CA1043895A - Method for producing semiconductor matrix of light-emitting elements - Google Patents

Abstract

ABSTRACT OF THE DISCLOSURE
Disclosure is made of a method for producing a semicon-ductor array of light-emitting elements, whereby a mask is first applied onto an n-layer of an epitaxial structure consisting of a substrate GaAs of the p+-type of conductivity with layers Ga1-xAlxAs of the p-type and Ga1-yAlyAs of the n-type applied successively onto it, which layers from a light-emitting p-n junction. The mask is produced by applying a photoresist layer onto the n-layer with subsequent exposure and etching. This is followed by introducing into the n-type layer, through said mask, an acceptor addition by means of ion implantation. After this the photoresist layer is removed, and a layer of SiO2 is applied onto the uncovered n-layer. After this diffusion heat treatment is carried out for a time and at a temperature sufficient to pro-duce in the n-layer regions of the p-type conductivity whose depth is at least equal to the thickness of the n-layer.

Description

LZ~3895 lZhe present in~ention rela~ei~ to manu~acturi~g semicon- -ductor devices and, more particularly, to methods for produc~
ing Zlemiconductor arrays o~ light-emitting elements- ~he de-mand for highly e~ective semicenductor array~ i~ due to the dsveZlopme~t of mean~Z for repre~0nting digital, alphabetic and s~mbolic information o~ Qingle-digit and multi;digit displa~s, illuminateZd board~ a~d i~cree~ Semiconductor matriceZ~ o~
light-emitting elements are indi:sputably adYan~ageou~ over ot~er types of matriceZs (li~uid cry~*al and pla~ma cell matri~
ces, etc.) becauæe they are unique i~ beirlg able to m~at the most _trigent requirement~, including higb ef~lcisncy, m~oha- -nicRl ~trength~ ~witchl~g speed~ reliability9 compatib~ t~
with silicon lnt~grated circuits, and a broad working tempara-ture range~
At present thsre i9 know~ a m~thod ~or pxoducing:a ~eZmi- -conductor arra~ o~ light-eZmi~bi~g elemen~s on the ba~i~ o~ an epitaxial ~b~ucture comprisi~g~a ~ub~trat~Z GaA~ o~ the ~+ `t~p~Z ';
o~ csnductivib~ onto which there i~ applied an n-*yp~ la~er G~Ae1 ~ Z_ ~ ~ or GaPZ~ b~ producing a mask ~ro~ a di- ~.
eleGitr~c coatinZg on the ~urfac~ o~ ~e ~ type lay~r, introduc- ~
*herctbrough i~to the ~-tgp0 la~er an acceptor zi~c mix*ure ;
~nd carr~ing ou~ di~usion burnin~ at a temperature and ~or a time that are su~fici~nt to produce local light-emitting p-n - .
jun~tion~. :
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In an array thu~ produced each light-emitting element haq a structure of the n+-type of conductivity whose radiation is directed through the highly doped upper n-type layer, which ~
resu7ts in substantial (theoretically, no less than 200 to 300 ~ :
percent) radiation power losses due to the absorption in free holes. The foregoing array producing method does not make it .
possible to produce light-emitting elements with small linear dimensions on the structures n GaAs - nGal xAlxAs due to rapid difusion of zinc close to the surface along the border between ~ :
GaL ~AlxAs and the dielectric coating, the difference between the linear dimensions of the light-emitting element and those of the original photomask i~ no less than 70 to 100 mu. .
` Likewise, this method does not make it possible to em- ~.
., ploy the most progressive and controllable methods of in~roducing ~
acceptor zinc mixture by ion implantation, as the zinc ion .
.. implantation leads to the formation in the active area of the ~ p-type of conductivity of additional radiation-less recombination .~ . ., centers which reduce the quantum efficiency of light-emitting : . .
elements.
: There is also known a method for producing a semi- :
conductor array of light~emitting elements using of the most ;' effective epitaxial ~tructure comprising a substrate GaAs of the p~-type of conductivity with successively applied onto it layers .;
9-~ Gal xAlxAs of the p-type and Gal yAlyAs of the n-type, which ,:: , ., " ......

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maXe up a light-emitting ju~ction, by means o~ etching the mesa-structures.
I ~his method also ~as a number of disad~antagss. :
.' In an array produced with the aid oY this method the p-n - junction area is not protected, ~his met~od doe~ not make it possible to have an enlarged contact area and produce me~a- :
-structure~ with reprod~cibls dimenions o~ less than 70 to .j 100 mu~ .
i In addition) the latter method ~as disad~antages inhsrent .~ in semiconductor instruments manufactured by usîng me~a tech-ni~ue in contrast ~o those manufactured by using pla~ar tech~
ni~u~
ha closest to the method of the p~esent invention is a .' :
I ~ m~thod ~or p~oduoi~ a semico~duotor arra~ o~ hb-emitting :
i elemen~s on the basis of an epitiaxial s~ructure comprising a sub trate Ga~s of the p~-type of conductivity ~ith succe~sl~el~
Q- J ~ x 1 9 ~ y As 1 ~ ~pplied onto it la~ers CQ~ X~S of the p-type a~d G~
}~ Or the n-typ~ which ~srm a liZg~t-emitting~p-~ ~u~ctio~ along which on the sur~aceZl o~ the n-t~pZe la~er there is pxoduced a~: ;
Z mask o~ Al203 t~rou~h which there is introducad in a sealed ampoule an a¢ceptor zi~c mi~tura ~rom the vapor phase and dif-~u~io~ bur~ing i~ carried out at a temperaturo (700C) An~ ~or ;: .
1~ ~ A bime (2 hour~) th~t are ~u~icie~t to produoe in t~e n-type Z~ layer areaZs of the p-~pe o~ conduc~ivit~ whose depth i9 eZ~Ua1 ::
taZ at lea3t the t~ickne~ of the n-la~er- :.
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q`his met~od makes it necessary to e~ploy the mask o~
~ such a di~lectric material (A1203) which is opaque ~or di~fu- -.~ sin~ zinc atoms. ~his method does not make it possible to ~ .
produce light-emitting elemen~s with small linear dimensions, . .
as, due to rapid zinc di-~fus on close to the surface alon~
the border between G~1 g l~9 and ~l203, the di~fsrence be~
ween the linear dimensions of the lig~-emitting element and . those of the original photomask is no less than 70 to 100 mu.
'!;' ~ccoraing to this method, the introduction of zinc atoms ~ and ~he dig~u3ion heat treatmen~ are carried out in a ~ealed ::~
i.~ ampoule, which, on the one hand~ considerably complicate~ the productio~ proces~ and7 on the other, makes it impossible to ~ :~
i~ reproduce~the rasulbs as to the depth o~ zi~c di~fu~io~ due to the fact that it is impossible to reproduc~ t~e degres o~
vaouum ~na the prsssure of arsenic ~apors i~ the ampoule-3~ ~ ~inall~, in a light-ffQfmitting elemfefnt matri~ manu~ac~urfeffd in ~laocorda~of3 with this method the light~emittin~ alement~ Aare . `
;~ sefpara*f~d ~rfcffm on~ anot;llf3fr by lo~ re~istance plG~1-gly~pa- .:
¢inæf~, which makes it impos~ible to produce enlargffffd obmifr :~ ¢ontafrfts to the lif~ht-emitting elemen~ or e~ect a~y inter-elef~trodf~ connections in the matrix~
;1 !I!hus, tih0 con~re~tional methods o:~ produoing a ~emicon- ~i. ~ duotor array o~ ght-emitting clement~ on the baf~is of f~
i~f3~cial ~tructure comprif~ g a substrata GaA~ o~ Ifihe p+-~lfi~pe o~ cfonductiYity with ~ucce~si~rfPfly applifeffd o~to it lagff2ffr~ o~

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Gal yAlyAs of the p-type and Gal yAlyAs of the n-type, ,which form a light-emitting p-n junction, does not make it possible to produce li~ht-emitting elements with linear dimenions of less than 70 to 100 mu. In addition, these methods necessitate the use of the dielectric coating A1203, whieh complicates the man ufacturing process: they also necessitate the introduction and diffusion of zinc in a sealed ampoule and do not make it possible :, . .
to produce enlarged phmic contact~ to light-emitting elements - -and effect any inter-element connections. ~ `
` It is the main object of the present invention to ~
, . , provide a method for producing a semiconductor array of light-emitting elements on the basis of an epitaxial strueture com- ~-prising a substrate GaAs of the p+-type of eonductivity with suceessively applied onto it layers of Gal xAlxAs of the p-type -~
and Gal yAlyAs of the n-type of conductivity, which form a light-emitting p-n junetion, whieh would make it possible to produce ` -.. . . . .
~ light-emitting elements with linear dimensions less than 70 to ;
. .
~' 100 mu.
.. ~ .
~, It is another object of the present invention to pro-vide a method for producing an array of light-emitting elements ~ whieh would dispense with technological complications resulting ;~s from the use of A1203 eoating.

~1 It is still another object of the pre~ent invention ;~:
, to provide a method whieh would make it unnecessary to carry out 'l diffusion burning in a sealed ampoule.
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It is yet another object of the present invention to provide a method for producing a semiconductor array of light- ~ .
emitting elements which would make it possible to produce en- ~ :
larged ohmic contacts to the light-emitting elements and make - :
for any type of inter-element connections. ::-In accordance with one embodiment, a method for pro- .. ~-~
ducing a semiconductor array of light-emitting elements using an ~.
epitaxial structure consisting of a substrate GaAs of the p -type .~
of conductivity with layers of Gal xAlxAs of the p-type and ~ :
Gal yAlyAs of the n-type of conductivity applied successively ~. :
onto it, which layers form a light-emitting p-n junction, whereby at first a mask is produced on said n-type layer of said epitaxial ~
structure, which mask protects portions of said n-type layer . :;
whlch correspond to a required configuration and size of said . : .
i,~; : light-emitting elements, by applying onto said layer a photoresist .i : '~ ' .
layer with subsequent exposure and etching~ which is followed by introducing an acceptor addition through said mask into said n- :
type layer by means of ion implantation, removing said photoresist : .
layer; applylnq onto the uncovered n-type layer a layer of SiO2, which is followed by diffusion firing carried out for a time and at a temperature suEficient to produce in the n-type Layer, under -~
portions that are not protected by said mask, p-type areas whose depth is e~ual to at least the thickness of said n-type layer. : :.
The proposed method makes it possible to produce an : s array of light-emitting elements on the basis of an epitaxial ; : :
structure comprising a substrate GaAs of the p~-type of conducti- ~:3 wi~h ~uccesslv~lv ~p~ d onto i= la~ers of Ga~ ~lxAs : `:

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GQI Y~Y A5 o~ the p-type and Ca~ y~o~ the n-t~pe, which form a light-emitting p-n junction with minimum linear dimensions of the elements in the order o~ 10 m~; the proposed method also makes it possible to carr~ out di~usio~ ~iring under a di- .
electric SiO2 coating in a~ open-type furnace, produca snlarged ohmic contacts to the light-emitting elements a~d make any :~ :
inter-eleme~t connections, as o~ the surface o~ the matri~ ; .
there is a solid dielectric la~er. It should al~o be pointed oub t~at ion implantation is utilized to its full ad~antage in the proposed method without causing any undesired e~fect~ like the;~ormation o~ additional radiationless recombinatio~ cen-. .
ters, because implantation o~ the acceptor addition is per~r-med in tho5e areas o~ the matrIx tha~ ar~ not~ligh~-~mi~ting. .
9th~r objects and advanta~e~;o~ the pre~ent invenbion ill beoome~more app ~ e~t ~rom the ~ollowing detailed~descrip~
d~ : bion o~a~pre~orred embodiment thereo~ ~aken in oonjunobion -~
wit~tha aacompanying drawings9 wherein:
ig.1 i~ a lo~gibudi~al ~eotio~ of an original epitaxial '~
:structuro~
ig.2 ~how~ the ~ame:a~ber bhe application o~ a ~a~k; ~ ;~
.3 ~how~ the ~ ~e:aft~r the applioation o~ a dielectria coating;
Fig.4 i~a lo~gi~udinal sectio~ o~ a semiconductor m~rix ~:
: o~ ht-omittinæ olemenb~
R~ rrine now~to the attached drawings, the epi~axial .
tructurs s~ow~ i~ Fig.1 compri3e~ a subs~rate 1 o~ ~a~s o~ :
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.. ~ -' . p+-type conductivit~ with ~uccessively applied onto it lilyers .
.~ . ~ s G~l Aly A~
;i ~ ~ 2 and ~, C. ~ o~ the p-type and-Ga1 Y~ l~A3 o* the n-type, :1 respectively9 w~ich form a light-emitting p-n junction 4.
, Unlike the epitaxial ~tructure of ~ig.1, the ~piti~xial :
~tructure shown i~ Fig~2 co~prise~ a photoreslst mask 5 ap- .;.
plied onto the sur~ace o~ the layer 3~
e arrow~ indicate an ion bei~m o~ an acceptor addition :-.~ which may be zinc, bsryllium or cadmi ~. Portion~ 7 located ~s .`.~ in the n-type layer ~ under windows i~ the mask 5 includ~ i~n implan~ed accepbor addition.
i: Fi&.3 sho~ the ~ame struoture a~ter removing the photo-re~ist mask 5 and applyi~g onto the~ ~r 3:a dié1ectric Si~ :
: coati~g 8.
In contrast to ~ig.3, Fig.4 show~ a semioonduGtor arri~y ~ o~:lig~t-emitting element~ 9 whio~ i~cludes~ in~tead~or~the :.J~ por~ion~ 7, ar~a~ 10 of~bh~ p-type o~ conduc~iv~t~ produced a~ a re3ult o~ di*~u~ion burning, t~e dot~ed line~:indioating ~
: th~ lower limib o~ ~ho penetra~ion of an acoeptor ~dditio~ .~ .
ir~u~ing ~rom the portion~ 7. ~h~ depth o~ thi~ penatra~io~ ~ ::
in exce~s o~ the ~hickness o~ the n-la~er 3. '; .
~ , .
he propo~ed~method i8 ~s~ iall~ carri0d out a~ ~ol- .. .
low On the original epit~ial ~ruckura s~ow~ in Fig.1 .`~
thero is applied a p~toresi~t la~er. !rhi~ layer i~ u~d ~o eOrm9 b~ means of e~po~ure t~xough a photon~k~ a~d subsequenb op~ation~ o* hardeni~ d ebchi~g, the ~sk 5 ~Fig,2) w~ich pro~ec~s area~ ~cor2~e~po~ g to a presslected con:~iguratio~

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and size of the light-emitting elements. The structure iq then bombaxded by an ion bea~ 6 o~ an acceptor addition, which process is carried out on an ion beam installatiQn, the irra-: diation dose being in the order of 103 to 104 microcoulombs per cm 2~ ~his results in t~e ~ormation o~ the portions 7 in the n-type la~er ~, under wi~dows in the masX 5, w~ich por-tion~ 7 contain implanted acceptor addition. A~t,3r the bom-bartlment the photoresist mask 5 is remeved by means o~ chemi-cal or ion-plasm etcbing, which is followed b~ applying onto the uncovered n-type layer 3, in any known manner, t~e di-electric l~yer 8 (Fig~3) o~ Si ~ . A~ter this the ~bructure is ~dif~u~ion-burned i~ an open ~ur~ace in a hydrogen flow at a . .
temperature o* 75~ to 900G during 4 to 0~5 hours3 as a re;
eult, there are ~ormed in t~e layer ~ ths areas 10 of th~a ~.
p-type o~ con~ucti~i~y, whost3 depth is equal to or somewhat~
greabetr t~ian the thiokne,~s of the n-bype la~er 3 t~ locallze the light-~mitti~g eleme~ts 9 , ~
~ he i~ve~tion will be better understood ~rom the Pollow-:;
~ g speci~ic example o~ a~ embodimenit thereo~ .
.. . .
Example ~ ho i~1tial epita~ial 3tructure compriæe,s the sub,3trat~s 1 . .;
¦ (~ig.1) &a~ o~ t~e P~ pe co~duoti~ity with.~ucoes,slvel~
A applied o~bo ib the la~er3 Z a~d 3 oX ~a~ ~o o~. ~he p-type ;
and ~ o~ the n-type) re~pe¢ti~sly9 wh~ch ~o~m t~3 ~ -:
f~

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p-n junction 4. The function of the substrate 1 GaAs of the p~-type of conductivity is performed by GaAs plates that are zinc-alloyed to a concentration of t6+8)~1018 cm 3, oriented in the plane (100) and opticall polished on both sides. The layers 2 and 3 Gal x~lxAs of the p-type and Gal yAlyAs of the --n-type, respectively, are applied by means of liquid-phase epitaxy from an arsenic-saturated gallium melt at a temperature of 950C from a GaAs feeder. The p-type layer 2 is zinc-alloyed to a concentration of 5~101 cm ~ The aluminum content (referred to as "x" in the formula of the compound) amounts to 35 at .%. The n-type layer 3 is produced by counteralloying the same melt with a tellurium addition in an amount sufficient ~1 to obtain an electron concentration of (1+2).1018cm 3. The ~ aluminum content in the n-type layer 3 (referred to as "y" in ¦ the formula of the compound) amounts to 47 to 50 at .% due to l' additionally alloying thP same melt with aluminum. The thick~
. ~ . .
ness of the layers 2 and 3 amounts to 20 and 3+4 mu, respectively~ ' A positive photoresii~t layer is applied onto the initial ';
~1 epitaxial~structure, which layer is based upon naphthoquinone - ;;
diazide having a vi aosity of 8 cs and a thickness of 4 to 5 mu.
This is followed by exposure through a photomaak having dark areas with dimensionæ of 200 x 40 mu2, and then by hardening and etching with a polish etchant containing 1 part of deionized ;
water, 1 part o~ hydrogen peroxide, and 3 parts of ,,~ ~ , , .
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~ 9 sulfuric acid. ~hus the photore~ist ma~k 5 (~ig.2) is produced which protect~ the initial structure portions ha~ing the size of 200 x 40 mu ~
~ e structure is then bombarded with ions of an acceptor zinc addition ~ mean~ o~ an ion-bea~ i~stallation. In the cour~ of bombardment the energ~ o~ the Yinc atoms amounts to 40 keV~ the irradiation do~e amounts to 3~103 microcoulombs per cm 2. ~he bombardme~t is carried out in vacuum at 10 5 ~
torrs. `
~ he bombardment results in the ~ormation o* the portions 7 containi~g implanted ~inc addition ~nd ha~ing a depth of ;-0~2 mu.
A*ter t~e bombardment the pho-tor0~ist ma~k 5 is removed ~ `~
b~ c~emic~l etching ~n a- ~ix*ur~ o~ dioxan (1 part) and di~
mebh~l ~o~mamide (1 part?~heated to reach -the boiling polnt.
On t~e unco~ered n~type layer 3 ther~ i~ applied the di-electrlc layer 8 (Figc3) o~ SiO2 with a thicknss~ of 0.34 mu, the applioation being e~fected b~ means o~ pla~ma ~puttering ; of ~ quartz targetO
~ he thick~es~ o~ the dielectric layer 8 i~ ~electad to ; ` en~ura transpareno~ o~ the matri~ o~ the lumi~ascence ~ave leng~h.
A~ter thi~ the ~tr~cture is subjacted to di~fu~io~ ~lring in an ope~ ~ur~acs in a 4~droge~ ~low at a temperaturs of 8000 durlng 1.5 hour~ o. under tha Gonditio~ ~hat a~e ;;
oo~duoive ~o the forma~io~ ~L~ t~e layer 3 o~ ~he area~ 10 9 ;~

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(~ig.~ o~ the p-type of conductivity w~ich localize tha ligb~--emitti~g elements 9. -Then contact windows havi~g the ~ize o~ 120 ~ 10 mu2 are ~ photolit~ographic~lly produced in the di~lectxic la~er 8, in : the centers o~ the light-emitting elements 9; this i~ ~ollowed by applying a two-layer obmic contact by means o~ thermal sputtering to the layer 2 containin~ 88 perce~t of Au and 12 per¢ent o~ ~e and having a thicknesæ o~ 0.3 mu and to a 0.2 mu~
-thick la~er o~ nickel, and the common ohmic contact con~aining~
99 percen~ o~ A~ and 1 percent of Zn is applied to Ga~ o~ the .
p+-tgp0 of conductivity.
~*ter photelithograp~y contact $trips wibh a size o~ - -130 x 15 mu are le~t in t~e upper two-layer contact coating, :~
a~d ~he upp~r and lower 8bmic contact~ are fused-i~ in R flow ~: o~ h~drogen.
In order to produce an enlarged o~mic co~tact, there i~ ;
J~ depo~it~d on t~ structure o~ each light-emitting eleme~t 9 having a ~ize conv~ni~n~ Yor ultra~onic welding o~ aluml~um wire l~ad~ a~ ~luminum la~er; photolithograpb~ i~ then car-ried out with the u9e of photoma~k to en~urc a required sizo : ~nd location o~ bhe enlarged obmi~ con~ac~s.
~ he result o~ the process i~ a ~nish~d array o~ seml-"1 co~duct~r light-e~ bting ~leme~t~ w~ich meets all the re~uir~-~ msn~ im~osed upon a monolibhic pl~ex in~egra~8d circuitO

.~ .~, .
. ................................................ .

Claims

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:-

1. A method for producing a semiconductor array of light-emitting elements using an epitaxial structure consisting of a substrate GaAs of the p+-type of conductivity with layers of Ga1-xAlxAs of the p-type and Ga1-yAlyAs of the n-type of conducti-vity applied successively onto it, which layers form a light-emitting p-n junction, whereby at first a mask is produced on said n-type layer of said epitaxial structure, which mask protects portions of said n-type layer which correspond to a required con-figuration and size of said light-emitting elements, by applying onto said layer a photoresist layer with subsequent exposure and etching; which is followed by introducing an acceptor addition through said mask into said n-type layer by means of ion implantation; removing said photoresist layer; applying onto the uncovered n-type layer a layer of SiO2; which is followed by diffusion firing carried out for a time and at a temperature sufficient to produce in the n-type layer, under portions that are not protected by said mask, p-type areas whose depth is equal to at least the thickness of said n-type layer.