according to a first embodiment of the invention , illustrated on fig2 , a pattern 200 to be transferred onto a substrate 10 is provided , typically in the form of a computer file in a suitable format , and fractured using fracturing algorithms known from the prior art . a rule - based selection , using suitable rule parameters , is then applied to the fractured pattern 210 ( also in the form of a computer file ) to identify removable elementary shapes . otherwise stated , each elementary shape 2000 of the fractured pattern 200 is tested to check whether it complies with at least one of a set of predetermined rules , in which case it is removed ; otherwise the elementary shape is kept ( it is also possible to take removal as the default choice and use a complementary set of rules for identifying elementary shapes to be kept ). reference 220 identifies a fractured pattern modified by the removal of elementary shape 2000 , which leaves a “ void ” 2100 . then , optionally , at least one elementary shape 2001 , adjacent to the removed shape 2000 , is modified in order to compensate for the removal of 2000 by filling , in whole or in part , the void 2100 . in the example of fig2 , this is obtained by repositioning the right edge of shape 2001 , shifting it toward the right ; this way , the slightly enlarged shape 2001 ′ partially overlaps with void 2100 ( and , incidentally , with other elementary shapes of the fractured pattern ). removal compensation could also be performed by increasing the dose of shape 2001 , which results in its broadening due to proximity effects . it is important to note that the inventive method simplifies the already - fractured pattern , while the shot - count reduction methods known from the prior art are implemented before the fracturing step . this distinctive feature leads to a greater relevance and precision . moreover the invention does not only consider the pattern contour , as e . g . the jog realignment method , but the shot themselves ; therefore it is more closely related to the physics of direct writing , which further increases its relevance . also , it is easy to combine the inventive method with the prior art : indeed , a known technique such as jog realignment can be applied before the fracturing step , and the inventive one after it . fig3 illustrates some possible rules which can be used to identify a removable shape : 1 . maximal height “ a ” lower ( or lower or equal ) than a preset value a 0 , e . g . 5 nm . 2 . maximal jog length “ b ” lower ( or lower or equal ) than a preset value “ b 0 ”, e . g . 1000 nm . 3 . distance “ c ” from the pattern edge higher ( or higher or equal ) than a preset value “ c 0 ”, e . g . 2α , where α is the short - range point - spread function ( psf ) of the particle or photon beam , i . e . the contribution of forward - scattering to its psf . for electron - beam lithography , a is usually of the order of 30 nm , therefore c 0 may have a value of about 60 nm . in the example of fig3 , c 0 = 0 , which allows removing shapes on the pattern edge . in the example , moreover , c = c 0 = 0 and parameter “ c ” is not represented . 4 . fraction “ p ” of the perimeter of the shape belonging to the edge of the pattern lower ( or lower or equal ) than a preset value “ p 0 ”, e . g . 20 %. 5 . distance “ h ” of a peripheral elementary shape from the nearest neighboring pattern higher ( or higher or equal ) than a preset value “ h 0 ”, e . g . of the order of the critical dimension , which is typically 200 nm . 6 . minimal width “ d ” of the region of the pattern where the elementary shape is situated larger ( or larger or equal ) than a preset value “ d 0 ”, e . g . 200 nm . narrower regions , which are usually generated by the opc algorithm , should not be modified . 7 . surface “ f ” of the elementary shape lower , or lower or equal , than a preset value “ f 0 ”, e . g . 1000 nm 2 . 8 . maximal length “ g ” of the translation of an edge of an adjacent elementary shape necessary to compensate for the removal , lower , or lower or equal , than a preset value “ g 0 ”, e . g . a 0 / 1 . 5 . 9 . distance “ e ” of the closed elementary shape already recognized as “ removable ”, smaller ( or smaller or equal ) than a preset value “ e 0 ”, e . g . 3α ( typically about 90 nm ). if two shapes , whose distance is lower than “ e 0 ”, are identified as being removable by applying the other rules , only one of them will be removed . the choice is preferably performed by identifying , on the basis of parameters a , b , etc ., the shape whose removal is likely to have the least impact on the transferred pattern . 10 . elementary shape not belonging or to a critical region of the pattern . if an elementary shape belongs to a region which has been defined as critical , it cannot be removed even if it meets the requirements of all the other applicable rules . rules 1 , 2 , 6 , 9 and 10 are particularly important . for instance , according to an embodiment of the invention , an elementary shape may be identified as being removable if rules 1 and 2 are satisfied . according to another , preferred , embodiment , the elementary shape is identified as being removable if rules 1 , 2 , 6 and 9 are satisfied . in an even more preferred embodiment , the elementary shape is only identified as being removable if rules 1 , 2 , 6 , 9 and 10 are satisfied . other rules may involve the orientation of the elementary shape , a “ criticality ” of the pattern region , etc . most of these rules involve geometrical parameters , but not necessarily all of them ( cf . the case of the “ criticality ”). the simple rules above may be used in isolation or combined into more complex one using logical operators such as “ and ”, “ or ”, “ exclusive or ”, “ not ”. an exemplary complex rule , combining elementary rules 1 , 2 , 7 and the exclusion of critical regions , might be : “ remove all the elementary shapes with [( a & lt ; a 0 or b & gt ; b 0 ) and ( f & lt ; f 0 ) and not ( shape belongs to a critical region of the pattern )]”. the optimal set of rules and the numerical values or the rules parameter a 0 , b 0 . . . depend on the direct writing technology and may be determined empirically , based on experience and / or numerical simulations . it will be understood that many removable shapes will be “ slivers ”, i . e . elementary shapes having at least one dimension comparable with the critical dimension ( or resolution limit ) of the direct writing technology ; however , some elementary shapes may be removable even if they do not qualify as “ slivers ”. therefore , the inventive method may induce a greater shot - count reduction than e . g . jog alignment , which only prevents the formation of a particular subset of slivers . fig4 illustrates an alternative embodiment of the invention , based on numerical modeling of the direct writing process . as in the preceding embodiment , a pattern 300 is fractured , and then the elementary shapes 3000 of the resulting fractured pattern 310 are examined one by one . for each “ candidate ” elementary shape 3000 , a modified pattern 320 is obtained by removing it from the fractured pattern 310 , and optionally by compensating for the removal , as discussed above ( the void left when the candidate elementary shape is removed is identified by reference 3100 ; no compensation is shown on the figure ). then , suitable numerical models of the electron beam propagation , of the electrons - substrate interaction , of the resist response , etc . are used to perform a “ local ” numerical simulation of the direct writing process , i . e . of the transfer of the modified pattern 320 onto the substrate . the simulation is qualified as “ local ” because it does not necessarily involve the whole fractured pattern , but may only concern a region centered on the candidate shape 3000 and extending over an area depending on the range of proximity effects ( at least theoretically , a single global simulation could replace the multiple local simulations , but such an approach would require a huge computing power ). the simulation result is a numerical representation 330 of a transferred pattern , from which a contour 360 can be extracted using conventional image processing algorithms . a similar local simulation is performed , using the original fractured pattern and the same numerical models , to obtain a “ reference ” pattern from which a “ target ” contour 340 is extracted . user defined tolerances allow tracing a “ tolerance envelope ” 350 around said target contour . then , it is checked whether the contour 360 corresponding to the modified fractured pattern is comprised within this tolerance envelope 350 (“ consistency check ”); the candidate shape 3000 is labeled as removable only in the affirmative . advantageously , the width of the tolerance envelope is not predetermined and uniform over the whole pattern , but is computed locally as a function of parameters such as : the edge placement error ( epe ), i . e . the displacement of the edge pattern once transferred onto the resist ; the energy latitude ( el ), expressing the sensitivity of the pattern to variations of the dose ; the line edge roughness ( ler ), i . e . the deviation on an edge from an ideal line after the exposure step . one simple measure of the ler is the rms ( root mean square ) deviation of an edge from the best fit straight line . it can be simulated using a “ ler model ” taking for example the dose and the el as inputs . the left panel of fig5 a shows a portion of a fractured pattern 300 comprising a candidate shape 3000 , the contour 340 of the corresponding transferred pattern and the associated tolerance envelope 350 . the right panel of the figure shows the modified fractured pattern 320 obtained by removing candidate shape 3000 , and the contour 360 of the corresponding transferred pattern . it can be seen that the modified contour 360 remains within the tolerance envelope 350 : candidate shape 3000 is then considered removable . the left panel of fig5 b shows a portion of a slightly different fractured pattern 301 , comprising a candidate shape 3001 which is larger than the candidate shape 3000 of fig5 a , the contour 341 of the corresponding transferred pattern and the associated tolerance envelope 351 . the right panel of the figure shows the modified fractured pattern 321 obtained by removing candidate shape 3001 , and the contour 361 of the corresponding transferred pattern . it can be seen that the modified contour 361 is not fully within the tolerance envelope 351 : candidate shape 3001 is then considered non - removable . considering contours alone may not be sufficient to assess the removability of elementary shape , especially of those which are situated deep inside the pattern . a more satisfactory local comparison between the modified and reference transferred patterns also takes into account the spatial distribution of the dose , which may be computed using the numerical models , in particular to verify that it exceeds the resist threshold across the whole modified pattern . this is illustrated on fig6 a and 6b . the left panel of fig6 a shows a portion of a fractured pattern comprising 10 slivers and 8 larger elementary shapes ; the right panel shows the dose distribution across line aa ′: the dose is almost constant , well above the resist threshold th . the left panel of fig6 b shows the corresponding portion of the modified fractured pattern obtained by removing the 10 slivers ; the right panel shows the associated distribution : it is less uniform than in the case of fig6 a , but still well above the threshold , suggesting that the slivers are indeed removable . in the rule - based embodiment ( fig2 and 3 ) there is no consistency check . instead the rules are chosen such that , in the vast majority of case , the removal of selected elementary shapes will induce modifications of the transferred pattern within a preset tolerance . the embodiments of fig2 - 3 and 4 are not mutually exclusive and can advantageously be combined . for instance , a rule - based approach ( cf . fig2 ) may be used to pre - select candidate shapes whose removability is checked using a more accurate — but much more computationally intensive — model - based approach ( cf . fig4 ). in a simpler implementation , the pre - selection step only excludes elementary shapes belonging to particularly sensible zones of the pattern . the inventive method is typically implemented by executing a suitable program on a computer . said computer may directly drive the ebl apparatus ( cf . computer or processor 40 on fig1 ) or simply produce data to be provided to the ebl apparatus . the program comprises instruction code for fracturing an input pattern ( or receiving as its input an already - fractured pattern ), for identifying removable elementary shapes using one of the methods described above and for outputting a modified fractured pattern obtained by removing the elementary shapes identified as being removable . it may also comprise instruction code for driving the ebl apparatus accordingly . the program itself , the file ( s ) representing the pattern ( s ), the rule parameters ( for the embodiment of fig2 and 3 ), the model and tolerance data ( for embodiment of fig4 ) may be stored on the same or on different , and possibly remote , computer - readable storage media . for example , the program and the files mentioned above may be stored in the memory device 41 of the processor of fig1 .