Note: Descriptions are shown in the official language in which they were submitted.
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P~TEN~
~ ~ 2 ~ i 7
M~T}IOD FOR PRE3PARING LAMINATES ~F ZnSe and ZnS
BAC~ROUNI) OP I~E lrlv~ ~ lON
~ield of ~e Im~sntion
Thi~ invention relat~ gene~a~ly to me~hods o~
preparin~ ~nSe~Zn~ lamina~e~ or "~andwiche~ h~mic~1
v~por depo~itlon te~h~islue~ and the lamin;3~es ~o m~de.
)e~criPtlon t~f ~he Plior ~rt
Infrared transn~iss~re t~lndow~i ar~ cul~rencl3r u3~d a~c
th~ en'cr~nce ap~rture~ of n~any airborne reconnai~san~e or
navi~tion ~yst~m~. Material~ used for such win~ow~ have
to sati~fy se~e~l crite~a, includin~ ) th~ window
sholllcl not ~ignific~ntiy dee~e $e th~ ineomin~ ha~ or
render th~ Qi~nsl noi~y, ancl ~b~ th~ window ~n~te~
~houl~ be strong eno~gh ~o with~tand dust and rain e~o~ion
encount~ed ~u~inB, high speed flight. Zinc ~eleni~e
(ZnSe~, a hi~5hly tran3mi~1ve m~terial tn the i~frare~
~egion~ ~a~i~fie criterion ~a) ~te~y w~ll and i~ 1~hu~
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consid~ret an ideal candidate for ~uch window
applications. Ilow~ver, ZI~Se is a "so t" m~terlal
~ha~dne~ ~b~ut l~O knoop, flexural stren~h ~bou~c 8~0
psi) which dne~ not effectively resist rain and du~t
ero~ion during ~igh ~peed flight . Z~nc sulfide ¢~nS~ 7
al~a ~n infsared tr~nsmi~sive material, doe~ n~t have the
superior opti~al propertie~ of ~ina ~elenide but is much
~tron~er ~haI~dne~ ab~u~c ~40 knoop, flexural ~t2enlsth
about 15 ,001) psi~, ancl iq capable of withs'c~nA~ng the
cond~t~on~ vf hi~Sh ~peed flight at least up to about M~ch
~Jo. 1.
It i9 known th~t ~ laye~ oi ~nS ~out l~m ~chick
deposited on ZnSe is sufficient to p~o~uce ~ window with
rain erosion ~es~stan~e equivalent ~co that o~ pure ZnS
w~thout a ~ignificant lo~ t~ opti~al prcspe~tie3 of
the 2n5e, tlow~ver, there are problem3 a~_oci~t:ed in
I a~ e ~uch a ZnSe~nS "sandwich'~. One of the ruain
problem~ is ~he production of a strong bond ~tweer~ th~
ZnSe and ZnS ~ayers. Pre~riou~ attempt~ at -ki~Es suc~ ~
~andwich frequently re ulted in produe~ which the ZnS
layer peeled <~ff during poli~hing and ~ab~ication
proceduresl. T~us, the~e ha~ been a nee~ for a process by
which ZnSe/ZnS ~andwlches carl be made whi~h haYe a
~tron~Sly ~dherent bond betwe~n the ZnSe subs~rate arld ~he
ZnS layer.
One attempt at such a proce3~ hac ~een t~ ehe~ ally
etch ~he Zn~e ~ubst2ate prior to apply~n~ ~e ZrlS laye~
While the tran~mi~ n propertie8 of the~ resulting
~ndwich were no~ 81E~nifican~ly a~fec:ted, the streng~:h ~f
~che bund hetween the ~nSe and Zn5 la~e~s wa~ no'c ~ o~ed.
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~'AT~NT
7~7
U. S . Patent No . 4, 303, 63S, i~,sued December 1, 1981 to
Aldin~er, ~t ~1. di~closes op~ic~l grade zinc ~ulfide
bodie~ made by the ohemic;~l Yapor depos~tion (~ID)
tectmique. They a~e ~ub.iected to an afte~ t~e~tment und~
high gas pres~ure and at eleva~ed temperatu~e. ~Ihile the
CVD tec}mi~ue in general i~ discloset, the ~inc ~ulfide
bodies 7,r~ not fo~med on a ZnSe s~l~stra~e, ~,o the problem
o~ boncl streng~h is not addresset.
U.S. ~atent No. 4,447,4~9, is~ued May 8~ 1~84 to
Peter~, di~,clo~,es a low temperatu~e process ~or
depo~iting, e.~S., ZnS on a ~,ub~trate by reacting ~ v~por
phaqe reactant ~e.g. dimethyl zirlc~ anc~ neutral,
charge-fee ~ul~~ ato~.
U.5. P~ce~ No. 4,770,479, i~e~i SepteMber 131 19
to Tu~ison, and U.S~ P~tent No. 4,772,~80, ~s~uet
September 20~ lg~8 to Tutison gene~ally dl~close the
p:t~oduction of optical windows of 2nSe or ~nS by the CV~
n-e'chod .
Japane~e~ Patent J5 ~130-804 di~close 2nSe prepaxed by
react~ng hy~rogen and ~el~ni~m vapor to pro~uce hy~ro~en
~elenide which 1S ln turn reacted wi~h zinc vapor by a CV~
raethod to p~o~e ~ ZnSe articlç.
Japane~e P~tent J5 ~130-805 di~closes the production
of ZnSe by ,~ t ~inc and selenium vapor~ which ~auses
depositio~ o~ ZnS~.
Japane~e Patent J~ 9146-915-~ di~c~4se~ a proces~ ln
which met~llic zin~ is tirected toward a ~ub~t~ate while
~ulfur and/or se~ ium compound ga~ ls 5uppliecl, ~0 tha~
ZnS and/or ZnSe is adhe~ed to the ~ubst~ate.
Japane3e E'a~'ce}~t J~ 711~-004 discloses a proce89 in
whic~ ~ydro~en ~e~en~de is diluted with an inacti~2 gas
~nd i~ ~upplie~ to a re~ct ion tube in a high t~n~perature
~u~na~e. 4~ inacti~e carrier ga~ iQ dir;~ted on~o molter
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PATEN~
~inc ~o 'chat zin~ vap~r i~ obt~ine~ ~o gt~o~ Zn~e on a
~ubs Lrate .
Japanooe Paten~ J6 0~69-~62-A ~ m~th~d ~or; ~ P
in~rax~ed tran~mittin~ materi~ o~ ZnS-ZnSe ~a~rin,~
excellent adherence ~o a ~ub~trate when sub~e&ted to heat
çycle~. A mlxed çryxtal layer i~ ~ormod at ~che in~cerface
~etween ~he 2nS ~nd ZnSe whic:h i~ e~~ec:t~ve in ~ ,- sovlnE:
the adher~nce of the Zn~ to the ZnSe. The p~oce3s
involve~ pla~inE ~ 2~n~e board i~ltO a CV~ ~ys~the~ usn~ce
~d intro~cin~5 %ino vapo~ toge~her with H~ nd H2Se
ga~ he flow rat~ o~ the H2Se i8 v~ried ~rom 100% H~SR
to OZ H2Se (100X H2S)~ a~er which only H S i~ pr~ ent.
StnMA~ OF THE~ ;h ~ ION
In ~ceortance wit~ the pre~ent invention, there is
provi~e~d an ~ d method o~ forming a ZnS lay~r on a
~nSe ~t~b~t~ate ky the chemical vapor deposition o~ ZnS
onto ~che ZnSe in which the impr~vemer~t ~omE~riso~
contac:tinE~ a 2nSe sub~trate, prior to the chemic~ apo~
deposition of the ZnS, with Hz S in the absence of zinc
metal v~por at a ~emperature and for a tim~ ~ufficien~ to
callse ~ r~eaction of the t~S with the surfa~e o~ the ZnSe
sub~t~at~
Also p~ot~rid~d ln accordance w~th t~is inYention i~ a
mechod o~ form~ng a 2nS ].ayer on a ZnSe ~3ub~xa~e by the
chemical vapor d~po~it~on of ZnS onto the ZnSe ~ said
metho~ comp~ n~,:
A. he~tin~ a ZnSe substrate in a chemical vap~r
depo~ition chamber, in the a~senc~ of zinc me~al
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P~T~NT
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vapor, to a temperature ~ll~ficient to caus~ a
~ea~tio~ between the Zn~e and ~I~S;
. con~actin~ th~ ZnS~ with H,~S, in the a~ence o~
~inc met 1 vapor, ~ntil the ~S Ie~cts with thc
~ur~ace of the ZnSe; an~
C. introduclng zinc metal vapol into the chamber in
the presenc~ of H~S an~ depositing ~ layer of
ZnS onto the ZnSe by c~nen~ic2~ vapor depo~ n.
There 1~ al o pr~ide~ in ac~ordance with thiR
invention, a method o~ improvln~, the a~heren~ of a
c~emical vapoz ~eposited l~yer o~ ZnS ~o a Z~S~ ~ub~ te
which comprises, prior to ~epositi~g the ZnS onto th~ ZnSe
cor~tactine the ZnSe w~ H2S, in ~he ~l~sence of zin~:: metal
vapor~ at a tempera'cure an~ for a time ~uI'f$cient to c~use
~che H2S to react wit~ the ZnSe.
Further prot~rided in ~ccordance with thi~ invention
aI~e the prod~ct~ pro~ue~d by the ~bove p~oces~e3
In accordance wi~ch ~he pre3ent invent vn there i~
furthel~ proYided ~n infrared optical element co~pri~in~,
ZnSe ~ubstrate ha~il~g a ZnS layer deposited onto the
~ur~ce of sail ~ub~trate by chemi~al ~apo~ depo~ition,
where~n thc sur~ace o~ th~ ZnSe ~stra~ce ha~ been reac~ed
with H2S prior ~o the deposition of the ~nS where~y the
~urf~ce of s~ ubstrate is roughened.
Also pro~ided ~ccordin~ ~o the pre~ent in~rention i~
an impro~red infra~ed opticz} el~m~nt compr- sin~ a ZnSe
sub~tra~ce havin~ a ZnS layer dept)3i~ed on~co the su~face o~
said ~ubstria~ by c1Lemical vapor depo~i~cion~ the
impro~ nt compri~ing the sur~~ce o~ the ZnS2 subs~crate
h~vin8 bel!n reacted w~'ch ~2S prio~ ~o the deposit~on o~
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PAT~T 2 ~ ~ 7 6 ~ 7
the ~ laye~ where~y ~he s~fac~ o~ said ~b~tr~te i3
rouE~hqn~d .
~F.T~ n l)~SC~IPTI~:)N OF 'l~ Ih~It5n L lON
A~icle8 com:pri~inES a ZnSe ~ub~trate with a ZnS layer
o~ coating, ~n it (sc~metime~ called a "laminate" or
"sa~dwich") can be mac~e by chemlcal vapor tepo~itior~
techniques. In ~eneral, this techniq~e invol~ves forming
the ZnSe sub~trate ~y known chemical vapo~ ~lepo~ition
method3, ~haping and poli~hin~ the 2nSe ~ub~trate ~ if
desi2~ed, an~ thesl d~po~iting the layer o~ 2nS onto the
sur~ce of the ~nSe ~u~strate by chemical vapor
depo~îtion. The reYultinES "5andwich" i~ ~hen 8hape~ to a
des~ed configuration and poli~hed.
pre~ent in~ention provide~ a method of, ~in~
'che~c ZnSelZnS "~andwiche~" which impr~ves the adhe~ion
between the ZnSe ~nd ZnS re~lt~nK in a ~tron~ er boncl
between t~e layers and fewe~ in~tances of delamination
du~ing fa~ricat:ion b~ t~e final product. The inc~ased
adhesion ~etwe~n the ZnSe and ZnS layer i~ evitenced by
the fact t~at, wh~n tect~d ~or f~exur~l st~engt~, 'chc
"~andwiche~'l fractu~e a~os~ the bond rather than along :Lt
(a8 would, be the ca~e i~ adh~ion bel~ween the layer~ were
we~k)~ ~)ne of the primary ~rantage~ of the pre3ent
inven~ion is t~at t~i~ incre~se~l adhesion ~ achieved more
cons~t~n~ly th~n with known meth~ds, thus lncr~asin~ the
yield oiE u~able "~andwiche3".
Anothe~ advanJc~e of the prese~t in~Je~tion is th~t
~nifor~n growth ~f ~he ZnS laye~ on the ZnSo 3ub~tr~te is
mor~ ~on~isten'cly achieved ~haLn wi~h ~rlo~n met}~ts.
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~ he metho~ of the pre~nt invention ~ssentiall~
inv~lve~ contactin~ a ZnSe substrate ~w~i~h in mozt c~es
i~ pre-~ormed) with H~S at ~ te~pe~t~re an~ ~or a time
8U~flCient tD caw~e the H2S to react with the sur~ace of
the ZnSe s~b~rate. W~ile n~t li~iting thi~ in~en~ y
any p~rticular theory, it ~ ~elieve~ tha~ the reac~o~ of
the H~S and ZnSe .. 3'v~8 oxyeen and other cont ~nant~
from the ~urfac~ of the ZnSe ~ubst~ate ~nd con~rt~ 30m~
of the Zn~e to ~nS.
TSe t ,e ~tur~ employe~ in the method of thi~
in~ention is not critîca}, it being only neces~a~y.that
the temp~rature be high e~ough to p~rmit the H25 and Zn~e
to re~ct, i.e. ~out 20~~C, and low enough that the ZnSe
i~ not ad~ers~ly affectet.
~ t 18 e~ential to the p~e~en~ inven~ion that She H2S
be allowed to ~eact wi~h the ZnSe in the absence of zin&
~etal vapor. This can be acco~p~i~hed in two ways. The
fi~st i~ to phy~ically confine ~he zinc met~l vapo~ So
tha~ it can not contact the ~nSe or H~S. Thi5 allows the
Zn5e and HlS to seact at a temperatu~e hi~her tha~ ~he
~porizat~on te~perat~e of the zl~c metal. ~ho se~on~,
and pre~e~red, me~hod i te react the ZnSe and K2S at ~
te~pe~ature below t~e v~porization temperature o~ the zinc
~et~l) l.e. a~ a~o~t 419~C to about 685~G. Thi~ permit~
the 'l~andwl~" to be c~nveniently m~de by placln~ both the
~nSe ~nd zinc metal ~ut n~t it~ vapo~) in the ~ame
chemic~l vapor depo~ition cham~er and reacting the ZnBe
~nd H25 in the pre~ence of the zin~ metal ~b~t not ~y
~ub~tanti~l ~mo~nt o~ it.~ vapo~), On~e the ~S has
reacted su~iciently with the ZnSe, t~e chemica~ vap~r
depo~itlon of the ZnS may be be~n ~imply by inc~easin~
the temperatu~e o~ th~ chambe~ t~ vaporize the zine metal
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Th~ H,S m~t ~e pennitt~d to con~act ~he Zn~e for a
time ~u~ficient to per1nit it to react wi'ch the ZnSe. A~
will be apparent to one ~killed in the a~t ~ ttli3 ~eaction
tim~ c~n ~ary cunsid~rably depending upon the condition~
(e.~3., temperatu~e, pre~sure, H~S flow rate~ e~pl4yed in
the chemic~1 v~por dep~sition c}~m~e~. In g~rleral
minim~ reacti~n time o~ about Z ha~r~ wîll be re~u~ Tec~
One ~killed n the ~rt carl xea~ily deter~nine the necessary
re~ction tiDle un~er~ a particular ~et o~ condition~ ~ince
the reaction o~ the ZnSe sub tr~te and H2S i~ 41CC ~ ~nie~
by an ets~ g o~ roughening of the ~urface of the ZnSe
~ub~rate which can be cle~ected vi~ually. Th~ the
ZnSe ~ S beerl con~acted wlth the HsS lon~ en~u~h to det~.cc
etching or rough~ni~S o~ th~ ~ur~ace o~ the ZnSe thi~
provide~ an ind~c~tion that reaction has occur~cd. While
the 1~ may, of cour~e, co~tact the ~nSe for l~n~er than
the minimun time for the two to react w~thout a~ver~e
co~equence8, such lon~er co~tact times do not pro~ide any
particular bene~it.
In the c~. -rcial pr~du~tion of the Zn~e~ZnS
"s~n~wiche~" in accordance with ~he present ~nve~tion
teterminat~on of 'n~ r~ac~ion time is na~ ~ ~actor.
In a typical c~ ci31 p~cedur~ the H25 is allowed ka
eonta~t ~e ZnSe ~ub~t~ate while the temperature of the
~hemical ~por tepo~ition cham~e~ is ~ai~ed ~ro~ a~out
419~C (the mel~in~ poin~ of zinc metal) ~o ~he deposition
temperature of t~e ~inc metal (about 6~5~C). While ~hi~
time will be di~~e~e~t depPnding upon the par~icul~r
equlp~ent a~ p~cedures emp10yed, in a typi~l eomm~cl~l
p~oce~ it i~ ~o~e han ~ufficient to allow the ~S and
ZnSe to react~
The p~e8~nt ihve~tlon i9 illu~trat~d by ~h~ ~ollowin~
~x~mple.
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E~AMPLE
a ZnSo ~b3trat~s (which h~d been p~e-foa~71ed by a
corlY~nt~ al chemical Yapor ~epo~ition m~t~od, shap~d to a
de~ired c:onfigu*atiorl ~nd polished) wa~ plac~d in a
cor~vention~l vapor depo~l~cion ~h~r ~er alvn~S with zlne
~etal. Tl~c chr ber W~8 purnpe~ down to vacuum and heatecl
co ~b~t 300UC. A ~low ~E argon into th~ ~h~mber was
begun ~hile th~ temper~ture in the ch~ er w~ ~al~edl to
a~out 6~0~C. No ~inc Yapor wa~ present in ~h~ c~b~ A
~low o~ H~ lor~g wltl!~ ~rgon) into the ch~mb~r wa3 beE~un
and continued ~or abQut 12 hour~. No zinc vapo~ ~as
pre~en~ in the cha~ber ~uring thi~ ti~e. rrl~e ch~mbe~
tempe~atu~ a~ ~ais~t to ~bou~ 690~C and a ~low o~ zinç
me~l vap~ (along wl~ch argon) into ~che ch~ ~r w~ begwn
while the flow of H;~S contlnued. ~nS wa13 thçn depo~ited
on the ZrlSe ~ub~rste ~rl a conventian~ r.
Tl~e ~e~ulting 2nSe/ZnS "~andwich" had a strong bond
betw~en the ~nSo s,nd ZnS layer~ and wa~ fabricated and
poli~ed wlthout delalslination o~ th~ lay~r3.
_ _ _.. _ _ .. _ .. ... . ... , ... . _ .. .. . .. _ ... _ _ .. .......... .....
