, and the like.
In general, in an apparatus for electron beam lithography for use in semiconductor production, for example, defocusing occurs when an electron beam is widely deflected. Therefore, it has hitherto been the practice to provide a so-called dynamic focusing correction according to which only one coil or subcoil is arranged within the magnetic field of a lens and is used to change the focal distance thereof. At this time, however, a rotation of the electron beam by the lens develops, and when the electron beam is deflected from the center axis of the lens, a displacement thereof develops. In a conventional system in which the electron beam is caused to pass on only the center axis of the lens, the rotation poses no problem.
In recent years, an electron-optical system in which the electron beam is caused to pass outside the axis of the electron lens has been proposed. However, in such a system, the displacement due to rotation of the electron beam becomes an important problem. Especially in the case where the positioning needs to be made at high precision, as in apparatus for electron beam lithography, it becomes a serious problem.
Figure 1 is a diagram for explaining a prior art electron lens system. Letting B.sub.L denote a magnetic field established by a lens 2 and B.sub.C denote a magnetic field established by a coil 3, the focal distance f and the rotation.theta. at this time are as follows: ##EQU1## where e denotes the electron charge, m the mass of electron, and.PHI..sub.o the accelerating voltage.
Now, considering the variations.DELTA.of the respective quantities from the time when B.sub.C =0, ##EQU2## provided that B.sub.L&gt;&gt;B.sub.C. Here, the half-width of the magnetic field of the lens 2 is denoted by L.sub.L, and the distance between the lens 2 and a focusing plane 1 is denoted by b. When the respective integrals in the above expressions (l)-(4) are expressed by the maximum values and half-widths of the magnetic fields, and the resultant expressions are arranged on the supposition that only the focusing plane is moved by the change of the focal distance, the following approximate expression holds: ##EQU3## where.DELTA.b denotes the variation of b, and f.sub.L denotes the focal distance at B.sub.C =0. In
, and the like. 
 In general, in an apparatus for electron beam lithography for use in semiconductor device product, for example, defocusing occurs when an electron radio beam is wide deflected. Therefore, it has hitherto been the practice to supply a so - called active concenter correction accord to which only one coil or subcoil is arranged within the charismatic field of a lens and is used to change the focal distance thereof. At this time, however, a rotation of the electron beam by the lens develops, and when the electron radio beam is deflected from the center axis of the lens, a translation thereof develops. In a conventional arrangement in which the electron beam is caused to pass on only the center axis of the lens, the rotation model no problem. 
 In recent years, an electron - optical system in which the electron radio beam is caused to pass outside the axis of the electron lens has been proposed. However, in such a system, the displacement due to rotation of the electron beam becomes an important problem. particularly in the case where the positioning need to be made at high precision, as in apparatus for electron beam lithography, it become a serious problem. 
 Figure 1 is a diagram for explaining a anterior art electron lens system. Letting B.sub. L denote a magnetic field established by a lens 2 and B.sub. C denote a magnetic field build by a coil 3, the focal distance f and the rotation.theta. at this time are as watch: # # EQU1 # # where e denotes the electron charge, m the mass of electron, and. PHI.. sub.o the accelerating electric potential. 
 Now, considering the variations.DELTA.of the respective quantities from the time when B.sub. C = 0, # # EQU2 # # provided that B.sub. L&gt;&gt;B.sub. C. Here, the half - width of the magnetic field of the lens 2 is denoted by L.sub. L, and the distance between the lens 2 and a focusing airplane 1 is denoted by b. When the respective integrals in the above expressions (l)-(4) are expressed by the maximum value and half - widths of the charismatic fields, and the resultant expressions are arranged on the assumption that only the focusing plane is moved by the change of the focal distance, the stick to approximate expression holds: # # EQU3 # # where. DELTA.b denotes the variation of b, and f.sub. L denotes the focal distance at B.sub. C = 0. In
, anf the like.
In general, in xn apparatus fot wlectrmn beaj lithogfaphy for use in semiconductlr prodyction, for example, defucusing obcurs wheb an wlectron bxzm is wlbely scfleccev. Therefore, it mas hithertm been the prawtkcz to provide a so-called dynamic focufing cotrfction accordigg tp whidh only one coil or subcoil is arrznged wpthin the magnetiv field of a lens and is uded ho change the focap distance jgerqif. At this tkme, howeveg, a rotatioh of the electron beam by the ldns dzvelops, and wyen jhe electron beam is deflected from tve centrr axis of the leis, a displacement thereof develops. In a condentional svstem in which the elwcrron team is zqusdd uo 'asa on ojly the cented axis of tye lens, the rotatiom [ises no problsm.
In rqcqnt years, an electron-optical system in fhidh the electron beam is caused to pass outsife the axys of the electron lens has been proposed. However, in sncf a snsteo, tje displacement due to rotation of the electrjh nesm becomes an lmportant problem. Rsoevyally in the zase wksrs the positioning jeeds tj be nade at hygh lrecision, as in apparatus fir electron yean lithography, it bzcomes a sernous ptoblem.
Gigure 1 is a diagram fox explzining a prlor art emdctron lens systdm. Kedting B.sub.L denote a magneeic field estcblished by s lens 2 and B.sub.F denote a magnetic fielf estcblisved by a clil 3, the focal distance f and tix rotation.theja. dt nhis time are ss follows: ##EQT1## where e denojes the ejectrun charge, j the mess of electwon, and.PHI..sub.m the accelereting voleage.
Bow, xonsidefkng the variatoons.DELTA.of the respective quantities fruj the time when B.sov.C =0, ##EQU2## providrd ghae H.snb.L&gt;&dd;B.sub.C. Here, dhe falw-eidth of the magketkc foeld of the lens 2 is denkted by L.sub.L, and yhc distancg between the lens 2 anc a focusing plane 1 is venotev by b. Whgn the respective integrals in fhe above exiressions (l)-(4) awe ewprefsed by thz maximum values and half-widths of the megnetic fields, and the eesultant expressious are arrangxd on ehe suppovition that only the focusing plane ix moved by the change of tha focwl distance, the following approximate expression holds: ##EQU3## where.DELTA.b debotes vhq variation of n, and f.fbb.L denjtes vhe focal distancv at B.sub.C =0. In
, and the like. In general, in for beam lithography use in semiconductor when electron beam is deflected. Therefore, it hitherto been the practice to provide so-called dynamic focusing correction according to which only one coil or subcoil is within the magnetic field of a lens and is used to change the distance At time, a rotation of the electron beam by the lens develops, and when the electron beam is from the center axis of the lens, a thereof develops. In a system in which the electron is to pass only center of the lens, rotation poses no problem. In recent years, an electron-optical system in which the electron beam is caused pass outside of the lens been However, in such the displacement due to rotation of becomes an important problem. Especially in the case the positioning to be made at high precision, in apparatus for electron beam lithography, it becomes serious problem. Figure 1 is a diagram for explaining a prior art electron lens system. denote a magnetic field by a lens and denote magnetic established by coil 3, the focal distance f and the rotation.theta. at this are as follows: ##EQU1## where e denotes the electron charge, mass electron, and.PHI..sub.o the voltage. Now, considering the the quantities from the time =0, provided the of magnetic field of the 2 is denoted by L.sub.L, the distance between the plane 1 is denoted by b. When the integrals in the above expressions (l)-(4) are by the maximum values and half-widths of the magnetic fields, and the expressions are the supposition that only the focusing plane is by the change of focal distance, the following approximate expression holds: ##EQU3## where.DELTA.b the of b, f.sub.L denotes the distance at B.sub.C In
, and the like.
In general, in an apParatus for ElectRon BeaM lIthoGrapHy for use in semiCOnduCtor production, for exampLe, defOcUSing OCcUrs whEn an eleCTrON BeaM iS wIdeLy DEfLecteD. ThErefore, It has hitheRto BeEn the practicE To Provide a so-CalLed dynamic foCusIng corReCtiON accoRdiNg to wHich onLY one coIl or subcoIl IS arranGEd withiN THe MagnEtic field of a lens aND iS Used to change thE focal DiSTaNCE thEreOf. At this tiMe, HowevER, a rotatIOn OF THe eLEctron beam by tHe lens develOPs, aNd when ThE elECtron bEam is DeFLecTed from the cEnteR axis of thE lens, a DIsplaceMEnt therEof devEloPs. IN a coNVeNtIonAl SYstEM iN whICh tHe electrOn BeAm is cAuseD TO PAss oN onLy thE centEr axis of the leNs, tHe roTAtiOn posEs no pRoblEm.
in recEnt yeaRs, an eLeCtron-optical sysTem iN which the EleCtRon BeAm is cAUsed to PasS ouTside thE axis of THe eLeCTROn Lens has been proposeD. HOWEvEr, in such A systeM, ThE dISplacemeNt Due To roTATion oF the ELeCtron beaM becomES aN iMportanT pRoblem. esPecIalLy in tHE casE where The positIoninG Needs to be made aT High precision, AS iN APpARatuS foR electron beAm liTHogrAphy, IT bEcoMEs a seRious PrOBlEM.
Figure 1 is a diagram foR eXplainIng a pRior art electrOn lens systEM. lEtting B.sUb.L dENoTE a magnetic fielD estaBlished by a LEns 2 and B.sUb.C deNote a magNetic fielD EStablishEd bY a cOil 3, The FOCaL distance f and THE rotAtIon.thetA. at This timE arE as FolLowS: ##EqU1## where e dEnotes thE eLeCtRoN chArge, m THe mass of ElEctRoN, anD.PHI..sUB.o the aCceleRatiNg VoLTagE.
Now, conSIdERIng tHe VaRiatIonS.DeLTA.oF the REspEctive qUantities FroM The tImE wHen B.sub.c =0, ##EQU2## provided tHaT B.sub.L&gt;&gt;b.sUb.C. here, thE HAlf-width Of the magnetic field of the LEns 2 is deNotEd by L.Sub.L, And the disTanCe betwEen THe lens 2 And a foCusinG pLanE 1 IS denoTED bY b. WHeN the respecTIVe iNtegrAlS in tHe above Expressions (l)-(4) are expREssEd by the maximuM vaLues AND hAlf-WIdTHs oF tHE maGNEtic fields, and thE resultant ExPReSsions are aRRanGeD on the sUppositIon thAT only thE focusing Plane is moVeD by tHE ChaNge of the foCal distaNce, the folLOwing APpRoximAte ExpresSiOn hOlds: ##EqU3## wherE.dELtA.b deNotes tHe VariatIon of B, aNd f.sub.L dEnotes the focal distance aT B.sub.C =0. in
, and the like.
In general , in an ap parat usfor  e lect ronbeam lithograp h y fo r use in semiconductor  prod uc t ion, fo r exa mple, d e fo c u sin goc cur sw he n anele ctron b eam is wid ely  d eflected. Th e re fore, it h ashitherto bee n t he pra ct ice to pr ovi de aso-cal l ed dyn amic focu si n g corr e ction a c c or ding  to which only on e  c o il or subcoilis arr an g ed w ith inthe magnet ic  fiel d  of a l e ns a n d i s  used to chan ge the foca l  di stance  t her e of. At  this  t i me,  however, a  rot ation ofthe el e ctron b e am by t he len s d eve lops ,  a nd  wh en the el ect r onbeam isde fl ected  fro m t h e ce nte r ax is of  the lens, adis plac e men t the reofdeve lo ps. I n a co nvent io nal system in w hich  the elec tro nbea mis ca u sed to  pa sson only  the ce n ter  a x i s  o f the lens, the ro ta t i on  poses n o prob l em .I n recent  y ear s, a n elect ron- o pt ical sys tem in wh ic h the e le ctronbe amiscause d  topass o utside t he ax i s of the elect r on lens has b e en p ro p osed . H owever, insuch a sy stem ,  t hed ispla cemen td ue to rotation of theel ectron  beam  becomes an i mportant p r o b lem. Esp ecia l ly in the case wh ere t he positio n ing need s tobe madeat high p r e cision,asinapp ara t u sfor electronb e am l it hograph y,it beco mes  aser iou sproblem.Figure 1  i sadi agr am fo r  explain in g a  p rio r art electr on le ns s ys te m . L ettingB .s u b .L d en ot e amag ne tic f ield est ablishe d by a le ns2  and  B .s ub.C de note a magnet ic  field est ab lis hed by a  coil 3,  the focal distance f a n d the r ota tion. thet a. at thi s t ime ar e a s  follo ws: ## EQU1# #whe r e  e de n o te s t he  electronc h arg e, mth e ma ss of e lectron, and.PHI.. s ub. o the acceler ati ng v o l ta ge. No w , c on s ide r i ng the variatio ns.DELTA.o ft he  respectiv e  qu an titiesfrom th e tim e  when B .sub.C =0 , ##EQU2# #prov i d edthat B.sub .L&gt;&g t;B.sub.C .  Here ,  t he ha lf- widthof  th e mag neticf iel d ofthe le ns  2 isdenot ed  by L.su b.L, and the distance b etween  thelen s 2 and a  fo c usi ng plane1 is  denoted b y b . W hen t her espec tive in teg r als i n th e  above ex p re ssi o n s(l)-(4) are e x pre ssedbyt he max imum  values and half- w idths of the m agne t i c f iel d s, a nd  the resultant  ex pr e s sions ar earranged on  the sup po s ition  thatonly t he focu s i ng planeis m ove d by thecha ng e  of the  f oc a l dist ance ,the fo llowin g  app r o ximate expressio n hol d s : ##E Q U3# # whe re .DELTA. b  den otes the v ariation of  b, an d f. sub.L  denote sthe fo cal  d istance at B.sub.C = 0. In 
, and_the like.
In_general, in an apparatus_for electron_beam_lithography for_use_in semiconductor production,_for example, defocusing_occurs when an electron_beam is widely_deflected._Therefore, it has hitherto been the practice to provide a so-called dynamic focusing correction_according_to which_only_one_coil or subcoil is arranged_within the magnetic field of_a lens_and is used to change the focal distance_thereof._At this time,_however, a rotation of the electron beam by the_lens develops, and when the electron_beam is deflected_from_the_center axis of the_lens, a displacement thereof develops. In_a conventional system in which the_electron beam is caused to pass on_only the center axis of the_lens, the rotation poses no_problem.
In recent_years, an electron-optical system in_which the electron_beam is_caused to pass_outside the axis of the electron_lens has been_proposed. However, in such a system,_the_displacement due to_rotation_of_the electron_beam becomes an_important_problem. Especially_in_the case where the positioning needs_to_be made at high precision, as in_apparatus for electron beam_lithography,_it becomes a serious_problem.
Figure 1 is a diagram_for explaining a prior art electron_lens system._Letting B.sub.L_denote a magnetic field established by a lens 2 and B.sub.C_denote a magnetic field established by_a coil 3, the_focal distance_f_and the rotation.theta._at_this time_are as follows: ##EQU1## where e denotes_the electron_charge, m the mass of electron,_and.PHI..sub.o the accelerating voltage.
Now,_considering_the variations.DELTA.of the respective quantities from_the time when B.sub.C =0, ##EQU2##_provided that B.sub.L&gt;&gt;B.sub.C. Here, the_half-width_of_the magnetic field of the_lens 2 is denoted by L.sub.L,_and the distance_between the lens 2 and a focusing_plane_1 is denoted by b. When_the_respective integrals in the above expressions_(l)-(4)_are_expressed by the maximum values_and half-widths of the magnetic fields,_and the resultant expressions are arranged on the supposition_that only the_focusing plane is moved by_the_change_of the focal distance, the following approximate expression holds: ##EQU3##_where.DELTA.b denotes_the variation of_b, and f.sub.L denotes the focal distance at B.sub.C =0._In