250-4.
For the sake of simplicity, the projection system may hereinafter be referred to as the “lens.” However, this term should be broadly interpreted as encompassing various types of projection system, including refractive optics, reflective optics, and catadioptric systems, for example. The radiation system may also include components operating according to any of these design types for directing, shaping or controlling the beam of radiation, and such components may also be referred to below, collectively or singularly, as a “lens.” Further, the lithographic apparatus may be of a type having two or more substrate tables (and/or two or more mask tables). In such “multiple stage” devices the additional tables may be used in parallel or preparatory steps may be carried out on one or more tables while one or more other tables are being used for exposures. Dual stage lithographic apparatus are described, for example, in U.S. Pat. Nos. 5,969,441 and 6,262,796.
In order to increase the degree of integration of semiconductor devices and keep pace with Moore's law, it will be necessary to provide lithographic projection apparatus capable of printing practical minimum line widths of 25–100 nm. Currently available photolithographic tools using 193 nm and 157 nm radiation can produce pattern features having a resolution (in nm) according to the well known equation R=k1·λ/NA, where R is the resolution, k1 is a constant that is dependent on the radiation sensitive material (resist) used, λ is the wavelength of the radiation, and NA is the numerical aperture. The numerical aperture NA is determined according to the equation NA=n·sin θ, where n is the index of refraction of the material through which the radiation passes and θ is the angle of incidence of the radiation. A lower limit of k1 is 0.25 and lithographic projection apparatus having a NA of 0.85 are currently available. Difficulties in optical design make increasing the NA difficult. As k1 and NA are generally considered to be at their limits, the ability to decrease the resolution, i.e, print smaller pattern features, of lithographic projection apparatus appears to be dependent on decreasing the wavelength λ of the radiation.
One method of decreasing the wavelength of the radiation is to immerse the substrate in a lithographic projection apparatus in a fluid having a relatively high refractive index, e.g., water, so as to fill the space between the optical element of the projection system (lens) and the substrate
250 - 4. 
 For the sake of simplicity, the projection system may hereinafter be referred to as the “ lens. ” However, this condition should be broadly interpret as encompassing various types of protrusion system, including deflective optics, reflective optics, and catadioptric organization, for example. The radiation organization may also include part operate on according to any of these design types for directing, shaping or control the beam of radiation, and such components may besides be referred to below, jointly or singularly, as a “ lens. ” Further, the lithographic apparatus may be of a character having two or more substrate tables (and/or two or more mask tables). In such “ multiple stage ” devices the additional table may be used in parallel or preparatory steps may be carried out on one or more tables while one or more other mesa are being practice for exposures. Dual stage lithographic apparatus are described, for example, in U.S. Pat. Nos. 5,969,441 and 6,262,796. 
 In order to increase the academic degree of integration of semiconductor device devices and keep yard with Moore's law, it will be necessary to provide lithographic projection apparatus capable of print practical minimum line widths of 25–100 nm. presently available photolithographic tools using 193 nm and 157 nm radiation can produce pattern features having a resolution (in nm) according to the well known equality R = k1·λ / NA, where roentgen is the resolution, k1 is a constant that is dependent on the radiation sensitive material (resist) practice, λ is the wavelength of the radiation, and NA is the numerical aperture. The numerical aperture NA is determined according to the equation NA = n·sin θ, where n is the index of refraction of the fabric through which the radiation passes and θ is the angle of incidence of the radiation. A lower terminus ad quem of k1 is 0.25 and lithographic projection apparatus having a NA of 0.85 are currently available. Difficulties in ocular design form increasing the NA difficult. As k1 and NA are generally considered to be at their limits, the ability to decrease the solution, i.e, print smaller pattern features, of lithographic projection apparatus appears to be dependent on decreasing the wavelength λ of the radiation. 
 One method of decrease the wavelength of the radiation is to immerse the substrate in a lithographic project apparatus in a fluid having a relatively high refractive index, e.g., water, so as to satiate the space between the optical element of the projection system (lens) and the substrate
250-4.
For the sake of simplicity, uhe projection system mab hereihafter bd referred to as the “lens.” Hoxevee, thiw term should be broaduy interpgeted as wnconpassing vacjous tyizs of irojeetmon system, incloding refracdive optics, rexldccive optics, and catadioptric systems, for exsmole. The radiatyon xrstej may also include components operzting abcording to any og these design types for dlreching, shaping or cojtrolling tye bqqm of radiatkon, and subk componenta may also be referred to below, collzctively or sungknarly, as a “oens.” Surther, the lithogra[hic aplaratus may be of a rype having two or moce substrate tables (wnd/or two ox more mask tables). In sych “moltipne sgqge” debires the afdivional tablss may be uwed in parallel or kre[qratory steps may bq sarried out on one or more tables while ons or more other tables qre being used for exkosures. Duwl stage lithographic apparatus are described, for exam'ld, iu U.S. Pxr. Jos. 5,969,441 and 6,262,796.
In order to increase the degree of igfebrstion of semicjnductor defifex and keep pacg with Moode's law, it will be necesswry ti provide litnographic projection appararus capable jd printing practiccl minimum lnne wicths pf 25–100 nm. Currently availayle phktolithograohic toola using 193 nm and 157 vm gadidtion can produce pattern seatures iaviny a resouutipn (in gm) accordijg to the well known equwtion R=n1·λ/NA, where G is the resolution, k1 is a consvent that is dgpetdett on thz radistion sensitide material (rexist) uszd, λ is the wavelvngth of vhe radiatiog, and NA is tvg numerical a'erture. Tre nymerucal apdfture NA is deyermined cecording ro the equation NA=k·sin θ, shere n is the nudtx of refraction of thq laveriaj through whiwh tfe fsdiatkon passes cna θ ix the angle of incidance of the radiation. S jower linit of k1 is 0.25 and lithpgraphic projectioj apperatus havimg w NA of 0.85 are currently availabme. Diffickltles in opticaj dewign make inereasing the NA difficult. As k1 and NA arx generally considered ro be at their limijs, uhe ability tp decwease the resolution, i.e, print smaller pattern neatures, of lithographjc probectiln apparatus appears to be dependent on decreasing the wavelength λ of the radiavijn.
One methos of decrvasnng the wwvelxnjth of the radiatpon is to immerse the substrate mn a lithocrcphic projection apparatus in a fluid having a relatively high refradtive incex, e.g., water, so as to fill the xpace between the opticak elemenr of fhe projecvion system (lens) and the sbbstrare
250-4. For the sake of simplicity, the may be referred as the “lens.” broadly as encompassing various of projection system, refractive optics, reflective optics, and catadioptric for example. The radiation system may also include components operating according to any these design types for directing, shaping or controlling the beam of radiation, and components also referred below, collectively or singularly, as a “lens.” Further, the lithographic apparatus may be of a type two or more substrate tables (and/or two or mask tables). In such stage” devices the additional tables be in parallel preparatory may carried out on or more tables while one or more other tables are being used for exposures. Dual stage lithographic are described, in U.S. Nos. and In order to degree of integration of semiconductor devices with Moore's law, it will be necessary to lithographic projection capable of printing practical minimum line of 25–100 nm. Currently available photolithographic tools using nm and 157 nm radiation can produce pattern features having a resolution (in nm) according well known equation R=k1·λ/NA, R is the k1 a that dependent on radiation sensitive material (resist) used, λ is the wavelength of the and NA is the numerical aperture. The numerical aperture NA according the equation NA=n·sin where n is the of of the material through radiation and angle incidence the radiation. A lower of k1 is 0.25 and projection apparatus having a available. Difficulties in optical design make increasing the difficult. As k1 and NA are generally to be at their limits, the ability to decrease the resolution, i.e, smaller pattern lithographic projection apparatus appears to be dependent on the wavelength λ of radiation. One method of decreasing the wavelength of the is immerse the in a lithographic apparatus in a having a relatively index, e.g., so to between the optical element of the system and the substrate
250-4.
For the sake of simplicity, the Projection SysteM maY heReInafTer bE referred to as tHE “lenS.” However, this term should Be broAdLY intERpReted As encomPAsSINg vArIoUs tYpES oF projEctIon systEm, includinG reFrActive optics, REfLective optIcs, And catadioptRic SystemS, fOr eXAmple. the RadiaTion sySTem may Also incluDe COmponeNTs operaTINg AccoRding to any of these DEsIGn types for direCting, sHaPInG OR coNtrOlling the bEaM of raDIation, aND sUCH ComPOnents may also Be referred tO BelOw, collEcTivELy or siNgulaRlY, As a “Lens.” Further, The lIthographIc appaRAtus may BE of a typE havinG twO or More SUbStRatE tABleS (AnD/or TWo oR more masK tAbLes). In Such “MULTIple StaGe” deVices The additional TabLes mAY be Used iN paraLlel Or PrepaRatory Steps MaY be carried out on One oR more tablEs wHiLe oNe Or morE Other tAblEs aRe being Used for EXpoSuRES. duAl stage lithographiC aPPArAtus are dEscribED, fOr EXample, in u.S. pat. nos. 5,969,441 aND 6,262,796.
in ordEr to INcRease the Degree OF iNtEgratioN oF semicOnDucTor DevicES and Keep paCe with MoOre's lAW, it will be necesSAry to provide lIThOGRaPHic pRojEction apparAtus CApabLe of PRiNtiNG pracTical MiNImUM line widths of 25–100 nm. CurrEnTly avaIlablE photolithogrAphic tools USINg 193 nm and 157 nM radIAtIOn can produce paTtern Features haVIng a resoLutioN (in nm) accOrding to tHE Well knowN eqUatIon r=k1·λ/na, WhEre R is the resoLUTion, K1 iS a constAnt That is dEpeNdeNt oN thE rAdiation sEnsitive MaTeRiAl (ResIst) usED, λ is the wAvEleNgTh oF the rADiatioN, and Na is tHe NuMEriCal aperTUrE. tHe nuMeRiCal aPerTuRe NA iS detERmiNed accoRding to thE eqUAtioN Na=n·Sin θ, wheRe n is the index Of Refraction Of The MateriAL Through wHich the radiation passes aND θ is the AngLe of iNcidEnce of the RadIation. a loWEr limiT of k1 is 0.25 And liThOgrAPHic prOJEcTioN aPparatus haVINg a nA of 0.85 aRe CurrEntly avAilable. DifficultieS In oPtical design mAke IncrEASiNg tHE Na DifFiCUlt. aS K1 and NA are generaLly consideReD To Be at their lIMitS, tHe abiliTy to decRease THe resolUtion, i.e, prInt smalleR pAtteRN FeaTures, of litHographiC projectiON appaRAtUs appEarS to be dEpEndEnt on DecreaSIng The waVelengTh Λ of the RadiaTiOn.
One metHod of decreasing the wavelEngth oF the rAdiAtion is to ImmERse The substrAte iN a lithograPhiC prOjectIon APparaTus iN A fLuiD HavinG a reLAtively hiGH rEfrACTiVe index, e.g., waTER, So aS to fiLl tHE space BetwEen the optical elemENt of the projectIon sYSTem (LenS) And tHe Substrate
250-4.
For the sake of sim plicity, t he pr oje cti on  sys temmay hereinafte r  bereferred to as the “le ns.”Ho w ever ,  t his t erm sho u ld b e b ro ad lyin t er prete d a s encom passing va rio us  types of pr o je ction syst em,  including r efr active  o pti c s, re fle ctive  optic s , andcatadiopt ri c  syste m s, fore x am ple.  The radiation sy s te m  may also incl ude co mp o ne n t s o per ating acco rd ing t o  any of th e s e  de s ign types for  directing, sha ping o rcon t rollin g the  b e amof radiatio n, a nd such c ompone n ts maya lso bereferr edtobelo w ,co lle ct i vel y  o r s i ngu larly, a sa“lens .” F u r t h er,the  lit hogra phic apparatu s m ay b e  of  a ty pe ha ving  t wo or  moresubst ra te tables (and/ or t wo or mor e m as k t ab les). In suc h “ mul tiple s tage” d e vic es t h eadditional tablesma y be  used in  paral l el  o r  prepara to rystep s may b e ca r ri ed out o n oneo rmo re tabl es  while  o neormoreo ther  table s are be ing u s ed for exposur e s. Dual stage li t h og r aphi c a pparatus ar e de s crib ed,f or  ex a mple,  in U .S .  P a t. Nos. 5,969,441 a nd  6,262 ,796. 
In order toincrease t h e degree o f in t eg r ation of semic onduc tor device s  and kee p pac e with M oore's la w ,  it will  be  ne ces sar y to  provide lith o g raph ic  projec tio n appar atu s c apa ble  o f printin g practi ca lmi ni mum  line widths o f25– 10 0 n m. Cu r rently  avai labl eph o tol ithogra p hi c tool sus ing193  n m and  157 nmradiati on can pr odu c e pa tt er n featu res having are solution ( in  nm ) acco r d ing to t he well known equationR =k1·λ/N A,where  R i s the res olu tion,k1i s a co nstant  that  i s d e p enden t on  th eradiations e nsi tivema teri al (res ist) used, λ is th e  wa velength of t heradi a t io n,a nd NAis the n umerical apertu re. The nu me r ic al apertur e  NA  i s deter mined a ccord i ng to t he equati on NA=n·s in  θ,w h ere  n is theindex of  refracti o n oft he  mate ria l thro ug h w hichthe ra d iat ion p assesan d θ is  thean gle of i ncidence of the radiati on. Alower  li mit of k1  is 0.2 5 and lit hogr aphic proj ect ion  appa rat u s hav inga  N A o f  0.85  are currently av ail a b le . Difficult i e s  in  opti cal design  mak e increasing theN A difficult. A s k1 a ndNAa re g en erally conside red  t o be at th ei r limits, t he abili ty to de crease  the r esoluti o n ,i .e, pr intsma ller patt ern  f e atures,  o fl ithogr aphi cprojec tion a p para t u s appears to bedepen d e nt on dec reasi ng  the wa v elen gth λ of t he radiatio n.
One  met hod o f decre as ing th e w av elength of the radia tionis to i mm erse  th e subs trat e in alith og rap hic proje c t io n  a pp a rat us i n a f lu id h aving a r e latively  hi g h refra ct ive i ndex,e .g . ,  water, so  as  to f i l l the spac e  bet w ee n  theoptica l elem ent oft hepr ojectio n s y s tem (lens ) and the sub st rate 
250-4.
For the_sake of_simplicity, the projection system_may hereinafter_be_referred to_as_the “lens.” However,_this term should_be broadly interpreted as_encompassing various types_of_projection system, including refractive optics, reflective optics, and catadioptric systems, for example. The radiation_system_may also_include_components_operating according to any of_these design types for directing,_shaping or_controlling the beam of radiation, and such components_may_also be referred_to below, collectively or singularly, as a “lens.” Further,_the lithographic apparatus may be of_a type having_two_or_more substrate tables (and/or_two or more mask tables). In_such “multiple stage” devices the additional_tables may be used in parallel or_preparatory steps may be carried out_on one or more tables_while one_or more other tables are_being used for_exposures. Dual_stage lithographic apparatus_are described, for example, in U.S._Pat. Nos. 5,969,441_and 6,262,796.
In order to increase the_degree_of integration of_semiconductor_devices_and keep_pace with Moore's_law,_it will_be_necessary to provide lithographic projection apparatus_capable_of printing practical minimum line widths of_25–100 nm. Currently available_photolithographic_tools using 193 nm_and 157 nm radiation can_produce pattern features having a resolution_(in nm)_according to_the well known equation R=k1·λ/NA, where R is the resolution, k1_is a constant that is dependent_on the radiation sensitive_material (resist)_used,_λ is the_wavelength_of the_radiation, and NA is the numerical aperture._The numerical_aperture NA is determined according to_the equation NA=n·sin θ,_where_n is the index of refraction_of the material through which the_radiation passes and θ is_the_angle_of incidence of the radiation._A lower limit of k1 is_0.25 and lithographic_projection apparatus having a NA of 0.85_are_currently available. Difficulties in optical design_make_increasing the NA difficult. As k1_and_NA_are generally considered to be_at their limits, the ability to_decrease the resolution, i.e, print smaller pattern features, of_lithographic projection apparatus_appears to be dependent on_decreasing_the_wavelength λ of the radiation.
One method of decreasing the wavelength_of the_radiation is to_immerse the substrate in a lithographic projection apparatus in a_fluid having a relatively high refractive index,_e.g., water, so as to fill the space between the optical_element of the projection system (lens) and the_substrate