dung ULTS
dung Boxcar Kep [65],
I h e o (26), neu x e t cho chuyen t i e p P - N (vai N^ >> N^), he cho phep - 4
quan s a t diioe t i n h i e u DLTS v o l nong do tam Np nho rihat l a 5. 10 N^,. g) Xii ly t i n h i e u qua do d i e n dung o dau vao Khoi Boxcar
Doi v a i he do JAJTS, eo h a i l o a i xung phan cute Kich t h i e h nau:
*f Xung t i e m bao hoa: Xung nay chuyen d i o t riharih vao t r a n g t h a i phan cue t h u i n v a t i e m h a t t a i Khong c o ban vao vung ngheo dang quan s a t .
« Xung h a t t a i co ban: Xung nay l a giam dot ngot t h e phan ciic t i i p
g i a p cua d i o t v a diia h a t t a i co ban vao phan ngheo cua d i o t .
Xung h a t t a i co ban l a xung d i o c dung thUong xuyin t r o n g cac phep
dọ No g i y r a dang qua do d i e n dung rihut t r e n Hirih 3. 11 (sau TSNP). T i n h i e u do gan c a 2 p h i a , t r o n g do phan can t h i e t eho xii l y Boxcar l a p h i n mia t r e n , chiia diiong cong qua do . T i n h i e u nay diioc duta vao diem B ciia Khoi t i i n Khuyech d a i (Hirih 3. 12) de lam tang do nhay cua h e dọ P h i a nuta diioi ciia t i n h i e u Khuyech d a i Ien g i y t a c dung xau eho
65
Khoi nach Khoa dung T r a n s i s t o r t n i o n g . caiirih do d i e u nay ma mot yeu c ^ dlioc d a t r a cho Khoi t i e n Khuyech d a i l a e a t bo t i n h i e u o p h i a
Khong c ^ t h i e t . Ctiung t i i da lap r a p mach t h e o so do rihu: Hirih 3. 21.
>out
Hirih 3. 21 : So do mach t i e n KD v a c a t xung.
Diot Z lam rihiem vu c a t xung o p h i a im v a cho t i n h i i u qua do d i qu£L Mute c a t o p h i a im diioc d i e u chirih b o i c h i e t ap R.
h) Ctnian n h i e t dọ
Viee c h u a i rihiit do diioc chung t o i tboic h i i n t n i c t i e p t r e n t i i
ghị Dlia t r i n bang tiiong quan cho s a n giiia n h i i t do v a sđ cua cap
rihiet Cu - Const, q u e t rihiet do mau tut 77 K - 300 K, doc g i a t r i sđ t r e n von Ke v a xac dirih v i t r i Kim o i a tii ghi t h e o t r u e X, Tu: do xac dirih diioc thang rihiet do tiiong ung t r i n . De eo do tuyen
t i r i h can t h i e t , co t h i I a n rihieu t h a n g do rihii v i y o cac d a i h e p hon, vung ma cac dirih DLTS thutong r o i vaọ Qua t r i n h c h u a i rihiet do diioc t i e n harih t r o n g d i i u Kien t h a i g i a n q u e t n h i e t du d a i v a v i t r i gan
• 6 6 -
d i o t phan arih trung thiic rihiet do cua man Cac d i e u Kien do diiac thiic h i e n t r o n g n » t birih mau (Dewar) viia dap iing cac yeu cau ve thong so Kieh t h i e h (dien, quang) viia dam bao t i n h e hi n h xac cho Khói do n h i e t do eua naụ
Cau tao Dewar cua he do diioe trinh bay tren Hinh 3. 22. 1. Vol do N2
2. Vol thong Khi 3. Ong ngoai 4. Ong trong 5. Van chin Khong 6. Biu dutng N^ 7. Cuta so quang 8. Mau do
9. Cap rihiet diin
Hinh 3. 22- Dewar eiia he do
2. 4 Ung dung.
^n r
LI
I
He do d i e n dung qua do dung cong Boear Kep l a mot h e do l a p r a p tii nhurig lirih Kien r a i r a c nen Khong t r a r i h Khoi rihiing rihutoe diem n h a t
dinh. No Khong t h e so sanh v a i cac t h i e t b i chuan dblqc san xuat cong
n g h i e p rihii cau d i e n dung, cac bo xut lỵ . . ve Fhiiong d i e n c h a t liiong lirih Kien, do on d i n h mach- Song, ngiioc l a i , no co mot so d i i m t h u a n t i e n ma c i u do d i e n dung e h u i n Khong eo, do l a hang so t h a i g i a n riho {CO 10 s ) , bu t n i t u dong d i e n dung trarih h i e n tiiong l e c h cau qua Ion, cc mach c a t xung ngutoc. v. v. . .
•
67
Do l a t h i e t b i tii laip nen r a t de dang h i i u chirih t h e o rihu cau, t r o n g Khi can t h i e p vao cac nay cong n ^ h i i p l a d i e u can diioc suy x e t Ky liiSng.
Hi do CO t h e thiic h i e n diioc rihieu chiic nang, do dae trurig C (V), do t h e o cac phiiong phap TSCAP (Thermally S t i m u l a t e d C a p a c i t a n c e ) , PC
(Foto C a p a c i t a n c e ) , HUTS dung d i i n dung qua do, Foto-DLTS.
He do da dlioc sii dung vao n g h i i n eutu s a i hong d i i m t r o n g ban dan n o i Chung v a t r o n g S i l i c c h i e u x a e l e c t r o n n o i r i e n g [10, 13], gop p h i n thiic h i e n d i t a i nghien eutu Khoa hoc c o ban cap riha mioc 48-04-01-OIB t r o n g g i a i doan 1980 - 1985.
Ngay nay, v o l sii p h a t t r i e n cua ngarih T i n hoc, v i i c ghep n o i h e do
v o l may t i r i h wo r a Kha nang Khai t h a c Ket qua do n » t each t h u i n t i e n
- 68 -
$3-XAY D(JNG re DO M-TS DUNG D0N3 UffiO KY THJAT TS)B A-B 3. 1-Nguyen ly do
T i cac cong thiic (1. 16), (3. 5 ) , t i n h i e u dong qua do J ( t , T) t a i not
rihiet do T nao d^y diioi t a c dung eiia xung p h i n eiie ngiioc mot c h i e u s e cho dang:
J = Jit) j
T = c o n s t
Bang v i e e c h i a chu Ky xung Kich mau r a lam 4 i4ian bang rihau, a bo xut ly, t i n h i e u J ( t ) c h i diioc thong qua a 2 Khoang t h o i g i a n :
Tf/4 < t < Tf/2 v a 3Tf/4 < t <Tf
Neu goi t i n h i e u J ( t ) t r o n g Khoang d i u l a A t h i t r o n g Khoang s a u l a R Co t h e so sanh h a i d i e n t i c h A v a B riho bo t a c h song.
Phep do se thiic h i i n o dang R = R(T) v o l R t y l e v o l do Ion eua A v a B Qua moi h e xii l y , t i n h i i u diioc d^c t n i n g b o i ham t n i y e n rihii phiiong t r i r i h (3. 7 ) : Tf f . R(t) = I C(t) F(t) dt J 0
Doi voi he tach song dong bo A-B , ham 19c F(t) co dang :
0 tai 0 < t < Tf/4
F(t) = 2/Tf = 2f tai Tf/4 < t < Tf/2 (3.25) O tai Tf/2 < t < 3Tf/4
69 -
Trong do Tf la chu Ky lap lai ciia xung Kich nau, f la t ^ so xung Kich maiL Ham t n i y e n (3. 7) co dang C f o r R ( t ) = en e x p ( - e / 4 f ) - e x p ( - e / 2 f ) - e x p ( - e / 4 f ) + e x p ( - e / f ) (3.26) n n n n '
Tii (3. 26) t i m diioe ale tri cua ham t n i y e n b a i g 0, 1330^ doi v o i
d i e n dung qua do v a 0, 403 CQ doi v o i dong qua do . Ciia so t ^ c do t i n h .
dlioc bang 1, 72f d^i v o l d i e n dung qua do v a 3, 76f doi v o l dong qua dọ
TlBic c h a t ciia qua t r i r i h thiic nghiem l a cho rihiit do ciia mau t h a y doi v a dirih t n i o c êo (bang t ^ so f ) . Dirih ciic dai cua pho K^TS cho
t a xac dirih dblqc rihiet do T^Q. Lap l a i phep do rih:ii v i y v o l cac ej^^,
Khac rihau v a tiiong urig co cac g i a t r i T^ị Tii cae cap g i a t r i nay,
ciing giong nhii o tie do d i i n dung qua do dung cong t i c h phan Boxcar
2
Kep, l a p (^ t h i phu thuoc ciia L n ( e n i / T ) t h e o (1/KT). DUong b i e u d i e n
cho b i e t nang liiong i o n h o a Bj., t i e t d i e n b a t h a t t a i cua cac niic s i u . Nhan x e t : Bang v i i c l a y h i i u h a i Khoang A v a B t r i n diiong t i n h i e u dong qua do, phep do da chuyen quan h e h a i b i e n so J ( t , T) sang quan h e mot b i e n so AJ(T) mot each t i i dong.
R i e p do nhii v i y co t h i x i y dilng diioc t r e n h i analog dung tii ghị
3. 2-Sq do cac Khoi chute nang:
So do Khói h e do pho DTLS dong qua do dung Ky t h u i t TSIB A-B diioc
70 Tao Tao xung ^ (J ^ ^ T •• - ^ ? "v ^ Xufly t Volt ke X^ 1 Tach song • •> Y Tughi Hinh 3. 23 So do Khoi h e do dong
IX-TS dung Ta)B A-B
A ' .
*(Kh6i t a o xung c6 nhiem vu cung cap eac xung cho mau do, xung ctio bo xut l y t i n h i e u va Khoi t a c h song A-B. Khoi t a o xung diioe Kieh b ^ i g
mot nay p h a t im t i n hirih s i n <& de dang t h a y d o i diioc t i n sọ Mach
t a o xung Kim Kich nau ciioc thiic h i e n t r e n mot mach NAND h a i l o i vao v o l sut lam t r e siion xung t r i n mot l o i so vol l o i K i a Do rong xung Kich mau co t h e dieu c h i n h diioc bang n a c h RC. Tnioc Khi den mai, xung nay diioc qua l o i Khuyech d a i cong s u ^ t l o i r a D (Hirih 3. 24 ). Cac l o i
r a A, B, C cua Khoi t a o xung co dac diem rihii s a u : l o i B co tan so
gap doi l o i A, C; l o i A, C l a h a i l o i r a n ^ c h daọ Loi B dioc dung de xii l y t i n h i e u qua do : l a y mau t a i h a i Khoang d i i n t i c h A (phan t i i thut h a i ) va d i e n t i c h B ( p h a i t i i thii t i i ) . Loi A, C dutoe dung de t a c h cac d i i n t i c h A, B t h a n h cac mic d i e n ap mot c h i e u r i i n g r e t a i Khoi t a c h song A-R
JtKhoi xii l y t i n h i e u dutoe thiic h i i n t r e n Khoa d i e n t i i SỊ T i n h i e u dong qua do l a y t r i n t r o t a i R^ diioc diia den Khoa Sị Xung B
dlioc diia den cong d i i u Khien Khoa T a i l o i E, t h u diioc h a i phan d i i n t i c h A, B cua t i n h i e u qua do v a l o a i bo h a i p h i n Khong sii dung (phin t i i thut rihat va phan tii thut b a ) .
- 71
»Kh6i t a c h song A-B tniic h i e n v i e e t a c h r i e n g cac d i e n t i c h A, B
t u duong t i n h i e u o l o i E cua Khoi xu lỵ Khoa S2 dung xung C d i e u
Khien, tarih duac d i e n t i c h A t h e h i e n mic n e t c h i e u t a i lói Yl. Khoa S3 dung xung A d i e u Khien, t a c h diioc d i e n t i c h B t h e h i e n mj:c mot chieu t a i l o i Y2. Cae l o i Yl, Y2 nay eo t h e diioc diia vao t r u e Y h a i l o i vao eua may tii ghi hoac diia vao bo Khuyech dai so sanh. Miic d i e n ap mot c h i e u o l o i r a eua bo Khuyech d a i so sanh t h a y doi t h e o rihiit do nau dọ T r i n may tii ^ h i , do chirih l a pho DLTS dong su: dung Ky t h u i t TSDB A-B. 74B4 74B4 m r e ' 74B4 TTWO ©—H- t^~ © S2 4) 4) _nnrũ\ 4) ^ D n ri A B
72
T r i n Hirih 3. 24, cac lirih Kien diioc sii dung gom: - c:ac Khoa SI, S2, S3 diing t r a n s i t o r JFET. »
- Cac Khuyech d a i t h u a t t o a n dung IC UA 741 [41]
- Cae nach l o g i c diing IC TTL ho 74 (NAND)
- Cac bo c h i a 2 dung IC JK F l i p f l o p s SN 7473 [62]. He da h o a t dong phii hop v o l rihSng y i u cau d a t r a
Qua qua t r i r i h sii dung, h e do t h e h i i n not so diem t h u i n t i e n rihii :
1) V i i c d a t ciia so t o e do r a t don gian. No e h i i*3ụ thuoc vao moi
tan so f n a t h o i [ 1 6 ] : e ^ = 3, 76f.
2) Do dung Ky t h u a t TSDB A-B, arih hiiong cae d i pha riho, d i t a n riho dlioc t i i dong l o a i trut sau Khi t i n h i e u til 2 Kirih T ^ B da d i qua bo
Khuyech d a i so sarih (hoac vao l o i vao doi xurig Yj, Yg). Mot yeu t o nijta lam t y so S/N cua t o a n h e do tSng dang Ki l a t r o n g qua t r i r i h nay rihieu
t r e n h a i Kenh TS)B t\l d i p t a t 1 ^ rihaii
3. 3-Chiian v a d i e u c h inh h e
a) Cling giong rihii h i do d i i n dung UJTS dung Ky t h u i t Boxcar Kep,
v i e e chuan rihiet do t r i n h e do nay ciong dutoe xac d i n h t n i c t i e p t r i n tii ghị Viee q u e t rihiet do ciing diioc thiic h i e n t h e o h a i c h i i u t h u i n n g h i e h v o l t h a i g i a n q u e t du d a i , s a u do xac l a p cae thang rihiet do
t r o n g tiing d a i quan tam Man do v a p i n rihiet d i i n ciing diioc d a t t r o n g
birih mau tiiong t i i rihii h e do d i e n dung ELTS,
b) Trong qua t r i n h e h u i n hoa, mot nau e h u i n (Si c h i e u xa e l e c t r o n ) Aioc dung de dọ Rio ghi diiae t r e n h e da so sarih v o i pho ghi t r e n
t h i e t b i o raioc ngoaị Ket qua cho do jtni liqp cao [10].