BSTJ 50: 10. December 1971: Zero Loss Transfer Across Gaps in a CCD. (Krambeck, R.H.)

2.5 MB·English

Zero Loss Transfer Across Gaps in a CCD

by RH. KRAMBECK,

Wen a chorye-coupled device in made with a single layer of metlica
tion, anjasent eleroos ute placed seeral micrometer apart. Ae @
rant tore ming be some dfety Sn moving the chase fam one eetode
to another thi poper it wil be whos ta, for any aubsrte atrial
Moran wie range of srkrface chars far which complete traafer can
te aohieead repartee of elaine swparoion. 11 sell further be shown
‘at fir poubseate woth doping of Tew than 10"/ou, the natwrat
Chara Jour in a goed guaity thermally grow layer of SiO, fa alvaye
ff the appropriate aie awd motte ts enoure epee anaes. Thne-
fora, fo nip fabrewsion of e CCD ih ne ayer of ste te substrate
alert fe te approprite choi.

Tn chargeenpied daviee,' chorge is transferred from a potential
‘yall under me wealistion to @ deeper potontal well under an djscent
Iota, Sie the mitals eanot ton one rufber, his poees involves
Passing through an interscetrce yop IT the potential pattor is such
that there isa potential baron ct pocencial wel in the epueo wt th

cof transfer, then wompiele eharge teanefer i impossible. Tf bvo
a of mctalzction are ved (while mpatatel by an insulting
layer of LOOD 33, ro boner o wel ns: (om This 2reuies mro eom=
plex ceenology eo it would be devine make a CCD with ore
layer of retaliztion,

Tm ehis paper ths efecto jotarfars charge and substrate doping
potenti we eae barr furan sil be analyzed, H wil be shown
hat, for any’ given substrate ping and drive voltages, there is an
Sitesi change Tv whish neither well nor Bari frm. "The caloula-
tions in this payer will aime a infntelslome gap whi wil ensure
‘hat no yin lose will eral fom small variations in gap width or
sre sarge magi
S170 ce ott avwsmne rROUNICAL JURA, ROR aH

‘The abjective of thi analyst wil he to find che eonditons whieh
will omit compte ehangs transi, Tis therfore neeesany to resting
{he alate of the CCD at thy sl af the eraser of only the ieyeat ONE.
“het con be atooramodatod. Tht i, i the hewest ONE. is tenner
“sithout lore, than any’ pie of information could be transfered with
Zo lows uf change. Our objective then ie to find frcecurice density ws
postion at Ue snd of tonsfer. 1 ne nother pone nora minim
2t free charge density iv Die spaoe, then the space x wot Pteroring
Fish toaster

"To ind fce-camienderaity un he stave, we must Sind val euuee
charge donsiy an enbaat fe large density. he Ast pat ofthe
problem is to ind chatge densi ve eeilon at the end of trensfor.
{This simplified by the fact det ws tie ud of transfor ofthe larga
posible ONE, the poiieeadustur sichuor is an equipotental (the
Iavement of foe eange will na stop uni an equipotent achive)

"The quometry of the inerleele spaoe is shown in ig. 1. Jost
below the senicondsetor sirius the field ie wafer beouuse the
‘Surfer sa enuipotersial, The dxplcement felis ven by

b= ViNeFa @

where i fa eeaoondura dpiog, «(8 the cemioondustor deters
Constant, ¥ Sa the wurlaye ewventil, and g is tee leetnnie charg.
Tost alae the steoe he Fl

De = Dg On @

where ne Hho frewelectron devsity (en) nl Qn, is the densi of
Charge! states ether inthe ovide ur ab the semiocnduetor surieoe
fprispe subsirwe has bron assumed with eletrone ge froc enti)
torn equation (1) and @)

an = Py, — VIREVG+ On 8

Since Qu, vied Fats constants difereseos in elation density from
fone poi to another are areetly vated to changes in. by

Du

an a

‘This means that if Py, watts monotonically from de region under
cone sleet to the region wider the ajaoeat electrode, tes ellen
dni aso varies monotonieslly andr harvicr orwell ests, Tn Fig. 2
Fig 1 Coes mse fw channel rae hg Ue ites sp

possible vations of B,, rth pstiow are eon, Rast, £3
Fig. 20 VF and VV, whens Py and Fae the voagen epic
tu th exo metals. Ia this ase, Dy it pine uedae Bota rete’ hit
drops ta zor in betwern for alent ree separation). This mrs
Uloetron donsty 3 lower inthe spare between tke eletees Ti i
is unver oir of them, and 96 a reel a baie wt bs holding ale
aege. Seeund, in Pig. BoP > Vand P > P. Hore Bi menace
‘usdet ear locale bs again any in tke ep. This means leeteon
lens ie higher in Se ace thaa under ithe lest, m0» potential

acct gp oe hay aie
US aS me See
well mut be present. Hinally, in Fig, 20. & Vy and ¥ = Wa. Hore
Da, 2.0 under tote t, Dy, % 0 under melul 2, nnd D,
‘where in haven, Thi isthe tation desiced. Tes therfore noe
‘ofl ly what wake of Q, will pane le susfac potential at the end
bf trols Lo be in betroen Ye to mata voltages

Tat secure rth 1 i giving ils charge to mst 2. The te
‘end of taanaer freecootney Menrty rer mcta 1 i geo. ‘Therefore
rows equation

20. ®
Wa VENGPS. a

ee VINE Pa ®
Aven evap, wits f= Fo, ¢ 10" Demand Fy = 1 vol,

"Thi seriion ee Any Teer value would give
ine Coa barren ‘To reson oration ofa rl, we hove V2. Unde
levis 2

Day BO
‘Theneiore
@. 2 VINGE— o

fee largest aloe Qa ing used, Ba, — Onn F = Vy Ale,
frum enoetion (8

‘Thereore
where it the oxide diletve wonetant, The maximum value of
Qi, is Chron

0. 5 Venton + 50 — 19 an

Tring Vy = 10 volts and the sare munbene as above forthe other
parameters giver

520 10"em

7

equations (8) and (00) speci the allowable range for (2, wich &
the res nseced,

‘The provi setion show thal eosin ange of Qu, ppp
for unt" given setrate doping wri pair 0 devine valle Tes
section tis abtasnability ofthis range wil be discussed The range 3
hewn graphisely 1g. 3 for tho deving vecagae V0 — 1 volt and
¥) = Lovolt

1 tures out that for a teemmaly grown oxide on silicon Qi in

bP a

“EE SGAGaNOT md mei tae sae ate sir =
SI7A sme mE svsniae Teenwteat Format, BRCRUSEE Ent

the oxide ie normally in tho ring 10" to 6 x 10)"fom. Therefore
for a ype eubetate any dosing wake 10°/ea? wil ensure compote
tanter, or oiher sulairaes and oxidee come doping must be ine
troduced, Probsbly dhe eat wy’ would he & uniform ion implant
fhceca 20 the total charge including oxide charge lcs in the alioned.
range

“An important pont ubuul Fig 8 isthe width of the allowed range
For drive voltage of J volt sod 10 yile (he allowed rango of cherge
fetends over st lewit ono ner of magnitude for any substrate doging
‘blow 19!"/om which ensures thal » proper amant of change can be
btained cyen with rulnluatil slcetoalioe veriatiors in charge. Te
‘Goo tne Thal aging eect axe unllaly to ebange the amount of
Charger ton vals tide of te desired an,

Tin the uualyie it wae aasoned there i sisiont ten for complet
crane tv agear. Aa appropriate quewion is Iw rue Tonge transfor
takes wo separates the rata, RJ. Strain rl N. 1 Searynr neve
how that uw CCD te rata of eenie low inversely proportional 2
The ses of dhe enpatannes betoeen surfyce and wibetrate an between
sunfeo and meta. Sing shit um iz roue higher when the suri it
covered hy tinels, Uw low eapacitares gap ‘ill no guionatly
Ineente umsafer time a€ Jong oe the gyp ix shorter shan the metel

irom the abo kesion$t am bp en chat the simplest sey to
beatin complete trurfer ia charge-coupled davies, with w thermal
SiO, layer used inmiator, ie tne a8 Pubetzate caatril p-type
sileon vith a doping of les than 10" im

‘e ean be forehercopeluded thw for wher subszate zeatevals and
for other inmuasvors a apprepriale chorgn mange alvays exis, and
that this charge monee nw abuaized by ion impntstie eer the
titi sarfuor af (veal ithout use of « phatogmibie nakag rep.
Selec npr of th region betroen the motala and the regions
tnder te eager ef the mszaleeosld ep eliminate porential bor
ind wells, However, beatse of fringe Telds, thie ean be scbioved
tly by exten of He kl of toe change denoibution for a spectie
Aistiner under each metal, but thie would be 4 mone dient wy to
nohiowe complete tne.

Summavng, ik lnwld lear that potential barvore and eli
in the spaces botucen elerandes in ebargeovvplel deviees ean be
"inate msl henefve the possibility of incomplete oharge rane
ran tase macs aun

should sob be cited as a reat far ming lle abornally
doeely on wing fen layers a metalization. Por mort apoliasions
future CCD should be roade on peigie sbeteates with Tess chan
Wem ding snes the proper chany neatly obtain

2, Sui Be a eyo No pe wk