LCH S VT L
TI: LCH S CHT BN DN ( HISTORY OF SEMICONDUCTORS )
GII THIU Thit b bn dn c mt giai on pht trin kh di v n lm cho th
gii thay i vt xa s tng tng ca con ngi lc . Cht bn dn gip con ngi c
th truyn thng tin v x l d liu, mt cch d dng v t tn thi gian hn nhiu
ln so vi bng chn khng Ni dung trnh by: Lch s ban u ca cht bn dn. L
thuyt v hot ng. Cc thit b thc t. Tm tt ngn. 1. Lch s ban u ca cht
bn dn. Theo G. Busch Thut ng "bn dn" c s dng ln u tin bi Alessandro
Volta vo nm 1782. Quan st u tin ghi nhn c hiu ng cht bn dn l ca
Michael Faraday (1833), ngi nhn thy rng in tr ca sulfide bc gim
theo nhit , khc vi s ph thuc quan st thy trong cc kim loi (in tr
gim khi nhit tng). Mt phn tch nh lng s ph thuc nhit vo dn in ca
Ag2S v Cu2S c xut bn vo nm 1851 bi Johann Hittorf. i vi nhng nm tip
sau lch s ca bn dn tp trung vo hai c tnh quan trng l khc phc ca lp
chuyn tip bn dn kim loi v nhy ca cht bn dn vi nh sng. 1.1. Mch chnh
lu: Nm 1874, Karl Ferdinand Braun (1850-1918) quan st v pht hin dn
truyn v tch sng trong tip xc kim loi-bn dn. Mc d khm ph ca Braun
ngay lp tc khng c nh gi cao, nhng sau n ng mt vai tr ng k trong pht
trin radio v pht hin bc x vi sng trong h thng radar Th chin II ( vo
nm 1909, Braun chia s gii Nben vt l vi Marconi ). Nm 1874, Arthur
Schuster quan st mch chnh lu c lm bng dy ng bao bc cc con c.
Schuster nhn thy rng tnh chnh lu ch xut hin sau khi mch khng c dng
mt thi gian. Ngay khi ng y lm sch cc u dy (xo b c -xt ng), tnh chnh
lu bin mt. Bng cch ny ng y khm ph ra -xt ng nh l cht bn dn mi. Vo
nm 1929, Walter Schottky bng th nghim xc nhn hin din ca mt ro chn
trong lp chuyn tip bn dn kim loi. 1.2. Quang dn v quang in:
LCH S VT L
Nm 1839, Alexander Edmund Becquerel (ngi cha ca mt nh khoa hc
Henri Becquerel) pht hin ra hiu ng quang in ti mt ng giao nhau gia
mt cht bn dn v cht dn in. Quang dn trong cht rn c pht hin bi
Willoughby Smith vo nm 1873 trong cng vic ca mnh th nghim cp trn tu
ngm m yu cu in tr ng tin cy vi tr khng cao. Smith th nghim vi in tr
selen v quan st thy rng nh sng gy ra gim ng k tr khng ca in tr.
Adams v Day l ngi u tin khm ph ra hiu ng quang in trong mt vt liu
rn (1876). H nhn thy rng s c mt ca nh sng c th thay i hng ca dng in
thng qua selen kt ni vi mt pin. Cc t bo nng lng mt tri u tin hot ng
c xy dng bi Charles Fritts vo nm 1883. N bao gm mt tm kim loi v mt
lp mng ca selen c ph mt lp rt mng ca vng. Hiu qu ca t bo ny l di
1%. hientuongquangdien.FLV 2. L thuyt v hot ng. Nm 1878, Edwin
Herbert Hall pht hin ra rng cc s chuyn di ca ht trong cht rn b chch
hng trong t trng (hiu ng Hall). Hin tng ny, sau c s dng nghin cu cc
tnh cht ca cht bn dn. Ngay sau khi pht hin ra cc in t ca JJ
Thomson, cc nh khoa hc xut l thuyt dn in t da trn kim loi. L thuyt
ca Eduard Riecke (1899) l c bit th v, ng y cho rng s hin din ca 2
loi in tch m v dng vi cc mt khc nhau dn dn tnh linh ng ca n. Khong
nm 1908, Karl Baedeker quan st thy s ph thuc ca dn ca ng it ha hc
nh lng (bn cht ca it). ng cng o hiu ng Hall trong ti liu ny, trong
ch ra s dch chuyn i vi in tch dng. Nm 1914, Johan Koenigsberger
chia vt liu th rn thnh ba nhm da vo tnh dn in ca chng: kim loi, cht
cch in v bn dn ". Nm 1928, Ferdinand Bloch pht trin l thuyt ca cc
electron trong lattices. Nm 1930, Bernhard Gudden bo co rng cc tnh
cht quan st thy ca cht bn dn l c trng cho s c mt ca tp cht v bn dn
tinh khit v phng din ha hc khng tn ti.
LCH S VT L
Hnh 1. L thuyt ca Alan Wilson ca cc nhm vt liu dn trong cht rn.
Nm 1930, Rudolf Peierls trnh by cc khi nim v vng cm ca cht rn bng
vng Brillouin cng nm. Cng vo nm 1930, Kronig v Penney pht trin mt m
hnh n gin, hm th nng tun hon. Nm 1931, Alan Wilson pht trin l thuyt
nhm ca cc cht rn da trn tng ca cc vng trng v vng cha y nng lng (Hnh
1). Wilson cng xc nhn rng dn in ca cht bn dn l do cc tp cht. Trong
cng nm , Heisenberg pht trin khi nim ca l trng (m cha trong cc tin
ca Rudolf Peierls). Nm 1938, Walter Schottky v Neville F. Mott (gii
Nobel nm 1977) pht trin c lp cc m hnh ca cc hng ro th nng v dng in
chy qua lp tip xc kim loi-bn dn. Mt nm , Schottky ci thin m hnh ca
ng bao gm c s c mt ca in tch khng gian. Nm 1938, Boris Davydov trnh
by mt l thuyt chnh lu ca -xit ng bao gm c s hin din ca mt lp tip xc
p-n, d l trng v hin tng ti t hp. ng cng hiu tm quan trng b mt ca vt
dn. Nm 1942, Hans Bethe pht trin cc l thuyt v s pht ra nhit in t
(nhn gii Nobel nm 1967). 3. Cc thit b thc t. 3.1. im tip xc chnh
lu: Nm 1904, JC Bose nhn c mt bng sng ch cho PBS im tip xc chnh lu.
G. Pickard l ngi u tin cho thy im tip xc chnh lu silic hu ch trong
vic pht hin cc sng v tuyn (bng sng ch vo nm 1906). Selen v chnh lu
-xit ng c pht trin, tng ng, [vo nm 1925 bi E. Presser v nm 1926 bi
L. O. Grondahl ]. Chnh lu selen c s dng nhiu trong Th chin II trong
thng tin lin lc qun s v thit b radar. 3.2. Tip xc p-n: Trong cng
vic ca mnh trn cc pht hin ca sng v tuyn Russel Ohl nhn ra rng cc vn
vi thit b d tinh th c gy ra bi cht lng xu ca cht bn dn. ng lm tan
chy silic trong cc ng thch anh v sau cho n ngui. Cc kt qu thu c
silic vn cn a tinh th, nhng cc kim tra ton din
LCH S VT L
chng minh rng tnh cht ng u hn. Ohl xc nh cc tp cht to ra cc lp
tip gip p-n rng ng v tnh thu c trong qu trnh th nghim cng ngh ca
mnh. ng gi 4 bng pht minh trn my d silic v tip gip p-n.
Tip xc p-n 3.3. Transistor lng cc: Nm 1945, William Shockley a
ra mt khi nim ca mt b khuch i bn dn hot ng bng ni dung ca nguyn tc
bin i trng. tng l cc ng dng ca mt in trng ngang s thay i dn ca mt
lp bn dn. Tht khng may pht biu ny khng c quan st thc nghim. John
Bardeen ngh rng iu ny l do trng thi b mt kim tra s lng ln ca vt liu
t trng ny (Hnh 2). L thuyt b mt ca ng c xut bn nm 1947.
Hnh 2. tng b mt.
LCH S VT L
Trong khi lm vic trn cc thit b cm ng in trng, trong thng 12 nm
1947, John Bardeen v Walter Brattain to ra mt transistor tip xc im
bng nguyn t germanium (Hnh 3) v chng minh rng thit b ny c th lm tng
cng sut in. Tuy nhin, s khng chc chn lin quan n c ch chu trch nhim
v hot ng ca bn dn. Bardeen v Brattain b thuyt phc rng cc hin tng
lin quan n b mt c vai tr chi phi trong hot ng ca thit b mi trong
khi Shockley ng h dn s lng ln cc ht mang thiu s. Khong mt thng sau
, ng pht trin mt l thuyt v mt ng tip xc p-n v mt bng bn dn tip xc.
Shockley, Bardeen v Brattain nhn c gii thng Nobel v vt l vo nm 1956
(John Bardeen nhn c mt s khc vo nm 1972 cho l thuyt ca ng c tnh siu
dn). Trong thng hai nm 1948, John Shive chng minh mt bng bn dn im
tip xc hot ng mt cch chnh xc vi emitter v collector c t hai bn i
din ca mt lt ct rt mng germanium (0.01cm). Cu hnh ny cho thy rng s
dn in thc s din ra vi s lng ln, khng phi dc theo b mt (khong cch
gia pht v thu gom dc theo b mt s cn di hn nhiu). Sau Shockley trnh
by l thuyt ca ng v hot ng bng bn dn cho cc ng nghip. l gi tr ghi nh
rng cc thuc tnh quan trng ca cht bn dn ti thi im ny l "cu trc nhy
cm" v ph thuc nhiu vo tinh khit ca mu. Cc vt liu bn dn m Bardeen v
Brattain lm vic c chun b bng cch s dng mt k thut c pht trin bi
Gordon K.Teal v John B. t da vo phng php Czochralski. Tinh th sau c
lm tinh khit bng cch s dng phng php tinh ch vng c xut bi William G.
Pfann.
LCH S VT L
Hnh 3. Cc bng bn dn im tip xc u tin. Bng bn dn tip xc im c ch to
u tin, nhng n cc k khng n nh v c tnh in kh kim sot. Cc bng bn dn
tip xc u tin c sn xut vo nm 1952. N tt hn nhiu khi so snh vi bng bn
dn tip xc im, nhng vic sn xut gp nhiu kh khn hn. Nh mt kt qu ca mt
qu trnh truyn kch thch phc tp vo tinh th pht trin bao gm ba khu vc
to thnh mt cu trc NPN. N c chia thnh cc thit b ring l v tip xc thc
hin. Qu trnh kh khn v khng th c t ng mt cch d dng. Hn na, rt nhiu
vt liu bn dn b lng ph. Nm 1952, bng bn dn tip xc hp kim c bo co
(hai vin hp kim indium hai bn i din ca mt ming silicon). Sn xut n l
n gin v t tn vt liu v c th c t ng ha mt phn. Chiu rng c s thu c l
khong 10m, cho php thit b hot ng MHz trn 1s. Cc bng bn dn u tin
khuch tn Ge (khuch tn c s dng to thnh khu vc c bn, trong khi
emitter l hp kim) vi mt hnh dng c trng "mesa" c bo co vo nm 1954.
Chiu rng c s l 1m v tn s ct 500 MHz. N c hiu rng i vi cc bng bn dn
silicon hu ht cc ng dng s l tt hn so vi nhng germanium do dng ngc
thp hn. Cc thit b silicon thng mi u tin (pht trin ng tip xc) c sn
xut vo nm 1954 bi Gordon Teal. Bng bn dn Si khuch tn u tin xut hin
vo nm 1955. gim in tr sut cc thu v hn ch tc hot ng m khng lm gim in
p phn tch qu nhiu John sm ngh cu to ca n bao gm hai lp. Mt bng
bn
LCH S VT L
dn vi lp epitaxy c bo co vo nm 1960. Trong cng nm , Jean Hoerni
xut cc bng bn dn phng (c hai c s v khu vc ngun bc x khuch tn). Oxit
c tc dng nh l mt mt n c loi b v hot ng nh l mt lp lm gim nh hng.
Tip tc ci thin tc c xut bi Herbert Kroemer. in trng ni ti c a vo c
s dng cc nng lng kch thch. Mt cch khc gii thiu in trng trong cc c s
ng ngh n phn loi thnh phn ca vt liu bn dn, dn n phn loi nhm khe h.
Khi nim d th khng th c a vo thc hnh d dng bi v vn ch to. (* Herbert
Kroemer sinh ngy 25 thng 8 nm 1928 ti Weimar (c). Kroemer c trao
Gii Nobel v cc bn dn c cu trc d thng gn lin vi transistor. u nhng
nm 1960 c mt pht minh mi gi l hiu ng Gunn. ng l ngi u tin gii thch
mt cch y v hiu ng ny.) 3.4. Vi mch: Cc bng bn dn tt hn rt nhiu, lm
vic nhanh hn v to ra t nhit khi so snh vi cc ng chn khng. V vy, n c
d on rng cc h thng ln (thng tin, my tnh) c th c xy dng bng cch s
dng cc thit b ny. Khong cch gia chng c, tuy nhin, (s kt ni cc thit
b) cng ngn cng tt gim thiu s chm tr gy ra bi lin kt ni. Nm 1958,
Jack Kilby chng minh cc mch tch hp u tin m mt s thit b c ch to
trong mt cht nn silicon v ni vi nhau bng phng tin lin kt dy. Kilby
nhn ra rng iu ny s l mt bt li do trong bng sng ch ca mnh, ng xut
hnh thnh cc lin kt ni bng cch lng ng nhm trn mt lp SiO2 bao gm cc
vt liu bn dn. iu ny c thc hin c lp bi Robert Noyce vo nm 1959. Nm
2000, Jack Kilby nhn c mt gii thng cao qu trong vt l cho cc thnh tu
ca ng. 3.5. Diode ng hm: Leo Esaki nghin cu dng cht kch thch tm ra
c s ca mt bng bn dn lng cc c th dc kch thch trc khi bm bc x ti cc
ng ba tr thnh khng y . ng y thc rng trong nhng ch ni rt hp s xuyn
hm c th xy ra. ng c c diode Ge 1 ng hm vo nm 1957 v l mt trong
silicon vo nm 1958. Esaki trnh by ti Hi ngh quc t Vt l nh nc rn ti
cc electron v Telecommunicationsin 1958 c nh gi cao bi Shockley.
Tht khng may, Shockley th hin s thiu quan tm y khi Robert Noyce n
trnh by tng ca mt diode ng hm hai nm trc . V kt qu l Noyce chuyn n
cc d n khc. Cc diode ng hm c bit chng cc iu kin mi trng do thc t l
dn c khng da trn cc mng dn tc thiu s hoc cc hiu ng nhit. Hn na, thi
gian ca n chuyn i ngn hn nhiu so vi bng bn dn. Leo Esaki nhn c gii
thng Nobel v vt l vo nm 1973 cho cng vic ca mnh trn ng hm v
superlattices. 3.6. Transistor trng, Cht bn dn xit Kim loi
(MOSFET): Nm 1930 v 1933, Julius Lilienfeld mi ngi nhn c bng sng ch
cho cc thit b tng t nh MESFET v MOSFET. Nm 1934, Oskar Heil np n
xin cp bng sng ch cho cng tc l lun ca ng v kim sot in dung
LCH S VT L
trong cc transistor hiu ng trng. Cc bng bn dn lng cc u tin l hon
ton khng tt bi v b mt cht bn dn khng ng cch th ng ha. Mt nhm c nh
hng bi MM Atalla lm vic v vn ny v pht hin ra rng mt lp silicon
dioxide s c th l cu tr li.Trong qu trnh lm vic ny mt khi nim mi ca
mt bng bn dn hiu ng trng c pht trin v thit b thc t c sn xut. Tht
khng may, cc thit b khng ph hp vi hiu sut ca bng bn dn lng cc vo
thi im v b lng qun. Mt vi nm trc khi phng th nghim Bell chng minh
mt bng bn dn MOS Paul Weimer v Torkel Wallmark ca RCA lm vic trn cc
thit b nh vy. Weimer lm ra bng bn dn ca cadmium sulfide v cadmium
selenide. Nm 1963, Steven Hofstein v Fredric Heiman xut bn mt bi bo
trn mt MOSFET silicon (Hnh 4). Trong cng nm , cc mch CMOS u tin c
xut bi Frank Wanlass. Nm 1970, Willard Boyle v George Smith trnh by
cc khi nim v cc thit b tch in kp (CCD) tng ng vi cht bn dn ca cc
bong bng t. C hai nh khoa hc nhn gii Nobel vt l nm 2009 cho cng vic
ca h trn CCD.
Hnh 4. Mt mt ct ngang ca mt bng bn dn kim loi-oxit-bn dn. u cc
MOSFETs c cng nhm. Pht trin mt cng poly-Si dn n mt thit b
selfaligned, cng chnh n to thnh mt n (lp bo v) cho ngun v truyn in
qua cng. Bng cch ny c th kim sot c s chng cho ln nhau ca in dung
cng ngun v cng kt hp. K t silic a tinh th c tr khng tng i cao, cng
c lm bng silicides ca kim loi vt liu chu nhit c xut. Gim kch thc ca
thit b dn n ci gi l hiu ng knh ngn (SCE), bao gm cun in p ngng v h
thp ro chn (ro th) gy ra. Cc cch i ph vi vn ny bao gm vic gim su ca
ngun v mng kt hp vi nhng n lc trnh tng tr khng, (tng ngun / cng (S
/ D) hoc c th l ro Schottky S / D). Ngng in p v nh thng (th) kim
sot bng phng php mt ct kch tp (bn dn) thch hp ca cc knh m lm cho n
c th duy tr tnh di ng b mt tng i tt. Knh tc ng ngn c gim ng k khi
cng oxit mng. Nh l mt h qu khi gim bt dy, dng in r cng tng ln, gia
tng tiu th in nng ca ton b chp, v l tc dng ngoi mun i vi h
LCH S VT L
thng di ng chy bng pin. Ngi ta c tnh rng s tng dng in r cng hin
nay tng xp x 30 ln mi th h cng ngh, tri ngc vi tng 3-5 ln thi gian
tng ca dng in r knh hin ti. Ngoi dng in r hin nay, vic gim dy oxit
cng lm nhy ca thit b ti s thm nhp boron t cng poly-Si vo trong knh.
Mt s vt cht cao khc nhau c tm kim m rng.
Hnh 5. Mt mt ct ngang ca mt MOSFET SOI.
LCH S VT L
Hnh 6. Mutigate transistor: (a) tng gp i ca khu; (b) FinFET, (c)
xung quanh ca khu.
LCH S VT L
Mt phn m rng th v ca cc MOSFET s lng ln c in l silicon trn cht
cch in (SOI) (xem hnh 5). u im ca SOI l s d dng c lp in ca thit b t
phn cn li ca mt mch tch hp, lm gia tng mt ng gi. Hn na, khu vc ca
cc mi ni ngun v mng c gim ng k, do gim in dung. Cui cng, s suy gim
chiu rng c gii hn dy Sibody, do n c nhiu ngi tin rng SOI gip gim
hiu ng knh ngn, tr khi ngun cng ni thng qua cc knh v BOX khng th b
qua. Cc thuc tnh ca thit b SOI c ci thin vi vic gim dy ca bng bn
dn. Ngi ta tin rng c th y depletedultra mng SOI (FD UTB SOI) l mt
trong nhng gii php nhn rng tt nht. Do kim sot ca khu xut sc ca knh
cc thit b ny c th l undoped hoc rt nh c kch tp. Trong cch ny, tnh
di ng l khng b suy thoi v in p ngng l t ph thuc vo bin ng ca nng
doping. Mt u im khc ca cng ngh SOI l n to iu kin pht trin ca khi
nim thit b mi (Hnh 6), nhng y l mt cu chuyn khc. 3.7. Laser bn dn:
Cht bn dn c s dng rng ri cho s pht x v pht hin bc x. Bo co u tin v
nh sng pht ra bi mt cht bn dn xut hin vo nm 1907 trong mt lu bi HJ
Round. Bo co u tin v nh sng pht ra bi mt cht bn dn xut hin vo nm
1907 trong mt lu bi HJ Round. Cng vic c bn trong lnh vc ny c tin
hnh, trong s khc, bi Losev. Mt m t rt th v ca s pht trin ca diode
pht ra nh sng khi lch s ca pin quang in c tho lun. Trong phn ny ch
laser bn dn c cp n mt thi gian ngn. Cc laser bn dn u tin c pht trin
vo khong nm 1962 bng bn nhm nghin cu M. Tip tc nghin cu trong lnh
vc ny theo hai hng l rng hn quang ph ca vt cht c c phm vi bc sng
rng hn v khi nim v cu trc thit b mi. Herbert Kroemer v Zhores
Alferov c lp ny ra tng v laser bn dn c xy dng trn heterostructures.
Zhores Alferov l mt thnh vin ca nhm nghin cu (ngi Lin-X) to ra c
tip gip p-n bng bn dn u tin vo nm 1953. ng trc tip tham gia vo
nghin cu nhm pht trin cc thit b bn dn chuyn ngnh cho cc tu ngm ht
nhn Nga. Cc vn quan trng nh vy i vi cc quan chc Lin X v ng thng hay
nhn nhng cuc in thoi t cc quan chc chnh ph rt cao, nhng ngi mun cng
vic c thc hin nhanh hn. Thc hin y nhng yu cu Alferov phi chuyn n
phng th nghim v sng . Sau , ng lm vic trn cc thit b in v tr nn quen
thuc vi cu trc p-i-n v p-n-n. Khi bo co u tin v laser bn dn xut
hin, ng nhn ra rng cu trc khng ng nht (heterostructures) i ca loi
p-i-n c s dng trong cc thit b ny. ng thu c cc thit b d th thc t u
tin v laser d th u tin. Nm 2000, Alferov v Kroemer nhn c mt gii
Nobel Prizein vt l cho nhng thnh tu ca h trong khu vc ca
heterostructures bn dn c s dng tc cao v quang in t. Lch s ca s tin
b ng k ca cht bn dn trong laser bn dn c lin kt khc, vi vic s dng ca
ging lng t v vt liu mi, c bit l gallium nitride.
LCH S VT L
4. Tm tt thng tin. Silicon c th c coi l nh cung cp vn chuyn thng
tin ca thi i chng ta. Trong lch s thng tin c hai cuc cch mng (cch
nhau khong 500 nm). Vic u tin l ca Johan Gutenberg nhng ngi thc hin
thng tin c sn cho nhiu ngi, l pht minh ra bng bn dn. Hin ti, s lng
thng tin ton cu tng gp i mi nm. Nhiu vic chng ta cho l ng nhin
(chng hn nh, v d, my tnh, Internet v in thoi di ng) s khng th c nu
khng c vi in t silicon. Mch in t cng c mt trong xe hi, gia dng, my
mc, thit b quang in l quan trng nh nhau trong cuc sng hng ngy, v d
nh, truyn thng cp quang truyn d liu, lu tr d liu (CD v DVD ghi), my
nh k thut s, vv. T s khi u ca in t cht bn dn s bng bn dn ra i trong
mt mch tch hp v ang tng vn vt vi thi gian. Xu hng ny c ch bi Gordon
Moore v c gi l nh lut Moore. nh lut ny c minh ha trong hnh 7, s lng
bng bn dn trong b vi x l Intel mi c v nh l mt chc nng ca thi
gian.
Hnh 7. S lng Transistor trong b vi x l Intel k tip nh l mt chc
nng ca thi gian. Mc d cc cng ngh lng cc c thay th phn ln bi CMOS
(hn 90% ca mch tch hp c sn xut trong cng ngh CMOS), nh lut Moore l
stilltrue trong nhiu kha cnh ca cc xu hng pht trin ca vi in t
silicon (r
LCH S VT L
rng, vi hng s thi im thch hp). Cc bng bn dn MOS c ci thin v s ln
nhng trn tt c nhng th khc n c thu nh
Hnh 8. Kch thc tnh nng nh l mt hm ca thi gian. ngoi sc tng tng.
Gim kch thc tnh nng, trnh by trong hnh 8, nhiu hn hoc t hn theo cp
s nhn. S lng bng bn dn c sn xut mi nm v gi trung bnh c hin th nh l
mt hm ca thi gian trong hnh 9 (mt ln na s thay i theo cp s nhn). N
c d on rng trong nm 2010 khong mt t bng bn dn s c sn xut cho tt c
mi ngi sng trn tri t.
Hnh 9. S lng bng bn dn c sn xut mi nm v gi bng bn dn nh l mt hm
ca thi gian.
LCH S VT L
V trong tng lai chc hn vn cn nhiu iu ngc nhin na. Nhng nghin cu
su rng ang c thc hin trn graphene, in t hu c, cc thit b lng t, vi,
tch hp silic vi cc vt liu khc v nhiu vn khc,
Gio vin hng dn: Sinh vin thc hin:
NGUYN NHT QUANG
VN TH HIN L TH MINH TRM L TH THU HIN TRN XUN VIT CNG V TNG PHM
MINH TRUNG L MNG TRN QUANG VINH
