262 Integrated circuits0
77fj~j~
Fi. 4 Mde ntgatd-icutfariaio qupmn. a Dffsonfunce b)Atophrc-resrecemca 8J
deoito (V) ()Lo-rssr CD d)Vcumeaprto.(a o ipane.(I onatmakalge.Wg1Dr.
stN-nwae mahn.(0 lsa th
th pialltorphctcnqus scpal fd- rpcly.Aiorpi thn tksavJtg.f 1
finig 1lim(4 iO in)gemeties Elctrn- eren rectiitis o th diferet cystl pant dj
Fing. surac. Traitonaly integrated-circuit fabricatineupet-a Dfuiong deviaces in) etcoshed ic-regiosuore onchemia .
stiponhas employned wet chesmcal prchesse toecYaes
lines opiand featuores.phese techniques, uilizepathe ch em- Asowithly diffsoiowtcheia etching advntae,.f6" iske
icalpractivity wodeitane featchssusantioflthesmatleria tohbe toin eterms ofsie ofde ethelies orafeaturesutO be fo*
etched. Tedfeecbewethethrtofhe (of lhessitan 3-4iffrne.m or 1.2-1.6 etching .),'
maskngmterncialvad thaoghlthgay of subtrteisrelatethe mores impothrtanote apecmts thraticfthce ofeatu
to this cemistry.d Thet chemical ethrgofcryss talliet ires,.hi egtt-it rto.Dnepci
materas can beauei.ther istropniue oriliisotropic.e In small deiceusize, requr cheighalpetcthrang is
isotropicetcingt wthea etchant attck the catrysal Dobntry plasmaes e ftching recives ionfeatching to be d
ecequll inhal diffrenctions twithouth regadtoh rthe diffeeth mligae advlsstance tecniue beo .216 04ing ,
desitroicesoatomsindh strctural fatureks inthe difrenta ovrcolamae theimits ofachiemical etching, OI -
directions in a crystal. Amorphous materials etch iso- etching (Fig. 14h), the most advanced of thee.
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