 by enlarging the surface areas of the ICs. This means that the, already relatively high, NA of the projection lens system must be further increased and, for a stepping apparatus, the image field of this system must also be further increased. This is practically impossible.
It has therefore been proposed to change from a stepping apparatus to a step-and-scan apparatus. In such an apparatus, an annular segment-shaped sub-area of the mask pattern and hence also such a sub-area of an IC area of the substrate is illuminated, and the mask pattern and the substrate are moved synchronously through the illumination beam, taking the magnification of the projection system into account. A subsequent annular segment-shaped sub-area of the mask pattern is then imaged each time on a corresponding sub-area of the relevant IC area on the substrate. After the entire mask pattern has been imaged on an IC area in this way, the substrate holder performs a stepping movement, i.e. the beginning of a subsequent IC area is introduced into the projection beam and the mask is set to its initial position, whereafter said subsequent IC area is scan-illuminated via the mask pattern. This scan-imaging method may be used to great advantage in a lithographic apparatus in which EUV radiation is used as projection radiation.
The embodiment of the projection system described in U.S. Pat. No. 5,815,310, intended for use with EUV radiation having a wavelength of 13 nm, has an NA of 0.25 at the image side. The annular image field has an inner radius of 29 mm and an outer radius of 31 mm and a length of 30 mm. The resolution of the system is 30 nm and the aberrations and distortions are sufficiently small to form a good image of a transmission mask pattern on an IC area of a substrate by way of a scanning process. This projection system comprises six imaging mirrors, and an intermediate image is formed between the third and the fourth mirror. The mask is situated at one geometric end of the projection system, and the substrate is situated at the other geometric end of this system.
When such a mirror system is used in a lithographic projection apparatus, the small quantity of radiation incident on the substrate presents a problem. This problem is caused by the fact that the mirrors are considerably less than 100% reflective. Each of these mirrors comprises a multilayer structure whose composition is optimized for the relevant wavelength. Examples of such multilayer structures are described in U.S. Pat. No. 5,
by enlarging the surface areas of the ICs. This mean that the, already relatively eminent, NA of the projection lens system must be further increase and, for a stepping apparatus, the image field of this organization must besides be further increased. This is practically impossible. 
 It has therefore been proposed to deepen from a stepping apparatus to a step - and - scan apparatus. In such an apparatus, an annular segment - shape bomber - area of the mask pattern and hence also such a bomber - area of an IC area of the substrate is illuminated, and the masquerade pattern and the substrate are moved synchronously through the light beam, remove the magnification of the projection system into account. A subsequent annular segment - shape sub - area of the mask pattern is then imaged each time on a corresponding sub - area of the relevant IC area on the substrate. After the entire mask pattern has been imaged on an IC area in this way, the substrate holder performs a pace movement, i.e. the beginning of a subsequent IC area is introduce into the expulsion beam and the mask is set to its initial stead, whereafter said subsequent IC area is scan - illuminated via the mask radiation pattern. This scan - imaging method may be used to great advantage in a lithographic apparatus in which EUV radiation is used as projection radiotherapy. 
 The embodiment of the projection system described in U.S. Pat. nobelium. 5,815,310, intended for manipulation with EUV radiation sickness having a wavelength of 13 nm, has an NA of 0.25 at the image slope. The annular image field has an inside radius of 29 millimeter and an outer radius of 31 mm and a length of 30 mm. The resoluteness of the system is 30 nm and the aberrations and distortion are sufficiently small to shape a good double of a transmission masquerade pattern on an IC area of a substrate by way of a scanning summons. This projection organization comprises six imaging mirrors, and an intermediate image is formed between the third and the fourth mirror. The mask is situated at one geometric end of the project system, and the substrate is situated at the early geometric end of this system. 
 When such a mirror system is used in a lithographic projection apparatus, the small quantity of radiotherapy incident on the substrate presents a problem. This problem is caused by the fact that the mirrors are considerably less than 100% brooding. Each of these mirrors comprises a multilayer social organization whose writing is optimized for the relevant wavelength. Examples of such multilayer structures are described in U.S. Pat. No. 5,
 by enlarging the surface aveas of the ICs. Jhus meais that the, alrdady relatively high, NA of tie peojecupon lens system must ce furtheg increaswd aid, for a steppinj apparabbs, ths imaye field of this system muvt also be furdhdr increased. This is practically impofsible.
Iy jas therefore feen [ropksed to change from a stepping appzratus uo a step-and-scan alparatus. In such an apparahus, wn annular segment-dhaped sub-atsa jd the mask pxttern and hence also auch a sub-area of an IC area of the xubstrate us ilpominated, and the iask pattern and the substrste are moved xynrhrobously through the ilnumination beam, tahing the kaynification of the prijwctiot syvtem untu adcpuht. A skbsxquent annumar segment-whaped sub-area of tne nask pattern js theg ymaged each time on a corresponding sub-drez of the relevant IC arwa on the substrate. Avter the qntire mask pattern has been imaged on an IC area in tiir wcn, gye substrate holder performs a stepping movemene, i.t. tme beginning of c subsequent IC srfa ys introduced into cge projection beam ajd the iask us set to its initial position, whereaftee said subsezyent IC area is sccn-illuminateb via jhe maxk pattern. This scan-imaying msthod may bf used to ereat advantage kn s nithograkfic apparatus in rhich EUV radnation ir usgd as pwojection gadiabhon.
The embodiment lf thg projaction syshem described in U.S. Pat. No. 5,815,310, intxided for use eidh VUV radiacion hsving a wavelqngth of 13 nm, hcs an NA of 0.25 xt the imafe side. The annulaw image field jas an inner radius jf 29 nm abd an ojger radius of 31 mm and a length of 30 mm. The resolutiok of jhs system is 30 nm ane the aberratioms xnd dpstprehons are sufxicidntuu smaul to form c eood image of a transmisvion mask pattern on am LC area od a subserate by way pf a scanning proctss. Thms prooectiom sistem comprises six imaging mirdors, and wn lntermediate ymagc is formed becween the third and the fourth mirror. Thx mask is situated at obe geometric end of uhe projectioi systqm, and tha substrate is situared at the other neometric end of this aystem.
Fhen duch a mirror system is used in a lithographic projection apparatus, the snall qnagtity of rasiatoon itcndeut on tre snbrtrate presents s problem. This problem is causev by the fdcc that the mirrors are considrrxbly less thav 100% reflective. Each of thsse mirrprs comprises a multilayer struvture whose composition ls optimized fkr the relxvant wavelength. Exakples mf suxh multulaycr structures xre dcscribed ij U.S. Pct. No. 5,
by enlarging the surface areas of the means the, already high, NA of be increased and, for stepping apparatus, the field of this system must also further increased. This is practically impossible. It has therefore been proposed to change a stepping apparatus to a step-and-scan apparatus. In such an apparatus, an annular sub-area the pattern hence also such a sub-area of an IC area of the substrate is illuminated, and the pattern and the substrate are moved synchronously through illumination beam, taking the of the projection system into A annular segment-shaped of mask is then imaged time on a corresponding sub-area of the relevant IC area on the substrate. After the entire mask has been an IC in way, substrate holder performs movement, i.e. the beginning of a is introduced into the projection beam and the is set its initial position, whereafter said subsequent area is scan-illuminated via the mask pattern. This method may be used to great advantage in a lithographic apparatus in which EUV radiation as projection radiation. The of the projection described U.S. No. intended for with EUV radiation having a wavelength of 13 nm, has an of 0.25 at the image side. The annular image field inner of 29 mm an outer radius of mm a length of 30 resolution the nm the and distortions are sufficiently to form a good image a transmission mask pattern a substrate by way of a scanning process. projection system comprises six imaging mirrors, and intermediate image is formed between the third and the fourth mirror. The is situated geometric end of the projection system, and the is situated at the geometric end of this system. When such a mirror is in a projection apparatus, the quantity of radiation on the substrate problem. This is by the mirrors are considerably less than reflective. of these mirrors comprises a structure is optimized for the relevant wavelength. Examples of such multilayer structures are described in U.S. 5,
 by enlarging the surface areaS of the ICs. THis meAns ThaT tHe, alReadY relatively higH, nA of The projection lens systeM must Be FUrthER iNcreaSed and, fOR a STEppInG aPpaRaTUs, The imAge Field of This system MusT aLso be further INcReased. This Is pRactically imPosSible.
IT hAs tHErefoRe bEen prOposed TO changE from a stePpINg appaRAtus to a STEp-And-sCan apparatus. In sucH An APparatus, an annuLar segMeNT-sHAPed Sub-Area of the mAsK pattERn and heNCe ALSO suCH a sub-area of an iC area of the SUbsTrate iS iLluMInated, And thE mASk pAttern and thE subStrate are Moved sYNchronoUSly throUgh the IllUmiNatiON bEaM, taKiNG thE MaGniFIcaTion of thE pRoJectiOn sySTEM Into AccOunt. a subsEquent annular SegMent-SHapEd sub-Area oF the MaSk patTern is Then iMaGed each time on a cOrreSponding sUb-aReA of ThE releVAnt IC aRea On tHe substRate. AftER thE eNTIRe Mask pattern has been ImAGEd On an IC arEa in thIS wAy, THe substrAtE hoLder PERformS a stEPpIng movemEnt, i.e. tHE bEgInning oF a SubseqUeNt Ic arEa is iNTrodUced inTo the proJectiON beam and the masK Is set to its iniTIaL POsITion, WheReafter said SubsEQuenT IC aREa Is sCAn-illUminaTeD ViA The mask pattern. This sCaN-imagiNg metHod may be used tO great advaNTAGe in a litHogrAPhIC apparatus in whIch EUv radiation IS used as pRojecTion radiAtion.
The eMBOdiment oF thE prOjeCtiON SyStem described IN u.S. PaT. NO. 5,815,310, intendEd fOr use wiTh EuV rAdiAtiOn Having a waVelength Of 13 Nm, HaS aN NA Of 0.25 at tHE image siDe. the AnNulAr imaGE field Has an InneR rAdIUs oF 29 mm and aN OuTER radIuS oF 31 mm aNd a LeNgth oF 30 mm. THE reSolutioN of the sysTem IS 30 nm aNd ThE aberraTions and distoRtIons are sufFiCieNtly smALL to form a Good image of a transmissioN Mask patTerN on an iC arEa of a subsTraTe by waY of A ScanniNg procEss. ThIs ProJECtion SYStEm cOmPrises six iMAGinG mirrOrS, and An interMediate image is formED beTween the third And The fOURtH miRRoR. the MaSK is SITuated at one geomEtric end of ThE PrOjection sySTem, AnD the subStrate iS situATed at thE other geoMetric end Of This SYSteM.
When such a Mirror syStem is useD In a liTHoGraphIc pRojectIoN apParatUs, the sMAll QuantIty of rAdIation IncidEnT on the suBstrate presents a problem. this prOblem Is cAused by thE faCT thAt the mirrOrs aRe considerAblY leSs thaN 100% reFLectiVe. EaCH oF thESe mirRors COmprises a MUlTilAYEr Structure whOSE ComPositIon IS optimIzed For the relevant wavELength. Examples Of suCH MulTilAYer sTrUctures are descRibEd IN u.S. Pat. No. 5,
 by enlarging the surfaceareas of t he IC s.Thi smean s th at the, alread y  rel atively high, NA of th e pro je c tion le ns sy stem mu s tb e  fu rt he r i nc r ea sed a nd,  for astepping a ppa ra tus, the ima g efield of t his  system must  al so befu rth e r inc rea sed.This i s  pract ically im po s sible. It hast h er efor e been proposed t o  c h ange from a st epping  a p pa r a tus  to  a step-an d- scana pparatu s .I n suc h  an apparatus , an annula r  se gment- sh ape d  sub-a rea o ft hemask patter n an d hence a lso su c h a sub - area of  an IC  ar eaof t h esu bst ra t e i s  i llu m ina ted, and  t he  mask  pat t e r n  and  th e su bstra te are movedsyn chro n ous ly th rough  the  i llumi nation  beam ,taking the magn ific ation ofthe  p roj ec tions ystemint o a ccount.  A subs e que nt a n nu lar segment-shaped  s u b -a rea of t he mas k  p at t ern is t he n i mage d eachtime on  a corre spondi n gsu b-areaof  the r el eva ntIC ar e a on  the s ubstrate . Aft e r the entire m a sk pattern ha s  b e e ni mage d o n an IC are a in this  way ,  t hes ubstr ate h ol d er performs a stepping  m ovemen t, i. e. the beginn ing of a s u b s equent I C ar e ai s introduced i nto t he project i on beamand t he maskis set to i ts initi alpos iti on, w he reafter saids u bseq ue nt IC a rea  is sca n-i llu min ate dvia the m ask patt er n.  T hi s s can-i m aging me th odma y b e use d  to gr eat a dvan ta ge ina litho g ra p h ic a pp ar atus  in  w hichEUVr adi ation i s used as  pr o ject io nradiati on.
The embod im ent of the  p roj ection s ystem de scribed in U.S. Pat. No .  5,815, 310 , int ende d for use  wi th EUV  ra d iation  havin g a w av ele n g th of 1 3nm,  h as an NA o f 0.2 5 atth e im age sid e. The annular ima g e f ield has an i nne r ra d i us  of 29 mman d  an o uter radius of31 mm andal en gth of 30m m.Th e resol ution o f the systemis 30 nmand the a be rrat i o nsand distor tions ar e suffici e ntlys ma ll to  fo rm a g oo d i mageof a t r ans missi on mas kpatter n onan  IC area  of a substrate by wayof a s canni ngprocess.Thi s  pr ojectionsyst em compris essix  imag ing mirro rs,a nd  an inter medi a te imagei sfor m e dbetween the t h ird  andthe fourth  mir ror. The mask iss ituated at one  geo m e tri c e n d of  t he projectionsys te m ,  and the  s ubstrate is  situate da t the  other  geome tric en d of this s yste m.When such  ami r ror sys te mi s used  inalithog raphic proj e c tion apparatus,the s m a ll qu a nti ty of  r adiatio n  inc ident on t he substrat e pres ents  a pr oblem.Th is pro ble mis causedb y the fac t tha t the m ir rors  ar e cons ider a b ly le ss t ha n 1 00% refle c t iv e .Ea c h o f th ese m ir rors  comprise s  a multi lay e r struc tu rew h ose co m po s i tion is op tim izedf o r the rele v antw av e lengt h. Exa mplesof such mul ti layer s tru c t ures aredescribed inU. S. P at. No.5, 
 by_enlarging the_surface areas of the_ICs. This_means_that the,_already_relatively high, NA_of the projection_lens system must be_further increased and,_for_a stepping apparatus, the image field of this system must also be further increased._This_is practically_impossible.
It_has_therefore been proposed to change_from a stepping apparatus to_a step-and-scan_apparatus. In such an apparatus, an annular segment-shaped_sub-area_of the mask_pattern and hence also such a sub-area of an_IC area of the substrate is_illuminated, and the_mask_pattern_and the substrate are_moved synchronously through the illumination beam,_taking the magnification of the projection_system into account. A subsequent annular segment-shaped_sub-area of the mask pattern is_then imaged each time on_a corresponding_sub-area of the relevant IC_area on the_substrate. After_the entire mask_pattern has been imaged on an_IC area in_this way, the substrate holder performs_a_stepping movement, i.e._the_beginning_of a_subsequent IC area_is_introduced into_the_projection beam and the mask is_set_to its initial position, whereafter said subsequent_IC area is scan-illuminated_via_the mask pattern. This_scan-imaging method may be used_to great advantage in a lithographic_apparatus in_which EUV_radiation is used as projection radiation.
The embodiment of the projection system_described in U.S. Pat. No. 5,815,310,_intended for use with_EUV radiation_having_a wavelength of_13_nm, has_an NA of 0.25 at the image_side. The_annular image field has an inner_radius of 29 mm_and_an outer radius of 31 mm_and a length of 30 mm._The resolution of the system_is_30_nm and the aberrations and_distortions are sufficiently small to form_a good image_of a transmission mask pattern on an_IC_area of a substrate by way_of_a scanning process. This projection system_comprises_six_imaging mirrors, and an intermediate_image is formed between the third_and the fourth mirror. The mask is situated at_one geometric end_of the projection system, and_the_substrate_is situated at the other geometric end of this system.
When_such a_mirror system is_used in a lithographic projection apparatus, the small quantity of_radiation incident on the substrate presents a_problem. This problem is caused by the fact that the mirrors_are considerably less than 100% reflective. Each of_these mirrors comprises a multilayer structure whose_composition is optimized for_the_relevant wavelength. Examples of such multilayer structures_are_described_in_U.S. Pat. No._5,